1 /*
   2  * Copyright (c) 1999, 2015, 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 "memory/allocation.inline.hpp"
  36 #include "memory/filemap.hpp"
  37 #include "mutex_linux.inline.hpp"
  38 #include "oops/oop.inline.hpp"
  39 #include "os_linux.inline.hpp"
  40 #include "os_share_linux.hpp"
  41 #include "prims/jniFastGetField.hpp"
  42 #include "prims/jvm.h"
  43 #include "prims/jvm_misc.hpp"
  44 #include "runtime/arguments.hpp"
  45 #include "runtime/atomic.inline.hpp"
  46 #include "runtime/extendedPC.hpp"
  47 #include "runtime/globals.hpp"
  48 #include "runtime/interfaceSupport.hpp"
  49 #include "runtime/init.hpp"
  50 #include "runtime/java.hpp"
  51 #include "runtime/javaCalls.hpp"
  52 #include "runtime/mutexLocker.hpp"
  53 #include "runtime/objectMonitor.hpp"
  54 #include "runtime/orderAccess.inline.hpp"
  55 #include "runtime/osThread.hpp"
  56 #include "runtime/perfMemory.hpp"
  57 #include "runtime/sharedRuntime.hpp"
  58 #include "runtime/statSampler.hpp"
  59 #include "runtime/stubRoutines.hpp"
  60 #include "runtime/thread.inline.hpp"
  61 #include "runtime/threadCritical.hpp"
  62 #include "runtime/timer.hpp"
  63 #include "semaphore_posix.hpp"
  64 #include "services/attachListener.hpp"
  65 #include "services/memTracker.hpp"
  66 #include "services/runtimeService.hpp"
  67 #include "utilities/decoder.hpp"
  68 #include "utilities/defaultStream.hpp"
  69 #include "utilities/events.hpp"
  70 #include "utilities/elfFile.hpp"
  71 #include "utilities/growableArray.hpp"
  72 #include "utilities/macros.hpp"
  73 #include "utilities/vmError.hpp"
  74 
  75 // put OS-includes here
  76 # include <sys/types.h>
  77 # include <sys/mman.h>
  78 # include <sys/stat.h>
  79 # include <sys/select.h>
  80 # include <pthread.h>
  81 # include <signal.h>
  82 # include <errno.h>
  83 # include <dlfcn.h>
  84 # include <stdio.h>
  85 # include <unistd.h>
  86 # include <sys/resource.h>
  87 # include <pthread.h>
  88 # include <sys/stat.h>
  89 # include <sys/time.h>
  90 # include <sys/times.h>
  91 # include <sys/utsname.h>
  92 # include <sys/socket.h>
  93 # include <sys/wait.h>
  94 # include <pwd.h>
  95 # include <poll.h>
  96 # include <semaphore.h>
  97 # include <fcntl.h>
  98 # include <string.h>
  99 # include <syscall.h>
 100 # include <sys/sysinfo.h>
 101 # include <gnu/libc-version.h>
 102 # include <sys/ipc.h>
 103 # include <sys/shm.h>
 104 # include <link.h>
 105 # include <stdint.h>
 106 # include <inttypes.h>
 107 # include <sys/ioctl.h>
 108 
 109 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
 110 
 111 // if RUSAGE_THREAD for getrusage() has not been defined, do it here. The code calling
 112 // getrusage() is prepared to handle the associated failure.
 113 #ifndef RUSAGE_THREAD
 114   #define RUSAGE_THREAD   (1)               /* only the calling thread */
 115 #endif
 116 
 117 #define MAX_PATH    (2 * K)
 118 
 119 #define MAX_SECS 100000000
 120 
 121 // for timer info max values which include all bits
 122 #define ALL_64_BITS CONST64(0xFFFFFFFFFFFFFFFF)
 123 
 124 #define LARGEPAGES_BIT (1 << 6)
 125 ////////////////////////////////////////////////////////////////////////////////
 126 // global variables
 127 julong os::Linux::_physical_memory = 0;
 128 
 129 address   os::Linux::_initial_thread_stack_bottom = NULL;
 130 uintptr_t os::Linux::_initial_thread_stack_size   = 0;
 131 
 132 int (*os::Linux::_clock_gettime)(clockid_t, struct timespec *) = NULL;
 133 int (*os::Linux::_pthread_getcpuclockid)(pthread_t, clockid_t *) = NULL;
 134 int (*os::Linux::_pthread_setname_np)(pthread_t, const char*) = NULL;
 135 Mutex* os::Linux::_createThread_lock = NULL;
 136 pthread_t os::Linux::_main_thread;
 137 int os::Linux::_page_size = -1;
 138 const int os::Linux::_vm_default_page_size = (8 * K);
 139 bool os::Linux::_supports_fast_thread_cpu_time = false;
 140 const char * os::Linux::_glibc_version = NULL;
 141 const char * os::Linux::_libpthread_version = NULL;
 142 pthread_condattr_t os::Linux::_condattr[1];
 143 
 144 static jlong initial_time_count=0;
 145 
 146 static int clock_tics_per_sec = 100;
 147 
 148 // For diagnostics to print a message once. see run_periodic_checks
 149 static sigset_t check_signal_done;
 150 static bool check_signals = true;
 151 
 152 // Signal number used to suspend/resume a thread
 153 
 154 // do not use any signal number less than SIGSEGV, see 4355769
 155 static int SR_signum = SIGUSR2;
 156 sigset_t SR_sigset;
 157 
 158 // Declarations
 159 static void unpackTime(timespec* absTime, bool isAbsolute, jlong time);
 160 
 161 // utility functions
 162 
 163 static int SR_initialize();
 164 
 165 julong os::available_memory() {
 166   return Linux::available_memory();
 167 }
 168 
 169 julong os::Linux::available_memory() {
 170   // values in struct sysinfo are "unsigned long"
 171   struct sysinfo si;
 172   sysinfo(&si);
 173 
 174   return (julong)si.freeram * si.mem_unit;
 175 }
 176 
 177 julong os::physical_memory() {
 178   return Linux::physical_memory();
 179 }
 180 
 181 // Return true if user is running as root.
 182 
 183 bool os::have_special_privileges() {
 184   static bool init = false;
 185   static bool privileges = false;
 186   if (!init) {
 187     privileges = (getuid() != geteuid()) || (getgid() != getegid());
 188     init = true;
 189   }
 190   return privileges;
 191 }
 192 
 193 
 194 #ifndef SYS_gettid
 195 // i386: 224, ia64: 1105, amd64: 186, sparc 143
 196   #ifdef __ia64__
 197     #define SYS_gettid 1105
 198   #else
 199     #ifdef __i386__
 200       #define SYS_gettid 224
 201     #else
 202       #ifdef __amd64__
 203         #define SYS_gettid 186
 204       #else
 205         #ifdef __sparc__
 206           #define SYS_gettid 143
 207         #else
 208           #error define gettid for the arch
 209         #endif
 210       #endif
 211     #endif
 212   #endif
 213 #endif
 214 
 215 // Cpu architecture string
 216 static char cpu_arch[] = HOTSPOT_LIB_ARCH;
 217 
 218 
 219 // pid_t gettid()
 220 //
 221 // Returns the kernel thread id of the currently running thread. Kernel
 222 // thread id is used to access /proc.
 223 pid_t os::Linux::gettid() {
 224   int rslt = syscall(SYS_gettid);
 225   assert(rslt != -1, "must be."); // old linuxthreads implementation?
 226   return (pid_t)rslt;
 227 }
 228 
 229 // Most versions of linux have a bug where the number of processors are
 230 // determined by looking at the /proc file system.  In a chroot environment,
 231 // the system call returns 1.  This causes the VM to act as if it is
 232 // a single processor and elide locking (see is_MP() call).
 233 static bool unsafe_chroot_detected = false;
 234 static const char *unstable_chroot_error = "/proc file system not found.\n"
 235                      "Java may be unstable running multithreaded in a chroot "
 236                      "environment on Linux when /proc filesystem is not mounted.";
 237 
 238 void os::Linux::initialize_system_info() {
 239   set_processor_count(sysconf(_SC_NPROCESSORS_CONF));
 240   if (processor_count() == 1) {
 241     pid_t pid = os::Linux::gettid();
 242     char fname[32];
 243     jio_snprintf(fname, sizeof(fname), "/proc/%d", pid);
 244     FILE *fp = fopen(fname, "r");
 245     if (fp == NULL) {
 246       unsafe_chroot_detected = true;
 247     } else {
 248       fclose(fp);
 249     }
 250   }
 251   _physical_memory = (julong)sysconf(_SC_PHYS_PAGES) * (julong)sysconf(_SC_PAGESIZE);
 252   assert(processor_count() > 0, "linux error");
 253 }
 254 
 255 void os::init_system_properties_values() {
 256   // The next steps are taken in the product version:
 257   //
 258   // Obtain the JAVA_HOME value from the location of libjvm.so.
 259   // This library should be located at:
 260   // <JAVA_HOME>/jre/lib/<arch>/{client|server}/libjvm.so.
 261   //
 262   // If "/jre/lib/" appears at the right place in the path, then we
 263   // assume libjvm.so is installed in a JDK and we use this path.
 264   //
 265   // Otherwise exit with message: "Could not create the Java virtual machine."
 266   //
 267   // The following extra steps are taken in the debugging version:
 268   //
 269   // If "/jre/lib/" does NOT appear at the right place in the path
 270   // instead of exit check for $JAVA_HOME environment variable.
 271   //
 272   // If it is defined and we are able to locate $JAVA_HOME/jre/lib/<arch>,
 273   // then we append a fake suffix "hotspot/libjvm.so" to this path so
 274   // it looks like libjvm.so is installed there
 275   // <JAVA_HOME>/jre/lib/<arch>/hotspot/libjvm.so.
 276   //
 277   // Otherwise exit.
 278   //
 279   // Important note: if the location of libjvm.so changes this
 280   // code needs to be changed accordingly.
 281 
 282   // See ld(1):
 283   //      The linker uses the following search paths to locate required
 284   //      shared libraries:
 285   //        1: ...
 286   //        ...
 287   //        7: The default directories, normally /lib and /usr/lib.
 288 #if defined(AMD64) || defined(_LP64) && (defined(SPARC) || defined(PPC) || defined(S390))
 289   #define DEFAULT_LIBPATH "/usr/lib64:/lib64:/lib:/usr/lib"
 290 #else
 291   #define DEFAULT_LIBPATH "/lib:/usr/lib"
 292 #endif
 293 
 294 // Base path of extensions installed on the system.
 295 #define SYS_EXT_DIR     "/usr/java/packages"
 296 #define EXTENSIONS_DIR  "/lib/ext"
 297 
 298   // Buffer that fits several sprintfs.
 299   // Note that the space for the colon and the trailing null are provided
 300   // by the nulls included by the sizeof operator.
 301   const size_t bufsize =
 302     MAX2((size_t)MAXPATHLEN,  // For dll_dir & friends.
 303          (size_t)MAXPATHLEN + sizeof(EXTENSIONS_DIR) + sizeof(SYS_EXT_DIR) + sizeof(EXTENSIONS_DIR)); // extensions dir
 304   char *buf = (char *)NEW_C_HEAP_ARRAY(char, bufsize, mtInternal);
 305 
 306   // sysclasspath, java_home, dll_dir
 307   {
 308     char *pslash;
 309     os::jvm_path(buf, bufsize);
 310 
 311     // Found the full path to libjvm.so.
 312     // Now cut the path to <java_home>/jre if we can.
 313     pslash = strrchr(buf, '/');
 314     if (pslash != NULL) {
 315       *pslash = '\0';            // Get rid of /libjvm.so.
 316     }
 317     pslash = strrchr(buf, '/');
 318     if (pslash != NULL) {
 319       *pslash = '\0';            // Get rid of /{client|server|hotspot}.
 320     }
 321     Arguments::set_dll_dir(buf);
 322 
 323     if (pslash != NULL) {
 324       pslash = strrchr(buf, '/');
 325       if (pslash != NULL) {
 326         *pslash = '\0';          // Get rid of /<arch>.
 327         pslash = strrchr(buf, '/');
 328         if (pslash != NULL) {
 329           *pslash = '\0';        // Get rid of /lib.
 330         }
 331       }
 332     }
 333     Arguments::set_java_home(buf);
 334     set_boot_path('/', ':');
 335   }
 336 
 337   // Where to look for native libraries.
 338   //
 339   // Note: Due to a legacy implementation, most of the library path
 340   // is set in the launcher. This was to accomodate linking restrictions
 341   // on legacy Linux implementations (which are no longer supported).
 342   // Eventually, all the library path setting will be done here.
 343   //
 344   // However, to prevent the proliferation of improperly built native
 345   // libraries, the new path component /usr/java/packages is added here.
 346   // Eventually, all the library path setting will be done here.
 347   {
 348     // Get the user setting of LD_LIBRARY_PATH, and prepended it. It
 349     // should always exist (until the legacy problem cited above is
 350     // addressed).
 351     const char *v = ::getenv("LD_LIBRARY_PATH");
 352     const char *v_colon = ":";
 353     if (v == NULL) { v = ""; v_colon = ""; }
 354     // That's +1 for the colon and +1 for the trailing '\0'.
 355     char *ld_library_path = (char *)NEW_C_HEAP_ARRAY(char,
 356                                                      strlen(v) + 1 +
 357                                                      sizeof(SYS_EXT_DIR) + sizeof("/lib/") + strlen(cpu_arch) + sizeof(DEFAULT_LIBPATH) + 1,
 358                                                      mtInternal);
 359     sprintf(ld_library_path, "%s%s" SYS_EXT_DIR "/lib/%s:" DEFAULT_LIBPATH, v, v_colon, cpu_arch);
 360     Arguments::set_library_path(ld_library_path);
 361     FREE_C_HEAP_ARRAY(char, ld_library_path);
 362   }
 363 
 364   // Extensions directories.
 365   sprintf(buf, "%s" EXTENSIONS_DIR ":" SYS_EXT_DIR EXTENSIONS_DIR, Arguments::get_java_home());
 366   Arguments::set_ext_dirs(buf);
 367 
 368   FREE_C_HEAP_ARRAY(char, buf);
 369 
 370 #undef DEFAULT_LIBPATH
 371 #undef SYS_EXT_DIR
 372 #undef EXTENSIONS_DIR
 373 }
 374 
 375 ////////////////////////////////////////////////////////////////////////////////
 376 // breakpoint support
 377 
 378 void os::breakpoint() {
 379   BREAKPOINT;
 380 }
 381 
 382 extern "C" void breakpoint() {
 383   // use debugger to set breakpoint here
 384 }
 385 
 386 ////////////////////////////////////////////////////////////////////////////////
 387 // signal support
 388 
 389 debug_only(static bool signal_sets_initialized = false);
 390 static sigset_t unblocked_sigs, vm_sigs, allowdebug_blocked_sigs;
 391 
 392 bool os::Linux::is_sig_ignored(int sig) {
 393   struct sigaction oact;
 394   sigaction(sig, (struct sigaction*)NULL, &oact);
 395   void* ohlr = oact.sa_sigaction ? CAST_FROM_FN_PTR(void*,  oact.sa_sigaction)
 396                                  : CAST_FROM_FN_PTR(void*,  oact.sa_handler);
 397   if (ohlr == CAST_FROM_FN_PTR(void*, SIG_IGN)) {
 398     return true;
 399   } else {
 400     return false;
 401   }
 402 }
 403 
 404 void os::Linux::signal_sets_init() {
 405   // Should also have an assertion stating we are still single-threaded.
 406   assert(!signal_sets_initialized, "Already initialized");
 407   // Fill in signals that are necessarily unblocked for all threads in
 408   // the VM. Currently, we unblock the following signals:
 409   // SHUTDOWN{1,2,3}_SIGNAL: for shutdown hooks support (unless over-ridden
 410   //                         by -Xrs (=ReduceSignalUsage));
 411   // BREAK_SIGNAL which is unblocked only by the VM thread and blocked by all
 412   // other threads. The "ReduceSignalUsage" boolean tells us not to alter
 413   // the dispositions or masks wrt these signals.
 414   // Programs embedding the VM that want to use the above signals for their
 415   // own purposes must, at this time, use the "-Xrs" option to prevent
 416   // interference with shutdown hooks and BREAK_SIGNAL thread dumping.
 417   // (See bug 4345157, and other related bugs).
 418   // In reality, though, unblocking these signals is really a nop, since
 419   // these signals are not blocked by default.
 420   sigemptyset(&unblocked_sigs);
 421   sigemptyset(&allowdebug_blocked_sigs);
 422   sigaddset(&unblocked_sigs, SIGILL);
 423   sigaddset(&unblocked_sigs, SIGSEGV);
 424   sigaddset(&unblocked_sigs, SIGBUS);
 425   sigaddset(&unblocked_sigs, SIGFPE);
 426 #if defined(PPC64)
 427   sigaddset(&unblocked_sigs, SIGTRAP);
 428 #endif
 429   sigaddset(&unblocked_sigs, SR_signum);
 430 
 431   if (!ReduceSignalUsage) {
 432     if (!os::Linux::is_sig_ignored(SHUTDOWN1_SIGNAL)) {
 433       sigaddset(&unblocked_sigs, SHUTDOWN1_SIGNAL);
 434       sigaddset(&allowdebug_blocked_sigs, SHUTDOWN1_SIGNAL);
 435     }
 436     if (!os::Linux::is_sig_ignored(SHUTDOWN2_SIGNAL)) {
 437       sigaddset(&unblocked_sigs, SHUTDOWN2_SIGNAL);
 438       sigaddset(&allowdebug_blocked_sigs, SHUTDOWN2_SIGNAL);
 439     }
 440     if (!os::Linux::is_sig_ignored(SHUTDOWN3_SIGNAL)) {
 441       sigaddset(&unblocked_sigs, SHUTDOWN3_SIGNAL);
 442       sigaddset(&allowdebug_blocked_sigs, SHUTDOWN3_SIGNAL);
 443     }
 444   }
 445   // Fill in signals that are blocked by all but the VM thread.
 446   sigemptyset(&vm_sigs);
 447   if (!ReduceSignalUsage) {
 448     sigaddset(&vm_sigs, BREAK_SIGNAL);
 449   }
 450   debug_only(signal_sets_initialized = true);
 451 
 452 }
 453 
 454 // These are signals that are unblocked while a thread is running Java.
 455 // (For some reason, they get blocked by default.)
 456 sigset_t* os::Linux::unblocked_signals() {
 457   assert(signal_sets_initialized, "Not initialized");
 458   return &unblocked_sigs;
 459 }
 460 
 461 // These are the signals that are blocked while a (non-VM) thread is
 462 // running Java. Only the VM thread handles these signals.
 463 sigset_t* os::Linux::vm_signals() {
 464   assert(signal_sets_initialized, "Not initialized");
 465   return &vm_sigs;
 466 }
 467 
 468 // These are signals that are blocked during cond_wait to allow debugger in
 469 sigset_t* os::Linux::allowdebug_blocked_signals() {
 470   assert(signal_sets_initialized, "Not initialized");
 471   return &allowdebug_blocked_sigs;
 472 }
 473 
 474 void os::Linux::hotspot_sigmask(Thread* thread) {
 475 
 476   //Save caller's signal mask before setting VM signal mask
 477   sigset_t caller_sigmask;
 478   pthread_sigmask(SIG_BLOCK, NULL, &caller_sigmask);
 479 
 480   OSThread* osthread = thread->osthread();
 481   osthread->set_caller_sigmask(caller_sigmask);
 482 
 483   pthread_sigmask(SIG_UNBLOCK, os::Linux::unblocked_signals(), NULL);
 484 
 485   if (!ReduceSignalUsage) {
 486     if (thread->is_VM_thread()) {
 487       // Only the VM thread handles BREAK_SIGNAL ...
 488       pthread_sigmask(SIG_UNBLOCK, vm_signals(), NULL);
 489     } else {
 490       // ... all other threads block BREAK_SIGNAL
 491       pthread_sigmask(SIG_BLOCK, vm_signals(), NULL);
 492     }
 493   }
 494 }
 495 
 496 //////////////////////////////////////////////////////////////////////////////
 497 // detecting pthread library
 498 
 499 void os::Linux::libpthread_init() {
 500   // Save glibc and pthread version strings.
 501 #if !defined(_CS_GNU_LIBC_VERSION) || \
 502     !defined(_CS_GNU_LIBPTHREAD_VERSION)
 503   #error "glibc too old (< 2.3.2)"
 504 #endif
 505 
 506   size_t n = confstr(_CS_GNU_LIBC_VERSION, NULL, 0);
 507   assert(n > 0, "cannot retrieve glibc version");
 508   char *str = (char *)malloc(n, mtInternal);
 509   confstr(_CS_GNU_LIBC_VERSION, str, n);
 510   os::Linux::set_glibc_version(str);
 511 
 512   n = confstr(_CS_GNU_LIBPTHREAD_VERSION, NULL, 0);
 513   assert(n > 0, "cannot retrieve pthread version");
 514   str = (char *)malloc(n, mtInternal);
 515   confstr(_CS_GNU_LIBPTHREAD_VERSION, str, n);
 516   os::Linux::set_libpthread_version(str);
 517 }
 518 
 519 /////////////////////////////////////////////////////////////////////////////
 520 // thread stack expansion
 521 
 522 // os::Linux::manually_expand_stack() takes care of expanding the thread
 523 // stack. Note that this is normally not needed: pthread stacks allocate
 524 // thread stack using mmap() without MAP_NORESERVE, so the stack is already
 525 // committed. Therefore it is not necessary to expand the stack manually.
 526 //
 527 // Manually expanding the stack was historically needed on LinuxThreads
 528 // thread stacks, which were allocated with mmap(MAP_GROWSDOWN). Nowadays
 529 // it is kept to deal with very rare corner cases:
 530 //
 531 // For one, user may run the VM on an own implementation of threads
 532 // whose stacks are - like the old LinuxThreads - implemented using
 533 // mmap(MAP_GROWSDOWN).
 534 //
 535 // Also, this coding may be needed if the VM is running on the primordial
 536 // thread. Normally we avoid running on the primordial thread; however,
 537 // user may still invoke the VM on the primordial thread.
 538 //
 539 // The following historical comment describes the details about running
 540 // on a thread stack allocated with mmap(MAP_GROWSDOWN):
 541 
 542 
 543 // Force Linux kernel to expand current thread stack. If "bottom" is close
 544 // to the stack guard, caller should block all signals.
 545 //
 546 // MAP_GROWSDOWN:
 547 //   A special mmap() flag that is used to implement thread stacks. It tells
 548 //   kernel that the memory region should extend downwards when needed. This
 549 //   allows early versions of LinuxThreads to only mmap the first few pages
 550 //   when creating a new thread. Linux kernel will automatically expand thread
 551 //   stack as needed (on page faults).
 552 //
 553 //   However, because the memory region of a MAP_GROWSDOWN stack can grow on
 554 //   demand, if a page fault happens outside an already mapped MAP_GROWSDOWN
 555 //   region, it's hard to tell if the fault is due to a legitimate stack
 556 //   access or because of reading/writing non-exist memory (e.g. buffer
 557 //   overrun). As a rule, if the fault happens below current stack pointer,
 558 //   Linux kernel does not expand stack, instead a SIGSEGV is sent to the
 559 //   application (see Linux kernel fault.c).
 560 //
 561 //   This Linux feature can cause SIGSEGV when VM bangs thread stack for
 562 //   stack overflow detection.
 563 //
 564 //   Newer version of LinuxThreads (since glibc-2.2, or, RH-7.x) and NPTL do
 565 //   not use MAP_GROWSDOWN.
 566 //
 567 // To get around the problem and allow stack banging on Linux, we need to
 568 // manually expand thread stack after receiving the SIGSEGV.
 569 //
 570 // There are two ways to expand thread stack to address "bottom", we used
 571 // both of them in JVM before 1.5:
 572 //   1. adjust stack pointer first so that it is below "bottom", and then
 573 //      touch "bottom"
 574 //   2. mmap() the page in question
 575 //
 576 // Now alternate signal stack is gone, it's harder to use 2. For instance,
 577 // if current sp is already near the lower end of page 101, and we need to
 578 // call mmap() to map page 100, it is possible that part of the mmap() frame
 579 // will be placed in page 100. When page 100 is mapped, it is zero-filled.
 580 // That will destroy the mmap() frame and cause VM to crash.
 581 //
 582 // The following code works by adjusting sp first, then accessing the "bottom"
 583 // page to force a page fault. Linux kernel will then automatically expand the
 584 // stack mapping.
 585 //
 586 // _expand_stack_to() assumes its frame size is less than page size, which
 587 // should always be true if the function is not inlined.
 588 
 589 #if __GNUC__ < 3    // gcc 2.x does not support noinline attribute
 590   #define NOINLINE
 591 #else
 592   #define NOINLINE __attribute__ ((noinline))
 593 #endif
 594 
 595 static void _expand_stack_to(address bottom) NOINLINE;
 596 
 597 static void _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_yellow_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   ThreadLocalStorage::set_thread(thread);
 652 
 653   OSThread* osthread = thread->osthread();
 654   Monitor* sync = osthread->startThread_lock();
 655 
 656   // thread_id is kernel thread id (similar to Solaris LWP id)
 657   osthread->set_thread_id(os::Linux::gettid());
 658 
 659   if (UseNUMA) {
 660     int lgrp_id = os::numa_get_group_id();
 661     if (lgrp_id != -1) {
 662       thread->set_lgrp_id(lgrp_id);
 663     }
 664   }
 665   // initialize signal mask for this thread
 666   os::Linux::hotspot_sigmask(thread);
 667 
 668   // initialize floating point control register
 669   os::Linux::init_thread_fpu_state();
 670 
 671   // handshaking with parent thread
 672   {
 673     MutexLockerEx ml(sync, Mutex::_no_safepoint_check_flag);
 674 
 675     // notify parent thread
 676     osthread->set_state(INITIALIZED);
 677     sync->notify_all();
 678 
 679     // wait until os::start_thread()
 680     while (osthread->get_state() == INITIALIZED) {
 681       sync->wait(Mutex::_no_safepoint_check_flag);
 682     }
 683   }
 684 
 685   // call one more level start routine
 686   thread->run();
 687 
 688   return 0;
 689 }
 690 
 691 bool os::create_thread(Thread* thread, ThreadType thr_type,
 692                        size_t stack_size) {
 693   assert(thread->osthread() == NULL, "caller responsible");
 694 
 695   // Allocate the OSThread object
 696   OSThread* osthread = new OSThread(NULL, NULL);
 697   if (osthread == NULL) {
 698     return false;
 699   }
 700 
 701   // set the correct thread state
 702   osthread->set_thread_type(thr_type);
 703 
 704   // Initial state is ALLOCATED but not INITIALIZED
 705   osthread->set_state(ALLOCATED);
 706 
 707   thread->set_osthread(osthread);
 708 
 709   // init thread attributes
 710   pthread_attr_t attr;
 711   pthread_attr_init(&attr);
 712   pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
 713 
 714   // stack size
 715   if (os::Linux::supports_variable_stack_size()) {
 716     // calculate stack size if it's not specified by caller
 717     if (stack_size == 0) {
 718       stack_size = os::Linux::default_stack_size(thr_type);
 719 
 720       switch (thr_type) {
 721       case os::java_thread:
 722         // Java threads use ThreadStackSize which default value can be
 723         // changed with the flag -Xss
 724         assert(JavaThread::stack_size_at_create() > 0, "this should be set");
 725         stack_size = JavaThread::stack_size_at_create();
 726         break;
 727       case os::compiler_thread:
 728         if (CompilerThreadStackSize > 0) {
 729           stack_size = (size_t)(CompilerThreadStackSize * K);
 730           break;
 731         } // else fall through:
 732           // use VMThreadStackSize if CompilerThreadStackSize is not defined
 733       case os::vm_thread:
 734       case os::pgc_thread:
 735       case os::cgc_thread:
 736       case os::watcher_thread:
 737         if (VMThreadStackSize > 0) stack_size = (size_t)(VMThreadStackSize * K);
 738         break;
 739       }
 740     }
 741 
 742     stack_size = MAX2(stack_size, os::Linux::min_stack_allowed);
 743     pthread_attr_setstacksize(&attr, stack_size);
 744   } else {
 745     // let pthread_create() pick the default value.
 746   }
 747 
 748   // glibc guard page
 749   pthread_attr_setguardsize(&attr, os::Linux::default_guard_size(thr_type));
 750 
 751   ThreadState state;
 752 
 753   {
 754     pthread_t tid;
 755     int ret = pthread_create(&tid, &attr, (void* (*)(void*)) java_start, thread);
 756 
 757     pthread_attr_destroy(&attr);
 758 
 759     if (ret != 0) {
 760       if (PrintMiscellaneous && (Verbose || WizardMode)) {
 761         perror("pthread_create()");
 762       }
 763       // Need to clean up stuff we've allocated so far
 764       thread->set_osthread(NULL);
 765       delete osthread;
 766       return false;
 767     }
 768 
 769     // Store pthread info into the OSThread
 770     osthread->set_pthread_id(tid);
 771 
 772     // Wait until child thread is either initialized or aborted
 773     {
 774       Monitor* sync_with_child = osthread->startThread_lock();
 775       MutexLockerEx ml(sync_with_child, Mutex::_no_safepoint_check_flag);
 776       while ((state = osthread->get_state()) == ALLOCATED) {
 777         sync_with_child->wait(Mutex::_no_safepoint_check_flag);
 778       }
 779     }
 780   }
 781 
 782   // Aborted due to thread limit being reached
 783   if (state == ZOMBIE) {
 784     thread->set_osthread(NULL);
 785     delete osthread;
 786     return false;
 787   }
 788 
 789   // The thread is returned suspended (in state INITIALIZED),
 790   // and is started higher up in the call chain
 791   assert(state == INITIALIZED, "race condition");
 792   return true;
 793 }
 794 
 795 /////////////////////////////////////////////////////////////////////////////
 796 // attach existing thread
 797 
 798 // bootstrap the main thread
 799 bool os::create_main_thread(JavaThread* thread) {
 800   assert(os::Linux::_main_thread == pthread_self(), "should be called inside main thread");
 801   return create_attached_thread(thread);
 802 }
 803 
 804 bool os::create_attached_thread(JavaThread* thread) {
 805 #ifdef ASSERT
 806   thread->verify_not_published();
 807 #endif
 808 
 809   // Allocate the OSThread object
 810   OSThread* osthread = new OSThread(NULL, NULL);
 811 
 812   if (osthread == NULL) {
 813     return false;
 814   }
 815 
 816   // Store pthread info into the OSThread
 817   osthread->set_thread_id(os::Linux::gettid());
 818   osthread->set_pthread_id(::pthread_self());
 819 
 820   // initialize floating point control register
 821   os::Linux::init_thread_fpu_state();
 822 
 823   // Initial thread state is RUNNABLE
 824   osthread->set_state(RUNNABLE);
 825 
 826   thread->set_osthread(osthread);
 827 
 828   if (UseNUMA) {
 829     int lgrp_id = os::numa_get_group_id();
 830     if (lgrp_id != -1) {
 831       thread->set_lgrp_id(lgrp_id);
 832     }
 833   }
 834 
 835   if (os::Linux::is_initial_thread()) {
 836     // If current thread is initial thread, its stack is mapped on demand,
 837     // see notes about MAP_GROWSDOWN. Here we try to force kernel to map
 838     // the entire stack region to avoid SEGV in stack banging.
 839     // It is also useful to get around the heap-stack-gap problem on SuSE
 840     // kernel (see 4821821 for details). We first expand stack to the top
 841     // of yellow zone, then enable stack yellow zone (order is significant,
 842     // enabling yellow zone first will crash JVM on SuSE Linux), so there
 843     // is no gap between the last two virtual memory regions.
 844 
 845     JavaThread *jt = (JavaThread *)thread;
 846     address addr = jt->stack_yellow_zone_base();
 847     assert(addr != NULL, "initialization problem?");
 848     assert(jt->stack_available(addr) > 0, "stack guard should not be enabled");
 849 
 850     osthread->set_expanding_stack();
 851     os::Linux::manually_expand_stack(jt, addr);
 852     osthread->clear_expanding_stack();
 853   }
 854 
 855   // initialize signal mask for this thread
 856   // and save the caller's signal mask
 857   os::Linux::hotspot_sigmask(thread);
 858 
 859   return true;
 860 }
 861 
 862 void os::pd_start_thread(Thread* thread) {
 863   OSThread * osthread = thread->osthread();
 864   assert(osthread->get_state() != INITIALIZED, "just checking");
 865   Monitor* sync_with_child = osthread->startThread_lock();
 866   MutexLockerEx ml(sync_with_child, Mutex::_no_safepoint_check_flag);
 867   sync_with_child->notify();
 868 }
 869 
 870 // Free Linux resources related to the OSThread
 871 void os::free_thread(OSThread* osthread) {
 872   assert(osthread != NULL, "osthread not set");
 873 
 874   if (Thread::current()->osthread() == osthread) {
 875     // Restore caller's signal mask
 876     sigset_t sigmask = osthread->caller_sigmask();
 877     pthread_sigmask(SIG_SETMASK, &sigmask, NULL);
 878   }
 879 
 880   delete osthread;
 881 }
 882 
 883 //////////////////////////////////////////////////////////////////////////////
 884 // thread local storage
 885 
 886 // Restore the thread pointer if the destructor is called. This is in case
 887 // someone from JNI code sets up a destructor with pthread_key_create to run
 888 // detachCurrentThread on thread death. Unless we restore the thread pointer we
 889 // will hang or crash. When detachCurrentThread is called the key will be set
 890 // to null and we will not be called again. If detachCurrentThread is never
 891 // called we could loop forever depending on the pthread implementation.
 892 static void restore_thread_pointer(void* p) {
 893   Thread* thread = (Thread*) p;
 894   os::thread_local_storage_at_put(ThreadLocalStorage::thread_index(), thread);
 895 }
 896 
 897 int os::allocate_thread_local_storage() {
 898   pthread_key_t key;
 899   int rslt = pthread_key_create(&key, restore_thread_pointer);
 900   assert(rslt == 0, "cannot allocate thread local storage");
 901   return (int)key;
 902 }
 903 
 904 // Note: This is currently not used by VM, as we don't destroy TLS key
 905 // on VM exit.
 906 void os::free_thread_local_storage(int index) {
 907   int rslt = pthread_key_delete((pthread_key_t)index);
 908   assert(rslt == 0, "invalid index");
 909 }
 910 
 911 void os::thread_local_storage_at_put(int index, void* value) {
 912   int rslt = pthread_setspecific((pthread_key_t)index, value);
 913   assert(rslt == 0, "pthread_setspecific failed");
 914 }
 915 
 916 extern "C" Thread* get_thread() {
 917   return ThreadLocalStorage::thread();
 918 }
 919 
 920 //////////////////////////////////////////////////////////////////////////////
 921 // initial thread
 922 
 923 // Check if current thread is the initial thread, similar to Solaris thr_main.
 924 bool os::Linux::is_initial_thread(void) {
 925   char dummy;
 926   // If called before init complete, thread stack bottom will be null.
 927   // Can be called if fatal error occurs before initialization.
 928   if (initial_thread_stack_bottom() == NULL) return false;
 929   assert(initial_thread_stack_bottom() != NULL &&
 930          initial_thread_stack_size()   != 0,
 931          "os::init did not locate initial thread's stack region");
 932   if ((address)&dummy >= initial_thread_stack_bottom() &&
 933       (address)&dummy < initial_thread_stack_bottom() + initial_thread_stack_size()) {
 934     return true;
 935   } else {
 936     return false;
 937   }
 938 }
 939 
 940 // Find the virtual memory area that contains addr
 941 static bool find_vma(address addr, address* vma_low, address* vma_high) {
 942   FILE *fp = fopen("/proc/self/maps", "r");
 943   if (fp) {
 944     address low, high;
 945     while (!feof(fp)) {
 946       if (fscanf(fp, "%p-%p", &low, &high) == 2) {
 947         if (low <= addr && addr < high) {
 948           if (vma_low)  *vma_low  = low;
 949           if (vma_high) *vma_high = high;
 950           fclose(fp);
 951           return true;
 952         }
 953       }
 954       for (;;) {
 955         int ch = fgetc(fp);
 956         if (ch == EOF || ch == (int)'\n') break;
 957       }
 958     }
 959     fclose(fp);
 960   }
 961   return false;
 962 }
 963 
 964 // Locate initial thread stack. This special handling of initial thread stack
 965 // is needed because pthread_getattr_np() on most (all?) Linux distros returns
 966 // bogus value for initial thread.
 967 void os::Linux::capture_initial_stack(size_t max_size) {
 968   // stack size is the easy part, get it from RLIMIT_STACK
 969   size_t stack_size;
 970   struct rlimit rlim;
 971   getrlimit(RLIMIT_STACK, &rlim);
 972   stack_size = rlim.rlim_cur;
 973 
 974   // 6308388: a bug in ld.so will relocate its own .data section to the
 975   //   lower end of primordial stack; reduce ulimit -s value a little bit
 976   //   so we won't install guard page on ld.so's data section.
 977   stack_size -= 2 * page_size();
 978 
 979   // 4441425: avoid crash with "unlimited" stack size on SuSE 7.1 or Redhat
 980   //   7.1, in both cases we will get 2G in return value.
 981   // 4466587: glibc 2.2.x compiled w/o "--enable-kernel=2.4.0" (RH 7.0,
 982   //   SuSE 7.2, Debian) can not handle alternate signal stack correctly
 983   //   for initial thread if its stack size exceeds 6M. Cap it at 2M,
 984   //   in case other parts in glibc still assumes 2M max stack size.
 985   // FIXME: alt signal stack is gone, maybe we can relax this constraint?
 986   // Problem still exists RH7.2 (IA64 anyway) but 2MB is a little small
 987   if (stack_size > 2 * K * K IA64_ONLY(*2)) {
 988     stack_size = 2 * K * K IA64_ONLY(*2);
 989   }
 990   // Try to figure out where the stack base (top) is. This is harder.
 991   //
 992   // When an application is started, glibc saves the initial stack pointer in
 993   // a global variable "__libc_stack_end", which is then used by system
 994   // libraries. __libc_stack_end should be pretty close to stack top. The
 995   // variable is available since the very early days. However, because it is
 996   // a private interface, it could disappear in the future.
 997   //
 998   // Linux kernel saves start_stack information in /proc/<pid>/stat. Similar
 999   // to __libc_stack_end, it is very close to stack top, but isn't the real
1000   // stack top. Note that /proc may not exist if VM is running as a chroot
1001   // program, so reading /proc/<pid>/stat could fail. Also the contents of
1002   // /proc/<pid>/stat could change in the future (though unlikely).
1003   //
1004   // We try __libc_stack_end first. If that doesn't work, look for
1005   // /proc/<pid>/stat. If neither of them works, we use current stack pointer
1006   // as a hint, which should work well in most cases.
1007 
1008   uintptr_t stack_start;
1009 
1010   // try __libc_stack_end first
1011   uintptr_t *p = (uintptr_t *)dlsym(RTLD_DEFAULT, "__libc_stack_end");
1012   if (p && *p) {
1013     stack_start = *p;
1014   } else {
1015     // see if we can get the start_stack field from /proc/self/stat
1016     FILE *fp;
1017     int pid;
1018     char state;
1019     int ppid;
1020     int pgrp;
1021     int session;
1022     int nr;
1023     int tpgrp;
1024     unsigned long flags;
1025     unsigned long minflt;
1026     unsigned long cminflt;
1027     unsigned long majflt;
1028     unsigned long cmajflt;
1029     unsigned long utime;
1030     unsigned long stime;
1031     long cutime;
1032     long cstime;
1033     long prio;
1034     long nice;
1035     long junk;
1036     long it_real;
1037     uintptr_t start;
1038     uintptr_t vsize;
1039     intptr_t rss;
1040     uintptr_t rsslim;
1041     uintptr_t scodes;
1042     uintptr_t ecode;
1043     int i;
1044 
1045     // Figure what the primordial thread stack base is. Code is inspired
1046     // by email from Hans Boehm. /proc/self/stat begins with current pid,
1047     // followed by command name surrounded by parentheses, state, etc.
1048     char stat[2048];
1049     int statlen;
1050 
1051     fp = fopen("/proc/self/stat", "r");
1052     if (fp) {
1053       statlen = fread(stat, 1, 2047, fp);
1054       stat[statlen] = '\0';
1055       fclose(fp);
1056 
1057       // Skip pid and the command string. Note that we could be dealing with
1058       // weird command names, e.g. user could decide to rename java launcher
1059       // to "java 1.4.2 :)", then the stat file would look like
1060       //                1234 (java 1.4.2 :)) R ... ...
1061       // We don't really need to know the command string, just find the last
1062       // occurrence of ")" and then start parsing from there. See bug 4726580.
1063       char * s = strrchr(stat, ')');
1064 
1065       i = 0;
1066       if (s) {
1067         // Skip blank chars
1068         do { s++; } while (s && isspace(*s));
1069 
1070 #define _UFM UINTX_FORMAT
1071 #define _DFM INTX_FORMAT
1072 
1073         //                                     1   1   1   1   1   1   1   1   1   1   2   2    2    2    2    2    2    2    2
1074         //              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
1075         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,
1076                    &state,          // 3  %c
1077                    &ppid,           // 4  %d
1078                    &pgrp,           // 5  %d
1079                    &session,        // 6  %d
1080                    &nr,             // 7  %d
1081                    &tpgrp,          // 8  %d
1082                    &flags,          // 9  %lu
1083                    &minflt,         // 10 %lu
1084                    &cminflt,        // 11 %lu
1085                    &majflt,         // 12 %lu
1086                    &cmajflt,        // 13 %lu
1087                    &utime,          // 14 %lu
1088                    &stime,          // 15 %lu
1089                    &cutime,         // 16 %ld
1090                    &cstime,         // 17 %ld
1091                    &prio,           // 18 %ld
1092                    &nice,           // 19 %ld
1093                    &junk,           // 20 %ld
1094                    &it_real,        // 21 %ld
1095                    &start,          // 22 UINTX_FORMAT
1096                    &vsize,          // 23 UINTX_FORMAT
1097                    &rss,            // 24 INTX_FORMAT
1098                    &rsslim,         // 25 UINTX_FORMAT
1099                    &scodes,         // 26 UINTX_FORMAT
1100                    &ecode,          // 27 UINTX_FORMAT
1101                    &stack_start);   // 28 UINTX_FORMAT
1102       }
1103 
1104 #undef _UFM
1105 #undef _DFM
1106 
1107       if (i != 28 - 2) {
1108         assert(false, "Bad conversion from /proc/self/stat");
1109         // product mode - assume we are the initial thread, good luck in the
1110         // embedded case.
1111         warning("Can't detect initial thread stack location - bad conversion");
1112         stack_start = (uintptr_t) &rlim;
1113       }
1114     } else {
1115       // For some reason we can't open /proc/self/stat (for example, running on
1116       // FreeBSD with a Linux emulator, or inside chroot), this should work for
1117       // most cases, so don't abort:
1118       warning("Can't detect initial thread stack location - no /proc/self/stat");
1119       stack_start = (uintptr_t) &rlim;
1120     }
1121   }
1122 
1123   // Now we have a pointer (stack_start) very close to the stack top, the
1124   // next thing to do is to figure out the exact location of stack top. We
1125   // can find out the virtual memory area that contains stack_start by
1126   // reading /proc/self/maps, it should be the last vma in /proc/self/maps,
1127   // and its upper limit is the real stack top. (again, this would fail if
1128   // running inside chroot, because /proc may not exist.)
1129 
1130   uintptr_t stack_top;
1131   address low, high;
1132   if (find_vma((address)stack_start, &low, &high)) {
1133     // success, "high" is the true stack top. (ignore "low", because initial
1134     // thread stack grows on demand, its real bottom is high - RLIMIT_STACK.)
1135     stack_top = (uintptr_t)high;
1136   } else {
1137     // failed, likely because /proc/self/maps does not exist
1138     warning("Can't detect initial thread stack location - find_vma failed");
1139     // best effort: stack_start is normally within a few pages below the real
1140     // stack top, use it as stack top, and reduce stack size so we won't put
1141     // guard page outside stack.
1142     stack_top = stack_start;
1143     stack_size -= 16 * page_size();
1144   }
1145 
1146   // stack_top could be partially down the page so align it
1147   stack_top = align_size_up(stack_top, page_size());
1148 
1149   if (max_size && stack_size > max_size) {
1150     _initial_thread_stack_size = max_size;
1151   } else {
1152     _initial_thread_stack_size = stack_size;
1153   }
1154 
1155   _initial_thread_stack_size = align_size_down(_initial_thread_stack_size, page_size());
1156   _initial_thread_stack_bottom = (address)stack_top - _initial_thread_stack_size;
1157 }
1158 
1159 ////////////////////////////////////////////////////////////////////////////////
1160 // time support
1161 
1162 // Time since start-up in seconds to a fine granularity.
1163 // Used by VMSelfDestructTimer and the MemProfiler.
1164 double os::elapsedTime() {
1165 
1166   return ((double)os::elapsed_counter()) / os::elapsed_frequency(); // nanosecond resolution
1167 }
1168 
1169 jlong os::elapsed_counter() {
1170   return javaTimeNanos() - initial_time_count;
1171 }
1172 
1173 jlong os::elapsed_frequency() {
1174   return NANOSECS_PER_SEC; // nanosecond resolution
1175 }
1176 
1177 bool os::supports_vtime() { return true; }
1178 bool os::enable_vtime()   { return false; }
1179 bool os::vtime_enabled()  { return false; }
1180 
1181 double os::elapsedVTime() {
1182   struct rusage usage;
1183   int retval = getrusage(RUSAGE_THREAD, &usage);
1184   if (retval == 0) {
1185     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);
1186   } else {
1187     // better than nothing, but not much
1188     return elapsedTime();
1189   }
1190 }
1191 
1192 jlong os::javaTimeMillis() {
1193   timeval time;
1194   int status = gettimeofday(&time, NULL);
1195   assert(status != -1, "linux error");
1196   return jlong(time.tv_sec) * 1000  +  jlong(time.tv_usec / 1000);
1197 }
1198 
1199 void os::javaTimeSystemUTC(jlong &seconds, jlong &nanos) {
1200   timeval time;
1201   int status = gettimeofday(&time, NULL);
1202   assert(status != -1, "linux error");
1203   seconds = jlong(time.tv_sec);
1204   nanos = jlong(time.tv_usec) * 1000;
1205 }
1206 
1207 
1208 #ifndef CLOCK_MONOTONIC
1209   #define CLOCK_MONOTONIC (1)
1210 #endif
1211 
1212 void os::Linux::clock_init() {
1213   // we do dlopen's in this particular order due to bug in linux
1214   // dynamical loader (see 6348968) leading to crash on exit
1215   void* handle = dlopen("librt.so.1", RTLD_LAZY);
1216   if (handle == NULL) {
1217     handle = dlopen("librt.so", RTLD_LAZY);
1218   }
1219 
1220   if (handle) {
1221     int (*clock_getres_func)(clockid_t, struct timespec*) =
1222            (int(*)(clockid_t, struct timespec*))dlsym(handle, "clock_getres");
1223     int (*clock_gettime_func)(clockid_t, struct timespec*) =
1224            (int(*)(clockid_t, struct timespec*))dlsym(handle, "clock_gettime");
1225     if (clock_getres_func && clock_gettime_func) {
1226       // See if monotonic clock is supported by the kernel. Note that some
1227       // early implementations simply return kernel jiffies (updated every
1228       // 1/100 or 1/1000 second). It would be bad to use such a low res clock
1229       // for nano time (though the monotonic property is still nice to have).
1230       // It's fixed in newer kernels, however clock_getres() still returns
1231       // 1/HZ. We check if clock_getres() works, but will ignore its reported
1232       // resolution for now. Hopefully as people move to new kernels, this
1233       // won't be a problem.
1234       struct timespec res;
1235       struct timespec tp;
1236       if (clock_getres_func (CLOCK_MONOTONIC, &res) == 0 &&
1237           clock_gettime_func(CLOCK_MONOTONIC, &tp)  == 0) {
1238         // yes, monotonic clock is supported
1239         _clock_gettime = clock_gettime_func;
1240         return;
1241       } else {
1242         // close librt if there is no monotonic clock
1243         dlclose(handle);
1244       }
1245     }
1246   }
1247   warning("No monotonic clock was available - timed services may " \
1248           "be adversely affected if the time-of-day clock changes");
1249 }
1250 
1251 #ifndef SYS_clock_getres
1252   #if defined(IA32) || defined(AMD64)
1253     #define SYS_clock_getres IA32_ONLY(266)  AMD64_ONLY(229)
1254     #define sys_clock_getres(x,y)  ::syscall(SYS_clock_getres, x, y)
1255   #else
1256     #warning "SYS_clock_getres not defined for this platform, disabling fast_thread_cpu_time"
1257     #define sys_clock_getres(x,y)  -1
1258   #endif
1259 #else
1260   #define sys_clock_getres(x,y)  ::syscall(SYS_clock_getres, x, y)
1261 #endif
1262 
1263 void os::Linux::fast_thread_clock_init() {
1264   if (!UseLinuxPosixThreadCPUClocks) {
1265     return;
1266   }
1267   clockid_t clockid;
1268   struct timespec tp;
1269   int (*pthread_getcpuclockid_func)(pthread_t, clockid_t *) =
1270       (int(*)(pthread_t, clockid_t *)) dlsym(RTLD_DEFAULT, "pthread_getcpuclockid");
1271 
1272   // Switch to using fast clocks for thread cpu time if
1273   // the sys_clock_getres() returns 0 error code.
1274   // Note, that some kernels may support the current thread
1275   // clock (CLOCK_THREAD_CPUTIME_ID) but not the clocks
1276   // returned by the pthread_getcpuclockid().
1277   // If the fast Posix clocks are supported then the sys_clock_getres()
1278   // must return at least tp.tv_sec == 0 which means a resolution
1279   // better than 1 sec. This is extra check for reliability.
1280 
1281   if (pthread_getcpuclockid_func &&
1282       pthread_getcpuclockid_func(_main_thread, &clockid) == 0 &&
1283       sys_clock_getres(clockid, &tp) == 0 && tp.tv_sec == 0) {
1284     _supports_fast_thread_cpu_time = true;
1285     _pthread_getcpuclockid = pthread_getcpuclockid_func;
1286   }
1287 }
1288 
1289 jlong os::javaTimeNanos() {
1290   if (os::supports_monotonic_clock()) {
1291     struct timespec tp;
1292     int status = Linux::clock_gettime(CLOCK_MONOTONIC, &tp);
1293     assert(status == 0, "gettime error");
1294     jlong result = jlong(tp.tv_sec) * (1000 * 1000 * 1000) + jlong(tp.tv_nsec);
1295     return result;
1296   } else {
1297     timeval time;
1298     int status = gettimeofday(&time, NULL);
1299     assert(status != -1, "linux error");
1300     jlong usecs = jlong(time.tv_sec) * (1000 * 1000) + jlong(time.tv_usec);
1301     return 1000 * usecs;
1302   }
1303 }
1304 
1305 void os::javaTimeNanos_info(jvmtiTimerInfo *info_ptr) {
1306   if (os::supports_monotonic_clock()) {
1307     info_ptr->max_value = ALL_64_BITS;
1308 
1309     // CLOCK_MONOTONIC - amount of time since some arbitrary point in the past
1310     info_ptr->may_skip_backward = false;      // not subject to resetting or drifting
1311     info_ptr->may_skip_forward = false;       // not subject to resetting or drifting
1312   } else {
1313     // gettimeofday - based on time in seconds since the Epoch thus does not wrap
1314     info_ptr->max_value = ALL_64_BITS;
1315 
1316     // gettimeofday is a real time clock so it skips
1317     info_ptr->may_skip_backward = true;
1318     info_ptr->may_skip_forward = true;
1319   }
1320 
1321   info_ptr->kind = JVMTI_TIMER_ELAPSED;                // elapsed not CPU time
1322 }
1323 
1324 // Return the real, user, and system times in seconds from an
1325 // arbitrary fixed point in the past.
1326 bool os::getTimesSecs(double* process_real_time,
1327                       double* process_user_time,
1328                       double* process_system_time) {
1329   struct tms ticks;
1330   clock_t real_ticks = times(&ticks);
1331 
1332   if (real_ticks == (clock_t) (-1)) {
1333     return false;
1334   } else {
1335     double ticks_per_second = (double) clock_tics_per_sec;
1336     *process_user_time = ((double) ticks.tms_utime) / ticks_per_second;
1337     *process_system_time = ((double) ticks.tms_stime) / ticks_per_second;
1338     *process_real_time = ((double) real_ticks) / ticks_per_second;
1339 
1340     return true;
1341   }
1342 }
1343 
1344 
1345 char * os::local_time_string(char *buf, size_t buflen) {
1346   struct tm t;
1347   time_t long_time;
1348   time(&long_time);
1349   localtime_r(&long_time, &t);
1350   jio_snprintf(buf, buflen, "%d-%02d-%02d %02d:%02d:%02d",
1351                t.tm_year + 1900, t.tm_mon + 1, t.tm_mday,
1352                t.tm_hour, t.tm_min, t.tm_sec);
1353   return buf;
1354 }
1355 
1356 struct tm* os::localtime_pd(const time_t* clock, struct tm*  res) {
1357   return localtime_r(clock, res);
1358 }
1359 
1360 ////////////////////////////////////////////////////////////////////////////////
1361 // runtime exit support
1362 
1363 // Note: os::shutdown() might be called very early during initialization, or
1364 // called from signal handler. Before adding something to os::shutdown(), make
1365 // sure it is async-safe and can handle partially initialized VM.
1366 void os::shutdown() {
1367 
1368   // allow PerfMemory to attempt cleanup of any persistent resources
1369   perfMemory_exit();
1370 
1371   // needs to remove object in file system
1372   AttachListener::abort();
1373 
1374   // flush buffered output, finish log files
1375   ostream_abort();
1376 
1377   // Check for abort hook
1378   abort_hook_t abort_hook = Arguments::abort_hook();
1379   if (abort_hook != NULL) {
1380     abort_hook();
1381   }
1382 
1383 }
1384 
1385 // Note: os::abort() might be called very early during initialization, or
1386 // called from signal handler. Before adding something to os::abort(), make
1387 // sure it is async-safe and can handle partially initialized VM.
1388 void os::abort(bool dump_core, void* siginfo, void* context) {
1389   os::shutdown();
1390   if (dump_core) {
1391 #ifndef PRODUCT
1392     fdStream out(defaultStream::output_fd());
1393     out.print_raw("Current thread is ");
1394     char buf[16];
1395     jio_snprintf(buf, sizeof(buf), UINTX_FORMAT, os::current_thread_id());
1396     out.print_raw_cr(buf);
1397     out.print_raw_cr("Dumping core ...");
1398 #endif
1399     ::abort(); // dump core
1400   }
1401 
1402   ::exit(1);
1403 }
1404 
1405 // Die immediately, no exit hook, no abort hook, no cleanup.
1406 void os::die() {
1407   ::abort();
1408 }
1409 
1410 
1411 // This method is a copy of JDK's sysGetLastErrorString
1412 // from src/solaris/hpi/src/system_md.c
1413 
1414 size_t os::lasterror(char *buf, size_t len) {
1415   if (errno == 0)  return 0;
1416 
1417   const char *s = ::strerror(errno);
1418   size_t n = ::strlen(s);
1419   if (n >= len) {
1420     n = len - 1;
1421   }
1422   ::strncpy(buf, s, n);
1423   buf[n] = '\0';
1424   return n;
1425 }
1426 
1427 intx os::current_thread_id() { return (intx)pthread_self(); }
1428 int os::current_process_id() {
1429   return ::getpid();
1430 }
1431 
1432 // DLL functions
1433 
1434 const char* os::dll_file_extension() { return ".so"; }
1435 
1436 // This must be hard coded because it's the system's temporary
1437 // directory not the java application's temp directory, ala java.io.tmpdir.
1438 const char* os::get_temp_directory() { return "/tmp"; }
1439 
1440 static bool file_exists(const char* filename) {
1441   struct stat statbuf;
1442   if (filename == NULL || strlen(filename) == 0) {
1443     return false;
1444   }
1445   return os::stat(filename, &statbuf) == 0;
1446 }
1447 
1448 bool os::dll_build_name(char* buffer, size_t buflen,
1449                         const char* pname, const char* fname) {
1450   bool retval = false;
1451   // Copied from libhpi
1452   const size_t pnamelen = pname ? strlen(pname) : 0;
1453 
1454   // Return error on buffer overflow.
1455   if (pnamelen + strlen(fname) + 10 > (size_t) buflen) {
1456     return retval;
1457   }
1458 
1459   if (pnamelen == 0) {
1460     snprintf(buffer, buflen, "lib%s.so", fname);
1461     retval = true;
1462   } else if (strchr(pname, *os::path_separator()) != NULL) {
1463     int n;
1464     char** pelements = split_path(pname, &n);
1465     if (pelements == NULL) {
1466       return false;
1467     }
1468     for (int i = 0; i < n; i++) {
1469       // Really shouldn't be NULL, but check can't hurt
1470       if (pelements[i] == NULL || strlen(pelements[i]) == 0) {
1471         continue; // skip the empty path values
1472       }
1473       snprintf(buffer, buflen, "%s/lib%s.so", pelements[i], fname);
1474       if (file_exists(buffer)) {
1475         retval = true;
1476         break;
1477       }
1478     }
1479     // release the storage
1480     for (int i = 0; i < n; i++) {
1481       if (pelements[i] != NULL) {
1482         FREE_C_HEAP_ARRAY(char, pelements[i]);
1483       }
1484     }
1485     if (pelements != NULL) {
1486       FREE_C_HEAP_ARRAY(char*, pelements);
1487     }
1488   } else {
1489     snprintf(buffer, buflen, "%s/lib%s.so", pname, fname);
1490     retval = true;
1491   }
1492   return retval;
1493 }
1494 
1495 // check if addr is inside libjvm.so
1496 bool os::address_is_in_vm(address addr) {
1497   static address libjvm_base_addr;
1498   Dl_info dlinfo;
1499 
1500   if (libjvm_base_addr == NULL) {
1501     if (dladdr(CAST_FROM_FN_PTR(void *, os::address_is_in_vm), &dlinfo) != 0) {
1502       libjvm_base_addr = (address)dlinfo.dli_fbase;
1503     }
1504     assert(libjvm_base_addr !=NULL, "Cannot obtain base address for libjvm");
1505   }
1506 
1507   if (dladdr((void *)addr, &dlinfo) != 0) {
1508     if (libjvm_base_addr == (address)dlinfo.dli_fbase) return true;
1509   }
1510 
1511   return false;
1512 }
1513 
1514 bool os::dll_address_to_function_name(address addr, char *buf,
1515                                       int buflen, int *offset,
1516                                       bool demangle) {
1517   // buf is not optional, but offset is optional
1518   assert(buf != NULL, "sanity check");
1519 
1520   Dl_info dlinfo;
1521 
1522   if (dladdr((void*)addr, &dlinfo) != 0) {
1523     // see if we have a matching symbol
1524     if (dlinfo.dli_saddr != NULL && dlinfo.dli_sname != NULL) {
1525       if (!(demangle && Decoder::demangle(dlinfo.dli_sname, buf, buflen))) {
1526         jio_snprintf(buf, buflen, "%s", dlinfo.dli_sname);
1527       }
1528       if (offset != NULL) *offset = addr - (address)dlinfo.dli_saddr;
1529       return true;
1530     }
1531     // no matching symbol so try for just file info
1532     if (dlinfo.dli_fname != NULL && dlinfo.dli_fbase != NULL) {
1533       if (Decoder::decode((address)(addr - (address)dlinfo.dli_fbase),
1534                           buf, buflen, offset, dlinfo.dli_fname, demangle)) {
1535         return true;
1536       }
1537     }
1538   }
1539 
1540   buf[0] = '\0';
1541   if (offset != NULL) *offset = -1;
1542   return false;
1543 }
1544 
1545 struct _address_to_library_name {
1546   address addr;          // input : memory address
1547   size_t  buflen;        //         size of fname
1548   char*   fname;         // output: library name
1549   address base;          //         library base addr
1550 };
1551 
1552 static int address_to_library_name_callback(struct dl_phdr_info *info,
1553                                             size_t size, void *data) {
1554   int i;
1555   bool found = false;
1556   address libbase = NULL;
1557   struct _address_to_library_name * d = (struct _address_to_library_name *)data;
1558 
1559   // iterate through all loadable segments
1560   for (i = 0; i < info->dlpi_phnum; i++) {
1561     address segbase = (address)(info->dlpi_addr + info->dlpi_phdr[i].p_vaddr);
1562     if (info->dlpi_phdr[i].p_type == PT_LOAD) {
1563       // base address of a library is the lowest address of its loaded
1564       // segments.
1565       if (libbase == NULL || libbase > segbase) {
1566         libbase = segbase;
1567       }
1568       // see if 'addr' is within current segment
1569       if (segbase <= d->addr &&
1570           d->addr < segbase + info->dlpi_phdr[i].p_memsz) {
1571         found = true;
1572       }
1573     }
1574   }
1575 
1576   // dlpi_name is NULL or empty if the ELF file is executable, return 0
1577   // so dll_address_to_library_name() can fall through to use dladdr() which
1578   // can figure out executable name from argv[0].
1579   if (found && info->dlpi_name && info->dlpi_name[0]) {
1580     d->base = libbase;
1581     if (d->fname) {
1582       jio_snprintf(d->fname, d->buflen, "%s", info->dlpi_name);
1583     }
1584     return 1;
1585   }
1586   return 0;
1587 }
1588 
1589 bool os::dll_address_to_library_name(address addr, char* buf,
1590                                      int buflen, int* offset) {
1591   // buf is not optional, but offset is optional
1592   assert(buf != NULL, "sanity check");
1593 
1594   Dl_info dlinfo;
1595   struct _address_to_library_name data;
1596 
1597   // There is a bug in old glibc dladdr() implementation that it could resolve
1598   // to wrong library name if the .so file has a base address != NULL. Here
1599   // we iterate through the program headers of all loaded libraries to find
1600   // out which library 'addr' really belongs to. This workaround can be
1601   // removed once the minimum requirement for glibc is moved to 2.3.x.
1602   data.addr = addr;
1603   data.fname = buf;
1604   data.buflen = buflen;
1605   data.base = NULL;
1606   int rslt = dl_iterate_phdr(address_to_library_name_callback, (void *)&data);
1607 
1608   if (rslt) {
1609     // buf already contains library name
1610     if (offset) *offset = addr - data.base;
1611     return true;
1612   }
1613   if (dladdr((void*)addr, &dlinfo) != 0) {
1614     if (dlinfo.dli_fname != NULL) {
1615       jio_snprintf(buf, buflen, "%s", dlinfo.dli_fname);
1616     }
1617     if (dlinfo.dli_fbase != NULL && offset != NULL) {
1618       *offset = addr - (address)dlinfo.dli_fbase;
1619     }
1620     return true;
1621   }
1622 
1623   buf[0] = '\0';
1624   if (offset) *offset = -1;
1625   return false;
1626 }
1627 
1628 // Loads .dll/.so and
1629 // in case of error it checks if .dll/.so was built for the
1630 // same architecture as Hotspot is running on
1631 
1632 
1633 // Remember the stack's state. The Linux dynamic linker will change
1634 // the stack to 'executable' at most once, so we must safepoint only once.
1635 bool os::Linux::_stack_is_executable = false;
1636 
1637 // VM operation that loads a library.  This is necessary if stack protection
1638 // of the Java stacks can be lost during loading the library.  If we
1639 // do not stop the Java threads, they can stack overflow before the stacks
1640 // are protected again.
1641 class VM_LinuxDllLoad: public VM_Operation {
1642  private:
1643   const char *_filename;
1644   char *_ebuf;
1645   int _ebuflen;
1646   void *_lib;
1647  public:
1648   VM_LinuxDllLoad(const char *fn, char *ebuf, int ebuflen) :
1649     _filename(fn), _ebuf(ebuf), _ebuflen(ebuflen), _lib(NULL) {}
1650   VMOp_Type type() const { return VMOp_LinuxDllLoad; }
1651   void doit() {
1652     _lib = os::Linux::dll_load_in_vmthread(_filename, _ebuf, _ebuflen);
1653     os::Linux::_stack_is_executable = true;
1654   }
1655   void* loaded_library() { return _lib; }
1656 };
1657 
1658 void * os::dll_load(const char *filename, char *ebuf, int ebuflen) {
1659   void * result = NULL;
1660   bool load_attempted = false;
1661 
1662   // Check whether the library to load might change execution rights
1663   // of the stack. If they are changed, the protection of the stack
1664   // guard pages will be lost. We need a safepoint to fix this.
1665   //
1666   // See Linux man page execstack(8) for more info.
1667   if (os::uses_stack_guard_pages() && !os::Linux::_stack_is_executable) {
1668     ElfFile ef(filename);
1669     if (!ef.specifies_noexecstack()) {
1670       if (!is_init_completed()) {
1671         os::Linux::_stack_is_executable = true;
1672         // This is OK - No Java threads have been created yet, and hence no
1673         // stack guard pages to fix.
1674         //
1675         // This should happen only when you are building JDK7 using a very
1676         // old version of JDK6 (e.g., with JPRT) and running test_gamma.
1677         //
1678         // Dynamic loader will make all stacks executable after
1679         // this function returns, and will not do that again.
1680         assert(Threads::first() == NULL, "no Java threads should exist yet.");
1681       } else {
1682         warning("You have loaded library %s which might have disabled stack guard. "
1683                 "The VM will try to fix the stack guard now.\n"
1684                 "It's highly recommended that you fix the library with "
1685                 "'execstack -c <libfile>', or link it with '-z noexecstack'.",
1686                 filename);
1687 
1688         assert(Thread::current()->is_Java_thread(), "must be Java thread");
1689         JavaThread *jt = JavaThread::current();
1690         if (jt->thread_state() != _thread_in_native) {
1691           // This happens when a compiler thread tries to load a hsdis-<arch>.so file
1692           // that requires ExecStack. Cannot enter safe point. Let's give up.
1693           warning("Unable to fix stack guard. Giving up.");
1694         } else {
1695           if (!LoadExecStackDllInVMThread) {
1696             // This is for the case where the DLL has an static
1697             // constructor function that executes JNI code. We cannot
1698             // load such DLLs in the VMThread.
1699             result = os::Linux::dlopen_helper(filename, ebuf, ebuflen);
1700           }
1701 
1702           ThreadInVMfromNative tiv(jt);
1703           debug_only(VMNativeEntryWrapper vew;)
1704 
1705           VM_LinuxDllLoad op(filename, ebuf, ebuflen);
1706           VMThread::execute(&op);
1707           if (LoadExecStackDllInVMThread) {
1708             result = op.loaded_library();
1709           }
1710           load_attempted = true;
1711         }
1712       }
1713     }
1714   }
1715 
1716   if (!load_attempted) {
1717     result = os::Linux::dlopen_helper(filename, ebuf, ebuflen);
1718   }
1719 
1720   if (result != NULL) {
1721     // Successful loading
1722     return result;
1723   }
1724 
1725   Elf32_Ehdr elf_head;
1726   int diag_msg_max_length=ebuflen-strlen(ebuf);
1727   char* diag_msg_buf=ebuf+strlen(ebuf);
1728 
1729   if (diag_msg_max_length==0) {
1730     // No more space in ebuf for additional diagnostics message
1731     return NULL;
1732   }
1733 
1734 
1735   int file_descriptor= ::open(filename, O_RDONLY | O_NONBLOCK);
1736 
1737   if (file_descriptor < 0) {
1738     // Can't open library, report dlerror() message
1739     return NULL;
1740   }
1741 
1742   bool failed_to_read_elf_head=
1743     (sizeof(elf_head)!=
1744      (::read(file_descriptor, &elf_head,sizeof(elf_head))));
1745 
1746   ::close(file_descriptor);
1747   if (failed_to_read_elf_head) {
1748     // file i/o error - report dlerror() msg
1749     return NULL;
1750   }
1751 
1752   typedef struct {
1753     Elf32_Half  code;         // Actual value as defined in elf.h
1754     Elf32_Half  compat_class; // Compatibility of archs at VM's sense
1755     char        elf_class;    // 32 or 64 bit
1756     char        endianess;    // MSB or LSB
1757     char*       name;         // String representation
1758   } arch_t;
1759 
1760 #ifndef EM_486
1761   #define EM_486          6               /* Intel 80486 */
1762 #endif
1763 #ifndef EM_AARCH64
1764   #define EM_AARCH64    183               /* ARM AARCH64 */
1765 #endif
1766 
1767   static const arch_t arch_array[]={
1768     {EM_386,         EM_386,     ELFCLASS32, ELFDATA2LSB, (char*)"IA 32"},
1769     {EM_486,         EM_386,     ELFCLASS32, ELFDATA2LSB, (char*)"IA 32"},
1770     {EM_IA_64,       EM_IA_64,   ELFCLASS64, ELFDATA2LSB, (char*)"IA 64"},
1771     {EM_X86_64,      EM_X86_64,  ELFCLASS64, ELFDATA2LSB, (char*)"AMD 64"},
1772     {EM_SPARC,       EM_SPARC,   ELFCLASS32, ELFDATA2MSB, (char*)"Sparc 32"},
1773     {EM_SPARC32PLUS, EM_SPARC,   ELFCLASS32, ELFDATA2MSB, (char*)"Sparc 32"},
1774     {EM_SPARCV9,     EM_SPARCV9, ELFCLASS64, ELFDATA2MSB, (char*)"Sparc v9 64"},
1775     {EM_PPC,         EM_PPC,     ELFCLASS32, ELFDATA2MSB, (char*)"Power PC 32"},
1776 #if defined(VM_LITTLE_ENDIAN)
1777     {EM_PPC64,       EM_PPC64,   ELFCLASS64, ELFDATA2LSB, (char*)"Power PC 64"},
1778 #else
1779     {EM_PPC64,       EM_PPC64,   ELFCLASS64, ELFDATA2MSB, (char*)"Power PC 64"},
1780 #endif
1781     {EM_ARM,         EM_ARM,     ELFCLASS32,   ELFDATA2LSB, (char*)"ARM"},
1782     {EM_S390,        EM_S390,    ELFCLASSNONE, ELFDATA2MSB, (char*)"IBM System/390"},
1783     {EM_ALPHA,       EM_ALPHA,   ELFCLASS64, ELFDATA2LSB, (char*)"Alpha"},
1784     {EM_MIPS_RS3_LE, EM_MIPS_RS3_LE, ELFCLASS32, ELFDATA2LSB, (char*)"MIPSel"},
1785     {EM_MIPS,        EM_MIPS,    ELFCLASS32, ELFDATA2MSB, (char*)"MIPS"},
1786     {EM_PARISC,      EM_PARISC,  ELFCLASS32, ELFDATA2MSB, (char*)"PARISC"},
1787     {EM_68K,         EM_68K,     ELFCLASS32, ELFDATA2MSB, (char*)"M68k"},
1788     {EM_AARCH64,     EM_AARCH64, ELFCLASS64, ELFDATA2LSB, (char*)"AARCH64"},
1789   };
1790 
1791 #if  (defined IA32)
1792   static  Elf32_Half running_arch_code=EM_386;
1793 #elif   (defined AMD64)
1794   static  Elf32_Half running_arch_code=EM_X86_64;
1795 #elif  (defined IA64)
1796   static  Elf32_Half running_arch_code=EM_IA_64;
1797 #elif  (defined __sparc) && (defined _LP64)
1798   static  Elf32_Half running_arch_code=EM_SPARCV9;
1799 #elif  (defined __sparc) && (!defined _LP64)
1800   static  Elf32_Half running_arch_code=EM_SPARC;
1801 #elif  (defined __powerpc64__)
1802   static  Elf32_Half running_arch_code=EM_PPC64;
1803 #elif  (defined __powerpc__)
1804   static  Elf32_Half running_arch_code=EM_PPC;
1805 #elif  (defined ARM)
1806   static  Elf32_Half running_arch_code=EM_ARM;
1807 #elif  (defined S390)
1808   static  Elf32_Half running_arch_code=EM_S390;
1809 #elif  (defined ALPHA)
1810   static  Elf32_Half running_arch_code=EM_ALPHA;
1811 #elif  (defined MIPSEL)
1812   static  Elf32_Half running_arch_code=EM_MIPS_RS3_LE;
1813 #elif  (defined PARISC)
1814   static  Elf32_Half running_arch_code=EM_PARISC;
1815 #elif  (defined MIPS)
1816   static  Elf32_Half running_arch_code=EM_MIPS;
1817 #elif  (defined M68K)
1818   static  Elf32_Half running_arch_code=EM_68K;
1819 #elif  (defined AARCH64)
1820   static  Elf32_Half running_arch_code=EM_AARCH64;
1821 #else
1822     #error Method os::dll_load requires that one of following is defined:\
1823          IA32, AMD64, IA64, __sparc, __powerpc__, ARM, S390, ALPHA, MIPS, MIPSEL, PARISC, M68K, AARCH64
1824 #endif
1825 
1826   // Identify compatability class for VM's architecture and library's architecture
1827   // Obtain string descriptions for architectures
1828 
1829   arch_t lib_arch={elf_head.e_machine,0,elf_head.e_ident[EI_CLASS], elf_head.e_ident[EI_DATA], NULL};
1830   int running_arch_index=-1;
1831 
1832   for (unsigned int i=0; i < ARRAY_SIZE(arch_array); i++) {
1833     if (running_arch_code == arch_array[i].code) {
1834       running_arch_index    = i;
1835     }
1836     if (lib_arch.code == arch_array[i].code) {
1837       lib_arch.compat_class = arch_array[i].compat_class;
1838       lib_arch.name         = arch_array[i].name;
1839     }
1840   }
1841 
1842   assert(running_arch_index != -1,
1843          "Didn't find running architecture code (running_arch_code) in arch_array");
1844   if (running_arch_index == -1) {
1845     // Even though running architecture detection failed
1846     // we may still continue with reporting dlerror() message
1847     return NULL;
1848   }
1849 
1850   if (lib_arch.endianess != arch_array[running_arch_index].endianess) {
1851     ::snprintf(diag_msg_buf, diag_msg_max_length-1," (Possible cause: endianness mismatch)");
1852     return NULL;
1853   }
1854 
1855 #ifndef S390
1856   if (lib_arch.elf_class != arch_array[running_arch_index].elf_class) {
1857     ::snprintf(diag_msg_buf, diag_msg_max_length-1," (Possible cause: architecture word width mismatch)");
1858     return NULL;
1859   }
1860 #endif // !S390
1861 
1862   if (lib_arch.compat_class != arch_array[running_arch_index].compat_class) {
1863     if (lib_arch.name!=NULL) {
1864       ::snprintf(diag_msg_buf, diag_msg_max_length-1,
1865                  " (Possible cause: can't load %s-bit .so on a %s-bit platform)",
1866                  lib_arch.name, arch_array[running_arch_index].name);
1867     } else {
1868       ::snprintf(diag_msg_buf, diag_msg_max_length-1,
1869                  " (Possible cause: can't load this .so (machine code=0x%x) on a %s-bit platform)",
1870                  lib_arch.code,
1871                  arch_array[running_arch_index].name);
1872     }
1873   }
1874 
1875   return NULL;
1876 }
1877 
1878 void * os::Linux::dlopen_helper(const char *filename, char *ebuf,
1879                                 int ebuflen) {
1880   void * result = ::dlopen(filename, RTLD_LAZY);
1881   if (result == NULL) {
1882     ::strncpy(ebuf, ::dlerror(), ebuflen - 1);
1883     ebuf[ebuflen-1] = '\0';
1884   }
1885   return result;
1886 }
1887 
1888 void * os::Linux::dll_load_in_vmthread(const char *filename, char *ebuf,
1889                                        int ebuflen) {
1890   void * result = NULL;
1891   if (LoadExecStackDllInVMThread) {
1892     result = dlopen_helper(filename, ebuf, ebuflen);
1893   }
1894 
1895   // Since 7019808, libjvm.so is linked with -noexecstack. If the VM loads a
1896   // library that requires an executable stack, or which does not have this
1897   // stack attribute set, dlopen changes the stack attribute to executable. The
1898   // read protection of the guard pages gets lost.
1899   //
1900   // Need to check _stack_is_executable again as multiple VM_LinuxDllLoad
1901   // may have been queued at the same time.
1902 
1903   if (!_stack_is_executable) {
1904     JavaThread *jt = Threads::first();
1905 
1906     while (jt) {
1907       if (!jt->stack_guard_zone_unused() &&        // Stack not yet fully initialized
1908           jt->stack_yellow_zone_enabled()) {       // No pending stack overflow exceptions
1909         if (!os::guard_memory((char *) jt->stack_red_zone_base() - jt->stack_red_zone_size(),
1910                               jt->stack_yellow_zone_size() + jt->stack_red_zone_size())) {
1911           warning("Attempt to reguard stack yellow zone failed.");
1912         }
1913       }
1914       jt = jt->next();
1915     }
1916   }
1917 
1918   return result;
1919 }
1920 
1921 void* os::dll_lookup(void* handle, const char* name) {
1922   void* res = dlsym(handle, name);
1923   return res;
1924 }
1925 
1926 void* os::get_default_process_handle() {
1927   return (void*)::dlopen(NULL, RTLD_LAZY);
1928 }
1929 
1930 static bool _print_ascii_file(const char* filename, outputStream* st) {
1931   int fd = ::open(filename, O_RDONLY);
1932   if (fd == -1) {
1933     return false;
1934   }
1935 
1936   char buf[32];
1937   int bytes;
1938   while ((bytes = ::read(fd, buf, sizeof(buf))) > 0) {
1939     st->print_raw(buf, bytes);
1940   }
1941 
1942   ::close(fd);
1943 
1944   return true;
1945 }
1946 
1947 void os::print_dll_info(outputStream *st) {
1948   st->print_cr("Dynamic libraries:");
1949 
1950   char fname[32];
1951   pid_t pid = os::Linux::gettid();
1952 
1953   jio_snprintf(fname, sizeof(fname), "/proc/%d/maps", pid);
1954 
1955   if (!_print_ascii_file(fname, st)) {
1956     st->print("Can not get library information for pid = %d\n", pid);
1957   }
1958 }
1959 
1960 int os::get_loaded_modules_info(os::LoadedModulesCallbackFunc callback, void *param) {
1961   FILE *procmapsFile = NULL;
1962 
1963   // Open the procfs maps file for the current process
1964   if ((procmapsFile = fopen("/proc/self/maps", "r")) != NULL) {
1965     // Allocate PATH_MAX for file name plus a reasonable size for other fields.
1966     char line[PATH_MAX + 100];
1967 
1968     // Read line by line from 'file'
1969     while (fgets(line, sizeof(line), procmapsFile) != NULL) {
1970       u8 base, top, offset, inode;
1971       char permissions[5];
1972       char device[6];
1973       char name[PATH_MAX + 1];
1974 
1975       // Parse fields from line
1976       sscanf(line, "%lx-%lx %4s %lx %5s %ld %s", &base, &top, permissions, &offset, device, &inode, name);
1977 
1978       // Filter by device id '00:00' so that we only get file system mapped files.
1979       if (strcmp(device, "00:00") != 0) {
1980 
1981         // Call callback with the fields of interest
1982         if(callback(name, (address)base, (address)top, param)) {
1983           // Oops abort, callback aborted
1984           fclose(procmapsFile);
1985           return 1;
1986         }
1987       }
1988     }
1989     fclose(procmapsFile);
1990   }
1991   return 0;
1992 }
1993 
1994 void os::print_os_info_brief(outputStream* st) {
1995   os::Linux::print_distro_info(st);
1996 
1997   os::Posix::print_uname_info(st);
1998 
1999   os::Linux::print_libversion_info(st);
2000 
2001 }
2002 
2003 void os::print_os_info(outputStream* st) {
2004   st->print("OS:");
2005 
2006   os::Linux::print_distro_info(st);
2007 
2008   os::Posix::print_uname_info(st);
2009 
2010   // Print warning if unsafe chroot environment detected
2011   if (unsafe_chroot_detected) {
2012     st->print("WARNING!! ");
2013     st->print_cr("%s", unstable_chroot_error);
2014   }
2015 
2016   os::Linux::print_libversion_info(st);
2017 
2018   os::Posix::print_rlimit_info(st);
2019 
2020   os::Posix::print_load_average(st);
2021 
2022   os::Linux::print_full_memory_info(st);
2023 }
2024 
2025 // Try to identify popular distros.
2026 // Most Linux distributions have a /etc/XXX-release file, which contains
2027 // the OS version string. Newer Linux distributions have a /etc/lsb-release
2028 // file that also contains the OS version string. Some have more than one
2029 // /etc/XXX-release file (e.g. Mandrake has both /etc/mandrake-release and
2030 // /etc/redhat-release.), so the order is important.
2031 // Any Linux that is based on Redhat (i.e. Oracle, Mandrake, Sun JDS...) have
2032 // their own specific XXX-release file as well as a redhat-release file.
2033 // Because of this the XXX-release file needs to be searched for before the
2034 // redhat-release file.
2035 // Since Red Hat has a lsb-release file that is not very descriptive the
2036 // search for redhat-release needs to be before lsb-release.
2037 // Since the lsb-release file is the new standard it needs to be searched
2038 // before the older style release files.
2039 // Searching system-release (Red Hat) and os-release (other Linuxes) are a
2040 // next to last resort.  The os-release file is a new standard that contains
2041 // distribution information and the system-release file seems to be an old
2042 // standard that has been replaced by the lsb-release and os-release files.
2043 // Searching for the debian_version file is the last resort.  It contains
2044 // an informative string like "6.0.6" or "wheezy/sid". Because of this
2045 // "Debian " is printed before the contents of the debian_version file.
2046 void os::Linux::print_distro_info(outputStream* st) {
2047   if (!_print_ascii_file("/etc/oracle-release", st) &&
2048       !_print_ascii_file("/etc/mandriva-release", st) &&
2049       !_print_ascii_file("/etc/mandrake-release", st) &&
2050       !_print_ascii_file("/etc/sun-release", st) &&
2051       !_print_ascii_file("/etc/redhat-release", st) &&
2052       !_print_ascii_file("/etc/lsb-release", st) &&
2053       !_print_ascii_file("/etc/SuSE-release", st) &&
2054       !_print_ascii_file("/etc/turbolinux-release", st) &&
2055       !_print_ascii_file("/etc/gentoo-release", st) &&
2056       !_print_ascii_file("/etc/ltib-release", st) &&
2057       !_print_ascii_file("/etc/angstrom-version", st) &&
2058       !_print_ascii_file("/etc/system-release", st) &&
2059       !_print_ascii_file("/etc/os-release", st)) {
2060 























2061     if (file_exists("/etc/debian_version")) {
2062       st->print("Debian ");
2063       _print_ascii_file("/etc/debian_version", st);
2064     } else {
2065       st->print("Linux");
2066     }
2067   }
2068   st->cr();
2069 }
2070 
















































2071 void os::Linux::print_libversion_info(outputStream* st) {
2072   // libc, pthread
2073   st->print("libc:");
2074   st->print("%s ", os::Linux::glibc_version());
2075   st->print("%s ", os::Linux::libpthread_version());
2076   st->cr();
2077 }
2078 
2079 void os::Linux::print_full_memory_info(outputStream* st) {
2080   st->print("\n/proc/meminfo:\n");
2081   _print_ascii_file("/proc/meminfo", st);
2082   st->cr();
2083 }
2084 
2085 void os::print_memory_info(outputStream* st) {
2086 
2087   st->print("Memory:");
2088   st->print(" %dk page", os::vm_page_size()>>10);
2089 
2090   // values in struct sysinfo are "unsigned long"
2091   struct sysinfo si;
2092   sysinfo(&si);
2093 
2094   st->print(", physical " UINT64_FORMAT "k",
2095             os::physical_memory() >> 10);
2096   st->print("(" UINT64_FORMAT "k free)",
2097             os::available_memory() >> 10);
2098   st->print(", swap " UINT64_FORMAT "k",
2099             ((jlong)si.totalswap * si.mem_unit) >> 10);
2100   st->print("(" UINT64_FORMAT "k free)",
2101             ((jlong)si.freeswap * si.mem_unit) >> 10);
2102   st->cr();
2103 }
2104 
2105 // Print the first "model name" line and the first "flags" line
2106 // that we find and nothing more. We assume "model name" comes
2107 // before "flags" so if we find a second "model name", then the
2108 // "flags" field is considered missing.
2109 static bool print_model_name_and_flags(outputStream* st, char* buf, size_t buflen) {
2110 #if defined(IA32) || defined(AMD64)
2111   // Other platforms have less repetitive cpuinfo files
2112   FILE *fp = fopen("/proc/cpuinfo", "r");
2113   if (fp) {
2114     while (!feof(fp)) {
2115       if (fgets(buf, buflen, fp)) {
2116         // Assume model name comes before flags
2117         bool model_name_printed = false;
2118         if (strstr(buf, "model name") != NULL) {
2119           if (!model_name_printed) {
2120             st->print_raw("\nCPU Model and flags from /proc/cpuinfo:\n");
2121             st->print_raw(buf);
2122             model_name_printed = true;
2123           } else {
2124             // model name printed but not flags?  Odd, just return
2125             fclose(fp);
2126             return true;
2127           }
2128         }
2129         // print the flags line too
2130         if (strstr(buf, "flags") != NULL) {
2131           st->print_raw(buf);
2132           fclose(fp);
2133           return true;
2134         }
2135       }
2136     }
2137     fclose(fp);
2138   }
2139 #endif // x86 platforms
2140   return false;
2141 }
2142 
2143 void os::pd_print_cpu_info(outputStream* st, char* buf, size_t buflen) {
2144   // Only print the model name if the platform provides this as a summary
2145   if (!print_model_name_and_flags(st, buf, buflen)) {
2146     st->print("\n/proc/cpuinfo:\n");
2147     if (!_print_ascii_file("/proc/cpuinfo", st)) {
2148       st->print_cr("  <Not Available>");
2149     }
2150   }









































2151 }
2152 
2153 void os::print_siginfo(outputStream* st, void* siginfo) {
2154   const siginfo_t* si = (const siginfo_t*)siginfo;
2155 
2156   os::Posix::print_siginfo_brief(st, si);
2157 #if INCLUDE_CDS
2158   if (si && (si->si_signo == SIGBUS || si->si_signo == SIGSEGV) &&
2159       UseSharedSpaces) {
2160     FileMapInfo* mapinfo = FileMapInfo::current_info();
2161     if (mapinfo->is_in_shared_space(si->si_addr)) {
2162       st->print("\n\nError accessing class data sharing archive."   \
2163                 " Mapped file inaccessible during execution, "      \
2164                 " possible disk/network problem.");
2165     }
2166   }
2167 #endif
2168   st->cr();
2169 }
2170 
2171 
2172 static void print_signal_handler(outputStream* st, int sig,
2173                                  char* buf, size_t buflen);
2174 
2175 void os::print_signal_handlers(outputStream* st, char* buf, size_t buflen) {
2176   st->print_cr("Signal Handlers:");
2177   print_signal_handler(st, SIGSEGV, buf, buflen);
2178   print_signal_handler(st, SIGBUS , buf, buflen);
2179   print_signal_handler(st, SIGFPE , buf, buflen);
2180   print_signal_handler(st, SIGPIPE, buf, buflen);
2181   print_signal_handler(st, SIGXFSZ, buf, buflen);
2182   print_signal_handler(st, SIGILL , buf, buflen);
2183   print_signal_handler(st, INTERRUPT_SIGNAL, buf, buflen);
2184   print_signal_handler(st, SR_signum, buf, buflen);
2185   print_signal_handler(st, SHUTDOWN1_SIGNAL, buf, buflen);
2186   print_signal_handler(st, SHUTDOWN2_SIGNAL , buf, buflen);
2187   print_signal_handler(st, SHUTDOWN3_SIGNAL , buf, buflen);
2188   print_signal_handler(st, BREAK_SIGNAL, buf, buflen);
2189 #if defined(PPC64)
2190   print_signal_handler(st, SIGTRAP, buf, buflen);
2191 #endif
2192 }
2193 
2194 static char saved_jvm_path[MAXPATHLEN] = {0};
2195 
2196 // Find the full path to the current module, libjvm.so
2197 void os::jvm_path(char *buf, jint buflen) {
2198   // Error checking.
2199   if (buflen < MAXPATHLEN) {
2200     assert(false, "must use a large-enough buffer");
2201     buf[0] = '\0';
2202     return;
2203   }
2204   // Lazy resolve the path to current module.
2205   if (saved_jvm_path[0] != 0) {
2206     strcpy(buf, saved_jvm_path);
2207     return;
2208   }
2209 
2210   char dli_fname[MAXPATHLEN];
2211   bool ret = dll_address_to_library_name(
2212                                          CAST_FROM_FN_PTR(address, os::jvm_path),
2213                                          dli_fname, sizeof(dli_fname), NULL);
2214   assert(ret, "cannot locate libjvm");
2215   char *rp = NULL;
2216   if (ret && dli_fname[0] != '\0') {
2217     rp = realpath(dli_fname, buf);
2218   }
2219   if (rp == NULL) {
2220     return;
2221   }
2222 
2223   if (Arguments::sun_java_launcher_is_altjvm()) {
2224     // Support for the java launcher's '-XXaltjvm=<path>' option. Typical
2225     // value for buf is "<JAVA_HOME>/jre/lib/<arch>/<vmtype>/libjvm.so".
2226     // If "/jre/lib/" appears at the right place in the string, then
2227     // assume we are installed in a JDK and we're done. Otherwise, check
2228     // for a JAVA_HOME environment variable and fix up the path so it
2229     // looks like libjvm.so is installed there (append a fake suffix
2230     // hotspot/libjvm.so).
2231     const char *p = buf + strlen(buf) - 1;
2232     for (int count = 0; p > buf && count < 5; ++count) {
2233       for (--p; p > buf && *p != '/'; --p)
2234         /* empty */ ;
2235     }
2236 
2237     if (strncmp(p, "/jre/lib/", 9) != 0) {
2238       // Look for JAVA_HOME in the environment.
2239       char* java_home_var = ::getenv("JAVA_HOME");
2240       if (java_home_var != NULL && java_home_var[0] != 0) {
2241         char* jrelib_p;
2242         int len;
2243 
2244         // Check the current module name "libjvm.so".
2245         p = strrchr(buf, '/');
2246         if (p == NULL) {
2247           return;
2248         }
2249         assert(strstr(p, "/libjvm") == p, "invalid library name");
2250 
2251         rp = realpath(java_home_var, buf);
2252         if (rp == NULL) {
2253           return;
2254         }
2255 
2256         // determine if this is a legacy image or modules image
2257         // modules image doesn't have "jre" subdirectory
2258         len = strlen(buf);
2259         assert(len < buflen, "Ran out of buffer room");
2260         jrelib_p = buf + len;
2261         snprintf(jrelib_p, buflen-len, "/jre/lib/%s", cpu_arch);
2262         if (0 != access(buf, F_OK)) {
2263           snprintf(jrelib_p, buflen-len, "/lib/%s", cpu_arch);
2264         }
2265 
2266         if (0 == access(buf, F_OK)) {
2267           // Use current module name "libjvm.so"
2268           len = strlen(buf);
2269           snprintf(buf + len, buflen-len, "/hotspot/libjvm.so");
2270         } else {
2271           // Go back to path of .so
2272           rp = realpath(dli_fname, buf);
2273           if (rp == NULL) {
2274             return;
2275           }
2276         }
2277       }
2278     }
2279   }
2280 
2281   strncpy(saved_jvm_path, buf, MAXPATHLEN);
2282   saved_jvm_path[MAXPATHLEN - 1] = '\0';
2283 }
2284 
2285 void os::print_jni_name_prefix_on(outputStream* st, int args_size) {
2286   // no prefix required, not even "_"
2287 }
2288 
2289 void os::print_jni_name_suffix_on(outputStream* st, int args_size) {
2290   // no suffix required
2291 }
2292 
2293 ////////////////////////////////////////////////////////////////////////////////
2294 // sun.misc.Signal support
2295 
2296 static volatile jint sigint_count = 0;
2297 
2298 static void UserHandler(int sig, void *siginfo, void *context) {
2299   // 4511530 - sem_post is serialized and handled by the manager thread. When
2300   // the program is interrupted by Ctrl-C, SIGINT is sent to every thread. We
2301   // don't want to flood the manager thread with sem_post requests.
2302   if (sig == SIGINT && Atomic::add(1, &sigint_count) > 1) {
2303     return;
2304   }
2305 
2306   // Ctrl-C is pressed during error reporting, likely because the error
2307   // handler fails to abort. Let VM die immediately.
2308   if (sig == SIGINT && is_error_reported()) {
2309     os::die();
2310   }
2311 
2312   os::signal_notify(sig);
2313 }
2314 
2315 void* os::user_handler() {
2316   return CAST_FROM_FN_PTR(void*, UserHandler);
2317 }
2318 
2319 struct timespec PosixSemaphore::create_timespec(unsigned int sec, int nsec) {
2320   struct timespec ts;
2321   // Semaphore's are always associated with CLOCK_REALTIME
2322   os::Linux::clock_gettime(CLOCK_REALTIME, &ts);
2323   // see unpackTime for discussion on overflow checking
2324   if (sec >= MAX_SECS) {
2325     ts.tv_sec += MAX_SECS;
2326     ts.tv_nsec = 0;
2327   } else {
2328     ts.tv_sec += sec;
2329     ts.tv_nsec += nsec;
2330     if (ts.tv_nsec >= NANOSECS_PER_SEC) {
2331       ts.tv_nsec -= NANOSECS_PER_SEC;
2332       ++ts.tv_sec; // note: this must be <= max_secs
2333     }
2334   }
2335 
2336   return ts;
2337 }
2338 
2339 extern "C" {
2340   typedef void (*sa_handler_t)(int);
2341   typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
2342 }
2343 
2344 void* os::signal(int signal_number, void* handler) {
2345   struct sigaction sigAct, oldSigAct;
2346 
2347   sigfillset(&(sigAct.sa_mask));
2348   sigAct.sa_flags   = SA_RESTART|SA_SIGINFO;
2349   sigAct.sa_handler = CAST_TO_FN_PTR(sa_handler_t, handler);
2350 
2351   if (sigaction(signal_number, &sigAct, &oldSigAct)) {
2352     // -1 means registration failed
2353     return (void *)-1;
2354   }
2355 
2356   return CAST_FROM_FN_PTR(void*, oldSigAct.sa_handler);
2357 }
2358 
2359 void os::signal_raise(int signal_number) {
2360   ::raise(signal_number);
2361 }
2362 
2363 // The following code is moved from os.cpp for making this
2364 // code platform specific, which it is by its very nature.
2365 
2366 // Will be modified when max signal is changed to be dynamic
2367 int os::sigexitnum_pd() {
2368   return NSIG;
2369 }
2370 
2371 // a counter for each possible signal value
2372 static volatile jint pending_signals[NSIG+1] = { 0 };
2373 
2374 // Linux(POSIX) specific hand shaking semaphore.
2375 static sem_t sig_sem;
2376 static PosixSemaphore sr_semaphore;
2377 
2378 void os::signal_init_pd() {
2379   // Initialize signal structures
2380   ::memset((void*)pending_signals, 0, sizeof(pending_signals));
2381 
2382   // Initialize signal semaphore
2383   ::sem_init(&sig_sem, 0, 0);
2384 }
2385 
2386 void os::signal_notify(int sig) {
2387   Atomic::inc(&pending_signals[sig]);
2388   ::sem_post(&sig_sem);
2389 }
2390 
2391 static int check_pending_signals(bool wait) {
2392   Atomic::store(0, &sigint_count);
2393   for (;;) {
2394     for (int i = 0; i < NSIG + 1; i++) {
2395       jint n = pending_signals[i];
2396       if (n > 0 && n == Atomic::cmpxchg(n - 1, &pending_signals[i], n)) {
2397         return i;
2398       }
2399     }
2400     if (!wait) {
2401       return -1;
2402     }
2403     JavaThread *thread = JavaThread::current();
2404     ThreadBlockInVM tbivm(thread);
2405 
2406     bool threadIsSuspended;
2407     do {
2408       thread->set_suspend_equivalent();
2409       // cleared by handle_special_suspend_equivalent_condition() or java_suspend_self()
2410       ::sem_wait(&sig_sem);
2411 
2412       // were we externally suspended while we were waiting?
2413       threadIsSuspended = thread->handle_special_suspend_equivalent_condition();
2414       if (threadIsSuspended) {
2415         // The semaphore has been incremented, but while we were waiting
2416         // another thread suspended us. We don't want to continue running
2417         // while suspended because that would surprise the thread that
2418         // suspended us.
2419         ::sem_post(&sig_sem);
2420 
2421         thread->java_suspend_self();
2422       }
2423     } while (threadIsSuspended);
2424   }
2425 }
2426 
2427 int os::signal_lookup() {
2428   return check_pending_signals(false);
2429 }
2430 
2431 int os::signal_wait() {
2432   return check_pending_signals(true);
2433 }
2434 
2435 ////////////////////////////////////////////////////////////////////////////////
2436 // Virtual Memory
2437 
2438 int os::vm_page_size() {
2439   // Seems redundant as all get out
2440   assert(os::Linux::page_size() != -1, "must call os::init");
2441   return os::Linux::page_size();
2442 }
2443 
2444 // Solaris allocates memory by pages.
2445 int os::vm_allocation_granularity() {
2446   assert(os::Linux::page_size() != -1, "must call os::init");
2447   return os::Linux::page_size();
2448 }
2449 
2450 // Rationale behind this function:
2451 //  current (Mon Apr 25 20:12:18 MSD 2005) oprofile drops samples without executable
2452 //  mapping for address (see lookup_dcookie() in the kernel module), thus we cannot get
2453 //  samples for JITted code. Here we create private executable mapping over the code cache
2454 //  and then we can use standard (well, almost, as mapping can change) way to provide
2455 //  info for the reporting script by storing timestamp and location of symbol
2456 void linux_wrap_code(char* base, size_t size) {
2457   static volatile jint cnt = 0;
2458 
2459   if (!UseOprofile) {
2460     return;
2461   }
2462 
2463   char buf[PATH_MAX+1];
2464   int num = Atomic::add(1, &cnt);
2465 
2466   snprintf(buf, sizeof(buf), "%s/hs-vm-%d-%d",
2467            os::get_temp_directory(), os::current_process_id(), num);
2468   unlink(buf);
2469 
2470   int fd = ::open(buf, O_CREAT | O_RDWR, S_IRWXU);
2471 
2472   if (fd != -1) {
2473     off_t rv = ::lseek(fd, size-2, SEEK_SET);
2474     if (rv != (off_t)-1) {
2475       if (::write(fd, "", 1) == 1) {
2476         mmap(base, size,
2477              PROT_READ|PROT_WRITE|PROT_EXEC,
2478              MAP_PRIVATE|MAP_FIXED|MAP_NORESERVE, fd, 0);
2479       }
2480     }
2481     ::close(fd);
2482     unlink(buf);
2483   }
2484 }
2485 
2486 static bool recoverable_mmap_error(int err) {
2487   // See if the error is one we can let the caller handle. This
2488   // list of errno values comes from JBS-6843484. I can't find a
2489   // Linux man page that documents this specific set of errno
2490   // values so while this list currently matches Solaris, it may
2491   // change as we gain experience with this failure mode.
2492   switch (err) {
2493   case EBADF:
2494   case EINVAL:
2495   case ENOTSUP:
2496     // let the caller deal with these errors
2497     return true;
2498 
2499   default:
2500     // Any remaining errors on this OS can cause our reserved mapping
2501     // to be lost. That can cause confusion where different data
2502     // structures think they have the same memory mapped. The worst
2503     // scenario is if both the VM and a library think they have the
2504     // same memory mapped.
2505     return false;
2506   }
2507 }
2508 
2509 static void warn_fail_commit_memory(char* addr, size_t size, bool exec,
2510                                     int err) {
2511   warning("INFO: os::commit_memory(" PTR_FORMAT ", " SIZE_FORMAT
2512           ", %d) failed; error='%s' (errno=%d)", addr, size, exec,
2513           strerror(err), err);
2514 }
2515 
2516 static void warn_fail_commit_memory(char* addr, size_t size,
2517                                     size_t alignment_hint, bool exec,
2518                                     int err) {
2519   warning("INFO: os::commit_memory(" PTR_FORMAT ", " SIZE_FORMAT
2520           ", " SIZE_FORMAT ", %d) failed; error='%s' (errno=%d)", addr, size,
2521           alignment_hint, exec, strerror(err), err);
2522 }
2523 
2524 // NOTE: Linux kernel does not really reserve the pages for us.
2525 //       All it does is to check if there are enough free pages
2526 //       left at the time of mmap(). This could be a potential
2527 //       problem.
2528 int os::Linux::commit_memory_impl(char* addr, size_t size, bool exec) {
2529   int prot = exec ? PROT_READ|PROT_WRITE|PROT_EXEC : PROT_READ|PROT_WRITE;
2530   uintptr_t res = (uintptr_t) ::mmap(addr, size, prot,
2531                                      MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0);
2532   if (res != (uintptr_t) MAP_FAILED) {
2533     if (UseNUMAInterleaving) {
2534       numa_make_global(addr, size);
2535     }
2536     return 0;
2537   }
2538 
2539   int err = errno;  // save errno from mmap() call above
2540 
2541   if (!recoverable_mmap_error(err)) {
2542     warn_fail_commit_memory(addr, size, exec, err);
2543     vm_exit_out_of_memory(size, OOM_MMAP_ERROR, "committing reserved memory.");
2544   }
2545 
2546   return err;
2547 }
2548 
2549 bool os::pd_commit_memory(char* addr, size_t size, bool exec) {
2550   return os::Linux::commit_memory_impl(addr, size, exec) == 0;
2551 }
2552 
2553 void os::pd_commit_memory_or_exit(char* addr, size_t size, bool exec,
2554                                   const char* mesg) {
2555   assert(mesg != NULL, "mesg must be specified");
2556   int err = os::Linux::commit_memory_impl(addr, size, exec);
2557   if (err != 0) {
2558     // the caller wants all commit errors to exit with the specified mesg:
2559     warn_fail_commit_memory(addr, size, exec, err);
2560     vm_exit_out_of_memory(size, OOM_MMAP_ERROR, mesg);
2561   }
2562 }
2563 
2564 // Define MAP_HUGETLB here so we can build HotSpot on old systems.
2565 #ifndef MAP_HUGETLB
2566   #define MAP_HUGETLB 0x40000
2567 #endif
2568 
2569 // Define MADV_HUGEPAGE here so we can build HotSpot on old systems.
2570 #ifndef MADV_HUGEPAGE
2571   #define MADV_HUGEPAGE 14
2572 #endif
2573 
2574 int os::Linux::commit_memory_impl(char* addr, size_t size,
2575                                   size_t alignment_hint, bool exec) {
2576   int err = os::Linux::commit_memory_impl(addr, size, exec);
2577   if (err == 0) {
2578     realign_memory(addr, size, alignment_hint);
2579   }
2580   return err;
2581 }
2582 
2583 bool os::pd_commit_memory(char* addr, size_t size, size_t alignment_hint,
2584                           bool exec) {
2585   return os::Linux::commit_memory_impl(addr, size, alignment_hint, exec) == 0;
2586 }
2587 
2588 void os::pd_commit_memory_or_exit(char* addr, size_t size,
2589                                   size_t alignment_hint, bool exec,
2590                                   const char* mesg) {
2591   assert(mesg != NULL, "mesg must be specified");
2592   int err = os::Linux::commit_memory_impl(addr, size, alignment_hint, exec);
2593   if (err != 0) {
2594     // the caller wants all commit errors to exit with the specified mesg:
2595     warn_fail_commit_memory(addr, size, alignment_hint, exec, err);
2596     vm_exit_out_of_memory(size, OOM_MMAP_ERROR, mesg);
2597   }
2598 }
2599 
2600 void os::pd_realign_memory(char *addr, size_t bytes, size_t alignment_hint) {
2601   if (UseTransparentHugePages && alignment_hint > (size_t)vm_page_size()) {
2602     // We don't check the return value: madvise(MADV_HUGEPAGE) may not
2603     // be supported or the memory may already be backed by huge pages.
2604     ::madvise(addr, bytes, MADV_HUGEPAGE);
2605   }
2606 }
2607 
2608 void os::pd_free_memory(char *addr, size_t bytes, size_t alignment_hint) {
2609   // This method works by doing an mmap over an existing mmaping and effectively discarding
2610   // the existing pages. However it won't work for SHM-based large pages that cannot be
2611   // uncommitted at all. We don't do anything in this case to avoid creating a segment with
2612   // small pages on top of the SHM segment. This method always works for small pages, so we
2613   // allow that in any case.
2614   if (alignment_hint <= (size_t)os::vm_page_size() || can_commit_large_page_memory()) {
2615     commit_memory(addr, bytes, alignment_hint, !ExecMem);
2616   }
2617 }
2618 
2619 void os::numa_make_global(char *addr, size_t bytes) {
2620   Linux::numa_interleave_memory(addr, bytes);
2621 }
2622 
2623 // Define for numa_set_bind_policy(int). Setting the argument to 0 will set the
2624 // bind policy to MPOL_PREFERRED for the current thread.
2625 #define USE_MPOL_PREFERRED 0
2626 
2627 void os::numa_make_local(char *addr, size_t bytes, int lgrp_hint) {
2628   // To make NUMA and large pages more robust when both enabled, we need to ease
2629   // the requirements on where the memory should be allocated. MPOL_BIND is the
2630   // default policy and it will force memory to be allocated on the specified
2631   // node. Changing this to MPOL_PREFERRED will prefer to allocate the memory on
2632   // the specified node, but will not force it. Using this policy will prevent
2633   // getting SIGBUS when trying to allocate large pages on NUMA nodes with no
2634   // free large pages.
2635   Linux::numa_set_bind_policy(USE_MPOL_PREFERRED);
2636   Linux::numa_tonode_memory(addr, bytes, lgrp_hint);
2637 }
2638 
2639 bool os::numa_topology_changed() { return false; }
2640 
2641 size_t os::numa_get_groups_num() {
2642   int max_node = Linux::numa_max_node();
2643   return max_node > 0 ? max_node + 1 : 1;
2644 }
2645 
2646 int os::numa_get_group_id() {
2647   int cpu_id = Linux::sched_getcpu();
2648   if (cpu_id != -1) {
2649     int lgrp_id = Linux::get_node_by_cpu(cpu_id);
2650     if (lgrp_id != -1) {
2651       return lgrp_id;
2652     }
2653   }
2654   return 0;
2655 }
2656 
2657 size_t os::numa_get_leaf_groups(int *ids, size_t size) {
2658   for (size_t i = 0; i < size; i++) {
2659     ids[i] = i;
2660   }
2661   return size;
2662 }
2663 
2664 bool os::get_page_info(char *start, page_info* info) {
2665   return false;
2666 }
2667 
2668 char *os::scan_pages(char *start, char* end, page_info* page_expected,
2669                      page_info* page_found) {
2670   return end;
2671 }
2672 
2673 
2674 int os::Linux::sched_getcpu_syscall(void) {
2675   unsigned int cpu;
2676   int retval = -1;
2677 
2678 #if defined(IA32)
2679   #ifndef SYS_getcpu
2680     #define SYS_getcpu 318
2681   #endif
2682   retval = syscall(SYS_getcpu, &cpu, NULL, NULL);
2683 #elif defined(AMD64)
2684 // Unfortunately we have to bring all these macros here from vsyscall.h
2685 // to be able to compile on old linuxes.
2686   #define __NR_vgetcpu 2
2687   #define VSYSCALL_START (-10UL << 20)
2688   #define VSYSCALL_SIZE 1024
2689   #define VSYSCALL_ADDR(vsyscall_nr) (VSYSCALL_START+VSYSCALL_SIZE*(vsyscall_nr))
2690   typedef long (*vgetcpu_t)(unsigned int *cpu, unsigned int *node, unsigned long *tcache);
2691   vgetcpu_t vgetcpu = (vgetcpu_t)VSYSCALL_ADDR(__NR_vgetcpu);
2692   retval = vgetcpu(&cpu, NULL, NULL);
2693 #endif
2694 
2695   return (retval == -1) ? retval : cpu;
2696 }
2697 
2698 // Something to do with the numa-aware allocator needs these symbols
2699 extern "C" JNIEXPORT void numa_warn(int number, char *where, ...) { }
2700 extern "C" JNIEXPORT void numa_error(char *where) { }
2701 extern "C" JNIEXPORT int fork1() { return fork(); }
2702 
2703 
2704 // If we are running with libnuma version > 2, then we should
2705 // be trying to use symbols with versions 1.1
2706 // If we are running with earlier version, which did not have symbol versions,
2707 // we should use the base version.
2708 void* os::Linux::libnuma_dlsym(void* handle, const char *name) {
2709   void *f = dlvsym(handle, name, "libnuma_1.1");
2710   if (f == NULL) {
2711     f = dlsym(handle, name);
2712   }
2713   return f;
2714 }
2715 
2716 bool os::Linux::libnuma_init() {
2717   // sched_getcpu() should be in libc.
2718   set_sched_getcpu(CAST_TO_FN_PTR(sched_getcpu_func_t,
2719                                   dlsym(RTLD_DEFAULT, "sched_getcpu")));
2720 
2721   // If it's not, try a direct syscall.
2722   if (sched_getcpu() == -1) {
2723     set_sched_getcpu(CAST_TO_FN_PTR(sched_getcpu_func_t,
2724                                     (void*)&sched_getcpu_syscall));
2725   }
2726 
2727   if (sched_getcpu() != -1) { // Does it work?
2728     void *handle = dlopen("libnuma.so.1", RTLD_LAZY);
2729     if (handle != NULL) {
2730       set_numa_node_to_cpus(CAST_TO_FN_PTR(numa_node_to_cpus_func_t,
2731                                            libnuma_dlsym(handle, "numa_node_to_cpus")));
2732       set_numa_max_node(CAST_TO_FN_PTR(numa_max_node_func_t,
2733                                        libnuma_dlsym(handle, "numa_max_node")));
2734       set_numa_available(CAST_TO_FN_PTR(numa_available_func_t,
2735                                         libnuma_dlsym(handle, "numa_available")));
2736       set_numa_tonode_memory(CAST_TO_FN_PTR(numa_tonode_memory_func_t,
2737                                             libnuma_dlsym(handle, "numa_tonode_memory")));
2738       set_numa_interleave_memory(CAST_TO_FN_PTR(numa_interleave_memory_func_t,
2739                                                 libnuma_dlsym(handle, "numa_interleave_memory")));
2740       set_numa_set_bind_policy(CAST_TO_FN_PTR(numa_set_bind_policy_func_t,
2741                                               libnuma_dlsym(handle, "numa_set_bind_policy")));
2742 
2743 
2744       if (numa_available() != -1) {
2745         set_numa_all_nodes((unsigned long*)libnuma_dlsym(handle, "numa_all_nodes"));
2746         // Create a cpu -> node mapping
2747         _cpu_to_node = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<int>(0, true);
2748         rebuild_cpu_to_node_map();
2749         return true;
2750       }
2751     }
2752   }
2753   return false;
2754 }
2755 
2756 // rebuild_cpu_to_node_map() constructs a table mapping cpud id to node id.
2757 // The table is later used in get_node_by_cpu().
2758 void os::Linux::rebuild_cpu_to_node_map() {
2759   const size_t NCPUS = 32768; // Since the buffer size computation is very obscure
2760                               // in libnuma (possible values are starting from 16,
2761                               // and continuing up with every other power of 2, but less
2762                               // than the maximum number of CPUs supported by kernel), and
2763                               // is a subject to change (in libnuma version 2 the requirements
2764                               // are more reasonable) we'll just hardcode the number they use
2765                               // in the library.
2766   const size_t BitsPerCLong = sizeof(long) * CHAR_BIT;
2767 
2768   size_t cpu_num = os::active_processor_count();
2769   size_t cpu_map_size = NCPUS / BitsPerCLong;
2770   size_t cpu_map_valid_size =
2771     MIN2((cpu_num + BitsPerCLong - 1) / BitsPerCLong, cpu_map_size);
2772 
2773   cpu_to_node()->clear();
2774   cpu_to_node()->at_grow(cpu_num - 1);
2775   size_t node_num = numa_get_groups_num();
2776 
2777   unsigned long *cpu_map = NEW_C_HEAP_ARRAY(unsigned long, cpu_map_size, mtInternal);
2778   for (size_t i = 0; i < node_num; i++) {
2779     if (numa_node_to_cpus(i, cpu_map, cpu_map_size * sizeof(unsigned long)) != -1) {
2780       for (size_t j = 0; j < cpu_map_valid_size; j++) {
2781         if (cpu_map[j] != 0) {
2782           for (size_t k = 0; k < BitsPerCLong; k++) {
2783             if (cpu_map[j] & (1UL << k)) {
2784               cpu_to_node()->at_put(j * BitsPerCLong + k, i);
2785             }
2786           }
2787         }
2788       }
2789     }
2790   }
2791   FREE_C_HEAP_ARRAY(unsigned long, cpu_map);
2792 }
2793 
2794 int os::Linux::get_node_by_cpu(int cpu_id) {
2795   if (cpu_to_node() != NULL && cpu_id >= 0 && cpu_id < cpu_to_node()->length()) {
2796     return cpu_to_node()->at(cpu_id);
2797   }
2798   return -1;
2799 }
2800 
2801 GrowableArray<int>* os::Linux::_cpu_to_node;
2802 os::Linux::sched_getcpu_func_t os::Linux::_sched_getcpu;
2803 os::Linux::numa_node_to_cpus_func_t os::Linux::_numa_node_to_cpus;
2804 os::Linux::numa_max_node_func_t os::Linux::_numa_max_node;
2805 os::Linux::numa_available_func_t os::Linux::_numa_available;
2806 os::Linux::numa_tonode_memory_func_t os::Linux::_numa_tonode_memory;
2807 os::Linux::numa_interleave_memory_func_t os::Linux::_numa_interleave_memory;
2808 os::Linux::numa_set_bind_policy_func_t os::Linux::_numa_set_bind_policy;
2809 unsigned long* os::Linux::_numa_all_nodes;
2810 
2811 bool os::pd_uncommit_memory(char* addr, size_t size) {
2812   uintptr_t res = (uintptr_t) ::mmap(addr, size, PROT_NONE,
2813                                      MAP_PRIVATE|MAP_FIXED|MAP_NORESERVE|MAP_ANONYMOUS, -1, 0);
2814   return res  != (uintptr_t) MAP_FAILED;
2815 }
2816 
2817 static address get_stack_commited_bottom(address bottom, size_t size) {
2818   address nbot = bottom;
2819   address ntop = bottom + size;
2820 
2821   size_t page_sz = os::vm_page_size();
2822   unsigned pages = size / page_sz;
2823 
2824   unsigned char vec[1];
2825   unsigned imin = 1, imax = pages + 1, imid;
2826   int mincore_return_value = 0;
2827 
2828   assert(imin <= imax, "Unexpected page size");
2829 
2830   while (imin < imax) {
2831     imid = (imax + imin) / 2;
2832     nbot = ntop - (imid * page_sz);
2833 
2834     // Use a trick with mincore to check whether the page is mapped or not.
2835     // mincore sets vec to 1 if page resides in memory and to 0 if page
2836     // is swapped output but if page we are asking for is unmapped
2837     // it returns -1,ENOMEM
2838     mincore_return_value = mincore(nbot, page_sz, vec);
2839 
2840     if (mincore_return_value == -1) {
2841       // Page is not mapped go up
2842       // to find first mapped page
2843       if (errno != EAGAIN) {
2844         assert(errno == ENOMEM, "Unexpected mincore errno");
2845         imax = imid;
2846       }
2847     } else {
2848       // Page is mapped go down
2849       // to find first not mapped page
2850       imin = imid + 1;
2851     }
2852   }
2853 
2854   nbot = nbot + page_sz;
2855 
2856   // Adjust stack bottom one page up if last checked page is not mapped
2857   if (mincore_return_value == -1) {
2858     nbot = nbot + page_sz;
2859   }
2860 
2861   return nbot;
2862 }
2863 
2864 
2865 // Linux uses a growable mapping for the stack, and if the mapping for
2866 // the stack guard pages is not removed when we detach a thread the
2867 // stack cannot grow beyond the pages where the stack guard was
2868 // mapped.  If at some point later in the process the stack expands to
2869 // that point, the Linux kernel cannot expand the stack any further
2870 // because the guard pages are in the way, and a segfault occurs.
2871 //
2872 // However, it's essential not to split the stack region by unmapping
2873 // a region (leaving a hole) that's already part of the stack mapping,
2874 // so if the stack mapping has already grown beyond the guard pages at
2875 // the time we create them, we have to truncate the stack mapping.
2876 // So, we need to know the extent of the stack mapping when
2877 // create_stack_guard_pages() is called.
2878 
2879 // We only need this for stacks that are growable: at the time of
2880 // writing thread stacks don't use growable mappings (i.e. those
2881 // creeated with MAP_GROWSDOWN), and aren't marked "[stack]", so this
2882 // only applies to the main thread.
2883 
2884 // If the (growable) stack mapping already extends beyond the point
2885 // where we're going to put our guard pages, truncate the mapping at
2886 // that point by munmap()ping it.  This ensures that when we later
2887 // munmap() the guard pages we don't leave a hole in the stack
2888 // mapping. This only affects the main/initial thread
2889 
2890 bool os::pd_create_stack_guard_pages(char* addr, size_t size) {
2891   if (os::Linux::is_initial_thread()) {
2892     // As we manually grow stack up to bottom inside create_attached_thread(),
2893     // it's likely that os::Linux::initial_thread_stack_bottom is mapped and
2894     // we don't need to do anything special.
2895     // Check it first, before calling heavy function.
2896     uintptr_t stack_extent = (uintptr_t) os::Linux::initial_thread_stack_bottom();
2897     unsigned char vec[1];
2898 
2899     if (mincore((address)stack_extent, os::vm_page_size(), vec) == -1) {
2900       // Fallback to slow path on all errors, including EAGAIN
2901       stack_extent = (uintptr_t) get_stack_commited_bottom(
2902                                                            os::Linux::initial_thread_stack_bottom(),
2903                                                            (size_t)addr - stack_extent);
2904     }
2905 
2906     if (stack_extent < (uintptr_t)addr) {
2907       ::munmap((void*)stack_extent, (uintptr_t)(addr - stack_extent));
2908     }
2909   }
2910 
2911   return os::commit_memory(addr, size, !ExecMem);
2912 }
2913 
2914 // If this is a growable mapping, remove the guard pages entirely by
2915 // munmap()ping them.  If not, just call uncommit_memory(). This only
2916 // affects the main/initial thread, but guard against future OS changes
2917 // It's safe to always unmap guard pages for initial thread because we
2918 // always place it right after end of the mapped region
2919 
2920 bool os::remove_stack_guard_pages(char* addr, size_t size) {
2921   uintptr_t stack_extent, stack_base;
2922 
2923   if (os::Linux::is_initial_thread()) {
2924     return ::munmap(addr, size) == 0;
2925   }
2926 
2927   return os::uncommit_memory(addr, size);
2928 }
2929 
2930 // If 'fixed' is true, anon_mmap() will attempt to reserve anonymous memory
2931 // at 'requested_addr'. If there are existing memory mappings at the same
2932 // location, however, they will be overwritten. If 'fixed' is false,
2933 // 'requested_addr' is only treated as a hint, the return value may or
2934 // may not start from the requested address. Unlike Linux mmap(), this
2935 // function returns NULL to indicate failure.
2936 static char* anon_mmap(char* requested_addr, size_t bytes, bool fixed) {
2937   char * addr;
2938   int flags;
2939 
2940   flags = MAP_PRIVATE | MAP_NORESERVE | MAP_ANONYMOUS;
2941   if (fixed) {
2942     assert((uintptr_t)requested_addr % os::Linux::page_size() == 0, "unaligned address");
2943     flags |= MAP_FIXED;
2944   }
2945 
2946   // Map reserved/uncommitted pages PROT_NONE so we fail early if we
2947   // touch an uncommitted page. Otherwise, the read/write might
2948   // succeed if we have enough swap space to back the physical page.
2949   addr = (char*)::mmap(requested_addr, bytes, PROT_NONE,
2950                        flags, -1, 0);
2951 
2952   return addr == MAP_FAILED ? NULL : addr;
2953 }
2954 
2955 static int anon_munmap(char * addr, size_t size) {
2956   return ::munmap(addr, size) == 0;
2957 }
2958 
2959 char* os::pd_reserve_memory(size_t bytes, char* requested_addr,
2960                             size_t alignment_hint) {
2961   return anon_mmap(requested_addr, bytes, (requested_addr != NULL));
2962 }
2963 
2964 bool os::pd_release_memory(char* addr, size_t size) {
2965   return anon_munmap(addr, size);
2966 }
2967 
2968 static bool linux_mprotect(char* addr, size_t size, int prot) {
2969   // Linux wants the mprotect address argument to be page aligned.
2970   char* bottom = (char*)align_size_down((intptr_t)addr, os::Linux::page_size());
2971 
2972   // According to SUSv3, mprotect() should only be used with mappings
2973   // established by mmap(), and mmap() always maps whole pages. Unaligned
2974   // 'addr' likely indicates problem in the VM (e.g. trying to change
2975   // protection of malloc'ed or statically allocated memory). Check the
2976   // caller if you hit this assert.
2977   assert(addr == bottom, "sanity check");
2978 
2979   size = align_size_up(pointer_delta(addr, bottom, 1) + size, os::Linux::page_size());
2980   return ::mprotect(bottom, size, prot) == 0;
2981 }
2982 
2983 // Set protections specified
2984 bool os::protect_memory(char* addr, size_t bytes, ProtType prot,
2985                         bool is_committed) {
2986   unsigned int p = 0;
2987   switch (prot) {
2988   case MEM_PROT_NONE: p = PROT_NONE; break;
2989   case MEM_PROT_READ: p = PROT_READ; break;
2990   case MEM_PROT_RW:   p = PROT_READ|PROT_WRITE; break;
2991   case MEM_PROT_RWX:  p = PROT_READ|PROT_WRITE|PROT_EXEC; break;
2992   default:
2993     ShouldNotReachHere();
2994   }
2995   // is_committed is unused.
2996   return linux_mprotect(addr, bytes, p);
2997 }
2998 
2999 bool os::guard_memory(char* addr, size_t size) {
3000   return linux_mprotect(addr, size, PROT_NONE);
3001 }
3002 
3003 bool os::unguard_memory(char* addr, size_t size) {
3004   return linux_mprotect(addr, size, PROT_READ|PROT_WRITE);
3005 }
3006 
3007 bool os::Linux::transparent_huge_pages_sanity_check(bool warn,
3008                                                     size_t page_size) {
3009   bool result = false;
3010   void *p = mmap(NULL, page_size * 2, PROT_READ|PROT_WRITE,
3011                  MAP_ANONYMOUS|MAP_PRIVATE,
3012                  -1, 0);
3013   if (p != MAP_FAILED) {
3014     void *aligned_p = align_ptr_up(p, page_size);
3015 
3016     result = madvise(aligned_p, page_size, MADV_HUGEPAGE) == 0;
3017 
3018     munmap(p, page_size * 2);
3019   }
3020 
3021   if (warn && !result) {
3022     warning("TransparentHugePages is not supported by the operating system.");
3023   }
3024 
3025   return result;
3026 }
3027 
3028 bool os::Linux::hugetlbfs_sanity_check(bool warn, size_t page_size) {
3029   bool result = false;
3030   void *p = mmap(NULL, page_size, PROT_READ|PROT_WRITE,
3031                  MAP_ANONYMOUS|MAP_PRIVATE|MAP_HUGETLB,
3032                  -1, 0);
3033 
3034   if (p != MAP_FAILED) {
3035     // We don't know if this really is a huge page or not.
3036     FILE *fp = fopen("/proc/self/maps", "r");
3037     if (fp) {
3038       while (!feof(fp)) {
3039         char chars[257];
3040         long x = 0;
3041         if (fgets(chars, sizeof(chars), fp)) {
3042           if (sscanf(chars, "%lx-%*x", &x) == 1
3043               && x == (long)p) {
3044             if (strstr (chars, "hugepage")) {
3045               result = true;
3046               break;
3047             }
3048           }
3049         }
3050       }
3051       fclose(fp);
3052     }
3053     munmap(p, page_size);
3054   }
3055 
3056   if (warn && !result) {
3057     warning("HugeTLBFS is not supported by the operating system.");
3058   }
3059 
3060   return result;
3061 }
3062 
3063 // Set the coredump_filter bits to include largepages in core dump (bit 6)
3064 //
3065 // From the coredump_filter documentation:
3066 //
3067 // - (bit 0) anonymous private memory
3068 // - (bit 1) anonymous shared memory
3069 // - (bit 2) file-backed private memory
3070 // - (bit 3) file-backed shared memory
3071 // - (bit 4) ELF header pages in file-backed private memory areas (it is
3072 //           effective only if the bit 2 is cleared)
3073 // - (bit 5) hugetlb private memory
3074 // - (bit 6) hugetlb shared memory
3075 //
3076 static void set_coredump_filter(void) {
3077   FILE *f;
3078   long cdm;
3079 
3080   if ((f = fopen("/proc/self/coredump_filter", "r+")) == NULL) {
3081     return;
3082   }
3083 
3084   if (fscanf(f, "%lx", &cdm) != 1) {
3085     fclose(f);
3086     return;
3087   }
3088 
3089   rewind(f);
3090 
3091   if ((cdm & LARGEPAGES_BIT) == 0) {
3092     cdm |= LARGEPAGES_BIT;
3093     fprintf(f, "%#lx", cdm);
3094   }
3095 
3096   fclose(f);
3097 }
3098 
3099 // Large page support
3100 
3101 static size_t _large_page_size = 0;
3102 
3103 size_t os::Linux::find_large_page_size() {
3104   size_t large_page_size = 0;
3105 
3106   // large_page_size on Linux is used to round up heap size. x86 uses either
3107   // 2M or 4M page, depending on whether PAE (Physical Address Extensions)
3108   // mode is enabled. AMD64/EM64T uses 2M page in 64bit mode. IA64 can use
3109   // page as large as 256M.
3110   //
3111   // Here we try to figure out page size by parsing /proc/meminfo and looking
3112   // for a line with the following format:
3113   //    Hugepagesize:     2048 kB
3114   //
3115   // If we can't determine the value (e.g. /proc is not mounted, or the text
3116   // format has been changed), we'll use the largest page size supported by
3117   // the processor.
3118 
3119 #ifndef ZERO
3120   large_page_size = IA32_ONLY(4 * M) AMD64_ONLY(2 * M) IA64_ONLY(256 * M) SPARC_ONLY(4 * M)
3121                      ARM32_ONLY(2 * M) PPC_ONLY(4 * M) AARCH64_ONLY(2 * M);
3122 #endif // ZERO
3123 
3124   FILE *fp = fopen("/proc/meminfo", "r");
3125   if (fp) {
3126     while (!feof(fp)) {
3127       int x = 0;
3128       char buf[16];
3129       if (fscanf(fp, "Hugepagesize: %d", &x) == 1) {
3130         if (x && fgets(buf, sizeof(buf), fp) && strcmp(buf, " kB\n") == 0) {
3131           large_page_size = x * K;
3132           break;
3133         }
3134       } else {
3135         // skip to next line
3136         for (;;) {
3137           int ch = fgetc(fp);
3138           if (ch == EOF || ch == (int)'\n') break;
3139         }
3140       }
3141     }
3142     fclose(fp);
3143   }
3144 
3145   if (!FLAG_IS_DEFAULT(LargePageSizeInBytes) && LargePageSizeInBytes != large_page_size) {
3146     warning("Setting LargePageSizeInBytes has no effect on this OS. Large page size is "
3147             SIZE_FORMAT "%s.", byte_size_in_proper_unit(large_page_size),
3148             proper_unit_for_byte_size(large_page_size));
3149   }
3150 
3151   return large_page_size;
3152 }
3153 
3154 size_t os::Linux::setup_large_page_size() {
3155   _large_page_size = Linux::find_large_page_size();
3156   const size_t default_page_size = (size_t)Linux::page_size();
3157   if (_large_page_size > default_page_size) {
3158     _page_sizes[0] = _large_page_size;
3159     _page_sizes[1] = default_page_size;
3160     _page_sizes[2] = 0;
3161   }
3162 
3163   return _large_page_size;
3164 }
3165 
3166 bool os::Linux::setup_large_page_type(size_t page_size) {
3167   if (FLAG_IS_DEFAULT(UseHugeTLBFS) &&
3168       FLAG_IS_DEFAULT(UseSHM) &&
3169       FLAG_IS_DEFAULT(UseTransparentHugePages)) {
3170 
3171     // The type of large pages has not been specified by the user.
3172 
3173     // Try UseHugeTLBFS and then UseSHM.
3174     UseHugeTLBFS = UseSHM = true;
3175 
3176     // Don't try UseTransparentHugePages since there are known
3177     // performance issues with it turned on. This might change in the future.
3178     UseTransparentHugePages = false;
3179   }
3180 
3181   if (UseTransparentHugePages) {
3182     bool warn_on_failure = !FLAG_IS_DEFAULT(UseTransparentHugePages);
3183     if (transparent_huge_pages_sanity_check(warn_on_failure, page_size)) {
3184       UseHugeTLBFS = false;
3185       UseSHM = false;
3186       return true;
3187     }
3188     UseTransparentHugePages = false;
3189   }
3190 
3191   if (UseHugeTLBFS) {
3192     bool warn_on_failure = !FLAG_IS_DEFAULT(UseHugeTLBFS);
3193     if (hugetlbfs_sanity_check(warn_on_failure, page_size)) {
3194       UseSHM = false;
3195       return true;
3196     }
3197     UseHugeTLBFS = false;
3198   }
3199 
3200   return UseSHM;
3201 }
3202 
3203 void os::large_page_init() {
3204   if (!UseLargePages &&
3205       !UseTransparentHugePages &&
3206       !UseHugeTLBFS &&
3207       !UseSHM) {
3208     // Not using large pages.
3209     return;
3210   }
3211 
3212   if (!FLAG_IS_DEFAULT(UseLargePages) && !UseLargePages) {
3213     // The user explicitly turned off large pages.
3214     // Ignore the rest of the large pages flags.
3215     UseTransparentHugePages = false;
3216     UseHugeTLBFS = false;
3217     UseSHM = false;
3218     return;
3219   }
3220 
3221   size_t large_page_size = Linux::setup_large_page_size();
3222   UseLargePages          = Linux::setup_large_page_type(large_page_size);
3223 
3224   set_coredump_filter();
3225 }
3226 
3227 #ifndef SHM_HUGETLB
3228   #define SHM_HUGETLB 04000
3229 #endif
3230 
3231 char* os::Linux::reserve_memory_special_shm(size_t bytes, size_t alignment,
3232                                             char* req_addr, bool exec) {
3233   // "exec" is passed in but not used.  Creating the shared image for
3234   // the code cache doesn't have an SHM_X executable permission to check.
3235   assert(UseLargePages && UseSHM, "only for SHM large pages");
3236   assert(is_ptr_aligned(req_addr, os::large_page_size()), "Unaligned address");
3237 
3238   if (!is_size_aligned(bytes, os::large_page_size()) || alignment > os::large_page_size()) {
3239     return NULL; // Fallback to small pages.
3240   }
3241 
3242   key_t key = IPC_PRIVATE;
3243   char *addr;
3244 
3245   bool warn_on_failure = UseLargePages &&
3246                         (!FLAG_IS_DEFAULT(UseLargePages) ||
3247                          !FLAG_IS_DEFAULT(UseSHM) ||
3248                          !FLAG_IS_DEFAULT(LargePageSizeInBytes));
3249   char msg[128];
3250 
3251   // Create a large shared memory region to attach to based on size.
3252   // Currently, size is the total size of the heap
3253   int shmid = shmget(key, bytes, SHM_HUGETLB|IPC_CREAT|SHM_R|SHM_W);
3254   if (shmid == -1) {
3255     // Possible reasons for shmget failure:
3256     // 1. shmmax is too small for Java heap.
3257     //    > check shmmax value: cat /proc/sys/kernel/shmmax
3258     //    > increase shmmax value: echo "0xffffffff" > /proc/sys/kernel/shmmax
3259     // 2. not enough large page memory.
3260     //    > check available large pages: cat /proc/meminfo
3261     //    > increase amount of large pages:
3262     //          echo new_value > /proc/sys/vm/nr_hugepages
3263     //      Note 1: different Linux may use different name for this property,
3264     //            e.g. on Redhat AS-3 it is "hugetlb_pool".
3265     //      Note 2: it's possible there's enough physical memory available but
3266     //            they are so fragmented after a long run that they can't
3267     //            coalesce into large pages. Try to reserve large pages when
3268     //            the system is still "fresh".
3269     if (warn_on_failure) {
3270       jio_snprintf(msg, sizeof(msg), "Failed to reserve shared memory (errno = %d).", errno);
3271       warning("%s", msg);
3272     }
3273     return NULL;
3274   }
3275 
3276   // attach to the region
3277   addr = (char*)shmat(shmid, req_addr, 0);
3278   int err = errno;
3279 
3280   // Remove shmid. If shmat() is successful, the actual shared memory segment
3281   // will be deleted when it's detached by shmdt() or when the process
3282   // terminates. If shmat() is not successful this will remove the shared
3283   // segment immediately.
3284   shmctl(shmid, IPC_RMID, NULL);
3285 
3286   if ((intptr_t)addr == -1) {
3287     if (warn_on_failure) {
3288       jio_snprintf(msg, sizeof(msg), "Failed to attach shared memory (errno = %d).", err);
3289       warning("%s", msg);
3290     }
3291     return NULL;
3292   }
3293 
3294   return addr;
3295 }
3296 
3297 static void warn_on_large_pages_failure(char* req_addr, size_t bytes,
3298                                         int error) {
3299   assert(error == ENOMEM, "Only expect to fail if no memory is available");
3300 
3301   bool warn_on_failure = UseLargePages &&
3302       (!FLAG_IS_DEFAULT(UseLargePages) ||
3303        !FLAG_IS_DEFAULT(UseHugeTLBFS) ||
3304        !FLAG_IS_DEFAULT(LargePageSizeInBytes));
3305 
3306   if (warn_on_failure) {
3307     char msg[128];
3308     jio_snprintf(msg, sizeof(msg), "Failed to reserve large pages memory req_addr: "
3309                  PTR_FORMAT " bytes: " SIZE_FORMAT " (errno = %d).", req_addr, bytes, error);
3310     warning("%s", msg);
3311   }
3312 }
3313 
3314 char* os::Linux::reserve_memory_special_huge_tlbfs_only(size_t bytes,
3315                                                         char* req_addr,
3316                                                         bool exec) {
3317   assert(UseLargePages && UseHugeTLBFS, "only for Huge TLBFS large pages");
3318   assert(is_size_aligned(bytes, os::large_page_size()), "Unaligned size");
3319   assert(is_ptr_aligned(req_addr, os::large_page_size()), "Unaligned address");
3320 
3321   int prot = exec ? PROT_READ|PROT_WRITE|PROT_EXEC : PROT_READ|PROT_WRITE;
3322   char* addr = (char*)::mmap(req_addr, bytes, prot,
3323                              MAP_PRIVATE|MAP_ANONYMOUS|MAP_HUGETLB,
3324                              -1, 0);
3325 
3326   if (addr == MAP_FAILED) {
3327     warn_on_large_pages_failure(req_addr, bytes, errno);
3328     return NULL;
3329   }
3330 
3331   assert(is_ptr_aligned(addr, os::large_page_size()), "Must be");
3332 
3333   return addr;
3334 }
3335 
3336 // Helper for os::Linux::reserve_memory_special_huge_tlbfs_mixed().
3337 // Allocate (using mmap, NO_RESERVE, with small pages) at either a given request address
3338 //   (req_addr != NULL) or with a given alignment.
3339 //  - bytes shall be a multiple of alignment.
3340 //  - req_addr can be NULL. If not NULL, it must be a multiple of alignment.
3341 //  - alignment sets the alignment at which memory shall be allocated.
3342 //     It must be a multiple of allocation granularity.
3343 // Returns address of memory or NULL. If req_addr was not NULL, will only return
3344 //  req_addr or NULL.
3345 static char* anon_mmap_aligned(size_t bytes, size_t alignment, char* req_addr) {
3346 
3347   size_t extra_size = bytes;
3348   if (req_addr == NULL && alignment > 0) {
3349     extra_size += alignment;
3350   }
3351 
3352   char* start = (char*) ::mmap(req_addr, extra_size, PROT_NONE,
3353     MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE,
3354     -1, 0);
3355   if (start == MAP_FAILED) {
3356     start = NULL;
3357   } else {
3358     if (req_addr != NULL) {
3359       if (start != req_addr) {
3360         ::munmap(start, extra_size);
3361         start = NULL;
3362       }
3363     } else {
3364       char* const start_aligned = (char*) align_ptr_up(start, alignment);
3365       char* const end_aligned = start_aligned + bytes;
3366       char* const end = start + extra_size;
3367       if (start_aligned > start) {
3368         ::munmap(start, start_aligned - start);
3369       }
3370       if (end_aligned < end) {
3371         ::munmap(end_aligned, end - end_aligned);
3372       }
3373       start = start_aligned;
3374     }
3375   }
3376   return start;
3377 
3378 }
3379 
3380 // Reserve memory using mmap(MAP_HUGETLB).
3381 //  - bytes shall be a multiple of alignment.
3382 //  - req_addr can be NULL. If not NULL, it must be a multiple of alignment.
3383 //  - alignment sets the alignment at which memory shall be allocated.
3384 //     It must be a multiple of allocation granularity.
3385 // Returns address of memory or NULL. If req_addr was not NULL, will only return
3386 //  req_addr or NULL.
3387 char* os::Linux::reserve_memory_special_huge_tlbfs_mixed(size_t bytes,
3388                                                          size_t alignment,
3389                                                          char* req_addr,
3390                                                          bool exec) {
3391   size_t large_page_size = os::large_page_size();
3392   assert(bytes >= large_page_size, "Shouldn't allocate large pages for small sizes");
3393 
3394   assert(is_ptr_aligned(req_addr, alignment), "Must be");
3395   assert(is_size_aligned(bytes, alignment), "Must be");
3396 
3397   // First reserve - but not commit - the address range in small pages.
3398   char* const start = anon_mmap_aligned(bytes, alignment, req_addr);
3399 
3400   if (start == NULL) {
3401     return NULL;
3402   }
3403 
3404   assert(is_ptr_aligned(start, alignment), "Must be");
3405 
3406   char* end = start + bytes;
3407 
3408   // Find the regions of the allocated chunk that can be promoted to large pages.
3409   char* lp_start = (char*)align_ptr_up(start, large_page_size);
3410   char* lp_end   = (char*)align_ptr_down(end, large_page_size);
3411 
3412   size_t lp_bytes = lp_end - lp_start;
3413 
3414   assert(is_size_aligned(lp_bytes, large_page_size), "Must be");
3415 
3416   if (lp_bytes == 0) {
3417     // The mapped region doesn't even span the start and the end of a large page.
3418     // Fall back to allocate a non-special area.
3419     ::munmap(start, end - start);
3420     return NULL;
3421   }
3422 
3423   int prot = exec ? PROT_READ|PROT_WRITE|PROT_EXEC : PROT_READ|PROT_WRITE;
3424 
3425   void* result;
3426 
3427   // Commit small-paged leading area.
3428   if (start != lp_start) {
3429     result = ::mmap(start, lp_start - start, prot,
3430                     MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED,
3431                     -1, 0);
3432     if (result == MAP_FAILED) {
3433       ::munmap(lp_start, end - lp_start);
3434       return NULL;
3435     }
3436   }
3437 
3438   // Commit large-paged area.
3439   result = ::mmap(lp_start, lp_bytes, prot,
3440                   MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED|MAP_HUGETLB,
3441                   -1, 0);
3442   if (result == MAP_FAILED) {
3443     warn_on_large_pages_failure(lp_start, lp_bytes, errno);
3444     // If the mmap above fails, the large pages region will be unmapped and we
3445     // have regions before and after with small pages. Release these regions.
3446     //
3447     // |  mapped  |  unmapped  |  mapped  |
3448     // ^          ^            ^          ^
3449     // start      lp_start     lp_end     end
3450     //
3451     ::munmap(start, lp_start - start);
3452     ::munmap(lp_end, end - lp_end);
3453     return NULL;
3454   }
3455 
3456   // Commit small-paged trailing area.
3457   if (lp_end != end) {
3458     result = ::mmap(lp_end, end - lp_end, prot,
3459                     MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED,
3460                     -1, 0);
3461     if (result == MAP_FAILED) {
3462       ::munmap(start, lp_end - start);
3463       return NULL;
3464     }
3465   }
3466 
3467   return start;
3468 }
3469 
3470 char* os::Linux::reserve_memory_special_huge_tlbfs(size_t bytes,
3471                                                    size_t alignment,
3472                                                    char* req_addr,
3473                                                    bool exec) {
3474   assert(UseLargePages && UseHugeTLBFS, "only for Huge TLBFS large pages");
3475   assert(is_ptr_aligned(req_addr, alignment), "Must be");
3476   assert(is_size_aligned(alignment, os::vm_allocation_granularity()), "Must be");
3477   assert(is_power_of_2(os::large_page_size()), "Must be");
3478   assert(bytes >= os::large_page_size(), "Shouldn't allocate large pages for small sizes");
3479 
3480   if (is_size_aligned(bytes, os::large_page_size()) && alignment <= os::large_page_size()) {
3481     return reserve_memory_special_huge_tlbfs_only(bytes, req_addr, exec);
3482   } else {
3483     return reserve_memory_special_huge_tlbfs_mixed(bytes, alignment, req_addr, exec);
3484   }
3485 }
3486 
3487 char* os::reserve_memory_special(size_t bytes, size_t alignment,
3488                                  char* req_addr, bool exec) {
3489   assert(UseLargePages, "only for large pages");
3490 
3491   char* addr;
3492   if (UseSHM) {
3493     addr = os::Linux::reserve_memory_special_shm(bytes, alignment, req_addr, exec);
3494   } else {
3495     assert(UseHugeTLBFS, "must be");
3496     addr = os::Linux::reserve_memory_special_huge_tlbfs(bytes, alignment, req_addr, exec);
3497   }
3498 
3499   if (addr != NULL) {
3500     if (UseNUMAInterleaving) {
3501       numa_make_global(addr, bytes);
3502     }
3503 
3504     // The memory is committed
3505     MemTracker::record_virtual_memory_reserve_and_commit((address)addr, bytes, CALLER_PC);
3506   }
3507 
3508   return addr;
3509 }
3510 
3511 bool os::Linux::release_memory_special_shm(char* base, size_t bytes) {
3512   // detaching the SHM segment will also delete it, see reserve_memory_special_shm()
3513   return shmdt(base) == 0;
3514 }
3515 
3516 bool os::Linux::release_memory_special_huge_tlbfs(char* base, size_t bytes) {
3517   return pd_release_memory(base, bytes);
3518 }
3519 
3520 bool os::release_memory_special(char* base, size_t bytes) {
3521   bool res;
3522   if (MemTracker::tracking_level() > NMT_minimal) {
3523     Tracker tkr = MemTracker::get_virtual_memory_release_tracker();
3524     res = os::Linux::release_memory_special_impl(base, bytes);
3525     if (res) {
3526       tkr.record((address)base, bytes);
3527     }
3528 
3529   } else {
3530     res = os::Linux::release_memory_special_impl(base, bytes);
3531   }
3532   return res;
3533 }
3534 
3535 bool os::Linux::release_memory_special_impl(char* base, size_t bytes) {
3536   assert(UseLargePages, "only for large pages");
3537   bool res;
3538 
3539   if (UseSHM) {
3540     res = os::Linux::release_memory_special_shm(base, bytes);
3541   } else {
3542     assert(UseHugeTLBFS, "must be");
3543     res = os::Linux::release_memory_special_huge_tlbfs(base, bytes);
3544   }
3545   return res;
3546 }
3547 
3548 size_t os::large_page_size() {
3549   return _large_page_size;
3550 }
3551 
3552 // With SysV SHM the entire memory region must be allocated as shared
3553 // memory.
3554 // HugeTLBFS allows application to commit large page memory on demand.
3555 // However, when committing memory with HugeTLBFS fails, the region
3556 // that was supposed to be committed will lose the old reservation
3557 // and allow other threads to steal that memory region. Because of this
3558 // behavior we can't commit HugeTLBFS memory.
3559 bool os::can_commit_large_page_memory() {
3560   return UseTransparentHugePages;
3561 }
3562 
3563 bool os::can_execute_large_page_memory() {
3564   return UseTransparentHugePages || UseHugeTLBFS;
3565 }
3566 
3567 // Reserve memory at an arbitrary address, only if that area is
3568 // available (and not reserved for something else).
3569 
3570 char* os::pd_attempt_reserve_memory_at(size_t bytes, char* requested_addr) {
3571   const int max_tries = 10;
3572   char* base[max_tries];
3573   size_t size[max_tries];
3574   const size_t gap = 0x000000;
3575 
3576   // Assert only that the size is a multiple of the page size, since
3577   // that's all that mmap requires, and since that's all we really know
3578   // about at this low abstraction level.  If we need higher alignment,
3579   // we can either pass an alignment to this method or verify alignment
3580   // in one of the methods further up the call chain.  See bug 5044738.
3581   assert(bytes % os::vm_page_size() == 0, "reserving unexpected size block");
3582 
3583   // Repeatedly allocate blocks until the block is allocated at the
3584   // right spot.
3585 
3586   // Linux mmap allows caller to pass an address as hint; give it a try first,
3587   // if kernel honors the hint then we can return immediately.
3588   char * addr = anon_mmap(requested_addr, bytes, false);
3589   if (addr == requested_addr) {
3590     return requested_addr;
3591   }
3592 
3593   if (addr != NULL) {
3594     // mmap() is successful but it fails to reserve at the requested address
3595     anon_munmap(addr, bytes);
3596   }
3597 
3598   int i;
3599   for (i = 0; i < max_tries; ++i) {
3600     base[i] = reserve_memory(bytes);
3601 
3602     if (base[i] != NULL) {
3603       // Is this the block we wanted?
3604       if (base[i] == requested_addr) {
3605         size[i] = bytes;
3606         break;
3607       }
3608 
3609       // Does this overlap the block we wanted? Give back the overlapped
3610       // parts and try again.
3611 
3612       ptrdiff_t top_overlap = requested_addr + (bytes + gap) - base[i];
3613       if (top_overlap >= 0 && (size_t)top_overlap < bytes) {
3614         unmap_memory(base[i], top_overlap);
3615         base[i] += top_overlap;
3616         size[i] = bytes - top_overlap;
3617       } else {
3618         ptrdiff_t bottom_overlap = base[i] + bytes - requested_addr;
3619         if (bottom_overlap >= 0 && (size_t)bottom_overlap < bytes) {
3620           unmap_memory(requested_addr, bottom_overlap);
3621           size[i] = bytes - bottom_overlap;
3622         } else {
3623           size[i] = bytes;
3624         }
3625       }
3626     }
3627   }
3628 
3629   // Give back the unused reserved pieces.
3630 
3631   for (int j = 0; j < i; ++j) {
3632     if (base[j] != NULL) {
3633       unmap_memory(base[j], size[j]);
3634     }
3635   }
3636 
3637   if (i < max_tries) {
3638     return requested_addr;
3639   } else {
3640     return NULL;
3641   }
3642 }
3643 
3644 size_t os::read(int fd, void *buf, unsigned int nBytes) {
3645   return ::read(fd, buf, nBytes);
3646 }
3647 
3648 size_t os::read_at(int fd, void *buf, unsigned int nBytes, jlong offset) {
3649   return ::pread(fd, buf, nBytes, offset);
3650 }
3651 
3652 // Short sleep, direct OS call.
3653 //
3654 // Note: certain versions of Linux CFS scheduler (since 2.6.23) do not guarantee
3655 // sched_yield(2) will actually give up the CPU:
3656 //
3657 //   * Alone on this pariticular CPU, keeps running.
3658 //   * Before the introduction of "skip_buddy" with "compat_yield" disabled
3659 //     (pre 2.6.39).
3660 //
3661 // So calling this with 0 is an alternative.
3662 //
3663 void os::naked_short_sleep(jlong ms) {
3664   struct timespec req;
3665 
3666   assert(ms < 1000, "Un-interruptable sleep, short time use only");
3667   req.tv_sec = 0;
3668   if (ms > 0) {
3669     req.tv_nsec = (ms % 1000) * 1000000;
3670   } else {
3671     req.tv_nsec = 1;
3672   }
3673 
3674   nanosleep(&req, NULL);
3675 
3676   return;
3677 }
3678 
3679 // Sleep forever; naked call to OS-specific sleep; use with CAUTION
3680 void os::infinite_sleep() {
3681   while (true) {    // sleep forever ...
3682     ::sleep(100);   // ... 100 seconds at a time
3683   }
3684 }
3685 
3686 // Used to convert frequent JVM_Yield() to nops
3687 bool os::dont_yield() {
3688   return DontYieldALot;
3689 }
3690 
3691 void os::naked_yield() {
3692   sched_yield();
3693 }
3694 
3695 ////////////////////////////////////////////////////////////////////////////////
3696 // thread priority support
3697 
3698 // Note: Normal Linux applications are run with SCHED_OTHER policy. SCHED_OTHER
3699 // only supports dynamic priority, static priority must be zero. For real-time
3700 // applications, Linux supports SCHED_RR which allows static priority (1-99).
3701 // However, for large multi-threaded applications, SCHED_RR is not only slower
3702 // than SCHED_OTHER, but also very unstable (my volano tests hang hard 4 out
3703 // of 5 runs - Sep 2005).
3704 //
3705 // The following code actually changes the niceness of kernel-thread/LWP. It
3706 // has an assumption that setpriority() only modifies one kernel-thread/LWP,
3707 // not the entire user process, and user level threads are 1:1 mapped to kernel
3708 // threads. It has always been the case, but could change in the future. For
3709 // this reason, the code should not be used as default (ThreadPriorityPolicy=0).
3710 // It is only used when ThreadPriorityPolicy=1 and requires root privilege.
3711 
3712 int os::java_to_os_priority[CriticalPriority + 1] = {
3713   19,              // 0 Entry should never be used
3714 
3715    4,              // 1 MinPriority
3716    3,              // 2
3717    2,              // 3
3718 
3719    1,              // 4
3720    0,              // 5 NormPriority
3721   -1,              // 6
3722 
3723   -2,              // 7
3724   -3,              // 8
3725   -4,              // 9 NearMaxPriority
3726 
3727   -5,              // 10 MaxPriority
3728 
3729   -5               // 11 CriticalPriority
3730 };
3731 
3732 static int prio_init() {
3733   if (ThreadPriorityPolicy == 1) {
3734     // Only root can raise thread priority. Don't allow ThreadPriorityPolicy=1
3735     // if effective uid is not root. Perhaps, a more elegant way of doing
3736     // this is to test CAP_SYS_NICE capability, but that will require libcap.so
3737     if (geteuid() != 0) {
3738       if (!FLAG_IS_DEFAULT(ThreadPriorityPolicy)) {
3739         warning("-XX:ThreadPriorityPolicy requires root privilege on Linux");
3740       }
3741       ThreadPriorityPolicy = 0;
3742     }
3743   }
3744   if (UseCriticalJavaThreadPriority) {
3745     os::java_to_os_priority[MaxPriority] = os::java_to_os_priority[CriticalPriority];
3746   }
3747   return 0;
3748 }
3749 
3750 OSReturn os::set_native_priority(Thread* thread, int newpri) {
3751   if (!UseThreadPriorities || ThreadPriorityPolicy == 0) return OS_OK;
3752 
3753   int ret = setpriority(PRIO_PROCESS, thread->osthread()->thread_id(), newpri);
3754   return (ret == 0) ? OS_OK : OS_ERR;
3755 }
3756 
3757 OSReturn os::get_native_priority(const Thread* const thread,
3758                                  int *priority_ptr) {
3759   if (!UseThreadPriorities || ThreadPriorityPolicy == 0) {
3760     *priority_ptr = java_to_os_priority[NormPriority];
3761     return OS_OK;
3762   }
3763 
3764   errno = 0;
3765   *priority_ptr = getpriority(PRIO_PROCESS, thread->osthread()->thread_id());
3766   return (*priority_ptr != -1 || errno == 0 ? OS_OK : OS_ERR);
3767 }
3768 
3769 // Hint to the underlying OS that a task switch would not be good.
3770 // Void return because it's a hint and can fail.
3771 void os::hint_no_preempt() {}
3772 
3773 ////////////////////////////////////////////////////////////////////////////////
3774 // suspend/resume support
3775 
3776 //  the low-level signal-based suspend/resume support is a remnant from the
3777 //  old VM-suspension that used to be for java-suspension, safepoints etc,
3778 //  within hotspot. Now there is a single use-case for this:
3779 //    - calling get_thread_pc() on the VMThread by the flat-profiler task
3780 //      that runs in the watcher thread.
3781 //  The remaining code is greatly simplified from the more general suspension
3782 //  code that used to be used.
3783 //
3784 //  The protocol is quite simple:
3785 //  - suspend:
3786 //      - sends a signal to the target thread
3787 //      - polls the suspend state of the osthread using a yield loop
3788 //      - target thread signal handler (SR_handler) sets suspend state
3789 //        and blocks in sigsuspend until continued
3790 //  - resume:
3791 //      - sets target osthread state to continue
3792 //      - sends signal to end the sigsuspend loop in the SR_handler
3793 //
3794 //  Note that the SR_lock plays no role in this suspend/resume protocol.
3795 
3796 static void resume_clear_context(OSThread *osthread) {
3797   osthread->set_ucontext(NULL);
3798   osthread->set_siginfo(NULL);
3799 }
3800 
3801 static void suspend_save_context(OSThread *osthread, siginfo_t* siginfo,
3802                                  ucontext_t* context) {
3803   osthread->set_ucontext(context);
3804   osthread->set_siginfo(siginfo);
3805 }
3806 
3807 // Handler function invoked when a thread's execution is suspended or
3808 // resumed. We have to be careful that only async-safe functions are
3809 // called here (Note: most pthread functions are not async safe and
3810 // should be avoided.)
3811 //
3812 // Note: sigwait() is a more natural fit than sigsuspend() from an
3813 // interface point of view, but sigwait() prevents the signal hander
3814 // from being run. libpthread would get very confused by not having
3815 // its signal handlers run and prevents sigwait()'s use with the
3816 // mutex granting granting signal.
3817 //
3818 // Currently only ever called on the VMThread and JavaThreads (PC sampling)
3819 //
3820 static void SR_handler(int sig, siginfo_t* siginfo, ucontext_t* context) {
3821   // Save and restore errno to avoid confusing native code with EINTR
3822   // after sigsuspend.
3823   int old_errno = errno;
3824 
3825   Thread* thread = Thread::current();
3826   OSThread* osthread = thread->osthread();
3827   assert(thread->is_VM_thread() || thread->is_Java_thread(), "Must be VMThread or JavaThread");
3828 
3829   os::SuspendResume::State current = osthread->sr.state();
3830   if (current == os::SuspendResume::SR_SUSPEND_REQUEST) {
3831     suspend_save_context(osthread, siginfo, context);
3832 
3833     // attempt to switch the state, we assume we had a SUSPEND_REQUEST
3834     os::SuspendResume::State state = osthread->sr.suspended();
3835     if (state == os::SuspendResume::SR_SUSPENDED) {
3836       sigset_t suspend_set;  // signals for sigsuspend()
3837 
3838       // get current set of blocked signals and unblock resume signal
3839       pthread_sigmask(SIG_BLOCK, NULL, &suspend_set);
3840       sigdelset(&suspend_set, SR_signum);
3841 
3842       sr_semaphore.signal();
3843       // wait here until we are resumed
3844       while (1) {
3845         sigsuspend(&suspend_set);
3846 
3847         os::SuspendResume::State result = osthread->sr.running();
3848         if (result == os::SuspendResume::SR_RUNNING) {
3849           sr_semaphore.signal();
3850           break;
3851         }
3852       }
3853 
3854     } else if (state == os::SuspendResume::SR_RUNNING) {
3855       // request was cancelled, continue
3856     } else {
3857       ShouldNotReachHere();
3858     }
3859 
3860     resume_clear_context(osthread);
3861   } else if (current == os::SuspendResume::SR_RUNNING) {
3862     // request was cancelled, continue
3863   } else if (current == os::SuspendResume::SR_WAKEUP_REQUEST) {
3864     // ignore
3865   } else {
3866     // ignore
3867   }
3868 
3869   errno = old_errno;
3870 }
3871 
3872 
3873 static int SR_initialize() {
3874   struct sigaction act;
3875   char *s;
3876   // Get signal number to use for suspend/resume
3877   if ((s = ::getenv("_JAVA_SR_SIGNUM")) != 0) {
3878     int sig = ::strtol(s, 0, 10);
3879     if (sig > 0 || sig < _NSIG) {
3880       SR_signum = sig;
3881     }
3882   }
3883 
3884   assert(SR_signum > SIGSEGV && SR_signum > SIGBUS,
3885          "SR_signum must be greater than max(SIGSEGV, SIGBUS), see 4355769");
3886 
3887   sigemptyset(&SR_sigset);
3888   sigaddset(&SR_sigset, SR_signum);
3889 
3890   // Set up signal handler for suspend/resume
3891   act.sa_flags = SA_RESTART|SA_SIGINFO;
3892   act.sa_handler = (void (*)(int)) SR_handler;
3893 
3894   // SR_signum is blocked by default.
3895   // 4528190 - We also need to block pthread restart signal (32 on all
3896   // supported Linux platforms). Note that LinuxThreads need to block
3897   // this signal for all threads to work properly. So we don't have
3898   // to use hard-coded signal number when setting up the mask.
3899   pthread_sigmask(SIG_BLOCK, NULL, &act.sa_mask);
3900 
3901   if (sigaction(SR_signum, &act, 0) == -1) {
3902     return -1;
3903   }
3904 
3905   // Save signal flag
3906   os::Linux::set_our_sigflags(SR_signum, act.sa_flags);
3907   return 0;
3908 }
3909 
3910 static int sr_notify(OSThread* osthread) {
3911   int status = pthread_kill(osthread->pthread_id(), SR_signum);
3912   assert_status(status == 0, status, "pthread_kill");
3913   return status;
3914 }
3915 
3916 // "Randomly" selected value for how long we want to spin
3917 // before bailing out on suspending a thread, also how often
3918 // we send a signal to a thread we want to resume
3919 static const int RANDOMLY_LARGE_INTEGER = 1000000;
3920 static const int RANDOMLY_LARGE_INTEGER2 = 100;
3921 
3922 // returns true on success and false on error - really an error is fatal
3923 // but this seems the normal response to library errors
3924 static bool do_suspend(OSThread* osthread) {
3925   assert(osthread->sr.is_running(), "thread should be running");
3926   assert(!sr_semaphore.trywait(), "semaphore has invalid state");
3927 
3928   // mark as suspended and send signal
3929   if (osthread->sr.request_suspend() != os::SuspendResume::SR_SUSPEND_REQUEST) {
3930     // failed to switch, state wasn't running?
3931     ShouldNotReachHere();
3932     return false;
3933   }
3934 
3935   if (sr_notify(osthread) != 0) {
3936     ShouldNotReachHere();
3937   }
3938 
3939   // managed to send the signal and switch to SUSPEND_REQUEST, now wait for SUSPENDED
3940   while (true) {
3941     if (sr_semaphore.timedwait(0, 2 * NANOSECS_PER_MILLISEC)) {
3942       break;
3943     } else {
3944       // timeout
3945       os::SuspendResume::State cancelled = osthread->sr.cancel_suspend();
3946       if (cancelled == os::SuspendResume::SR_RUNNING) {
3947         return false;
3948       } else if (cancelled == os::SuspendResume::SR_SUSPENDED) {
3949         // make sure that we consume the signal on the semaphore as well
3950         sr_semaphore.wait();
3951         break;
3952       } else {
3953         ShouldNotReachHere();
3954         return false;
3955       }
3956     }
3957   }
3958 
3959   guarantee(osthread->sr.is_suspended(), "Must be suspended");
3960   return true;
3961 }
3962 
3963 static void do_resume(OSThread* osthread) {
3964   assert(osthread->sr.is_suspended(), "thread should be suspended");
3965   assert(!sr_semaphore.trywait(), "invalid semaphore state");
3966 
3967   if (osthread->sr.request_wakeup() != os::SuspendResume::SR_WAKEUP_REQUEST) {
3968     // failed to switch to WAKEUP_REQUEST
3969     ShouldNotReachHere();
3970     return;
3971   }
3972 
3973   while (true) {
3974     if (sr_notify(osthread) == 0) {
3975       if (sr_semaphore.timedwait(0, 2 * NANOSECS_PER_MILLISEC)) {
3976         if (osthread->sr.is_running()) {
3977           return;
3978         }
3979       }
3980     } else {
3981       ShouldNotReachHere();
3982     }
3983   }
3984 
3985   guarantee(osthread->sr.is_running(), "Must be running!");
3986 }
3987 
3988 ///////////////////////////////////////////////////////////////////////////////////
3989 // signal handling (except suspend/resume)
3990 
3991 // This routine may be used by user applications as a "hook" to catch signals.
3992 // The user-defined signal handler must pass unrecognized signals to this
3993 // routine, and if it returns true (non-zero), then the signal handler must
3994 // return immediately.  If the flag "abort_if_unrecognized" is true, then this
3995 // routine will never retun false (zero), but instead will execute a VM panic
3996 // routine kill the process.
3997 //
3998 // If this routine returns false, it is OK to call it again.  This allows
3999 // the user-defined signal handler to perform checks either before or after
4000 // the VM performs its own checks.  Naturally, the user code would be making
4001 // a serious error if it tried to handle an exception (such as a null check
4002 // or breakpoint) that the VM was generating for its own correct operation.
4003 //
4004 // This routine may recognize any of the following kinds of signals:
4005 //    SIGBUS, SIGSEGV, SIGILL, SIGFPE, SIGQUIT, SIGPIPE, SIGXFSZ, SIGUSR1.
4006 // It should be consulted by handlers for any of those signals.
4007 //
4008 // The caller of this routine must pass in the three arguments supplied
4009 // to the function referred to in the "sa_sigaction" (not the "sa_handler")
4010 // field of the structure passed to sigaction().  This routine assumes that
4011 // the sa_flags field passed to sigaction() includes SA_SIGINFO and SA_RESTART.
4012 //
4013 // Note that the VM will print warnings if it detects conflicting signal
4014 // handlers, unless invoked with the option "-XX:+AllowUserSignalHandlers".
4015 //
4016 extern "C" JNIEXPORT int JVM_handle_linux_signal(int signo,
4017                                                  siginfo_t* siginfo,
4018                                                  void* ucontext,
4019                                                  int abort_if_unrecognized);
4020 
4021 void signalHandler(int sig, siginfo_t* info, void* uc) {
4022   assert(info != NULL && uc != NULL, "it must be old kernel");
4023   int orig_errno = errno;  // Preserve errno value over signal handler.
4024   JVM_handle_linux_signal(sig, info, uc, true);
4025   errno = orig_errno;
4026 }
4027 
4028 
4029 // This boolean allows users to forward their own non-matching signals
4030 // to JVM_handle_linux_signal, harmlessly.
4031 bool os::Linux::signal_handlers_are_installed = false;
4032 
4033 // For signal-chaining
4034 struct sigaction os::Linux::sigact[MAXSIGNUM];
4035 unsigned int os::Linux::sigs = 0;
4036 bool os::Linux::libjsig_is_loaded = false;
4037 typedef struct sigaction *(*get_signal_t)(int);
4038 get_signal_t os::Linux::get_signal_action = NULL;
4039 
4040 struct sigaction* os::Linux::get_chained_signal_action(int sig) {
4041   struct sigaction *actp = NULL;
4042 
4043   if (libjsig_is_loaded) {
4044     // Retrieve the old signal handler from libjsig
4045     actp = (*get_signal_action)(sig);
4046   }
4047   if (actp == NULL) {
4048     // Retrieve the preinstalled signal handler from jvm
4049     actp = get_preinstalled_handler(sig);
4050   }
4051 
4052   return actp;
4053 }
4054 
4055 static bool call_chained_handler(struct sigaction *actp, int sig,
4056                                  siginfo_t *siginfo, void *context) {
4057   // Call the old signal handler
4058   if (actp->sa_handler == SIG_DFL) {
4059     // It's more reasonable to let jvm treat it as an unexpected exception
4060     // instead of taking the default action.
4061     return false;
4062   } else if (actp->sa_handler != SIG_IGN) {
4063     if ((actp->sa_flags & SA_NODEFER) == 0) {
4064       // automaticlly block the signal
4065       sigaddset(&(actp->sa_mask), sig);
4066     }
4067 
4068     sa_handler_t hand;
4069     sa_sigaction_t sa;
4070     bool siginfo_flag_set = (actp->sa_flags & SA_SIGINFO) != 0;
4071     // retrieve the chained handler
4072     if (siginfo_flag_set) {
4073       sa = actp->sa_sigaction;
4074     } else {
4075       hand = actp->sa_handler;
4076     }
4077 
4078     if ((actp->sa_flags & SA_RESETHAND) != 0) {
4079       actp->sa_handler = SIG_DFL;
4080     }
4081 
4082     // try to honor the signal mask
4083     sigset_t oset;
4084     pthread_sigmask(SIG_SETMASK, &(actp->sa_mask), &oset);
4085 
4086     // call into the chained handler
4087     if (siginfo_flag_set) {
4088       (*sa)(sig, siginfo, context);
4089     } else {
4090       (*hand)(sig);
4091     }
4092 
4093     // restore the signal mask
4094     pthread_sigmask(SIG_SETMASK, &oset, 0);
4095   }
4096   // Tell jvm's signal handler the signal is taken care of.
4097   return true;
4098 }
4099 
4100 bool os::Linux::chained_handler(int sig, siginfo_t* siginfo, void* context) {
4101   bool chained = false;
4102   // signal-chaining
4103   if (UseSignalChaining) {
4104     struct sigaction *actp = get_chained_signal_action(sig);
4105     if (actp != NULL) {
4106       chained = call_chained_handler(actp, sig, siginfo, context);
4107     }
4108   }
4109   return chained;
4110 }
4111 
4112 struct sigaction* os::Linux::get_preinstalled_handler(int sig) {
4113   if ((((unsigned int)1 << sig) & sigs) != 0) {
4114     return &sigact[sig];
4115   }
4116   return NULL;
4117 }
4118 
4119 void os::Linux::save_preinstalled_handler(int sig, struct sigaction& oldAct) {
4120   assert(sig > 0 && sig < MAXSIGNUM, "vm signal out of expected range");
4121   sigact[sig] = oldAct;
4122   sigs |= (unsigned int)1 << sig;
4123 }
4124 
4125 // for diagnostic
4126 int os::Linux::sigflags[MAXSIGNUM];
4127 
4128 int os::Linux::get_our_sigflags(int sig) {
4129   assert(sig > 0 && sig < MAXSIGNUM, "vm signal out of expected range");
4130   return sigflags[sig];
4131 }
4132 
4133 void os::Linux::set_our_sigflags(int sig, int flags) {
4134   assert(sig > 0 && sig < MAXSIGNUM, "vm signal out of expected range");
4135   sigflags[sig] = flags;
4136 }
4137 
4138 void os::Linux::set_signal_handler(int sig, bool set_installed) {
4139   // Check for overwrite.
4140   struct sigaction oldAct;
4141   sigaction(sig, (struct sigaction*)NULL, &oldAct);
4142 
4143   void* oldhand = oldAct.sa_sigaction
4144                 ? CAST_FROM_FN_PTR(void*,  oldAct.sa_sigaction)
4145                 : CAST_FROM_FN_PTR(void*,  oldAct.sa_handler);
4146   if (oldhand != CAST_FROM_FN_PTR(void*, SIG_DFL) &&
4147       oldhand != CAST_FROM_FN_PTR(void*, SIG_IGN) &&
4148       oldhand != CAST_FROM_FN_PTR(void*, (sa_sigaction_t)signalHandler)) {
4149     if (AllowUserSignalHandlers || !set_installed) {
4150       // Do not overwrite; user takes responsibility to forward to us.
4151       return;
4152     } else if (UseSignalChaining) {
4153       // save the old handler in jvm
4154       save_preinstalled_handler(sig, oldAct);
4155       // libjsig also interposes the sigaction() call below and saves the
4156       // old sigaction on it own.
4157     } else {
4158       fatal(err_msg("Encountered unexpected pre-existing sigaction handler "
4159                     "%#lx for signal %d.", (long)oldhand, sig));
4160     }
4161   }
4162 
4163   struct sigaction sigAct;
4164   sigfillset(&(sigAct.sa_mask));
4165   sigAct.sa_handler = SIG_DFL;
4166   if (!set_installed) {
4167     sigAct.sa_flags = SA_SIGINFO|SA_RESTART;
4168   } else {
4169     sigAct.sa_sigaction = signalHandler;
4170     sigAct.sa_flags = SA_SIGINFO|SA_RESTART;
4171   }
4172   // Save flags, which are set by ours
4173   assert(sig > 0 && sig < MAXSIGNUM, "vm signal out of expected range");
4174   sigflags[sig] = sigAct.sa_flags;
4175 
4176   int ret = sigaction(sig, &sigAct, &oldAct);
4177   assert(ret == 0, "check");
4178 
4179   void* oldhand2  = oldAct.sa_sigaction
4180                   ? CAST_FROM_FN_PTR(void*, oldAct.sa_sigaction)
4181                   : CAST_FROM_FN_PTR(void*, oldAct.sa_handler);
4182   assert(oldhand2 == oldhand, "no concurrent signal handler installation");
4183 }
4184 
4185 // install signal handlers for signals that HotSpot needs to
4186 // handle in order to support Java-level exception handling.
4187 
4188 void os::Linux::install_signal_handlers() {
4189   if (!signal_handlers_are_installed) {
4190     signal_handlers_are_installed = true;
4191 
4192     // signal-chaining
4193     typedef void (*signal_setting_t)();
4194     signal_setting_t begin_signal_setting = NULL;
4195     signal_setting_t end_signal_setting = NULL;
4196     begin_signal_setting = CAST_TO_FN_PTR(signal_setting_t,
4197                                           dlsym(RTLD_DEFAULT, "JVM_begin_signal_setting"));
4198     if (begin_signal_setting != NULL) {
4199       end_signal_setting = CAST_TO_FN_PTR(signal_setting_t,
4200                                           dlsym(RTLD_DEFAULT, "JVM_end_signal_setting"));
4201       get_signal_action = CAST_TO_FN_PTR(get_signal_t,
4202                                          dlsym(RTLD_DEFAULT, "JVM_get_signal_action"));
4203       libjsig_is_loaded = true;
4204       assert(UseSignalChaining, "should enable signal-chaining");
4205     }
4206     if (libjsig_is_loaded) {
4207       // Tell libjsig jvm is setting signal handlers
4208       (*begin_signal_setting)();
4209     }
4210 
4211     set_signal_handler(SIGSEGV, true);
4212     set_signal_handler(SIGPIPE, true);
4213     set_signal_handler(SIGBUS, true);
4214     set_signal_handler(SIGILL, true);
4215     set_signal_handler(SIGFPE, true);
4216 #if defined(PPC64)
4217     set_signal_handler(SIGTRAP, true);
4218 #endif
4219     set_signal_handler(SIGXFSZ, true);
4220 
4221     if (libjsig_is_loaded) {
4222       // Tell libjsig jvm finishes setting signal handlers
4223       (*end_signal_setting)();
4224     }
4225 
4226     // We don't activate signal checker if libjsig is in place, we trust ourselves
4227     // and if UserSignalHandler is installed all bets are off.
4228     // Log that signal checking is off only if -verbose:jni is specified.
4229     if (CheckJNICalls) {
4230       if (libjsig_is_loaded) {
4231         if (PrintJNIResolving) {
4232           tty->print_cr("Info: libjsig is activated, all active signal checking is disabled");
4233         }
4234         check_signals = false;
4235       }
4236       if (AllowUserSignalHandlers) {
4237         if (PrintJNIResolving) {
4238           tty->print_cr("Info: AllowUserSignalHandlers is activated, all active signal checking is disabled");
4239         }
4240         check_signals = false;
4241       }
4242     }
4243   }
4244 }
4245 
4246 // This is the fastest way to get thread cpu time on Linux.
4247 // Returns cpu time (user+sys) for any thread, not only for current.
4248 // POSIX compliant clocks are implemented in the kernels 2.6.16+.
4249 // It might work on 2.6.10+ with a special kernel/glibc patch.
4250 // For reference, please, see IEEE Std 1003.1-2004:
4251 //   http://www.unix.org/single_unix_specification
4252 
4253 jlong os::Linux::fast_thread_cpu_time(clockid_t clockid) {
4254   struct timespec tp;
4255   int rc = os::Linux::clock_gettime(clockid, &tp);
4256   assert(rc == 0, "clock_gettime is expected to return 0 code");
4257 
4258   return (tp.tv_sec * NANOSECS_PER_SEC) + tp.tv_nsec;
4259 }
4260 
4261 /////
4262 // glibc on Linux platform uses non-documented flag
4263 // to indicate, that some special sort of signal
4264 // trampoline is used.
4265 // We will never set this flag, and we should
4266 // ignore this flag in our diagnostic
4267 #ifdef SIGNIFICANT_SIGNAL_MASK
4268   #undef SIGNIFICANT_SIGNAL_MASK
4269 #endif
4270 #define SIGNIFICANT_SIGNAL_MASK (~0x04000000)
4271 
4272 static const char* get_signal_handler_name(address handler,
4273                                            char* buf, int buflen) {
4274   int offset;
4275   bool found = os::dll_address_to_library_name(handler, buf, buflen, &offset);
4276   if (found) {
4277     // skip directory names
4278     const char *p1, *p2;
4279     p1 = buf;
4280     size_t len = strlen(os::file_separator());
4281     while ((p2 = strstr(p1, os::file_separator())) != NULL) p1 = p2 + len;
4282     jio_snprintf(buf, buflen, "%s+0x%x", p1, offset);
4283   } else {
4284     jio_snprintf(buf, buflen, PTR_FORMAT, handler);
4285   }
4286   return buf;
4287 }
4288 
4289 static void print_signal_handler(outputStream* st, int sig,
4290                                  char* buf, size_t buflen) {
4291   struct sigaction sa;
4292 
4293   sigaction(sig, NULL, &sa);
4294 
4295   // See comment for SIGNIFICANT_SIGNAL_MASK define
4296   sa.sa_flags &= SIGNIFICANT_SIGNAL_MASK;
4297 
4298   st->print("%s: ", os::exception_name(sig, buf, buflen));
4299 
4300   address handler = (sa.sa_flags & SA_SIGINFO)
4301     ? CAST_FROM_FN_PTR(address, sa.sa_sigaction)
4302     : CAST_FROM_FN_PTR(address, sa.sa_handler);
4303 
4304   if (handler == CAST_FROM_FN_PTR(address, SIG_DFL)) {
4305     st->print("SIG_DFL");
4306   } else if (handler == CAST_FROM_FN_PTR(address, SIG_IGN)) {
4307     st->print("SIG_IGN");
4308   } else {
4309     st->print("[%s]", get_signal_handler_name(handler, buf, buflen));
4310   }
4311 
4312   st->print(", sa_mask[0]=");
4313   os::Posix::print_signal_set_short(st, &sa.sa_mask);
4314 
4315   address rh = VMError::get_resetted_sighandler(sig);
4316   // May be, handler was resetted by VMError?
4317   if (rh != NULL) {
4318     handler = rh;
4319     sa.sa_flags = VMError::get_resetted_sigflags(sig) & SIGNIFICANT_SIGNAL_MASK;
4320   }
4321 
4322   st->print(", sa_flags=");
4323   os::Posix::print_sa_flags(st, sa.sa_flags);
4324 
4325   // Check: is it our handler?
4326   if (handler == CAST_FROM_FN_PTR(address, (sa_sigaction_t)signalHandler) ||
4327       handler == CAST_FROM_FN_PTR(address, (sa_sigaction_t)SR_handler)) {
4328     // It is our signal handler
4329     // check for flags, reset system-used one!
4330     if ((int)sa.sa_flags != os::Linux::get_our_sigflags(sig)) {
4331       st->print(
4332                 ", flags was changed from " PTR32_FORMAT ", consider using jsig library",
4333                 os::Linux::get_our_sigflags(sig));
4334     }
4335   }
4336   st->cr();
4337 }
4338 
4339 
4340 #define DO_SIGNAL_CHECK(sig)                      \
4341   do {                                            \
4342     if (!sigismember(&check_signal_done, sig)) {  \
4343       os::Linux::check_signal_handler(sig);       \
4344     }                                             \
4345   } while (0)
4346 
4347 // This method is a periodic task to check for misbehaving JNI applications
4348 // under CheckJNI, we can add any periodic checks here
4349 
4350 void os::run_periodic_checks() {
4351   if (check_signals == false) return;
4352 
4353   // SEGV and BUS if overridden could potentially prevent
4354   // generation of hs*.log in the event of a crash, debugging
4355   // such a case can be very challenging, so we absolutely
4356   // check the following for a good measure:
4357   DO_SIGNAL_CHECK(SIGSEGV);
4358   DO_SIGNAL_CHECK(SIGILL);
4359   DO_SIGNAL_CHECK(SIGFPE);
4360   DO_SIGNAL_CHECK(SIGBUS);
4361   DO_SIGNAL_CHECK(SIGPIPE);
4362   DO_SIGNAL_CHECK(SIGXFSZ);
4363 #if defined(PPC64)
4364   DO_SIGNAL_CHECK(SIGTRAP);
4365 #endif
4366 
4367   // ReduceSignalUsage allows the user to override these handlers
4368   // see comments at the very top and jvm_solaris.h
4369   if (!ReduceSignalUsage) {
4370     DO_SIGNAL_CHECK(SHUTDOWN1_SIGNAL);
4371     DO_SIGNAL_CHECK(SHUTDOWN2_SIGNAL);
4372     DO_SIGNAL_CHECK(SHUTDOWN3_SIGNAL);
4373     DO_SIGNAL_CHECK(BREAK_SIGNAL);
4374   }
4375 
4376   DO_SIGNAL_CHECK(SR_signum);
4377   DO_SIGNAL_CHECK(INTERRUPT_SIGNAL);
4378 }
4379 
4380 typedef int (*os_sigaction_t)(int, const struct sigaction *, struct sigaction *);
4381 
4382 static os_sigaction_t os_sigaction = NULL;
4383 
4384 void os::Linux::check_signal_handler(int sig) {
4385   char buf[O_BUFLEN];
4386   address jvmHandler = NULL;
4387 
4388 
4389   struct sigaction act;
4390   if (os_sigaction == NULL) {
4391     // only trust the default sigaction, in case it has been interposed
4392     os_sigaction = (os_sigaction_t)dlsym(RTLD_DEFAULT, "sigaction");
4393     if (os_sigaction == NULL) return;
4394   }
4395 
4396   os_sigaction(sig, (struct sigaction*)NULL, &act);
4397 
4398 
4399   act.sa_flags &= SIGNIFICANT_SIGNAL_MASK;
4400 
4401   address thisHandler = (act.sa_flags & SA_SIGINFO)
4402     ? CAST_FROM_FN_PTR(address, act.sa_sigaction)
4403     : CAST_FROM_FN_PTR(address, act.sa_handler);
4404 
4405 
4406   switch (sig) {
4407   case SIGSEGV:
4408   case SIGBUS:
4409   case SIGFPE:
4410   case SIGPIPE:
4411   case SIGILL:
4412   case SIGXFSZ:
4413     jvmHandler = CAST_FROM_FN_PTR(address, (sa_sigaction_t)signalHandler);
4414     break;
4415 
4416   case SHUTDOWN1_SIGNAL:
4417   case SHUTDOWN2_SIGNAL:
4418   case SHUTDOWN3_SIGNAL:
4419   case BREAK_SIGNAL:
4420     jvmHandler = (address)user_handler();
4421     break;
4422 
4423   case INTERRUPT_SIGNAL:
4424     jvmHandler = CAST_FROM_FN_PTR(address, SIG_DFL);
4425     break;
4426 
4427   default:
4428     if (sig == SR_signum) {
4429       jvmHandler = CAST_FROM_FN_PTR(address, (sa_sigaction_t)SR_handler);
4430     } else {
4431       return;
4432     }
4433     break;
4434   }
4435 
4436   if (thisHandler != jvmHandler) {
4437     tty->print("Warning: %s handler ", exception_name(sig, buf, O_BUFLEN));
4438     tty->print("expected:%s", get_signal_handler_name(jvmHandler, buf, O_BUFLEN));
4439     tty->print_cr("  found:%s", get_signal_handler_name(thisHandler, buf, O_BUFLEN));
4440     // No need to check this sig any longer
4441     sigaddset(&check_signal_done, sig);
4442     // Running under non-interactive shell, SHUTDOWN2_SIGNAL will be reassigned SIG_IGN
4443     if (sig == SHUTDOWN2_SIGNAL && !isatty(fileno(stdin))) {
4444       tty->print_cr("Running in non-interactive shell, %s handler is replaced by shell",
4445                     exception_name(sig, buf, O_BUFLEN));
4446     }
4447   } else if(os::Linux::get_our_sigflags(sig) != 0 && (int)act.sa_flags != os::Linux::get_our_sigflags(sig)) {
4448     tty->print("Warning: %s handler flags ", exception_name(sig, buf, O_BUFLEN));
4449     tty->print("expected:" PTR32_FORMAT, os::Linux::get_our_sigflags(sig));
4450     tty->print_cr("  found:" PTR32_FORMAT, act.sa_flags);
4451     // No need to check this sig any longer
4452     sigaddset(&check_signal_done, sig);
4453   }
4454 
4455   // Dump all the signal
4456   if (sigismember(&check_signal_done, sig)) {
4457     print_signal_handlers(tty, buf, O_BUFLEN);
4458   }
4459 }
4460 
4461 extern void report_error(char* file_name, int line_no, char* title,
4462                          char* format, ...);
4463 
4464 extern bool signal_name(int signo, char* buf, size_t len);
4465 
4466 const char* os::exception_name(int exception_code, char* buf, size_t size) {
4467   if (0 < exception_code && exception_code <= SIGRTMAX) {
4468     // signal
4469     if (!signal_name(exception_code, buf, size)) {
4470       jio_snprintf(buf, size, "SIG%d", exception_code);
4471     }
4472     return buf;
4473   } else {
4474     return NULL;
4475   }
4476 }
4477 
4478 // this is called _before_ the most of global arguments have been parsed
4479 void os::init(void) {
4480   char dummy;   // used to get a guess on initial stack address
4481 //  first_hrtime = gethrtime();
4482 
4483   clock_tics_per_sec = sysconf(_SC_CLK_TCK);
4484 
4485   init_random(1234567);
4486 
4487   ThreadCritical::initialize();
4488 
4489   Linux::set_page_size(sysconf(_SC_PAGESIZE));
4490   if (Linux::page_size() == -1) {
4491     fatal(err_msg("os_linux.cpp: os::init: sysconf failed (%s)",
4492                   strerror(errno)));
4493   }
4494   init_page_sizes((size_t) Linux::page_size());
4495 
4496   Linux::initialize_system_info();
4497 
4498   // main_thread points to the aboriginal thread
4499   Linux::_main_thread = pthread_self();
4500 
4501   Linux::clock_init();
4502   initial_time_count = javaTimeNanos();
4503 
4504   // pthread_condattr initialization for monotonic clock
4505   int status;
4506   pthread_condattr_t* _condattr = os::Linux::condAttr();
4507   if ((status = pthread_condattr_init(_condattr)) != 0) {
4508     fatal(err_msg("pthread_condattr_init: %s", strerror(status)));
4509   }
4510   // Only set the clock if CLOCK_MONOTONIC is available
4511   if (os::supports_monotonic_clock()) {
4512     if ((status = pthread_condattr_setclock(_condattr, CLOCK_MONOTONIC)) != 0) {
4513       if (status == EINVAL) {
4514         warning("Unable to use monotonic clock with relative timed-waits" \
4515                 " - changes to the time-of-day clock may have adverse affects");
4516       } else {
4517         fatal(err_msg("pthread_condattr_setclock: %s", strerror(status)));
4518       }
4519     }
4520   }
4521   // else it defaults to CLOCK_REALTIME
4522 
4523   // If the pagesize of the VM is greater than 8K determine the appropriate
4524   // number of initial guard pages.  The user can change this with the
4525   // command line arguments, if needed.
4526   if (vm_page_size() > (int)Linux::vm_default_page_size()) {
4527     StackYellowPages = 1;
4528     StackRedPages = 1;
4529     StackShadowPages = round_to((StackShadowPages*Linux::vm_default_page_size()), vm_page_size()) / vm_page_size();
4530   }
4531 
4532   // retrieve entry point for pthread_setname_np
4533   Linux::_pthread_setname_np =
4534     (int(*)(pthread_t, const char*))dlsym(RTLD_DEFAULT, "pthread_setname_np");
4535 
4536 }
4537 
4538 // To install functions for atexit system call
4539 extern "C" {
4540   static void perfMemory_exit_helper() {
4541     perfMemory_exit();
4542   }
4543 }
4544 
4545 // this is called _after_ the global arguments have been parsed
4546 jint os::init_2(void) {
4547   Linux::fast_thread_clock_init();
4548 
4549   // Allocate a single page and mark it as readable for safepoint polling
4550   address polling_page = (address) ::mmap(NULL, Linux::page_size(), PROT_READ, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
4551   guarantee(polling_page != MAP_FAILED, "os::init_2: failed to allocate polling page");
4552 
4553   os::set_polling_page(polling_page);
4554 
4555 #ifndef PRODUCT
4556   if (Verbose && PrintMiscellaneous) {
4557     tty->print("[SafePoint Polling address: " INTPTR_FORMAT "]\n",
4558                (intptr_t)polling_page);
4559   }
4560 #endif
4561 
4562   if (!UseMembar) {
4563     address mem_serialize_page = (address) ::mmap(NULL, Linux::page_size(), PROT_READ | PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
4564     guarantee(mem_serialize_page != MAP_FAILED, "mmap Failed for memory serialize page");
4565     os::set_memory_serialize_page(mem_serialize_page);
4566 
4567 #ifndef PRODUCT
4568     if (Verbose && PrintMiscellaneous) {
4569       tty->print("[Memory Serialize  Page address: " INTPTR_FORMAT "]\n",
4570                  (intptr_t)mem_serialize_page);
4571     }
4572 #endif
4573   }
4574 
4575   // initialize suspend/resume support - must do this before signal_sets_init()
4576   if (SR_initialize() != 0) {
4577     perror("SR_initialize failed");
4578     return JNI_ERR;
4579   }
4580 
4581   Linux::signal_sets_init();
4582   Linux::install_signal_handlers();
4583 
4584   // Check minimum allowable stack size for thread creation and to initialize
4585   // the java system classes, including StackOverflowError - depends on page
4586   // size.  Add a page for compiler2 recursion in main thread.
4587   // Add in 2*BytesPerWord times page size to account for VM stack during
4588   // class initialization depending on 32 or 64 bit VM.
4589   os::Linux::min_stack_allowed = MAX2(os::Linux::min_stack_allowed,
4590                                       (size_t)(StackYellowPages+StackRedPages+StackShadowPages) * Linux::page_size() +
4591                                       (2*BytesPerWord COMPILER2_PRESENT(+1)) * Linux::vm_default_page_size());
4592 
4593   size_t threadStackSizeInBytes = ThreadStackSize * K;
4594   if (threadStackSizeInBytes != 0 &&
4595       threadStackSizeInBytes < os::Linux::min_stack_allowed) {
4596     tty->print_cr("\nThe stack size specified is too small, "
4597                   "Specify at least %dk",
4598                   os::Linux::min_stack_allowed/ K);
4599     return JNI_ERR;
4600   }
4601 
4602   // Make the stack size a multiple of the page size so that
4603   // the yellow/red zones can be guarded.
4604   JavaThread::set_stack_size_at_create(round_to(threadStackSizeInBytes,
4605                                                 vm_page_size()));
4606 
4607   Linux::capture_initial_stack(JavaThread::stack_size_at_create());
4608 
4609 #if defined(IA32)
4610   workaround_expand_exec_shield_cs_limit();
4611 #endif
4612 
4613   Linux::libpthread_init();
4614   if (PrintMiscellaneous && (Verbose || WizardMode)) {
4615     tty->print_cr("[HotSpot is running with %s, %s]\n",
4616                   Linux::glibc_version(), Linux::libpthread_version());
4617   }
4618 
4619   if (UseNUMA) {
4620     if (!Linux::libnuma_init()) {
4621       UseNUMA = false;
4622     } else {
4623       if ((Linux::numa_max_node() < 1)) {
4624         // There's only one node(they start from 0), disable NUMA.
4625         UseNUMA = false;
4626       }
4627     }
4628     // With SHM and HugeTLBFS large pages we cannot uncommit a page, so there's no way
4629     // we can make the adaptive lgrp chunk resizing work. If the user specified
4630     // both UseNUMA and UseLargePages (or UseSHM/UseHugeTLBFS) on the command line - warn and
4631     // disable adaptive resizing.
4632     if (UseNUMA && UseLargePages && !can_commit_large_page_memory()) {
4633       if (FLAG_IS_DEFAULT(UseNUMA)) {
4634         UseNUMA = false;
4635       } else {
4636         if (FLAG_IS_DEFAULT(UseLargePages) &&
4637             FLAG_IS_DEFAULT(UseSHM) &&
4638             FLAG_IS_DEFAULT(UseHugeTLBFS)) {
4639           UseLargePages = false;
4640         } else if (UseAdaptiveSizePolicy || UseAdaptiveNUMAChunkSizing) {
4641           warning("UseNUMA is not fully compatible with SHM/HugeTLBFS large pages, disabling adaptive resizing (-XX:-UseAdaptiveSizePolicy -XX:-UseAdaptiveNUMAChunkSizing)");
4642           UseAdaptiveSizePolicy = false;
4643           UseAdaptiveNUMAChunkSizing = false;
4644         }
4645       }
4646     }
4647     if (!UseNUMA && ForceNUMA) {
4648       UseNUMA = true;
4649     }
4650   }
4651 
4652   if (MaxFDLimit) {
4653     // set the number of file descriptors to max. print out error
4654     // if getrlimit/setrlimit fails but continue regardless.
4655     struct rlimit nbr_files;
4656     int status = getrlimit(RLIMIT_NOFILE, &nbr_files);
4657     if (status != 0) {
4658       if (PrintMiscellaneous && (Verbose || WizardMode)) {
4659         perror("os::init_2 getrlimit failed");
4660       }
4661     } else {
4662       nbr_files.rlim_cur = nbr_files.rlim_max;
4663       status = setrlimit(RLIMIT_NOFILE, &nbr_files);
4664       if (status != 0) {
4665         if (PrintMiscellaneous && (Verbose || WizardMode)) {
4666           perror("os::init_2 setrlimit failed");
4667         }
4668       }
4669     }
4670   }
4671 
4672   // Initialize lock used to serialize thread creation (see os::create_thread)
4673   Linux::set_createThread_lock(new Mutex(Mutex::leaf, "createThread_lock", false));
4674 
4675   // at-exit methods are called in the reverse order of their registration.
4676   // atexit functions are called on return from main or as a result of a
4677   // call to exit(3C). There can be only 32 of these functions registered
4678   // and atexit() does not set errno.
4679 
4680   if (PerfAllowAtExitRegistration) {
4681     // only register atexit functions if PerfAllowAtExitRegistration is set.
4682     // atexit functions can be delayed until process exit time, which
4683     // can be problematic for embedded VM situations. Embedded VMs should
4684     // call DestroyJavaVM() to assure that VM resources are released.
4685 
4686     // note: perfMemory_exit_helper atexit function may be removed in
4687     // the future if the appropriate cleanup code can be added to the
4688     // VM_Exit VMOperation's doit method.
4689     if (atexit(perfMemory_exit_helper) != 0) {
4690       warning("os::init_2 atexit(perfMemory_exit_helper) failed");
4691     }
4692   }
4693 
4694   // initialize thread priority policy
4695   prio_init();
4696 
4697   return JNI_OK;
4698 }
4699 
4700 // Mark the polling page as unreadable
4701 void os::make_polling_page_unreadable(void) {
4702   if (!guard_memory((char*)_polling_page, Linux::page_size())) {
4703     fatal("Could not disable polling page");
4704   }
4705 }
4706 
4707 // Mark the polling page as readable
4708 void os::make_polling_page_readable(void) {
4709   if (!linux_mprotect((char *)_polling_page, Linux::page_size(), PROT_READ)) {
4710     fatal("Could not enable polling page");
4711   }
4712 }
4713 
4714 int os::active_processor_count() {
4715   // Linux doesn't yet have a (official) notion of processor sets,
4716   // so just return the number of online processors.
4717   int online_cpus = ::sysconf(_SC_NPROCESSORS_ONLN);
4718   assert(online_cpus > 0 && online_cpus <= processor_count(), "sanity check");
4719   return online_cpus;
4720 }
4721 
4722 void os::set_native_thread_name(const char *name) {
4723   if (Linux::_pthread_setname_np) {
4724     char buf [16]; // according to glibc manpage, 16 chars incl. '/0'
4725     snprintf(buf, sizeof(buf), "%s", name);
4726     buf[sizeof(buf) - 1] = '\0';
4727     const int rc = Linux::_pthread_setname_np(pthread_self(), buf);
4728     // ERANGE should not happen; all other errors should just be ignored.
4729     assert(rc != ERANGE, "pthread_setname_np failed");
4730   }
4731 }
4732 
4733 bool os::distribute_processes(uint length, uint* distribution) {
4734   // Not yet implemented.
4735   return false;
4736 }
4737 
4738 bool os::bind_to_processor(uint processor_id) {
4739   // Not yet implemented.
4740   return false;
4741 }
4742 
4743 ///
4744 
4745 void os::SuspendedThreadTask::internal_do_task() {
4746   if (do_suspend(_thread->osthread())) {
4747     SuspendedThreadTaskContext context(_thread, _thread->osthread()->ucontext());
4748     do_task(context);
4749     do_resume(_thread->osthread());
4750   }
4751 }
4752 
4753 class PcFetcher : public os::SuspendedThreadTask {
4754  public:
4755   PcFetcher(Thread* thread) : os::SuspendedThreadTask(thread) {}
4756   ExtendedPC result();
4757  protected:
4758   void do_task(const os::SuspendedThreadTaskContext& context);
4759  private:
4760   ExtendedPC _epc;
4761 };
4762 
4763 ExtendedPC PcFetcher::result() {
4764   guarantee(is_done(), "task is not done yet.");
4765   return _epc;
4766 }
4767 
4768 void PcFetcher::do_task(const os::SuspendedThreadTaskContext& context) {
4769   Thread* thread = context.thread();
4770   OSThread* osthread = thread->osthread();
4771   if (osthread->ucontext() != NULL) {
4772     _epc = os::Linux::ucontext_get_pc((ucontext_t *) context.ucontext());
4773   } else {
4774     // NULL context is unexpected, double-check this is the VMThread
4775     guarantee(thread->is_VM_thread(), "can only be called for VMThread");
4776   }
4777 }
4778 
4779 // Suspends the target using the signal mechanism and then grabs the PC before
4780 // resuming the target. Used by the flat-profiler only
4781 ExtendedPC os::get_thread_pc(Thread* thread) {
4782   // Make sure that it is called by the watcher for the VMThread
4783   assert(Thread::current()->is_Watcher_thread(), "Must be watcher");
4784   assert(thread->is_VM_thread(), "Can only be called for VMThread");
4785 
4786   PcFetcher fetcher(thread);
4787   fetcher.run();
4788   return fetcher.result();
4789 }
4790 
4791 ////////////////////////////////////////////////////////////////////////////////
4792 // debug support
4793 
4794 bool os::find(address addr, outputStream* st) {
4795   Dl_info dlinfo;
4796   memset(&dlinfo, 0, sizeof(dlinfo));
4797   if (dladdr(addr, &dlinfo) != 0) {
4798     st->print(PTR_FORMAT ": ", addr);
4799     if (dlinfo.dli_sname != NULL && dlinfo.dli_saddr != NULL) {
4800       st->print("%s+%#x", dlinfo.dli_sname,
4801                 addr - (intptr_t)dlinfo.dli_saddr);
4802     } else if (dlinfo.dli_fbase != NULL) {
4803       st->print("<offset %#x>", addr - (intptr_t)dlinfo.dli_fbase);
4804     } else {
4805       st->print("<absolute address>");
4806     }
4807     if (dlinfo.dli_fname != NULL) {
4808       st->print(" in %s", dlinfo.dli_fname);
4809     }
4810     if (dlinfo.dli_fbase != NULL) {
4811       st->print(" at " PTR_FORMAT, dlinfo.dli_fbase);
4812     }
4813     st->cr();
4814 
4815     if (Verbose) {
4816       // decode some bytes around the PC
4817       address begin = clamp_address_in_page(addr-40, addr, os::vm_page_size());
4818       address end   = clamp_address_in_page(addr+40, addr, os::vm_page_size());
4819       address       lowest = (address) dlinfo.dli_sname;
4820       if (!lowest)  lowest = (address) dlinfo.dli_fbase;
4821       if (begin < lowest)  begin = lowest;
4822       Dl_info dlinfo2;
4823       if (dladdr(end, &dlinfo2) != 0 && dlinfo2.dli_saddr != dlinfo.dli_saddr
4824           && end > dlinfo2.dli_saddr && dlinfo2.dli_saddr > begin) {
4825         end = (address) dlinfo2.dli_saddr;
4826       }
4827       Disassembler::decode(begin, end, st);
4828     }
4829     return true;
4830   }
4831   return false;
4832 }
4833 
4834 ////////////////////////////////////////////////////////////////////////////////
4835 // misc
4836 
4837 // This does not do anything on Linux. This is basically a hook for being
4838 // able to use structured exception handling (thread-local exception filters)
4839 // on, e.g., Win32.
4840 void
4841 os::os_exception_wrapper(java_call_t f, JavaValue* value, methodHandle* method,
4842                          JavaCallArguments* args, Thread* thread) {
4843   f(value, method, args, thread);
4844 }
4845 
4846 void os::print_statistics() {
4847 }
4848 
4849 int os::message_box(const char* title, const char* message) {
4850   int i;
4851   fdStream err(defaultStream::error_fd());
4852   for (i = 0; i < 78; i++) err.print_raw("=");
4853   err.cr();
4854   err.print_raw_cr(title);
4855   for (i = 0; i < 78; i++) err.print_raw("-");
4856   err.cr();
4857   err.print_raw_cr(message);
4858   for (i = 0; i < 78; i++) err.print_raw("=");
4859   err.cr();
4860 
4861   char buf[16];
4862   // Prevent process from exiting upon "read error" without consuming all CPU
4863   while (::read(0, buf, sizeof(buf)) <= 0) { ::sleep(100); }
4864 
4865   return buf[0] == 'y' || buf[0] == 'Y';
4866 }
4867 
4868 int os::stat(const char *path, struct stat *sbuf) {
4869   char pathbuf[MAX_PATH];
4870   if (strlen(path) > MAX_PATH - 1) {
4871     errno = ENAMETOOLONG;
4872     return -1;
4873   }
4874   os::native_path(strcpy(pathbuf, path));
4875   return ::stat(pathbuf, sbuf);
4876 }
4877 
4878 bool os::check_heap(bool force) {
4879   return true;
4880 }
4881 
4882 // Is a (classpath) directory empty?
4883 bool os::dir_is_empty(const char* path) {
4884   DIR *dir = NULL;
4885   struct dirent *ptr;
4886 
4887   dir = opendir(path);
4888   if (dir == NULL) return true;
4889 
4890   // Scan the directory
4891   bool result = true;
4892   char buf[sizeof(struct dirent) + MAX_PATH];
4893   while (result && (ptr = ::readdir(dir)) != NULL) {
4894     if (strcmp(ptr->d_name, ".") != 0 && strcmp(ptr->d_name, "..") != 0) {
4895       result = false;
4896     }
4897   }
4898   closedir(dir);
4899   return result;
4900 }
4901 
4902 // This code originates from JDK's sysOpen and open64_w
4903 // from src/solaris/hpi/src/system_md.c
4904 
4905 int os::open(const char *path, int oflag, int mode) {
4906   if (strlen(path) > MAX_PATH - 1) {
4907     errno = ENAMETOOLONG;
4908     return -1;
4909   }
4910 
4911   // All file descriptors that are opened in the Java process and not
4912   // specifically destined for a subprocess should have the close-on-exec
4913   // flag set.  If we don't set it, then careless 3rd party native code
4914   // might fork and exec without closing all appropriate file descriptors
4915   // (e.g. as we do in closeDescriptors in UNIXProcess.c), and this in
4916   // turn might:
4917   //
4918   // - cause end-of-file to fail to be detected on some file
4919   //   descriptors, resulting in mysterious hangs, or
4920   //
4921   // - might cause an fopen in the subprocess to fail on a system
4922   //   suffering from bug 1085341.
4923   //
4924   // (Yes, the default setting of the close-on-exec flag is a Unix
4925   // design flaw)
4926   //
4927   // See:
4928   // 1085341: 32-bit stdio routines should support file descriptors >255
4929   // 4843136: (process) pipe file descriptor from Runtime.exec not being closed
4930   // 6339493: (process) Runtime.exec does not close all file descriptors on Solaris 9
4931   //
4932   // Modern Linux kernels (after 2.6.23 2007) support O_CLOEXEC with open().
4933   // O_CLOEXEC is preferable to using FD_CLOEXEC on an open file descriptor
4934   // because it saves a system call and removes a small window where the flag
4935   // is unset.  On ancient Linux kernels the O_CLOEXEC flag will be ignored
4936   // and we fall back to using FD_CLOEXEC (see below).
4937 #ifdef O_CLOEXEC
4938   oflag |= O_CLOEXEC;
4939 #endif
4940 
4941   int fd = ::open64(path, oflag, mode);
4942   if (fd == -1) return -1;
4943 
4944   //If the open succeeded, the file might still be a directory
4945   {
4946     struct stat64 buf64;
4947     int ret = ::fstat64(fd, &buf64);
4948     int st_mode = buf64.st_mode;
4949 
4950     if (ret != -1) {
4951       if ((st_mode & S_IFMT) == S_IFDIR) {
4952         errno = EISDIR;
4953         ::close(fd);
4954         return -1;
4955       }
4956     } else {
4957       ::close(fd);
4958       return -1;
4959     }
4960   }
4961 
4962 #ifdef FD_CLOEXEC
4963   // Validate that the use of the O_CLOEXEC flag on open above worked.
4964   // With recent kernels, we will perform this check exactly once.
4965   static sig_atomic_t O_CLOEXEC_is_known_to_work = 0;
4966   if (!O_CLOEXEC_is_known_to_work) {
4967     int flags = ::fcntl(fd, F_GETFD);
4968     if (flags != -1) {
4969       if ((flags & FD_CLOEXEC) != 0)
4970         O_CLOEXEC_is_known_to_work = 1;
4971       else
4972         ::fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
4973     }
4974   }
4975 #endif
4976 
4977   return fd;
4978 }
4979 
4980 
4981 // create binary file, rewriting existing file if required
4982 int os::create_binary_file(const char* path, bool rewrite_existing) {
4983   int oflags = O_WRONLY | O_CREAT;
4984   if (!rewrite_existing) {
4985     oflags |= O_EXCL;
4986   }
4987   return ::open64(path, oflags, S_IREAD | S_IWRITE);
4988 }
4989 
4990 // return current position of file pointer
4991 jlong os::current_file_offset(int fd) {
4992   return (jlong)::lseek64(fd, (off64_t)0, SEEK_CUR);
4993 }
4994 
4995 // move file pointer to the specified offset
4996 jlong os::seek_to_file_offset(int fd, jlong offset) {
4997   return (jlong)::lseek64(fd, (off64_t)offset, SEEK_SET);
4998 }
4999 
5000 // This code originates from JDK's sysAvailable
5001 // from src/solaris/hpi/src/native_threads/src/sys_api_td.c
5002 
5003 int os::available(int fd, jlong *bytes) {
5004   jlong cur, end;
5005   int mode;
5006   struct stat64 buf64;
5007 
5008   if (::fstat64(fd, &buf64) >= 0) {
5009     mode = buf64.st_mode;
5010     if (S_ISCHR(mode) || S_ISFIFO(mode) || S_ISSOCK(mode)) {
5011       // XXX: is the following call interruptible? If so, this might
5012       // need to go through the INTERRUPT_IO() wrapper as for other
5013       // blocking, interruptible calls in this file.
5014       int n;
5015       if (::ioctl(fd, FIONREAD, &n) >= 0) {
5016         *bytes = n;
5017         return 1;
5018       }
5019     }
5020   }
5021   if ((cur = ::lseek64(fd, 0L, SEEK_CUR)) == -1) {
5022     return 0;
5023   } else if ((end = ::lseek64(fd, 0L, SEEK_END)) == -1) {
5024     return 0;
5025   } else if (::lseek64(fd, cur, SEEK_SET) == -1) {
5026     return 0;
5027   }
5028   *bytes = end - cur;
5029   return 1;
5030 }
5031 
5032 // Map a block of memory.
5033 char* os::pd_map_memory(int fd, const char* file_name, size_t file_offset,
5034                         char *addr, size_t bytes, bool read_only,
5035                         bool allow_exec) {
5036   int prot;
5037   int flags = MAP_PRIVATE;
5038 
5039   if (read_only) {
5040     prot = PROT_READ;
5041   } else {
5042     prot = PROT_READ | PROT_WRITE;
5043   }
5044 
5045   if (allow_exec) {
5046     prot |= PROT_EXEC;
5047   }
5048 
5049   if (addr != NULL) {
5050     flags |= MAP_FIXED;
5051   }
5052 
5053   char* mapped_address = (char*)mmap(addr, (size_t)bytes, prot, flags,
5054                                      fd, file_offset);
5055   if (mapped_address == MAP_FAILED) {
5056     return NULL;
5057   }
5058   return mapped_address;
5059 }
5060 
5061 
5062 // Remap a block of memory.
5063 char* os::pd_remap_memory(int fd, const char* file_name, size_t file_offset,
5064                           char *addr, size_t bytes, bool read_only,
5065                           bool allow_exec) {
5066   // same as map_memory() on this OS
5067   return os::map_memory(fd, file_name, file_offset, addr, bytes, read_only,
5068                         allow_exec);
5069 }
5070 
5071 
5072 // Unmap a block of memory.
5073 bool os::pd_unmap_memory(char* addr, size_t bytes) {
5074   return munmap(addr, bytes) == 0;
5075 }
5076 
5077 static jlong slow_thread_cpu_time(Thread *thread, bool user_sys_cpu_time);
5078 
5079 static clockid_t thread_cpu_clockid(Thread* thread) {
5080   pthread_t tid = thread->osthread()->pthread_id();
5081   clockid_t clockid;
5082 
5083   // Get thread clockid
5084   int rc = os::Linux::pthread_getcpuclockid(tid, &clockid);
5085   assert(rc == 0, "pthread_getcpuclockid is expected to return 0 code");
5086   return clockid;
5087 }
5088 
5089 // current_thread_cpu_time(bool) and thread_cpu_time(Thread*, bool)
5090 // are used by JVM M&M and JVMTI to get user+sys or user CPU time
5091 // of a thread.
5092 //
5093 // current_thread_cpu_time() and thread_cpu_time(Thread*) returns
5094 // the fast estimate available on the platform.
5095 
5096 jlong os::current_thread_cpu_time() {
5097   if (os::Linux::supports_fast_thread_cpu_time()) {
5098     return os::Linux::fast_thread_cpu_time(CLOCK_THREAD_CPUTIME_ID);
5099   } else {
5100     // return user + sys since the cost is the same
5101     return slow_thread_cpu_time(Thread::current(), true /* user + sys */);
5102   }
5103 }
5104 
5105 jlong os::thread_cpu_time(Thread* thread) {
5106   // consistent with what current_thread_cpu_time() returns
5107   if (os::Linux::supports_fast_thread_cpu_time()) {
5108     return os::Linux::fast_thread_cpu_time(thread_cpu_clockid(thread));
5109   } else {
5110     return slow_thread_cpu_time(thread, true /* user + sys */);
5111   }
5112 }
5113 
5114 jlong os::current_thread_cpu_time(bool user_sys_cpu_time) {
5115   if (user_sys_cpu_time && os::Linux::supports_fast_thread_cpu_time()) {
5116     return os::Linux::fast_thread_cpu_time(CLOCK_THREAD_CPUTIME_ID);
5117   } else {
5118     return slow_thread_cpu_time(Thread::current(), user_sys_cpu_time);
5119   }
5120 }
5121 
5122 jlong os::thread_cpu_time(Thread *thread, bool user_sys_cpu_time) {
5123   if (user_sys_cpu_time && os::Linux::supports_fast_thread_cpu_time()) {
5124     return os::Linux::fast_thread_cpu_time(thread_cpu_clockid(thread));
5125   } else {
5126     return slow_thread_cpu_time(thread, user_sys_cpu_time);
5127   }
5128 }
5129 
5130 //  -1 on error.
5131 static jlong slow_thread_cpu_time(Thread *thread, bool user_sys_cpu_time) {
5132   pid_t  tid = thread->osthread()->thread_id();
5133   char *s;
5134   char stat[2048];
5135   int statlen;
5136   char proc_name[64];
5137   int count;
5138   long sys_time, user_time;
5139   char cdummy;
5140   int idummy;
5141   long ldummy;
5142   FILE *fp;
5143 
5144   snprintf(proc_name, 64, "/proc/self/task/%d/stat", tid);
5145   fp = fopen(proc_name, "r");
5146   if (fp == NULL) return -1;
5147   statlen = fread(stat, 1, 2047, fp);
5148   stat[statlen] = '\0';
5149   fclose(fp);
5150 
5151   // Skip pid and the command string. Note that we could be dealing with
5152   // weird command names, e.g. user could decide to rename java launcher
5153   // to "java 1.4.2 :)", then the stat file would look like
5154   //                1234 (java 1.4.2 :)) R ... ...
5155   // We don't really need to know the command string, just find the last
5156   // occurrence of ")" and then start parsing from there. See bug 4726580.
5157   s = strrchr(stat, ')');
5158   if (s == NULL) return -1;
5159 
5160   // Skip blank chars
5161   do { s++; } while (s && isspace(*s));
5162 
5163   count = sscanf(s,"%c %d %d %d %d %d %lu %lu %lu %lu %lu %lu %lu",
5164                  &cdummy, &idummy, &idummy, &idummy, &idummy, &idummy,
5165                  &ldummy, &ldummy, &ldummy, &ldummy, &ldummy,
5166                  &user_time, &sys_time);
5167   if (count != 13) return -1;
5168   if (user_sys_cpu_time) {
5169     return ((jlong)sys_time + (jlong)user_time) * (1000000000 / clock_tics_per_sec);
5170   } else {
5171     return (jlong)user_time * (1000000000 / clock_tics_per_sec);
5172   }
5173 }
5174 
5175 void os::current_thread_cpu_time_info(jvmtiTimerInfo *info_ptr) {
5176   info_ptr->max_value = ALL_64_BITS;       // will not wrap in less than 64 bits
5177   info_ptr->may_skip_backward = false;     // elapsed time not wall time
5178   info_ptr->may_skip_forward = false;      // elapsed time not wall time
5179   info_ptr->kind = JVMTI_TIMER_TOTAL_CPU;  // user+system time is returned
5180 }
5181 
5182 void os::thread_cpu_time_info(jvmtiTimerInfo *info_ptr) {
5183   info_ptr->max_value = ALL_64_BITS;       // will not wrap in less than 64 bits
5184   info_ptr->may_skip_backward = false;     // elapsed time not wall time
5185   info_ptr->may_skip_forward = false;      // elapsed time not wall time
5186   info_ptr->kind = JVMTI_TIMER_TOTAL_CPU;  // user+system time is returned
5187 }
5188 
5189 bool os::is_thread_cpu_time_supported() {
5190   return true;
5191 }
5192 
5193 // System loadavg support.  Returns -1 if load average cannot be obtained.
5194 // Linux doesn't yet have a (official) notion of processor sets,
5195 // so just return the system wide load average.
5196 int os::loadavg(double loadavg[], int nelem) {
5197   return ::getloadavg(loadavg, nelem);
5198 }
5199 
5200 void os::pause() {
5201   char filename[MAX_PATH];
5202   if (PauseAtStartupFile && PauseAtStartupFile[0]) {
5203     jio_snprintf(filename, MAX_PATH, PauseAtStartupFile);
5204   } else {
5205     jio_snprintf(filename, MAX_PATH, "./vm.paused.%d", current_process_id());
5206   }
5207 
5208   int fd = ::open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
5209   if (fd != -1) {
5210     struct stat buf;
5211     ::close(fd);
5212     while (::stat(filename, &buf) == 0) {
5213       (void)::poll(NULL, 0, 100);
5214     }
5215   } else {
5216     jio_fprintf(stderr,
5217                 "Could not open pause file '%s', continuing immediately.\n", filename);
5218   }
5219 }
5220 
5221 
5222 // Refer to the comments in os_solaris.cpp park-unpark. The next two
5223 // comment paragraphs are worth repeating here:
5224 //
5225 // Assumption:
5226 //    Only one parker can exist on an event, which is why we allocate
5227 //    them per-thread. Multiple unparkers can coexist.
5228 //
5229 // _Event serves as a restricted-range semaphore.
5230 //   -1 : thread is blocked, i.e. there is a waiter
5231 //    0 : neutral: thread is running or ready,
5232 //        could have been signaled after a wait started
5233 //    1 : signaled - thread is running or ready
5234 //
5235 // Beware -- Some versions of NPTL embody a flaw where pthread_cond_timedwait() can
5236 // hang indefinitely.  For instance NPTL 0.60 on 2.4.21-4ELsmp is vulnerable.
5237 // For specifics regarding the bug see GLIBC BUGID 261237 :
5238 //    http://www.mail-archive.com/debian-glibc@lists.debian.org/msg10837.html.
5239 // Briefly, pthread_cond_timedwait() calls with an expiry time that's not in the future
5240 // will either hang or corrupt the condvar, resulting in subsequent hangs if the condvar
5241 // is used.  (The simple C test-case provided in the GLIBC bug report manifests the
5242 // hang).  The JVM is vulernable via sleep(), Object.wait(timo), LockSupport.parkNanos()
5243 // and monitorenter when we're using 1-0 locking.  All those operations may result in
5244 // calls to pthread_cond_timedwait().  Using LD_ASSUME_KERNEL to use an older version
5245 // of libpthread avoids the problem, but isn't practical.
5246 //
5247 // Possible remedies:
5248 //
5249 // 1.   Establish a minimum relative wait time.  50 to 100 msecs seems to work.
5250 //      This is palliative and probabilistic, however.  If the thread is preempted
5251 //      between the call to compute_abstime() and pthread_cond_timedwait(), more
5252 //      than the minimum period may have passed, and the abstime may be stale (in the
5253 //      past) resultin in a hang.   Using this technique reduces the odds of a hang
5254 //      but the JVM is still vulnerable, particularly on heavily loaded systems.
5255 //
5256 // 2.   Modify park-unpark to use per-thread (per ParkEvent) pipe-pairs instead
5257 //      of the usual flag-condvar-mutex idiom.  The write side of the pipe is set
5258 //      NDELAY. unpark() reduces to write(), park() reduces to read() and park(timo)
5259 //      reduces to poll()+read().  This works well, but consumes 2 FDs per extant
5260 //      thread.
5261 //
5262 // 3.   Embargo pthread_cond_timedwait() and implement a native "chron" thread
5263 //      that manages timeouts.  We'd emulate pthread_cond_timedwait() by enqueuing
5264 //      a timeout request to the chron thread and then blocking via pthread_cond_wait().
5265 //      This also works well.  In fact it avoids kernel-level scalability impediments
5266 //      on certain platforms that don't handle lots of active pthread_cond_timedwait()
5267 //      timers in a graceful fashion.
5268 //
5269 // 4.   When the abstime value is in the past it appears that control returns
5270 //      correctly from pthread_cond_timedwait(), but the condvar is left corrupt.
5271 //      Subsequent timedwait/wait calls may hang indefinitely.  Given that, we
5272 //      can avoid the problem by reinitializing the condvar -- by cond_destroy()
5273 //      followed by cond_init() -- after all calls to pthread_cond_timedwait().
5274 //      It may be possible to avoid reinitialization by checking the return
5275 //      value from pthread_cond_timedwait().  In addition to reinitializing the
5276 //      condvar we must establish the invariant that cond_signal() is only called
5277 //      within critical sections protected by the adjunct mutex.  This prevents
5278 //      cond_signal() from "seeing" a condvar that's in the midst of being
5279 //      reinitialized or that is corrupt.  Sadly, this invariant obviates the
5280 //      desirable signal-after-unlock optimization that avoids futile context switching.
5281 //
5282 //      I'm also concerned that some versions of NTPL might allocate an auxilliary
5283 //      structure when a condvar is used or initialized.  cond_destroy()  would
5284 //      release the helper structure.  Our reinitialize-after-timedwait fix
5285 //      put excessive stress on malloc/free and locks protecting the c-heap.
5286 //
5287 // We currently use (4).  See the WorkAroundNTPLTimedWaitHang flag.
5288 // It may be possible to refine (4) by checking the kernel and NTPL verisons
5289 // and only enabling the work-around for vulnerable environments.
5290 
5291 // utility to compute the abstime argument to timedwait:
5292 // millis is the relative timeout time
5293 // abstime will be the absolute timeout time
5294 // TODO: replace compute_abstime() with unpackTime()
5295 
5296 static struct timespec* compute_abstime(timespec* abstime, jlong millis) {
5297   if (millis < 0)  millis = 0;
5298 
5299   jlong seconds = millis / 1000;
5300   millis %= 1000;
5301   if (seconds > 50000000) { // see man cond_timedwait(3T)
5302     seconds = 50000000;
5303   }
5304 
5305   if (os::supports_monotonic_clock()) {
5306     struct timespec now;
5307     int status = os::Linux::clock_gettime(CLOCK_MONOTONIC, &now);
5308     assert_status(status == 0, status, "clock_gettime");
5309     abstime->tv_sec = now.tv_sec  + seconds;
5310     long nanos = now.tv_nsec + millis * NANOSECS_PER_MILLISEC;
5311     if (nanos >= NANOSECS_PER_SEC) {
5312       abstime->tv_sec += 1;
5313       nanos -= NANOSECS_PER_SEC;
5314     }
5315     abstime->tv_nsec = nanos;
5316   } else {
5317     struct timeval now;
5318     int status = gettimeofday(&now, NULL);
5319     assert(status == 0, "gettimeofday");
5320     abstime->tv_sec = now.tv_sec  + seconds;
5321     long usec = now.tv_usec + millis * 1000;
5322     if (usec >= 1000000) {
5323       abstime->tv_sec += 1;
5324       usec -= 1000000;
5325     }
5326     abstime->tv_nsec = usec * 1000;
5327   }
5328   return abstime;
5329 }
5330 
5331 void os::PlatformEvent::park() {       // AKA "down()"
5332   // Transitions for _Event:
5333   //   -1 => -1 : illegal
5334   //    1 =>  0 : pass - return immediately
5335   //    0 => -1 : block; then set _Event to 0 before returning
5336 
5337   // Invariant: Only the thread associated with the Event/PlatformEvent
5338   // may call park().
5339   // TODO: assert that _Assoc != NULL or _Assoc == Self
5340   assert(_nParked == 0, "invariant");
5341 
5342   int v;
5343   for (;;) {
5344     v = _Event;
5345     if (Atomic::cmpxchg(v-1, &_Event, v) == v) break;
5346   }
5347   guarantee(v >= 0, "invariant");
5348   if (v == 0) {
5349     // Do this the hard way by blocking ...
5350     int status = pthread_mutex_lock(_mutex);
5351     assert_status(status == 0, status, "mutex_lock");
5352     guarantee(_nParked == 0, "invariant");
5353     ++_nParked;
5354     while (_Event < 0) {
5355       status = pthread_cond_wait(_cond, _mutex);
5356       // for some reason, under 2.7 lwp_cond_wait() may return ETIME ...
5357       // Treat this the same as if the wait was interrupted
5358       if (status == ETIME) { status = EINTR; }
5359       assert_status(status == 0 || status == EINTR, status, "cond_wait");
5360     }
5361     --_nParked;
5362 
5363     _Event = 0;
5364     status = pthread_mutex_unlock(_mutex);
5365     assert_status(status == 0, status, "mutex_unlock");
5366     // Paranoia to ensure our locked and lock-free paths interact
5367     // correctly with each other.
5368     OrderAccess::fence();
5369   }
5370   guarantee(_Event >= 0, "invariant");
5371 }
5372 
5373 int os::PlatformEvent::park(jlong millis) {
5374   // Transitions for _Event:
5375   //   -1 => -1 : illegal
5376   //    1 =>  0 : pass - return immediately
5377   //    0 => -1 : block; then set _Event to 0 before returning
5378 
5379   guarantee(_nParked == 0, "invariant");
5380 
5381   int v;
5382   for (;;) {
5383     v = _Event;
5384     if (Atomic::cmpxchg(v-1, &_Event, v) == v) break;
5385   }
5386   guarantee(v >= 0, "invariant");
5387   if (v != 0) return OS_OK;
5388 
5389   // We do this the hard way, by blocking the thread.
5390   // Consider enforcing a minimum timeout value.
5391   struct timespec abst;
5392   compute_abstime(&abst, millis);
5393 
5394   int ret = OS_TIMEOUT;
5395   int status = pthread_mutex_lock(_mutex);
5396   assert_status(status == 0, status, "mutex_lock");
5397   guarantee(_nParked == 0, "invariant");
5398   ++_nParked;
5399 
5400   // Object.wait(timo) will return because of
5401   // (a) notification
5402   // (b) timeout
5403   // (c) thread.interrupt
5404   //
5405   // Thread.interrupt and object.notify{All} both call Event::set.
5406   // That is, we treat thread.interrupt as a special case of notification.
5407   // We ignore spurious OS wakeups unless FilterSpuriousWakeups is false.
5408   // We assume all ETIME returns are valid.
5409   //
5410   // TODO: properly differentiate simultaneous notify+interrupt.
5411   // In that case, we should propagate the notify to another waiter.
5412 
5413   while (_Event < 0) {
5414     status = pthread_cond_timedwait(_cond, _mutex, &abst);
5415     if (status != 0 && WorkAroundNPTLTimedWaitHang) {
5416       pthread_cond_destroy(_cond);
5417       pthread_cond_init(_cond, os::Linux::condAttr());
5418     }
5419     assert_status(status == 0 || status == EINTR ||
5420                   status == ETIME || status == ETIMEDOUT,
5421                   status, "cond_timedwait");
5422     if (!FilterSpuriousWakeups) break;                 // previous semantics
5423     if (status == ETIME || status == ETIMEDOUT) break;
5424     // We consume and ignore EINTR and spurious wakeups.
5425   }
5426   --_nParked;
5427   if (_Event >= 0) {
5428     ret = OS_OK;
5429   }
5430   _Event = 0;
5431   status = pthread_mutex_unlock(_mutex);
5432   assert_status(status == 0, status, "mutex_unlock");
5433   assert(_nParked == 0, "invariant");
5434   // Paranoia to ensure our locked and lock-free paths interact
5435   // correctly with each other.
5436   OrderAccess::fence();
5437   return ret;
5438 }
5439 
5440 void os::PlatformEvent::unpark() {
5441   // Transitions for _Event:
5442   //    0 => 1 : just return
5443   //    1 => 1 : just return
5444   //   -1 => either 0 or 1; must signal target thread
5445   //         That is, we can safely transition _Event from -1 to either
5446   //         0 or 1.
5447   // See also: "Semaphores in Plan 9" by Mullender & Cox
5448   //
5449   // Note: Forcing a transition from "-1" to "1" on an unpark() means
5450   // that it will take two back-to-back park() calls for the owning
5451   // thread to block. This has the benefit of forcing a spurious return
5452   // from the first park() call after an unpark() call which will help
5453   // shake out uses of park() and unpark() without condition variables.
5454 
5455   if (Atomic::xchg(1, &_Event) >= 0) return;
5456 
5457   // Wait for the thread associated with the event to vacate
5458   int status = pthread_mutex_lock(_mutex);
5459   assert_status(status == 0, status, "mutex_lock");
5460   int AnyWaiters = _nParked;
5461   assert(AnyWaiters == 0 || AnyWaiters == 1, "invariant");
5462   if (AnyWaiters != 0 && WorkAroundNPTLTimedWaitHang) {
5463     AnyWaiters = 0;
5464     pthread_cond_signal(_cond);
5465   }
5466   status = pthread_mutex_unlock(_mutex);
5467   assert_status(status == 0, status, "mutex_unlock");
5468   if (AnyWaiters != 0) {
5469     // Note that we signal() *after* dropping the lock for "immortal" Events.
5470     // This is safe and avoids a common class of  futile wakeups.  In rare
5471     // circumstances this can cause a thread to return prematurely from
5472     // cond_{timed}wait() but the spurious wakeup is benign and the victim
5473     // will simply re-test the condition and re-park itself.
5474     // This provides particular benefit if the underlying platform does not
5475     // provide wait morphing.
5476     status = pthread_cond_signal(_cond);
5477     assert_status(status == 0, status, "cond_signal");
5478   }
5479 }
5480 
5481 
5482 // JSR166
5483 // -------------------------------------------------------
5484 
5485 // The solaris and linux implementations of park/unpark are fairly
5486 // conservative for now, but can be improved. They currently use a
5487 // mutex/condvar pair, plus a a count.
5488 // Park decrements count if > 0, else does a condvar wait.  Unpark
5489 // sets count to 1 and signals condvar.  Only one thread ever waits
5490 // on the condvar. Contention seen when trying to park implies that someone
5491 // is unparking you, so don't wait. And spurious returns are fine, so there
5492 // is no need to track notifications.
5493 
5494 // This code is common to linux and solaris and will be moved to a
5495 // common place in dolphin.
5496 //
5497 // The passed in time value is either a relative time in nanoseconds
5498 // or an absolute time in milliseconds. Either way it has to be unpacked
5499 // into suitable seconds and nanoseconds components and stored in the
5500 // given timespec structure.
5501 // Given time is a 64-bit value and the time_t used in the timespec is only
5502 // a signed-32-bit value (except on 64-bit Linux) we have to watch for
5503 // overflow if times way in the future are given. Further on Solaris versions
5504 // prior to 10 there is a restriction (see cond_timedwait) that the specified
5505 // number of seconds, in abstime, is less than current_time  + 100,000,000.
5506 // As it will be 28 years before "now + 100000000" will overflow we can
5507 // ignore overflow and just impose a hard-limit on seconds using the value
5508 // of "now + 100,000,000". This places a limit on the timeout of about 3.17
5509 // years from "now".
5510 
5511 static void unpackTime(timespec* absTime, bool isAbsolute, jlong time) {
5512   assert(time > 0, "convertTime");
5513   time_t max_secs = 0;
5514 
5515   if (!os::supports_monotonic_clock() || isAbsolute) {
5516     struct timeval now;
5517     int status = gettimeofday(&now, NULL);
5518     assert(status == 0, "gettimeofday");
5519 
5520     max_secs = now.tv_sec + MAX_SECS;
5521 
5522     if (isAbsolute) {
5523       jlong secs = time / 1000;
5524       if (secs > max_secs) {
5525         absTime->tv_sec = max_secs;
5526       } else {
5527         absTime->tv_sec = secs;
5528       }
5529       absTime->tv_nsec = (time % 1000) * NANOSECS_PER_MILLISEC;
5530     } else {
5531       jlong secs = time / NANOSECS_PER_SEC;
5532       if (secs >= MAX_SECS) {
5533         absTime->tv_sec = max_secs;
5534         absTime->tv_nsec = 0;
5535       } else {
5536         absTime->tv_sec = now.tv_sec + secs;
5537         absTime->tv_nsec = (time % NANOSECS_PER_SEC) + now.tv_usec*1000;
5538         if (absTime->tv_nsec >= NANOSECS_PER_SEC) {
5539           absTime->tv_nsec -= NANOSECS_PER_SEC;
5540           ++absTime->tv_sec; // note: this must be <= max_secs
5541         }
5542       }
5543     }
5544   } else {
5545     // must be relative using monotonic clock
5546     struct timespec now;
5547     int status = os::Linux::clock_gettime(CLOCK_MONOTONIC, &now);
5548     assert_status(status == 0, status, "clock_gettime");
5549     max_secs = now.tv_sec + MAX_SECS;
5550     jlong secs = time / NANOSECS_PER_SEC;
5551     if (secs >= MAX_SECS) {
5552       absTime->tv_sec = max_secs;
5553       absTime->tv_nsec = 0;
5554     } else {
5555       absTime->tv_sec = now.tv_sec + secs;
5556       absTime->tv_nsec = (time % NANOSECS_PER_SEC) + now.tv_nsec;
5557       if (absTime->tv_nsec >= NANOSECS_PER_SEC) {
5558         absTime->tv_nsec -= NANOSECS_PER_SEC;
5559         ++absTime->tv_sec; // note: this must be <= max_secs
5560       }
5561     }
5562   }
5563   assert(absTime->tv_sec >= 0, "tv_sec < 0");
5564   assert(absTime->tv_sec <= max_secs, "tv_sec > max_secs");
5565   assert(absTime->tv_nsec >= 0, "tv_nsec < 0");
5566   assert(absTime->tv_nsec < NANOSECS_PER_SEC, "tv_nsec >= nanos_per_sec");
5567 }
5568 
5569 void Parker::park(bool isAbsolute, jlong time) {
5570   // Ideally we'd do something useful while spinning, such
5571   // as calling unpackTime().
5572 
5573   // Optional fast-path check:
5574   // Return immediately if a permit is available.
5575   // We depend on Atomic::xchg() having full barrier semantics
5576   // since we are doing a lock-free update to _counter.
5577   if (Atomic::xchg(0, &_counter) > 0) return;
5578 
5579   Thread* thread = Thread::current();
5580   assert(thread->is_Java_thread(), "Must be JavaThread");
5581   JavaThread *jt = (JavaThread *)thread;
5582 
5583   // Optional optimization -- avoid state transitions if there's an interrupt pending.
5584   // Check interrupt before trying to wait
5585   if (Thread::is_interrupted(thread, false)) {
5586     return;
5587   }
5588 
5589   // Next, demultiplex/decode time arguments
5590   timespec absTime;
5591   if (time < 0 || (isAbsolute && time == 0)) { // don't wait at all
5592     return;
5593   }
5594   if (time > 0) {
5595     unpackTime(&absTime, isAbsolute, time);
5596   }
5597 
5598 
5599   // Enter safepoint region
5600   // Beware of deadlocks such as 6317397.
5601   // The per-thread Parker:: mutex is a classic leaf-lock.
5602   // In particular a thread must never block on the Threads_lock while
5603   // holding the Parker:: mutex.  If safepoints are pending both the
5604   // the ThreadBlockInVM() CTOR and DTOR may grab Threads_lock.
5605   ThreadBlockInVM tbivm(jt);
5606 
5607   // Don't wait if cannot get lock since interference arises from
5608   // unblocking.  Also. check interrupt before trying wait
5609   if (Thread::is_interrupted(thread, false) || pthread_mutex_trylock(_mutex) != 0) {
5610     return;
5611   }
5612 
5613   int status;
5614   if (_counter > 0)  { // no wait needed
5615     _counter = 0;
5616     status = pthread_mutex_unlock(_mutex);
5617     assert(status == 0, "invariant");
5618     // Paranoia to ensure our locked and lock-free paths interact
5619     // correctly with each other and Java-level accesses.
5620     OrderAccess::fence();
5621     return;
5622   }
5623 
5624 #ifdef ASSERT
5625   // Don't catch signals while blocked; let the running threads have the signals.
5626   // (This allows a debugger to break into the running thread.)
5627   sigset_t oldsigs;
5628   sigset_t* allowdebug_blocked = os::Linux::allowdebug_blocked_signals();
5629   pthread_sigmask(SIG_BLOCK, allowdebug_blocked, &oldsigs);
5630 #endif
5631 
5632   OSThreadWaitState osts(thread->osthread(), false /* not Object.wait() */);
5633   jt->set_suspend_equivalent();
5634   // cleared by handle_special_suspend_equivalent_condition() or java_suspend_self()
5635 
5636   assert(_cur_index == -1, "invariant");
5637   if (time == 0) {
5638     _cur_index = REL_INDEX; // arbitrary choice when not timed
5639     status = pthread_cond_wait(&_cond[_cur_index], _mutex);
5640   } else {
5641     _cur_index = isAbsolute ? ABS_INDEX : REL_INDEX;
5642     status = pthread_cond_timedwait(&_cond[_cur_index], _mutex, &absTime);
5643     if (status != 0 && WorkAroundNPTLTimedWaitHang) {
5644       pthread_cond_destroy(&_cond[_cur_index]);
5645       pthread_cond_init(&_cond[_cur_index], isAbsolute ? NULL : os::Linux::condAttr());
5646     }
5647   }
5648   _cur_index = -1;
5649   assert_status(status == 0 || status == EINTR ||
5650                 status == ETIME || status == ETIMEDOUT,
5651                 status, "cond_timedwait");
5652 
5653 #ifdef ASSERT
5654   pthread_sigmask(SIG_SETMASK, &oldsigs, NULL);
5655 #endif
5656 
5657   _counter = 0;
5658   status = pthread_mutex_unlock(_mutex);
5659   assert_status(status == 0, status, "invariant");
5660   // Paranoia to ensure our locked and lock-free paths interact
5661   // correctly with each other and Java-level accesses.
5662   OrderAccess::fence();
5663 
5664   // If externally suspended while waiting, re-suspend
5665   if (jt->handle_special_suspend_equivalent_condition()) {
5666     jt->java_suspend_self();
5667   }
5668 }
5669 
5670 void Parker::unpark() {
5671   int status = pthread_mutex_lock(_mutex);
5672   assert(status == 0, "invariant");
5673   const int s = _counter;
5674   _counter = 1;
5675   if (s < 1) {
5676     // thread might be parked
5677     if (_cur_index != -1) {
5678       // thread is definitely parked
5679       if (WorkAroundNPTLTimedWaitHang) {
5680         status = pthread_cond_signal(&_cond[_cur_index]);
5681         assert(status == 0, "invariant");
5682         status = pthread_mutex_unlock(_mutex);
5683         assert(status == 0, "invariant");
5684       } else {
5685         status = pthread_mutex_unlock(_mutex);
5686         assert(status == 0, "invariant");
5687         status = pthread_cond_signal(&_cond[_cur_index]);
5688         assert(status == 0, "invariant");
5689       }
5690     } else {
5691       pthread_mutex_unlock(_mutex);
5692       assert(status == 0, "invariant");
5693     }
5694   } else {
5695     pthread_mutex_unlock(_mutex);
5696     assert(status == 0, "invariant");
5697   }
5698 }
5699 
5700 
5701 extern char** environ;
5702 
5703 // Run the specified command in a separate process. Return its exit value,
5704 // or -1 on failure (e.g. can't fork a new process).
5705 // Unlike system(), this function can be called from signal handler. It
5706 // doesn't block SIGINT et al.
5707 int os::fork_and_exec(char* cmd) {
5708   const char * argv[4] = {"sh", "-c", cmd, NULL};
5709 
5710   pid_t pid = fork();
5711 
5712   if (pid < 0) {
5713     // fork failed
5714     return -1;
5715 
5716   } else if (pid == 0) {
5717     // child process
5718 
5719     execve("/bin/sh", (char* const*)argv, environ);
5720 
5721     // execve failed
5722     _exit(-1);
5723 
5724   } else  {
5725     // copied from J2SE ..._waitForProcessExit() in UNIXProcess_md.c; we don't
5726     // care about the actual exit code, for now.
5727 
5728     int status;
5729 
5730     // Wait for the child process to exit.  This returns immediately if
5731     // the child has already exited. */
5732     while (waitpid(pid, &status, 0) < 0) {
5733       switch (errno) {
5734       case ECHILD: return 0;
5735       case EINTR: break;
5736       default: return -1;
5737       }
5738     }
5739 
5740     if (WIFEXITED(status)) {
5741       // The child exited normally; get its exit code.
5742       return WEXITSTATUS(status);
5743     } else if (WIFSIGNALED(status)) {
5744       // The child exited because of a signal
5745       // The best value to return is 0x80 + signal number,
5746       // because that is what all Unix shells do, and because
5747       // it allows callers to distinguish between process exit and
5748       // process death by signal.
5749       return 0x80 + WTERMSIG(status);
5750     } else {
5751       // Unknown exit code; pass it through
5752       return status;
5753     }
5754   }
5755 }
5756 
5757 // is_headless_jre()
5758 //
5759 // Test for the existence of xawt/libmawt.so or libawt_xawt.so
5760 // in order to report if we are running in a headless jre
5761 //
5762 // Since JDK8 xawt/libmawt.so was moved into the same directory
5763 // as libawt.so, and renamed libawt_xawt.so
5764 //
5765 bool os::is_headless_jre() {
5766   struct stat statbuf;
5767   char buf[MAXPATHLEN];
5768   char libmawtpath[MAXPATHLEN];
5769   const char *xawtstr  = "/xawt/libmawt.so";
5770   const char *new_xawtstr = "/libawt_xawt.so";
5771   char *p;
5772 
5773   // Get path to libjvm.so
5774   os::jvm_path(buf, sizeof(buf));
5775 
5776   // Get rid of libjvm.so
5777   p = strrchr(buf, '/');
5778   if (p == NULL) {
5779     return false;
5780   } else {
5781     *p = '\0';
5782   }
5783 
5784   // Get rid of client or server
5785   p = strrchr(buf, '/');
5786   if (p == NULL) {
5787     return false;
5788   } else {
5789     *p = '\0';
5790   }
5791 
5792   // check xawt/libmawt.so
5793   strcpy(libmawtpath, buf);
5794   strcat(libmawtpath, xawtstr);
5795   if (::stat(libmawtpath, &statbuf) == 0) return false;
5796 
5797   // check libawt_xawt.so
5798   strcpy(libmawtpath, buf);
5799   strcat(libmawtpath, new_xawtstr);
5800   if (::stat(libmawtpath, &statbuf) == 0) return false;
5801 
5802   return true;
5803 }
5804 
5805 // Get the default path to the core file
5806 // Returns the length of the string
5807 int os::get_core_path(char* buffer, size_t bufferSize) {
5808   /*
5809    * Max length of /proc/sys/kernel/core_pattern is 128 characters.
5810    * See https://www.kernel.org/doc/Documentation/sysctl/kernel.txt
5811    */
5812   const int core_pattern_len = 129;
5813   char core_pattern[core_pattern_len] = {0};
5814 
5815   int core_pattern_file = ::open("/proc/sys/kernel/core_pattern", O_RDONLY);
5816   if (core_pattern_file != -1) {
5817     ssize_t ret = ::read(core_pattern_file, core_pattern, core_pattern_len);
5818     ::close(core_pattern_file);
5819 
5820     if (ret > 0) {
5821       char *last_char = core_pattern + strlen(core_pattern) - 1;
5822 
5823       if (*last_char == '\n') {
5824         *last_char = '\0';
5825       }
5826     }
5827   }
5828 
5829   if (strlen(core_pattern) == 0) {
5830     return -1;
5831   }
5832 
5833   char *pid_pos = strstr(core_pattern, "%p");
5834   int written;
5835 
5836   if (core_pattern[0] == '/') {
5837     written = jio_snprintf(buffer, bufferSize, core_pattern);
5838   } else {
5839     char cwd[PATH_MAX];
5840 
5841     const char* p = get_current_directory(cwd, PATH_MAX);
5842     if (p == NULL) {
5843       return -1;
5844     }
5845 
5846     if (core_pattern[0] == '|') {
5847       written = jio_snprintf(buffer, bufferSize,
5848                         "\"%s\" (or dumping to %s/core.%d)",
5849                                      &core_pattern[1], p, current_process_id());
5850     } else {
5851       written = jio_snprintf(buffer, bufferSize, "%s/%s", p, core_pattern);
5852     }
5853   }
5854 
5855   if (written < 0) {
5856     return -1;
5857   }
5858 
5859   if (((size_t)written < bufferSize) && (pid_pos == NULL) && (core_pattern[0] != '|')) {
5860     int core_uses_pid_file = ::open("/proc/sys/kernel/core_uses_pid", O_RDONLY);
5861 
5862     if (core_uses_pid_file != -1) {
5863       char core_uses_pid = 0;
5864       ssize_t ret = ::read(core_uses_pid_file, &core_uses_pid, 1);
5865       ::close(core_uses_pid_file);
5866 
5867       if (core_uses_pid == '1') {
5868         jio_snprintf(buffer + written, bufferSize - written,
5869                                           ".%d", current_process_id());
5870       }
5871     }
5872   }
5873 
5874   return strlen(buffer);
5875 }
5876 
5877 /////////////// Unit tests ///////////////
5878 
5879 #ifndef PRODUCT
5880 
5881 #define test_log(...)              \
5882   do {                             \
5883     if (VerboseInternalVMTests) {  \
5884       tty->print_cr(__VA_ARGS__);  \
5885       tty->flush();                \
5886     }                              \
5887   } while (false)
5888 
5889 class TestReserveMemorySpecial : AllStatic {
5890  public:
5891   static void small_page_write(void* addr, size_t size) {
5892     size_t page_size = os::vm_page_size();
5893 
5894     char* end = (char*)addr + size;
5895     for (char* p = (char*)addr; p < end; p += page_size) {
5896       *p = 1;
5897     }
5898   }
5899 
5900   static void test_reserve_memory_special_huge_tlbfs_only(size_t size) {
5901     if (!UseHugeTLBFS) {
5902       return;
5903     }
5904 
5905     test_log("test_reserve_memory_special_huge_tlbfs_only(" SIZE_FORMAT ")", size);
5906 
5907     char* addr = os::Linux::reserve_memory_special_huge_tlbfs_only(size, NULL, false);
5908 
5909     if (addr != NULL) {
5910       small_page_write(addr, size);
5911 
5912       os::Linux::release_memory_special_huge_tlbfs(addr, size);
5913     }
5914   }
5915 
5916   static void test_reserve_memory_special_huge_tlbfs_only() {
5917     if (!UseHugeTLBFS) {
5918       return;
5919     }
5920 
5921     size_t lp = os::large_page_size();
5922 
5923     for (size_t size = lp; size <= lp * 10; size += lp) {
5924       test_reserve_memory_special_huge_tlbfs_only(size);
5925     }
5926   }
5927 
5928   static void test_reserve_memory_special_huge_tlbfs_mixed() {
5929     size_t lp = os::large_page_size();
5930     size_t ag = os::vm_allocation_granularity();
5931 
5932     // sizes to test
5933     const size_t sizes[] = {
5934       lp, lp + ag, lp + lp / 2, lp * 2,
5935       lp * 2 + ag, lp * 2 - ag, lp * 2 + lp / 2,
5936       lp * 10, lp * 10 + lp / 2
5937     };
5938     const int num_sizes = sizeof(sizes) / sizeof(size_t);
5939 
5940     // For each size/alignment combination, we test three scenarios:
5941     // 1) with req_addr == NULL
5942     // 2) with a non-null req_addr at which we expect to successfully allocate
5943     // 3) with a non-null req_addr which contains a pre-existing mapping, at which we
5944     //    expect the allocation to either fail or to ignore req_addr
5945 
5946     // Pre-allocate two areas; they shall be as large as the largest allocation
5947     //  and aligned to the largest alignment we will be testing.
5948     const size_t mapping_size = sizes[num_sizes - 1] * 2;
5949     char* const mapping1 = (char*) ::mmap(NULL, mapping_size,
5950       PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE,
5951       -1, 0);
5952     assert(mapping1 != MAP_FAILED, "should work");
5953 
5954     char* const mapping2 = (char*) ::mmap(NULL, mapping_size,
5955       PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE,
5956       -1, 0);
5957     assert(mapping2 != MAP_FAILED, "should work");
5958 
5959     // Unmap the first mapping, but leave the second mapping intact: the first
5960     // mapping will serve as a value for a "good" req_addr (case 2). The second
5961     // mapping, still intact, as "bad" req_addr (case 3).
5962     ::munmap(mapping1, mapping_size);
5963 
5964     // Case 1
5965     test_log("%s, req_addr NULL:", __FUNCTION__);
5966     test_log("size            align           result");
5967 
5968     for (int i = 0; i < num_sizes; i++) {
5969       const size_t size = sizes[i];
5970       for (size_t alignment = ag; is_size_aligned(size, alignment); alignment *= 2) {
5971         char* p = os::Linux::reserve_memory_special_huge_tlbfs_mixed(size, alignment, NULL, false);
5972         test_log(SIZE_FORMAT_HEX " " SIZE_FORMAT_HEX " ->  " PTR_FORMAT " %s",
5973             size, alignment, p, (p != NULL ? "" : "(failed)"));
5974         if (p != NULL) {
5975           assert(is_ptr_aligned(p, alignment), "must be");
5976           small_page_write(p, size);
5977           os::Linux::release_memory_special_huge_tlbfs(p, size);
5978         }
5979       }
5980     }
5981 
5982     // Case 2
5983     test_log("%s, req_addr non-NULL:", __FUNCTION__);
5984     test_log("size            align           req_addr         result");
5985 
5986     for (int i = 0; i < num_sizes; i++) {
5987       const size_t size = sizes[i];
5988       for (size_t alignment = ag; is_size_aligned(size, alignment); alignment *= 2) {
5989         char* const req_addr = (char*) align_ptr_up(mapping1, alignment);
5990         char* p = os::Linux::reserve_memory_special_huge_tlbfs_mixed(size, alignment, req_addr, false);
5991         test_log(SIZE_FORMAT_HEX " " SIZE_FORMAT_HEX " " PTR_FORMAT " ->  " PTR_FORMAT " %s",
5992             size, alignment, req_addr, p,
5993             ((p != NULL ? (p == req_addr ? "(exact match)" : "") : "(failed)")));
5994         if (p != NULL) {
5995           assert(p == req_addr, "must be");
5996           small_page_write(p, size);
5997           os::Linux::release_memory_special_huge_tlbfs(p, size);
5998         }
5999       }
6000     }
6001 
6002     // Case 3
6003     test_log("%s, req_addr non-NULL with preexisting mapping:", __FUNCTION__);
6004     test_log("size            align           req_addr         result");
6005 
6006     for (int i = 0; i < num_sizes; i++) {
6007       const size_t size = sizes[i];
6008       for (size_t alignment = ag; is_size_aligned(size, alignment); alignment *= 2) {
6009         char* const req_addr = (char*) align_ptr_up(mapping2, alignment);
6010         char* p = os::Linux::reserve_memory_special_huge_tlbfs_mixed(size, alignment, req_addr, false);
6011         test_log(SIZE_FORMAT_HEX " " SIZE_FORMAT_HEX " " PTR_FORMAT " ->  " PTR_FORMAT " %s",
6012             size, alignment, req_addr, p,
6013             ((p != NULL ? "" : "(failed)")));
6014         // as the area around req_addr contains already existing mappings, the API should always
6015         // return NULL (as per contract, it cannot return another address)
6016         assert(p == NULL, "must be");
6017       }
6018     }
6019 
6020     ::munmap(mapping2, mapping_size);
6021 
6022   }
6023 
6024   static void test_reserve_memory_special_huge_tlbfs() {
6025     if (!UseHugeTLBFS) {
6026       return;
6027     }
6028 
6029     test_reserve_memory_special_huge_tlbfs_only();
6030     test_reserve_memory_special_huge_tlbfs_mixed();
6031   }
6032 
6033   static void test_reserve_memory_special_shm(size_t size, size_t alignment) {
6034     if (!UseSHM) {
6035       return;
6036     }
6037 
6038     test_log("test_reserve_memory_special_shm(" SIZE_FORMAT ", " SIZE_FORMAT ")", size, alignment);
6039 
6040     char* addr = os::Linux::reserve_memory_special_shm(size, alignment, NULL, false);
6041 
6042     if (addr != NULL) {
6043       assert(is_ptr_aligned(addr, alignment), "Check");
6044       assert(is_ptr_aligned(addr, os::large_page_size()), "Check");
6045 
6046       small_page_write(addr, size);
6047 
6048       os::Linux::release_memory_special_shm(addr, size);
6049     }
6050   }
6051 
6052   static void test_reserve_memory_special_shm() {
6053     size_t lp = os::large_page_size();
6054     size_t ag = os::vm_allocation_granularity();
6055 
6056     for (size_t size = ag; size < lp * 3; size += ag) {
6057       for (size_t alignment = ag; is_size_aligned(size, alignment); alignment *= 2) {
6058         test_reserve_memory_special_shm(size, alignment);
6059       }
6060     }
6061   }
6062 
6063   static void test() {
6064     test_reserve_memory_special_huge_tlbfs();
6065     test_reserve_memory_special_shm();
6066   }
6067 };
6068 
6069 void TestReserveMemorySpecial_test() {
6070   TestReserveMemorySpecial::test();
6071 }
6072 
6073 #endif
--- EOF ---