1 /*
   2  * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_RUNTIME_OS_HPP
  26 #define SHARE_VM_RUNTIME_OS_HPP
  27 
  28 #include "jvm.h"
  29 #include "jvmtifiles/jvmti.h"
  30 #include "metaprogramming/isRegisteredEnum.hpp"
  31 #include "metaprogramming/integralConstant.hpp"
  32 #include "runtime/extendedPC.hpp"
  33 #include "utilities/exceptions.hpp"
  34 #include "utilities/ostream.hpp"
  35 #include "utilities/macros.hpp"
  36 #ifndef _WINDOWS
  37 # include <setjmp.h>
  38 #endif
  39 #ifdef __APPLE__
  40 # include <mach/mach_time.h>
  41 #endif
  42 
  43 class AgentLibrary;
  44 class frame;
  45 
  46 // os defines the interface to operating system; this includes traditional
  47 // OS services (time, I/O) as well as other functionality with system-
  48 // dependent code.
  49 
  50 typedef void (*dll_func)(...);
  51 
  52 class Thread;
  53 class JavaThread;
  54 class Event;
  55 class DLL;
  56 class FileHandle;
  57 class NativeCallStack;
  58 class methodHandle;
  59 
  60 template<class E> class GrowableArray;
  61 
  62 // %%%%% Moved ThreadState, START_FN, OSThread to new osThread.hpp. -- Rose
  63 
  64 // Platform-independent error return values from OS functions
  65 enum OSReturn {
  66   OS_OK         =  0,        // Operation was successful
  67   OS_ERR        = -1,        // Operation failed
  68   OS_INTRPT     = -2,        // Operation was interrupted
  69   OS_TIMEOUT    = -3,        // Operation timed out
  70   OS_NOMEM      = -5,        // Operation failed for lack of memory
  71   OS_NORESOURCE = -6         // Operation failed for lack of nonmemory resource
  72 };
  73 
  74 enum ThreadPriority {        // JLS 20.20.1-3
  75   NoPriority       = -1,     // Initial non-priority value
  76   MinPriority      =  1,     // Minimum priority
  77   NormPriority     =  5,     // Normal (non-daemon) priority
  78   NearMaxPriority  =  9,     // High priority, used for VMThread
  79   MaxPriority      = 10,     // Highest priority, used for WatcherThread
  80                              // ensures that VMThread doesn't starve profiler
  81   CriticalPriority = 11      // Critical thread priority
  82 };
  83 
  84 // Executable parameter flag for os::commit_memory() and
  85 // os::commit_memory_or_exit().
  86 const bool ExecMem = true;
  87 
  88 // Typedef for structured exception handling support
  89 typedef void (*java_call_t)(JavaValue* value, const methodHandle& method, JavaCallArguments* args, Thread* thread);
  90 
  91 class MallocTracker;
  92 
  93 class os: AllStatic {
  94   friend class VMStructs;
  95   friend class JVMCIVMStructs;
  96   friend class MallocTracker;
  97  public:
  98   enum { page_sizes_max = 9 }; // Size of _page_sizes array (8 plus a sentinel)
  99 
 100  private:
 101   static OSThread*          _starting_thread;
 102   static address            _polling_page;
 103   static volatile int32_t * _mem_serialize_page;
 104   static uintptr_t          _serialize_page_mask;
 105  public:
 106   static size_t             _page_sizes[page_sizes_max];
 107 
 108  private:
 109   static void init_page_sizes(size_t default_page_size) {
 110     _page_sizes[0] = default_page_size;
 111     _page_sizes[1] = 0; // sentinel
 112   }
 113 
 114   static char*  pd_reserve_memory(size_t bytes, char* addr = 0,
 115                                   size_t alignment_hint = 0);
 116   static char*  pd_attempt_reserve_memory_at(size_t bytes, char* addr);
 117   static char*  pd_attempt_reserve_memory_at(size_t bytes, char* addr, int file_desc);
 118   static void   pd_split_reserved_memory(char *base, size_t size,
 119                                       size_t split, bool realloc);
 120   static bool   pd_commit_memory(char* addr, size_t bytes, bool executable);
 121   static bool   pd_commit_memory(char* addr, size_t size, size_t alignment_hint,
 122                                  bool executable);
 123   // Same as pd_commit_memory() that either succeeds or calls
 124   // vm_exit_out_of_memory() with the specified mesg.
 125   static void   pd_commit_memory_or_exit(char* addr, size_t bytes,
 126                                          bool executable, const char* mesg);
 127   static void   pd_commit_memory_or_exit(char* addr, size_t size,
 128                                          size_t alignment_hint,
 129                                          bool executable, const char* mesg);
 130   static bool   pd_uncommit_memory(char* addr, size_t bytes);
 131   static bool   pd_release_memory(char* addr, size_t bytes);
 132 
 133   static char*  pd_map_memory(int fd, const char* file_name, size_t file_offset,
 134                            char *addr, size_t bytes, bool read_only = false,
 135                            bool allow_exec = false);
 136   static char*  pd_remap_memory(int fd, const char* file_name, size_t file_offset,
 137                              char *addr, size_t bytes, bool read_only,
 138                              bool allow_exec);
 139   static bool   pd_unmap_memory(char *addr, size_t bytes);
 140   static void   pd_free_memory(char *addr, size_t bytes, size_t alignment_hint);
 141   static void   pd_realign_memory(char *addr, size_t bytes, size_t alignment_hint);
 142 
 143   static size_t page_size_for_region(size_t region_size, size_t min_pages, bool must_be_aligned);
 144 
 145   // Get summary strings for system information in buffer provided
 146   static void  get_summary_cpu_info(char* buf, size_t buflen);
 147   static void  get_summary_os_info(char* buf, size_t buflen);
 148 
 149   static void initialize_initial_active_processor_count();
 150 
 151   LINUX_ONLY(static void pd_init_container_support();)
 152 
 153  public:
 154   static void init(void);                      // Called before command line parsing
 155 
 156   static void init_container_support() {       // Called during command line parsing.
 157      LINUX_ONLY(pd_init_container_support();)
 158   }
 159 
 160   static void init_before_ergo(void);          // Called after command line parsing
 161                                                // before VM ergonomics processing.
 162   static jint init_2(void);                    // Called after command line parsing
 163                                                // and VM ergonomics processing
 164   static void init_globals(void) {             // Called from init_globals() in init.cpp
 165     init_globals_ext();
 166   }
 167 
 168   // File names are case-insensitive on windows only
 169   // Override me as needed
 170   static int    file_name_strncmp(const char* s1, const char* s2, size_t num);
 171 
 172   // unset environment variable
 173   static bool unsetenv(const char* name);
 174 
 175   static bool have_special_privileges();
 176 
 177   static jlong  javaTimeMillis();
 178   static jlong  javaTimeNanos();
 179   static void   javaTimeNanos_info(jvmtiTimerInfo *info_ptr);
 180   static void   javaTimeSystemUTC(jlong &seconds, jlong &nanos);
 181   static void   run_periodic_checks();
 182   static bool   supports_monotonic_clock();
 183 
 184   // Returns the elapsed time in seconds since the vm started.
 185   static double elapsedTime();
 186 
 187   // Returns real time in seconds since an arbitrary point
 188   // in the past.
 189   static bool getTimesSecs(double* process_real_time,
 190                            double* process_user_time,
 191                            double* process_system_time);
 192 
 193   // Interface to the performance counter
 194   static jlong elapsed_counter();
 195   static jlong elapsed_frequency();
 196 
 197   // The "virtual time" of a thread is the amount of time a thread has
 198   // actually run.  The first function indicates whether the OS supports
 199   // this functionality for the current thread, and if so:
 200   //   * the second enables vtime tracking (if that is required).
 201   //   * the third tells whether vtime is enabled.
 202   //   * the fourth returns the elapsed virtual time for the current
 203   //     thread.
 204   static bool supports_vtime();
 205   static bool enable_vtime();
 206   static bool vtime_enabled();
 207   static double elapsedVTime();
 208 
 209   // Return current local time in a string (YYYY-MM-DD HH:MM:SS).
 210   // It is MT safe, but not async-safe, as reading time zone
 211   // information may require a lock on some platforms.
 212   static char*      local_time_string(char *buf, size_t buflen);
 213   static struct tm* localtime_pd     (const time_t* clock, struct tm*  res);
 214   static struct tm* gmtime_pd        (const time_t* clock, struct tm*  res);
 215   // Fill in buffer with current local time as an ISO-8601 string.
 216   // E.g., YYYY-MM-DDThh:mm:ss.mmm+zzzz.
 217   // Returns buffer, or NULL if it failed.
 218   static char* iso8601_time(char* buffer, size_t buffer_length, bool utc = false);
 219 
 220   // Interface for detecting multiprocessor system
 221   static inline bool is_MP() {
 222     // During bootstrap if _processor_count is not yet initialized
 223     // we claim to be MP as that is safest. If any platform has a
 224     // stub generator that might be triggered in this phase and for
 225     // which being declared MP when in fact not, is a problem - then
 226     // the bootstrap routine for the stub generator needs to check
 227     // the processor count directly and leave the bootstrap routine
 228     // in place until called after initialization has ocurred.
 229     return AssumeMP || (_processor_count != 1);
 230   }
 231   static julong available_memory();
 232   static julong physical_memory();
 233   static bool has_allocatable_memory_limit(julong* limit);
 234   static bool is_server_class_machine();
 235 
 236   // 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   // Methods for tracing page sizes returned by the above method.
 306   // The region_{min,max}_size parameters should be the values
 307   // passed to page_size_for_region() and page_size should be the result of that
 308   // call.  The (optional) base and size parameters should come from the
 309   // ReservedSpace base() and size() methods.
 310   static void trace_page_sizes(const char* str, const size_t* page_sizes, int count);
 311   static void trace_page_sizes(const char* str,
 312                                const size_t region_min_size,
 313                                const size_t region_max_size,
 314                                const size_t page_size,
 315                                const char* base,
 316                                const size_t size);
 317   static void trace_page_sizes_for_requested_size(const char* str,
 318                                                   const size_t requested_size,
 319                                                   const size_t page_size,
 320                                                   const size_t alignment,
 321                                                   const char* base,
 322                                                   const size_t size);
 323 
 324   static int    vm_allocation_granularity();
 325   static char*  reserve_memory(size_t bytes, char* addr = 0,
 326                                size_t alignment_hint = 0, int file_desc = -1);
 327   static char*  reserve_memory(size_t bytes, char* addr,
 328                                size_t alignment_hint, MEMFLAGS flags);
 329   static char*  reserve_memory_aligned(size_t size, size_t alignment, int file_desc = -1);
 330   static char*  attempt_reserve_memory_at(size_t bytes, char* addr, int file_desc = -1);
 331   static void   split_reserved_memory(char *base, size_t size,
 332                                       size_t split, bool realloc);
 333   static bool   commit_memory(char* addr, size_t bytes, bool executable);
 334   static bool   commit_memory(char* addr, size_t size, size_t alignment_hint,
 335                               bool executable);
 336   // Same as commit_memory() that either succeeds or calls
 337   // vm_exit_out_of_memory() with the specified mesg.
 338   static void   commit_memory_or_exit(char* addr, size_t bytes,
 339                                       bool executable, const char* mesg);
 340   static void   commit_memory_or_exit(char* addr, size_t size,
 341                                       size_t alignment_hint,
 342                                       bool executable, const char* mesg);
 343   static bool   uncommit_memory(char* addr, size_t bytes);
 344   static bool   release_memory(char* addr, size_t bytes);
 345 
 346   // Touch memory pages that cover the memory range from start to end (exclusive)
 347   // to make the OS back the memory range with actual memory.
 348   // Current implementation may not touch the last page if unaligned addresses
 349   // are passed.
 350   static void   pretouch_memory(void* start, void* end, size_t page_size = vm_page_size());
 351 
 352   enum ProtType { MEM_PROT_NONE, MEM_PROT_READ, MEM_PROT_RW, MEM_PROT_RWX };
 353   static bool   protect_memory(char* addr, size_t bytes, ProtType prot,
 354                                bool is_committed = true);
 355 
 356   static bool   guard_memory(char* addr, size_t bytes);
 357   static bool   unguard_memory(char* addr, size_t bytes);
 358   static bool   create_stack_guard_pages(char* addr, size_t bytes);
 359   static bool   pd_create_stack_guard_pages(char* addr, size_t bytes);
 360   static bool   remove_stack_guard_pages(char* addr, size_t bytes);
 361   // Helper function to create a new file with template jvmheap.XXXXXX.
 362   // Returns a valid fd on success or else returns -1
 363   static int create_file_for_heap(const char* dir);
 364   // Map memory to the file referred by fd. This function is slightly different from map_memory()
 365   // and is added to be used for implementation of -XX:AllocateHeapAt
 366   static char* map_memory_to_file(char* base, size_t size, int fd);
 367   // Replace existing reserved memory with file mapping
 368   static char* replace_existing_mapping_with_file_mapping(char* base, size_t size, int fd);
 369 
 370   static char*  map_memory(int fd, const char* file_name, size_t file_offset,
 371                            char *addr, size_t bytes, bool read_only = false,
 372                            bool allow_exec = false);
 373   static char*  remap_memory(int fd, const char* file_name, size_t file_offset,
 374                              char *addr, size_t bytes, bool read_only,
 375                              bool allow_exec);
 376   static bool   unmap_memory(char *addr, size_t bytes);
 377   static void   free_memory(char *addr, size_t bytes, size_t alignment_hint);
 378   static void   realign_memory(char *addr, size_t bytes, size_t alignment_hint);
 379 
 380   // NUMA-specific interface
 381   static bool   numa_has_static_binding();
 382   static bool   numa_has_group_homing();
 383   static void   numa_make_local(char *addr, size_t bytes, int lgrp_hint);
 384   static void   numa_make_global(char *addr, size_t bytes);
 385   static size_t numa_get_groups_num();
 386   static size_t numa_get_leaf_groups(int *ids, size_t size);
 387   static bool   numa_topology_changed();
 388   static int    numa_get_group_id();
 389 
 390   // Page manipulation
 391   struct page_info {
 392     size_t size;
 393     int lgrp_id;
 394   };
 395   static bool   get_page_info(char *start, page_info* info);
 396   static char*  scan_pages(char *start, char* end, page_info* page_expected, page_info* page_found);
 397 
 398   static char*  non_memory_address_word();
 399   // reserve, commit and pin the entire memory region
 400   static char*  reserve_memory_special(size_t size, size_t alignment,
 401                                        char* addr, bool executable);
 402   static bool   release_memory_special(char* addr, size_t bytes);
 403   static void   large_page_init();
 404   static size_t large_page_size();
 405   static bool   can_commit_large_page_memory();
 406   static bool   can_execute_large_page_memory();
 407 
 408   // OS interface to polling page
 409   static address get_polling_page()             { return _polling_page; }
 410   static void    set_polling_page(address page) { _polling_page = page; }
 411   static bool    is_poll_address(address addr)  { return addr >= _polling_page && addr < (_polling_page + os::vm_page_size()); }
 412   static void    make_polling_page_unreadable();
 413   static void    make_polling_page_readable();
 414 
 415   // Check if pointer points to readable memory (by 4-byte read access)
 416   static bool    is_readable_pointer(const void* p);
 417 
 418   // Routines used to serialize the thread state without using membars
 419   static void    serialize_thread_states();
 420 
 421   // Since we write to the serialize page from every thread, we
 422   // want stores to be on unique cache lines whenever possible
 423   // in order to minimize CPU cross talk.  We pre-compute the
 424   // amount to shift the thread* to make this offset unique to
 425   // each thread.
 426   static int     get_serialize_page_shift_count() {
 427     return SerializePageShiftCount;
 428   }
 429 
 430   static void     set_serialize_page_mask(uintptr_t mask) {
 431     _serialize_page_mask = mask;
 432   }
 433 
 434   static unsigned int  get_serialize_page_mask() {
 435     return _serialize_page_mask;
 436   }
 437 
 438   static void    set_memory_serialize_page(address page);
 439 
 440   static address get_memory_serialize_page() {
 441     return (address)_mem_serialize_page;
 442   }
 443 
 444   static inline void write_memory_serialize_page(JavaThread *thread) {
 445     uintptr_t page_offset = ((uintptr_t)thread >>
 446                             get_serialize_page_shift_count()) &
 447                             get_serialize_page_mask();
 448     *(volatile int32_t *)((uintptr_t)_mem_serialize_page+page_offset) = 1;
 449   }
 450 
 451   static bool    is_memory_serialize_page(JavaThread *thread, address addr) {
 452     if (UseMembar) return false;
 453     // Previously this function calculated the exact address of this
 454     // thread's serialize page, and checked if the faulting address
 455     // was equal.  However, some platforms mask off faulting addresses
 456     // to the page size, so now we just check that the address is
 457     // within the page.  This makes the thread argument unnecessary,
 458     // but we retain the NULL check to preserve existing behavior.
 459     if (thread == NULL) return false;
 460     address page = (address) _mem_serialize_page;
 461     return addr >= page && addr < (page + os::vm_page_size());
 462   }
 463 
 464   static void block_on_serialize_page_trap();
 465 
 466   // threads
 467 
 468   enum ThreadType {
 469     vm_thread,
 470     cgc_thread,        // Concurrent GC thread
 471     pgc_thread,        // Parallel GC thread
 472     java_thread,       // Java, CodeCacheSweeper, JVMTIAgent and Service threads.
 473     compiler_thread,
 474     watcher_thread,
 475     os_thread
 476   };
 477 
 478   static bool create_thread(Thread* thread,
 479                             ThreadType thr_type,
 480                             size_t req_stack_size = 0);
 481 
 482   // The "main thread", also known as "starting thread", is the thread
 483   // that loads/creates the JVM via JNI_CreateJavaVM.
 484   static bool create_main_thread(JavaThread* thread);
 485 
 486   // The primordial thread is the initial process thread. The java
 487   // launcher never uses the primordial thread as the main thread, but
 488   // applications that host the JVM directly may do so. Some platforms
 489   // need special-case handling of the primordial thread if it attaches
 490   // to the VM.
 491   static bool is_primordial_thread(void)
 492 #if defined(_WINDOWS) || defined(BSD)
 493     // No way to identify the primordial thread.
 494     { return false; }
 495 #else
 496   ;
 497 #endif
 498 
 499   static bool create_attached_thread(JavaThread* thread);
 500   static void pd_start_thread(Thread* thread);
 501   static void start_thread(Thread* thread);
 502 
 503   static void initialize_thread(Thread* thr);
 504   static void free_thread(OSThread* osthread);
 505 
 506   // thread id on Linux/64bit is 64bit, on Windows and Solaris, it's 32bit
 507   static intx current_thread_id();
 508   static int current_process_id();
 509   static int sleep(Thread* thread, jlong ms, bool interruptable);
 510   // Short standalone OS sleep suitable for slow path spin loop.
 511   // Ignores Thread.interrupt() (so keep it short).
 512   // ms = 0, will sleep for the least amount of time allowed by the OS.
 513   static void naked_short_sleep(jlong ms);
 514   static void infinite_sleep(); // never returns, use with CAUTION
 515   static void naked_yield () ;
 516   static OSReturn set_priority(Thread* thread, ThreadPriority priority);
 517   static OSReturn get_priority(const Thread* const thread, ThreadPriority& priority);
 518 
 519   static void interrupt(Thread* thread);
 520   static bool is_interrupted(Thread* thread, bool clear_interrupted);
 521 
 522   static int pd_self_suspend_thread(Thread* thread);
 523 
 524   static ExtendedPC fetch_frame_from_context(const void* ucVoid, intptr_t** sp, intptr_t** fp);
 525   static frame      fetch_frame_from_context(const void* ucVoid);
 526   static frame      fetch_frame_from_ucontext(Thread* thread, void* ucVoid);
 527 
 528   static void breakpoint();
 529   static bool start_debugging(char *buf, int buflen);
 530 
 531   static address current_stack_pointer();
 532   static address current_stack_base();
 533   static size_t current_stack_size();
 534 
 535   static void verify_stack_alignment() PRODUCT_RETURN;
 536 
 537   static bool message_box(const char* title, const char* message);
 538   static char* do_you_want_to_debug(const char* message);
 539 
 540   // run cmd in a separate process and return its exit code; or -1 on failures
 541   static int fork_and_exec(char *cmd);
 542 
 543   // Call ::exit() on all platforms but Windows
 544   static void exit(int num);
 545 
 546   // Terminate the VM, but don't exit the process
 547   static void shutdown();
 548 
 549   // Terminate with an error.  Default is to generate a core file on platforms
 550   // that support such things.  This calls shutdown() and then aborts.
 551   static void abort(bool dump_core, void *siginfo, const void *context);
 552   static void abort(bool dump_core = true);
 553 
 554   // Die immediately, no exit hook, no abort hook, no cleanup.
 555   static void die();
 556 
 557   // File i/o operations
 558   static const int default_file_open_flags();
 559   static int open(const char *path, int oflag, int mode);
 560   static FILE* open(int fd, const char* mode);
 561   static FILE* fopen(const char* path, const char* mode);
 562   static int close(int fd);
 563   static jlong lseek(int fd, jlong offset, int whence);
 564   // This function, on Windows, canonicalizes a given path (see os_windows.cpp for details).
 565   // On Posix, this function is a noop: it does not change anything and just returns
 566   // the input pointer.
 567   static char* native_path(char *path);
 568   static int ftruncate(int fd, jlong length);
 569   static int fsync(int fd);
 570   static int available(int fd, jlong *bytes);
 571   static int get_fileno(FILE* fp);
 572   static void flockfile(FILE* fp);
 573   static void funlockfile(FILE* fp);
 574 
 575   static int compare_file_modified_times(const char* file1, const char* file2);
 576 
 577   //File i/o operations
 578 
 579   static size_t read(int fd, void *buf, unsigned int nBytes);
 580   static size_t read_at(int fd, void *buf, unsigned int nBytes, jlong offset);
 581   static size_t restartable_read(int fd, void *buf, unsigned int nBytes);
 582   static size_t write(int fd, const void *buf, unsigned int nBytes);
 583 
 584   // Reading directories.
 585   static DIR*           opendir(const char* dirname);
 586   static struct dirent* readdir(DIR* dirp);
 587   static int            closedir(DIR* dirp);
 588 
 589   // Dynamic library extension
 590   static const char*    dll_file_extension();
 591 
 592   static const char*    get_temp_directory();
 593   static const char*    get_current_directory(char *buf, size_t buflen);
 594 
 595   // Builds the platform-specific name of a library.
 596   // Returns false if the buffer is too small.
 597   static bool           dll_build_name(char* buffer, size_t size,
 598                                        const char* fname);
 599 
 600   // Builds a platform-specific full library path given an ld path and
 601   // unadorned library name. Returns true if the buffer contains a full
 602   // path to an existing file, false otherwise. If pathname is empty,
 603   // uses the path to the current directory.
 604   static bool           dll_locate_lib(char* buffer, size_t size,
 605                                        const char* pathname, const char* fname);
 606 
 607   // Symbol lookup, find nearest function name; basically it implements
 608   // dladdr() for all platforms. Name of the nearest function is copied
 609   // to buf. Distance from its base address is optionally returned as offset.
 610   // If function name is not found, buf[0] is set to '\0' and offset is
 611   // set to -1 (if offset is non-NULL).
 612   static bool dll_address_to_function_name(address addr, char* buf,
 613                                            int buflen, int* offset,
 614                                            bool demangle = true);
 615 
 616   // Locate DLL/DSO. On success, full path of the library is copied to
 617   // buf, and offset is optionally set to be the distance between addr
 618   // and the library's base address. On failure, buf[0] is set to '\0'
 619   // and offset is set to -1 (if offset is non-NULL).
 620   static bool dll_address_to_library_name(address addr, char* buf,
 621                                           int buflen, int* offset);
 622 
 623   // Find out whether the pc is in the static code for jvm.dll/libjvm.so.
 624   static bool address_is_in_vm(address addr);
 625 
 626   // Loads .dll/.so and
 627   // in case of error it checks if .dll/.so was built for the
 628   // same architecture as HotSpot is running on
 629   static void* dll_load(const char *name, char *ebuf, int ebuflen);
 630 
 631   // lookup symbol in a shared library
 632   static void* dll_lookup(void* handle, const char* name);
 633 
 634   // Unload library
 635   static void  dll_unload(void *lib);
 636 
 637   // Callback for loaded module information
 638   // Input parameters:
 639   //    char*     module_file_name,
 640   //    address   module_base_addr,
 641   //    address   module_top_addr,
 642   //    void*     param
 643   typedef int (*LoadedModulesCallbackFunc)(const char *, address, address, void *);
 644 
 645   static int get_loaded_modules_info(LoadedModulesCallbackFunc callback, void *param);
 646 
 647   // Return the handle of this process
 648   static void* get_default_process_handle();
 649 
 650   // Check for static linked agent library
 651   static bool find_builtin_agent(AgentLibrary *agent_lib, const char *syms[],
 652                                  size_t syms_len);
 653 
 654   // Find agent entry point
 655   static void *find_agent_function(AgentLibrary *agent_lib, bool check_lib,
 656                                    const char *syms[], size_t syms_len);
 657 
 658   // Provide C99 compliant versions of these functions, since some versions
 659   // of some platforms don't.
 660   static int vsnprintf(char* buf, size_t len, const char* fmt, va_list args) ATTRIBUTE_PRINTF(3, 0);
 661   static int snprintf(char* buf, size_t len, const char* fmt, ...) ATTRIBUTE_PRINTF(3, 4);
 662 
 663   // Get host name in buffer provided
 664   static bool get_host_name(char* buf, size_t buflen);
 665 
 666   // Print out system information; they are called by fatal error handler.
 667   // Output format may be different on different platforms.
 668   static void print_os_info(outputStream* st);
 669   static void print_os_info_brief(outputStream* st);
 670   static void print_cpu_info(outputStream* st, char* buf, size_t buflen);
 671   static void pd_print_cpu_info(outputStream* st, char* buf, size_t buflen);
 672   static void print_summary_info(outputStream* st, char* buf, size_t buflen);
 673   static void print_memory_info(outputStream* st);
 674   static void print_dll_info(outputStream* st);
 675   static void print_environment_variables(outputStream* st, const char** env_list);
 676   static void print_context(outputStream* st, const void* context);
 677   static void print_register_info(outputStream* st, const void* context);
 678   static void print_siginfo(outputStream* st, const void* siginfo);
 679   static void print_signal_handlers(outputStream* st, char* buf, size_t buflen);
 680   static void print_date_and_time(outputStream* st, char* buf, size_t buflen);
 681 
 682   static void print_location(outputStream* st, intptr_t x, bool verbose = false);
 683   static size_t lasterror(char *buf, size_t len);
 684   static int get_last_error();
 685 
 686   // Replacement for strerror().
 687   // Will return the english description of the error (e.g. "File not found", as
 688   //  suggested in the POSIX standard.
 689   // Will return "Unknown error" for an unknown errno value.
 690   // Will not attempt to localize the returned string.
 691   // Will always return a valid string which is a static constant.
 692   // Will not change the value of errno.
 693   static const char* strerror(int e);
 694 
 695   // Will return the literalized version of the given errno (e.g. "EINVAL"
 696   //  for EINVAL).
 697   // Will return "Unknown error" for an unknown errno value.
 698   // Will always return a valid string which is a static constant.
 699   // Will not change the value of errno.
 700   static const char* errno_name(int e);
 701 
 702   // Determines whether the calling process is being debugged by a user-mode debugger.
 703   static bool is_debugger_attached();
 704 
 705   // wait for a key press if PauseAtExit is set
 706   static void wait_for_keypress_at_exit(void);
 707 
 708   // The following two functions are used by fatal error handler to trace
 709   // native (C) frames. They are not part of frame.hpp/frame.cpp because
 710   // frame.hpp/cpp assume thread is JavaThread, and also because different
 711   // OS/compiler may have different convention or provide different API to
 712   // walk C frames.
 713   //
 714   // We don't attempt to become a debugger, so we only follow frames if that
 715   // does not require a lookup in the unwind table, which is part of the binary
 716   // file but may be unsafe to read after a fatal error. So on x86, we can
 717   // only walk stack if %ebp is used as frame pointer; on ia64, it's not
 718   // possible to walk C stack without having the unwind table.
 719   static bool is_first_C_frame(frame *fr);
 720   static frame get_sender_for_C_frame(frame *fr);
 721 
 722   // return current frame. pc() and sp() are set to NULL on failure.
 723   static frame      current_frame();
 724 
 725   static void print_hex_dump(outputStream* st, address start, address end, int unitsize);
 726 
 727   // returns a string to describe the exception/signal;
 728   // returns NULL if exception_code is not an OS exception/signal.
 729   static const char* exception_name(int exception_code, char* buf, size_t buflen);
 730 
 731   // Returns the signal number (e.g. 11) for a given signal name (SIGSEGV).
 732   static int get_signal_number(const char* signal_name);
 733 
 734   // Returns native Java library, loads if necessary
 735   static void*    native_java_library();
 736 
 737   // Fills in path to jvm.dll/libjvm.so (used by the Disassembler)
 738   static void     jvm_path(char *buf, jint buflen);
 739 
 740   // JNI names
 741   static void     print_jni_name_prefix_on(outputStream* st, int args_size);
 742   static void     print_jni_name_suffix_on(outputStream* st, int args_size);
 743 
 744   // Init os specific system properties values
 745   static void init_system_properties_values();
 746 
 747   // IO operations, non-JVM_ version.
 748   static int stat(const char* path, struct stat* sbuf);
 749   static bool dir_is_empty(const char* path);
 750 
 751   // IO operations on binary files
 752   static int create_binary_file(const char* path, bool rewrite_existing);
 753   static jlong current_file_offset(int fd);
 754   static jlong seek_to_file_offset(int fd, jlong offset);
 755 
 756   // Retrieve native stack frames.
 757   // Parameter:
 758   //   stack:  an array to storage stack pointers.
 759   //   frames: size of above array.
 760   //   toSkip: number of stack frames to skip at the beginning.
 761   // Return: number of stack frames captured.
 762   static int get_native_stack(address* stack, int size, int toSkip = 0);
 763 
 764   // General allocation (must be MT-safe)
 765   static void* malloc  (size_t size, MEMFLAGS flags, const NativeCallStack& stack);
 766   static void* malloc  (size_t size, MEMFLAGS flags);
 767   static void* realloc (void *memblock, size_t size, MEMFLAGS flag, const NativeCallStack& stack);
 768   static void* realloc (void *memblock, size_t size, MEMFLAGS flag);
 769 
 770   static void  free    (void *memblock);
 771   static char* strdup(const char *, MEMFLAGS flags = mtInternal);  // Like strdup
 772   // Like strdup, but exit VM when strdup() returns NULL
 773   static char* strdup_check_oom(const char*, MEMFLAGS flags = mtInternal);
 774 
 775 #ifndef PRODUCT
 776   static julong num_mallocs;         // # of calls to malloc/realloc
 777   static julong alloc_bytes;         // # of bytes allocated
 778   static julong num_frees;           // # of calls to free
 779   static julong free_bytes;          // # of bytes freed
 780 #endif
 781 
 782   // SocketInterface (ex HPI SocketInterface )
 783   static int socket(int domain, int type, int protocol);
 784   static int socket_close(int fd);
 785   static int recv(int fd, char* buf, size_t nBytes, uint flags);
 786   static int send(int fd, char* buf, size_t nBytes, uint flags);
 787   static int raw_send(int fd, char* buf, size_t nBytes, uint flags);
 788   static int connect(int fd, struct sockaddr* him, socklen_t len);
 789   static struct hostent* get_host_by_name(char* name);
 790 
 791   // Support for signals (see JVM_RaiseSignal, JVM_RegisterSignal)
 792   static void  initialize_jdk_signal_support(TRAPS);
 793   static void  signal_notify(int signal_number);
 794   static void* signal(int signal_number, void* handler);
 795   static void  signal_raise(int signal_number);
 796   static int   signal_wait();
 797   static void* user_handler();
 798   static void  terminate_signal_thread();
 799   static int   sigexitnum_pd();
 800 
 801   // random number generation
 802   static int random();                     // return 32bit pseudorandom number
 803   static void init_random(unsigned int initval);    // initialize random sequence
 804 
 805   // Structured OS Exception support
 806   static void os_exception_wrapper(java_call_t f, JavaValue* value, const methodHandle& method, JavaCallArguments* args, Thread* thread);
 807 
 808   // On Posix compatible OS it will simply check core dump limits while on Windows
 809   // it will check if dump file can be created. Check or prepare a core dump to be
 810   // taken at a later point in the same thread in os::abort(). Use the caller
 811   // provided buffer as a scratch buffer. The status message which will be written
 812   // into the error log either is file location or a short error message, depending
 813   // on the checking result.
 814   static void check_dump_limit(char* buffer, size_t bufferSize);
 815 
 816   // Get the default path to the core file
 817   // Returns the length of the string
 818   static int get_core_path(char* buffer, size_t bufferSize);
 819 
 820   // JVMTI & JVM monitoring and management support
 821   // The thread_cpu_time() and current_thread_cpu_time() are only
 822   // supported if is_thread_cpu_time_supported() returns true.
 823   // They are not supported on Solaris T1.
 824 
 825   // Thread CPU Time - return the fast estimate on a platform
 826   // On Solaris - call gethrvtime (fast) - user time only
 827   // On Linux   - fast clock_gettime where available - user+sys
 828   //            - otherwise: very slow /proc fs - user+sys
 829   // On Windows - GetThreadTimes - user+sys
 830   static jlong current_thread_cpu_time();
 831   static jlong thread_cpu_time(Thread* t);
 832 
 833   // Thread CPU Time with user_sys_cpu_time parameter.
 834   //
 835   // If user_sys_cpu_time is true, user+sys time is returned.
 836   // Otherwise, only user time is returned
 837   static jlong current_thread_cpu_time(bool user_sys_cpu_time);
 838   static jlong thread_cpu_time(Thread* t, bool user_sys_cpu_time);
 839 
 840   // Return a bunch of info about the timers.
 841   // Note that the returned info for these two functions may be different
 842   // on some platforms
 843   static void current_thread_cpu_time_info(jvmtiTimerInfo *info_ptr);
 844   static void thread_cpu_time_info(jvmtiTimerInfo *info_ptr);
 845 
 846   static bool is_thread_cpu_time_supported();
 847 
 848   // System loadavg support.  Returns -1 if load average cannot be obtained.
 849   static int loadavg(double loadavg[], int nelem);
 850 
 851   // Hook for os specific jvm options that we don't want to abort on seeing
 852   static bool obsolete_option(const JavaVMOption *option);
 853 
 854   // Amount beyond the callee frame size that we bang the stack.
 855   static int extra_bang_size_in_bytes();
 856 
 857   static char** split_path(const char* path, int* n);
 858 
 859   // Extensions
 860 #include "runtime/os_ext.hpp"
 861 
 862  public:
 863   class CrashProtectionCallback : public StackObj {
 864   public:
 865     virtual void call() = 0;
 866   };
 867 
 868   // Platform dependent stuff
 869 #ifndef _WINDOWS
 870 # include "os_posix.hpp"
 871 #endif
 872 #include OS_CPU_HEADER(os)
 873 #include OS_HEADER(os)
 874 
 875 #ifndef OS_NATIVE_THREAD_CREATION_FAILED_MSG
 876 #define OS_NATIVE_THREAD_CREATION_FAILED_MSG "unable to create native thread: possibly out of memory or process/resource limits reached"
 877 #endif
 878 
 879  public:
 880 #ifndef PLATFORM_PRINT_NATIVE_STACK
 881   // No platform-specific code for printing the native stack.
 882   static bool platform_print_native_stack(outputStream* st, const void* context,
 883                                           char *buf, int buf_size) {
 884     return false;
 885   }
 886 #endif
 887 
 888   // debugging support (mostly used by debug.cpp but also fatal error handler)
 889   static bool find(address pc, outputStream* st = tty); // OS specific function to make sense out of an address
 890 
 891   static bool dont_yield();                     // when true, JVM_Yield() is nop
 892   static void print_statistics();
 893 
 894   // Thread priority helpers (implemented in OS-specific part)
 895   static OSReturn set_native_priority(Thread* thread, int native_prio);
 896   static OSReturn get_native_priority(const Thread* const thread, int* priority_ptr);
 897   static int java_to_os_priority[CriticalPriority + 1];
 898   // Hint to the underlying OS that a task switch would not be good.
 899   // Void return because it's a hint and can fail.
 900   static const char* native_thread_creation_failed_msg() {
 901     return OS_NATIVE_THREAD_CREATION_FAILED_MSG;
 902   }
 903 
 904   // Used at creation if requested by the diagnostic flag PauseAtStartup.
 905   // Causes the VM to wait until an external stimulus has been applied
 906   // (for Unix, that stimulus is a signal, for Windows, an external
 907   // ResumeThread call)
 908   static void pause();
 909 
 910   // Builds a platform dependent Agent_OnLoad_<libname> function name
 911   // which is used to find statically linked in agents.
 912   static char*  build_agent_function_name(const char *sym, const char *cname,
 913                                           bool is_absolute_path);
 914 
 915   class SuspendedThreadTaskContext {
 916   public:
 917     SuspendedThreadTaskContext(Thread* thread, void *ucontext) : _thread(thread), _ucontext(ucontext) {}
 918     Thread* thread() const { return _thread; }
 919     void* ucontext() const { return _ucontext; }
 920   private:
 921     Thread* _thread;
 922     void* _ucontext;
 923   };
 924 
 925   class SuspendedThreadTask {
 926   public:
 927     SuspendedThreadTask(Thread* thread) : _thread(thread), _done(false) {}
 928     void run();
 929     bool is_done() { return _done; }
 930     virtual void do_task(const SuspendedThreadTaskContext& context) = 0;
 931   protected:
 932     ~SuspendedThreadTask() {}
 933   private:
 934     void internal_do_task();
 935     Thread* _thread;
 936     bool _done;
 937   };
 938 
 939 #ifndef _WINDOWS
 940   // Suspend/resume support
 941   // Protocol:
 942   //
 943   // a thread starts in SR_RUNNING
 944   //
 945   // SR_RUNNING can go to
 946   //   * SR_SUSPEND_REQUEST when the WatcherThread wants to suspend it
 947   // SR_SUSPEND_REQUEST can go to
 948   //   * SR_RUNNING if WatcherThread decides it waited for SR_SUSPENDED too long (timeout)
 949   //   * SR_SUSPENDED if the stopped thread receives the signal and switches state
 950   // SR_SUSPENDED can go to
 951   //   * SR_WAKEUP_REQUEST when the WatcherThread has done the work and wants to resume
 952   // SR_WAKEUP_REQUEST can go to
 953   //   * SR_RUNNING when the stopped thread receives the signal
 954   //   * SR_WAKEUP_REQUEST on timeout (resend the signal and try again)
 955   class SuspendResume {
 956    public:
 957     enum State {
 958       SR_RUNNING,
 959       SR_SUSPEND_REQUEST,
 960       SR_SUSPENDED,
 961       SR_WAKEUP_REQUEST
 962     };
 963 
 964   private:
 965     volatile State _state;
 966 
 967   private:
 968     /* try to switch state from state "from" to state "to"
 969      * returns the state set after the method is complete
 970      */
 971     State switch_state(State from, State to);
 972 
 973   public:
 974     SuspendResume() : _state(SR_RUNNING) { }
 975 
 976     State state() const { return _state; }
 977 
 978     State request_suspend() {
 979       return switch_state(SR_RUNNING, SR_SUSPEND_REQUEST);
 980     }
 981 
 982     State cancel_suspend() {
 983       return switch_state(SR_SUSPEND_REQUEST, SR_RUNNING);
 984     }
 985 
 986     State suspended() {
 987       return switch_state(SR_SUSPEND_REQUEST, SR_SUSPENDED);
 988     }
 989 
 990     State request_wakeup() {
 991       return switch_state(SR_SUSPENDED, SR_WAKEUP_REQUEST);
 992     }
 993 
 994     State running() {
 995       return switch_state(SR_WAKEUP_REQUEST, SR_RUNNING);
 996     }
 997 
 998     bool is_running() const {
 999       return _state == SR_RUNNING;
1000     }
1001 
1002     bool is_suspend_request() const {
1003       return _state == SR_SUSPEND_REQUEST;
1004     }
1005 
1006     bool is_suspended() const {
1007       return _state == SR_SUSPENDED;
1008     }
1009   };
1010 #endif // !WINDOWS
1011 
1012 
1013  protected:
1014   static volatile unsigned int _rand_seed;    // seed for random number generator
1015   static int _processor_count;                // number of processors
1016   static int _initial_active_processor_count; // number of active processors during initialization.
1017 
1018   static char* format_boot_path(const char* format_string,
1019                                 const char* home,
1020                                 int home_len,
1021                                 char fileSep,
1022                                 char pathSep);
1023   static bool set_boot_path(char fileSep, char pathSep);
1024 
1025 };
1026 
1027 #ifndef _WINDOWS
1028 template<> struct IsRegisteredEnum<os::SuspendResume::State> : public TrueType {};
1029 #endif // !_WINDOWS
1030 
1031 // Note that "PAUSE" is almost always used with synchronization
1032 // so arguably we should provide Atomic::SpinPause() instead
1033 // of the global SpinPause() with C linkage.
1034 // It'd also be eligible for inlining on many platforms.
1035 
1036 extern "C" int SpinPause();
1037 
1038 #endif // SHARE_VM_RUNTIME_OS_HPP