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