1 /*
   2  * Copyright (c) 1999, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 // no precompiled headers
  26 #include "jvm.h"
  27 #include "classfile/classLoader.hpp"
  28 #include "classfile/systemDictionary.hpp"
  29 #include "classfile/vmSymbols.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "code/vtableStubs.hpp"
  32 #include "compiler/compileBroker.hpp"
  33 #include "compiler/disassembler.hpp"
  34 #include "interpreter/interpreter.hpp"
  35 #include "logging/log.hpp"
  36 #include "memory/allocation.inline.hpp"
  37 #include "memory/filemap.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_misc.hpp"
  43 #include "runtime/arguments.hpp"
  44 #include "runtime/atomic.hpp"
  45 #include "runtime/extendedPC.hpp"
  46 #include "runtime/globals.hpp"
  47 #include "runtime/interfaceSupport.hpp"
  48 #include "runtime/init.hpp"
  49 #include "runtime/java.hpp"
  50 #include "runtime/javaCalls.hpp"
  51 #include "runtime/mutexLocker.hpp"
  52 #include "runtime/objectMonitor.hpp"
  53 #include "runtime/orderAccess.inline.hpp"
  54 #include "runtime/osThread.hpp"
  55 #include "runtime/perfMemory.hpp"
  56 #include "runtime/sharedRuntime.hpp"
  57 #include "runtime/statSampler.hpp"
  58 #include "runtime/stubRoutines.hpp"
  59 #include "runtime/thread.inline.hpp"
  60 #include "runtime/threadCritical.hpp"
  61 #include "runtime/timer.hpp"
  62 #include "semaphore_posix.hpp"
  63 #include "services/attachListener.hpp"
  64 #include "services/memTracker.hpp"
  65 #include "services/runtimeService.hpp"
  66 #include "utilities/align.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 #ifndef _GNU_SOURCE
 110   #define _GNU_SOURCE
 111   #include <sched.h>
 112   #undef _GNU_SOURCE
 113 #else
 114   #include <sched.h>
 115 #endif
 116 
 117 // if RUSAGE_THREAD for getrusage() has not been defined, do it here. The code calling
 118 // getrusage() is prepared to handle the associated failure.
 119 #ifndef RUSAGE_THREAD
 120   #define RUSAGE_THREAD   (1)               /* only the calling thread */
 121 #endif
 122 
 123 #define MAX_PATH    (2 * K)
 124 
 125 #define MAX_SECS 100000000
 126 
 127 // for timer info max values which include all bits
 128 #define ALL_64_BITS CONST64(0xFFFFFFFFFFFFFFFF)
 129 
 130 #define LARGEPAGES_BIT (1 << 6)
 131 #define DAX_SHARED_BIT (1 << 8)
 132 ////////////////////////////////////////////////////////////////////////////////
 133 // global variables
 134 julong os::Linux::_physical_memory = 0;
 135 
 136 address   os::Linux::_initial_thread_stack_bottom = NULL;
 137 uintptr_t os::Linux::_initial_thread_stack_size   = 0;
 138 
 139 int (*os::Linux::_clock_gettime)(clockid_t, struct timespec *) = NULL;
 140 int (*os::Linux::_pthread_getcpuclockid)(pthread_t, clockid_t *) = NULL;
 141 int (*os::Linux::_pthread_setname_np)(pthread_t, const char*) = NULL;
 142 Mutex* os::Linux::_createThread_lock = NULL;
 143 pthread_t os::Linux::_main_thread;
 144 int os::Linux::_page_size = -1;
 145 bool os::Linux::_supports_fast_thread_cpu_time = false;
 146 uint32_t os::Linux::_os_version = 0;
 147 const char * os::Linux::_glibc_version = NULL;
 148 const char * os::Linux::_libpthread_version = NULL;
 149 
 150 static jlong initial_time_count=0;
 151 
 152 static int clock_tics_per_sec = 100;
 153 
 154 // For diagnostics to print a message once. see run_periodic_checks
 155 static sigset_t check_signal_done;
 156 static bool check_signals = true;
 157 
 158 // Signal number used to suspend/resume a thread
 159 
 160 // do not use any signal number less than SIGSEGV, see 4355769
 161 static int SR_signum = SIGUSR2;
 162 sigset_t SR_sigset;
 163 
 164 // utility functions
 165 
 166 static int SR_initialize();
 167 
 168 julong os::available_memory() {
 169   return Linux::available_memory();
 170 }
 171 
 172 julong os::Linux::available_memory() {
 173   // values in struct sysinfo are "unsigned long"
 174   struct sysinfo si;
 175   sysinfo(&si);
 176 
 177   return (julong)si.freeram * si.mem_unit;
 178 }
 179 
 180 julong os::physical_memory() {
 181   return Linux::physical_memory();
 182 }
 183 
 184 // Return true if user is running as root.
 185 
 186 bool os::have_special_privileges() {
 187   static bool init = false;
 188   static bool privileges = false;
 189   if (!init) {
 190     privileges = (getuid() != geteuid()) || (getgid() != getegid());
 191     init = true;
 192   }
 193   return privileges;
 194 }
 195 
 196 
 197 #ifndef SYS_gettid
 198 // i386: 224, ia64: 1105, amd64: 186, sparc 143
 199   #ifdef __ia64__
 200     #define SYS_gettid 1105
 201   #else
 202     #ifdef __i386__
 203       #define SYS_gettid 224
 204     #else
 205       #ifdef __amd64__
 206         #define SYS_gettid 186
 207       #else
 208         #ifdef __sparc__
 209           #define SYS_gettid 143
 210         #else
 211           #error define gettid for the arch
 212         #endif
 213       #endif
 214     #endif
 215   #endif
 216 #endif
 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>/lib/{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(PPC64) || 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 /lib.
 327       }
 328     }
 329     Arguments::set_java_home(buf);
 330     set_boot_path('/', ':');
 331   }
 332 
 333   // Where to look for native libraries.
 334   //
 335   // Note: Due to a legacy implementation, most of the library path
 336   // is set in the launcher. This was to accomodate linking restrictions
 337   // on legacy Linux implementations (which are no longer supported).
 338   // Eventually, all the library path setting will be done here.
 339   //
 340   // However, to prevent the proliferation of improperly built native
 341   // libraries, the new path component /usr/java/packages is added here.
 342   // Eventually, all the library path setting will be done here.
 343   {
 344     // Get the user setting of LD_LIBRARY_PATH, and prepended it. It
 345     // should always exist (until the legacy problem cited above is
 346     // addressed).
 347     const char *v = ::getenv("LD_LIBRARY_PATH");
 348     const char *v_colon = ":";
 349     if (v == NULL) { v = ""; v_colon = ""; }
 350     // That's +1 for the colon and +1 for the trailing '\0'.
 351     char *ld_library_path = (char *)NEW_C_HEAP_ARRAY(char,
 352                                                      strlen(v) + 1 +
 353                                                      sizeof(SYS_EXT_DIR) + sizeof("/lib/") + sizeof(DEFAULT_LIBPATH) + 1,
 354                                                      mtInternal);
 355     sprintf(ld_library_path, "%s%s" SYS_EXT_DIR "/lib:" DEFAULT_LIBPATH, v, v_colon);
 356     Arguments::set_library_path(ld_library_path);
 357     FREE_C_HEAP_ARRAY(char, ld_library_path);
 358   }
 359 
 360   // Extensions directories.
 361   sprintf(buf, "%s" EXTENSIONS_DIR ":" SYS_EXT_DIR EXTENSIONS_DIR, Arguments::get_java_home());
 362   Arguments::set_ext_dirs(buf);
 363 
 364   FREE_C_HEAP_ARRAY(char, buf);
 365 
 366 #undef DEFAULT_LIBPATH
 367 #undef SYS_EXT_DIR
 368 #undef EXTENSIONS_DIR
 369 }
 370 
 371 ////////////////////////////////////////////////////////////////////////////////
 372 // breakpoint support
 373 
 374 void os::breakpoint() {
 375   BREAKPOINT;
 376 }
 377 
 378 extern "C" void breakpoint() {
 379   // use debugger to set breakpoint here
 380 }
 381 
 382 ////////////////////////////////////////////////////////////////////////////////
 383 // signal support
 384 
 385 debug_only(static bool signal_sets_initialized = false);
 386 static sigset_t unblocked_sigs, vm_sigs;
 387 
 388 bool os::Linux::is_sig_ignored(int sig) {
 389   struct sigaction oact;
 390   sigaction(sig, (struct sigaction*)NULL, &oact);
 391   void* ohlr = oact.sa_sigaction ? CAST_FROM_FN_PTR(void*,  oact.sa_sigaction)
 392                                  : CAST_FROM_FN_PTR(void*,  oact.sa_handler);
 393   if (ohlr == CAST_FROM_FN_PTR(void*, SIG_IGN)) {
 394     return true;
 395   } else {
 396     return false;
 397   }
 398 }
 399 
 400 void os::Linux::signal_sets_init() {
 401   // Should also have an assertion stating we are still single-threaded.
 402   assert(!signal_sets_initialized, "Already initialized");
 403   // Fill in signals that are necessarily unblocked for all threads in
 404   // the VM. Currently, we unblock the following signals:
 405   // SHUTDOWN{1,2,3}_SIGNAL: for shutdown hooks support (unless over-ridden
 406   //                         by -Xrs (=ReduceSignalUsage));
 407   // BREAK_SIGNAL which is unblocked only by the VM thread and blocked by all
 408   // other threads. The "ReduceSignalUsage" boolean tells us not to alter
 409   // the dispositions or masks wrt these signals.
 410   // Programs embedding the VM that want to use the above signals for their
 411   // own purposes must, at this time, use the "-Xrs" option to prevent
 412   // interference with shutdown hooks and BREAK_SIGNAL thread dumping.
 413   // (See bug 4345157, and other related bugs).
 414   // In reality, though, unblocking these signals is really a nop, since
 415   // these signals are not blocked by default.
 416   sigemptyset(&unblocked_sigs);
 417   sigaddset(&unblocked_sigs, SIGILL);
 418   sigaddset(&unblocked_sigs, SIGSEGV);
 419   sigaddset(&unblocked_sigs, SIGBUS);
 420   sigaddset(&unblocked_sigs, SIGFPE);
 421 #if defined(PPC64)
 422   sigaddset(&unblocked_sigs, SIGTRAP);
 423 #endif
 424   sigaddset(&unblocked_sigs, SR_signum);
 425 
 426   if (!ReduceSignalUsage) {
 427     if (!os::Linux::is_sig_ignored(SHUTDOWN1_SIGNAL)) {
 428       sigaddset(&unblocked_sigs, SHUTDOWN1_SIGNAL);
 429     }
 430     if (!os::Linux::is_sig_ignored(SHUTDOWN2_SIGNAL)) {
 431       sigaddset(&unblocked_sigs, SHUTDOWN2_SIGNAL);
 432     }
 433     if (!os::Linux::is_sig_ignored(SHUTDOWN3_SIGNAL)) {
 434       sigaddset(&unblocked_sigs, SHUTDOWN3_SIGNAL);
 435     }
 436   }
 437   // Fill in signals that are blocked by all but the VM thread.
 438   sigemptyset(&vm_sigs);
 439   if (!ReduceSignalUsage) {
 440     sigaddset(&vm_sigs, BREAK_SIGNAL);
 441   }
 442   debug_only(signal_sets_initialized = true);
 443 
 444 }
 445 
 446 // These are signals that are unblocked while a thread is running Java.
 447 // (For some reason, they get blocked by default.)
 448 sigset_t* os::Linux::unblocked_signals() {
 449   assert(signal_sets_initialized, "Not initialized");
 450   return &unblocked_sigs;
 451 }
 452 
 453 // These are the signals that are blocked while a (non-VM) thread is
 454 // running Java. Only the VM thread handles these signals.
 455 sigset_t* os::Linux::vm_signals() {
 456   assert(signal_sets_initialized, "Not initialized");
 457   return &vm_sigs;
 458 }
 459 
 460 void os::Linux::hotspot_sigmask(Thread* thread) {
 461 
 462   //Save caller's signal mask before setting VM signal mask
 463   sigset_t caller_sigmask;
 464   pthread_sigmask(SIG_BLOCK, NULL, &caller_sigmask);
 465 
 466   OSThread* osthread = thread->osthread();
 467   osthread->set_caller_sigmask(caller_sigmask);
 468 
 469   pthread_sigmask(SIG_UNBLOCK, os::Linux::unblocked_signals(), NULL);
 470 
 471   if (!ReduceSignalUsage) {
 472     if (thread->is_VM_thread()) {
 473       // Only the VM thread handles BREAK_SIGNAL ...
 474       pthread_sigmask(SIG_UNBLOCK, vm_signals(), NULL);
 475     } else {
 476       // ... all other threads block BREAK_SIGNAL
 477       pthread_sigmask(SIG_BLOCK, vm_signals(), NULL);
 478     }
 479   }
 480 }
 481 
 482 //////////////////////////////////////////////////////////////////////////////
 483 // detecting pthread library
 484 
 485 void os::Linux::libpthread_init() {
 486   // Save glibc and pthread version strings.
 487 #if !defined(_CS_GNU_LIBC_VERSION) || \
 488     !defined(_CS_GNU_LIBPTHREAD_VERSION)
 489   #error "glibc too old (< 2.3.2)"
 490 #endif
 491 
 492   size_t n = confstr(_CS_GNU_LIBC_VERSION, NULL, 0);
 493   assert(n > 0, "cannot retrieve glibc version");
 494   char *str = (char *)malloc(n, mtInternal);
 495   confstr(_CS_GNU_LIBC_VERSION, str, n);
 496   os::Linux::set_glibc_version(str);
 497 
 498   n = confstr(_CS_GNU_LIBPTHREAD_VERSION, NULL, 0);
 499   assert(n > 0, "cannot retrieve pthread version");
 500   str = (char *)malloc(n, mtInternal);
 501   confstr(_CS_GNU_LIBPTHREAD_VERSION, str, n);
 502   os::Linux::set_libpthread_version(str);
 503 }
 504 
 505 /////////////////////////////////////////////////////////////////////////////
 506 // thread stack expansion
 507 
 508 // os::Linux::manually_expand_stack() takes care of expanding the thread
 509 // stack. Note that this is normally not needed: pthread stacks allocate
 510 // thread stack using mmap() without MAP_NORESERVE, so the stack is already
 511 // committed. Therefore it is not necessary to expand the stack manually.
 512 //
 513 // Manually expanding the stack was historically needed on LinuxThreads
 514 // thread stacks, which were allocated with mmap(MAP_GROWSDOWN). Nowadays
 515 // it is kept to deal with very rare corner cases:
 516 //
 517 // For one, user may run the VM on an own implementation of threads
 518 // whose stacks are - like the old LinuxThreads - implemented using
 519 // mmap(MAP_GROWSDOWN).
 520 //
 521 // Also, this coding may be needed if the VM is running on the primordial
 522 // thread. Normally we avoid running on the primordial thread; however,
 523 // user may still invoke the VM on the primordial thread.
 524 //
 525 // The following historical comment describes the details about running
 526 // on a thread stack allocated with mmap(MAP_GROWSDOWN):
 527 
 528 
 529 // Force Linux kernel to expand current thread stack. If "bottom" is close
 530 // to the stack guard, caller should block all signals.
 531 //
 532 // MAP_GROWSDOWN:
 533 //   A special mmap() flag that is used to implement thread stacks. It tells
 534 //   kernel that the memory region should extend downwards when needed. This
 535 //   allows early versions of LinuxThreads to only mmap the first few pages
 536 //   when creating a new thread. Linux kernel will automatically expand thread
 537 //   stack as needed (on page faults).
 538 //
 539 //   However, because the memory region of a MAP_GROWSDOWN stack can grow on
 540 //   demand, if a page fault happens outside an already mapped MAP_GROWSDOWN
 541 //   region, it's hard to tell if the fault is due to a legitimate stack
 542 //   access or because of reading/writing non-exist memory (e.g. buffer
 543 //   overrun). As a rule, if the fault happens below current stack pointer,
 544 //   Linux kernel does not expand stack, instead a SIGSEGV is sent to the
 545 //   application (see Linux kernel fault.c).
 546 //
 547 //   This Linux feature can cause SIGSEGV when VM bangs thread stack for
 548 //   stack overflow detection.
 549 //
 550 //   Newer version of LinuxThreads (since glibc-2.2, or, RH-7.x) and NPTL do
 551 //   not use MAP_GROWSDOWN.
 552 //
 553 // To get around the problem and allow stack banging on Linux, we need to
 554 // manually expand thread stack after receiving the SIGSEGV.
 555 //
 556 // There are two ways to expand thread stack to address "bottom", we used
 557 // both of them in JVM before 1.5:
 558 //   1. adjust stack pointer first so that it is below "bottom", and then
 559 //      touch "bottom"
 560 //   2. mmap() the page in question
 561 //
 562 // Now alternate signal stack is gone, it's harder to use 2. For instance,
 563 // if current sp is already near the lower end of page 101, and we need to
 564 // call mmap() to map page 100, it is possible that part of the mmap() frame
 565 // will be placed in page 100. When page 100 is mapped, it is zero-filled.
 566 // That will destroy the mmap() frame and cause VM to crash.
 567 //
 568 // The following code works by adjusting sp first, then accessing the "bottom"
 569 // page to force a page fault. Linux kernel will then automatically expand the
 570 // stack mapping.
 571 //
 572 // _expand_stack_to() assumes its frame size is less than page size, which
 573 // should always be true if the function is not inlined.
 574 
 575 static void NOINLINE _expand_stack_to(address bottom) {
 576   address sp;
 577   size_t size;
 578   volatile char *p;
 579 
 580   // Adjust bottom to point to the largest address within the same page, it
 581   // gives us a one-page buffer if alloca() allocates slightly more memory.
 582   bottom = (address)align_down((uintptr_t)bottom, os::Linux::page_size());
 583   bottom += os::Linux::page_size() - 1;
 584 
 585   // sp might be slightly above current stack pointer; if that's the case, we
 586   // will alloca() a little more space than necessary, which is OK. Don't use
 587   // os::current_stack_pointer(), as its result can be slightly below current
 588   // stack pointer, causing us to not alloca enough to reach "bottom".
 589   sp = (address)&sp;
 590 
 591   if (sp > bottom) {
 592     size = sp - bottom;
 593     p = (volatile char *)alloca(size);
 594     assert(p != NULL && p <= (volatile char *)bottom, "alloca problem?");
 595     p[0] = '\0';
 596   }
 597 }
 598 
 599 bool os::Linux::manually_expand_stack(JavaThread * t, address addr) {
 600   assert(t!=NULL, "just checking");
 601   assert(t->osthread()->expanding_stack(), "expand should be set");
 602   assert(t->stack_base() != NULL, "stack_base was not initialized");
 603 
 604   if (addr <  t->stack_base() && addr >= t->stack_reserved_zone_base()) {
 605     sigset_t mask_all, old_sigset;
 606     sigfillset(&mask_all);
 607     pthread_sigmask(SIG_SETMASK, &mask_all, &old_sigset);
 608     _expand_stack_to(addr);
 609     pthread_sigmask(SIG_SETMASK, &old_sigset, NULL);
 610     return true;
 611   }
 612   return false;
 613 }
 614 
 615 //////////////////////////////////////////////////////////////////////////////
 616 // create new thread
 617 
 618 // Thread start routine for all newly created threads
 619 static void *thread_native_entry(Thread *thread) {
 620   // Try to randomize the cache line index of hot stack frames.
 621   // This helps when threads of the same stack traces evict each other's
 622   // cache lines. The threads can be either from the same JVM instance, or
 623   // from different JVM instances. The benefit is especially true for
 624   // processors with hyperthreading technology.
 625   static int counter = 0;
 626   int pid = os::current_process_id();
 627   alloca(((pid ^ counter++) & 7) * 128);
 628 
 629   thread->initialize_thread_current();
 630 
 631   OSThread* osthread = thread->osthread();
 632   Monitor* sync = osthread->startThread_lock();
 633 
 634   osthread->set_thread_id(os::current_thread_id());
 635 
 636   log_info(os, thread)("Thread is alive (tid: " UINTX_FORMAT ", pthread id: " UINTX_FORMAT ").",
 637     os::current_thread_id(), (uintx) pthread_self());
 638 
 639   if (UseNUMA) {
 640     int lgrp_id = os::numa_get_group_id();
 641     if (lgrp_id != -1) {
 642       thread->set_lgrp_id(lgrp_id);
 643     }
 644   }
 645   // initialize signal mask for this thread
 646   os::Linux::hotspot_sigmask(thread);
 647 
 648   // initialize floating point control register
 649   os::Linux::init_thread_fpu_state();
 650 
 651   // handshaking with parent thread
 652   {
 653     MutexLockerEx ml(sync, Mutex::_no_safepoint_check_flag);
 654 
 655     // notify parent thread
 656     osthread->set_state(INITIALIZED);
 657     sync->notify_all();
 658 
 659     // wait until os::start_thread()
 660     while (osthread->get_state() == INITIALIZED) {
 661       sync->wait(Mutex::_no_safepoint_check_flag);
 662     }
 663   }
 664 
 665   // call one more level start routine
 666   thread->run();
 667 
 668   log_info(os, thread)("Thread finished (tid: " UINTX_FORMAT ", pthread id: " UINTX_FORMAT ").",
 669     os::current_thread_id(), (uintx) pthread_self());
 670 
 671   // If a thread has not deleted itself ("delete this") as part of its
 672   // termination sequence, we have to ensure thread-local-storage is
 673   // cleared before we actually terminate. No threads should ever be
 674   // deleted asynchronously with respect to their termination.
 675   if (Thread::current_or_null_safe() != NULL) {
 676     assert(Thread::current_or_null_safe() == thread, "current thread is wrong");
 677     thread->clear_thread_current();
 678   }
 679 
 680   return 0;
 681 }
 682 
 683 bool os::create_thread(Thread* thread, ThreadType thr_type,
 684                        size_t req_stack_size) {
 685   assert(thread->osthread() == NULL, "caller responsible");
 686 
 687   // Allocate the OSThread object
 688   OSThread* osthread = new OSThread(NULL, NULL);
 689   if (osthread == NULL) {
 690     return false;
 691   }
 692 
 693   // set the correct thread state
 694   osthread->set_thread_type(thr_type);
 695 
 696   // Initial state is ALLOCATED but not INITIALIZED
 697   osthread->set_state(ALLOCATED);
 698 
 699   thread->set_osthread(osthread);
 700 
 701   // init thread attributes
 702   pthread_attr_t attr;
 703   pthread_attr_init(&attr);
 704   pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
 705 
 706   // Calculate stack size if it's not specified by caller.
 707   size_t stack_size = os::Posix::get_initial_stack_size(thr_type, req_stack_size);
 708   // In the Linux NPTL pthread implementation the guard size mechanism
 709   // is not implemented properly. The posix standard requires adding
 710   // the size of the guard pages to the stack size, instead Linux
 711   // takes the space out of 'stacksize'. Thus we adapt the requested
 712   // stack_size by the size of the guard pages to mimick proper
 713   // behaviour. However, be careful not to end up with a size
 714   // of zero due to overflow. Don't add the guard page in that case.
 715   size_t guard_size = os::Linux::default_guard_size(thr_type);
 716   if (stack_size <= SIZE_MAX - guard_size) {
 717     stack_size += guard_size;
 718   }
 719   assert(is_aligned(stack_size, os::vm_page_size()), "stack_size not aligned");
 720 
 721   int status = pthread_attr_setstacksize(&attr, stack_size);
 722   assert_status(status == 0, status, "pthread_attr_setstacksize");
 723 
 724   // Configure glibc guard page.
 725   pthread_attr_setguardsize(&attr, os::Linux::default_guard_size(thr_type));
 726 
 727   ThreadState state;
 728 
 729   {
 730     pthread_t tid;
 731     int ret = pthread_create(&tid, &attr, (void* (*)(void*)) thread_native_entry, thread);
 732 
 733     char buf[64];
 734     if (ret == 0) {
 735       log_info(os, thread)("Thread started (pthread id: " UINTX_FORMAT ", attributes: %s). ",
 736         (uintx) tid, os::Posix::describe_pthread_attr(buf, sizeof(buf), &attr));
 737     } else {
 738       log_warning(os, thread)("Failed to start thread - pthread_create failed (%s) for attributes: %s.",
 739         os::errno_name(ret), os::Posix::describe_pthread_attr(buf, sizeof(buf), &attr));
 740     }
 741 
 742     pthread_attr_destroy(&attr);
 743 
 744     if (ret != 0) {
 745       // Need to clean up stuff we've allocated so far
 746       thread->set_osthread(NULL);
 747       delete osthread;
 748       return false;
 749     }
 750 
 751     // Store pthread info into the OSThread
 752     osthread->set_pthread_id(tid);
 753 
 754     // Wait until child thread is either initialized or aborted
 755     {
 756       Monitor* sync_with_child = osthread->startThread_lock();
 757       MutexLockerEx ml(sync_with_child, Mutex::_no_safepoint_check_flag);
 758       while ((state = osthread->get_state()) == ALLOCATED) {
 759         sync_with_child->wait(Mutex::_no_safepoint_check_flag);
 760       }
 761     }
 762   }
 763 
 764   // Aborted due to thread limit being reached
 765   if (state == ZOMBIE) {
 766     thread->set_osthread(NULL);
 767     delete osthread;
 768     return false;
 769   }
 770 
 771   // The thread is returned suspended (in state INITIALIZED),
 772   // and is started higher up in the call chain
 773   assert(state == INITIALIZED, "race condition");
 774   return true;
 775 }
 776 
 777 /////////////////////////////////////////////////////////////////////////////
 778 // attach existing thread
 779 
 780 // bootstrap the main thread
 781 bool os::create_main_thread(JavaThread* thread) {
 782   assert(os::Linux::_main_thread == pthread_self(), "should be called inside main thread");
 783   return create_attached_thread(thread);
 784 }
 785 
 786 bool os::create_attached_thread(JavaThread* thread) {
 787 #ifdef ASSERT
 788   thread->verify_not_published();
 789 #endif
 790 
 791   // Allocate the OSThread object
 792   OSThread* osthread = new OSThread(NULL, NULL);
 793 
 794   if (osthread == NULL) {
 795     return false;
 796   }
 797 
 798   // Store pthread info into the OSThread
 799   osthread->set_thread_id(os::Linux::gettid());
 800   osthread->set_pthread_id(::pthread_self());
 801 
 802   // initialize floating point control register
 803   os::Linux::init_thread_fpu_state();
 804 
 805   // Initial thread state is RUNNABLE
 806   osthread->set_state(RUNNABLE);
 807 
 808   thread->set_osthread(osthread);
 809 
 810   if (UseNUMA) {
 811     int lgrp_id = os::numa_get_group_id();
 812     if (lgrp_id != -1) {
 813       thread->set_lgrp_id(lgrp_id);
 814     }
 815   }
 816 
 817   if (os::Linux::is_initial_thread()) {
 818     // If current thread is initial thread, its stack is mapped on demand,
 819     // see notes about MAP_GROWSDOWN. Here we try to force kernel to map
 820     // the entire stack region to avoid SEGV in stack banging.
 821     // It is also useful to get around the heap-stack-gap problem on SuSE
 822     // kernel (see 4821821 for details). We first expand stack to the top
 823     // of yellow zone, then enable stack yellow zone (order is significant,
 824     // enabling yellow zone first will crash JVM on SuSE Linux), so there
 825     // is no gap between the last two virtual memory regions.
 826 
 827     JavaThread *jt = (JavaThread *)thread;
 828     address addr = jt->stack_reserved_zone_base();
 829     assert(addr != NULL, "initialization problem?");
 830     assert(jt->stack_available(addr) > 0, "stack guard should not be enabled");
 831 
 832     osthread->set_expanding_stack();
 833     os::Linux::manually_expand_stack(jt, addr);
 834     osthread->clear_expanding_stack();
 835   }
 836 
 837   // initialize signal mask for this thread
 838   // and save the caller's signal mask
 839   os::Linux::hotspot_sigmask(thread);
 840 
 841   log_info(os, thread)("Thread attached (tid: " UINTX_FORMAT ", pthread id: " UINTX_FORMAT ").",
 842     os::current_thread_id(), (uintx) pthread_self());
 843 
 844   return true;
 845 }
 846 
 847 void os::pd_start_thread(Thread* thread) {
 848   OSThread * osthread = thread->osthread();
 849   assert(osthread->get_state() != INITIALIZED, "just checking");
 850   Monitor* sync_with_child = osthread->startThread_lock();
 851   MutexLockerEx ml(sync_with_child, Mutex::_no_safepoint_check_flag);
 852   sync_with_child->notify();
 853 }
 854 
 855 // Free Linux resources related to the OSThread
 856 void os::free_thread(OSThread* osthread) {
 857   assert(osthread != NULL, "osthread not set");
 858 
 859   // We are told to free resources of the argument thread,
 860   // but we can only really operate on the current thread.
 861   assert(Thread::current()->osthread() == osthread,
 862          "os::free_thread but not current thread");
 863 
 864 #ifdef ASSERT
 865   sigset_t current;
 866   sigemptyset(&current);
 867   pthread_sigmask(SIG_SETMASK, NULL, &current);
 868   assert(!sigismember(&current, SR_signum), "SR signal should not be blocked!");
 869 #endif
 870 
 871   // Restore caller's signal mask
 872   sigset_t sigmask = osthread->caller_sigmask();
 873   pthread_sigmask(SIG_SETMASK, &sigmask, NULL);
 874 
 875   delete osthread;
 876 }
 877 
 878 //////////////////////////////////////////////////////////////////////////////
 879 // initial thread
 880 
 881 // Check if current thread is the initial thread, similar to Solaris thr_main.
 882 bool os::Linux::is_initial_thread(void) {
 883   char dummy;
 884   // If called before init complete, thread stack bottom will be null.
 885   // Can be called if fatal error occurs before initialization.
 886   if (initial_thread_stack_bottom() == NULL) return false;
 887   assert(initial_thread_stack_bottom() != NULL &&
 888          initial_thread_stack_size()   != 0,
 889          "os::init did not locate initial thread's stack region");
 890   if ((address)&dummy >= initial_thread_stack_bottom() &&
 891       (address)&dummy < initial_thread_stack_bottom() + initial_thread_stack_size()) {
 892     return true;
 893   } else {
 894     return false;
 895   }
 896 }
 897 
 898 // Find the virtual memory area that contains addr
 899 static bool find_vma(address addr, address* vma_low, address* vma_high) {
 900   FILE *fp = fopen("/proc/self/maps", "r");
 901   if (fp) {
 902     address low, high;
 903     while (!feof(fp)) {
 904       if (fscanf(fp, "%p-%p", &low, &high) == 2) {
 905         if (low <= addr && addr < high) {
 906           if (vma_low)  *vma_low  = low;
 907           if (vma_high) *vma_high = high;
 908           fclose(fp);
 909           return true;
 910         }
 911       }
 912       for (;;) {
 913         int ch = fgetc(fp);
 914         if (ch == EOF || ch == (int)'\n') break;
 915       }
 916     }
 917     fclose(fp);
 918   }
 919   return false;
 920 }
 921 
 922 // Locate initial thread stack. This special handling of initial thread stack
 923 // is needed because pthread_getattr_np() on most (all?) Linux distros returns
 924 // bogus value for the primordial process thread. While the launcher has created
 925 // the VM in a new thread since JDK 6, we still have to allow for the use of the
 926 // JNI invocation API from a primordial thread.
 927 void os::Linux::capture_initial_stack(size_t max_size) {
 928 
 929   // max_size is either 0 (which means accept OS default for thread stacks) or
 930   // a user-specified value known to be at least the minimum needed. If we
 931   // are actually on the primordial thread we can make it appear that we have a
 932   // smaller max_size stack by inserting the guard pages at that location. But we
 933   // cannot do anything to emulate a larger stack than what has been provided by
 934   // the OS or threading library. In fact if we try to use a stack greater than
 935   // what is set by rlimit then we will crash the hosting process.
 936 
 937   // Maximum stack size is the easy part, get it from RLIMIT_STACK.
 938   // If this is "unlimited" then it will be a huge value.
 939   struct rlimit rlim;
 940   getrlimit(RLIMIT_STACK, &rlim);
 941   size_t stack_size = rlim.rlim_cur;
 942 
 943   // 6308388: a bug in ld.so will relocate its own .data section to the
 944   //   lower end of primordial stack; reduce ulimit -s value a little bit
 945   //   so we won't install guard page on ld.so's data section.
 946   stack_size -= 2 * page_size();
 947 
 948   // Try to figure out where the stack base (top) is. This is harder.
 949   //
 950   // When an application is started, glibc saves the initial stack pointer in
 951   // a global variable "__libc_stack_end", which is then used by system
 952   // libraries. __libc_stack_end should be pretty close to stack top. The
 953   // variable is available since the very early days. However, because it is
 954   // a private interface, it could disappear in the future.
 955   //
 956   // Linux kernel saves start_stack information in /proc/<pid>/stat. Similar
 957   // to __libc_stack_end, it is very close to stack top, but isn't the real
 958   // stack top. Note that /proc may not exist if VM is running as a chroot
 959   // program, so reading /proc/<pid>/stat could fail. Also the contents of
 960   // /proc/<pid>/stat could change in the future (though unlikely).
 961   //
 962   // We try __libc_stack_end first. If that doesn't work, look for
 963   // /proc/<pid>/stat. If neither of them works, we use current stack pointer
 964   // as a hint, which should work well in most cases.
 965 
 966   uintptr_t stack_start;
 967 
 968   // try __libc_stack_end first
 969   uintptr_t *p = (uintptr_t *)dlsym(RTLD_DEFAULT, "__libc_stack_end");
 970   if (p && *p) {
 971     stack_start = *p;
 972   } else {
 973     // see if we can get the start_stack field from /proc/self/stat
 974     FILE *fp;
 975     int pid;
 976     char state;
 977     int ppid;
 978     int pgrp;
 979     int session;
 980     int nr;
 981     int tpgrp;
 982     unsigned long flags;
 983     unsigned long minflt;
 984     unsigned long cminflt;
 985     unsigned long majflt;
 986     unsigned long cmajflt;
 987     unsigned long utime;
 988     unsigned long stime;
 989     long cutime;
 990     long cstime;
 991     long prio;
 992     long nice;
 993     long junk;
 994     long it_real;
 995     uintptr_t start;
 996     uintptr_t vsize;
 997     intptr_t rss;
 998     uintptr_t rsslim;
 999     uintptr_t scodes;
1000     uintptr_t ecode;
1001     int i;
1002 
1003     // Figure what the primordial thread stack base is. Code is inspired
1004     // by email from Hans Boehm. /proc/self/stat begins with current pid,
1005     // followed by command name surrounded by parentheses, state, etc.
1006     char stat[2048];
1007     int statlen;
1008 
1009     fp = fopen("/proc/self/stat", "r");
1010     if (fp) {
1011       statlen = fread(stat, 1, 2047, fp);
1012       stat[statlen] = '\0';
1013       fclose(fp);
1014 
1015       // Skip pid and the command string. Note that we could be dealing with
1016       // weird command names, e.g. user could decide to rename java launcher
1017       // to "java 1.4.2 :)", then the stat file would look like
1018       //                1234 (java 1.4.2 :)) R ... ...
1019       // We don't really need to know the command string, just find the last
1020       // occurrence of ")" and then start parsing from there. See bug 4726580.
1021       char * s = strrchr(stat, ')');
1022 
1023       i = 0;
1024       if (s) {
1025         // Skip blank chars
1026         do { s++; } while (s && isspace(*s));
1027 
1028 #define _UFM UINTX_FORMAT
1029 #define _DFM INTX_FORMAT
1030 
1031         //                                     1   1   1   1   1   1   1   1   1   1   2   2    2    2    2    2    2    2    2
1032         //              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
1033         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,
1034                    &state,          // 3  %c
1035                    &ppid,           // 4  %d
1036                    &pgrp,           // 5  %d
1037                    &session,        // 6  %d
1038                    &nr,             // 7  %d
1039                    &tpgrp,          // 8  %d
1040                    &flags,          // 9  %lu
1041                    &minflt,         // 10 %lu
1042                    &cminflt,        // 11 %lu
1043                    &majflt,         // 12 %lu
1044                    &cmajflt,        // 13 %lu
1045                    &utime,          // 14 %lu
1046                    &stime,          // 15 %lu
1047                    &cutime,         // 16 %ld
1048                    &cstime,         // 17 %ld
1049                    &prio,           // 18 %ld
1050                    &nice,           // 19 %ld
1051                    &junk,           // 20 %ld
1052                    &it_real,        // 21 %ld
1053                    &start,          // 22 UINTX_FORMAT
1054                    &vsize,          // 23 UINTX_FORMAT
1055                    &rss,            // 24 INTX_FORMAT
1056                    &rsslim,         // 25 UINTX_FORMAT
1057                    &scodes,         // 26 UINTX_FORMAT
1058                    &ecode,          // 27 UINTX_FORMAT
1059                    &stack_start);   // 28 UINTX_FORMAT
1060       }
1061 
1062 #undef _UFM
1063 #undef _DFM
1064 
1065       if (i != 28 - 2) {
1066         assert(false, "Bad conversion from /proc/self/stat");
1067         // product mode - assume we are the initial thread, good luck in the
1068         // embedded case.
1069         warning("Can't detect initial thread stack location - bad conversion");
1070         stack_start = (uintptr_t) &rlim;
1071       }
1072     } else {
1073       // For some reason we can't open /proc/self/stat (for example, running on
1074       // FreeBSD with a Linux emulator, or inside chroot), this should work for
1075       // most cases, so don't abort:
1076       warning("Can't detect initial thread stack location - no /proc/self/stat");
1077       stack_start = (uintptr_t) &rlim;
1078     }
1079   }
1080 
1081   // Now we have a pointer (stack_start) very close to the stack top, the
1082   // next thing to do is to figure out the exact location of stack top. We
1083   // can find out the virtual memory area that contains stack_start by
1084   // reading /proc/self/maps, it should be the last vma in /proc/self/maps,
1085   // and its upper limit is the real stack top. (again, this would fail if
1086   // running inside chroot, because /proc may not exist.)
1087 
1088   uintptr_t stack_top;
1089   address low, high;
1090   if (find_vma((address)stack_start, &low, &high)) {
1091     // success, "high" is the true stack top. (ignore "low", because initial
1092     // thread stack grows on demand, its real bottom is high - RLIMIT_STACK.)
1093     stack_top = (uintptr_t)high;
1094   } else {
1095     // failed, likely because /proc/self/maps does not exist
1096     warning("Can't detect initial thread stack location - find_vma failed");
1097     // best effort: stack_start is normally within a few pages below the real
1098     // stack top, use it as stack top, and reduce stack size so we won't put
1099     // guard page outside stack.
1100     stack_top = stack_start;
1101     stack_size -= 16 * page_size();
1102   }
1103 
1104   // stack_top could be partially down the page so align it
1105   stack_top = align_up(stack_top, page_size());
1106 
1107   // Allowed stack value is minimum of max_size and what we derived from rlimit
1108   if (max_size > 0) {
1109     _initial_thread_stack_size = MIN2(max_size, stack_size);
1110   } else {
1111     // Accept the rlimit max, but if stack is unlimited then it will be huge, so
1112     // clamp it at 8MB as we do on Solaris
1113     _initial_thread_stack_size = MIN2(stack_size, 8*M);
1114   }
1115   _initial_thread_stack_size = align_down(_initial_thread_stack_size, page_size());
1116   _initial_thread_stack_bottom = (address)stack_top - _initial_thread_stack_size;
1117 
1118   assert(_initial_thread_stack_bottom < (address)stack_top, "overflow!");
1119 
1120   if (log_is_enabled(Info, os, thread)) {
1121     // See if we seem to be on primordial process thread
1122     bool primordial = uintptr_t(&rlim) > uintptr_t(_initial_thread_stack_bottom) &&
1123                       uintptr_t(&rlim) < stack_top;
1124 
1125     log_info(os, thread)("Capturing initial stack in %s thread: req. size: " SIZE_FORMAT "K, actual size: "
1126                          SIZE_FORMAT "K, top=" INTPTR_FORMAT ", bottom=" INTPTR_FORMAT,
1127                          primordial ? "primordial" : "user", max_size / K,  _initial_thread_stack_size / K,
1128                          stack_top, intptr_t(_initial_thread_stack_bottom));
1129   }
1130 }
1131 
1132 ////////////////////////////////////////////////////////////////////////////////
1133 // time support
1134 
1135 // Time since start-up in seconds to a fine granularity.
1136 // Used by VMSelfDestructTimer and the MemProfiler.
1137 double os::elapsedTime() {
1138 
1139   return ((double)os::elapsed_counter()) / os::elapsed_frequency(); // nanosecond resolution
1140 }
1141 
1142 jlong os::elapsed_counter() {
1143   return javaTimeNanos() - initial_time_count;
1144 }
1145 
1146 jlong os::elapsed_frequency() {
1147   return NANOSECS_PER_SEC; // nanosecond resolution
1148 }
1149 
1150 bool os::supports_vtime() { return true; }
1151 bool os::enable_vtime()   { return false; }
1152 bool os::vtime_enabled()  { return false; }
1153 
1154 double os::elapsedVTime() {
1155   struct rusage usage;
1156   int retval = getrusage(RUSAGE_THREAD, &usage);
1157   if (retval == 0) {
1158     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);
1159   } else {
1160     // better than nothing, but not much
1161     return elapsedTime();
1162   }
1163 }
1164 
1165 jlong os::javaTimeMillis() {
1166   timeval time;
1167   int status = gettimeofday(&time, NULL);
1168   assert(status != -1, "linux error");
1169   return jlong(time.tv_sec) * 1000  +  jlong(time.tv_usec / 1000);
1170 }
1171 
1172 void os::javaTimeSystemUTC(jlong &seconds, jlong &nanos) {
1173   timeval time;
1174   int status = gettimeofday(&time, NULL);
1175   assert(status != -1, "linux error");
1176   seconds = jlong(time.tv_sec);
1177   nanos = jlong(time.tv_usec) * 1000;
1178 }
1179 
1180 
1181 #ifndef CLOCK_MONOTONIC
1182   #define CLOCK_MONOTONIC (1)
1183 #endif
1184 
1185 void os::Linux::clock_init() {
1186   // we do dlopen's in this particular order due to bug in linux
1187   // dynamical loader (see 6348968) leading to crash on exit
1188   void* handle = dlopen("librt.so.1", RTLD_LAZY);
1189   if (handle == NULL) {
1190     handle = dlopen("librt.so", RTLD_LAZY);
1191   }
1192 
1193   if (handle) {
1194     int (*clock_getres_func)(clockid_t, struct timespec*) =
1195            (int(*)(clockid_t, struct timespec*))dlsym(handle, "clock_getres");
1196     int (*clock_gettime_func)(clockid_t, struct timespec*) =
1197            (int(*)(clockid_t, struct timespec*))dlsym(handle, "clock_gettime");
1198     if (clock_getres_func && clock_gettime_func) {
1199       // See if monotonic clock is supported by the kernel. Note that some
1200       // early implementations simply return kernel jiffies (updated every
1201       // 1/100 or 1/1000 second). It would be bad to use such a low res clock
1202       // for nano time (though the monotonic property is still nice to have).
1203       // It's fixed in newer kernels, however clock_getres() still returns
1204       // 1/HZ. We check if clock_getres() works, but will ignore its reported
1205       // resolution for now. Hopefully as people move to new kernels, this
1206       // won't be a problem.
1207       struct timespec res;
1208       struct timespec tp;
1209       if (clock_getres_func (CLOCK_MONOTONIC, &res) == 0 &&
1210           clock_gettime_func(CLOCK_MONOTONIC, &tp)  == 0) {
1211         // yes, monotonic clock is supported
1212         _clock_gettime = clock_gettime_func;
1213         return;
1214       } else {
1215         // close librt if there is no monotonic clock
1216         dlclose(handle);
1217       }
1218     }
1219   }
1220   warning("No monotonic clock was available - timed services may " \
1221           "be adversely affected if the time-of-day clock changes");
1222 }
1223 
1224 #ifndef SYS_clock_getres
1225   #if defined(X86) || defined(PPC64) || defined(S390)
1226     #define SYS_clock_getres AMD64_ONLY(229) IA32_ONLY(266) PPC64_ONLY(247) S390_ONLY(261)
1227     #define sys_clock_getres(x,y)  ::syscall(SYS_clock_getres, x, y)
1228   #else
1229     #warning "SYS_clock_getres not defined for this platform, disabling fast_thread_cpu_time"
1230     #define sys_clock_getres(x,y)  -1
1231   #endif
1232 #else
1233   #define sys_clock_getres(x,y)  ::syscall(SYS_clock_getres, x, y)
1234 #endif
1235 
1236 void os::Linux::fast_thread_clock_init() {
1237   if (!UseLinuxPosixThreadCPUClocks) {
1238     return;
1239   }
1240   clockid_t clockid;
1241   struct timespec tp;
1242   int (*pthread_getcpuclockid_func)(pthread_t, clockid_t *) =
1243       (int(*)(pthread_t, clockid_t *)) dlsym(RTLD_DEFAULT, "pthread_getcpuclockid");
1244 
1245   // Switch to using fast clocks for thread cpu time if
1246   // the sys_clock_getres() returns 0 error code.
1247   // Note, that some kernels may support the current thread
1248   // clock (CLOCK_THREAD_CPUTIME_ID) but not the clocks
1249   // returned by the pthread_getcpuclockid().
1250   // If the fast Posix clocks are supported then the sys_clock_getres()
1251   // must return at least tp.tv_sec == 0 which means a resolution
1252   // better than 1 sec. This is extra check for reliability.
1253 
1254   if (pthread_getcpuclockid_func &&
1255       pthread_getcpuclockid_func(_main_thread, &clockid) == 0 &&
1256       sys_clock_getres(clockid, &tp) == 0 && tp.tv_sec == 0) {
1257     _supports_fast_thread_cpu_time = true;
1258     _pthread_getcpuclockid = pthread_getcpuclockid_func;
1259   }
1260 }
1261 
1262 jlong os::javaTimeNanos() {
1263   if (os::supports_monotonic_clock()) {
1264     struct timespec tp;
1265     int status = Linux::clock_gettime(CLOCK_MONOTONIC, &tp);
1266     assert(status == 0, "gettime error");
1267     jlong result = jlong(tp.tv_sec) * (1000 * 1000 * 1000) + jlong(tp.tv_nsec);
1268     return result;
1269   } else {
1270     timeval time;
1271     int status = gettimeofday(&time, NULL);
1272     assert(status != -1, "linux error");
1273     jlong usecs = jlong(time.tv_sec) * (1000 * 1000) + jlong(time.tv_usec);
1274     return 1000 * usecs;
1275   }
1276 }
1277 
1278 void os::javaTimeNanos_info(jvmtiTimerInfo *info_ptr) {
1279   if (os::supports_monotonic_clock()) {
1280     info_ptr->max_value = ALL_64_BITS;
1281 
1282     // CLOCK_MONOTONIC - amount of time since some arbitrary point in the past
1283     info_ptr->may_skip_backward = false;      // not subject to resetting or drifting
1284     info_ptr->may_skip_forward = false;       // not subject to resetting or drifting
1285   } else {
1286     // gettimeofday - based on time in seconds since the Epoch thus does not wrap
1287     info_ptr->max_value = ALL_64_BITS;
1288 
1289     // gettimeofday is a real time clock so it skips
1290     info_ptr->may_skip_backward = true;
1291     info_ptr->may_skip_forward = true;
1292   }
1293 
1294   info_ptr->kind = JVMTI_TIMER_ELAPSED;                // elapsed not CPU time
1295 }
1296 
1297 // Return the real, user, and system times in seconds from an
1298 // arbitrary fixed point in the past.
1299 bool os::getTimesSecs(double* process_real_time,
1300                       double* process_user_time,
1301                       double* process_system_time) {
1302   struct tms ticks;
1303   clock_t real_ticks = times(&ticks);
1304 
1305   if (real_ticks == (clock_t) (-1)) {
1306     return false;
1307   } else {
1308     double ticks_per_second = (double) clock_tics_per_sec;
1309     *process_user_time = ((double) ticks.tms_utime) / ticks_per_second;
1310     *process_system_time = ((double) ticks.tms_stime) / ticks_per_second;
1311     *process_real_time = ((double) real_ticks) / ticks_per_second;
1312 
1313     return true;
1314   }
1315 }
1316 
1317 
1318 char * os::local_time_string(char *buf, size_t buflen) {
1319   struct tm t;
1320   time_t long_time;
1321   time(&long_time);
1322   localtime_r(&long_time, &t);
1323   jio_snprintf(buf, buflen, "%d-%02d-%02d %02d:%02d:%02d",
1324                t.tm_year + 1900, t.tm_mon + 1, t.tm_mday,
1325                t.tm_hour, t.tm_min, t.tm_sec);
1326   return buf;
1327 }
1328 
1329 struct tm* os::localtime_pd(const time_t* clock, struct tm*  res) {
1330   return localtime_r(clock, res);
1331 }
1332 
1333 ////////////////////////////////////////////////////////////////////////////////
1334 // runtime exit support
1335 
1336 // Note: os::shutdown() might be called very early during initialization, or
1337 // called from signal handler. Before adding something to os::shutdown(), make
1338 // sure it is async-safe and can handle partially initialized VM.
1339 void os::shutdown() {
1340 
1341   // allow PerfMemory to attempt cleanup of any persistent resources
1342   perfMemory_exit();
1343 
1344   // needs to remove object in file system
1345   AttachListener::abort();
1346 
1347   // flush buffered output, finish log files
1348   ostream_abort();
1349 
1350   // Check for abort hook
1351   abort_hook_t abort_hook = Arguments::abort_hook();
1352   if (abort_hook != NULL) {
1353     abort_hook();
1354   }
1355 
1356 }
1357 
1358 // Note: os::abort() might be called very early during initialization, or
1359 // called from signal handler. Before adding something to os::abort(), make
1360 // sure it is async-safe and can handle partially initialized VM.
1361 void os::abort(bool dump_core, void* siginfo, const void* context) {
1362   os::shutdown();
1363   if (dump_core) {
1364 #ifndef PRODUCT
1365     fdStream out(defaultStream::output_fd());
1366     out.print_raw("Current thread is ");
1367     char buf[16];
1368     jio_snprintf(buf, sizeof(buf), UINTX_FORMAT, os::current_thread_id());
1369     out.print_raw_cr(buf);
1370     out.print_raw_cr("Dumping core ...");
1371 #endif
1372     ::abort(); // dump core
1373   }
1374 
1375   ::exit(1);
1376 }
1377 
1378 // Die immediately, no exit hook, no abort hook, no cleanup.
1379 void os::die() {
1380   ::abort();
1381 }
1382 
1383 
1384 // This method is a copy of JDK's sysGetLastErrorString
1385 // from src/solaris/hpi/src/system_md.c
1386 
1387 size_t os::lasterror(char *buf, size_t len) {
1388   if (errno == 0)  return 0;
1389 
1390   const char *s = os::strerror(errno);
1391   size_t n = ::strlen(s);
1392   if (n >= len) {
1393     n = len - 1;
1394   }
1395   ::strncpy(buf, s, n);
1396   buf[n] = '\0';
1397   return n;
1398 }
1399 
1400 // thread_id is kernel thread id (similar to Solaris LWP id)
1401 intx os::current_thread_id() { return os::Linux::gettid(); }
1402 int os::current_process_id() {
1403   return ::getpid();
1404 }
1405 
1406 // DLL functions
1407 
1408 const char* os::dll_file_extension() { return ".so"; }
1409 
1410 // This must be hard coded because it's the system's temporary
1411 // directory not the java application's temp directory, ala java.io.tmpdir.
1412 const char* os::get_temp_directory() { return "/tmp"; }
1413 
1414 static bool file_exists(const char* filename) {
1415   struct stat statbuf;
1416   if (filename == NULL || strlen(filename) == 0) {
1417     return false;
1418   }
1419   return os::stat(filename, &statbuf) == 0;
1420 }
1421 
1422 // check if addr is inside libjvm.so
1423 bool os::address_is_in_vm(address addr) {
1424   static address libjvm_base_addr;
1425   Dl_info dlinfo;
1426 
1427   if (libjvm_base_addr == NULL) {
1428     if (dladdr(CAST_FROM_FN_PTR(void *, os::address_is_in_vm), &dlinfo) != 0) {
1429       libjvm_base_addr = (address)dlinfo.dli_fbase;
1430     }
1431     assert(libjvm_base_addr !=NULL, "Cannot obtain base address for libjvm");
1432   }
1433 
1434   if (dladdr((void *)addr, &dlinfo) != 0) {
1435     if (libjvm_base_addr == (address)dlinfo.dli_fbase) return true;
1436   }
1437 
1438   return false;
1439 }
1440 
1441 bool os::dll_address_to_function_name(address addr, char *buf,
1442                                       int buflen, int *offset,
1443                                       bool demangle) {
1444   // buf is not optional, but offset is optional
1445   assert(buf != NULL, "sanity check");
1446 
1447   Dl_info dlinfo;
1448 
1449   if (dladdr((void*)addr, &dlinfo) != 0) {
1450     // see if we have a matching symbol
1451     if (dlinfo.dli_saddr != NULL && dlinfo.dli_sname != NULL) {
1452       if (!(demangle && Decoder::demangle(dlinfo.dli_sname, buf, buflen))) {
1453         jio_snprintf(buf, buflen, "%s", dlinfo.dli_sname);
1454       }
1455       if (offset != NULL) *offset = addr - (address)dlinfo.dli_saddr;
1456       return true;
1457     }
1458     // no matching symbol so try for just file info
1459     if (dlinfo.dli_fname != NULL && dlinfo.dli_fbase != NULL) {
1460       if (Decoder::decode((address)(addr - (address)dlinfo.dli_fbase),
1461                           buf, buflen, offset, dlinfo.dli_fname, demangle)) {
1462         return true;
1463       }
1464     }
1465   }
1466 
1467   buf[0] = '\0';
1468   if (offset != NULL) *offset = -1;
1469   return false;
1470 }
1471 
1472 struct _address_to_library_name {
1473   address addr;          // input : memory address
1474   size_t  buflen;        //         size of fname
1475   char*   fname;         // output: library name
1476   address base;          //         library base addr
1477 };
1478 
1479 static int address_to_library_name_callback(struct dl_phdr_info *info,
1480                                             size_t size, void *data) {
1481   int i;
1482   bool found = false;
1483   address libbase = NULL;
1484   struct _address_to_library_name * d = (struct _address_to_library_name *)data;
1485 
1486   // iterate through all loadable segments
1487   for (i = 0; i < info->dlpi_phnum; i++) {
1488     address segbase = (address)(info->dlpi_addr + info->dlpi_phdr[i].p_vaddr);
1489     if (info->dlpi_phdr[i].p_type == PT_LOAD) {
1490       // base address of a library is the lowest address of its loaded
1491       // segments.
1492       if (libbase == NULL || libbase > segbase) {
1493         libbase = segbase;
1494       }
1495       // see if 'addr' is within current segment
1496       if (segbase <= d->addr &&
1497           d->addr < segbase + info->dlpi_phdr[i].p_memsz) {
1498         found = true;
1499       }
1500     }
1501   }
1502 
1503   // dlpi_name is NULL or empty if the ELF file is executable, return 0
1504   // so dll_address_to_library_name() can fall through to use dladdr() which
1505   // can figure out executable name from argv[0].
1506   if (found && info->dlpi_name && info->dlpi_name[0]) {
1507     d->base = libbase;
1508     if (d->fname) {
1509       jio_snprintf(d->fname, d->buflen, "%s", info->dlpi_name);
1510     }
1511     return 1;
1512   }
1513   return 0;
1514 }
1515 
1516 bool os::dll_address_to_library_name(address addr, char* buf,
1517                                      int buflen, int* offset) {
1518   // buf is not optional, but offset is optional
1519   assert(buf != NULL, "sanity check");
1520 
1521   Dl_info dlinfo;
1522   struct _address_to_library_name data;
1523 
1524   // There is a bug in old glibc dladdr() implementation that it could resolve
1525   // to wrong library name if the .so file has a base address != NULL. Here
1526   // we iterate through the program headers of all loaded libraries to find
1527   // out which library 'addr' really belongs to. This workaround can be
1528   // removed once the minimum requirement for glibc is moved to 2.3.x.
1529   data.addr = addr;
1530   data.fname = buf;
1531   data.buflen = buflen;
1532   data.base = NULL;
1533   int rslt = dl_iterate_phdr(address_to_library_name_callback, (void *)&data);
1534 
1535   if (rslt) {
1536     // buf already contains library name
1537     if (offset) *offset = addr - data.base;
1538     return true;
1539   }
1540   if (dladdr((void*)addr, &dlinfo) != 0) {
1541     if (dlinfo.dli_fname != NULL) {
1542       jio_snprintf(buf, buflen, "%s", dlinfo.dli_fname);
1543     }
1544     if (dlinfo.dli_fbase != NULL && offset != NULL) {
1545       *offset = addr - (address)dlinfo.dli_fbase;
1546     }
1547     return true;
1548   }
1549 
1550   buf[0] = '\0';
1551   if (offset) *offset = -1;
1552   return false;
1553 }
1554 
1555 // Loads .dll/.so and
1556 // in case of error it checks if .dll/.so was built for the
1557 // same architecture as Hotspot is running on
1558 
1559 
1560 // Remember the stack's state. The Linux dynamic linker will change
1561 // the stack to 'executable' at most once, so we must safepoint only once.
1562 bool os::Linux::_stack_is_executable = false;
1563 
1564 // VM operation that loads a library.  This is necessary if stack protection
1565 // of the Java stacks can be lost during loading the library.  If we
1566 // do not stop the Java threads, they can stack overflow before the stacks
1567 // are protected again.
1568 class VM_LinuxDllLoad: public VM_Operation {
1569  private:
1570   const char *_filename;
1571   char *_ebuf;
1572   int _ebuflen;
1573   void *_lib;
1574  public:
1575   VM_LinuxDllLoad(const char *fn, char *ebuf, int ebuflen) :
1576     _filename(fn), _ebuf(ebuf), _ebuflen(ebuflen), _lib(NULL) {}
1577   VMOp_Type type() const { return VMOp_LinuxDllLoad; }
1578   void doit() {
1579     _lib = os::Linux::dll_load_in_vmthread(_filename, _ebuf, _ebuflen);
1580     os::Linux::_stack_is_executable = true;
1581   }
1582   void* loaded_library() { return _lib; }
1583 };
1584 
1585 void * os::dll_load(const char *filename, char *ebuf, int ebuflen) {
1586   void * result = NULL;
1587   bool load_attempted = false;
1588 
1589   // Check whether the library to load might change execution rights
1590   // of the stack. If they are changed, the protection of the stack
1591   // guard pages will be lost. We need a safepoint to fix this.
1592   //
1593   // See Linux man page execstack(8) for more info.
1594   if (os::uses_stack_guard_pages() && !os::Linux::_stack_is_executable) {
1595     if (!ElfFile::specifies_noexecstack(filename)) {
1596       if (!is_init_completed()) {
1597         os::Linux::_stack_is_executable = true;
1598         // This is OK - No Java threads have been created yet, and hence no
1599         // stack guard pages to fix.
1600         //
1601         // This should happen only when you are building JDK7 using a very
1602         // old version of JDK6 (e.g., with JPRT) and running test_gamma.
1603         //
1604         // Dynamic loader will make all stacks executable after
1605         // this function returns, and will not do that again.
1606         assert(Threads::first() == NULL, "no Java threads should exist yet.");
1607       } else {
1608         warning("You have loaded library %s which might have disabled stack guard. "
1609                 "The VM will try to fix the stack guard now.\n"
1610                 "It's highly recommended that you fix the library with "
1611                 "'execstack -c <libfile>', or link it with '-z noexecstack'.",
1612                 filename);
1613 
1614         assert(Thread::current()->is_Java_thread(), "must be Java thread");
1615         JavaThread *jt = JavaThread::current();
1616         if (jt->thread_state() != _thread_in_native) {
1617           // This happens when a compiler thread tries to load a hsdis-<arch>.so file
1618           // that requires ExecStack. Cannot enter safe point. Let's give up.
1619           warning("Unable to fix stack guard. Giving up.");
1620         } else {
1621           if (!LoadExecStackDllInVMThread) {
1622             // This is for the case where the DLL has an static
1623             // constructor function that executes JNI code. We cannot
1624             // load such DLLs in the VMThread.
1625             result = os::Linux::dlopen_helper(filename, ebuf, ebuflen);
1626           }
1627 
1628           ThreadInVMfromNative tiv(jt);
1629           debug_only(VMNativeEntryWrapper vew;)
1630 
1631           VM_LinuxDllLoad op(filename, ebuf, ebuflen);
1632           VMThread::execute(&op);
1633           if (LoadExecStackDllInVMThread) {
1634             result = op.loaded_library();
1635           }
1636           load_attempted = true;
1637         }
1638       }
1639     }
1640   }
1641 
1642   if (!load_attempted) {
1643     result = os::Linux::dlopen_helper(filename, ebuf, ebuflen);
1644   }
1645 
1646   if (result != NULL) {
1647     // Successful loading
1648     return result;
1649   }
1650 
1651   Elf32_Ehdr elf_head;
1652   int diag_msg_max_length=ebuflen-strlen(ebuf);
1653   char* diag_msg_buf=ebuf+strlen(ebuf);
1654 
1655   if (diag_msg_max_length==0) {
1656     // No more space in ebuf for additional diagnostics message
1657     return NULL;
1658   }
1659 
1660 
1661   int file_descriptor= ::open(filename, O_RDONLY | O_NONBLOCK);
1662 
1663   if (file_descriptor < 0) {
1664     // Can't open library, report dlerror() message
1665     return NULL;
1666   }
1667 
1668   bool failed_to_read_elf_head=
1669     (sizeof(elf_head)!=
1670      (::read(file_descriptor, &elf_head,sizeof(elf_head))));
1671 
1672   ::close(file_descriptor);
1673   if (failed_to_read_elf_head) {
1674     // file i/o error - report dlerror() msg
1675     return NULL;
1676   }
1677 
1678   typedef struct {
1679     Elf32_Half    code;         // Actual value as defined in elf.h
1680     Elf32_Half    compat_class; // Compatibility of archs at VM's sense
1681     unsigned char elf_class;    // 32 or 64 bit
1682     unsigned char endianess;    // MSB or LSB
1683     char*         name;         // String representation
1684   } arch_t;
1685 
1686 #ifndef EM_486
1687   #define EM_486          6               /* Intel 80486 */
1688 #endif
1689 #ifndef EM_AARCH64
1690   #define EM_AARCH64    183               /* ARM AARCH64 */
1691 #endif
1692 
1693   static const arch_t arch_array[]={
1694     {EM_386,         EM_386,     ELFCLASS32, ELFDATA2LSB, (char*)"IA 32"},
1695     {EM_486,         EM_386,     ELFCLASS32, ELFDATA2LSB, (char*)"IA 32"},
1696     {EM_IA_64,       EM_IA_64,   ELFCLASS64, ELFDATA2LSB, (char*)"IA 64"},
1697     {EM_X86_64,      EM_X86_64,  ELFCLASS64, ELFDATA2LSB, (char*)"AMD 64"},
1698     {EM_SPARC,       EM_SPARC,   ELFCLASS32, ELFDATA2MSB, (char*)"Sparc 32"},
1699     {EM_SPARC32PLUS, EM_SPARC,   ELFCLASS32, ELFDATA2MSB, (char*)"Sparc 32"},
1700     {EM_SPARCV9,     EM_SPARCV9, ELFCLASS64, ELFDATA2MSB, (char*)"Sparc v9 64"},
1701     {EM_PPC,         EM_PPC,     ELFCLASS32, ELFDATA2MSB, (char*)"Power PC 32"},
1702 #if defined(VM_LITTLE_ENDIAN)
1703     {EM_PPC64,       EM_PPC64,   ELFCLASS64, ELFDATA2LSB, (char*)"Power PC 64 LE"},
1704     {EM_SH,          EM_SH,      ELFCLASS32, ELFDATA2LSB, (char*)"SuperH"},
1705 #else
1706     {EM_PPC64,       EM_PPC64,   ELFCLASS64, ELFDATA2MSB, (char*)"Power PC 64"},
1707     {EM_SH,          EM_SH,      ELFCLASS32, ELFDATA2MSB, (char*)"SuperH BE"},
1708 #endif
1709     {EM_ARM,         EM_ARM,     ELFCLASS32,   ELFDATA2LSB, (char*)"ARM"},
1710     {EM_S390,        EM_S390,    ELFCLASSNONE, ELFDATA2MSB, (char*)"IBM System/390"},
1711     {EM_ALPHA,       EM_ALPHA,   ELFCLASS64, ELFDATA2LSB, (char*)"Alpha"},
1712     {EM_MIPS_RS3_LE, EM_MIPS_RS3_LE, ELFCLASS32, ELFDATA2LSB, (char*)"MIPSel"},
1713     {EM_MIPS,        EM_MIPS,    ELFCLASS32, ELFDATA2MSB, (char*)"MIPS"},
1714     {EM_PARISC,      EM_PARISC,  ELFCLASS32, ELFDATA2MSB, (char*)"PARISC"},
1715     {EM_68K,         EM_68K,     ELFCLASS32, ELFDATA2MSB, (char*)"M68k"},
1716     {EM_AARCH64,     EM_AARCH64, ELFCLASS64, ELFDATA2LSB, (char*)"AARCH64"},
1717   };
1718 
1719 #if  (defined IA32)
1720   static  Elf32_Half running_arch_code=EM_386;
1721 #elif   (defined AMD64)
1722   static  Elf32_Half running_arch_code=EM_X86_64;
1723 #elif  (defined IA64)
1724   static  Elf32_Half running_arch_code=EM_IA_64;
1725 #elif  (defined __sparc) && (defined _LP64)
1726   static  Elf32_Half running_arch_code=EM_SPARCV9;
1727 #elif  (defined __sparc) && (!defined _LP64)
1728   static  Elf32_Half running_arch_code=EM_SPARC;
1729 #elif  (defined __powerpc64__)
1730   static  Elf32_Half running_arch_code=EM_PPC64;
1731 #elif  (defined __powerpc__)
1732   static  Elf32_Half running_arch_code=EM_PPC;
1733 #elif  (defined AARCH64)
1734   static  Elf32_Half running_arch_code=EM_AARCH64;
1735 #elif  (defined ARM)
1736   static  Elf32_Half running_arch_code=EM_ARM;
1737 #elif  (defined S390)
1738   static  Elf32_Half running_arch_code=EM_S390;
1739 #elif  (defined ALPHA)
1740   static  Elf32_Half running_arch_code=EM_ALPHA;
1741 #elif  (defined MIPSEL)
1742   static  Elf32_Half running_arch_code=EM_MIPS_RS3_LE;
1743 #elif  (defined PARISC)
1744   static  Elf32_Half running_arch_code=EM_PARISC;
1745 #elif  (defined MIPS)
1746   static  Elf32_Half running_arch_code=EM_MIPS;
1747 #elif  (defined M68K)
1748   static  Elf32_Half running_arch_code=EM_68K;
1749 #elif  (defined SH)
1750   static  Elf32_Half running_arch_code=EM_SH;
1751 #else
1752     #error Method os::dll_load requires that one of following is defined:\
1753         AARCH64, ALPHA, ARM, AMD64, IA32, IA64, M68K, MIPS, MIPSEL, PARISC, __powerpc__, __powerpc64__, S390, SH, __sparc
1754 #endif
1755 
1756   // Identify compatability class for VM's architecture and library's architecture
1757   // Obtain string descriptions for architectures
1758 
1759   arch_t lib_arch={elf_head.e_machine,0,elf_head.e_ident[EI_CLASS], elf_head.e_ident[EI_DATA], NULL};
1760   int running_arch_index=-1;
1761 
1762   for (unsigned int i=0; i < ARRAY_SIZE(arch_array); i++) {
1763     if (running_arch_code == arch_array[i].code) {
1764       running_arch_index    = i;
1765     }
1766     if (lib_arch.code == arch_array[i].code) {
1767       lib_arch.compat_class = arch_array[i].compat_class;
1768       lib_arch.name         = arch_array[i].name;
1769     }
1770   }
1771 
1772   assert(running_arch_index != -1,
1773          "Didn't find running architecture code (running_arch_code) in arch_array");
1774   if (running_arch_index == -1) {
1775     // Even though running architecture detection failed
1776     // we may still continue with reporting dlerror() message
1777     return NULL;
1778   }
1779 
1780   if (lib_arch.endianess != arch_array[running_arch_index].endianess) {
1781     ::snprintf(diag_msg_buf, diag_msg_max_length-1," (Possible cause: endianness mismatch)");
1782     return NULL;
1783   }
1784 
1785 #ifndef S390
1786   if (lib_arch.elf_class != arch_array[running_arch_index].elf_class) {
1787     ::snprintf(diag_msg_buf, diag_msg_max_length-1," (Possible cause: architecture word width mismatch)");
1788     return NULL;
1789   }
1790 #endif // !S390
1791 
1792   if (lib_arch.compat_class != arch_array[running_arch_index].compat_class) {
1793     if (lib_arch.name!=NULL) {
1794       ::snprintf(diag_msg_buf, diag_msg_max_length-1,
1795                  " (Possible cause: can't load %s-bit .so on a %s-bit platform)",
1796                  lib_arch.name, arch_array[running_arch_index].name);
1797     } else {
1798       ::snprintf(diag_msg_buf, diag_msg_max_length-1,
1799                  " (Possible cause: can't load this .so (machine code=0x%x) on a %s-bit platform)",
1800                  lib_arch.code,
1801                  arch_array[running_arch_index].name);
1802     }
1803   }
1804 
1805   return NULL;
1806 }
1807 
1808 void * os::Linux::dlopen_helper(const char *filename, char *ebuf,
1809                                 int ebuflen) {
1810   void * result = ::dlopen(filename, RTLD_LAZY);
1811   if (result == NULL) {
1812     ::strncpy(ebuf, ::dlerror(), ebuflen - 1);
1813     ebuf[ebuflen-1] = '\0';
1814   }
1815   return result;
1816 }
1817 
1818 void * os::Linux::dll_load_in_vmthread(const char *filename, char *ebuf,
1819                                        int ebuflen) {
1820   void * result = NULL;
1821   if (LoadExecStackDllInVMThread) {
1822     result = dlopen_helper(filename, ebuf, ebuflen);
1823   }
1824 
1825   // Since 7019808, libjvm.so is linked with -noexecstack. If the VM loads a
1826   // library that requires an executable stack, or which does not have this
1827   // stack attribute set, dlopen changes the stack attribute to executable. The
1828   // read protection of the guard pages gets lost.
1829   //
1830   // Need to check _stack_is_executable again as multiple VM_LinuxDllLoad
1831   // may have been queued at the same time.
1832 
1833   if (!_stack_is_executable) {
1834     JavaThread *jt = Threads::first();
1835 
1836     while (jt) {
1837       if (!jt->stack_guard_zone_unused() &&     // Stack not yet fully initialized
1838           jt->stack_guards_enabled()) {         // No pending stack overflow exceptions
1839         if (!os::guard_memory((char *)jt->stack_end(), jt->stack_guard_zone_size())) {
1840           warning("Attempt to reguard stack yellow zone failed.");
1841         }
1842       }
1843       jt = jt->next();
1844     }
1845   }
1846 
1847   return result;
1848 }
1849 
1850 void* os::dll_lookup(void* handle, const char* name) {
1851   void* res = dlsym(handle, name);
1852   return res;
1853 }
1854 
1855 void* os::get_default_process_handle() {
1856   return (void*)::dlopen(NULL, RTLD_LAZY);
1857 }
1858 
1859 static bool _print_ascii_file(const char* filename, outputStream* st) {
1860   int fd = ::open(filename, O_RDONLY);
1861   if (fd == -1) {
1862     return false;
1863   }
1864 
1865   char buf[33];
1866   int bytes;
1867   buf[32] = '\0';
1868   while ((bytes = ::read(fd, buf, sizeof(buf)-1)) > 0) {
1869     st->print_raw(buf, bytes);
1870   }
1871 
1872   ::close(fd);
1873 
1874   return true;
1875 }
1876 
1877 void os::print_dll_info(outputStream *st) {
1878   st->print_cr("Dynamic libraries:");
1879 
1880   char fname[32];
1881   pid_t pid = os::Linux::gettid();
1882 
1883   jio_snprintf(fname, sizeof(fname), "/proc/%d/maps", pid);
1884 
1885   if (!_print_ascii_file(fname, st)) {
1886     st->print("Can not get library information for pid = %d\n", pid);
1887   }
1888 }
1889 
1890 int os::get_loaded_modules_info(os::LoadedModulesCallbackFunc callback, void *param) {
1891   FILE *procmapsFile = NULL;
1892 
1893   // Open the procfs maps file for the current process
1894   if ((procmapsFile = fopen("/proc/self/maps", "r")) != NULL) {
1895     // Allocate PATH_MAX for file name plus a reasonable size for other fields.
1896     char line[PATH_MAX + 100];
1897 
1898     // Read line by line from 'file'
1899     while (fgets(line, sizeof(line), procmapsFile) != NULL) {
1900       u8 base, top, offset, inode;
1901       char permissions[5];
1902       char device[6];
1903       char name[PATH_MAX + 1];
1904 
1905       // Parse fields from line
1906       sscanf(line, UINT64_FORMAT_X "-" UINT64_FORMAT_X " %4s " UINT64_FORMAT_X " %5s " INT64_FORMAT " %s",
1907              &base, &top, permissions, &offset, device, &inode, name);
1908 
1909       // Filter by device id '00:00' so that we only get file system mapped files.
1910       if (strcmp(device, "00:00") != 0) {
1911 
1912         // Call callback with the fields of interest
1913         if(callback(name, (address)base, (address)top, param)) {
1914           // Oops abort, callback aborted
1915           fclose(procmapsFile);
1916           return 1;
1917         }
1918       }
1919     }
1920     fclose(procmapsFile);
1921   }
1922   return 0;
1923 }
1924 
1925 void os::print_os_info_brief(outputStream* st) {
1926   os::Linux::print_distro_info(st);
1927 
1928   os::Posix::print_uname_info(st);
1929 
1930   os::Linux::print_libversion_info(st);
1931 
1932 }
1933 
1934 void os::print_os_info(outputStream* st) {
1935   st->print("OS:");
1936 
1937   os::Linux::print_distro_info(st);
1938 
1939   os::Posix::print_uname_info(st);
1940 
1941   // Print warning if unsafe chroot environment detected
1942   if (unsafe_chroot_detected) {
1943     st->print("WARNING!! ");
1944     st->print_cr("%s", unstable_chroot_error);
1945   }
1946 
1947   os::Linux::print_libversion_info(st);
1948 
1949   os::Posix::print_rlimit_info(st);
1950 
1951   os::Posix::print_load_average(st);
1952 
1953   os::Linux::print_full_memory_info(st);
1954 }
1955 
1956 // Try to identify popular distros.
1957 // Most Linux distributions have a /etc/XXX-release file, which contains
1958 // the OS version string. Newer Linux distributions have a /etc/lsb-release
1959 // file that also contains the OS version string. Some have more than one
1960 // /etc/XXX-release file (e.g. Mandrake has both /etc/mandrake-release and
1961 // /etc/redhat-release.), so the order is important.
1962 // Any Linux that is based on Redhat (i.e. Oracle, Mandrake, Sun JDS...) have
1963 // their own specific XXX-release file as well as a redhat-release file.
1964 // Because of this the XXX-release file needs to be searched for before the
1965 // redhat-release file.
1966 // Since Red Hat and SuSE have an lsb-release file that is not very descriptive the
1967 // search for redhat-release / SuSE-release needs to be before lsb-release.
1968 // Since the lsb-release file is the new standard it needs to be searched
1969 // before the older style release files.
1970 // Searching system-release (Red Hat) and os-release (other Linuxes) are a
1971 // next to last resort.  The os-release file is a new standard that contains
1972 // distribution information and the system-release file seems to be an old
1973 // standard that has been replaced by the lsb-release and os-release files.
1974 // Searching for the debian_version file is the last resort.  It contains
1975 // an informative string like "6.0.6" or "wheezy/sid". Because of this
1976 // "Debian " is printed before the contents of the debian_version file.
1977 
1978 const char* distro_files[] = {
1979   "/etc/oracle-release",
1980   "/etc/mandriva-release",
1981   "/etc/mandrake-release",
1982   "/etc/sun-release",
1983   "/etc/redhat-release",
1984   "/etc/SuSE-release",
1985   "/etc/lsb-release",
1986   "/etc/turbolinux-release",
1987   "/etc/gentoo-release",
1988   "/etc/ltib-release",
1989   "/etc/angstrom-version",
1990   "/etc/system-release",
1991   "/etc/os-release",
1992   NULL };
1993 
1994 void os::Linux::print_distro_info(outputStream* st) {
1995   for (int i = 0;; i++) {
1996     const char* file = distro_files[i];
1997     if (file == NULL) {
1998       break;  // done
1999     }
2000     // If file prints, we found it.
2001     if (_print_ascii_file(file, st)) {
2002       return;
2003     }
2004   }
2005 
2006   if (file_exists("/etc/debian_version")) {
2007     st->print("Debian ");
2008     _print_ascii_file("/etc/debian_version", st);
2009   } else {
2010     st->print("Linux");
2011   }
2012   st->cr();
2013 }
2014 
2015 static void parse_os_info_helper(FILE* fp, char* distro, size_t length, bool get_first_line) {
2016   char buf[256];
2017   while (fgets(buf, sizeof(buf), fp)) {
2018     // Edit out extra stuff in expected format
2019     if (strstr(buf, "DISTRIB_DESCRIPTION=") != NULL || strstr(buf, "PRETTY_NAME=") != NULL) {
2020       char* ptr = strstr(buf, "\"");  // the name is in quotes
2021       if (ptr != NULL) {
2022         ptr++; // go beyond first quote
2023         char* nl = strchr(ptr, '\"');
2024         if (nl != NULL) *nl = '\0';
2025         strncpy(distro, ptr, length);
2026       } else {
2027         ptr = strstr(buf, "=");
2028         ptr++; // go beyond equals then
2029         char* nl = strchr(ptr, '\n');
2030         if (nl != NULL) *nl = '\0';
2031         strncpy(distro, ptr, length);
2032       }
2033       return;
2034     } else if (get_first_line) {
2035       char* nl = strchr(buf, '\n');
2036       if (nl != NULL) *nl = '\0';
2037       strncpy(distro, buf, length);
2038       return;
2039     }
2040   }
2041   // print last line and close
2042   char* nl = strchr(buf, '\n');
2043   if (nl != NULL) *nl = '\0';
2044   strncpy(distro, buf, length);
2045 }
2046 
2047 static void parse_os_info(char* distro, size_t length, const char* file) {
2048   FILE* fp = fopen(file, "r");
2049   if (fp != NULL) {
2050     // if suse format, print out first line
2051     bool get_first_line = (strcmp(file, "/etc/SuSE-release") == 0);
2052     parse_os_info_helper(fp, distro, length, get_first_line);
2053     fclose(fp);
2054   }
2055 }
2056 
2057 void os::get_summary_os_info(char* buf, size_t buflen) {
2058   for (int i = 0;; i++) {
2059     const char* file = distro_files[i];
2060     if (file == NULL) {
2061       break; // ran out of distro_files
2062     }
2063     if (file_exists(file)) {
2064       parse_os_info(buf, buflen, file);
2065       return;
2066     }
2067   }
2068   // special case for debian
2069   if (file_exists("/etc/debian_version")) {
2070     strncpy(buf, "Debian ", buflen);
2071     parse_os_info(&buf[7], buflen-7, "/etc/debian_version");
2072   } else {
2073     strncpy(buf, "Linux", buflen);
2074   }
2075 }
2076 
2077 void os::Linux::print_libversion_info(outputStream* st) {
2078   // libc, pthread
2079   st->print("libc:");
2080   st->print("%s ", os::Linux::glibc_version());
2081   st->print("%s ", os::Linux::libpthread_version());
2082   st->cr();
2083 }
2084 
2085 void os::Linux::print_full_memory_info(outputStream* st) {
2086   st->print("\n/proc/meminfo:\n");
2087   _print_ascii_file("/proc/meminfo", st);
2088   st->cr();
2089 }
2090 
2091 void os::print_memory_info(outputStream* st) {
2092 
2093   st->print("Memory:");
2094   st->print(" %dk page", os::vm_page_size()>>10);
2095 
2096   // values in struct sysinfo are "unsigned long"
2097   struct sysinfo si;
2098   sysinfo(&si);
2099 
2100   st->print(", physical " UINT64_FORMAT "k",
2101             os::physical_memory() >> 10);
2102   st->print("(" UINT64_FORMAT "k free)",
2103             os::available_memory() >> 10);
2104   st->print(", swap " UINT64_FORMAT "k",
2105             ((jlong)si.totalswap * si.mem_unit) >> 10);
2106   st->print("(" UINT64_FORMAT "k free)",
2107             ((jlong)si.freeswap * si.mem_unit) >> 10);
2108   st->cr();
2109 }
2110 
2111 // Print the first "model name" line and the first "flags" line
2112 // that we find and nothing more. We assume "model name" comes
2113 // before "flags" so if we find a second "model name", then the
2114 // "flags" field is considered missing.
2115 static bool print_model_name_and_flags(outputStream* st, char* buf, size_t buflen) {
2116 #if defined(IA32) || defined(AMD64)
2117   // Other platforms have less repetitive cpuinfo files
2118   FILE *fp = fopen("/proc/cpuinfo", "r");
2119   if (fp) {
2120     while (!feof(fp)) {
2121       if (fgets(buf, buflen, fp)) {
2122         // Assume model name comes before flags
2123         bool model_name_printed = false;
2124         if (strstr(buf, "model name") != NULL) {
2125           if (!model_name_printed) {
2126             st->print_raw("CPU Model and flags from /proc/cpuinfo:\n");
2127             st->print_raw(buf);
2128             model_name_printed = true;
2129           } else {
2130             // model name printed but not flags?  Odd, just return
2131             fclose(fp);
2132             return true;
2133           }
2134         }
2135         // print the flags line too
2136         if (strstr(buf, "flags") != NULL) {
2137           st->print_raw(buf);
2138           fclose(fp);
2139           return true;
2140         }
2141       }
2142     }
2143     fclose(fp);
2144   }
2145 #endif // x86 platforms
2146   return false;
2147 }
2148 
2149 void os::pd_print_cpu_info(outputStream* st, char* buf, size_t buflen) {
2150   // Only print the model name if the platform provides this as a summary
2151   if (!print_model_name_and_flags(st, buf, buflen)) {
2152     st->print("\n/proc/cpuinfo:\n");
2153     if (!_print_ascii_file("/proc/cpuinfo", st)) {
2154       st->print_cr("  <Not Available>");
2155     }
2156   }
2157 }
2158 
2159 #if defined(AMD64) || defined(IA32) || defined(X32)
2160 const char* search_string = "model name";
2161 #elif defined(M68K)
2162 const char* search_string = "CPU";
2163 #elif defined(PPC64)
2164 const char* search_string = "cpu";
2165 #elif defined(S390)
2166 const char* search_string = "processor";
2167 #elif defined(SPARC)
2168 const char* search_string = "cpu";
2169 #else
2170 const char* search_string = "Processor";
2171 #endif
2172 
2173 // Parses the cpuinfo file for string representing the model name.
2174 void os::get_summary_cpu_info(char* cpuinfo, size_t length) {
2175   FILE* fp = fopen("/proc/cpuinfo", "r");
2176   if (fp != NULL) {
2177     while (!feof(fp)) {
2178       char buf[256];
2179       if (fgets(buf, sizeof(buf), fp)) {
2180         char* start = strstr(buf, search_string);
2181         if (start != NULL) {
2182           char *ptr = start + strlen(search_string);
2183           char *end = buf + strlen(buf);
2184           while (ptr != end) {
2185              // skip whitespace and colon for the rest of the name.
2186              if (*ptr != ' ' && *ptr != '\t' && *ptr != ':') {
2187                break;
2188              }
2189              ptr++;
2190           }
2191           if (ptr != end) {
2192             // reasonable string, get rid of newline and keep the rest
2193             char* nl = strchr(buf, '\n');
2194             if (nl != NULL) *nl = '\0';
2195             strncpy(cpuinfo, ptr, length);
2196             fclose(fp);
2197             return;
2198           }
2199         }
2200       }
2201     }
2202     fclose(fp);
2203   }
2204   // cpuinfo not found or parsing failed, just print generic string.  The entire
2205   // /proc/cpuinfo file will be printed later in the file (or enough of it for x86)
2206 #if   defined(AARCH64)
2207   strncpy(cpuinfo, "AArch64", length);
2208 #elif defined(AMD64)
2209   strncpy(cpuinfo, "x86_64", length);
2210 #elif defined(ARM)  // Order wrt. AARCH64 is relevant!
2211   strncpy(cpuinfo, "ARM", length);
2212 #elif defined(IA32)
2213   strncpy(cpuinfo, "x86_32", length);
2214 #elif defined(IA64)
2215   strncpy(cpuinfo, "IA64", length);
2216 #elif defined(PPC)
2217   strncpy(cpuinfo, "PPC64", length);
2218 #elif defined(S390)
2219   strncpy(cpuinfo, "S390", length);
2220 #elif defined(SPARC)
2221   strncpy(cpuinfo, "sparcv9", length);
2222 #elif defined(ZERO_LIBARCH)
2223   strncpy(cpuinfo, ZERO_LIBARCH, length);
2224 #else
2225   strncpy(cpuinfo, "unknown", length);
2226 #endif
2227 }
2228 
2229 static void print_signal_handler(outputStream* st, int sig,
2230                                  char* buf, size_t buflen);
2231 
2232 void os::print_signal_handlers(outputStream* st, char* buf, size_t buflen) {
2233   st->print_cr("Signal Handlers:");
2234   print_signal_handler(st, SIGSEGV, buf, buflen);
2235   print_signal_handler(st, SIGBUS , buf, buflen);
2236   print_signal_handler(st, SIGFPE , buf, buflen);
2237   print_signal_handler(st, SIGPIPE, buf, buflen);
2238   print_signal_handler(st, SIGXFSZ, buf, buflen);
2239   print_signal_handler(st, SIGILL , buf, buflen);
2240   print_signal_handler(st, SR_signum, buf, buflen);
2241   print_signal_handler(st, SHUTDOWN1_SIGNAL, buf, buflen);
2242   print_signal_handler(st, SHUTDOWN2_SIGNAL , buf, buflen);
2243   print_signal_handler(st, SHUTDOWN3_SIGNAL , buf, buflen);
2244   print_signal_handler(st, BREAK_SIGNAL, buf, buflen);
2245 #if defined(PPC64)
2246   print_signal_handler(st, SIGTRAP, buf, buflen);
2247 #endif
2248 }
2249 
2250 static char saved_jvm_path[MAXPATHLEN] = {0};
2251 
2252 // Find the full path to the current module, libjvm.so
2253 void os::jvm_path(char *buf, jint buflen) {
2254   // Error checking.
2255   if (buflen < MAXPATHLEN) {
2256     assert(false, "must use a large-enough buffer");
2257     buf[0] = '\0';
2258     return;
2259   }
2260   // Lazy resolve the path to current module.
2261   if (saved_jvm_path[0] != 0) {
2262     strcpy(buf, saved_jvm_path);
2263     return;
2264   }
2265 
2266   char dli_fname[MAXPATHLEN];
2267   bool ret = dll_address_to_library_name(
2268                                          CAST_FROM_FN_PTR(address, os::jvm_path),
2269                                          dli_fname, sizeof(dli_fname), NULL);
2270   assert(ret, "cannot locate libjvm");
2271   char *rp = NULL;
2272   if (ret && dli_fname[0] != '\0') {
2273     rp = os::Posix::realpath(dli_fname, buf, buflen);
2274   }
2275   if (rp == NULL) {
2276     return;
2277   }
2278 
2279   if (Arguments::sun_java_launcher_is_altjvm()) {
2280     // Support for the java launcher's '-XXaltjvm=<path>' option. Typical
2281     // value for buf is "<JAVA_HOME>/jre/lib/<vmtype>/libjvm.so".
2282     // If "/jre/lib/" appears at the right place in the string, then
2283     // assume we are installed in a JDK and we're done. Otherwise, check
2284     // for a JAVA_HOME environment variable and fix up the path so it
2285     // looks like libjvm.so is installed there (append a fake suffix
2286     // hotspot/libjvm.so).
2287     const char *p = buf + strlen(buf) - 1;
2288     for (int count = 0; p > buf && count < 5; ++count) {
2289       for (--p; p > buf && *p != '/'; --p)
2290         /* empty */ ;
2291     }
2292 
2293     if (strncmp(p, "/jre/lib/", 9) != 0) {
2294       // Look for JAVA_HOME in the environment.
2295       char* java_home_var = ::getenv("JAVA_HOME");
2296       if (java_home_var != NULL && java_home_var[0] != 0) {
2297         char* jrelib_p;
2298         int len;
2299 
2300         // Check the current module name "libjvm.so".
2301         p = strrchr(buf, '/');
2302         if (p == NULL) {
2303           return;
2304         }
2305         assert(strstr(p, "/libjvm") == p, "invalid library name");
2306 
2307         rp = os::Posix::realpath(java_home_var, buf, buflen);
2308         if (rp == NULL) {
2309           return;
2310         }
2311 
2312         // determine if this is a legacy image or modules image
2313         // modules image doesn't have "jre" subdirectory
2314         len = strlen(buf);
2315         assert(len < buflen, "Ran out of buffer room");
2316         jrelib_p = buf + len;
2317         snprintf(jrelib_p, buflen-len, "/jre/lib");
2318         if (0 != access(buf, F_OK)) {
2319           snprintf(jrelib_p, buflen-len, "/lib");
2320         }
2321 
2322         if (0 == access(buf, F_OK)) {
2323           // Use current module name "libjvm.so"
2324           len = strlen(buf);
2325           snprintf(buf + len, buflen-len, "/hotspot/libjvm.so");
2326         } else {
2327           // Go back to path of .so
2328           rp = os::Posix::realpath(dli_fname, buf, buflen);
2329           if (rp == NULL) {
2330             return;
2331           }
2332         }
2333       }
2334     }
2335   }
2336 
2337   strncpy(saved_jvm_path, buf, MAXPATHLEN);
2338   saved_jvm_path[MAXPATHLEN - 1] = '\0';
2339 }
2340 
2341 void os::print_jni_name_prefix_on(outputStream* st, int args_size) {
2342   // no prefix required, not even "_"
2343 }
2344 
2345 void os::print_jni_name_suffix_on(outputStream* st, int args_size) {
2346   // no suffix required
2347 }
2348 
2349 ////////////////////////////////////////////////////////////////////////////////
2350 // sun.misc.Signal support
2351 
2352 static volatile jint sigint_count = 0;
2353 
2354 static void UserHandler(int sig, void *siginfo, void *context) {
2355   // 4511530 - sem_post is serialized and handled by the manager thread. When
2356   // the program is interrupted by Ctrl-C, SIGINT is sent to every thread. We
2357   // don't want to flood the manager thread with sem_post requests.
2358   if (sig == SIGINT && Atomic::add(1, &sigint_count) > 1) {
2359     return;
2360   }
2361 
2362   // Ctrl-C is pressed during error reporting, likely because the error
2363   // handler fails to abort. Let VM die immediately.
2364   if (sig == SIGINT && VMError::is_error_reported()) {
2365     os::die();
2366   }
2367 
2368   os::signal_notify(sig);
2369 }
2370 
2371 void* os::user_handler() {
2372   return CAST_FROM_FN_PTR(void*, UserHandler);
2373 }
2374 
2375 struct timespec PosixSemaphore::create_timespec(unsigned int sec, int nsec) {
2376   struct timespec ts;
2377   // Semaphore's are always associated with CLOCK_REALTIME
2378   os::Linux::clock_gettime(CLOCK_REALTIME, &ts);
2379   // see unpackTime for discussion on overflow checking
2380   if (sec >= MAX_SECS) {
2381     ts.tv_sec += MAX_SECS;
2382     ts.tv_nsec = 0;
2383   } else {
2384     ts.tv_sec += sec;
2385     ts.tv_nsec += nsec;
2386     if (ts.tv_nsec >= NANOSECS_PER_SEC) {
2387       ts.tv_nsec -= NANOSECS_PER_SEC;
2388       ++ts.tv_sec; // note: this must be <= max_secs
2389     }
2390   }
2391 
2392   return ts;
2393 }
2394 
2395 extern "C" {
2396   typedef void (*sa_handler_t)(int);
2397   typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
2398 }
2399 
2400 void* os::signal(int signal_number, void* handler) {
2401   struct sigaction sigAct, oldSigAct;
2402 
2403   sigfillset(&(sigAct.sa_mask));
2404   sigAct.sa_flags   = SA_RESTART|SA_SIGINFO;
2405   sigAct.sa_handler = CAST_TO_FN_PTR(sa_handler_t, handler);
2406 
2407   if (sigaction(signal_number, &sigAct, &oldSigAct)) {
2408     // -1 means registration failed
2409     return (void *)-1;
2410   }
2411 
2412   return CAST_FROM_FN_PTR(void*, oldSigAct.sa_handler);
2413 }
2414 
2415 void os::signal_raise(int signal_number) {
2416   ::raise(signal_number);
2417 }
2418 
2419 // The following code is moved from os.cpp for making this
2420 // code platform specific, which it is by its very nature.
2421 
2422 // Will be modified when max signal is changed to be dynamic
2423 int os::sigexitnum_pd() {
2424   return NSIG;
2425 }
2426 
2427 // a counter for each possible signal value
2428 static volatile jint pending_signals[NSIG+1] = { 0 };
2429 
2430 // Linux(POSIX) specific hand shaking semaphore.
2431 static sem_t sig_sem;
2432 static PosixSemaphore sr_semaphore;
2433 
2434 void os::signal_init_pd() {
2435   // Initialize signal structures
2436   ::memset((void*)pending_signals, 0, sizeof(pending_signals));
2437 
2438   // Initialize signal semaphore
2439   ::sem_init(&sig_sem, 0, 0);
2440 }
2441 
2442 void os::signal_notify(int sig) {
2443   Atomic::inc(&pending_signals[sig]);
2444   ::sem_post(&sig_sem);
2445 }
2446 
2447 static int check_pending_signals(bool wait) {
2448   Atomic::store(0, &sigint_count);
2449   for (;;) {
2450     for (int i = 0; i < NSIG + 1; i++) {
2451       jint n = pending_signals[i];
2452       if (n > 0 && n == Atomic::cmpxchg(n - 1, &pending_signals[i], n)) {
2453         return i;
2454       }
2455     }
2456     if (!wait) {
2457       return -1;
2458     }
2459     JavaThread *thread = JavaThread::current();
2460     ThreadBlockInVM tbivm(thread);
2461 
2462     bool threadIsSuspended;
2463     do {
2464       thread->set_suspend_equivalent();
2465       // cleared by handle_special_suspend_equivalent_condition() or java_suspend_self()
2466       ::sem_wait(&sig_sem);
2467 
2468       // were we externally suspended while we were waiting?
2469       threadIsSuspended = thread->handle_special_suspend_equivalent_condition();
2470       if (threadIsSuspended) {
2471         // The semaphore has been incremented, but while we were waiting
2472         // another thread suspended us. We don't want to continue running
2473         // while suspended because that would surprise the thread that
2474         // suspended us.
2475         ::sem_post(&sig_sem);
2476 
2477         thread->java_suspend_self();
2478       }
2479     } while (threadIsSuspended);
2480   }
2481 }
2482 
2483 int os::signal_lookup() {
2484   return check_pending_signals(false);
2485 }
2486 
2487 int os::signal_wait() {
2488   return check_pending_signals(true);
2489 }
2490 
2491 ////////////////////////////////////////////////////////////////////////////////
2492 // Virtual Memory
2493 
2494 int os::vm_page_size() {
2495   // Seems redundant as all get out
2496   assert(os::Linux::page_size() != -1, "must call os::init");
2497   return os::Linux::page_size();
2498 }
2499 
2500 // Solaris allocates memory by pages.
2501 int os::vm_allocation_granularity() {
2502   assert(os::Linux::page_size() != -1, "must call os::init");
2503   return os::Linux::page_size();
2504 }
2505 
2506 // Rationale behind this function:
2507 //  current (Mon Apr 25 20:12:18 MSD 2005) oprofile drops samples without executable
2508 //  mapping for address (see lookup_dcookie() in the kernel module), thus we cannot get
2509 //  samples for JITted code. Here we create private executable mapping over the code cache
2510 //  and then we can use standard (well, almost, as mapping can change) way to provide
2511 //  info for the reporting script by storing timestamp and location of symbol
2512 void linux_wrap_code(char* base, size_t size) {
2513   static volatile jint cnt = 0;
2514 
2515   if (!UseOprofile) {
2516     return;
2517   }
2518 
2519   char buf[PATH_MAX+1];
2520   int num = Atomic::add(1, &cnt);
2521 
2522   snprintf(buf, sizeof(buf), "%s/hs-vm-%d-%d",
2523            os::get_temp_directory(), os::current_process_id(), num);
2524   unlink(buf);
2525 
2526   int fd = ::open(buf, O_CREAT | O_RDWR, S_IRWXU);
2527 
2528   if (fd != -1) {
2529     off_t rv = ::lseek(fd, size-2, SEEK_SET);
2530     if (rv != (off_t)-1) {
2531       if (::write(fd, "", 1) == 1) {
2532         mmap(base, size,
2533              PROT_READ|PROT_WRITE|PROT_EXEC,
2534              MAP_PRIVATE|MAP_FIXED|MAP_NORESERVE, fd, 0);
2535       }
2536     }
2537     ::close(fd);
2538     unlink(buf);
2539   }
2540 }
2541 
2542 static bool recoverable_mmap_error(int err) {
2543   // See if the error is one we can let the caller handle. This
2544   // list of errno values comes from JBS-6843484. I can't find a
2545   // Linux man page that documents this specific set of errno
2546   // values so while this list currently matches Solaris, it may
2547   // change as we gain experience with this failure mode.
2548   switch (err) {
2549   case EBADF:
2550   case EINVAL:
2551   case ENOTSUP:
2552     // let the caller deal with these errors
2553     return true;
2554 
2555   default:
2556     // Any remaining errors on this OS can cause our reserved mapping
2557     // to be lost. That can cause confusion where different data
2558     // structures think they have the same memory mapped. The worst
2559     // scenario is if both the VM and a library think they have the
2560     // same memory mapped.
2561     return false;
2562   }
2563 }
2564 
2565 static void warn_fail_commit_memory(char* addr, size_t size, bool exec,
2566                                     int err) {
2567   warning("INFO: os::commit_memory(" PTR_FORMAT ", " SIZE_FORMAT
2568           ", %d) failed; error='%s' (errno=%d)", p2i(addr), size, exec,
2569           os::strerror(err), err);
2570 }
2571 
2572 static void warn_fail_commit_memory(char* addr, size_t size,
2573                                     size_t alignment_hint, bool exec,
2574                                     int err) {
2575   warning("INFO: os::commit_memory(" PTR_FORMAT ", " SIZE_FORMAT
2576           ", " SIZE_FORMAT ", %d) failed; error='%s' (errno=%d)", p2i(addr), size,
2577           alignment_hint, exec, os::strerror(err), err);
2578 }
2579 
2580 // NOTE: Linux kernel does not really reserve the pages for us.
2581 //       All it does is to check if there are enough free pages
2582 //       left at the time of mmap(). This could be a potential
2583 //       problem.
2584 int os::Linux::commit_memory_impl(char* addr, size_t size, bool exec) {
2585   int prot = exec ? PROT_READ|PROT_WRITE|PROT_EXEC : PROT_READ|PROT_WRITE;
2586   uintptr_t res = (uintptr_t) ::mmap(addr, size, prot,
2587                                      MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0);
2588   if (res != (uintptr_t) MAP_FAILED) {
2589     if (UseNUMAInterleaving) {
2590       numa_make_global(addr, size);
2591     }
2592     return 0;
2593   }
2594 
2595   int err = errno;  // save errno from mmap() call above
2596 
2597   if (!recoverable_mmap_error(err)) {
2598     warn_fail_commit_memory(addr, size, exec, err);
2599     vm_exit_out_of_memory(size, OOM_MMAP_ERROR, "committing reserved memory.");
2600   }
2601 
2602   return err;
2603 }
2604 
2605 bool os::pd_commit_memory(char* addr, size_t size, bool exec) {
2606   return os::Linux::commit_memory_impl(addr, size, exec) == 0;
2607 }
2608 
2609 void os::pd_commit_memory_or_exit(char* addr, size_t size, bool exec,
2610                                   const char* mesg) {
2611   assert(mesg != NULL, "mesg must be specified");
2612   int err = os::Linux::commit_memory_impl(addr, size, exec);
2613   if (err != 0) {
2614     // the caller wants all commit errors to exit with the specified mesg:
2615     warn_fail_commit_memory(addr, size, exec, err);
2616     vm_exit_out_of_memory(size, OOM_MMAP_ERROR, "%s", mesg);
2617   }
2618 }
2619 
2620 // Define MAP_HUGETLB here so we can build HotSpot on old systems.
2621 #ifndef MAP_HUGETLB
2622   #define MAP_HUGETLB 0x40000
2623 #endif
2624 
2625 // Define MADV_HUGEPAGE here so we can build HotSpot on old systems.
2626 #ifndef MADV_HUGEPAGE
2627   #define MADV_HUGEPAGE 14
2628 #endif
2629 
2630 int os::Linux::commit_memory_impl(char* addr, size_t size,
2631                                   size_t alignment_hint, bool exec) {
2632   int err = os::Linux::commit_memory_impl(addr, size, exec);
2633   if (err == 0) {
2634     realign_memory(addr, size, alignment_hint);
2635   }
2636   return err;
2637 }
2638 
2639 bool os::pd_commit_memory(char* addr, size_t size, size_t alignment_hint,
2640                           bool exec) {
2641   return os::Linux::commit_memory_impl(addr, size, alignment_hint, exec) == 0;
2642 }
2643 
2644 void os::pd_commit_memory_or_exit(char* addr, size_t size,
2645                                   size_t alignment_hint, bool exec,
2646                                   const char* mesg) {
2647   assert(mesg != NULL, "mesg must be specified");
2648   int err = os::Linux::commit_memory_impl(addr, size, alignment_hint, exec);
2649   if (err != 0) {
2650     // the caller wants all commit errors to exit with the specified mesg:
2651     warn_fail_commit_memory(addr, size, alignment_hint, exec, err);
2652     vm_exit_out_of_memory(size, OOM_MMAP_ERROR, "%s", mesg);
2653   }
2654 }
2655 
2656 void os::pd_realign_memory(char *addr, size_t bytes, size_t alignment_hint) {
2657   if (UseTransparentHugePages && alignment_hint > (size_t)vm_page_size()) {
2658     // We don't check the return value: madvise(MADV_HUGEPAGE) may not
2659     // be supported or the memory may already be backed by huge pages.
2660     ::madvise(addr, bytes, MADV_HUGEPAGE);
2661   }
2662 }
2663 
2664 void os::pd_free_memory(char *addr, size_t bytes, size_t alignment_hint) {
2665   // This method works by doing an mmap over an existing mmaping and effectively discarding
2666   // the existing pages. However it won't work for SHM-based large pages that cannot be
2667   // uncommitted at all. We don't do anything in this case to avoid creating a segment with
2668   // small pages on top of the SHM segment. This method always works for small pages, so we
2669   // allow that in any case.
2670   if (alignment_hint <= (size_t)os::vm_page_size() || can_commit_large_page_memory()) {
2671     commit_memory(addr, bytes, alignment_hint, !ExecMem);
2672   }
2673 }
2674 
2675 void os::numa_make_global(char *addr, size_t bytes) {
2676   Linux::numa_interleave_memory(addr, bytes);
2677 }
2678 
2679 // Define for numa_set_bind_policy(int). Setting the argument to 0 will set the
2680 // bind policy to MPOL_PREFERRED for the current thread.
2681 #define USE_MPOL_PREFERRED 0
2682 
2683 void os::numa_make_local(char *addr, size_t bytes, int lgrp_hint) {
2684   // To make NUMA and large pages more robust when both enabled, we need to ease
2685   // the requirements on where the memory should be allocated. MPOL_BIND is the
2686   // default policy and it will force memory to be allocated on the specified
2687   // node. Changing this to MPOL_PREFERRED will prefer to allocate the memory on
2688   // the specified node, but will not force it. Using this policy will prevent
2689   // getting SIGBUS when trying to allocate large pages on NUMA nodes with no
2690   // free large pages.
2691   Linux::numa_set_bind_policy(USE_MPOL_PREFERRED);
2692   Linux::numa_tonode_memory(addr, bytes, lgrp_hint);
2693 }
2694 
2695 bool os::numa_topology_changed() { return false; }
2696 
2697 size_t os::numa_get_groups_num() {
2698   // Return just the number of nodes in which it's possible to allocate memory
2699   // (in numa terminology, configured nodes).
2700   return Linux::numa_num_configured_nodes();
2701 }
2702 
2703 int os::numa_get_group_id() {
2704   int cpu_id = Linux::sched_getcpu();
2705   if (cpu_id != -1) {
2706     int lgrp_id = Linux::get_node_by_cpu(cpu_id);
2707     if (lgrp_id != -1) {
2708       return lgrp_id;
2709     }
2710   }
2711   return 0;
2712 }
2713 
2714 int os::Linux::get_existing_num_nodes() {
2715   size_t node;
2716   size_t highest_node_number = Linux::numa_max_node();
2717   int num_nodes = 0;
2718 
2719   // Get the total number of nodes in the system including nodes without memory.
2720   for (node = 0; node <= highest_node_number; node++) {
2721     if (isnode_in_existing_nodes(node)) {
2722       num_nodes++;
2723     }
2724   }
2725   return num_nodes;
2726 }
2727 
2728 size_t os::numa_get_leaf_groups(int *ids, size_t size) {
2729   size_t highest_node_number = Linux::numa_max_node();
2730   size_t i = 0;
2731 
2732   // Map all node ids in which is possible to allocate memory. Also nodes are
2733   // not always consecutively available, i.e. available from 0 to the highest
2734   // node number.
2735   for (size_t node = 0; node <= highest_node_number; node++) {
2736     if (Linux::isnode_in_configured_nodes(node)) {
2737       ids[i++] = node;
2738     }
2739   }
2740   return i;
2741 }
2742 
2743 bool os::get_page_info(char *start, page_info* info) {
2744   return false;
2745 }
2746 
2747 char *os::scan_pages(char *start, char* end, page_info* page_expected,
2748                      page_info* page_found) {
2749   return end;
2750 }
2751 
2752 
2753 int os::Linux::sched_getcpu_syscall(void) {
2754   unsigned int cpu = 0;
2755   int retval = -1;
2756 
2757 #if defined(IA32)
2758   #ifndef SYS_getcpu
2759     #define SYS_getcpu 318
2760   #endif
2761   retval = syscall(SYS_getcpu, &cpu, NULL, NULL);
2762 #elif defined(AMD64)
2763 // Unfortunately we have to bring all these macros here from vsyscall.h
2764 // to be able to compile on old linuxes.
2765   #define __NR_vgetcpu 2
2766   #define VSYSCALL_START (-10UL << 20)
2767   #define VSYSCALL_SIZE 1024
2768   #define VSYSCALL_ADDR(vsyscall_nr) (VSYSCALL_START+VSYSCALL_SIZE*(vsyscall_nr))
2769   typedef long (*vgetcpu_t)(unsigned int *cpu, unsigned int *node, unsigned long *tcache);
2770   vgetcpu_t vgetcpu = (vgetcpu_t)VSYSCALL_ADDR(__NR_vgetcpu);
2771   retval = vgetcpu(&cpu, NULL, NULL);
2772 #endif
2773 
2774   return (retval == -1) ? retval : cpu;
2775 }
2776 
2777 void os::Linux::sched_getcpu_init() {
2778   // sched_getcpu() should be in libc.
2779   set_sched_getcpu(CAST_TO_FN_PTR(sched_getcpu_func_t,
2780                                   dlsym(RTLD_DEFAULT, "sched_getcpu")));
2781 
2782   // If it's not, try a direct syscall.
2783   if (sched_getcpu() == -1) {
2784     set_sched_getcpu(CAST_TO_FN_PTR(sched_getcpu_func_t,
2785                                     (void*)&sched_getcpu_syscall));
2786   }
2787 }
2788 
2789 // Something to do with the numa-aware allocator needs these symbols
2790 extern "C" JNIEXPORT void numa_warn(int number, char *where, ...) { }
2791 extern "C" JNIEXPORT void numa_error(char *where) { }
2792 
2793 // Handle request to load libnuma symbol version 1.1 (API v1). If it fails
2794 // load symbol from base version instead.
2795 void* os::Linux::libnuma_dlsym(void* handle, const char *name) {
2796   void *f = dlvsym(handle, name, "libnuma_1.1");
2797   if (f == NULL) {
2798     f = dlsym(handle, name);
2799   }
2800   return f;
2801 }
2802 
2803 // Handle request to load libnuma symbol version 1.2 (API v2) only.
2804 // Return NULL if the symbol is not defined in this particular version.
2805 void* os::Linux::libnuma_v2_dlsym(void* handle, const char* name) {
2806   return dlvsym(handle, name, "libnuma_1.2");
2807 }
2808 
2809 bool os::Linux::libnuma_init() {
2810   if (sched_getcpu() != -1) { // Requires sched_getcpu() support
2811     void *handle = dlopen("libnuma.so.1", RTLD_LAZY);
2812     if (handle != NULL) {
2813       set_numa_node_to_cpus(CAST_TO_FN_PTR(numa_node_to_cpus_func_t,
2814                                            libnuma_dlsym(handle, "numa_node_to_cpus")));
2815       set_numa_max_node(CAST_TO_FN_PTR(numa_max_node_func_t,
2816                                        libnuma_dlsym(handle, "numa_max_node")));
2817       set_numa_num_configured_nodes(CAST_TO_FN_PTR(numa_num_configured_nodes_func_t,
2818                                                    libnuma_dlsym(handle, "numa_num_configured_nodes")));
2819       set_numa_available(CAST_TO_FN_PTR(numa_available_func_t,
2820                                         libnuma_dlsym(handle, "numa_available")));
2821       set_numa_tonode_memory(CAST_TO_FN_PTR(numa_tonode_memory_func_t,
2822                                             libnuma_dlsym(handle, "numa_tonode_memory")));
2823       set_numa_interleave_memory(CAST_TO_FN_PTR(numa_interleave_memory_func_t,
2824                                                 libnuma_dlsym(handle, "numa_interleave_memory")));
2825       set_numa_interleave_memory_v2(CAST_TO_FN_PTR(numa_interleave_memory_v2_func_t,
2826                                                 libnuma_v2_dlsym(handle, "numa_interleave_memory")));
2827       set_numa_set_bind_policy(CAST_TO_FN_PTR(numa_set_bind_policy_func_t,
2828                                               libnuma_dlsym(handle, "numa_set_bind_policy")));
2829       set_numa_bitmask_isbitset(CAST_TO_FN_PTR(numa_bitmask_isbitset_func_t,
2830                                                libnuma_dlsym(handle, "numa_bitmask_isbitset")));
2831       set_numa_distance(CAST_TO_FN_PTR(numa_distance_func_t,
2832                                        libnuma_dlsym(handle, "numa_distance")));
2833 
2834       if (numa_available() != -1) {
2835         set_numa_all_nodes((unsigned long*)libnuma_dlsym(handle, "numa_all_nodes"));
2836         set_numa_all_nodes_ptr((struct bitmask **)libnuma_dlsym(handle, "numa_all_nodes_ptr"));
2837         set_numa_nodes_ptr((struct bitmask **)libnuma_dlsym(handle, "numa_nodes_ptr"));
2838         // Create an index -> node mapping, since nodes are not always consecutive
2839         _nindex_to_node = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<int>(0, true);
2840         rebuild_nindex_to_node_map();
2841         // Create a cpu -> node mapping
2842         _cpu_to_node = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<int>(0, true);
2843         rebuild_cpu_to_node_map();
2844         return true;
2845       }
2846     }
2847   }
2848   return false;
2849 }
2850 
2851 size_t os::Linux::default_guard_size(os::ThreadType thr_type) {
2852   // Creating guard page is very expensive. Java thread has HotSpot
2853   // guard pages, only enable glibc guard page for non-Java threads.
2854   // (Remember: compiler thread is a Java thread, too!)
2855   return ((thr_type == java_thread || thr_type == compiler_thread) ? 0 : page_size());
2856 }
2857 
2858 void os::Linux::rebuild_nindex_to_node_map() {
2859   int highest_node_number = Linux::numa_max_node();
2860 
2861   nindex_to_node()->clear();
2862   for (int node = 0; node <= highest_node_number; node++) {
2863     if (Linux::isnode_in_existing_nodes(node)) {
2864       nindex_to_node()->append(node);
2865     }
2866   }
2867 }
2868 
2869 // rebuild_cpu_to_node_map() constructs a table mapping cpud id to node id.
2870 // The table is later used in get_node_by_cpu().
2871 void os::Linux::rebuild_cpu_to_node_map() {
2872   const size_t NCPUS = 32768; // Since the buffer size computation is very obscure
2873                               // in libnuma (possible values are starting from 16,
2874                               // and continuing up with every other power of 2, but less
2875                               // than the maximum number of CPUs supported by kernel), and
2876                               // is a subject to change (in libnuma version 2 the requirements
2877                               // are more reasonable) we'll just hardcode the number they use
2878                               // in the library.
2879   const size_t BitsPerCLong = sizeof(long) * CHAR_BIT;
2880 
2881   size_t cpu_num = processor_count();
2882   size_t cpu_map_size = NCPUS / BitsPerCLong;
2883   size_t cpu_map_valid_size =
2884     MIN2((cpu_num + BitsPerCLong - 1) / BitsPerCLong, cpu_map_size);
2885 
2886   cpu_to_node()->clear();
2887   cpu_to_node()->at_grow(cpu_num - 1);
2888 
2889   size_t node_num = get_existing_num_nodes();
2890 
2891   int distance = 0;
2892   int closest_distance = INT_MAX;
2893   int closest_node = 0;
2894   unsigned long *cpu_map = NEW_C_HEAP_ARRAY(unsigned long, cpu_map_size, mtInternal);
2895   for (size_t i = 0; i < node_num; i++) {
2896     // Check if node is configured (not a memory-less node). If it is not, find
2897     // the closest configured node.
2898     if (!isnode_in_configured_nodes(nindex_to_node()->at(i))) {
2899       closest_distance = INT_MAX;
2900       // Check distance from all remaining nodes in the system. Ignore distance
2901       // from itself and from another non-configured node.
2902       for (size_t m = 0; m < node_num; m++) {
2903         if (m != i && isnode_in_configured_nodes(nindex_to_node()->at(m))) {
2904           distance = numa_distance(nindex_to_node()->at(i), nindex_to_node()->at(m));
2905           // If a closest node is found, update. There is always at least one
2906           // configured node in the system so there is always at least one node
2907           // close.
2908           if (distance != 0 && distance < closest_distance) {
2909             closest_distance = distance;
2910             closest_node = nindex_to_node()->at(m);
2911           }
2912         }
2913       }
2914      } else {
2915        // Current node is already a configured node.
2916        closest_node = nindex_to_node()->at(i);
2917      }
2918 
2919     // Get cpus from the original node and map them to the closest node. If node
2920     // is a configured node (not a memory-less node), then original node and
2921     // closest node are the same.
2922     if (numa_node_to_cpus(nindex_to_node()->at(i), cpu_map, cpu_map_size * sizeof(unsigned long)) != -1) {
2923       for (size_t j = 0; j < cpu_map_valid_size; j++) {
2924         if (cpu_map[j] != 0) {
2925           for (size_t k = 0; k < BitsPerCLong; k++) {
2926             if (cpu_map[j] & (1UL << k)) {
2927               cpu_to_node()->at_put(j * BitsPerCLong + k, closest_node);
2928             }
2929           }
2930         }
2931       }
2932     }
2933   }
2934   FREE_C_HEAP_ARRAY(unsigned long, cpu_map);
2935 }
2936 
2937 int os::Linux::get_node_by_cpu(int cpu_id) {
2938   if (cpu_to_node() != NULL && cpu_id >= 0 && cpu_id < cpu_to_node()->length()) {
2939     return cpu_to_node()->at(cpu_id);
2940   }
2941   return -1;
2942 }
2943 
2944 GrowableArray<int>* os::Linux::_cpu_to_node;
2945 GrowableArray<int>* os::Linux::_nindex_to_node;
2946 os::Linux::sched_getcpu_func_t os::Linux::_sched_getcpu;
2947 os::Linux::numa_node_to_cpus_func_t os::Linux::_numa_node_to_cpus;
2948 os::Linux::numa_max_node_func_t os::Linux::_numa_max_node;
2949 os::Linux::numa_num_configured_nodes_func_t os::Linux::_numa_num_configured_nodes;
2950 os::Linux::numa_available_func_t os::Linux::_numa_available;
2951 os::Linux::numa_tonode_memory_func_t os::Linux::_numa_tonode_memory;
2952 os::Linux::numa_interleave_memory_func_t os::Linux::_numa_interleave_memory;
2953 os::Linux::numa_interleave_memory_v2_func_t os::Linux::_numa_interleave_memory_v2;
2954 os::Linux::numa_set_bind_policy_func_t os::Linux::_numa_set_bind_policy;
2955 os::Linux::numa_bitmask_isbitset_func_t os::Linux::_numa_bitmask_isbitset;
2956 os::Linux::numa_distance_func_t os::Linux::_numa_distance;
2957 unsigned long* os::Linux::_numa_all_nodes;
2958 struct bitmask* os::Linux::_numa_all_nodes_ptr;
2959 struct bitmask* os::Linux::_numa_nodes_ptr;
2960 
2961 bool os::pd_uncommit_memory(char* addr, size_t size) {
2962   uintptr_t res = (uintptr_t) ::mmap(addr, size, PROT_NONE,
2963                                      MAP_PRIVATE|MAP_FIXED|MAP_NORESERVE|MAP_ANONYMOUS, -1, 0);
2964   return res  != (uintptr_t) MAP_FAILED;
2965 }
2966 
2967 static address get_stack_commited_bottom(address bottom, size_t size) {
2968   address nbot = bottom;
2969   address ntop = bottom + size;
2970 
2971   size_t page_sz = os::vm_page_size();
2972   unsigned pages = size / page_sz;
2973 
2974   unsigned char vec[1];
2975   unsigned imin = 1, imax = pages + 1, imid;
2976   int mincore_return_value = 0;
2977 
2978   assert(imin <= imax, "Unexpected page size");
2979 
2980   while (imin < imax) {
2981     imid = (imax + imin) / 2;
2982     nbot = ntop - (imid * page_sz);
2983 
2984     // Use a trick with mincore to check whether the page is mapped or not.
2985     // mincore sets vec to 1 if page resides in memory and to 0 if page
2986     // is swapped output but if page we are asking for is unmapped
2987     // it returns -1,ENOMEM
2988     mincore_return_value = mincore(nbot, page_sz, vec);
2989 
2990     if (mincore_return_value == -1) {
2991       // Page is not mapped go up
2992       // to find first mapped page
2993       if (errno != EAGAIN) {
2994         assert(errno == ENOMEM, "Unexpected mincore errno");
2995         imax = imid;
2996       }
2997     } else {
2998       // Page is mapped go down
2999       // to find first not mapped page
3000       imin = imid + 1;
3001     }
3002   }
3003 
3004   nbot = nbot + page_sz;
3005 
3006   // Adjust stack bottom one page up if last checked page is not mapped
3007   if (mincore_return_value == -1) {
3008     nbot = nbot + page_sz;
3009   }
3010 
3011   return nbot;
3012 }
3013 
3014 
3015 // Linux uses a growable mapping for the stack, and if the mapping for
3016 // the stack guard pages is not removed when we detach a thread the
3017 // stack cannot grow beyond the pages where the stack guard was
3018 // mapped.  If at some point later in the process the stack expands to
3019 // that point, the Linux kernel cannot expand the stack any further
3020 // because the guard pages are in the way, and a segfault occurs.
3021 //
3022 // However, it's essential not to split the stack region by unmapping
3023 // a region (leaving a hole) that's already part of the stack mapping,
3024 // so if the stack mapping has already grown beyond the guard pages at
3025 // the time we create them, we have to truncate the stack mapping.
3026 // So, we need to know the extent of the stack mapping when
3027 // create_stack_guard_pages() is called.
3028 
3029 // We only need this for stacks that are growable: at the time of
3030 // writing thread stacks don't use growable mappings (i.e. those
3031 // creeated with MAP_GROWSDOWN), and aren't marked "[stack]", so this
3032 // only applies to the main thread.
3033 
3034 // If the (growable) stack mapping already extends beyond the point
3035 // where we're going to put our guard pages, truncate the mapping at
3036 // that point by munmap()ping it.  This ensures that when we later
3037 // munmap() the guard pages we don't leave a hole in the stack
3038 // mapping. This only affects the main/initial thread
3039 
3040 bool os::pd_create_stack_guard_pages(char* addr, size_t size) {
3041   if (os::Linux::is_initial_thread()) {
3042     // As we manually grow stack up to bottom inside create_attached_thread(),
3043     // it's likely that os::Linux::initial_thread_stack_bottom is mapped and
3044     // we don't need to do anything special.
3045     // Check it first, before calling heavy function.
3046     uintptr_t stack_extent = (uintptr_t) os::Linux::initial_thread_stack_bottom();
3047     unsigned char vec[1];
3048 
3049     if (mincore((address)stack_extent, os::vm_page_size(), vec) == -1) {
3050       // Fallback to slow path on all errors, including EAGAIN
3051       stack_extent = (uintptr_t) get_stack_commited_bottom(
3052                                                            os::Linux::initial_thread_stack_bottom(),
3053                                                            (size_t)addr - stack_extent);
3054     }
3055 
3056     if (stack_extent < (uintptr_t)addr) {
3057       ::munmap((void*)stack_extent, (uintptr_t)(addr - stack_extent));
3058     }
3059   }
3060 
3061   return os::commit_memory(addr, size, !ExecMem);
3062 }
3063 
3064 // If this is a growable mapping, remove the guard pages entirely by
3065 // munmap()ping them.  If not, just call uncommit_memory(). This only
3066 // affects the main/initial thread, but guard against future OS changes
3067 // It's safe to always unmap guard pages for initial thread because we
3068 // always place it right after end of the mapped region
3069 
3070 bool os::remove_stack_guard_pages(char* addr, size_t size) {
3071   uintptr_t stack_extent, stack_base;
3072 
3073   if (os::Linux::is_initial_thread()) {
3074     return ::munmap(addr, size) == 0;
3075   }
3076 
3077   return os::uncommit_memory(addr, size);
3078 }
3079 
3080 // If 'fixed' is true, anon_mmap() will attempt to reserve anonymous memory
3081 // at 'requested_addr'. If there are existing memory mappings at the same
3082 // location, however, they will be overwritten. If 'fixed' is false,
3083 // 'requested_addr' is only treated as a hint, the return value may or
3084 // may not start from the requested address. Unlike Linux mmap(), this
3085 // function returns NULL to indicate failure.
3086 static char* anon_mmap(char* requested_addr, size_t bytes, bool fixed) {
3087   char * addr;
3088   int flags;
3089 
3090   flags = MAP_PRIVATE | MAP_NORESERVE | MAP_ANONYMOUS;
3091   if (fixed) {
3092     assert((uintptr_t)requested_addr % os::Linux::page_size() == 0, "unaligned address");
3093     flags |= MAP_FIXED;
3094   }
3095 
3096   // Map reserved/uncommitted pages PROT_NONE so we fail early if we
3097   // touch an uncommitted page. Otherwise, the read/write might
3098   // succeed if we have enough swap space to back the physical page.
3099   addr = (char*)::mmap(requested_addr, bytes, PROT_NONE,
3100                        flags, -1, 0);
3101 
3102   return addr == MAP_FAILED ? NULL : addr;
3103 }
3104 
3105 // Allocate (using mmap, NO_RESERVE, with small pages) at either a given request address
3106 //   (req_addr != NULL) or with a given alignment.
3107 //  - bytes shall be a multiple of alignment.
3108 //  - req_addr can be NULL. If not NULL, it must be a multiple of alignment.
3109 //  - alignment sets the alignment at which memory shall be allocated.
3110 //     It must be a multiple of allocation granularity.
3111 // Returns address of memory or NULL. If req_addr was not NULL, will only return
3112 //  req_addr or NULL.
3113 static char* anon_mmap_aligned(size_t bytes, size_t alignment, char* req_addr) {
3114 
3115   size_t extra_size = bytes;
3116   if (req_addr == NULL && alignment > 0) {
3117     extra_size += alignment;
3118   }
3119 
3120   char* start = (char*) ::mmap(req_addr, extra_size, PROT_NONE,
3121     MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE,
3122     -1, 0);
3123   if (start == MAP_FAILED) {
3124     start = NULL;
3125   } else {
3126     if (req_addr != NULL) {
3127       if (start != req_addr) {
3128         ::munmap(start, extra_size);
3129         start = NULL;
3130       }
3131     } else {
3132       char* const start_aligned = align_up(start, alignment);
3133       char* const end_aligned = start_aligned + bytes;
3134       char* const end = start + extra_size;
3135       if (start_aligned > start) {
3136         ::munmap(start, start_aligned - start);
3137       }
3138       if (end_aligned < end) {
3139         ::munmap(end_aligned, end - end_aligned);
3140       }
3141       start = start_aligned;
3142     }
3143   }
3144   return start;
3145 }
3146 
3147 static int anon_munmap(char * addr, size_t size) {
3148   return ::munmap(addr, size) == 0;
3149 }
3150 
3151 char* os::pd_reserve_memory(size_t bytes, char* requested_addr,
3152                             size_t alignment_hint) {
3153   return anon_mmap(requested_addr, bytes, (requested_addr != NULL));
3154 }
3155 
3156 bool os::pd_release_memory(char* addr, size_t size) {
3157   return anon_munmap(addr, size);
3158 }
3159 
3160 static bool linux_mprotect(char* addr, size_t size, int prot) {
3161   // Linux wants the mprotect address argument to be page aligned.
3162   char* bottom = (char*)align_down((intptr_t)addr, os::Linux::page_size());
3163 
3164   // According to SUSv3, mprotect() should only be used with mappings
3165   // established by mmap(), and mmap() always maps whole pages. Unaligned
3166   // 'addr' likely indicates problem in the VM (e.g. trying to change
3167   // protection of malloc'ed or statically allocated memory). Check the
3168   // caller if you hit this assert.
3169   assert(addr == bottom, "sanity check");
3170 
3171   size = align_up(pointer_delta(addr, bottom, 1) + size, os::Linux::page_size());
3172   return ::mprotect(bottom, size, prot) == 0;
3173 }
3174 
3175 // Set protections specified
3176 bool os::protect_memory(char* addr, size_t bytes, ProtType prot,
3177                         bool is_committed) {
3178   unsigned int p = 0;
3179   switch (prot) {
3180   case MEM_PROT_NONE: p = PROT_NONE; break;
3181   case MEM_PROT_READ: p = PROT_READ; break;
3182   case MEM_PROT_RW:   p = PROT_READ|PROT_WRITE; break;
3183   case MEM_PROT_RWX:  p = PROT_READ|PROT_WRITE|PROT_EXEC; break;
3184   default:
3185     ShouldNotReachHere();
3186   }
3187   // is_committed is unused.
3188   return linux_mprotect(addr, bytes, p);
3189 }
3190 
3191 bool os::guard_memory(char* addr, size_t size) {
3192   return linux_mprotect(addr, size, PROT_NONE);
3193 }
3194 
3195 bool os::unguard_memory(char* addr, size_t size) {
3196   return linux_mprotect(addr, size, PROT_READ|PROT_WRITE);
3197 }
3198 
3199 bool os::Linux::transparent_huge_pages_sanity_check(bool warn,
3200                                                     size_t page_size) {
3201   bool result = false;
3202   void *p = mmap(NULL, page_size * 2, PROT_READ|PROT_WRITE,
3203                  MAP_ANONYMOUS|MAP_PRIVATE,
3204                  -1, 0);
3205   if (p != MAP_FAILED) {
3206     void *aligned_p = align_up(p, page_size);
3207 
3208     result = madvise(aligned_p, page_size, MADV_HUGEPAGE) == 0;
3209 
3210     munmap(p, page_size * 2);
3211   }
3212 
3213   if (warn && !result) {
3214     warning("TransparentHugePages is not supported by the operating system.");
3215   }
3216 
3217   return result;
3218 }
3219 
3220 bool os::Linux::hugetlbfs_sanity_check(bool warn, size_t page_size) {
3221   bool result = false;
3222   void *p = mmap(NULL, page_size, PROT_READ|PROT_WRITE,
3223                  MAP_ANONYMOUS|MAP_PRIVATE|MAP_HUGETLB,
3224                  -1, 0);
3225 
3226   if (p != MAP_FAILED) {
3227     // We don't know if this really is a huge page or not.
3228     FILE *fp = fopen("/proc/self/maps", "r");
3229     if (fp) {
3230       while (!feof(fp)) {
3231         char chars[257];
3232         long x = 0;
3233         if (fgets(chars, sizeof(chars), fp)) {
3234           if (sscanf(chars, "%lx-%*x", &x) == 1
3235               && x == (long)p) {
3236             if (strstr (chars, "hugepage")) {
3237               result = true;
3238               break;
3239             }
3240           }
3241         }
3242       }
3243       fclose(fp);
3244     }
3245     munmap(p, page_size);
3246   }
3247 
3248   if (warn && !result) {
3249     warning("HugeTLBFS is not supported by the operating system.");
3250   }
3251 
3252   return result;
3253 }
3254 
3255 // Set the coredump_filter bits to include largepages in core dump (bit 6)
3256 //
3257 // From the coredump_filter documentation:
3258 //
3259 // - (bit 0) anonymous private memory
3260 // - (bit 1) anonymous shared memory
3261 // - (bit 2) file-backed private memory
3262 // - (bit 3) file-backed shared memory
3263 // - (bit 4) ELF header pages in file-backed private memory areas (it is
3264 //           effective only if the bit 2 is cleared)
3265 // - (bit 5) hugetlb private memory
3266 // - (bit 6) hugetlb shared memory
3267 // - (bit 7) dax private memory
3268 // - (bit 8) dax shared memory
3269 //
3270 static void set_coredump_filter(bool largepages, bool dax_shared) {
3271   FILE *f;
3272   long cdm;
3273   bool filter_changed = false;
3274 
3275   if ((f = fopen("/proc/self/coredump_filter", "r+")) == NULL) {
3276     return;
3277   }
3278 
3279   if (fscanf(f, "%lx", &cdm) != 1) {
3280     fclose(f);
3281     return;
3282   }
3283 
3284   rewind(f);
3285 
3286   if (largepages && (cdm & LARGEPAGES_BIT) == 0) {
3287     cdm |= LARGEPAGES_BIT;
3288     filter_changed = true;
3289   }
3290   if (dax_shared && (cdm & DAX_SHARED_BIT) == 0) {
3291     cdm |= DAX_SHARED_BIT;
3292     filter_changed = true;
3293   }
3294   if (filter_changed) {
3295     fprintf(f, "%#lx", cdm);
3296   }
3297 
3298   fclose(f);
3299 }
3300 
3301 // Large page support
3302 
3303 static size_t _large_page_size = 0;
3304 
3305 size_t os::Linux::find_large_page_size() {
3306   size_t large_page_size = 0;
3307 
3308   // large_page_size on Linux is used to round up heap size. x86 uses either
3309   // 2M or 4M page, depending on whether PAE (Physical Address Extensions)
3310   // mode is enabled. AMD64/EM64T uses 2M page in 64bit mode. IA64 can use
3311   // page as large as 256M.
3312   //
3313   // Here we try to figure out page size by parsing /proc/meminfo and looking
3314   // for a line with the following format:
3315   //    Hugepagesize:     2048 kB
3316   //
3317   // If we can't determine the value (e.g. /proc is not mounted, or the text
3318   // format has been changed), we'll use the largest page size supported by
3319   // the processor.
3320 
3321 #ifndef ZERO
3322   large_page_size =
3323     AARCH64_ONLY(2 * M)
3324     AMD64_ONLY(2 * M)
3325     ARM32_ONLY(2 * M)
3326     IA32_ONLY(4 * M)
3327     IA64_ONLY(256 * M)
3328     PPC_ONLY(4 * M)
3329     S390_ONLY(1 * M)
3330     SPARC_ONLY(4 * M);
3331 #endif // ZERO
3332 
3333   FILE *fp = fopen("/proc/meminfo", "r");
3334   if (fp) {
3335     while (!feof(fp)) {
3336       int x = 0;
3337       char buf[16];
3338       if (fscanf(fp, "Hugepagesize: %d", &x) == 1) {
3339         if (x && fgets(buf, sizeof(buf), fp) && strcmp(buf, " kB\n") == 0) {
3340           large_page_size = x * K;
3341           break;
3342         }
3343       } else {
3344         // skip to next line
3345         for (;;) {
3346           int ch = fgetc(fp);
3347           if (ch == EOF || ch == (int)'\n') break;
3348         }
3349       }
3350     }
3351     fclose(fp);
3352   }
3353 
3354   if (!FLAG_IS_DEFAULT(LargePageSizeInBytes) && LargePageSizeInBytes != large_page_size) {
3355     warning("Setting LargePageSizeInBytes has no effect on this OS. Large page size is "
3356             SIZE_FORMAT "%s.", byte_size_in_proper_unit(large_page_size),
3357             proper_unit_for_byte_size(large_page_size));
3358   }
3359 
3360   return large_page_size;
3361 }
3362 
3363 size_t os::Linux::setup_large_page_size() {
3364   _large_page_size = Linux::find_large_page_size();
3365   const size_t default_page_size = (size_t)Linux::page_size();
3366   if (_large_page_size > default_page_size) {
3367     _page_sizes[0] = _large_page_size;
3368     _page_sizes[1] = default_page_size;
3369     _page_sizes[2] = 0;
3370   }
3371 
3372   return _large_page_size;
3373 }
3374 
3375 bool os::Linux::setup_large_page_type(size_t page_size) {
3376   if (FLAG_IS_DEFAULT(UseHugeTLBFS) &&
3377       FLAG_IS_DEFAULT(UseSHM) &&
3378       FLAG_IS_DEFAULT(UseTransparentHugePages)) {
3379 
3380     // The type of large pages has not been specified by the user.
3381 
3382     // Try UseHugeTLBFS and then UseSHM.
3383     UseHugeTLBFS = UseSHM = true;
3384 
3385     // Don't try UseTransparentHugePages since there are known
3386     // performance issues with it turned on. This might change in the future.
3387     UseTransparentHugePages = false;
3388   }
3389 
3390   if (UseTransparentHugePages) {
3391     bool warn_on_failure = !FLAG_IS_DEFAULT(UseTransparentHugePages);
3392     if (transparent_huge_pages_sanity_check(warn_on_failure, page_size)) {
3393       UseHugeTLBFS = false;
3394       UseSHM = false;
3395       return true;
3396     }
3397     UseTransparentHugePages = false;
3398   }
3399 
3400   if (UseHugeTLBFS) {
3401     bool warn_on_failure = !FLAG_IS_DEFAULT(UseHugeTLBFS);
3402     if (hugetlbfs_sanity_check(warn_on_failure, page_size)) {
3403       UseSHM = false;
3404       return true;
3405     }
3406     UseHugeTLBFS = false;
3407   }
3408 
3409   return UseSHM;
3410 }
3411 
3412 void os::large_page_init() {
3413   if (!UseLargePages &&
3414       !UseTransparentHugePages &&
3415       !UseHugeTLBFS &&
3416       !UseSHM) {
3417     // Not using large pages.
3418     return;
3419   }
3420 
3421   if (!FLAG_IS_DEFAULT(UseLargePages) && !UseLargePages) {
3422     // The user explicitly turned off large pages.
3423     // Ignore the rest of the large pages flags.
3424     UseTransparentHugePages = false;
3425     UseHugeTLBFS = false;
3426     UseSHM = false;
3427     return;
3428   }
3429 
3430   size_t large_page_size = Linux::setup_large_page_size();
3431   UseLargePages          = Linux::setup_large_page_type(large_page_size);
3432 
3433   set_coredump_filter(true /*largepages*/, false /*dax_shared*/);
3434 }
3435 
3436 #ifndef SHM_HUGETLB
3437   #define SHM_HUGETLB 04000
3438 #endif
3439 
3440 #define shm_warning_format(format, ...)              \
3441   do {                                               \
3442     if (UseLargePages &&                             \
3443         (!FLAG_IS_DEFAULT(UseLargePages) ||          \
3444          !FLAG_IS_DEFAULT(UseSHM) ||                 \
3445          !FLAG_IS_DEFAULT(LargePageSizeInBytes))) {  \
3446       warning(format, __VA_ARGS__);                  \
3447     }                                                \
3448   } while (0)
3449 
3450 #define shm_warning(str) shm_warning_format("%s", str)
3451 
3452 #define shm_warning_with_errno(str)                \
3453   do {                                             \
3454     int err = errno;                               \
3455     shm_warning_format(str " (error = %d)", err);  \
3456   } while (0)
3457 
3458 static char* shmat_with_alignment(int shmid, size_t bytes, size_t alignment) {
3459   assert(is_aligned(bytes, alignment), "Must be divisible by the alignment");
3460 
3461   if (!is_aligned(alignment, SHMLBA)) {
3462     assert(false, "Code below assumes that alignment is at least SHMLBA aligned");
3463     return NULL;
3464   }
3465 
3466   // To ensure that we get 'alignment' aligned memory from shmat,
3467   // we pre-reserve aligned virtual memory and then attach to that.
3468 
3469   char* pre_reserved_addr = anon_mmap_aligned(bytes, alignment, NULL);
3470   if (pre_reserved_addr == NULL) {
3471     // Couldn't pre-reserve aligned memory.
3472     shm_warning("Failed to pre-reserve aligned memory for shmat.");
3473     return NULL;
3474   }
3475 
3476   // SHM_REMAP is needed to allow shmat to map over an existing mapping.
3477   char* addr = (char*)shmat(shmid, pre_reserved_addr, SHM_REMAP);
3478 
3479   if ((intptr_t)addr == -1) {
3480     int err = errno;
3481     shm_warning_with_errno("Failed to attach shared memory.");
3482 
3483     assert(err != EACCES, "Unexpected error");
3484     assert(err != EIDRM,  "Unexpected error");
3485     assert(err != EINVAL, "Unexpected error");
3486 
3487     // Since we don't know if the kernel unmapped the pre-reserved memory area
3488     // we can't unmap it, since that would potentially unmap memory that was
3489     // mapped from other threads.
3490     return NULL;
3491   }
3492 
3493   return addr;
3494 }
3495 
3496 static char* shmat_at_address(int shmid, char* req_addr) {
3497   if (!is_aligned(req_addr, SHMLBA)) {
3498     assert(false, "Requested address needs to be SHMLBA aligned");
3499     return NULL;
3500   }
3501 
3502   char* addr = (char*)shmat(shmid, req_addr, 0);
3503 
3504   if ((intptr_t)addr == -1) {
3505     shm_warning_with_errno("Failed to attach shared memory.");
3506     return NULL;
3507   }
3508 
3509   return addr;
3510 }
3511 
3512 static char* shmat_large_pages(int shmid, size_t bytes, size_t alignment, char* req_addr) {
3513   // If a req_addr has been provided, we assume that the caller has already aligned the address.
3514   if (req_addr != NULL) {
3515     assert(is_aligned(req_addr, os::large_page_size()), "Must be divisible by the large page size");
3516     assert(is_aligned(req_addr, alignment), "Must be divisible by given alignment");
3517     return shmat_at_address(shmid, req_addr);
3518   }
3519 
3520   // Since shmid has been setup with SHM_HUGETLB, shmat will automatically
3521   // return large page size aligned memory addresses when req_addr == NULL.
3522   // However, if the alignment is larger than the large page size, we have
3523   // to manually ensure that the memory returned is 'alignment' aligned.
3524   if (alignment > os::large_page_size()) {
3525     assert(is_aligned(alignment, os::large_page_size()), "Must be divisible by the large page size");
3526     return shmat_with_alignment(shmid, bytes, alignment);
3527   } else {
3528     return shmat_at_address(shmid, NULL);
3529   }
3530 }
3531 
3532 char* os::Linux::reserve_memory_special_shm(size_t bytes, size_t alignment,
3533                                             char* req_addr, bool exec) {
3534   // "exec" is passed in but not used.  Creating the shared image for
3535   // the code cache doesn't have an SHM_X executable permission to check.
3536   assert(UseLargePages && UseSHM, "only for SHM large pages");
3537   assert(is_aligned(req_addr, os::large_page_size()), "Unaligned address");
3538   assert(is_aligned(req_addr, alignment), "Unaligned address");
3539 
3540   if (!is_aligned(bytes, os::large_page_size())) {
3541     return NULL; // Fallback to small pages.
3542   }
3543 
3544   // Create a large shared memory region to attach to based on size.
3545   // Currently, size is the total size of the heap.
3546   int shmid = shmget(IPC_PRIVATE, bytes, SHM_HUGETLB|IPC_CREAT|SHM_R|SHM_W);
3547   if (shmid == -1) {
3548     // Possible reasons for shmget failure:
3549     // 1. shmmax is too small for Java heap.
3550     //    > check shmmax value: cat /proc/sys/kernel/shmmax
3551     //    > increase shmmax value: echo "0xffffffff" > /proc/sys/kernel/shmmax
3552     // 2. not enough large page memory.
3553     //    > check available large pages: cat /proc/meminfo
3554     //    > increase amount of large pages:
3555     //          echo new_value > /proc/sys/vm/nr_hugepages
3556     //      Note 1: different Linux may use different name for this property,
3557     //            e.g. on Redhat AS-3 it is "hugetlb_pool".
3558     //      Note 2: it's possible there's enough physical memory available but
3559     //            they are so fragmented after a long run that they can't
3560     //            coalesce into large pages. Try to reserve large pages when
3561     //            the system is still "fresh".
3562     shm_warning_with_errno("Failed to reserve shared memory.");
3563     return NULL;
3564   }
3565 
3566   // Attach to the region.
3567   char* addr = shmat_large_pages(shmid, bytes, alignment, req_addr);
3568 
3569   // Remove shmid. If shmat() is successful, the actual shared memory segment
3570   // will be deleted when it's detached by shmdt() or when the process
3571   // terminates. If shmat() is not successful this will remove the shared
3572   // segment immediately.
3573   shmctl(shmid, IPC_RMID, NULL);
3574 
3575   return addr;
3576 }
3577 
3578 static void warn_on_large_pages_failure(char* req_addr, size_t bytes,
3579                                         int error) {
3580   assert(error == ENOMEM, "Only expect to fail if no memory is available");
3581 
3582   bool warn_on_failure = UseLargePages &&
3583       (!FLAG_IS_DEFAULT(UseLargePages) ||
3584        !FLAG_IS_DEFAULT(UseHugeTLBFS) ||
3585        !FLAG_IS_DEFAULT(LargePageSizeInBytes));
3586 
3587   if (warn_on_failure) {
3588     char msg[128];
3589     jio_snprintf(msg, sizeof(msg), "Failed to reserve large pages memory req_addr: "
3590                  PTR_FORMAT " bytes: " SIZE_FORMAT " (errno = %d).", req_addr, bytes, error);
3591     warning("%s", msg);
3592   }
3593 }
3594 
3595 char* os::Linux::reserve_memory_special_huge_tlbfs_only(size_t bytes,
3596                                                         char* req_addr,
3597                                                         bool exec) {
3598   assert(UseLargePages && UseHugeTLBFS, "only for Huge TLBFS large pages");
3599   assert(is_aligned(bytes, os::large_page_size()), "Unaligned size");
3600   assert(is_aligned(req_addr, os::large_page_size()), "Unaligned address");
3601 
3602   int prot = exec ? PROT_READ|PROT_WRITE|PROT_EXEC : PROT_READ|PROT_WRITE;
3603   char* addr = (char*)::mmap(req_addr, bytes, prot,
3604                              MAP_PRIVATE|MAP_ANONYMOUS|MAP_HUGETLB,
3605                              -1, 0);
3606 
3607   if (addr == MAP_FAILED) {
3608     warn_on_large_pages_failure(req_addr, bytes, errno);
3609     return NULL;
3610   }
3611 
3612   assert(is_aligned(addr, os::large_page_size()), "Must be");
3613 
3614   return addr;
3615 }
3616 
3617 // Reserve memory using mmap(MAP_HUGETLB).
3618 //  - bytes shall be a multiple of alignment.
3619 //  - req_addr can be NULL. If not NULL, it must be a multiple of alignment.
3620 //  - alignment sets the alignment at which memory shall be allocated.
3621 //     It must be a multiple of allocation granularity.
3622 // Returns address of memory or NULL. If req_addr was not NULL, will only return
3623 //  req_addr or NULL.
3624 char* os::Linux::reserve_memory_special_huge_tlbfs_mixed(size_t bytes,
3625                                                          size_t alignment,
3626                                                          char* req_addr,
3627                                                          bool exec) {
3628   size_t large_page_size = os::large_page_size();
3629   assert(bytes >= large_page_size, "Shouldn't allocate large pages for small sizes");
3630 
3631   assert(is_aligned(req_addr, alignment), "Must be");
3632   assert(is_aligned(bytes, alignment), "Must be");
3633 
3634   // First reserve - but not commit - the address range in small pages.
3635   char* const start = anon_mmap_aligned(bytes, alignment, req_addr);
3636 
3637   if (start == NULL) {
3638     return NULL;
3639   }
3640 
3641   assert(is_aligned(start, alignment), "Must be");
3642 
3643   char* end = start + bytes;
3644 
3645   // Find the regions of the allocated chunk that can be promoted to large pages.
3646   char* lp_start = align_up(start, large_page_size);
3647   char* lp_end   = align_down(end, large_page_size);
3648 
3649   size_t lp_bytes = lp_end - lp_start;
3650 
3651   assert(is_aligned(lp_bytes, large_page_size), "Must be");
3652 
3653   if (lp_bytes == 0) {
3654     // The mapped region doesn't even span the start and the end of a large page.
3655     // Fall back to allocate a non-special area.
3656     ::munmap(start, end - start);
3657     return NULL;
3658   }
3659 
3660   int prot = exec ? PROT_READ|PROT_WRITE|PROT_EXEC : PROT_READ|PROT_WRITE;
3661 
3662   void* result;
3663 
3664   // Commit small-paged leading area.
3665   if (start != lp_start) {
3666     result = ::mmap(start, lp_start - start, prot,
3667                     MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED,
3668                     -1, 0);
3669     if (result == MAP_FAILED) {
3670       ::munmap(lp_start, end - lp_start);
3671       return NULL;
3672     }
3673   }
3674 
3675   // Commit large-paged area.
3676   result = ::mmap(lp_start, lp_bytes, prot,
3677                   MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED|MAP_HUGETLB,
3678                   -1, 0);
3679   if (result == MAP_FAILED) {
3680     warn_on_large_pages_failure(lp_start, lp_bytes, errno);
3681     // If the mmap above fails, the large pages region will be unmapped and we
3682     // have regions before and after with small pages. Release these regions.
3683     //
3684     // |  mapped  |  unmapped  |  mapped  |
3685     // ^          ^            ^          ^
3686     // start      lp_start     lp_end     end
3687     //
3688     ::munmap(start, lp_start - start);
3689     ::munmap(lp_end, end - lp_end);
3690     return NULL;
3691   }
3692 
3693   // Commit small-paged trailing area.
3694   if (lp_end != end) {
3695     result = ::mmap(lp_end, end - lp_end, prot,
3696                     MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED,
3697                     -1, 0);
3698     if (result == MAP_FAILED) {
3699       ::munmap(start, lp_end - start);
3700       return NULL;
3701     }
3702   }
3703 
3704   return start;
3705 }
3706 
3707 char* os::Linux::reserve_memory_special_huge_tlbfs(size_t bytes,
3708                                                    size_t alignment,
3709                                                    char* req_addr,
3710                                                    bool exec) {
3711   assert(UseLargePages && UseHugeTLBFS, "only for Huge TLBFS large pages");
3712   assert(is_aligned(req_addr, alignment), "Must be");
3713   assert(is_aligned(alignment, os::vm_allocation_granularity()), "Must be");
3714   assert(is_power_of_2(os::large_page_size()), "Must be");
3715   assert(bytes >= os::large_page_size(), "Shouldn't allocate large pages for small sizes");
3716 
3717   if (is_aligned(bytes, os::large_page_size()) && alignment <= os::large_page_size()) {
3718     return reserve_memory_special_huge_tlbfs_only(bytes, req_addr, exec);
3719   } else {
3720     return reserve_memory_special_huge_tlbfs_mixed(bytes, alignment, req_addr, exec);
3721   }
3722 }
3723 
3724 char* os::reserve_memory_special(size_t bytes, size_t alignment,
3725                                  char* req_addr, bool exec) {
3726   assert(UseLargePages, "only for large pages");
3727 
3728   char* addr;
3729   if (UseSHM) {
3730     addr = os::Linux::reserve_memory_special_shm(bytes, alignment, req_addr, exec);
3731   } else {
3732     assert(UseHugeTLBFS, "must be");
3733     addr = os::Linux::reserve_memory_special_huge_tlbfs(bytes, alignment, req_addr, exec);
3734   }
3735 
3736   if (addr != NULL) {
3737     if (UseNUMAInterleaving) {
3738       numa_make_global(addr, bytes);
3739     }
3740 
3741     // The memory is committed
3742     MemTracker::record_virtual_memory_reserve_and_commit((address)addr, bytes, CALLER_PC);
3743   }
3744 
3745   return addr;
3746 }
3747 
3748 bool os::Linux::release_memory_special_shm(char* base, size_t bytes) {
3749   // detaching the SHM segment will also delete it, see reserve_memory_special_shm()
3750   return shmdt(base) == 0;
3751 }
3752 
3753 bool os::Linux::release_memory_special_huge_tlbfs(char* base, size_t bytes) {
3754   return pd_release_memory(base, bytes);
3755 }
3756 
3757 bool os::release_memory_special(char* base, size_t bytes) {
3758   bool res;
3759   if (MemTracker::tracking_level() > NMT_minimal) {
3760     Tracker tkr = MemTracker::get_virtual_memory_release_tracker();
3761     res = os::Linux::release_memory_special_impl(base, bytes);
3762     if (res) {
3763       tkr.record((address)base, bytes);
3764     }
3765 
3766   } else {
3767     res = os::Linux::release_memory_special_impl(base, bytes);
3768   }
3769   return res;
3770 }
3771 
3772 bool os::Linux::release_memory_special_impl(char* base, size_t bytes) {
3773   assert(UseLargePages, "only for large pages");
3774   bool res;
3775 
3776   if (UseSHM) {
3777     res = os::Linux::release_memory_special_shm(base, bytes);
3778   } else {
3779     assert(UseHugeTLBFS, "must be");
3780     res = os::Linux::release_memory_special_huge_tlbfs(base, bytes);
3781   }
3782   return res;
3783 }
3784 
3785 size_t os::large_page_size() {
3786   return _large_page_size;
3787 }
3788 
3789 // With SysV SHM the entire memory region must be allocated as shared
3790 // memory.
3791 // HugeTLBFS allows application to commit large page memory on demand.
3792 // However, when committing memory with HugeTLBFS fails, the region
3793 // that was supposed to be committed will lose the old reservation
3794 // and allow other threads to steal that memory region. Because of this
3795 // behavior we can't commit HugeTLBFS memory.
3796 bool os::can_commit_large_page_memory() {
3797   return UseTransparentHugePages;
3798 }
3799 
3800 bool os::can_execute_large_page_memory() {
3801   return UseTransparentHugePages || UseHugeTLBFS;
3802 }
3803 
3804 char* os::pd_attempt_reserve_memory_at(size_t bytes, char* requested_addr, int file_desc) {
3805   assert(file_desc >= 0, "file_desc is not valid");
3806   char* result = pd_attempt_reserve_memory_at(bytes, requested_addr);
3807   if (result != NULL) {
3808     if (replace_existing_mapping_with_file_mapping(result, bytes, file_desc) == NULL) {
3809       vm_exit_during_initialization(err_msg("Error in mapping Java heap at the given filesystem directory"));
3810     }
3811   }
3812   return result;
3813 }
3814 
3815 // Reserve memory at an arbitrary address, only if that area is
3816 // available (and not reserved for something else).
3817 
3818 char* os::pd_attempt_reserve_memory_at(size_t bytes, char* requested_addr) {
3819   const int max_tries = 10;
3820   char* base[max_tries];
3821   size_t size[max_tries];
3822   const size_t gap = 0x000000;
3823 
3824   // Assert only that the size is a multiple of the page size, since
3825   // that's all that mmap requires, and since that's all we really know
3826   // about at this low abstraction level.  If we need higher alignment,
3827   // we can either pass an alignment to this method or verify alignment
3828   // in one of the methods further up the call chain.  See bug 5044738.
3829   assert(bytes % os::vm_page_size() == 0, "reserving unexpected size block");
3830 
3831   // Repeatedly allocate blocks until the block is allocated at the
3832   // right spot.
3833 
3834   // Linux mmap allows caller to pass an address as hint; give it a try first,
3835   // if kernel honors the hint then we can return immediately.
3836   char * addr = anon_mmap(requested_addr, bytes, false);
3837   if (addr == requested_addr) {
3838     return requested_addr;
3839   }
3840 
3841   if (addr != NULL) {
3842     // mmap() is successful but it fails to reserve at the requested address
3843     anon_munmap(addr, bytes);
3844   }
3845 
3846   int i;
3847   for (i = 0; i < max_tries; ++i) {
3848     base[i] = reserve_memory(bytes);
3849 
3850     if (base[i] != NULL) {
3851       // Is this the block we wanted?
3852       if (base[i] == requested_addr) {
3853         size[i] = bytes;
3854         break;
3855       }
3856 
3857       // Does this overlap the block we wanted? Give back the overlapped
3858       // parts and try again.
3859 
3860       ptrdiff_t top_overlap = requested_addr + (bytes + gap) - base[i];
3861       if (top_overlap >= 0 && (size_t)top_overlap < bytes) {
3862         unmap_memory(base[i], top_overlap);
3863         base[i] += top_overlap;
3864         size[i] = bytes - top_overlap;
3865       } else {
3866         ptrdiff_t bottom_overlap = base[i] + bytes - requested_addr;
3867         if (bottom_overlap >= 0 && (size_t)bottom_overlap < bytes) {
3868           unmap_memory(requested_addr, bottom_overlap);
3869           size[i] = bytes - bottom_overlap;
3870         } else {
3871           size[i] = bytes;
3872         }
3873       }
3874     }
3875   }
3876 
3877   // Give back the unused reserved pieces.
3878 
3879   for (int j = 0; j < i; ++j) {
3880     if (base[j] != NULL) {
3881       unmap_memory(base[j], size[j]);
3882     }
3883   }
3884 
3885   if (i < max_tries) {
3886     return requested_addr;
3887   } else {
3888     return NULL;
3889   }
3890 }
3891 
3892 size_t os::read(int fd, void *buf, unsigned int nBytes) {
3893   return ::read(fd, buf, nBytes);
3894 }
3895 
3896 size_t os::read_at(int fd, void *buf, unsigned int nBytes, jlong offset) {
3897   return ::pread(fd, buf, nBytes, offset);
3898 }
3899 
3900 // Short sleep, direct OS call.
3901 //
3902 // Note: certain versions of Linux CFS scheduler (since 2.6.23) do not guarantee
3903 // sched_yield(2) will actually give up the CPU:
3904 //
3905 //   * Alone on this pariticular CPU, keeps running.
3906 //   * Before the introduction of "skip_buddy" with "compat_yield" disabled
3907 //     (pre 2.6.39).
3908 //
3909 // So calling this with 0 is an alternative.
3910 //
3911 void os::naked_short_sleep(jlong ms) {
3912   struct timespec req;
3913 
3914   assert(ms < 1000, "Un-interruptable sleep, short time use only");
3915   req.tv_sec = 0;
3916   if (ms > 0) {
3917     req.tv_nsec = (ms % 1000) * 1000000;
3918   } else {
3919     req.tv_nsec = 1;
3920   }
3921 
3922   nanosleep(&req, NULL);
3923 
3924   return;
3925 }
3926 
3927 // Sleep forever; naked call to OS-specific sleep; use with CAUTION
3928 void os::infinite_sleep() {
3929   while (true) {    // sleep forever ...
3930     ::sleep(100);   // ... 100 seconds at a time
3931   }
3932 }
3933 
3934 // Used to convert frequent JVM_Yield() to nops
3935 bool os::dont_yield() {
3936   return DontYieldALot;
3937 }
3938 
3939 void os::naked_yield() {
3940   sched_yield();
3941 }
3942 
3943 ////////////////////////////////////////////////////////////////////////////////
3944 // thread priority support
3945 
3946 // Note: Normal Linux applications are run with SCHED_OTHER policy. SCHED_OTHER
3947 // only supports dynamic priority, static priority must be zero. For real-time
3948 // applications, Linux supports SCHED_RR which allows static priority (1-99).
3949 // However, for large multi-threaded applications, SCHED_RR is not only slower
3950 // than SCHED_OTHER, but also very unstable (my volano tests hang hard 4 out
3951 // of 5 runs - Sep 2005).
3952 //
3953 // The following code actually changes the niceness of kernel-thread/LWP. It
3954 // has an assumption that setpriority() only modifies one kernel-thread/LWP,
3955 // not the entire user process, and user level threads are 1:1 mapped to kernel
3956 // threads. It has always been the case, but could change in the future. For
3957 // this reason, the code should not be used as default (ThreadPriorityPolicy=0).
3958 // It is only used when ThreadPriorityPolicy=1 and requires root privilege.
3959 
3960 int os::java_to_os_priority[CriticalPriority + 1] = {
3961   19,              // 0 Entry should never be used
3962 
3963    4,              // 1 MinPriority
3964    3,              // 2
3965    2,              // 3
3966 
3967    1,              // 4
3968    0,              // 5 NormPriority
3969   -1,              // 6
3970 
3971   -2,              // 7
3972   -3,              // 8
3973   -4,              // 9 NearMaxPriority
3974 
3975   -5,              // 10 MaxPriority
3976 
3977   -5               // 11 CriticalPriority
3978 };
3979 
3980 static int prio_init() {
3981   if (ThreadPriorityPolicy == 1) {
3982     // Only root can raise thread priority. Don't allow ThreadPriorityPolicy=1
3983     // if effective uid is not root. Perhaps, a more elegant way of doing
3984     // this is to test CAP_SYS_NICE capability, but that will require libcap.so
3985     if (geteuid() != 0) {
3986       if (!FLAG_IS_DEFAULT(ThreadPriorityPolicy)) {
3987         warning("-XX:ThreadPriorityPolicy requires root privilege on Linux");
3988       }
3989       ThreadPriorityPolicy = 0;
3990     }
3991   }
3992   if (UseCriticalJavaThreadPriority) {
3993     os::java_to_os_priority[MaxPriority] = os::java_to_os_priority[CriticalPriority];
3994   }
3995   return 0;
3996 }
3997 
3998 OSReturn os::set_native_priority(Thread* thread, int newpri) {
3999   if (!UseThreadPriorities || ThreadPriorityPolicy == 0) return OS_OK;
4000 
4001   int ret = setpriority(PRIO_PROCESS, thread->osthread()->thread_id(), newpri);
4002   return (ret == 0) ? OS_OK : OS_ERR;
4003 }
4004 
4005 OSReturn os::get_native_priority(const Thread* const thread,
4006                                  int *priority_ptr) {
4007   if (!UseThreadPriorities || ThreadPriorityPolicy == 0) {
4008     *priority_ptr = java_to_os_priority[NormPriority];
4009     return OS_OK;
4010   }
4011 
4012   errno = 0;
4013   *priority_ptr = getpriority(PRIO_PROCESS, thread->osthread()->thread_id());
4014   return (*priority_ptr != -1 || errno == 0 ? OS_OK : OS_ERR);
4015 }
4016 
4017 // Hint to the underlying OS that a task switch would not be good.
4018 // Void return because it's a hint and can fail.
4019 void os::hint_no_preempt() {}
4020 
4021 ////////////////////////////////////////////////////////////////////////////////
4022 // suspend/resume support
4023 
4024 //  The low-level signal-based suspend/resume support is a remnant from the
4025 //  old VM-suspension that used to be for java-suspension, safepoints etc,
4026 //  within hotspot. Currently used by JFR's OSThreadSampler
4027 //
4028 //  The remaining code is greatly simplified from the more general suspension
4029 //  code that used to be used.
4030 //
4031 //  The protocol is quite simple:
4032 //  - suspend:
4033 //      - sends a signal to the target thread
4034 //      - polls the suspend state of the osthread using a yield loop
4035 //      - target thread signal handler (SR_handler) sets suspend state
4036 //        and blocks in sigsuspend until continued
4037 //  - resume:
4038 //      - sets target osthread state to continue
4039 //      - sends signal to end the sigsuspend loop in the SR_handler
4040 //
4041 //  Note that the SR_lock plays no role in this suspend/resume protocol,
4042 //  but is checked for NULL in SR_handler as a thread termination indicator.
4043 //  The SR_lock is, however, used by JavaThread::java_suspend()/java_resume() APIs.
4044 //
4045 //  Note that resume_clear_context() and suspend_save_context() are needed
4046 //  by SR_handler(), so that fetch_frame_from_ucontext() works,
4047 //  which in part is used by:
4048 //    - Forte Analyzer: AsyncGetCallTrace()
4049 //    - StackBanging: get_frame_at_stack_banging_point()
4050 
4051 static void resume_clear_context(OSThread *osthread) {
4052   osthread->set_ucontext(NULL);
4053   osthread->set_siginfo(NULL);
4054 }
4055 
4056 static void suspend_save_context(OSThread *osthread, siginfo_t* siginfo,
4057                                  ucontext_t* context) {
4058   osthread->set_ucontext(context);
4059   osthread->set_siginfo(siginfo);
4060 }
4061 
4062 // Handler function invoked when a thread's execution is suspended or
4063 // resumed. We have to be careful that only async-safe functions are
4064 // called here (Note: most pthread functions are not async safe and
4065 // should be avoided.)
4066 //
4067 // Note: sigwait() is a more natural fit than sigsuspend() from an
4068 // interface point of view, but sigwait() prevents the signal hander
4069 // from being run. libpthread would get very confused by not having
4070 // its signal handlers run and prevents sigwait()'s use with the
4071 // mutex granting granting signal.
4072 //
4073 // Currently only ever called on the VMThread and JavaThreads (PC sampling)
4074 //
4075 static void SR_handler(int sig, siginfo_t* siginfo, ucontext_t* context) {
4076   // Save and restore errno to avoid confusing native code with EINTR
4077   // after sigsuspend.
4078   int old_errno = errno;
4079 
4080   Thread* thread = Thread::current_or_null_safe();
4081   assert(thread != NULL, "Missing current thread in SR_handler");
4082 
4083   // On some systems we have seen signal delivery get "stuck" until the signal
4084   // mask is changed as part of thread termination. Check that the current thread
4085   // has not already terminated (via SR_lock()) - else the following assertion
4086   // will fail because the thread is no longer a JavaThread as the ~JavaThread
4087   // destructor has completed.
4088 
4089   if (thread->SR_lock() == NULL) {
4090     return;
4091   }
4092 
4093   assert(thread->is_VM_thread() || thread->is_Java_thread(), "Must be VMThread or JavaThread");
4094 
4095   OSThread* osthread = thread->osthread();
4096 
4097   os::SuspendResume::State current = osthread->sr.state();
4098   if (current == os::SuspendResume::SR_SUSPEND_REQUEST) {
4099     suspend_save_context(osthread, siginfo, context);
4100 
4101     // attempt to switch the state, we assume we had a SUSPEND_REQUEST
4102     os::SuspendResume::State state = osthread->sr.suspended();
4103     if (state == os::SuspendResume::SR_SUSPENDED) {
4104       sigset_t suspend_set;  // signals for sigsuspend()
4105       sigemptyset(&suspend_set);
4106       // get current set of blocked signals and unblock resume signal
4107       pthread_sigmask(SIG_BLOCK, NULL, &suspend_set);
4108       sigdelset(&suspend_set, SR_signum);
4109 
4110       sr_semaphore.signal();
4111       // wait here until we are resumed
4112       while (1) {
4113         sigsuspend(&suspend_set);
4114 
4115         os::SuspendResume::State result = osthread->sr.running();
4116         if (result == os::SuspendResume::SR_RUNNING) {
4117           sr_semaphore.signal();
4118           break;
4119         }
4120       }
4121 
4122     } else if (state == os::SuspendResume::SR_RUNNING) {
4123       // request was cancelled, continue
4124     } else {
4125       ShouldNotReachHere();
4126     }
4127 
4128     resume_clear_context(osthread);
4129   } else if (current == os::SuspendResume::SR_RUNNING) {
4130     // request was cancelled, continue
4131   } else if (current == os::SuspendResume::SR_WAKEUP_REQUEST) {
4132     // ignore
4133   } else {
4134     // ignore
4135   }
4136 
4137   errno = old_errno;
4138 }
4139 
4140 static int SR_initialize() {
4141   struct sigaction act;
4142   char *s;
4143 
4144   // Get signal number to use for suspend/resume
4145   if ((s = ::getenv("_JAVA_SR_SIGNUM")) != 0) {
4146     int sig = ::strtol(s, 0, 10);
4147     if (sig > MAX2(SIGSEGV, SIGBUS) &&  // See 4355769.
4148         sig < NSIG) {                   // Must be legal signal and fit into sigflags[].
4149       SR_signum = sig;
4150     } else {
4151       warning("You set _JAVA_SR_SIGNUM=%d. It must be in range [%d, %d]. Using %d instead.",
4152               sig, MAX2(SIGSEGV, SIGBUS)+1, NSIG-1, SR_signum);
4153     }
4154   }
4155 
4156   assert(SR_signum > SIGSEGV && SR_signum > SIGBUS,
4157          "SR_signum must be greater than max(SIGSEGV, SIGBUS), see 4355769");
4158 
4159   sigemptyset(&SR_sigset);
4160   sigaddset(&SR_sigset, SR_signum);
4161 
4162   // Set up signal handler for suspend/resume
4163   act.sa_flags = SA_RESTART|SA_SIGINFO;
4164   act.sa_handler = (void (*)(int)) SR_handler;
4165 
4166   // SR_signum is blocked by default.
4167   // 4528190 - We also need to block pthread restart signal (32 on all
4168   // supported Linux platforms). Note that LinuxThreads need to block
4169   // this signal for all threads to work properly. So we don't have
4170   // to use hard-coded signal number when setting up the mask.
4171   pthread_sigmask(SIG_BLOCK, NULL, &act.sa_mask);
4172 
4173   if (sigaction(SR_signum, &act, 0) == -1) {
4174     return -1;
4175   }
4176 
4177   // Save signal flag
4178   os::Linux::set_our_sigflags(SR_signum, act.sa_flags);
4179   return 0;
4180 }
4181 
4182 static int sr_notify(OSThread* osthread) {
4183   int status = pthread_kill(osthread->pthread_id(), SR_signum);
4184   assert_status(status == 0, status, "pthread_kill");
4185   return status;
4186 }
4187 
4188 // "Randomly" selected value for how long we want to spin
4189 // before bailing out on suspending a thread, also how often
4190 // we send a signal to a thread we want to resume
4191 static const int RANDOMLY_LARGE_INTEGER = 1000000;
4192 static const int RANDOMLY_LARGE_INTEGER2 = 100;
4193 
4194 // returns true on success and false on error - really an error is fatal
4195 // but this seems the normal response to library errors
4196 static bool do_suspend(OSThread* osthread) {
4197   assert(osthread->sr.is_running(), "thread should be running");
4198   assert(!sr_semaphore.trywait(), "semaphore has invalid state");
4199 
4200   // mark as suspended and send signal
4201   if (osthread->sr.request_suspend() != os::SuspendResume::SR_SUSPEND_REQUEST) {
4202     // failed to switch, state wasn't running?
4203     ShouldNotReachHere();
4204     return false;
4205   }
4206 
4207   if (sr_notify(osthread) != 0) {
4208     ShouldNotReachHere();
4209   }
4210 
4211   // managed to send the signal and switch to SUSPEND_REQUEST, now wait for SUSPENDED
4212   while (true) {
4213     if (sr_semaphore.timedwait(0, 2 * NANOSECS_PER_MILLISEC)) {
4214       break;
4215     } else {
4216       // timeout
4217       os::SuspendResume::State cancelled = osthread->sr.cancel_suspend();
4218       if (cancelled == os::SuspendResume::SR_RUNNING) {
4219         return false;
4220       } else if (cancelled == os::SuspendResume::SR_SUSPENDED) {
4221         // make sure that we consume the signal on the semaphore as well
4222         sr_semaphore.wait();
4223         break;
4224       } else {
4225         ShouldNotReachHere();
4226         return false;
4227       }
4228     }
4229   }
4230 
4231   guarantee(osthread->sr.is_suspended(), "Must be suspended");
4232   return true;
4233 }
4234 
4235 static void do_resume(OSThread* osthread) {
4236   assert(osthread->sr.is_suspended(), "thread should be suspended");
4237   assert(!sr_semaphore.trywait(), "invalid semaphore state");
4238 
4239   if (osthread->sr.request_wakeup() != os::SuspendResume::SR_WAKEUP_REQUEST) {
4240     // failed to switch to WAKEUP_REQUEST
4241     ShouldNotReachHere();
4242     return;
4243   }
4244 
4245   while (true) {
4246     if (sr_notify(osthread) == 0) {
4247       if (sr_semaphore.timedwait(0, 2 * NANOSECS_PER_MILLISEC)) {
4248         if (osthread->sr.is_running()) {
4249           return;
4250         }
4251       }
4252     } else {
4253       ShouldNotReachHere();
4254     }
4255   }
4256 
4257   guarantee(osthread->sr.is_running(), "Must be running!");
4258 }
4259 
4260 ///////////////////////////////////////////////////////////////////////////////////
4261 // signal handling (except suspend/resume)
4262 
4263 // This routine may be used by user applications as a "hook" to catch signals.
4264 // The user-defined signal handler must pass unrecognized signals to this
4265 // routine, and if it returns true (non-zero), then the signal handler must
4266 // return immediately.  If the flag "abort_if_unrecognized" is true, then this
4267 // routine will never retun false (zero), but instead will execute a VM panic
4268 // routine kill the process.
4269 //
4270 // If this routine returns false, it is OK to call it again.  This allows
4271 // the user-defined signal handler to perform checks either before or after
4272 // the VM performs its own checks.  Naturally, the user code would be making
4273 // a serious error if it tried to handle an exception (such as a null check
4274 // or breakpoint) that the VM was generating for its own correct operation.
4275 //
4276 // This routine may recognize any of the following kinds of signals:
4277 //    SIGBUS, SIGSEGV, SIGILL, SIGFPE, SIGQUIT, SIGPIPE, SIGXFSZ, SIGUSR1.
4278 // It should be consulted by handlers for any of those signals.
4279 //
4280 // The caller of this routine must pass in the three arguments supplied
4281 // to the function referred to in the "sa_sigaction" (not the "sa_handler")
4282 // field of the structure passed to sigaction().  This routine assumes that
4283 // the sa_flags field passed to sigaction() includes SA_SIGINFO and SA_RESTART.
4284 //
4285 // Note that the VM will print warnings if it detects conflicting signal
4286 // handlers, unless invoked with the option "-XX:+AllowUserSignalHandlers".
4287 //
4288 extern "C" JNIEXPORT int JVM_handle_linux_signal(int signo,
4289                                                  siginfo_t* siginfo,
4290                                                  void* ucontext,
4291                                                  int abort_if_unrecognized);
4292 
4293 void signalHandler(int sig, siginfo_t* info, void* uc) {
4294   assert(info != NULL && uc != NULL, "it must be old kernel");
4295   int orig_errno = errno;  // Preserve errno value over signal handler.
4296   JVM_handle_linux_signal(sig, info, uc, true);
4297   errno = orig_errno;
4298 }
4299 
4300 
4301 // This boolean allows users to forward their own non-matching signals
4302 // to JVM_handle_linux_signal, harmlessly.
4303 bool os::Linux::signal_handlers_are_installed = false;
4304 
4305 // For signal-chaining
4306 struct sigaction sigact[NSIG];
4307 uint64_t sigs = 0;
4308 #if (64 < NSIG-1)
4309 #error "Not all signals can be encoded in sigs. Adapt its type!"
4310 #endif
4311 bool os::Linux::libjsig_is_loaded = false;
4312 typedef struct sigaction *(*get_signal_t)(int);
4313 get_signal_t os::Linux::get_signal_action = NULL;
4314 
4315 struct sigaction* os::Linux::get_chained_signal_action(int sig) {
4316   struct sigaction *actp = NULL;
4317 
4318   if (libjsig_is_loaded) {
4319     // Retrieve the old signal handler from libjsig
4320     actp = (*get_signal_action)(sig);
4321   }
4322   if (actp == NULL) {
4323     // Retrieve the preinstalled signal handler from jvm
4324     actp = get_preinstalled_handler(sig);
4325   }
4326 
4327   return actp;
4328 }
4329 
4330 static bool call_chained_handler(struct sigaction *actp, int sig,
4331                                  siginfo_t *siginfo, void *context) {
4332   // Call the old signal handler
4333   if (actp->sa_handler == SIG_DFL) {
4334     // It's more reasonable to let jvm treat it as an unexpected exception
4335     // instead of taking the default action.
4336     return false;
4337   } else if (actp->sa_handler != SIG_IGN) {
4338     if ((actp->sa_flags & SA_NODEFER) == 0) {
4339       // automaticlly block the signal
4340       sigaddset(&(actp->sa_mask), sig);
4341     }
4342 
4343     sa_handler_t hand = NULL;
4344     sa_sigaction_t sa = NULL;
4345     bool siginfo_flag_set = (actp->sa_flags & SA_SIGINFO) != 0;
4346     // retrieve the chained handler
4347     if (siginfo_flag_set) {
4348       sa = actp->sa_sigaction;
4349     } else {
4350       hand = actp->sa_handler;
4351     }
4352 
4353     if ((actp->sa_flags & SA_RESETHAND) != 0) {
4354       actp->sa_handler = SIG_DFL;
4355     }
4356 
4357     // try to honor the signal mask
4358     sigset_t oset;
4359     sigemptyset(&oset);
4360     pthread_sigmask(SIG_SETMASK, &(actp->sa_mask), &oset);
4361 
4362     // call into the chained handler
4363     if (siginfo_flag_set) {
4364       (*sa)(sig, siginfo, context);
4365     } else {
4366       (*hand)(sig);
4367     }
4368 
4369     // restore the signal mask
4370     pthread_sigmask(SIG_SETMASK, &oset, NULL);
4371   }
4372   // Tell jvm's signal handler the signal is taken care of.
4373   return true;
4374 }
4375 
4376 bool os::Linux::chained_handler(int sig, siginfo_t* siginfo, void* context) {
4377   bool chained = false;
4378   // signal-chaining
4379   if (UseSignalChaining) {
4380     struct sigaction *actp = get_chained_signal_action(sig);
4381     if (actp != NULL) {
4382       chained = call_chained_handler(actp, sig, siginfo, context);
4383     }
4384   }
4385   return chained;
4386 }
4387 
4388 struct sigaction* os::Linux::get_preinstalled_handler(int sig) {
4389   if ((((uint64_t)1 << (sig-1)) & sigs) != 0) {
4390     return &sigact[sig];
4391   }
4392   return NULL;
4393 }
4394 
4395 void os::Linux::save_preinstalled_handler(int sig, struct sigaction& oldAct) {
4396   assert(sig > 0 && sig < NSIG, "vm signal out of expected range");
4397   sigact[sig] = oldAct;
4398   sigs |= (uint64_t)1 << (sig-1);
4399 }
4400 
4401 // for diagnostic
4402 int sigflags[NSIG];
4403 
4404 int os::Linux::get_our_sigflags(int sig) {
4405   assert(sig > 0 && sig < NSIG, "vm signal out of expected range");
4406   return sigflags[sig];
4407 }
4408 
4409 void os::Linux::set_our_sigflags(int sig, int flags) {
4410   assert(sig > 0 && sig < NSIG, "vm signal out of expected range");
4411   if (sig > 0 && sig < NSIG) {
4412     sigflags[sig] = flags;
4413   }
4414 }
4415 
4416 void os::Linux::set_signal_handler(int sig, bool set_installed) {
4417   // Check for overwrite.
4418   struct sigaction oldAct;
4419   sigaction(sig, (struct sigaction*)NULL, &oldAct);
4420 
4421   void* oldhand = oldAct.sa_sigaction
4422                 ? CAST_FROM_FN_PTR(void*,  oldAct.sa_sigaction)
4423                 : CAST_FROM_FN_PTR(void*,  oldAct.sa_handler);
4424   if (oldhand != CAST_FROM_FN_PTR(void*, SIG_DFL) &&
4425       oldhand != CAST_FROM_FN_PTR(void*, SIG_IGN) &&
4426       oldhand != CAST_FROM_FN_PTR(void*, (sa_sigaction_t)signalHandler)) {
4427     if (AllowUserSignalHandlers || !set_installed) {
4428       // Do not overwrite; user takes responsibility to forward to us.
4429       return;
4430     } else if (UseSignalChaining) {
4431       // save the old handler in jvm
4432       save_preinstalled_handler(sig, oldAct);
4433       // libjsig also interposes the sigaction() call below and saves the
4434       // old sigaction on it own.
4435     } else {
4436       fatal("Encountered unexpected pre-existing sigaction handler "
4437             "%#lx for signal %d.", (long)oldhand, sig);
4438     }
4439   }
4440 
4441   struct sigaction sigAct;
4442   sigfillset(&(sigAct.sa_mask));
4443   sigAct.sa_handler = SIG_DFL;
4444   if (!set_installed) {
4445     sigAct.sa_flags = SA_SIGINFO|SA_RESTART;
4446   } else {
4447     sigAct.sa_sigaction = signalHandler;
4448     sigAct.sa_flags = SA_SIGINFO|SA_RESTART;
4449   }
4450   // Save flags, which are set by ours
4451   assert(sig > 0 && sig < NSIG, "vm signal out of expected range");
4452   sigflags[sig] = sigAct.sa_flags;
4453 
4454   int ret = sigaction(sig, &sigAct, &oldAct);
4455   assert(ret == 0, "check");
4456 
4457   void* oldhand2  = oldAct.sa_sigaction
4458                   ? CAST_FROM_FN_PTR(void*, oldAct.sa_sigaction)
4459                   : CAST_FROM_FN_PTR(void*, oldAct.sa_handler);
4460   assert(oldhand2 == oldhand, "no concurrent signal handler installation");
4461 }
4462 
4463 // install signal handlers for signals that HotSpot needs to
4464 // handle in order to support Java-level exception handling.
4465 
4466 void os::Linux::install_signal_handlers() {
4467   if (!signal_handlers_are_installed) {
4468     signal_handlers_are_installed = true;
4469 
4470     // signal-chaining
4471     typedef void (*signal_setting_t)();
4472     signal_setting_t begin_signal_setting = NULL;
4473     signal_setting_t end_signal_setting = NULL;
4474     begin_signal_setting = CAST_TO_FN_PTR(signal_setting_t,
4475                                           dlsym(RTLD_DEFAULT, "JVM_begin_signal_setting"));
4476     if (begin_signal_setting != NULL) {
4477       end_signal_setting = CAST_TO_FN_PTR(signal_setting_t,
4478                                           dlsym(RTLD_DEFAULT, "JVM_end_signal_setting"));
4479       get_signal_action = CAST_TO_FN_PTR(get_signal_t,
4480                                          dlsym(RTLD_DEFAULT, "JVM_get_signal_action"));
4481       libjsig_is_loaded = true;
4482       assert(UseSignalChaining, "should enable signal-chaining");
4483     }
4484     if (libjsig_is_loaded) {
4485       // Tell libjsig jvm is setting signal handlers
4486       (*begin_signal_setting)();
4487     }
4488 
4489     set_signal_handler(SIGSEGV, true);
4490     set_signal_handler(SIGPIPE, true);
4491     set_signal_handler(SIGBUS, true);
4492     set_signal_handler(SIGILL, true);
4493     set_signal_handler(SIGFPE, true);
4494 #if defined(PPC64)
4495     set_signal_handler(SIGTRAP, true);
4496 #endif
4497     set_signal_handler(SIGXFSZ, true);
4498 
4499     if (libjsig_is_loaded) {
4500       // Tell libjsig jvm finishes setting signal handlers
4501       (*end_signal_setting)();
4502     }
4503 
4504     // We don't activate signal checker if libjsig is in place, we trust ourselves
4505     // and if UserSignalHandler is installed all bets are off.
4506     // Log that signal checking is off only if -verbose:jni is specified.
4507     if (CheckJNICalls) {
4508       if (libjsig_is_loaded) {
4509         if (PrintJNIResolving) {
4510           tty->print_cr("Info: libjsig is activated, all active signal checking is disabled");
4511         }
4512         check_signals = false;
4513       }
4514       if (AllowUserSignalHandlers) {
4515         if (PrintJNIResolving) {
4516           tty->print_cr("Info: AllowUserSignalHandlers is activated, all active signal checking is disabled");
4517         }
4518         check_signals = false;
4519       }
4520     }
4521   }
4522 }
4523 
4524 // This is the fastest way to get thread cpu time on Linux.
4525 // Returns cpu time (user+sys) for any thread, not only for current.
4526 // POSIX compliant clocks are implemented in the kernels 2.6.16+.
4527 // It might work on 2.6.10+ with a special kernel/glibc patch.
4528 // For reference, please, see IEEE Std 1003.1-2004:
4529 //   http://www.unix.org/single_unix_specification
4530 
4531 jlong os::Linux::fast_thread_cpu_time(clockid_t clockid) {
4532   struct timespec tp;
4533   int rc = os::Linux::clock_gettime(clockid, &tp);
4534   assert(rc == 0, "clock_gettime is expected to return 0 code");
4535 
4536   return (tp.tv_sec * NANOSECS_PER_SEC) + tp.tv_nsec;
4537 }
4538 
4539 void os::Linux::initialize_os_info() {
4540   assert(_os_version == 0, "OS info already initialized");
4541 
4542   struct utsname _uname;
4543 
4544   uint32_t major;
4545   uint32_t minor;
4546   uint32_t fix;
4547 
4548   int rc;
4549 
4550   // Kernel version is unknown if
4551   // verification below fails.
4552   _os_version = 0x01000000;
4553 
4554   rc = uname(&_uname);
4555   if (rc != -1) {
4556 
4557     rc = sscanf(_uname.release,"%d.%d.%d", &major, &minor, &fix);
4558     if (rc == 3) {
4559 
4560       if (major < 256 && minor < 256 && fix < 256) {
4561         // Kernel version format is as expected,
4562         // set it overriding unknown state.
4563         _os_version = (major << 16) |
4564                       (minor << 8 ) |
4565                       (fix   << 0 ) ;
4566       }
4567     }
4568   }
4569 }
4570 
4571 uint32_t os::Linux::os_version() {
4572   assert(_os_version != 0, "not initialized");
4573   return _os_version & 0x00FFFFFF;
4574 }
4575 
4576 bool os::Linux::os_version_is_known() {
4577   assert(_os_version != 0, "not initialized");
4578   return _os_version & 0x01000000 ? false : true;
4579 }
4580 
4581 /////
4582 // glibc on Linux platform uses non-documented flag
4583 // to indicate, that some special sort of signal
4584 // trampoline is used.
4585 // We will never set this flag, and we should
4586 // ignore this flag in our diagnostic
4587 #ifdef SIGNIFICANT_SIGNAL_MASK
4588   #undef SIGNIFICANT_SIGNAL_MASK
4589 #endif
4590 #define SIGNIFICANT_SIGNAL_MASK (~0x04000000)
4591 
4592 static const char* get_signal_handler_name(address handler,
4593                                            char* buf, int buflen) {
4594   int offset = 0;
4595   bool found = os::dll_address_to_library_name(handler, buf, buflen, &offset);
4596   if (found) {
4597     // skip directory names
4598     const char *p1, *p2;
4599     p1 = buf;
4600     size_t len = strlen(os::file_separator());
4601     while ((p2 = strstr(p1, os::file_separator())) != NULL) p1 = p2 + len;
4602     jio_snprintf(buf, buflen, "%s+0x%x", p1, offset);
4603   } else {
4604     jio_snprintf(buf, buflen, PTR_FORMAT, handler);
4605   }
4606   return buf;
4607 }
4608 
4609 static void print_signal_handler(outputStream* st, int sig,
4610                                  char* buf, size_t buflen) {
4611   struct sigaction sa;
4612 
4613   sigaction(sig, NULL, &sa);
4614 
4615   // See comment for SIGNIFICANT_SIGNAL_MASK define
4616   sa.sa_flags &= SIGNIFICANT_SIGNAL_MASK;
4617 
4618   st->print("%s: ", os::exception_name(sig, buf, buflen));
4619 
4620   address handler = (sa.sa_flags & SA_SIGINFO)
4621     ? CAST_FROM_FN_PTR(address, sa.sa_sigaction)
4622     : CAST_FROM_FN_PTR(address, sa.sa_handler);
4623 
4624   if (handler == CAST_FROM_FN_PTR(address, SIG_DFL)) {
4625     st->print("SIG_DFL");
4626   } else if (handler == CAST_FROM_FN_PTR(address, SIG_IGN)) {
4627     st->print("SIG_IGN");
4628   } else {
4629     st->print("[%s]", get_signal_handler_name(handler, buf, buflen));
4630   }
4631 
4632   st->print(", sa_mask[0]=");
4633   os::Posix::print_signal_set_short(st, &sa.sa_mask);
4634 
4635   address rh = VMError::get_resetted_sighandler(sig);
4636   // May be, handler was resetted by VMError?
4637   if (rh != NULL) {
4638     handler = rh;
4639     sa.sa_flags = VMError::get_resetted_sigflags(sig) & SIGNIFICANT_SIGNAL_MASK;
4640   }
4641 
4642   st->print(", sa_flags=");
4643   os::Posix::print_sa_flags(st, sa.sa_flags);
4644 
4645   // Check: is it our handler?
4646   if (handler == CAST_FROM_FN_PTR(address, (sa_sigaction_t)signalHandler) ||
4647       handler == CAST_FROM_FN_PTR(address, (sa_sigaction_t)SR_handler)) {
4648     // It is our signal handler
4649     // check for flags, reset system-used one!
4650     if ((int)sa.sa_flags != os::Linux::get_our_sigflags(sig)) {
4651       st->print(
4652                 ", flags was changed from " PTR32_FORMAT ", consider using jsig library",
4653                 os::Linux::get_our_sigflags(sig));
4654     }
4655   }
4656   st->cr();
4657 }
4658 
4659 
4660 #define DO_SIGNAL_CHECK(sig)                      \
4661   do {                                            \
4662     if (!sigismember(&check_signal_done, sig)) {  \
4663       os::Linux::check_signal_handler(sig);       \
4664     }                                             \
4665   } while (0)
4666 
4667 // This method is a periodic task to check for misbehaving JNI applications
4668 // under CheckJNI, we can add any periodic checks here
4669 
4670 void os::run_periodic_checks() {
4671   if (check_signals == false) return;
4672 
4673   // SEGV and BUS if overridden could potentially prevent
4674   // generation of hs*.log in the event of a crash, debugging
4675   // such a case can be very challenging, so we absolutely
4676   // check the following for a good measure:
4677   DO_SIGNAL_CHECK(SIGSEGV);
4678   DO_SIGNAL_CHECK(SIGILL);
4679   DO_SIGNAL_CHECK(SIGFPE);
4680   DO_SIGNAL_CHECK(SIGBUS);
4681   DO_SIGNAL_CHECK(SIGPIPE);
4682   DO_SIGNAL_CHECK(SIGXFSZ);
4683 #if defined(PPC64)
4684   DO_SIGNAL_CHECK(SIGTRAP);
4685 #endif
4686 
4687   // ReduceSignalUsage allows the user to override these handlers
4688   // see comments at the very top and jvm_md.h
4689   if (!ReduceSignalUsage) {
4690     DO_SIGNAL_CHECK(SHUTDOWN1_SIGNAL);
4691     DO_SIGNAL_CHECK(SHUTDOWN2_SIGNAL);
4692     DO_SIGNAL_CHECK(SHUTDOWN3_SIGNAL);
4693     DO_SIGNAL_CHECK(BREAK_SIGNAL);
4694   }
4695 
4696   DO_SIGNAL_CHECK(SR_signum);
4697 }
4698 
4699 typedef int (*os_sigaction_t)(int, const struct sigaction *, struct sigaction *);
4700 
4701 static os_sigaction_t os_sigaction = NULL;
4702 
4703 void os::Linux::check_signal_handler(int sig) {
4704   char buf[O_BUFLEN];
4705   address jvmHandler = NULL;
4706 
4707 
4708   struct sigaction act;
4709   if (os_sigaction == NULL) {
4710     // only trust the default sigaction, in case it has been interposed
4711     os_sigaction = (os_sigaction_t)dlsym(RTLD_DEFAULT, "sigaction");
4712     if (os_sigaction == NULL) return;
4713   }
4714 
4715   os_sigaction(sig, (struct sigaction*)NULL, &act);
4716 
4717 
4718   act.sa_flags &= SIGNIFICANT_SIGNAL_MASK;
4719 
4720   address thisHandler = (act.sa_flags & SA_SIGINFO)
4721     ? CAST_FROM_FN_PTR(address, act.sa_sigaction)
4722     : CAST_FROM_FN_PTR(address, act.sa_handler);
4723 
4724 
4725   switch (sig) {
4726   case SIGSEGV:
4727   case SIGBUS:
4728   case SIGFPE:
4729   case SIGPIPE:
4730   case SIGILL:
4731   case SIGXFSZ:
4732     jvmHandler = CAST_FROM_FN_PTR(address, (sa_sigaction_t)signalHandler);
4733     break;
4734 
4735   case SHUTDOWN1_SIGNAL:
4736   case SHUTDOWN2_SIGNAL:
4737   case SHUTDOWN3_SIGNAL:
4738   case BREAK_SIGNAL:
4739     jvmHandler = (address)user_handler();
4740     break;
4741 
4742   default:
4743     if (sig == SR_signum) {
4744       jvmHandler = CAST_FROM_FN_PTR(address, (sa_sigaction_t)SR_handler);
4745     } else {
4746       return;
4747     }
4748     break;
4749   }
4750 
4751   if (thisHandler != jvmHandler) {
4752     tty->print("Warning: %s handler ", exception_name(sig, buf, O_BUFLEN));
4753     tty->print("expected:%s", get_signal_handler_name(jvmHandler, buf, O_BUFLEN));
4754     tty->print_cr("  found:%s", get_signal_handler_name(thisHandler, buf, O_BUFLEN));
4755     // No need to check this sig any longer
4756     sigaddset(&check_signal_done, sig);
4757     // Running under non-interactive shell, SHUTDOWN2_SIGNAL will be reassigned SIG_IGN
4758     if (sig == SHUTDOWN2_SIGNAL && !isatty(fileno(stdin))) {
4759       tty->print_cr("Running in non-interactive shell, %s handler is replaced by shell",
4760                     exception_name(sig, buf, O_BUFLEN));
4761     }
4762   } else if(os::Linux::get_our_sigflags(sig) != 0 && (int)act.sa_flags != os::Linux::get_our_sigflags(sig)) {
4763     tty->print("Warning: %s handler flags ", exception_name(sig, buf, O_BUFLEN));
4764     tty->print("expected:");
4765     os::Posix::print_sa_flags(tty, os::Linux::get_our_sigflags(sig));
4766     tty->cr();
4767     tty->print("  found:");
4768     os::Posix::print_sa_flags(tty, act.sa_flags);
4769     tty->cr();
4770     // No need to check this sig any longer
4771     sigaddset(&check_signal_done, sig);
4772   }
4773 
4774   // Dump all the signal
4775   if (sigismember(&check_signal_done, sig)) {
4776     print_signal_handlers(tty, buf, O_BUFLEN);
4777   }
4778 }
4779 
4780 extern void report_error(char* file_name, int line_no, char* title,
4781                          char* format, ...);
4782 
4783 // this is called _before_ the most of global arguments have been parsed
4784 void os::init(void) {
4785   char dummy;   // used to get a guess on initial stack address
4786 //  first_hrtime = gethrtime();
4787 
4788   clock_tics_per_sec = sysconf(_SC_CLK_TCK);
4789 
4790   init_random(1234567);
4791 
4792   Linux::set_page_size(sysconf(_SC_PAGESIZE));
4793   if (Linux::page_size() == -1) {
4794     fatal("os_linux.cpp: os::init: sysconf failed (%s)",
4795           os::strerror(errno));
4796   }
4797   init_page_sizes((size_t) Linux::page_size());
4798 
4799   Linux::initialize_system_info();
4800 
4801   Linux::initialize_os_info();
4802 
4803   // main_thread points to the aboriginal thread
4804   Linux::_main_thread = pthread_self();
4805 
4806   Linux::clock_init();
4807   initial_time_count = javaTimeNanos();
4808 
4809   // retrieve entry point for pthread_setname_np
4810   Linux::_pthread_setname_np =
4811     (int(*)(pthread_t, const char*))dlsym(RTLD_DEFAULT, "pthread_setname_np");
4812 
4813   os::Posix::init();
4814 }
4815 
4816 // To install functions for atexit system call
4817 extern "C" {
4818   static void perfMemory_exit_helper() {
4819     perfMemory_exit();
4820   }
4821 }
4822 
4823 // this is called _after_ the global arguments have been parsed
4824 jint os::init_2(void) {
4825 
4826   os::Posix::init_2();
4827 
4828   Linux::fast_thread_clock_init();
4829 
4830   // Allocate a single page and mark it as readable for safepoint polling
4831   address polling_page = (address) ::mmap(NULL, Linux::page_size(), PROT_READ, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
4832   guarantee(polling_page != MAP_FAILED, "os::init_2: failed to allocate polling page");
4833 
4834   os::set_polling_page(polling_page);
4835   log_info(os)("SafePoint Polling address: " INTPTR_FORMAT, p2i(polling_page));
4836 
4837   if (!UseMembar) {
4838     address mem_serialize_page = (address) ::mmap(NULL, Linux::page_size(), PROT_READ | PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
4839     guarantee(mem_serialize_page != MAP_FAILED, "mmap Failed for memory serialize page");
4840     os::set_memory_serialize_page(mem_serialize_page);
4841     log_info(os)("Memory Serialize Page address: " INTPTR_FORMAT, p2i(mem_serialize_page));
4842   }
4843 
4844   // initialize suspend/resume support - must do this before signal_sets_init()
4845   if (SR_initialize() != 0) {
4846     perror("SR_initialize failed");
4847     return JNI_ERR;
4848   }
4849 
4850   Linux::signal_sets_init();
4851   Linux::install_signal_handlers();
4852 
4853   // Check and sets minimum stack sizes against command line options
4854   if (Posix::set_minimum_stack_sizes() == JNI_ERR) {
4855     return JNI_ERR;
4856   }
4857   Linux::capture_initial_stack(JavaThread::stack_size_at_create());
4858 
4859 #if defined(IA32)
4860   workaround_expand_exec_shield_cs_limit();
4861 #endif
4862 
4863   Linux::libpthread_init();
4864   Linux::sched_getcpu_init();
4865   log_info(os)("HotSpot is running with %s, %s",
4866                Linux::glibc_version(), Linux::libpthread_version());
4867 
4868   if (UseNUMA) {
4869     if (!Linux::libnuma_init()) {
4870       UseNUMA = false;
4871     } else {
4872       if ((Linux::numa_max_node() < 1)) {
4873         // There's only one node(they start from 0), disable NUMA.
4874         UseNUMA = false;
4875       }
4876     }
4877     // With SHM and HugeTLBFS large pages we cannot uncommit a page, so there's no way
4878     // we can make the adaptive lgrp chunk resizing work. If the user specified
4879     // both UseNUMA and UseLargePages (or UseSHM/UseHugeTLBFS) on the command line - warn and
4880     // disable adaptive resizing.
4881     if (UseNUMA && UseLargePages && !can_commit_large_page_memory()) {
4882       if (FLAG_IS_DEFAULT(UseNUMA)) {
4883         UseNUMA = false;
4884       } else {
4885         if (FLAG_IS_DEFAULT(UseLargePages) &&
4886             FLAG_IS_DEFAULT(UseSHM) &&
4887             FLAG_IS_DEFAULT(UseHugeTLBFS)) {
4888           UseLargePages = false;
4889         } else if (UseAdaptiveSizePolicy || UseAdaptiveNUMAChunkSizing) {
4890           warning("UseNUMA is not fully compatible with SHM/HugeTLBFS large pages, disabling adaptive resizing (-XX:-UseAdaptiveSizePolicy -XX:-UseAdaptiveNUMAChunkSizing)");
4891           UseAdaptiveSizePolicy = false;
4892           UseAdaptiveNUMAChunkSizing = false;
4893         }
4894       }
4895     }
4896     if (!UseNUMA && ForceNUMA) {
4897       UseNUMA = true;
4898     }
4899   }
4900 
4901   if (MaxFDLimit) {
4902     // set the number of file descriptors to max. print out error
4903     // if getrlimit/setrlimit fails but continue regardless.
4904     struct rlimit nbr_files;
4905     int status = getrlimit(RLIMIT_NOFILE, &nbr_files);
4906     if (status != 0) {
4907       log_info(os)("os::init_2 getrlimit failed: %s", os::strerror(errno));
4908     } else {
4909       nbr_files.rlim_cur = nbr_files.rlim_max;
4910       status = setrlimit(RLIMIT_NOFILE, &nbr_files);
4911       if (status != 0) {
4912         log_info(os)("os::init_2 setrlimit failed: %s", os::strerror(errno));
4913       }
4914     }
4915   }
4916 
4917   // Initialize lock used to serialize thread creation (see os::create_thread)
4918   Linux::set_createThread_lock(new Mutex(Mutex::leaf, "createThread_lock", false));
4919 
4920   // at-exit methods are called in the reverse order of their registration.
4921   // atexit functions are called on return from main or as a result of a
4922   // call to exit(3C). There can be only 32 of these functions registered
4923   // and atexit() does not set errno.
4924 
4925   if (PerfAllowAtExitRegistration) {
4926     // only register atexit functions if PerfAllowAtExitRegistration is set.
4927     // atexit functions can be delayed until process exit time, which
4928     // can be problematic for embedded VM situations. Embedded VMs should
4929     // call DestroyJavaVM() to assure that VM resources are released.
4930 
4931     // note: perfMemory_exit_helper atexit function may be removed in
4932     // the future if the appropriate cleanup code can be added to the
4933     // VM_Exit VMOperation's doit method.
4934     if (atexit(perfMemory_exit_helper) != 0) {
4935       warning("os::init_2 atexit(perfMemory_exit_helper) failed");
4936     }
4937   }
4938 
4939   // initialize thread priority policy
4940   prio_init();
4941 
4942   if (!FLAG_IS_DEFAULT(AllocateHeapAt)) {
4943     set_coredump_filter(false /*largepages*/, true /*dax_shared*/); 
4944   }
4945   return JNI_OK;
4946 }
4947 
4948 // Mark the polling page as unreadable
4949 void os::make_polling_page_unreadable(void) {
4950   if (!guard_memory((char*)_polling_page, Linux::page_size())) {
4951     fatal("Could not disable polling page");
4952   }
4953 }
4954 
4955 // Mark the polling page as readable
4956 void os::make_polling_page_readable(void) {
4957   if (!linux_mprotect((char *)_polling_page, Linux::page_size(), PROT_READ)) {
4958     fatal("Could not enable polling page");
4959   }
4960 }
4961 
4962 // older glibc versions don't have this macro (which expands to
4963 // an optimized bit-counting function) so we have to roll our own
4964 #ifndef CPU_COUNT
4965 
4966 static int _cpu_count(const cpu_set_t* cpus) {
4967   int count = 0;
4968   // only look up to the number of configured processors
4969   for (int i = 0; i < os::processor_count(); i++) {
4970     if (CPU_ISSET(i, cpus)) {
4971       count++;
4972     }
4973   }
4974   return count;
4975 }
4976 
4977 #define CPU_COUNT(cpus) _cpu_count(cpus)
4978 
4979 #endif // CPU_COUNT
4980 
4981 // Get the current number of available processors for this process.
4982 // This value can change at any time during a process's lifetime.
4983 // sched_getaffinity gives an accurate answer as it accounts for cpusets.
4984 // If it appears there may be more than 1024 processors then we do a
4985 // dynamic check - see 6515172 for details.
4986 // If anything goes wrong we fallback to returning the number of online
4987 // processors - which can be greater than the number available to the process.
4988 int os::active_processor_count() {
4989   cpu_set_t cpus;  // can represent at most 1024 (CPU_SETSIZE) processors
4990   cpu_set_t* cpus_p = &cpus;
4991   int cpus_size = sizeof(cpu_set_t);
4992 
4993   int configured_cpus = processor_count();  // upper bound on available cpus
4994   int cpu_count = 0;
4995 
4996 // old build platforms may not support dynamic cpu sets
4997 #ifdef CPU_ALLOC
4998 
4999   // To enable easy testing of the dynamic path on different platforms we
5000   // introduce a diagnostic flag: UseCpuAllocPath
5001   if (configured_cpus >= CPU_SETSIZE || UseCpuAllocPath) {
5002     // kernel may use a mask bigger than cpu_set_t
5003     log_trace(os)("active_processor_count: using dynamic path %s"
5004                   "- configured processors: %d",
5005                   UseCpuAllocPath ? "(forced) " : "",
5006                   configured_cpus);
5007     cpus_p = CPU_ALLOC(configured_cpus);
5008     if (cpus_p != NULL) {
5009       cpus_size = CPU_ALLOC_SIZE(configured_cpus);
5010       // zero it just to be safe
5011       CPU_ZERO_S(cpus_size, cpus_p);
5012     }
5013     else {
5014        // failed to allocate so fallback to online cpus
5015        int online_cpus = ::sysconf(_SC_NPROCESSORS_ONLN);
5016        log_trace(os)("active_processor_count: "
5017                      "CPU_ALLOC failed (%s) - using "
5018                      "online processor count: %d",
5019                      os::strerror(errno), online_cpus);
5020        return online_cpus;
5021     }
5022   }
5023   else {
5024     log_trace(os)("active_processor_count: using static path - configured processors: %d",
5025                   configured_cpus);
5026   }
5027 #else // CPU_ALLOC
5028 // these stubs won't be executed
5029 #define CPU_COUNT_S(size, cpus) -1
5030 #define CPU_FREE(cpus)
5031 
5032   log_trace(os)("active_processor_count: only static path available - configured processors: %d",
5033                 configured_cpus);
5034 #endif // CPU_ALLOC
5035 
5036   // pid 0 means the current thread - which we have to assume represents the process
5037   if (sched_getaffinity(0, cpus_size, cpus_p) == 0) {
5038     if (cpus_p != &cpus) { // can only be true when CPU_ALLOC used
5039       cpu_count = CPU_COUNT_S(cpus_size, cpus_p);
5040     }
5041     else {
5042       cpu_count = CPU_COUNT(cpus_p);
5043     }
5044     log_trace(os)("active_processor_count: sched_getaffinity processor count: %d", cpu_count);
5045   }
5046   else {
5047     cpu_count = ::sysconf(_SC_NPROCESSORS_ONLN);
5048     warning("sched_getaffinity failed (%s)- using online processor count (%d) "
5049             "which may exceed available processors", os::strerror(errno), cpu_count);
5050   }
5051 
5052   if (cpus_p != &cpus) { // can only be true when CPU_ALLOC used
5053     CPU_FREE(cpus_p);
5054   }
5055 
5056   assert(cpu_count > 0 && cpu_count <= processor_count(), "sanity check");
5057   return cpu_count;
5058 }
5059 
5060 void os::set_native_thread_name(const char *name) {
5061   if (Linux::_pthread_setname_np) {
5062     char buf [16]; // according to glibc manpage, 16 chars incl. '/0'
5063     snprintf(buf, sizeof(buf), "%s", name);
5064     buf[sizeof(buf) - 1] = '\0';
5065     const int rc = Linux::_pthread_setname_np(pthread_self(), buf);
5066     // ERANGE should not happen; all other errors should just be ignored.
5067     assert(rc != ERANGE, "pthread_setname_np failed");
5068   }
5069 }
5070 
5071 bool os::distribute_processes(uint length, uint* distribution) {
5072   // Not yet implemented.
5073   return false;
5074 }
5075 
5076 bool os::bind_to_processor(uint processor_id) {
5077   // Not yet implemented.
5078   return false;
5079 }
5080 
5081 ///
5082 
5083 void os::SuspendedThreadTask::internal_do_task() {
5084   if (do_suspend(_thread->osthread())) {
5085     SuspendedThreadTaskContext context(_thread, _thread->osthread()->ucontext());
5086     do_task(context);
5087     do_resume(_thread->osthread());
5088   }
5089 }
5090 
5091 ////////////////////////////////////////////////////////////////////////////////
5092 // debug support
5093 
5094 bool os::find(address addr, outputStream* st) {
5095   Dl_info dlinfo;
5096   memset(&dlinfo, 0, sizeof(dlinfo));
5097   if (dladdr(addr, &dlinfo) != 0) {
5098     st->print(PTR_FORMAT ": ", p2i(addr));
5099     if (dlinfo.dli_sname != NULL && dlinfo.dli_saddr != NULL) {
5100       st->print("%s+" PTR_FORMAT, dlinfo.dli_sname,
5101                 p2i(addr) - p2i(dlinfo.dli_saddr));
5102     } else if (dlinfo.dli_fbase != NULL) {
5103       st->print("<offset " PTR_FORMAT ">", p2i(addr) - p2i(dlinfo.dli_fbase));
5104     } else {
5105       st->print("<absolute address>");
5106     }
5107     if (dlinfo.dli_fname != NULL) {
5108       st->print(" in %s", dlinfo.dli_fname);
5109     }
5110     if (dlinfo.dli_fbase != NULL) {
5111       st->print(" at " PTR_FORMAT, p2i(dlinfo.dli_fbase));
5112     }
5113     st->cr();
5114 
5115     if (Verbose) {
5116       // decode some bytes around the PC
5117       address begin = clamp_address_in_page(addr-40, addr, os::vm_page_size());
5118       address end   = clamp_address_in_page(addr+40, addr, os::vm_page_size());
5119       address       lowest = (address) dlinfo.dli_sname;
5120       if (!lowest)  lowest = (address) dlinfo.dli_fbase;
5121       if (begin < lowest)  begin = lowest;
5122       Dl_info dlinfo2;
5123       if (dladdr(end, &dlinfo2) != 0 && dlinfo2.dli_saddr != dlinfo.dli_saddr
5124           && end > dlinfo2.dli_saddr && dlinfo2.dli_saddr > begin) {
5125         end = (address) dlinfo2.dli_saddr;
5126       }
5127       Disassembler::decode(begin, end, st);
5128     }
5129     return true;
5130   }
5131   return false;
5132 }
5133 
5134 ////////////////////////////////////////////////////////////////////////////////
5135 // misc
5136 
5137 // This does not do anything on Linux. This is basically a hook for being
5138 // able to use structured exception handling (thread-local exception filters)
5139 // on, e.g., Win32.
5140 void
5141 os::os_exception_wrapper(java_call_t f, JavaValue* value, const methodHandle& method,
5142                          JavaCallArguments* args, Thread* thread) {
5143   f(value, method, args, thread);
5144 }
5145 
5146 void os::print_statistics() {
5147 }
5148 
5149 bool os::message_box(const char* title, const char* message) {
5150   int i;
5151   fdStream err(defaultStream::error_fd());
5152   for (i = 0; i < 78; i++) err.print_raw("=");
5153   err.cr();
5154   err.print_raw_cr(title);
5155   for (i = 0; i < 78; i++) err.print_raw("-");
5156   err.cr();
5157   err.print_raw_cr(message);
5158   for (i = 0; i < 78; i++) err.print_raw("=");
5159   err.cr();
5160 
5161   char buf[16];
5162   // Prevent process from exiting upon "read error" without consuming all CPU
5163   while (::read(0, buf, sizeof(buf)) <= 0) { ::sleep(100); }
5164 
5165   return buf[0] == 'y' || buf[0] == 'Y';
5166 }
5167 
5168 int os::stat(const char *path, struct stat *sbuf) {
5169   char pathbuf[MAX_PATH];
5170   if (strlen(path) > MAX_PATH - 1) {
5171     errno = ENAMETOOLONG;
5172     return -1;
5173   }
5174   os::native_path(strcpy(pathbuf, path));
5175   return ::stat(pathbuf, sbuf);
5176 }
5177 
5178 // Is a (classpath) directory empty?
5179 bool os::dir_is_empty(const char* path) {
5180   DIR *dir = NULL;
5181   struct dirent *ptr;
5182 
5183   dir = opendir(path);
5184   if (dir == NULL) return true;
5185 
5186   // Scan the directory
5187   bool result = true;
5188   char buf[sizeof(struct dirent) + MAX_PATH];
5189   while (result && (ptr = ::readdir(dir)) != NULL) {
5190     if (strcmp(ptr->d_name, ".") != 0 && strcmp(ptr->d_name, "..") != 0) {
5191       result = false;
5192     }
5193   }
5194   closedir(dir);
5195   return result;
5196 }
5197 
5198 // This code originates from JDK's sysOpen and open64_w
5199 // from src/solaris/hpi/src/system_md.c
5200 
5201 int os::open(const char *path, int oflag, int mode) {
5202   if (strlen(path) > MAX_PATH - 1) {
5203     errno = ENAMETOOLONG;
5204     return -1;
5205   }
5206 
5207   // All file descriptors that are opened in the Java process and not
5208   // specifically destined for a subprocess should have the close-on-exec
5209   // flag set.  If we don't set it, then careless 3rd party native code
5210   // might fork and exec without closing all appropriate file descriptors
5211   // (e.g. as we do in closeDescriptors in UNIXProcess.c), and this in
5212   // turn might:
5213   //
5214   // - cause end-of-file to fail to be detected on some file
5215   //   descriptors, resulting in mysterious hangs, or
5216   //
5217   // - might cause an fopen in the subprocess to fail on a system
5218   //   suffering from bug 1085341.
5219   //
5220   // (Yes, the default setting of the close-on-exec flag is a Unix
5221   // design flaw)
5222   //
5223   // See:
5224   // 1085341: 32-bit stdio routines should support file descriptors >255
5225   // 4843136: (process) pipe file descriptor from Runtime.exec not being closed
5226   // 6339493: (process) Runtime.exec does not close all file descriptors on Solaris 9
5227   //
5228   // Modern Linux kernels (after 2.6.23 2007) support O_CLOEXEC with open().
5229   // O_CLOEXEC is preferable to using FD_CLOEXEC on an open file descriptor
5230   // because it saves a system call and removes a small window where the flag
5231   // is unset.  On ancient Linux kernels the O_CLOEXEC flag will be ignored
5232   // and we fall back to using FD_CLOEXEC (see below).
5233 #ifdef O_CLOEXEC
5234   oflag |= O_CLOEXEC;
5235 #endif
5236 
5237   int fd = ::open64(path, oflag, mode);
5238   if (fd == -1) return -1;
5239 
5240   //If the open succeeded, the file might still be a directory
5241   {
5242     struct stat64 buf64;
5243     int ret = ::fstat64(fd, &buf64);
5244     int st_mode = buf64.st_mode;
5245 
5246     if (ret != -1) {
5247       if ((st_mode & S_IFMT) == S_IFDIR) {
5248         errno = EISDIR;
5249         ::close(fd);
5250         return -1;
5251       }
5252     } else {
5253       ::close(fd);
5254       return -1;
5255     }
5256   }
5257 
5258 #ifdef FD_CLOEXEC
5259   // Validate that the use of the O_CLOEXEC flag on open above worked.
5260   // With recent kernels, we will perform this check exactly once.
5261   static sig_atomic_t O_CLOEXEC_is_known_to_work = 0;
5262   if (!O_CLOEXEC_is_known_to_work) {
5263     int flags = ::fcntl(fd, F_GETFD);
5264     if (flags != -1) {
5265       if ((flags & FD_CLOEXEC) != 0)
5266         O_CLOEXEC_is_known_to_work = 1;
5267       else
5268         ::fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
5269     }
5270   }
5271 #endif
5272 
5273   return fd;
5274 }
5275 
5276 
5277 // create binary file, rewriting existing file if required
5278 int os::create_binary_file(const char* path, bool rewrite_existing) {
5279   int oflags = O_WRONLY | O_CREAT;
5280   if (!rewrite_existing) {
5281     oflags |= O_EXCL;
5282   }
5283   return ::open64(path, oflags, S_IREAD | S_IWRITE);
5284 }
5285 
5286 // return current position of file pointer
5287 jlong os::current_file_offset(int fd) {
5288   return (jlong)::lseek64(fd, (off64_t)0, SEEK_CUR);
5289 }
5290 
5291 // move file pointer to the specified offset
5292 jlong os::seek_to_file_offset(int fd, jlong offset) {
5293   return (jlong)::lseek64(fd, (off64_t)offset, SEEK_SET);
5294 }
5295 
5296 // This code originates from JDK's sysAvailable
5297 // from src/solaris/hpi/src/native_threads/src/sys_api_td.c
5298 
5299 int os::available(int fd, jlong *bytes) {
5300   jlong cur, end;
5301   int mode;
5302   struct stat64 buf64;
5303 
5304   if (::fstat64(fd, &buf64) >= 0) {
5305     mode = buf64.st_mode;
5306     if (S_ISCHR(mode) || S_ISFIFO(mode) || S_ISSOCK(mode)) {
5307       int n;
5308       if (::ioctl(fd, FIONREAD, &n) >= 0) {
5309         *bytes = n;
5310         return 1;
5311       }
5312     }
5313   }
5314   if ((cur = ::lseek64(fd, 0L, SEEK_CUR)) == -1) {
5315     return 0;
5316   } else if ((end = ::lseek64(fd, 0L, SEEK_END)) == -1) {
5317     return 0;
5318   } else if (::lseek64(fd, cur, SEEK_SET) == -1) {
5319     return 0;
5320   }
5321   *bytes = end - cur;
5322   return 1;
5323 }
5324 
5325 // Map a block of memory.
5326 char* os::pd_map_memory(int fd, const char* file_name, size_t file_offset,
5327                         char *addr, size_t bytes, bool read_only,
5328                         bool allow_exec) {
5329   int prot;
5330   int flags = MAP_PRIVATE;
5331 
5332   if (read_only) {
5333     prot = PROT_READ;
5334   } else {
5335     prot = PROT_READ | PROT_WRITE;
5336   }
5337 
5338   if (allow_exec) {
5339     prot |= PROT_EXEC;
5340   }
5341 
5342   if (addr != NULL) {
5343     flags |= MAP_FIXED;
5344   }
5345 
5346   char* mapped_address = (char*)mmap(addr, (size_t)bytes, prot, flags,
5347                                      fd, file_offset);
5348   if (mapped_address == MAP_FAILED) {
5349     return NULL;
5350   }
5351   return mapped_address;
5352 }
5353 
5354 
5355 // Remap a block of memory.
5356 char* os::pd_remap_memory(int fd, const char* file_name, size_t file_offset,
5357                           char *addr, size_t bytes, bool read_only,
5358                           bool allow_exec) {
5359   // same as map_memory() on this OS
5360   return os::map_memory(fd, file_name, file_offset, addr, bytes, read_only,
5361                         allow_exec);
5362 }
5363 
5364 
5365 // Unmap a block of memory.
5366 bool os::pd_unmap_memory(char* addr, size_t bytes) {
5367   return munmap(addr, bytes) == 0;
5368 }
5369 
5370 static jlong slow_thread_cpu_time(Thread *thread, bool user_sys_cpu_time);
5371 
5372 static clockid_t thread_cpu_clockid(Thread* thread) {
5373   pthread_t tid = thread->osthread()->pthread_id();
5374   clockid_t clockid;
5375 
5376   // Get thread clockid
5377   int rc = os::Linux::pthread_getcpuclockid(tid, &clockid);
5378   assert(rc == 0, "pthread_getcpuclockid is expected to return 0 code");
5379   return clockid;
5380 }
5381 
5382 // current_thread_cpu_time(bool) and thread_cpu_time(Thread*, bool)
5383 // are used by JVM M&M and JVMTI to get user+sys or user CPU time
5384 // of a thread.
5385 //
5386 // current_thread_cpu_time() and thread_cpu_time(Thread*) returns
5387 // the fast estimate available on the platform.
5388 
5389 jlong os::current_thread_cpu_time() {
5390   if (os::Linux::supports_fast_thread_cpu_time()) {
5391     return os::Linux::fast_thread_cpu_time(CLOCK_THREAD_CPUTIME_ID);
5392   } else {
5393     // return user + sys since the cost is the same
5394     return slow_thread_cpu_time(Thread::current(), true /* user + sys */);
5395   }
5396 }
5397 
5398 jlong os::thread_cpu_time(Thread* thread) {
5399   // consistent with what current_thread_cpu_time() returns
5400   if (os::Linux::supports_fast_thread_cpu_time()) {
5401     return os::Linux::fast_thread_cpu_time(thread_cpu_clockid(thread));
5402   } else {
5403     return slow_thread_cpu_time(thread, true /* user + sys */);
5404   }
5405 }
5406 
5407 jlong os::current_thread_cpu_time(bool user_sys_cpu_time) {
5408   if (user_sys_cpu_time && os::Linux::supports_fast_thread_cpu_time()) {
5409     return os::Linux::fast_thread_cpu_time(CLOCK_THREAD_CPUTIME_ID);
5410   } else {
5411     return slow_thread_cpu_time(Thread::current(), user_sys_cpu_time);
5412   }
5413 }
5414 
5415 jlong os::thread_cpu_time(Thread *thread, bool user_sys_cpu_time) {
5416   if (user_sys_cpu_time && os::Linux::supports_fast_thread_cpu_time()) {
5417     return os::Linux::fast_thread_cpu_time(thread_cpu_clockid(thread));
5418   } else {
5419     return slow_thread_cpu_time(thread, user_sys_cpu_time);
5420   }
5421 }
5422 
5423 //  -1 on error.
5424 static jlong slow_thread_cpu_time(Thread *thread, bool user_sys_cpu_time) {
5425   pid_t  tid = thread->osthread()->thread_id();
5426   char *s;
5427   char stat[2048];
5428   int statlen;
5429   char proc_name[64];
5430   int count;
5431   long sys_time, user_time;
5432   char cdummy;
5433   int idummy;
5434   long ldummy;
5435   FILE *fp;
5436 
5437   snprintf(proc_name, 64, "/proc/self/task/%d/stat", tid);
5438   fp = fopen(proc_name, "r");
5439   if (fp == NULL) return -1;
5440   statlen = fread(stat, 1, 2047, fp);
5441   stat[statlen] = '\0';
5442   fclose(fp);
5443 
5444   // Skip pid and the command string. Note that we could be dealing with
5445   // weird command names, e.g. user could decide to rename java launcher
5446   // to "java 1.4.2 :)", then the stat file would look like
5447   //                1234 (java 1.4.2 :)) R ... ...
5448   // We don't really need to know the command string, just find the last
5449   // occurrence of ")" and then start parsing from there. See bug 4726580.
5450   s = strrchr(stat, ')');
5451   if (s == NULL) return -1;
5452 
5453   // Skip blank chars
5454   do { s++; } while (s && isspace(*s));
5455 
5456   count = sscanf(s,"%c %d %d %d %d %d %lu %lu %lu %lu %lu %lu %lu",
5457                  &cdummy, &idummy, &idummy, &idummy, &idummy, &idummy,
5458                  &ldummy, &ldummy, &ldummy, &ldummy, &ldummy,
5459                  &user_time, &sys_time);
5460   if (count != 13) return -1;
5461   if (user_sys_cpu_time) {
5462     return ((jlong)sys_time + (jlong)user_time) * (1000000000 / clock_tics_per_sec);
5463   } else {
5464     return (jlong)user_time * (1000000000 / clock_tics_per_sec);
5465   }
5466 }
5467 
5468 void os::current_thread_cpu_time_info(jvmtiTimerInfo *info_ptr) {
5469   info_ptr->max_value = ALL_64_BITS;       // will not wrap in less than 64 bits
5470   info_ptr->may_skip_backward = false;     // elapsed time not wall time
5471   info_ptr->may_skip_forward = false;      // elapsed time not wall time
5472   info_ptr->kind = JVMTI_TIMER_TOTAL_CPU;  // user+system time is returned
5473 }
5474 
5475 void os::thread_cpu_time_info(jvmtiTimerInfo *info_ptr) {
5476   info_ptr->max_value = ALL_64_BITS;       // will not wrap in less than 64 bits
5477   info_ptr->may_skip_backward = false;     // elapsed time not wall time
5478   info_ptr->may_skip_forward = false;      // elapsed time not wall time
5479   info_ptr->kind = JVMTI_TIMER_TOTAL_CPU;  // user+system time is returned
5480 }
5481 
5482 bool os::is_thread_cpu_time_supported() {
5483   return true;
5484 }
5485 
5486 // System loadavg support.  Returns -1 if load average cannot be obtained.
5487 // Linux doesn't yet have a (official) notion of processor sets,
5488 // so just return the system wide load average.
5489 int os::loadavg(double loadavg[], int nelem) {
5490   return ::getloadavg(loadavg, nelem);
5491 }
5492 
5493 void os::pause() {
5494   char filename[MAX_PATH];
5495   if (PauseAtStartupFile && PauseAtStartupFile[0]) {
5496     jio_snprintf(filename, MAX_PATH, "%s", PauseAtStartupFile);
5497   } else {
5498     jio_snprintf(filename, MAX_PATH, "./vm.paused.%d", current_process_id());
5499   }
5500 
5501   int fd = ::open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
5502   if (fd != -1) {
5503     struct stat buf;
5504     ::close(fd);
5505     while (::stat(filename, &buf) == 0) {
5506       (void)::poll(NULL, 0, 100);
5507     }
5508   } else {
5509     jio_fprintf(stderr,
5510                 "Could not open pause file '%s', continuing immediately.\n", filename);
5511   }
5512 }
5513 
5514 extern char** environ;
5515 
5516 // Run the specified command in a separate process. Return its exit value,
5517 // or -1 on failure (e.g. can't fork a new process).
5518 // Unlike system(), this function can be called from signal handler. It
5519 // doesn't block SIGINT et al.
5520 int os::fork_and_exec(char* cmd) {
5521   const char * argv[4] = {"sh", "-c", cmd, NULL};
5522 
5523   pid_t pid = fork();
5524 
5525   if (pid < 0) {
5526     // fork failed
5527     return -1;
5528 
5529   } else if (pid == 0) {
5530     // child process
5531 
5532     execve("/bin/sh", (char* const*)argv, environ);
5533 
5534     // execve failed
5535     _exit(-1);
5536 
5537   } else  {
5538     // copied from J2SE ..._waitForProcessExit() in UNIXProcess_md.c; we don't
5539     // care about the actual exit code, for now.
5540 
5541     int status;
5542 
5543     // Wait for the child process to exit.  This returns immediately if
5544     // the child has already exited. */
5545     while (waitpid(pid, &status, 0) < 0) {
5546       switch (errno) {
5547       case ECHILD: return 0;
5548       case EINTR: break;
5549       default: return -1;
5550       }
5551     }
5552 
5553     if (WIFEXITED(status)) {
5554       // The child exited normally; get its exit code.
5555       return WEXITSTATUS(status);
5556     } else if (WIFSIGNALED(status)) {
5557       // The child exited because of a signal
5558       // The best value to return is 0x80 + signal number,
5559       // because that is what all Unix shells do, and because
5560       // it allows callers to distinguish between process exit and
5561       // process death by signal.
5562       return 0x80 + WTERMSIG(status);
5563     } else {
5564       // Unknown exit code; pass it through
5565       return status;
5566     }
5567   }
5568 }
5569 
5570 // is_headless_jre()
5571 //
5572 // Test for the existence of xawt/libmawt.so or libawt_xawt.so
5573 // in order to report if we are running in a headless jre
5574 //
5575 // Since JDK8 xawt/libmawt.so was moved into the same directory
5576 // as libawt.so, and renamed libawt_xawt.so
5577 //
5578 bool os::is_headless_jre() {
5579   struct stat statbuf;
5580   char buf[MAXPATHLEN];
5581   char libmawtpath[MAXPATHLEN];
5582   const char *xawtstr  = "/xawt/libmawt.so";
5583   const char *new_xawtstr = "/libawt_xawt.so";
5584   char *p;
5585 
5586   // Get path to libjvm.so
5587   os::jvm_path(buf, sizeof(buf));
5588 
5589   // Get rid of libjvm.so
5590   p = strrchr(buf, '/');
5591   if (p == NULL) {
5592     return false;
5593   } else {
5594     *p = '\0';
5595   }
5596 
5597   // Get rid of client or server
5598   p = strrchr(buf, '/');
5599   if (p == NULL) {
5600     return false;
5601   } else {
5602     *p = '\0';
5603   }
5604 
5605   // check xawt/libmawt.so
5606   strcpy(libmawtpath, buf);
5607   strcat(libmawtpath, xawtstr);
5608   if (::stat(libmawtpath, &statbuf) == 0) return false;
5609 
5610   // check libawt_xawt.so
5611   strcpy(libmawtpath, buf);
5612   strcat(libmawtpath, new_xawtstr);
5613   if (::stat(libmawtpath, &statbuf) == 0) return false;
5614 
5615   return true;
5616 }
5617 
5618 // Get the default path to the core file
5619 // Returns the length of the string
5620 int os::get_core_path(char* buffer, size_t bufferSize) {
5621   /*
5622    * Max length of /proc/sys/kernel/core_pattern is 128 characters.
5623    * See https://www.kernel.org/doc/Documentation/sysctl/kernel.txt
5624    */
5625   const int core_pattern_len = 129;
5626   char core_pattern[core_pattern_len] = {0};
5627 
5628   int core_pattern_file = ::open("/proc/sys/kernel/core_pattern", O_RDONLY);
5629   if (core_pattern_file == -1) {
5630     return -1;
5631   }
5632 
5633   ssize_t ret = ::read(core_pattern_file, core_pattern, core_pattern_len);
5634   ::close(core_pattern_file);
5635   if (ret <= 0 || ret >= core_pattern_len || core_pattern[0] == '\n') {
5636     return -1;
5637   }
5638   if (core_pattern[ret-1] == '\n') {
5639     core_pattern[ret-1] = '\0';
5640   } else {
5641     core_pattern[ret] = '\0';
5642   }
5643 
5644   char *pid_pos = strstr(core_pattern, "%p");
5645   int written;
5646 
5647   if (core_pattern[0] == '/') {
5648     written = jio_snprintf(buffer, bufferSize, "%s", core_pattern);
5649   } else {
5650     char cwd[PATH_MAX];
5651 
5652     const char* p = get_current_directory(cwd, PATH_MAX);
5653     if (p == NULL) {
5654       return -1;
5655     }
5656 
5657     if (core_pattern[0] == '|') {
5658       written = jio_snprintf(buffer, bufferSize,
5659                              "\"%s\" (or dumping to %s/core.%d)",
5660                              &core_pattern[1], p, current_process_id());
5661     } else {
5662       written = jio_snprintf(buffer, bufferSize, "%s/%s", p, core_pattern);
5663     }
5664   }
5665 
5666   if (written < 0) {
5667     return -1;
5668   }
5669 
5670   if (((size_t)written < bufferSize) && (pid_pos == NULL) && (core_pattern[0] != '|')) {
5671     int core_uses_pid_file = ::open("/proc/sys/kernel/core_uses_pid", O_RDONLY);
5672 
5673     if (core_uses_pid_file != -1) {
5674       char core_uses_pid = 0;
5675       ssize_t ret = ::read(core_uses_pid_file, &core_uses_pid, 1);
5676       ::close(core_uses_pid_file);
5677 
5678       if (core_uses_pid == '1') {
5679         jio_snprintf(buffer + written, bufferSize - written,
5680                                           ".%d", current_process_id());
5681       }
5682     }
5683   }
5684 
5685   return strlen(buffer);
5686 }
5687 
5688 bool os::start_debugging(char *buf, int buflen) {
5689   int len = (int)strlen(buf);
5690   char *p = &buf[len];
5691 
5692   jio_snprintf(p, buflen-len,
5693                "\n\n"
5694                "Do you want to debug the problem?\n\n"
5695                "To debug, run 'gdb /proc/%d/exe %d'; then switch to thread " UINTX_FORMAT " (" INTPTR_FORMAT ")\n"
5696                "Enter 'yes' to launch gdb automatically (PATH must include gdb)\n"
5697                "Otherwise, press RETURN to abort...",
5698                os::current_process_id(), os::current_process_id(),
5699                os::current_thread_id(), os::current_thread_id());
5700 
5701   bool yes = os::message_box("Unexpected Error", buf);
5702 
5703   if (yes) {
5704     // yes, user asked VM to launch debugger
5705     jio_snprintf(buf, sizeof(char)*buflen, "gdb /proc/%d/exe %d",
5706                  os::current_process_id(), os::current_process_id());
5707 
5708     os::fork_and_exec(buf);
5709     yes = false;
5710   }
5711   return yes;
5712 }
5713 
5714 
5715 // Java/Compiler thread:
5716 //
5717 //   Low memory addresses
5718 // P0 +------------------------+
5719 //    |                        |\  Java thread created by VM does not have glibc
5720 //    |    glibc guard page    | - guard page, attached Java thread usually has
5721 //    |                        |/  1 glibc guard page.
5722 // P1 +------------------------+ Thread::stack_base() - Thread::stack_size()
5723 //    |                        |\
5724 //    |  HotSpot Guard Pages   | - red, yellow and reserved pages
5725 //    |                        |/
5726 //    +------------------------+ JavaThread::stack_reserved_zone_base()
5727 //    |                        |\
5728 //    |      Normal Stack      | -
5729 //    |                        |/
5730 // P2 +------------------------+ Thread::stack_base()
5731 //
5732 // Non-Java thread:
5733 //
5734 //   Low memory addresses
5735 // P0 +------------------------+
5736 //    |                        |\
5737 //    |  glibc guard page      | - usually 1 page
5738 //    |                        |/
5739 // P1 +------------------------+ Thread::stack_base() - Thread::stack_size()
5740 //    |                        |\
5741 //    |      Normal Stack      | -
5742 //    |                        |/
5743 // P2 +------------------------+ Thread::stack_base()
5744 //
5745 // ** P1 (aka bottom) and size (P2 = P1 - size) are the address and stack size
5746 //    returned from pthread_attr_getstack().
5747 // ** Due to NPTL implementation error, linux takes the glibc guard page out
5748 //    of the stack size given in pthread_attr. We work around this for
5749 //    threads created by the VM. (We adapt bottom to be P1 and size accordingly.)
5750 //
5751 #ifndef ZERO
5752 static void current_stack_region(address * bottom, size_t * size) {
5753   if (os::Linux::is_initial_thread()) {
5754     // initial thread needs special handling because pthread_getattr_np()
5755     // may return bogus value.
5756     *bottom = os::Linux::initial_thread_stack_bottom();
5757     *size   = os::Linux::initial_thread_stack_size();
5758   } else {
5759     pthread_attr_t attr;
5760 
5761     int rslt = pthread_getattr_np(pthread_self(), &attr);
5762 
5763     // JVM needs to know exact stack location, abort if it fails
5764     if (rslt != 0) {
5765       if (rslt == ENOMEM) {
5766         vm_exit_out_of_memory(0, OOM_MMAP_ERROR, "pthread_getattr_np");
5767       } else {
5768         fatal("pthread_getattr_np failed with error = %d", rslt);
5769       }
5770     }
5771 
5772     if (pthread_attr_getstack(&attr, (void **)bottom, size) != 0) {
5773       fatal("Cannot locate current stack attributes!");
5774     }
5775 
5776     // Work around NPTL stack guard error.
5777     size_t guard_size = 0;
5778     rslt = pthread_attr_getguardsize(&attr, &guard_size);
5779     if (rslt != 0) {
5780       fatal("pthread_attr_getguardsize failed with error = %d", rslt);
5781     }
5782     *bottom += guard_size;
5783     *size   -= guard_size;
5784 
5785     pthread_attr_destroy(&attr);
5786 
5787   }
5788   assert(os::current_stack_pointer() >= *bottom &&
5789          os::current_stack_pointer() < *bottom + *size, "just checking");
5790 }
5791 
5792 address os::current_stack_base() {
5793   address bottom;
5794   size_t size;
5795   current_stack_region(&bottom, &size);
5796   return (bottom + size);
5797 }
5798 
5799 size_t os::current_stack_size() {
5800   // This stack size includes the usable stack and HotSpot guard pages
5801   // (for the threads that have Hotspot guard pages).
5802   address bottom;
5803   size_t size;
5804   current_stack_region(&bottom, &size);
5805   return size;
5806 }
5807 #endif
5808 
5809 static inline struct timespec get_mtime(const char* filename) {
5810   struct stat st;
5811   int ret = os::stat(filename, &st);
5812   assert(ret == 0, "failed to stat() file '%s': %s", filename, strerror(errno));
5813   return st.st_mtim;
5814 }
5815 
5816 int os::compare_file_modified_times(const char* file1, const char* file2) {
5817   struct timespec filetime1 = get_mtime(file1);
5818   struct timespec filetime2 = get_mtime(file2);
5819   int diff = filetime1.tv_sec - filetime2.tv_sec;
5820   if (diff == 0) {
5821     return filetime1.tv_nsec - filetime2.tv_nsec;
5822   }
5823   return diff;
5824 }
5825 
5826 /////////////// Unit tests ///////////////
5827 
5828 #ifndef PRODUCT
5829 
5830 #define test_log(...)              \
5831   do {                             \
5832     if (VerboseInternalVMTests) {  \
5833       tty->print_cr(__VA_ARGS__);  \
5834       tty->flush();                \
5835     }                              \
5836   } while (false)
5837 
5838 class TestReserveMemorySpecial : AllStatic {
5839  public:
5840   static void small_page_write(void* addr, size_t size) {
5841     size_t page_size = os::vm_page_size();
5842 
5843     char* end = (char*)addr + size;
5844     for (char* p = (char*)addr; p < end; p += page_size) {
5845       *p = 1;
5846     }
5847   }
5848 
5849   static void test_reserve_memory_special_huge_tlbfs_only(size_t size) {
5850     if (!UseHugeTLBFS) {
5851       return;
5852     }
5853 
5854     test_log("test_reserve_memory_special_huge_tlbfs_only(" SIZE_FORMAT ")", size);
5855 
5856     char* addr = os::Linux::reserve_memory_special_huge_tlbfs_only(size, NULL, false);
5857 
5858     if (addr != NULL) {
5859       small_page_write(addr, size);
5860 
5861       os::Linux::release_memory_special_huge_tlbfs(addr, size);
5862     }
5863   }
5864 
5865   static void test_reserve_memory_special_huge_tlbfs_only() {
5866     if (!UseHugeTLBFS) {
5867       return;
5868     }
5869 
5870     size_t lp = os::large_page_size();
5871 
5872     for (size_t size = lp; size <= lp * 10; size += lp) {
5873       test_reserve_memory_special_huge_tlbfs_only(size);
5874     }
5875   }
5876 
5877   static void test_reserve_memory_special_huge_tlbfs_mixed() {
5878     size_t lp = os::large_page_size();
5879     size_t ag = os::vm_allocation_granularity();
5880 
5881     // sizes to test
5882     const size_t sizes[] = {
5883       lp, lp + ag, lp + lp / 2, lp * 2,
5884       lp * 2 + ag, lp * 2 - ag, lp * 2 + lp / 2,
5885       lp * 10, lp * 10 + lp / 2
5886     };
5887     const int num_sizes = sizeof(sizes) / sizeof(size_t);
5888 
5889     // For each size/alignment combination, we test three scenarios:
5890     // 1) with req_addr == NULL
5891     // 2) with a non-null req_addr at which we expect to successfully allocate
5892     // 3) with a non-null req_addr which contains a pre-existing mapping, at which we
5893     //    expect the allocation to either fail or to ignore req_addr
5894 
5895     // Pre-allocate two areas; they shall be as large as the largest allocation
5896     //  and aligned to the largest alignment we will be testing.
5897     const size_t mapping_size = sizes[num_sizes - 1] * 2;
5898     char* const mapping1 = (char*) ::mmap(NULL, mapping_size,
5899       PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE,
5900       -1, 0);
5901     assert(mapping1 != MAP_FAILED, "should work");
5902 
5903     char* const mapping2 = (char*) ::mmap(NULL, mapping_size,
5904       PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE,
5905       -1, 0);
5906     assert(mapping2 != MAP_FAILED, "should work");
5907 
5908     // Unmap the first mapping, but leave the second mapping intact: the first
5909     // mapping will serve as a value for a "good" req_addr (case 2). The second
5910     // mapping, still intact, as "bad" req_addr (case 3).
5911     ::munmap(mapping1, mapping_size);
5912 
5913     // Case 1
5914     test_log("%s, req_addr NULL:", __FUNCTION__);
5915     test_log("size            align           result");
5916 
5917     for (int i = 0; i < num_sizes; i++) {
5918       const size_t size = sizes[i];
5919       for (size_t alignment = ag; is_aligned(size, alignment); alignment *= 2) {
5920         char* p = os::Linux::reserve_memory_special_huge_tlbfs_mixed(size, alignment, NULL, false);
5921         test_log(SIZE_FORMAT_HEX " " SIZE_FORMAT_HEX " ->  " PTR_FORMAT " %s",
5922                  size, alignment, p2i(p), (p != NULL ? "" : "(failed)"));
5923         if (p != NULL) {
5924           assert(is_aligned(p, alignment), "must be");
5925           small_page_write(p, size);
5926           os::Linux::release_memory_special_huge_tlbfs(p, size);
5927         }
5928       }
5929     }
5930 
5931     // Case 2
5932     test_log("%s, req_addr non-NULL:", __FUNCTION__);
5933     test_log("size            align           req_addr         result");
5934 
5935     for (int i = 0; i < num_sizes; i++) {
5936       const size_t size = sizes[i];
5937       for (size_t alignment = ag; is_aligned(size, alignment); alignment *= 2) {
5938         char* const req_addr = align_up(mapping1, alignment);
5939         char* p = os::Linux::reserve_memory_special_huge_tlbfs_mixed(size, alignment, req_addr, false);
5940         test_log(SIZE_FORMAT_HEX " " SIZE_FORMAT_HEX " " PTR_FORMAT " ->  " PTR_FORMAT " %s",
5941                  size, alignment, p2i(req_addr), p2i(p),
5942                  ((p != NULL ? (p == req_addr ? "(exact match)" : "") : "(failed)")));
5943         if (p != NULL) {
5944           assert(p == req_addr, "must be");
5945           small_page_write(p, size);
5946           os::Linux::release_memory_special_huge_tlbfs(p, size);
5947         }
5948       }
5949     }
5950 
5951     // Case 3
5952     test_log("%s, req_addr non-NULL with preexisting mapping:", __FUNCTION__);
5953     test_log("size            align           req_addr         result");
5954 
5955     for (int i = 0; i < num_sizes; i++) {
5956       const size_t size = sizes[i];
5957       for (size_t alignment = ag; is_aligned(size, alignment); alignment *= 2) {
5958         char* const req_addr = align_up(mapping2, alignment);
5959         char* p = os::Linux::reserve_memory_special_huge_tlbfs_mixed(size, alignment, req_addr, false);
5960         test_log(SIZE_FORMAT_HEX " " SIZE_FORMAT_HEX " " PTR_FORMAT " ->  " PTR_FORMAT " %s",
5961                  size, alignment, p2i(req_addr), p2i(p), ((p != NULL ? "" : "(failed)")));
5962         // as the area around req_addr contains already existing mappings, the API should always
5963         // return NULL (as per contract, it cannot return another address)
5964         assert(p == NULL, "must be");
5965       }
5966     }
5967 
5968     ::munmap(mapping2, mapping_size);
5969 
5970   }
5971 
5972   static void test_reserve_memory_special_huge_tlbfs() {
5973     if (!UseHugeTLBFS) {
5974       return;
5975     }
5976 
5977     test_reserve_memory_special_huge_tlbfs_only();
5978     test_reserve_memory_special_huge_tlbfs_mixed();
5979   }
5980 
5981   static void test_reserve_memory_special_shm(size_t size, size_t alignment) {
5982     if (!UseSHM) {
5983       return;
5984     }
5985 
5986     test_log("test_reserve_memory_special_shm(" SIZE_FORMAT ", " SIZE_FORMAT ")", size, alignment);
5987 
5988     char* addr = os::Linux::reserve_memory_special_shm(size, alignment, NULL, false);
5989 
5990     if (addr != NULL) {
5991       assert(is_aligned(addr, alignment), "Check");
5992       assert(is_aligned(addr, os::large_page_size()), "Check");
5993 
5994       small_page_write(addr, size);
5995 
5996       os::Linux::release_memory_special_shm(addr, size);
5997     }
5998   }
5999 
6000   static void test_reserve_memory_special_shm() {
6001     size_t lp = os::large_page_size();
6002     size_t ag = os::vm_allocation_granularity();
6003 
6004     for (size_t size = ag; size < lp * 3; size += ag) {
6005       for (size_t alignment = ag; is_aligned(size, alignment); alignment *= 2) {
6006         test_reserve_memory_special_shm(size, alignment);
6007       }
6008     }
6009   }
6010 
6011   static void test() {
6012     test_reserve_memory_special_huge_tlbfs();
6013     test_reserve_memory_special_shm();
6014   }
6015 };
6016 
6017 void TestReserveMemorySpecial_test() {
6018   TestReserveMemorySpecial::test();
6019 }
6020 
6021 #endif