1 /*
   2  * Copyright (c) 1997, 2019, 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 #include "precompiled.hpp"
  26 #include "jvm.h"
  27 #include "classfile/classLoader.hpp"
  28 #include "classfile/javaClasses.hpp"
  29 #include "classfile/moduleEntry.hpp"
  30 #include "classfile/systemDictionary.hpp"
  31 #include "classfile/vmSymbols.hpp"
  32 #include "code/codeCache.hpp"
  33 #include "code/icBuffer.hpp"
  34 #include "code/vtableStubs.hpp"
  35 #include "gc/shared/gcVMOperations.hpp"
  36 #include "logging/log.hpp"
  37 #include "interpreter/interpreter.hpp"
  38 #include "logging/log.hpp"
  39 #include "logging/logStream.hpp"
  40 #include "memory/allocation.inline.hpp"
  41 #include "memory/guardedMemory.hpp"
  42 #include "memory/resourceArea.hpp"
  43 #include "memory/universe.hpp"
  44 #include "oops/compressedOops.inline.hpp"
  45 #include "oops/oop.inline.hpp"
  46 #include "prims/jvm_misc.hpp"
  47 #include "runtime/arguments.hpp"
  48 #include "runtime/atomic.hpp"
  49 #include "runtime/frame.inline.hpp"
  50 #include "runtime/handles.inline.hpp"
  51 #include "runtime/interfaceSupport.inline.hpp"
  52 #include "runtime/java.hpp"
  53 #include "runtime/javaCalls.hpp"
  54 #include "runtime/mutexLocker.hpp"
  55 #include "runtime/os.inline.hpp"
  56 #include "runtime/sharedRuntime.hpp"
  57 #include "runtime/stubRoutines.hpp"
  58 #include "runtime/thread.inline.hpp"
  59 #include "runtime/threadSMR.hpp"
  60 #include "runtime/vm_version.hpp"
  61 #include "services/attachListener.hpp"
  62 #include "services/mallocTracker.hpp"
  63 #include "services/memTracker.hpp"
  64 #include "services/nmtCommon.hpp"
  65 #include "services/threadService.hpp"
  66 #include "utilities/align.hpp"
  67 #include "utilities/defaultStream.hpp"
  68 #include "utilities/events.hpp"
  69 
  70 # include <signal.h>
  71 # include <errno.h>
  72 
  73 OSThread*         os::_starting_thread    = NULL;
  74 address           os::_polling_page       = NULL;
  75 volatile unsigned int os::_rand_seed      = 1;
  76 int               os::_processor_count    = 0;
  77 int               os::_initial_active_processor_count = 0;
  78 size_t            os::_page_sizes[os::page_sizes_max];
  79 
  80 #ifndef PRODUCT
  81 julong os::num_mallocs = 0;         // # of calls to malloc/realloc
  82 julong os::alloc_bytes = 0;         // # of bytes allocated
  83 julong os::num_frees = 0;           // # of calls to free
  84 julong os::free_bytes = 0;          // # of bytes freed
  85 #endif
  86 
  87 static size_t cur_malloc_words = 0;  // current size for MallocMaxTestWords
  88 
  89 DEBUG_ONLY(bool os::_mutex_init_done = false;)
  90 
  91 void os_init_globals() {
  92   // Called from init_globals().
  93   // See Threads::create_vm() in thread.cpp, and init.cpp.
  94   os::init_globals();
  95 }
  96 
  97 static time_t get_timezone(const struct tm* time_struct) {
  98 #if defined(_ALLBSD_SOURCE)
  99   return time_struct->tm_gmtoff;
 100 #elif defined(_WINDOWS)
 101   long zone;
 102   _get_timezone(&zone);
 103   return static_cast<time_t>(zone);
 104 #else
 105   return timezone;
 106 #endif
 107 }
 108 
 109 int os::snprintf(char* buf, size_t len, const char* fmt, ...) {
 110   va_list args;
 111   va_start(args, fmt);
 112   int result = os::vsnprintf(buf, len, fmt, args);
 113   va_end(args);
 114   return result;
 115 }
 116 
 117 // Fill in buffer with current local time as an ISO-8601 string.
 118 // E.g., yyyy-mm-ddThh:mm:ss-zzzz.
 119 // Returns buffer, or NULL if it failed.
 120 // This would mostly be a call to
 121 //     strftime(...., "%Y-%m-%d" "T" "%H:%M:%S" "%z", ....)
 122 // except that on Windows the %z behaves badly, so we do it ourselves.
 123 // Also, people wanted milliseconds on there,
 124 // and strftime doesn't do milliseconds.
 125 char* os::iso8601_time(char* buffer, size_t buffer_length, bool utc) {
 126   // Output will be of the form "YYYY-MM-DDThh:mm:ss.mmm+zzzz\0"
 127   //                                      1         2
 128   //                             12345678901234567890123456789
 129   // format string: "%04d-%02d-%02dT%02d:%02d:%02d.%03d%c%02d%02d"
 130   static const size_t needed_buffer = 29;
 131 
 132   // Sanity check the arguments
 133   if (buffer == NULL) {
 134     assert(false, "NULL buffer");
 135     return NULL;
 136   }
 137   if (buffer_length < needed_buffer) {
 138     assert(false, "buffer_length too small");
 139     return NULL;
 140   }
 141   // Get the current time
 142   jlong milliseconds_since_19700101 = javaTimeMillis();
 143   const int milliseconds_per_microsecond = 1000;
 144   const time_t seconds_since_19700101 =
 145     milliseconds_since_19700101 / milliseconds_per_microsecond;
 146   const int milliseconds_after_second =
 147     milliseconds_since_19700101 % milliseconds_per_microsecond;
 148   // Convert the time value to a tm and timezone variable
 149   struct tm time_struct;
 150   if (utc) {
 151     if (gmtime_pd(&seconds_since_19700101, &time_struct) == NULL) {
 152       assert(false, "Failed gmtime_pd");
 153       return NULL;
 154     }
 155   } else {
 156     if (localtime_pd(&seconds_since_19700101, &time_struct) == NULL) {
 157       assert(false, "Failed localtime_pd");
 158       return NULL;
 159     }
 160   }
 161   const time_t zone = get_timezone(&time_struct);
 162 
 163   // If daylight savings time is in effect,
 164   // we are 1 hour East of our time zone
 165   const time_t seconds_per_minute = 60;
 166   const time_t minutes_per_hour = 60;
 167   const time_t seconds_per_hour = seconds_per_minute * minutes_per_hour;
 168   time_t UTC_to_local = zone;
 169   if (time_struct.tm_isdst > 0) {
 170     UTC_to_local = UTC_to_local - seconds_per_hour;
 171   }
 172 
 173   // No offset when dealing with UTC
 174   if (utc) {
 175     UTC_to_local = 0;
 176   }
 177 
 178   // Compute the time zone offset.
 179   //    localtime_pd() sets timezone to the difference (in seconds)
 180   //    between UTC and and local time.
 181   //    ISO 8601 says we need the difference between local time and UTC,
 182   //    we change the sign of the localtime_pd() result.
 183   const time_t local_to_UTC = -(UTC_to_local);
 184   // Then we have to figure out if if we are ahead (+) or behind (-) UTC.
 185   char sign_local_to_UTC = '+';
 186   time_t abs_local_to_UTC = local_to_UTC;
 187   if (local_to_UTC < 0) {
 188     sign_local_to_UTC = '-';
 189     abs_local_to_UTC = -(abs_local_to_UTC);
 190   }
 191   // Convert time zone offset seconds to hours and minutes.
 192   const time_t zone_hours = (abs_local_to_UTC / seconds_per_hour);
 193   const time_t zone_min =
 194     ((abs_local_to_UTC % seconds_per_hour) / seconds_per_minute);
 195 
 196   // Print an ISO 8601 date and time stamp into the buffer
 197   const int year = 1900 + time_struct.tm_year;
 198   const int month = 1 + time_struct.tm_mon;
 199   const int printed = jio_snprintf(buffer, buffer_length,
 200                                    "%04d-%02d-%02dT%02d:%02d:%02d.%03d%c%02d%02d",
 201                                    year,
 202                                    month,
 203                                    time_struct.tm_mday,
 204                                    time_struct.tm_hour,
 205                                    time_struct.tm_min,
 206                                    time_struct.tm_sec,
 207                                    milliseconds_after_second,
 208                                    sign_local_to_UTC,
 209                                    zone_hours,
 210                                    zone_min);
 211   if (printed == 0) {
 212     assert(false, "Failed jio_printf");
 213     return NULL;
 214   }
 215   return buffer;
 216 }
 217 
 218 OSReturn os::set_priority(Thread* thread, ThreadPriority p) {
 219   debug_only(Thread::check_for_dangling_thread_pointer(thread);)
 220 
 221   if ((p >= MinPriority && p <= MaxPriority) ||
 222       (p == CriticalPriority && thread->is_ConcurrentGC_thread())) {
 223     int priority = java_to_os_priority[p];
 224     return set_native_priority(thread, priority);
 225   } else {
 226     assert(false, "Should not happen");
 227     return OS_ERR;
 228   }
 229 }
 230 
 231 // The mapping from OS priority back to Java priority may be inexact because
 232 // Java priorities can map M:1 with native priorities. If you want the definite
 233 // Java priority then use JavaThread::java_priority()
 234 OSReturn os::get_priority(const Thread* const thread, ThreadPriority& priority) {
 235   int p;
 236   int os_prio;
 237   OSReturn ret = get_native_priority(thread, &os_prio);
 238   if (ret != OS_OK) return ret;
 239 
 240   if (java_to_os_priority[MaxPriority] > java_to_os_priority[MinPriority]) {
 241     for (p = MaxPriority; p > MinPriority && java_to_os_priority[p] > os_prio; p--) ;
 242   } else {
 243     // niceness values are in reverse order
 244     for (p = MaxPriority; p > MinPriority && java_to_os_priority[p] < os_prio; p--) ;
 245   }
 246   priority = (ThreadPriority)p;
 247   return OS_OK;
 248 }
 249 
 250 bool os::dll_build_name(char* buffer, size_t size, const char* fname) {
 251   int n = jio_snprintf(buffer, size, "%s%s%s", JNI_LIB_PREFIX, fname, JNI_LIB_SUFFIX);
 252   return (n != -1);
 253 }
 254 
 255 #if !defined(LINUX) && !defined(_WINDOWS)
 256 bool os::committed_in_range(address start, size_t size, address& committed_start, size_t& committed_size) {
 257   committed_start = start;
 258   committed_size = size;
 259   return true;
 260 }
 261 #endif
 262 
 263 // Helper for dll_locate_lib.
 264 // Pass buffer and printbuffer as we already printed the path to buffer
 265 // when we called get_current_directory. This way we avoid another buffer
 266 // of size MAX_PATH.
 267 static bool conc_path_file_and_check(char *buffer, char *printbuffer, size_t printbuflen,
 268                                      const char* pname, char lastchar, const char* fname) {
 269 
 270   // Concatenate path and file name, but don't print double path separators.
 271   const char *filesep = (WINDOWS_ONLY(lastchar == ':' ||) lastchar == os::file_separator()[0]) ?
 272                         "" : os::file_separator();
 273   int ret = jio_snprintf(printbuffer, printbuflen, "%s%s%s", pname, filesep, fname);
 274   // Check whether file exists.
 275   if (ret != -1) {
 276     struct stat statbuf;
 277     return os::stat(buffer, &statbuf) == 0;
 278   }
 279   return false;
 280 }
 281 
 282 bool os::dll_locate_lib(char *buffer, size_t buflen,
 283                         const char* pname, const char* fname) {
 284   bool retval = false;
 285 
 286   size_t fullfnamelen = strlen(JNI_LIB_PREFIX) + strlen(fname) + strlen(JNI_LIB_SUFFIX);
 287   char* fullfname = (char*)NEW_C_HEAP_ARRAY(char, fullfnamelen + 1, mtInternal);
 288   if (dll_build_name(fullfname, fullfnamelen + 1, fname)) {
 289     const size_t pnamelen = pname ? strlen(pname) : 0;
 290 
 291     if (pnamelen == 0) {
 292       // If no path given, use current working directory.
 293       const char* p = get_current_directory(buffer, buflen);
 294       if (p != NULL) {
 295         const size_t plen = strlen(buffer);
 296         const char lastchar = buffer[plen - 1];
 297         retval = conc_path_file_and_check(buffer, &buffer[plen], buflen - plen,
 298                                           "", lastchar, fullfname);
 299       }
 300     } else if (strchr(pname, *os::path_separator()) != NULL) {
 301       // A list of paths. Search for the path that contains the library.
 302       int n;
 303       char** pelements = split_path(pname, &n);
 304       if (pelements != NULL) {
 305         for (int i = 0; i < n; i++) {
 306           char* path = pelements[i];
 307           // Really shouldn't be NULL, but check can't hurt.
 308           size_t plen = (path == NULL) ? 0 : strlen(path);
 309           if (plen == 0) {
 310             continue; // Skip the empty path values.
 311           }
 312           const char lastchar = path[plen - 1];
 313           retval = conc_path_file_and_check(buffer, buffer, buflen, path, lastchar, fullfname);
 314           if (retval) break;
 315         }
 316         // Release the storage allocated by split_path.
 317         for (int i = 0; i < n; i++) {
 318           if (pelements[i] != NULL) {
 319             FREE_C_HEAP_ARRAY(char, pelements[i]);
 320           }
 321         }
 322         FREE_C_HEAP_ARRAY(char*, pelements);
 323       }
 324     } else {
 325       // A definite path.
 326       const char lastchar = pname[pnamelen-1];
 327       retval = conc_path_file_and_check(buffer, buffer, buflen, pname, lastchar, fullfname);
 328     }
 329   }
 330 
 331   FREE_C_HEAP_ARRAY(char*, fullfname);
 332   return retval;
 333 }
 334 
 335 // --------------------- sun.misc.Signal (optional) ---------------------
 336 
 337 
 338 // SIGBREAK is sent by the keyboard to query the VM state
 339 #ifndef SIGBREAK
 340 #define SIGBREAK SIGQUIT
 341 #endif
 342 
 343 // sigexitnum_pd is a platform-specific special signal used for terminating the Signal thread.
 344 
 345 
 346 static void signal_thread_entry(JavaThread* thread, TRAPS) {
 347   os::set_priority(thread, NearMaxPriority);
 348   while (true) {
 349     int sig;
 350     {
 351       // FIXME : Currently we have not decided what should be the status
 352       //         for this java thread blocked here. Once we decide about
 353       //         that we should fix this.
 354       sig = os::signal_wait();
 355     }
 356     if (sig == os::sigexitnum_pd()) {
 357        // Terminate the signal thread
 358        return;
 359     }
 360 
 361     switch (sig) {
 362       case SIGBREAK: {
 363         // Check if the signal is a trigger to start the Attach Listener - in that
 364         // case don't print stack traces.
 365         if (!DisableAttachMechanism) {
 366           // Attempt to transit state to AL_INITIALIZING.
 367           AttachListenerState cur_state = AttachListener::transit_state(AL_INITIALIZING, AL_NOT_INITIALIZED);
 368           if (cur_state == AL_INITIALIZING) {
 369             // Attach Listener has been started to initialize. Ignore this signal.
 370             continue;
 371           } else if (cur_state == AL_NOT_INITIALIZED) {
 372             // Start to initialize.
 373             if (!AttachListener::is_init_trigger()) {
 374               // Attach Listener could not be started.
 375               // So we need to transit the state to AL_NOT_INITIALIZED.
 376               AttachListener::set_state(AL_NOT_INITIALIZED);
 377             }
 378             continue;
 379           } else if (AttachListener::check_socket_file()) {
 380             // Attach Listener has been started, but unix domain socket file
 381             // does not exist. So restart Attach Listener.
 382             continue;
 383           }
 384         }
 385         // Print stack traces
 386         // Any SIGBREAK operations added here should make sure to flush
 387         // the output stream (e.g. tty->flush()) after output.  See 4803766.
 388         // Each module also prints an extra carriage return after its output.
 389         VM_PrintThreads op;
 390         VMThread::execute(&op);
 391         VM_PrintJNI jni_op;
 392         VMThread::execute(&jni_op);
 393         VM_FindDeadlocks op1(tty);
 394         VMThread::execute(&op1);
 395         Universe::print_heap_at_SIGBREAK();
 396         if (PrintClassHistogram) {
 397           VM_GC_HeapInspection op1(tty, true /* force full GC before heap inspection */);
 398           VMThread::execute(&op1);
 399         }
 400         if (JvmtiExport::should_post_data_dump()) {
 401           JvmtiExport::post_data_dump();
 402         }
 403         break;
 404       }
 405       default: {
 406         // Dispatch the signal to java
 407         HandleMark hm(THREAD);
 408         Klass* klass = SystemDictionary::resolve_or_null(vmSymbols::jdk_internal_misc_Signal(), THREAD);
 409         if (klass != NULL) {
 410           JavaValue result(T_VOID);
 411           JavaCallArguments args;
 412           args.push_int(sig);
 413           JavaCalls::call_static(
 414             &result,
 415             klass,
 416             vmSymbols::dispatch_name(),
 417             vmSymbols::int_void_signature(),
 418             &args,
 419             THREAD
 420           );
 421         }
 422         if (HAS_PENDING_EXCEPTION) {
 423           // tty is initialized early so we don't expect it to be null, but
 424           // if it is we can't risk doing an initialization that might
 425           // trigger additional out-of-memory conditions
 426           if (tty != NULL) {
 427             char klass_name[256];
 428             char tmp_sig_name[16];
 429             const char* sig_name = "UNKNOWN";
 430             InstanceKlass::cast(PENDING_EXCEPTION->klass())->
 431               name()->as_klass_external_name(klass_name, 256);
 432             if (os::exception_name(sig, tmp_sig_name, 16) != NULL)
 433               sig_name = tmp_sig_name;
 434             warning("Exception %s occurred dispatching signal %s to handler"
 435                     "- the VM may need to be forcibly terminated",
 436                     klass_name, sig_name );
 437           }
 438           CLEAR_PENDING_EXCEPTION;
 439         }
 440       }
 441     }
 442   }
 443 }
 444 
 445 void os::init_before_ergo() {
 446   initialize_initial_active_processor_count();
 447   // We need to initialize large page support here because ergonomics takes some
 448   // decisions depending on large page support and the calculated large page size.
 449   large_page_init();
 450 
 451   // We need to adapt the configured number of stack protection pages given
 452   // in 4K pages to the actual os page size. We must do this before setting
 453   // up minimal stack sizes etc. in os::init_2().
 454   JavaThread::set_stack_red_zone_size     (align_up(StackRedPages      * 4 * K, vm_page_size()));
 455   JavaThread::set_stack_yellow_zone_size  (align_up(StackYellowPages   * 4 * K, vm_page_size()));
 456   JavaThread::set_stack_reserved_zone_size(align_up(StackReservedPages * 4 * K, vm_page_size()));
 457   JavaThread::set_stack_shadow_zone_size  (align_up(StackShadowPages   * 4 * K, vm_page_size()));
 458 
 459   // VM version initialization identifies some characteristics of the
 460   // platform that are used during ergonomic decisions.
 461   VM_Version::init_before_ergo();
 462 }
 463 
 464 void os::initialize_jdk_signal_support(TRAPS) {
 465   if (!ReduceSignalUsage) {
 466     // Setup JavaThread for processing signals
 467     const char thread_name[] = "Signal Dispatcher";
 468     Handle string = java_lang_String::create_from_str(thread_name, CHECK);
 469 
 470     // Initialize thread_oop to put it into the system threadGroup
 471     Handle thread_group (THREAD, Universe::system_thread_group());
 472     Handle thread_oop = JavaCalls::construct_new_instance(SystemDictionary::Thread_klass(),
 473                            vmSymbols::threadgroup_string_void_signature(),
 474                            thread_group,
 475                            string,
 476                            CHECK);
 477 
 478     Klass* group = SystemDictionary::ThreadGroup_klass();
 479     JavaValue result(T_VOID);
 480     JavaCalls::call_special(&result,
 481                             thread_group,
 482                             group,
 483                             vmSymbols::add_method_name(),
 484                             vmSymbols::thread_void_signature(),
 485                             thread_oop,
 486                             CHECK);
 487 
 488     { MutexLocker mu(Threads_lock);
 489       JavaThread* signal_thread = new JavaThread(&signal_thread_entry);
 490 
 491       // At this point it may be possible that no osthread was created for the
 492       // JavaThread due to lack of memory. We would have to throw an exception
 493       // in that case. However, since this must work and we do not allow
 494       // exceptions anyway, check and abort if this fails.
 495       if (signal_thread == NULL || signal_thread->osthread() == NULL) {
 496         vm_exit_during_initialization("java.lang.OutOfMemoryError",
 497                                       os::native_thread_creation_failed_msg());
 498       }
 499 
 500       java_lang_Thread::set_thread(thread_oop(), signal_thread);
 501       java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);
 502       java_lang_Thread::set_daemon(thread_oop());
 503 
 504       signal_thread->set_threadObj(thread_oop());
 505       Threads::add(signal_thread);
 506       Thread::start(signal_thread);
 507     }
 508     // Handle ^BREAK
 509     os::signal(SIGBREAK, os::user_handler());
 510   }
 511 }
 512 
 513 
 514 void os::terminate_signal_thread() {
 515   if (!ReduceSignalUsage)
 516     signal_notify(sigexitnum_pd());
 517 }
 518 
 519 
 520 // --------------------- loading libraries ---------------------
 521 
 522 typedef jint (JNICALL *JNI_OnLoad_t)(JavaVM *, void *);
 523 extern struct JavaVM_ main_vm;
 524 
 525 static void* _native_java_library = NULL;
 526 
 527 void* os::native_java_library() {
 528   if (_native_java_library == NULL) {
 529     char buffer[JVM_MAXPATHLEN];
 530     char ebuf[1024];
 531 
 532     // Try to load verify dll first. In 1.3 java dll depends on it and is not
 533     // always able to find it when the loading executable is outside the JDK.
 534     // In order to keep working with 1.2 we ignore any loading errors.
 535     if (dll_locate_lib(buffer, sizeof(buffer), Arguments::get_dll_dir(),
 536                        "verify")) {
 537       dll_load(buffer, ebuf, sizeof(ebuf));
 538     }
 539 
 540     // Load java dll
 541     if (dll_locate_lib(buffer, sizeof(buffer), Arguments::get_dll_dir(),
 542                        "java")) {
 543       _native_java_library = dll_load(buffer, ebuf, sizeof(ebuf));
 544     }
 545     if (_native_java_library == NULL) {
 546       vm_exit_during_initialization("Unable to load native library", ebuf);
 547     }
 548 
 549 #if defined(__OpenBSD__)
 550     // Work-around OpenBSD's lack of $ORIGIN support by pre-loading libnet.so
 551     // ignore errors
 552     if (dll_locate_lib(buffer, sizeof(buffer), Arguments::get_dll_dir(),
 553                        "net")) {
 554       dll_load(buffer, ebuf, sizeof(ebuf));
 555     }
 556 #endif
 557   }
 558   return _native_java_library;
 559 }
 560 
 561 /*
 562  * Support for finding Agent_On(Un)Load/Attach<_lib_name> if it exists.
 563  * If check_lib == true then we are looking for an
 564  * Agent_OnLoad_lib_name or Agent_OnAttach_lib_name function to determine if
 565  * this library is statically linked into the image.
 566  * If check_lib == false then we will look for the appropriate symbol in the
 567  * executable if agent_lib->is_static_lib() == true or in the shared library
 568  * referenced by 'handle'.
 569  */
 570 void* os::find_agent_function(AgentLibrary *agent_lib, bool check_lib,
 571                               const char *syms[], size_t syms_len) {
 572   assert(agent_lib != NULL, "sanity check");
 573   const char *lib_name;
 574   void *handle = agent_lib->os_lib();
 575   void *entryName = NULL;
 576   char *agent_function_name;
 577   size_t i;
 578 
 579   // If checking then use the agent name otherwise test is_static_lib() to
 580   // see how to process this lookup
 581   lib_name = ((check_lib || agent_lib->is_static_lib()) ? agent_lib->name() : NULL);
 582   for (i = 0; i < syms_len; i++) {
 583     agent_function_name = build_agent_function_name(syms[i], lib_name, agent_lib->is_absolute_path());
 584     if (agent_function_name == NULL) {
 585       break;
 586     }
 587     entryName = dll_lookup(handle, agent_function_name);
 588     FREE_C_HEAP_ARRAY(char, agent_function_name);
 589     if (entryName != NULL) {
 590       break;
 591     }
 592   }
 593   return entryName;
 594 }
 595 
 596 // See if the passed in agent is statically linked into the VM image.
 597 bool os::find_builtin_agent(AgentLibrary *agent_lib, const char *syms[],
 598                             size_t syms_len) {
 599   void *ret;
 600   void *proc_handle;
 601   void *save_handle;
 602 
 603   assert(agent_lib != NULL, "sanity check");
 604   if (agent_lib->name() == NULL) {
 605     return false;
 606   }
 607   proc_handle = get_default_process_handle();
 608   // Check for Agent_OnLoad/Attach_lib_name function
 609   save_handle = agent_lib->os_lib();
 610   // We want to look in this process' symbol table.
 611   agent_lib->set_os_lib(proc_handle);
 612   ret = find_agent_function(agent_lib, true, syms, syms_len);
 613   if (ret != NULL) {
 614     // Found an entry point like Agent_OnLoad_lib_name so we have a static agent
 615     agent_lib->set_valid();
 616     agent_lib->set_static_lib(true);
 617     return true;
 618   }
 619   agent_lib->set_os_lib(save_handle);
 620   return false;
 621 }
 622 
 623 // --------------------- heap allocation utilities ---------------------
 624 
 625 char *os::strdup(const char *str, MEMFLAGS flags) {
 626   size_t size = strlen(str);
 627   char *dup_str = (char *)malloc(size + 1, flags);
 628   if (dup_str == NULL) return NULL;
 629   strcpy(dup_str, str);
 630   return dup_str;
 631 }
 632 
 633 char* os::strdup_check_oom(const char* str, MEMFLAGS flags) {
 634   char* p = os::strdup(str, flags);
 635   if (p == NULL) {
 636     vm_exit_out_of_memory(strlen(str) + 1, OOM_MALLOC_ERROR, "os::strdup_check_oom");
 637   }
 638   return p;
 639 }
 640 
 641 
 642 #define paranoid                 0  /* only set to 1 if you suspect checking code has bug */
 643 
 644 #ifdef ASSERT
 645 
 646 static void verify_memory(void* ptr) {
 647   GuardedMemory guarded(ptr);
 648   if (!guarded.verify_guards()) {
 649     LogTarget(Warning, malloc, free) lt;
 650     ResourceMark rm;
 651     LogStream ls(lt);
 652     ls.print_cr("## nof_mallocs = " UINT64_FORMAT ", nof_frees = " UINT64_FORMAT, os::num_mallocs, os::num_frees);
 653     ls.print_cr("## memory stomp:");
 654     guarded.print_on(&ls);
 655     fatal("memory stomping error");
 656   }
 657 }
 658 
 659 #endif
 660 
 661 //
 662 // This function supports testing of the malloc out of memory
 663 // condition without really running the system out of memory.
 664 //
 665 static bool has_reached_max_malloc_test_peak(size_t alloc_size) {
 666   if (MallocMaxTestWords > 0) {
 667     size_t words = (alloc_size / BytesPerWord);
 668 
 669     if ((cur_malloc_words + words) > MallocMaxTestWords) {
 670       return true;
 671     }
 672     Atomic::add(words, &cur_malloc_words);
 673   }
 674   return false;
 675 }
 676 
 677 void* os::malloc(size_t size, MEMFLAGS flags) {
 678   return os::malloc(size, flags, CALLER_PC);
 679 }
 680 
 681 void* os::malloc(size_t size, MEMFLAGS memflags, const NativeCallStack& stack) {
 682   NOT_PRODUCT(inc_stat_counter(&num_mallocs, 1));
 683   NOT_PRODUCT(inc_stat_counter(&alloc_bytes, size));
 684 
 685   // Since os::malloc can be called when the libjvm.{dll,so} is
 686   // first loaded and we don't have a thread yet we must accept NULL also here.
 687   assert(!os::ThreadCrashProtection::is_crash_protected(Thread::current_or_null()),
 688          "malloc() not allowed when crash protection is set");
 689 
 690   if (size == 0) {
 691     // return a valid pointer if size is zero
 692     // if NULL is returned the calling functions assume out of memory.
 693     size = 1;
 694   }
 695 
 696   // NMT support
 697   NMT_TrackingLevel level = MemTracker::tracking_level();
 698   size_t            nmt_header_size = MemTracker::malloc_header_size(level);
 699 
 700 #ifndef ASSERT
 701   const size_t alloc_size = size + nmt_header_size;
 702 #else
 703   const size_t alloc_size = GuardedMemory::get_total_size(size + nmt_header_size);
 704   if (size + nmt_header_size > alloc_size) { // Check for rollover.
 705     return NULL;
 706   }
 707 #endif
 708 
 709   // For the test flag -XX:MallocMaxTestWords
 710   if (has_reached_max_malloc_test_peak(size)) {
 711     return NULL;
 712   }
 713 
 714   u_char* ptr;
 715   ptr = (u_char*)::malloc(alloc_size);
 716 
 717 #ifdef ASSERT
 718   if (ptr == NULL) {
 719     return NULL;
 720   }
 721   // Wrap memory with guard
 722   GuardedMemory guarded(ptr, size + nmt_header_size);
 723   ptr = guarded.get_user_ptr();
 724 
 725   if ((intptr_t)ptr == (intptr_t)MallocCatchPtr) {
 726     log_warning(malloc, free)("os::malloc caught, " SIZE_FORMAT " bytes --> " PTR_FORMAT, size, p2i(ptr));
 727     breakpoint();
 728   }
 729   if (paranoid) {
 730     verify_memory(ptr);
 731   }
 732 #endif
 733 
 734   // we do not track guard memory
 735   return MemTracker::record_malloc((address)ptr, size, memflags, stack, level);
 736 }
 737 
 738 void* os::realloc(void *memblock, size_t size, MEMFLAGS flags) {
 739   return os::realloc(memblock, size, flags, CALLER_PC);
 740 }
 741 
 742 void* os::realloc(void *memblock, size_t size, MEMFLAGS memflags, const NativeCallStack& stack) {
 743 
 744   // For the test flag -XX:MallocMaxTestWords
 745   if (has_reached_max_malloc_test_peak(size)) {
 746     return NULL;
 747   }
 748 
 749   if (size == 0) {
 750     // return a valid pointer if size is zero
 751     // if NULL is returned the calling functions assume out of memory.
 752     size = 1;
 753   }
 754 
 755 #ifndef ASSERT
 756   NOT_PRODUCT(inc_stat_counter(&num_mallocs, 1));
 757   NOT_PRODUCT(inc_stat_counter(&alloc_bytes, size));
 758    // NMT support
 759   void* membase = MemTracker::record_free(memblock);
 760   NMT_TrackingLevel level = MemTracker::tracking_level();
 761   size_t  nmt_header_size = MemTracker::malloc_header_size(level);
 762   void* ptr = ::realloc(membase, size + nmt_header_size);
 763   return MemTracker::record_malloc(ptr, size, memflags, stack, level);
 764 #else
 765   if (memblock == NULL) {
 766     return os::malloc(size, memflags, stack);
 767   }
 768   if ((intptr_t)memblock == (intptr_t)MallocCatchPtr) {
 769     log_warning(malloc, free)("os::realloc caught " PTR_FORMAT, p2i(memblock));
 770     breakpoint();
 771   }
 772   // NMT support
 773   void* membase = MemTracker::malloc_base(memblock);
 774   verify_memory(membase);
 775   // always move the block
 776   void* ptr = os::malloc(size, memflags, stack);
 777   // Copy to new memory if malloc didn't fail
 778   if (ptr != NULL ) {
 779     GuardedMemory guarded(MemTracker::malloc_base(memblock));
 780     // Guard's user data contains NMT header
 781     size_t memblock_size = guarded.get_user_size() - MemTracker::malloc_header_size(memblock);
 782     memcpy(ptr, memblock, MIN2(size, memblock_size));
 783     if (paranoid) {
 784       verify_memory(MemTracker::malloc_base(ptr));
 785     }
 786     os::free(memblock);
 787   }
 788   return ptr;
 789 #endif
 790 }
 791 
 792 
 793 void  os::free(void *memblock) {
 794   NOT_PRODUCT(inc_stat_counter(&num_frees, 1));
 795 #ifdef ASSERT
 796   if (memblock == NULL) return;
 797   if ((intptr_t)memblock == (intptr_t)MallocCatchPtr) {
 798     log_warning(malloc, free)("os::free caught " PTR_FORMAT, p2i(memblock));
 799     breakpoint();
 800   }
 801   void* membase = MemTracker::record_free(memblock);
 802   verify_memory(membase);
 803 
 804   GuardedMemory guarded(membase);
 805   size_t size = guarded.get_user_size();
 806   inc_stat_counter(&free_bytes, size);
 807   membase = guarded.release_for_freeing();
 808   ::free(membase);
 809 #else
 810   void* membase = MemTracker::record_free(memblock);
 811   ::free(membase);
 812 #endif
 813 }
 814 
 815 void os::init_random(unsigned int initval) {
 816   _rand_seed = initval;
 817 }
 818 
 819 
 820 static int random_helper(unsigned int rand_seed) {
 821   /* standard, well-known linear congruential random generator with
 822    * next_rand = (16807*seed) mod (2**31-1)
 823    * see
 824    * (1) "Random Number Generators: Good Ones Are Hard to Find",
 825    *      S.K. Park and K.W. Miller, Communications of the ACM 31:10 (Oct 1988),
 826    * (2) "Two Fast Implementations of the 'Minimal Standard' Random
 827    *     Number Generator", David G. Carta, Comm. ACM 33, 1 (Jan 1990), pp. 87-88.
 828   */
 829   const unsigned int a = 16807;
 830   const unsigned int m = 2147483647;
 831   const int q = m / a;        assert(q == 127773, "weird math");
 832   const int r = m % a;        assert(r == 2836, "weird math");
 833 
 834   // compute az=2^31p+q
 835   unsigned int lo = a * (rand_seed & 0xFFFF);
 836   unsigned int hi = a * (rand_seed >> 16);
 837   lo += (hi & 0x7FFF) << 16;
 838 
 839   // if q overflowed, ignore the overflow and increment q
 840   if (lo > m) {
 841     lo &= m;
 842     ++lo;
 843   }
 844   lo += hi >> 15;
 845 
 846   // if (p+q) overflowed, ignore the overflow and increment (p+q)
 847   if (lo > m) {
 848     lo &= m;
 849     ++lo;
 850   }
 851   return lo;
 852 }
 853 
 854 int os::random() {
 855   // Make updating the random seed thread safe.
 856   while (true) {
 857     unsigned int seed = _rand_seed;
 858     unsigned int rand = random_helper(seed);
 859     if (Atomic::cmpxchg(rand, &_rand_seed, seed) == seed) {
 860       return static_cast<int>(rand);
 861     }
 862   }
 863 }
 864 
 865 // The INITIALIZED state is distinguished from the SUSPENDED state because the
 866 // conditions in which a thread is first started are different from those in which
 867 // a suspension is resumed.  These differences make it hard for us to apply the
 868 // tougher checks when starting threads that we want to do when resuming them.
 869 // However, when start_thread is called as a result of Thread.start, on a Java
 870 // thread, the operation is synchronized on the Java Thread object.  So there
 871 // cannot be a race to start the thread and hence for the thread to exit while
 872 // we are working on it.  Non-Java threads that start Java threads either have
 873 // to do so in a context in which races are impossible, or should do appropriate
 874 // locking.
 875 
 876 void os::start_thread(Thread* thread) {
 877   // guard suspend/resume
 878   MutexLocker ml(thread->SR_lock(), Mutex::_no_safepoint_check_flag);
 879   OSThread* osthread = thread->osthread();
 880   osthread->set_state(RUNNABLE);
 881   pd_start_thread(thread);
 882 }
 883 
 884 void os::abort(bool dump_core) {
 885   abort(dump_core && CreateCoredumpOnCrash, NULL, NULL);
 886 }
 887 
 888 //---------------------------------------------------------------------------
 889 // Helper functions for fatal error handler
 890 
 891 void os::print_hex_dump(outputStream* st, address start, address end, int unitsize) {
 892   assert(unitsize == 1 || unitsize == 2 || unitsize == 4 || unitsize == 8, "just checking");
 893 
 894   start = align_down(start, unitsize);
 895 
 896   int cols = 0;
 897   int cols_per_line = 0;
 898   switch (unitsize) {
 899     case 1: cols_per_line = 16; break;
 900     case 2: cols_per_line = 8;  break;
 901     case 4: cols_per_line = 4;  break;
 902     case 8: cols_per_line = 2;  break;
 903     default: return;
 904   }
 905 
 906   address p = start;
 907   st->print(PTR_FORMAT ":   ", p2i(start));
 908   while (p < end) {
 909     if (is_readable_pointer(p)) {
 910       switch (unitsize) {
 911         case 1: st->print("%02x", *(u1*)p); break;
 912         case 2: st->print("%04x", *(u2*)p); break;
 913         case 4: st->print("%08x", *(u4*)p); break;
 914         case 8: st->print("%016" FORMAT64_MODIFIER "x", *(u8*)p); break;
 915       }
 916     } else {
 917       st->print("%*.*s", 2*unitsize, 2*unitsize, "????????????????");
 918     }
 919     p += unitsize;
 920     cols++;
 921     if (cols >= cols_per_line && p < end) {
 922        cols = 0;
 923        st->cr();
 924        st->print(PTR_FORMAT ":   ", p2i(p));
 925     } else {
 926        st->print(" ");
 927     }
 928   }
 929   st->cr();
 930 }
 931 
 932 void os::print_instructions(outputStream* st, address pc, int unitsize) {
 933   st->print_cr("Instructions: (pc=" PTR_FORMAT ")", p2i(pc));
 934   print_hex_dump(st, pc - 256, pc + 256, unitsize);
 935 }
 936 
 937 void os::print_environment_variables(outputStream* st, const char** env_list) {
 938   if (env_list) {
 939     st->print_cr("Environment Variables:");
 940 
 941     for (int i = 0; env_list[i] != NULL; i++) {
 942       char *envvar = ::getenv(env_list[i]);
 943       if (envvar != NULL) {
 944         st->print("%s", env_list[i]);
 945         st->print("=");
 946         st->print_cr("%s", envvar);
 947       }
 948     }
 949   }
 950 }
 951 
 952 void os::print_cpu_info(outputStream* st, char* buf, size_t buflen) {
 953   // cpu
 954   st->print("CPU:");
 955   st->print("total %d", os::processor_count());
 956   // It's not safe to query number of active processors after crash
 957   // st->print("(active %d)", os::active_processor_count()); but we can
 958   // print the initial number of active processors.
 959   // We access the raw value here because the assert in the accessor will
 960   // fail if the crash occurs before initialization of this value.
 961   st->print(" (initial active %d)", _initial_active_processor_count);
 962   st->print(" %s", VM_Version::features_string());
 963   st->cr();
 964   pd_print_cpu_info(st, buf, buflen);
 965 }
 966 
 967 // Print a one line string summarizing the cpu, number of cores, memory, and operating system version
 968 void os::print_summary_info(outputStream* st, char* buf, size_t buflen) {
 969   st->print("Host: ");
 970 #ifndef PRODUCT
 971   if (get_host_name(buf, buflen)) {
 972     st->print("%s, ", buf);
 973   }
 974 #endif // PRODUCT
 975   get_summary_cpu_info(buf, buflen);
 976   st->print("%s, ", buf);
 977   size_t mem = physical_memory()/G;
 978   if (mem == 0) {  // for low memory systems
 979     mem = physical_memory()/M;
 980     st->print("%d cores, " SIZE_FORMAT "M, ", processor_count(), mem);
 981   } else {
 982     st->print("%d cores, " SIZE_FORMAT "G, ", processor_count(), mem);
 983   }
 984   get_summary_os_info(buf, buflen);
 985   st->print_raw(buf);
 986   st->cr();
 987 }
 988 
 989 void os::print_date_and_time(outputStream *st, char* buf, size_t buflen) {
 990   const int secs_per_day  = 86400;
 991   const int secs_per_hour = 3600;
 992   const int secs_per_min  = 60;
 993 
 994   time_t tloc;
 995   (void)time(&tloc);
 996   char* timestring = ctime(&tloc);  // ctime adds newline.
 997   // edit out the newline
 998   char* nl = strchr(timestring, '\n');
 999   if (nl != NULL) {
1000     *nl = '\0';
1001   }
1002 
1003   struct tm tz;
1004   if (localtime_pd(&tloc, &tz) != NULL) {
1005     ::strftime(buf, buflen, "%Z", &tz);
1006     st->print("Time: %s %s", timestring, buf);
1007   } else {
1008     st->print("Time: %s", timestring);
1009   }
1010 
1011   double t = os::elapsedTime();
1012   // NOTE: It tends to crash after a SEGV if we want to printf("%f",...) in
1013   //       Linux. Must be a bug in glibc ? Workaround is to round "t" to int
1014   //       before printf. We lost some precision, but who cares?
1015   int eltime = (int)t;  // elapsed time in seconds
1016 
1017   // print elapsed time in a human-readable format:
1018   int eldays = eltime / secs_per_day;
1019   int day_secs = eldays * secs_per_day;
1020   int elhours = (eltime - day_secs) / secs_per_hour;
1021   int hour_secs = elhours * secs_per_hour;
1022   int elmins = (eltime - day_secs - hour_secs) / secs_per_min;
1023   int minute_secs = elmins * secs_per_min;
1024   int elsecs = (eltime - day_secs - hour_secs - minute_secs);
1025   st->print_cr(" elapsed time: %d seconds (%dd %dh %dm %ds)", eltime, eldays, elhours, elmins, elsecs);
1026 }
1027 
1028 
1029 // Check if pointer can be read from (4-byte read access).
1030 // Helps to prove validity of a not-NULL pointer.
1031 // Returns true in very early stages of VM life when stub is not yet generated.
1032 #define SAFEFETCH_DEFAULT true
1033 bool os::is_readable_pointer(const void* p) {
1034   if (!CanUseSafeFetch32()) {
1035     return SAFEFETCH_DEFAULT;
1036   }
1037   int* const aligned = (int*) align_down((intptr_t)p, 4);
1038   int cafebabe = 0xcafebabe;  // tester value 1
1039   int deadbeef = 0xdeadbeef;  // tester value 2
1040   return (SafeFetch32(aligned, cafebabe) != cafebabe) || (SafeFetch32(aligned, deadbeef) != deadbeef);
1041 }
1042 
1043 bool os::is_readable_range(const void* from, const void* to) {
1044   if ((uintptr_t)from >= (uintptr_t)to) return false;
1045   for (uintptr_t p = align_down((uintptr_t)from, min_page_size()); p < (uintptr_t)to; p += min_page_size()) {
1046     if (!is_readable_pointer((const void*)p)) {
1047       return false;
1048     }
1049   }
1050   return true;
1051 }
1052 
1053 
1054 // moved from debug.cpp (used to be find()) but still called from there
1055 // The verbose parameter is only set by the debug code in one case
1056 void os::print_location(outputStream* st, intptr_t x, bool verbose) {
1057   address addr = (address)x;
1058   // Handle NULL first, so later checks don't need to protect against it.
1059   if (addr == NULL) {
1060     st->print_cr("0x0 is NULL");
1061     return;
1062   }
1063 
1064   // Check if addr points into a code blob.
1065   CodeBlob* b = CodeCache::find_blob_unsafe(addr);
1066   if (b != NULL) {
1067     b->dump_for_addr(addr, st, verbose);
1068     return;
1069   }
1070 
1071   // Check if addr points into Java heap.
1072   if (Universe::heap()->is_in(addr)) {
1073     oop o = oopDesc::oop_or_null(addr);
1074     if (o != NULL) {
1075       if ((HeapWord*)o == (HeapWord*)addr) {
1076         st->print(INTPTR_FORMAT " is an oop: ", p2i(addr));
1077       } else {
1078         st->print(INTPTR_FORMAT " is pointing into object: " , p2i(addr));
1079       }
1080       o->print_on(st);
1081       return;
1082     }
1083   } else if (Universe::heap()->is_in_reserved(addr)) {
1084     st->print_cr(INTPTR_FORMAT " is an unallocated location in the heap", p2i(addr));
1085     return;
1086   }
1087 
1088   // Compressed oop needs to be decoded first.
1089 #ifdef _LP64
1090   if (UseCompressedOops && ((uintptr_t)addr &~ (uintptr_t)max_juint) == 0) {
1091     narrowOop narrow_oop = (narrowOop)(uintptr_t)addr;
1092     oop o = CompressedOops::decode_raw(narrow_oop);
1093 
1094     if (oopDesc::is_valid(o)) {
1095       st->print(UINT32_FORMAT " is a compressed pointer to object: ", narrow_oop);
1096       o->print_on(st);
1097       return;
1098     }
1099   }
1100 #endif
1101 
1102   bool accessible = is_readable_pointer(addr);
1103 
1104   // Check if addr is a JNI handle.
1105   if (align_down((intptr_t)addr, sizeof(intptr_t)) != 0 && accessible) {
1106     if (JNIHandles::is_global_handle((jobject) addr)) {
1107       st->print_cr(INTPTR_FORMAT " is a global jni handle", p2i(addr));
1108       return;
1109     }
1110     if (JNIHandles::is_weak_global_handle((jobject) addr)) {
1111       st->print_cr(INTPTR_FORMAT " is a weak global jni handle", p2i(addr));
1112       return;
1113     }
1114 #ifndef PRODUCT
1115     // we don't keep the block list in product mode
1116     if (JNIHandles::is_local_handle((jobject) addr)) {
1117       st->print_cr(INTPTR_FORMAT " is a local jni handle", p2i(addr));
1118       return;
1119     }
1120 #endif
1121   }
1122 
1123   // Check if addr belongs to a Java thread.
1124   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thread = jtiwh.next(); ) {
1125     // If the addr is a java thread print information about that.
1126     if (addr == (address)thread) {
1127       if (verbose) {
1128         thread->print_on(st);
1129       } else {
1130         st->print_cr(INTPTR_FORMAT " is a thread", p2i(addr));
1131       }
1132       return;
1133     }
1134     // If the addr is in the stack region for this thread then report that
1135     // and print thread info
1136     if (thread->on_local_stack(addr)) {
1137       st->print_cr(INTPTR_FORMAT " is pointing into the stack for thread: "
1138                    INTPTR_FORMAT, p2i(addr), p2i(thread));
1139       if (verbose) thread->print_on(st);
1140       return;
1141     }
1142   }
1143 
1144   // Check if in metaspace and print types that have vptrs
1145   if (Metaspace::contains(addr)) {
1146     if (Klass::is_valid((Klass*)addr)) {
1147       st->print_cr(INTPTR_FORMAT " is a pointer to class: ", p2i(addr));
1148       ((Klass*)addr)->print_on(st);
1149     } else if (Method::is_valid_method((const Method*)addr)) {
1150       ((Method*)addr)->print_value_on(st);
1151       st->cr();
1152     } else {
1153       // Use addr->print() from the debugger instead (not here)
1154       st->print_cr(INTPTR_FORMAT " is pointing into metadata", p2i(addr));
1155     }
1156     return;
1157   }
1158 
1159   // Compressed klass needs to be decoded first.
1160 #ifdef _LP64
1161   if (UseCompressedClassPointers && ((uintptr_t)addr &~ (uintptr_t)max_juint) == 0) {
1162     narrowKlass narrow_klass = (narrowKlass)(uintptr_t)addr;
1163     Klass* k = CompressedKlassPointers::decode_raw(narrow_klass);
1164 
1165     if (Klass::is_valid(k)) {
1166       st->print_cr(UINT32_FORMAT " is a compressed pointer to class: " INTPTR_FORMAT, narrow_klass, p2i((HeapWord*)k));
1167       k->print_on(st);
1168       return;
1169     }
1170   }
1171 #endif
1172 
1173   // Try an OS specific find
1174   if (os::find(addr, st)) {
1175     return;
1176   }
1177 
1178   if (accessible) {
1179     st->print(INTPTR_FORMAT " points into unknown readable memory:", p2i(addr));
1180     for (address p = addr; p < align_up(addr + 1, sizeof(intptr_t)); ++p) {
1181       st->print(" %02x", *(u1*)p);
1182     }
1183     st->cr();
1184     return;
1185   }
1186 
1187   st->print_cr(INTPTR_FORMAT " is an unknown value", p2i(addr));
1188 }
1189 
1190 // Looks like all platforms can use the same function to check if C
1191 // stack is walkable beyond current frame. The check for fp() is not
1192 // necessary on Sparc, but it's harmless.
1193 bool os::is_first_C_frame(frame* fr) {
1194   // Load up sp, fp, sender sp and sender fp, check for reasonable values.
1195   // Check usp first, because if that's bad the other accessors may fault
1196   // on some architectures.  Ditto ufp second, etc.
1197   uintptr_t fp_align_mask = (uintptr_t)(sizeof(address)-1);
1198   // sp on amd can be 32 bit aligned.
1199   uintptr_t sp_align_mask = (uintptr_t)(sizeof(int)-1);
1200 
1201   uintptr_t usp    = (uintptr_t)fr->sp();
1202   if ((usp & sp_align_mask) != 0) return true;
1203 
1204   uintptr_t ufp    = (uintptr_t)fr->fp();
1205   if ((ufp & fp_align_mask) != 0) return true;
1206 
1207   uintptr_t old_sp = (uintptr_t)fr->sender_sp();
1208   if ((old_sp & sp_align_mask) != 0) return true;
1209   if (old_sp == 0 || old_sp == (uintptr_t)-1) return true;
1210 
1211   uintptr_t old_fp = (uintptr_t)fr->link();
1212   if ((old_fp & fp_align_mask) != 0) return true;
1213   if (old_fp == 0 || old_fp == (uintptr_t)-1 || old_fp == ufp) return true;
1214 
1215   // stack grows downwards; if old_fp is below current fp or if the stack
1216   // frame is too large, either the stack is corrupted or fp is not saved
1217   // on stack (i.e. on x86, ebp may be used as general register). The stack
1218   // is not walkable beyond current frame.
1219   if (old_fp < ufp) return true;
1220   if (old_fp - ufp > 64 * K) return true;
1221 
1222   return false;
1223 }
1224 
1225 
1226 // Set up the boot classpath.
1227 
1228 char* os::format_boot_path(const char* format_string,
1229                            const char* home,
1230                            int home_len,
1231                            char fileSep,
1232                            char pathSep) {
1233     assert((fileSep == '/' && pathSep == ':') ||
1234            (fileSep == '\\' && pathSep == ';'), "unexpected separator chars");
1235 
1236     // Scan the format string to determine the length of the actual
1237     // boot classpath, and handle platform dependencies as well.
1238     int formatted_path_len = 0;
1239     const char* p;
1240     for (p = format_string; *p != 0; ++p) {
1241         if (*p == '%') formatted_path_len += home_len - 1;
1242         ++formatted_path_len;
1243     }
1244 
1245     char* formatted_path = NEW_C_HEAP_ARRAY(char, formatted_path_len + 1, mtInternal);
1246     if (formatted_path == NULL) {
1247         return NULL;
1248     }
1249 
1250     // Create boot classpath from format, substituting separator chars and
1251     // java home directory.
1252     char* q = formatted_path;
1253     for (p = format_string; *p != 0; ++p) {
1254         switch (*p) {
1255         case '%':
1256             strcpy(q, home);
1257             q += home_len;
1258             break;
1259         case '/':
1260             *q++ = fileSep;
1261             break;
1262         case ':':
1263             *q++ = pathSep;
1264             break;
1265         default:
1266             *q++ = *p;
1267         }
1268     }
1269     *q = '\0';
1270 
1271     assert((q - formatted_path) == formatted_path_len, "formatted_path size botched");
1272     return formatted_path;
1273 }
1274 
1275 // This function is a proxy to fopen, it tries to add a non standard flag ('e' or 'N')
1276 // that ensures automatic closing of the file on exec. If it can not find support in
1277 // the underlying c library, it will make an extra system call (fcntl) to ensure automatic
1278 // closing of the file on exec.
1279 FILE* os::fopen(const char* path, const char* mode) {
1280   char modified_mode[20];
1281   assert(strlen(mode) + 1 < sizeof(modified_mode), "mode chars plus one extra must fit in buffer");
1282   sprintf(modified_mode, "%s" LINUX_ONLY("e") BSD_ONLY("e") WINDOWS_ONLY("N"), mode);
1283   FILE* file = ::fopen(path, modified_mode);
1284 
1285 #if !(defined LINUX || defined BSD || defined _WINDOWS)
1286   // assume fcntl FD_CLOEXEC support as a backup solution when 'e' or 'N'
1287   // is not supported as mode in fopen
1288   if (file != NULL) {
1289     int fd = fileno(file);
1290     if (fd != -1) {
1291       int fd_flags = fcntl(fd, F_GETFD);
1292       if (fd_flags != -1) {
1293         fcntl(fd, F_SETFD, fd_flags | FD_CLOEXEC);
1294       }
1295     }
1296   }
1297 #endif
1298 
1299   return file;
1300 }
1301 
1302 bool os::set_boot_path(char fileSep, char pathSep) {
1303   const char* home = Arguments::get_java_home();
1304   int home_len = (int)strlen(home);
1305 
1306   struct stat st;
1307 
1308   // modular image if "modules" jimage exists
1309   char* jimage = format_boot_path("%/lib/" MODULES_IMAGE_NAME, home, home_len, fileSep, pathSep);
1310   if (jimage == NULL) return false;
1311   bool has_jimage = (os::stat(jimage, &st) == 0);
1312   if (has_jimage) {
1313     Arguments::set_sysclasspath(jimage, true);
1314     FREE_C_HEAP_ARRAY(char, jimage);
1315     return true;
1316   }
1317   FREE_C_HEAP_ARRAY(char, jimage);
1318 
1319   // check if developer build with exploded modules
1320   char* base_classes = format_boot_path("%/modules/" JAVA_BASE_NAME, home, home_len, fileSep, pathSep);
1321   if (base_classes == NULL) return false;
1322   if (os::stat(base_classes, &st) == 0) {
1323     Arguments::set_sysclasspath(base_classes, false);
1324     FREE_C_HEAP_ARRAY(char, base_classes);
1325     return true;
1326   }
1327   FREE_C_HEAP_ARRAY(char, base_classes);
1328 
1329   return false;
1330 }
1331 
1332 /*
1333  * Splits a path, based on its separator, the number of
1334  * elements is returned back in n.
1335  * It is the callers responsibility to:
1336  *   a> check the value of n, and n may be 0.
1337  *   b> ignore any empty path elements
1338  *   c> free up the data.
1339  */
1340 char** os::split_path(const char* path, int* n) {
1341   *n = 0;
1342   if (path == NULL || strlen(path) == 0) {
1343     return NULL;
1344   }
1345   const char psepchar = *os::path_separator();
1346   char* inpath = (char*)NEW_C_HEAP_ARRAY(char, strlen(path) + 1, mtInternal);
1347   if (inpath == NULL) {
1348     return NULL;
1349   }
1350   strcpy(inpath, path);
1351   int count = 1;
1352   char* p = strchr(inpath, psepchar);
1353   // Get a count of elements to allocate memory
1354   while (p != NULL) {
1355     count++;
1356     p++;
1357     p = strchr(p, psepchar);
1358   }
1359   char** opath = (char**) NEW_C_HEAP_ARRAY(char*, count, mtInternal);
1360   if (opath == NULL) {
1361     return NULL;
1362   }
1363 
1364   // do the actual splitting
1365   p = inpath;
1366   for (int i = 0 ; i < count ; i++) {
1367     size_t len = strcspn(p, os::path_separator());
1368     if (len > JVM_MAXPATHLEN) {
1369       return NULL;
1370     }
1371     // allocate the string and add terminator storage
1372     char* s  = (char*)NEW_C_HEAP_ARRAY(char, len + 1, mtInternal);
1373     if (s == NULL) {
1374       return NULL;
1375     }
1376     strncpy(s, p, len);
1377     s[len] = '\0';
1378     opath[i] = s;
1379     p += len + 1;
1380   }
1381   FREE_C_HEAP_ARRAY(char, inpath);
1382   *n = count;
1383   return opath;
1384 }
1385 
1386 // Returns true if the current stack pointer is above the stack shadow
1387 // pages, false otherwise.
1388 bool os::stack_shadow_pages_available(Thread *thread, const methodHandle& method, address sp) {
1389   if (!thread->is_Java_thread()) return false;
1390   // Check if we have StackShadowPages above the yellow zone.  This parameter
1391   // is dependent on the depth of the maximum VM call stack possible from
1392   // the handler for stack overflow.  'instanceof' in the stack overflow
1393   // handler or a println uses at least 8k stack of VM and native code
1394   // respectively.
1395   const int framesize_in_bytes =
1396     Interpreter::size_top_interpreter_activation(method()) * wordSize;
1397 
1398   address limit = ((JavaThread*)thread)->stack_end() +
1399                   (JavaThread::stack_guard_zone_size() + JavaThread::stack_shadow_zone_size());
1400 
1401   return sp > (limit + framesize_in_bytes);
1402 }
1403 
1404 size_t os::page_size_for_region(size_t region_size, size_t min_pages, bool must_be_aligned) {
1405   assert(min_pages > 0, "sanity");
1406   if (UseLargePages) {
1407     const size_t max_page_size = region_size / min_pages;
1408 
1409     for (size_t i = 0; _page_sizes[i] != 0; ++i) {
1410       const size_t page_size = _page_sizes[i];
1411       if (page_size <= max_page_size) {
1412         if (!must_be_aligned || is_aligned(region_size, page_size)) {
1413           return page_size;
1414         }
1415       }
1416     }
1417   }
1418 
1419   return vm_page_size();
1420 }
1421 
1422 size_t os::page_size_for_region_aligned(size_t region_size, size_t min_pages) {
1423   return page_size_for_region(region_size, min_pages, true);
1424 }
1425 
1426 size_t os::page_size_for_region_unaligned(size_t region_size, size_t min_pages) {
1427   return page_size_for_region(region_size, min_pages, false);
1428 }
1429 
1430 static const char* errno_to_string (int e, bool short_text) {
1431   #define ALL_SHARED_ENUMS(X) \
1432     X(E2BIG, "Argument list too long") \
1433     X(EACCES, "Permission denied") \
1434     X(EADDRINUSE, "Address in use") \
1435     X(EADDRNOTAVAIL, "Address not available") \
1436     X(EAFNOSUPPORT, "Address family not supported") \
1437     X(EAGAIN, "Resource unavailable, try again") \
1438     X(EALREADY, "Connection already in progress") \
1439     X(EBADF, "Bad file descriptor") \
1440     X(EBADMSG, "Bad message") \
1441     X(EBUSY, "Device or resource busy") \
1442     X(ECANCELED, "Operation canceled") \
1443     X(ECHILD, "No child processes") \
1444     X(ECONNABORTED, "Connection aborted") \
1445     X(ECONNREFUSED, "Connection refused") \
1446     X(ECONNRESET, "Connection reset") \
1447     X(EDEADLK, "Resource deadlock would occur") \
1448     X(EDESTADDRREQ, "Destination address required") \
1449     X(EDOM, "Mathematics argument out of domain of function") \
1450     X(EEXIST, "File exists") \
1451     X(EFAULT, "Bad address") \
1452     X(EFBIG, "File too large") \
1453     X(EHOSTUNREACH, "Host is unreachable") \
1454     X(EIDRM, "Identifier removed") \
1455     X(EILSEQ, "Illegal byte sequence") \
1456     X(EINPROGRESS, "Operation in progress") \
1457     X(EINTR, "Interrupted function") \
1458     X(EINVAL, "Invalid argument") \
1459     X(EIO, "I/O error") \
1460     X(EISCONN, "Socket is connected") \
1461     X(EISDIR, "Is a directory") \
1462     X(ELOOP, "Too many levels of symbolic links") \
1463     X(EMFILE, "Too many open files") \
1464     X(EMLINK, "Too many links") \
1465     X(EMSGSIZE, "Message too large") \
1466     X(ENAMETOOLONG, "Filename too long") \
1467     X(ENETDOWN, "Network is down") \
1468     X(ENETRESET, "Connection aborted by network") \
1469     X(ENETUNREACH, "Network unreachable") \
1470     X(ENFILE, "Too many files open in system") \
1471     X(ENOBUFS, "No buffer space available") \
1472     X(ENODATA, "No message is available on the STREAM head read queue") \
1473     X(ENODEV, "No such device") \
1474     X(ENOENT, "No such file or directory") \
1475     X(ENOEXEC, "Executable file format error") \
1476     X(ENOLCK, "No locks available") \
1477     X(ENOLINK, "Reserved") \
1478     X(ENOMEM, "Not enough space") \
1479     X(ENOMSG, "No message of the desired type") \
1480     X(ENOPROTOOPT, "Protocol not available") \
1481     X(ENOSPC, "No space left on device") \
1482     X(ENOSR, "No STREAM resources") \
1483     X(ENOSTR, "Not a STREAM") \
1484     X(ENOSYS, "Function not supported") \
1485     X(ENOTCONN, "The socket is not connected") \
1486     X(ENOTDIR, "Not a directory") \
1487     X(ENOTEMPTY, "Directory not empty") \
1488     X(ENOTSOCK, "Not a socket") \
1489     X(ENOTSUP, "Not supported") \
1490     X(ENOTTY, "Inappropriate I/O control operation") \
1491     X(ENXIO, "No such device or address") \
1492     X(EOPNOTSUPP, "Operation not supported on socket") \
1493     X(EOVERFLOW, "Value too large to be stored in data type") \
1494     X(EPERM, "Operation not permitted") \
1495     X(EPIPE, "Broken pipe") \
1496     X(EPROTO, "Protocol error") \
1497     X(EPROTONOSUPPORT, "Protocol not supported") \
1498     X(EPROTOTYPE, "Protocol wrong type for socket") \
1499     X(ERANGE, "Result too large") \
1500     X(EROFS, "Read-only file system") \
1501     X(ESPIPE, "Invalid seek") \
1502     X(ESRCH, "No such process") \
1503     X(ETIME, "Stream ioctl() timeout") \
1504     X(ETIMEDOUT, "Connection timed out") \
1505     X(ETXTBSY, "Text file busy") \
1506     X(EWOULDBLOCK, "Operation would block") \
1507     X(EXDEV, "Cross-device link")
1508 
1509   #define DEFINE_ENTRY(e, text) { e, #e, text },
1510 
1511   static const struct {
1512     int v;
1513     const char* short_text;
1514     const char* long_text;
1515   } table [] = {
1516 
1517     ALL_SHARED_ENUMS(DEFINE_ENTRY)
1518 
1519     // The following enums are not defined on all platforms.
1520     #ifdef ESTALE
1521     DEFINE_ENTRY(ESTALE, "Reserved")
1522     #endif
1523     #ifdef EDQUOT
1524     DEFINE_ENTRY(EDQUOT, "Reserved")
1525     #endif
1526     #ifdef EMULTIHOP
1527     DEFINE_ENTRY(EMULTIHOP, "Reserved")
1528     #endif
1529 
1530     // End marker.
1531     { -1, "Unknown errno", "Unknown error" }
1532 
1533   };
1534 
1535   #undef DEFINE_ENTRY
1536   #undef ALL_FLAGS
1537 
1538   int i = 0;
1539   while (table[i].v != -1 && table[i].v != e) {
1540     i ++;
1541   }
1542 
1543   return short_text ? table[i].short_text : table[i].long_text;
1544 
1545 }
1546 
1547 const char* os::strerror(int e) {
1548   return errno_to_string(e, false);
1549 }
1550 
1551 const char* os::errno_name(int e) {
1552   return errno_to_string(e, true);
1553 }
1554 
1555 void os::trace_page_sizes(const char* str, const size_t* page_sizes, int count) {
1556   LogTarget(Info, pagesize) log;
1557   if (log.is_enabled()) {
1558     LogStream out(log);
1559 
1560     out.print("%s: ", str);
1561     for (int i = 0; i < count; ++i) {
1562       out.print(" " SIZE_FORMAT, page_sizes[i]);
1563     }
1564     out.cr();
1565   }
1566 }
1567 
1568 #define trace_page_size_params(size) byte_size_in_exact_unit(size), exact_unit_for_byte_size(size)
1569 
1570 void os::trace_page_sizes(const char* str,
1571                           const size_t region_min_size,
1572                           const size_t region_max_size,
1573                           const size_t page_size,
1574                           const char* base,
1575                           const size_t size) {
1576 
1577   log_info(pagesize)("%s: "
1578                      " min=" SIZE_FORMAT "%s"
1579                      " max=" SIZE_FORMAT "%s"
1580                      " base=" PTR_FORMAT
1581                      " page_size=" SIZE_FORMAT "%s"
1582                      " size=" SIZE_FORMAT "%s",
1583                      str,
1584                      trace_page_size_params(region_min_size),
1585                      trace_page_size_params(region_max_size),
1586                      p2i(base),
1587                      trace_page_size_params(page_size),
1588                      trace_page_size_params(size));
1589 }
1590 
1591 void os::trace_page_sizes_for_requested_size(const char* str,
1592                                              const size_t requested_size,
1593                                              const size_t page_size,
1594                                              const size_t alignment,
1595                                              const char* base,
1596                                              const size_t size) {
1597 
1598   log_info(pagesize)("%s:"
1599                      " req_size=" SIZE_FORMAT "%s"
1600                      " base=" PTR_FORMAT
1601                      " page_size=" SIZE_FORMAT "%s"
1602                      " alignment=" SIZE_FORMAT "%s"
1603                      " size=" SIZE_FORMAT "%s",
1604                      str,
1605                      trace_page_size_params(requested_size),
1606                      p2i(base),
1607                      trace_page_size_params(page_size),
1608                      trace_page_size_params(alignment),
1609                      trace_page_size_params(size));
1610 }
1611 
1612 
1613 // This is the working definition of a server class machine:
1614 // >= 2 physical CPU's and >=2GB of memory, with some fuzz
1615 // because the graphics memory (?) sometimes masks physical memory.
1616 // If you want to change the definition of a server class machine
1617 // on some OS or platform, e.g., >=4GB on Windows platforms,
1618 // then you'll have to parameterize this method based on that state,
1619 // as was done for logical processors here, or replicate and
1620 // specialize this method for each platform.  (Or fix os to have
1621 // some inheritance structure and use subclassing.  Sigh.)
1622 // If you want some platform to always or never behave as a server
1623 // class machine, change the setting of AlwaysActAsServerClassMachine
1624 // and NeverActAsServerClassMachine in globals*.hpp.
1625 bool os::is_server_class_machine() {
1626   // First check for the early returns
1627   if (NeverActAsServerClassMachine) {
1628     return false;
1629   }
1630   if (AlwaysActAsServerClassMachine) {
1631     return true;
1632   }
1633   // Then actually look at the machine
1634   bool         result            = false;
1635   const unsigned int    server_processors = 2;
1636   const julong server_memory     = 2UL * G;
1637   // We seem not to get our full complement of memory.
1638   //     We allow some part (1/8?) of the memory to be "missing",
1639   //     based on the sizes of DIMMs, and maybe graphics cards.
1640   const julong missing_memory   = 256UL * M;
1641 
1642   /* Is this a server class machine? */
1643   if ((os::active_processor_count() >= (int)server_processors) &&
1644       (os::physical_memory() >= (server_memory - missing_memory))) {
1645     const unsigned int logical_processors =
1646       VM_Version::logical_processors_per_package();
1647     if (logical_processors > 1) {
1648       const unsigned int physical_packages =
1649         os::active_processor_count() / logical_processors;
1650       if (physical_packages >= server_processors) {
1651         result = true;
1652       }
1653     } else {
1654       result = true;
1655     }
1656   }
1657   return result;
1658 }
1659 
1660 void os::initialize_initial_active_processor_count() {
1661   assert(_initial_active_processor_count == 0, "Initial active processor count already set.");
1662   _initial_active_processor_count = active_processor_count();
1663   log_debug(os)("Initial active processor count set to %d" , _initial_active_processor_count);
1664 }
1665 
1666 void os::SuspendedThreadTask::run() {
1667   internal_do_task();
1668   _done = true;
1669 }
1670 
1671 bool os::create_stack_guard_pages(char* addr, size_t bytes) {
1672   return os::pd_create_stack_guard_pages(addr, bytes);
1673 }
1674 
1675 char* os::reserve_memory(size_t bytes, char* addr, size_t alignment_hint, int file_desc) {
1676   char* result = NULL;
1677 
1678   if (file_desc != -1) {
1679     // Could have called pd_reserve_memory() followed by replace_existing_mapping_with_file_mapping(),
1680     // but AIX may use SHM in which case its more trouble to detach the segment and remap memory to the file.
1681     result = os::map_memory_to_file(addr, bytes, file_desc);
1682     if (result != NULL) {
1683       MemTracker::record_virtual_memory_reserve_and_commit((address)result, bytes, CALLER_PC);
1684     }
1685   } else {
1686     result = pd_reserve_memory(bytes, addr, alignment_hint);
1687     if (result != NULL) {
1688       MemTracker::record_virtual_memory_reserve((address)result, bytes, CALLER_PC);
1689     }
1690   }
1691 
1692   return result;
1693 }
1694 
1695 char* os::reserve_memory(size_t bytes, char* addr, size_t alignment_hint,
1696    MEMFLAGS flags) {
1697   char* result = pd_reserve_memory(bytes, addr, alignment_hint);
1698   if (result != NULL) {
1699     MemTracker::record_virtual_memory_reserve((address)result, bytes, CALLER_PC);
1700     MemTracker::record_virtual_memory_type((address)result, flags);
1701   }
1702 
1703   return result;
1704 }
1705 
1706 char* os::attempt_reserve_memory_at(size_t bytes, char* addr, int file_desc) {
1707   char* result = NULL;
1708   if (file_desc != -1) {
1709     result = pd_attempt_reserve_memory_at(bytes, addr, file_desc);
1710     if (result != NULL) {
1711       MemTracker::record_virtual_memory_reserve_and_commit((address)result, bytes, CALLER_PC);
1712     }
1713   } else {
1714     result = pd_attempt_reserve_memory_at(bytes, addr);
1715     if (result != NULL) {
1716       MemTracker::record_virtual_memory_reserve((address)result, bytes, CALLER_PC);
1717     }
1718   }
1719   return result;
1720 }
1721 
1722 void os::split_reserved_memory(char *base, size_t size,
1723                                  size_t split, bool realloc) {
1724   pd_split_reserved_memory(base, size, split, realloc);
1725 }
1726 
1727 bool os::commit_memory(char* addr, size_t bytes, bool executable) {
1728   bool res = pd_commit_memory(addr, bytes, executable);
1729   if (res) {
1730     MemTracker::record_virtual_memory_commit((address)addr, bytes, CALLER_PC);
1731   }
1732   return res;
1733 }
1734 
1735 bool os::commit_memory(char* addr, size_t size, size_t alignment_hint,
1736                               bool executable) {
1737   bool res = os::pd_commit_memory(addr, size, alignment_hint, executable);
1738   if (res) {
1739     MemTracker::record_virtual_memory_commit((address)addr, size, CALLER_PC);
1740   }
1741   return res;
1742 }
1743 
1744 void os::commit_memory_or_exit(char* addr, size_t bytes, bool executable,
1745                                const char* mesg) {
1746   pd_commit_memory_or_exit(addr, bytes, executable, mesg);
1747   MemTracker::record_virtual_memory_commit((address)addr, bytes, CALLER_PC);
1748 }
1749 
1750 void os::commit_memory_or_exit(char* addr, size_t size, size_t alignment_hint,
1751                                bool executable, const char* mesg) {
1752   os::pd_commit_memory_or_exit(addr, size, alignment_hint, executable, mesg);
1753   MemTracker::record_virtual_memory_commit((address)addr, size, CALLER_PC);
1754 }
1755 
1756 bool os::uncommit_memory(char* addr, size_t bytes) {
1757   bool res;
1758   if (MemTracker::tracking_level() > NMT_minimal) {
1759     Tracker tkr(Tracker::uncommit);
1760     res = pd_uncommit_memory(addr, bytes);
1761     if (res) {
1762       tkr.record((address)addr, bytes);
1763     }
1764   } else {
1765     res = pd_uncommit_memory(addr, bytes);
1766   }
1767   return res;
1768 }
1769 
1770 bool os::release_memory(char* addr, size_t bytes) {
1771   bool res;
1772   if (MemTracker::tracking_level() > NMT_minimal) {
1773     Tracker tkr(Tracker::release);
1774     res = pd_release_memory(addr, bytes);
1775     if (res) {
1776       tkr.record((address)addr, bytes);
1777     }
1778   } else {
1779     res = pd_release_memory(addr, bytes);
1780   }
1781   return res;
1782 }
1783 
1784 void os::pretouch_memory(void* start, void* end, size_t page_size) {
1785   for (volatile char *p = (char*)start; p < (char*)end; p += page_size) {
1786     *p = 0;
1787   }
1788 }
1789 
1790 char* os::map_memory(int fd, const char* file_name, size_t file_offset,
1791                            char *addr, size_t bytes, bool read_only,
1792                            bool allow_exec) {
1793   char* result = pd_map_memory(fd, file_name, file_offset, addr, bytes, read_only, allow_exec);
1794   if (result != NULL) {
1795     MemTracker::record_virtual_memory_reserve_and_commit((address)result, bytes, CALLER_PC);
1796   }
1797   return result;
1798 }
1799 
1800 char* os::remap_memory(int fd, const char* file_name, size_t file_offset,
1801                              char *addr, size_t bytes, bool read_only,
1802                              bool allow_exec) {
1803   return pd_remap_memory(fd, file_name, file_offset, addr, bytes,
1804                     read_only, allow_exec);
1805 }
1806 
1807 bool os::unmap_memory(char *addr, size_t bytes) {
1808   bool result;
1809   if (MemTracker::tracking_level() > NMT_minimal) {
1810     Tracker tkr(Tracker::release);
1811     result = pd_unmap_memory(addr, bytes);
1812     if (result) {
1813       tkr.record((address)addr, bytes);
1814     }
1815   } else {
1816     result = pd_unmap_memory(addr, bytes);
1817   }
1818   return result;
1819 }
1820 
1821 void os::free_memory(char *addr, size_t bytes, size_t alignment_hint) {
1822   pd_free_memory(addr, bytes, alignment_hint);
1823 }
1824 
1825 void os::realign_memory(char *addr, size_t bytes, size_t alignment_hint) {
1826   pd_realign_memory(addr, bytes, alignment_hint);
1827 }
1828 
1829 #ifndef _WINDOWS
1830 /* try to switch state from state "from" to state "to"
1831  * returns the state set after the method is complete
1832  */
1833 os::SuspendResume::State os::SuspendResume::switch_state(os::SuspendResume::State from,
1834                                                          os::SuspendResume::State to)
1835 {
1836   os::SuspendResume::State result = Atomic::cmpxchg(to, &_state, from);
1837   if (result == from) {
1838     // success
1839     return to;
1840   }
1841   return result;
1842 }
1843 #endif