1 /*
   2  * Copyright (c) 1997, 2013, 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 "jvmtifiles/jvmti.h"
  29 #include "runtime/atomic.hpp"
  30 #include "runtime/extendedPC.hpp"
  31 #include "runtime/handles.hpp"
  32 #include "utilities/top.hpp"
  33 #ifdef TARGET_OS_FAMILY_linux
  34 # include "jvm_linux.h"
  35 #endif
  36 #ifdef TARGET_OS_FAMILY_solaris
  37 # include "jvm_solaris.h"
  38 #endif
  39 #ifdef TARGET_OS_FAMILY_windows
  40 # include "jvm_windows.h"
  41 #endif
  42 #ifdef TARGET_OS_FAMILY_bsd
  43 # include "jvm_bsd.h"
  44 #endif
  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 template<class E> class GrowableArray;
  58 
  59 // %%%%% Moved ThreadState, START_FN, OSThread to new osThread.hpp. -- Rose
  60 
  61 // Platform-independent error return values from OS functions
  62 enum OSReturn {
  63   OS_OK         =  0,        // Operation was successful
  64   OS_ERR        = -1,        // Operation failed
  65   OS_INTRPT     = -2,        // Operation was interrupted
  66   OS_TIMEOUT    = -3,        // Operation timed out
  67   OS_NOMEM      = -5,        // Operation failed for lack of memory
  68   OS_NORESOURCE = -6         // Operation failed for lack of nonmemory resource
  69 };
  70 
  71 enum ThreadPriority {        // JLS 20.20.1-3
  72   NoPriority       = -1,     // Initial non-priority value
  73   MinPriority      =  1,     // Minimum priority
  74   NormPriority     =  5,     // Normal (non-daemon) priority
  75   NearMaxPriority  =  9,     // High priority, used for VMThread
  76   MaxPriority      = 10,     // Highest priority, used for WatcherThread
  77                              // ensures that VMThread doesn't starve profiler
  78   CriticalPriority = 11      // Critical thread priority
  79 };
  80 
  81 // Typedef for structured exception handling support
  82 typedef void (*java_call_t)(JavaValue* value, methodHandle* method, JavaCallArguments* args, Thread* thread);
  83 
  84 class os: AllStatic {
  85  public:
  86   enum { page_sizes_max = 9 }; // Size of _page_sizes array (8 plus a sentinel)
  87 
  88  private:
  89   static OSThread*          _starting_thread;
  90   static address            _polling_page;
  91   static volatile int32_t * _mem_serialize_page;
  92   static uintptr_t          _serialize_page_mask;
  93  public:
  94   static size_t             _page_sizes[page_sizes_max];
  95 
  96  private:
  97   static void init_page_sizes(size_t default_page_size) {
  98     _page_sizes[0] = default_page_size;
  99     _page_sizes[1] = 0; // sentinel
 100   }
 101 
 102   static char*  pd_reserve_memory(size_t bytes, char* addr = 0,
 103                                size_t alignment_hint = 0);
 104   static char*  pd_attempt_reserve_memory_at(size_t bytes, char* addr);
 105   static void   pd_split_reserved_memory(char *base, size_t size,
 106                                       size_t split, bool realloc);
 107   static bool   pd_commit_memory(char* addr, size_t bytes, bool executable = false);
 108   static bool   pd_commit_memory(char* addr, size_t size, size_t alignment_hint,
 109                               bool executable = false);
 110   static bool   pd_uncommit_memory(char* addr, size_t bytes);
 111   static bool   pd_release_memory(char* addr, size_t bytes);
 112 
 113   static char*  pd_map_memory(int fd, const char* file_name, size_t file_offset,
 114                            char *addr, size_t bytes, bool read_only = false,
 115                            bool allow_exec = false);
 116   static char*  pd_remap_memory(int fd, const char* file_name, size_t file_offset,
 117                              char *addr, size_t bytes, bool read_only,
 118                              bool allow_exec);
 119   static bool   pd_unmap_memory(char *addr, size_t bytes);
 120   static void   pd_free_memory(char *addr, size_t bytes, size_t alignment_hint);
 121   static void   pd_realign_memory(char *addr, size_t bytes, size_t alignment_hint);
 122 
 123 
 124  public:
 125   static void init(void);                      // Called before command line parsing
 126   static jint init_2(void);                    // Called after command line parsing
 127   static void init_globals(void) {             // Called from init_globals() in init.cpp
 128     init_globals_ext();
 129   }
 130   static void init_3(void);                    // Called at the end of vm init
 131 
 132   // File names are case-insensitive on windows only
 133   // Override me as needed
 134   static int    file_name_strcmp(const char* s1, const char* s2);
 135 
 136   static bool getenv(const char* name, char* buffer, int len);
 137   static bool have_special_privileges();
 138 
 139   static jlong  javaTimeMillis();
 140   static jlong  javaTimeNanos();
 141   static void   javaTimeNanos_info(jvmtiTimerInfo *info_ptr);
 142   static void   run_periodic_checks();
 143 
 144 
 145   // Returns the elapsed time in seconds since the vm started.
 146   static double elapsedTime();
 147 
 148   // Returns real time in seconds since an arbitrary point
 149   // in the past.
 150   static bool getTimesSecs(double* process_real_time,
 151                            double* process_user_time,
 152                            double* process_system_time);
 153 
 154   // Interface to the performance counter
 155   static jlong elapsed_counter();
 156   static jlong elapsed_frequency();
 157 
 158   // The "virtual time" of a thread is the amount of time a thread has
 159   // actually run.  The first function indicates whether the OS supports
 160   // this functionality for the current thread, and if so:
 161   //   * the second enables vtime tracking (if that is required).
 162   //   * the third tells whether vtime is enabled.
 163   //   * the fourth returns the elapsed virtual time for the current
 164   //     thread.
 165   static bool supports_vtime();
 166   static bool enable_vtime();
 167   static bool vtime_enabled();
 168   static double elapsedVTime();
 169 
 170   // Return current local time in a string (YYYY-MM-DD HH:MM:SS).
 171   // It is MT safe, but not async-safe, as reading time zone
 172   // information may require a lock on some platforms.
 173   static char*      local_time_string(char *buf, size_t buflen);
 174   static struct tm* localtime_pd     (const time_t* clock, struct tm*  res);
 175   // Fill in buffer with current local time as an ISO-8601 string.
 176   // E.g., YYYY-MM-DDThh:mm:ss.mmm+zzzz.
 177   // Returns buffer, or NULL if it failed.
 178   static char* iso8601_time(char* buffer, size_t buffer_length);
 179 
 180   // Interface for detecting multiprocessor system
 181   static inline bool is_MP() {
 182     assert(_processor_count > 0, "invalid processor count");
 183     return _processor_count > 1 || AssumeMP;
 184   }
 185   static julong available_memory();
 186   static julong physical_memory();
 187   static bool has_allocatable_memory_limit(julong* limit);
 188   static bool is_server_class_machine();
 189 
 190   // number of CPUs
 191   static int processor_count() {
 192     return _processor_count;
 193   }
 194   static void set_processor_count(int count) { _processor_count = count; }
 195 
 196   // Returns the number of CPUs this process is currently allowed to run on.
 197   // Note that on some OSes this can change dynamically.
 198   static int active_processor_count();
 199 
 200   // Bind processes to processors.
 201   //     This is a two step procedure:
 202   //     first you generate a distribution of processes to processors,
 203   //     then you bind processes according to that distribution.
 204   // Compute a distribution for number of processes to processors.
 205   //    Stores the processor id's into the distribution array argument.
 206   //    Returns true if it worked, false if it didn't.
 207   static bool distribute_processes(uint length, uint* distribution);
 208   // Binds the current process to a processor.
 209   //    Returns true if it worked, false if it didn't.
 210   static bool bind_to_processor(uint processor_id);
 211 
 212   // Give a name to the current thread.
 213   static void set_native_thread_name(const char *name);
 214 
 215   // Interface for stack banging (predetect possible stack overflow for
 216   // exception processing)  There are guard pages, and above that shadow
 217   // pages for stack overflow checking.
 218   static bool uses_stack_guard_pages();
 219   static bool allocate_stack_guard_pages();
 220   static void bang_stack_shadow_pages();
 221   static bool stack_shadow_pages_available(Thread *thread, methodHandle method);
 222 
 223   // OS interface to Virtual Memory
 224 
 225   // Return the default page size.
 226   static int    vm_page_size();
 227 
 228   // Return the page size to use for a region of memory.  The min_pages argument
 229   // is a hint intended to limit fragmentation; it says the returned page size
 230   // should be <= region_max_size / min_pages.  Because min_pages is a hint,
 231   // this routine may return a size larger than region_max_size / min_pages.
 232   //
 233   // The current implementation ignores min_pages if a larger page size is an
 234   // exact multiple of both region_min_size and region_max_size.  This allows
 235   // larger pages to be used when doing so would not cause fragmentation; in
 236   // particular, a single page can be used when region_min_size ==
 237   // region_max_size == a supported page size.
 238   static size_t page_size_for_region(size_t region_min_size,
 239                                      size_t region_max_size,
 240                                      uint min_pages);
 241 
 242   // Methods for tracing page sizes returned by the above method; enabled by
 243   // TracePageSizes.  The region_{min,max}_size parameters should be the values
 244   // passed to page_size_for_region() and page_size should be the result of that
 245   // call.  The (optional) base and size parameters should come from the
 246   // ReservedSpace base() and size() methods.
 247   static void trace_page_sizes(const char* str, const size_t* page_sizes,
 248                                int count) PRODUCT_RETURN;
 249   static void trace_page_sizes(const char* str, const size_t region_min_size,
 250                                const size_t region_max_size,
 251                                const size_t page_size,
 252                                const char* base = NULL,
 253                                const size_t size = 0) PRODUCT_RETURN;
 254 
 255   static int    vm_allocation_granularity();
 256   static char*  reserve_memory(size_t bytes, char* addr = 0,
 257                                size_t alignment_hint = 0);
 258   static char*  reserve_memory(size_t bytes, char* addr,
 259                                size_t alignment_hint, MEMFLAGS flags);
 260   static char*  reserve_memory_aligned(size_t size, size_t alignment);
 261   static char*  attempt_reserve_memory_at(size_t bytes, char* addr);
 262   static void   split_reserved_memory(char *base, size_t size,
 263                                       size_t split, bool realloc);
 264   static bool   commit_memory(char* addr, size_t bytes, bool executable = false);
 265   static bool   commit_memory(char* addr, size_t size, size_t alignment_hint,
 266                               bool executable = false);
 267   static bool   uncommit_memory(char* addr, size_t bytes);
 268   static bool   release_memory(char* addr, size_t bytes);
 269 
 270   enum ProtType { MEM_PROT_NONE, MEM_PROT_READ, MEM_PROT_RW, MEM_PROT_RWX };
 271   static bool   protect_memory(char* addr, size_t bytes, ProtType prot,
 272                                bool is_committed = true);
 273 
 274   static bool   guard_memory(char* addr, size_t bytes);
 275   static bool   unguard_memory(char* addr, size_t bytes);
 276   static bool   create_stack_guard_pages(char* addr, size_t bytes);
 277   static bool   pd_create_stack_guard_pages(char* addr, size_t bytes);
 278   static bool   remove_stack_guard_pages(char* addr, size_t bytes);
 279 
 280   static char*  map_memory(int fd, const char* file_name, size_t file_offset,
 281                            char *addr, size_t bytes, bool read_only = false,
 282                            bool allow_exec = false);
 283   static char*  remap_memory(int fd, const char* file_name, size_t file_offset,
 284                              char *addr, size_t bytes, bool read_only,
 285                              bool allow_exec);
 286   static bool   unmap_memory(char *addr, size_t bytes);
 287   static void   free_memory(char *addr, size_t bytes, size_t alignment_hint);
 288   static void   realign_memory(char *addr, size_t bytes, size_t alignment_hint);
 289 
 290   // NUMA-specific interface
 291   static bool   numa_has_static_binding();
 292   static bool   numa_has_group_homing();
 293   static void   numa_make_local(char *addr, size_t bytes, int lgrp_hint);
 294   static void   numa_make_global(char *addr, size_t bytes);
 295   static size_t numa_get_groups_num();
 296   static size_t numa_get_leaf_groups(int *ids, size_t size);
 297   static bool   numa_topology_changed();
 298   static int    numa_get_group_id();
 299 
 300   // Page manipulation
 301   struct page_info {
 302     size_t size;
 303     int lgrp_id;
 304   };
 305   static bool   get_page_info(char *start, page_info* info);
 306   static char*  scan_pages(char *start, char* end, page_info* page_expected, page_info* page_found);
 307 
 308   static char*  non_memory_address_word();
 309   // reserve, commit and pin the entire memory region
 310   static char*  reserve_memory_special(size_t size, char* addr = NULL,
 311                 bool executable = false);
 312   static bool   release_memory_special(char* addr, size_t bytes);
 313   static void   large_page_init();
 314   static size_t large_page_size();
 315   static bool   can_commit_large_page_memory();
 316   static bool   can_execute_large_page_memory();
 317 
 318   // OS interface to polling page
 319   static address get_polling_page()             { return _polling_page; }
 320   static void    set_polling_page(address page) { _polling_page = page; }
 321   static bool    is_poll_address(address addr)  { return addr >= _polling_page && addr < (_polling_page + os::vm_page_size()); }
 322   static void    make_polling_page_unreadable();
 323   static void    make_polling_page_readable();
 324 
 325   // Routines used to serialize the thread state without using membars
 326   static void    serialize_thread_states();
 327 
 328   // Since we write to the serialize page from every thread, we
 329   // want stores to be on unique cache lines whenever possible
 330   // in order to minimize CPU cross talk.  We pre-compute the
 331   // amount to shift the thread* to make this offset unique to
 332   // each thread.
 333   static int     get_serialize_page_shift_count() {
 334     return SerializePageShiftCount;
 335   }
 336 
 337   static void     set_serialize_page_mask(uintptr_t mask) {
 338     _serialize_page_mask = mask;
 339   }
 340 
 341   static unsigned int  get_serialize_page_mask() {
 342     return _serialize_page_mask;
 343   }
 344 
 345   static void    set_memory_serialize_page(address page);
 346 
 347   static address get_memory_serialize_page() {
 348     return (address)_mem_serialize_page;
 349   }
 350 
 351   static inline void write_memory_serialize_page(JavaThread *thread) {
 352     uintptr_t page_offset = ((uintptr_t)thread >>
 353                             get_serialize_page_shift_count()) &
 354                             get_serialize_page_mask();
 355     *(volatile int32_t *)((uintptr_t)_mem_serialize_page+page_offset) = 1;
 356   }
 357 
 358   static bool    is_memory_serialize_page(JavaThread *thread, address addr) {
 359     if (UseMembar) return false;
 360     // Previously this function calculated the exact address of this
 361     // thread's serialize page, and checked if the faulting address
 362     // was equal.  However, some platforms mask off faulting addresses
 363     // to the page size, so now we just check that the address is
 364     // within the page.  This makes the thread argument unnecessary,
 365     // but we retain the NULL check to preserve existing behaviour.
 366     if (thread == NULL) return false;
 367     address page = (address) _mem_serialize_page;
 368     return addr >= page && addr < (page + os::vm_page_size());
 369   }
 370 
 371   static void block_on_serialize_page_trap();
 372 
 373   // threads
 374 
 375   enum ThreadType {
 376     vm_thread,
 377     cgc_thread,        // Concurrent GC thread
 378     pgc_thread,        // Parallel GC thread
 379     java_thread,
 380     compiler_thread,
 381     watcher_thread,
 382     os_thread
 383   };
 384 
 385   static bool create_thread(Thread* thread,
 386                             ThreadType thr_type,
 387                             size_t stack_size = 0);
 388   static bool create_main_thread(JavaThread* thread);
 389   static bool create_attached_thread(JavaThread* thread);
 390   static void pd_start_thread(Thread* thread);
 391   static void start_thread(Thread* thread);
 392 
 393   static void initialize_thread(Thread* thr);
 394   static void free_thread(OSThread* osthread);
 395 
 396   // thread id on Linux/64bit is 64bit, on Windows and Solaris, it's 32bit
 397   static intx current_thread_id();
 398   static int current_process_id();
 399   static int sleep(Thread* thread, jlong ms, bool interruptable);
 400   static int naked_sleep();
 401   static void infinite_sleep(); // never returns, use with CAUTION
 402   static void yield();        // Yields to all threads with same priority
 403   enum YieldResult {
 404     YIELD_SWITCHED = 1,         // caller descheduled, other ready threads exist & ran
 405     YIELD_NONEREADY = 0,        // No other runnable/ready threads.
 406                                 // platform-specific yield return immediately
 407     YIELD_UNKNOWN = -1          // Unknown: platform doesn't support _SWITCHED or _NONEREADY
 408     // YIELD_SWITCHED and YIELD_NONREADY imply the platform supports a "strong"
 409     // yield that can be used in lieu of blocking.
 410   } ;
 411   static YieldResult NakedYield () ;
 412   static void yield_all(int attempts = 0); // Yields to all other threads including lower priority
 413   static void loop_breaker(int attempts);  // called from within tight loops to possibly influence time-sharing
 414   static OSReturn set_priority(Thread* thread, ThreadPriority priority);
 415   static OSReturn get_priority(const Thread* const thread, ThreadPriority& priority);
 416 
 417   static void interrupt(Thread* thread);
 418   static bool is_interrupted(Thread* thread, bool clear_interrupted);
 419 
 420   static int pd_self_suspend_thread(Thread* thread);
 421 
 422   static ExtendedPC fetch_frame_from_context(void* ucVoid, intptr_t** sp, intptr_t** fp);
 423   static frame      fetch_frame_from_context(void* ucVoid);
 424 
 425   static ExtendedPC get_thread_pc(Thread *thread);
 426   static void breakpoint();
 427 
 428   static address current_stack_pointer();
 429   static address current_stack_base();
 430   static size_t current_stack_size();
 431 
 432   static void verify_stack_alignment() PRODUCT_RETURN;
 433 
 434   static int message_box(const char* title, const char* message);
 435   static char* do_you_want_to_debug(const char* message);
 436 
 437   // run cmd in a separate process and return its exit code; or -1 on failures
 438   static int fork_and_exec(char *cmd);
 439 
 440   // Set file to send error reports.
 441   static void set_error_file(const char *logfile);
 442 
 443   // os::exit() is merged with vm_exit()
 444   // static void exit(int num);
 445 
 446   // Terminate the VM, but don't exit the process
 447   static void shutdown();
 448 
 449   // Terminate with an error.  Default is to generate a core file on platforms
 450   // that support such things.  This calls shutdown() and then aborts.
 451   static void abort(bool dump_core = true);
 452 
 453   // Die immediately, no exit hook, no abort hook, no cleanup.
 454   static void die();
 455 
 456   // File i/o operations
 457   static const int default_file_open_flags();
 458   static int open(const char *path, int oflag, int mode);
 459   static FILE* open(int fd, const char* mode);
 460   static int close(int fd);
 461   static jlong lseek(int fd, jlong offset, int whence);
 462   static char* native_path(char *path);
 463   static int ftruncate(int fd, jlong length);
 464   static int fsync(int fd);
 465   static int available(int fd, jlong *bytes);
 466 
 467   //File i/o operations
 468 
 469   static size_t read(int fd, void *buf, unsigned int nBytes);
 470   static size_t restartable_read(int fd, void *buf, unsigned int nBytes);
 471   static size_t write(int fd, const void *buf, unsigned int nBytes);
 472 
 473   // Reading directories.
 474   static DIR*           opendir(const char* dirname);
 475   static int            readdir_buf_size(const char *path);
 476   static struct dirent* readdir(DIR* dirp, dirent* dbuf);
 477   static int            closedir(DIR* dirp);
 478 
 479   // Dynamic library extension
 480   static const char*    dll_file_extension();
 481 
 482   static const char*    get_temp_directory();
 483   static const char*    get_current_directory(char *buf, size_t buflen);
 484 
 485   // Builds a platform-specific full library path given a ld path and lib name
 486   // Returns true if buffer contains full path to existing file, false otherwise
 487   static bool           dll_build_name(char* buffer, size_t size,
 488                                        const char* pathname, const char* fname);
 489 
 490   // Symbol lookup, find nearest function name; basically it implements
 491   // dladdr() for all platforms. Name of the nearest function is copied
 492   // to buf. Distance from its base address is returned as offset.
 493   // If function name is not found, buf[0] is set to '\0' and offset is
 494   // set to -1.
 495   static bool dll_address_to_function_name(address addr, char* buf,
 496                                            int buflen, int* offset);
 497 
 498   // Locate DLL/DSO. On success, full path of the library is copied to
 499   // buf, and offset is set to be the distance between addr and the
 500   // library's base address. On failure, buf[0] is set to '\0' and
 501   // offset is set to -1.
 502   static bool dll_address_to_library_name(address addr, char* buf,
 503                                           int buflen, int* offset);
 504 
 505   // Find out whether the pc is in the static code for jvm.dll/libjvm.so.
 506   static bool address_is_in_vm(address addr);
 507 
 508   // Loads .dll/.so and
 509   // in case of error it checks if .dll/.so was built for the
 510   // same architecture as Hotspot is running on
 511   static void* dll_load(const char *name, char *ebuf, int ebuflen);
 512 
 513   // lookup symbol in a shared library
 514   static void* dll_lookup(void* handle, const char* name);
 515 
 516   // Unload library
 517   static void  dll_unload(void *lib);
 518 
 519   // Print out system information; they are called by fatal error handler.
 520   // Output format may be different on different platforms.
 521   static void print_os_info(outputStream* st);
 522   static void print_os_info_brief(outputStream* st);
 523   static void print_cpu_info(outputStream* st);
 524   static void pd_print_cpu_info(outputStream* st);
 525   static void print_memory_info(outputStream* st);
 526   static void print_dll_info(outputStream* st);
 527   static void print_environment_variables(outputStream* st, const char** env_list, char* buffer, int len);
 528   static void print_context(outputStream* st, void* context);
 529   static void print_register_info(outputStream* st, void* context);
 530   static void print_siginfo(outputStream* st, void* siginfo);
 531   static void print_signal_handlers(outputStream* st, char* buf, size_t buflen);
 532   static void print_date_and_time(outputStream* st);
 533 
 534   static void print_location(outputStream* st, intptr_t x, bool verbose = false);
 535   static size_t lasterror(char *buf, size_t len);
 536   static int get_last_error();
 537 
 538   // Determines whether the calling process is being debugged by a user-mode debugger.
 539   static bool is_debugger_attached();
 540 
 541   // wait for a key press if PauseAtExit is set
 542   static void wait_for_keypress_at_exit(void);
 543 
 544   // The following two functions are used by fatal error handler to trace
 545   // native (C) frames. They are not part of frame.hpp/frame.cpp because
 546   // frame.hpp/cpp assume thread is JavaThread, and also because different
 547   // OS/compiler may have different convention or provide different API to
 548   // walk C frames.
 549   //
 550   // We don't attempt to become a debugger, so we only follow frames if that
 551   // does not require a lookup in the unwind table, which is part of the binary
 552   // file but may be unsafe to read after a fatal error. So on x86, we can
 553   // only walk stack if %ebp is used as frame pointer; on ia64, it's not
 554   // possible to walk C stack without having the unwind table.
 555   static bool is_first_C_frame(frame *fr);
 556   static frame get_sender_for_C_frame(frame *fr);
 557 
 558   // return current frame. pc() and sp() are set to NULL on failure.
 559   static frame      current_frame();
 560 
 561   static void print_hex_dump(outputStream* st, address start, address end, int unitsize);
 562 
 563   // returns a string to describe the exception/signal;
 564   // returns NULL if exception_code is not an OS exception/signal.
 565   static const char* exception_name(int exception_code, char* buf, size_t buflen);
 566 
 567   // Returns native Java library, loads if necessary
 568   static void*    native_java_library();
 569 
 570   // Fills in path to jvm.dll/libjvm.so (used by the Disassembler)
 571   static void     jvm_path(char *buf, jint buflen);
 572 
 573   // Returns true if we are running in a headless jre.
 574   static bool     is_headless_jre();
 575 
 576   // JNI names
 577   static void     print_jni_name_prefix_on(outputStream* st, int args_size);
 578   static void     print_jni_name_suffix_on(outputStream* st, int args_size);
 579 
 580   // File conventions
 581   static const char* file_separator();
 582   static const char* line_separator();
 583   static const char* path_separator();
 584 
 585   // Init os specific system properties values
 586   static void init_system_properties_values();
 587 
 588   // IO operations, non-JVM_ version.
 589   static int stat(const char* path, struct stat* sbuf);
 590   static bool dir_is_empty(const char* path);
 591 
 592   // IO operations on binary files
 593   static int create_binary_file(const char* path, bool rewrite_existing);
 594   static jlong current_file_offset(int fd);
 595   static jlong seek_to_file_offset(int fd, jlong offset);
 596 
 597   // Thread Local Storage
 598   static int   allocate_thread_local_storage();
 599   static void  thread_local_storage_at_put(int index, void* value);
 600   static void* thread_local_storage_at(int index);
 601   static void  free_thread_local_storage(int index);
 602 
 603   // Stack walk
 604   static address get_caller_pc(int n = 0);
 605 
 606   // General allocation (must be MT-safe)
 607   static void* malloc  (size_t size, MEMFLAGS flags, address caller_pc = 0);
 608   static void* realloc (void *memblock, size_t size, MEMFLAGS flags, address caller_pc = 0);
 609   static void  free    (void *memblock, MEMFLAGS flags = mtNone);
 610   static bool  check_heap(bool force = false);      // verify C heap integrity
 611   static char* strdup(const char *, MEMFLAGS flags = mtInternal);  // Like strdup
 612 
 613 #ifndef PRODUCT
 614   static julong num_mallocs;         // # of calls to malloc/realloc
 615   static julong alloc_bytes;         // # of bytes allocated
 616   static julong num_frees;           // # of calls to free
 617   static julong free_bytes;          // # of bytes freed
 618 #endif
 619 
 620   // SocketInterface (ex HPI SocketInterface )
 621   static int socket(int domain, int type, int protocol);
 622   static int socket_close(int fd);
 623   static int socket_shutdown(int fd, int howto);
 624   static int recv(int fd, char* buf, size_t nBytes, uint flags);
 625   static int send(int fd, char* buf, size_t nBytes, uint flags);
 626   static int raw_send(int fd, char* buf, size_t nBytes, uint flags);
 627   static int timeout(int fd, long timeout);
 628   static int listen(int fd, int count);
 629   static int connect(int fd, struct sockaddr* him, socklen_t len);
 630   static int bind(int fd, struct sockaddr* him, socklen_t len);
 631   static int accept(int fd, struct sockaddr* him, socklen_t* len);
 632   static int recvfrom(int fd, char* buf, size_t nbytes, uint flags,
 633                       struct sockaddr* from, socklen_t* fromlen);
 634   static int get_sock_name(int fd, struct sockaddr* him, socklen_t* len);
 635   static int sendto(int fd, char* buf, size_t len, uint flags,
 636                     struct sockaddr* to, socklen_t tolen);
 637   static int socket_available(int fd, jint* pbytes);
 638 
 639   static int get_sock_opt(int fd, int level, int optname,
 640                           char* optval, socklen_t* optlen);
 641   static int set_sock_opt(int fd, int level, int optname,
 642                           const char* optval, socklen_t optlen);
 643   static int get_host_name(char* name, int namelen);
 644 
 645   static struct hostent* get_host_by_name(char* name);
 646 
 647   // Support for signals (see JVM_RaiseSignal, JVM_RegisterSignal)
 648   static void  signal_init();
 649   static void  signal_init_pd();
 650   static void  signal_notify(int signal_number);
 651   static void* signal(int signal_number, void* handler);
 652   static void  signal_raise(int signal_number);
 653   static int   signal_wait();
 654   static int   signal_lookup();
 655   static void* user_handler();
 656   static void  terminate_signal_thread();
 657   static int   sigexitnum_pd();
 658 
 659   // random number generation
 660   static long random();                    // return 32bit pseudorandom number
 661   static void init_random(long initval);   // initialize random sequence
 662 
 663   // Structured OS Exception support
 664   static void os_exception_wrapper(java_call_t f, JavaValue* value, methodHandle* method, JavaCallArguments* args, Thread* thread);
 665 
 666   // On Windows this will create an actual minidump, on Linux/Solaris it will simply check core dump limits
 667   static void check_or_create_dump(void* exceptionRecord, void* contextRecord, char* buffer, size_t bufferSize);
 668 
 669   // Get the default path to the core file
 670   // Returns the length of the string
 671   static int get_core_path(char* buffer, size_t bufferSize);
 672 
 673   // JVMTI & JVM monitoring and management support
 674   // The thread_cpu_time() and current_thread_cpu_time() are only
 675   // supported if is_thread_cpu_time_supported() returns true.
 676   // They are not supported on Solaris T1.
 677 
 678   // Thread CPU Time - return the fast estimate on a platform
 679   // On Solaris - call gethrvtime (fast) - user time only
 680   // On Linux   - fast clock_gettime where available - user+sys
 681   //            - otherwise: very slow /proc fs - user+sys
 682   // On Windows - GetThreadTimes - user+sys
 683   static jlong current_thread_cpu_time();
 684   static jlong thread_cpu_time(Thread* t);
 685 
 686   // Thread CPU Time with user_sys_cpu_time parameter.
 687   //
 688   // If user_sys_cpu_time is true, user+sys time is returned.
 689   // Otherwise, only user time is returned
 690   static jlong current_thread_cpu_time(bool user_sys_cpu_time);
 691   static jlong thread_cpu_time(Thread* t, bool user_sys_cpu_time);
 692 
 693   // Return a bunch of info about the timers.
 694   // Note that the returned info for these two functions may be different
 695   // on some platforms
 696   static void current_thread_cpu_time_info(jvmtiTimerInfo *info_ptr);
 697   static void thread_cpu_time_info(jvmtiTimerInfo *info_ptr);
 698 
 699   static bool is_thread_cpu_time_supported();
 700 
 701   // System loadavg support.  Returns -1 if load average cannot be obtained.
 702   static int loadavg(double loadavg[], int nelem);
 703 
 704   // Hook for os specific jvm options that we don't want to abort on seeing
 705   static bool obsolete_option(const JavaVMOption *option);
 706 
 707   // Read file line by line. If line is longer than bsize,
 708   // rest of line is skipped. Returns number of bytes read or -1 on EOF
 709   static int get_line_chars(int fd, char *buf, const size_t bsize);
 710 
 711   // Extensions
 712 #include "runtime/os_ext.hpp"
 713 
 714  public:
 715 
 716   // Platform dependent stuff
 717 #ifdef TARGET_OS_FAMILY_linux
 718 # include "os_linux.hpp"
 719 # include "os_posix.hpp"
 720 #endif
 721 #ifdef TARGET_OS_FAMILY_solaris
 722 # include "os_solaris.hpp"
 723 # include "os_posix.hpp"
 724 #endif
 725 #ifdef TARGET_OS_FAMILY_windows
 726 # include "os_windows.hpp"
 727 #endif
 728 #ifdef TARGET_OS_FAMILY_bsd
 729 # include "os_posix.hpp"
 730 # include "os_bsd.hpp"
 731 #endif
 732 #ifdef TARGET_OS_ARCH_linux_x86
 733 # include "os_linux_x86.hpp"
 734 #endif
 735 #ifdef TARGET_OS_ARCH_linux_sparc
 736 # include "os_linux_sparc.hpp"
 737 #endif
 738 #ifdef TARGET_OS_ARCH_linux_zero
 739 # include "os_linux_zero.hpp"
 740 #endif
 741 #ifdef TARGET_OS_ARCH_solaris_x86
 742 # include "os_solaris_x86.hpp"
 743 #endif
 744 #ifdef TARGET_OS_ARCH_solaris_sparc
 745 # include "os_solaris_sparc.hpp"
 746 #endif
 747 #ifdef TARGET_OS_ARCH_windows_x86
 748 # include "os_windows_x86.hpp"
 749 #endif
 750 #ifdef TARGET_OS_ARCH_linux_arm
 751 # include "os_linux_arm.hpp"
 752 #endif
 753 #ifdef TARGET_OS_ARCH_linux_ppc
 754 # include "os_linux_ppc.hpp"
 755 #endif
 756 #ifdef TARGET_OS_ARCH_bsd_x86
 757 # include "os_bsd_x86.hpp"
 758 #endif
 759 #ifdef TARGET_OS_ARCH_bsd_zero
 760 # include "os_bsd_zero.hpp"
 761 #endif
 762 
 763  public:
 764   // debugging support (mostly used by debug.cpp but also fatal error handler)
 765   static bool find(address pc, outputStream* st = tty); // OS specific function to make sense out of an address
 766 
 767   static bool dont_yield();                     // when true, JVM_Yield() is nop
 768   static void print_statistics();
 769 
 770   // Thread priority helpers (implemented in OS-specific part)
 771   static OSReturn set_native_priority(Thread* thread, int native_prio);
 772   static OSReturn get_native_priority(const Thread* const thread, int* priority_ptr);
 773   static int java_to_os_priority[CriticalPriority + 1];
 774   // Hint to the underlying OS that a task switch would not be good.
 775   // Void return because it's a hint and can fail.
 776   static void hint_no_preempt();
 777 
 778   // Used at creation if requested by the diagnostic flag PauseAtStartup.
 779   // Causes the VM to wait until an external stimulus has been applied
 780   // (for Unix, that stimulus is a signal, for Windows, an external
 781   // ResumeThread call)
 782   static void pause();
 783 
 784   class SuspendedThreadTaskContext {
 785   public:
 786     SuspendedThreadTaskContext(Thread* thread, void *ucontext) : _thread(thread), _ucontext(ucontext) {}
 787     Thread* thread() const { return _thread; }
 788     void* ucontext() const { return _ucontext; }
 789   private:
 790     Thread* _thread;
 791     void* _ucontext;
 792   };
 793 
 794   class SuspendedThreadTask {
 795   public:
 796     SuspendedThreadTask(Thread* thread) : _thread(thread), _done(false) {}
 797     virtual ~SuspendedThreadTask() {}
 798     void run();
 799     bool is_done() { return _done; }
 800     virtual void do_task(const SuspendedThreadTaskContext& context) = 0;
 801   protected:
 802   private:
 803     void internal_do_task();
 804     Thread* _thread;
 805     bool _done;
 806   };
 807 
 808 #ifndef TARGET_OS_FAMILY_windows
 809   // Suspend/resume support
 810   // Protocol:
 811   //
 812   // a thread starts in SR_RUNNING
 813   //
 814   // SR_RUNNING can go to
 815   //   * SR_SUSPEND_REQUEST when the WatcherThread wants to suspend it
 816   // SR_SUSPEND_REQUEST can go to
 817   //   * SR_RUNNING if WatcherThread decides it waited for SR_SUSPENDED too long (timeout)
 818   //   * SR_SUSPENDED if the stopped thread receives the signal and switches state
 819   // SR_SUSPENDED can go to
 820   //   * SR_WAKEUP_REQUEST when the WatcherThread has done the work and wants to resume
 821   // SR_WAKEUP_REQUEST can go to
 822   //   * SR_RUNNING when the stopped thread receives the signal
 823   //   * SR_WAKEUP_REQUEST on timeout (resend the signal and try again)
 824   class SuspendResume {
 825    public:
 826     enum State {
 827       SR_RUNNING,
 828       SR_SUSPEND_REQUEST,
 829       SR_SUSPENDED,
 830       SR_WAKEUP_REQUEST
 831     };
 832 
 833   private:
 834     volatile State _state;
 835 
 836   private:
 837     /* try to switch state from state "from" to state "to"
 838      * returns the state set after the method is complete
 839      */
 840     State switch_state(State from, State to);
 841 
 842   public:
 843     SuspendResume() : _state(SR_RUNNING) { }
 844 
 845     State state() const { return _state; }
 846 
 847     State request_suspend() {
 848       return switch_state(SR_RUNNING, SR_SUSPEND_REQUEST);
 849     }
 850 
 851     State cancel_suspend() {
 852       return switch_state(SR_SUSPEND_REQUEST, SR_RUNNING);
 853     }
 854 
 855     State suspended() {
 856       return switch_state(SR_SUSPEND_REQUEST, SR_SUSPENDED);
 857     }
 858 
 859     State request_wakeup() {
 860       return switch_state(SR_SUSPENDED, SR_WAKEUP_REQUEST);
 861     }
 862 
 863     State running() {
 864       return switch_state(SR_WAKEUP_REQUEST, SR_RUNNING);
 865     }
 866 
 867     bool is_running() const {
 868       return _state == SR_RUNNING;
 869     }
 870 
 871     bool is_suspend_request() const {
 872       return _state == SR_SUSPEND_REQUEST;
 873     }
 874 
 875     bool is_suspended() const {
 876       return _state == SR_SUSPENDED;
 877     }
 878   };
 879 #endif
 880 
 881 
 882  protected:
 883   static long _rand_seed;                   // seed for random number generator
 884   static int _processor_count;              // number of processors
 885 
 886   static char* format_boot_path(const char* format_string,
 887                                 const char* home,
 888                                 int home_len,
 889                                 char fileSep,
 890                                 char pathSep);
 891   static bool set_boot_path(char fileSep, char pathSep);
 892   static char** split_path(const char* path, int* n);
 893 };
 894 
 895 // Note that "PAUSE" is almost always used with synchronization
 896 // so arguably we should provide Atomic::SpinPause() instead
 897 // of the global SpinPause() with C linkage.
 898 // It'd also be eligible for inlining on many platforms.
 899 
 900 extern "C" int SpinPause () ;
 901 extern "C" int SafeFetch32 (int * adr, int errValue) ;
 902 extern "C" intptr_t SafeFetchN (intptr_t * adr, intptr_t errValue) ;
 903 
 904 #endif // SHARE_VM_RUNTIME_OS_HPP