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