1 /*
   2  * Copyright (c) 1997, 2018, 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 #ifndef SHARE_VM_RUNTIME_OS_HPP
  26 #define SHARE_VM_RUNTIME_OS_HPP
  27 
  28 #include "jvm.h"
  29 #include "jvmtifiles/jvmti.h"
  30 #include "metaprogramming/isRegisteredEnum.hpp"
  31 #include "metaprogramming/integralConstant.hpp"
  32 #include "runtime/extendedPC.hpp"
  33 #include "utilities/exceptions.hpp"
  34 #include "utilities/ostream.hpp"
  35 #include "utilities/macros.hpp"
  36 #ifndef _WINDOWS
  37 # include <setjmp.h>
  38 #endif
  39 #ifdef __APPLE__
  40 # include <mach/mach_time.h>
  41 #endif
  42 
  43 class AgentLibrary;
  44 class frame;
  45 
  46 // os defines the interface to operating system; this includes traditional
  47 // OS services (time, I/O) as well as other functionality with system-
  48 // dependent code.
  49 
  50 typedef void (*dll_func)(...);
  51 
  52 class Thread;
  53 class JavaThread;
  54 class Event;
  55 class DLL;
  56 class FileHandle;
  57 class NativeCallStack;
  58 class methodHandle;
  59 
  60 template<class E> class GrowableArray;
  61 
  62 // %%%%% Moved ThreadState, START_FN, OSThread to new osThread.hpp. -- Rose
  63 
  64 // Platform-independent error return values from OS functions
  65 enum OSReturn {
  66   OS_OK         =  0,        // Operation was successful
  67   OS_ERR        = -1,        // Operation failed
  68   OS_INTRPT     = -2,        // Operation was interrupted
  69   OS_TIMEOUT    = -3,        // Operation timed out
  70   OS_NOMEM      = -5,        // Operation failed for lack of memory
  71   OS_NORESOURCE = -6         // Operation failed for lack of nonmemory resource
  72 };
  73 
  74 enum ThreadPriority {        // JLS 20.20.1-3
  75   NoPriority       = -1,     // Initial non-priority value
  76   MinPriority      =  1,     // Minimum priority
  77   NormPriority     =  5,     // Normal (non-daemon) priority
  78   NearMaxPriority  =  9,     // High priority, used for VMThread
  79   MaxPriority      = 10,     // Highest priority, used for WatcherThread
  80                              // ensures that VMThread doesn't starve profiler
  81   CriticalPriority = 11      // Critical thread priority
  82 };
  83 
  84 // Executable parameter flag for os::commit_memory() and
  85 // os::commit_memory_or_exit().
  86 const bool ExecMem = true;
  87 
  88 // Typedef for structured exception handling support
  89 typedef void (*java_call_t)(JavaValue* value, const methodHandle& method, JavaCallArguments* args, Thread* thread);
  90 
  91 class MallocTracker;
  92 
  93 class os: AllStatic {
  94   friend class VMStructs;
  95   friend class JVMCIVMStructs;
  96   friend class MallocTracker;
  97  public:
  98   enum { page_sizes_max = 9 }; // Size of _page_sizes array (8 plus a sentinel)
  99 
 100  private:
 101   static OSThread*          _starting_thread;
 102   static address            _polling_page;
 103   static volatile int32_t * _mem_serialize_page;
 104   static uintptr_t          _serialize_page_mask;
 105  public:
 106   static size_t             _page_sizes[page_sizes_max];
 107 
 108  private:
 109   static void init_page_sizes(size_t default_page_size) {
 110     _page_sizes[0] = default_page_size;
 111     _page_sizes[1] = 0; // sentinel
 112   }
 113 
 114   static char*  pd_reserve_memory(size_t bytes, char* addr = 0,
 115                                   size_t alignment_hint = 0);
 116   static char*  pd_attempt_reserve_memory_at(size_t bytes, char* addr);
 117   static char*  pd_attempt_reserve_memory_at(size_t bytes, char* addr, int file_desc);
 118   static void   pd_split_reserved_memory(char *base, size_t size,
 119                                       size_t split, bool realloc);
 120   static bool   pd_commit_memory(char* addr, size_t bytes, bool executable);
 121   static bool   pd_commit_memory(char* addr, size_t size, size_t alignment_hint,
 122                                  bool executable);
 123   // Same as pd_commit_memory() that either succeeds or calls
 124   // vm_exit_out_of_memory() with the specified mesg.
 125   static void   pd_commit_memory_or_exit(char* addr, size_t bytes,
 126                                          bool executable, const char* mesg);
 127   static void   pd_commit_memory_or_exit(char* addr, size_t size,
 128                                          size_t alignment_hint,
 129                                          bool executable, const char* mesg);
 130   static bool   pd_uncommit_memory(char* addr, size_t bytes);
 131   static bool   pd_release_memory(char* addr, size_t bytes);
 132 
 133   static char*  pd_map_memory(int fd, const char* file_name, size_t file_offset,
 134                            char *addr, size_t bytes, bool read_only = false,
 135                            bool allow_exec = false);
 136   static char*  pd_remap_memory(int fd, const char* file_name, size_t file_offset,
 137                              char *addr, size_t bytes, bool read_only,
 138                              bool allow_exec);
 139   static bool   pd_unmap_memory(char *addr, size_t bytes);
 140   static void   pd_free_memory(char *addr, size_t bytes, size_t alignment_hint);
 141   static void   pd_realign_memory(char *addr, size_t bytes, size_t alignment_hint);
 142 
 143   static size_t page_size_for_region(size_t region_size, size_t min_pages, bool must_be_aligned);
 144 
 145   // Get summary strings for system information in buffer provided
 146   static void  get_summary_cpu_info(char* buf, size_t buflen);
 147   static void  get_summary_os_info(char* buf, size_t buflen);
 148 
 149   static void initialize_initial_active_processor_count();
 150 
 151   LINUX_ONLY(static void pd_init_container_support();)
 152 
 153  public:
 154   static void init(void);                      // Called before command line parsing
 155 
 156   static void init_container_support() {       // Called during command line parsing.
 157      LINUX_ONLY(pd_init_container_support();)
 158   }
 159 
 160   static void init_before_ergo(void);          // Called after command line parsing
 161                                                // before VM ergonomics processing.
 162   static jint init_2(void);                    // Called after command line parsing
 163                                                // and VM ergonomics processing
 164   static void init_globals(void) {             // Called from init_globals() in init.cpp
 165     init_globals_ext();
 166   }
 167 
 168   // File names are case-insensitive on windows only
 169   // Override me as needed
 170   static int    file_name_strcmp(const char* s1, const char* s2);
 171 
 172   // unset environment variable
 173   static bool unsetenv(const char* name);
 174 
 175   static bool have_special_privileges();
 176 
 177   static jlong  javaTimeMillis();
 178   static jlong  javaTimeNanos();
 179   static void   javaTimeNanos_info(jvmtiTimerInfo *info_ptr);
 180   static void   javaTimeSystemUTC(jlong &seconds, jlong &nanos);
 181   static void   run_periodic_checks();
 182   static bool   supports_monotonic_clock();
 183 
 184   // Returns the elapsed time in seconds since the vm started.
 185   static double elapsedTime();
 186 
 187   // Returns real time in seconds since an arbitrary point
 188   // in the past.
 189   static bool getTimesSecs(double* process_real_time,
 190                            double* process_user_time,
 191                            double* process_system_time);
 192 
 193   // Interface to the performance counter
 194   static jlong elapsed_counter();
 195   static jlong elapsed_frequency();
 196 
 197   // The "virtual time" of a thread is the amount of time a thread has
 198   // actually run.  The first function indicates whether the OS supports
 199   // this functionality for the current thread, and if so:
 200   //   * the second enables vtime tracking (if that is required).
 201   //   * the third tells whether vtime is enabled.
 202   //   * the fourth returns the elapsed virtual time for the current
 203   //     thread.
 204   static bool supports_vtime();
 205   static bool enable_vtime();
 206   static bool vtime_enabled();
 207   static double elapsedVTime();
 208 
 209   // Return current local time in a string (YYYY-MM-DD HH:MM:SS).
 210   // It is MT safe, but not async-safe, as reading time zone
 211   // information may require a lock on some platforms.
 212   static char*      local_time_string(char *buf, size_t buflen);
 213   static struct tm* localtime_pd     (const time_t* clock, struct tm*  res);
 214   static struct tm* gmtime_pd        (const time_t* clock, struct tm*  res);
 215   // Fill in buffer with current local time as an ISO-8601 string.
 216   // E.g., YYYY-MM-DDThh:mm:ss.mmm+zzzz.
 217   // Returns buffer, or NULL if it failed.
 218   static char* iso8601_time(char* buffer, size_t buffer_length, bool utc = false);
 219 
 220   // Interface for detecting multiprocessor system
 221   static inline bool is_MP() {
 222     // During bootstrap if _processor_count is not yet initialized
 223     // we claim to be MP as that is safest. If any platform has a
 224     // stub generator that might be triggered in this phase and for
 225     // which being declared MP when in fact not, is a problem - then
 226     // the bootstrap routine for the stub generator needs to check
 227     // the processor count directly and leave the bootstrap routine
 228     // in place until called after initialization has ocurred.
 229     return AssumeMP || (_processor_count != 1);
 230   }
 231   static julong available_memory();
 232   static julong physical_memory();
 233   static bool has_allocatable_memory_limit(julong* limit);
 234   static bool is_server_class_machine();
 235 
 236   // number of CPUs
 237   static int processor_count() {
 238     return _processor_count;
 239   }
 240   static void set_processor_count(int count) { _processor_count = count; }
 241 
 242   // Returns the number of CPUs this process is currently allowed to run on.
 243   // Note that on some OSes this can change dynamically.
 244   static int active_processor_count();
 245 
 246   // At startup the number of active CPUs this process is allowed to run on.
 247   // This value does not change dynamically. May be different from active_processor_count().
 248   static int initial_active_processor_count() {
 249     assert(_initial_active_processor_count > 0, "Initial active processor count not set yet.");
 250     return _initial_active_processor_count;
 251   }
 252 
 253   // Bind processes to processors.
 254   //     This is a two step procedure:
 255   //     first you generate a distribution of processes to processors,
 256   //     then you bind processes according to that distribution.
 257   // Compute a distribution for number of processes to processors.
 258   //    Stores the processor id's into the distribution array argument.
 259   //    Returns true if it worked, false if it didn't.
 260   static bool distribute_processes(uint length, uint* distribution);
 261   // Binds the current process to a processor.
 262   //    Returns true if it worked, false if it didn't.
 263   static bool bind_to_processor(uint processor_id);
 264 
 265   // Give a name to the current thread.
 266   static void set_native_thread_name(const char *name);
 267 
 268   // Interface for stack banging (predetect possible stack overflow for
 269   // exception processing)  There are guard pages, and above that shadow
 270   // pages for stack overflow checking.
 271   static bool uses_stack_guard_pages();
 272   static bool must_commit_stack_guard_pages();
 273   static void map_stack_shadow_pages(address sp);
 274   static bool stack_shadow_pages_available(Thread *thread, const methodHandle& method, address sp);
 275 
 276   // Find committed memory region within specified range (start, start + size),
 277   // return true if found any
 278   static bool committed_in_range(address start, size_t size, address& committed_start, size_t& committed_size);
 279 
 280   // OS interface to Virtual Memory
 281 
 282   // Return the default page size.
 283   static int    vm_page_size();
 284 
 285   // Returns the page size to use for a region of memory.
 286   // region_size / min_pages will always be greater than or equal to the
 287   // returned value. The returned value will divide region_size.
 288   static size_t page_size_for_region_aligned(size_t region_size, size_t min_pages);
 289 
 290   // Returns the page size to use for a region of memory.
 291   // region_size / min_pages will always be greater than or equal to the
 292   // returned value. The returned value might not divide region_size.
 293   static size_t page_size_for_region_unaligned(size_t region_size, size_t min_pages);
 294 
 295   // Return the largest page size that can be used
 296   static size_t max_page_size() {
 297     // The _page_sizes array is sorted in descending order.
 298     return _page_sizes[0];
 299   }
 300 
 301   // Methods for tracing page sizes returned by the above method.
 302   // The region_{min,max}_size parameters should be the values
 303   // passed to page_size_for_region() and page_size should be the result of that
 304   // call.  The (optional) base and size parameters should come from the
 305   // ReservedSpace base() and size() methods.
 306   static void trace_page_sizes(const char* str, const size_t* page_sizes, int count);
 307   static void trace_page_sizes(const char* str,
 308                                const size_t region_min_size,
 309                                const size_t region_max_size,
 310                                const size_t page_size,
 311                                const char* base,
 312                                const size_t size);
 313   static void trace_page_sizes_for_requested_size(const char* str,
 314                                                   const size_t requested_size,
 315                                                   const size_t page_size,
 316                                                   const size_t alignment,
 317                                                   const char* base,
 318                                                   const size_t size);
 319 
 320   static int    vm_allocation_granularity();
 321   static char*  reserve_memory(size_t bytes, char* addr = 0,
 322                                size_t alignment_hint = 0, int file_desc = -1);
 323   static char*  reserve_memory(size_t bytes, char* addr,
 324                                size_t alignment_hint, MEMFLAGS flags);
 325   static char*  reserve_memory_aligned(size_t size, size_t alignment, int file_desc = -1);
 326   static char*  attempt_reserve_memory_at(size_t bytes, char* addr, int file_desc = -1);
 327   static void   split_reserved_memory(char *base, size_t size,
 328                                       size_t split, bool realloc);
 329   static bool   commit_memory(char* addr, size_t bytes, bool executable);
 330   static bool   commit_memory(char* addr, size_t size, size_t alignment_hint,
 331                               bool executable);
 332   // Same as commit_memory() that either succeeds or calls
 333   // vm_exit_out_of_memory() with the specified mesg.
 334   static void   commit_memory_or_exit(char* addr, size_t bytes,
 335                                       bool executable, const char* mesg);
 336   static void   commit_memory_or_exit(char* addr, size_t size,
 337                                       size_t alignment_hint,
 338                                       bool executable, const char* mesg);
 339   static bool   uncommit_memory(char* addr, size_t bytes);
 340   static bool   release_memory(char* addr, size_t bytes);
 341 
 342   // Touch memory pages that cover the memory range from start to end (exclusive)
 343   // to make the OS back the memory range with actual memory.
 344   // Current implementation may not touch the last page if unaligned addresses
 345   // are passed.
 346   static void   pretouch_memory(void* start, void* end, size_t page_size = vm_page_size());
 347 
 348   enum ProtType { MEM_PROT_NONE, MEM_PROT_READ, MEM_PROT_RW, MEM_PROT_RWX };
 349   static bool   protect_memory(char* addr, size_t bytes, ProtType prot,
 350                                bool is_committed = true);
 351 
 352   static bool   guard_memory(char* addr, size_t bytes);
 353   static bool   unguard_memory(char* addr, size_t bytes);
 354   static bool   create_stack_guard_pages(char* addr, size_t bytes);
 355   static bool   pd_create_stack_guard_pages(char* addr, size_t bytes);
 356   static bool   remove_stack_guard_pages(char* addr, size_t bytes);
 357   // Helper function to create a new file with template jvmheap.XXXXXX.
 358   // Returns a valid fd on success or else returns -1
 359   static int create_file_for_heap(const char* dir);
 360   // Map memory to the file referred by fd. This function is slightly different from map_memory()
 361   // and is added to be used for implementation of -XX:AllocateHeapAt
 362   static char* map_memory_to_file(char* base, size_t size, int fd);
 363   // Replace existing reserved memory with file mapping
 364   static char* replace_existing_mapping_with_file_mapping(char* base, size_t size, int fd);
 365 
 366   static char*  map_memory(int fd, const char* file_name, size_t file_offset,
 367                            char *addr, size_t bytes, bool read_only = false,
 368                            bool allow_exec = false);
 369   static char*  remap_memory(int fd, const char* file_name, size_t file_offset,
 370                              char *addr, size_t bytes, bool read_only,
 371                              bool allow_exec);
 372   static bool   unmap_memory(char *addr, size_t bytes);
 373   static void   free_memory(char *addr, size_t bytes, size_t alignment_hint);
 374   static void   realign_memory(char *addr, size_t bytes, size_t alignment_hint);
 375 
 376   // NUMA-specific interface
 377   static bool   numa_has_static_binding();
 378   static bool   numa_has_group_homing();
 379   static void   numa_make_local(char *addr, size_t bytes, int lgrp_hint);
 380   static void   numa_make_global(char *addr, size_t bytes);
 381   static size_t numa_get_groups_num();
 382   static size_t numa_get_leaf_groups(int *ids, size_t size);
 383   static bool   numa_topology_changed();
 384   static int    numa_get_group_id();
 385 
 386   // Page manipulation
 387   struct page_info {
 388     size_t size;
 389     int lgrp_id;
 390   };
 391   static bool   get_page_info(char *start, page_info* info);
 392   static char*  scan_pages(char *start, char* end, page_info* page_expected, page_info* page_found);
 393 
 394   static char*  non_memory_address_word();
 395   // reserve, commit and pin the entire memory region
 396   static char*  reserve_memory_special(size_t size, size_t alignment,
 397                                        char* addr, bool executable);
 398   static bool   release_memory_special(char* addr, size_t bytes);
 399   static void   large_page_init();
 400   static size_t large_page_size();
 401   static bool   can_commit_large_page_memory();
 402   static bool   can_execute_large_page_memory();
 403 
 404   // OS interface to polling page
 405   static address get_polling_page()             { return _polling_page; }
 406   static void    set_polling_page(address page) { _polling_page = page; }
 407   static bool    is_poll_address(address addr)  { return addr >= _polling_page && addr < (_polling_page + os::vm_page_size()); }
 408   static void    make_polling_page_unreadable();
 409   static void    make_polling_page_readable();
 410 
 411   // Routines used to serialize the thread state without using membars
 412   static void    serialize_thread_states();
 413 
 414   // Since we write to the serialize page from every thread, we
 415   // want stores to be on unique cache lines whenever possible
 416   // in order to minimize CPU cross talk.  We pre-compute the
 417   // amount to shift the thread* to make this offset unique to
 418   // each thread.
 419   static int     get_serialize_page_shift_count() {
 420     return SerializePageShiftCount;
 421   }
 422 
 423   static void     set_serialize_page_mask(uintptr_t mask) {
 424     _serialize_page_mask = mask;
 425   }
 426 
 427   static unsigned int  get_serialize_page_mask() {
 428     return _serialize_page_mask;
 429   }
 430 
 431   static void    set_memory_serialize_page(address page);
 432 
 433   static address get_memory_serialize_page() {
 434     return (address)_mem_serialize_page;
 435   }
 436 
 437   static inline void write_memory_serialize_page(JavaThread *thread) {
 438     uintptr_t page_offset = ((uintptr_t)thread >>
 439                             get_serialize_page_shift_count()) &
 440                             get_serialize_page_mask();
 441     *(volatile int32_t *)((uintptr_t)_mem_serialize_page+page_offset) = 1;
 442   }
 443 
 444   static bool    is_memory_serialize_page(JavaThread *thread, address addr) {
 445     if (UseMembar) return false;
 446     // Previously this function calculated the exact address of this
 447     // thread's serialize page, and checked if the faulting address
 448     // was equal.  However, some platforms mask off faulting addresses
 449     // to the page size, so now we just check that the address is
 450     // within the page.  This makes the thread argument unnecessary,
 451     // but we retain the NULL check to preserve existing behavior.
 452     if (thread == NULL) return false;
 453     address page = (address) _mem_serialize_page;
 454     return addr >= page && addr < (page + os::vm_page_size());
 455   }
 456 
 457   static void block_on_serialize_page_trap();
 458 
 459   // threads
 460 
 461   enum ThreadType {
 462     vm_thread,
 463     cgc_thread,        // Concurrent GC thread
 464     pgc_thread,        // Parallel GC thread
 465     java_thread,       // Java, CodeCacheSweeper, JVMTIAgent and Service threads.
 466     compiler_thread,
 467     watcher_thread,
 468     os_thread
 469   };
 470 
 471   static bool create_thread(Thread* thread,
 472                             ThreadType thr_type,
 473                             size_t req_stack_size = 0);
 474 
 475   // The "main thread", also known as "starting thread", is the thread
 476   // that loads/creates the JVM via JNI_CreateJavaVM.
 477   static bool create_main_thread(JavaThread* thread);
 478 
 479   // The primordial thread is the initial process thread. The java
 480   // launcher never uses the primordial thread as the main thread, but
 481   // applications that host the JVM directly may do so. Some platforms
 482   // need special-case handling of the primordial thread if it attaches
 483   // to the VM.
 484   static bool is_primordial_thread(void)
 485 #if defined(_WINDOWS) || defined(BSD)
 486     // No way to identify the primordial thread.
 487     { return false; }
 488 #else
 489   ;
 490 #endif
 491 
 492   static bool create_attached_thread(JavaThread* thread);
 493   static void pd_start_thread(Thread* thread);
 494   static void start_thread(Thread* thread);
 495 
 496   static void initialize_thread(Thread* thr);
 497   static void free_thread(OSThread* osthread);
 498 
 499   // thread id on Linux/64bit is 64bit, on Windows and Solaris, it's 32bit
 500   static intx current_thread_id();
 501   static int current_process_id();
 502   static int sleep(Thread* thread, jlong ms, bool interruptable);
 503   // Short standalone OS sleep suitable for slow path spin loop.
 504   // Ignores Thread.interrupt() (so keep it short).
 505   // ms = 0, will sleep for the least amount of time allowed by the OS.
 506   static void naked_short_sleep(jlong ms);
 507   static void infinite_sleep(); // never returns, use with CAUTION
 508   static void naked_yield () ;
 509   static OSReturn set_priority(Thread* thread, ThreadPriority priority);
 510   static OSReturn get_priority(const Thread* const thread, ThreadPriority& priority);
 511 
 512   static void interrupt(Thread* thread);
 513   static bool is_interrupted(Thread* thread, bool clear_interrupted);
 514 
 515   static int pd_self_suspend_thread(Thread* thread);
 516 
 517   static ExtendedPC fetch_frame_from_context(const void* ucVoid, intptr_t** sp, intptr_t** fp);
 518   static frame      fetch_frame_from_context(const void* ucVoid);
 519   static frame      fetch_frame_from_ucontext(Thread* thread, void* ucVoid);
 520 
 521   static void breakpoint();
 522   static bool start_debugging(char *buf, int buflen);
 523 
 524   static address current_stack_pointer();
 525   static address current_stack_base();
 526   static size_t current_stack_size();
 527 
 528   static void verify_stack_alignment() PRODUCT_RETURN;
 529 
 530   static bool message_box(const char* title, const char* message);
 531   static char* do_you_want_to_debug(const char* message);
 532 
 533   // run cmd in a separate process and return its exit code; or -1 on failures
 534   static int fork_and_exec(char *cmd);
 535 
 536   // Call ::exit() on all platforms but Windows
 537   static void exit(int num);
 538 
 539   // Terminate the VM, but don't exit the process
 540   static void shutdown();
 541 
 542   // Terminate with an error.  Default is to generate a core file on platforms
 543   // that support such things.  This calls shutdown() and then aborts.
 544   static void abort(bool dump_core, void *siginfo, const void *context);
 545   static void abort(bool dump_core = true);
 546 
 547   // Die immediately, no exit hook, no abort hook, no cleanup.
 548   static void die();
 549 
 550   // File i/o operations
 551   static const int default_file_open_flags();
 552   static int open(const char *path, int oflag, int mode);
 553   static FILE* open(int fd, const char* mode);
 554   static FILE* fopen(const char* path, const char* mode);
 555   static int close(int fd);
 556   static jlong lseek(int fd, jlong offset, int whence);
 557   static char* native_path(char *path);
 558   static int ftruncate(int fd, jlong length);
 559   static int fsync(int fd);
 560   static int available(int fd, jlong *bytes);
 561   static int get_fileno(FILE* fp);
 562   static void flockfile(FILE* fp);
 563   static void funlockfile(FILE* fp);
 564 
 565   static int compare_file_modified_times(const char* file1, const char* file2);
 566 
 567   //File i/o operations
 568 
 569   static size_t read(int fd, void *buf, unsigned int nBytes);
 570   static size_t read_at(int fd, void *buf, unsigned int nBytes, jlong offset);
 571   static size_t restartable_read(int fd, void *buf, unsigned int nBytes);
 572   static size_t write(int fd, const void *buf, unsigned int nBytes);
 573 
 574   // Reading directories.
 575   static DIR*           opendir(const char* dirname);
 576   static int            readdir_buf_size(const char *path);
 577   static struct dirent* readdir(DIR* dirp, dirent* dbuf);
 578   static int            closedir(DIR* dirp);
 579 
 580   // Dynamic library extension
 581   static const char*    dll_file_extension();
 582 
 583   static const char*    get_temp_directory();
 584   static const char*    get_current_directory(char *buf, size_t buflen);
 585 
 586   // Builds the platform-specific name of a library.
 587   // Returns false if the buffer is too small.
 588   static bool           dll_build_name(char* buffer, size_t size,
 589                                        const char* fname);
 590 
 591   // Builds a platform-specific full library path given an ld path and
 592   // unadorned library name. Returns true if the buffer contains a full
 593   // path to an existing file, false otherwise. If pathname is empty,
 594   // uses the path to the current directory.
 595   static bool           dll_locate_lib(char* buffer, size_t size,
 596                                        const char* pathname, const char* fname);
 597 
 598   // Symbol lookup, find nearest function name; basically it implements
 599   // dladdr() for all platforms. Name of the nearest function is copied
 600   // to buf. Distance from its base address is optionally returned as offset.
 601   // If function name is not found, buf[0] is set to '\0' and offset is
 602   // set to -1 (if offset is non-NULL).
 603   static bool dll_address_to_function_name(address addr, char* buf,
 604                                            int buflen, int* offset,
 605                                            bool demangle = true);
 606 
 607   // Locate DLL/DSO. On success, full path of the library is copied to
 608   // buf, and offset is optionally set to be the distance between addr
 609   // and the library's base address. On failure, buf[0] is set to '\0'
 610   // and offset is set to -1 (if offset is non-NULL).
 611   static bool dll_address_to_library_name(address addr, char* buf,
 612                                           int buflen, int* offset);
 613 
 614   // Find out whether the pc is in the static code for jvm.dll/libjvm.so.
 615   static bool address_is_in_vm(address addr);
 616 
 617   // Loads .dll/.so and
 618   // in case of error it checks if .dll/.so was built for the
 619   // same architecture as HotSpot is running on
 620   static void* dll_load(const char *name, char *ebuf, int ebuflen);
 621 
 622   // lookup symbol in a shared library
 623   static void* dll_lookup(void* handle, const char* name);
 624 
 625   // Unload library
 626   static void  dll_unload(void *lib);
 627 
 628   // Callback for loaded module information
 629   // Input parameters:
 630   //    char*     module_file_name,
 631   //    address   module_base_addr,
 632   //    address   module_top_addr,
 633   //    void*     param
 634   typedef int (*LoadedModulesCallbackFunc)(const char *, address, address, void *);
 635 
 636   static int get_loaded_modules_info(LoadedModulesCallbackFunc callback, void *param);
 637 
 638   // Return the handle of this process
 639   static void* get_default_process_handle();
 640 
 641   // Check for static linked agent library
 642   static bool find_builtin_agent(AgentLibrary *agent_lib, const char *syms[],
 643                                  size_t syms_len);
 644 
 645   // Find agent entry point
 646   static void *find_agent_function(AgentLibrary *agent_lib, bool check_lib,
 647                                    const char *syms[], size_t syms_len);
 648 
 649   // Provide C99 compliant versions of these functions, since some versions
 650   // of some platforms don't.
 651   static int vsnprintf(char* buf, size_t len, const char* fmt, va_list args) ATTRIBUTE_PRINTF(3, 0);
 652   static int snprintf(char* buf, size_t len, const char* fmt, ...) ATTRIBUTE_PRINTF(3, 4);
 653 
 654   // Get host name in buffer provided
 655   static bool get_host_name(char* buf, size_t buflen);
 656 
 657   // Print out system information; they are called by fatal error handler.
 658   // Output format may be different on different platforms.
 659   static void print_os_info(outputStream* st);
 660   static void print_os_info_brief(outputStream* st);
 661   static void print_cpu_info(outputStream* st, char* buf, size_t buflen);
 662   static void pd_print_cpu_info(outputStream* st, char* buf, size_t buflen);
 663   static void print_summary_info(outputStream* st, char* buf, size_t buflen);
 664   static void print_memory_info(outputStream* st);
 665   static void print_dll_info(outputStream* st);
 666   static void print_environment_variables(outputStream* st, const char** env_list);
 667   static void print_context(outputStream* st, const void* context);
 668   static void print_register_info(outputStream* st, const void* context);
 669   static void print_siginfo(outputStream* st, const void* siginfo);
 670   static void print_signal_handlers(outputStream* st, char* buf, size_t buflen);
 671   static void print_date_and_time(outputStream* st, char* buf, size_t buflen);
 672 
 673   static void print_location(outputStream* st, intptr_t x, bool verbose = false);
 674   static size_t lasterror(char *buf, size_t len);
 675   static int get_last_error();
 676 
 677   // Replacement for strerror().
 678   // Will return the english description of the error (e.g. "File not found", as
 679   //  suggested in the POSIX standard.
 680   // Will return "Unknown error" for an unknown errno value.
 681   // Will not attempt to localize the returned string.
 682   // Will always return a valid string which is a static constant.
 683   // Will not change the value of errno.
 684   static const char* strerror(int e);
 685 
 686   // Will return the literalized version of the given errno (e.g. "EINVAL"
 687   //  for EINVAL).
 688   // Will return "Unknown error" for an unknown errno value.
 689   // Will always return a valid string which is a static constant.
 690   // Will not change the value of errno.
 691   static const char* errno_name(int e);
 692 
 693   // Determines whether the calling process is being debugged by a user-mode debugger.
 694   static bool is_debugger_attached();
 695 
 696   // wait for a key press if PauseAtExit is set
 697   static void wait_for_keypress_at_exit(void);
 698 
 699   // The following two functions are used by fatal error handler to trace
 700   // native (C) frames. They are not part of frame.hpp/frame.cpp because
 701   // frame.hpp/cpp assume thread is JavaThread, and also because different
 702   // OS/compiler may have different convention or provide different API to
 703   // walk C frames.
 704   //
 705   // We don't attempt to become a debugger, so we only follow frames if that
 706   // does not require a lookup in the unwind table, which is part of the binary
 707   // file but may be unsafe to read after a fatal error. So on x86, we can
 708   // only walk stack if %ebp is used as frame pointer; on ia64, it's not
 709   // possible to walk C stack without having the unwind table.
 710   static bool is_first_C_frame(frame *fr);
 711   static frame get_sender_for_C_frame(frame *fr);
 712 
 713   // return current frame. pc() and sp() are set to NULL on failure.
 714   static frame      current_frame();
 715 
 716   static void print_hex_dump(outputStream* st, address start, address end, int unitsize);
 717 
 718   // returns a string to describe the exception/signal;
 719   // returns NULL if exception_code is not an OS exception/signal.
 720   static const char* exception_name(int exception_code, char* buf, size_t buflen);
 721 
 722   // Returns the signal number (e.g. 11) for a given signal name (SIGSEGV).
 723   static int get_signal_number(const char* signal_name);
 724 
 725   // Returns native Java library, loads if necessary
 726   static void*    native_java_library();
 727 
 728   // Fills in path to jvm.dll/libjvm.so (used by the Disassembler)
 729   static void     jvm_path(char *buf, jint buflen);
 730 
 731   // JNI names
 732   static void     print_jni_name_prefix_on(outputStream* st, int args_size);
 733   static void     print_jni_name_suffix_on(outputStream* st, int args_size);
 734 
 735   // Init os specific system properties values
 736   static void init_system_properties_values();
 737 
 738   // IO operations, non-JVM_ version.
 739   static int stat(const char* path, struct stat* sbuf);
 740   static bool dir_is_empty(const char* path);
 741 
 742   // IO operations on binary files
 743   static int create_binary_file(const char* path, bool rewrite_existing);
 744   static jlong current_file_offset(int fd);
 745   static jlong seek_to_file_offset(int fd, jlong offset);
 746 
 747   // Retrieve native stack frames.
 748   // Parameter:
 749   //   stack:  an array to storage stack pointers.
 750   //   frames: size of above array.
 751   //   toSkip: number of stack frames to skip at the beginning.
 752   // Return: number of stack frames captured.
 753   static int get_native_stack(address* stack, int size, int toSkip = 0);
 754 
 755   // General allocation (must be MT-safe)
 756   static void* malloc  (size_t size, MEMFLAGS flags, const NativeCallStack& stack);
 757   static void* malloc  (size_t size, MEMFLAGS flags);
 758   static void* realloc (void *memblock, size_t size, MEMFLAGS flag, const NativeCallStack& stack);
 759   static void* realloc (void *memblock, size_t size, MEMFLAGS flag);
 760 
 761   static void  free    (void *memblock);
 762   static char* strdup(const char *, MEMFLAGS flags = mtInternal);  // Like strdup
 763   // Like strdup, but exit VM when strdup() returns NULL
 764   static char* strdup_check_oom(const char*, MEMFLAGS flags = mtInternal);
 765 
 766 #ifndef PRODUCT
 767   static julong num_mallocs;         // # of calls to malloc/realloc
 768   static julong alloc_bytes;         // # of bytes allocated
 769   static julong num_frees;           // # of calls to free
 770   static julong free_bytes;          // # of bytes freed
 771 #endif
 772 
 773   // SocketInterface (ex HPI SocketInterface )
 774   static int socket(int domain, int type, int protocol);
 775   static int socket_close(int fd);
 776   static int recv(int fd, char* buf, size_t nBytes, uint flags);
 777   static int send(int fd, char* buf, size_t nBytes, uint flags);
 778   static int raw_send(int fd, char* buf, size_t nBytes, uint flags);
 779   static int connect(int fd, struct sockaddr* him, socklen_t len);
 780   static struct hostent* get_host_by_name(char* name);
 781 
 782   // Support for signals (see JVM_RaiseSignal, JVM_RegisterSignal)
 783   static void  initialize_jdk_signal_support(TRAPS);
 784   static void  signal_notify(int signal_number);
 785   static void* signal(int signal_number, void* handler);
 786   static void  signal_raise(int signal_number);
 787   static int   signal_wait();
 788   static void* user_handler();
 789   static void  terminate_signal_thread();
 790   static int   sigexitnum_pd();
 791 
 792   // random number generation
 793   static int random();                     // return 32bit pseudorandom number
 794   static void init_random(unsigned int initval);    // initialize random sequence
 795 
 796   // Structured OS Exception support
 797   static void os_exception_wrapper(java_call_t f, JavaValue* value, const methodHandle& method, JavaCallArguments* args, Thread* thread);
 798 
 799   // On Posix compatible OS it will simply check core dump limits while on Windows
 800   // it will check if dump file can be created. Check or prepare a core dump to be
 801   // taken at a later point in the same thread in os::abort(). Use the caller
 802   // provided buffer as a scratch buffer. The status message which will be written
 803   // into the error log either is file location or a short error message, depending
 804   // on the checking result.
 805   static void check_dump_limit(char* buffer, size_t bufferSize);
 806 
 807   // Get the default path to the core file
 808   // Returns the length of the string
 809   static int get_core_path(char* buffer, size_t bufferSize);
 810 
 811   // JVMTI & JVM monitoring and management support
 812   // The thread_cpu_time() and current_thread_cpu_time() are only
 813   // supported if is_thread_cpu_time_supported() returns true.
 814   // They are not supported on Solaris T1.
 815 
 816   // Thread CPU Time - return the fast estimate on a platform
 817   // On Solaris - call gethrvtime (fast) - user time only
 818   // On Linux   - fast clock_gettime where available - user+sys
 819   //            - otherwise: very slow /proc fs - user+sys
 820   // On Windows - GetThreadTimes - user+sys
 821   static jlong current_thread_cpu_time();
 822   static jlong thread_cpu_time(Thread* t);
 823 
 824   // Thread CPU Time with user_sys_cpu_time parameter.
 825   //
 826   // If user_sys_cpu_time is true, user+sys time is returned.
 827   // Otherwise, only user time is returned
 828   static jlong current_thread_cpu_time(bool user_sys_cpu_time);
 829   static jlong thread_cpu_time(Thread* t, bool user_sys_cpu_time);
 830 
 831   // Return a bunch of info about the timers.
 832   // Note that the returned info for these two functions may be different
 833   // on some platforms
 834   static void current_thread_cpu_time_info(jvmtiTimerInfo *info_ptr);
 835   static void thread_cpu_time_info(jvmtiTimerInfo *info_ptr);
 836 
 837   static bool is_thread_cpu_time_supported();
 838 
 839   // System loadavg support.  Returns -1 if load average cannot be obtained.
 840   static int loadavg(double loadavg[], int nelem);
 841 
 842   // Hook for os specific jvm options that we don't want to abort on seeing
 843   static bool obsolete_option(const JavaVMOption *option);
 844 
 845   // Amount beyond the callee frame size that we bang the stack.
 846   static int extra_bang_size_in_bytes();
 847 
 848   static char** split_path(const char* path, int* n);
 849 
 850   // Extensions
 851 #include "runtime/os_ext.hpp"
 852 
 853  public:
 854   class CrashProtectionCallback : public StackObj {
 855   public:
 856     virtual void call() = 0;
 857   };
 858 
 859   // Platform dependent stuff
 860 #ifndef _WINDOWS
 861 # include "os_posix.hpp"
 862 #endif
 863 #include OS_CPU_HEADER(os)
 864 #include OS_HEADER(os)
 865 
 866 #ifndef OS_NATIVE_THREAD_CREATION_FAILED_MSG
 867 #define OS_NATIVE_THREAD_CREATION_FAILED_MSG "unable to create native thread: possibly out of memory or process/resource limits reached"
 868 #endif
 869 
 870  public:
 871 #ifndef PLATFORM_PRINT_NATIVE_STACK
 872   // No platform-specific code for printing the native stack.
 873   static bool platform_print_native_stack(outputStream* st, const void* context,
 874                                           char *buf, int buf_size) {
 875     return false;
 876   }
 877 #endif
 878 
 879   // debugging support (mostly used by debug.cpp but also fatal error handler)
 880   static bool find(address pc, outputStream* st = tty); // OS specific function to make sense out of an address
 881 
 882   static bool dont_yield();                     // when true, JVM_Yield() is nop
 883   static void print_statistics();
 884 
 885   // Thread priority helpers (implemented in OS-specific part)
 886   static OSReturn set_native_priority(Thread* thread, int native_prio);
 887   static OSReturn get_native_priority(const Thread* const thread, int* priority_ptr);
 888   static int java_to_os_priority[CriticalPriority + 1];
 889   // Hint to the underlying OS that a task switch would not be good.
 890   // Void return because it's a hint and can fail.
 891   static void hint_no_preempt();
 892   static const char* native_thread_creation_failed_msg() {
 893     return OS_NATIVE_THREAD_CREATION_FAILED_MSG;
 894   }
 895 
 896   // Used at creation if requested by the diagnostic flag PauseAtStartup.
 897   // Causes the VM to wait until an external stimulus has been applied
 898   // (for Unix, that stimulus is a signal, for Windows, an external
 899   // ResumeThread call)
 900   static void pause();
 901 
 902   // Builds a platform dependent Agent_OnLoad_<libname> function name
 903   // which is used to find statically linked in agents.
 904   static char*  build_agent_function_name(const char *sym, const char *cname,
 905                                           bool is_absolute_path);
 906 
 907   class SuspendedThreadTaskContext {
 908   public:
 909     SuspendedThreadTaskContext(Thread* thread, void *ucontext) : _thread(thread), _ucontext(ucontext) {}
 910     Thread* thread() const { return _thread; }
 911     void* ucontext() const { return _ucontext; }
 912   private:
 913     Thread* _thread;
 914     void* _ucontext;
 915   };
 916 
 917   class SuspendedThreadTask {
 918   public:
 919     SuspendedThreadTask(Thread* thread) : _thread(thread), _done(false) {}
 920     void run();
 921     bool is_done() { return _done; }
 922     virtual void do_task(const SuspendedThreadTaskContext& context) = 0;
 923   protected:
 924     ~SuspendedThreadTask() {}
 925   private:
 926     void internal_do_task();
 927     Thread* _thread;
 928     bool _done;
 929   };
 930 
 931 #ifndef _WINDOWS
 932   // Suspend/resume support
 933   // Protocol:
 934   //
 935   // a thread starts in SR_RUNNING
 936   //
 937   // SR_RUNNING can go to
 938   //   * SR_SUSPEND_REQUEST when the WatcherThread wants to suspend it
 939   // SR_SUSPEND_REQUEST can go to
 940   //   * SR_RUNNING if WatcherThread decides it waited for SR_SUSPENDED too long (timeout)
 941   //   * SR_SUSPENDED if the stopped thread receives the signal and switches state
 942   // SR_SUSPENDED can go to
 943   //   * SR_WAKEUP_REQUEST when the WatcherThread has done the work and wants to resume
 944   // SR_WAKEUP_REQUEST can go to
 945   //   * SR_RUNNING when the stopped thread receives the signal
 946   //   * SR_WAKEUP_REQUEST on timeout (resend the signal and try again)
 947   class SuspendResume {
 948    public:
 949     enum State {
 950       SR_RUNNING,
 951       SR_SUSPEND_REQUEST,
 952       SR_SUSPENDED,
 953       SR_WAKEUP_REQUEST
 954     };
 955 
 956   private:
 957     volatile State _state;
 958 
 959   private:
 960     /* try to switch state from state "from" to state "to"
 961      * returns the state set after the method is complete
 962      */
 963     State switch_state(State from, State to);
 964 
 965   public:
 966     SuspendResume() : _state(SR_RUNNING) { }
 967 
 968     State state() const { return _state; }
 969 
 970     State request_suspend() {
 971       return switch_state(SR_RUNNING, SR_SUSPEND_REQUEST);
 972     }
 973 
 974     State cancel_suspend() {
 975       return switch_state(SR_SUSPEND_REQUEST, SR_RUNNING);
 976     }
 977 
 978     State suspended() {
 979       return switch_state(SR_SUSPEND_REQUEST, SR_SUSPENDED);
 980     }
 981 
 982     State request_wakeup() {
 983       return switch_state(SR_SUSPENDED, SR_WAKEUP_REQUEST);
 984     }
 985 
 986     State running() {
 987       return switch_state(SR_WAKEUP_REQUEST, SR_RUNNING);
 988     }
 989 
 990     bool is_running() const {
 991       return _state == SR_RUNNING;
 992     }
 993 
 994     bool is_suspend_request() const {
 995       return _state == SR_SUSPEND_REQUEST;
 996     }
 997 
 998     bool is_suspended() const {
 999       return _state == SR_SUSPENDED;
1000     }
1001   };
1002 #endif // !WINDOWS
1003 
1004 
1005  protected:
1006   static volatile unsigned int _rand_seed;    // seed for random number generator
1007   static int _processor_count;                // number of processors
1008   static int _initial_active_processor_count; // number of active processors during initialization.
1009 
1010   static char* format_boot_path(const char* format_string,
1011                                 const char* home,
1012                                 int home_len,
1013                                 char fileSep,
1014                                 char pathSep);
1015   static bool set_boot_path(char fileSep, char pathSep);
1016 
1017 };
1018 
1019 #ifndef _WINDOWS
1020 template<> struct IsRegisteredEnum<os::SuspendResume::State> : public TrueType {};
1021 #endif // !_WINDOWS
1022 
1023 // Note that "PAUSE" is almost always used with synchronization
1024 // so arguably we should provide Atomic::SpinPause() instead
1025 // of the global SpinPause() with C linkage.
1026 // It'd also be eligible for inlining on many platforms.
1027 
1028 extern "C" int SpinPause();
1029 
1030 #endif // SHARE_VM_RUNTIME_OS_HPP