1 /*
   2  * Copyright (c) 1999, 2016, 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 "classfile/classLoader.hpp"
  27 #include "classfile/systemDictionary.hpp"
  28 #include "classfile/vmSymbols.hpp"
  29 #include "code/icBuffer.hpp"
  30 #include "code/vtableStubs.hpp"
  31 #include "compiler/compileBroker.hpp"
  32 #include "compiler/disassembler.hpp"
  33 #include "interpreter/interpreter.hpp"
  34 #include "jvm_linux.h"
  35 #include "logging/log.hpp"
  36 #include "memory/allocation.inline.hpp"
  37 #include "memory/filemap.hpp"
  38 #include "mutex_linux.inline.hpp"
  39 #include "oops/oop.inline.hpp"
  40 #include "os_linux.inline.hpp"
  41 #include "os_share_linux.hpp"
  42 #include "prims/jniFastGetField.hpp"
  43 #include "prims/jvm.h"
  44 #include "prims/jvm_misc.hpp"
  45 #include "runtime/arguments.hpp"
  46 #include "runtime/atomic.inline.hpp"
  47 #include "runtime/extendedPC.hpp"
  48 #include "runtime/globals.hpp"
  49 #include "runtime/interfaceSupport.hpp"
  50 #include "runtime/init.hpp"
  51 #include "runtime/java.hpp"
  52 #include "runtime/javaCalls.hpp"
  53 #include "runtime/mutexLocker.hpp"
  54 #include "runtime/objectMonitor.hpp"
  55 #include "runtime/orderAccess.inline.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/timer.hpp"
  64 #include "semaphore_posix.hpp"
  65 #include "services/attachListener.hpp"
  66 #include "services/memTracker.hpp"
  67 #include "services/runtimeService.hpp"
  68 #include "utilities/decoder.hpp"
  69 #include "utilities/defaultStream.hpp"
  70 #include "utilities/events.hpp"
  71 #include "utilities/elfFile.hpp"
  72 #include "utilities/growableArray.hpp"
  73 #include "utilities/macros.hpp"
  74 #include "utilities/vmError.hpp"
  75 
  76 // put OS-includes here
  77 # include <sys/types.h>
  78 # include <sys/mman.h>
  79 # include <sys/stat.h>
  80 # include <sys/select.h>
  81 # include <pthread.h>
  82 # include <signal.h>
  83 # include <errno.h>
  84 # include <dlfcn.h>
  85 # include <stdio.h>
  86 # include <unistd.h>
  87 # include <sys/resource.h>
  88 # include <pthread.h>
  89 # include <sys/stat.h>
  90 # include <sys/time.h>
  91 # include <sys/times.h>
  92 # include <sys/utsname.h>
  93 # include <sys/socket.h>
  94 # include <sys/wait.h>
  95 # include <pwd.h>
  96 # include <poll.h>
  97 # include <semaphore.h>
  98 # include <fcntl.h>
  99 # include <string.h>
 100 # include <syscall.h>
 101 # include <sys/sysinfo.h>
 102 # include <gnu/libc-version.h>
 103 # include <sys/ipc.h>
 104 # include <sys/shm.h>
 105 # include <link.h>
 106 # include <stdint.h>
 107 # include <inttypes.h>
 108 # include <sys/ioctl.h>
 109 
 110 #ifndef _GNU_SOURCE
 111   #define _GNU_SOURCE
 112   #include <sched.h>
 113   #undef _GNU_SOURCE
 114 #else
 115   #include <sched.h>
 116 #endif
 117 
 118 // if RUSAGE_THREAD for getrusage() has not been defined, do it here. The code calling
 119 // getrusage() is prepared to handle the associated failure.
 120 #ifndef RUSAGE_THREAD
 121   #define RUSAGE_THREAD   (1)               /* only the calling thread */
 122 #endif
 123 
 124 #define MAX_PATH    (2 * K)
 125 
 126 #define MAX_SECS 100000000
 127 
 128 // for timer info max values which include all bits
 129 #define ALL_64_BITS CONST64(0xFFFFFFFFFFFFFFFF)
 130 
 131 #define LARGEPAGES_BIT (1 << 6)
 132 ////////////////////////////////////////////////////////////////////////////////
 133 // global variables
 134 julong os::Linux::_physical_memory = 0;
 135 
 136 address   os::Linux::_initial_thread_stack_bottom = NULL;
 137 uintptr_t os::Linux::_initial_thread_stack_size   = 0;
 138 
 139 int (*os::Linux::_clock_gettime)(clockid_t, struct timespec *) = NULL;
 140 int (*os::Linux::_pthread_getcpuclockid)(pthread_t, clockid_t *) = NULL;
 141 int (*os::Linux::_pthread_setname_np)(pthread_t, const char*) = NULL;
 142 Mutex* os::Linux::_createThread_lock = NULL;
 143 pthread_t os::Linux::_main_thread;
 144 int os::Linux::_page_size = -1;
 145 const int os::Linux::_vm_default_page_size = (8 * K);
 146 bool os::Linux::_supports_fast_thread_cpu_time = false;
 147 uint32_t os::Linux::_os_version = 0;
 148 const char * os::Linux::_glibc_version = NULL;
 149 const char * os::Linux::_libpthread_version = NULL;
 150 pthread_condattr_t os::Linux::_condattr[1];
 151 
 152 static jlong initial_time_count=0;
 153 
 154 static int clock_tics_per_sec = 100;
 155 
 156 // For diagnostics to print a message once. see run_periodic_checks
 157 static sigset_t check_signal_done;
 158 static bool check_signals = true;
 159 
 160 // Signal number used to suspend/resume a thread
 161 
 162 // do not use any signal number less than SIGSEGV, see 4355769
 163 static int SR_signum = SIGUSR2;
 164 sigset_t SR_sigset;
 165 
 166 // Declarations
 167 static void unpackTime(timespec* absTime, bool isAbsolute, jlong time);
 168 
 169 // utility functions
 170 
 171 static int SR_initialize();
 172 
 173 julong os::available_memory() {
 174   return Linux::available_memory();
 175 }
 176 
 177 julong os::Linux::available_memory() {
 178   // values in struct sysinfo are "unsigned long"
 179   struct sysinfo si;
 180   sysinfo(&si);
 181 
 182   return (julong)si.freeram * si.mem_unit;
 183 }
 184 
 185 julong os::physical_memory() {
 186   return Linux::physical_memory();
 187 }
 188 
 189 // Return true if user is running as root.
 190 
 191 bool os::have_special_privileges() {
 192   static bool init = false;
 193   static bool privileges = false;
 194   if (!init) {
 195     privileges = (getuid() != geteuid()) || (getgid() != getegid());
 196     init = true;
 197   }
 198   return privileges;
 199 }
 200 
 201 
 202 #ifndef SYS_gettid
 203 // i386: 224, ia64: 1105, amd64: 186, sparc 143
 204   #ifdef __ia64__
 205     #define SYS_gettid 1105
 206   #else
 207     #ifdef __i386__
 208       #define SYS_gettid 224
 209     #else
 210       #ifdef __amd64__
 211         #define SYS_gettid 186
 212       #else
 213         #ifdef __sparc__
 214           #define SYS_gettid 143
 215         #else
 216           #error define gettid for the arch
 217         #endif
 218       #endif
 219     #endif
 220   #endif
 221 #endif
 222 
 223 // Cpu architecture string
 224 static char cpu_arch[] = HOTSPOT_LIB_ARCH;
 225 
 226 
 227 // pid_t gettid()
 228 //
 229 // Returns the kernel thread id of the currently running thread. Kernel
 230 // thread id is used to access /proc.
 231 pid_t os::Linux::gettid() {
 232   int rslt = syscall(SYS_gettid);
 233   assert(rslt != -1, "must be."); // old linuxthreads implementation?
 234   return (pid_t)rslt;
 235 }
 236 
 237 // Most versions of linux have a bug where the number of processors are
 238 // determined by looking at the /proc file system.  In a chroot environment,
 239 // the system call returns 1.  This causes the VM to act as if it is
 240 // a single processor and elide locking (see is_MP() call).
 241 static bool unsafe_chroot_detected = false;
 242 static const char *unstable_chroot_error = "/proc file system not found.\n"
 243                      "Java may be unstable running multithreaded in a chroot "
 244                      "environment on Linux when /proc filesystem is not mounted.";
 245 
 246 void os::Linux::initialize_system_info() {
 247   set_processor_count(sysconf(_SC_NPROCESSORS_CONF));
 248   if (processor_count() == 1) {
 249     pid_t pid = os::Linux::gettid();
 250     char fname[32];
 251     jio_snprintf(fname, sizeof(fname), "/proc/%d", pid);
 252     FILE *fp = fopen(fname, "r");
 253     if (fp == NULL) {
 254       unsafe_chroot_detected = true;
 255     } else {
 256       fclose(fp);
 257     }
 258   }
 259   _physical_memory = (julong)sysconf(_SC_PHYS_PAGES) * (julong)sysconf(_SC_PAGESIZE);
 260   assert(processor_count() > 0, "linux error");
 261 }
 262 
 263 void os::init_system_properties_values() {
 264   // The next steps are taken in the product version:
 265   //
 266   // Obtain the JAVA_HOME value from the location of libjvm.so.
 267   // This library should be located at:
 268   // <JAVA_HOME>/jre/lib/<arch>/{client|server}/libjvm.so.
 269   //
 270   // If "/jre/lib/" appears at the right place in the path, then we
 271   // assume libjvm.so is installed in a JDK and we use this path.
 272   //
 273   // Otherwise exit with message: "Could not create the Java virtual machine."
 274   //
 275   // The following extra steps are taken in the debugging version:
 276   //
 277   // If "/jre/lib/" does NOT appear at the right place in the path
 278   // instead of exit check for $JAVA_HOME environment variable.
 279   //
 280   // If it is defined and we are able to locate $JAVA_HOME/jre/lib/<arch>,
 281   // then we append a fake suffix "hotspot/libjvm.so" to this path so
 282   // it looks like libjvm.so is installed there
 283   // <JAVA_HOME>/jre/lib/<arch>/hotspot/libjvm.so.
 284   //
 285   // Otherwise exit.
 286   //
 287   // Important note: if the location of libjvm.so changes this
 288   // code needs to be changed accordingly.
 289 
 290   // See ld(1):
 291   //      The linker uses the following search paths to locate required
 292   //      shared libraries:
 293   //        1: ...
 294   //        ...
 295   //        7: The default directories, normally /lib and /usr/lib.
 296 #if defined(AMD64) || defined(_LP64) && (defined(SPARC) || defined(PPC) || defined(S390))
 297   #define DEFAULT_LIBPATH "/usr/lib64:/lib64:/lib:/usr/lib"
 298 #else
 299   #define DEFAULT_LIBPATH "/lib:/usr/lib"
 300 #endif
 301 
 302 // Base path of extensions installed on the system.
 303 #define SYS_EXT_DIR     "/usr/java/packages"
 304 #define EXTENSIONS_DIR  "/lib/ext"
 305 
 306   // Buffer that fits several sprintfs.
 307   // Note that the space for the colon and the trailing null are provided
 308   // by the nulls included by the sizeof operator.
 309   const size_t bufsize =
 310     MAX2((size_t)MAXPATHLEN,  // For dll_dir & friends.
 311          (size_t)MAXPATHLEN + sizeof(EXTENSIONS_DIR) + sizeof(SYS_EXT_DIR) + sizeof(EXTENSIONS_DIR)); // extensions dir
 312   char *buf = (char *)NEW_C_HEAP_ARRAY(char, bufsize, mtInternal);
 313 
 314   // sysclasspath, java_home, dll_dir
 315   {
 316     char *pslash;
 317     os::jvm_path(buf, bufsize);
 318 
 319     // Found the full path to libjvm.so.
 320     // Now cut the path to <java_home>/jre if we can.
 321     pslash = strrchr(buf, '/');
 322     if (pslash != NULL) {
 323       *pslash = '\0';            // Get rid of /libjvm.so.
 324     }
 325     pslash = strrchr(buf, '/');
 326     if (pslash != NULL) {
 327       *pslash = '\0';            // Get rid of /{client|server|hotspot}.
 328     }
 329     Arguments::set_dll_dir(buf);
 330 
 331     if (pslash != NULL) {
 332       pslash = strrchr(buf, '/');
 333       if (pslash != NULL) {
 334         *pslash = '\0';          // Get rid of /<arch>.
 335         pslash = strrchr(buf, '/');
 336         if (pslash != NULL) {
 337           *pslash = '\0';        // Get rid of /lib.
 338         }
 339       }
 340     }
 341     Arguments::set_java_home(buf);
 342     set_boot_path('/', ':');
 343   }
 344 
 345   // Where to look for native libraries.
 346   //
 347   // Note: Due to a legacy implementation, most of the library path
 348   // is set in the launcher. This was to accomodate linking restrictions
 349   // on legacy Linux implementations (which are no longer supported).
 350   // Eventually, all the library path setting will be done here.
 351   //
 352   // However, to prevent the proliferation of improperly built native
 353   // libraries, the new path component /usr/java/packages is added here.
 354   // Eventually, all the library path setting will be done here.
 355   {
 356     // Get the user setting of LD_LIBRARY_PATH, and prepended it. It
 357     // should always exist (until the legacy problem cited above is
 358     // addressed).
 359     const char *v = ::getenv("LD_LIBRARY_PATH");
 360     const char *v_colon = ":";
 361     if (v == NULL) { v = ""; v_colon = ""; }
 362     // That's +1 for the colon and +1 for the trailing '\0'.
 363     char *ld_library_path = (char *)NEW_C_HEAP_ARRAY(char,
 364                                                      strlen(v) + 1 +
 365                                                      sizeof(SYS_EXT_DIR) + sizeof("/lib/") + strlen(cpu_arch) + sizeof(DEFAULT_LIBPATH) + 1,
 366                                                      mtInternal);
 367     sprintf(ld_library_path, "%s%s" SYS_EXT_DIR "/lib/%s:" DEFAULT_LIBPATH, v, v_colon, cpu_arch);
 368     Arguments::set_library_path(ld_library_path);
 369     FREE_C_HEAP_ARRAY(char, ld_library_path);
 370   }
 371 
 372   // Extensions directories.
 373   sprintf(buf, "%s" EXTENSIONS_DIR ":" SYS_EXT_DIR EXTENSIONS_DIR, Arguments::get_java_home());
 374   Arguments::set_ext_dirs(buf);
 375 
 376   FREE_C_HEAP_ARRAY(char, buf);
 377 
 378 #undef DEFAULT_LIBPATH
 379 #undef SYS_EXT_DIR
 380 #undef EXTENSIONS_DIR
 381 }
 382 
 383 ////////////////////////////////////////////////////////////////////////////////
 384 // breakpoint support
 385 
 386 void os::breakpoint() {
 387   BREAKPOINT;
 388 }
 389 
 390 extern "C" void breakpoint() {
 391   // use debugger to set breakpoint here
 392 }
 393 
 394 ////////////////////////////////////////////////////////////////////////////////
 395 // signal support
 396 
 397 debug_only(static bool signal_sets_initialized = false);
 398 static sigset_t unblocked_sigs, vm_sigs, allowdebug_blocked_sigs;
 399 
 400 bool os::Linux::is_sig_ignored(int sig) {
 401   struct sigaction oact;
 402   sigaction(sig, (struct sigaction*)NULL, &oact);
 403   void* ohlr = oact.sa_sigaction ? CAST_FROM_FN_PTR(void*,  oact.sa_sigaction)
 404                                  : CAST_FROM_FN_PTR(void*,  oact.sa_handler);
 405   if (ohlr == CAST_FROM_FN_PTR(void*, SIG_IGN)) {
 406     return true;
 407   } else {
 408     return false;
 409   }
 410 }
 411 
 412 void os::Linux::signal_sets_init() {
 413   // Should also have an assertion stating we are still single-threaded.
 414   assert(!signal_sets_initialized, "Already initialized");
 415   // Fill in signals that are necessarily unblocked for all threads in
 416   // the VM. Currently, we unblock the following signals:
 417   // SHUTDOWN{1,2,3}_SIGNAL: for shutdown hooks support (unless over-ridden
 418   //                         by -Xrs (=ReduceSignalUsage));
 419   // BREAK_SIGNAL which is unblocked only by the VM thread and blocked by all
 420   // other threads. The "ReduceSignalUsage" boolean tells us not to alter
 421   // the dispositions or masks wrt these signals.
 422   // Programs embedding the VM that want to use the above signals for their
 423   // own purposes must, at this time, use the "-Xrs" option to prevent
 424   // interference with shutdown hooks and BREAK_SIGNAL thread dumping.
 425   // (See bug 4345157, and other related bugs).
 426   // In reality, though, unblocking these signals is really a nop, since
 427   // these signals are not blocked by default.
 428   sigemptyset(&unblocked_sigs);
 429   sigemptyset(&allowdebug_blocked_sigs);
 430   sigaddset(&unblocked_sigs, SIGILL);
 431   sigaddset(&unblocked_sigs, SIGSEGV);
 432   sigaddset(&unblocked_sigs, SIGBUS);
 433   sigaddset(&unblocked_sigs, SIGFPE);
 434 #if defined(PPC64)
 435   sigaddset(&unblocked_sigs, SIGTRAP);
 436 #endif
 437   sigaddset(&unblocked_sigs, SR_signum);
 438 
 439   if (!ReduceSignalUsage) {
 440     if (!os::Linux::is_sig_ignored(SHUTDOWN1_SIGNAL)) {
 441       sigaddset(&unblocked_sigs, SHUTDOWN1_SIGNAL);
 442       sigaddset(&allowdebug_blocked_sigs, SHUTDOWN1_SIGNAL);
 443     }
 444     if (!os::Linux::is_sig_ignored(SHUTDOWN2_SIGNAL)) {
 445       sigaddset(&unblocked_sigs, SHUTDOWN2_SIGNAL);
 446       sigaddset(&allowdebug_blocked_sigs, SHUTDOWN2_SIGNAL);
 447     }
 448     if (!os::Linux::is_sig_ignored(SHUTDOWN3_SIGNAL)) {
 449       sigaddset(&unblocked_sigs, SHUTDOWN3_SIGNAL);
 450       sigaddset(&allowdebug_blocked_sigs, SHUTDOWN3_SIGNAL);
 451     }
 452   }
 453   // Fill in signals that are blocked by all but the VM thread.
 454   sigemptyset(&vm_sigs);
 455   if (!ReduceSignalUsage) {
 456     sigaddset(&vm_sigs, BREAK_SIGNAL);
 457   }
 458   debug_only(signal_sets_initialized = true);
 459 
 460 }
 461 
 462 // These are signals that are unblocked while a thread is running Java.
 463 // (For some reason, they get blocked by default.)
 464 sigset_t* os::Linux::unblocked_signals() {
 465   assert(signal_sets_initialized, "Not initialized");
 466   return &unblocked_sigs;
 467 }
 468 
 469 // These are the signals that are blocked while a (non-VM) thread is
 470 // running Java. Only the VM thread handles these signals.
 471 sigset_t* os::Linux::vm_signals() {
 472   assert(signal_sets_initialized, "Not initialized");
 473   return &vm_sigs;
 474 }
 475 
 476 // These are signals that are blocked during cond_wait to allow debugger in
 477 sigset_t* os::Linux::allowdebug_blocked_signals() {
 478   assert(signal_sets_initialized, "Not initialized");
 479   return &allowdebug_blocked_sigs;
 480 }
 481 
 482 void os::Linux::hotspot_sigmask(Thread* thread) {
 483 
 484   //Save caller's signal mask before setting VM signal mask
 485   sigset_t caller_sigmask;
 486   pthread_sigmask(SIG_BLOCK, NULL, &caller_sigmask);
 487 
 488   OSThread* osthread = thread->osthread();
 489   osthread->set_caller_sigmask(caller_sigmask);
 490 
 491   pthread_sigmask(SIG_UNBLOCK, os::Linux::unblocked_signals(), NULL);
 492 
 493   if (!ReduceSignalUsage) {
 494     if (thread->is_VM_thread()) {
 495       // Only the VM thread handles BREAK_SIGNAL ...
 496       pthread_sigmask(SIG_UNBLOCK, vm_signals(), NULL);
 497     } else {
 498       // ... all other threads block BREAK_SIGNAL
 499       pthread_sigmask(SIG_BLOCK, vm_signals(), NULL);
 500     }
 501   }
 502 }
 503 
 504 //////////////////////////////////////////////////////////////////////////////
 505 // detecting pthread library
 506 
 507 void os::Linux::libpthread_init() {
 508   // Save glibc and pthread version strings.
 509 #if !defined(_CS_GNU_LIBC_VERSION) || \
 510     !defined(_CS_GNU_LIBPTHREAD_VERSION)
 511   #error "glibc too old (< 2.3.2)"
 512 #endif
 513 
 514   size_t n = confstr(_CS_GNU_LIBC_VERSION, NULL, 0);
 515   assert(n > 0, "cannot retrieve glibc version");
 516   char *str = (char *)malloc(n, mtInternal);
 517   confstr(_CS_GNU_LIBC_VERSION, str, n);
 518   os::Linux::set_glibc_version(str);
 519 
 520   n = confstr(_CS_GNU_LIBPTHREAD_VERSION, NULL, 0);
 521   assert(n > 0, "cannot retrieve pthread version");
 522   str = (char *)malloc(n, mtInternal);
 523   confstr(_CS_GNU_LIBPTHREAD_VERSION, str, n);
 524   os::Linux::set_libpthread_version(str);
 525 }
 526 
 527 /////////////////////////////////////////////////////////////////////////////
 528 // thread stack expansion
 529 
 530 // os::Linux::manually_expand_stack() takes care of expanding the thread
 531 // stack. Note that this is normally not needed: pthread stacks allocate
 532 // thread stack using mmap() without MAP_NORESERVE, so the stack is already
 533 // committed. Therefore it is not necessary to expand the stack manually.
 534 //
 535 // Manually expanding the stack was historically needed on LinuxThreads
 536 // thread stacks, which were allocated with mmap(MAP_GROWSDOWN). Nowadays
 537 // it is kept to deal with very rare corner cases:
 538 //
 539 // For one, user may run the VM on an own implementation of threads
 540 // whose stacks are - like the old LinuxThreads - implemented using
 541 // mmap(MAP_GROWSDOWN).
 542 //
 543 // Also, this coding may be needed if the VM is running on the primordial
 544 // thread. Normally we avoid running on the primordial thread; however,
 545 // user may still invoke the VM on the primordial thread.
 546 //
 547 // The following historical comment describes the details about running
 548 // on a thread stack allocated with mmap(MAP_GROWSDOWN):
 549 
 550 
 551 // Force Linux kernel to expand current thread stack. If "bottom" is close
 552 // to the stack guard, caller should block all signals.
 553 //
 554 // MAP_GROWSDOWN:
 555 //   A special mmap() flag that is used to implement thread stacks. It tells
 556 //   kernel that the memory region should extend downwards when needed. This
 557 //   allows early versions of LinuxThreads to only mmap the first few pages
 558 //   when creating a new thread. Linux kernel will automatically expand thread
 559 //   stack as needed (on page faults).
 560 //
 561 //   However, because the memory region of a MAP_GROWSDOWN stack can grow on
 562 //   demand, if a page fault happens outside an already mapped MAP_GROWSDOWN
 563 //   region, it's hard to tell if the fault is due to a legitimate stack
 564 //   access or because of reading/writing non-exist memory (e.g. buffer
 565 //   overrun). As a rule, if the fault happens below current stack pointer,
 566 //   Linux kernel does not expand stack, instead a SIGSEGV is sent to the
 567 //   application (see Linux kernel fault.c).
 568 //
 569 //   This Linux feature can cause SIGSEGV when VM bangs thread stack for
 570 //   stack overflow detection.
 571 //
 572 //   Newer version of LinuxThreads (since glibc-2.2, or, RH-7.x) and NPTL do
 573 //   not use MAP_GROWSDOWN.
 574 //
 575 // To get around the problem and allow stack banging on Linux, we need to
 576 // manually expand thread stack after receiving the SIGSEGV.
 577 //
 578 // There are two ways to expand thread stack to address "bottom", we used
 579 // both of them in JVM before 1.5:
 580 //   1. adjust stack pointer first so that it is below "bottom", and then
 581 //      touch "bottom"
 582 //   2. mmap() the page in question
 583 //
 584 // Now alternate signal stack is gone, it's harder to use 2. For instance,
 585 // if current sp is already near the lower end of page 101, and we need to
 586 // call mmap() to map page 100, it is possible that part of the mmap() frame
 587 // will be placed in page 100. When page 100 is mapped, it is zero-filled.
 588 // That will destroy the mmap() frame and cause VM to crash.
 589 //
 590 // The following code works by adjusting sp first, then accessing the "bottom"
 591 // page to force a page fault. Linux kernel will then automatically expand the
 592 // stack mapping.
 593 //
 594 // _expand_stack_to() assumes its frame size is less than page size, which
 595 // should always be true if the function is not inlined.
 596 
 597 static void NOINLINE _expand_stack_to(address bottom) {
 598   address sp;
 599   size_t size;
 600   volatile char *p;
 601 
 602   // Adjust bottom to point to the largest address within the same page, it
 603   // gives us a one-page buffer if alloca() allocates slightly more memory.
 604   bottom = (address)align_size_down((uintptr_t)bottom, os::Linux::page_size());
 605   bottom += os::Linux::page_size() - 1;
 606 
 607   // sp might be slightly above current stack pointer; if that's the case, we
 608   // will alloca() a little more space than necessary, which is OK. Don't use
 609   // os::current_stack_pointer(), as its result can be slightly below current
 610   // stack pointer, causing us to not alloca enough to reach "bottom".
 611   sp = (address)&sp;
 612 
 613   if (sp > bottom) {
 614     size = sp - bottom;
 615     p = (volatile char *)alloca(size);
 616     assert(p != NULL && p <= (volatile char *)bottom, "alloca problem?");
 617     p[0] = '\0';
 618   }
 619 }
 620 
 621 bool os::Linux::manually_expand_stack(JavaThread * t, address addr) {
 622   assert(t!=NULL, "just checking");
 623   assert(t->osthread()->expanding_stack(), "expand should be set");
 624   assert(t->stack_base() != NULL, "stack_base was not initialized");
 625 
 626   if (addr <  t->stack_base() && addr >= t->stack_reserved_zone_base()) {
 627     sigset_t mask_all, old_sigset;
 628     sigfillset(&mask_all);
 629     pthread_sigmask(SIG_SETMASK, &mask_all, &old_sigset);
 630     _expand_stack_to(addr);
 631     pthread_sigmask(SIG_SETMASK, &old_sigset, NULL);
 632     return true;
 633   }
 634   return false;
 635 }
 636 
 637 //////////////////////////////////////////////////////////////////////////////
 638 // create new thread
 639 
 640 // Thread start routine for all newly created threads
 641 static void *java_start(Thread *thread) {
 642   // Try to randomize the cache line index of hot stack frames.
 643   // This helps when threads of the same stack traces evict each other's
 644   // cache lines. The threads can be either from the same JVM instance, or
 645   // from different JVM instances. The benefit is especially true for
 646   // processors with hyperthreading technology.
 647   static int counter = 0;
 648   int pid = os::current_process_id();
 649   alloca(((pid ^ counter++) & 7) * 128);
 650 
 651   thread->initialize_thread_current();
 652 
 653   OSThread* osthread = thread->osthread();
 654   Monitor* sync = osthread->startThread_lock();
 655 
 656   osthread->set_thread_id(os::current_thread_id());
 657 
 658   log_info(os, thread)("Thread is alive (tid: " UINTX_FORMAT ", pthread id: " UINTX_FORMAT ").",
 659     os::current_thread_id(), (uintx) pthread_self());
 660 
 661   if (UseNUMA) {
 662     int lgrp_id = os::numa_get_group_id();
 663     if (lgrp_id != -1) {
 664       thread->set_lgrp_id(lgrp_id);
 665     }
 666   }
 667   // initialize signal mask for this thread
 668   os::Linux::hotspot_sigmask(thread);
 669 
 670   // initialize floating point control register
 671   os::Linux::init_thread_fpu_state();
 672 
 673   // handshaking with parent thread
 674   {
 675     MutexLockerEx ml(sync, Mutex::_no_safepoint_check_flag);
 676 
 677     // notify parent thread
 678     osthread->set_state(INITIALIZED);
 679     sync->notify_all();
 680 
 681     // wait until os::start_thread()
 682     while (osthread->get_state() == INITIALIZED) {
 683       sync->wait(Mutex::_no_safepoint_check_flag);
 684     }
 685   }
 686 
 687   // call one more level start routine
 688   thread->run();
 689 
 690   log_info(os, thread)("Thread finished (tid: " UINTX_FORMAT ", pthread id: " UINTX_FORMAT ").",
 691     os::current_thread_id(), (uintx) pthread_self());
 692 
 693   return 0;
 694 }
 695 
 696 bool os::create_thread(Thread* thread, ThreadType thr_type,
 697                        size_t stack_size) {
 698   assert(thread->osthread() == NULL, "caller responsible");
 699 
 700   // Allocate the OSThread object
 701   OSThread* osthread = new OSThread(NULL, NULL);
 702   if (osthread == NULL) {
 703     return false;
 704   }
 705 
 706   // set the correct thread state
 707   osthread->set_thread_type(thr_type);
 708 
 709   // Initial state is ALLOCATED but not INITIALIZED
 710   osthread->set_state(ALLOCATED);
 711 
 712   thread->set_osthread(osthread);
 713 
 714   // init thread attributes
 715   pthread_attr_t attr;
 716   pthread_attr_init(&attr);
 717   pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
 718 
 719   // stack size
 720   // calculate stack size if it's not specified by caller
 721   if (stack_size == 0) {
 722     stack_size = os::Linux::default_stack_size(thr_type);
 723 
 724     switch (thr_type) {
 725     case os::java_thread:
 726       // Java threads use ThreadStackSize which default value can be
 727       // changed with the flag -Xss
 728       assert(JavaThread::stack_size_at_create() > 0, "this should be set");
 729       stack_size = JavaThread::stack_size_at_create();
 730       break;
 731     case os::compiler_thread:
 732       if (CompilerThreadStackSize > 0) {
 733         stack_size = (size_t)(CompilerThreadStackSize * K);
 734         break;
 735       } // else fall through:
 736         // use VMThreadStackSize if CompilerThreadStackSize is not defined
 737     case os::vm_thread:
 738     case os::pgc_thread:
 739     case os::cgc_thread:
 740     case os::watcher_thread:
 741       if (VMThreadStackSize > 0) stack_size = (size_t)(VMThreadStackSize * K);
 742       break;
 743     }
 744   }
 745 
 746   stack_size = MAX2(stack_size, os::Linux::min_stack_allowed);
 747   pthread_attr_setstacksize(&attr, stack_size);
 748 
 749   // glibc guard page
 750   pthread_attr_setguardsize(&attr, os::Linux::default_guard_size(thr_type));
 751 
 752   ThreadState state;
 753 
 754   {
 755     pthread_t tid;
 756     int ret = pthread_create(&tid, &attr, (void* (*)(void*)) java_start, thread);
 757 
 758     char buf[64];
 759     if (ret == 0) {
 760       log_info(os, thread)("Thread started (pthread id: " UINTX_FORMAT ", attributes: %s). ",
 761         (uintx) tid, os::Posix::describe_pthread_attr(buf, sizeof(buf), &attr));
 762     } else {
 763       log_warning(os, thread)("Failed to start thread - pthread_create failed (%s) for attributes: %s.",
 764         os::errno_name(ret), os::Posix::describe_pthread_attr(buf, sizeof(buf), &attr));
 765     }
 766 
 767     pthread_attr_destroy(&attr);
 768 
 769     if (ret != 0) {
 770       // Need to clean up stuff we've allocated so far
 771       thread->set_osthread(NULL);
 772       delete osthread;
 773       return false;
 774     }
 775 
 776     // Store pthread info into the OSThread
 777     osthread->set_pthread_id(tid);
 778 
 779     // Wait until child thread is either initialized or aborted
 780     {
 781       Monitor* sync_with_child = osthread->startThread_lock();
 782       MutexLockerEx ml(sync_with_child, Mutex::_no_safepoint_check_flag);
 783       while ((state = osthread->get_state()) == ALLOCATED) {
 784         sync_with_child->wait(Mutex::_no_safepoint_check_flag);
 785       }
 786     }
 787   }
 788 
 789   // Aborted due to thread limit being reached
 790   if (state == ZOMBIE) {
 791     thread->set_osthread(NULL);
 792     delete osthread;
 793     return false;
 794   }
 795 
 796   // The thread is returned suspended (in state INITIALIZED),
 797   // and is started higher up in the call chain
 798   assert(state == INITIALIZED, "race condition");
 799   return true;
 800 }
 801 
 802 /////////////////////////////////////////////////////////////////////////////
 803 // attach existing thread
 804 
 805 // bootstrap the main thread
 806 bool os::create_main_thread(JavaThread* thread) {
 807   assert(os::Linux::_main_thread == pthread_self(), "should be called inside main thread");
 808   return create_attached_thread(thread);
 809 }
 810 
 811 bool os::create_attached_thread(JavaThread* thread) {
 812 #ifdef ASSERT
 813   thread->verify_not_published();
 814 #endif
 815 
 816   // Allocate the OSThread object
 817   OSThread* osthread = new OSThread(NULL, NULL);
 818 
 819   if (osthread == NULL) {
 820     return false;
 821   }
 822 
 823   // Store pthread info into the OSThread
 824   osthread->set_thread_id(os::Linux::gettid());
 825   osthread->set_pthread_id(::pthread_self());
 826 
 827   // initialize floating point control register
 828   os::Linux::init_thread_fpu_state();
 829 
 830   // Initial thread state is RUNNABLE
 831   osthread->set_state(RUNNABLE);
 832 
 833   thread->set_osthread(osthread);
 834 
 835   if (UseNUMA) {
 836     int lgrp_id = os::numa_get_group_id();
 837     if (lgrp_id != -1) {
 838       thread->set_lgrp_id(lgrp_id);
 839     }
 840   }
 841 
 842   if (os::Linux::is_initial_thread()) {
 843     // If current thread is initial thread, its stack is mapped on demand,
 844     // see notes about MAP_GROWSDOWN. Here we try to force kernel to map
 845     // the entire stack region to avoid SEGV in stack banging.
 846     // It is also useful to get around the heap-stack-gap problem on SuSE
 847     // kernel (see 4821821 for details). We first expand stack to the top
 848     // of yellow zone, then enable stack yellow zone (order is significant,
 849     // enabling yellow zone first will crash JVM on SuSE Linux), so there
 850     // is no gap between the last two virtual memory regions.
 851 
 852     JavaThread *jt = (JavaThread *)thread;
 853     address addr = jt->stack_reserved_zone_base();
 854     assert(addr != NULL, "initialization problem?");
 855     assert(jt->stack_available(addr) > 0, "stack guard should not be enabled");
 856 
 857     osthread->set_expanding_stack();
 858     os::Linux::manually_expand_stack(jt, addr);
 859     osthread->clear_expanding_stack();
 860   }
 861 
 862   // initialize signal mask for this thread
 863   // and save the caller's signal mask
 864   os::Linux::hotspot_sigmask(thread);
 865 
 866   log_info(os, thread)("Thread attached (tid: " UINTX_FORMAT ", pthread id: " UINTX_FORMAT ").",
 867     os::current_thread_id(), (uintx) pthread_self());
 868 
 869   return true;
 870 }
 871 
 872 void os::pd_start_thread(Thread* thread) {
 873   OSThread * osthread = thread->osthread();
 874   assert(osthread->get_state() != INITIALIZED, "just checking");
 875   Monitor* sync_with_child = osthread->startThread_lock();
 876   MutexLockerEx ml(sync_with_child, Mutex::_no_safepoint_check_flag);
 877   sync_with_child->notify();
 878 }
 879 
 880 // Free Linux resources related to the OSThread
 881 void os::free_thread(OSThread* osthread) {
 882   assert(osthread != NULL, "osthread not set");
 883 
 884   if (Thread::current()->osthread() == osthread) {
 885 #ifdef ASSERT
 886     sigset_t current;
 887     sigemptyset(&current);
 888     pthread_sigmask(SIG_SETMASK, NULL, &current);
 889     assert(!sigismember(&current, SR_signum), "SR signal should not be blocked!");
 890 #endif
 891 
 892     // Restore caller's signal mask
 893     sigset_t sigmask = osthread->caller_sigmask();
 894     pthread_sigmask(SIG_SETMASK, &sigmask, NULL);
 895   }
 896 
 897   delete osthread;
 898 }
 899 
 900 //////////////////////////////////////////////////////////////////////////////
 901 // initial thread
 902 
 903 // Check if current thread is the initial thread, similar to Solaris thr_main.
 904 bool os::Linux::is_initial_thread(void) {
 905   char dummy;
 906   // If called before init complete, thread stack bottom will be null.
 907   // Can be called if fatal error occurs before initialization.
 908   if (initial_thread_stack_bottom() == NULL) return false;
 909   assert(initial_thread_stack_bottom() != NULL &&
 910          initial_thread_stack_size()   != 0,
 911          "os::init did not locate initial thread's stack region");
 912   if ((address)&dummy >= initial_thread_stack_bottom() &&
 913       (address)&dummy < initial_thread_stack_bottom() + initial_thread_stack_size()) {
 914     return true;
 915   } else {
 916     return false;
 917   }
 918 }
 919 
 920 // Find the virtual memory area that contains addr
 921 static bool find_vma(address addr, address* vma_low, address* vma_high) {
 922   FILE *fp = fopen("/proc/self/maps", "r");
 923   if (fp) {
 924     address low, high;
 925     while (!feof(fp)) {
 926       if (fscanf(fp, "%p-%p", &low, &high) == 2) {
 927         if (low <= addr && addr < high) {
 928           if (vma_low)  *vma_low  = low;
 929           if (vma_high) *vma_high = high;
 930           fclose(fp);
 931           return true;
 932         }
 933       }
 934       for (;;) {
 935         int ch = fgetc(fp);
 936         if (ch == EOF || ch == (int)'\n') break;
 937       }
 938     }
 939     fclose(fp);
 940   }
 941   return false;
 942 }
 943 
 944 // Locate initial thread stack. This special handling of initial thread stack
 945 // is needed because pthread_getattr_np() on most (all?) Linux distros returns
 946 // bogus value for initial thread.
 947 void os::Linux::capture_initial_stack(size_t max_size) {
 948   // stack size is the easy part, get it from RLIMIT_STACK
 949   size_t stack_size;
 950   struct rlimit rlim;
 951   getrlimit(RLIMIT_STACK, &rlim);
 952   stack_size = rlim.rlim_cur;
 953 
 954   // 6308388: a bug in ld.so will relocate its own .data section to the
 955   //   lower end of primordial stack; reduce ulimit -s value a little bit
 956   //   so we won't install guard page on ld.so's data section.
 957   stack_size -= 2 * page_size();
 958 
 959   // 4441425: avoid crash with "unlimited" stack size on SuSE 7.1 or Redhat
 960   //   7.1, in both cases we will get 2G in return value.
 961   // 4466587: glibc 2.2.x compiled w/o "--enable-kernel=2.4.0" (RH 7.0,
 962   //   SuSE 7.2, Debian) can not handle alternate signal stack correctly
 963   //   for initial thread if its stack size exceeds 6M. Cap it at 2M,
 964   //   in case other parts in glibc still assumes 2M max stack size.
 965   // FIXME: alt signal stack is gone, maybe we can relax this constraint?
 966   // Problem still exists RH7.2 (IA64 anyway) but 2MB is a little small
 967   if (stack_size > 2 * K * K IA64_ONLY(*2)) {
 968     stack_size = 2 * K * K IA64_ONLY(*2);
 969   }
 970   // Try to figure out where the stack base (top) is. This is harder.
 971   //
 972   // When an application is started, glibc saves the initial stack pointer in
 973   // a global variable "__libc_stack_end", which is then used by system
 974   // libraries. __libc_stack_end should be pretty close to stack top. The
 975   // variable is available since the very early days. However, because it is
 976   // a private interface, it could disappear in the future.
 977   //
 978   // Linux kernel saves start_stack information in /proc/<pid>/stat. Similar
 979   // to __libc_stack_end, it is very close to stack top, but isn't the real
 980   // stack top. Note that /proc may not exist if VM is running as a chroot
 981   // program, so reading /proc/<pid>/stat could fail. Also the contents of
 982   // /proc/<pid>/stat could change in the future (though unlikely).
 983   //
 984   // We try __libc_stack_end first. If that doesn't work, look for
 985   // /proc/<pid>/stat. If neither of them works, we use current stack pointer
 986   // as a hint, which should work well in most cases.
 987 
 988   uintptr_t stack_start;
 989 
 990   // try __libc_stack_end first
 991   uintptr_t *p = (uintptr_t *)dlsym(RTLD_DEFAULT, "__libc_stack_end");
 992   if (p && *p) {
 993     stack_start = *p;
 994   } else {
 995     // see if we can get the start_stack field from /proc/self/stat
 996     FILE *fp;
 997     int pid;
 998     char state;
 999     int ppid;
1000     int pgrp;
1001     int session;
1002     int nr;
1003     int tpgrp;
1004     unsigned long flags;
1005     unsigned long minflt;
1006     unsigned long cminflt;
1007     unsigned long majflt;
1008     unsigned long cmajflt;
1009     unsigned long utime;
1010     unsigned long stime;
1011     long cutime;
1012     long cstime;
1013     long prio;
1014     long nice;
1015     long junk;
1016     long it_real;
1017     uintptr_t start;
1018     uintptr_t vsize;
1019     intptr_t rss;
1020     uintptr_t rsslim;
1021     uintptr_t scodes;
1022     uintptr_t ecode;
1023     int i;
1024 
1025     // Figure what the primordial thread stack base is. Code is inspired
1026     // by email from Hans Boehm. /proc/self/stat begins with current pid,
1027     // followed by command name surrounded by parentheses, state, etc.
1028     char stat[2048];
1029     int statlen;
1030 
1031     fp = fopen("/proc/self/stat", "r");
1032     if (fp) {
1033       statlen = fread(stat, 1, 2047, fp);
1034       stat[statlen] = '\0';
1035       fclose(fp);
1036 
1037       // Skip pid and the command string. Note that we could be dealing with
1038       // weird command names, e.g. user could decide to rename java launcher
1039       // to "java 1.4.2 :)", then the stat file would look like
1040       //                1234 (java 1.4.2 :)) R ... ...
1041       // We don't really need to know the command string, just find the last
1042       // occurrence of ")" and then start parsing from there. See bug 4726580.
1043       char * s = strrchr(stat, ')');
1044 
1045       i = 0;
1046       if (s) {
1047         // Skip blank chars
1048         do { s++; } while (s && isspace(*s));
1049 
1050 #define _UFM UINTX_FORMAT
1051 #define _DFM INTX_FORMAT
1052 
1053         //                                     1   1   1   1   1   1   1   1   1   1   2   2    2    2    2    2    2    2    2
1054         //              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
1055         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,
1056                    &state,          // 3  %c
1057                    &ppid,           // 4  %d
1058                    &pgrp,           // 5  %d
1059                    &session,        // 6  %d
1060                    &nr,             // 7  %d
1061                    &tpgrp,          // 8  %d
1062                    &flags,          // 9  %lu
1063                    &minflt,         // 10 %lu
1064                    &cminflt,        // 11 %lu
1065                    &majflt,         // 12 %lu
1066                    &cmajflt,        // 13 %lu
1067                    &utime,          // 14 %lu
1068                    &stime,          // 15 %lu
1069                    &cutime,         // 16 %ld
1070                    &cstime,         // 17 %ld
1071                    &prio,           // 18 %ld
1072                    &nice,           // 19 %ld
1073                    &junk,           // 20 %ld
1074                    &it_real,        // 21 %ld
1075                    &start,          // 22 UINTX_FORMAT
1076                    &vsize,          // 23 UINTX_FORMAT
1077                    &rss,            // 24 INTX_FORMAT
1078                    &rsslim,         // 25 UINTX_FORMAT
1079                    &scodes,         // 26 UINTX_FORMAT
1080                    &ecode,          // 27 UINTX_FORMAT
1081                    &stack_start);   // 28 UINTX_FORMAT
1082       }
1083 
1084 #undef _UFM
1085 #undef _DFM
1086 
1087       if (i != 28 - 2) {
1088         assert(false, "Bad conversion from /proc/self/stat");
1089         // product mode - assume we are the initial thread, good luck in the
1090         // embedded case.
1091         warning("Can't detect initial thread stack location - bad conversion");
1092         stack_start = (uintptr_t) &rlim;
1093       }
1094     } else {
1095       // For some reason we can't open /proc/self/stat (for example, running on
1096       // FreeBSD with a Linux emulator, or inside chroot), this should work for
1097       // most cases, so don't abort:
1098       warning("Can't detect initial thread stack location - no /proc/self/stat");
1099       stack_start = (uintptr_t) &rlim;
1100     }
1101   }
1102 
1103   // Now we have a pointer (stack_start) very close to the stack top, the
1104   // next thing to do is to figure out the exact location of stack top. We
1105   // can find out the virtual memory area that contains stack_start by
1106   // reading /proc/self/maps, it should be the last vma in /proc/self/maps,
1107   // and its upper limit is the real stack top. (again, this would fail if
1108   // running inside chroot, because /proc may not exist.)
1109 
1110   uintptr_t stack_top;
1111   address low, high;
1112   if (find_vma((address)stack_start, &low, &high)) {
1113     // success, "high" is the true stack top. (ignore "low", because initial
1114     // thread stack grows on demand, its real bottom is high - RLIMIT_STACK.)
1115     stack_top = (uintptr_t)high;
1116   } else {
1117     // failed, likely because /proc/self/maps does not exist
1118     warning("Can't detect initial thread stack location - find_vma failed");
1119     // best effort: stack_start is normally within a few pages below the real
1120     // stack top, use it as stack top, and reduce stack size so we won't put
1121     // guard page outside stack.
1122     stack_top = stack_start;
1123     stack_size -= 16 * page_size();
1124   }
1125 
1126   // stack_top could be partially down the page so align it
1127   stack_top = align_size_up(stack_top, page_size());
1128 
1129   if (max_size && stack_size > max_size) {
1130     _initial_thread_stack_size = max_size;
1131   } else {
1132     _initial_thread_stack_size = stack_size;
1133   }
1134 
1135   _initial_thread_stack_size = align_size_down(_initial_thread_stack_size, page_size());
1136   _initial_thread_stack_bottom = (address)stack_top - _initial_thread_stack_size;
1137 }
1138 
1139 ////////////////////////////////////////////////////////////////////////////////
1140 // time support
1141 
1142 // Time since start-up in seconds to a fine granularity.
1143 // Used by VMSelfDestructTimer and the MemProfiler.
1144 double os::elapsedTime() {
1145 
1146   return ((double)os::elapsed_counter()) / os::elapsed_frequency(); // nanosecond resolution
1147 }
1148 
1149 jlong os::elapsed_counter() {
1150   return javaTimeNanos() - initial_time_count;
1151 }
1152 
1153 jlong os::elapsed_frequency() {
1154   return NANOSECS_PER_SEC; // nanosecond resolution
1155 }
1156 
1157 bool os::supports_vtime() { return true; }
1158 bool os::enable_vtime()   { return false; }
1159 bool os::vtime_enabled()  { return false; }
1160 
1161 double os::elapsedVTime() {
1162   struct rusage usage;
1163   int retval = getrusage(RUSAGE_THREAD, &usage);
1164   if (retval == 0) {
1165     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);
1166   } else {
1167     // better than nothing, but not much
1168     return elapsedTime();
1169   }
1170 }
1171 
1172 jlong os::javaTimeMillis() {
1173   timeval time;
1174   int status = gettimeofday(&time, NULL);
1175   assert(status != -1, "linux error");
1176   return jlong(time.tv_sec) * 1000  +  jlong(time.tv_usec / 1000);
1177 }
1178 
1179 void os::javaTimeSystemUTC(jlong &seconds, jlong &nanos) {
1180   timeval time;
1181   int status = gettimeofday(&time, NULL);
1182   assert(status != -1, "linux error");
1183   seconds = jlong(time.tv_sec);
1184   nanos = jlong(time.tv_usec) * 1000;
1185 }
1186 
1187 
1188 #ifndef CLOCK_MONOTONIC
1189   #define CLOCK_MONOTONIC (1)
1190 #endif
1191 
1192 void os::Linux::clock_init() {
1193   // we do dlopen's in this particular order due to bug in linux
1194   // dynamical loader (see 6348968) leading to crash on exit
1195   void* handle = dlopen("librt.so.1", RTLD_LAZY);
1196   if (handle == NULL) {
1197     handle = dlopen("librt.so", RTLD_LAZY);
1198   }
1199 
1200   if (handle) {
1201     int (*clock_getres_func)(clockid_t, struct timespec*) =
1202            (int(*)(clockid_t, struct timespec*))dlsym(handle, "clock_getres");
1203     int (*clock_gettime_func)(clockid_t, struct timespec*) =
1204            (int(*)(clockid_t, struct timespec*))dlsym(handle, "clock_gettime");
1205     if (clock_getres_func && clock_gettime_func) {
1206       // See if monotonic clock is supported by the kernel. Note that some
1207       // early implementations simply return kernel jiffies (updated every
1208       // 1/100 or 1/1000 second). It would be bad to use such a low res clock
1209       // for nano time (though the monotonic property is still nice to have).
1210       // It's fixed in newer kernels, however clock_getres() still returns
1211       // 1/HZ. We check if clock_getres() works, but will ignore its reported
1212       // resolution for now. Hopefully as people move to new kernels, this
1213       // won't be a problem.
1214       struct timespec res;
1215       struct timespec tp;
1216       if (clock_getres_func (CLOCK_MONOTONIC, &res) == 0 &&
1217           clock_gettime_func(CLOCK_MONOTONIC, &tp)  == 0) {
1218         // yes, monotonic clock is supported
1219         _clock_gettime = clock_gettime_func;
1220         return;
1221       } else {
1222         // close librt if there is no monotonic clock
1223         dlclose(handle);
1224       }
1225     }
1226   }
1227   warning("No monotonic clock was available - timed services may " \
1228           "be adversely affected if the time-of-day clock changes");
1229 }
1230 
1231 #ifndef SYS_clock_getres
1232   #if defined(IA32) || defined(AMD64)
1233     #define SYS_clock_getres IA32_ONLY(266)  AMD64_ONLY(229)
1234     #define sys_clock_getres(x,y)  ::syscall(SYS_clock_getres, x, y)
1235   #else
1236     #warning "SYS_clock_getres not defined for this platform, disabling fast_thread_cpu_time"
1237     #define sys_clock_getres(x,y)  -1
1238   #endif
1239 #else
1240   #define sys_clock_getres(x,y)  ::syscall(SYS_clock_getres, x, y)
1241 #endif
1242 
1243 void os::Linux::fast_thread_clock_init() {
1244   if (!UseLinuxPosixThreadCPUClocks) {
1245     return;
1246   }
1247   clockid_t clockid;
1248   struct timespec tp;
1249   int (*pthread_getcpuclockid_func)(pthread_t, clockid_t *) =
1250       (int(*)(pthread_t, clockid_t *)) dlsym(RTLD_DEFAULT, "pthread_getcpuclockid");
1251 
1252   // Switch to using fast clocks for thread cpu time if
1253   // the sys_clock_getres() returns 0 error code.
1254   // Note, that some kernels may support the current thread
1255   // clock (CLOCK_THREAD_CPUTIME_ID) but not the clocks
1256   // returned by the pthread_getcpuclockid().
1257   // If the fast Posix clocks are supported then the sys_clock_getres()
1258   // must return at least tp.tv_sec == 0 which means a resolution
1259   // better than 1 sec. This is extra check for reliability.
1260 
1261   if (pthread_getcpuclockid_func &&
1262       pthread_getcpuclockid_func(_main_thread, &clockid) == 0 &&
1263       sys_clock_getres(clockid, &tp) == 0 && tp.tv_sec == 0) {
1264     _supports_fast_thread_cpu_time = true;
1265     _pthread_getcpuclockid = pthread_getcpuclockid_func;
1266   }
1267 }
1268 
1269 jlong os::javaTimeNanos() {
1270   if (os::supports_monotonic_clock()) {
1271     struct timespec tp;
1272     int status = Linux::clock_gettime(CLOCK_MONOTONIC, &tp);
1273     assert(status == 0, "gettime error");
1274     jlong result = jlong(tp.tv_sec) * (1000 * 1000 * 1000) + jlong(tp.tv_nsec);
1275     return result;
1276   } else {
1277     timeval time;
1278     int status = gettimeofday(&time, NULL);
1279     assert(status != -1, "linux error");
1280     jlong usecs = jlong(time.tv_sec) * (1000 * 1000) + jlong(time.tv_usec);
1281     return 1000 * usecs;
1282   }
1283 }
1284 
1285 void os::javaTimeNanos_info(jvmtiTimerInfo *info_ptr) {
1286   if (os::supports_monotonic_clock()) {
1287     info_ptr->max_value = ALL_64_BITS;
1288 
1289     // CLOCK_MONOTONIC - amount of time since some arbitrary point in the past
1290     info_ptr->may_skip_backward = false;      // not subject to resetting or drifting
1291     info_ptr->may_skip_forward = false;       // not subject to resetting or drifting
1292   } else {
1293     // gettimeofday - based on time in seconds since the Epoch thus does not wrap
1294     info_ptr->max_value = ALL_64_BITS;
1295 
1296     // gettimeofday is a real time clock so it skips
1297     info_ptr->may_skip_backward = true;
1298     info_ptr->may_skip_forward = true;
1299   }
1300 
1301   info_ptr->kind = JVMTI_TIMER_ELAPSED;                // elapsed not CPU time
1302 }
1303 
1304 // Return the real, user, and system times in seconds from an
1305 // arbitrary fixed point in the past.
1306 bool os::getTimesSecs(double* process_real_time,
1307                       double* process_user_time,
1308                       double* process_system_time) {
1309   struct tms ticks;
1310   clock_t real_ticks = times(&ticks);
1311 
1312   if (real_ticks == (clock_t) (-1)) {
1313     return false;
1314   } else {
1315     double ticks_per_second = (double) clock_tics_per_sec;
1316     *process_user_time = ((double) ticks.tms_utime) / ticks_per_second;
1317     *process_system_time = ((double) ticks.tms_stime) / ticks_per_second;
1318     *process_real_time = ((double) real_ticks) / ticks_per_second;
1319 
1320     return true;
1321   }
1322 }
1323 
1324 
1325 char * os::local_time_string(char *buf, size_t buflen) {
1326   struct tm t;
1327   time_t long_time;
1328   time(&long_time);
1329   localtime_r(&long_time, &t);
1330   jio_snprintf(buf, buflen, "%d-%02d-%02d %02d:%02d:%02d",
1331                t.tm_year + 1900, t.tm_mon + 1, t.tm_mday,
1332                t.tm_hour, t.tm_min, t.tm_sec);
1333   return buf;
1334 }
1335 
1336 struct tm* os::localtime_pd(const time_t* clock, struct tm*  res) {
1337   return localtime_r(clock, res);
1338 }
1339 
1340 ////////////////////////////////////////////////////////////////////////////////
1341 // runtime exit support
1342 
1343 // Note: os::shutdown() might be called very early during initialization, or
1344 // called from signal handler. Before adding something to os::shutdown(), make
1345 // sure it is async-safe and can handle partially initialized VM.
1346 void os::shutdown() {
1347 
1348   // allow PerfMemory to attempt cleanup of any persistent resources
1349   perfMemory_exit();
1350 
1351   // needs to remove object in file system
1352   AttachListener::abort();
1353 
1354   // flush buffered output, finish log files
1355   ostream_abort();
1356 
1357   // Check for abort hook
1358   abort_hook_t abort_hook = Arguments::abort_hook();
1359   if (abort_hook != NULL) {
1360     abort_hook();
1361   }
1362 
1363 }
1364 
1365 // Note: os::abort() might be called very early during initialization, or
1366 // called from signal handler. Before adding something to os::abort(), make
1367 // sure it is async-safe and can handle partially initialized VM.
1368 void os::abort(bool dump_core, void* siginfo, const void* context) {
1369   os::shutdown();
1370   if (dump_core) {
1371 #ifndef PRODUCT
1372     fdStream out(defaultStream::output_fd());
1373     out.print_raw("Current thread is ");
1374     char buf[16];
1375     jio_snprintf(buf, sizeof(buf), UINTX_FORMAT, os::current_thread_id());
1376     out.print_raw_cr(buf);
1377     out.print_raw_cr("Dumping core ...");
1378 #endif
1379     ::abort(); // dump core
1380   }
1381 
1382   ::exit(1);
1383 }
1384 
1385 // Die immediately, no exit hook, no abort hook, no cleanup.
1386 void os::die() {
1387   ::abort();
1388 }
1389 
1390 
1391 // This method is a copy of JDK's sysGetLastErrorString
1392 // from src/solaris/hpi/src/system_md.c
1393 
1394 size_t os::lasterror(char *buf, size_t len) {
1395   if (errno == 0)  return 0;
1396 
1397   const char *s = os::strerror(errno);
1398   size_t n = ::strlen(s);
1399   if (n >= len) {
1400     n = len - 1;
1401   }
1402   ::strncpy(buf, s, n);
1403   buf[n] = '\0';
1404   return n;
1405 }
1406 
1407 // thread_id is kernel thread id (similar to Solaris LWP id)
1408 intx os::current_thread_id() { return os::Linux::gettid(); }
1409 int os::current_process_id() {
1410   return ::getpid();
1411 }
1412 
1413 // DLL functions
1414 
1415 const char* os::dll_file_extension() { return ".so"; }
1416 
1417 // This must be hard coded because it's the system's temporary
1418 // directory not the java application's temp directory, ala java.io.tmpdir.
1419 const char* os::get_temp_directory() { return "/tmp"; }
1420 
1421 static bool file_exists(const char* filename) {
1422   struct stat statbuf;
1423   if (filename == NULL || strlen(filename) == 0) {
1424     return false;
1425   }
1426   return os::stat(filename, &statbuf) == 0;
1427 }
1428 
1429 bool os::dll_build_name(char* buffer, size_t buflen,
1430                         const char* pname, const char* fname) {
1431   bool retval = false;
1432   // Copied from libhpi
1433   const size_t pnamelen = pname ? strlen(pname) : 0;
1434 
1435   // Return error on buffer overflow.
1436   if (pnamelen + strlen(fname) + 10 > (size_t) buflen) {
1437     return retval;
1438   }
1439 
1440   if (pnamelen == 0) {
1441     snprintf(buffer, buflen, "lib%s.so", fname);
1442     retval = true;
1443   } else if (strchr(pname, *os::path_separator()) != NULL) {
1444     int n;
1445     char** pelements = split_path(pname, &n);
1446     if (pelements == NULL) {
1447       return false;
1448     }
1449     for (int i = 0; i < n; i++) {
1450       // Really shouldn't be NULL, but check can't hurt
1451       if (pelements[i] == NULL || strlen(pelements[i]) == 0) {
1452         continue; // skip the empty path values
1453       }
1454       snprintf(buffer, buflen, "%s/lib%s.so", pelements[i], fname);
1455       if (file_exists(buffer)) {
1456         retval = true;
1457         break;
1458       }
1459     }
1460     // release the storage
1461     for (int i = 0; i < n; i++) {
1462       if (pelements[i] != NULL) {
1463         FREE_C_HEAP_ARRAY(char, pelements[i]);
1464       }
1465     }
1466     if (pelements != NULL) {
1467       FREE_C_HEAP_ARRAY(char*, pelements);
1468     }
1469   } else {
1470     snprintf(buffer, buflen, "%s/lib%s.so", pname, fname);
1471     retval = true;
1472   }
1473   return retval;
1474 }
1475 
1476 // check if addr is inside libjvm.so
1477 bool os::address_is_in_vm(address addr) {
1478   static address libjvm_base_addr;
1479   Dl_info dlinfo;
1480 
1481   if (libjvm_base_addr == NULL) {
1482     if (dladdr(CAST_FROM_FN_PTR(void *, os::address_is_in_vm), &dlinfo) != 0) {
1483       libjvm_base_addr = (address)dlinfo.dli_fbase;
1484     }
1485     assert(libjvm_base_addr !=NULL, "Cannot obtain base address for libjvm");
1486   }
1487 
1488   if (dladdr((void *)addr, &dlinfo) != 0) {
1489     if (libjvm_base_addr == (address)dlinfo.dli_fbase) return true;
1490   }
1491 
1492   return false;
1493 }
1494 
1495 bool os::dll_address_to_function_name(address addr, char *buf,
1496                                       int buflen, int *offset,
1497                                       bool demangle) {
1498   // buf is not optional, but offset is optional
1499   assert(buf != NULL, "sanity check");
1500 
1501   Dl_info dlinfo;
1502 
1503   if (dladdr((void*)addr, &dlinfo) != 0) {
1504     // see if we have a matching symbol
1505     if (dlinfo.dli_saddr != NULL && dlinfo.dli_sname != NULL) {
1506       if (!(demangle && Decoder::demangle(dlinfo.dli_sname, buf, buflen))) {
1507         jio_snprintf(buf, buflen, "%s", dlinfo.dli_sname);
1508       }
1509       if (offset != NULL) *offset = addr - (address)dlinfo.dli_saddr;
1510       return true;
1511     }
1512     // no matching symbol so try for just file info
1513     if (dlinfo.dli_fname != NULL && dlinfo.dli_fbase != NULL) {
1514       if (Decoder::decode((address)(addr - (address)dlinfo.dli_fbase),
1515                           buf, buflen, offset, dlinfo.dli_fname, demangle)) {
1516         return true;
1517       }
1518     }
1519   }
1520 
1521   buf[0] = '\0';
1522   if (offset != NULL) *offset = -1;
1523   return false;
1524 }
1525 
1526 struct _address_to_library_name {
1527   address addr;          // input : memory address
1528   size_t  buflen;        //         size of fname
1529   char*   fname;         // output: library name
1530   address base;          //         library base addr
1531 };
1532 
1533 static int address_to_library_name_callback(struct dl_phdr_info *info,
1534                                             size_t size, void *data) {
1535   int i;
1536   bool found = false;
1537   address libbase = NULL;
1538   struct _address_to_library_name * d = (struct _address_to_library_name *)data;
1539 
1540   // iterate through all loadable segments
1541   for (i = 0; i < info->dlpi_phnum; i++) {
1542     address segbase = (address)(info->dlpi_addr + info->dlpi_phdr[i].p_vaddr);
1543     if (info->dlpi_phdr[i].p_type == PT_LOAD) {
1544       // base address of a library is the lowest address of its loaded
1545       // segments.
1546       if (libbase == NULL || libbase > segbase) {
1547         libbase = segbase;
1548       }
1549       // see if 'addr' is within current segment
1550       if (segbase <= d->addr &&
1551           d->addr < segbase + info->dlpi_phdr[i].p_memsz) {
1552         found = true;
1553       }
1554     }
1555   }
1556 
1557   // dlpi_name is NULL or empty if the ELF file is executable, return 0
1558   // so dll_address_to_library_name() can fall through to use dladdr() which
1559   // can figure out executable name from argv[0].
1560   if (found && info->dlpi_name && info->dlpi_name[0]) {
1561     d->base = libbase;
1562     if (d->fname) {
1563       jio_snprintf(d->fname, d->buflen, "%s", info->dlpi_name);
1564     }
1565     return 1;
1566   }
1567   return 0;
1568 }
1569 
1570 bool os::dll_address_to_library_name(address addr, char* buf,
1571                                      int buflen, int* offset) {
1572   // buf is not optional, but offset is optional
1573   assert(buf != NULL, "sanity check");
1574 
1575   Dl_info dlinfo;
1576   struct _address_to_library_name data;
1577 
1578   // There is a bug in old glibc dladdr() implementation that it could resolve
1579   // to wrong library name if the .so file has a base address != NULL. Here
1580   // we iterate through the program headers of all loaded libraries to find
1581   // out which library 'addr' really belongs to. This workaround can be
1582   // removed once the minimum requirement for glibc is moved to 2.3.x.
1583   data.addr = addr;
1584   data.fname = buf;
1585   data.buflen = buflen;
1586   data.base = NULL;
1587   int rslt = dl_iterate_phdr(address_to_library_name_callback, (void *)&data);
1588 
1589   if (rslt) {
1590     // buf already contains library name
1591     if (offset) *offset = addr - data.base;
1592     return true;
1593   }
1594   if (dladdr((void*)addr, &dlinfo) != 0) {
1595     if (dlinfo.dli_fname != NULL) {
1596       jio_snprintf(buf, buflen, "%s", dlinfo.dli_fname);
1597     }
1598     if (dlinfo.dli_fbase != NULL && offset != NULL) {
1599       *offset = addr - (address)dlinfo.dli_fbase;
1600     }
1601     return true;
1602   }
1603 
1604   buf[0] = '\0';
1605   if (offset) *offset = -1;
1606   return false;
1607 }
1608 
1609 // Loads .dll/.so and
1610 // in case of error it checks if .dll/.so was built for the
1611 // same architecture as Hotspot is running on
1612 
1613 
1614 // Remember the stack's state. The Linux dynamic linker will change
1615 // the stack to 'executable' at most once, so we must safepoint only once.
1616 bool os::Linux::_stack_is_executable = false;
1617 
1618 // VM operation that loads a library.  This is necessary if stack protection
1619 // of the Java stacks can be lost during loading the library.  If we
1620 // do not stop the Java threads, they can stack overflow before the stacks
1621 // are protected again.
1622 class VM_LinuxDllLoad: public VM_Operation {
1623  private:
1624   const char *_filename;
1625   char *_ebuf;
1626   int _ebuflen;
1627   void *_lib;
1628  public:
1629   VM_LinuxDllLoad(const char *fn, char *ebuf, int ebuflen) :
1630     _filename(fn), _ebuf(ebuf), _ebuflen(ebuflen), _lib(NULL) {}
1631   VMOp_Type type() const { return VMOp_LinuxDllLoad; }
1632   void doit() {
1633     _lib = os::Linux::dll_load_in_vmthread(_filename, _ebuf, _ebuflen);
1634     os::Linux::_stack_is_executable = true;
1635   }
1636   void* loaded_library() { return _lib; }
1637 };
1638 
1639 void * os::dll_load(const char *filename, char *ebuf, int ebuflen) {
1640   void * result = NULL;
1641   bool load_attempted = false;
1642 
1643   // Check whether the library to load might change execution rights
1644   // of the stack. If they are changed, the protection of the stack
1645   // guard pages will be lost. We need a safepoint to fix this.
1646   //
1647   // See Linux man page execstack(8) for more info.
1648   if (os::uses_stack_guard_pages() && !os::Linux::_stack_is_executable) {
1649     ElfFile ef(filename);
1650     if (!ef.specifies_noexecstack()) {
1651       if (!is_init_completed()) {
1652         os::Linux::_stack_is_executable = true;
1653         // This is OK - No Java threads have been created yet, and hence no
1654         // stack guard pages to fix.
1655         //
1656         // This should happen only when you are building JDK7 using a very
1657         // old version of JDK6 (e.g., with JPRT) and running test_gamma.
1658         //
1659         // Dynamic loader will make all stacks executable after
1660         // this function returns, and will not do that again.
1661         assert(Threads::first() == NULL, "no Java threads should exist yet.");
1662       } else {
1663         warning("You have loaded library %s which might have disabled stack guard. "
1664                 "The VM will try to fix the stack guard now.\n"
1665                 "It's highly recommended that you fix the library with "
1666                 "'execstack -c <libfile>', or link it with '-z noexecstack'.",
1667                 filename);
1668 
1669         assert(Thread::current()->is_Java_thread(), "must be Java thread");
1670         JavaThread *jt = JavaThread::current();
1671         if (jt->thread_state() != _thread_in_native) {
1672           // This happens when a compiler thread tries to load a hsdis-<arch>.so file
1673           // that requires ExecStack. Cannot enter safe point. Let's give up.
1674           warning("Unable to fix stack guard. Giving up.");
1675         } else {
1676           if (!LoadExecStackDllInVMThread) {
1677             // This is for the case where the DLL has an static
1678             // constructor function that executes JNI code. We cannot
1679             // load such DLLs in the VMThread.
1680             result = os::Linux::dlopen_helper(filename, ebuf, ebuflen);
1681           }
1682 
1683           ThreadInVMfromNative tiv(jt);
1684           debug_only(VMNativeEntryWrapper vew;)
1685 
1686           VM_LinuxDllLoad op(filename, ebuf, ebuflen);
1687           VMThread::execute(&op);
1688           if (LoadExecStackDllInVMThread) {
1689             result = op.loaded_library();
1690           }
1691           load_attempted = true;
1692         }
1693       }
1694     }
1695   }
1696 
1697   if (!load_attempted) {
1698     result = os::Linux::dlopen_helper(filename, ebuf, ebuflen);
1699   }
1700 
1701   if (result != NULL) {
1702     // Successful loading
1703     return result;
1704   }
1705 
1706   Elf32_Ehdr elf_head;
1707   int diag_msg_max_length=ebuflen-strlen(ebuf);
1708   char* diag_msg_buf=ebuf+strlen(ebuf);
1709 
1710   if (diag_msg_max_length==0) {
1711     // No more space in ebuf for additional diagnostics message
1712     return NULL;
1713   }
1714 
1715 
1716   int file_descriptor= ::open(filename, O_RDONLY | O_NONBLOCK);
1717 
1718   if (file_descriptor < 0) {
1719     // Can't open library, report dlerror() message
1720     return NULL;
1721   }
1722 
1723   bool failed_to_read_elf_head=
1724     (sizeof(elf_head)!=
1725      (::read(file_descriptor, &elf_head,sizeof(elf_head))));
1726 
1727   ::close(file_descriptor);
1728   if (failed_to_read_elf_head) {
1729     // file i/o error - report dlerror() msg
1730     return NULL;
1731   }
1732 
1733   typedef struct {
1734     Elf32_Half  code;         // Actual value as defined in elf.h
1735     Elf32_Half  compat_class; // Compatibility of archs at VM's sense
1736     char        elf_class;    // 32 or 64 bit
1737     char        endianess;    // MSB or LSB
1738     char*       name;         // String representation
1739   } arch_t;
1740 
1741 #ifndef EM_486
1742   #define EM_486          6               /* Intel 80486 */
1743 #endif
1744 #ifndef EM_AARCH64
1745   #define EM_AARCH64    183               /* ARM AARCH64 */
1746 #endif
1747 
1748   static const arch_t arch_array[]={
1749     {EM_386,         EM_386,     ELFCLASS32, ELFDATA2LSB, (char*)"IA 32"},
1750     {EM_486,         EM_386,     ELFCLASS32, ELFDATA2LSB, (char*)"IA 32"},
1751     {EM_IA_64,       EM_IA_64,   ELFCLASS64, ELFDATA2LSB, (char*)"IA 64"},
1752     {EM_X86_64,      EM_X86_64,  ELFCLASS64, ELFDATA2LSB, (char*)"AMD 64"},
1753     {EM_SPARC,       EM_SPARC,   ELFCLASS32, ELFDATA2MSB, (char*)"Sparc 32"},
1754     {EM_SPARC32PLUS, EM_SPARC,   ELFCLASS32, ELFDATA2MSB, (char*)"Sparc 32"},
1755     {EM_SPARCV9,     EM_SPARCV9, ELFCLASS64, ELFDATA2MSB, (char*)"Sparc v9 64"},
1756     {EM_PPC,         EM_PPC,     ELFCLASS32, ELFDATA2MSB, (char*)"Power PC 32"},
1757 #if defined(VM_LITTLE_ENDIAN)
1758     {EM_PPC64,       EM_PPC64,   ELFCLASS64, ELFDATA2LSB, (char*)"Power PC 64"},
1759 #else
1760     {EM_PPC64,       EM_PPC64,   ELFCLASS64, ELFDATA2MSB, (char*)"Power PC 64 LE"},
1761 #endif
1762     {EM_ARM,         EM_ARM,     ELFCLASS32,   ELFDATA2LSB, (char*)"ARM"},
1763     {EM_S390,        EM_S390,    ELFCLASSNONE, ELFDATA2MSB, (char*)"IBM System/390"},
1764     {EM_ALPHA,       EM_ALPHA,   ELFCLASS64, ELFDATA2LSB, (char*)"Alpha"},
1765     {EM_MIPS_RS3_LE, EM_MIPS_RS3_LE, ELFCLASS32, ELFDATA2LSB, (char*)"MIPSel"},
1766     {EM_MIPS,        EM_MIPS,    ELFCLASS32, ELFDATA2MSB, (char*)"MIPS"},
1767     {EM_PARISC,      EM_PARISC,  ELFCLASS32, ELFDATA2MSB, (char*)"PARISC"},
1768     {EM_68K,         EM_68K,     ELFCLASS32, ELFDATA2MSB, (char*)"M68k"},
1769     {EM_AARCH64,     EM_AARCH64, ELFCLASS64, ELFDATA2LSB, (char*)"AARCH64"},
1770   };
1771 
1772 #if  (defined IA32)
1773   static  Elf32_Half running_arch_code=EM_386;
1774 #elif   (defined AMD64)
1775   static  Elf32_Half running_arch_code=EM_X86_64;
1776 #elif  (defined IA64)
1777   static  Elf32_Half running_arch_code=EM_IA_64;
1778 #elif  (defined __sparc) && (defined _LP64)
1779   static  Elf32_Half running_arch_code=EM_SPARCV9;
1780 #elif  (defined __sparc) && (!defined _LP64)
1781   static  Elf32_Half running_arch_code=EM_SPARC;
1782 #elif  (defined __powerpc64__)
1783   static  Elf32_Half running_arch_code=EM_PPC64;
1784 #elif  (defined __powerpc__)
1785   static  Elf32_Half running_arch_code=EM_PPC;
1786 #elif  (defined ARM)
1787   static  Elf32_Half running_arch_code=EM_ARM;
1788 #elif  (defined S390)
1789   static  Elf32_Half running_arch_code=EM_S390;
1790 #elif  (defined ALPHA)
1791   static  Elf32_Half running_arch_code=EM_ALPHA;
1792 #elif  (defined MIPSEL)
1793   static  Elf32_Half running_arch_code=EM_MIPS_RS3_LE;
1794 #elif  (defined PARISC)
1795   static  Elf32_Half running_arch_code=EM_PARISC;
1796 #elif  (defined MIPS)
1797   static  Elf32_Half running_arch_code=EM_MIPS;
1798 #elif  (defined M68K)
1799   static  Elf32_Half running_arch_code=EM_68K;
1800 #elif  (defined AARCH64)
1801   static  Elf32_Half running_arch_code=EM_AARCH64;
1802 #else
1803     #error Method os::dll_load requires that one of following is defined:\
1804          IA32, AMD64, IA64, __sparc, __powerpc__, ARM, S390, ALPHA, MIPS, MIPSEL, PARISC, M68K, AARCH64
1805 #endif
1806 
1807   // Identify compatability class for VM's architecture and library's architecture
1808   // Obtain string descriptions for architectures
1809 
1810   arch_t lib_arch={elf_head.e_machine,0,elf_head.e_ident[EI_CLASS], elf_head.e_ident[EI_DATA], NULL};
1811   int running_arch_index=-1;
1812 
1813   for (unsigned int i=0; i < ARRAY_SIZE(arch_array); i++) {
1814     if (running_arch_code == arch_array[i].code) {
1815       running_arch_index    = i;
1816     }
1817     if (lib_arch.code == arch_array[i].code) {
1818       lib_arch.compat_class = arch_array[i].compat_class;
1819       lib_arch.name         = arch_array[i].name;
1820     }
1821   }
1822 
1823   assert(running_arch_index != -1,
1824          "Didn't find running architecture code (running_arch_code) in arch_array");
1825   if (running_arch_index == -1) {
1826     // Even though running architecture detection failed
1827     // we may still continue with reporting dlerror() message
1828     return NULL;
1829   }
1830 
1831   if (lib_arch.endianess != arch_array[running_arch_index].endianess) {
1832     ::snprintf(diag_msg_buf, diag_msg_max_length-1," (Possible cause: endianness mismatch)");
1833     return NULL;
1834   }
1835 
1836 #ifndef S390
1837   if (lib_arch.elf_class != arch_array[running_arch_index].elf_class) {
1838     ::snprintf(diag_msg_buf, diag_msg_max_length-1," (Possible cause: architecture word width mismatch)");
1839     return NULL;
1840   }
1841 #endif // !S390
1842 
1843   if (lib_arch.compat_class != arch_array[running_arch_index].compat_class) {
1844     if (lib_arch.name!=NULL) {
1845       ::snprintf(diag_msg_buf, diag_msg_max_length-1,
1846                  " (Possible cause: can't load %s-bit .so on a %s-bit platform)",
1847                  lib_arch.name, arch_array[running_arch_index].name);
1848     } else {
1849       ::snprintf(diag_msg_buf, diag_msg_max_length-1,
1850                  " (Possible cause: can't load this .so (machine code=0x%x) on a %s-bit platform)",
1851                  lib_arch.code,
1852                  arch_array[running_arch_index].name);
1853     }
1854   }
1855 
1856   return NULL;
1857 }
1858 
1859 void * os::Linux::dlopen_helper(const char *filename, char *ebuf,
1860                                 int ebuflen) {
1861   void * result = ::dlopen(filename, RTLD_LAZY);
1862   if (result == NULL) {
1863     ::strncpy(ebuf, ::dlerror(), ebuflen - 1);
1864     ebuf[ebuflen-1] = '\0';
1865   }
1866   return result;
1867 }
1868 
1869 void * os::Linux::dll_load_in_vmthread(const char *filename, char *ebuf,
1870                                        int ebuflen) {
1871   void * result = NULL;
1872   if (LoadExecStackDllInVMThread) {
1873     result = dlopen_helper(filename, ebuf, ebuflen);
1874   }
1875 
1876   // Since 7019808, libjvm.so is linked with -noexecstack. If the VM loads a
1877   // library that requires an executable stack, or which does not have this
1878   // stack attribute set, dlopen changes the stack attribute to executable. The
1879   // read protection of the guard pages gets lost.
1880   //
1881   // Need to check _stack_is_executable again as multiple VM_LinuxDllLoad
1882   // may have been queued at the same time.
1883 
1884   if (!_stack_is_executable) {
1885     JavaThread *jt = Threads::first();
1886 
1887     while (jt) {
1888       if (!jt->stack_guard_zone_unused() &&     // Stack not yet fully initialized
1889           jt->stack_guards_enabled()) {         // No pending stack overflow exceptions
1890         if (!os::guard_memory((char *)jt->stack_end(), jt->stack_guard_zone_size())) {
1891           warning("Attempt to reguard stack yellow zone failed.");
1892         }
1893       }
1894       jt = jt->next();
1895     }
1896   }
1897 
1898   return result;
1899 }
1900 
1901 void* os::dll_lookup(void* handle, const char* name) {
1902   void* res = dlsym(handle, name);
1903   return res;
1904 }
1905 
1906 void* os::get_default_process_handle() {
1907   return (void*)::dlopen(NULL, RTLD_LAZY);
1908 }
1909 
1910 static bool _print_ascii_file(const char* filename, outputStream* st) {
1911   int fd = ::open(filename, O_RDONLY);
1912   if (fd == -1) {
1913     return false;
1914   }
1915 
1916   char buf[33];
1917   int bytes;
1918   buf[32] = '\0';
1919   while ((bytes = ::read(fd, buf, sizeof(buf)-1)) > 0) {
1920     st->print_raw(buf, bytes);
1921   }
1922 
1923   ::close(fd);
1924 
1925   return true;
1926 }
1927 
1928 void os::print_dll_info(outputStream *st) {
1929   st->print_cr("Dynamic libraries:");
1930 
1931   char fname[32];
1932   pid_t pid = os::Linux::gettid();
1933 
1934   jio_snprintf(fname, sizeof(fname), "/proc/%d/maps", pid);
1935 
1936   if (!_print_ascii_file(fname, st)) {
1937     st->print("Can not get library information for pid = %d\n", pid);
1938   }
1939 }
1940 
1941 int os::get_loaded_modules_info(os::LoadedModulesCallbackFunc callback, void *param) {
1942   FILE *procmapsFile = NULL;
1943 
1944   // Open the procfs maps file for the current process
1945   if ((procmapsFile = fopen("/proc/self/maps", "r")) != NULL) {
1946     // Allocate PATH_MAX for file name plus a reasonable size for other fields.
1947     char line[PATH_MAX + 100];
1948 
1949     // Read line by line from 'file'
1950     while (fgets(line, sizeof(line), procmapsFile) != NULL) {
1951       u8 base, top, offset, inode;
1952       char permissions[5];
1953       char device[6];
1954       char name[PATH_MAX + 1];
1955 
1956       // Parse fields from line
1957       sscanf(line, UINT64_FORMAT_X "-" UINT64_FORMAT_X " %4s " UINT64_FORMAT_X " %5s " INT64_FORMAT " %s",
1958              &base, &top, permissions, &offset, device, &inode, name);
1959 
1960       // Filter by device id '00:00' so that we only get file system mapped files.
1961       if (strcmp(device, "00:00") != 0) {
1962 
1963         // Call callback with the fields of interest
1964         if(callback(name, (address)base, (address)top, param)) {
1965           // Oops abort, callback aborted
1966           fclose(procmapsFile);
1967           return 1;
1968         }
1969       }
1970     }
1971     fclose(procmapsFile);
1972   }
1973   return 0;
1974 }
1975 
1976 void os::print_os_info_brief(outputStream* st) {
1977   os::Linux::print_distro_info(st);
1978 
1979   os::Posix::print_uname_info(st);
1980 
1981   os::Linux::print_libversion_info(st);
1982 
1983 }
1984 
1985 void os::print_os_info(outputStream* st) {
1986   st->print("OS:");
1987 
1988   os::Linux::print_distro_info(st);
1989 
1990   os::Posix::print_uname_info(st);
1991 
1992   // Print warning if unsafe chroot environment detected
1993   if (unsafe_chroot_detected) {
1994     st->print("WARNING!! ");
1995     st->print_cr("%s", unstable_chroot_error);
1996   }
1997 
1998   os::Linux::print_libversion_info(st);
1999 
2000   os::Posix::print_rlimit_info(st);
2001 
2002   os::Posix::print_load_average(st);
2003 
2004   os::Linux::print_full_memory_info(st);
2005 }
2006 
2007 // Try to identify popular distros.
2008 // Most Linux distributions have a /etc/XXX-release file, which contains
2009 // the OS version string. Newer Linux distributions have a /etc/lsb-release
2010 // file that also contains the OS version string. Some have more than one
2011 // /etc/XXX-release file (e.g. Mandrake has both /etc/mandrake-release and
2012 // /etc/redhat-release.), so the order is important.
2013 // Any Linux that is based on Redhat (i.e. Oracle, Mandrake, Sun JDS...) have
2014 // their own specific XXX-release file as well as a redhat-release file.
2015 // Because of this the XXX-release file needs to be searched for before the
2016 // redhat-release file.
2017 // Since Red Hat has a lsb-release file that is not very descriptive the
2018 // search for redhat-release needs to be before lsb-release.
2019 // Since the lsb-release file is the new standard it needs to be searched
2020 // before the older style release files.
2021 // Searching system-release (Red Hat) and os-release (other Linuxes) are a
2022 // next to last resort.  The os-release file is a new standard that contains
2023 // distribution information and the system-release file seems to be an old
2024 // standard that has been replaced by the lsb-release and os-release files.
2025 // Searching for the debian_version file is the last resort.  It contains
2026 // an informative string like "6.0.6" or "wheezy/sid". Because of this
2027 // "Debian " is printed before the contents of the debian_version file.
2028 
2029 const char* distro_files[] = {
2030   "/etc/oracle-release",
2031   "/etc/mandriva-release",
2032   "/etc/mandrake-release",
2033   "/etc/sun-release",
2034   "/etc/redhat-release",
2035   "/etc/lsb-release",
2036   "/etc/SuSE-release",
2037   "/etc/turbolinux-release",
2038   "/etc/gentoo-release",
2039   "/etc/ltib-release",
2040   "/etc/angstrom-version",
2041   "/etc/system-release",
2042   "/etc/os-release",
2043   NULL };
2044 
2045 void os::Linux::print_distro_info(outputStream* st) {
2046   for (int i = 0;; i++) {
2047     const char* file = distro_files[i];
2048     if (file == NULL) {
2049       break;  // done
2050     }
2051     // If file prints, we found it.
2052     if (_print_ascii_file(file, st)) {
2053       return;
2054     }
2055   }
2056 
2057   if (file_exists("/etc/debian_version")) {
2058     st->print("Debian ");
2059     _print_ascii_file("/etc/debian_version", st);
2060   } else {
2061     st->print("Linux");
2062   }
2063   st->cr();
2064 }
2065 
2066 static void parse_os_info(char* distro, size_t length, const char* file) {
2067   FILE* fp = fopen(file, "r");
2068   if (fp != NULL) {
2069     char buf[256];
2070     // get last line of the file.
2071     while (fgets(buf, sizeof(buf), fp)) { }
2072     // Edit out extra stuff in expected ubuntu format
2073     if (strstr(buf, "DISTRIB_DESCRIPTION=") != NULL) {
2074       char* ptr = strstr(buf, "\"");  // the name is in quotes
2075       if (ptr != NULL) {
2076         ptr++; // go beyond first quote
2077         char* nl = strchr(ptr, '\"');
2078         if (nl != NULL) *nl = '\0';
2079         strncpy(distro, ptr, length);
2080       } else {
2081         ptr = strstr(buf, "=");
2082         ptr++; // go beyond equals then
2083         char* nl = strchr(ptr, '\n');
2084         if (nl != NULL) *nl = '\0';
2085         strncpy(distro, ptr, length);
2086       }
2087     } else {
2088       // if not in expected Ubuntu format, print out whole line minus \n
2089       char* nl = strchr(buf, '\n');
2090       if (nl != NULL) *nl = '\0';
2091       strncpy(distro, buf, length);
2092     }
2093     // close distro file
2094     fclose(fp);
2095   }
2096 }
2097 
2098 void os::get_summary_os_info(char* buf, size_t buflen) {
2099   for (int i = 0;; i++) {
2100     const char* file = distro_files[i];
2101     if (file == NULL) {
2102       break; // ran out of distro_files
2103     }
2104     if (file_exists(file)) {
2105       parse_os_info(buf, buflen, file);
2106       return;
2107     }
2108   }
2109   // special case for debian
2110   if (file_exists("/etc/debian_version")) {
2111     strncpy(buf, "Debian ", buflen);
2112     parse_os_info(&buf[7], buflen-7, "/etc/debian_version");
2113   } else {
2114     strncpy(buf, "Linux", buflen);
2115   }
2116 }
2117 
2118 void os::Linux::print_libversion_info(outputStream* st) {
2119   // libc, pthread
2120   st->print("libc:");
2121   st->print("%s ", os::Linux::glibc_version());
2122   st->print("%s ", os::Linux::libpthread_version());
2123   st->cr();
2124 }
2125 
2126 void os::Linux::print_full_memory_info(outputStream* st) {
2127   st->print("\n/proc/meminfo:\n");
2128   _print_ascii_file("/proc/meminfo", st);
2129   st->cr();
2130 }
2131 
2132 void os::print_memory_info(outputStream* st) {
2133 
2134   st->print("Memory:");
2135   st->print(" %dk page", os::vm_page_size()>>10);
2136 
2137   // values in struct sysinfo are "unsigned long"
2138   struct sysinfo si;
2139   sysinfo(&si);
2140 
2141   st->print(", physical " UINT64_FORMAT "k",
2142             os::physical_memory() >> 10);
2143   st->print("(" UINT64_FORMAT "k free)",
2144             os::available_memory() >> 10);
2145   st->print(", swap " UINT64_FORMAT "k",
2146             ((jlong)si.totalswap * si.mem_unit) >> 10);
2147   st->print("(" UINT64_FORMAT "k free)",
2148             ((jlong)si.freeswap * si.mem_unit) >> 10);
2149   st->cr();
2150 }
2151 
2152 // Print the first "model name" line and the first "flags" line
2153 // that we find and nothing more. We assume "model name" comes
2154 // before "flags" so if we find a second "model name", then the
2155 // "flags" field is considered missing.
2156 static bool print_model_name_and_flags(outputStream* st, char* buf, size_t buflen) {
2157 #if defined(IA32) || defined(AMD64)
2158   // Other platforms have less repetitive cpuinfo files
2159   FILE *fp = fopen("/proc/cpuinfo", "r");
2160   if (fp) {
2161     while (!feof(fp)) {
2162       if (fgets(buf, buflen, fp)) {
2163         // Assume model name comes before flags
2164         bool model_name_printed = false;
2165         if (strstr(buf, "model name") != NULL) {
2166           if (!model_name_printed) {
2167             st->print_raw("CPU Model and flags from /proc/cpuinfo:\n");
2168             st->print_raw(buf);
2169             model_name_printed = true;
2170           } else {
2171             // model name printed but not flags?  Odd, just return
2172             fclose(fp);
2173             return true;
2174           }
2175         }
2176         // print the flags line too
2177         if (strstr(buf, "flags") != NULL) {
2178           st->print_raw(buf);
2179           fclose(fp);
2180           return true;
2181         }
2182       }
2183     }
2184     fclose(fp);
2185   }
2186 #endif // x86 platforms
2187   return false;
2188 }
2189 
2190 void os::pd_print_cpu_info(outputStream* st, char* buf, size_t buflen) {
2191   // Only print the model name if the platform provides this as a summary
2192   if (!print_model_name_and_flags(st, buf, buflen)) {
2193     st->print("\n/proc/cpuinfo:\n");
2194     if (!_print_ascii_file("/proc/cpuinfo", st)) {
2195       st->print_cr("  <Not Available>");
2196     }
2197   }
2198 }
2199 
2200 #if defined(AMD64) || defined(IA32) || defined(X32)
2201 const char* search_string = "model name";
2202 #elif defined(SPARC)
2203 const char* search_string = "cpu";
2204 #elif defined(PPC64)
2205 const char* search_string = "cpu";
2206 #else
2207 const char* search_string = "Processor";
2208 #endif
2209 
2210 // Parses the cpuinfo file for string representing the model name.
2211 void os::get_summary_cpu_info(char* cpuinfo, size_t length) {
2212   FILE* fp = fopen("/proc/cpuinfo", "r");
2213   if (fp != NULL) {
2214     while (!feof(fp)) {
2215       char buf[256];
2216       if (fgets(buf, sizeof(buf), fp)) {
2217         char* start = strstr(buf, search_string);
2218         if (start != NULL) {
2219           char *ptr = start + strlen(search_string);
2220           char *end = buf + strlen(buf);
2221           while (ptr != end) {
2222              // skip whitespace and colon for the rest of the name.
2223              if (*ptr != ' ' && *ptr != '\t' && *ptr != ':') {
2224                break;
2225              }
2226              ptr++;
2227           }
2228           if (ptr != end) {
2229             // reasonable string, get rid of newline and keep the rest
2230             char* nl = strchr(buf, '\n');
2231             if (nl != NULL) *nl = '\0';
2232             strncpy(cpuinfo, ptr, length);
2233             fclose(fp);
2234             return;
2235           }
2236         }
2237       }
2238     }
2239     fclose(fp);
2240   }
2241   // cpuinfo not found or parsing failed, just print generic string.  The entire
2242   // /proc/cpuinfo file will be printed later in the file (or enough of it for x86)
2243 #if defined(AMD64)
2244   strncpy(cpuinfo, "x86_64", length);
2245 #elif defined(IA32)
2246   strncpy(cpuinfo, "x86_32", length);
2247 #elif defined(IA64)
2248   strncpy(cpuinfo, "IA64", length);
2249 #elif defined(SPARC)
2250   strncpy(cpuinfo, "sparcv9", length);
2251 #elif defined(AARCH64)
2252   strncpy(cpuinfo, "AArch64", length);
2253 #elif defined(ARM)
2254   strncpy(cpuinfo, "ARM", length);
2255 #elif defined(PPC)
2256   strncpy(cpuinfo, "PPC64", length);
2257 #elif defined(ZERO_LIBARCH)
2258   strncpy(cpuinfo, ZERO_LIBARCH, length);
2259 #else
2260   strncpy(cpuinfo, "unknown", length);
2261 #endif
2262 }
2263 
2264 static void print_signal_handler(outputStream* st, int sig,
2265                                  char* buf, size_t buflen);
2266 
2267 void os::print_signal_handlers(outputStream* st, char* buf, size_t buflen) {
2268   st->print_cr("Signal Handlers:");
2269   print_signal_handler(st, SIGSEGV, buf, buflen);
2270   print_signal_handler(st, SIGBUS , buf, buflen);
2271   print_signal_handler(st, SIGFPE , buf, buflen);
2272   print_signal_handler(st, SIGPIPE, buf, buflen);
2273   print_signal_handler(st, SIGXFSZ, buf, buflen);
2274   print_signal_handler(st, SIGILL , buf, buflen);
2275   print_signal_handler(st, SR_signum, buf, buflen);
2276   print_signal_handler(st, SHUTDOWN1_SIGNAL, buf, buflen);
2277   print_signal_handler(st, SHUTDOWN2_SIGNAL , buf, buflen);
2278   print_signal_handler(st, SHUTDOWN3_SIGNAL , buf, buflen);
2279   print_signal_handler(st, BREAK_SIGNAL, buf, buflen);
2280 #if defined(PPC64)
2281   print_signal_handler(st, SIGTRAP, buf, buflen);
2282 #endif
2283 }
2284 
2285 static char saved_jvm_path[MAXPATHLEN] = {0};
2286 
2287 // Find the full path to the current module, libjvm.so
2288 void os::jvm_path(char *buf, jint buflen) {
2289   // Error checking.
2290   if (buflen < MAXPATHLEN) {
2291     assert(false, "must use a large-enough buffer");
2292     buf[0] = '\0';
2293     return;
2294   }
2295   // Lazy resolve the path to current module.
2296   if (saved_jvm_path[0] != 0) {
2297     strcpy(buf, saved_jvm_path);
2298     return;
2299   }
2300 
2301   char dli_fname[MAXPATHLEN];
2302   bool ret = dll_address_to_library_name(
2303                                          CAST_FROM_FN_PTR(address, os::jvm_path),
2304                                          dli_fname, sizeof(dli_fname), NULL);
2305   assert(ret, "cannot locate libjvm");
2306   char *rp = NULL;
2307   if (ret && dli_fname[0] != '\0') {
2308     rp = realpath(dli_fname, buf);
2309   }
2310   if (rp == NULL) {
2311     return;
2312   }
2313 
2314   if (Arguments::sun_java_launcher_is_altjvm()) {
2315     // Support for the java launcher's '-XXaltjvm=<path>' option. Typical
2316     // value for buf is "<JAVA_HOME>/jre/lib/<arch>/<vmtype>/libjvm.so".
2317     // If "/jre/lib/" appears at the right place in the string, then
2318     // assume we are installed in a JDK and we're done. Otherwise, check
2319     // for a JAVA_HOME environment variable and fix up the path so it
2320     // looks like libjvm.so is installed there (append a fake suffix
2321     // hotspot/libjvm.so).
2322     const char *p = buf + strlen(buf) - 1;
2323     for (int count = 0; p > buf && count < 5; ++count) {
2324       for (--p; p > buf && *p != '/'; --p)
2325         /* empty */ ;
2326     }
2327 
2328     if (strncmp(p, "/jre/lib/", 9) != 0) {
2329       // Look for JAVA_HOME in the environment.
2330       char* java_home_var = ::getenv("JAVA_HOME");
2331       if (java_home_var != NULL && java_home_var[0] != 0) {
2332         char* jrelib_p;
2333         int len;
2334 
2335         // Check the current module name "libjvm.so".
2336         p = strrchr(buf, '/');
2337         if (p == NULL) {
2338           return;
2339         }
2340         assert(strstr(p, "/libjvm") == p, "invalid library name");
2341 
2342         rp = realpath(java_home_var, buf);
2343         if (rp == NULL) {
2344           return;
2345         }
2346 
2347         // determine if this is a legacy image or modules image
2348         // modules image doesn't have "jre" subdirectory
2349         len = strlen(buf);
2350         assert(len < buflen, "Ran out of buffer room");
2351         jrelib_p = buf + len;
2352         snprintf(jrelib_p, buflen-len, "/jre/lib/%s", cpu_arch);
2353         if (0 != access(buf, F_OK)) {
2354           snprintf(jrelib_p, buflen-len, "/lib/%s", cpu_arch);
2355         }
2356 
2357         if (0 == access(buf, F_OK)) {
2358           // Use current module name "libjvm.so"
2359           len = strlen(buf);
2360           snprintf(buf + len, buflen-len, "/hotspot/libjvm.so");
2361         } else {
2362           // Go back to path of .so
2363           rp = realpath(dli_fname, buf);
2364           if (rp == NULL) {
2365             return;
2366           }
2367         }
2368       }
2369     }
2370   }
2371 
2372   strncpy(saved_jvm_path, buf, MAXPATHLEN);
2373   saved_jvm_path[MAXPATHLEN - 1] = '\0';
2374 }
2375 
2376 void os::print_jni_name_prefix_on(outputStream* st, int args_size) {
2377   // no prefix required, not even "_"
2378 }
2379 
2380 void os::print_jni_name_suffix_on(outputStream* st, int args_size) {
2381   // no suffix required
2382 }
2383 
2384 ////////////////////////////////////////////////////////////////////////////////
2385 // sun.misc.Signal support
2386 
2387 static volatile jint sigint_count = 0;
2388 
2389 static void UserHandler(int sig, void *siginfo, void *context) {
2390   // 4511530 - sem_post is serialized and handled by the manager thread. When
2391   // the program is interrupted by Ctrl-C, SIGINT is sent to every thread. We
2392   // don't want to flood the manager thread with sem_post requests.
2393   if (sig == SIGINT && Atomic::add(1, &sigint_count) > 1) {
2394     return;
2395   }
2396 
2397   // Ctrl-C is pressed during error reporting, likely because the error
2398   // handler fails to abort. Let VM die immediately.
2399   if (sig == SIGINT && is_error_reported()) {
2400     os::die();
2401   }
2402 
2403   os::signal_notify(sig);
2404 }
2405 
2406 void* os::user_handler() {
2407   return CAST_FROM_FN_PTR(void*, UserHandler);
2408 }
2409 
2410 struct timespec PosixSemaphore::create_timespec(unsigned int sec, int nsec) {
2411   struct timespec ts;
2412   // Semaphore's are always associated with CLOCK_REALTIME
2413   os::Linux::clock_gettime(CLOCK_REALTIME, &ts);
2414   // see unpackTime for discussion on overflow checking
2415   if (sec >= MAX_SECS) {
2416     ts.tv_sec += MAX_SECS;
2417     ts.tv_nsec = 0;
2418   } else {
2419     ts.tv_sec += sec;
2420     ts.tv_nsec += nsec;
2421     if (ts.tv_nsec >= NANOSECS_PER_SEC) {
2422       ts.tv_nsec -= NANOSECS_PER_SEC;
2423       ++ts.tv_sec; // note: this must be <= max_secs
2424     }
2425   }
2426 
2427   return ts;
2428 }
2429 
2430 extern "C" {
2431   typedef void (*sa_handler_t)(int);
2432   typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
2433 }
2434 
2435 void* os::signal(int signal_number, void* handler) {
2436   struct sigaction sigAct, oldSigAct;
2437 
2438   sigfillset(&(sigAct.sa_mask));
2439   sigAct.sa_flags   = SA_RESTART|SA_SIGINFO;
2440   sigAct.sa_handler = CAST_TO_FN_PTR(sa_handler_t, handler);
2441 
2442   if (sigaction(signal_number, &sigAct, &oldSigAct)) {
2443     // -1 means registration failed
2444     return (void *)-1;
2445   }
2446 
2447   return CAST_FROM_FN_PTR(void*, oldSigAct.sa_handler);
2448 }
2449 
2450 void os::signal_raise(int signal_number) {
2451   ::raise(signal_number);
2452 }
2453 
2454 // The following code is moved from os.cpp for making this
2455 // code platform specific, which it is by its very nature.
2456 
2457 // Will be modified when max signal is changed to be dynamic
2458 int os::sigexitnum_pd() {
2459   return NSIG;
2460 }
2461 
2462 // a counter for each possible signal value
2463 static volatile jint pending_signals[NSIG+1] = { 0 };
2464 
2465 // Linux(POSIX) specific hand shaking semaphore.
2466 static sem_t sig_sem;
2467 static PosixSemaphore sr_semaphore;
2468 
2469 void os::signal_init_pd() {
2470   // Initialize signal structures
2471   ::memset((void*)pending_signals, 0, sizeof(pending_signals));
2472 
2473   // Initialize signal semaphore
2474   ::sem_init(&sig_sem, 0, 0);
2475 }
2476 
2477 void os::signal_notify(int sig) {
2478   Atomic::inc(&pending_signals[sig]);
2479   ::sem_post(&sig_sem);
2480 }
2481 
2482 static int check_pending_signals(bool wait) {
2483   Atomic::store(0, &sigint_count);
2484   for (;;) {
2485     for (int i = 0; i < NSIG + 1; i++) {
2486       jint n = pending_signals[i];
2487       if (n > 0 && n == Atomic::cmpxchg(n - 1, &pending_signals[i], n)) {
2488         return i;
2489       }
2490     }
2491     if (!wait) {
2492       return -1;
2493     }
2494     JavaThread *thread = JavaThread::current();
2495     ThreadBlockInVM tbivm(thread);
2496 
2497     bool threadIsSuspended;
2498     do {
2499       thread->set_suspend_equivalent();
2500       // cleared by handle_special_suspend_equivalent_condition() or java_suspend_self()
2501       ::sem_wait(&sig_sem);
2502 
2503       // were we externally suspended while we were waiting?
2504       threadIsSuspended = thread->handle_special_suspend_equivalent_condition();
2505       if (threadIsSuspended) {
2506         // The semaphore has been incremented, but while we were waiting
2507         // another thread suspended us. We don't want to continue running
2508         // while suspended because that would surprise the thread that
2509         // suspended us.
2510         ::sem_post(&sig_sem);
2511 
2512         thread->java_suspend_self();
2513       }
2514     } while (threadIsSuspended);
2515   }
2516 }
2517 
2518 int os::signal_lookup() {
2519   return check_pending_signals(false);
2520 }
2521 
2522 int os::signal_wait() {
2523   return check_pending_signals(true);
2524 }
2525 
2526 ////////////////////////////////////////////////////////////////////////////////
2527 // Virtual Memory
2528 
2529 int os::vm_page_size() {
2530   // Seems redundant as all get out
2531   assert(os::Linux::page_size() != -1, "must call os::init");
2532   return os::Linux::page_size();
2533 }
2534 
2535 // Solaris allocates memory by pages.
2536 int os::vm_allocation_granularity() {
2537   assert(os::Linux::page_size() != -1, "must call os::init");
2538   return os::Linux::page_size();
2539 }
2540 
2541 // Rationale behind this function:
2542 //  current (Mon Apr 25 20:12:18 MSD 2005) oprofile drops samples without executable
2543 //  mapping for address (see lookup_dcookie() in the kernel module), thus we cannot get
2544 //  samples for JITted code. Here we create private executable mapping over the code cache
2545 //  and then we can use standard (well, almost, as mapping can change) way to provide
2546 //  info for the reporting script by storing timestamp and location of symbol
2547 void linux_wrap_code(char* base, size_t size) {
2548   static volatile jint cnt = 0;
2549 
2550   if (!UseOprofile) {
2551     return;
2552   }
2553 
2554   char buf[PATH_MAX+1];
2555   int num = Atomic::add(1, &cnt);
2556 
2557   snprintf(buf, sizeof(buf), "%s/hs-vm-%d-%d",
2558            os::get_temp_directory(), os::current_process_id(), num);
2559   unlink(buf);
2560 
2561   int fd = ::open(buf, O_CREAT | O_RDWR, S_IRWXU);
2562 
2563   if (fd != -1) {
2564     off_t rv = ::lseek(fd, size-2, SEEK_SET);
2565     if (rv != (off_t)-1) {
2566       if (::write(fd, "", 1) == 1) {
2567         mmap(base, size,
2568              PROT_READ|PROT_WRITE|PROT_EXEC,
2569              MAP_PRIVATE|MAP_FIXED|MAP_NORESERVE, fd, 0);
2570       }
2571     }
2572     ::close(fd);
2573     unlink(buf);
2574   }
2575 }
2576 
2577 static bool recoverable_mmap_error(int err) {
2578   // See if the error is one we can let the caller handle. This
2579   // list of errno values comes from JBS-6843484. I can't find a
2580   // Linux man page that documents this specific set of errno
2581   // values so while this list currently matches Solaris, it may
2582   // change as we gain experience with this failure mode.
2583   switch (err) {
2584   case EBADF:
2585   case EINVAL:
2586   case ENOTSUP:
2587     // let the caller deal with these errors
2588     return true;
2589 
2590   default:
2591     // Any remaining errors on this OS can cause our reserved mapping
2592     // to be lost. That can cause confusion where different data
2593     // structures think they have the same memory mapped. The worst
2594     // scenario is if both the VM and a library think they have the
2595     // same memory mapped.
2596     return false;
2597   }
2598 }
2599 
2600 static void warn_fail_commit_memory(char* addr, size_t size, bool exec,
2601                                     int err) {
2602   warning("INFO: os::commit_memory(" PTR_FORMAT ", " SIZE_FORMAT
2603           ", %d) failed; error='%s' (errno=%d)", p2i(addr), size, exec,
2604           os::strerror(err), err);
2605 }
2606 
2607 static void warn_fail_commit_memory(char* addr, size_t size,
2608                                     size_t alignment_hint, bool exec,
2609                                     int err) {
2610   warning("INFO: os::commit_memory(" PTR_FORMAT ", " SIZE_FORMAT
2611           ", " SIZE_FORMAT ", %d) failed; error='%s' (errno=%d)", p2i(addr), size,
2612           alignment_hint, exec, os::strerror(err), err);
2613 }
2614 
2615 // NOTE: Linux kernel does not really reserve the pages for us.
2616 //       All it does is to check if there are enough free pages
2617 //       left at the time of mmap(). This could be a potential
2618 //       problem.
2619 int os::Linux::commit_memory_impl(char* addr, size_t size, bool exec) {
2620   int prot = exec ? PROT_READ|PROT_WRITE|PROT_EXEC : PROT_READ|PROT_WRITE;
2621   uintptr_t res = (uintptr_t) ::mmap(addr, size, prot,
2622                                      MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0);
2623   if (res != (uintptr_t) MAP_FAILED) {
2624     if (UseNUMAInterleaving) {
2625       numa_make_global(addr, size);
2626     }
2627     return 0;
2628   }
2629 
2630   int err = errno;  // save errno from mmap() call above
2631 
2632   if (!recoverable_mmap_error(err)) {
2633     warn_fail_commit_memory(addr, size, exec, err);
2634     vm_exit_out_of_memory(size, OOM_MMAP_ERROR, "committing reserved memory.");
2635   }
2636 
2637   return err;
2638 }
2639 
2640 bool os::pd_commit_memory(char* addr, size_t size, bool exec) {
2641   return os::Linux::commit_memory_impl(addr, size, exec) == 0;
2642 }
2643 
2644 void os::pd_commit_memory_or_exit(char* addr, size_t size, bool exec,
2645                                   const char* mesg) {
2646   assert(mesg != NULL, "mesg must be specified");
2647   int err = os::Linux::commit_memory_impl(addr, size, exec);
2648   if (err != 0) {
2649     // the caller wants all commit errors to exit with the specified mesg:
2650     warn_fail_commit_memory(addr, size, exec, err);
2651     vm_exit_out_of_memory(size, OOM_MMAP_ERROR, "%s", mesg);
2652   }
2653 }
2654 
2655 // Define MAP_HUGETLB here so we can build HotSpot on old systems.
2656 #ifndef MAP_HUGETLB
2657   #define MAP_HUGETLB 0x40000
2658 #endif
2659 
2660 // Define MADV_HUGEPAGE here so we can build HotSpot on old systems.
2661 #ifndef MADV_HUGEPAGE
2662   #define MADV_HUGEPAGE 14
2663 #endif
2664 
2665 int os::Linux::commit_memory_impl(char* addr, size_t size,
2666                                   size_t alignment_hint, bool exec) {
2667   int err = os::Linux::commit_memory_impl(addr, size, exec);
2668   if (err == 0) {
2669     realign_memory(addr, size, alignment_hint);
2670   }
2671   return err;
2672 }
2673 
2674 bool os::pd_commit_memory(char* addr, size_t size, size_t alignment_hint,
2675                           bool exec) {
2676   return os::Linux::commit_memory_impl(addr, size, alignment_hint, exec) == 0;
2677 }
2678 
2679 void os::pd_commit_memory_or_exit(char* addr, size_t size,
2680                                   size_t alignment_hint, bool exec,
2681                                   const char* mesg) {
2682   assert(mesg != NULL, "mesg must be specified");
2683   int err = os::Linux::commit_memory_impl(addr, size, alignment_hint, exec);
2684   if (err != 0) {
2685     // the caller wants all commit errors to exit with the specified mesg:
2686     warn_fail_commit_memory(addr, size, alignment_hint, exec, err);
2687     vm_exit_out_of_memory(size, OOM_MMAP_ERROR, "%s", mesg);
2688   }
2689 }
2690 
2691 void os::pd_realign_memory(char *addr, size_t bytes, size_t alignment_hint) {
2692   if (UseTransparentHugePages && alignment_hint > (size_t)vm_page_size()) {
2693     // We don't check the return value: madvise(MADV_HUGEPAGE) may not
2694     // be supported or the memory may already be backed by huge pages.
2695     ::madvise(addr, bytes, MADV_HUGEPAGE);
2696   }
2697 }
2698 
2699 void os::pd_free_memory(char *addr, size_t bytes, size_t alignment_hint) {
2700   // This method works by doing an mmap over an existing mmaping and effectively discarding
2701   // the existing pages. However it won't work for SHM-based large pages that cannot be
2702   // uncommitted at all. We don't do anything in this case to avoid creating a segment with
2703   // small pages on top of the SHM segment. This method always works for small pages, so we
2704   // allow that in any case.
2705   if (alignment_hint <= (size_t)os::vm_page_size() || can_commit_large_page_memory()) {
2706     commit_memory(addr, bytes, alignment_hint, !ExecMem);
2707   }
2708 }
2709 
2710 void os::numa_make_global(char *addr, size_t bytes) {
2711   Linux::numa_interleave_memory(addr, bytes);
2712 }
2713 
2714 // Define for numa_set_bind_policy(int). Setting the argument to 0 will set the
2715 // bind policy to MPOL_PREFERRED for the current thread.
2716 #define USE_MPOL_PREFERRED 0
2717 
2718 void os::numa_make_local(char *addr, size_t bytes, int lgrp_hint) {
2719   // To make NUMA and large pages more robust when both enabled, we need to ease
2720   // the requirements on where the memory should be allocated. MPOL_BIND is the
2721   // default policy and it will force memory to be allocated on the specified
2722   // node. Changing this to MPOL_PREFERRED will prefer to allocate the memory on
2723   // the specified node, but will not force it. Using this policy will prevent
2724   // getting SIGBUS when trying to allocate large pages on NUMA nodes with no
2725   // free large pages.
2726   Linux::numa_set_bind_policy(USE_MPOL_PREFERRED);
2727   Linux::numa_tonode_memory(addr, bytes, lgrp_hint);
2728 }
2729 
2730 bool os::numa_topology_changed() { return false; }
2731 
2732 size_t os::numa_get_groups_num() {
2733   int max_node = Linux::numa_max_node();
2734   return max_node > 0 ? max_node + 1 : 1;
2735 }
2736 
2737 int os::numa_get_group_id() {
2738   int cpu_id = Linux::sched_getcpu();
2739   if (cpu_id != -1) {
2740     int lgrp_id = Linux::get_node_by_cpu(cpu_id);
2741     if (lgrp_id != -1) {
2742       return lgrp_id;
2743     }
2744   }
2745   return 0;
2746 }
2747 
2748 size_t os::numa_get_leaf_groups(int *ids, size_t size) {
2749   for (size_t i = 0; i < size; i++) {
2750     ids[i] = i;
2751   }
2752   return size;
2753 }
2754 
2755 bool os::get_page_info(char *start, page_info* info) {
2756   return false;
2757 }
2758 
2759 char *os::scan_pages(char *start, char* end, page_info* page_expected,
2760                      page_info* page_found) {
2761   return end;
2762 }
2763 
2764 
2765 int os::Linux::sched_getcpu_syscall(void) {
2766   unsigned int cpu = 0;
2767   int retval = -1;
2768 
2769 #if defined(IA32)
2770   #ifndef SYS_getcpu
2771     #define SYS_getcpu 318
2772   #endif
2773   retval = syscall(SYS_getcpu, &cpu, NULL, NULL);
2774 #elif defined(AMD64)
2775 // Unfortunately we have to bring all these macros here from vsyscall.h
2776 // to be able to compile on old linuxes.
2777   #define __NR_vgetcpu 2
2778   #define VSYSCALL_START (-10UL << 20)
2779   #define VSYSCALL_SIZE 1024
2780   #define VSYSCALL_ADDR(vsyscall_nr) (VSYSCALL_START+VSYSCALL_SIZE*(vsyscall_nr))
2781   typedef long (*vgetcpu_t)(unsigned int *cpu, unsigned int *node, unsigned long *tcache);
2782   vgetcpu_t vgetcpu = (vgetcpu_t)VSYSCALL_ADDR(__NR_vgetcpu);
2783   retval = vgetcpu(&cpu, NULL, NULL);
2784 #endif
2785 
2786   return (retval == -1) ? retval : cpu;
2787 }
2788 
2789 // Something to do with the numa-aware allocator needs these symbols
2790 extern "C" JNIEXPORT void numa_warn(int number, char *where, ...) { }
2791 extern "C" JNIEXPORT void numa_error(char *where) { }
2792 
2793 
2794 // If we are running with libnuma version > 2, then we should
2795 // be trying to use symbols with versions 1.1
2796 // If we are running with earlier version, which did not have symbol versions,
2797 // we should use the base version.
2798 void* os::Linux::libnuma_dlsym(void* handle, const char *name) {
2799   void *f = dlvsym(handle, name, "libnuma_1.1");
2800   if (f == NULL) {
2801     f = dlsym(handle, name);
2802   }
2803   return f;
2804 }
2805 
2806 bool os::Linux::libnuma_init() {
2807   // sched_getcpu() should be in libc.
2808   set_sched_getcpu(CAST_TO_FN_PTR(sched_getcpu_func_t,
2809                                   dlsym(RTLD_DEFAULT, "sched_getcpu")));
2810 
2811   // If it's not, try a direct syscall.
2812   if (sched_getcpu() == -1) {
2813     set_sched_getcpu(CAST_TO_FN_PTR(sched_getcpu_func_t,
2814                                     (void*)&sched_getcpu_syscall));
2815   }
2816 
2817   if (sched_getcpu() != -1) { // Does it work?
2818     void *handle = dlopen("libnuma.so.1", RTLD_LAZY);
2819     if (handle != NULL) {
2820       set_numa_node_to_cpus(CAST_TO_FN_PTR(numa_node_to_cpus_func_t,
2821                                            libnuma_dlsym(handle, "numa_node_to_cpus")));
2822       set_numa_max_node(CAST_TO_FN_PTR(numa_max_node_func_t,
2823                                        libnuma_dlsym(handle, "numa_max_node")));
2824       set_numa_available(CAST_TO_FN_PTR(numa_available_func_t,
2825                                         libnuma_dlsym(handle, "numa_available")));
2826       set_numa_tonode_memory(CAST_TO_FN_PTR(numa_tonode_memory_func_t,
2827                                             libnuma_dlsym(handle, "numa_tonode_memory")));
2828       set_numa_interleave_memory(CAST_TO_FN_PTR(numa_interleave_memory_func_t,
2829                                                 libnuma_dlsym(handle, "numa_interleave_memory")));
2830       set_numa_set_bind_policy(CAST_TO_FN_PTR(numa_set_bind_policy_func_t,
2831                                               libnuma_dlsym(handle, "numa_set_bind_policy")));
2832 
2833 
2834       if (numa_available() != -1) {
2835         set_numa_all_nodes((unsigned long*)libnuma_dlsym(handle, "numa_all_nodes"));
2836         // Create a cpu -> node mapping
2837         _cpu_to_node = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<int>(0, true);
2838         rebuild_cpu_to_node_map();
2839         return true;
2840       }
2841     }
2842   }
2843   return false;
2844 }
2845 
2846 // rebuild_cpu_to_node_map() constructs a table mapping cpud id to node id.
2847 // The table is later used in get_node_by_cpu().
2848 void os::Linux::rebuild_cpu_to_node_map() {
2849   const size_t NCPUS = 32768; // Since the buffer size computation is very obscure
2850                               // in libnuma (possible values are starting from 16,
2851                               // and continuing up with every other power of 2, but less
2852                               // than the maximum number of CPUs supported by kernel), and
2853                               // is a subject to change (in libnuma version 2 the requirements
2854                               // are more reasonable) we'll just hardcode the number they use
2855                               // in the library.
2856   const size_t BitsPerCLong = sizeof(long) * CHAR_BIT;
2857 
2858   size_t cpu_num = os::active_processor_count();
2859   size_t cpu_map_size = NCPUS / BitsPerCLong;
2860   size_t cpu_map_valid_size =
2861     MIN2((cpu_num + BitsPerCLong - 1) / BitsPerCLong, cpu_map_size);
2862 
2863   cpu_to_node()->clear();
2864   cpu_to_node()->at_grow(cpu_num - 1);
2865   size_t node_num = numa_get_groups_num();
2866 
2867   unsigned long *cpu_map = NEW_C_HEAP_ARRAY(unsigned long, cpu_map_size, mtInternal);
2868   for (size_t i = 0; i < node_num; i++) {
2869     if (numa_node_to_cpus(i, cpu_map, cpu_map_size * sizeof(unsigned long)) != -1) {
2870       for (size_t j = 0; j < cpu_map_valid_size; j++) {
2871         if (cpu_map[j] != 0) {
2872           for (size_t k = 0; k < BitsPerCLong; k++) {
2873             if (cpu_map[j] & (1UL << k)) {
2874               cpu_to_node()->at_put(j * BitsPerCLong + k, i);
2875             }
2876           }
2877         }
2878       }
2879     }
2880   }
2881   FREE_C_HEAP_ARRAY(unsigned long, cpu_map);
2882 }
2883 
2884 int os::Linux::get_node_by_cpu(int cpu_id) {
2885   if (cpu_to_node() != NULL && cpu_id >= 0 && cpu_id < cpu_to_node()->length()) {
2886     return cpu_to_node()->at(cpu_id);
2887   }
2888   return -1;
2889 }
2890 
2891 GrowableArray<int>* os::Linux::_cpu_to_node;
2892 os::Linux::sched_getcpu_func_t os::Linux::_sched_getcpu;
2893 os::Linux::numa_node_to_cpus_func_t os::Linux::_numa_node_to_cpus;
2894 os::Linux::numa_max_node_func_t os::Linux::_numa_max_node;
2895 os::Linux::numa_available_func_t os::Linux::_numa_available;
2896 os::Linux::numa_tonode_memory_func_t os::Linux::_numa_tonode_memory;
2897 os::Linux::numa_interleave_memory_func_t os::Linux::_numa_interleave_memory;
2898 os::Linux::numa_set_bind_policy_func_t os::Linux::_numa_set_bind_policy;
2899 unsigned long* os::Linux::_numa_all_nodes;
2900 
2901 bool os::pd_uncommit_memory(char* addr, size_t size) {
2902   uintptr_t res = (uintptr_t) ::mmap(addr, size, PROT_NONE,
2903                                      MAP_PRIVATE|MAP_FIXED|MAP_NORESERVE|MAP_ANONYMOUS, -1, 0);
2904   return res  != (uintptr_t) MAP_FAILED;
2905 }
2906 
2907 static address get_stack_commited_bottom(address bottom, size_t size) {
2908   address nbot = bottom;
2909   address ntop = bottom + size;
2910 
2911   size_t page_sz = os::vm_page_size();
2912   unsigned pages = size / page_sz;
2913 
2914   unsigned char vec[1];
2915   unsigned imin = 1, imax = pages + 1, imid;
2916   int mincore_return_value = 0;
2917 
2918   assert(imin <= imax, "Unexpected page size");
2919 
2920   while (imin < imax) {
2921     imid = (imax + imin) / 2;
2922     nbot = ntop - (imid * page_sz);
2923 
2924     // Use a trick with mincore to check whether the page is mapped or not.
2925     // mincore sets vec to 1 if page resides in memory and to 0 if page
2926     // is swapped output but if page we are asking for is unmapped
2927     // it returns -1,ENOMEM
2928     mincore_return_value = mincore(nbot, page_sz, vec);
2929 
2930     if (mincore_return_value == -1) {
2931       // Page is not mapped go up
2932       // to find first mapped page
2933       if (errno != EAGAIN) {
2934         assert(errno == ENOMEM, "Unexpected mincore errno");
2935         imax = imid;
2936       }
2937     } else {
2938       // Page is mapped go down
2939       // to find first not mapped page
2940       imin = imid + 1;
2941     }
2942   }
2943 
2944   nbot = nbot + page_sz;
2945 
2946   // Adjust stack bottom one page up if last checked page is not mapped
2947   if (mincore_return_value == -1) {
2948     nbot = nbot + page_sz;
2949   }
2950 
2951   return nbot;
2952 }
2953 
2954 
2955 // Linux uses a growable mapping for the stack, and if the mapping for
2956 // the stack guard pages is not removed when we detach a thread the
2957 // stack cannot grow beyond the pages where the stack guard was
2958 // mapped.  If at some point later in the process the stack expands to
2959 // that point, the Linux kernel cannot expand the stack any further
2960 // because the guard pages are in the way, and a segfault occurs.
2961 //
2962 // However, it's essential not to split the stack region by unmapping
2963 // a region (leaving a hole) that's already part of the stack mapping,
2964 // so if the stack mapping has already grown beyond the guard pages at
2965 // the time we create them, we have to truncate the stack mapping.
2966 // So, we need to know the extent of the stack mapping when
2967 // create_stack_guard_pages() is called.
2968 
2969 // We only need this for stacks that are growable: at the time of
2970 // writing thread stacks don't use growable mappings (i.e. those
2971 // creeated with MAP_GROWSDOWN), and aren't marked "[stack]", so this
2972 // only applies to the main thread.
2973 
2974 // If the (growable) stack mapping already extends beyond the point
2975 // where we're going to put our guard pages, truncate the mapping at
2976 // that point by munmap()ping it.  This ensures that when we later
2977 // munmap() the guard pages we don't leave a hole in the stack
2978 // mapping. This only affects the main/initial thread
2979 
2980 bool os::pd_create_stack_guard_pages(char* addr, size_t size) {
2981   if (os::Linux::is_initial_thread()) {
2982     // As we manually grow stack up to bottom inside create_attached_thread(),
2983     // it's likely that os::Linux::initial_thread_stack_bottom is mapped and
2984     // we don't need to do anything special.
2985     // Check it first, before calling heavy function.
2986     uintptr_t stack_extent = (uintptr_t) os::Linux::initial_thread_stack_bottom();
2987     unsigned char vec[1];
2988 
2989     if (mincore((address)stack_extent, os::vm_page_size(), vec) == -1) {
2990       // Fallback to slow path on all errors, including EAGAIN
2991       stack_extent = (uintptr_t) get_stack_commited_bottom(
2992                                                            os::Linux::initial_thread_stack_bottom(),
2993                                                            (size_t)addr - stack_extent);
2994     }
2995 
2996     if (stack_extent < (uintptr_t)addr) {
2997       ::munmap((void*)stack_extent, (uintptr_t)(addr - stack_extent));
2998     }
2999   }
3000 
3001   return os::commit_memory(addr, size, !ExecMem);
3002 }
3003 
3004 // If this is a growable mapping, remove the guard pages entirely by
3005 // munmap()ping them.  If not, just call uncommit_memory(). This only
3006 // affects the main/initial thread, but guard against future OS changes
3007 // It's safe to always unmap guard pages for initial thread because we
3008 // always place it right after end of the mapped region
3009 
3010 bool os::remove_stack_guard_pages(char* addr, size_t size) {
3011   uintptr_t stack_extent, stack_base;
3012 
3013   if (os::Linux::is_initial_thread()) {
3014     return ::munmap(addr, size) == 0;
3015   }
3016 
3017   return os::uncommit_memory(addr, size);
3018 }
3019 
3020 // If 'fixed' is true, anon_mmap() will attempt to reserve anonymous memory
3021 // at 'requested_addr'. If there are existing memory mappings at the same
3022 // location, however, they will be overwritten. If 'fixed' is false,
3023 // 'requested_addr' is only treated as a hint, the return value may or
3024 // may not start from the requested address. Unlike Linux mmap(), this
3025 // function returns NULL to indicate failure.
3026 static char* anon_mmap(char* requested_addr, size_t bytes, bool fixed) {
3027   char * addr;
3028   int flags;
3029 
3030   flags = MAP_PRIVATE | MAP_NORESERVE | MAP_ANONYMOUS;
3031   if (fixed) {
3032     assert((uintptr_t)requested_addr % os::Linux::page_size() == 0, "unaligned address");
3033     flags |= MAP_FIXED;
3034   }
3035 
3036   // Map reserved/uncommitted pages PROT_NONE so we fail early if we
3037   // touch an uncommitted page. Otherwise, the read/write might
3038   // succeed if we have enough swap space to back the physical page.
3039   addr = (char*)::mmap(requested_addr, bytes, PROT_NONE,
3040                        flags, -1, 0);
3041 
3042   return addr == MAP_FAILED ? NULL : addr;
3043 }
3044 
3045 static int anon_munmap(char * addr, size_t size) {
3046   return ::munmap(addr, size) == 0;
3047 }
3048 
3049 char* os::pd_reserve_memory(size_t bytes, char* requested_addr,
3050                             size_t alignment_hint) {
3051   return anon_mmap(requested_addr, bytes, (requested_addr != NULL));
3052 }
3053 
3054 bool os::pd_release_memory(char* addr, size_t size) {
3055   return anon_munmap(addr, size);
3056 }
3057 
3058 static bool linux_mprotect(char* addr, size_t size, int prot) {
3059   // Linux wants the mprotect address argument to be page aligned.
3060   char* bottom = (char*)align_size_down((intptr_t)addr, os::Linux::page_size());
3061 
3062   // According to SUSv3, mprotect() should only be used with mappings
3063   // established by mmap(), and mmap() always maps whole pages. Unaligned
3064   // 'addr' likely indicates problem in the VM (e.g. trying to change
3065   // protection of malloc'ed or statically allocated memory). Check the
3066   // caller if you hit this assert.
3067   assert(addr == bottom, "sanity check");
3068 
3069   size = align_size_up(pointer_delta(addr, bottom, 1) + size, os::Linux::page_size());
3070   return ::mprotect(bottom, size, prot) == 0;
3071 }
3072 
3073 // Set protections specified
3074 bool os::protect_memory(char* addr, size_t bytes, ProtType prot,
3075                         bool is_committed) {
3076   unsigned int p = 0;
3077   switch (prot) {
3078   case MEM_PROT_NONE: p = PROT_NONE; break;
3079   case MEM_PROT_READ: p = PROT_READ; break;
3080   case MEM_PROT_RW:   p = PROT_READ|PROT_WRITE; break;
3081   case MEM_PROT_RWX:  p = PROT_READ|PROT_WRITE|PROT_EXEC; break;
3082   default:
3083     ShouldNotReachHere();
3084   }
3085   // is_committed is unused.
3086   return linux_mprotect(addr, bytes, p);
3087 }
3088 
3089 bool os::guard_memory(char* addr, size_t size) {
3090   return linux_mprotect(addr, size, PROT_NONE);
3091 }
3092 
3093 bool os::unguard_memory(char* addr, size_t size) {
3094   return linux_mprotect(addr, size, PROT_READ|PROT_WRITE);
3095 }
3096 
3097 bool os::Linux::transparent_huge_pages_sanity_check(bool warn,
3098                                                     size_t page_size) {
3099   bool result = false;
3100   void *p = mmap(NULL, page_size * 2, PROT_READ|PROT_WRITE,
3101                  MAP_ANONYMOUS|MAP_PRIVATE,
3102                  -1, 0);
3103   if (p != MAP_FAILED) {
3104     void *aligned_p = align_ptr_up(p, page_size);
3105 
3106     result = madvise(aligned_p, page_size, MADV_HUGEPAGE) == 0;
3107 
3108     munmap(p, page_size * 2);
3109   }
3110 
3111   if (warn && !result) {
3112     warning("TransparentHugePages is not supported by the operating system.");
3113   }
3114 
3115   return result;
3116 }
3117 
3118 bool os::Linux::hugetlbfs_sanity_check(bool warn, size_t page_size) {
3119   bool result = false;
3120   void *p = mmap(NULL, page_size, PROT_READ|PROT_WRITE,
3121                  MAP_ANONYMOUS|MAP_PRIVATE|MAP_HUGETLB,
3122                  -1, 0);
3123 
3124   if (p != MAP_FAILED) {
3125     // We don't know if this really is a huge page or not.
3126     FILE *fp = fopen("/proc/self/maps", "r");
3127     if (fp) {
3128       while (!feof(fp)) {
3129         char chars[257];
3130         long x = 0;
3131         if (fgets(chars, sizeof(chars), fp)) {
3132           if (sscanf(chars, "%lx-%*x", &x) == 1
3133               && x == (long)p) {
3134             if (strstr (chars, "hugepage")) {
3135               result = true;
3136               break;
3137             }
3138           }
3139         }
3140       }
3141       fclose(fp);
3142     }
3143     munmap(p, page_size);
3144   }
3145 
3146   if (warn && !result) {
3147     warning("HugeTLBFS is not supported by the operating system.");
3148   }
3149 
3150   return result;
3151 }
3152 
3153 // Set the coredump_filter bits to include largepages in core dump (bit 6)
3154 //
3155 // From the coredump_filter documentation:
3156 //
3157 // - (bit 0) anonymous private memory
3158 // - (bit 1) anonymous shared memory
3159 // - (bit 2) file-backed private memory
3160 // - (bit 3) file-backed shared memory
3161 // - (bit 4) ELF header pages in file-backed private memory areas (it is
3162 //           effective only if the bit 2 is cleared)
3163 // - (bit 5) hugetlb private memory
3164 // - (bit 6) hugetlb shared memory
3165 //
3166 static void set_coredump_filter(void) {
3167   FILE *f;
3168   long cdm;
3169 
3170   if ((f = fopen("/proc/self/coredump_filter", "r+")) == NULL) {
3171     return;
3172   }
3173 
3174   if (fscanf(f, "%lx", &cdm) != 1) {
3175     fclose(f);
3176     return;
3177   }
3178 
3179   rewind(f);
3180 
3181   if ((cdm & LARGEPAGES_BIT) == 0) {
3182     cdm |= LARGEPAGES_BIT;
3183     fprintf(f, "%#lx", cdm);
3184   }
3185 
3186   fclose(f);
3187 }
3188 
3189 // Large page support
3190 
3191 static size_t _large_page_size = 0;
3192 
3193 size_t os::Linux::find_large_page_size() {
3194   size_t large_page_size = 0;
3195 
3196   // large_page_size on Linux is used to round up heap size. x86 uses either
3197   // 2M or 4M page, depending on whether PAE (Physical Address Extensions)
3198   // mode is enabled. AMD64/EM64T uses 2M page in 64bit mode. IA64 can use
3199   // page as large as 256M.
3200   //
3201   // Here we try to figure out page size by parsing /proc/meminfo and looking
3202   // for a line with the following format:
3203   //    Hugepagesize:     2048 kB
3204   //
3205   // If we can't determine the value (e.g. /proc is not mounted, or the text
3206   // format has been changed), we'll use the largest page size supported by
3207   // the processor.
3208 
3209 #ifndef ZERO
3210   large_page_size = IA32_ONLY(4 * M) AMD64_ONLY(2 * M) IA64_ONLY(256 * M) SPARC_ONLY(4 * M)
3211                      ARM32_ONLY(2 * M) PPC_ONLY(4 * M) AARCH64_ONLY(2 * M);
3212 #endif // ZERO
3213 
3214   FILE *fp = fopen("/proc/meminfo", "r");
3215   if (fp) {
3216     while (!feof(fp)) {
3217       int x = 0;
3218       char buf[16];
3219       if (fscanf(fp, "Hugepagesize: %d", &x) == 1) {
3220         if (x && fgets(buf, sizeof(buf), fp) && strcmp(buf, " kB\n") == 0) {
3221           large_page_size = x * K;
3222           break;
3223         }
3224       } else {
3225         // skip to next line
3226         for (;;) {
3227           int ch = fgetc(fp);
3228           if (ch == EOF || ch == (int)'\n') break;
3229         }
3230       }
3231     }
3232     fclose(fp);
3233   }
3234 
3235   if (!FLAG_IS_DEFAULT(LargePageSizeInBytes) && LargePageSizeInBytes != large_page_size) {
3236     warning("Setting LargePageSizeInBytes has no effect on this OS. Large page size is "
3237             SIZE_FORMAT "%s.", byte_size_in_proper_unit(large_page_size),
3238             proper_unit_for_byte_size(large_page_size));
3239   }
3240 
3241   return large_page_size;
3242 }
3243 
3244 size_t os::Linux::setup_large_page_size() {
3245   _large_page_size = Linux::find_large_page_size();
3246   const size_t default_page_size = (size_t)Linux::page_size();
3247   if (_large_page_size > default_page_size) {
3248     _page_sizes[0] = _large_page_size;
3249     _page_sizes[1] = default_page_size;
3250     _page_sizes[2] = 0;
3251   }
3252 
3253   return _large_page_size;
3254 }
3255 
3256 bool os::Linux::setup_large_page_type(size_t page_size) {
3257   if (FLAG_IS_DEFAULT(UseHugeTLBFS) &&
3258       FLAG_IS_DEFAULT(UseSHM) &&
3259       FLAG_IS_DEFAULT(UseTransparentHugePages)) {
3260 
3261     // The type of large pages has not been specified by the user.
3262 
3263     // Try UseHugeTLBFS and then UseSHM.
3264     UseHugeTLBFS = UseSHM = true;
3265 
3266     // Don't try UseTransparentHugePages since there are known
3267     // performance issues with it turned on. This might change in the future.
3268     UseTransparentHugePages = false;
3269   }
3270 
3271   if (UseTransparentHugePages) {
3272     bool warn_on_failure = !FLAG_IS_DEFAULT(UseTransparentHugePages);
3273     if (transparent_huge_pages_sanity_check(warn_on_failure, page_size)) {
3274       UseHugeTLBFS = false;
3275       UseSHM = false;
3276       return true;
3277     }
3278     UseTransparentHugePages = false;
3279   }
3280 
3281   if (UseHugeTLBFS) {
3282     bool warn_on_failure = !FLAG_IS_DEFAULT(UseHugeTLBFS);
3283     if (hugetlbfs_sanity_check(warn_on_failure, page_size)) {
3284       UseSHM = false;
3285       return true;
3286     }
3287     UseHugeTLBFS = false;
3288   }
3289 
3290   return UseSHM;
3291 }
3292 
3293 void os::large_page_init() {
3294   if (!UseLargePages &&
3295       !UseTransparentHugePages &&
3296       !UseHugeTLBFS &&
3297       !UseSHM) {
3298     // Not using large pages.
3299     return;
3300   }
3301 
3302   if (!FLAG_IS_DEFAULT(UseLargePages) && !UseLargePages) {
3303     // The user explicitly turned off large pages.
3304     // Ignore the rest of the large pages flags.
3305     UseTransparentHugePages = false;
3306     UseHugeTLBFS = false;
3307     UseSHM = false;
3308     return;
3309   }
3310 
3311   size_t large_page_size = Linux::setup_large_page_size();
3312   UseLargePages          = Linux::setup_large_page_type(large_page_size);
3313 
3314   set_coredump_filter();
3315 }
3316 
3317 #ifndef SHM_HUGETLB
3318   #define SHM_HUGETLB 04000
3319 #endif
3320 
3321 char* os::Linux::reserve_memory_special_shm(size_t bytes, size_t alignment,
3322                                             char* req_addr, bool exec) {
3323   // "exec" is passed in but not used.  Creating the shared image for
3324   // the code cache doesn't have an SHM_X executable permission to check.
3325   assert(UseLargePages && UseSHM, "only for SHM large pages");
3326   assert(is_ptr_aligned(req_addr, os::large_page_size()), "Unaligned address");
3327 
3328   if (!is_size_aligned(bytes, os::large_page_size()) || alignment > os::large_page_size()) {
3329     return NULL; // Fallback to small pages.
3330   }
3331 
3332   key_t key = IPC_PRIVATE;
3333   char *addr;
3334 
3335   bool warn_on_failure = UseLargePages &&
3336                         (!FLAG_IS_DEFAULT(UseLargePages) ||
3337                          !FLAG_IS_DEFAULT(UseSHM) ||
3338                          !FLAG_IS_DEFAULT(LargePageSizeInBytes));
3339   char msg[128];
3340 
3341   // Create a large shared memory region to attach to based on size.
3342   // Currently, size is the total size of the heap
3343   int shmid = shmget(key, bytes, SHM_HUGETLB|IPC_CREAT|SHM_R|SHM_W);
3344   if (shmid == -1) {
3345     // Possible reasons for shmget failure:
3346     // 1. shmmax is too small for Java heap.
3347     //    > check shmmax value: cat /proc/sys/kernel/shmmax
3348     //    > increase shmmax value: echo "0xffffffff" > /proc/sys/kernel/shmmax
3349     // 2. not enough large page memory.
3350     //    > check available large pages: cat /proc/meminfo
3351     //    > increase amount of large pages:
3352     //          echo new_value > /proc/sys/vm/nr_hugepages
3353     //      Note 1: different Linux may use different name for this property,
3354     //            e.g. on Redhat AS-3 it is "hugetlb_pool".
3355     //      Note 2: it's possible there's enough physical memory available but
3356     //            they are so fragmented after a long run that they can't
3357     //            coalesce into large pages. Try to reserve large pages when
3358     //            the system is still "fresh".
3359     if (warn_on_failure) {
3360       jio_snprintf(msg, sizeof(msg), "Failed to reserve shared memory (errno = %d).", errno);
3361       warning("%s", msg);
3362     }
3363     return NULL;
3364   }
3365 
3366   // attach to the region
3367   addr = (char*)shmat(shmid, req_addr, 0);
3368   int err = errno;
3369 
3370   // Remove shmid. If shmat() is successful, the actual shared memory segment
3371   // will be deleted when it's detached by shmdt() or when the process
3372   // terminates. If shmat() is not successful this will remove the shared
3373   // segment immediately.
3374   shmctl(shmid, IPC_RMID, NULL);
3375 
3376   if ((intptr_t)addr == -1) {
3377     if (warn_on_failure) {
3378       jio_snprintf(msg, sizeof(msg), "Failed to attach shared memory (errno = %d).", err);
3379       warning("%s", msg);
3380     }
3381     return NULL;
3382   }
3383 
3384   return addr;
3385 }
3386 
3387 static void warn_on_large_pages_failure(char* req_addr, size_t bytes,
3388                                         int error) {
3389   assert(error == ENOMEM, "Only expect to fail if no memory is available");
3390 
3391   bool warn_on_failure = UseLargePages &&
3392       (!FLAG_IS_DEFAULT(UseLargePages) ||
3393        !FLAG_IS_DEFAULT(UseHugeTLBFS) ||
3394        !FLAG_IS_DEFAULT(LargePageSizeInBytes));
3395 
3396   if (warn_on_failure) {
3397     char msg[128];
3398     jio_snprintf(msg, sizeof(msg), "Failed to reserve large pages memory req_addr: "
3399                  PTR_FORMAT " bytes: " SIZE_FORMAT " (errno = %d).", req_addr, bytes, error);
3400     warning("%s", msg);
3401   }
3402 }
3403 
3404 char* os::Linux::reserve_memory_special_huge_tlbfs_only(size_t bytes,
3405                                                         char* req_addr,
3406                                                         bool exec) {
3407   assert(UseLargePages && UseHugeTLBFS, "only for Huge TLBFS large pages");
3408   assert(is_size_aligned(bytes, os::large_page_size()), "Unaligned size");
3409   assert(is_ptr_aligned(req_addr, os::large_page_size()), "Unaligned address");
3410 
3411   int prot = exec ? PROT_READ|PROT_WRITE|PROT_EXEC : PROT_READ|PROT_WRITE;
3412   char* addr = (char*)::mmap(req_addr, bytes, prot,
3413                              MAP_PRIVATE|MAP_ANONYMOUS|MAP_HUGETLB,
3414                              -1, 0);
3415 
3416   if (addr == MAP_FAILED) {
3417     warn_on_large_pages_failure(req_addr, bytes, errno);
3418     return NULL;
3419   }
3420 
3421   assert(is_ptr_aligned(addr, os::large_page_size()), "Must be");
3422 
3423   return addr;
3424 }
3425 
3426 // Helper for os::Linux::reserve_memory_special_huge_tlbfs_mixed().
3427 // Allocate (using mmap, NO_RESERVE, with small pages) at either a given request address
3428 //   (req_addr != NULL) or with a given alignment.
3429 //  - bytes shall be a multiple of alignment.
3430 //  - req_addr can be NULL. If not NULL, it must be a multiple of alignment.
3431 //  - alignment sets the alignment at which memory shall be allocated.
3432 //     It must be a multiple of allocation granularity.
3433 // Returns address of memory or NULL. If req_addr was not NULL, will only return
3434 //  req_addr or NULL.
3435 static char* anon_mmap_aligned(size_t bytes, size_t alignment, char* req_addr) {
3436 
3437   size_t extra_size = bytes;
3438   if (req_addr == NULL && alignment > 0) {
3439     extra_size += alignment;
3440   }
3441 
3442   char* start = (char*) ::mmap(req_addr, extra_size, PROT_NONE,
3443     MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE,
3444     -1, 0);
3445   if (start == MAP_FAILED) {
3446     start = NULL;
3447   } else {
3448     if (req_addr != NULL) {
3449       if (start != req_addr) {
3450         ::munmap(start, extra_size);
3451         start = NULL;
3452       }
3453     } else {
3454       char* const start_aligned = (char*) align_ptr_up(start, alignment);
3455       char* const end_aligned = start_aligned + bytes;
3456       char* const end = start + extra_size;
3457       if (start_aligned > start) {
3458         ::munmap(start, start_aligned - start);
3459       }
3460       if (end_aligned < end) {
3461         ::munmap(end_aligned, end - end_aligned);
3462       }
3463       start = start_aligned;
3464     }
3465   }
3466   return start;
3467 
3468 }
3469 
3470 // Reserve memory using mmap(MAP_HUGETLB).
3471 //  - bytes shall be a multiple of alignment.
3472 //  - req_addr can be NULL. If not NULL, it must be a multiple of alignment.
3473 //  - alignment sets the alignment at which memory shall be allocated.
3474 //     It must be a multiple of allocation granularity.
3475 // Returns address of memory or NULL. If req_addr was not NULL, will only return
3476 //  req_addr or NULL.
3477 char* os::Linux::reserve_memory_special_huge_tlbfs_mixed(size_t bytes,
3478                                                          size_t alignment,
3479                                                          char* req_addr,
3480                                                          bool exec) {
3481   size_t large_page_size = os::large_page_size();
3482   assert(bytes >= large_page_size, "Shouldn't allocate large pages for small sizes");
3483 
3484   assert(is_ptr_aligned(req_addr, alignment), "Must be");
3485   assert(is_size_aligned(bytes, alignment), "Must be");
3486 
3487   // First reserve - but not commit - the address range in small pages.
3488   char* const start = anon_mmap_aligned(bytes, alignment, req_addr);
3489 
3490   if (start == NULL) {
3491     return NULL;
3492   }
3493 
3494   assert(is_ptr_aligned(start, alignment), "Must be");
3495 
3496   char* end = start + bytes;
3497 
3498   // Find the regions of the allocated chunk that can be promoted to large pages.
3499   char* lp_start = (char*)align_ptr_up(start, large_page_size);
3500   char* lp_end   = (char*)align_ptr_down(end, large_page_size);
3501 
3502   size_t lp_bytes = lp_end - lp_start;
3503 
3504   assert(is_size_aligned(lp_bytes, large_page_size), "Must be");
3505 
3506   if (lp_bytes == 0) {
3507     // The mapped region doesn't even span the start and the end of a large page.
3508     // Fall back to allocate a non-special area.
3509     ::munmap(start, end - start);
3510     return NULL;
3511   }
3512 
3513   int prot = exec ? PROT_READ|PROT_WRITE|PROT_EXEC : PROT_READ|PROT_WRITE;
3514 
3515   void* result;
3516 
3517   // Commit small-paged leading area.
3518   if (start != lp_start) {
3519     result = ::mmap(start, lp_start - start, prot,
3520                     MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED,
3521                     -1, 0);
3522     if (result == MAP_FAILED) {
3523       ::munmap(lp_start, end - lp_start);
3524       return NULL;
3525     }
3526   }
3527 
3528   // Commit large-paged area.
3529   result = ::mmap(lp_start, lp_bytes, prot,
3530                   MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED|MAP_HUGETLB,
3531                   -1, 0);
3532   if (result == MAP_FAILED) {
3533     warn_on_large_pages_failure(lp_start, lp_bytes, errno);
3534     // If the mmap above fails, the large pages region will be unmapped and we
3535     // have regions before and after with small pages. Release these regions.
3536     //
3537     // |  mapped  |  unmapped  |  mapped  |
3538     // ^          ^            ^          ^
3539     // start      lp_start     lp_end     end
3540     //
3541     ::munmap(start, lp_start - start);
3542     ::munmap(lp_end, end - lp_end);
3543     return NULL;
3544   }
3545 
3546   // Commit small-paged trailing area.
3547   if (lp_end != end) {
3548     result = ::mmap(lp_end, end - lp_end, prot,
3549                     MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED,
3550                     -1, 0);
3551     if (result == MAP_FAILED) {
3552       ::munmap(start, lp_end - start);
3553       return NULL;
3554     }
3555   }
3556 
3557   return start;
3558 }
3559 
3560 char* os::Linux::reserve_memory_special_huge_tlbfs(size_t bytes,
3561                                                    size_t alignment,
3562                                                    char* req_addr,
3563                                                    bool exec) {
3564   assert(UseLargePages && UseHugeTLBFS, "only for Huge TLBFS large pages");
3565   assert(is_ptr_aligned(req_addr, alignment), "Must be");
3566   assert(is_size_aligned(alignment, os::vm_allocation_granularity()), "Must be");
3567   assert(is_power_of_2(os::large_page_size()), "Must be");
3568   assert(bytes >= os::large_page_size(), "Shouldn't allocate large pages for small sizes");
3569 
3570   if (is_size_aligned(bytes, os::large_page_size()) && alignment <= os::large_page_size()) {
3571     return reserve_memory_special_huge_tlbfs_only(bytes, req_addr, exec);
3572   } else {
3573     return reserve_memory_special_huge_tlbfs_mixed(bytes, alignment, req_addr, exec);
3574   }
3575 }
3576 
3577 char* os::reserve_memory_special(size_t bytes, size_t alignment,
3578                                  char* req_addr, bool exec) {
3579   assert(UseLargePages, "only for large pages");
3580 
3581   char* addr;
3582   if (UseSHM) {
3583     addr = os::Linux::reserve_memory_special_shm(bytes, alignment, req_addr, exec);
3584   } else {
3585     assert(UseHugeTLBFS, "must be");
3586     addr = os::Linux::reserve_memory_special_huge_tlbfs(bytes, alignment, req_addr, exec);
3587   }
3588 
3589   if (addr != NULL) {
3590     if (UseNUMAInterleaving) {
3591       numa_make_global(addr, bytes);
3592     }
3593 
3594     // The memory is committed
3595     MemTracker::record_virtual_memory_reserve_and_commit((address)addr, bytes, CALLER_PC);
3596   }
3597 
3598   return addr;
3599 }
3600 
3601 bool os::Linux::release_memory_special_shm(char* base, size_t bytes) {
3602   // detaching the SHM segment will also delete it, see reserve_memory_special_shm()
3603   return shmdt(base) == 0;
3604 }
3605 
3606 bool os::Linux::release_memory_special_huge_tlbfs(char* base, size_t bytes) {
3607   return pd_release_memory(base, bytes);
3608 }
3609 
3610 bool os::release_memory_special(char* base, size_t bytes) {
3611   bool res;
3612   if (MemTracker::tracking_level() > NMT_minimal) {
3613     Tracker tkr = MemTracker::get_virtual_memory_release_tracker();
3614     res = os::Linux::release_memory_special_impl(base, bytes);
3615     if (res) {
3616       tkr.record((address)base, bytes);
3617     }
3618 
3619   } else {
3620     res = os::Linux::release_memory_special_impl(base, bytes);
3621   }
3622   return res;
3623 }
3624 
3625 bool os::Linux::release_memory_special_impl(char* base, size_t bytes) {
3626   assert(UseLargePages, "only for large pages");
3627   bool res;
3628 
3629   if (UseSHM) {
3630     res = os::Linux::release_memory_special_shm(base, bytes);
3631   } else {
3632     assert(UseHugeTLBFS, "must be");
3633     res = os::Linux::release_memory_special_huge_tlbfs(base, bytes);
3634   }
3635   return res;
3636 }
3637 
3638 size_t os::large_page_size() {
3639   return _large_page_size;
3640 }
3641 
3642 // With SysV SHM the entire memory region must be allocated as shared
3643 // memory.
3644 // HugeTLBFS allows application to commit large page memory on demand.
3645 // However, when committing memory with HugeTLBFS fails, the region
3646 // that was supposed to be committed will lose the old reservation
3647 // and allow other threads to steal that memory region. Because of this
3648 // behavior we can't commit HugeTLBFS memory.
3649 bool os::can_commit_large_page_memory() {
3650   return UseTransparentHugePages;
3651 }
3652 
3653 bool os::can_execute_large_page_memory() {
3654   return UseTransparentHugePages || UseHugeTLBFS;
3655 }
3656 
3657 // Reserve memory at an arbitrary address, only if that area is
3658 // available (and not reserved for something else).
3659 
3660 char* os::pd_attempt_reserve_memory_at(size_t bytes, char* requested_addr) {
3661   const int max_tries = 10;
3662   char* base[max_tries];
3663   size_t size[max_tries];
3664   const size_t gap = 0x000000;
3665 
3666   // Assert only that the size is a multiple of the page size, since
3667   // that's all that mmap requires, and since that's all we really know
3668   // about at this low abstraction level.  If we need higher alignment,
3669   // we can either pass an alignment to this method or verify alignment
3670   // in one of the methods further up the call chain.  See bug 5044738.
3671   assert(bytes % os::vm_page_size() == 0, "reserving unexpected size block");
3672 
3673   // Repeatedly allocate blocks until the block is allocated at the
3674   // right spot.
3675 
3676   // Linux mmap allows caller to pass an address as hint; give it a try first,
3677   // if kernel honors the hint then we can return immediately.
3678   char * addr = anon_mmap(requested_addr, bytes, false);
3679   if (addr == requested_addr) {
3680     return requested_addr;
3681   }
3682 
3683   if (addr != NULL) {
3684     // mmap() is successful but it fails to reserve at the requested address
3685     anon_munmap(addr, bytes);
3686   }
3687 
3688   int i;
3689   for (i = 0; i < max_tries; ++i) {
3690     base[i] = reserve_memory(bytes);
3691 
3692     if (base[i] != NULL) {
3693       // Is this the block we wanted?
3694       if (base[i] == requested_addr) {
3695         size[i] = bytes;
3696         break;
3697       }
3698 
3699       // Does this overlap the block we wanted? Give back the overlapped
3700       // parts and try again.
3701 
3702       ptrdiff_t top_overlap = requested_addr + (bytes + gap) - base[i];
3703       if (top_overlap >= 0 && (size_t)top_overlap < bytes) {
3704         unmap_memory(base[i], top_overlap);
3705         base[i] += top_overlap;
3706         size[i] = bytes - top_overlap;
3707       } else {
3708         ptrdiff_t bottom_overlap = base[i] + bytes - requested_addr;
3709         if (bottom_overlap >= 0 && (size_t)bottom_overlap < bytes) {
3710           unmap_memory(requested_addr, bottom_overlap);
3711           size[i] = bytes - bottom_overlap;
3712         } else {
3713           size[i] = bytes;
3714         }
3715       }
3716     }
3717   }
3718 
3719   // Give back the unused reserved pieces.
3720 
3721   for (int j = 0; j < i; ++j) {
3722     if (base[j] != NULL) {
3723       unmap_memory(base[j], size[j]);
3724     }
3725   }
3726 
3727   if (i < max_tries) {
3728     return requested_addr;
3729   } else {
3730     return NULL;
3731   }
3732 }
3733 
3734 size_t os::read(int fd, void *buf, unsigned int nBytes) {
3735   return ::read(fd, buf, nBytes);
3736 }
3737 
3738 size_t os::read_at(int fd, void *buf, unsigned int nBytes, jlong offset) {
3739   return ::pread(fd, buf, nBytes, offset);
3740 }
3741 
3742 // Short sleep, direct OS call.
3743 //
3744 // Note: certain versions of Linux CFS scheduler (since 2.6.23) do not guarantee
3745 // sched_yield(2) will actually give up the CPU:
3746 //
3747 //   * Alone on this pariticular CPU, keeps running.
3748 //   * Before the introduction of "skip_buddy" with "compat_yield" disabled
3749 //     (pre 2.6.39).
3750 //
3751 // So calling this with 0 is an alternative.
3752 //
3753 void os::naked_short_sleep(jlong ms) {
3754   struct timespec req;
3755 
3756   assert(ms < 1000, "Un-interruptable sleep, short time use only");
3757   req.tv_sec = 0;
3758   if (ms > 0) {
3759     req.tv_nsec = (ms % 1000) * 1000000;
3760   } else {
3761     req.tv_nsec = 1;
3762   }
3763 
3764   nanosleep(&req, NULL);
3765 
3766   return;
3767 }
3768 
3769 // Sleep forever; naked call to OS-specific sleep; use with CAUTION
3770 void os::infinite_sleep() {
3771   while (true) {    // sleep forever ...
3772     ::sleep(100);   // ... 100 seconds at a time
3773   }
3774 }
3775 
3776 // Used to convert frequent JVM_Yield() to nops
3777 bool os::dont_yield() {
3778   return DontYieldALot;
3779 }
3780 
3781 void os::naked_yield() {
3782   sched_yield();
3783 }
3784 
3785 ////////////////////////////////////////////////////////////////////////////////
3786 // thread priority support
3787 
3788 // Note: Normal Linux applications are run with SCHED_OTHER policy. SCHED_OTHER
3789 // only supports dynamic priority, static priority must be zero. For real-time
3790 // applications, Linux supports SCHED_RR which allows static priority (1-99).
3791 // However, for large multi-threaded applications, SCHED_RR is not only slower
3792 // than SCHED_OTHER, but also very unstable (my volano tests hang hard 4 out
3793 // of 5 runs - Sep 2005).
3794 //
3795 // The following code actually changes the niceness of kernel-thread/LWP. It
3796 // has an assumption that setpriority() only modifies one kernel-thread/LWP,
3797 // not the entire user process, and user level threads are 1:1 mapped to kernel
3798 // threads. It has always been the case, but could change in the future. For
3799 // this reason, the code should not be used as default (ThreadPriorityPolicy=0).
3800 // It is only used when ThreadPriorityPolicy=1 and requires root privilege.
3801 
3802 int os::java_to_os_priority[CriticalPriority + 1] = {
3803   19,              // 0 Entry should never be used
3804 
3805    4,              // 1 MinPriority
3806    3,              // 2
3807    2,              // 3
3808 
3809    1,              // 4
3810    0,              // 5 NormPriority
3811   -1,              // 6
3812 
3813   -2,              // 7
3814   -3,              // 8
3815   -4,              // 9 NearMaxPriority
3816 
3817   -5,              // 10 MaxPriority
3818 
3819   -5               // 11 CriticalPriority
3820 };
3821 
3822 static int prio_init() {
3823   if (ThreadPriorityPolicy == 1) {
3824     // Only root can raise thread priority. Don't allow ThreadPriorityPolicy=1
3825     // if effective uid is not root. Perhaps, a more elegant way of doing
3826     // this is to test CAP_SYS_NICE capability, but that will require libcap.so
3827     if (geteuid() != 0) {
3828       if (!FLAG_IS_DEFAULT(ThreadPriorityPolicy)) {
3829         warning("-XX:ThreadPriorityPolicy requires root privilege on Linux");
3830       }
3831       ThreadPriorityPolicy = 0;
3832     }
3833   }
3834   if (UseCriticalJavaThreadPriority) {
3835     os::java_to_os_priority[MaxPriority] = os::java_to_os_priority[CriticalPriority];
3836   }
3837   return 0;
3838 }
3839 
3840 OSReturn os::set_native_priority(Thread* thread, int newpri) {
3841   if (!UseThreadPriorities || ThreadPriorityPolicy == 0) return OS_OK;
3842 
3843   int ret = setpriority(PRIO_PROCESS, thread->osthread()->thread_id(), newpri);
3844   return (ret == 0) ? OS_OK : OS_ERR;
3845 }
3846 
3847 OSReturn os::get_native_priority(const Thread* const thread,
3848                                  int *priority_ptr) {
3849   if (!UseThreadPriorities || ThreadPriorityPolicy == 0) {
3850     *priority_ptr = java_to_os_priority[NormPriority];
3851     return OS_OK;
3852   }
3853 
3854   errno = 0;
3855   *priority_ptr = getpriority(PRIO_PROCESS, thread->osthread()->thread_id());
3856   return (*priority_ptr != -1 || errno == 0 ? OS_OK : OS_ERR);
3857 }
3858 
3859 // Hint to the underlying OS that a task switch would not be good.
3860 // Void return because it's a hint and can fail.
3861 void os::hint_no_preempt() {}
3862 
3863 ////////////////////////////////////////////////////////////////////////////////
3864 // suspend/resume support
3865 
3866 //  the low-level signal-based suspend/resume support is a remnant from the
3867 //  old VM-suspension that used to be for java-suspension, safepoints etc,
3868 //  within hotspot. Now there is a single use-case for this:
3869 //    - calling get_thread_pc() on the VMThread by the flat-profiler task
3870 //      that runs in the watcher thread.
3871 //  The remaining code is greatly simplified from the more general suspension
3872 //  code that used to be used.
3873 //
3874 //  The protocol is quite simple:
3875 //  - suspend:
3876 //      - sends a signal to the target thread
3877 //      - polls the suspend state of the osthread using a yield loop
3878 //      - target thread signal handler (SR_handler) sets suspend state
3879 //        and blocks in sigsuspend until continued
3880 //  - resume:
3881 //      - sets target osthread state to continue
3882 //      - sends signal to end the sigsuspend loop in the SR_handler
3883 //
3884 //  Note that the SR_lock plays no role in this suspend/resume protocol.
3885 
3886 static void resume_clear_context(OSThread *osthread) {
3887   osthread->set_ucontext(NULL);
3888   osthread->set_siginfo(NULL);
3889 }
3890 
3891 static void suspend_save_context(OSThread *osthread, siginfo_t* siginfo,
3892                                  ucontext_t* context) {
3893   osthread->set_ucontext(context);
3894   osthread->set_siginfo(siginfo);
3895 }
3896 
3897 // Handler function invoked when a thread's execution is suspended or
3898 // resumed. We have to be careful that only async-safe functions are
3899 // called here (Note: most pthread functions are not async safe and
3900 // should be avoided.)
3901 //
3902 // Note: sigwait() is a more natural fit than sigsuspend() from an
3903 // interface point of view, but sigwait() prevents the signal hander
3904 // from being run. libpthread would get very confused by not having
3905 // its signal handlers run and prevents sigwait()'s use with the
3906 // mutex granting granting signal.
3907 //
3908 // Currently only ever called on the VMThread and JavaThreads (PC sampling)
3909 //
3910 static void SR_handler(int sig, siginfo_t* siginfo, ucontext_t* context) {
3911   // Save and restore errno to avoid confusing native code with EINTR
3912   // after sigsuspend.
3913   int old_errno = errno;
3914 
3915   Thread* thread = Thread::current_or_null_safe();
3916   assert(thread != NULL, "Missing current thread in SR_handler");
3917   OSThread* osthread = thread->osthread();
3918   assert(thread->is_VM_thread() || thread->is_Java_thread(), "Must be VMThread or JavaThread");
3919 
3920   os::SuspendResume::State current = osthread->sr.state();
3921   if (current == os::SuspendResume::SR_SUSPEND_REQUEST) {
3922     suspend_save_context(osthread, siginfo, context);
3923 
3924     // attempt to switch the state, we assume we had a SUSPEND_REQUEST
3925     os::SuspendResume::State state = osthread->sr.suspended();
3926     if (state == os::SuspendResume::SR_SUSPENDED) {
3927       sigset_t suspend_set;  // signals for sigsuspend()
3928       sigemptyset(&suspend_set);
3929       // get current set of blocked signals and unblock resume signal
3930       pthread_sigmask(SIG_BLOCK, NULL, &suspend_set);
3931       sigdelset(&suspend_set, SR_signum);
3932 
3933       sr_semaphore.signal();
3934       // wait here until we are resumed
3935       while (1) {
3936         sigsuspend(&suspend_set);
3937 
3938         os::SuspendResume::State result = osthread->sr.running();
3939         if (result == os::SuspendResume::SR_RUNNING) {
3940           sr_semaphore.signal();
3941           break;
3942         }
3943       }
3944 
3945     } else if (state == os::SuspendResume::SR_RUNNING) {
3946       // request was cancelled, continue
3947     } else {
3948       ShouldNotReachHere();
3949     }
3950 
3951     resume_clear_context(osthread);
3952   } else if (current == os::SuspendResume::SR_RUNNING) {
3953     // request was cancelled, continue
3954   } else if (current == os::SuspendResume::SR_WAKEUP_REQUEST) {
3955     // ignore
3956   } else {
3957     // ignore
3958   }
3959 
3960   errno = old_errno;
3961 }
3962 
3963 static int SR_initialize() {
3964   struct sigaction act;
3965   char *s;
3966 
3967   // Get signal number to use for suspend/resume
3968   if ((s = ::getenv("_JAVA_SR_SIGNUM")) != 0) {
3969     int sig = ::strtol(s, 0, 10);
3970     if (sig > MAX2(SIGSEGV, SIGBUS) &&  // See 4355769.
3971         sig < NSIG) {                   // Must be legal signal and fit into sigflags[].
3972       SR_signum = sig;
3973     } else {
3974       warning("You set _JAVA_SR_SIGNUM=%d. It must be in range [%d, %d]. Using %d instead.",
3975               sig, MAX2(SIGSEGV, SIGBUS)+1, NSIG-1, SR_signum);
3976     }
3977   }
3978 
3979   assert(SR_signum > SIGSEGV && SR_signum > SIGBUS,
3980          "SR_signum must be greater than max(SIGSEGV, SIGBUS), see 4355769");
3981 
3982   sigemptyset(&SR_sigset);
3983   sigaddset(&SR_sigset, SR_signum);
3984 
3985   // Set up signal handler for suspend/resume
3986   act.sa_flags = SA_RESTART|SA_SIGINFO;
3987   act.sa_handler = (void (*)(int)) SR_handler;
3988 
3989   // SR_signum is blocked by default.
3990   // 4528190 - We also need to block pthread restart signal (32 on all
3991   // supported Linux platforms). Note that LinuxThreads need to block
3992   // this signal for all threads to work properly. So we don't have
3993   // to use hard-coded signal number when setting up the mask.
3994   pthread_sigmask(SIG_BLOCK, NULL, &act.sa_mask);
3995 
3996   if (sigaction(SR_signum, &act, 0) == -1) {
3997     return -1;
3998   }
3999 
4000   // Save signal flag
4001   os::Linux::set_our_sigflags(SR_signum, act.sa_flags);
4002   return 0;
4003 }
4004 
4005 static int sr_notify(OSThread* osthread) {
4006   int status = pthread_kill(osthread->pthread_id(), SR_signum);
4007   assert_status(status == 0, status, "pthread_kill");
4008   return status;
4009 }
4010 
4011 // "Randomly" selected value for how long we want to spin
4012 // before bailing out on suspending a thread, also how often
4013 // we send a signal to a thread we want to resume
4014 static const int RANDOMLY_LARGE_INTEGER = 1000000;
4015 static const int RANDOMLY_LARGE_INTEGER2 = 100;
4016 
4017 // returns true on success and false on error - really an error is fatal
4018 // but this seems the normal response to library errors
4019 static bool do_suspend(OSThread* osthread) {
4020   assert(osthread->sr.is_running(), "thread should be running");
4021   assert(!sr_semaphore.trywait(), "semaphore has invalid state");
4022 
4023   // mark as suspended and send signal
4024   if (osthread->sr.request_suspend() != os::SuspendResume::SR_SUSPEND_REQUEST) {
4025     // failed to switch, state wasn't running?
4026     ShouldNotReachHere();
4027     return false;
4028   }
4029 
4030   if (sr_notify(osthread) != 0) {
4031     ShouldNotReachHere();
4032   }
4033 
4034   // managed to send the signal and switch to SUSPEND_REQUEST, now wait for SUSPENDED
4035   while (true) {
4036     if (sr_semaphore.timedwait(0, 2 * NANOSECS_PER_MILLISEC)) {
4037       break;
4038     } else {
4039       // timeout
4040       os::SuspendResume::State cancelled = osthread->sr.cancel_suspend();
4041       if (cancelled == os::SuspendResume::SR_RUNNING) {
4042         return false;
4043       } else if (cancelled == os::SuspendResume::SR_SUSPENDED) {
4044         // make sure that we consume the signal on the semaphore as well
4045         sr_semaphore.wait();
4046         break;
4047       } else {
4048         ShouldNotReachHere();
4049         return false;
4050       }
4051     }
4052   }
4053 
4054   guarantee(osthread->sr.is_suspended(), "Must be suspended");
4055   return true;
4056 }
4057 
4058 static void do_resume(OSThread* osthread) {
4059   assert(osthread->sr.is_suspended(), "thread should be suspended");
4060   assert(!sr_semaphore.trywait(), "invalid semaphore state");
4061 
4062   if (osthread->sr.request_wakeup() != os::SuspendResume::SR_WAKEUP_REQUEST) {
4063     // failed to switch to WAKEUP_REQUEST
4064     ShouldNotReachHere();
4065     return;
4066   }
4067 
4068   while (true) {
4069     if (sr_notify(osthread) == 0) {
4070       if (sr_semaphore.timedwait(0, 2 * NANOSECS_PER_MILLISEC)) {
4071         if (osthread->sr.is_running()) {
4072           return;
4073         }
4074       }
4075     } else {
4076       ShouldNotReachHere();
4077     }
4078   }
4079 
4080   guarantee(osthread->sr.is_running(), "Must be running!");
4081 }
4082 
4083 ///////////////////////////////////////////////////////////////////////////////////
4084 // signal handling (except suspend/resume)
4085 
4086 // This routine may be used by user applications as a "hook" to catch signals.
4087 // The user-defined signal handler must pass unrecognized signals to this
4088 // routine, and if it returns true (non-zero), then the signal handler must
4089 // return immediately.  If the flag "abort_if_unrecognized" is true, then this
4090 // routine will never retun false (zero), but instead will execute a VM panic
4091 // routine kill the process.
4092 //
4093 // If this routine returns false, it is OK to call it again.  This allows
4094 // the user-defined signal handler to perform checks either before or after
4095 // the VM performs its own checks.  Naturally, the user code would be making
4096 // a serious error if it tried to handle an exception (such as a null check
4097 // or breakpoint) that the VM was generating for its own correct operation.
4098 //
4099 // This routine may recognize any of the following kinds of signals:
4100 //    SIGBUS, SIGSEGV, SIGILL, SIGFPE, SIGQUIT, SIGPIPE, SIGXFSZ, SIGUSR1.
4101 // It should be consulted by handlers for any of those signals.
4102 //
4103 // The caller of this routine must pass in the three arguments supplied
4104 // to the function referred to in the "sa_sigaction" (not the "sa_handler")
4105 // field of the structure passed to sigaction().  This routine assumes that
4106 // the sa_flags field passed to sigaction() includes SA_SIGINFO and SA_RESTART.
4107 //
4108 // Note that the VM will print warnings if it detects conflicting signal
4109 // handlers, unless invoked with the option "-XX:+AllowUserSignalHandlers".
4110 //
4111 extern "C" JNIEXPORT int JVM_handle_linux_signal(int signo,
4112                                                  siginfo_t* siginfo,
4113                                                  void* ucontext,
4114                                                  int abort_if_unrecognized);
4115 
4116 void signalHandler(int sig, siginfo_t* info, void* uc) {
4117   assert(info != NULL && uc != NULL, "it must be old kernel");
4118   int orig_errno = errno;  // Preserve errno value over signal handler.
4119   JVM_handle_linux_signal(sig, info, uc, true);
4120   errno = orig_errno;
4121 }
4122 
4123 
4124 // This boolean allows users to forward their own non-matching signals
4125 // to JVM_handle_linux_signal, harmlessly.
4126 bool os::Linux::signal_handlers_are_installed = false;
4127 
4128 // For signal-chaining
4129 struct sigaction sigact[NSIG];
4130 uint64_t sigs = 0;
4131 #if (64 < NSIG-1)
4132 #error "Not all signals can be encoded in sigs. Adapt its type!"
4133 #endif
4134 bool os::Linux::libjsig_is_loaded = false;
4135 typedef struct sigaction *(*get_signal_t)(int);
4136 get_signal_t os::Linux::get_signal_action = NULL;
4137 
4138 struct sigaction* os::Linux::get_chained_signal_action(int sig) {
4139   struct sigaction *actp = NULL;
4140 
4141   if (libjsig_is_loaded) {
4142     // Retrieve the old signal handler from libjsig
4143     actp = (*get_signal_action)(sig);
4144   }
4145   if (actp == NULL) {
4146     // Retrieve the preinstalled signal handler from jvm
4147     actp = get_preinstalled_handler(sig);
4148   }
4149 
4150   return actp;
4151 }
4152 
4153 static bool call_chained_handler(struct sigaction *actp, int sig,
4154                                  siginfo_t *siginfo, void *context) {
4155   // Call the old signal handler
4156   if (actp->sa_handler == SIG_DFL) {
4157     // It's more reasonable to let jvm treat it as an unexpected exception
4158     // instead of taking the default action.
4159     return false;
4160   } else if (actp->sa_handler != SIG_IGN) {
4161     if ((actp->sa_flags & SA_NODEFER) == 0) {
4162       // automaticlly block the signal
4163       sigaddset(&(actp->sa_mask), sig);
4164     }
4165 
4166     sa_handler_t hand = NULL;
4167     sa_sigaction_t sa = NULL;
4168     bool siginfo_flag_set = (actp->sa_flags & SA_SIGINFO) != 0;
4169     // retrieve the chained handler
4170     if (siginfo_flag_set) {
4171       sa = actp->sa_sigaction;
4172     } else {
4173       hand = actp->sa_handler;
4174     }
4175 
4176     if ((actp->sa_flags & SA_RESETHAND) != 0) {
4177       actp->sa_handler = SIG_DFL;
4178     }
4179 
4180     // try to honor the signal mask
4181     sigset_t oset;
4182     sigemptyset(&oset);
4183     pthread_sigmask(SIG_SETMASK, &(actp->sa_mask), &oset);
4184 
4185     // call into the chained handler
4186     if (siginfo_flag_set) {
4187       (*sa)(sig, siginfo, context);
4188     } else {
4189       (*hand)(sig);
4190     }
4191 
4192     // restore the signal mask
4193     pthread_sigmask(SIG_SETMASK, &oset, NULL);
4194   }
4195   // Tell jvm's signal handler the signal is taken care of.
4196   return true;
4197 }
4198 
4199 bool os::Linux::chained_handler(int sig, siginfo_t* siginfo, void* context) {
4200   bool chained = false;
4201   // signal-chaining
4202   if (UseSignalChaining) {
4203     struct sigaction *actp = get_chained_signal_action(sig);
4204     if (actp != NULL) {
4205       chained = call_chained_handler(actp, sig, siginfo, context);
4206     }
4207   }
4208   return chained;
4209 }
4210 
4211 struct sigaction* os::Linux::get_preinstalled_handler(int sig) {
4212   if ((((uint64_t)1 << (sig-1)) & sigs) != 0) {
4213     return &sigact[sig];
4214   }
4215   return NULL;
4216 }
4217 
4218 void os::Linux::save_preinstalled_handler(int sig, struct sigaction& oldAct) {
4219   assert(sig > 0 && sig < NSIG, "vm signal out of expected range");
4220   sigact[sig] = oldAct;
4221   sigs |= (uint64_t)1 << (sig-1);
4222 }
4223 
4224 // for diagnostic
4225 int sigflags[NSIG];
4226 
4227 int os::Linux::get_our_sigflags(int sig) {
4228   assert(sig > 0 && sig < NSIG, "vm signal out of expected range");
4229   return sigflags[sig];
4230 }
4231 
4232 void os::Linux::set_our_sigflags(int sig, int flags) {
4233   assert(sig > 0 && sig < NSIG, "vm signal out of expected range");
4234   if (sig > 0 && sig < NSIG) {
4235     sigflags[sig] = flags;
4236   }
4237 }
4238 
4239 void os::Linux::set_signal_handler(int sig, bool set_installed) {
4240   // Check for overwrite.
4241   struct sigaction oldAct;
4242   sigaction(sig, (struct sigaction*)NULL, &oldAct);
4243 
4244   void* oldhand = oldAct.sa_sigaction
4245                 ? CAST_FROM_FN_PTR(void*,  oldAct.sa_sigaction)
4246                 : CAST_FROM_FN_PTR(void*,  oldAct.sa_handler);
4247   if (oldhand != CAST_FROM_FN_PTR(void*, SIG_DFL) &&
4248       oldhand != CAST_FROM_FN_PTR(void*, SIG_IGN) &&
4249       oldhand != CAST_FROM_FN_PTR(void*, (sa_sigaction_t)signalHandler)) {
4250     if (AllowUserSignalHandlers || !set_installed) {
4251       // Do not overwrite; user takes responsibility to forward to us.
4252       return;
4253     } else if (UseSignalChaining) {
4254       // save the old handler in jvm
4255       save_preinstalled_handler(sig, oldAct);
4256       // libjsig also interposes the sigaction() call below and saves the
4257       // old sigaction on it own.
4258     } else {
4259       fatal("Encountered unexpected pre-existing sigaction handler "
4260             "%#lx for signal %d.", (long)oldhand, sig);
4261     }
4262   }
4263 
4264   struct sigaction sigAct;
4265   sigfillset(&(sigAct.sa_mask));
4266   sigAct.sa_handler = SIG_DFL;
4267   if (!set_installed) {
4268     sigAct.sa_flags = SA_SIGINFO|SA_RESTART;
4269   } else {
4270     sigAct.sa_sigaction = signalHandler;
4271     sigAct.sa_flags = SA_SIGINFO|SA_RESTART;
4272   }
4273   // Save flags, which are set by ours
4274   assert(sig > 0 && sig < NSIG, "vm signal out of expected range");
4275   sigflags[sig] = sigAct.sa_flags;
4276 
4277   int ret = sigaction(sig, &sigAct, &oldAct);
4278   assert(ret == 0, "check");
4279 
4280   void* oldhand2  = oldAct.sa_sigaction
4281                   ? CAST_FROM_FN_PTR(void*, oldAct.sa_sigaction)
4282                   : CAST_FROM_FN_PTR(void*, oldAct.sa_handler);
4283   assert(oldhand2 == oldhand, "no concurrent signal handler installation");
4284 }
4285 
4286 // install signal handlers for signals that HotSpot needs to
4287 // handle in order to support Java-level exception handling.
4288 
4289 void os::Linux::install_signal_handlers() {
4290   if (!signal_handlers_are_installed) {
4291     signal_handlers_are_installed = true;
4292 
4293     // signal-chaining
4294     typedef void (*signal_setting_t)();
4295     signal_setting_t begin_signal_setting = NULL;
4296     signal_setting_t end_signal_setting = NULL;
4297     begin_signal_setting = CAST_TO_FN_PTR(signal_setting_t,
4298                                           dlsym(RTLD_DEFAULT, "JVM_begin_signal_setting"));
4299     if (begin_signal_setting != NULL) {
4300       end_signal_setting = CAST_TO_FN_PTR(signal_setting_t,
4301                                           dlsym(RTLD_DEFAULT, "JVM_end_signal_setting"));
4302       get_signal_action = CAST_TO_FN_PTR(get_signal_t,
4303                                          dlsym(RTLD_DEFAULT, "JVM_get_signal_action"));
4304       libjsig_is_loaded = true;
4305       assert(UseSignalChaining, "should enable signal-chaining");
4306     }
4307     if (libjsig_is_loaded) {
4308       // Tell libjsig jvm is setting signal handlers
4309       (*begin_signal_setting)();
4310     }
4311 
4312     set_signal_handler(SIGSEGV, true);
4313     set_signal_handler(SIGPIPE, true);
4314     set_signal_handler(SIGBUS, true);
4315     set_signal_handler(SIGILL, true);
4316     set_signal_handler(SIGFPE, true);
4317 #if defined(PPC64)
4318     set_signal_handler(SIGTRAP, true);
4319 #endif
4320     set_signal_handler(SIGXFSZ, true);
4321 
4322     if (libjsig_is_loaded) {
4323       // Tell libjsig jvm finishes setting signal handlers
4324       (*end_signal_setting)();
4325     }
4326 
4327     // We don't activate signal checker if libjsig is in place, we trust ourselves
4328     // and if UserSignalHandler is installed all bets are off.
4329     // Log that signal checking is off only if -verbose:jni is specified.
4330     if (CheckJNICalls) {
4331       if (libjsig_is_loaded) {
4332         if (PrintJNIResolving) {
4333           tty->print_cr("Info: libjsig is activated, all active signal checking is disabled");
4334         }
4335         check_signals = false;
4336       }
4337       if (AllowUserSignalHandlers) {
4338         if (PrintJNIResolving) {
4339           tty->print_cr("Info: AllowUserSignalHandlers is activated, all active signal checking is disabled");
4340         }
4341         check_signals = false;
4342       }
4343     }
4344   }
4345 }
4346 
4347 // This is the fastest way to get thread cpu time on Linux.
4348 // Returns cpu time (user+sys) for any thread, not only for current.
4349 // POSIX compliant clocks are implemented in the kernels 2.6.16+.
4350 // It might work on 2.6.10+ with a special kernel/glibc patch.
4351 // For reference, please, see IEEE Std 1003.1-2004:
4352 //   http://www.unix.org/single_unix_specification
4353 
4354 jlong os::Linux::fast_thread_cpu_time(clockid_t clockid) {
4355   struct timespec tp;
4356   int rc = os::Linux::clock_gettime(clockid, &tp);
4357   assert(rc == 0, "clock_gettime is expected to return 0 code");
4358 
4359   return (tp.tv_sec * NANOSECS_PER_SEC) + tp.tv_nsec;
4360 }
4361 
4362 void os::Linux::initialize_os_info() {
4363   assert(_os_version == 0, "OS info already initialized");
4364 
4365   struct utsname _uname;
4366 
4367   uint32_t major;
4368   uint32_t minor;
4369   uint32_t fix;
4370 
4371   int rc;
4372 
4373   // Kernel version is unknown if
4374   // verification below fails.
4375   _os_version = 0x01000000;
4376 
4377   rc = uname(&_uname);
4378   if (rc != -1) {
4379 
4380     rc = sscanf(_uname.release,"%d.%d.%d", &major, &minor, &fix);
4381     if (rc == 3) {
4382 
4383       if (major < 256 && minor < 256 && fix < 256) {
4384         // Kernel version format is as expected,
4385         // set it overriding unknown state.
4386         _os_version = (major << 16) |
4387                       (minor << 8 ) |
4388                       (fix   << 0 ) ;
4389       }
4390     }
4391   }
4392 }
4393 
4394 uint32_t os::Linux::os_version() {
4395   assert(_os_version != 0, "not initialized");
4396   return _os_version & 0x00FFFFFF;
4397 }
4398 
4399 bool os::Linux::os_version_is_known() {
4400   assert(_os_version != 0, "not initialized");
4401   return _os_version & 0x01000000 ? false : true;
4402 }
4403 
4404 /////
4405 // glibc on Linux platform uses non-documented flag
4406 // to indicate, that some special sort of signal
4407 // trampoline is used.
4408 // We will never set this flag, and we should
4409 // ignore this flag in our diagnostic
4410 #ifdef SIGNIFICANT_SIGNAL_MASK
4411   #undef SIGNIFICANT_SIGNAL_MASK
4412 #endif
4413 #define SIGNIFICANT_SIGNAL_MASK (~0x04000000)
4414 
4415 static const char* get_signal_handler_name(address handler,
4416                                            char* buf, int buflen) {
4417   int offset = 0;
4418   bool found = os::dll_address_to_library_name(handler, buf, buflen, &offset);
4419   if (found) {
4420     // skip directory names
4421     const char *p1, *p2;
4422     p1 = buf;
4423     size_t len = strlen(os::file_separator());
4424     while ((p2 = strstr(p1, os::file_separator())) != NULL) p1 = p2 + len;
4425     jio_snprintf(buf, buflen, "%s+0x%x", p1, offset);
4426   } else {
4427     jio_snprintf(buf, buflen, PTR_FORMAT, handler);
4428   }
4429   return buf;
4430 }
4431 
4432 static void print_signal_handler(outputStream* st, int sig,
4433                                  char* buf, size_t buflen) {
4434   struct sigaction sa;
4435 
4436   sigaction(sig, NULL, &sa);
4437 
4438   // See comment for SIGNIFICANT_SIGNAL_MASK define
4439   sa.sa_flags &= SIGNIFICANT_SIGNAL_MASK;
4440 
4441   st->print("%s: ", os::exception_name(sig, buf, buflen));
4442 
4443   address handler = (sa.sa_flags & SA_SIGINFO)
4444     ? CAST_FROM_FN_PTR(address, sa.sa_sigaction)
4445     : CAST_FROM_FN_PTR(address, sa.sa_handler);
4446 
4447   if (handler == CAST_FROM_FN_PTR(address, SIG_DFL)) {
4448     st->print("SIG_DFL");
4449   } else if (handler == CAST_FROM_FN_PTR(address, SIG_IGN)) {
4450     st->print("SIG_IGN");
4451   } else {
4452     st->print("[%s]", get_signal_handler_name(handler, buf, buflen));
4453   }
4454 
4455   st->print(", sa_mask[0]=");
4456   os::Posix::print_signal_set_short(st, &sa.sa_mask);
4457 
4458   address rh = VMError::get_resetted_sighandler(sig);
4459   // May be, handler was resetted by VMError?
4460   if (rh != NULL) {
4461     handler = rh;
4462     sa.sa_flags = VMError::get_resetted_sigflags(sig) & SIGNIFICANT_SIGNAL_MASK;
4463   }
4464 
4465   st->print(", sa_flags=");
4466   os::Posix::print_sa_flags(st, sa.sa_flags);
4467 
4468   // Check: is it our handler?
4469   if (handler == CAST_FROM_FN_PTR(address, (sa_sigaction_t)signalHandler) ||
4470       handler == CAST_FROM_FN_PTR(address, (sa_sigaction_t)SR_handler)) {
4471     // It is our signal handler
4472     // check for flags, reset system-used one!
4473     if ((int)sa.sa_flags != os::Linux::get_our_sigflags(sig)) {
4474       st->print(
4475                 ", flags was changed from " PTR32_FORMAT ", consider using jsig library",
4476                 os::Linux::get_our_sigflags(sig));
4477     }
4478   }
4479   st->cr();
4480 }
4481 
4482 
4483 #define DO_SIGNAL_CHECK(sig)                      \
4484   do {                                            \
4485     if (!sigismember(&check_signal_done, sig)) {  \
4486       os::Linux::check_signal_handler(sig);       \
4487     }                                             \
4488   } while (0)
4489 
4490 // This method is a periodic task to check for misbehaving JNI applications
4491 // under CheckJNI, we can add any periodic checks here
4492 
4493 void os::run_periodic_checks() {
4494   if (check_signals == false) return;
4495 
4496   // SEGV and BUS if overridden could potentially prevent
4497   // generation of hs*.log in the event of a crash, debugging
4498   // such a case can be very challenging, so we absolutely
4499   // check the following for a good measure:
4500   DO_SIGNAL_CHECK(SIGSEGV);
4501   DO_SIGNAL_CHECK(SIGILL);
4502   DO_SIGNAL_CHECK(SIGFPE);
4503   DO_SIGNAL_CHECK(SIGBUS);
4504   DO_SIGNAL_CHECK(SIGPIPE);
4505   DO_SIGNAL_CHECK(SIGXFSZ);
4506 #if defined(PPC64)
4507   DO_SIGNAL_CHECK(SIGTRAP);
4508 #endif
4509 
4510   // ReduceSignalUsage allows the user to override these handlers
4511   // see comments at the very top and jvm_solaris.h
4512   if (!ReduceSignalUsage) {
4513     DO_SIGNAL_CHECK(SHUTDOWN1_SIGNAL);
4514     DO_SIGNAL_CHECK(SHUTDOWN2_SIGNAL);
4515     DO_SIGNAL_CHECK(SHUTDOWN3_SIGNAL);
4516     DO_SIGNAL_CHECK(BREAK_SIGNAL);
4517   }
4518 
4519   DO_SIGNAL_CHECK(SR_signum);
4520 }
4521 
4522 typedef int (*os_sigaction_t)(int, const struct sigaction *, struct sigaction *);
4523 
4524 static os_sigaction_t os_sigaction = NULL;
4525 
4526 void os::Linux::check_signal_handler(int sig) {
4527   char buf[O_BUFLEN];
4528   address jvmHandler = NULL;
4529 
4530 
4531   struct sigaction act;
4532   if (os_sigaction == NULL) {
4533     // only trust the default sigaction, in case it has been interposed
4534     os_sigaction = (os_sigaction_t)dlsym(RTLD_DEFAULT, "sigaction");
4535     if (os_sigaction == NULL) return;
4536   }
4537 
4538   os_sigaction(sig, (struct sigaction*)NULL, &act);
4539 
4540 
4541   act.sa_flags &= SIGNIFICANT_SIGNAL_MASK;
4542 
4543   address thisHandler = (act.sa_flags & SA_SIGINFO)
4544     ? CAST_FROM_FN_PTR(address, act.sa_sigaction)
4545     : CAST_FROM_FN_PTR(address, act.sa_handler);
4546 
4547 
4548   switch (sig) {
4549   case SIGSEGV:
4550   case SIGBUS:
4551   case SIGFPE:
4552   case SIGPIPE:
4553   case SIGILL:
4554   case SIGXFSZ:
4555     jvmHandler = CAST_FROM_FN_PTR(address, (sa_sigaction_t)signalHandler);
4556     break;
4557 
4558   case SHUTDOWN1_SIGNAL:
4559   case SHUTDOWN2_SIGNAL:
4560   case SHUTDOWN3_SIGNAL:
4561   case BREAK_SIGNAL:
4562     jvmHandler = (address)user_handler();
4563     break;
4564 
4565   default:
4566     if (sig == SR_signum) {
4567       jvmHandler = CAST_FROM_FN_PTR(address, (sa_sigaction_t)SR_handler);
4568     } else {
4569       return;
4570     }
4571     break;
4572   }
4573 
4574   if (thisHandler != jvmHandler) {
4575     tty->print("Warning: %s handler ", exception_name(sig, buf, O_BUFLEN));
4576     tty->print("expected:%s", get_signal_handler_name(jvmHandler, buf, O_BUFLEN));
4577     tty->print_cr("  found:%s", get_signal_handler_name(thisHandler, buf, O_BUFLEN));
4578     // No need to check this sig any longer
4579     sigaddset(&check_signal_done, sig);
4580     // Running under non-interactive shell, SHUTDOWN2_SIGNAL will be reassigned SIG_IGN
4581     if (sig == SHUTDOWN2_SIGNAL && !isatty(fileno(stdin))) {
4582       tty->print_cr("Running in non-interactive shell, %s handler is replaced by shell",
4583                     exception_name(sig, buf, O_BUFLEN));
4584     }
4585   } else if(os::Linux::get_our_sigflags(sig) != 0 && (int)act.sa_flags != os::Linux::get_our_sigflags(sig)) {
4586     tty->print("Warning: %s handler flags ", exception_name(sig, buf, O_BUFLEN));
4587     tty->print("expected:");
4588     os::Posix::print_sa_flags(tty, os::Linux::get_our_sigflags(sig));
4589     tty->cr();
4590     tty->print("  found:");
4591     os::Posix::print_sa_flags(tty, act.sa_flags);
4592     tty->cr();
4593     // No need to check this sig any longer
4594     sigaddset(&check_signal_done, sig);
4595   }
4596 
4597   // Dump all the signal
4598   if (sigismember(&check_signal_done, sig)) {
4599     print_signal_handlers(tty, buf, O_BUFLEN);
4600   }
4601 }
4602 
4603 extern void report_error(char* file_name, int line_no, char* title,
4604                          char* format, ...);
4605 
4606 // this is called _before_ the most of global arguments have been parsed
4607 void os::init(void) {
4608   char dummy;   // used to get a guess on initial stack address
4609 //  first_hrtime = gethrtime();
4610 
4611   clock_tics_per_sec = sysconf(_SC_CLK_TCK);
4612 
4613   init_random(1234567);
4614 
4615   ThreadCritical::initialize();
4616 
4617   Linux::set_page_size(sysconf(_SC_PAGESIZE));
4618   if (Linux::page_size() == -1) {
4619     fatal("os_linux.cpp: os::init: sysconf failed (%s)",
4620           os::strerror(errno));
4621   }
4622   init_page_sizes((size_t) Linux::page_size());
4623 
4624   Linux::initialize_system_info();
4625 
4626   Linux::initialize_os_info();
4627 
4628   // main_thread points to the aboriginal thread
4629   Linux::_main_thread = pthread_self();
4630 
4631   Linux::clock_init();
4632   initial_time_count = javaTimeNanos();
4633 
4634   // pthread_condattr initialization for monotonic clock
4635   int status;
4636   pthread_condattr_t* _condattr = os::Linux::condAttr();
4637   if ((status = pthread_condattr_init(_condattr)) != 0) {
4638     fatal("pthread_condattr_init: %s", os::strerror(status));
4639   }
4640   // Only set the clock if CLOCK_MONOTONIC is available
4641   if (os::supports_monotonic_clock()) {
4642     if ((status = pthread_condattr_setclock(_condattr, CLOCK_MONOTONIC)) != 0) {
4643       if (status == EINVAL) {
4644         warning("Unable to use monotonic clock with relative timed-waits" \
4645                 " - changes to the time-of-day clock may have adverse affects");
4646       } else {
4647         fatal("pthread_condattr_setclock: %s", os::strerror(status));
4648       }
4649     }
4650   }
4651   // else it defaults to CLOCK_REALTIME
4652 
4653   // retrieve entry point for pthread_setname_np
4654   Linux::_pthread_setname_np =
4655     (int(*)(pthread_t, const char*))dlsym(RTLD_DEFAULT, "pthread_setname_np");
4656 
4657 }
4658 
4659 // To install functions for atexit system call
4660 extern "C" {
4661   static void perfMemory_exit_helper() {
4662     perfMemory_exit();
4663   }
4664 }
4665 
4666 // this is called _after_ the global arguments have been parsed
4667 jint os::init_2(void) {
4668   Linux::fast_thread_clock_init();
4669 
4670   // Allocate a single page and mark it as readable for safepoint polling
4671   address polling_page = (address) ::mmap(NULL, Linux::page_size(), PROT_READ, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
4672   guarantee(polling_page != MAP_FAILED, "os::init_2: failed to allocate polling page");
4673 
4674   os::set_polling_page(polling_page);
4675   log_info(os)("SafePoint Polling address: " INTPTR_FORMAT, p2i(polling_page));
4676 
4677   if (!UseMembar) {
4678     address mem_serialize_page = (address) ::mmap(NULL, Linux::page_size(), PROT_READ | PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
4679     guarantee(mem_serialize_page != MAP_FAILED, "mmap Failed for memory serialize page");
4680     os::set_memory_serialize_page(mem_serialize_page);
4681     log_info(os)("Memory Serialize Page address: " INTPTR_FORMAT, p2i(mem_serialize_page));
4682   }
4683 
4684   // initialize suspend/resume support - must do this before signal_sets_init()
4685   if (SR_initialize() != 0) {
4686     perror("SR_initialize failed");
4687     return JNI_ERR;
4688   }
4689 
4690   Linux::signal_sets_init();
4691   Linux::install_signal_handlers();
4692 
4693   // Check minimum allowable stack size for thread creation and to initialize
4694   // the java system classes, including StackOverflowError - depends on page
4695   // size.  Add a page for compiler2 recursion in main thread.
4696   // Add in 2*BytesPerWord times page size to account for VM stack during
4697   // class initialization depending on 32 or 64 bit VM.
4698   os::Linux::min_stack_allowed = MAX2(os::Linux::min_stack_allowed,
4699                                       JavaThread::stack_guard_zone_size() +
4700                                       JavaThread::stack_shadow_zone_size() +
4701                                       (2*BytesPerWord COMPILER2_PRESENT(+1)) * Linux::vm_default_page_size());
4702 
4703   size_t threadStackSizeInBytes = ThreadStackSize * K;
4704   if (threadStackSizeInBytes != 0 &&
4705       threadStackSizeInBytes < os::Linux::min_stack_allowed) {
4706     tty->print_cr("\nThe stack size specified is too small, "
4707                   "Specify at least " SIZE_FORMAT "k",
4708                   os::Linux::min_stack_allowed/ K);
4709     return JNI_ERR;
4710   }
4711 
4712   // Make the stack size a multiple of the page size so that
4713   // the yellow/red zones can be guarded.
4714   JavaThread::set_stack_size_at_create(round_to(threadStackSizeInBytes,
4715                                                 vm_page_size()));
4716 
4717   Linux::capture_initial_stack(JavaThread::stack_size_at_create());
4718 
4719 #if defined(IA32)
4720   workaround_expand_exec_shield_cs_limit();
4721 #endif
4722 
4723   Linux::libpthread_init();
4724   log_info(os)("HotSpot is running with %s, %s",
4725                Linux::glibc_version(), Linux::libpthread_version());
4726 
4727   if (UseNUMA) {
4728     if (!Linux::libnuma_init()) {
4729       UseNUMA = false;
4730     } else {
4731       if ((Linux::numa_max_node() < 1)) {
4732         // There's only one node(they start from 0), disable NUMA.
4733         UseNUMA = false;
4734       }
4735     }
4736     // With SHM and HugeTLBFS large pages we cannot uncommit a page, so there's no way
4737     // we can make the adaptive lgrp chunk resizing work. If the user specified
4738     // both UseNUMA and UseLargePages (or UseSHM/UseHugeTLBFS) on the command line - warn and
4739     // disable adaptive resizing.
4740     if (UseNUMA && UseLargePages && !can_commit_large_page_memory()) {
4741       if (FLAG_IS_DEFAULT(UseNUMA)) {
4742         UseNUMA = false;
4743       } else {
4744         if (FLAG_IS_DEFAULT(UseLargePages) &&
4745             FLAG_IS_DEFAULT(UseSHM) &&
4746             FLAG_IS_DEFAULT(UseHugeTLBFS)) {
4747           UseLargePages = false;
4748         } else if (UseAdaptiveSizePolicy || UseAdaptiveNUMAChunkSizing) {
4749           warning("UseNUMA is not fully compatible with SHM/HugeTLBFS large pages, disabling adaptive resizing (-XX:-UseAdaptiveSizePolicy -XX:-UseAdaptiveNUMAChunkSizing)");
4750           UseAdaptiveSizePolicy = false;
4751           UseAdaptiveNUMAChunkSizing = false;
4752         }
4753       }
4754     }
4755     if (!UseNUMA && ForceNUMA) {
4756       UseNUMA = true;
4757     }
4758   }
4759 
4760   if (MaxFDLimit) {
4761     // set the number of file descriptors to max. print out error
4762     // if getrlimit/setrlimit fails but continue regardless.
4763     struct rlimit nbr_files;
4764     int status = getrlimit(RLIMIT_NOFILE, &nbr_files);
4765     if (status != 0) {
4766       log_info(os)("os::init_2 getrlimit failed: %s", os::strerror(errno));
4767     } else {
4768       nbr_files.rlim_cur = nbr_files.rlim_max;
4769       status = setrlimit(RLIMIT_NOFILE, &nbr_files);
4770       if (status != 0) {
4771         log_info(os)("os::init_2 setrlimit failed: %s", os::strerror(errno));
4772       }
4773     }
4774   }
4775 
4776   // Initialize lock used to serialize thread creation (see os::create_thread)
4777   Linux::set_createThread_lock(new Mutex(Mutex::leaf, "createThread_lock", false));
4778 
4779   // at-exit methods are called in the reverse order of their registration.
4780   // atexit functions are called on return from main or as a result of a
4781   // call to exit(3C). There can be only 32 of these functions registered
4782   // and atexit() does not set errno.
4783 
4784   if (PerfAllowAtExitRegistration) {
4785     // only register atexit functions if PerfAllowAtExitRegistration is set.
4786     // atexit functions can be delayed until process exit time, which
4787     // can be problematic for embedded VM situations. Embedded VMs should
4788     // call DestroyJavaVM() to assure that VM resources are released.
4789 
4790     // note: perfMemory_exit_helper atexit function may be removed in
4791     // the future if the appropriate cleanup code can be added to the
4792     // VM_Exit VMOperation's doit method.
4793     if (atexit(perfMemory_exit_helper) != 0) {
4794       warning("os::init_2 atexit(perfMemory_exit_helper) failed");
4795     }
4796   }
4797 
4798   // initialize thread priority policy
4799   prio_init();
4800 
4801   return JNI_OK;
4802 }
4803 
4804 // Mark the polling page as unreadable
4805 void os::make_polling_page_unreadable(void) {
4806   if (!guard_memory((char*)_polling_page, Linux::page_size())) {
4807     fatal("Could not disable polling page");
4808   }
4809 }
4810 
4811 // Mark the polling page as readable
4812 void os::make_polling_page_readable(void) {
4813   if (!linux_mprotect((char *)_polling_page, Linux::page_size(), PROT_READ)) {
4814     fatal("Could not enable polling page");
4815   }
4816 }
4817 
4818 // older glibc versions don't have this macro (which expands to
4819 // an optimized bit-counting function) so we have to roll our own
4820 #ifndef CPU_COUNT
4821 
4822 static int _cpu_count(const cpu_set_t* cpus) {
4823   int count = 0;
4824   // only look up to the number of configured processors
4825   for (int i = 0; i < os::processor_count(); i++) {
4826     if (CPU_ISSET(i, cpus)) {
4827       count++;
4828     }
4829   }
4830   return count;
4831 }
4832 
4833 #define CPU_COUNT(cpus) _cpu_count(cpus)
4834 
4835 #endif // CPU_COUNT
4836 
4837 // Get the current number of available processors for this process.
4838 // This value can change at any time during a process's lifetime.
4839 // sched_getaffinity gives an accurate answer as it accounts for cpusets.
4840 // If it appears there may be more than 1024 processors then we do a
4841 // dynamic check - see 6515172 for details.
4842 // If anything goes wrong we fallback to returning the number of online
4843 // processors - which can be greater than the number available to the process.
4844 int os::active_processor_count() {
4845   cpu_set_t cpus;  // can represent at most 1024 (CPU_SETSIZE) processors
4846   cpu_set_t* cpus_p = &cpus;
4847   int cpus_size = sizeof(cpu_set_t);
4848 
4849   int configured_cpus = processor_count();  // upper bound on available cpus
4850   int cpu_count = 0;
4851 
4852 // old build platforms may not support dynamic cpu sets
4853 #ifdef CPU_ALLOC
4854 
4855   // To enable easy testing of the dynamic path on different platforms we
4856   // introduce a diagnostic flag: UseCpuAllocPath
4857   if (configured_cpus >= CPU_SETSIZE || UseCpuAllocPath) {
4858     // kernel may use a mask bigger than cpu_set_t
4859     log_trace(os)("active_processor_count: using dynamic path %s"
4860                   "- configured processors: %d",
4861                   UseCpuAllocPath ? "(forced) " : "",
4862                   configured_cpus);
4863     cpus_p = CPU_ALLOC(configured_cpus);
4864     if (cpus_p != NULL) {
4865       cpus_size = CPU_ALLOC_SIZE(configured_cpus);
4866       // zero it just to be safe
4867       CPU_ZERO_S(cpus_size, cpus_p);
4868     }
4869     else {
4870        // failed to allocate so fallback to online cpus
4871        int online_cpus = ::sysconf(_SC_NPROCESSORS_ONLN);
4872        log_trace(os)("active_processor_count: "
4873                      "CPU_ALLOC failed (%s) - using "
4874                      "online processor count: %d",
4875                      os::strerror(errno), online_cpus);
4876        return online_cpus;
4877     }
4878   }
4879   else {
4880     log_trace(os)("active_processor_count: using static path - configured processors: %d",
4881                   configured_cpus);
4882   }
4883 #else // CPU_ALLOC
4884 // these stubs won't be executed
4885 #define CPU_COUNT_S(size, cpus) -1
4886 #define CPU_FREE(cpus)
4887 
4888   log_trace(os)("active_processor_count: only static path available - configured processors: %d",
4889                 configured_cpus);
4890 #endif // CPU_ALLOC
4891 
4892   // pid 0 means the current thread - which we have to assume represents the process
4893   if (sched_getaffinity(0, cpus_size, cpus_p) == 0) {
4894     if (cpus_p != &cpus) { // can only be true when CPU_ALLOC used
4895       cpu_count = CPU_COUNT_S(cpus_size, cpus_p);
4896     }
4897     else {
4898       cpu_count = CPU_COUNT(cpus_p);
4899     }
4900     log_trace(os)("active_processor_count: sched_getaffinity processor count: %d", cpu_count);
4901   }
4902   else {
4903     cpu_count = ::sysconf(_SC_NPROCESSORS_ONLN);
4904     warning("sched_getaffinity failed (%s)- using online processor count (%d) "
4905             "which may exceed available processors", os::strerror(errno), cpu_count);
4906   }
4907 
4908   if (cpus_p != &cpus) { // can only be true when CPU_ALLOC used
4909     CPU_FREE(cpus_p);
4910   }
4911 
4912   assert(cpu_count > 0 && cpu_count <= processor_count(), "sanity check");
4913   return cpu_count;
4914 }
4915 
4916 void os::set_native_thread_name(const char *name) {
4917   if (Linux::_pthread_setname_np) {
4918     char buf [16]; // according to glibc manpage, 16 chars incl. '/0'
4919     snprintf(buf, sizeof(buf), "%s", name);
4920     buf[sizeof(buf) - 1] = '\0';
4921     const int rc = Linux::_pthread_setname_np(pthread_self(), buf);
4922     // ERANGE should not happen; all other errors should just be ignored.
4923     assert(rc != ERANGE, "pthread_setname_np failed");
4924   }
4925 }
4926 
4927 bool os::distribute_processes(uint length, uint* distribution) {
4928   // Not yet implemented.
4929   return false;
4930 }
4931 
4932 bool os::bind_to_processor(uint processor_id) {
4933   // Not yet implemented.
4934   return false;
4935 }
4936 
4937 ///
4938 
4939 void os::SuspendedThreadTask::internal_do_task() {
4940   if (do_suspend(_thread->osthread())) {
4941     SuspendedThreadTaskContext context(_thread, _thread->osthread()->ucontext());
4942     do_task(context);
4943     do_resume(_thread->osthread());
4944   }
4945 }
4946 
4947 class PcFetcher : public os::SuspendedThreadTask {
4948  public:
4949   PcFetcher(Thread* thread) : os::SuspendedThreadTask(thread) {}
4950   ExtendedPC result();
4951  protected:
4952   void do_task(const os::SuspendedThreadTaskContext& context);
4953  private:
4954   ExtendedPC _epc;
4955 };
4956 
4957 ExtendedPC PcFetcher::result() {
4958   guarantee(is_done(), "task is not done yet.");
4959   return _epc;
4960 }
4961 
4962 void PcFetcher::do_task(const os::SuspendedThreadTaskContext& context) {
4963   Thread* thread = context.thread();
4964   OSThread* osthread = thread->osthread();
4965   if (osthread->ucontext() != NULL) {
4966     _epc = os::Linux::ucontext_get_pc((const ucontext_t *) context.ucontext());
4967   } else {
4968     // NULL context is unexpected, double-check this is the VMThread
4969     guarantee(thread->is_VM_thread(), "can only be called for VMThread");
4970   }
4971 }
4972 
4973 // Suspends the target using the signal mechanism and then grabs the PC before
4974 // resuming the target. Used by the flat-profiler only
4975 ExtendedPC os::get_thread_pc(Thread* thread) {
4976   // Make sure that it is called by the watcher for the VMThread
4977   assert(Thread::current()->is_Watcher_thread(), "Must be watcher");
4978   assert(thread->is_VM_thread(), "Can only be called for VMThread");
4979 
4980   PcFetcher fetcher(thread);
4981   fetcher.run();
4982   return fetcher.result();
4983 }
4984 
4985 ////////////////////////////////////////////////////////////////////////////////
4986 // debug support
4987 
4988 bool os::find(address addr, outputStream* st) {
4989   Dl_info dlinfo;
4990   memset(&dlinfo, 0, sizeof(dlinfo));
4991   if (dladdr(addr, &dlinfo) != 0) {
4992     st->print(PTR_FORMAT ": ", p2i(addr));
4993     if (dlinfo.dli_sname != NULL && dlinfo.dli_saddr != NULL) {
4994       st->print("%s+" PTR_FORMAT, dlinfo.dli_sname,
4995                 p2i(addr) - p2i(dlinfo.dli_saddr));
4996     } else if (dlinfo.dli_fbase != NULL) {
4997       st->print("<offset " PTR_FORMAT ">", p2i(addr) - p2i(dlinfo.dli_fbase));
4998     } else {
4999       st->print("<absolute address>");
5000     }
5001     if (dlinfo.dli_fname != NULL) {
5002       st->print(" in %s", dlinfo.dli_fname);
5003     }
5004     if (dlinfo.dli_fbase != NULL) {
5005       st->print(" at " PTR_FORMAT, p2i(dlinfo.dli_fbase));
5006     }
5007     st->cr();
5008 
5009     if (Verbose) {
5010       // decode some bytes around the PC
5011       address begin = clamp_address_in_page(addr-40, addr, os::vm_page_size());
5012       address end   = clamp_address_in_page(addr+40, addr, os::vm_page_size());
5013       address       lowest = (address) dlinfo.dli_sname;
5014       if (!lowest)  lowest = (address) dlinfo.dli_fbase;
5015       if (begin < lowest)  begin = lowest;
5016       Dl_info dlinfo2;
5017       if (dladdr(end, &dlinfo2) != 0 && dlinfo2.dli_saddr != dlinfo.dli_saddr
5018           && end > dlinfo2.dli_saddr && dlinfo2.dli_saddr > begin) {
5019         end = (address) dlinfo2.dli_saddr;
5020       }
5021       Disassembler::decode(begin, end, st);
5022     }
5023     return true;
5024   }
5025   return false;
5026 }
5027 
5028 ////////////////////////////////////////////////////////////////////////////////
5029 // misc
5030 
5031 // This does not do anything on Linux. This is basically a hook for being
5032 // able to use structured exception handling (thread-local exception filters)
5033 // on, e.g., Win32.
5034 void
5035 os::os_exception_wrapper(java_call_t f, JavaValue* value, const methodHandle& method,
5036                          JavaCallArguments* args, Thread* thread) {
5037   f(value, method, args, thread);
5038 }
5039 
5040 void os::print_statistics() {
5041 }
5042 
5043 bool os::message_box(const char* title, const char* message) {
5044   int i;
5045   fdStream err(defaultStream::error_fd());
5046   for (i = 0; i < 78; i++) err.print_raw("=");
5047   err.cr();
5048   err.print_raw_cr(title);
5049   for (i = 0; i < 78; i++) err.print_raw("-");
5050   err.cr();
5051   err.print_raw_cr(message);
5052   for (i = 0; i < 78; i++) err.print_raw("=");
5053   err.cr();
5054 
5055   char buf[16];
5056   // Prevent process from exiting upon "read error" without consuming all CPU
5057   while (::read(0, buf, sizeof(buf)) <= 0) { ::sleep(100); }
5058 
5059   return buf[0] == 'y' || buf[0] == 'Y';
5060 }
5061 
5062 int os::stat(const char *path, struct stat *sbuf) {
5063   char pathbuf[MAX_PATH];
5064   if (strlen(path) > MAX_PATH - 1) {
5065     errno = ENAMETOOLONG;
5066     return -1;
5067   }
5068   os::native_path(strcpy(pathbuf, path));
5069   return ::stat(pathbuf, sbuf);
5070 }
5071 
5072 bool os::check_heap(bool force) {
5073   return true;
5074 }
5075 
5076 // Is a (classpath) directory empty?
5077 bool os::dir_is_empty(const char* path) {
5078   DIR *dir = NULL;
5079   struct dirent *ptr;
5080 
5081   dir = opendir(path);
5082   if (dir == NULL) return true;
5083 
5084   // Scan the directory
5085   bool result = true;
5086   char buf[sizeof(struct dirent) + MAX_PATH];
5087   while (result && (ptr = ::readdir(dir)) != NULL) {
5088     if (strcmp(ptr->d_name, ".") != 0 && strcmp(ptr->d_name, "..") != 0) {
5089       result = false;
5090     }
5091   }
5092   closedir(dir);
5093   return result;
5094 }
5095 
5096 // This code originates from JDK's sysOpen and open64_w
5097 // from src/solaris/hpi/src/system_md.c
5098 
5099 int os::open(const char *path, int oflag, int mode) {
5100   if (strlen(path) > MAX_PATH - 1) {
5101     errno = ENAMETOOLONG;
5102     return -1;
5103   }
5104 
5105   // All file descriptors that are opened in the Java process and not
5106   // specifically destined for a subprocess should have the close-on-exec
5107   // flag set.  If we don't set it, then careless 3rd party native code
5108   // might fork and exec without closing all appropriate file descriptors
5109   // (e.g. as we do in closeDescriptors in UNIXProcess.c), and this in
5110   // turn might:
5111   //
5112   // - cause end-of-file to fail to be detected on some file
5113   //   descriptors, resulting in mysterious hangs, or
5114   //
5115   // - might cause an fopen in the subprocess to fail on a system
5116   //   suffering from bug 1085341.
5117   //
5118   // (Yes, the default setting of the close-on-exec flag is a Unix
5119   // design flaw)
5120   //
5121   // See:
5122   // 1085341: 32-bit stdio routines should support file descriptors >255
5123   // 4843136: (process) pipe file descriptor from Runtime.exec not being closed
5124   // 6339493: (process) Runtime.exec does not close all file descriptors on Solaris 9
5125   //
5126   // Modern Linux kernels (after 2.6.23 2007) support O_CLOEXEC with open().
5127   // O_CLOEXEC is preferable to using FD_CLOEXEC on an open file descriptor
5128   // because it saves a system call and removes a small window where the flag
5129   // is unset.  On ancient Linux kernels the O_CLOEXEC flag will be ignored
5130   // and we fall back to using FD_CLOEXEC (see below).
5131 #ifdef O_CLOEXEC
5132   oflag |= O_CLOEXEC;
5133 #endif
5134 
5135   int fd = ::open64(path, oflag, mode);
5136   if (fd == -1) return -1;
5137 
5138   //If the open succeeded, the file might still be a directory
5139   {
5140     struct stat64 buf64;
5141     int ret = ::fstat64(fd, &buf64);
5142     int st_mode = buf64.st_mode;
5143 
5144     if (ret != -1) {
5145       if ((st_mode & S_IFMT) == S_IFDIR) {
5146         errno = EISDIR;
5147         ::close(fd);
5148         return -1;
5149       }
5150     } else {
5151       ::close(fd);
5152       return -1;
5153     }
5154   }
5155 
5156 #ifdef FD_CLOEXEC
5157   // Validate that the use of the O_CLOEXEC flag on open above worked.
5158   // With recent kernels, we will perform this check exactly once.
5159   static sig_atomic_t O_CLOEXEC_is_known_to_work = 0;
5160   if (!O_CLOEXEC_is_known_to_work) {
5161     int flags = ::fcntl(fd, F_GETFD);
5162     if (flags != -1) {
5163       if ((flags & FD_CLOEXEC) != 0)
5164         O_CLOEXEC_is_known_to_work = 1;
5165       else
5166         ::fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
5167     }
5168   }
5169 #endif
5170 
5171   return fd;
5172 }
5173 
5174 
5175 // create binary file, rewriting existing file if required
5176 int os::create_binary_file(const char* path, bool rewrite_existing) {
5177   int oflags = O_WRONLY | O_CREAT;
5178   if (!rewrite_existing) {
5179     oflags |= O_EXCL;
5180   }
5181   return ::open64(path, oflags, S_IREAD | S_IWRITE);
5182 }
5183 
5184 // return current position of file pointer
5185 jlong os::current_file_offset(int fd) {
5186   return (jlong)::lseek64(fd, (off64_t)0, SEEK_CUR);
5187 }
5188 
5189 // move file pointer to the specified offset
5190 jlong os::seek_to_file_offset(int fd, jlong offset) {
5191   return (jlong)::lseek64(fd, (off64_t)offset, SEEK_SET);
5192 }
5193 
5194 // This code originates from JDK's sysAvailable
5195 // from src/solaris/hpi/src/native_threads/src/sys_api_td.c
5196 
5197 int os::available(int fd, jlong *bytes) {
5198   jlong cur, end;
5199   int mode;
5200   struct stat64 buf64;
5201 
5202   if (::fstat64(fd, &buf64) >= 0) {
5203     mode = buf64.st_mode;
5204     if (S_ISCHR(mode) || S_ISFIFO(mode) || S_ISSOCK(mode)) {
5205       int n;
5206       if (::ioctl(fd, FIONREAD, &n) >= 0) {
5207         *bytes = n;
5208         return 1;
5209       }
5210     }
5211   }
5212   if ((cur = ::lseek64(fd, 0L, SEEK_CUR)) == -1) {
5213     return 0;
5214   } else if ((end = ::lseek64(fd, 0L, SEEK_END)) == -1) {
5215     return 0;
5216   } else if (::lseek64(fd, cur, SEEK_SET) == -1) {
5217     return 0;
5218   }
5219   *bytes = end - cur;
5220   return 1;
5221 }
5222 
5223 // Map a block of memory.
5224 char* os::pd_map_memory(int fd, const char* file_name, size_t file_offset,
5225                         char *addr, size_t bytes, bool read_only,
5226                         bool allow_exec) {
5227   int prot;
5228   int flags = MAP_PRIVATE;
5229 
5230   if (read_only) {
5231     prot = PROT_READ;
5232   } else {
5233     prot = PROT_READ | PROT_WRITE;
5234   }
5235 
5236   if (allow_exec) {
5237     prot |= PROT_EXEC;
5238   }
5239 
5240   if (addr != NULL) {
5241     flags |= MAP_FIXED;
5242   }
5243 
5244   char* mapped_address = (char*)mmap(addr, (size_t)bytes, prot, flags,
5245                                      fd, file_offset);
5246   if (mapped_address == MAP_FAILED) {
5247     return NULL;
5248   }
5249   return mapped_address;
5250 }
5251 
5252 
5253 // Remap a block of memory.
5254 char* os::pd_remap_memory(int fd, const char* file_name, size_t file_offset,
5255                           char *addr, size_t bytes, bool read_only,
5256                           bool allow_exec) {
5257   // same as map_memory() on this OS
5258   return os::map_memory(fd, file_name, file_offset, addr, bytes, read_only,
5259                         allow_exec);
5260 }
5261 
5262 
5263 // Unmap a block of memory.
5264 bool os::pd_unmap_memory(char* addr, size_t bytes) {
5265   return munmap(addr, bytes) == 0;
5266 }
5267 
5268 static jlong slow_thread_cpu_time(Thread *thread, bool user_sys_cpu_time);
5269 
5270 static clockid_t thread_cpu_clockid(Thread* thread) {
5271   pthread_t tid = thread->osthread()->pthread_id();
5272   clockid_t clockid;
5273 
5274   // Get thread clockid
5275   int rc = os::Linux::pthread_getcpuclockid(tid, &clockid);
5276   assert(rc == 0, "pthread_getcpuclockid is expected to return 0 code");
5277   return clockid;
5278 }
5279 
5280 // current_thread_cpu_time(bool) and thread_cpu_time(Thread*, bool)
5281 // are used by JVM M&M and JVMTI to get user+sys or user CPU time
5282 // of a thread.
5283 //
5284 // current_thread_cpu_time() and thread_cpu_time(Thread*) returns
5285 // the fast estimate available on the platform.
5286 
5287 jlong os::current_thread_cpu_time() {
5288   if (os::Linux::supports_fast_thread_cpu_time()) {
5289     return os::Linux::fast_thread_cpu_time(CLOCK_THREAD_CPUTIME_ID);
5290   } else {
5291     // return user + sys since the cost is the same
5292     return slow_thread_cpu_time(Thread::current(), true /* user + sys */);
5293   }
5294 }
5295 
5296 jlong os::thread_cpu_time(Thread* thread) {
5297   // consistent with what current_thread_cpu_time() returns
5298   if (os::Linux::supports_fast_thread_cpu_time()) {
5299     return os::Linux::fast_thread_cpu_time(thread_cpu_clockid(thread));
5300   } else {
5301     return slow_thread_cpu_time(thread, true /* user + sys */);
5302   }
5303 }
5304 
5305 jlong os::current_thread_cpu_time(bool user_sys_cpu_time) {
5306   if (user_sys_cpu_time && os::Linux::supports_fast_thread_cpu_time()) {
5307     return os::Linux::fast_thread_cpu_time(CLOCK_THREAD_CPUTIME_ID);
5308   } else {
5309     return slow_thread_cpu_time(Thread::current(), user_sys_cpu_time);
5310   }
5311 }
5312 
5313 jlong os::thread_cpu_time(Thread *thread, bool user_sys_cpu_time) {
5314   if (user_sys_cpu_time && os::Linux::supports_fast_thread_cpu_time()) {
5315     return os::Linux::fast_thread_cpu_time(thread_cpu_clockid(thread));
5316   } else {
5317     return slow_thread_cpu_time(thread, user_sys_cpu_time);
5318   }
5319 }
5320 
5321 //  -1 on error.
5322 static jlong slow_thread_cpu_time(Thread *thread, bool user_sys_cpu_time) {
5323   pid_t  tid = thread->osthread()->thread_id();
5324   char *s;
5325   char stat[2048];
5326   int statlen;
5327   char proc_name[64];
5328   int count;
5329   long sys_time, user_time;
5330   char cdummy;
5331   int idummy;
5332   long ldummy;
5333   FILE *fp;
5334 
5335   snprintf(proc_name, 64, "/proc/self/task/%d/stat", tid);
5336   fp = fopen(proc_name, "r");
5337   if (fp == NULL) return -1;
5338   statlen = fread(stat, 1, 2047, fp);
5339   stat[statlen] = '\0';
5340   fclose(fp);
5341 
5342   // Skip pid and the command string. Note that we could be dealing with
5343   // weird command names, e.g. user could decide to rename java launcher
5344   // to "java 1.4.2 :)", then the stat file would look like
5345   //                1234 (java 1.4.2 :)) R ... ...
5346   // We don't really need to know the command string, just find the last
5347   // occurrence of ")" and then start parsing from there. See bug 4726580.
5348   s = strrchr(stat, ')');
5349   if (s == NULL) return -1;
5350 
5351   // Skip blank chars
5352   do { s++; } while (s && isspace(*s));
5353 
5354   count = sscanf(s,"%c %d %d %d %d %d %lu %lu %lu %lu %lu %lu %lu",
5355                  &cdummy, &idummy, &idummy, &idummy, &idummy, &idummy,
5356                  &ldummy, &ldummy, &ldummy, &ldummy, &ldummy,
5357                  &user_time, &sys_time);
5358   if (count != 13) return -1;
5359   if (user_sys_cpu_time) {
5360     return ((jlong)sys_time + (jlong)user_time) * (1000000000 / clock_tics_per_sec);
5361   } else {
5362     return (jlong)user_time * (1000000000 / clock_tics_per_sec);
5363   }
5364 }
5365 
5366 void os::current_thread_cpu_time_info(jvmtiTimerInfo *info_ptr) {
5367   info_ptr->max_value = ALL_64_BITS;       // will not wrap in less than 64 bits
5368   info_ptr->may_skip_backward = false;     // elapsed time not wall time
5369   info_ptr->may_skip_forward = false;      // elapsed time not wall time
5370   info_ptr->kind = JVMTI_TIMER_TOTAL_CPU;  // user+system time is returned
5371 }
5372 
5373 void os::thread_cpu_time_info(jvmtiTimerInfo *info_ptr) {
5374   info_ptr->max_value = ALL_64_BITS;       // will not wrap in less than 64 bits
5375   info_ptr->may_skip_backward = false;     // elapsed time not wall time
5376   info_ptr->may_skip_forward = false;      // elapsed time not wall time
5377   info_ptr->kind = JVMTI_TIMER_TOTAL_CPU;  // user+system time is returned
5378 }
5379 
5380 bool os::is_thread_cpu_time_supported() {
5381   return true;
5382 }
5383 
5384 // System loadavg support.  Returns -1 if load average cannot be obtained.
5385 // Linux doesn't yet have a (official) notion of processor sets,
5386 // so just return the system wide load average.
5387 int os::loadavg(double loadavg[], int nelem) {
5388   return ::getloadavg(loadavg, nelem);
5389 }
5390 
5391 void os::pause() {
5392   char filename[MAX_PATH];
5393   if (PauseAtStartupFile && PauseAtStartupFile[0]) {
5394     jio_snprintf(filename, MAX_PATH, "%s", PauseAtStartupFile);
5395   } else {
5396     jio_snprintf(filename, MAX_PATH, "./vm.paused.%d", current_process_id());
5397   }
5398 
5399   int fd = ::open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
5400   if (fd != -1) {
5401     struct stat buf;
5402     ::close(fd);
5403     while (::stat(filename, &buf) == 0) {
5404       (void)::poll(NULL, 0, 100);
5405     }
5406   } else {
5407     jio_fprintf(stderr,
5408                 "Could not open pause file '%s', continuing immediately.\n", filename);
5409   }
5410 }
5411 
5412 
5413 // Refer to the comments in os_solaris.cpp park-unpark. The next two
5414 // comment paragraphs are worth repeating here:
5415 //
5416 // Assumption:
5417 //    Only one parker can exist on an event, which is why we allocate
5418 //    them per-thread. Multiple unparkers can coexist.
5419 //
5420 // _Event serves as a restricted-range semaphore.
5421 //   -1 : thread is blocked, i.e. there is a waiter
5422 //    0 : neutral: thread is running or ready,
5423 //        could have been signaled after a wait started
5424 //    1 : signaled - thread is running or ready
5425 //
5426 
5427 // utility to compute the abstime argument to timedwait:
5428 // millis is the relative timeout time
5429 // abstime will be the absolute timeout time
5430 // TODO: replace compute_abstime() with unpackTime()
5431 
5432 static struct timespec* compute_abstime(timespec* abstime, jlong millis) {
5433   if (millis < 0)  millis = 0;
5434 
5435   jlong seconds = millis / 1000;
5436   millis %= 1000;
5437   if (seconds > 50000000) { // see man cond_timedwait(3T)
5438     seconds = 50000000;
5439   }
5440 
5441   if (os::supports_monotonic_clock()) {
5442     struct timespec now;
5443     int status = os::Linux::clock_gettime(CLOCK_MONOTONIC, &now);
5444     assert_status(status == 0, status, "clock_gettime");
5445     abstime->tv_sec = now.tv_sec  + seconds;
5446     long nanos = now.tv_nsec + millis * NANOSECS_PER_MILLISEC;
5447     if (nanos >= NANOSECS_PER_SEC) {
5448       abstime->tv_sec += 1;
5449       nanos -= NANOSECS_PER_SEC;
5450     }
5451     abstime->tv_nsec = nanos;
5452   } else {
5453     struct timeval now;
5454     int status = gettimeofday(&now, NULL);
5455     assert(status == 0, "gettimeofday");
5456     abstime->tv_sec = now.tv_sec  + seconds;
5457     long usec = now.tv_usec + millis * 1000;
5458     if (usec >= 1000000) {
5459       abstime->tv_sec += 1;
5460       usec -= 1000000;
5461     }
5462     abstime->tv_nsec = usec * 1000;
5463   }
5464   return abstime;
5465 }
5466 
5467 void os::PlatformEvent::park() {       // AKA "down()"
5468   // Transitions for _Event:
5469   //   -1 => -1 : illegal
5470   //    1 =>  0 : pass - return immediately
5471   //    0 => -1 : block; then set _Event to 0 before returning
5472 
5473   // Invariant: Only the thread associated with the Event/PlatformEvent
5474   // may call park().
5475   // TODO: assert that _Assoc != NULL or _Assoc == Self
5476   assert(_nParked == 0, "invariant");
5477 
5478   int v;
5479   for (;;) {
5480     v = _Event;
5481     if (Atomic::cmpxchg(v-1, &_Event, v) == v) break;
5482   }
5483   guarantee(v >= 0, "invariant");
5484   if (v == 0) {
5485     // Do this the hard way by blocking ...
5486     int status = pthread_mutex_lock(_mutex);
5487     assert_status(status == 0, status, "mutex_lock");
5488     guarantee(_nParked == 0, "invariant");
5489     ++_nParked;
5490     while (_Event < 0) {
5491       status = pthread_cond_wait(_cond, _mutex);
5492       // for some reason, under 2.7 lwp_cond_wait() may return ETIME ...
5493       // Treat this the same as if the wait was interrupted
5494       if (status == ETIME) { status = EINTR; }
5495       assert_status(status == 0 || status == EINTR, status, "cond_wait");
5496     }
5497     --_nParked;
5498 
5499     _Event = 0;
5500     status = pthread_mutex_unlock(_mutex);
5501     assert_status(status == 0, status, "mutex_unlock");
5502     // Paranoia to ensure our locked and lock-free paths interact
5503     // correctly with each other.
5504     OrderAccess::fence();
5505   }
5506   guarantee(_Event >= 0, "invariant");
5507 }
5508 
5509 int os::PlatformEvent::park(jlong millis) {
5510   // Transitions for _Event:
5511   //   -1 => -1 : illegal
5512   //    1 =>  0 : pass - return immediately
5513   //    0 => -1 : block; then set _Event to 0 before returning
5514 
5515   guarantee(_nParked == 0, "invariant");
5516 
5517   int v;
5518   for (;;) {
5519     v = _Event;
5520     if (Atomic::cmpxchg(v-1, &_Event, v) == v) break;
5521   }
5522   guarantee(v >= 0, "invariant");
5523   if (v != 0) return OS_OK;
5524 
5525   // We do this the hard way, by blocking the thread.
5526   // Consider enforcing a minimum timeout value.
5527   struct timespec abst;
5528   compute_abstime(&abst, millis);
5529 
5530   int ret = OS_TIMEOUT;
5531   int status = pthread_mutex_lock(_mutex);
5532   assert_status(status == 0, status, "mutex_lock");
5533   guarantee(_nParked == 0, "invariant");
5534   ++_nParked;
5535 
5536   // Object.wait(timo) will return because of
5537   // (a) notification
5538   // (b) timeout
5539   // (c) thread.interrupt
5540   //
5541   // Thread.interrupt and object.notify{All} both call Event::set.
5542   // That is, we treat thread.interrupt as a special case of notification.
5543   // We ignore spurious OS wakeups unless FilterSpuriousWakeups is false.
5544   // We assume all ETIME returns are valid.
5545   //
5546   // TODO: properly differentiate simultaneous notify+interrupt.
5547   // In that case, we should propagate the notify to another waiter.
5548 
5549   while (_Event < 0) {
5550     status = pthread_cond_timedwait(_cond, _mutex, &abst);
5551     assert_status(status == 0 || status == EINTR ||
5552                   status == ETIME || status == ETIMEDOUT,
5553                   status, "cond_timedwait");
5554     if (!FilterSpuriousWakeups) break;                 // previous semantics
5555     if (status == ETIME || status == ETIMEDOUT) break;
5556     // We consume and ignore EINTR and spurious wakeups.
5557   }
5558   --_nParked;
5559   if (_Event >= 0) {
5560     ret = OS_OK;
5561   }
5562   _Event = 0;
5563   status = pthread_mutex_unlock(_mutex);
5564   assert_status(status == 0, status, "mutex_unlock");
5565   assert(_nParked == 0, "invariant");
5566   // Paranoia to ensure our locked and lock-free paths interact
5567   // correctly with each other.
5568   OrderAccess::fence();
5569   return ret;
5570 }
5571 
5572 void os::PlatformEvent::unpark() {
5573   // Transitions for _Event:
5574   //    0 => 1 : just return
5575   //    1 => 1 : just return
5576   //   -1 => either 0 or 1; must signal target thread
5577   //         That is, we can safely transition _Event from -1 to either
5578   //         0 or 1.
5579   // See also: "Semaphores in Plan 9" by Mullender & Cox
5580   //
5581   // Note: Forcing a transition from "-1" to "1" on an unpark() means
5582   // that it will take two back-to-back park() calls for the owning
5583   // thread to block. This has the benefit of forcing a spurious return
5584   // from the first park() call after an unpark() call which will help
5585   // shake out uses of park() and unpark() without condition variables.
5586 
5587   if (Atomic::xchg(1, &_Event) >= 0) return;
5588 
5589   // Wait for the thread associated with the event to vacate
5590   int status = pthread_mutex_lock(_mutex);
5591   assert_status(status == 0, status, "mutex_lock");
5592   int AnyWaiters = _nParked;
5593   assert(AnyWaiters == 0 || AnyWaiters == 1, "invariant");
5594   status = pthread_mutex_unlock(_mutex);
5595   assert_status(status == 0, status, "mutex_unlock");
5596   if (AnyWaiters != 0) {
5597     // Note that we signal() *after* dropping the lock for "immortal" Events.
5598     // This is safe and avoids a common class of  futile wakeups.  In rare
5599     // circumstances this can cause a thread to return prematurely from
5600     // cond_{timed}wait() but the spurious wakeup is benign and the victim
5601     // will simply re-test the condition and re-park itself.
5602     // This provides particular benefit if the underlying platform does not
5603     // provide wait morphing.
5604     status = pthread_cond_signal(_cond);
5605     assert_status(status == 0, status, "cond_signal");
5606   }
5607 }
5608 
5609 
5610 // JSR166
5611 // -------------------------------------------------------
5612 
5613 // The solaris and linux implementations of park/unpark are fairly
5614 // conservative for now, but can be improved. They currently use a
5615 // mutex/condvar pair, plus a a count.
5616 // Park decrements count if > 0, else does a condvar wait.  Unpark
5617 // sets count to 1 and signals condvar.  Only one thread ever waits
5618 // on the condvar. Contention seen when trying to park implies that someone
5619 // is unparking you, so don't wait. And spurious returns are fine, so there
5620 // is no need to track notifications.
5621 
5622 // This code is common to linux and solaris and will be moved to a
5623 // common place in dolphin.
5624 //
5625 // The passed in time value is either a relative time in nanoseconds
5626 // or an absolute time in milliseconds. Either way it has to be unpacked
5627 // into suitable seconds and nanoseconds components and stored in the
5628 // given timespec structure.
5629 // Given time is a 64-bit value and the time_t used in the timespec is only
5630 // a signed-32-bit value (except on 64-bit Linux) we have to watch for
5631 // overflow if times way in the future are given. Further on Solaris versions
5632 // prior to 10 there is a restriction (see cond_timedwait) that the specified
5633 // number of seconds, in abstime, is less than current_time  + 100,000,000.
5634 // As it will be 28 years before "now + 100000000" will overflow we can
5635 // ignore overflow and just impose a hard-limit on seconds using the value
5636 // of "now + 100,000,000". This places a limit on the timeout of about 3.17
5637 // years from "now".
5638 
5639 static void unpackTime(timespec* absTime, bool isAbsolute, jlong time) {
5640   assert(time > 0, "convertTime");
5641   time_t max_secs = 0;
5642 
5643   if (!os::supports_monotonic_clock() || isAbsolute) {
5644     struct timeval now;
5645     int status = gettimeofday(&now, NULL);
5646     assert(status == 0, "gettimeofday");
5647 
5648     max_secs = now.tv_sec + MAX_SECS;
5649 
5650     if (isAbsolute) {
5651       jlong secs = time / 1000;
5652       if (secs > max_secs) {
5653         absTime->tv_sec = max_secs;
5654       } else {
5655         absTime->tv_sec = secs;
5656       }
5657       absTime->tv_nsec = (time % 1000) * NANOSECS_PER_MILLISEC;
5658     } else {
5659       jlong secs = time / NANOSECS_PER_SEC;
5660       if (secs >= MAX_SECS) {
5661         absTime->tv_sec = max_secs;
5662         absTime->tv_nsec = 0;
5663       } else {
5664         absTime->tv_sec = now.tv_sec + secs;
5665         absTime->tv_nsec = (time % NANOSECS_PER_SEC) + now.tv_usec*1000;
5666         if (absTime->tv_nsec >= NANOSECS_PER_SEC) {
5667           absTime->tv_nsec -= NANOSECS_PER_SEC;
5668           ++absTime->tv_sec; // note: this must be <= max_secs
5669         }
5670       }
5671     }
5672   } else {
5673     // must be relative using monotonic clock
5674     struct timespec now;
5675     int status = os::Linux::clock_gettime(CLOCK_MONOTONIC, &now);
5676     assert_status(status == 0, status, "clock_gettime");
5677     max_secs = now.tv_sec + MAX_SECS;
5678     jlong secs = time / NANOSECS_PER_SEC;
5679     if (secs >= MAX_SECS) {
5680       absTime->tv_sec = max_secs;
5681       absTime->tv_nsec = 0;
5682     } else {
5683       absTime->tv_sec = now.tv_sec + secs;
5684       absTime->tv_nsec = (time % NANOSECS_PER_SEC) + now.tv_nsec;
5685       if (absTime->tv_nsec >= NANOSECS_PER_SEC) {
5686         absTime->tv_nsec -= NANOSECS_PER_SEC;
5687         ++absTime->tv_sec; // note: this must be <= max_secs
5688       }
5689     }
5690   }
5691   assert(absTime->tv_sec >= 0, "tv_sec < 0");
5692   assert(absTime->tv_sec <= max_secs, "tv_sec > max_secs");
5693   assert(absTime->tv_nsec >= 0, "tv_nsec < 0");
5694   assert(absTime->tv_nsec < NANOSECS_PER_SEC, "tv_nsec >= nanos_per_sec");
5695 }
5696 
5697 void Parker::park(bool isAbsolute, jlong time) {
5698   // Ideally we'd do something useful while spinning, such
5699   // as calling unpackTime().
5700 
5701   // Optional fast-path check:
5702   // Return immediately if a permit is available.
5703   // We depend on Atomic::xchg() having full barrier semantics
5704   // since we are doing a lock-free update to _counter.
5705   if (Atomic::xchg(0, &_counter) > 0) return;
5706 
5707   Thread* thread = Thread::current();
5708   assert(thread->is_Java_thread(), "Must be JavaThread");
5709   JavaThread *jt = (JavaThread *)thread;
5710 
5711   // Optional optimization -- avoid state transitions if there's an interrupt pending.
5712   // Check interrupt before trying to wait
5713   if (Thread::is_interrupted(thread, false)) {
5714     return;
5715   }
5716 
5717   // Next, demultiplex/decode time arguments
5718   timespec absTime;
5719   if (time < 0 || (isAbsolute && time == 0)) { // don't wait at all
5720     return;
5721   }
5722   if (time > 0) {
5723     unpackTime(&absTime, isAbsolute, time);
5724   }
5725 
5726 
5727   // Enter safepoint region
5728   // Beware of deadlocks such as 6317397.
5729   // The per-thread Parker:: mutex is a classic leaf-lock.
5730   // In particular a thread must never block on the Threads_lock while
5731   // holding the Parker:: mutex.  If safepoints are pending both the
5732   // the ThreadBlockInVM() CTOR and DTOR may grab Threads_lock.
5733   ThreadBlockInVM tbivm(jt);
5734 
5735   // Don't wait if cannot get lock since interference arises from
5736   // unblocking.  Also. check interrupt before trying wait
5737   if (Thread::is_interrupted(thread, false) || pthread_mutex_trylock(_mutex) != 0) {
5738     return;
5739   }
5740 
5741   int status;
5742   if (_counter > 0)  { // no wait needed
5743     _counter = 0;
5744     status = pthread_mutex_unlock(_mutex);
5745     assert_status(status == 0, status, "invariant");
5746     // Paranoia to ensure our locked and lock-free paths interact
5747     // correctly with each other and Java-level accesses.
5748     OrderAccess::fence();
5749     return;
5750   }
5751 
5752 #ifdef ASSERT
5753   // Don't catch signals while blocked; let the running threads have the signals.
5754   // (This allows a debugger to break into the running thread.)
5755   sigset_t oldsigs;
5756   sigemptyset(&oldsigs);
5757   sigset_t* allowdebug_blocked = os::Linux::allowdebug_blocked_signals();
5758   pthread_sigmask(SIG_BLOCK, allowdebug_blocked, &oldsigs);
5759 #endif
5760 
5761   OSThreadWaitState osts(thread->osthread(), false /* not Object.wait() */);
5762   jt->set_suspend_equivalent();
5763   // cleared by handle_special_suspend_equivalent_condition() or java_suspend_self()
5764 
5765   assert(_cur_index == -1, "invariant");
5766   if (time == 0) {
5767     _cur_index = REL_INDEX; // arbitrary choice when not timed
5768     status = pthread_cond_wait(&_cond[_cur_index], _mutex);
5769   } else {
5770     _cur_index = isAbsolute ? ABS_INDEX : REL_INDEX;
5771     status = pthread_cond_timedwait(&_cond[_cur_index], _mutex, &absTime);
5772   }
5773   _cur_index = -1;
5774   assert_status(status == 0 || status == EINTR ||
5775                 status == ETIME || status == ETIMEDOUT,
5776                 status, "cond_timedwait");
5777 
5778 #ifdef ASSERT
5779   pthread_sigmask(SIG_SETMASK, &oldsigs, NULL);
5780 #endif
5781 
5782   _counter = 0;
5783   status = pthread_mutex_unlock(_mutex);
5784   assert_status(status == 0, status, "invariant");
5785   // Paranoia to ensure our locked and lock-free paths interact
5786   // correctly with each other and Java-level accesses.
5787   OrderAccess::fence();
5788 
5789   // If externally suspended while waiting, re-suspend
5790   if (jt->handle_special_suspend_equivalent_condition()) {
5791     jt->java_suspend_self();
5792   }
5793 }
5794 
5795 void Parker::unpark() {
5796   int status = pthread_mutex_lock(_mutex);
5797   assert_status(status == 0, status, "invariant");
5798   const int s = _counter;
5799   _counter = 1;
5800   // must capture correct index before unlocking
5801   int index = _cur_index;
5802   status = pthread_mutex_unlock(_mutex);
5803   assert_status(status == 0, status, "invariant");
5804   if (s < 1 && index != -1) {
5805     // thread is definitely parked
5806     status = pthread_cond_signal(&_cond[index]);
5807     assert_status(status == 0, status, "invariant");
5808   }
5809 }
5810 
5811 
5812 extern char** environ;
5813 
5814 // Run the specified command in a separate process. Return its exit value,
5815 // or -1 on failure (e.g. can't fork a new process).
5816 // Unlike system(), this function can be called from signal handler. It
5817 // doesn't block SIGINT et al.
5818 int os::fork_and_exec(char* cmd) {
5819   const char * argv[4] = {"sh", "-c", cmd, NULL};
5820 
5821   pid_t pid = fork();
5822 
5823   if (pid < 0) {
5824     // fork failed
5825     return -1;
5826 
5827   } else if (pid == 0) {
5828     // child process
5829 
5830     execve("/bin/sh", (char* const*)argv, environ);
5831 
5832     // execve failed
5833     _exit(-1);
5834 
5835   } else  {
5836     // copied from J2SE ..._waitForProcessExit() in UNIXProcess_md.c; we don't
5837     // care about the actual exit code, for now.
5838 
5839     int status;
5840 
5841     // Wait for the child process to exit.  This returns immediately if
5842     // the child has already exited. */
5843     while (waitpid(pid, &status, 0) < 0) {
5844       switch (errno) {
5845       case ECHILD: return 0;
5846       case EINTR: break;
5847       default: return -1;
5848       }
5849     }
5850 
5851     if (WIFEXITED(status)) {
5852       // The child exited normally; get its exit code.
5853       return WEXITSTATUS(status);
5854     } else if (WIFSIGNALED(status)) {
5855       // The child exited because of a signal
5856       // The best value to return is 0x80 + signal number,
5857       // because that is what all Unix shells do, and because
5858       // it allows callers to distinguish between process exit and
5859       // process death by signal.
5860       return 0x80 + WTERMSIG(status);
5861     } else {
5862       // Unknown exit code; pass it through
5863       return status;
5864     }
5865   }
5866 }
5867 
5868 // is_headless_jre()
5869 //
5870 // Test for the existence of xawt/libmawt.so or libawt_xawt.so
5871 // in order to report if we are running in a headless jre
5872 //
5873 // Since JDK8 xawt/libmawt.so was moved into the same directory
5874 // as libawt.so, and renamed libawt_xawt.so
5875 //
5876 bool os::is_headless_jre() {
5877   struct stat statbuf;
5878   char buf[MAXPATHLEN];
5879   char libmawtpath[MAXPATHLEN];
5880   const char *xawtstr  = "/xawt/libmawt.so";
5881   const char *new_xawtstr = "/libawt_xawt.so";
5882   char *p;
5883 
5884   // Get path to libjvm.so
5885   os::jvm_path(buf, sizeof(buf));
5886 
5887   // Get rid of libjvm.so
5888   p = strrchr(buf, '/');
5889   if (p == NULL) {
5890     return false;
5891   } else {
5892     *p = '\0';
5893   }
5894 
5895   // Get rid of client or server
5896   p = strrchr(buf, '/');
5897   if (p == NULL) {
5898     return false;
5899   } else {
5900     *p = '\0';
5901   }
5902 
5903   // check xawt/libmawt.so
5904   strcpy(libmawtpath, buf);
5905   strcat(libmawtpath, xawtstr);
5906   if (::stat(libmawtpath, &statbuf) == 0) return false;
5907 
5908   // check libawt_xawt.so
5909   strcpy(libmawtpath, buf);
5910   strcat(libmawtpath, new_xawtstr);
5911   if (::stat(libmawtpath, &statbuf) == 0) return false;
5912 
5913   return true;
5914 }
5915 
5916 // Get the default path to the core file
5917 // Returns the length of the string
5918 int os::get_core_path(char* buffer, size_t bufferSize) {
5919   /*
5920    * Max length of /proc/sys/kernel/core_pattern is 128 characters.
5921    * See https://www.kernel.org/doc/Documentation/sysctl/kernel.txt
5922    */
5923   const int core_pattern_len = 129;
5924   char core_pattern[core_pattern_len] = {0};
5925 
5926   int core_pattern_file = ::open("/proc/sys/kernel/core_pattern", O_RDONLY);
5927   if (core_pattern_file == -1) {
5928     return -1;
5929   }
5930 
5931   ssize_t ret = ::read(core_pattern_file, core_pattern, core_pattern_len);
5932   ::close(core_pattern_file);
5933   if (ret <= 0 || ret >= core_pattern_len || core_pattern[0] == '\n') {
5934     return -1;
5935   }
5936   if (core_pattern[ret-1] == '\n') {
5937     core_pattern[ret-1] = '\0';
5938   } else {
5939     core_pattern[ret] = '\0';
5940   }
5941 
5942   char *pid_pos = strstr(core_pattern, "%p");
5943   int written;
5944 
5945   if (core_pattern[0] == '/') {
5946     written = jio_snprintf(buffer, bufferSize, "%s", core_pattern);
5947   } else {
5948     char cwd[PATH_MAX];
5949 
5950     const char* p = get_current_directory(cwd, PATH_MAX);
5951     if (p == NULL) {
5952       return -1;
5953     }
5954 
5955     if (core_pattern[0] == '|') {
5956       written = jio_snprintf(buffer, bufferSize,
5957                         "\"%s\" (or dumping to %s/core.%d)",
5958                                      &core_pattern[1], p, current_process_id());
5959     } else {
5960       written = jio_snprintf(buffer, bufferSize, "%s/%s", p, core_pattern);
5961     }
5962   }
5963 
5964   if (written < 0) {
5965     return -1;
5966   }
5967 
5968   if (((size_t)written < bufferSize) && (pid_pos == NULL) && (core_pattern[0] != '|')) {
5969     int core_uses_pid_file = ::open("/proc/sys/kernel/core_uses_pid", O_RDONLY);
5970 
5971     if (core_uses_pid_file != -1) {
5972       char core_uses_pid = 0;
5973       ssize_t ret = ::read(core_uses_pid_file, &core_uses_pid, 1);
5974       ::close(core_uses_pid_file);
5975 
5976       if (core_uses_pid == '1') {
5977         jio_snprintf(buffer + written, bufferSize - written,
5978                                           ".%d", current_process_id());
5979       }
5980     }
5981   }
5982 
5983   return strlen(buffer);
5984 }
5985 
5986 bool os::start_debugging(char *buf, int buflen) {
5987   int len = (int)strlen(buf);
5988   char *p = &buf[len];
5989 
5990   jio_snprintf(p, buflen-len,
5991              "\n\n"
5992              "Do you want to debug the problem?\n\n"
5993              "To debug, run 'gdb /proc/%d/exe %d'; then switch to thread " UINTX_FORMAT " (" INTPTR_FORMAT ")\n"
5994              "Enter 'yes' to launch gdb automatically (PATH must include gdb)\n"
5995              "Otherwise, press RETURN to abort...",
5996              os::current_process_id(), os::current_process_id(),
5997              os::current_thread_id(), os::current_thread_id());
5998 
5999   bool yes = os::message_box("Unexpected Error", buf);
6000 
6001   if (yes) {
6002     // yes, user asked VM to launch debugger
6003     jio_snprintf(buf, sizeof(char)*buflen, "gdb /proc/%d/exe %d",
6004                      os::current_process_id(), os::current_process_id());
6005 
6006     os::fork_and_exec(buf);
6007     yes = false;
6008   }
6009   return yes;
6010 }
6011 
6012 static inline struct timespec get_mtime(const char* filename) {
6013   struct stat st;
6014   int ret = os::stat(filename, &st);
6015   assert(ret == 0, "failed to stat() file '%s': %s", filename, strerror(errno));
6016   return st.st_mtim;
6017 }
6018 
6019 int os::compare_file_modified_times(const char* file1, const char* file2) {
6020   struct timespec filetime1 = get_mtime(file1);
6021   struct timespec filetime2 = get_mtime(file2);
6022   int diff = filetime1.tv_sec - filetime2.tv_sec;
6023   if (diff == 0) {
6024     return filetime1.tv_nsec - filetime2.tv_nsec;
6025   }
6026   return diff;
6027 }
6028 
6029 /////////////// Unit tests ///////////////
6030 
6031 #ifndef PRODUCT
6032 
6033 #define test_log(...)              \
6034   do {                             \
6035     if (VerboseInternalVMTests) {  \
6036       tty->print_cr(__VA_ARGS__);  \
6037       tty->flush();                \
6038     }                              \
6039   } while (false)
6040 
6041 class TestReserveMemorySpecial : AllStatic {
6042  public:
6043   static void small_page_write(void* addr, size_t size) {
6044     size_t page_size = os::vm_page_size();
6045 
6046     char* end = (char*)addr + size;
6047     for (char* p = (char*)addr; p < end; p += page_size) {
6048       *p = 1;
6049     }
6050   }
6051 
6052   static void test_reserve_memory_special_huge_tlbfs_only(size_t size) {
6053     if (!UseHugeTLBFS) {
6054       return;
6055     }
6056 
6057     test_log("test_reserve_memory_special_huge_tlbfs_only(" SIZE_FORMAT ")", size);
6058 
6059     char* addr = os::Linux::reserve_memory_special_huge_tlbfs_only(size, NULL, false);
6060 
6061     if (addr != NULL) {
6062       small_page_write(addr, size);
6063 
6064       os::Linux::release_memory_special_huge_tlbfs(addr, size);
6065     }
6066   }
6067 
6068   static void test_reserve_memory_special_huge_tlbfs_only() {
6069     if (!UseHugeTLBFS) {
6070       return;
6071     }
6072 
6073     size_t lp = os::large_page_size();
6074 
6075     for (size_t size = lp; size <= lp * 10; size += lp) {
6076       test_reserve_memory_special_huge_tlbfs_only(size);
6077     }
6078   }
6079 
6080   static void test_reserve_memory_special_huge_tlbfs_mixed() {
6081     size_t lp = os::large_page_size();
6082     size_t ag = os::vm_allocation_granularity();
6083 
6084     // sizes to test
6085     const size_t sizes[] = {
6086       lp, lp + ag, lp + lp / 2, lp * 2,
6087       lp * 2 + ag, lp * 2 - ag, lp * 2 + lp / 2,
6088       lp * 10, lp * 10 + lp / 2
6089     };
6090     const int num_sizes = sizeof(sizes) / sizeof(size_t);
6091 
6092     // For each size/alignment combination, we test three scenarios:
6093     // 1) with req_addr == NULL
6094     // 2) with a non-null req_addr at which we expect to successfully allocate
6095     // 3) with a non-null req_addr which contains a pre-existing mapping, at which we
6096     //    expect the allocation to either fail or to ignore req_addr
6097 
6098     // Pre-allocate two areas; they shall be as large as the largest allocation
6099     //  and aligned to the largest alignment we will be testing.
6100     const size_t mapping_size = sizes[num_sizes - 1] * 2;
6101     char* const mapping1 = (char*) ::mmap(NULL, mapping_size,
6102       PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE,
6103       -1, 0);
6104     assert(mapping1 != MAP_FAILED, "should work");
6105 
6106     char* const mapping2 = (char*) ::mmap(NULL, mapping_size,
6107       PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE,
6108       -1, 0);
6109     assert(mapping2 != MAP_FAILED, "should work");
6110 
6111     // Unmap the first mapping, but leave the second mapping intact: the first
6112     // mapping will serve as a value for a "good" req_addr (case 2). The second
6113     // mapping, still intact, as "bad" req_addr (case 3).
6114     ::munmap(mapping1, mapping_size);
6115 
6116     // Case 1
6117     test_log("%s, req_addr NULL:", __FUNCTION__);
6118     test_log("size            align           result");
6119 
6120     for (int i = 0; i < num_sizes; i++) {
6121       const size_t size = sizes[i];
6122       for (size_t alignment = ag; is_size_aligned(size, alignment); alignment *= 2) {
6123         char* p = os::Linux::reserve_memory_special_huge_tlbfs_mixed(size, alignment, NULL, false);
6124         test_log(SIZE_FORMAT_HEX " " SIZE_FORMAT_HEX " ->  " PTR_FORMAT " %s",
6125                  size, alignment, p2i(p), (p != NULL ? "" : "(failed)"));
6126         if (p != NULL) {
6127           assert(is_ptr_aligned(p, alignment), "must be");
6128           small_page_write(p, size);
6129           os::Linux::release_memory_special_huge_tlbfs(p, size);
6130         }
6131       }
6132     }
6133 
6134     // Case 2
6135     test_log("%s, req_addr non-NULL:", __FUNCTION__);
6136     test_log("size            align           req_addr         result");
6137 
6138     for (int i = 0; i < num_sizes; i++) {
6139       const size_t size = sizes[i];
6140       for (size_t alignment = ag; is_size_aligned(size, alignment); alignment *= 2) {
6141         char* const req_addr = (char*) align_ptr_up(mapping1, alignment);
6142         char* p = os::Linux::reserve_memory_special_huge_tlbfs_mixed(size, alignment, req_addr, false);
6143         test_log(SIZE_FORMAT_HEX " " SIZE_FORMAT_HEX " " PTR_FORMAT " ->  " PTR_FORMAT " %s",
6144                  size, alignment, p2i(req_addr), p2i(p),
6145                  ((p != NULL ? (p == req_addr ? "(exact match)" : "") : "(failed)")));
6146         if (p != NULL) {
6147           assert(p == req_addr, "must be");
6148           small_page_write(p, size);
6149           os::Linux::release_memory_special_huge_tlbfs(p, size);
6150         }
6151       }
6152     }
6153 
6154     // Case 3
6155     test_log("%s, req_addr non-NULL with preexisting mapping:", __FUNCTION__);
6156     test_log("size            align           req_addr         result");
6157 
6158     for (int i = 0; i < num_sizes; i++) {
6159       const size_t size = sizes[i];
6160       for (size_t alignment = ag; is_size_aligned(size, alignment); alignment *= 2) {
6161         char* const req_addr = (char*) align_ptr_up(mapping2, alignment);
6162         char* p = os::Linux::reserve_memory_special_huge_tlbfs_mixed(size, alignment, req_addr, false);
6163         test_log(SIZE_FORMAT_HEX " " SIZE_FORMAT_HEX " " PTR_FORMAT " ->  " PTR_FORMAT " %s",
6164                  size, alignment, p2i(req_addr), p2i(p), ((p != NULL ? "" : "(failed)")));
6165         // as the area around req_addr contains already existing mappings, the API should always
6166         // return NULL (as per contract, it cannot return another address)
6167         assert(p == NULL, "must be");
6168       }
6169     }
6170 
6171     ::munmap(mapping2, mapping_size);
6172 
6173   }
6174 
6175   static void test_reserve_memory_special_huge_tlbfs() {
6176     if (!UseHugeTLBFS) {
6177       return;
6178     }
6179 
6180     test_reserve_memory_special_huge_tlbfs_only();
6181     test_reserve_memory_special_huge_tlbfs_mixed();
6182   }
6183 
6184   static void test_reserve_memory_special_shm(size_t size, size_t alignment) {
6185     if (!UseSHM) {
6186       return;
6187     }
6188 
6189     test_log("test_reserve_memory_special_shm(" SIZE_FORMAT ", " SIZE_FORMAT ")", size, alignment);
6190 
6191     char* addr = os::Linux::reserve_memory_special_shm(size, alignment, NULL, false);
6192 
6193     if (addr != NULL) {
6194       assert(is_ptr_aligned(addr, alignment), "Check");
6195       assert(is_ptr_aligned(addr, os::large_page_size()), "Check");
6196 
6197       small_page_write(addr, size);
6198 
6199       os::Linux::release_memory_special_shm(addr, size);
6200     }
6201   }
6202 
6203   static void test_reserve_memory_special_shm() {
6204     size_t lp = os::large_page_size();
6205     size_t ag = os::vm_allocation_granularity();
6206 
6207     for (size_t size = ag; size < lp * 3; size += ag) {
6208       for (size_t alignment = ag; is_size_aligned(size, alignment); alignment *= 2) {
6209         test_reserve_memory_special_shm(size, alignment);
6210       }
6211     }
6212   }
6213 
6214   static void test() {
6215     test_reserve_memory_special_huge_tlbfs();
6216     test_reserve_memory_special_shm();
6217   }
6218 };
6219 
6220 void TestReserveMemorySpecial_test() {
6221   TestReserveMemorySpecial::test();
6222 }
6223 
6224 #endif