1 /*
   2  * Copyright (c) 1999, 2020, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 // no precompiled headers
  26 #include "jvm.h"
  27 #include "classfile/classLoader.hpp"
  28 #include "classfile/systemDictionary.hpp"
  29 #include "classfile/vmSymbols.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "code/vtableStubs.hpp"
  32 #include "compiler/compileBroker.hpp"
  33 #include "compiler/disassembler.hpp"
  34 #include "interpreter/interpreter.hpp"
  35 #include "logging/log.hpp"
  36 #include "logging/logStream.hpp"
  37 #include "memory/allocation.inline.hpp"
  38 #include "memory/filemap.hpp"
  39 #include "oops/oop.inline.hpp"
  40 #include "os_linux.inline.hpp"
  41 #include "os_posix.inline.hpp"
  42 #include "os_share_linux.hpp"
  43 #include "osContainer_linux.hpp"
  44 #include "prims/jniFastGetField.hpp"
  45 #include "prims/jvm_misc.hpp"
  46 #include "runtime/arguments.hpp"
  47 #include "runtime/atomic.hpp"
  48 #include "runtime/globals.hpp"
  49 #include "runtime/interfaceSupport.inline.hpp"
  50 #include "runtime/init.hpp"
  51 #include "runtime/java.hpp"
  52 #include "runtime/javaCalls.hpp"
  53 #include "runtime/mutexLocker.hpp"
  54 #include "runtime/objectMonitor.hpp"
  55 #include "runtime/osThread.hpp"
  56 #include "runtime/perfMemory.hpp"
  57 #include "runtime/sharedRuntime.hpp"
  58 #include "runtime/statSampler.hpp"
  59 #include "runtime/stubRoutines.hpp"
  60 #include "runtime/thread.inline.hpp"
  61 #include "runtime/threadCritical.hpp"
  62 #include "runtime/threadSMR.hpp"
  63 #include "runtime/timer.hpp"
  64 #include "runtime/vm_version.hpp"
  65 #include "semaphore_posix.hpp"
  66 #include "services/attachListener.hpp"
  67 #include "services/memTracker.hpp"
  68 #include "services/runtimeService.hpp"
  69 #include "utilities/align.hpp"
  70 #include "utilities/decoder.hpp"
  71 #include "utilities/defaultStream.hpp"
  72 #include "utilities/events.hpp"
  73 #include "utilities/elfFile.hpp"
  74 #include "utilities/growableArray.hpp"
  75 #include "utilities/macros.hpp"
  76 #include "utilities/powerOfTwo.hpp"
  77 #include "utilities/vmError.hpp"
  78 
  79 // put OS-includes here
  80 # include <sys/types.h>
  81 # include <sys/mman.h>
  82 # include <sys/stat.h>
  83 # include <sys/select.h>
  84 # include <pthread.h>
  85 # include <signal.h>
  86 # include <endian.h>
  87 # include <errno.h>
  88 # include <dlfcn.h>
  89 # include <stdio.h>
  90 # include <unistd.h>
  91 # include <sys/resource.h>
  92 # include <pthread.h>
  93 # include <sys/stat.h>
  94 # include <sys/time.h>
  95 # include <sys/times.h>
  96 # include <sys/utsname.h>
  97 # include <sys/socket.h>
  98 # include <sys/wait.h>
  99 # include <pwd.h>
 100 # include <poll.h>
 101 # include <fcntl.h>
 102 # include <string.h>
 103 # include <syscall.h>
 104 # include <sys/sysinfo.h>
 105 # include <gnu/libc-version.h>
 106 # include <sys/ipc.h>
 107 # include <sys/shm.h>
 108 # include <link.h>
 109 # include <stdint.h>
 110 # include <inttypes.h>
 111 # include <sys/ioctl.h>
 112 # include <linux/elf-em.h>
 113 #ifdef __GLIBC__
 114 # include <malloc.h>
 115 #endif
 116 
 117 #ifndef _GNU_SOURCE
 118   #define _GNU_SOURCE
 119   #include <sched.h>
 120   #undef _GNU_SOURCE
 121 #else
 122   #include <sched.h>
 123 #endif
 124 
 125 // if RUSAGE_THREAD for getrusage() has not been defined, do it here. The code calling
 126 // getrusage() is prepared to handle the associated failure.
 127 #ifndef RUSAGE_THREAD
 128   #define RUSAGE_THREAD   (1)               /* only the calling thread */
 129 #endif
 130 
 131 #define MAX_PATH    (2 * K)
 132 
 133 #define MAX_SECS 100000000
 134 
 135 // for timer info max values which include all bits
 136 #define ALL_64_BITS CONST64(0xFFFFFFFFFFFFFFFF)
 137 
 138 enum CoredumpFilterBit {
 139   FILE_BACKED_PVT_BIT = 1 << 2,
 140   FILE_BACKED_SHARED_BIT = 1 << 3,
 141   LARGEPAGES_BIT = 1 << 6,
 142   DAX_SHARED_BIT = 1 << 8
 143 };
 144 
 145 ////////////////////////////////////////////////////////////////////////////////
 146 // global variables
 147 julong os::Linux::_physical_memory = 0;
 148 
 149 address   os::Linux::_initial_thread_stack_bottom = NULL;
 150 uintptr_t os::Linux::_initial_thread_stack_size   = 0;
 151 
 152 int (*os::Linux::_pthread_getcpuclockid)(pthread_t, clockid_t *) = NULL;
 153 int (*os::Linux::_pthread_setname_np)(pthread_t, const char*) = NULL;
 154 pthread_t os::Linux::_main_thread;
 155 int os::Linux::_page_size = -1;
 156 bool os::Linux::_supports_fast_thread_cpu_time = false;
 157 const char * os::Linux::_glibc_version = NULL;
 158 const char * os::Linux::_libpthread_version = NULL;
 159 size_t os::Linux::_default_large_page_size = 0;
 160 
 161 static jlong initial_time_count=0;
 162 
 163 static int clock_tics_per_sec = 100;
 164 
 165 // If the VM might have been created on the primordial thread, we need to resolve the
 166 // primordial thread stack bounds and check if the current thread might be the
 167 // primordial thread in places. If we know that the primordial thread is never used,
 168 // such as when the VM was created by one of the standard java launchers, we can
 169 // avoid this
 170 static bool suppress_primordial_thread_resolution = false;
 171 
 172 // For diagnostics to print a message once. see run_periodic_checks
 173 static sigset_t check_signal_done;
 174 static bool check_signals = true;
 175 
 176 // Signal number used to suspend/resume a thread
 177 
 178 // do not use any signal number less than SIGSEGV, see 4355769
 179 static int SR_signum = SIGUSR2;
 180 sigset_t SR_sigset;
 181 
 182 // utility functions
 183 
 184 static int SR_initialize();
 185 
 186 julong os::available_memory() {
 187   return Linux::available_memory();
 188 }
 189 
 190 julong os::Linux::available_memory() {
 191   // values in struct sysinfo are "unsigned long"
 192   struct sysinfo si;
 193   julong avail_mem;
 194 
 195   if (OSContainer::is_containerized()) {
 196     jlong mem_limit, mem_usage;
 197     if ((mem_limit = OSContainer::memory_limit_in_bytes()) < 1) {
 198       log_debug(os, container)("container memory limit %s: " JLONG_FORMAT ", using host value",
 199                              mem_limit == OSCONTAINER_ERROR ? "failed" : "unlimited", mem_limit);
 200     }
 201     if (mem_limit > 0 && (mem_usage = OSContainer::memory_usage_in_bytes()) < 1) {
 202       log_debug(os, container)("container memory usage failed: " JLONG_FORMAT ", using host value", mem_usage);
 203     }
 204     if (mem_limit > 0 && mem_usage > 0 ) {
 205       avail_mem = mem_limit > mem_usage ? (julong)mem_limit - (julong)mem_usage : 0;
 206       log_trace(os)("available container memory: " JULONG_FORMAT, avail_mem);
 207       return avail_mem;
 208     }
 209   }
 210 
 211   sysinfo(&si);
 212   avail_mem = (julong)si.freeram * si.mem_unit;
 213   log_trace(os)("available memory: " JULONG_FORMAT, avail_mem);
 214   return avail_mem;
 215 }
 216 
 217 julong os::physical_memory() {
 218   jlong phys_mem = 0;
 219   if (OSContainer::is_containerized()) {
 220     jlong mem_limit;
 221     if ((mem_limit = OSContainer::memory_limit_in_bytes()) > 0) {
 222       log_trace(os)("total container memory: " JLONG_FORMAT, mem_limit);
 223       return mem_limit;
 224     }
 225     log_debug(os, container)("container memory limit %s: " JLONG_FORMAT ", using host value",
 226                             mem_limit == OSCONTAINER_ERROR ? "failed" : "unlimited", mem_limit);
 227   }
 228 
 229   phys_mem = Linux::physical_memory();
 230   log_trace(os)("total system memory: " JLONG_FORMAT, phys_mem);
 231   return phys_mem;
 232 }
 233 
 234 static uint64_t initial_total_ticks = 0;
 235 static uint64_t initial_steal_ticks = 0;
 236 static bool     has_initial_tick_info = false;
 237 
 238 static void next_line(FILE *f) {
 239   int c;
 240   do {
 241     c = fgetc(f);
 242   } while (c != '\n' && c != EOF);
 243 }
 244 
 245 bool os::Linux::get_tick_information(CPUPerfTicks* pticks, int which_logical_cpu) {
 246   FILE*         fh;
 247   uint64_t      userTicks, niceTicks, systemTicks, idleTicks;
 248   // since at least kernel 2.6 : iowait: time waiting for I/O to complete
 249   // irq: time  servicing interrupts; softirq: time servicing softirqs
 250   uint64_t      iowTicks = 0, irqTicks = 0, sirqTicks= 0;
 251   // steal (since kernel 2.6.11): time spent in other OS when running in a virtualized environment
 252   uint64_t      stealTicks = 0;
 253   // guest (since kernel 2.6.24): time spent running a virtual CPU for guest OS under the
 254   // control of the Linux kernel
 255   uint64_t      guestNiceTicks = 0;
 256   int           logical_cpu = -1;
 257   const int     required_tickinfo_count = (which_logical_cpu == -1) ? 4 : 5;
 258   int           n;
 259 
 260   memset(pticks, 0, sizeof(CPUPerfTicks));
 261 
 262   if ((fh = fopen("/proc/stat", "r")) == NULL) {
 263     return false;
 264   }
 265 
 266   if (which_logical_cpu == -1) {
 267     n = fscanf(fh, "cpu " UINT64_FORMAT " " UINT64_FORMAT " " UINT64_FORMAT " "
 268             UINT64_FORMAT " " UINT64_FORMAT " " UINT64_FORMAT " " UINT64_FORMAT " "
 269             UINT64_FORMAT " " UINT64_FORMAT " ",
 270             &userTicks, &niceTicks, &systemTicks, &idleTicks,
 271             &iowTicks, &irqTicks, &sirqTicks,
 272             &stealTicks, &guestNiceTicks);
 273   } else {
 274     // Move to next line
 275     next_line(fh);
 276 
 277     // find the line for requested cpu faster to just iterate linefeeds?
 278     for (int i = 0; i < which_logical_cpu; i++) {
 279       next_line(fh);
 280     }
 281 
 282     n = fscanf(fh, "cpu%u " UINT64_FORMAT " " UINT64_FORMAT " " UINT64_FORMAT " "
 283                UINT64_FORMAT " " UINT64_FORMAT " " UINT64_FORMAT " " UINT64_FORMAT " "
 284                UINT64_FORMAT " " UINT64_FORMAT " ",
 285                &logical_cpu, &userTicks, &niceTicks,
 286                &systemTicks, &idleTicks, &iowTicks, &irqTicks, &sirqTicks,
 287                &stealTicks, &guestNiceTicks);
 288   }
 289 
 290   fclose(fh);
 291   if (n < required_tickinfo_count || logical_cpu != which_logical_cpu) {
 292     return false;
 293   }
 294   pticks->used       = userTicks + niceTicks;
 295   pticks->usedKernel = systemTicks + irqTicks + sirqTicks;
 296   pticks->total      = userTicks + niceTicks + systemTicks + idleTicks +
 297                        iowTicks + irqTicks + sirqTicks + stealTicks + guestNiceTicks;
 298 
 299   if (n > required_tickinfo_count + 3) {
 300     pticks->steal = stealTicks;
 301     pticks->has_steal_ticks = true;
 302   } else {
 303     pticks->steal = 0;
 304     pticks->has_steal_ticks = false;
 305   }
 306 
 307   return true;
 308 }
 309 
 310 // Return true if user is running as root.
 311 
 312 bool os::have_special_privileges() {
 313   static bool init = false;
 314   static bool privileges = false;
 315   if (!init) {
 316     privileges = (getuid() != geteuid()) || (getgid() != getegid());
 317     init = true;
 318   }
 319   return privileges;
 320 }
 321 
 322 
 323 #ifndef SYS_gettid
 324 // i386: 224, ia64: 1105, amd64: 186, sparc 143
 325   #ifdef __ia64__
 326     #define SYS_gettid 1105
 327   #else
 328     #ifdef __i386__
 329       #define SYS_gettid 224
 330     #else
 331       #ifdef __amd64__
 332         #define SYS_gettid 186
 333       #else
 334         #ifdef __sparc__
 335           #define SYS_gettid 143
 336         #else
 337           #error define gettid for the arch
 338         #endif
 339       #endif
 340     #endif
 341   #endif
 342 #endif
 343 
 344 
 345 // pid_t gettid()
 346 //
 347 // Returns the kernel thread id of the currently running thread. Kernel
 348 // thread id is used to access /proc.
 349 pid_t os::Linux::gettid() {
 350   int rslt = syscall(SYS_gettid);
 351   assert(rslt != -1, "must be."); // old linuxthreads implementation?
 352   return (pid_t)rslt;
 353 }
 354 
 355 // Most versions of linux have a bug where the number of processors are
 356 // determined by looking at the /proc file system.  In a chroot environment,
 357 // the system call returns 1.
 358 static bool unsafe_chroot_detected = false;
 359 static const char *unstable_chroot_error = "/proc file system not found.\n"
 360                      "Java may be unstable running multithreaded in a chroot "
 361                      "environment on Linux when /proc filesystem is not mounted.";
 362 
 363 void os::Linux::initialize_system_info() {
 364   set_processor_count(sysconf(_SC_NPROCESSORS_CONF));
 365   if (processor_count() == 1) {
 366     pid_t pid = os::Linux::gettid();
 367     char fname[32];
 368     jio_snprintf(fname, sizeof(fname), "/proc/%d", pid);
 369     FILE *fp = fopen(fname, "r");
 370     if (fp == NULL) {
 371       unsafe_chroot_detected = true;
 372     } else {
 373       fclose(fp);
 374     }
 375   }
 376   _physical_memory = (julong)sysconf(_SC_PHYS_PAGES) * (julong)sysconf(_SC_PAGESIZE);
 377   assert(processor_count() > 0, "linux error");
 378 }
 379 
 380 void os::init_system_properties_values() {
 381   // The next steps are taken in the product version:
 382   //
 383   // Obtain the JAVA_HOME value from the location of libjvm.so.
 384   // This library should be located at:
 385   // <JAVA_HOME>/lib/{client|server}/libjvm.so.
 386   //
 387   // If "/jre/lib/" appears at the right place in the path, then we
 388   // assume libjvm.so is installed in a JDK and we use this path.
 389   //
 390   // Otherwise exit with message: "Could not create the Java virtual machine."
 391   //
 392   // The following extra steps are taken in the debugging version:
 393   //
 394   // If "/jre/lib/" does NOT appear at the right place in the path
 395   // instead of exit check for $JAVA_HOME environment variable.
 396   //
 397   // If it is defined and we are able to locate $JAVA_HOME/jre/lib/<arch>,
 398   // then we append a fake suffix "hotspot/libjvm.so" to this path so
 399   // it looks like libjvm.so is installed there
 400   // <JAVA_HOME>/jre/lib/<arch>/hotspot/libjvm.so.
 401   //
 402   // Otherwise exit.
 403   //
 404   // Important note: if the location of libjvm.so changes this
 405   // code needs to be changed accordingly.
 406 
 407   // See ld(1):
 408   //      The linker uses the following search paths to locate required
 409   //      shared libraries:
 410   //        1: ...
 411   //        ...
 412   //        7: The default directories, normally /lib and /usr/lib.
 413 #ifndef OVERRIDE_LIBPATH
 414   #if defined(AMD64) || (defined(_LP64) && defined(SPARC)) || defined(PPC64) || defined(S390)
 415     #define DEFAULT_LIBPATH "/usr/lib64:/lib64:/lib:/usr/lib"
 416   #else
 417     #define DEFAULT_LIBPATH "/lib:/usr/lib"
 418   #endif
 419 #else
 420   #define DEFAULT_LIBPATH OVERRIDE_LIBPATH
 421 #endif
 422 
 423 // Base path of extensions installed on the system.
 424 #define SYS_EXT_DIR     "/usr/java/packages"
 425 #define EXTENSIONS_DIR  "/lib/ext"
 426 
 427   // Buffer that fits several sprintfs.
 428   // Note that the space for the colon and the trailing null are provided
 429   // by the nulls included by the sizeof operator.
 430   const size_t bufsize =
 431     MAX2((size_t)MAXPATHLEN,  // For dll_dir & friends.
 432          (size_t)MAXPATHLEN + sizeof(EXTENSIONS_DIR) + sizeof(SYS_EXT_DIR) + sizeof(EXTENSIONS_DIR)); // extensions dir
 433   char *buf = NEW_C_HEAP_ARRAY(char, bufsize, mtInternal);
 434 
 435   // sysclasspath, java_home, dll_dir
 436   {
 437     char *pslash;
 438     os::jvm_path(buf, bufsize);
 439 
 440     // Found the full path to libjvm.so.
 441     // Now cut the path to <java_home>/jre if we can.
 442     pslash = strrchr(buf, '/');
 443     if (pslash != NULL) {
 444       *pslash = '\0';            // Get rid of /libjvm.so.
 445     }
 446     pslash = strrchr(buf, '/');
 447     if (pslash != NULL) {
 448       *pslash = '\0';            // Get rid of /{client|server|hotspot}.
 449     }
 450     Arguments::set_dll_dir(buf);
 451 
 452     if (pslash != NULL) {
 453       pslash = strrchr(buf, '/');
 454       if (pslash != NULL) {
 455         *pslash = '\0';        // Get rid of /lib.
 456       }
 457     }
 458     Arguments::set_java_home(buf);
 459     if (!set_boot_path('/', ':')) {
 460       vm_exit_during_initialization("Failed setting boot class path.", NULL);
 461     }
 462   }
 463 
 464   // Where to look for native libraries.
 465   //
 466   // Note: Due to a legacy implementation, most of the library path
 467   // is set in the launcher. This was to accomodate linking restrictions
 468   // on legacy Linux implementations (which are no longer supported).
 469   // Eventually, all the library path setting will be done here.
 470   //
 471   // However, to prevent the proliferation of improperly built native
 472   // libraries, the new path component /usr/java/packages is added here.
 473   // Eventually, all the library path setting will be done here.
 474   {
 475     // Get the user setting of LD_LIBRARY_PATH, and prepended it. It
 476     // should always exist (until the legacy problem cited above is
 477     // addressed).
 478     const char *v = ::getenv("LD_LIBRARY_PATH");
 479     const char *v_colon = ":";
 480     if (v == NULL) { v = ""; v_colon = ""; }
 481     // That's +1 for the colon and +1 for the trailing '\0'.
 482     char *ld_library_path = NEW_C_HEAP_ARRAY(char,
 483                                              strlen(v) + 1 +
 484                                              sizeof(SYS_EXT_DIR) + sizeof("/lib/") + sizeof(DEFAULT_LIBPATH) + 1,
 485                                              mtInternal);
 486     sprintf(ld_library_path, "%s%s" SYS_EXT_DIR "/lib:" DEFAULT_LIBPATH, v, v_colon);
 487     Arguments::set_library_path(ld_library_path);
 488     FREE_C_HEAP_ARRAY(char, ld_library_path);
 489   }
 490 
 491   // Extensions directories.
 492   sprintf(buf, "%s" EXTENSIONS_DIR ":" SYS_EXT_DIR EXTENSIONS_DIR, Arguments::get_java_home());
 493   Arguments::set_ext_dirs(buf);
 494 
 495   FREE_C_HEAP_ARRAY(char, buf);
 496 
 497 #undef DEFAULT_LIBPATH
 498 #undef SYS_EXT_DIR
 499 #undef EXTENSIONS_DIR
 500 }
 501 
 502 ////////////////////////////////////////////////////////////////////////////////
 503 // breakpoint support
 504 
 505 void os::breakpoint() {
 506   BREAKPOINT;
 507 }
 508 
 509 extern "C" void breakpoint() {
 510   // use debugger to set breakpoint here
 511 }
 512 
 513 ////////////////////////////////////////////////////////////////////////////////
 514 // signal support
 515 
 516 debug_only(static bool signal_sets_initialized = false);
 517 static sigset_t unblocked_sigs, vm_sigs;
 518 
 519 void os::Linux::signal_sets_init() {
 520   // Should also have an assertion stating we are still single-threaded.
 521   assert(!signal_sets_initialized, "Already initialized");
 522   // Fill in signals that are necessarily unblocked for all threads in
 523   // the VM. Currently, we unblock the following signals:
 524   // SHUTDOWN{1,2,3}_SIGNAL: for shutdown hooks support (unless over-ridden
 525   //                         by -Xrs (=ReduceSignalUsage));
 526   // BREAK_SIGNAL which is unblocked only by the VM thread and blocked by all
 527   // other threads. The "ReduceSignalUsage" boolean tells us not to alter
 528   // the dispositions or masks wrt these signals.
 529   // Programs embedding the VM that want to use the above signals for their
 530   // own purposes must, at this time, use the "-Xrs" option to prevent
 531   // interference with shutdown hooks and BREAK_SIGNAL thread dumping.
 532   // (See bug 4345157, and other related bugs).
 533   // In reality, though, unblocking these signals is really a nop, since
 534   // these signals are not blocked by default.
 535   sigemptyset(&unblocked_sigs);
 536   sigaddset(&unblocked_sigs, SIGILL);
 537   sigaddset(&unblocked_sigs, SIGSEGV);
 538   sigaddset(&unblocked_sigs, SIGBUS);
 539   sigaddset(&unblocked_sigs, SIGFPE);
 540 #if defined(PPC64)
 541   sigaddset(&unblocked_sigs, SIGTRAP);
 542 #endif
 543   sigaddset(&unblocked_sigs, SR_signum);
 544 
 545   if (!ReduceSignalUsage) {
 546     if (!os::Posix::is_sig_ignored(SHUTDOWN1_SIGNAL)) {
 547       sigaddset(&unblocked_sigs, SHUTDOWN1_SIGNAL);
 548     }
 549     if (!os::Posix::is_sig_ignored(SHUTDOWN2_SIGNAL)) {
 550       sigaddset(&unblocked_sigs, SHUTDOWN2_SIGNAL);
 551     }
 552     if (!os::Posix::is_sig_ignored(SHUTDOWN3_SIGNAL)) {
 553       sigaddset(&unblocked_sigs, SHUTDOWN3_SIGNAL);
 554     }
 555   }
 556   // Fill in signals that are blocked by all but the VM thread.
 557   sigemptyset(&vm_sigs);
 558   if (!ReduceSignalUsage) {
 559     sigaddset(&vm_sigs, BREAK_SIGNAL);
 560   }
 561   debug_only(signal_sets_initialized = true);
 562 
 563 }
 564 
 565 // These are signals that are unblocked while a thread is running Java.
 566 // (For some reason, they get blocked by default.)
 567 sigset_t* os::Linux::unblocked_signals() {
 568   assert(signal_sets_initialized, "Not initialized");
 569   return &unblocked_sigs;
 570 }
 571 
 572 // These are the signals that are blocked while a (non-VM) thread is
 573 // running Java. Only the VM thread handles these signals.
 574 sigset_t* os::Linux::vm_signals() {
 575   assert(signal_sets_initialized, "Not initialized");
 576   return &vm_sigs;
 577 }
 578 
 579 void os::Linux::hotspot_sigmask(Thread* thread) {
 580 
 581   //Save caller's signal mask before setting VM signal mask
 582   sigset_t caller_sigmask;
 583   pthread_sigmask(SIG_BLOCK, NULL, &caller_sigmask);
 584 
 585   OSThread* osthread = thread->osthread();
 586   osthread->set_caller_sigmask(caller_sigmask);
 587 
 588   pthread_sigmask(SIG_UNBLOCK, os::Linux::unblocked_signals(), NULL);
 589 
 590   if (!ReduceSignalUsage) {
 591     if (thread->is_VM_thread()) {
 592       // Only the VM thread handles BREAK_SIGNAL ...
 593       pthread_sigmask(SIG_UNBLOCK, vm_signals(), NULL);
 594     } else {
 595       // ... all other threads block BREAK_SIGNAL
 596       pthread_sigmask(SIG_BLOCK, vm_signals(), NULL);
 597     }
 598   }
 599 }
 600 
 601 //////////////////////////////////////////////////////////////////////////////
 602 // detecting pthread library
 603 
 604 void os::Linux::libpthread_init() {
 605   // Save glibc and pthread version strings.
 606 #if !defined(_CS_GNU_LIBC_VERSION) || \
 607     !defined(_CS_GNU_LIBPTHREAD_VERSION)
 608   #error "glibc too old (< 2.3.2)"
 609 #endif
 610 
 611   size_t n = confstr(_CS_GNU_LIBC_VERSION, NULL, 0);
 612   assert(n > 0, "cannot retrieve glibc version");
 613   char *str = (char *)malloc(n, mtInternal);
 614   confstr(_CS_GNU_LIBC_VERSION, str, n);
 615   os::Linux::set_glibc_version(str);
 616 
 617   n = confstr(_CS_GNU_LIBPTHREAD_VERSION, NULL, 0);
 618   assert(n > 0, "cannot retrieve pthread version");
 619   str = (char *)malloc(n, mtInternal);
 620   confstr(_CS_GNU_LIBPTHREAD_VERSION, str, n);
 621   os::Linux::set_libpthread_version(str);
 622 }
 623 
 624 /////////////////////////////////////////////////////////////////////////////
 625 // thread stack expansion
 626 
 627 // os::Linux::manually_expand_stack() takes care of expanding the thread
 628 // stack. Note that this is normally not needed: pthread stacks allocate
 629 // thread stack using mmap() without MAP_NORESERVE, so the stack is already
 630 // committed. Therefore it is not necessary to expand the stack manually.
 631 //
 632 // Manually expanding the stack was historically needed on LinuxThreads
 633 // thread stacks, which were allocated with mmap(MAP_GROWSDOWN). Nowadays
 634 // it is kept to deal with very rare corner cases:
 635 //
 636 // For one, user may run the VM on an own implementation of threads
 637 // whose stacks are - like the old LinuxThreads - implemented using
 638 // mmap(MAP_GROWSDOWN).
 639 //
 640 // Also, this coding may be needed if the VM is running on the primordial
 641 // thread. Normally we avoid running on the primordial thread; however,
 642 // user may still invoke the VM on the primordial thread.
 643 //
 644 // The following historical comment describes the details about running
 645 // on a thread stack allocated with mmap(MAP_GROWSDOWN):
 646 
 647 
 648 // Force Linux kernel to expand current thread stack. If "bottom" is close
 649 // to the stack guard, caller should block all signals.
 650 //
 651 // MAP_GROWSDOWN:
 652 //   A special mmap() flag that is used to implement thread stacks. It tells
 653 //   kernel that the memory region should extend downwards when needed. This
 654 //   allows early versions of LinuxThreads to only mmap the first few pages
 655 //   when creating a new thread. Linux kernel will automatically expand thread
 656 //   stack as needed (on page faults).
 657 //
 658 //   However, because the memory region of a MAP_GROWSDOWN stack can grow on
 659 //   demand, if a page fault happens outside an already mapped MAP_GROWSDOWN
 660 //   region, it's hard to tell if the fault is due to a legitimate stack
 661 //   access or because of reading/writing non-exist memory (e.g. buffer
 662 //   overrun). As a rule, if the fault happens below current stack pointer,
 663 //   Linux kernel does not expand stack, instead a SIGSEGV is sent to the
 664 //   application (see Linux kernel fault.c).
 665 //
 666 //   This Linux feature can cause SIGSEGV when VM bangs thread stack for
 667 //   stack overflow detection.
 668 //
 669 //   Newer version of LinuxThreads (since glibc-2.2, or, RH-7.x) and NPTL do
 670 //   not use MAP_GROWSDOWN.
 671 //
 672 // To get around the problem and allow stack banging on Linux, we need to
 673 // manually expand thread stack after receiving the SIGSEGV.
 674 //
 675 // There are two ways to expand thread stack to address "bottom", we used
 676 // both of them in JVM before 1.5:
 677 //   1. adjust stack pointer first so that it is below "bottom", and then
 678 //      touch "bottom"
 679 //   2. mmap() the page in question
 680 //
 681 // Now alternate signal stack is gone, it's harder to use 2. For instance,
 682 // if current sp is already near the lower end of page 101, and we need to
 683 // call mmap() to map page 100, it is possible that part of the mmap() frame
 684 // will be placed in page 100. When page 100 is mapped, it is zero-filled.
 685 // That will destroy the mmap() frame and cause VM to crash.
 686 //
 687 // The following code works by adjusting sp first, then accessing the "bottom"
 688 // page to force a page fault. Linux kernel will then automatically expand the
 689 // stack mapping.
 690 //
 691 // _expand_stack_to() assumes its frame size is less than page size, which
 692 // should always be true if the function is not inlined.
 693 
 694 static void NOINLINE _expand_stack_to(address bottom) {
 695   address sp;
 696   size_t size;
 697   volatile char *p;
 698 
 699   // Adjust bottom to point to the largest address within the same page, it
 700   // gives us a one-page buffer if alloca() allocates slightly more memory.
 701   bottom = (address)align_down((uintptr_t)bottom, os::Linux::page_size());
 702   bottom += os::Linux::page_size() - 1;
 703 
 704   // sp might be slightly above current stack pointer; if that's the case, we
 705   // will alloca() a little more space than necessary, which is OK. Don't use
 706   // os::current_stack_pointer(), as its result can be slightly below current
 707   // stack pointer, causing us to not alloca enough to reach "bottom".
 708   sp = (address)&sp;
 709 
 710   if (sp > bottom) {
 711     size = sp - bottom;
 712     p = (volatile char *)alloca(size);
 713     assert(p != NULL && p <= (volatile char *)bottom, "alloca problem?");
 714     p[0] = '\0';
 715   }
 716 }
 717 
 718 void os::Linux::expand_stack_to(address bottom) {
 719   _expand_stack_to(bottom);
 720 }
 721 
 722 bool os::Linux::manually_expand_stack(JavaThread * t, address addr) {
 723   assert(t!=NULL, "just checking");
 724   assert(t->osthread()->expanding_stack(), "expand should be set");
 725 
 726   if (t->is_in_usable_stack(addr)) {
 727     sigset_t mask_all, old_sigset;
 728     sigfillset(&mask_all);
 729     pthread_sigmask(SIG_SETMASK, &mask_all, &old_sigset);
 730     _expand_stack_to(addr);
 731     pthread_sigmask(SIG_SETMASK, &old_sigset, NULL);
 732     return true;
 733   }
 734   return false;
 735 }
 736 
 737 //////////////////////////////////////////////////////////////////////////////
 738 // create new thread
 739 
 740 // Thread start routine for all newly created threads
 741 static void *thread_native_entry(Thread *thread) {
 742 
 743   thread->record_stack_base_and_size();
 744 
 745   // Try to randomize the cache line index of hot stack frames.
 746   // This helps when threads of the same stack traces evict each other's
 747   // cache lines. The threads can be either from the same JVM instance, or
 748   // from different JVM instances. The benefit is especially true for
 749   // processors with hyperthreading technology.
 750   static int counter = 0;
 751   int pid = os::current_process_id();
 752   alloca(((pid ^ counter++) & 7) * 128);
 753 
 754   thread->initialize_thread_current();
 755 
 756   OSThread* osthread = thread->osthread();
 757   Monitor* sync = osthread->startThread_lock();
 758 
 759   osthread->set_thread_id(os::current_thread_id());
 760 
 761   log_info(os, thread)("Thread is alive (tid: " UINTX_FORMAT ", pthread id: " UINTX_FORMAT ").",
 762     os::current_thread_id(), (uintx) pthread_self());
 763 
 764   if (UseNUMA) {
 765     int lgrp_id = os::numa_get_group_id();
 766     if (lgrp_id != -1) {
 767       thread->set_lgrp_id(lgrp_id);
 768     }
 769   }
 770   // initialize signal mask for this thread
 771   os::Linux::hotspot_sigmask(thread);
 772 
 773   // initialize floating point control register
 774   os::Linux::init_thread_fpu_state();
 775 
 776   // handshaking with parent thread
 777   {
 778     MutexLocker ml(sync, Mutex::_no_safepoint_check_flag);
 779 
 780     // notify parent thread
 781     osthread->set_state(INITIALIZED);
 782     sync->notify_all();
 783 
 784     // wait until os::start_thread()
 785     while (osthread->get_state() == INITIALIZED) {
 786       sync->wait_without_safepoint_check();
 787     }
 788   }
 789 
 790   assert(osthread->pthread_id() != 0, "pthread_id was not set as expected");
 791 
 792   // call one more level start routine
 793   thread->call_run();
 794 
 795   // Note: at this point the thread object may already have deleted itself.
 796   // Prevent dereferencing it from here on out.
 797   thread = NULL;
 798 
 799   log_info(os, thread)("Thread finished (tid: " UINTX_FORMAT ", pthread id: " UINTX_FORMAT ").",
 800     os::current_thread_id(), (uintx) pthread_self());
 801 
 802   return 0;
 803 }
 804 
 805 // On Linux, glibc places static TLS blocks (for __thread variables) on
 806 // the thread stack. This decreases the stack size actually available
 807 // to threads.
 808 //
 809 // For large static TLS sizes, this may cause threads to malfunction due
 810 // to insufficient stack space. This is a well-known issue in glibc:
 811 // http://sourceware.org/bugzilla/show_bug.cgi?id=11787.
 812 //
 813 // As a workaround, we call a private but assumed-stable glibc function,
 814 // __pthread_get_minstack() to obtain the minstack size and derive the
 815 // static TLS size from it. We then increase the user requested stack
 816 // size by this TLS size.
 817 //
 818 // Due to compatibility concerns, this size adjustment is opt-in and
 819 // controlled via AdjustStackSizeForTLS.
 820 typedef size_t (*GetMinStack)(const pthread_attr_t *attr);
 821 
 822 GetMinStack _get_minstack_func = NULL;
 823 
 824 static void get_minstack_init() {
 825   _get_minstack_func =
 826         (GetMinStack)dlsym(RTLD_DEFAULT, "__pthread_get_minstack");
 827   log_info(os, thread)("Lookup of __pthread_get_minstack %s",
 828                        _get_minstack_func == NULL ? "failed" : "succeeded");
 829 }
 830 
 831 // Returns the size of the static TLS area glibc puts on thread stacks.
 832 // The value is cached on first use, which occurs when the first thread
 833 // is created during VM initialization.
 834 static size_t get_static_tls_area_size(const pthread_attr_t *attr) {
 835   size_t tls_size = 0;
 836   if (_get_minstack_func != NULL) {
 837     // Obtain the pthread minstack size by calling __pthread_get_minstack.
 838     size_t minstack_size = _get_minstack_func(attr);
 839 
 840     // Remove non-TLS area size included in minstack size returned
 841     // by __pthread_get_minstack() to get the static TLS size.
 842     // In glibc before 2.27, minstack size includes guard_size.
 843     // In glibc 2.27 and later, guard_size is automatically added
 844     // to the stack size by pthread_create and is no longer included
 845     // in minstack size. In both cases, the guard_size is taken into
 846     // account, so there is no need to adjust the result for that.
 847     //
 848     // Although __pthread_get_minstack() is a private glibc function,
 849     // it is expected to have a stable behavior across future glibc
 850     // versions while glibc still allocates the static TLS blocks off
 851     // the stack. Following is glibc 2.28 __pthread_get_minstack():
 852     //
 853     // size_t
 854     // __pthread_get_minstack (const pthread_attr_t *attr)
 855     // {
 856     //   return GLRO(dl_pagesize) + __static_tls_size + PTHREAD_STACK_MIN;
 857     // }
 858     //
 859     //
 860     // The following 'minstack_size > os::vm_page_size() + PTHREAD_STACK_MIN'
 861     // if check is done for precaution.
 862     if (minstack_size > (size_t)os::vm_page_size() + PTHREAD_STACK_MIN) {
 863       tls_size = minstack_size - os::vm_page_size() - PTHREAD_STACK_MIN;
 864     }
 865   }
 866 
 867   log_info(os, thread)("Stack size adjustment for TLS is " SIZE_FORMAT,
 868                        tls_size);
 869   return tls_size;
 870 }
 871 
 872 bool os::create_thread(Thread* thread, ThreadType thr_type,
 873                        size_t req_stack_size) {
 874   assert(thread->osthread() == NULL, "caller responsible");
 875 
 876   // Allocate the OSThread object
 877   OSThread* osthread = new OSThread(NULL, NULL);
 878   if (osthread == NULL) {
 879     return false;
 880   }
 881 
 882   // set the correct thread state
 883   osthread->set_thread_type(thr_type);
 884 
 885   // Initial state is ALLOCATED but not INITIALIZED
 886   osthread->set_state(ALLOCATED);
 887 
 888   thread->set_osthread(osthread);
 889 
 890   // init thread attributes
 891   pthread_attr_t attr;
 892   pthread_attr_init(&attr);
 893   pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
 894 
 895   // Calculate stack size if it's not specified by caller.
 896   size_t stack_size = os::Posix::get_initial_stack_size(thr_type, req_stack_size);
 897   // In glibc versions prior to 2.7 the guard size mechanism
 898   // is not implemented properly. The posix standard requires adding
 899   // the size of the guard pages to the stack size, instead Linux
 900   // takes the space out of 'stacksize'. Thus we adapt the requested
 901   // stack_size by the size of the guard pages to mimick proper
 902   // behaviour. However, be careful not to end up with a size
 903   // of zero due to overflow. Don't add the guard page in that case.
 904   size_t guard_size = os::Linux::default_guard_size(thr_type);
 905   // Configure glibc guard page. Must happen before calling
 906   // get_static_tls_area_size(), which uses the guard_size.
 907   pthread_attr_setguardsize(&attr, guard_size);
 908 
 909   size_t stack_adjust_size = 0;
 910   if (AdjustStackSizeForTLS) {
 911     // Adjust the stack_size for on-stack TLS - see get_static_tls_area_size().
 912     stack_adjust_size += get_static_tls_area_size(&attr);
 913   } else {
 914     stack_adjust_size += guard_size;
 915   }
 916 
 917   stack_adjust_size = align_up(stack_adjust_size, os::vm_page_size());
 918   if (stack_size <= SIZE_MAX - stack_adjust_size) {
 919     stack_size += stack_adjust_size;
 920   }
 921   assert(is_aligned(stack_size, os::vm_page_size()), "stack_size not aligned");
 922 
 923   int status = pthread_attr_setstacksize(&attr, stack_size);
 924   if (status != 0) {
 925     // pthread_attr_setstacksize() function can fail
 926     // if the stack size exceeds a system-imposed limit.
 927     assert_status(status == EINVAL, status, "pthread_attr_setstacksize");
 928     log_warning(os, thread)("The %sthread stack size specified is invalid: " SIZE_FORMAT "k",
 929                             (thr_type == compiler_thread) ? "compiler " : ((thr_type == java_thread) ? "" : "VM "),
 930                             stack_size / K);
 931     thread->set_osthread(NULL);
 932     delete osthread;
 933     return false;
 934   }
 935 
 936   ThreadState state;
 937 
 938   {
 939     pthread_t tid;
 940     int ret = pthread_create(&tid, &attr, (void* (*)(void*)) thread_native_entry, thread);
 941 
 942     char buf[64];
 943     if (ret == 0) {
 944       log_info(os, thread)("Thread started (pthread id: " UINTX_FORMAT ", attributes: %s). ",
 945         (uintx) tid, os::Posix::describe_pthread_attr(buf, sizeof(buf), &attr));
 946     } else {
 947       log_warning(os, thread)("Failed to start thread - pthread_create failed (%s) for attributes: %s.",
 948         os::errno_name(ret), os::Posix::describe_pthread_attr(buf, sizeof(buf), &attr));
 949       // Log some OS information which might explain why creating the thread failed.
 950       log_info(os, thread)("Number of threads approx. running in the VM: %d", Threads::number_of_threads());
 951       LogStream st(Log(os, thread)::info());
 952       os::Posix::print_rlimit_info(&st);
 953       os::print_memory_info(&st);
 954       os::Linux::print_proc_sys_info(&st);
 955       os::Linux::print_container_info(&st);
 956     }
 957 
 958     pthread_attr_destroy(&attr);
 959 
 960     if (ret != 0) {
 961       // Need to clean up stuff we've allocated so far
 962       thread->set_osthread(NULL);
 963       delete osthread;
 964       return false;
 965     }
 966 
 967     // Store pthread info into the OSThread
 968     osthread->set_pthread_id(tid);
 969 
 970     // Wait until child thread is either initialized or aborted
 971     {
 972       Monitor* sync_with_child = osthread->startThread_lock();
 973       MutexLocker ml(sync_with_child, Mutex::_no_safepoint_check_flag);
 974       while ((state = osthread->get_state()) == ALLOCATED) {
 975         sync_with_child->wait_without_safepoint_check();
 976       }
 977     }
 978   }
 979 
 980   // Aborted due to thread limit being reached
 981   if (state == ZOMBIE) {
 982     thread->set_osthread(NULL);
 983     delete osthread;
 984     return false;
 985   }
 986 
 987   // The thread is returned suspended (in state INITIALIZED),
 988   // and is started higher up in the call chain
 989   assert(state == INITIALIZED, "race condition");
 990   return true;
 991 }
 992 
 993 /////////////////////////////////////////////////////////////////////////////
 994 // attach existing thread
 995 
 996 // bootstrap the main thread
 997 bool os::create_main_thread(JavaThread* thread) {
 998   assert(os::Linux::_main_thread == pthread_self(), "should be called inside main thread");
 999   return create_attached_thread(thread);
1000 }
1001 
1002 bool os::create_attached_thread(JavaThread* thread) {
1003 #ifdef ASSERT
1004   thread->verify_not_published();
1005 #endif
1006 
1007   // Allocate the OSThread object
1008   OSThread* osthread = new OSThread(NULL, NULL);
1009 
1010   if (osthread == NULL) {
1011     return false;
1012   }
1013 
1014   // Store pthread info into the OSThread
1015   osthread->set_thread_id(os::Linux::gettid());
1016   osthread->set_pthread_id(::pthread_self());
1017 
1018   // initialize floating point control register
1019   os::Linux::init_thread_fpu_state();
1020 
1021   // Initial thread state is RUNNABLE
1022   osthread->set_state(RUNNABLE);
1023 
1024   thread->set_osthread(osthread);
1025 
1026   if (UseNUMA) {
1027     int lgrp_id = os::numa_get_group_id();
1028     if (lgrp_id != -1) {
1029       thread->set_lgrp_id(lgrp_id);
1030     }
1031   }
1032 
1033   if (os::is_primordial_thread()) {
1034     // If current thread is primordial thread, its stack is mapped on demand,
1035     // see notes about MAP_GROWSDOWN. Here we try to force kernel to map
1036     // the entire stack region to avoid SEGV in stack banging.
1037     // It is also useful to get around the heap-stack-gap problem on SuSE
1038     // kernel (see 4821821 for details). We first expand stack to the top
1039     // of yellow zone, then enable stack yellow zone (order is significant,
1040     // enabling yellow zone first will crash JVM on SuSE Linux), so there
1041     // is no gap between the last two virtual memory regions.
1042 
1043     JavaThread *jt = (JavaThread *)thread;
1044     address addr = jt->stack_reserved_zone_base();
1045     assert(addr != NULL, "initialization problem?");
1046     assert(jt->stack_available(addr) > 0, "stack guard should not be enabled");
1047 
1048     osthread->set_expanding_stack();
1049     os::Linux::manually_expand_stack(jt, addr);
1050     osthread->clear_expanding_stack();
1051   }
1052 
1053   // initialize signal mask for this thread
1054   // and save the caller's signal mask
1055   os::Linux::hotspot_sigmask(thread);
1056 
1057   log_info(os, thread)("Thread attached (tid: " UINTX_FORMAT ", pthread id: " UINTX_FORMAT ").",
1058     os::current_thread_id(), (uintx) pthread_self());
1059 
1060   return true;
1061 }
1062 
1063 void os::pd_start_thread(Thread* thread) {
1064   OSThread * osthread = thread->osthread();
1065   assert(osthread->get_state() != INITIALIZED, "just checking");
1066   Monitor* sync_with_child = osthread->startThread_lock();
1067   MutexLocker ml(sync_with_child, Mutex::_no_safepoint_check_flag);
1068   sync_with_child->notify();
1069 }
1070 
1071 // Free Linux resources related to the OSThread
1072 void os::free_thread(OSThread* osthread) {
1073   assert(osthread != NULL, "osthread not set");
1074 
1075   // We are told to free resources of the argument thread,
1076   // but we can only really operate on the current thread.
1077   assert(Thread::current()->osthread() == osthread,
1078          "os::free_thread but not current thread");
1079 
1080 #ifdef ASSERT
1081   sigset_t current;
1082   sigemptyset(&current);
1083   pthread_sigmask(SIG_SETMASK, NULL, &current);
1084   assert(!sigismember(&current, SR_signum), "SR signal should not be blocked!");
1085 #endif
1086 
1087   // Restore caller's signal mask
1088   sigset_t sigmask = osthread->caller_sigmask();
1089   pthread_sigmask(SIG_SETMASK, &sigmask, NULL);
1090 
1091   delete osthread;
1092 }
1093 
1094 //////////////////////////////////////////////////////////////////////////////
1095 // primordial thread
1096 
1097 // Check if current thread is the primordial thread, similar to Solaris thr_main.
1098 bool os::is_primordial_thread(void) {
1099   if (suppress_primordial_thread_resolution) {
1100     return false;
1101   }
1102   char dummy;
1103   // If called before init complete, thread stack bottom will be null.
1104   // Can be called if fatal error occurs before initialization.
1105   if (os::Linux::initial_thread_stack_bottom() == NULL) return false;
1106   assert(os::Linux::initial_thread_stack_bottom() != NULL &&
1107          os::Linux::initial_thread_stack_size()   != 0,
1108          "os::init did not locate primordial thread's stack region");
1109   if ((address)&dummy >= os::Linux::initial_thread_stack_bottom() &&
1110       (address)&dummy < os::Linux::initial_thread_stack_bottom() +
1111                         os::Linux::initial_thread_stack_size()) {
1112     return true;
1113   } else {
1114     return false;
1115   }
1116 }
1117 
1118 // Find the virtual memory area that contains addr
1119 static bool find_vma(address addr, address* vma_low, address* vma_high) {
1120   FILE *fp = fopen("/proc/self/maps", "r");
1121   if (fp) {
1122     address low, high;
1123     while (!feof(fp)) {
1124       if (fscanf(fp, "%p-%p", &low, &high) == 2) {
1125         if (low <= addr && addr < high) {
1126           if (vma_low)  *vma_low  = low;
1127           if (vma_high) *vma_high = high;
1128           fclose(fp);
1129           return true;
1130         }
1131       }
1132       for (;;) {
1133         int ch = fgetc(fp);
1134         if (ch == EOF || ch == (int)'\n') break;
1135       }
1136     }
1137     fclose(fp);
1138   }
1139   return false;
1140 }
1141 
1142 // Locate primordial thread stack. This special handling of primordial thread stack
1143 // is needed because pthread_getattr_np() on most (all?) Linux distros returns
1144 // bogus value for the primordial process thread. While the launcher has created
1145 // the VM in a new thread since JDK 6, we still have to allow for the use of the
1146 // JNI invocation API from a primordial thread.
1147 void os::Linux::capture_initial_stack(size_t max_size) {
1148 
1149   // max_size is either 0 (which means accept OS default for thread stacks) or
1150   // a user-specified value known to be at least the minimum needed. If we
1151   // are actually on the primordial thread we can make it appear that we have a
1152   // smaller max_size stack by inserting the guard pages at that location. But we
1153   // cannot do anything to emulate a larger stack than what has been provided by
1154   // the OS or threading library. In fact if we try to use a stack greater than
1155   // what is set by rlimit then we will crash the hosting process.
1156 
1157   // Maximum stack size is the easy part, get it from RLIMIT_STACK.
1158   // If this is "unlimited" then it will be a huge value.
1159   struct rlimit rlim;
1160   getrlimit(RLIMIT_STACK, &rlim);
1161   size_t stack_size = rlim.rlim_cur;
1162 
1163   // 6308388: a bug in ld.so will relocate its own .data section to the
1164   //   lower end of primordial stack; reduce ulimit -s value a little bit
1165   //   so we won't install guard page on ld.so's data section.
1166   //   But ensure we don't underflow the stack size - allow 1 page spare
1167   if (stack_size >= (size_t)(3 * page_size())) {
1168     stack_size -= 2 * page_size();
1169   }
1170 
1171   // Try to figure out where the stack base (top) is. This is harder.
1172   //
1173   // When an application is started, glibc saves the initial stack pointer in
1174   // a global variable "__libc_stack_end", which is then used by system
1175   // libraries. __libc_stack_end should be pretty close to stack top. The
1176   // variable is available since the very early days. However, because it is
1177   // a private interface, it could disappear in the future.
1178   //
1179   // Linux kernel saves start_stack information in /proc/<pid>/stat. Similar
1180   // to __libc_stack_end, it is very close to stack top, but isn't the real
1181   // stack top. Note that /proc may not exist if VM is running as a chroot
1182   // program, so reading /proc/<pid>/stat could fail. Also the contents of
1183   // /proc/<pid>/stat could change in the future (though unlikely).
1184   //
1185   // We try __libc_stack_end first. If that doesn't work, look for
1186   // /proc/<pid>/stat. If neither of them works, we use current stack pointer
1187   // as a hint, which should work well in most cases.
1188 
1189   uintptr_t stack_start;
1190 
1191   // try __libc_stack_end first
1192   uintptr_t *p = (uintptr_t *)dlsym(RTLD_DEFAULT, "__libc_stack_end");
1193   if (p && *p) {
1194     stack_start = *p;
1195   } else {
1196     // see if we can get the start_stack field from /proc/self/stat
1197     FILE *fp;
1198     int pid;
1199     char state;
1200     int ppid;
1201     int pgrp;
1202     int session;
1203     int nr;
1204     int tpgrp;
1205     unsigned long flags;
1206     unsigned long minflt;
1207     unsigned long cminflt;
1208     unsigned long majflt;
1209     unsigned long cmajflt;
1210     unsigned long utime;
1211     unsigned long stime;
1212     long cutime;
1213     long cstime;
1214     long prio;
1215     long nice;
1216     long junk;
1217     long it_real;
1218     uintptr_t start;
1219     uintptr_t vsize;
1220     intptr_t rss;
1221     uintptr_t rsslim;
1222     uintptr_t scodes;
1223     uintptr_t ecode;
1224     int i;
1225 
1226     // Figure what the primordial thread stack base is. Code is inspired
1227     // by email from Hans Boehm. /proc/self/stat begins with current pid,
1228     // followed by command name surrounded by parentheses, state, etc.
1229     char stat[2048];
1230     int statlen;
1231 
1232     fp = fopen("/proc/self/stat", "r");
1233     if (fp) {
1234       statlen = fread(stat, 1, 2047, fp);
1235       stat[statlen] = '\0';
1236       fclose(fp);
1237 
1238       // Skip pid and the command string. Note that we could be dealing with
1239       // weird command names, e.g. user could decide to rename java launcher
1240       // to "java 1.4.2 :)", then the stat file would look like
1241       //                1234 (java 1.4.2 :)) R ... ...
1242       // We don't really need to know the command string, just find the last
1243       // occurrence of ")" and then start parsing from there. See bug 4726580.
1244       char * s = strrchr(stat, ')');
1245 
1246       i = 0;
1247       if (s) {
1248         // Skip blank chars
1249         do { s++; } while (s && isspace(*s));
1250 
1251 #define _UFM UINTX_FORMAT
1252 #define _DFM INTX_FORMAT
1253 
1254         //                                     1   1   1   1   1   1   1   1   1   1   2   2    2    2    2    2    2    2    2
1255         //              3  4  5  6  7  8   9   0   1   2   3   4   5   6   7   8   9   0   1    2    3    4    5    6    7    8
1256         i = sscanf(s, "%c %d %d %d %d %d %lu %lu %lu %lu %lu %lu %lu %ld %ld %ld %ld %ld %ld " _UFM _UFM _DFM _UFM _UFM _UFM _UFM,
1257                    &state,          // 3  %c
1258                    &ppid,           // 4  %d
1259                    &pgrp,           // 5  %d
1260                    &session,        // 6  %d
1261                    &nr,             // 7  %d
1262                    &tpgrp,          // 8  %d
1263                    &flags,          // 9  %lu
1264                    &minflt,         // 10 %lu
1265                    &cminflt,        // 11 %lu
1266                    &majflt,         // 12 %lu
1267                    &cmajflt,        // 13 %lu
1268                    &utime,          // 14 %lu
1269                    &stime,          // 15 %lu
1270                    &cutime,         // 16 %ld
1271                    &cstime,         // 17 %ld
1272                    &prio,           // 18 %ld
1273                    &nice,           // 19 %ld
1274                    &junk,           // 20 %ld
1275                    &it_real,        // 21 %ld
1276                    &start,          // 22 UINTX_FORMAT
1277                    &vsize,          // 23 UINTX_FORMAT
1278                    &rss,            // 24 INTX_FORMAT
1279                    &rsslim,         // 25 UINTX_FORMAT
1280                    &scodes,         // 26 UINTX_FORMAT
1281                    &ecode,          // 27 UINTX_FORMAT
1282                    &stack_start);   // 28 UINTX_FORMAT
1283       }
1284 
1285 #undef _UFM
1286 #undef _DFM
1287 
1288       if (i != 28 - 2) {
1289         assert(false, "Bad conversion from /proc/self/stat");
1290         // product mode - assume we are the primordial thread, good luck in the
1291         // embedded case.
1292         warning("Can't detect primordial thread stack location - bad conversion");
1293         stack_start = (uintptr_t) &rlim;
1294       }
1295     } else {
1296       // For some reason we can't open /proc/self/stat (for example, running on
1297       // FreeBSD with a Linux emulator, or inside chroot), this should work for
1298       // most cases, so don't abort:
1299       warning("Can't detect primordial thread stack location - no /proc/self/stat");
1300       stack_start = (uintptr_t) &rlim;
1301     }
1302   }
1303 
1304   // Now we have a pointer (stack_start) very close to the stack top, the
1305   // next thing to do is to figure out the exact location of stack top. We
1306   // can find out the virtual memory area that contains stack_start by
1307   // reading /proc/self/maps, it should be the last vma in /proc/self/maps,
1308   // and its upper limit is the real stack top. (again, this would fail if
1309   // running inside chroot, because /proc may not exist.)
1310 
1311   uintptr_t stack_top;
1312   address low, high;
1313   if (find_vma((address)stack_start, &low, &high)) {
1314     // success, "high" is the true stack top. (ignore "low", because initial
1315     // thread stack grows on demand, its real bottom is high - RLIMIT_STACK.)
1316     stack_top = (uintptr_t)high;
1317   } else {
1318     // failed, likely because /proc/self/maps does not exist
1319     warning("Can't detect primordial thread stack location - find_vma failed");
1320     // best effort: stack_start is normally within a few pages below the real
1321     // stack top, use it as stack top, and reduce stack size so we won't put
1322     // guard page outside stack.
1323     stack_top = stack_start;
1324     stack_size -= 16 * page_size();
1325   }
1326 
1327   // stack_top could be partially down the page so align it
1328   stack_top = align_up(stack_top, page_size());
1329 
1330   // Allowed stack value is minimum of max_size and what we derived from rlimit
1331   if (max_size > 0) {
1332     _initial_thread_stack_size = MIN2(max_size, stack_size);
1333   } else {
1334     // Accept the rlimit max, but if stack is unlimited then it will be huge, so
1335     // clamp it at 8MB as we do on Solaris
1336     _initial_thread_stack_size = MIN2(stack_size, 8*M);
1337   }
1338   _initial_thread_stack_size = align_down(_initial_thread_stack_size, page_size());
1339   _initial_thread_stack_bottom = (address)stack_top - _initial_thread_stack_size;
1340 
1341   assert(_initial_thread_stack_bottom < (address)stack_top, "overflow!");
1342 
1343   if (log_is_enabled(Info, os, thread)) {
1344     // See if we seem to be on primordial process thread
1345     bool primordial = uintptr_t(&rlim) > uintptr_t(_initial_thread_stack_bottom) &&
1346                       uintptr_t(&rlim) < stack_top;
1347 
1348     log_info(os, thread)("Capturing initial stack in %s thread: req. size: " SIZE_FORMAT "K, actual size: "
1349                          SIZE_FORMAT "K, top=" INTPTR_FORMAT ", bottom=" INTPTR_FORMAT,
1350                          primordial ? "primordial" : "user", max_size / K,  _initial_thread_stack_size / K,
1351                          stack_top, intptr_t(_initial_thread_stack_bottom));
1352   }
1353 }
1354 
1355 ////////////////////////////////////////////////////////////////////////////////
1356 // time support
1357 
1358 #ifndef SUPPORTS_CLOCK_MONOTONIC
1359 #error "Build platform doesn't support clock_gettime and related functionality"
1360 #endif
1361 
1362 // Time since start-up in seconds to a fine granularity.
1363 // Used by VMSelfDestructTimer and the MemProfiler.
1364 double os::elapsedTime() {
1365 
1366   return ((double)os::elapsed_counter()) / os::elapsed_frequency(); // nanosecond resolution
1367 }
1368 
1369 jlong os::elapsed_counter() {
1370   return javaTimeNanos() - initial_time_count;
1371 }
1372 
1373 jlong os::elapsed_frequency() {
1374   return NANOSECS_PER_SEC; // nanosecond resolution
1375 }
1376 
1377 bool os::supports_vtime() { return true; }
1378 
1379 double os::elapsedVTime() {
1380   struct rusage usage;
1381   int retval = getrusage(RUSAGE_THREAD, &usage);
1382   if (retval == 0) {
1383     return (double) (usage.ru_utime.tv_sec + usage.ru_stime.tv_sec) + (double) (usage.ru_utime.tv_usec + usage.ru_stime.tv_usec) / (1000 * 1000);
1384   } else {
1385     // better than nothing, but not much
1386     return elapsedTime();
1387   }
1388 }
1389 
1390 jlong os::javaTimeMillis() {
1391   if (os::Posix::supports_clock_gettime()) {
1392     struct timespec ts;
1393     int status = os::Posix::clock_gettime(CLOCK_REALTIME, &ts);
1394     assert_status(status == 0, status, "gettime error");
1395     return jlong(ts.tv_sec) * MILLIUNITS +
1396            jlong(ts.tv_nsec) / NANOUNITS_PER_MILLIUNIT;
1397   } else {
1398     timeval time;
1399     int status = gettimeofday(&time, NULL);
1400     assert(status != -1, "linux error");
1401     return jlong(time.tv_sec) * MILLIUNITS  +
1402            jlong(time.tv_usec) / (MICROUNITS / MILLIUNITS);
1403   }
1404 }
1405 
1406 void os::javaTimeSystemUTC(jlong &seconds, jlong &nanos) {
1407   if (os::Posix::supports_clock_gettime()) {
1408     struct timespec ts;
1409     int status = os::Posix::clock_gettime(CLOCK_REALTIME, &ts);
1410     assert_status(status == 0, status, "gettime error");
1411     seconds = jlong(ts.tv_sec);
1412     nanos = jlong(ts.tv_nsec);
1413   } else {
1414     timeval time;
1415     int status = gettimeofday(&time, NULL);
1416     assert(status != -1, "linux error");
1417     seconds = jlong(time.tv_sec);
1418     nanos = jlong(time.tv_usec) * (NANOUNITS / MICROUNITS);
1419   }
1420 }
1421 
1422 void os::Linux::fast_thread_clock_init() {
1423   if (!UseLinuxPosixThreadCPUClocks) {
1424     return;
1425   }
1426   clockid_t clockid;
1427   struct timespec tp;
1428   int (*pthread_getcpuclockid_func)(pthread_t, clockid_t *) =
1429       (int(*)(pthread_t, clockid_t *)) dlsym(RTLD_DEFAULT, "pthread_getcpuclockid");
1430 
1431   // Switch to using fast clocks for thread cpu time if
1432   // the clock_getres() returns 0 error code.
1433   // Note, that some kernels may support the current thread
1434   // clock (CLOCK_THREAD_CPUTIME_ID) but not the clocks
1435   // returned by the pthread_getcpuclockid().
1436   // If the fast Posix clocks are supported then the clock_getres()
1437   // must return at least tp.tv_sec == 0 which means a resolution
1438   // better than 1 sec. This is extra check for reliability.
1439 
1440   if (pthread_getcpuclockid_func &&
1441       pthread_getcpuclockid_func(_main_thread, &clockid) == 0 &&
1442       os::Posix::clock_getres(clockid, &tp) == 0 && tp.tv_sec == 0) {
1443     _supports_fast_thread_cpu_time = true;
1444     _pthread_getcpuclockid = pthread_getcpuclockid_func;
1445   }
1446 }
1447 
1448 jlong os::javaTimeNanos() {
1449   if (os::supports_monotonic_clock()) {
1450     struct timespec tp;
1451     int status = os::Posix::clock_gettime(CLOCK_MONOTONIC, &tp);
1452     assert(status == 0, "gettime error");
1453     jlong result = jlong(tp.tv_sec) * (1000 * 1000 * 1000) + jlong(tp.tv_nsec);
1454     return result;
1455   } else {
1456     timeval time;
1457     int status = gettimeofday(&time, NULL);
1458     assert(status != -1, "linux error");
1459     jlong usecs = jlong(time.tv_sec) * (1000 * 1000) + jlong(time.tv_usec);
1460     return 1000 * usecs;
1461   }
1462 }
1463 
1464 void os::javaTimeNanos_info(jvmtiTimerInfo *info_ptr) {
1465   if (os::supports_monotonic_clock()) {
1466     info_ptr->max_value = ALL_64_BITS;
1467 
1468     // CLOCK_MONOTONIC - amount of time since some arbitrary point in the past
1469     info_ptr->may_skip_backward = false;      // not subject to resetting or drifting
1470     info_ptr->may_skip_forward = false;       // not subject to resetting or drifting
1471   } else {
1472     // gettimeofday - based on time in seconds since the Epoch thus does not wrap
1473     info_ptr->max_value = ALL_64_BITS;
1474 
1475     // gettimeofday is a real time clock so it skips
1476     info_ptr->may_skip_backward = true;
1477     info_ptr->may_skip_forward = true;
1478   }
1479 
1480   info_ptr->kind = JVMTI_TIMER_ELAPSED;                // elapsed not CPU time
1481 }
1482 
1483 // Return the real, user, and system times in seconds from an
1484 // arbitrary fixed point in the past.
1485 bool os::getTimesSecs(double* process_real_time,
1486                       double* process_user_time,
1487                       double* process_system_time) {
1488   struct tms ticks;
1489   clock_t real_ticks = times(&ticks);
1490 
1491   if (real_ticks == (clock_t) (-1)) {
1492     return false;
1493   } else {
1494     double ticks_per_second = (double) clock_tics_per_sec;
1495     *process_user_time = ((double) ticks.tms_utime) / ticks_per_second;
1496     *process_system_time = ((double) ticks.tms_stime) / ticks_per_second;
1497     *process_real_time = ((double) real_ticks) / ticks_per_second;
1498 
1499     return true;
1500   }
1501 }
1502 
1503 
1504 char * os::local_time_string(char *buf, size_t buflen) {
1505   struct tm t;
1506   time_t long_time;
1507   time(&long_time);
1508   localtime_r(&long_time, &t);
1509   jio_snprintf(buf, buflen, "%d-%02d-%02d %02d:%02d:%02d",
1510                t.tm_year + 1900, t.tm_mon + 1, t.tm_mday,
1511                t.tm_hour, t.tm_min, t.tm_sec);
1512   return buf;
1513 }
1514 
1515 struct tm* os::localtime_pd(const time_t* clock, struct tm*  res) {
1516   return localtime_r(clock, res);
1517 }
1518 
1519 ////////////////////////////////////////////////////////////////////////////////
1520 // runtime exit support
1521 
1522 // Note: os::shutdown() might be called very early during initialization, or
1523 // called from signal handler. Before adding something to os::shutdown(), make
1524 // sure it is async-safe and can handle partially initialized VM.
1525 void os::shutdown() {
1526 
1527   // allow PerfMemory to attempt cleanup of any persistent resources
1528   perfMemory_exit();
1529 
1530   // needs to remove object in file system
1531   AttachListener::abort();
1532 
1533   // flush buffered output, finish log files
1534   ostream_abort();
1535 
1536   // Check for abort hook
1537   abort_hook_t abort_hook = Arguments::abort_hook();
1538   if (abort_hook != NULL) {
1539     abort_hook();
1540   }
1541 
1542 }
1543 
1544 // Note: os::abort() might be called very early during initialization, or
1545 // called from signal handler. Before adding something to os::abort(), make
1546 // sure it is async-safe and can handle partially initialized VM.
1547 void os::abort(bool dump_core, void* siginfo, const void* context) {
1548   os::shutdown();
1549   if (dump_core) {
1550     if (DumpPrivateMappingsInCore) {
1551       ClassLoader::close_jrt_image();
1552     }
1553     ::abort(); // dump core
1554   }
1555 
1556   ::exit(1);
1557 }
1558 
1559 // Die immediately, no exit hook, no abort hook, no cleanup.
1560 // Dump a core file, if possible, for debugging.
1561 void os::die() {
1562   if (TestUnresponsiveErrorHandler && !CreateCoredumpOnCrash) {
1563     // For TimeoutInErrorHandlingTest.java, we just kill the VM
1564     // and don't take the time to generate a core file.
1565     os::signal_raise(SIGKILL);
1566   } else {
1567     ::abort();
1568   }
1569 }
1570 
1571 // thread_id is kernel thread id (similar to Solaris LWP id)
1572 intx os::current_thread_id() { return os::Linux::gettid(); }
1573 int os::current_process_id() {
1574   return ::getpid();
1575 }
1576 
1577 // DLL functions
1578 
1579 const char* os::dll_file_extension() { return ".so"; }
1580 
1581 // This must be hard coded because it's the system's temporary
1582 // directory not the java application's temp directory, ala java.io.tmpdir.
1583 const char* os::get_temp_directory() { return "/tmp"; }
1584 
1585 static bool file_exists(const char* filename) {
1586   struct stat statbuf;
1587   if (filename == NULL || strlen(filename) == 0) {
1588     return false;
1589   }
1590   return os::stat(filename, &statbuf) == 0;
1591 }
1592 
1593 // check if addr is inside libjvm.so
1594 bool os::address_is_in_vm(address addr) {
1595   static address libjvm_base_addr;
1596   Dl_info dlinfo;
1597 
1598   if (libjvm_base_addr == NULL) {
1599     if (dladdr(CAST_FROM_FN_PTR(void *, os::address_is_in_vm), &dlinfo) != 0) {
1600       libjvm_base_addr = (address)dlinfo.dli_fbase;
1601     }
1602     assert(libjvm_base_addr !=NULL, "Cannot obtain base address for libjvm");
1603   }
1604 
1605   if (dladdr((void *)addr, &dlinfo) != 0) {
1606     if (libjvm_base_addr == (address)dlinfo.dli_fbase) return true;
1607   }
1608 
1609   return false;
1610 }
1611 
1612 bool os::dll_address_to_function_name(address addr, char *buf,
1613                                       int buflen, int *offset,
1614                                       bool demangle) {
1615   // buf is not optional, but offset is optional
1616   assert(buf != NULL, "sanity check");
1617 
1618   Dl_info dlinfo;
1619 
1620   if (dladdr((void*)addr, &dlinfo) != 0) {
1621     // see if we have a matching symbol
1622     if (dlinfo.dli_saddr != NULL && dlinfo.dli_sname != NULL) {
1623       if (!(demangle && Decoder::demangle(dlinfo.dli_sname, buf, buflen))) {
1624         jio_snprintf(buf, buflen, "%s", dlinfo.dli_sname);
1625       }
1626       if (offset != NULL) *offset = addr - (address)dlinfo.dli_saddr;
1627       return true;
1628     }
1629     // no matching symbol so try for just file info
1630     if (dlinfo.dli_fname != NULL && dlinfo.dli_fbase != NULL) {
1631       if (Decoder::decode((address)(addr - (address)dlinfo.dli_fbase),
1632                           buf, buflen, offset, dlinfo.dli_fname, demangle)) {
1633         return true;
1634       }
1635     }
1636   }
1637 
1638   buf[0] = '\0';
1639   if (offset != NULL) *offset = -1;
1640   return false;
1641 }
1642 
1643 struct _address_to_library_name {
1644   address addr;          // input : memory address
1645   size_t  buflen;        //         size of fname
1646   char*   fname;         // output: library name
1647   address base;          //         library base addr
1648 };
1649 
1650 static int address_to_library_name_callback(struct dl_phdr_info *info,
1651                                             size_t size, void *data) {
1652   int i;
1653   bool found = false;
1654   address libbase = NULL;
1655   struct _address_to_library_name * d = (struct _address_to_library_name *)data;
1656 
1657   // iterate through all loadable segments
1658   for (i = 0; i < info->dlpi_phnum; i++) {
1659     address segbase = (address)(info->dlpi_addr + info->dlpi_phdr[i].p_vaddr);
1660     if (info->dlpi_phdr[i].p_type == PT_LOAD) {
1661       // base address of a library is the lowest address of its loaded
1662       // segments.
1663       if (libbase == NULL || libbase > segbase) {
1664         libbase = segbase;
1665       }
1666       // see if 'addr' is within current segment
1667       if (segbase <= d->addr &&
1668           d->addr < segbase + info->dlpi_phdr[i].p_memsz) {
1669         found = true;
1670       }
1671     }
1672   }
1673 
1674   // dlpi_name is NULL or empty if the ELF file is executable, return 0
1675   // so dll_address_to_library_name() can fall through to use dladdr() which
1676   // can figure out executable name from argv[0].
1677   if (found && info->dlpi_name && info->dlpi_name[0]) {
1678     d->base = libbase;
1679     if (d->fname) {
1680       jio_snprintf(d->fname, d->buflen, "%s", info->dlpi_name);
1681     }
1682     return 1;
1683   }
1684   return 0;
1685 }
1686 
1687 bool os::dll_address_to_library_name(address addr, char* buf,
1688                                      int buflen, int* offset) {
1689   // buf is not optional, but offset is optional
1690   assert(buf != NULL, "sanity check");
1691 
1692   Dl_info dlinfo;
1693   struct _address_to_library_name data;
1694 
1695   // There is a bug in old glibc dladdr() implementation that it could resolve
1696   // to wrong library name if the .so file has a base address != NULL. Here
1697   // we iterate through the program headers of all loaded libraries to find
1698   // out which library 'addr' really belongs to. This workaround can be
1699   // removed once the minimum requirement for glibc is moved to 2.3.x.
1700   data.addr = addr;
1701   data.fname = buf;
1702   data.buflen = buflen;
1703   data.base = NULL;
1704   int rslt = dl_iterate_phdr(address_to_library_name_callback, (void *)&data);
1705 
1706   if (rslt) {
1707     // buf already contains library name
1708     if (offset) *offset = addr - data.base;
1709     return true;
1710   }
1711   if (dladdr((void*)addr, &dlinfo) != 0) {
1712     if (dlinfo.dli_fname != NULL) {
1713       jio_snprintf(buf, buflen, "%s", dlinfo.dli_fname);
1714     }
1715     if (dlinfo.dli_fbase != NULL && offset != NULL) {
1716       *offset = addr - (address)dlinfo.dli_fbase;
1717     }
1718     return true;
1719   }
1720 
1721   buf[0] = '\0';
1722   if (offset) *offset = -1;
1723   return false;
1724 }
1725 
1726 // Loads .dll/.so and
1727 // in case of error it checks if .dll/.so was built for the
1728 // same architecture as Hotspot is running on
1729 
1730 
1731 // Remember the stack's state. The Linux dynamic linker will change
1732 // the stack to 'executable' at most once, so we must safepoint only once.
1733 bool os::Linux::_stack_is_executable = false;
1734 
1735 // VM operation that loads a library.  This is necessary if stack protection
1736 // of the Java stacks can be lost during loading the library.  If we
1737 // do not stop the Java threads, they can stack overflow before the stacks
1738 // are protected again.
1739 class VM_LinuxDllLoad: public VM_Operation {
1740  private:
1741   const char *_filename;
1742   char *_ebuf;
1743   int _ebuflen;
1744   void *_lib;
1745  public:
1746   VM_LinuxDllLoad(const char *fn, char *ebuf, int ebuflen) :
1747     _filename(fn), _ebuf(ebuf), _ebuflen(ebuflen), _lib(NULL) {}
1748   VMOp_Type type() const { return VMOp_LinuxDllLoad; }
1749   void doit() {
1750     _lib = os::Linux::dll_load_in_vmthread(_filename, _ebuf, _ebuflen);
1751     os::Linux::_stack_is_executable = true;
1752   }
1753   void* loaded_library() { return _lib; }
1754 };
1755 
1756 void * os::dll_load(const char *filename, char *ebuf, int ebuflen) {
1757   void * result = NULL;
1758   bool load_attempted = false;
1759 
1760   log_info(os)("attempting shared library load of %s", filename);
1761 
1762   // Check whether the library to load might change execution rights
1763   // of the stack. If they are changed, the protection of the stack
1764   // guard pages will be lost. We need a safepoint to fix this.
1765   //
1766   // See Linux man page execstack(8) for more info.
1767   if (os::uses_stack_guard_pages() && !os::Linux::_stack_is_executable) {
1768     if (!ElfFile::specifies_noexecstack(filename)) {
1769       if (!is_init_completed()) {
1770         os::Linux::_stack_is_executable = true;
1771         // This is OK - No Java threads have been created yet, and hence no
1772         // stack guard pages to fix.
1773         //
1774         // Dynamic loader will make all stacks executable after
1775         // this function returns, and will not do that again.
1776         assert(Threads::number_of_threads() == 0, "no Java threads should exist yet.");
1777       } else {
1778         warning("You have loaded library %s which might have disabled stack guard. "
1779                 "The VM will try to fix the stack guard now.\n"
1780                 "It's highly recommended that you fix the library with "
1781                 "'execstack -c <libfile>', or link it with '-z noexecstack'.",
1782                 filename);
1783 
1784         assert(Thread::current()->is_Java_thread(), "must be Java thread");
1785         JavaThread *jt = JavaThread::current();
1786         if (jt->thread_state() != _thread_in_native) {
1787           // This happens when a compiler thread tries to load a hsdis-<arch>.so file
1788           // that requires ExecStack. Cannot enter safe point. Let's give up.
1789           warning("Unable to fix stack guard. Giving up.");
1790         } else {
1791           if (!LoadExecStackDllInVMThread) {
1792             // This is for the case where the DLL has an static
1793             // constructor function that executes JNI code. We cannot
1794             // load such DLLs in the VMThread.
1795             result = os::Linux::dlopen_helper(filename, ebuf, ebuflen);
1796           }
1797 
1798           ThreadInVMfromNative tiv(jt);
1799           debug_only(VMNativeEntryWrapper vew;)
1800 
1801           VM_LinuxDllLoad op(filename, ebuf, ebuflen);
1802           VMThread::execute(&op);
1803           if (LoadExecStackDllInVMThread) {
1804             result = op.loaded_library();
1805           }
1806           load_attempted = true;
1807         }
1808       }
1809     }
1810   }
1811 
1812   if (!load_attempted) {
1813     result = os::Linux::dlopen_helper(filename, ebuf, ebuflen);
1814   }
1815 
1816   if (result != NULL) {
1817     // Successful loading
1818     return result;
1819   }
1820 
1821   Elf32_Ehdr elf_head;
1822   int diag_msg_max_length=ebuflen-strlen(ebuf);
1823   char* diag_msg_buf=ebuf+strlen(ebuf);
1824 
1825   if (diag_msg_max_length==0) {
1826     // No more space in ebuf for additional diagnostics message
1827     return NULL;
1828   }
1829 
1830 
1831   int file_descriptor= ::open(filename, O_RDONLY | O_NONBLOCK);
1832 
1833   if (file_descriptor < 0) {
1834     // Can't open library, report dlerror() message
1835     return NULL;
1836   }
1837 
1838   bool failed_to_read_elf_head=
1839     (sizeof(elf_head)!=
1840      (::read(file_descriptor, &elf_head,sizeof(elf_head))));
1841 
1842   ::close(file_descriptor);
1843   if (failed_to_read_elf_head) {
1844     // file i/o error - report dlerror() msg
1845     return NULL;
1846   }
1847 
1848   if (elf_head.e_ident[EI_DATA] != LITTLE_ENDIAN_ONLY(ELFDATA2LSB) BIG_ENDIAN_ONLY(ELFDATA2MSB)) {
1849     // handle invalid/out of range endianness values
1850     if (elf_head.e_ident[EI_DATA] == 0 || elf_head.e_ident[EI_DATA] > 2) {
1851       return NULL;
1852     }
1853 
1854 #if defined(VM_LITTLE_ENDIAN)
1855     // VM is LE, shared object BE
1856     elf_head.e_machine = be16toh(elf_head.e_machine);
1857 #else
1858     // VM is BE, shared object LE
1859     elf_head.e_machine = le16toh(elf_head.e_machine);
1860 #endif
1861   }
1862 
1863   typedef struct {
1864     Elf32_Half    code;         // Actual value as defined in elf.h
1865     Elf32_Half    compat_class; // Compatibility of archs at VM's sense
1866     unsigned char elf_class;    // 32 or 64 bit
1867     unsigned char endianness;   // MSB or LSB
1868     char*         name;         // String representation
1869   } arch_t;
1870 
1871 #ifndef EM_AARCH64
1872   #define EM_AARCH64    183               /* ARM AARCH64 */
1873 #endif
1874 #ifndef EM_RISCV
1875   #define EM_RISCV      243               /* RISC-V */
1876 #endif
1877 
1878   static const arch_t arch_array[]={
1879     {EM_386,         EM_386,     ELFCLASS32, ELFDATA2LSB, (char*)"IA 32"},
1880     {EM_486,         EM_386,     ELFCLASS32, ELFDATA2LSB, (char*)"IA 32"},
1881     {EM_IA_64,       EM_IA_64,   ELFCLASS64, ELFDATA2LSB, (char*)"IA 64"},
1882     {EM_X86_64,      EM_X86_64,  ELFCLASS64, ELFDATA2LSB, (char*)"AMD 64"},
1883     {EM_SPARC,       EM_SPARC,   ELFCLASS32, ELFDATA2MSB, (char*)"Sparc 32"},
1884     {EM_SPARC32PLUS, EM_SPARC,   ELFCLASS32, ELFDATA2MSB, (char*)"Sparc 32"},
1885     {EM_SPARCV9,     EM_SPARCV9, ELFCLASS64, ELFDATA2MSB, (char*)"Sparc v9 64"},
1886     {EM_PPC,         EM_PPC,     ELFCLASS32, ELFDATA2MSB, (char*)"Power PC 32"},
1887 #if defined(VM_LITTLE_ENDIAN)
1888     {EM_PPC64,       EM_PPC64,   ELFCLASS64, ELFDATA2LSB, (char*)"Power PC 64 LE"},
1889     {EM_SH,          EM_SH,      ELFCLASS32, ELFDATA2LSB, (char*)"SuperH"},
1890 #else
1891     {EM_PPC64,       EM_PPC64,   ELFCLASS64, ELFDATA2MSB, (char*)"Power PC 64"},
1892     {EM_SH,          EM_SH,      ELFCLASS32, ELFDATA2MSB, (char*)"SuperH BE"},
1893 #endif
1894     {EM_ARM,         EM_ARM,     ELFCLASS32, ELFDATA2LSB, (char*)"ARM"},
1895     // we only support 64 bit z architecture
1896     {EM_S390,        EM_S390,    ELFCLASS64, ELFDATA2MSB, (char*)"IBM System/390"},
1897     {EM_ALPHA,       EM_ALPHA,   ELFCLASS64, ELFDATA2LSB, (char*)"Alpha"},
1898     {EM_MIPS_RS3_LE, EM_MIPS_RS3_LE, ELFCLASS32, ELFDATA2LSB, (char*)"MIPSel"},
1899     {EM_MIPS,        EM_MIPS,    ELFCLASS32, ELFDATA2MSB, (char*)"MIPS"},
1900     {EM_PARISC,      EM_PARISC,  ELFCLASS32, ELFDATA2MSB, (char*)"PARISC"},
1901     {EM_68K,         EM_68K,     ELFCLASS32, ELFDATA2MSB, (char*)"M68k"},
1902     {EM_AARCH64,     EM_AARCH64, ELFCLASS64, ELFDATA2LSB, (char*)"AARCH64"},
1903     {EM_RISCV,       EM_RISCV,   ELFCLASS64, ELFDATA2LSB, (char*)"RISC-V"},
1904   };
1905 
1906 #if  (defined IA32)
1907   static  Elf32_Half running_arch_code=EM_386;
1908 #elif   (defined AMD64) || (defined X32)
1909   static  Elf32_Half running_arch_code=EM_X86_64;
1910 #elif  (defined IA64)
1911   static  Elf32_Half running_arch_code=EM_IA_64;
1912 #elif  (defined __sparc) && (defined _LP64)
1913   static  Elf32_Half running_arch_code=EM_SPARCV9;
1914 #elif  (defined __sparc) && (!defined _LP64)
1915   static  Elf32_Half running_arch_code=EM_SPARC;
1916 #elif  (defined __powerpc64__)
1917   static  Elf32_Half running_arch_code=EM_PPC64;
1918 #elif  (defined __powerpc__)
1919   static  Elf32_Half running_arch_code=EM_PPC;
1920 #elif  (defined AARCH64)
1921   static  Elf32_Half running_arch_code=EM_AARCH64;
1922 #elif  (defined ARM)
1923   static  Elf32_Half running_arch_code=EM_ARM;
1924 #elif  (defined S390)
1925   static  Elf32_Half running_arch_code=EM_S390;
1926 #elif  (defined ALPHA)
1927   static  Elf32_Half running_arch_code=EM_ALPHA;
1928 #elif  (defined MIPSEL)
1929   static  Elf32_Half running_arch_code=EM_MIPS_RS3_LE;
1930 #elif  (defined PARISC)
1931   static  Elf32_Half running_arch_code=EM_PARISC;
1932 #elif  (defined MIPS)
1933   static  Elf32_Half running_arch_code=EM_MIPS;
1934 #elif  (defined M68K)
1935   static  Elf32_Half running_arch_code=EM_68K;
1936 #elif  (defined SH)
1937   static  Elf32_Half running_arch_code=EM_SH;
1938 #elif  (defined RISCV)
1939   static  Elf32_Half running_arch_code=EM_RISCV;
1940 #else
1941     #error Method os::dll_load requires that one of following is defined:\
1942         AARCH64, ALPHA, ARM, AMD64, IA32, IA64, M68K, MIPS, MIPSEL, PARISC, __powerpc__, __powerpc64__, RISCV, S390, SH, __sparc
1943 #endif
1944 
1945   // Identify compatibility class for VM's architecture and library's architecture
1946   // Obtain string descriptions for architectures
1947 
1948   arch_t lib_arch={elf_head.e_machine,0,elf_head.e_ident[EI_CLASS], elf_head.e_ident[EI_DATA], NULL};
1949   int running_arch_index=-1;
1950 
1951   for (unsigned int i=0; i < ARRAY_SIZE(arch_array); i++) {
1952     if (running_arch_code == arch_array[i].code) {
1953       running_arch_index    = i;
1954     }
1955     if (lib_arch.code == arch_array[i].code) {
1956       lib_arch.compat_class = arch_array[i].compat_class;
1957       lib_arch.name         = arch_array[i].name;
1958     }
1959   }
1960 
1961   assert(running_arch_index != -1,
1962          "Didn't find running architecture code (running_arch_code) in arch_array");
1963   if (running_arch_index == -1) {
1964     // Even though running architecture detection failed
1965     // we may still continue with reporting dlerror() message
1966     return NULL;
1967   }
1968 
1969   if (lib_arch.compat_class != arch_array[running_arch_index].compat_class) {
1970     if (lib_arch.name != NULL) {
1971       ::snprintf(diag_msg_buf, diag_msg_max_length-1,
1972                  " (Possible cause: can't load %s .so on a %s platform)",
1973                  lib_arch.name, arch_array[running_arch_index].name);
1974     } else {
1975       ::snprintf(diag_msg_buf, diag_msg_max_length-1,
1976                  " (Possible cause: can't load this .so (machine code=0x%x) on a %s platform)",
1977                  lib_arch.code, arch_array[running_arch_index].name);
1978     }
1979     return NULL;
1980   }
1981 
1982   if (lib_arch.endianness != arch_array[running_arch_index].endianness) {
1983     ::snprintf(diag_msg_buf, diag_msg_max_length-1, " (Possible cause: endianness mismatch)");
1984     return NULL;
1985   }
1986 
1987   // ELF file class/capacity : 0 - invalid, 1 - 32bit, 2 - 64bit
1988   if (lib_arch.elf_class > 2 || lib_arch.elf_class < 1) {
1989     ::snprintf(diag_msg_buf, diag_msg_max_length-1, " (Possible cause: invalid ELF file class)");
1990     return NULL;
1991   }
1992 
1993   if (lib_arch.elf_class != arch_array[running_arch_index].elf_class) {
1994     ::snprintf(diag_msg_buf, diag_msg_max_length-1,
1995                " (Possible cause: architecture word width mismatch, can't load %d-bit .so on a %d-bit platform)",
1996                (int) lib_arch.elf_class * 32, arch_array[running_arch_index].elf_class * 32);
1997     return NULL;
1998   }
1999 
2000   return NULL;
2001 }
2002 
2003 void * os::Linux::dlopen_helper(const char *filename, char *ebuf,
2004                                 int ebuflen) {
2005   void * result = ::dlopen(filename, RTLD_LAZY);
2006   if (result == NULL) {
2007     const char* error_report = ::dlerror();
2008     if (error_report == NULL) {
2009       error_report = "dlerror returned no error description";
2010     }
2011     if (ebuf != NULL && ebuflen > 0) {
2012       ::strncpy(ebuf, error_report, ebuflen-1);
2013       ebuf[ebuflen-1]='\0';
2014     }
2015     Events::log(NULL, "Loading shared library %s failed, %s", filename, error_report);
2016     log_info(os)("shared library load of %s failed, %s", filename, error_report);
2017   } else {
2018     Events::log(NULL, "Loaded shared library %s", filename);
2019     log_info(os)("shared library load of %s was successful", filename);
2020   }
2021   return result;
2022 }
2023 
2024 void * os::Linux::dll_load_in_vmthread(const char *filename, char *ebuf,
2025                                        int ebuflen) {
2026   void * result = NULL;
2027   if (LoadExecStackDllInVMThread) {
2028     result = dlopen_helper(filename, ebuf, ebuflen);
2029   }
2030 
2031   // Since 7019808, libjvm.so is linked with -noexecstack. If the VM loads a
2032   // library that requires an executable stack, or which does not have this
2033   // stack attribute set, dlopen changes the stack attribute to executable. The
2034   // read protection of the guard pages gets lost.
2035   //
2036   // Need to check _stack_is_executable again as multiple VM_LinuxDllLoad
2037   // may have been queued at the same time.
2038 
2039   if (!_stack_is_executable) {
2040     for (JavaThreadIteratorWithHandle jtiwh; JavaThread *jt = jtiwh.next(); ) {
2041       if (!jt->stack_guard_zone_unused() &&     // Stack not yet fully initialized
2042           jt->stack_guards_enabled()) {         // No pending stack overflow exceptions
2043         if (!os::guard_memory((char *)jt->stack_end(), jt->stack_guard_zone_size())) {
2044           warning("Attempt to reguard stack yellow zone failed.");
2045         }
2046       }
2047     }
2048   }
2049 
2050   return result;
2051 }
2052 
2053 void* os::dll_lookup(void* handle, const char* name) {
2054   void* res = dlsym(handle, name);
2055   return res;
2056 }
2057 
2058 void* os::get_default_process_handle() {
2059   return (void*)::dlopen(NULL, RTLD_LAZY);
2060 }
2061 
2062 static bool _print_ascii_file(const char* filename, outputStream* st, const char* hdr = NULL) {
2063   int fd = ::open(filename, O_RDONLY);
2064   if (fd == -1) {
2065     return false;
2066   }
2067 
2068   if (hdr != NULL) {
2069     st->print_cr("%s", hdr);
2070   }
2071 
2072   char buf[33];
2073   int bytes;
2074   buf[32] = '\0';
2075   while ((bytes = ::read(fd, buf, sizeof(buf)-1)) > 0) {
2076     st->print_raw(buf, bytes);
2077   }
2078 
2079   ::close(fd);
2080 
2081   return true;
2082 }
2083 
2084 static void _print_ascii_file_h(const char* header, const char* filename, outputStream* st, bool same_line = true) {
2085   st->print("%s:%c", header, same_line ? ' ' : '\n');
2086   if (!_print_ascii_file(filename, st)) {
2087     st->print_cr("<Not Available>");
2088   }
2089 }
2090 
2091 void os::print_dll_info(outputStream *st) {
2092   st->print_cr("Dynamic libraries:");
2093 
2094   char fname[32];
2095   pid_t pid = os::Linux::gettid();
2096 
2097   jio_snprintf(fname, sizeof(fname), "/proc/%d/maps", pid);
2098 
2099   if (!_print_ascii_file(fname, st)) {
2100     st->print_cr("Can not get library information for pid = %d", pid);
2101   }
2102 }
2103 
2104 struct loaded_modules_info_param {
2105   os::LoadedModulesCallbackFunc callback;
2106   void *param;
2107 };
2108 
2109 static int dl_iterate_callback(struct dl_phdr_info *info, size_t size, void *data) {
2110   if ((info->dlpi_name == NULL) || (*info->dlpi_name == '\0')) {
2111     return 0;
2112   }
2113 
2114   struct loaded_modules_info_param *callback_param = reinterpret_cast<struct loaded_modules_info_param *>(data);
2115   address base = NULL;
2116   address top = NULL;
2117   for (int idx = 0; idx < info->dlpi_phnum; idx++) {
2118     const ElfW(Phdr) *phdr = info->dlpi_phdr + idx;
2119     if (phdr->p_type == PT_LOAD) {
2120       address raw_phdr_base = reinterpret_cast<address>(info->dlpi_addr + phdr->p_vaddr);
2121 
2122       address phdr_base = align_down(raw_phdr_base, phdr->p_align);
2123       if ((base == NULL) || (base > phdr_base)) {
2124         base = phdr_base;
2125       }
2126 
2127       address phdr_top = align_up(raw_phdr_base + phdr->p_memsz, phdr->p_align);
2128       if ((top == NULL) || (top < phdr_top)) {
2129         top = phdr_top;
2130       }
2131     }
2132   }
2133 
2134   return callback_param->callback(info->dlpi_name, base, top, callback_param->param);
2135 }
2136 
2137 int os::get_loaded_modules_info(os::LoadedModulesCallbackFunc callback, void *param) {
2138   struct loaded_modules_info_param callback_param = {callback, param};
2139   return dl_iterate_phdr(&dl_iterate_callback, &callback_param);
2140 }
2141 
2142 void os::print_os_info_brief(outputStream* st) {
2143   os::Linux::print_distro_info(st);
2144 
2145   os::Posix::print_uname_info(st);
2146 
2147   os::Linux::print_libversion_info(st);
2148 
2149 }
2150 
2151 void os::print_os_info(outputStream* st) {
2152   st->print_cr("OS:");
2153 
2154   os::Linux::print_distro_info(st);
2155 
2156   os::Posix::print_uname_info(st);
2157 
2158   os::Linux::print_uptime_info(st);
2159 
2160   // Print warning if unsafe chroot environment detected
2161   if (unsafe_chroot_detected) {
2162     st->print_cr("WARNING!! %s", unstable_chroot_error);
2163   }
2164 
2165   os::Linux::print_libversion_info(st);
2166 
2167   os::Posix::print_rlimit_info(st);
2168 
2169   os::Posix::print_load_average(st);
2170   st->cr();
2171 
2172   os::Linux::print_system_memory_info(st);
2173   st->cr();
2174 
2175   os::Linux::print_process_memory_info(st);
2176   st->cr();
2177 
2178   os::Linux::print_proc_sys_info(st);
2179   st->cr();
2180 
2181   if (os::Linux::print_ld_preload_file(st)) {
2182     st->cr();
2183   }
2184 
2185   if (os::Linux::print_container_info(st)) {
2186     st->cr();
2187   }
2188 
2189   VM_Version::print_platform_virtualization_info(st);
2190 
2191   os::Linux::print_steal_info(st);
2192 }
2193 
2194 // Try to identify popular distros.
2195 // Most Linux distributions have a /etc/XXX-release file, which contains
2196 // the OS version string. Newer Linux distributions have a /etc/lsb-release
2197 // file that also contains the OS version string. Some have more than one
2198 // /etc/XXX-release file (e.g. Mandrake has both /etc/mandrake-release and
2199 // /etc/redhat-release.), so the order is important.
2200 // Any Linux that is based on Redhat (i.e. Oracle, Mandrake, Sun JDS...) have
2201 // their own specific XXX-release file as well as a redhat-release file.
2202 // Because of this the XXX-release file needs to be searched for before the
2203 // redhat-release file.
2204 // Since Red Hat and SuSE have an lsb-release file that is not very descriptive the
2205 // search for redhat-release / SuSE-release needs to be before lsb-release.
2206 // Since the lsb-release file is the new standard it needs to be searched
2207 // before the older style release files.
2208 // Searching system-release (Red Hat) and os-release (other Linuxes) are a
2209 // next to last resort.  The os-release file is a new standard that contains
2210 // distribution information and the system-release file seems to be an old
2211 // standard that has been replaced by the lsb-release and os-release files.
2212 // Searching for the debian_version file is the last resort.  It contains
2213 // an informative string like "6.0.6" or "wheezy/sid". Because of this
2214 // "Debian " is printed before the contents of the debian_version file.
2215 
2216 const char* distro_files[] = {
2217   "/etc/oracle-release",
2218   "/etc/mandriva-release",
2219   "/etc/mandrake-release",
2220   "/etc/sun-release",
2221   "/etc/redhat-release",
2222   "/etc/SuSE-release",
2223   "/etc/lsb-release",
2224   "/etc/turbolinux-release",
2225   "/etc/gentoo-release",
2226   "/etc/ltib-release",
2227   "/etc/angstrom-version",
2228   "/etc/system-release",
2229   "/etc/os-release",
2230   NULL };
2231 
2232 void os::Linux::print_distro_info(outputStream* st) {
2233   for (int i = 0;; i++) {
2234     const char* file = distro_files[i];
2235     if (file == NULL) {
2236       break;  // done
2237     }
2238     // If file prints, we found it.
2239     if (_print_ascii_file(file, st)) {
2240       return;
2241     }
2242   }
2243 
2244   if (file_exists("/etc/debian_version")) {
2245     st->print("Debian ");
2246     _print_ascii_file("/etc/debian_version", st);
2247   } else {
2248     st->print_cr("Linux");
2249   }
2250 }
2251 
2252 static void parse_os_info_helper(FILE* fp, char* distro, size_t length, bool get_first_line) {
2253   char buf[256];
2254   while (fgets(buf, sizeof(buf), fp)) {
2255     // Edit out extra stuff in expected format
2256     if (strstr(buf, "DISTRIB_DESCRIPTION=") != NULL || strstr(buf, "PRETTY_NAME=") != NULL) {
2257       char* ptr = strstr(buf, "\"");  // the name is in quotes
2258       if (ptr != NULL) {
2259         ptr++; // go beyond first quote
2260         char* nl = strchr(ptr, '\"');
2261         if (nl != NULL) *nl = '\0';
2262         strncpy(distro, ptr, length);
2263       } else {
2264         ptr = strstr(buf, "=");
2265         ptr++; // go beyond equals then
2266         char* nl = strchr(ptr, '\n');
2267         if (nl != NULL) *nl = '\0';
2268         strncpy(distro, ptr, length);
2269       }
2270       return;
2271     } else if (get_first_line) {
2272       char* nl = strchr(buf, '\n');
2273       if (nl != NULL) *nl = '\0';
2274       strncpy(distro, buf, length);
2275       return;
2276     }
2277   }
2278   // print last line and close
2279   char* nl = strchr(buf, '\n');
2280   if (nl != NULL) *nl = '\0';
2281   strncpy(distro, buf, length);
2282 }
2283 
2284 static void parse_os_info(char* distro, size_t length, const char* file) {
2285   FILE* fp = fopen(file, "r");
2286   if (fp != NULL) {
2287     // if suse format, print out first line
2288     bool get_first_line = (strcmp(file, "/etc/SuSE-release") == 0);
2289     parse_os_info_helper(fp, distro, length, get_first_line);
2290     fclose(fp);
2291   }
2292 }
2293 
2294 void os::get_summary_os_info(char* buf, size_t buflen) {
2295   for (int i = 0;; i++) {
2296     const char* file = distro_files[i];
2297     if (file == NULL) {
2298       break; // ran out of distro_files
2299     }
2300     if (file_exists(file)) {
2301       parse_os_info(buf, buflen, file);
2302       return;
2303     }
2304   }
2305   // special case for debian
2306   if (file_exists("/etc/debian_version")) {
2307     strncpy(buf, "Debian ", buflen);
2308     if (buflen > 7) {
2309       parse_os_info(&buf[7], buflen-7, "/etc/debian_version");
2310     }
2311   } else {
2312     strncpy(buf, "Linux", buflen);
2313   }
2314 }
2315 
2316 void os::Linux::print_libversion_info(outputStream* st) {
2317   // libc, pthread
2318   st->print("libc: ");
2319   st->print("%s ", os::Linux::glibc_version());
2320   st->print("%s ", os::Linux::libpthread_version());
2321   st->cr();
2322 }
2323 
2324 void os::Linux::print_proc_sys_info(outputStream* st) {
2325   _print_ascii_file_h("/proc/sys/kernel/threads-max (system-wide limit on the number of threads)",
2326                       "/proc/sys/kernel/threads-max", st);
2327   _print_ascii_file_h("/proc/sys/vm/max_map_count (maximum number of memory map areas a process may have)",
2328                       "/proc/sys/vm/max_map_count", st);
2329   _print_ascii_file_h("/proc/sys/kernel/pid_max (system-wide limit on number of process identifiers)",
2330                       "/proc/sys/kernel/pid_max", st);
2331 }
2332 
2333 void os::Linux::print_system_memory_info(outputStream* st) {
2334   _print_ascii_file_h("/proc/meminfo", "/proc/meminfo", st, false);
2335   st->cr();
2336 
2337   // some information regarding THPs; for details see
2338   // https://www.kernel.org/doc/Documentation/vm/transhuge.txt
2339   _print_ascii_file_h("/sys/kernel/mm/transparent_hugepage/enabled",
2340                       "/sys/kernel/mm/transparent_hugepage/enabled", st);
2341   _print_ascii_file_h("/sys/kernel/mm/transparent_hugepage/defrag (defrag/compaction efforts parameter)",
2342                       "/sys/kernel/mm/transparent_hugepage/defrag", st);
2343 }
2344 
2345 void os::Linux::print_process_memory_info(outputStream* st) {
2346 
2347   st->print_cr("Process Memory:");
2348 
2349   // Print virtual and resident set size; peak values; swap; and for
2350   //  rss its components if the kernel is recent enough.
2351   ssize_t vmsize = -1, vmpeak = -1, vmswap = -1,
2352       vmrss = -1, vmhwm = -1, rssanon = -1, rssfile = -1, rssshmem = -1;
2353   const int num_values = 8;
2354   int num_found = 0;
2355   FILE* f = ::fopen("/proc/self/status", "r");
2356   char buf[256];
2357   while (::fgets(buf, sizeof(buf), f) != NULL && num_found < num_values) {
2358     if ( (vmsize == -1    && sscanf(buf, "VmSize: " SSIZE_FORMAT " kB", &vmsize) == 1) ||
2359          (vmpeak == -1    && sscanf(buf, "VmPeak: " SSIZE_FORMAT " kB", &vmpeak) == 1) ||
2360          (vmswap == -1    && sscanf(buf, "VmSwap: " SSIZE_FORMAT " kB", &vmswap) == 1) ||
2361          (vmhwm == -1     && sscanf(buf, "VmHWM: " SSIZE_FORMAT " kB", &vmhwm) == 1) ||
2362          (vmrss == -1     && sscanf(buf, "VmRSS: " SSIZE_FORMAT " kB", &vmrss) == 1) ||
2363          (rssanon == -1   && sscanf(buf, "RssAnon: " SSIZE_FORMAT " kB", &rssanon) == 1) ||
2364          (rssfile == -1   && sscanf(buf, "RssFile: " SSIZE_FORMAT " kB", &rssfile) == 1) ||
2365          (rssshmem == -1  && sscanf(buf, "RssShmem: " SSIZE_FORMAT " kB", &rssshmem) == 1)
2366          )
2367     {
2368       num_found ++;
2369     }
2370   }
2371   st->print_cr("Virtual Size: " SSIZE_FORMAT "K (peak: " SSIZE_FORMAT "K)", vmsize, vmpeak);
2372   st->print("Resident Set Size: " SSIZE_FORMAT "K (peak: " SSIZE_FORMAT "K)", vmrss, vmhwm);
2373   if (rssanon != -1) { // requires kernel >= 4.5
2374     st->print(" (anon: " SSIZE_FORMAT "K, file: " SSIZE_FORMAT "K, shmem: " SSIZE_FORMAT "K)",
2375                 rssanon, rssfile, rssshmem);
2376   }
2377   st->cr();
2378   if (vmswap != -1) { // requires kernel >= 2.6.34
2379     st->print_cr("Swapped out: " SSIZE_FORMAT "K", vmswap);
2380   }
2381 
2382   // Print glibc outstanding allocations.
2383   // (note: there is no implementation of mallinfo for muslc)
2384 #ifdef __GLIBC__
2385   struct mallinfo mi = ::mallinfo();
2386 
2387   // mallinfo is an old API. Member names mean next to nothing and, beyond that, are int.
2388   // So values may have wrapped around. Still useful enough to see how much glibc thinks
2389   // we allocated.
2390   const size_t total_allocated = (size_t)(unsigned)mi.uordblks;
2391   st->print("C-Heap outstanding allocations: " SIZE_FORMAT "K", total_allocated / K);
2392   // Since mallinfo members are int, glibc values may have wrapped. Warn about this.
2393   if ((vmrss * K) > UINT_MAX && (vmrss * K) > (total_allocated + UINT_MAX)) {
2394     st->print(" (may have wrapped)");
2395   }
2396   st->cr();
2397 
2398 #endif // __GLIBC__
2399 
2400 }
2401 
2402 bool os::Linux::print_ld_preload_file(outputStream* st) {
2403   return _print_ascii_file("/etc/ld.so.preload", st, "/etc/ld.so.preload:");
2404 }
2405 
2406 void os::Linux::print_uptime_info(outputStream* st) {
2407   struct sysinfo sinfo;
2408   int ret = sysinfo(&sinfo);
2409   if (ret == 0) {
2410     os::print_dhm(st, "OS uptime:", (long) sinfo.uptime);
2411   }
2412 }
2413 
2414 bool os::Linux::print_container_info(outputStream* st) {
2415   if (!OSContainer::is_containerized()) {
2416     return false;
2417   }
2418 
2419   st->print_cr("container (cgroup) information:");
2420 
2421   const char *p_ct = OSContainer::container_type();
2422   st->print_cr("container_type: %s", p_ct != NULL ? p_ct : "not supported");
2423 
2424   char *p = OSContainer::cpu_cpuset_cpus();
2425   st->print_cr("cpu_cpuset_cpus: %s", p != NULL ? p : "not supported");
2426   free(p);
2427 
2428   p = OSContainer::cpu_cpuset_memory_nodes();
2429   st->print_cr("cpu_memory_nodes: %s", p != NULL ? p : "not supported");
2430   free(p);
2431 
2432   int i = OSContainer::active_processor_count();
2433   st->print("active_processor_count: ");
2434   if (i > 0) {
2435     st->print_cr("%d", i);
2436   } else {
2437     st->print_cr("not supported");
2438   }
2439 
2440   i = OSContainer::cpu_quota();
2441   st->print("cpu_quota: ");
2442   if (i > 0) {
2443     st->print_cr("%d", i);
2444   } else {
2445     st->print_cr("%s", i == OSCONTAINER_ERROR ? "not supported" : "no quota");
2446   }
2447 
2448   i = OSContainer::cpu_period();
2449   st->print("cpu_period: ");
2450   if (i > 0) {
2451     st->print_cr("%d", i);
2452   } else {
2453     st->print_cr("%s", i == OSCONTAINER_ERROR ? "not supported" : "no period");
2454   }
2455 
2456   i = OSContainer::cpu_shares();
2457   st->print("cpu_shares: ");
2458   if (i > 0) {
2459     st->print_cr("%d", i);
2460   } else {
2461     st->print_cr("%s", i == OSCONTAINER_ERROR ? "not supported" : "no shares");
2462   }
2463 
2464   jlong j = OSContainer::memory_limit_in_bytes();
2465   st->print("memory_limit_in_bytes: ");
2466   if (j > 0) {
2467     st->print_cr(JLONG_FORMAT, j);
2468   } else {
2469     st->print_cr("%s", j == OSCONTAINER_ERROR ? "not supported" : "unlimited");
2470   }
2471 
2472   j = OSContainer::memory_and_swap_limit_in_bytes();
2473   st->print("memory_and_swap_limit_in_bytes: ");
2474   if (j > 0) {
2475     st->print_cr(JLONG_FORMAT, j);
2476   } else {
2477     st->print_cr("%s", j == OSCONTAINER_ERROR ? "not supported" : "unlimited");
2478   }
2479 
2480   j = OSContainer::memory_soft_limit_in_bytes();
2481   st->print("memory_soft_limit_in_bytes: ");
2482   if (j > 0) {
2483     st->print_cr(JLONG_FORMAT, j);
2484   } else {
2485     st->print_cr("%s", j == OSCONTAINER_ERROR ? "not supported" : "unlimited");
2486   }
2487 
2488   j = OSContainer::OSContainer::memory_usage_in_bytes();
2489   st->print("memory_usage_in_bytes: ");
2490   if (j > 0) {
2491     st->print_cr(JLONG_FORMAT, j);
2492   } else {
2493     st->print_cr("%s", j == OSCONTAINER_ERROR ? "not supported" : "unlimited");
2494   }
2495 
2496   j = OSContainer::OSContainer::memory_max_usage_in_bytes();
2497   st->print("memory_max_usage_in_bytes: ");
2498   if (j > 0) {
2499     st->print_cr(JLONG_FORMAT, j);
2500   } else {
2501     st->print_cr("%s", j == OSCONTAINER_ERROR ? "not supported" : "unlimited");
2502   }
2503 
2504   return true;
2505 }
2506 
2507 void os::Linux::print_steal_info(outputStream* st) {
2508   if (has_initial_tick_info) {
2509     CPUPerfTicks pticks;
2510     bool res = os::Linux::get_tick_information(&pticks, -1);
2511 
2512     if (res && pticks.has_steal_ticks) {
2513       uint64_t steal_ticks_difference = pticks.steal - initial_steal_ticks;
2514       uint64_t total_ticks_difference = pticks.total - initial_total_ticks;
2515       double steal_ticks_perc = 0.0;
2516       if (total_ticks_difference != 0) {
2517         steal_ticks_perc = (double) steal_ticks_difference / total_ticks_difference;
2518       }
2519       st->print_cr("Steal ticks since vm start: " UINT64_FORMAT, steal_ticks_difference);
2520       st->print_cr("Steal ticks percentage since vm start:%7.3f", steal_ticks_perc);
2521     }
2522   }
2523 }
2524 
2525 void os::print_memory_info(outputStream* st) {
2526 
2527   st->print("Memory:");
2528   st->print(" %dk page", os::vm_page_size()>>10);
2529 
2530   // values in struct sysinfo are "unsigned long"
2531   struct sysinfo si;
2532   sysinfo(&si);
2533 
2534   st->print(", physical " UINT64_FORMAT "k",
2535             os::physical_memory() >> 10);
2536   st->print("(" UINT64_FORMAT "k free)",
2537             os::available_memory() >> 10);
2538   st->print(", swap " UINT64_FORMAT "k",
2539             ((jlong)si.totalswap * si.mem_unit) >> 10);
2540   st->print("(" UINT64_FORMAT "k free)",
2541             ((jlong)si.freeswap * si.mem_unit) >> 10);
2542   st->cr();
2543 }
2544 
2545 // Print the first "model name" line and the first "flags" line
2546 // that we find and nothing more. We assume "model name" comes
2547 // before "flags" so if we find a second "model name", then the
2548 // "flags" field is considered missing.
2549 static bool print_model_name_and_flags(outputStream* st, char* buf, size_t buflen) {
2550 #if defined(IA32) || defined(AMD64)
2551   // Other platforms have less repetitive cpuinfo files
2552   FILE *fp = fopen("/proc/cpuinfo", "r");
2553   if (fp) {
2554     while (!feof(fp)) {
2555       if (fgets(buf, buflen, fp)) {
2556         // Assume model name comes before flags
2557         bool model_name_printed = false;
2558         if (strstr(buf, "model name") != NULL) {
2559           if (!model_name_printed) {
2560             st->print_raw("CPU Model and flags from /proc/cpuinfo:\n");
2561             st->print_raw(buf);
2562             model_name_printed = true;
2563           } else {
2564             // model name printed but not flags?  Odd, just return
2565             fclose(fp);
2566             return true;
2567           }
2568         }
2569         // print the flags line too
2570         if (strstr(buf, "flags") != NULL) {
2571           st->print_raw(buf);
2572           fclose(fp);
2573           return true;
2574         }
2575       }
2576     }
2577     fclose(fp);
2578   }
2579 #endif // x86 platforms
2580   return false;
2581 }
2582 
2583 // additional information about CPU e.g. available frequency ranges
2584 static void print_sys_devices_cpu_info(outputStream* st, char* buf, size_t buflen) {
2585   _print_ascii_file_h("Online cpus", "/sys/devices/system/cpu/online", st);
2586   _print_ascii_file_h("Offline cpus", "/sys/devices/system/cpu/offline", st);
2587 
2588   if (ExtensiveErrorReports) {
2589     // cache related info (cpu 0, should be similar for other CPUs)
2590     for (unsigned int i=0; i < 10; i++) { // handle max. 10 cache entries
2591       char hbuf_level[60];
2592       char hbuf_type[60];
2593       char hbuf_size[60];
2594       char hbuf_coherency_line_size[80];
2595       snprintf(hbuf_level, 60, "/sys/devices/system/cpu/cpu0/cache/index%u/level", i);
2596       snprintf(hbuf_type, 60, "/sys/devices/system/cpu/cpu0/cache/index%u/type", i);
2597       snprintf(hbuf_size, 60, "/sys/devices/system/cpu/cpu0/cache/index%u/size", i);
2598       snprintf(hbuf_coherency_line_size, 80, "/sys/devices/system/cpu/cpu0/cache/index%u/coherency_line_size", i);
2599       if (file_exists(hbuf_level)) {
2600         _print_ascii_file_h("cache level", hbuf_level, st);
2601         _print_ascii_file_h("cache type", hbuf_type, st);
2602         _print_ascii_file_h("cache size", hbuf_size, st);
2603         _print_ascii_file_h("cache coherency line size", hbuf_coherency_line_size, st);
2604       }
2605     }
2606   }
2607 
2608   // we miss the cpufreq entries on Power and s390x
2609 #if defined(IA32) || defined(AMD64)
2610   _print_ascii_file_h("BIOS frequency limitation", "/sys/devices/system/cpu/cpu0/cpufreq/bios_limit", st);
2611   _print_ascii_file_h("Frequency switch latency (ns)", "/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_transition_latency", st);
2612   _print_ascii_file_h("Available cpu frequencies", "/sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies", st);
2613   // min and max should be in the Available range but still print them (not all info might be available for all kernels)
2614   if (ExtensiveErrorReports) {
2615     _print_ascii_file_h("Maximum cpu frequency", "/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq", st);
2616     _print_ascii_file_h("Minimum cpu frequency", "/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_min_freq", st);
2617     _print_ascii_file_h("Current cpu frequency", "/sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq", st);
2618   }
2619   // governors are power schemes, see https://wiki.archlinux.org/index.php/CPU_frequency_scaling
2620   if (ExtensiveErrorReports) {
2621     _print_ascii_file_h("Available governors", "/sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors", st);
2622   }
2623   _print_ascii_file_h("Current governor", "/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor", st);
2624   // Core performance boost, see https://www.kernel.org/doc/Documentation/cpu-freq/boost.txt
2625   // Raise operating frequency of some cores in a multi-core package if certain conditions apply, e.g.
2626   // whole chip is not fully utilized
2627   _print_ascii_file_h("Core performance/turbo boost", "/sys/devices/system/cpu/cpufreq/boost", st);
2628 #endif
2629 }
2630 
2631 void os::pd_print_cpu_info(outputStream* st, char* buf, size_t buflen) {
2632   // Only print the model name if the platform provides this as a summary
2633   if (!print_model_name_and_flags(st, buf, buflen)) {
2634     _print_ascii_file_h("/proc/cpuinfo", "/proc/cpuinfo", st, false);
2635   }
2636   st->cr();
2637   print_sys_devices_cpu_info(st, buf, buflen);
2638 }
2639 
2640 #if defined(AMD64) || defined(IA32) || defined(X32)
2641 const char* search_string = "model name";
2642 #elif defined(M68K)
2643 const char* search_string = "CPU";
2644 #elif defined(PPC64)
2645 const char* search_string = "cpu";
2646 #elif defined(S390)
2647 const char* search_string = "machine =";
2648 #elif defined(SPARC)
2649 const char* search_string = "cpu";
2650 #else
2651 const char* search_string = "Processor";
2652 #endif
2653 
2654 // Parses the cpuinfo file for string representing the model name.
2655 void os::get_summary_cpu_info(char* cpuinfo, size_t length) {
2656   FILE* fp = fopen("/proc/cpuinfo", "r");
2657   if (fp != NULL) {
2658     while (!feof(fp)) {
2659       char buf[256];
2660       if (fgets(buf, sizeof(buf), fp)) {
2661         char* start = strstr(buf, search_string);
2662         if (start != NULL) {
2663           char *ptr = start + strlen(search_string);
2664           char *end = buf + strlen(buf);
2665           while (ptr != end) {
2666              // skip whitespace and colon for the rest of the name.
2667              if (*ptr != ' ' && *ptr != '\t' && *ptr != ':') {
2668                break;
2669              }
2670              ptr++;
2671           }
2672           if (ptr != end) {
2673             // reasonable string, get rid of newline and keep the rest
2674             char* nl = strchr(buf, '\n');
2675             if (nl != NULL) *nl = '\0';
2676             strncpy(cpuinfo, ptr, length);
2677             fclose(fp);
2678             return;
2679           }
2680         }
2681       }
2682     }
2683     fclose(fp);
2684   }
2685   // cpuinfo not found or parsing failed, just print generic string.  The entire
2686   // /proc/cpuinfo file will be printed later in the file (or enough of it for x86)
2687 #if   defined(AARCH64)
2688   strncpy(cpuinfo, "AArch64", length);
2689 #elif defined(AMD64)
2690   strncpy(cpuinfo, "x86_64", length);
2691 #elif defined(ARM)  // Order wrt. AARCH64 is relevant!
2692   strncpy(cpuinfo, "ARM", length);
2693 #elif defined(IA32)
2694   strncpy(cpuinfo, "x86_32", length);
2695 #elif defined(IA64)
2696   strncpy(cpuinfo, "IA64", length);
2697 #elif defined(PPC)
2698   strncpy(cpuinfo, "PPC64", length);
2699 #elif defined(S390)
2700   strncpy(cpuinfo, "S390", length);
2701 #elif defined(SPARC)
2702   strncpy(cpuinfo, "sparcv9", length);
2703 #elif defined(ZERO_LIBARCH)
2704   strncpy(cpuinfo, ZERO_LIBARCH, length);
2705 #else
2706   strncpy(cpuinfo, "unknown", length);
2707 #endif
2708 }
2709 
2710 static void print_signal_handler(outputStream* st, int sig,
2711                                  char* buf, size_t buflen);
2712 
2713 void os::print_signal_handlers(outputStream* st, char* buf, size_t buflen) {
2714   st->print_cr("Signal Handlers:");
2715   print_signal_handler(st, SIGSEGV, buf, buflen);
2716   print_signal_handler(st, SIGBUS , buf, buflen);
2717   print_signal_handler(st, SIGFPE , buf, buflen);
2718   print_signal_handler(st, SIGPIPE, buf, buflen);
2719   print_signal_handler(st, SIGXFSZ, buf, buflen);
2720   print_signal_handler(st, SIGILL , buf, buflen);
2721   print_signal_handler(st, SR_signum, buf, buflen);
2722   print_signal_handler(st, SHUTDOWN1_SIGNAL, buf, buflen);
2723   print_signal_handler(st, SHUTDOWN2_SIGNAL , buf, buflen);
2724   print_signal_handler(st, SHUTDOWN3_SIGNAL , buf, buflen);
2725   print_signal_handler(st, BREAK_SIGNAL, buf, buflen);
2726 #if defined(PPC64)
2727   print_signal_handler(st, SIGTRAP, buf, buflen);
2728 #endif
2729 }
2730 
2731 static char saved_jvm_path[MAXPATHLEN] = {0};
2732 
2733 // Find the full path to the current module, libjvm.so
2734 void os::jvm_path(char *buf, jint buflen) {
2735   // Error checking.
2736   if (buflen < MAXPATHLEN) {
2737     assert(false, "must use a large-enough buffer");
2738     buf[0] = '\0';
2739     return;
2740   }
2741   // Lazy resolve the path to current module.
2742   if (saved_jvm_path[0] != 0) {
2743     strcpy(buf, saved_jvm_path);
2744     return;
2745   }
2746 
2747   char dli_fname[MAXPATHLEN];
2748   bool ret = dll_address_to_library_name(
2749                                          CAST_FROM_FN_PTR(address, os::jvm_path),
2750                                          dli_fname, sizeof(dli_fname), NULL);
2751   assert(ret, "cannot locate libjvm");
2752   char *rp = NULL;
2753   if (ret && dli_fname[0] != '\0') {
2754     rp = os::Posix::realpath(dli_fname, buf, buflen);
2755   }
2756   if (rp == NULL) {
2757     return;
2758   }
2759 
2760   if (Arguments::sun_java_launcher_is_altjvm()) {
2761     // Support for the java launcher's '-XXaltjvm=<path>' option. Typical
2762     // value for buf is "<JAVA_HOME>/jre/lib/<vmtype>/libjvm.so".
2763     // If "/jre/lib/" appears at the right place in the string, then
2764     // assume we are installed in a JDK and we're done. Otherwise, check
2765     // for a JAVA_HOME environment variable and fix up the path so it
2766     // looks like libjvm.so is installed there (append a fake suffix
2767     // hotspot/libjvm.so).
2768     const char *p = buf + strlen(buf) - 1;
2769     for (int count = 0; p > buf && count < 5; ++count) {
2770       for (--p; p > buf && *p != '/'; --p)
2771         /* empty */ ;
2772     }
2773 
2774     if (strncmp(p, "/jre/lib/", 9) != 0) {
2775       // Look for JAVA_HOME in the environment.
2776       char* java_home_var = ::getenv("JAVA_HOME");
2777       if (java_home_var != NULL && java_home_var[0] != 0) {
2778         char* jrelib_p;
2779         int len;
2780 
2781         // Check the current module name "libjvm.so".
2782         p = strrchr(buf, '/');
2783         if (p == NULL) {
2784           return;
2785         }
2786         assert(strstr(p, "/libjvm") == p, "invalid library name");
2787 
2788         rp = os::Posix::realpath(java_home_var, buf, buflen);
2789         if (rp == NULL) {
2790           return;
2791         }
2792 
2793         // determine if this is a legacy image or modules image
2794         // modules image doesn't have "jre" subdirectory
2795         len = strlen(buf);
2796         assert(len < buflen, "Ran out of buffer room");
2797         jrelib_p = buf + len;
2798         snprintf(jrelib_p, buflen-len, "/jre/lib");
2799         if (0 != access(buf, F_OK)) {
2800           snprintf(jrelib_p, buflen-len, "/lib");
2801         }
2802 
2803         if (0 == access(buf, F_OK)) {
2804           // Use current module name "libjvm.so"
2805           len = strlen(buf);
2806           snprintf(buf + len, buflen-len, "/hotspot/libjvm.so");
2807         } else {
2808           // Go back to path of .so
2809           rp = os::Posix::realpath(dli_fname, buf, buflen);
2810           if (rp == NULL) {
2811             return;
2812           }
2813         }
2814       }
2815     }
2816   }
2817 
2818   strncpy(saved_jvm_path, buf, MAXPATHLEN);
2819   saved_jvm_path[MAXPATHLEN - 1] = '\0';
2820 }
2821 
2822 void os::print_jni_name_prefix_on(outputStream* st, int args_size) {
2823   // no prefix required, not even "_"
2824 }
2825 
2826 void os::print_jni_name_suffix_on(outputStream* st, int args_size) {
2827   // no suffix required
2828 }
2829 
2830 ////////////////////////////////////////////////////////////////////////////////
2831 // sun.misc.Signal support
2832 
2833 static void UserHandler(int sig, void *siginfo, void *context) {
2834   // Ctrl-C is pressed during error reporting, likely because the error
2835   // handler fails to abort. Let VM die immediately.
2836   if (sig == SIGINT && VMError::is_error_reported()) {
2837     os::die();
2838   }
2839 
2840   os::signal_notify(sig);
2841 }
2842 
2843 void* os::user_handler() {
2844   return CAST_FROM_FN_PTR(void*, UserHandler);
2845 }
2846 
2847 extern "C" {
2848   typedef void (*sa_handler_t)(int);
2849   typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
2850 }
2851 
2852 void* os::signal(int signal_number, void* handler) {
2853   struct sigaction sigAct, oldSigAct;
2854 
2855   sigfillset(&(sigAct.sa_mask));
2856   sigAct.sa_flags   = SA_RESTART|SA_SIGINFO;
2857   sigAct.sa_handler = CAST_TO_FN_PTR(sa_handler_t, handler);
2858 
2859   if (sigaction(signal_number, &sigAct, &oldSigAct)) {
2860     // -1 means registration failed
2861     return (void *)-1;
2862   }
2863 
2864   return CAST_FROM_FN_PTR(void*, oldSigAct.sa_handler);
2865 }
2866 
2867 void os::signal_raise(int signal_number) {
2868   ::raise(signal_number);
2869 }
2870 
2871 // The following code is moved from os.cpp for making this
2872 // code platform specific, which it is by its very nature.
2873 
2874 // Will be modified when max signal is changed to be dynamic
2875 int os::sigexitnum_pd() {
2876   return NSIG;
2877 }
2878 
2879 // a counter for each possible signal value
2880 static volatile jint pending_signals[NSIG+1] = { 0 };
2881 
2882 // Linux(POSIX) specific hand shaking semaphore.
2883 static Semaphore* sig_sem = NULL;
2884 static PosixSemaphore sr_semaphore;
2885 
2886 static void jdk_misc_signal_init() {
2887   // Initialize signal structures
2888   ::memset((void*)pending_signals, 0, sizeof(pending_signals));
2889 
2890   // Initialize signal semaphore
2891   sig_sem = new Semaphore();
2892 }
2893 
2894 void os::signal_notify(int sig) {
2895   if (sig_sem != NULL) {
2896     Atomic::inc(&pending_signals[sig]);
2897     sig_sem->signal();
2898   } else {
2899     // Signal thread is not created with ReduceSignalUsage and jdk_misc_signal_init
2900     // initialization isn't called.
2901     assert(ReduceSignalUsage, "signal semaphore should be created");
2902   }
2903 }
2904 
2905 static int check_pending_signals() {
2906   for (;;) {
2907     for (int i = 0; i < NSIG + 1; i++) {
2908       jint n = pending_signals[i];
2909       if (n > 0 && n == Atomic::cmpxchg(&pending_signals[i], n, n - 1)) {
2910         return i;
2911       }
2912     }
2913     JavaThread *thread = JavaThread::current();
2914     ThreadBlockInVM tbivm(thread);
2915 
2916     bool threadIsSuspended;
2917     do {
2918       thread->set_suspend_equivalent();
2919       // cleared by handle_special_suspend_equivalent_condition() or java_suspend_self()
2920       sig_sem->wait();
2921 
2922       // were we externally suspended while we were waiting?
2923       threadIsSuspended = thread->handle_special_suspend_equivalent_condition();
2924       if (threadIsSuspended) {
2925         // The semaphore has been incremented, but while we were waiting
2926         // another thread suspended us. We don't want to continue running
2927         // while suspended because that would surprise the thread that
2928         // suspended us.
2929         sig_sem->signal();
2930 
2931         thread->java_suspend_self();
2932       }
2933     } while (threadIsSuspended);
2934   }
2935 }
2936 
2937 int os::signal_wait() {
2938   return check_pending_signals();
2939 }
2940 
2941 ////////////////////////////////////////////////////////////////////////////////
2942 // Virtual Memory
2943 
2944 int os::vm_page_size() {
2945   // Seems redundant as all get out
2946   assert(os::Linux::page_size() != -1, "must call os::init");
2947   return os::Linux::page_size();
2948 }
2949 
2950 // Solaris allocates memory by pages.
2951 int os::vm_allocation_granularity() {
2952   assert(os::Linux::page_size() != -1, "must call os::init");
2953   return os::Linux::page_size();
2954 }
2955 
2956 // Rationale behind this function:
2957 //  current (Mon Apr 25 20:12:18 MSD 2005) oprofile drops samples without executable
2958 //  mapping for address (see lookup_dcookie() in the kernel module), thus we cannot get
2959 //  samples for JITted code. Here we create private executable mapping over the code cache
2960 //  and then we can use standard (well, almost, as mapping can change) way to provide
2961 //  info for the reporting script by storing timestamp and location of symbol
2962 void linux_wrap_code(char* base, size_t size) {
2963   static volatile jint cnt = 0;
2964 
2965   if (!UseOprofile) {
2966     return;
2967   }
2968 
2969   char buf[PATH_MAX+1];
2970   int num = Atomic::add(&cnt, 1);
2971 
2972   snprintf(buf, sizeof(buf), "%s/hs-vm-%d-%d",
2973            os::get_temp_directory(), os::current_process_id(), num);
2974   unlink(buf);
2975 
2976   int fd = ::open(buf, O_CREAT | O_RDWR, S_IRWXU);
2977 
2978   if (fd != -1) {
2979     off_t rv = ::lseek(fd, size-2, SEEK_SET);
2980     if (rv != (off_t)-1) {
2981       if (::write(fd, "", 1) == 1) {
2982         mmap(base, size,
2983              PROT_READ|PROT_WRITE|PROT_EXEC,
2984              MAP_PRIVATE|MAP_FIXED|MAP_NORESERVE, fd, 0);
2985       }
2986     }
2987     ::close(fd);
2988     unlink(buf);
2989   }
2990 }
2991 
2992 static bool recoverable_mmap_error(int err) {
2993   // See if the error is one we can let the caller handle. This
2994   // list of errno values comes from JBS-6843484. I can't find a
2995   // Linux man page that documents this specific set of errno
2996   // values so while this list currently matches Solaris, it may
2997   // change as we gain experience with this failure mode.
2998   switch (err) {
2999   case EBADF:
3000   case EINVAL:
3001   case ENOTSUP:
3002     // let the caller deal with these errors
3003     return true;
3004 
3005   default:
3006     // Any remaining errors on this OS can cause our reserved mapping
3007     // to be lost. That can cause confusion where different data
3008     // structures think they have the same memory mapped. The worst
3009     // scenario is if both the VM and a library think they have the
3010     // same memory mapped.
3011     return false;
3012   }
3013 }
3014 
3015 static void warn_fail_commit_memory(char* addr, size_t size, bool exec,
3016                                     int err) {
3017   warning("INFO: os::commit_memory(" PTR_FORMAT ", " SIZE_FORMAT
3018           ", %d) failed; error='%s' (errno=%d)", p2i(addr), size, exec,
3019           os::strerror(err), err);
3020 }
3021 
3022 static void warn_fail_commit_memory(char* addr, size_t size,
3023                                     size_t alignment_hint, bool exec,
3024                                     int err) {
3025   warning("INFO: os::commit_memory(" PTR_FORMAT ", " SIZE_FORMAT
3026           ", " SIZE_FORMAT ", %d) failed; error='%s' (errno=%d)", p2i(addr), size,
3027           alignment_hint, exec, os::strerror(err), err);
3028 }
3029 
3030 // NOTE: Linux kernel does not really reserve the pages for us.
3031 //       All it does is to check if there are enough free pages
3032 //       left at the time of mmap(). This could be a potential
3033 //       problem.
3034 int os::Linux::commit_memory_impl(char* addr, size_t size, bool exec) {
3035   int prot = exec ? PROT_READ|PROT_WRITE|PROT_EXEC : PROT_READ|PROT_WRITE;
3036   uintptr_t res = (uintptr_t) ::mmap(addr, size, prot,
3037                                      MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0);
3038   if (res != (uintptr_t) MAP_FAILED) {
3039     if (UseNUMAInterleaving) {
3040       numa_make_global(addr, size);
3041     }
3042     return 0;
3043   }
3044 
3045   int err = errno;  // save errno from mmap() call above
3046 
3047   if (!recoverable_mmap_error(err)) {
3048     warn_fail_commit_memory(addr, size, exec, err);
3049     vm_exit_out_of_memory(size, OOM_MMAP_ERROR, "committing reserved memory.");
3050   }
3051 
3052   return err;
3053 }
3054 
3055 bool os::pd_commit_memory(char* addr, size_t size, bool exec) {
3056   return os::Linux::commit_memory_impl(addr, size, exec) == 0;
3057 }
3058 
3059 void os::pd_commit_memory_or_exit(char* addr, size_t size, bool exec,
3060                                   const char* mesg) {
3061   assert(mesg != NULL, "mesg must be specified");
3062   int err = os::Linux::commit_memory_impl(addr, size, exec);
3063   if (err != 0) {
3064     // the caller wants all commit errors to exit with the specified mesg:
3065     warn_fail_commit_memory(addr, size, exec, err);
3066     vm_exit_out_of_memory(size, OOM_MMAP_ERROR, "%s", mesg);
3067   }
3068 }
3069 
3070 // Define MAP_HUGETLB here so we can build HotSpot on old systems.
3071 #ifndef MAP_HUGETLB
3072   #define MAP_HUGETLB 0x40000
3073 #endif
3074 
3075 // If mmap flags are set with MAP_HUGETLB and the system supports multiple
3076 // huge page sizes, flag bits [26:31] can be used to encode the log2 of the
3077 // desired huge page size. Otherwise, the system's default huge page size will be used.
3078 // See mmap(2) man page for more info (since Linux 3.8).
3079 // https://lwn.net/Articles/533499/
3080 #ifndef MAP_HUGE_SHIFT
3081   #define MAP_HUGE_SHIFT 26
3082 #endif
3083 
3084 // Define MADV_HUGEPAGE here so we can build HotSpot on old systems.
3085 #ifndef MADV_HUGEPAGE
3086   #define MADV_HUGEPAGE 14
3087 #endif
3088 
3089 int os::Linux::commit_memory_impl(char* addr, size_t size,
3090                                   size_t alignment_hint, bool exec) {
3091   int err = os::Linux::commit_memory_impl(addr, size, exec);
3092   if (err == 0) {
3093     realign_memory(addr, size, alignment_hint);
3094   }
3095   return err;
3096 }
3097 
3098 bool os::pd_commit_memory(char* addr, size_t size, size_t alignment_hint,
3099                           bool exec) {
3100   return os::Linux::commit_memory_impl(addr, size, alignment_hint, exec) == 0;
3101 }
3102 
3103 void os::pd_commit_memory_or_exit(char* addr, size_t size,
3104                                   size_t alignment_hint, bool exec,
3105                                   const char* mesg) {
3106   assert(mesg != NULL, "mesg must be specified");
3107   int err = os::Linux::commit_memory_impl(addr, size, alignment_hint, exec);
3108   if (err != 0) {
3109     // the caller wants all commit errors to exit with the specified mesg:
3110     warn_fail_commit_memory(addr, size, alignment_hint, exec, err);
3111     vm_exit_out_of_memory(size, OOM_MMAP_ERROR, "%s", mesg);
3112   }
3113 }
3114 
3115 void os::pd_realign_memory(char *addr, size_t bytes, size_t alignment_hint) {
3116   if (UseTransparentHugePages && alignment_hint > (size_t)vm_page_size()) {
3117     // We don't check the return value: madvise(MADV_HUGEPAGE) may not
3118     // be supported or the memory may already be backed by huge pages.
3119     ::madvise(addr, bytes, MADV_HUGEPAGE);
3120   }
3121 }
3122 
3123 void os::pd_free_memory(char *addr, size_t bytes, size_t alignment_hint) {
3124   // This method works by doing an mmap over an existing mmaping and effectively discarding
3125   // the existing pages. However it won't work for SHM-based large pages that cannot be
3126   // uncommitted at all. We don't do anything in this case to avoid creating a segment with
3127   // small pages on top of the SHM segment. This method always works for small pages, so we
3128   // allow that in any case.
3129   if (alignment_hint <= (size_t)os::vm_page_size() || can_commit_large_page_memory()) {
3130     commit_memory(addr, bytes, alignment_hint, !ExecMem);
3131   }
3132 }
3133 
3134 void os::numa_make_global(char *addr, size_t bytes) {
3135   Linux::numa_interleave_memory(addr, bytes);
3136 }
3137 
3138 // Define for numa_set_bind_policy(int). Setting the argument to 0 will set the
3139 // bind policy to MPOL_PREFERRED for the current thread.
3140 #define USE_MPOL_PREFERRED 0
3141 
3142 void os::numa_make_local(char *addr, size_t bytes, int lgrp_hint) {
3143   // To make NUMA and large pages more robust when both enabled, we need to ease
3144   // the requirements on where the memory should be allocated. MPOL_BIND is the
3145   // default policy and it will force memory to be allocated on the specified
3146   // node. Changing this to MPOL_PREFERRED will prefer to allocate the memory on
3147   // the specified node, but will not force it. Using this policy will prevent
3148   // getting SIGBUS when trying to allocate large pages on NUMA nodes with no
3149   // free large pages.
3150   Linux::numa_set_bind_policy(USE_MPOL_PREFERRED);
3151   Linux::numa_tonode_memory(addr, bytes, lgrp_hint);
3152 }
3153 
3154 bool os::numa_topology_changed() { return false; }
3155 
3156 size_t os::numa_get_groups_num() {
3157   // Return just the number of nodes in which it's possible to allocate memory
3158   // (in numa terminology, configured nodes).
3159   return Linux::numa_num_configured_nodes();
3160 }
3161 
3162 int os::numa_get_group_id() {
3163   int cpu_id = Linux::sched_getcpu();
3164   if (cpu_id != -1) {
3165     int lgrp_id = Linux::get_node_by_cpu(cpu_id);
3166     if (lgrp_id != -1) {
3167       return lgrp_id;
3168     }
3169   }
3170   return 0;
3171 }
3172 
3173 int os::numa_get_group_id_for_address(const void* address) {
3174   void** pages = const_cast<void**>(&address);
3175   int id = -1;
3176 
3177   if (os::Linux::numa_move_pages(0, 1, pages, NULL, &id, 0) == -1) {
3178     return -1;
3179   }
3180   if (id < 0) {
3181     return -1;
3182   }
3183   return id;
3184 }
3185 
3186 int os::Linux::get_existing_num_nodes() {
3187   int node;
3188   int highest_node_number = Linux::numa_max_node();
3189   int num_nodes = 0;
3190 
3191   // Get the total number of nodes in the system including nodes without memory.
3192   for (node = 0; node <= highest_node_number; node++) {
3193     if (is_node_in_existing_nodes(node)) {
3194       num_nodes++;
3195     }
3196   }
3197   return num_nodes;
3198 }
3199 
3200 size_t os::numa_get_leaf_groups(int *ids, size_t size) {
3201   int highest_node_number = Linux::numa_max_node();
3202   size_t i = 0;
3203 
3204   // Map all node ids in which it is possible to allocate memory. Also nodes are
3205   // not always consecutively available, i.e. available from 0 to the highest
3206   // node number. If the nodes have been bound explicitly using numactl membind,
3207   // then allocate memory from those nodes only.
3208   for (int node = 0; node <= highest_node_number; node++) {
3209     if (Linux::is_node_in_bound_nodes((unsigned int)node)) {
3210       ids[i++] = node;
3211     }
3212   }
3213   return i;
3214 }
3215 
3216 bool os::get_page_info(char *start, page_info* info) {
3217   return false;
3218 }
3219 
3220 char *os::scan_pages(char *start, char* end, page_info* page_expected,
3221                      page_info* page_found) {
3222   return end;
3223 }
3224 
3225 
3226 int os::Linux::sched_getcpu_syscall(void) {
3227   unsigned int cpu = 0;
3228   int retval = -1;
3229 
3230 #if defined(IA32)
3231   #ifndef SYS_getcpu
3232     #define SYS_getcpu 318
3233   #endif
3234   retval = syscall(SYS_getcpu, &cpu, NULL, NULL);
3235 #elif defined(AMD64)
3236 // Unfortunately we have to bring all these macros here from vsyscall.h
3237 // to be able to compile on old linuxes.
3238   #define __NR_vgetcpu 2
3239   #define VSYSCALL_START (-10UL << 20)
3240   #define VSYSCALL_SIZE 1024
3241   #define VSYSCALL_ADDR(vsyscall_nr) (VSYSCALL_START+VSYSCALL_SIZE*(vsyscall_nr))
3242   typedef long (*vgetcpu_t)(unsigned int *cpu, unsigned int *node, unsigned long *tcache);
3243   vgetcpu_t vgetcpu = (vgetcpu_t)VSYSCALL_ADDR(__NR_vgetcpu);
3244   retval = vgetcpu(&cpu, NULL, NULL);
3245 #endif
3246 
3247   return (retval == -1) ? retval : cpu;
3248 }
3249 
3250 void os::Linux::sched_getcpu_init() {
3251   // sched_getcpu() should be in libc.
3252   set_sched_getcpu(CAST_TO_FN_PTR(sched_getcpu_func_t,
3253                                   dlsym(RTLD_DEFAULT, "sched_getcpu")));
3254 
3255   // If it's not, try a direct syscall.
3256   if (sched_getcpu() == -1) {
3257     set_sched_getcpu(CAST_TO_FN_PTR(sched_getcpu_func_t,
3258                                     (void*)&sched_getcpu_syscall));
3259   }
3260 
3261   if (sched_getcpu() == -1) {
3262     vm_exit_during_initialization("getcpu(2) system call not supported by kernel");
3263   }
3264 }
3265 
3266 // Something to do with the numa-aware allocator needs these symbols
3267 extern "C" JNIEXPORT void numa_warn(int number, char *where, ...) { }
3268 extern "C" JNIEXPORT void numa_error(char *where) { }
3269 
3270 // Handle request to load libnuma symbol version 1.1 (API v1). If it fails
3271 // load symbol from base version instead.
3272 void* os::Linux::libnuma_dlsym(void* handle, const char *name) {
3273   void *f = dlvsym(handle, name, "libnuma_1.1");
3274   if (f == NULL) {
3275     f = dlsym(handle, name);
3276   }
3277   return f;
3278 }
3279 
3280 // Handle request to load libnuma symbol version 1.2 (API v2) only.
3281 // Return NULL if the symbol is not defined in this particular version.
3282 void* os::Linux::libnuma_v2_dlsym(void* handle, const char* name) {
3283   return dlvsym(handle, name, "libnuma_1.2");
3284 }
3285 
3286 bool os::Linux::libnuma_init() {
3287   if (sched_getcpu() != -1) { // Requires sched_getcpu() support
3288     void *handle = dlopen("libnuma.so.1", RTLD_LAZY);
3289     if (handle != NULL) {
3290       set_numa_node_to_cpus(CAST_TO_FN_PTR(numa_node_to_cpus_func_t,
3291                                            libnuma_dlsym(handle, "numa_node_to_cpus")));
3292       set_numa_max_node(CAST_TO_FN_PTR(numa_max_node_func_t,
3293                                        libnuma_dlsym(handle, "numa_max_node")));
3294       set_numa_num_configured_nodes(CAST_TO_FN_PTR(numa_num_configured_nodes_func_t,
3295                                                    libnuma_dlsym(handle, "numa_num_configured_nodes")));
3296       set_numa_available(CAST_TO_FN_PTR(numa_available_func_t,
3297                                         libnuma_dlsym(handle, "numa_available")));
3298       set_numa_tonode_memory(CAST_TO_FN_PTR(numa_tonode_memory_func_t,
3299                                             libnuma_dlsym(handle, "numa_tonode_memory")));
3300       set_numa_interleave_memory(CAST_TO_FN_PTR(numa_interleave_memory_func_t,
3301                                                 libnuma_dlsym(handle, "numa_interleave_memory")));
3302       set_numa_interleave_memory_v2(CAST_TO_FN_PTR(numa_interleave_memory_v2_func_t,
3303                                                 libnuma_v2_dlsym(handle, "numa_interleave_memory")));
3304       set_numa_set_bind_policy(CAST_TO_FN_PTR(numa_set_bind_policy_func_t,
3305                                               libnuma_dlsym(handle, "numa_set_bind_policy")));
3306       set_numa_bitmask_isbitset(CAST_TO_FN_PTR(numa_bitmask_isbitset_func_t,
3307                                                libnuma_dlsym(handle, "numa_bitmask_isbitset")));
3308       set_numa_distance(CAST_TO_FN_PTR(numa_distance_func_t,
3309                                        libnuma_dlsym(handle, "numa_distance")));
3310       set_numa_get_membind(CAST_TO_FN_PTR(numa_get_membind_func_t,
3311                                           libnuma_v2_dlsym(handle, "numa_get_membind")));
3312       set_numa_get_interleave_mask(CAST_TO_FN_PTR(numa_get_interleave_mask_func_t,
3313                                                   libnuma_v2_dlsym(handle, "numa_get_interleave_mask")));
3314       set_numa_move_pages(CAST_TO_FN_PTR(numa_move_pages_func_t,
3315                                          libnuma_dlsym(handle, "numa_move_pages")));
3316       set_numa_set_preferred(CAST_TO_FN_PTR(numa_set_preferred_func_t,
3317                                             libnuma_dlsym(handle, "numa_set_preferred")));
3318 
3319       if (numa_available() != -1) {
3320         set_numa_all_nodes((unsigned long*)libnuma_dlsym(handle, "numa_all_nodes"));
3321         set_numa_all_nodes_ptr((struct bitmask **)libnuma_dlsym(handle, "numa_all_nodes_ptr"));
3322         set_numa_nodes_ptr((struct bitmask **)libnuma_dlsym(handle, "numa_nodes_ptr"));
3323         set_numa_interleave_bitmask(_numa_get_interleave_mask());
3324         set_numa_membind_bitmask(_numa_get_membind());
3325         // Create an index -> node mapping, since nodes are not always consecutive
3326         _nindex_to_node = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<int>(0, mtInternal);
3327         rebuild_nindex_to_node_map();
3328         // Create a cpu -> node mapping
3329         _cpu_to_node = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<int>(0, mtInternal);
3330         rebuild_cpu_to_node_map();
3331         return true;
3332       }
3333     }
3334   }
3335   return false;
3336 }
3337 
3338 size_t os::Linux::default_guard_size(os::ThreadType thr_type) {
3339   // Creating guard page is very expensive. Java thread has HotSpot
3340   // guard pages, only enable glibc guard page for non-Java threads.
3341   // (Remember: compiler thread is a Java thread, too!)
3342   return ((thr_type == java_thread || thr_type == compiler_thread) ? 0 : page_size());
3343 }
3344 
3345 void os::Linux::rebuild_nindex_to_node_map() {
3346   int highest_node_number = Linux::numa_max_node();
3347 
3348   nindex_to_node()->clear();
3349   for (int node = 0; node <= highest_node_number; node++) {
3350     if (Linux::is_node_in_existing_nodes(node)) {
3351       nindex_to_node()->append(node);
3352     }
3353   }
3354 }
3355 
3356 // rebuild_cpu_to_node_map() constructs a table mapping cpud id to node id.
3357 // The table is later used in get_node_by_cpu().
3358 void os::Linux::rebuild_cpu_to_node_map() {
3359   const size_t NCPUS = 32768; // Since the buffer size computation is very obscure
3360                               // in libnuma (possible values are starting from 16,
3361                               // and continuing up with every other power of 2, but less
3362                               // than the maximum number of CPUs supported by kernel), and
3363                               // is a subject to change (in libnuma version 2 the requirements
3364                               // are more reasonable) we'll just hardcode the number they use
3365                               // in the library.
3366   const size_t BitsPerCLong = sizeof(long) * CHAR_BIT;
3367 
3368   size_t cpu_num = processor_count();
3369   size_t cpu_map_size = NCPUS / BitsPerCLong;
3370   size_t cpu_map_valid_size =
3371     MIN2((cpu_num + BitsPerCLong - 1) / BitsPerCLong, cpu_map_size);
3372 
3373   cpu_to_node()->clear();
3374   cpu_to_node()->at_grow(cpu_num - 1);
3375 
3376   size_t node_num = get_existing_num_nodes();
3377 
3378   int distance = 0;
3379   int closest_distance = INT_MAX;
3380   int closest_node = 0;
3381   unsigned long *cpu_map = NEW_C_HEAP_ARRAY(unsigned long, cpu_map_size, mtInternal);
3382   for (size_t i = 0; i < node_num; i++) {
3383     // Check if node is configured (not a memory-less node). If it is not, find
3384     // the closest configured node. Check also if node is bound, i.e. it's allowed
3385     // to allocate memory from the node. If it's not allowed, map cpus in that node
3386     // to the closest node from which memory allocation is allowed.
3387     if (!is_node_in_configured_nodes(nindex_to_node()->at(i)) ||
3388         !is_node_in_bound_nodes(nindex_to_node()->at(i))) {
3389       closest_distance = INT_MAX;
3390       // Check distance from all remaining nodes in the system. Ignore distance
3391       // from itself, from another non-configured node, and from another non-bound
3392       // node.
3393       for (size_t m = 0; m < node_num; m++) {
3394         if (m != i &&
3395             is_node_in_configured_nodes(nindex_to_node()->at(m)) &&
3396             is_node_in_bound_nodes(nindex_to_node()->at(m))) {
3397           distance = numa_distance(nindex_to_node()->at(i), nindex_to_node()->at(m));
3398           // If a closest node is found, update. There is always at least one
3399           // configured and bound node in the system so there is always at least
3400           // one node close.
3401           if (distance != 0 && distance < closest_distance) {
3402             closest_distance = distance;
3403             closest_node = nindex_to_node()->at(m);
3404           }
3405         }
3406       }
3407      } else {
3408        // Current node is already a configured node.
3409        closest_node = nindex_to_node()->at(i);
3410      }
3411 
3412     // Get cpus from the original node and map them to the closest node. If node
3413     // is a configured node (not a memory-less node), then original node and
3414     // closest node are the same.
3415     if (numa_node_to_cpus(nindex_to_node()->at(i), cpu_map, cpu_map_size * sizeof(unsigned long)) != -1) {
3416       for (size_t j = 0; j < cpu_map_valid_size; j++) {
3417         if (cpu_map[j] != 0) {
3418           for (size_t k = 0; k < BitsPerCLong; k++) {
3419             if (cpu_map[j] & (1UL << k)) {
3420               cpu_to_node()->at_put(j * BitsPerCLong + k, closest_node);
3421             }
3422           }
3423         }
3424       }
3425     }
3426   }
3427   FREE_C_HEAP_ARRAY(unsigned long, cpu_map);
3428 }
3429 
3430 int os::Linux::get_node_by_cpu(int cpu_id) {
3431   if (cpu_to_node() != NULL && cpu_id >= 0 && cpu_id < cpu_to_node()->length()) {
3432     return cpu_to_node()->at(cpu_id);
3433   }
3434   return -1;
3435 }
3436 
3437 GrowableArray<int>* os::Linux::_cpu_to_node;
3438 GrowableArray<int>* os::Linux::_nindex_to_node;
3439 os::Linux::sched_getcpu_func_t os::Linux::_sched_getcpu;
3440 os::Linux::numa_node_to_cpus_func_t os::Linux::_numa_node_to_cpus;
3441 os::Linux::numa_max_node_func_t os::Linux::_numa_max_node;
3442 os::Linux::numa_num_configured_nodes_func_t os::Linux::_numa_num_configured_nodes;
3443 os::Linux::numa_available_func_t os::Linux::_numa_available;
3444 os::Linux::numa_tonode_memory_func_t os::Linux::_numa_tonode_memory;
3445 os::Linux::numa_interleave_memory_func_t os::Linux::_numa_interleave_memory;
3446 os::Linux::numa_interleave_memory_v2_func_t os::Linux::_numa_interleave_memory_v2;
3447 os::Linux::numa_set_bind_policy_func_t os::Linux::_numa_set_bind_policy;
3448 os::Linux::numa_bitmask_isbitset_func_t os::Linux::_numa_bitmask_isbitset;
3449 os::Linux::numa_distance_func_t os::Linux::_numa_distance;
3450 os::Linux::numa_get_membind_func_t os::Linux::_numa_get_membind;
3451 os::Linux::numa_get_interleave_mask_func_t os::Linux::_numa_get_interleave_mask;
3452 os::Linux::numa_move_pages_func_t os::Linux::_numa_move_pages;
3453 os::Linux::numa_set_preferred_func_t os::Linux::_numa_set_preferred;
3454 os::Linux::NumaAllocationPolicy os::Linux::_current_numa_policy;
3455 unsigned long* os::Linux::_numa_all_nodes;
3456 struct bitmask* os::Linux::_numa_all_nodes_ptr;
3457 struct bitmask* os::Linux::_numa_nodes_ptr;
3458 struct bitmask* os::Linux::_numa_interleave_bitmask;
3459 struct bitmask* os::Linux::_numa_membind_bitmask;
3460 
3461 bool os::pd_uncommit_memory(char* addr, size_t size) {
3462   uintptr_t res = (uintptr_t) ::mmap(addr, size, PROT_NONE,
3463                                      MAP_PRIVATE|MAP_FIXED|MAP_NORESERVE|MAP_ANONYMOUS, -1, 0);
3464   return res  != (uintptr_t) MAP_FAILED;
3465 }
3466 
3467 static address get_stack_commited_bottom(address bottom, size_t size) {
3468   address nbot = bottom;
3469   address ntop = bottom + size;
3470 
3471   size_t page_sz = os::vm_page_size();
3472   unsigned pages = size / page_sz;
3473 
3474   unsigned char vec[1];
3475   unsigned imin = 1, imax = pages + 1, imid;
3476   int mincore_return_value = 0;
3477 
3478   assert(imin <= imax, "Unexpected page size");
3479 
3480   while (imin < imax) {
3481     imid = (imax + imin) / 2;
3482     nbot = ntop - (imid * page_sz);
3483 
3484     // Use a trick with mincore to check whether the page is mapped or not.
3485     // mincore sets vec to 1 if page resides in memory and to 0 if page
3486     // is swapped output but if page we are asking for is unmapped
3487     // it returns -1,ENOMEM
3488     mincore_return_value = mincore(nbot, page_sz, vec);
3489 
3490     if (mincore_return_value == -1) {
3491       // Page is not mapped go up
3492       // to find first mapped page
3493       if (errno != EAGAIN) {
3494         assert(errno == ENOMEM, "Unexpected mincore errno");
3495         imax = imid;
3496       }
3497     } else {
3498       // Page is mapped go down
3499       // to find first not mapped page
3500       imin = imid + 1;
3501     }
3502   }
3503 
3504   nbot = nbot + page_sz;
3505 
3506   // Adjust stack bottom one page up if last checked page is not mapped
3507   if (mincore_return_value == -1) {
3508     nbot = nbot + page_sz;
3509   }
3510 
3511   return nbot;
3512 }
3513 
3514 bool os::committed_in_range(address start, size_t size, address& committed_start, size_t& committed_size) {
3515   int mincore_return_value;
3516   const size_t stripe = 1024;  // query this many pages each time
3517   unsigned char vec[stripe + 1];
3518   // set a guard
3519   vec[stripe] = 'X';
3520 
3521   const size_t page_sz = os::vm_page_size();
3522   size_t pages = size / page_sz;
3523 
3524   assert(is_aligned(start, page_sz), "Start address must be page aligned");
3525   assert(is_aligned(size, page_sz), "Size must be page aligned");
3526 
3527   committed_start = NULL;
3528 
3529   int loops = (pages + stripe - 1) / stripe;
3530   int committed_pages = 0;
3531   address loop_base = start;
3532   bool found_range = false;
3533 
3534   for (int index = 0; index < loops && !found_range; index ++) {
3535     assert(pages > 0, "Nothing to do");
3536     int pages_to_query = (pages >= stripe) ? stripe : pages;
3537     pages -= pages_to_query;
3538 
3539     // Get stable read
3540     while ((mincore_return_value = mincore(loop_base, pages_to_query * page_sz, vec)) == -1 && errno == EAGAIN);
3541 
3542     // During shutdown, some memory goes away without properly notifying NMT,
3543     // E.g. ConcurrentGCThread/WatcherThread can exit without deleting thread object.
3544     // Bailout and return as not committed for now.
3545     if (mincore_return_value == -1 && errno == ENOMEM) {
3546       return false;
3547     }
3548 
3549     assert(vec[stripe] == 'X', "overflow guard");
3550     assert(mincore_return_value == 0, "Range must be valid");
3551     // Process this stripe
3552     for (int vecIdx = 0; vecIdx < pages_to_query; vecIdx ++) {
3553       if ((vec[vecIdx] & 0x01) == 0) { // not committed
3554         // End of current contiguous region
3555         if (committed_start != NULL) {
3556           found_range = true;
3557           break;
3558         }
3559       } else { // committed
3560         // Start of region
3561         if (committed_start == NULL) {
3562           committed_start = loop_base + page_sz * vecIdx;
3563         }
3564         committed_pages ++;
3565       }
3566     }
3567 
3568     loop_base += pages_to_query * page_sz;
3569   }
3570 
3571   if (committed_start != NULL) {
3572     assert(committed_pages > 0, "Must have committed region");
3573     assert(committed_pages <= int(size / page_sz), "Can not commit more than it has");
3574     assert(committed_start >= start && committed_start < start + size, "Out of range");
3575     committed_size = page_sz * committed_pages;
3576     return true;
3577   } else {
3578     assert(committed_pages == 0, "Should not have committed region");
3579     return false;
3580   }
3581 }
3582 
3583 
3584 // Linux uses a growable mapping for the stack, and if the mapping for
3585 // the stack guard pages is not removed when we detach a thread the
3586 // stack cannot grow beyond the pages where the stack guard was
3587 // mapped.  If at some point later in the process the stack expands to
3588 // that point, the Linux kernel cannot expand the stack any further
3589 // because the guard pages are in the way, and a segfault occurs.
3590 //
3591 // However, it's essential not to split the stack region by unmapping
3592 // a region (leaving a hole) that's already part of the stack mapping,
3593 // so if the stack mapping has already grown beyond the guard pages at
3594 // the time we create them, we have to truncate the stack mapping.
3595 // So, we need to know the extent of the stack mapping when
3596 // create_stack_guard_pages() is called.
3597 
3598 // We only need this for stacks that are growable: at the time of
3599 // writing thread stacks don't use growable mappings (i.e. those
3600 // creeated with MAP_GROWSDOWN), and aren't marked "[stack]", so this
3601 // only applies to the main thread.
3602 
3603 // If the (growable) stack mapping already extends beyond the point
3604 // where we're going to put our guard pages, truncate the mapping at
3605 // that point by munmap()ping it.  This ensures that when we later
3606 // munmap() the guard pages we don't leave a hole in the stack
3607 // mapping. This only affects the main/primordial thread
3608 
3609 bool os::pd_create_stack_guard_pages(char* addr, size_t size) {
3610   if (os::is_primordial_thread()) {
3611     // As we manually grow stack up to bottom inside create_attached_thread(),
3612     // it's likely that os::Linux::initial_thread_stack_bottom is mapped and
3613     // we don't need to do anything special.
3614     // Check it first, before calling heavy function.
3615     uintptr_t stack_extent = (uintptr_t) os::Linux::initial_thread_stack_bottom();
3616     unsigned char vec[1];
3617 
3618     if (mincore((address)stack_extent, os::vm_page_size(), vec) == -1) {
3619       // Fallback to slow path on all errors, including EAGAIN
3620       stack_extent = (uintptr_t) get_stack_commited_bottom(
3621                                                            os::Linux::initial_thread_stack_bottom(),
3622                                                            (size_t)addr - stack_extent);
3623     }
3624 
3625     if (stack_extent < (uintptr_t)addr) {
3626       ::munmap((void*)stack_extent, (uintptr_t)(addr - stack_extent));
3627     }
3628   }
3629 
3630   return os::commit_memory(addr, size, !ExecMem);
3631 }
3632 
3633 // If this is a growable mapping, remove the guard pages entirely by
3634 // munmap()ping them.  If not, just call uncommit_memory(). This only
3635 // affects the main/primordial thread, but guard against future OS changes.
3636 // It's safe to always unmap guard pages for primordial thread because we
3637 // always place it right after end of the mapped region.
3638 
3639 bool os::remove_stack_guard_pages(char* addr, size_t size) {
3640   uintptr_t stack_extent, stack_base;
3641 
3642   if (os::is_primordial_thread()) {
3643     return ::munmap(addr, size) == 0;
3644   }
3645 
3646   return os::uncommit_memory(addr, size);
3647 }
3648 
3649 // If 'fixed' is true, anon_mmap() will attempt to reserve anonymous memory
3650 // at 'requested_addr'. If there are existing memory mappings at the same
3651 // location, however, they will be overwritten. If 'fixed' is false,
3652 // 'requested_addr' is only treated as a hint, the return value may or
3653 // may not start from the requested address. Unlike Linux mmap(), this
3654 // function returns NULL to indicate failure.
3655 static char* anon_mmap(char* requested_addr, size_t bytes, bool fixed) {
3656   char * addr;
3657   int flags;
3658 
3659   flags = MAP_PRIVATE | MAP_NORESERVE | MAP_ANONYMOUS;
3660   if (fixed) {
3661     assert((uintptr_t)requested_addr % os::Linux::page_size() == 0, "unaligned address");
3662     flags |= MAP_FIXED;
3663   }
3664 
3665   // Map reserved/uncommitted pages PROT_NONE so we fail early if we
3666   // touch an uncommitted page. Otherwise, the read/write might
3667   // succeed if we have enough swap space to back the physical page.
3668   addr = (char*)::mmap(requested_addr, bytes, PROT_NONE,
3669                        flags, -1, 0);
3670 
3671   return addr == MAP_FAILED ? NULL : addr;
3672 }
3673 
3674 // Allocate (using mmap, NO_RESERVE, with small pages) at either a given request address
3675 //   (req_addr != NULL) or with a given alignment.
3676 //  - bytes shall be a multiple of alignment.
3677 //  - req_addr can be NULL. If not NULL, it must be a multiple of alignment.
3678 //  - alignment sets the alignment at which memory shall be allocated.
3679 //     It must be a multiple of allocation granularity.
3680 // Returns address of memory or NULL. If req_addr was not NULL, will only return
3681 //  req_addr or NULL.
3682 static char* anon_mmap_aligned(size_t bytes, size_t alignment, char* req_addr) {
3683 
3684   size_t extra_size = bytes;
3685   if (req_addr == NULL && alignment > 0) {
3686     extra_size += alignment;
3687   }
3688 
3689   char* start = (char*) ::mmap(req_addr, extra_size, PROT_NONE,
3690     MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE,
3691     -1, 0);
3692   if (start == MAP_FAILED) {
3693     start = NULL;
3694   } else {
3695     if (req_addr != NULL) {
3696       if (start != req_addr) {
3697         ::munmap(start, extra_size);
3698         start = NULL;
3699       }
3700     } else {
3701       char* const start_aligned = align_up(start, alignment);
3702       char* const end_aligned = start_aligned + bytes;
3703       char* const end = start + extra_size;
3704       if (start_aligned > start) {
3705         ::munmap(start, start_aligned - start);
3706       }
3707       if (end_aligned < end) {
3708         ::munmap(end_aligned, end - end_aligned);
3709       }
3710       start = start_aligned;
3711     }
3712   }
3713   return start;
3714 }
3715 
3716 static int anon_munmap(char * addr, size_t size) {
3717   return ::munmap(addr, size) == 0;
3718 }
3719 
3720 char* os::pd_reserve_memory(size_t bytes, char* requested_addr,
3721                             size_t alignment_hint) {
3722   return anon_mmap(requested_addr, bytes, (requested_addr != NULL));
3723 }
3724 
3725 bool os::pd_release_memory(char* addr, size_t size) {
3726   return anon_munmap(addr, size);
3727 }
3728 
3729 #ifdef CAN_SHOW_REGISTERS_ON_ASSERT
3730 extern char* g_assert_poison; // assertion poison page address
3731 #endif
3732 
3733 static bool linux_mprotect(char* addr, size_t size, int prot) {
3734   // Linux wants the mprotect address argument to be page aligned.
3735   char* bottom = (char*)align_down((intptr_t)addr, os::Linux::page_size());
3736 
3737   // According to SUSv3, mprotect() should only be used with mappings
3738   // established by mmap(), and mmap() always maps whole pages. Unaligned
3739   // 'addr' likely indicates problem in the VM (e.g. trying to change
3740   // protection of malloc'ed or statically allocated memory). Check the
3741   // caller if you hit this assert.
3742   assert(addr == bottom, "sanity check");
3743 
3744   size = align_up(pointer_delta(addr, bottom, 1) + size, os::Linux::page_size());
3745   // Don't log anything if we're executing in the poison page signal handling
3746   // context. It can lead to reentrant use of other parts of the VM code.
3747 #ifdef CAN_SHOW_REGISTERS_ON_ASSERT
3748   if (addr != g_assert_poison)
3749 #endif
3750   Events::log(NULL, "Protecting memory [" INTPTR_FORMAT "," INTPTR_FORMAT "] with protection modes %x", p2i(bottom), p2i(bottom+size), prot);
3751   return ::mprotect(bottom, size, prot) == 0;
3752 }
3753 
3754 // Set protections specified
3755 bool os::protect_memory(char* addr, size_t bytes, ProtType prot,
3756                         bool is_committed) {
3757   unsigned int p = 0;
3758   switch (prot) {
3759   case MEM_PROT_NONE: p = PROT_NONE; break;
3760   case MEM_PROT_READ: p = PROT_READ; break;
3761   case MEM_PROT_RW:   p = PROT_READ|PROT_WRITE; break;
3762   case MEM_PROT_RWX:  p = PROT_READ|PROT_WRITE|PROT_EXEC; break;
3763   default:
3764     ShouldNotReachHere();
3765   }
3766   // is_committed is unused.
3767   return linux_mprotect(addr, bytes, p);
3768 }
3769 
3770 bool os::guard_memory(char* addr, size_t size) {
3771   return linux_mprotect(addr, size, PROT_NONE);
3772 }
3773 
3774 bool os::unguard_memory(char* addr, size_t size) {
3775   return linux_mprotect(addr, size, PROT_READ|PROT_WRITE);
3776 }
3777 
3778 bool os::Linux::transparent_huge_pages_sanity_check(bool warn,
3779                                                     size_t page_size) {
3780   bool result = false;
3781   void *p = mmap(NULL, page_size * 2, PROT_READ|PROT_WRITE,
3782                  MAP_ANONYMOUS|MAP_PRIVATE,
3783                  -1, 0);
3784   if (p != MAP_FAILED) {
3785     void *aligned_p = align_up(p, page_size);
3786 
3787     result = madvise(aligned_p, page_size, MADV_HUGEPAGE) == 0;
3788 
3789     munmap(p, page_size * 2);
3790   }
3791 
3792   if (warn && !result) {
3793     warning("TransparentHugePages is not supported by the operating system.");
3794   }
3795 
3796   return result;
3797 }
3798 
3799 bool os::Linux::hugetlbfs_sanity_check(bool warn, size_t page_size) {
3800   bool result = false;
3801   void *p = mmap(NULL, page_size, PROT_READ|PROT_WRITE,
3802                  MAP_ANONYMOUS|MAP_PRIVATE|MAP_HUGETLB,
3803                  -1, 0);
3804 
3805   if (p != MAP_FAILED) {
3806     // We don't know if this really is a huge page or not.
3807     FILE *fp = fopen("/proc/self/maps", "r");
3808     if (fp) {
3809       while (!feof(fp)) {
3810         char chars[257];
3811         long x = 0;
3812         if (fgets(chars, sizeof(chars), fp)) {
3813           if (sscanf(chars, "%lx-%*x", &x) == 1
3814               && x == (long)p) {
3815             if (strstr (chars, "hugepage")) {
3816               result = true;
3817               break;
3818             }
3819           }
3820         }
3821       }
3822       fclose(fp);
3823     }
3824     munmap(p, page_size);
3825   }
3826 
3827   if (warn && !result) {
3828     warning("HugeTLBFS is not supported by the operating system.");
3829   }
3830 
3831   return result;
3832 }
3833 
3834 // From the coredump_filter documentation:
3835 //
3836 // - (bit 0) anonymous private memory
3837 // - (bit 1) anonymous shared memory
3838 // - (bit 2) file-backed private memory
3839 // - (bit 3) file-backed shared memory
3840 // - (bit 4) ELF header pages in file-backed private memory areas (it is
3841 //           effective only if the bit 2 is cleared)
3842 // - (bit 5) hugetlb private memory
3843 // - (bit 6) hugetlb shared memory
3844 // - (bit 7) dax private memory
3845 // - (bit 8) dax shared memory
3846 //
3847 static void set_coredump_filter(CoredumpFilterBit bit) {
3848   FILE *f;
3849   long cdm;
3850 
3851   if ((f = fopen("/proc/self/coredump_filter", "r+")) == NULL) {
3852     return;
3853   }
3854 
3855   if (fscanf(f, "%lx", &cdm) != 1) {
3856     fclose(f);
3857     return;
3858   }
3859 
3860   long saved_cdm = cdm;
3861   rewind(f);
3862   cdm |= bit;
3863 
3864   if (cdm != saved_cdm) {
3865     fprintf(f, "%#lx", cdm);
3866   }
3867 
3868   fclose(f);
3869 }
3870 
3871 // Large page support
3872 
3873 static size_t _large_page_size = 0;
3874 
3875 size_t os::Linux::find_default_large_page_size() {
3876   if (_default_large_page_size != 0) {
3877     return _default_large_page_size;
3878   }
3879   size_t large_page_size = 0;
3880 
3881   // large_page_size on Linux is used to round up heap size. x86 uses either
3882   // 2M or 4M page, depending on whether PAE (Physical Address Extensions)
3883   // mode is enabled. AMD64/EM64T uses 2M page in 64bit mode. IA64 can use
3884   // page as large as 256M.
3885   //
3886   // Here we try to figure out page size by parsing /proc/meminfo and looking
3887   // for a line with the following format:
3888   //    Hugepagesize:     2048 kB
3889   //
3890   // If we can't determine the value (e.g. /proc is not mounted, or the text
3891   // format has been changed), we'll use the largest page size supported by
3892   // the processor.
3893 
3894 #ifndef ZERO
3895   large_page_size =
3896     AARCH64_ONLY(2 * M)
3897     AMD64_ONLY(2 * M)
3898     ARM32_ONLY(2 * M)
3899     IA32_ONLY(4 * M)
3900     IA64_ONLY(256 * M)
3901     PPC_ONLY(4 * M)
3902     S390_ONLY(1 * M);
3903 #endif // ZERO
3904 
3905   FILE *fp = fopen("/proc/meminfo", "r");
3906   if (fp) {
3907     while (!feof(fp)) {
3908       int x = 0;
3909       char buf[16];
3910       if (fscanf(fp, "Hugepagesize: %d", &x) == 1) {
3911         if (x && fgets(buf, sizeof(buf), fp) && strcmp(buf, " kB\n") == 0) {
3912           large_page_size = x * K;
3913           break;
3914         }
3915       } else {
3916         // skip to next line
3917         for (;;) {
3918           int ch = fgetc(fp);
3919           if (ch == EOF || ch == (int)'\n') break;
3920         }
3921       }
3922     }
3923     fclose(fp);
3924   }
3925   return large_page_size;
3926 }
3927 
3928 size_t os::Linux::find_large_page_size(size_t large_page_size) {
3929   if (_default_large_page_size == 0) {
3930     _default_large_page_size = Linux::find_default_large_page_size();
3931   }
3932   // We need to scan /sys/kernel/mm/hugepages
3933   // to discover the available page sizes
3934   const char* sys_hugepages = "/sys/kernel/mm/hugepages";
3935 
3936   DIR *dir = opendir(sys_hugepages);
3937   if (dir == NULL) {
3938     return _default_large_page_size;
3939   }
3940 
3941   struct dirent *entry;
3942   size_t page_size;
3943   while ((entry = readdir(dir)) != NULL) {
3944     if (entry->d_type == DT_DIR &&
3945         sscanf(entry->d_name, "hugepages-%zukB", &page_size) == 1) {
3946       // The kernel is using kB, hotspot uses bytes
3947       if (large_page_size == page_size * K) {
3948         closedir(dir);
3949         return large_page_size;
3950       }
3951     }
3952   }
3953   closedir(dir);
3954   return _default_large_page_size;
3955 }
3956 
3957 size_t os::Linux::setup_large_page_size() {
3958   _default_large_page_size = Linux::find_default_large_page_size();
3959 
3960   if (!FLAG_IS_DEFAULT(LargePageSizeInBytes) && LargePageSizeInBytes != _default_large_page_size ) {
3961     _large_page_size = find_large_page_size(LargePageSizeInBytes);
3962     if (_large_page_size == _default_large_page_size) {
3963       warning("Setting LargePageSizeInBytes=" SIZE_FORMAT " has no effect on this OS. Using the default large page size "
3964               SIZE_FORMAT "%s.",
3965               LargePageSizeInBytes,
3966               byte_size_in_proper_unit(_large_page_size), proper_unit_for_byte_size(_large_page_size));
3967     }
3968   } else {
3969     _large_page_size = _default_large_page_size;
3970   }
3971 
3972   const size_t default_page_size = (size_t)Linux::page_size();
3973   if (_large_page_size > default_page_size) {
3974     _page_sizes[0] = _large_page_size;
3975     _page_sizes[1] = default_page_size;
3976     _page_sizes[2] = 0;
3977   }
3978 
3979   return _large_page_size;
3980 }
3981 
3982 size_t os::Linux::default_large_page_size() {
3983   return _default_large_page_size;
3984 }
3985 
3986 bool os::Linux::setup_large_page_type(size_t page_size) {
3987   if (FLAG_IS_DEFAULT(UseHugeTLBFS) &&
3988       FLAG_IS_DEFAULT(UseSHM) &&
3989       FLAG_IS_DEFAULT(UseTransparentHugePages)) {
3990 
3991     // The type of large pages has not been specified by the user.
3992 
3993     // Try UseHugeTLBFS and then UseSHM.
3994     UseHugeTLBFS = UseSHM = true;
3995 
3996     // Don't try UseTransparentHugePages since there are known
3997     // performance issues with it turned on. This might change in the future.
3998     UseTransparentHugePages = false;
3999   }
4000 
4001   if (UseTransparentHugePages) {
4002     bool warn_on_failure = !FLAG_IS_DEFAULT(UseTransparentHugePages);
4003     if (transparent_huge_pages_sanity_check(warn_on_failure, page_size)) {
4004       UseHugeTLBFS = false;
4005       UseSHM = false;
4006       return true;
4007     }
4008     UseTransparentHugePages = false;
4009   }
4010 
4011   if (UseHugeTLBFS) {
4012     bool warn_on_failure = !FLAG_IS_DEFAULT(UseHugeTLBFS);
4013     if (hugetlbfs_sanity_check(warn_on_failure, page_size)) {
4014       UseSHM = false;
4015       return true;
4016     }
4017     UseHugeTLBFS = false;
4018   }
4019 
4020   return UseSHM;
4021 }
4022 
4023 void os::large_page_init() {
4024   if (!UseLargePages &&
4025       !UseTransparentHugePages &&
4026       !UseHugeTLBFS &&
4027       !UseSHM) {
4028     // Not using large pages.
4029     return;
4030   }
4031 
4032   if (!FLAG_IS_DEFAULT(UseLargePages) && !UseLargePages) {
4033     // The user explicitly turned off large pages.
4034     // Ignore the rest of the large pages flags.
4035     UseTransparentHugePages = false;
4036     UseHugeTLBFS = false;
4037     UseSHM = false;
4038     return;
4039   }
4040 
4041   size_t large_page_size = Linux::setup_large_page_size();
4042   UseLargePages          = Linux::setup_large_page_type(large_page_size);
4043 
4044   set_coredump_filter(LARGEPAGES_BIT);
4045 }
4046 
4047 #ifndef SHM_HUGETLB
4048   #define SHM_HUGETLB 04000
4049 #endif
4050 
4051 #define shm_warning_format(format, ...)              \
4052   do {                                               \
4053     if (UseLargePages &&                             \
4054         (!FLAG_IS_DEFAULT(UseLargePages) ||          \
4055          !FLAG_IS_DEFAULT(UseSHM) ||                 \
4056          !FLAG_IS_DEFAULT(LargePageSizeInBytes))) {  \
4057       warning(format, __VA_ARGS__);                  \
4058     }                                                \
4059   } while (0)
4060 
4061 #define shm_warning(str) shm_warning_format("%s", str)
4062 
4063 #define shm_warning_with_errno(str)                \
4064   do {                                             \
4065     int err = errno;                               \
4066     shm_warning_format(str " (error = %d)", err);  \
4067   } while (0)
4068 
4069 static char* shmat_with_alignment(int shmid, size_t bytes, size_t alignment) {
4070   assert(is_aligned(bytes, alignment), "Must be divisible by the alignment");
4071 
4072   if (!is_aligned(alignment, SHMLBA)) {
4073     assert(false, "Code below assumes that alignment is at least SHMLBA aligned");
4074     return NULL;
4075   }
4076 
4077   // To ensure that we get 'alignment' aligned memory from shmat,
4078   // we pre-reserve aligned virtual memory and then attach to that.
4079 
4080   char* pre_reserved_addr = anon_mmap_aligned(bytes, alignment, NULL);
4081   if (pre_reserved_addr == NULL) {
4082     // Couldn't pre-reserve aligned memory.
4083     shm_warning("Failed to pre-reserve aligned memory for shmat.");
4084     return NULL;
4085   }
4086 
4087   // SHM_REMAP is needed to allow shmat to map over an existing mapping.
4088   char* addr = (char*)shmat(shmid, pre_reserved_addr, SHM_REMAP);
4089 
4090   if ((intptr_t)addr == -1) {
4091     int err = errno;
4092     shm_warning_with_errno("Failed to attach shared memory.");
4093 
4094     assert(err != EACCES, "Unexpected error");
4095     assert(err != EIDRM,  "Unexpected error");
4096     assert(err != EINVAL, "Unexpected error");
4097 
4098     // Since we don't know if the kernel unmapped the pre-reserved memory area
4099     // we can't unmap it, since that would potentially unmap memory that was
4100     // mapped from other threads.
4101     return NULL;
4102   }
4103 
4104   return addr;
4105 }
4106 
4107 static char* shmat_at_address(int shmid, char* req_addr) {
4108   if (!is_aligned(req_addr, SHMLBA)) {
4109     assert(false, "Requested address needs to be SHMLBA aligned");
4110     return NULL;
4111   }
4112 
4113   char* addr = (char*)shmat(shmid, req_addr, 0);
4114 
4115   if ((intptr_t)addr == -1) {
4116     shm_warning_with_errno("Failed to attach shared memory.");
4117     return NULL;
4118   }
4119 
4120   return addr;
4121 }
4122 
4123 static char* shmat_large_pages(int shmid, size_t bytes, size_t alignment, char* req_addr) {
4124   // If a req_addr has been provided, we assume that the caller has already aligned the address.
4125   if (req_addr != NULL) {
4126     assert(is_aligned(req_addr, os::large_page_size()), "Must be divisible by the large page size");
4127     assert(is_aligned(req_addr, alignment), "Must be divisible by given alignment");
4128     return shmat_at_address(shmid, req_addr);
4129   }
4130 
4131   // Since shmid has been setup with SHM_HUGETLB, shmat will automatically
4132   // return large page size aligned memory addresses when req_addr == NULL.
4133   // However, if the alignment is larger than the large page size, we have
4134   // to manually ensure that the memory returned is 'alignment' aligned.
4135   if (alignment > os::large_page_size()) {
4136     assert(is_aligned(alignment, os::large_page_size()), "Must be divisible by the large page size");
4137     return shmat_with_alignment(shmid, bytes, alignment);
4138   } else {
4139     return shmat_at_address(shmid, NULL);
4140   }
4141 }
4142 
4143 char* os::Linux::reserve_memory_special_shm(size_t bytes, size_t alignment,
4144                                             char* req_addr, bool exec) {
4145   // "exec" is passed in but not used.  Creating the shared image for
4146   // the code cache doesn't have an SHM_X executable permission to check.
4147   assert(UseLargePages && UseSHM, "only for SHM large pages");
4148   assert(is_aligned(req_addr, os::large_page_size()), "Unaligned address");
4149   assert(is_aligned(req_addr, alignment), "Unaligned address");
4150 
4151   if (!is_aligned(bytes, os::large_page_size())) {
4152     return NULL; // Fallback to small pages.
4153   }
4154 
4155   // Create a large shared memory region to attach to based on size.
4156   // Currently, size is the total size of the heap.
4157   int shmid = shmget(IPC_PRIVATE, bytes, SHM_HUGETLB|IPC_CREAT|SHM_R|SHM_W);
4158   if (shmid == -1) {
4159     // Possible reasons for shmget failure:
4160     // 1. shmmax is too small for Java heap.
4161     //    > check shmmax value: cat /proc/sys/kernel/shmmax
4162     //    > increase shmmax value: echo "0xffffffff" > /proc/sys/kernel/shmmax
4163     // 2. not enough large page memory.
4164     //    > check available large pages: cat /proc/meminfo
4165     //    > increase amount of large pages:
4166     //          echo new_value > /proc/sys/vm/nr_hugepages
4167     //      Note 1: different Linux may use different name for this property,
4168     //            e.g. on Redhat AS-3 it is "hugetlb_pool".
4169     //      Note 2: it's possible there's enough physical memory available but
4170     //            they are so fragmented after a long run that they can't
4171     //            coalesce into large pages. Try to reserve large pages when
4172     //            the system is still "fresh".
4173     shm_warning_with_errno("Failed to reserve shared memory.");
4174     return NULL;
4175   }
4176 
4177   // Attach to the region.
4178   char* addr = shmat_large_pages(shmid, bytes, alignment, req_addr);
4179 
4180   // Remove shmid. If shmat() is successful, the actual shared memory segment
4181   // will be deleted when it's detached by shmdt() or when the process
4182   // terminates. If shmat() is not successful this will remove the shared
4183   // segment immediately.
4184   shmctl(shmid, IPC_RMID, NULL);
4185 
4186   return addr;
4187 }
4188 
4189 static void warn_on_large_pages_failure(char* req_addr, size_t bytes,
4190                                         int error) {
4191   assert(error == ENOMEM, "Only expect to fail if no memory is available");
4192 
4193   bool warn_on_failure = UseLargePages &&
4194       (!FLAG_IS_DEFAULT(UseLargePages) ||
4195        !FLAG_IS_DEFAULT(UseHugeTLBFS) ||
4196        !FLAG_IS_DEFAULT(LargePageSizeInBytes));
4197 
4198   if (warn_on_failure) {
4199     char msg[128];
4200     jio_snprintf(msg, sizeof(msg), "Failed to reserve large pages memory req_addr: "
4201                  PTR_FORMAT " bytes: " SIZE_FORMAT " (errno = %d).", req_addr, bytes, error);
4202     warning("%s", msg);
4203   }
4204 }
4205 
4206 char* os::Linux::reserve_memory_special_huge_tlbfs_only(size_t bytes,
4207                                                         char* req_addr,
4208                                                         bool exec) {
4209   assert(UseLargePages && UseHugeTLBFS, "only for Huge TLBFS large pages");
4210   assert(is_aligned(bytes, os::large_page_size()), "Unaligned size");
4211   assert(is_aligned(req_addr, os::large_page_size()), "Unaligned address");
4212 
4213   int prot = exec ? PROT_READ|PROT_WRITE|PROT_EXEC : PROT_READ|PROT_WRITE;
4214   int flags = MAP_PRIVATE|MAP_ANONYMOUS|MAP_HUGETLB;
4215 
4216   if (os::large_page_size() != default_large_page_size()) {
4217     flags |= (exact_log2(os::large_page_size()) << MAP_HUGE_SHIFT);
4218   }
4219   char* addr = (char*)::mmap(req_addr, bytes, prot, flags, -1, 0);
4220 
4221   if (addr == MAP_FAILED) {
4222     warn_on_large_pages_failure(req_addr, bytes, errno);
4223     return NULL;
4224   }
4225 
4226   assert(is_aligned(addr, os::large_page_size()), "Must be");
4227 
4228   return addr;
4229 }
4230 
4231 // Reserve memory using mmap(MAP_HUGETLB).
4232 //  - bytes shall be a multiple of alignment.
4233 //  - req_addr can be NULL. If not NULL, it must be a multiple of alignment.
4234 //  - alignment sets the alignment at which memory shall be allocated.
4235 //     It must be a multiple of allocation granularity.
4236 // Returns address of memory or NULL. If req_addr was not NULL, will only return
4237 //  req_addr or NULL.
4238 char* os::Linux::reserve_memory_special_huge_tlbfs_mixed(size_t bytes,
4239                                                          size_t alignment,
4240                                                          char* req_addr,
4241                                                          bool exec) {
4242   size_t large_page_size = os::large_page_size();
4243   assert(bytes >= large_page_size, "Shouldn't allocate large pages for small sizes");
4244 
4245   assert(is_aligned(req_addr, alignment), "Must be");
4246   assert(is_aligned(bytes, alignment), "Must be");
4247 
4248   // First reserve - but not commit - the address range in small pages.
4249   char* const start = anon_mmap_aligned(bytes, alignment, req_addr);
4250 
4251   if (start == NULL) {
4252     return NULL;
4253   }
4254 
4255   assert(is_aligned(start, alignment), "Must be");
4256 
4257   char* end = start + bytes;
4258 
4259   // Find the regions of the allocated chunk that can be promoted to large pages.
4260   char* lp_start = align_up(start, large_page_size);
4261   char* lp_end   = align_down(end, large_page_size);
4262 
4263   size_t lp_bytes = lp_end - lp_start;
4264 
4265   assert(is_aligned(lp_bytes, large_page_size), "Must be");
4266 
4267   if (lp_bytes == 0) {
4268     // The mapped region doesn't even span the start and the end of a large page.
4269     // Fall back to allocate a non-special area.
4270     ::munmap(start, end - start);
4271     return NULL;
4272   }
4273 
4274   int prot = exec ? PROT_READ|PROT_WRITE|PROT_EXEC : PROT_READ|PROT_WRITE;
4275   int flags = MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED;
4276   void* result;
4277 
4278   // Commit small-paged leading area.
4279   if (start != lp_start) {
4280     result = ::mmap(start, lp_start - start, prot, flags, -1, 0);
4281     if (result == MAP_FAILED) {
4282       ::munmap(lp_start, end - lp_start);
4283       return NULL;
4284     }
4285   }
4286 
4287   // Commit large-paged area.
4288   flags |= MAP_HUGETLB;
4289 
4290   if (os::large_page_size() != default_large_page_size()) {
4291     flags |= (exact_log2(os::large_page_size()) << MAP_HUGE_SHIFT);
4292   }
4293 
4294   result = ::mmap(lp_start, lp_bytes, prot, flags, -1, 0);
4295   if (result == MAP_FAILED) {
4296     warn_on_large_pages_failure(lp_start, lp_bytes, errno);
4297     // If the mmap above fails, the large pages region will be unmapped and we
4298     // have regions before and after with small pages. Release these regions.
4299     //
4300     // |  mapped  |  unmapped  |  mapped  |
4301     // ^          ^            ^          ^
4302     // start      lp_start     lp_end     end
4303     //
4304     ::munmap(start, lp_start - start);
4305     ::munmap(lp_end, end - lp_end);
4306     return NULL;
4307   }
4308 
4309   // Commit small-paged trailing area.
4310   if (lp_end != end) {
4311     result = ::mmap(lp_end, end - lp_end, prot,
4312                     MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED,
4313                     -1, 0);
4314     if (result == MAP_FAILED) {
4315       ::munmap(start, lp_end - start);
4316       return NULL;
4317     }
4318   }
4319 
4320   return start;
4321 }
4322 
4323 char* os::Linux::reserve_memory_special_huge_tlbfs(size_t bytes,
4324                                                    size_t alignment,
4325                                                    char* req_addr,
4326                                                    bool exec) {
4327   assert(UseLargePages && UseHugeTLBFS, "only for Huge TLBFS large pages");
4328   assert(is_aligned(req_addr, alignment), "Must be");
4329   assert(is_aligned(alignment, os::vm_allocation_granularity()), "Must be");
4330   assert(is_power_of_2(os::large_page_size()), "Must be");
4331   assert(bytes >= os::large_page_size(), "Shouldn't allocate large pages for small sizes");
4332 
4333   if (is_aligned(bytes, os::large_page_size()) && alignment <= os::large_page_size()) {
4334     return reserve_memory_special_huge_tlbfs_only(bytes, req_addr, exec);
4335   } else {
4336     return reserve_memory_special_huge_tlbfs_mixed(bytes, alignment, req_addr, exec);
4337   }
4338 }
4339 
4340 char* os::pd_reserve_memory_special(size_t bytes, size_t alignment,
4341                                     char* req_addr, bool exec) {
4342   assert(UseLargePages, "only for large pages");
4343 
4344   char* addr;
4345   if (UseSHM) {
4346     addr = os::Linux::reserve_memory_special_shm(bytes, alignment, req_addr, exec);
4347   } else {
4348     assert(UseHugeTLBFS, "must be");
4349     addr = os::Linux::reserve_memory_special_huge_tlbfs(bytes, alignment, req_addr, exec);
4350   }
4351 
4352   if (addr != NULL) {
4353     if (UseNUMAInterleaving) {
4354       numa_make_global(addr, bytes);
4355     }
4356   }
4357 
4358   return addr;
4359 }
4360 
4361 bool os::Linux::release_memory_special_shm(char* base, size_t bytes) {
4362   // detaching the SHM segment will also delete it, see reserve_memory_special_shm()
4363   return shmdt(base) == 0;
4364 }
4365 
4366 bool os::Linux::release_memory_special_huge_tlbfs(char* base, size_t bytes) {
4367   return pd_release_memory(base, bytes);
4368 }
4369 
4370 bool os::pd_release_memory_special(char* base, size_t bytes) {
4371   assert(UseLargePages, "only for large pages");
4372   bool res;
4373 
4374   if (UseSHM) {
4375     res = os::Linux::release_memory_special_shm(base, bytes);
4376   } else {
4377     assert(UseHugeTLBFS, "must be");
4378     res = os::Linux::release_memory_special_huge_tlbfs(base, bytes);
4379   }
4380   return res;
4381 }
4382 
4383 size_t os::large_page_size() {
4384   return _large_page_size;
4385 }
4386 
4387 // With SysV SHM the entire memory region must be allocated as shared
4388 // memory.
4389 // HugeTLBFS allows application to commit large page memory on demand.
4390 // However, when committing memory with HugeTLBFS fails, the region
4391 // that was supposed to be committed will lose the old reservation
4392 // and allow other threads to steal that memory region. Because of this
4393 // behavior we can't commit HugeTLBFS memory.
4394 bool os::can_commit_large_page_memory() {
4395   return UseTransparentHugePages;
4396 }
4397 
4398 bool os::can_execute_large_page_memory() {
4399   return UseTransparentHugePages || UseHugeTLBFS;
4400 }
4401 
4402 char* os::pd_attempt_reserve_memory_at(size_t bytes, char* requested_addr, int file_desc) {
4403   assert(file_desc >= 0, "file_desc is not valid");
4404   char* result = pd_attempt_reserve_memory_at(bytes, requested_addr);
4405   if (result != NULL) {
4406     if (replace_existing_mapping_with_file_mapping(result, bytes, file_desc) == NULL) {
4407       vm_exit_during_initialization(err_msg("Error in mapping Java heap at the given filesystem directory"));
4408     }
4409   }
4410   return result;
4411 }
4412 
4413 // Reserve memory at an arbitrary address, only if that area is
4414 // available (and not reserved for something else).
4415 
4416 char* os::pd_attempt_reserve_memory_at(size_t bytes, char* requested_addr) {
4417   // Assert only that the size is a multiple of the page size, since
4418   // that's all that mmap requires, and since that's all we really know
4419   // about at this low abstraction level.  If we need higher alignment,
4420   // we can either pass an alignment to this method or verify alignment
4421   // in one of the methods further up the call chain.  See bug 5044738.
4422   assert(bytes % os::vm_page_size() == 0, "reserving unexpected size block");
4423 
4424   // Repeatedly allocate blocks until the block is allocated at the
4425   // right spot.
4426 
4427   // Linux mmap allows caller to pass an address as hint; give it a try first,
4428   // if kernel honors the hint then we can return immediately.
4429   char * addr = anon_mmap(requested_addr, bytes, false);
4430   if (addr == requested_addr) {
4431     return requested_addr;
4432   }
4433 
4434   if (addr != NULL) {
4435     // mmap() is successful but it fails to reserve at the requested address
4436     anon_munmap(addr, bytes);
4437   }
4438 
4439   return NULL;
4440 }
4441 
4442 // Sleep forever; naked call to OS-specific sleep; use with CAUTION
4443 void os::infinite_sleep() {
4444   while (true) {    // sleep forever ...
4445     ::sleep(100);   // ... 100 seconds at a time
4446   }
4447 }
4448 
4449 // Used to convert frequent JVM_Yield() to nops
4450 bool os::dont_yield() {
4451   return DontYieldALot;
4452 }
4453 
4454 // Linux CFS scheduler (since 2.6.23) does not guarantee sched_yield(2) will
4455 // actually give up the CPU. Since skip buddy (v2.6.28):
4456 //
4457 // * Sets the yielding task as skip buddy for current CPU's run queue.
4458 // * Picks next from run queue, if empty, picks a skip buddy (can be the yielding task).
4459 // * Clears skip buddies for this run queue (yielding task no longer a skip buddy).
4460 //
4461 // An alternative is calling os::naked_short_nanosleep with a small number to avoid
4462 // getting re-scheduled immediately.
4463 //
4464 void os::naked_yield() {
4465   sched_yield();
4466 }
4467 
4468 ////////////////////////////////////////////////////////////////////////////////
4469 // thread priority support
4470 
4471 // Note: Normal Linux applications are run with SCHED_OTHER policy. SCHED_OTHER
4472 // only supports dynamic priority, static priority must be zero. For real-time
4473 // applications, Linux supports SCHED_RR which allows static priority (1-99).
4474 // However, for large multi-threaded applications, SCHED_RR is not only slower
4475 // than SCHED_OTHER, but also very unstable (my volano tests hang hard 4 out
4476 // of 5 runs - Sep 2005).
4477 //
4478 // The following code actually changes the niceness of kernel-thread/LWP. It
4479 // has an assumption that setpriority() only modifies one kernel-thread/LWP,
4480 // not the entire user process, and user level threads are 1:1 mapped to kernel
4481 // threads. It has always been the case, but could change in the future. For
4482 // this reason, the code should not be used as default (ThreadPriorityPolicy=0).
4483 // It is only used when ThreadPriorityPolicy=1 and may require system level permission
4484 // (e.g., root privilege or CAP_SYS_NICE capability).
4485 
4486 int os::java_to_os_priority[CriticalPriority + 1] = {
4487   19,              // 0 Entry should never be used
4488 
4489    4,              // 1 MinPriority
4490    3,              // 2
4491    2,              // 3
4492 
4493    1,              // 4
4494    0,              // 5 NormPriority
4495   -1,              // 6
4496 
4497   -2,              // 7
4498   -3,              // 8
4499   -4,              // 9 NearMaxPriority
4500 
4501   -5,              // 10 MaxPriority
4502 
4503   -5               // 11 CriticalPriority
4504 };
4505 
4506 static int prio_init() {
4507   if (ThreadPriorityPolicy == 1) {
4508     if (geteuid() != 0) {
4509       if (!FLAG_IS_DEFAULT(ThreadPriorityPolicy) && !FLAG_IS_JIMAGE_RESOURCE(ThreadPriorityPolicy)) {
4510         warning("-XX:ThreadPriorityPolicy=1 may require system level permission, " \
4511                 "e.g., being the root user. If the necessary permission is not " \
4512                 "possessed, changes to priority will be silently ignored.");
4513       }
4514     }
4515   }
4516   if (UseCriticalJavaThreadPriority) {
4517     os::java_to_os_priority[MaxPriority] = os::java_to_os_priority[CriticalPriority];
4518   }
4519   return 0;
4520 }
4521 
4522 OSReturn os::set_native_priority(Thread* thread, int newpri) {
4523   if (!UseThreadPriorities || ThreadPriorityPolicy == 0) return OS_OK;
4524 
4525   int ret = setpriority(PRIO_PROCESS, thread->osthread()->thread_id(), newpri);
4526   return (ret == 0) ? OS_OK : OS_ERR;
4527 }
4528 
4529 OSReturn os::get_native_priority(const Thread* const thread,
4530                                  int *priority_ptr) {
4531   if (!UseThreadPriorities || ThreadPriorityPolicy == 0) {
4532     *priority_ptr = java_to_os_priority[NormPriority];
4533     return OS_OK;
4534   }
4535 
4536   errno = 0;
4537   *priority_ptr = getpriority(PRIO_PROCESS, thread->osthread()->thread_id());
4538   return (*priority_ptr != -1 || errno == 0 ? OS_OK : OS_ERR);
4539 }
4540 
4541 ////////////////////////////////////////////////////////////////////////////////
4542 // suspend/resume support
4543 
4544 //  The low-level signal-based suspend/resume support is a remnant from the
4545 //  old VM-suspension that used to be for java-suspension, safepoints etc,
4546 //  within hotspot. Currently used by JFR's OSThreadSampler
4547 //
4548 //  The remaining code is greatly simplified from the more general suspension
4549 //  code that used to be used.
4550 //
4551 //  The protocol is quite simple:
4552 //  - suspend:
4553 //      - sends a signal to the target thread
4554 //      - polls the suspend state of the osthread using a yield loop
4555 //      - target thread signal handler (SR_handler) sets suspend state
4556 //        and blocks in sigsuspend until continued
4557 //  - resume:
4558 //      - sets target osthread state to continue
4559 //      - sends signal to end the sigsuspend loop in the SR_handler
4560 //
4561 //  Note that the SR_lock plays no role in this suspend/resume protocol,
4562 //  but is checked for NULL in SR_handler as a thread termination indicator.
4563 //  The SR_lock is, however, used by JavaThread::java_suspend()/java_resume() APIs.
4564 //
4565 //  Note that resume_clear_context() and suspend_save_context() are needed
4566 //  by SR_handler(), so that fetch_frame_from_context() works,
4567 //  which in part is used by:
4568 //    - Forte Analyzer: AsyncGetCallTrace()
4569 //    - StackBanging: get_frame_at_stack_banging_point()
4570 
4571 static void resume_clear_context(OSThread *osthread) {
4572   osthread->set_ucontext(NULL);
4573   osthread->set_siginfo(NULL);
4574 }
4575 
4576 static void suspend_save_context(OSThread *osthread, siginfo_t* siginfo,
4577                                  ucontext_t* context) {
4578   osthread->set_ucontext(context);
4579   osthread->set_siginfo(siginfo);
4580 }
4581 
4582 // Handler function invoked when a thread's execution is suspended or
4583 // resumed. We have to be careful that only async-safe functions are
4584 // called here (Note: most pthread functions are not async safe and
4585 // should be avoided.)
4586 //
4587 // Note: sigwait() is a more natural fit than sigsuspend() from an
4588 // interface point of view, but sigwait() prevents the signal hander
4589 // from being run. libpthread would get very confused by not having
4590 // its signal handlers run and prevents sigwait()'s use with the
4591 // mutex granting granting signal.
4592 //
4593 // Currently only ever called on the VMThread and JavaThreads (PC sampling)
4594 //
4595 static void SR_handler(int sig, siginfo_t* siginfo, ucontext_t* context) {
4596   // Save and restore errno to avoid confusing native code with EINTR
4597   // after sigsuspend.
4598   int old_errno = errno;
4599 
4600   Thread* thread = Thread::current_or_null_safe();
4601   assert(thread != NULL, "Missing current thread in SR_handler");
4602 
4603   // On some systems we have seen signal delivery get "stuck" until the signal
4604   // mask is changed as part of thread termination. Check that the current thread
4605   // has not already terminated (via SR_lock()) - else the following assertion
4606   // will fail because the thread is no longer a JavaThread as the ~JavaThread
4607   // destructor has completed.
4608 
4609   if (thread->SR_lock() == NULL) {
4610     return;
4611   }
4612 
4613   assert(thread->is_VM_thread() || thread->is_Java_thread(), "Must be VMThread or JavaThread");
4614 
4615   OSThread* osthread = thread->osthread();
4616 
4617   os::SuspendResume::State current = osthread->sr.state();
4618   if (current == os::SuspendResume::SR_SUSPEND_REQUEST) {
4619     suspend_save_context(osthread, siginfo, context);
4620 
4621     // attempt to switch the state, we assume we had a SUSPEND_REQUEST
4622     os::SuspendResume::State state = osthread->sr.suspended();
4623     if (state == os::SuspendResume::SR_SUSPENDED) {
4624       sigset_t suspend_set;  // signals for sigsuspend()
4625       sigemptyset(&suspend_set);
4626       // get current set of blocked signals and unblock resume signal
4627       pthread_sigmask(SIG_BLOCK, NULL, &suspend_set);
4628       sigdelset(&suspend_set, SR_signum);
4629 
4630       sr_semaphore.signal();
4631       // wait here until we are resumed
4632       while (1) {
4633         sigsuspend(&suspend_set);
4634 
4635         os::SuspendResume::State result = osthread->sr.running();
4636         if (result == os::SuspendResume::SR_RUNNING) {
4637           sr_semaphore.signal();
4638           break;
4639         }
4640       }
4641 
4642     } else if (state == os::SuspendResume::SR_RUNNING) {
4643       // request was cancelled, continue
4644     } else {
4645       ShouldNotReachHere();
4646     }
4647 
4648     resume_clear_context(osthread);
4649   } else if (current == os::SuspendResume::SR_RUNNING) {
4650     // request was cancelled, continue
4651   } else if (current == os::SuspendResume::SR_WAKEUP_REQUEST) {
4652     // ignore
4653   } else {
4654     // ignore
4655   }
4656 
4657   errno = old_errno;
4658 }
4659 
4660 static int SR_initialize() {
4661   struct sigaction act;
4662   char *s;
4663 
4664   // Get signal number to use for suspend/resume
4665   if ((s = ::getenv("_JAVA_SR_SIGNUM")) != 0) {
4666     int sig = ::strtol(s, 0, 10);
4667     if (sig > MAX2(SIGSEGV, SIGBUS) &&  // See 4355769.
4668         sig < NSIG) {                   // Must be legal signal and fit into sigflags[].
4669       SR_signum = sig;
4670     } else {
4671       warning("You set _JAVA_SR_SIGNUM=%d. It must be in range [%d, %d]. Using %d instead.",
4672               sig, MAX2(SIGSEGV, SIGBUS)+1, NSIG-1, SR_signum);
4673     }
4674   }
4675 
4676   assert(SR_signum > SIGSEGV && SR_signum > SIGBUS,
4677          "SR_signum must be greater than max(SIGSEGV, SIGBUS), see 4355769");
4678 
4679   sigemptyset(&SR_sigset);
4680   sigaddset(&SR_sigset, SR_signum);
4681 
4682   // Set up signal handler for suspend/resume
4683   act.sa_flags = SA_RESTART|SA_SIGINFO;
4684   act.sa_handler = (void (*)(int)) SR_handler;
4685 
4686   // SR_signum is blocked by default.
4687   // 4528190 - We also need to block pthread restart signal (32 on all
4688   // supported Linux platforms). Note that LinuxThreads need to block
4689   // this signal for all threads to work properly. So we don't have
4690   // to use hard-coded signal number when setting up the mask.
4691   pthread_sigmask(SIG_BLOCK, NULL, &act.sa_mask);
4692 
4693   if (sigaction(SR_signum, &act, 0) == -1) {
4694     return -1;
4695   }
4696 
4697   // Save signal flag
4698   os::Linux::set_our_sigflags(SR_signum, act.sa_flags);
4699   return 0;
4700 }
4701 
4702 static int sr_notify(OSThread* osthread) {
4703   int status = pthread_kill(osthread->pthread_id(), SR_signum);
4704   assert_status(status == 0, status, "pthread_kill");
4705   return status;
4706 }
4707 
4708 // "Randomly" selected value for how long we want to spin
4709 // before bailing out on suspending a thread, also how often
4710 // we send a signal to a thread we want to resume
4711 static const int RANDOMLY_LARGE_INTEGER = 1000000;
4712 static const int RANDOMLY_LARGE_INTEGER2 = 100;
4713 
4714 // returns true on success and false on error - really an error is fatal
4715 // but this seems the normal response to library errors
4716 static bool do_suspend(OSThread* osthread) {
4717   assert(osthread->sr.is_running(), "thread should be running");
4718   assert(!sr_semaphore.trywait(), "semaphore has invalid state");
4719 
4720   // mark as suspended and send signal
4721   if (osthread->sr.request_suspend() != os::SuspendResume::SR_SUSPEND_REQUEST) {
4722     // failed to switch, state wasn't running?
4723     ShouldNotReachHere();
4724     return false;
4725   }
4726 
4727   if (sr_notify(osthread) != 0) {
4728     ShouldNotReachHere();
4729   }
4730 
4731   // managed to send the signal and switch to SUSPEND_REQUEST, now wait for SUSPENDED
4732   while (true) {
4733     if (sr_semaphore.timedwait(2)) {
4734       break;
4735     } else {
4736       // timeout
4737       os::SuspendResume::State cancelled = osthread->sr.cancel_suspend();
4738       if (cancelled == os::SuspendResume::SR_RUNNING) {
4739         return false;
4740       } else if (cancelled == os::SuspendResume::SR_SUSPENDED) {
4741         // make sure that we consume the signal on the semaphore as well
4742         sr_semaphore.wait();
4743         break;
4744       } else {
4745         ShouldNotReachHere();
4746         return false;
4747       }
4748     }
4749   }
4750 
4751   guarantee(osthread->sr.is_suspended(), "Must be suspended");
4752   return true;
4753 }
4754 
4755 static void do_resume(OSThread* osthread) {
4756   assert(osthread->sr.is_suspended(), "thread should be suspended");
4757   assert(!sr_semaphore.trywait(), "invalid semaphore state");
4758 
4759   if (osthread->sr.request_wakeup() != os::SuspendResume::SR_WAKEUP_REQUEST) {
4760     // failed to switch to WAKEUP_REQUEST
4761     ShouldNotReachHere();
4762     return;
4763   }
4764 
4765   while (true) {
4766     if (sr_notify(osthread) == 0) {
4767       if (sr_semaphore.timedwait(2)) {
4768         if (osthread->sr.is_running()) {
4769           return;
4770         }
4771       }
4772     } else {
4773       ShouldNotReachHere();
4774     }
4775   }
4776 
4777   guarantee(osthread->sr.is_running(), "Must be running!");
4778 }
4779 
4780 ///////////////////////////////////////////////////////////////////////////////////
4781 // signal handling (except suspend/resume)
4782 
4783 // This routine may be used by user applications as a "hook" to catch signals.
4784 // The user-defined signal handler must pass unrecognized signals to this
4785 // routine, and if it returns true (non-zero), then the signal handler must
4786 // return immediately.  If the flag "abort_if_unrecognized" is true, then this
4787 // routine will never retun false (zero), but instead will execute a VM panic
4788 // routine kill the process.
4789 //
4790 // If this routine returns false, it is OK to call it again.  This allows
4791 // the user-defined signal handler to perform checks either before or after
4792 // the VM performs its own checks.  Naturally, the user code would be making
4793 // a serious error if it tried to handle an exception (such as a null check
4794 // or breakpoint) that the VM was generating for its own correct operation.
4795 //
4796 // This routine may recognize any of the following kinds of signals:
4797 //    SIGBUS, SIGSEGV, SIGILL, SIGFPE, SIGQUIT, SIGPIPE, SIGXFSZ, SIGUSR1.
4798 // It should be consulted by handlers for any of those signals.
4799 //
4800 // The caller of this routine must pass in the three arguments supplied
4801 // to the function referred to in the "sa_sigaction" (not the "sa_handler")
4802 // field of the structure passed to sigaction().  This routine assumes that
4803 // the sa_flags field passed to sigaction() includes SA_SIGINFO and SA_RESTART.
4804 //
4805 // Note that the VM will print warnings if it detects conflicting signal
4806 // handlers, unless invoked with the option "-XX:+AllowUserSignalHandlers".
4807 //
4808 extern "C" JNIEXPORT int JVM_handle_linux_signal(int signo,
4809                                                  siginfo_t* siginfo,
4810                                                  void* ucontext,
4811                                                  int abort_if_unrecognized);
4812 
4813 static void signalHandler(int sig, siginfo_t* info, void* uc) {
4814   assert(info != NULL && uc != NULL, "it must be old kernel");
4815   int orig_errno = errno;  // Preserve errno value over signal handler.
4816   JVM_handle_linux_signal(sig, info, uc, true);
4817   errno = orig_errno;
4818 }
4819 
4820 
4821 // This boolean allows users to forward their own non-matching signals
4822 // to JVM_handle_linux_signal, harmlessly.
4823 bool os::Linux::signal_handlers_are_installed = false;
4824 
4825 // For signal-chaining
4826 bool os::Linux::libjsig_is_loaded = false;
4827 typedef struct sigaction *(*get_signal_t)(int);
4828 get_signal_t os::Linux::get_signal_action = NULL;
4829 
4830 struct sigaction* os::Linux::get_chained_signal_action(int sig) {
4831   struct sigaction *actp = NULL;
4832 
4833   if (libjsig_is_loaded) {
4834     // Retrieve the old signal handler from libjsig
4835     actp = (*get_signal_action)(sig);
4836   }
4837   if (actp == NULL) {
4838     // Retrieve the preinstalled signal handler from jvm
4839     actp = os::Posix::get_preinstalled_handler(sig);
4840   }
4841 
4842   return actp;
4843 }
4844 
4845 static bool call_chained_handler(struct sigaction *actp, int sig,
4846                                  siginfo_t *siginfo, void *context) {
4847   // Call the old signal handler
4848   if (actp->sa_handler == SIG_DFL) {
4849     // It's more reasonable to let jvm treat it as an unexpected exception
4850     // instead of taking the default action.
4851     return false;
4852   } else if (actp->sa_handler != SIG_IGN) {
4853     if ((actp->sa_flags & SA_NODEFER) == 0) {
4854       // automaticlly block the signal
4855       sigaddset(&(actp->sa_mask), sig);
4856     }
4857 
4858     sa_handler_t hand = NULL;
4859     sa_sigaction_t sa = NULL;
4860     bool siginfo_flag_set = (actp->sa_flags & SA_SIGINFO) != 0;
4861     // retrieve the chained handler
4862     if (siginfo_flag_set) {
4863       sa = actp->sa_sigaction;
4864     } else {
4865       hand = actp->sa_handler;
4866     }
4867 
4868     if ((actp->sa_flags & SA_RESETHAND) != 0) {
4869       actp->sa_handler = SIG_DFL;
4870     }
4871 
4872     // try to honor the signal mask
4873     sigset_t oset;
4874     sigemptyset(&oset);
4875     pthread_sigmask(SIG_SETMASK, &(actp->sa_mask), &oset);
4876 
4877     // call into the chained handler
4878     if (siginfo_flag_set) {
4879       (*sa)(sig, siginfo, context);
4880     } else {
4881       (*hand)(sig);
4882     }
4883 
4884     // restore the signal mask
4885     pthread_sigmask(SIG_SETMASK, &oset, NULL);
4886   }
4887   // Tell jvm's signal handler the signal is taken care of.
4888   return true;
4889 }
4890 
4891 bool os::Linux::chained_handler(int sig, siginfo_t* siginfo, void* context) {
4892   bool chained = false;
4893   // signal-chaining
4894   if (UseSignalChaining) {
4895     struct sigaction *actp = get_chained_signal_action(sig);
4896     if (actp != NULL) {
4897       chained = call_chained_handler(actp, sig, siginfo, context);
4898     }
4899   }
4900   return chained;
4901 }
4902 
4903 // for diagnostic
4904 int sigflags[NSIG];
4905 
4906 int os::Linux::get_our_sigflags(int sig) {
4907   assert(sig > 0 && sig < NSIG, "vm signal out of expected range");
4908   return sigflags[sig];
4909 }
4910 
4911 void os::Linux::set_our_sigflags(int sig, int flags) {
4912   assert(sig > 0 && sig < NSIG, "vm signal out of expected range");
4913   if (sig > 0 && sig < NSIG) {
4914     sigflags[sig] = flags;
4915   }
4916 }
4917 
4918 void os::Linux::set_signal_handler(int sig, bool set_installed) {
4919   // Check for overwrite.
4920   struct sigaction oldAct;
4921   sigaction(sig, (struct sigaction*)NULL, &oldAct);
4922 
4923   void* oldhand = oldAct.sa_sigaction
4924                 ? CAST_FROM_FN_PTR(void*,  oldAct.sa_sigaction)
4925                 : CAST_FROM_FN_PTR(void*,  oldAct.sa_handler);
4926   if (oldhand != CAST_FROM_FN_PTR(void*, SIG_DFL) &&
4927       oldhand != CAST_FROM_FN_PTR(void*, SIG_IGN) &&
4928       oldhand != CAST_FROM_FN_PTR(void*, (sa_sigaction_t)signalHandler)) {
4929     if (AllowUserSignalHandlers || !set_installed) {
4930       // Do not overwrite; user takes responsibility to forward to us.
4931       return;
4932     } else if (UseSignalChaining) {
4933       // save the old handler in jvm
4934       os::Posix::save_preinstalled_handler(sig, oldAct);
4935       // libjsig also interposes the sigaction() call below and saves the
4936       // old sigaction on it own.
4937     } else {
4938       fatal("Encountered unexpected pre-existing sigaction handler "
4939             "%#lx for signal %d.", (long)oldhand, sig);
4940     }
4941   }
4942 
4943   struct sigaction sigAct;
4944   sigfillset(&(sigAct.sa_mask));
4945   sigAct.sa_handler = SIG_DFL;
4946   if (!set_installed) {
4947     sigAct.sa_flags = SA_SIGINFO|SA_RESTART;
4948   } else {
4949     sigAct.sa_sigaction = signalHandler;
4950     sigAct.sa_flags = SA_SIGINFO|SA_RESTART;
4951   }
4952   // Save flags, which are set by ours
4953   assert(sig > 0 && sig < NSIG, "vm signal out of expected range");
4954   sigflags[sig] = sigAct.sa_flags;
4955 
4956   int ret = sigaction(sig, &sigAct, &oldAct);
4957   assert(ret == 0, "check");
4958 
4959   void* oldhand2  = oldAct.sa_sigaction
4960                   ? CAST_FROM_FN_PTR(void*, oldAct.sa_sigaction)
4961                   : CAST_FROM_FN_PTR(void*, oldAct.sa_handler);
4962   assert(oldhand2 == oldhand, "no concurrent signal handler installation");
4963 }
4964 
4965 // install signal handlers for signals that HotSpot needs to
4966 // handle in order to support Java-level exception handling.
4967 
4968 void os::Linux::install_signal_handlers() {
4969   if (!signal_handlers_are_installed) {
4970     signal_handlers_are_installed = true;
4971 
4972     // signal-chaining
4973     typedef void (*signal_setting_t)();
4974     signal_setting_t begin_signal_setting = NULL;
4975     signal_setting_t end_signal_setting = NULL;
4976     begin_signal_setting = CAST_TO_FN_PTR(signal_setting_t,
4977                                           dlsym(RTLD_DEFAULT, "JVM_begin_signal_setting"));
4978     if (begin_signal_setting != NULL) {
4979       end_signal_setting = CAST_TO_FN_PTR(signal_setting_t,
4980                                           dlsym(RTLD_DEFAULT, "JVM_end_signal_setting"));
4981       get_signal_action = CAST_TO_FN_PTR(get_signal_t,
4982                                          dlsym(RTLD_DEFAULT, "JVM_get_signal_action"));
4983       libjsig_is_loaded = true;
4984       assert(UseSignalChaining, "should enable signal-chaining");
4985     }
4986     if (libjsig_is_loaded) {
4987       // Tell libjsig jvm is setting signal handlers
4988       (*begin_signal_setting)();
4989     }
4990 
4991     set_signal_handler(SIGSEGV, true);
4992     set_signal_handler(SIGPIPE, true);
4993     set_signal_handler(SIGBUS, true);
4994     set_signal_handler(SIGILL, true);
4995     set_signal_handler(SIGFPE, true);
4996 #if defined(PPC64)
4997     set_signal_handler(SIGTRAP, true);
4998 #endif
4999     set_signal_handler(SIGXFSZ, true);
5000 
5001     if (libjsig_is_loaded) {
5002       // Tell libjsig jvm finishes setting signal handlers
5003       (*end_signal_setting)();
5004     }
5005 
5006     // We don't activate signal checker if libjsig is in place, we trust ourselves
5007     // and if UserSignalHandler is installed all bets are off.
5008     // Log that signal checking is off only if -verbose:jni is specified.
5009     if (CheckJNICalls) {
5010       if (libjsig_is_loaded) {
5011         log_debug(jni, resolve)("Info: libjsig is activated, all active signal checking is disabled");
5012         check_signals = false;
5013       }
5014       if (AllowUserSignalHandlers) {
5015         log_debug(jni, resolve)("Info: AllowUserSignalHandlers is activated, all active signal checking is disabled");
5016         check_signals = false;
5017       }
5018     }
5019   }
5020 }
5021 
5022 // This is the fastest way to get thread cpu time on Linux.
5023 // Returns cpu time (user+sys) for any thread, not only for current.
5024 // POSIX compliant clocks are implemented in the kernels 2.6.16+.
5025 // It might work on 2.6.10+ with a special kernel/glibc patch.
5026 // For reference, please, see IEEE Std 1003.1-2004:
5027 //   http://www.unix.org/single_unix_specification
5028 
5029 jlong os::Linux::fast_thread_cpu_time(clockid_t clockid) {
5030   struct timespec tp;
5031   int rc = os::Posix::clock_gettime(clockid, &tp);
5032   assert(rc == 0, "clock_gettime is expected to return 0 code");
5033 
5034   return (tp.tv_sec * NANOSECS_PER_SEC) + tp.tv_nsec;
5035 }
5036 
5037 /////
5038 // glibc on Linux platform uses non-documented flag
5039 // to indicate, that some special sort of signal
5040 // trampoline is used.
5041 // We will never set this flag, and we should
5042 // ignore this flag in our diagnostic
5043 #ifdef SIGNIFICANT_SIGNAL_MASK
5044   #undef SIGNIFICANT_SIGNAL_MASK
5045 #endif
5046 #define SIGNIFICANT_SIGNAL_MASK (~0x04000000)
5047 
5048 static const char* get_signal_handler_name(address handler,
5049                                            char* buf, int buflen) {
5050   int offset = 0;
5051   bool found = os::dll_address_to_library_name(handler, buf, buflen, &offset);
5052   if (found) {
5053     // skip directory names
5054     const char *p1, *p2;
5055     p1 = buf;
5056     size_t len = strlen(os::file_separator());
5057     while ((p2 = strstr(p1, os::file_separator())) != NULL) p1 = p2 + len;
5058     jio_snprintf(buf, buflen, "%s+0x%x", p1, offset);
5059   } else {
5060     jio_snprintf(buf, buflen, PTR_FORMAT, handler);
5061   }
5062   return buf;
5063 }
5064 
5065 static void print_signal_handler(outputStream* st, int sig,
5066                                  char* buf, size_t buflen) {
5067   struct sigaction sa;
5068 
5069   sigaction(sig, NULL, &sa);
5070 
5071   // See comment for SIGNIFICANT_SIGNAL_MASK define
5072   sa.sa_flags &= SIGNIFICANT_SIGNAL_MASK;
5073 
5074   st->print("%s: ", os::exception_name(sig, buf, buflen));
5075 
5076   address handler = (sa.sa_flags & SA_SIGINFO)
5077     ? CAST_FROM_FN_PTR(address, sa.sa_sigaction)
5078     : CAST_FROM_FN_PTR(address, sa.sa_handler);
5079 
5080   if (handler == CAST_FROM_FN_PTR(address, SIG_DFL)) {
5081     st->print("SIG_DFL");
5082   } else if (handler == CAST_FROM_FN_PTR(address, SIG_IGN)) {
5083     st->print("SIG_IGN");
5084   } else {
5085     st->print("[%s]", get_signal_handler_name(handler, buf, buflen));
5086   }
5087 
5088   st->print(", sa_mask[0]=");
5089   os::Posix::print_signal_set_short(st, &sa.sa_mask);
5090 
5091   address rh = VMError::get_resetted_sighandler(sig);
5092   // May be, handler was resetted by VMError?
5093   if (rh != NULL) {
5094     handler = rh;
5095     sa.sa_flags = VMError::get_resetted_sigflags(sig) & SIGNIFICANT_SIGNAL_MASK;
5096   }
5097 
5098   st->print(", sa_flags=");
5099   os::Posix::print_sa_flags(st, sa.sa_flags);
5100 
5101   // Check: is it our handler?
5102   if (handler == CAST_FROM_FN_PTR(address, (sa_sigaction_t)signalHandler) ||
5103       handler == CAST_FROM_FN_PTR(address, (sa_sigaction_t)SR_handler)) {
5104     // It is our signal handler
5105     // check for flags, reset system-used one!
5106     if ((int)sa.sa_flags != os::Linux::get_our_sigflags(sig)) {
5107       st->print(
5108                 ", flags was changed from " PTR32_FORMAT ", consider using jsig library",
5109                 os::Linux::get_our_sigflags(sig));
5110     }
5111   }
5112   st->cr();
5113 }
5114 
5115 
5116 #define DO_SIGNAL_CHECK(sig)                      \
5117   do {                                            \
5118     if (!sigismember(&check_signal_done, sig)) {  \
5119       os::Linux::check_signal_handler(sig);       \
5120     }                                             \
5121   } while (0)
5122 
5123 // This method is a periodic task to check for misbehaving JNI applications
5124 // under CheckJNI, we can add any periodic checks here
5125 
5126 void os::run_periodic_checks() {
5127   if (check_signals == false) return;
5128 
5129   // SEGV and BUS if overridden could potentially prevent
5130   // generation of hs*.log in the event of a crash, debugging
5131   // such a case can be very challenging, so we absolutely
5132   // check the following for a good measure:
5133   DO_SIGNAL_CHECK(SIGSEGV);
5134   DO_SIGNAL_CHECK(SIGILL);
5135   DO_SIGNAL_CHECK(SIGFPE);
5136   DO_SIGNAL_CHECK(SIGBUS);
5137   DO_SIGNAL_CHECK(SIGPIPE);
5138   DO_SIGNAL_CHECK(SIGXFSZ);
5139 #if defined(PPC64)
5140   DO_SIGNAL_CHECK(SIGTRAP);
5141 #endif
5142 
5143   // ReduceSignalUsage allows the user to override these handlers
5144   // see comments at the very top and jvm_md.h
5145   if (!ReduceSignalUsage) {
5146     DO_SIGNAL_CHECK(SHUTDOWN1_SIGNAL);
5147     DO_SIGNAL_CHECK(SHUTDOWN2_SIGNAL);
5148     DO_SIGNAL_CHECK(SHUTDOWN3_SIGNAL);
5149     DO_SIGNAL_CHECK(BREAK_SIGNAL);
5150   }
5151 
5152   DO_SIGNAL_CHECK(SR_signum);
5153 }
5154 
5155 typedef int (*os_sigaction_t)(int, const struct sigaction *, struct sigaction *);
5156 
5157 static os_sigaction_t os_sigaction = NULL;
5158 
5159 void os::Linux::check_signal_handler(int sig) {
5160   char buf[O_BUFLEN];
5161   address jvmHandler = NULL;
5162 
5163 
5164   struct sigaction act;
5165   if (os_sigaction == NULL) {
5166     // only trust the default sigaction, in case it has been interposed
5167     os_sigaction = (os_sigaction_t)dlsym(RTLD_DEFAULT, "sigaction");
5168     if (os_sigaction == NULL) return;
5169   }
5170 
5171   os_sigaction(sig, (struct sigaction*)NULL, &act);
5172 
5173 
5174   act.sa_flags &= SIGNIFICANT_SIGNAL_MASK;
5175 
5176   address thisHandler = (act.sa_flags & SA_SIGINFO)
5177     ? CAST_FROM_FN_PTR(address, act.sa_sigaction)
5178     : CAST_FROM_FN_PTR(address, act.sa_handler);
5179 
5180 
5181   switch (sig) {
5182   case SIGSEGV:
5183   case SIGBUS:
5184   case SIGFPE:
5185   case SIGPIPE:
5186   case SIGILL:
5187   case SIGXFSZ:
5188     jvmHandler = CAST_FROM_FN_PTR(address, (sa_sigaction_t)signalHandler);
5189     break;
5190 
5191   case SHUTDOWN1_SIGNAL:
5192   case SHUTDOWN2_SIGNAL:
5193   case SHUTDOWN3_SIGNAL:
5194   case BREAK_SIGNAL:
5195     jvmHandler = (address)user_handler();
5196     break;
5197 
5198   default:
5199     if (sig == SR_signum) {
5200       jvmHandler = CAST_FROM_FN_PTR(address, (sa_sigaction_t)SR_handler);
5201     } else {
5202       return;
5203     }
5204     break;
5205   }
5206 
5207   if (thisHandler != jvmHandler) {
5208     tty->print("Warning: %s handler ", exception_name(sig, buf, O_BUFLEN));
5209     tty->print("expected:%s", get_signal_handler_name(jvmHandler, buf, O_BUFLEN));
5210     tty->print_cr("  found:%s", get_signal_handler_name(thisHandler, buf, O_BUFLEN));
5211     // No need to check this sig any longer
5212     sigaddset(&check_signal_done, sig);
5213     // Running under non-interactive shell, SHUTDOWN2_SIGNAL will be reassigned SIG_IGN
5214     if (sig == SHUTDOWN2_SIGNAL && !isatty(fileno(stdin))) {
5215       tty->print_cr("Running in non-interactive shell, %s handler is replaced by shell",
5216                     exception_name(sig, buf, O_BUFLEN));
5217     }
5218   } else if(os::Linux::get_our_sigflags(sig) != 0 && (int)act.sa_flags != os::Linux::get_our_sigflags(sig)) {
5219     tty->print("Warning: %s handler flags ", exception_name(sig, buf, O_BUFLEN));
5220     tty->print("expected:");
5221     os::Posix::print_sa_flags(tty, os::Linux::get_our_sigflags(sig));
5222     tty->cr();
5223     tty->print("  found:");
5224     os::Posix::print_sa_flags(tty, act.sa_flags);
5225     tty->cr();
5226     // No need to check this sig any longer
5227     sigaddset(&check_signal_done, sig);
5228   }
5229 
5230   // Dump all the signal
5231   if (sigismember(&check_signal_done, sig)) {
5232     print_signal_handlers(tty, buf, O_BUFLEN);
5233   }
5234 }
5235 
5236 extern void report_error(char* file_name, int line_no, char* title,
5237                          char* format, ...);
5238 
5239 // this is called _before_ most of the global arguments have been parsed
5240 void os::init(void) {
5241   char dummy;   // used to get a guess on initial stack address
5242 
5243   clock_tics_per_sec = sysconf(_SC_CLK_TCK);
5244 
5245   init_random(1234567);
5246 
5247   Linux::set_page_size(sysconf(_SC_PAGESIZE));
5248   if (Linux::page_size() == -1) {
5249     fatal("os_linux.cpp: os::init: sysconf failed (%s)",
5250           os::strerror(errno));
5251   }
5252   init_page_sizes((size_t) Linux::page_size());
5253 
5254   Linux::initialize_system_info();
5255 
5256   os::Linux::CPUPerfTicks pticks;
5257   bool res = os::Linux::get_tick_information(&pticks, -1);
5258 
5259   if (res && pticks.has_steal_ticks) {
5260     has_initial_tick_info = true;
5261     initial_total_ticks = pticks.total;
5262     initial_steal_ticks = pticks.steal;
5263   }
5264 
5265   // _main_thread points to the thread that created/loaded the JVM.
5266   Linux::_main_thread = pthread_self();
5267 
5268   // retrieve entry point for pthread_setname_np
5269   Linux::_pthread_setname_np =
5270     (int(*)(pthread_t, const char*))dlsym(RTLD_DEFAULT, "pthread_setname_np");
5271 
5272   os::Posix::init();
5273 
5274   initial_time_count = javaTimeNanos();
5275 
5276   // Always warn if no monotonic clock available
5277   if (!os::Posix::supports_monotonic_clock()) {
5278     warning("No monotonic clock was available - timed services may "    \
5279             "be adversely affected if the time-of-day clock changes");
5280   }
5281 }
5282 
5283 // To install functions for atexit system call
5284 extern "C" {
5285   static void perfMemory_exit_helper() {
5286     perfMemory_exit();
5287   }
5288 }
5289 
5290 void os::pd_init_container_support() {
5291   OSContainer::init();
5292 }
5293 
5294 void os::Linux::numa_init() {
5295 
5296   // Java can be invoked as
5297   // 1. Without numactl and heap will be allocated/configured on all nodes as
5298   //    per the system policy.
5299   // 2. With numactl --interleave:
5300   //      Use numa_get_interleave_mask(v2) API to get nodes bitmask. The same
5301   //      API for membind case bitmask is reset.
5302   //      Interleave is only hint and Kernel can fallback to other nodes if
5303   //      no memory is available on the target nodes.
5304   // 3. With numactl --membind:
5305   //      Use numa_get_membind(v2) API to get nodes bitmask. The same API for
5306   //      interleave case returns bitmask of all nodes.
5307   // numa_all_nodes_ptr holds bitmask of all nodes.
5308   // numa_get_interleave_mask(v2) and numa_get_membind(v2) APIs returns correct
5309   // bitmask when externally configured to run on all or fewer nodes.
5310 
5311   if (!Linux::libnuma_init()) {
5312     FLAG_SET_ERGO(UseNUMA, false);
5313     FLAG_SET_ERGO(UseNUMAInterleaving, false); // Also depends on libnuma.
5314   } else {
5315     if ((Linux::numa_max_node() < 1) || Linux::is_bound_to_single_node()) {
5316       // If there's only one node (they start from 0) or if the process
5317       // is bound explicitly to a single node using membind, disable NUMA unless
5318       // user explicilty forces NUMA optimizations on single-node/UMA systems
5319       UseNUMA = ForceNUMA;
5320     } else {
5321 
5322       LogTarget(Info,os) log;
5323       LogStream ls(log);
5324 
5325       Linux::set_configured_numa_policy(Linux::identify_numa_policy());
5326 
5327       struct bitmask* bmp = Linux::_numa_membind_bitmask;
5328       const char* numa_mode = "membind";
5329 
5330       if (Linux::is_running_in_interleave_mode()) {
5331         bmp = Linux::_numa_interleave_bitmask;
5332         numa_mode = "interleave";
5333       }
5334 
5335       ls.print("UseNUMA is enabled and invoked in '%s' mode."
5336                " Heap will be configured using NUMA memory nodes:", numa_mode);
5337 
5338       for (int node = 0; node <= Linux::numa_max_node(); node++) {
5339         if (Linux::_numa_bitmask_isbitset(bmp, node)) {
5340           ls.print(" %d", node);
5341         }
5342       }
5343     }
5344   }
5345 
5346   // When NUMA requested, not-NUMA-aware allocations default to interleaving.
5347   if (UseNUMA && !UseNUMAInterleaving) {
5348     FLAG_SET_ERGO_IF_DEFAULT(UseNUMAInterleaving, true);
5349   }
5350 
5351   if (UseParallelGC && UseNUMA && UseLargePages && !can_commit_large_page_memory()) {
5352     // With SHM and HugeTLBFS large pages we cannot uncommit a page, so there's no way
5353     // we can make the adaptive lgrp chunk resizing work. If the user specified both
5354     // UseNUMA and UseLargePages (or UseSHM/UseHugeTLBFS) on the command line - warn
5355     // and disable adaptive resizing.
5356     if (UseAdaptiveSizePolicy || UseAdaptiveNUMAChunkSizing) {
5357       warning("UseNUMA is not fully compatible with SHM/HugeTLBFS large pages, "
5358               "disabling adaptive resizing (-XX:-UseAdaptiveSizePolicy -XX:-UseAdaptiveNUMAChunkSizing)");
5359       UseAdaptiveSizePolicy = false;
5360       UseAdaptiveNUMAChunkSizing = false;
5361     }
5362   }
5363 }
5364 
5365 // this is called _after_ the global arguments have been parsed
5366 jint os::init_2(void) {
5367 
5368   // This could be set after os::Posix::init() but all platforms
5369   // have to set it the same so we have to mirror Solaris.
5370   DEBUG_ONLY(os::set_mutex_init_done();)
5371 
5372   os::Posix::init_2();
5373 
5374   Linux::fast_thread_clock_init();
5375 
5376   // initialize suspend/resume support - must do this before signal_sets_init()
5377   if (SR_initialize() != 0) {
5378     perror("SR_initialize failed");
5379     return JNI_ERR;
5380   }
5381 
5382   Linux::signal_sets_init();
5383   Linux::install_signal_handlers();
5384   // Initialize data for jdk.internal.misc.Signal
5385   if (!ReduceSignalUsage) {
5386     jdk_misc_signal_init();
5387   }
5388 
5389   if (AdjustStackSizeForTLS) {
5390     get_minstack_init();
5391   }
5392 
5393   // Check and sets minimum stack sizes against command line options
5394   if (Posix::set_minimum_stack_sizes() == JNI_ERR) {
5395     return JNI_ERR;
5396   }
5397 
5398 #if defined(IA32)
5399   // Need to ensure we've determined the process's initial stack to
5400   // perform the workaround
5401   Linux::capture_initial_stack(JavaThread::stack_size_at_create());
5402   workaround_expand_exec_shield_cs_limit();
5403 #else
5404   suppress_primordial_thread_resolution = Arguments::created_by_java_launcher();
5405   if (!suppress_primordial_thread_resolution) {
5406     Linux::capture_initial_stack(JavaThread::stack_size_at_create());
5407   }
5408 #endif
5409 
5410   Linux::libpthread_init();
5411   Linux::sched_getcpu_init();
5412   log_info(os)("HotSpot is running with %s, %s",
5413                Linux::glibc_version(), Linux::libpthread_version());
5414 
5415   if (UseNUMA || UseNUMAInterleaving) {
5416     Linux::numa_init();
5417   }
5418 
5419   if (MaxFDLimit) {
5420     // set the number of file descriptors to max. print out error
5421     // if getrlimit/setrlimit fails but continue regardless.
5422     struct rlimit nbr_files;
5423     int status = getrlimit(RLIMIT_NOFILE, &nbr_files);
5424     if (status != 0) {
5425       log_info(os)("os::init_2 getrlimit failed: %s", os::strerror(errno));
5426     } else {
5427       nbr_files.rlim_cur = nbr_files.rlim_max;
5428       status = setrlimit(RLIMIT_NOFILE, &nbr_files);
5429       if (status != 0) {
5430         log_info(os)("os::init_2 setrlimit failed: %s", os::strerror(errno));
5431       }
5432     }
5433   }
5434 
5435   // at-exit methods are called in the reverse order of their registration.
5436   // atexit functions are called on return from main or as a result of a
5437   // call to exit(3C). There can be only 32 of these functions registered
5438   // and atexit() does not set errno.
5439 
5440   if (PerfAllowAtExitRegistration) {
5441     // only register atexit functions if PerfAllowAtExitRegistration is set.
5442     // atexit functions can be delayed until process exit time, which
5443     // can be problematic for embedded VM situations. Embedded VMs should
5444     // call DestroyJavaVM() to assure that VM resources are released.
5445 
5446     // note: perfMemory_exit_helper atexit function may be removed in
5447     // the future if the appropriate cleanup code can be added to the
5448     // VM_Exit VMOperation's doit method.
5449     if (atexit(perfMemory_exit_helper) != 0) {
5450       warning("os::init_2 atexit(perfMemory_exit_helper) failed");
5451     }
5452   }
5453 
5454   // initialize thread priority policy
5455   prio_init();
5456 
5457   if (!FLAG_IS_DEFAULT(AllocateHeapAt) || !FLAG_IS_DEFAULT(AllocateOldGenAt)) {
5458     set_coredump_filter(DAX_SHARED_BIT);
5459   }
5460 
5461   if (DumpPrivateMappingsInCore) {
5462     set_coredump_filter(FILE_BACKED_PVT_BIT);
5463   }
5464 
5465   if (DumpSharedMappingsInCore) {
5466     set_coredump_filter(FILE_BACKED_SHARED_BIT);
5467   }
5468 
5469   return JNI_OK;
5470 }
5471 
5472 // older glibc versions don't have this macro (which expands to
5473 // an optimized bit-counting function) so we have to roll our own
5474 #ifndef CPU_COUNT
5475 
5476 static int _cpu_count(const cpu_set_t* cpus) {
5477   int count = 0;
5478   // only look up to the number of configured processors
5479   for (int i = 0; i < os::processor_count(); i++) {
5480     if (CPU_ISSET(i, cpus)) {
5481       count++;
5482     }
5483   }
5484   return count;
5485 }
5486 
5487 #define CPU_COUNT(cpus) _cpu_count(cpus)
5488 
5489 #endif // CPU_COUNT
5490 
5491 // Get the current number of available processors for this process.
5492 // This value can change at any time during a process's lifetime.
5493 // sched_getaffinity gives an accurate answer as it accounts for cpusets.
5494 // If it appears there may be more than 1024 processors then we do a
5495 // dynamic check - see 6515172 for details.
5496 // If anything goes wrong we fallback to returning the number of online
5497 // processors - which can be greater than the number available to the process.
5498 int os::Linux::active_processor_count() {
5499   cpu_set_t cpus;  // can represent at most 1024 (CPU_SETSIZE) processors
5500   cpu_set_t* cpus_p = &cpus;
5501   int cpus_size = sizeof(cpu_set_t);
5502 
5503   int configured_cpus = os::processor_count();  // upper bound on available cpus
5504   int cpu_count = 0;
5505 
5506 // old build platforms may not support dynamic cpu sets
5507 #ifdef CPU_ALLOC
5508 
5509   // To enable easy testing of the dynamic path on different platforms we
5510   // introduce a diagnostic flag: UseCpuAllocPath
5511   if (configured_cpus >= CPU_SETSIZE || UseCpuAllocPath) {
5512     // kernel may use a mask bigger than cpu_set_t
5513     log_trace(os)("active_processor_count: using dynamic path %s"
5514                   "- configured processors: %d",
5515                   UseCpuAllocPath ? "(forced) " : "",
5516                   configured_cpus);
5517     cpus_p = CPU_ALLOC(configured_cpus);
5518     if (cpus_p != NULL) {
5519       cpus_size = CPU_ALLOC_SIZE(configured_cpus);
5520       // zero it just to be safe
5521       CPU_ZERO_S(cpus_size, cpus_p);
5522     }
5523     else {
5524        // failed to allocate so fallback to online cpus
5525        int online_cpus = ::sysconf(_SC_NPROCESSORS_ONLN);
5526        log_trace(os)("active_processor_count: "
5527                      "CPU_ALLOC failed (%s) - using "
5528                      "online processor count: %d",
5529                      os::strerror(errno), online_cpus);
5530        return online_cpus;
5531     }
5532   }
5533   else {
5534     log_trace(os)("active_processor_count: using static path - configured processors: %d",
5535                   configured_cpus);
5536   }
5537 #else // CPU_ALLOC
5538 // these stubs won't be executed
5539 #define CPU_COUNT_S(size, cpus) -1
5540 #define CPU_FREE(cpus)
5541 
5542   log_trace(os)("active_processor_count: only static path available - configured processors: %d",
5543                 configured_cpus);
5544 #endif // CPU_ALLOC
5545 
5546   // pid 0 means the current thread - which we have to assume represents the process
5547   if (sched_getaffinity(0, cpus_size, cpus_p) == 0) {
5548     if (cpus_p != &cpus) { // can only be true when CPU_ALLOC used
5549       cpu_count = CPU_COUNT_S(cpus_size, cpus_p);
5550     }
5551     else {
5552       cpu_count = CPU_COUNT(cpus_p);
5553     }
5554     log_trace(os)("active_processor_count: sched_getaffinity processor count: %d", cpu_count);
5555   }
5556   else {
5557     cpu_count = ::sysconf(_SC_NPROCESSORS_ONLN);
5558     warning("sched_getaffinity failed (%s)- using online processor count (%d) "
5559             "which may exceed available processors", os::strerror(errno), cpu_count);
5560   }
5561 
5562   if (cpus_p != &cpus) { // can only be true when CPU_ALLOC used
5563     CPU_FREE(cpus_p);
5564   }
5565 
5566   assert(cpu_count > 0 && cpu_count <= os::processor_count(), "sanity check");
5567   return cpu_count;
5568 }
5569 
5570 // Determine the active processor count from one of
5571 // three different sources:
5572 //
5573 // 1. User option -XX:ActiveProcessorCount
5574 // 2. kernel os calls (sched_getaffinity or sysconf(_SC_NPROCESSORS_ONLN)
5575 // 3. extracted from cgroup cpu subsystem (shares and quotas)
5576 //
5577 // Option 1, if specified, will always override.
5578 // If the cgroup subsystem is active and configured, we
5579 // will return the min of the cgroup and option 2 results.
5580 // This is required since tools, such as numactl, that
5581 // alter cpu affinity do not update cgroup subsystem
5582 // cpuset configuration files.
5583 int os::active_processor_count() {
5584   // User has overridden the number of active processors
5585   if (ActiveProcessorCount > 0) {
5586     log_trace(os)("active_processor_count: "
5587                   "active processor count set by user : %d",
5588                   ActiveProcessorCount);
5589     return ActiveProcessorCount;
5590   }
5591 
5592   int active_cpus;
5593   if (OSContainer::is_containerized()) {
5594     active_cpus = OSContainer::active_processor_count();
5595     log_trace(os)("active_processor_count: determined by OSContainer: %d",
5596                    active_cpus);
5597   } else {
5598     active_cpus = os::Linux::active_processor_count();
5599   }
5600 
5601   return active_cpus;
5602 }
5603 
5604 uint os::processor_id() {
5605   const int id = Linux::sched_getcpu();
5606   assert(id >= 0 && id < _processor_count, "Invalid processor id");
5607   return (uint)id;
5608 }
5609 
5610 void os::set_native_thread_name(const char *name) {
5611   if (Linux::_pthread_setname_np) {
5612     char buf [16]; // according to glibc manpage, 16 chars incl. '/0'
5613     snprintf(buf, sizeof(buf), "%s", name);
5614     buf[sizeof(buf) - 1] = '\0';
5615     const int rc = Linux::_pthread_setname_np(pthread_self(), buf);
5616     // ERANGE should not happen; all other errors should just be ignored.
5617     assert(rc != ERANGE, "pthread_setname_np failed");
5618   }
5619 }
5620 
5621 bool os::bind_to_processor(uint processor_id) {
5622   // Not yet implemented.
5623   return false;
5624 }
5625 
5626 ///
5627 
5628 void os::SuspendedThreadTask::internal_do_task() {
5629   if (do_suspend(_thread->osthread())) {
5630     SuspendedThreadTaskContext context(_thread, _thread->osthread()->ucontext());
5631     do_task(context);
5632     do_resume(_thread->osthread());
5633   }
5634 }
5635 
5636 ////////////////////////////////////////////////////////////////////////////////
5637 // debug support
5638 
5639 bool os::find(address addr, outputStream* st) {
5640   Dl_info dlinfo;
5641   memset(&dlinfo, 0, sizeof(dlinfo));
5642   if (dladdr(addr, &dlinfo) != 0) {
5643     st->print(PTR_FORMAT ": ", p2i(addr));
5644     if (dlinfo.dli_sname != NULL && dlinfo.dli_saddr != NULL) {
5645       st->print("%s+" PTR_FORMAT, dlinfo.dli_sname,
5646                 p2i(addr) - p2i(dlinfo.dli_saddr));
5647     } else if (dlinfo.dli_fbase != NULL) {
5648       st->print("<offset " PTR_FORMAT ">", p2i(addr) - p2i(dlinfo.dli_fbase));
5649     } else {
5650       st->print("<absolute address>");
5651     }
5652     if (dlinfo.dli_fname != NULL) {
5653       st->print(" in %s", dlinfo.dli_fname);
5654     }
5655     if (dlinfo.dli_fbase != NULL) {
5656       st->print(" at " PTR_FORMAT, p2i(dlinfo.dli_fbase));
5657     }
5658     st->cr();
5659 
5660     if (Verbose) {
5661       // decode some bytes around the PC
5662       address begin = clamp_address_in_page(addr-40, addr, os::vm_page_size());
5663       address end   = clamp_address_in_page(addr+40, addr, os::vm_page_size());
5664       address       lowest = (address) dlinfo.dli_sname;
5665       if (!lowest)  lowest = (address) dlinfo.dli_fbase;
5666       if (begin < lowest)  begin = lowest;
5667       Dl_info dlinfo2;
5668       if (dladdr(end, &dlinfo2) != 0 && dlinfo2.dli_saddr != dlinfo.dli_saddr
5669           && end > dlinfo2.dli_saddr && dlinfo2.dli_saddr > begin) {
5670         end = (address) dlinfo2.dli_saddr;
5671       }
5672       Disassembler::decode(begin, end, st);
5673     }
5674     return true;
5675   }
5676   return false;
5677 }
5678 
5679 ////////////////////////////////////////////////////////////////////////////////
5680 // misc
5681 
5682 // This does not do anything on Linux. This is basically a hook for being
5683 // able to use structured exception handling (thread-local exception filters)
5684 // on, e.g., Win32.
5685 void
5686 os::os_exception_wrapper(java_call_t f, JavaValue* value, const methodHandle& method,
5687                          JavaCallArguments* args, Thread* thread) {
5688   f(value, method, args, thread);
5689 }
5690 
5691 void os::print_statistics() {
5692 }
5693 
5694 bool os::message_box(const char* title, const char* message) {
5695   int i;
5696   fdStream err(defaultStream::error_fd());
5697   for (i = 0; i < 78; i++) err.print_raw("=");
5698   err.cr();
5699   err.print_raw_cr(title);
5700   for (i = 0; i < 78; i++) err.print_raw("-");
5701   err.cr();
5702   err.print_raw_cr(message);
5703   for (i = 0; i < 78; i++) err.print_raw("=");
5704   err.cr();
5705 
5706   char buf[16];
5707   // Prevent process from exiting upon "read error" without consuming all CPU
5708   while (::read(0, buf, sizeof(buf)) <= 0) { ::sleep(100); }
5709 
5710   return buf[0] == 'y' || buf[0] == 'Y';
5711 }
5712 
5713 // Is a (classpath) directory empty?
5714 bool os::dir_is_empty(const char* path) {
5715   DIR *dir = NULL;
5716   struct dirent *ptr;
5717 
5718   dir = opendir(path);
5719   if (dir == NULL) return true;
5720 
5721   // Scan the directory
5722   bool result = true;
5723   while (result && (ptr = readdir(dir)) != NULL) {
5724     if (strcmp(ptr->d_name, ".") != 0 && strcmp(ptr->d_name, "..") != 0) {
5725       result = false;
5726     }
5727   }
5728   closedir(dir);
5729   return result;
5730 }
5731 
5732 // This code originates from JDK's sysOpen and open64_w
5733 // from src/solaris/hpi/src/system_md.c
5734 
5735 int os::open(const char *path, int oflag, int mode) {
5736   if (strlen(path) > MAX_PATH - 1) {
5737     errno = ENAMETOOLONG;
5738     return -1;
5739   }
5740 
5741   // All file descriptors that are opened in the Java process and not
5742   // specifically destined for a subprocess should have the close-on-exec
5743   // flag set.  If we don't set it, then careless 3rd party native code
5744   // might fork and exec without closing all appropriate file descriptors
5745   // (e.g. as we do in closeDescriptors in UNIXProcess.c), and this in
5746   // turn might:
5747   //
5748   // - cause end-of-file to fail to be detected on some file
5749   //   descriptors, resulting in mysterious hangs, or
5750   //
5751   // - might cause an fopen in the subprocess to fail on a system
5752   //   suffering from bug 1085341.
5753   //
5754   // (Yes, the default setting of the close-on-exec flag is a Unix
5755   // design flaw)
5756   //
5757   // See:
5758   // 1085341: 32-bit stdio routines should support file descriptors >255
5759   // 4843136: (process) pipe file descriptor from Runtime.exec not being closed
5760   // 6339493: (process) Runtime.exec does not close all file descriptors on Solaris 9
5761   //
5762   // Modern Linux kernels (after 2.6.23 2007) support O_CLOEXEC with open().
5763   // O_CLOEXEC is preferable to using FD_CLOEXEC on an open file descriptor
5764   // because it saves a system call and removes a small window where the flag
5765   // is unset.  On ancient Linux kernels the O_CLOEXEC flag will be ignored
5766   // and we fall back to using FD_CLOEXEC (see below).
5767 #ifdef O_CLOEXEC
5768   oflag |= O_CLOEXEC;
5769 #endif
5770 
5771   int fd = ::open64(path, oflag, mode);
5772   if (fd == -1) return -1;
5773 
5774   //If the open succeeded, the file might still be a directory
5775   {
5776     struct stat64 buf64;
5777     int ret = ::fstat64(fd, &buf64);
5778     int st_mode = buf64.st_mode;
5779 
5780     if (ret != -1) {
5781       if ((st_mode & S_IFMT) == S_IFDIR) {
5782         errno = EISDIR;
5783         ::close(fd);
5784         return -1;
5785       }
5786     } else {
5787       ::close(fd);
5788       return -1;
5789     }
5790   }
5791 
5792 #ifdef FD_CLOEXEC
5793   // Validate that the use of the O_CLOEXEC flag on open above worked.
5794   // With recent kernels, we will perform this check exactly once.
5795   static sig_atomic_t O_CLOEXEC_is_known_to_work = 0;
5796   if (!O_CLOEXEC_is_known_to_work) {
5797     int flags = ::fcntl(fd, F_GETFD);
5798     if (flags != -1) {
5799       if ((flags & FD_CLOEXEC) != 0)
5800         O_CLOEXEC_is_known_to_work = 1;
5801       else
5802         ::fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
5803     }
5804   }
5805 #endif
5806 
5807   return fd;
5808 }
5809 
5810 
5811 // create binary file, rewriting existing file if required
5812 int os::create_binary_file(const char* path, bool rewrite_existing) {
5813   int oflags = O_WRONLY | O_CREAT;
5814   if (!rewrite_existing) {
5815     oflags |= O_EXCL;
5816   }
5817   return ::open64(path, oflags, S_IREAD | S_IWRITE);
5818 }
5819 
5820 // return current position of file pointer
5821 jlong os::current_file_offset(int fd) {
5822   return (jlong)::lseek64(fd, (off64_t)0, SEEK_CUR);
5823 }
5824 
5825 // move file pointer to the specified offset
5826 jlong os::seek_to_file_offset(int fd, jlong offset) {
5827   return (jlong)::lseek64(fd, (off64_t)offset, SEEK_SET);
5828 }
5829 
5830 // This code originates from JDK's sysAvailable
5831 // from src/solaris/hpi/src/native_threads/src/sys_api_td.c
5832 
5833 int os::available(int fd, jlong *bytes) {
5834   jlong cur, end;
5835   int mode;
5836   struct stat64 buf64;
5837 
5838   if (::fstat64(fd, &buf64) >= 0) {
5839     mode = buf64.st_mode;
5840     if (S_ISCHR(mode) || S_ISFIFO(mode) || S_ISSOCK(mode)) {
5841       int n;
5842       if (::ioctl(fd, FIONREAD, &n) >= 0) {
5843         *bytes = n;
5844         return 1;
5845       }
5846     }
5847   }
5848   if ((cur = ::lseek64(fd, 0L, SEEK_CUR)) == -1) {
5849     return 0;
5850   } else if ((end = ::lseek64(fd, 0L, SEEK_END)) == -1) {
5851     return 0;
5852   } else if (::lseek64(fd, cur, SEEK_SET) == -1) {
5853     return 0;
5854   }
5855   *bytes = end - cur;
5856   return 1;
5857 }
5858 
5859 // Map a block of memory.
5860 char* os::pd_map_memory(int fd, const char* file_name, size_t file_offset,
5861                         char *addr, size_t bytes, bool read_only,
5862                         bool allow_exec) {
5863   int prot;
5864   int flags = MAP_PRIVATE;
5865 
5866   if (read_only) {
5867     prot = PROT_READ;
5868   } else {
5869     prot = PROT_READ | PROT_WRITE;
5870   }
5871 
5872   if (allow_exec) {
5873     prot |= PROT_EXEC;
5874   }
5875 
5876   if (addr != NULL) {
5877     flags |= MAP_FIXED;
5878   }
5879 
5880   char* mapped_address = (char*)mmap(addr, (size_t)bytes, prot, flags,
5881                                      fd, file_offset);
5882   if (mapped_address == MAP_FAILED) {
5883     return NULL;
5884   }
5885   return mapped_address;
5886 }
5887 
5888 
5889 // Remap a block of memory.
5890 char* os::pd_remap_memory(int fd, const char* file_name, size_t file_offset,
5891                           char *addr, size_t bytes, bool read_only,
5892                           bool allow_exec) {
5893   // same as map_memory() on this OS
5894   return os::map_memory(fd, file_name, file_offset, addr, bytes, read_only,
5895                         allow_exec);
5896 }
5897 
5898 
5899 // Unmap a block of memory.
5900 bool os::pd_unmap_memory(char* addr, size_t bytes) {
5901   return munmap(addr, bytes) == 0;
5902 }
5903 
5904 static jlong slow_thread_cpu_time(Thread *thread, bool user_sys_cpu_time);
5905 
5906 static jlong fast_cpu_time(Thread *thread) {
5907     clockid_t clockid;
5908     int rc = os::Linux::pthread_getcpuclockid(thread->osthread()->pthread_id(),
5909                                               &clockid);
5910     if (rc == 0) {
5911       return os::Linux::fast_thread_cpu_time(clockid);
5912     } else {
5913       // It's possible to encounter a terminated native thread that failed
5914       // to detach itself from the VM - which should result in ESRCH.
5915       assert_status(rc == ESRCH, rc, "pthread_getcpuclockid failed");
5916       return -1;
5917     }
5918 }
5919 
5920 // current_thread_cpu_time(bool) and thread_cpu_time(Thread*, bool)
5921 // are used by JVM M&M and JVMTI to get user+sys or user CPU time
5922 // of a thread.
5923 //
5924 // current_thread_cpu_time() and thread_cpu_time(Thread*) returns
5925 // the fast estimate available on the platform.
5926 
5927 jlong os::current_thread_cpu_time() {
5928   if (os::Linux::supports_fast_thread_cpu_time()) {
5929     return os::Linux::fast_thread_cpu_time(CLOCK_THREAD_CPUTIME_ID);
5930   } else {
5931     // return user + sys since the cost is the same
5932     return slow_thread_cpu_time(Thread::current(), true /* user + sys */);
5933   }
5934 }
5935 
5936 jlong os::thread_cpu_time(Thread* thread) {
5937   // consistent with what current_thread_cpu_time() returns
5938   if (os::Linux::supports_fast_thread_cpu_time()) {
5939     return fast_cpu_time(thread);
5940   } else {
5941     return slow_thread_cpu_time(thread, true /* user + sys */);
5942   }
5943 }
5944 
5945 jlong os::current_thread_cpu_time(bool user_sys_cpu_time) {
5946   if (user_sys_cpu_time && os::Linux::supports_fast_thread_cpu_time()) {
5947     return os::Linux::fast_thread_cpu_time(CLOCK_THREAD_CPUTIME_ID);
5948   } else {
5949     return slow_thread_cpu_time(Thread::current(), user_sys_cpu_time);
5950   }
5951 }
5952 
5953 jlong os::thread_cpu_time(Thread *thread, bool user_sys_cpu_time) {
5954   if (user_sys_cpu_time && os::Linux::supports_fast_thread_cpu_time()) {
5955     return fast_cpu_time(thread);
5956   } else {
5957     return slow_thread_cpu_time(thread, user_sys_cpu_time);
5958   }
5959 }
5960 
5961 //  -1 on error.
5962 static jlong slow_thread_cpu_time(Thread *thread, bool user_sys_cpu_time) {
5963   pid_t  tid = thread->osthread()->thread_id();
5964   char *s;
5965   char stat[2048];
5966   int statlen;
5967   char proc_name[64];
5968   int count;
5969   long sys_time, user_time;
5970   char cdummy;
5971   int idummy;
5972   long ldummy;
5973   FILE *fp;
5974 
5975   snprintf(proc_name, 64, "/proc/self/task/%d/stat", tid);
5976   fp = fopen(proc_name, "r");
5977   if (fp == NULL) return -1;
5978   statlen = fread(stat, 1, 2047, fp);
5979   stat[statlen] = '\0';
5980   fclose(fp);
5981 
5982   // Skip pid and the command string. Note that we could be dealing with
5983   // weird command names, e.g. user could decide to rename java launcher
5984   // to "java 1.4.2 :)", then the stat file would look like
5985   //                1234 (java 1.4.2 :)) R ... ...
5986   // We don't really need to know the command string, just find the last
5987   // occurrence of ")" and then start parsing from there. See bug 4726580.
5988   s = strrchr(stat, ')');
5989   if (s == NULL) return -1;
5990 
5991   // Skip blank chars
5992   do { s++; } while (s && isspace(*s));
5993 
5994   count = sscanf(s,"%c %d %d %d %d %d %lu %lu %lu %lu %lu %lu %lu",
5995                  &cdummy, &idummy, &idummy, &idummy, &idummy, &idummy,
5996                  &ldummy, &ldummy, &ldummy, &ldummy, &ldummy,
5997                  &user_time, &sys_time);
5998   if (count != 13) return -1;
5999   if (user_sys_cpu_time) {
6000     return ((jlong)sys_time + (jlong)user_time) * (1000000000 / clock_tics_per_sec);
6001   } else {
6002     return (jlong)user_time * (1000000000 / clock_tics_per_sec);
6003   }
6004 }
6005 
6006 void os::current_thread_cpu_time_info(jvmtiTimerInfo *info_ptr) {
6007   info_ptr->max_value = ALL_64_BITS;       // will not wrap in less than 64 bits
6008   info_ptr->may_skip_backward = false;     // elapsed time not wall time
6009   info_ptr->may_skip_forward = false;      // elapsed time not wall time
6010   info_ptr->kind = JVMTI_TIMER_TOTAL_CPU;  // user+system time is returned
6011 }
6012 
6013 void os::thread_cpu_time_info(jvmtiTimerInfo *info_ptr) {
6014   info_ptr->max_value = ALL_64_BITS;       // will not wrap in less than 64 bits
6015   info_ptr->may_skip_backward = false;     // elapsed time not wall time
6016   info_ptr->may_skip_forward = false;      // elapsed time not wall time
6017   info_ptr->kind = JVMTI_TIMER_TOTAL_CPU;  // user+system time is returned
6018 }
6019 
6020 bool os::is_thread_cpu_time_supported() {
6021   return true;
6022 }
6023 
6024 // System loadavg support.  Returns -1 if load average cannot be obtained.
6025 // Linux doesn't yet have a (official) notion of processor sets,
6026 // so just return the system wide load average.
6027 int os::loadavg(double loadavg[], int nelem) {
6028   return ::getloadavg(loadavg, nelem);
6029 }
6030 
6031 void os::pause() {
6032   char filename[MAX_PATH];
6033   if (PauseAtStartupFile && PauseAtStartupFile[0]) {
6034     jio_snprintf(filename, MAX_PATH, "%s", PauseAtStartupFile);
6035   } else {
6036     jio_snprintf(filename, MAX_PATH, "./vm.paused.%d", current_process_id());
6037   }
6038 
6039   int fd = ::open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
6040   if (fd != -1) {
6041     struct stat buf;
6042     ::close(fd);
6043     while (::stat(filename, &buf) == 0) {
6044       (void)::poll(NULL, 0, 100);
6045     }
6046   } else {
6047     jio_fprintf(stderr,
6048                 "Could not open pause file '%s', continuing immediately.\n", filename);
6049   }
6050 }
6051 
6052 extern char** environ;
6053 
6054 // Run the specified command in a separate process. Return its exit value,
6055 // or -1 on failure (e.g. can't fork a new process).
6056 // Unlike system(), this function can be called from signal handler. It
6057 // doesn't block SIGINT et al.
6058 int os::fork_and_exec(char* cmd, bool use_vfork_if_available) {
6059   const char * argv[4] = {"sh", "-c", cmd, NULL};
6060 
6061   pid_t pid ;
6062 
6063   if (use_vfork_if_available) {
6064     pid = vfork();
6065   } else {
6066     pid = fork();
6067   }
6068 
6069   if (pid < 0) {
6070     // fork failed
6071     return -1;
6072 
6073   } else if (pid == 0) {
6074     // child process
6075 
6076     execve("/bin/sh", (char* const*)argv, environ);
6077 
6078     // execve failed
6079     _exit(-1);
6080 
6081   } else  {
6082     // copied from J2SE ..._waitForProcessExit() in UNIXProcess_md.c; we don't
6083     // care about the actual exit code, for now.
6084 
6085     int status;
6086 
6087     // Wait for the child process to exit.  This returns immediately if
6088     // the child has already exited. */
6089     while (waitpid(pid, &status, 0) < 0) {
6090       switch (errno) {
6091       case ECHILD: return 0;
6092       case EINTR: break;
6093       default: return -1;
6094       }
6095     }
6096 
6097     if (WIFEXITED(status)) {
6098       // The child exited normally; get its exit code.
6099       return WEXITSTATUS(status);
6100     } else if (WIFSIGNALED(status)) {
6101       // The child exited because of a signal
6102       // The best value to return is 0x80 + signal number,
6103       // because that is what all Unix shells do, and because
6104       // it allows callers to distinguish between process exit and
6105       // process death by signal.
6106       return 0x80 + WTERMSIG(status);
6107     } else {
6108       // Unknown exit code; pass it through
6109       return status;
6110     }
6111   }
6112 }
6113 
6114 // Get the default path to the core file
6115 // Returns the length of the string
6116 int os::get_core_path(char* buffer, size_t bufferSize) {
6117   /*
6118    * Max length of /proc/sys/kernel/core_pattern is 128 characters.
6119    * See https://www.kernel.org/doc/Documentation/sysctl/kernel.txt
6120    */
6121   const int core_pattern_len = 129;
6122   char core_pattern[core_pattern_len] = {0};
6123 
6124   int core_pattern_file = ::open("/proc/sys/kernel/core_pattern", O_RDONLY);
6125   if (core_pattern_file == -1) {
6126     return -1;
6127   }
6128 
6129   ssize_t ret = ::read(core_pattern_file, core_pattern, core_pattern_len);
6130   ::close(core_pattern_file);
6131   if (ret <= 0 || ret >= core_pattern_len || core_pattern[0] == '\n') {
6132     return -1;
6133   }
6134   if (core_pattern[ret-1] == '\n') {
6135     core_pattern[ret-1] = '\0';
6136   } else {
6137     core_pattern[ret] = '\0';
6138   }
6139 
6140   // Replace the %p in the core pattern with the process id. NOTE: we do this
6141   // only if the pattern doesn't start with "|", and we support only one %p in
6142   // the pattern.
6143   char *pid_pos = strstr(core_pattern, "%p");
6144   const char* tail = (pid_pos != NULL) ? (pid_pos + 2) : "";  // skip over the "%p"
6145   int written;
6146 
6147   if (core_pattern[0] == '/') {
6148     if (pid_pos != NULL) {
6149       *pid_pos = '\0';
6150       written = jio_snprintf(buffer, bufferSize, "%s%d%s", core_pattern,
6151                              current_process_id(), tail);
6152     } else {
6153       written = jio_snprintf(buffer, bufferSize, "%s", core_pattern);
6154     }
6155   } else {
6156     char cwd[PATH_MAX];
6157 
6158     const char* p = get_current_directory(cwd, PATH_MAX);
6159     if (p == NULL) {
6160       return -1;
6161     }
6162 
6163     if (core_pattern[0] == '|') {
6164       written = jio_snprintf(buffer, bufferSize,
6165                              "\"%s\" (or dumping to %s/core.%d)",
6166                              &core_pattern[1], p, current_process_id());
6167     } else if (pid_pos != NULL) {
6168       *pid_pos = '\0';
6169       written = jio_snprintf(buffer, bufferSize, "%s/%s%d%s", p, core_pattern,
6170                              current_process_id(), tail);
6171     } else {
6172       written = jio_snprintf(buffer, bufferSize, "%s/%s", p, core_pattern);
6173     }
6174   }
6175 
6176   if (written < 0) {
6177     return -1;
6178   }
6179 
6180   if (((size_t)written < bufferSize) && (pid_pos == NULL) && (core_pattern[0] != '|')) {
6181     int core_uses_pid_file = ::open("/proc/sys/kernel/core_uses_pid", O_RDONLY);
6182 
6183     if (core_uses_pid_file != -1) {
6184       char core_uses_pid = 0;
6185       ssize_t ret = ::read(core_uses_pid_file, &core_uses_pid, 1);
6186       ::close(core_uses_pid_file);
6187 
6188       if (core_uses_pid == '1') {
6189         jio_snprintf(buffer + written, bufferSize - written,
6190                                           ".%d", current_process_id());
6191       }
6192     }
6193   }
6194 
6195   return strlen(buffer);
6196 }
6197 
6198 bool os::start_debugging(char *buf, int buflen) {
6199   int len = (int)strlen(buf);
6200   char *p = &buf[len];
6201 
6202   jio_snprintf(p, buflen-len,
6203                "\n\n"
6204                "Do you want to debug the problem?\n\n"
6205                "To debug, run 'gdb /proc/%d/exe %d'; then switch to thread " UINTX_FORMAT " (" INTPTR_FORMAT ")\n"
6206                "Enter 'yes' to launch gdb automatically (PATH must include gdb)\n"
6207                "Otherwise, press RETURN to abort...",
6208                os::current_process_id(), os::current_process_id(),
6209                os::current_thread_id(), os::current_thread_id());
6210 
6211   bool yes = os::message_box("Unexpected Error", buf);
6212 
6213   if (yes) {
6214     // yes, user asked VM to launch debugger
6215     jio_snprintf(buf, sizeof(char)*buflen, "gdb /proc/%d/exe %d",
6216                  os::current_process_id(), os::current_process_id());
6217 
6218     os::fork_and_exec(buf);
6219     yes = false;
6220   }
6221   return yes;
6222 }
6223 
6224 
6225 // Java/Compiler thread:
6226 //
6227 //   Low memory addresses
6228 // P0 +------------------------+
6229 //    |                        |\  Java thread created by VM does not have glibc
6230 //    |    glibc guard page    | - guard page, attached Java thread usually has
6231 //    |                        |/  1 glibc guard page.
6232 // P1 +------------------------+ Thread::stack_base() - Thread::stack_size()
6233 //    |                        |\
6234 //    |  HotSpot Guard Pages   | - red, yellow and reserved pages
6235 //    |                        |/
6236 //    +------------------------+ JavaThread::stack_reserved_zone_base()
6237 //    |                        |\
6238 //    |      Normal Stack      | -
6239 //    |                        |/
6240 // P2 +------------------------+ Thread::stack_base()
6241 //
6242 // Non-Java thread:
6243 //
6244 //   Low memory addresses
6245 // P0 +------------------------+
6246 //    |                        |\
6247 //    |  glibc guard page      | - usually 1 page
6248 //    |                        |/
6249 // P1 +------------------------+ Thread::stack_base() - Thread::stack_size()
6250 //    |                        |\
6251 //    |      Normal Stack      | -
6252 //    |                        |/
6253 // P2 +------------------------+ Thread::stack_base()
6254 //
6255 // ** P1 (aka bottom) and size (P2 = P1 - size) are the address and stack size
6256 //    returned from pthread_attr_getstack().
6257 // ** Due to NPTL implementation error, linux takes the glibc guard page out
6258 //    of the stack size given in pthread_attr. We work around this for
6259 //    threads created by the VM. (We adapt bottom to be P1 and size accordingly.)
6260 //
6261 #ifndef ZERO
6262 static void current_stack_region(address * bottom, size_t * size) {
6263   if (os::is_primordial_thread()) {
6264     // primordial thread needs special handling because pthread_getattr_np()
6265     // may return bogus value.
6266     *bottom = os::Linux::initial_thread_stack_bottom();
6267     *size   = os::Linux::initial_thread_stack_size();
6268   } else {
6269     pthread_attr_t attr;
6270 
6271     int rslt = pthread_getattr_np(pthread_self(), &attr);
6272 
6273     // JVM needs to know exact stack location, abort if it fails
6274     if (rslt != 0) {
6275       if (rslt == ENOMEM) {
6276         vm_exit_out_of_memory(0, OOM_MMAP_ERROR, "pthread_getattr_np");
6277       } else {
6278         fatal("pthread_getattr_np failed with error = %d", rslt);
6279       }
6280     }
6281 
6282     if (pthread_attr_getstack(&attr, (void **)bottom, size) != 0) {
6283       fatal("Cannot locate current stack attributes!");
6284     }
6285 
6286     // Work around NPTL stack guard error.
6287     size_t guard_size = 0;
6288     rslt = pthread_attr_getguardsize(&attr, &guard_size);
6289     if (rslt != 0) {
6290       fatal("pthread_attr_getguardsize failed with error = %d", rslt);
6291     }
6292     *bottom += guard_size;
6293     *size   -= guard_size;
6294 
6295     pthread_attr_destroy(&attr);
6296 
6297   }
6298   assert(os::current_stack_pointer() >= *bottom &&
6299          os::current_stack_pointer() < *bottom + *size, "just checking");
6300 }
6301 
6302 address os::current_stack_base() {
6303   address bottom;
6304   size_t size;
6305   current_stack_region(&bottom, &size);
6306   return (bottom + size);
6307 }
6308 
6309 size_t os::current_stack_size() {
6310   // This stack size includes the usable stack and HotSpot guard pages
6311   // (for the threads that have Hotspot guard pages).
6312   address bottom;
6313   size_t size;
6314   current_stack_region(&bottom, &size);
6315   return size;
6316 }
6317 #endif
6318 
6319 static inline struct timespec get_mtime(const char* filename) {
6320   struct stat st;
6321   int ret = os::stat(filename, &st);
6322   assert(ret == 0, "failed to stat() file '%s': %s", filename, os::strerror(errno));
6323   return st.st_mtim;
6324 }
6325 
6326 int os::compare_file_modified_times(const char* file1, const char* file2) {
6327   struct timespec filetime1 = get_mtime(file1);
6328   struct timespec filetime2 = get_mtime(file2);
6329   int diff = filetime1.tv_sec - filetime2.tv_sec;
6330   if (diff == 0) {
6331     return filetime1.tv_nsec - filetime2.tv_nsec;
6332   }
6333   return diff;
6334 }
6335 
6336 bool os::supports_map_sync() {
6337   return true;
6338 }
6339 
6340 /////////////// Unit tests ///////////////
6341 
6342 #ifndef PRODUCT
6343 
6344 class TestReserveMemorySpecial : AllStatic {
6345  public:
6346   static void small_page_write(void* addr, size_t size) {
6347     size_t page_size = os::vm_page_size();
6348 
6349     char* end = (char*)addr + size;
6350     for (char* p = (char*)addr; p < end; p += page_size) {
6351       *p = 1;
6352     }
6353   }
6354 
6355   static void test_reserve_memory_special_huge_tlbfs_only(size_t size) {
6356     if (!UseHugeTLBFS) {
6357       return;
6358     }
6359 
6360     char* addr = os::Linux::reserve_memory_special_huge_tlbfs_only(size, NULL, false);
6361 
6362     if (addr != NULL) {
6363       small_page_write(addr, size);
6364 
6365       os::Linux::release_memory_special_huge_tlbfs(addr, size);
6366     }
6367   }
6368 
6369   static void test_reserve_memory_special_huge_tlbfs_only() {
6370     if (!UseHugeTLBFS) {
6371       return;
6372     }
6373 
6374     size_t lp = os::large_page_size();
6375 
6376     for (size_t size = lp; size <= lp * 10; size += lp) {
6377       test_reserve_memory_special_huge_tlbfs_only(size);
6378     }
6379   }
6380 
6381   static void test_reserve_memory_special_huge_tlbfs_mixed() {
6382     size_t lp = os::large_page_size();
6383     size_t ag = os::vm_allocation_granularity();
6384 
6385     // sizes to test
6386     const size_t sizes[] = {
6387       lp, lp + ag, lp + lp / 2, lp * 2,
6388       lp * 2 + ag, lp * 2 - ag, lp * 2 + lp / 2,
6389       lp * 10, lp * 10 + lp / 2
6390     };
6391     const int num_sizes = sizeof(sizes) / sizeof(size_t);
6392 
6393     // For each size/alignment combination, we test three scenarios:
6394     // 1) with req_addr == NULL
6395     // 2) with a non-null req_addr at which we expect to successfully allocate
6396     // 3) with a non-null req_addr which contains a pre-existing mapping, at which we
6397     //    expect the allocation to either fail or to ignore req_addr
6398 
6399     // Pre-allocate two areas; they shall be as large as the largest allocation
6400     //  and aligned to the largest alignment we will be testing.
6401     const size_t mapping_size = sizes[num_sizes - 1] * 2;
6402     char* const mapping1 = (char*) ::mmap(NULL, mapping_size,
6403       PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE,
6404       -1, 0);
6405     assert(mapping1 != MAP_FAILED, "should work");
6406 
6407     char* const mapping2 = (char*) ::mmap(NULL, mapping_size,
6408       PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE,
6409       -1, 0);
6410     assert(mapping2 != MAP_FAILED, "should work");
6411 
6412     // Unmap the first mapping, but leave the second mapping intact: the first
6413     // mapping will serve as a value for a "good" req_addr (case 2). The second
6414     // mapping, still intact, as "bad" req_addr (case 3).
6415     ::munmap(mapping1, mapping_size);
6416 
6417     // Case 1
6418     for (int i = 0; i < num_sizes; i++) {
6419       const size_t size = sizes[i];
6420       for (size_t alignment = ag; is_aligned(size, alignment); alignment *= 2) {
6421         char* p = os::Linux::reserve_memory_special_huge_tlbfs_mixed(size, alignment, NULL, false);
6422         if (p != NULL) {
6423           assert(is_aligned(p, alignment), "must be");
6424           small_page_write(p, size);
6425           os::Linux::release_memory_special_huge_tlbfs(p, size);
6426         }
6427       }
6428     }
6429 
6430     // Case 2
6431     for (int i = 0; i < num_sizes; i++) {
6432       const size_t size = sizes[i];
6433       for (size_t alignment = ag; is_aligned(size, alignment); alignment *= 2) {
6434         char* const req_addr = align_up(mapping1, alignment);
6435         char* p = os::Linux::reserve_memory_special_huge_tlbfs_mixed(size, alignment, req_addr, false);
6436         if (p != NULL) {
6437           assert(p == req_addr, "must be");
6438           small_page_write(p, size);
6439           os::Linux::release_memory_special_huge_tlbfs(p, size);
6440         }
6441       }
6442     }
6443 
6444     // Case 3
6445     for (int i = 0; i < num_sizes; i++) {
6446       const size_t size = sizes[i];
6447       for (size_t alignment = ag; is_aligned(size, alignment); alignment *= 2) {
6448         char* const req_addr = align_up(mapping2, alignment);
6449         char* p = os::Linux::reserve_memory_special_huge_tlbfs_mixed(size, alignment, req_addr, false);
6450         // as the area around req_addr contains already existing mappings, the API should always
6451         // return NULL (as per contract, it cannot return another address)
6452         assert(p == NULL, "must be");
6453       }
6454     }
6455 
6456     ::munmap(mapping2, mapping_size);
6457 
6458   }
6459 
6460   static void test_reserve_memory_special_huge_tlbfs() {
6461     if (!UseHugeTLBFS) {
6462       return;
6463     }
6464 
6465     test_reserve_memory_special_huge_tlbfs_only();
6466     test_reserve_memory_special_huge_tlbfs_mixed();
6467   }
6468 
6469   static void test_reserve_memory_special_shm(size_t size, size_t alignment) {
6470     if (!UseSHM) {
6471       return;
6472     }
6473 
6474     char* addr = os::Linux::reserve_memory_special_shm(size, alignment, NULL, false);
6475 
6476     if (addr != NULL) {
6477       assert(is_aligned(addr, alignment), "Check");
6478       assert(is_aligned(addr, os::large_page_size()), "Check");
6479 
6480       small_page_write(addr, size);
6481 
6482       os::Linux::release_memory_special_shm(addr, size);
6483     }
6484   }
6485 
6486   static void test_reserve_memory_special_shm() {
6487     size_t lp = os::large_page_size();
6488     size_t ag = os::vm_allocation_granularity();
6489 
6490     for (size_t size = ag; size < lp * 3; size += ag) {
6491       for (size_t alignment = ag; is_aligned(size, alignment); alignment *= 2) {
6492         test_reserve_memory_special_shm(size, alignment);
6493       }
6494     }
6495   }
6496 
6497   static void test() {
6498     test_reserve_memory_special_huge_tlbfs();
6499     test_reserve_memory_special_shm();
6500   }
6501 };
6502 
6503 void TestReserveMemorySpecial_test() {
6504   TestReserveMemorySpecial::test();
6505 }
6506 
6507 #endif