1 /*
   2  * Copyright (c) 1997, 2016, 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/extendedPC.hpp"
  30 #include "runtime/handles.hpp"
  31 #ifdef TARGET_OS_FAMILY_linux
  32 # include "jvm_linux.h"
  33 # include <setjmp.h>
  34 #endif
  35 #ifdef TARGET_OS_FAMILY_solaris
  36 # include "jvm_solaris.h"
  37 # include <setjmp.h>
  38 #endif
  39 #ifdef TARGET_OS_FAMILY_windows
  40 # include "jvm_windows.h"
  41 #endif
  42 #ifdef TARGET_OS_FAMILY_aix
  43 # include "jvm_aix.h"
  44 # include <setjmp.h>
  45 #endif
  46 #ifdef TARGET_OS_FAMILY_bsd
  47 # include "jvm_bsd.h"
  48 # include <setjmp.h>
  49 # ifdef __APPLE__
  50 #  include <mach/mach_time.h>
  51 # endif
  52 #endif
  53 
  54 class AgentLibrary;
  55 
  56 // os defines the interface to operating system; this includes traditional
  57 // OS services (time, I/O) as well as other functionality with system-
  58 // dependent code.
  59 
  60 typedef void (*dll_func)(...);
  61 
  62 class Thread;
  63 class JavaThread;
  64 class Event;
  65 class DLL;
  66 class FileHandle;
  67 class NativeCallStack;
  68 
  69 template<class E> class GrowableArray;
  70 
  71 // %%%%% Moved ThreadState, START_FN, OSThread to new osThread.hpp. -- Rose
  72 
  73 // Platform-independent error return values from OS functions
  74 enum OSReturn {
  75   OS_OK         =  0,        // Operation was successful
  76   OS_ERR        = -1,        // Operation failed
  77   OS_INTRPT     = -2,        // Operation was interrupted
  78   OS_TIMEOUT    = -3,        // Operation timed out
  79   OS_NOMEM      = -5,        // Operation failed for lack of memory
  80   OS_NORESOURCE = -6         // Operation failed for lack of nonmemory resource
  81 };
  82 
  83 enum ThreadPriority {        // JLS 20.20.1-3
  84   NoPriority       = -1,     // Initial non-priority value
  85   MinPriority      =  1,     // Minimum priority
  86   NormPriority     =  5,     // Normal (non-daemon) priority
  87   NearMaxPriority  =  9,     // High priority, used for VMThread
  88   MaxPriority      = 10,     // Highest priority, used for WatcherThread
  89                              // ensures that VMThread doesn't starve profiler
  90   CriticalPriority = 11      // Critical thread priority
  91 };
  92 
  93 // Executable parameter flag for os::commit_memory() and
  94 // os::commit_memory_or_exit().
  95 const bool ExecMem = true;
  96 
  97 // Typedef for structured exception handling support
  98 typedef void (*java_call_t)(JavaValue* value, const methodHandle& method, JavaCallArguments* args, Thread* thread);
  99 
 100 class MallocTracker;
 101 
 102 class os: AllStatic {
 103   friend class VMStructs;
 104   friend class JVMCIVMStructs;
 105   friend class MallocTracker;
 106  public:
 107   enum { page_sizes_max = 9 }; // Size of _page_sizes array (8 plus a sentinel)
 108 
 109  private:
 110   static OSThread*          _starting_thread;
 111   static address            _polling_page;
 112   static volatile int32_t * _mem_serialize_page;
 113   static uintptr_t          _serialize_page_mask;
 114  public:
 115   static size_t             _page_sizes[page_sizes_max];
 116 
 117  private:
 118   static void init_page_sizes(size_t default_page_size) {
 119     _page_sizes[0] = default_page_size;
 120     _page_sizes[1] = 0; // sentinel
 121   }
 122 
 123   static char*  pd_reserve_memory(size_t bytes, char* addr = 0,
 124                                size_t alignment_hint = 0);
 125   static char*  pd_attempt_reserve_memory_at(size_t bytes, char* addr);
 126   static void   pd_split_reserved_memory(char *base, size_t size,
 127                                       size_t split, bool realloc);
 128   static bool   pd_commit_memory(char* addr, size_t bytes, bool executable);
 129   static bool   pd_commit_memory(char* addr, size_t size, size_t alignment_hint,
 130                                  bool executable);
 131   // Same as pd_commit_memory() that either succeeds or calls
 132   // vm_exit_out_of_memory() with the specified mesg.
 133   static void   pd_commit_memory_or_exit(char* addr, size_t bytes,
 134                                          bool executable, const char* mesg);
 135   static void   pd_commit_memory_or_exit(char* addr, size_t size,
 136                                          size_t alignment_hint,
 137                                          bool executable, const char* mesg);
 138   static bool   pd_uncommit_memory(char* addr, size_t bytes);
 139   static bool   pd_release_memory(char* addr, size_t bytes);
 140 
 141   static char*  pd_map_memory(int fd, const char* file_name, size_t file_offset,
 142                            char *addr, size_t bytes, bool read_only = false,
 143                            bool allow_exec = false);
 144   static char*  pd_remap_memory(int fd, const char* file_name, size_t file_offset,
 145                              char *addr, size_t bytes, bool read_only,
 146                              bool allow_exec);
 147   static bool   pd_unmap_memory(char *addr, size_t bytes);
 148   static void   pd_free_memory(char *addr, size_t bytes, size_t alignment_hint);
 149   static void   pd_realign_memory(char *addr, size_t bytes, size_t alignment_hint);
 150 
 151   static size_t page_size_for_region(size_t region_size, size_t min_pages, bool must_be_aligned);
 152 
 153   // Get summary strings for system information in buffer provided
 154   static void  get_summary_cpu_info(char* buf, size_t buflen);
 155   static void  get_summary_os_info(char* buf, size_t buflen);
 156 
 157   static int create_tmpfile(const char* dir, size_t size, bool exec);
 158  public:
 159   static void init(void);                      // Called before command line parsing
 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   // 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);
 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) || AssumeMP;
 229   }
 230   static julong available_memory();
 231   static julong physical_memory();
 232   static bool has_allocatable_memory_limit(julong* limit);
 233   static bool is_server_class_machine();
 234 
 235   // number of CPUs
 236   static int processor_count() {
 237     return _processor_count;
 238   }
 239   static void set_processor_count(int count) { _processor_count = count; }
 240 
 241   // Returns the number of CPUs this process is currently allowed to run on.
 242   // Note that on some OSes this can change dynamically.
 243   static int active_processor_count();
 244 
 245   // Bind processes to processors.
 246   //     This is a two step procedure:
 247   //     first you generate a distribution of processes to processors,
 248   //     then you bind processes according to that distribution.
 249   // Compute a distribution for number of processes to processors.
 250   //    Stores the processor id's into the distribution array argument.
 251   //    Returns true if it worked, false if it didn't.
 252   static bool distribute_processes(uint length, uint* distribution);
 253   // Binds the current process to a processor.
 254   //    Returns true if it worked, false if it didn't.
 255   static bool bind_to_processor(uint processor_id);
 256 
 257   // Give a name to the current thread.
 258   static void set_native_thread_name(const char *name);
 259 
 260   // Interface for stack banging (predetect possible stack overflow for
 261   // exception processing)  There are guard pages, and above that shadow
 262   // pages for stack overflow checking.
 263   static bool uses_stack_guard_pages();
 264   static bool allocate_stack_guard_pages();
 265   static void map_stack_shadow_pages();
 266   static bool stack_shadow_pages_available(Thread *thread, const methodHandle& method);
 267 
 268   // OS interface to Virtual Memory
 269 
 270   // Return the default page size.
 271   static int    vm_page_size();
 272 
 273   // Returns the page size to use for a region of memory.
 274   // region_size / min_pages will always be greater than or equal to the
 275   // returned value. The returned value will divide region_size.
 276   static size_t page_size_for_region_aligned(size_t region_size, size_t min_pages);
 277 
 278   // Returns the page size to use for a region of memory.
 279   // region_size / min_pages will always be greater than or equal to the
 280   // returned value. The returned value might not divide region_size.
 281   static size_t page_size_for_region_unaligned(size_t region_size, size_t min_pages);
 282 
 283   // Return the largest page size that can be used
 284   static size_t max_page_size() {
 285     // The _page_sizes array is sorted in descending order.
 286     return _page_sizes[0];
 287   }
 288 
 289   // Methods for tracing page sizes returned by the above method.
 290   // The region_{min,max}_size parameters should be the values
 291   // passed to page_size_for_region() and page_size should be the result of that
 292   // call.  The (optional) base and size parameters should come from the
 293   // ReservedSpace base() and size() methods.
 294   static void trace_page_sizes(const char* str, const size_t* page_sizes, int count);
 295   static void trace_page_sizes(const char* str,
 296                                const size_t region_min_size,
 297                                const size_t region_max_size,
 298                                const size_t page_size,
 299                                const char* base,
 300                                const size_t size);
 301   static void trace_page_sizes_for_requested_size(const char* str,
 302                                                   const size_t requested_size,
 303                                                   const size_t page_size,
 304                                                   const size_t alignment,
 305                                                   const char* base,
 306                                                   const size_t size);
 307 
 308   static int    vm_allocation_granularity();
 309   static char*  reserve_memory(size_t bytes, char* addr = 0,
 310                                size_t alignment_hint = 0);
 311   static char*  reserve_memory(size_t bytes, char* addr,
 312                                size_t alignment_hint, MEMFLAGS flags);
 313   static char*  reserve_memory_aligned(size_t size, size_t alignment);
 314   static char*  attempt_reserve_memory_at(size_t bytes, char* addr);
 315 
 316   // Map the given address range to a temporary file created at the specified directory.
 317   // The address range must already be reserved for guaranteed success. If it not reserved, their could be an error while mapping leading to JVM shutdown
 318   static bool   map_memory_to_file(char* base, size_t size, const char* backing_filename);
 319   static void   split_reserved_memory(char *base, size_t size,
 320                                       size_t split, bool realloc);
 321   static bool   commit_memory(char* addr, size_t bytes, bool executable);
 322   static bool   commit_memory(char* addr, size_t size, size_t alignment_hint,
 323                               bool executable);
 324   // Same as commit_memory() that either succeeds or calls
 325   // vm_exit_out_of_memory() with the specified mesg.
 326   static void   commit_memory_or_exit(char* addr, size_t bytes,
 327                                       bool executable, const char* mesg);
 328   static void   commit_memory_or_exit(char* addr, size_t size,
 329                                       size_t alignment_hint,
 330                                       bool executable, const char* mesg);
 331   static bool   uncommit_memory(char* addr, size_t bytes);
 332   static bool   release_memory(char* addr, size_t bytes);
 333 
 334   // Touch memory pages that cover the memory range from start to end (exclusive)
 335   // to make the OS back the memory range with actual memory.
 336   // Current implementation may not touch the last page if unaligned addresses
 337   // are passed.
 338   static void   pretouch_memory(void* start, void* end);
 339 
 340   enum ProtType { MEM_PROT_NONE, MEM_PROT_READ, MEM_PROT_RW, MEM_PROT_RWX };
 341   static bool   protect_memory(char* addr, size_t bytes, ProtType prot,
 342                                bool is_committed = true);
 343 
 344   static bool   guard_memory(char* addr, size_t bytes);
 345   static bool   unguard_memory(char* addr, size_t bytes);
 346   static bool   create_stack_guard_pages(char* addr, size_t bytes);
 347   static bool   pd_create_stack_guard_pages(char* addr, size_t bytes);
 348   static bool   remove_stack_guard_pages(char* addr, size_t bytes);
 349 
 350   static char*  map_memory(int fd, const char* file_name, size_t file_offset,
 351                            char *addr, size_t bytes, bool read_only = false,
 352                            bool allow_exec = false);
 353   static char*  remap_memory(int fd, const char* file_name, size_t file_offset,
 354                              char *addr, size_t bytes, bool read_only,
 355                              bool allow_exec);
 356   static bool   unmap_memory(char *addr, size_t bytes);
 357   static void   free_memory(char *addr, size_t bytes, size_t alignment_hint);
 358   static void   realign_memory(char *addr, size_t bytes, size_t alignment_hint);
 359 
 360   // NUMA-specific interface
 361   static bool   numa_has_static_binding();
 362   static bool   numa_has_group_homing();
 363   static void   numa_make_local(char *addr, size_t bytes, int lgrp_hint);
 364   static void   numa_make_global(char *addr, size_t bytes);
 365   static size_t numa_get_groups_num();
 366   static size_t numa_get_leaf_groups(int *ids, size_t size);
 367   static bool   numa_topology_changed();
 368   static int    numa_get_group_id();
 369 
 370   // Page manipulation
 371   struct page_info {
 372     size_t size;
 373     int lgrp_id;
 374   };
 375   static bool   get_page_info(char *start, page_info* info);
 376   static char*  scan_pages(char *start, char* end, page_info* page_expected, page_info* page_found);
 377 
 378   static char*  non_memory_address_word();
 379   // reserve, commit and pin the entire memory region
 380   static char*  reserve_memory_special(size_t size, size_t alignment,
 381                                        char* addr, bool executable);
 382   static bool   release_memory_special(char* addr, size_t bytes);
 383   static void   large_page_init();
 384   static size_t large_page_size();
 385   static bool   can_commit_large_page_memory();
 386   static bool   can_execute_large_page_memory();
 387 
 388   // OS interface to polling page
 389   static address get_polling_page()             { return _polling_page; }
 390   static void    set_polling_page(address page) { _polling_page = page; }
 391   static bool    is_poll_address(address addr)  { return addr >= _polling_page && addr < (_polling_page + os::vm_page_size()); }
 392   static void    make_polling_page_unreadable();
 393   static void    make_polling_page_readable();
 394 
 395   // Routines used to serialize the thread state without using membars
 396   static void    serialize_thread_states();
 397 
 398   // Since we write to the serialize page from every thread, we
 399   // want stores to be on unique cache lines whenever possible
 400   // in order to minimize CPU cross talk.  We pre-compute the
 401   // amount to shift the thread* to make this offset unique to
 402   // each thread.
 403   static int     get_serialize_page_shift_count() {
 404     return SerializePageShiftCount;
 405   }
 406 
 407   static void     set_serialize_page_mask(uintptr_t mask) {
 408     _serialize_page_mask = mask;
 409   }
 410 
 411   static unsigned int  get_serialize_page_mask() {
 412     return _serialize_page_mask;
 413   }
 414 
 415   static void    set_memory_serialize_page(address page);
 416 
 417   static address get_memory_serialize_page() {
 418     return (address)_mem_serialize_page;
 419   }
 420 
 421   static inline void write_memory_serialize_page(JavaThread *thread) {
 422     uintptr_t page_offset = ((uintptr_t)thread >>
 423                             get_serialize_page_shift_count()) &
 424                             get_serialize_page_mask();
 425     *(volatile int32_t *)((uintptr_t)_mem_serialize_page+page_offset) = 1;
 426   }
 427 
 428   static bool    is_memory_serialize_page(JavaThread *thread, address addr) {
 429     if (UseMembar) return false;
 430     // Previously this function calculated the exact address of this
 431     // thread's serialize page, and checked if the faulting address
 432     // was equal.  However, some platforms mask off faulting addresses
 433     // to the page size, so now we just check that the address is
 434     // within the page.  This makes the thread argument unnecessary,
 435     // but we retain the NULL check to preserve existing behavior.
 436     if (thread == NULL) return false;
 437     address page = (address) _mem_serialize_page;
 438     return addr >= page && addr < (page + os::vm_page_size());
 439   }
 440 
 441   static void block_on_serialize_page_trap();
 442 
 443   // threads
 444 
 445   enum ThreadType {
 446     vm_thread,
 447     cgc_thread,        // Concurrent GC thread
 448     pgc_thread,        // Parallel GC thread
 449     java_thread,
 450     compiler_thread,
 451     watcher_thread,
 452     os_thread
 453   };
 454 
 455   static bool create_thread(Thread* thread,
 456                             ThreadType thr_type,
 457                             size_t stack_size = 0);
 458   static bool create_main_thread(JavaThread* thread);
 459   static bool create_attached_thread(JavaThread* thread);
 460   static void pd_start_thread(Thread* thread);
 461   static void start_thread(Thread* thread);
 462 
 463   static void initialize_thread(Thread* thr);
 464   static void free_thread(OSThread* osthread);
 465 
 466   // thread id on Linux/64bit is 64bit, on Windows and Solaris, it's 32bit
 467   static intx current_thread_id();
 468   static int current_process_id();
 469   static int sleep(Thread* thread, jlong ms, bool interruptable);
 470   // Short standalone OS sleep suitable for slow path spin loop.
 471   // Ignores Thread.interrupt() (so keep it short).
 472   // ms = 0, will sleep for the least amount of time allowed by the OS.
 473   static void naked_short_sleep(jlong ms);
 474   static void infinite_sleep(); // never returns, use with CAUTION
 475   static void naked_yield () ;
 476   static OSReturn set_priority(Thread* thread, ThreadPriority priority);
 477   static OSReturn get_priority(const Thread* const thread, ThreadPriority& priority);
 478 
 479   static void interrupt(Thread* thread);
 480   static bool is_interrupted(Thread* thread, bool clear_interrupted);
 481 
 482   static int pd_self_suspend_thread(Thread* thread);
 483 
 484   static ExtendedPC fetch_frame_from_context(const void* ucVoid, intptr_t** sp, intptr_t** fp);
 485   static frame      fetch_frame_from_context(const void* ucVoid);
 486   static frame      fetch_frame_from_ucontext(Thread* thread, void* ucVoid);
 487 
 488   static ExtendedPC get_thread_pc(Thread *thread);
 489   static void breakpoint();
 490   static bool start_debugging(char *buf, int buflen);
 491 
 492   static address current_stack_pointer();
 493   static address current_stack_base();
 494   static size_t current_stack_size();
 495 
 496   static void verify_stack_alignment() PRODUCT_RETURN;
 497 
 498   static bool message_box(const char* title, const char* message);
 499   static char* do_you_want_to_debug(const char* message);
 500 
 501   // run cmd in a separate process and return its exit code; or -1 on failures
 502   static int fork_and_exec(char *cmd);
 503 
 504   // Call ::exit() on all platforms but Windows
 505   static void exit(int num);
 506 
 507   // Terminate the VM, but don't exit the process
 508   static void shutdown();
 509 
 510   // Terminate with an error.  Default is to generate a core file on platforms
 511   // that support such things.  This calls shutdown() and then aborts.
 512   static void abort(bool dump_core, void *siginfo, const void *context);
 513   static void abort(bool dump_core = true);
 514 
 515   // Die immediately, no exit hook, no abort hook, no cleanup.
 516   static void die();
 517 
 518   // File i/o operations
 519   static const int default_file_open_flags();
 520   static int open(const char *path, int oflag, int mode);
 521   static FILE* open(int fd, const char* mode);
 522   static int close(int fd);
 523   static jlong lseek(int fd, jlong offset, int whence);
 524   static char* native_path(char *path);
 525   static int ftruncate(int fd, jlong length);
 526   static int fsync(int fd);
 527   static int available(int fd, jlong *bytes);
 528   static int get_fileno(FILE* fp);
 529   static void flockfile(FILE* fp);
 530   static void funlockfile(FILE* fp);
 531 
 532   static int compare_file_modified_times(const char* file1, const char* file2);
 533 
 534   //File i/o operations
 535 
 536   static size_t read(int fd, void *buf, unsigned int nBytes);
 537   static size_t read_at(int fd, void *buf, unsigned int nBytes, jlong offset);
 538   static size_t restartable_read(int fd, void *buf, unsigned int nBytes);
 539   static size_t write(int fd, const void *buf, unsigned int nBytes);
 540 
 541   // Reading directories.
 542   static DIR*           opendir(const char* dirname);
 543   static int            readdir_buf_size(const char *path);
 544   static struct dirent* readdir(DIR* dirp, dirent* dbuf);
 545   static int            closedir(DIR* dirp);
 546 
 547   // Dynamic library extension
 548   static const char*    dll_file_extension();
 549 
 550   static const char*    get_temp_directory();
 551   static const char*    get_current_directory(char *buf, size_t buflen);
 552 
 553   // Builds a platform-specific full library path given a ld path and lib name
 554   // Returns true if buffer contains full path to existing file, false otherwise
 555   static bool           dll_build_name(char* buffer, size_t size,
 556                                        const char* pathname, const char* fname);
 557 
 558   // Symbol lookup, find nearest function name; basically it implements
 559   // dladdr() for all platforms. Name of the nearest function is copied
 560   // to buf. Distance from its base address is optionally returned as offset.
 561   // If function name is not found, buf[0] is set to '\0' and offset is
 562   // set to -1 (if offset is non-NULL).
 563   static bool dll_address_to_function_name(address addr, char* buf,
 564                                            int buflen, int* offset,
 565                                            bool demangle = true);
 566 
 567   // Locate DLL/DSO. On success, full path of the library is copied to
 568   // buf, and offset is optionally set to be the distance between addr
 569   // and the library's base address. On failure, buf[0] is set to '\0'
 570   // and offset is set to -1 (if offset is non-NULL).
 571   static bool dll_address_to_library_name(address addr, char* buf,
 572                                           int buflen, int* offset);
 573 
 574   // Find out whether the pc is in the static code for jvm.dll/libjvm.so.
 575   static bool address_is_in_vm(address addr);
 576 
 577   // Loads .dll/.so and
 578   // in case of error it checks if .dll/.so was built for the
 579   // same architecture as HotSpot is running on
 580   static void* dll_load(const char *name, char *ebuf, int ebuflen);
 581 
 582   // lookup symbol in a shared library
 583   static void* dll_lookup(void* handle, const char* name);
 584 
 585   // Unload library
 586   static void  dll_unload(void *lib);
 587 
 588   // Callback for loaded module information
 589   // Input parameters:
 590   //    char*     module_file_name,
 591   //    address   module_base_addr,
 592   //    address   module_top_addr,
 593   //    void*     param
 594   typedef int (*LoadedModulesCallbackFunc)(const char *, address, address, void *);
 595 
 596   static int get_loaded_modules_info(LoadedModulesCallbackFunc callback, void *param);
 597 
 598   // Return the handle of this process
 599   static void* get_default_process_handle();
 600 
 601   // Check for static linked agent library
 602   static bool find_builtin_agent(AgentLibrary *agent_lib, const char *syms[],
 603                                  size_t syms_len);
 604 
 605   // Find agent entry point
 606   static void *find_agent_function(AgentLibrary *agent_lib, bool check_lib,
 607                                    const char *syms[], size_t syms_len);
 608 
 609   // Write to stream
 610   static int log_vsnprintf(char* buf, size_t len, const char* fmt, va_list args) ATTRIBUTE_PRINTF(3, 0);
 611 
 612   // Get host name in buffer provided
 613   static bool get_host_name(char* buf, size_t buflen);
 614 
 615   // Print out system information; they are called by fatal error handler.
 616   // Output format may be different on different platforms.
 617   static void print_os_info(outputStream* st);
 618   static void print_os_info_brief(outputStream* st);
 619   static void print_cpu_info(outputStream* st, char* buf, size_t buflen);
 620   static void pd_print_cpu_info(outputStream* st, char* buf, size_t buflen);
 621   static void print_summary_info(outputStream* st, char* buf, size_t buflen);
 622   static void print_memory_info(outputStream* st);
 623   static void print_dll_info(outputStream* st);
 624   static void print_environment_variables(outputStream* st, const char** env_list);
 625   static void print_context(outputStream* st, const void* context);
 626   static void print_register_info(outputStream* st, const void* context);
 627   static void print_siginfo(outputStream* st, const void* siginfo);
 628   static void print_signal_handlers(outputStream* st, char* buf, size_t buflen);
 629   static void print_date_and_time(outputStream* st, char* buf, size_t buflen);
 630 
 631   static void print_location(outputStream* st, intptr_t x, bool verbose = false);
 632   static size_t lasterror(char *buf, size_t len);
 633   static int get_last_error();
 634 
 635   // Replacement for strerror().
 636   // Will return the english description of the error (e.g. "File not found", as
 637   //  suggested in the POSIX standard.
 638   // Will return "Unknown error" for an unknown errno value.
 639   // Will not attempt to localize the returned string.
 640   // Will always return a valid string which is a static constant.
 641   // Will not change the value of errno.
 642   static const char* strerror(int e);
 643 
 644   // Will return the literalized version of the given errno (e.g. "EINVAL"
 645   //  for EINVAL).
 646   // Will return "Unknown error" for an unknown errno value.
 647   // Will always return a valid string which is a static constant.
 648   // Will not change the value of errno.
 649   static const char* errno_name(int e);
 650 
 651   // Determines whether the calling process is being debugged by a user-mode debugger.
 652   static bool is_debugger_attached();
 653 
 654   // wait for a key press if PauseAtExit is set
 655   static void wait_for_keypress_at_exit(void);
 656 
 657   // The following two functions are used by fatal error handler to trace
 658   // native (C) frames. They are not part of frame.hpp/frame.cpp because
 659   // frame.hpp/cpp assume thread is JavaThread, and also because different
 660   // OS/compiler may have different convention or provide different API to
 661   // walk C frames.
 662   //
 663   // We don't attempt to become a debugger, so we only follow frames if that
 664   // does not require a lookup in the unwind table, which is part of the binary
 665   // file but may be unsafe to read after a fatal error. So on x86, we can
 666   // only walk stack if %ebp is used as frame pointer; on ia64, it's not
 667   // possible to walk C stack without having the unwind table.
 668   static bool is_first_C_frame(frame *fr);
 669   static frame get_sender_for_C_frame(frame *fr);
 670 
 671   // return current frame. pc() and sp() are set to NULL on failure.
 672   static frame      current_frame();
 673 
 674   static void print_hex_dump(outputStream* st, address start, address end, int unitsize);
 675 
 676   // returns a string to describe the exception/signal;
 677   // returns NULL if exception_code is not an OS exception/signal.
 678   static const char* exception_name(int exception_code, char* buf, size_t buflen);
 679 
 680   // Returns the signal number (e.g. 11) for a given signal name (SIGSEGV).
 681   static int get_signal_number(const char* signal_name);
 682 
 683   // Returns native Java library, loads if necessary
 684   static void*    native_java_library();
 685 
 686   // Fills in path to jvm.dll/libjvm.so (used by the Disassembler)
 687   static void     jvm_path(char *buf, jint buflen);
 688 
 689   // Returns true if we are running in a headless jre.
 690   static bool     is_headless_jre();
 691 
 692   // JNI names
 693   static void     print_jni_name_prefix_on(outputStream* st, int args_size);
 694   static void     print_jni_name_suffix_on(outputStream* st, int args_size);
 695 
 696   // Init os specific system properties values
 697   static void init_system_properties_values();
 698 
 699   // IO operations, non-JVM_ version.
 700   static int stat(const char* path, struct stat* sbuf);
 701   static bool dir_is_empty(const char* path);
 702 
 703   // IO operations on binary files
 704   static int create_binary_file(const char* path, bool rewrite_existing);
 705   static jlong current_file_offset(int fd);
 706   static jlong seek_to_file_offset(int fd, jlong offset);
 707 
 708   // Retrieve native stack frames.
 709   // Parameter:
 710   //   stack:  an array to storage stack pointers.
 711   //   frames: size of above array.
 712   //   toSkip: number of stack frames to skip at the beginning.
 713   // Return: number of stack frames captured.
 714   static int get_native_stack(address* stack, int size, int toSkip = 0);
 715 
 716   // General allocation (must be MT-safe)
 717   static void* malloc  (size_t size, MEMFLAGS flags, const NativeCallStack& stack);
 718   static void* malloc  (size_t size, MEMFLAGS flags);
 719   static void* realloc (void *memblock, size_t size, MEMFLAGS flag, const NativeCallStack& stack);
 720   static void* realloc (void *memblock, size_t size, MEMFLAGS flag);
 721 
 722   static void  free    (void *memblock);
 723   static bool  check_heap(bool force = false);      // verify C heap integrity
 724   static char* strdup(const char *, MEMFLAGS flags = mtInternal);  // Like strdup
 725   // Like strdup, but exit VM when strdup() returns NULL
 726   static char* strdup_check_oom(const char*, MEMFLAGS flags = mtInternal);
 727 
 728 #ifndef PRODUCT
 729   static julong num_mallocs;         // # of calls to malloc/realloc
 730   static julong alloc_bytes;         // # of bytes allocated
 731   static julong num_frees;           // # of calls to free
 732   static julong free_bytes;          // # of bytes freed
 733 #endif
 734 
 735   // SocketInterface (ex HPI SocketInterface )
 736   static int socket(int domain, int type, int protocol);
 737   static int socket_close(int fd);
 738   static int recv(int fd, char* buf, size_t nBytes, uint flags);
 739   static int send(int fd, char* buf, size_t nBytes, uint flags);
 740   static int raw_send(int fd, char* buf, size_t nBytes, uint flags);
 741   static int connect(int fd, struct sockaddr* him, socklen_t len);
 742   static struct hostent* get_host_by_name(char* name);
 743 
 744   // Support for signals (see JVM_RaiseSignal, JVM_RegisterSignal)
 745   static void  signal_init();
 746   static void  signal_init_pd();
 747   static void  signal_notify(int signal_number);
 748   static void* signal(int signal_number, void* handler);
 749   static void  signal_raise(int signal_number);
 750   static int   signal_wait();
 751   static int   signal_lookup();
 752   static void* user_handler();
 753   static void  terminate_signal_thread();
 754   static int   sigexitnum_pd();
 755 
 756   // random number generation
 757   static long random();                    // return 32bit pseudorandom number
 758   static void init_random(long initval);   // initialize random sequence
 759 
 760   // Structured OS Exception support
 761   static void os_exception_wrapper(java_call_t f, JavaValue* value, const methodHandle& method, JavaCallArguments* args, Thread* thread);
 762 
 763   // On Posix compatible OS it will simply check core dump limits while on Windows
 764   // it will check if dump file can be created. Check or prepare a core dump to be
 765   // taken at a later point in the same thread in os::abort(). Use the caller
 766   // provided buffer as a scratch buffer. The status message which will be written
 767   // into the error log either is file location or a short error message, depending
 768   // on the checking result.
 769   static void check_dump_limit(char* buffer, size_t bufferSize);
 770 
 771   // Get the default path to the core file
 772   // Returns the length of the string
 773   static int get_core_path(char* buffer, size_t bufferSize);
 774 
 775   // JVMTI & JVM monitoring and management support
 776   // The thread_cpu_time() and current_thread_cpu_time() are only
 777   // supported if is_thread_cpu_time_supported() returns true.
 778   // They are not supported on Solaris T1.
 779 
 780   // Thread CPU Time - return the fast estimate on a platform
 781   // On Solaris - call gethrvtime (fast) - user time only
 782   // On Linux   - fast clock_gettime where available - user+sys
 783   //            - otherwise: very slow /proc fs - user+sys
 784   // On Windows - GetThreadTimes - user+sys
 785   static jlong current_thread_cpu_time();
 786   static jlong thread_cpu_time(Thread* t);
 787 
 788   // Thread CPU Time with user_sys_cpu_time parameter.
 789   //
 790   // If user_sys_cpu_time is true, user+sys time is returned.
 791   // Otherwise, only user time is returned
 792   static jlong current_thread_cpu_time(bool user_sys_cpu_time);
 793   static jlong thread_cpu_time(Thread* t, bool user_sys_cpu_time);
 794 
 795   // Return a bunch of info about the timers.
 796   // Note that the returned info for these two functions may be different
 797   // on some platforms
 798   static void current_thread_cpu_time_info(jvmtiTimerInfo *info_ptr);
 799   static void thread_cpu_time_info(jvmtiTimerInfo *info_ptr);
 800 
 801   static bool is_thread_cpu_time_supported();
 802 
 803   // System loadavg support.  Returns -1 if load average cannot be obtained.
 804   static int loadavg(double loadavg[], int nelem);
 805 
 806   // Hook for os specific jvm options that we don't want to abort on seeing
 807   static bool obsolete_option(const JavaVMOption *option);
 808 
 809   // Amount beyond the callee frame size that we bang the stack.
 810   static int extra_bang_size_in_bytes();
 811 
 812   static char** split_path(const char* path, int* n);
 813 
 814   // Extensions
 815 #include "runtime/os_ext.hpp"
 816 
 817  public:
 818   class CrashProtectionCallback : public StackObj {
 819   public:
 820     virtual void call() = 0;
 821   };
 822 
 823   // Platform dependent stuff
 824 #ifdef TARGET_OS_FAMILY_linux
 825 # include "os_linux.hpp"
 826 # include "os_posix.hpp"
 827 #endif
 828 #ifdef TARGET_OS_FAMILY_solaris
 829 # include "os_solaris.hpp"
 830 # include "os_posix.hpp"
 831 #endif
 832 #ifdef TARGET_OS_FAMILY_windows
 833 # include "os_windows.hpp"
 834 #endif
 835 #ifdef TARGET_OS_FAMILY_aix
 836 # include "os_aix.hpp"
 837 # include "os_posix.hpp"
 838 #endif
 839 #ifdef TARGET_OS_FAMILY_bsd
 840 # include "os_posix.hpp"
 841 # include "os_bsd.hpp"
 842 #endif
 843 #ifdef TARGET_OS_ARCH_linux_x86
 844 # include "os_linux_x86.hpp"
 845 #endif
 846 #ifdef TARGET_OS_ARCH_linux_sparc
 847 # include "os_linux_sparc.hpp"
 848 #endif
 849 #ifdef TARGET_OS_ARCH_linux_zero
 850 # include "os_linux_zero.hpp"
 851 #endif
 852 #ifdef TARGET_OS_ARCH_solaris_x86
 853 # include "os_solaris_x86.hpp"
 854 #endif
 855 #ifdef TARGET_OS_ARCH_solaris_sparc
 856 # include "os_solaris_sparc.hpp"
 857 #endif
 858 #ifdef TARGET_OS_ARCH_windows_x86
 859 # include "os_windows_x86.hpp"
 860 #endif
 861 #ifdef TARGET_OS_ARCH_linux_arm
 862 # include "os_linux_arm.hpp"
 863 #endif
 864 #ifdef TARGET_OS_ARCH_linux_ppc
 865 # include "os_linux_ppc.hpp"
 866 #endif
 867 #ifdef TARGET_OS_ARCH_aix_ppc
 868 # include "os_aix_ppc.hpp"
 869 #endif
 870 #ifdef TARGET_OS_ARCH_linux_aarch64
 871 # include "os_linux_aarch64.hpp"
 872 #endif
 873 #ifdef TARGET_OS_ARCH_bsd_x86
 874 # include "os_bsd_x86.hpp"
 875 #endif
 876 #ifdef TARGET_OS_ARCH_bsd_zero
 877 # include "os_bsd_zero.hpp"
 878 #endif
 879 
 880 #ifndef OS_NATIVE_THREAD_CREATION_FAILED_MSG
 881 #define OS_NATIVE_THREAD_CREATION_FAILED_MSG "unable to create native thread: possibly out of memory or process/resource limits reached"
 882 #endif
 883 
 884  public:
 885 #ifndef PLATFORM_PRINT_NATIVE_STACK
 886   // No platform-specific code for printing the native stack.
 887   static bool platform_print_native_stack(outputStream* st, const void* context,
 888                                           char *buf, int buf_size) {
 889     return false;
 890   }
 891 #endif
 892 
 893   // debugging support (mostly used by debug.cpp but also fatal error handler)
 894   static bool find(address pc, outputStream* st = tty); // OS specific function to make sense out of an address
 895 
 896   static bool dont_yield();                     // when true, JVM_Yield() is nop
 897   static void print_statistics();
 898 
 899   // Thread priority helpers (implemented in OS-specific part)
 900   static OSReturn set_native_priority(Thread* thread, int native_prio);
 901   static OSReturn get_native_priority(const Thread* const thread, int* priority_ptr);
 902   static int java_to_os_priority[CriticalPriority + 1];
 903   // Hint to the underlying OS that a task switch would not be good.
 904   // Void return because it's a hint and can fail.
 905   static void hint_no_preempt();
 906   static const char* native_thread_creation_failed_msg() {
 907     return OS_NATIVE_THREAD_CREATION_FAILED_MSG;
 908   }
 909 
 910   // Used at creation if requested by the diagnostic flag PauseAtStartup.
 911   // Causes the VM to wait until an external stimulus has been applied
 912   // (for Unix, that stimulus is a signal, for Windows, an external
 913   // ResumeThread call)
 914   static void pause();
 915 
 916   // Builds a platform dependent Agent_OnLoad_<libname> function name
 917   // which is used to find statically linked in agents.
 918   static char*  build_agent_function_name(const char *sym, const char *cname,
 919                                           bool is_absolute_path);
 920 
 921   class SuspendedThreadTaskContext {
 922   public:
 923     SuspendedThreadTaskContext(Thread* thread, void *ucontext) : _thread(thread), _ucontext(ucontext) {}
 924     Thread* thread() const { return _thread; }
 925     void* ucontext() const { return _ucontext; }
 926   private:
 927     Thread* _thread;
 928     void* _ucontext;
 929   };
 930 
 931   class SuspendedThreadTask {
 932   public:
 933     SuspendedThreadTask(Thread* thread) : _thread(thread), _done(false) {}
 934     virtual ~SuspendedThreadTask() {}
 935     void run();
 936     bool is_done() { return _done; }
 937     virtual void do_task(const SuspendedThreadTaskContext& context) = 0;
 938   protected:
 939   private:
 940     void internal_do_task();
 941     Thread* _thread;
 942     bool _done;
 943   };
 944 
 945 #ifndef TARGET_OS_FAMILY_windows
 946   // Suspend/resume support
 947   // Protocol:
 948   //
 949   // a thread starts in SR_RUNNING
 950   //
 951   // SR_RUNNING can go to
 952   //   * SR_SUSPEND_REQUEST when the WatcherThread wants to suspend it
 953   // SR_SUSPEND_REQUEST can go to
 954   //   * SR_RUNNING if WatcherThread decides it waited for SR_SUSPENDED too long (timeout)
 955   //   * SR_SUSPENDED if the stopped thread receives the signal and switches state
 956   // SR_SUSPENDED can go to
 957   //   * SR_WAKEUP_REQUEST when the WatcherThread has done the work and wants to resume
 958   // SR_WAKEUP_REQUEST can go to
 959   //   * SR_RUNNING when the stopped thread receives the signal
 960   //   * SR_WAKEUP_REQUEST on timeout (resend the signal and try again)
 961   class SuspendResume {
 962    public:
 963     enum State {
 964       SR_RUNNING,
 965       SR_SUSPEND_REQUEST,
 966       SR_SUSPENDED,
 967       SR_WAKEUP_REQUEST
 968     };
 969 
 970   private:
 971     volatile State _state;
 972 
 973   private:
 974     /* try to switch state from state "from" to state "to"
 975      * returns the state set after the method is complete
 976      */
 977     State switch_state(State from, State to);
 978 
 979   public:
 980     SuspendResume() : _state(SR_RUNNING) { }
 981 
 982     State state() const { return _state; }
 983 
 984     State request_suspend() {
 985       return switch_state(SR_RUNNING, SR_SUSPEND_REQUEST);
 986     }
 987 
 988     State cancel_suspend() {
 989       return switch_state(SR_SUSPEND_REQUEST, SR_RUNNING);
 990     }
 991 
 992     State suspended() {
 993       return switch_state(SR_SUSPEND_REQUEST, SR_SUSPENDED);
 994     }
 995 
 996     State request_wakeup() {
 997       return switch_state(SR_SUSPENDED, SR_WAKEUP_REQUEST);
 998     }
 999 
1000     State running() {
1001       return switch_state(SR_WAKEUP_REQUEST, SR_RUNNING);
1002     }
1003 
1004     bool is_running() const {
1005       return _state == SR_RUNNING;
1006     }
1007 
1008     bool is_suspend_request() const {
1009       return _state == SR_SUSPEND_REQUEST;
1010     }
1011 
1012     bool is_suspended() const {
1013       return _state == SR_SUSPENDED;
1014     }
1015   };
1016 #endif
1017 
1018 
1019  protected:
1020   static long _rand_seed;                   // seed for random number generator
1021   static int _processor_count;              // number of processors
1022 
1023   static char* format_boot_path(const char* format_string,
1024                                 const char* home,
1025                                 int home_len,
1026                                 char fileSep,
1027                                 char pathSep);
1028   static bool set_boot_path(char fileSep, char pathSep);
1029 
1030 };
1031 
1032 // Note that "PAUSE" is almost always used with synchronization
1033 // so arguably we should provide Atomic::SpinPause() instead
1034 // of the global SpinPause() with C linkage.
1035 // It'd also be eligible for inlining on many platforms.
1036 
1037 extern "C" int SpinPause();
1038 
1039 #endif // SHARE_VM_RUNTIME_OS_HPP