view src/share/vm/runtime/os.hpp @ 8746:7f39700be72a

8026324: hs_err improvement: Add summary section to hs_err file 8026333: hs_err improvement: Print GC Strategy 8026336: hs_err improvement: Print compilation mode, server, client or tiered Summary: Added command line, summary cpu and os information to summary section. Moved time of crash and duration in summary section. Add GC strategy and compiler setting (tiered) to enhanced version string in error report. Moved the stack trace sooner in hs_err file. Reviewed-by: dholmes, ctornqvi, ddmitriev
author coleenp
date Wed, 22 Jul 2015 00:03:45 -0400
parents c30414cbbd88
children 6ab7e19c9220
line wrap: on
line source
/*
 * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#ifndef SHARE_VM_RUNTIME_OS_HPP
#define SHARE_VM_RUNTIME_OS_HPP

#include "jvmtifiles/jvmti.h"
#include "runtime/extendedPC.hpp"
#include "runtime/handles.hpp"
#include "utilities/top.hpp"
#ifdef TARGET_OS_FAMILY_linux
# include "jvm_linux.h"
# include <setjmp.h>
#endif
#ifdef TARGET_OS_FAMILY_solaris
# include "jvm_solaris.h"
# include <setjmp.h>
#endif
#ifdef TARGET_OS_FAMILY_windows
# include "jvm_windows.h"
#endif
#ifdef TARGET_OS_FAMILY_aix
# include "jvm_aix.h"
# include <setjmp.h>
#endif
#ifdef TARGET_OS_FAMILY_bsd
# include "jvm_bsd.h"
# include <setjmp.h>
# ifdef __APPLE__
#  include <mach/mach_time.h>
# endif
#endif

class AgentLibrary;

// os defines the interface to operating system; this includes traditional
// OS services (time, I/O) as well as other functionality with system-
// dependent code.

typedef void (*dll_func)(...);

class Thread;
class JavaThread;
class Event;
class DLL;
class FileHandle;
class NativeCallStack;

template<class E> class GrowableArray;

// %%%%% Moved ThreadState, START_FN, OSThread to new osThread.hpp. -- Rose

// Platform-independent error return values from OS functions
enum OSReturn {
  OS_OK         =  0,        // Operation was successful
  OS_ERR        = -1,        // Operation failed
  OS_INTRPT     = -2,        // Operation was interrupted
  OS_TIMEOUT    = -3,        // Operation timed out
  OS_NOMEM      = -5,        // Operation failed for lack of memory
  OS_NORESOURCE = -6         // Operation failed for lack of nonmemory resource
};

enum ThreadPriority {        // JLS 20.20.1-3
  NoPriority       = -1,     // Initial non-priority value
  MinPriority      =  1,     // Minimum priority
  NormPriority     =  5,     // Normal (non-daemon) priority
  NearMaxPriority  =  9,     // High priority, used for VMThread
  MaxPriority      = 10,     // Highest priority, used for WatcherThread
                             // ensures that VMThread doesn't starve profiler
  CriticalPriority = 11      // Critical thread priority
};

// Executable parameter flag for os::commit_memory() and
// os::commit_memory_or_exit().
const bool ExecMem = true;

// Typedef for structured exception handling support
typedef void (*java_call_t)(JavaValue* value, methodHandle* method, JavaCallArguments* args, Thread* thread);

class MallocTracker;

class os: AllStatic {
  friend class VMStructs;
  friend class MallocTracker;
 public:
  enum { page_sizes_max = 9 }; // Size of _page_sizes array (8 plus a sentinel)

 private:
  static OSThread*          _starting_thread;
  static address            _polling_page;
  static volatile int32_t * _mem_serialize_page;
  static uintptr_t          _serialize_page_mask;
 public:
  static size_t             _page_sizes[page_sizes_max];

 private:
  static void init_page_sizes(size_t default_page_size) {
    _page_sizes[0] = default_page_size;
    _page_sizes[1] = 0; // sentinel
  }

  static char*  pd_reserve_memory(size_t bytes, char* addr = 0,
                               size_t alignment_hint = 0);
  static char*  pd_attempt_reserve_memory_at(size_t bytes, char* addr);
  static void   pd_split_reserved_memory(char *base, size_t size,
                                      size_t split, bool realloc);
  static bool   pd_commit_memory(char* addr, size_t bytes, bool executable);
  static bool   pd_commit_memory(char* addr, size_t size, size_t alignment_hint,
                                 bool executable);
  // Same as pd_commit_memory() that either succeeds or calls
  // vm_exit_out_of_memory() with the specified mesg.
  static void   pd_commit_memory_or_exit(char* addr, size_t bytes,
                                         bool executable, const char* mesg);
  static void   pd_commit_memory_or_exit(char* addr, size_t size,
                                         size_t alignment_hint,
                                         bool executable, const char* mesg);
  static bool   pd_uncommit_memory(char* addr, size_t bytes);
  static bool   pd_release_memory(char* addr, size_t bytes);

  static char*  pd_map_memory(int fd, const char* file_name, size_t file_offset,
                           char *addr, size_t bytes, bool read_only = false,
                           bool allow_exec = false);
  static char*  pd_remap_memory(int fd, const char* file_name, size_t file_offset,
                             char *addr, size_t bytes, bool read_only,
                             bool allow_exec);
  static bool   pd_unmap_memory(char *addr, size_t bytes);
  static void   pd_free_memory(char *addr, size_t bytes, size_t alignment_hint);
  static void   pd_realign_memory(char *addr, size_t bytes, size_t alignment_hint);

  static size_t page_size_for_region(size_t region_size, size_t min_pages, bool must_be_aligned);

  // Get summary strings for system information in buffer provided
  static bool  get_host_name(char* buf, size_t buflen) PRODUCT_RETURN_(return false;);  // true if available
  static void  get_summary_cpu_info(char* buf, size_t buflen);
  static void  get_summary_os_info(char* buf, size_t buflen);

 public:
  static void init(void);                      // Called before command line parsing
  static void init_before_ergo(void);          // Called after command line parsing
                                               // before VM ergonomics processing.
  static jint init_2(void);                    // Called after command line parsing
                                               // and VM ergonomics processing
  static void init_globals(void) {             // Called from init_globals() in init.cpp
    init_globals_ext();
  }

  // File names are case-insensitive on windows only
  // Override me as needed
  static int    file_name_strcmp(const char* s1, const char* s2);

  // unset environment variable
  static bool unsetenv(const char* name);

  static bool have_special_privileges();

  static jlong  javaTimeMillis();
  static jlong  javaTimeNanos();
  static void   javaTimeNanos_info(jvmtiTimerInfo *info_ptr);
  static void   javaTimeSystemUTC(jlong &seconds, jlong &nanos);
  static void   run_periodic_checks();
  static bool   supports_monotonic_clock();

  // Returns the elapsed time in seconds since the vm started.
  static double elapsedTime();

  // Returns real time in seconds since an arbitrary point
  // in the past.
  static bool getTimesSecs(double* process_real_time,
                           double* process_user_time,
                           double* process_system_time);

  // Interface to the performance counter
  static jlong elapsed_counter();
  static jlong elapsed_frequency();

  // The "virtual time" of a thread is the amount of time a thread has
  // actually run.  The first function indicates whether the OS supports
  // this functionality for the current thread, and if so:
  //   * the second enables vtime tracking (if that is required).
  //   * the third tells whether vtime is enabled.
  //   * the fourth returns the elapsed virtual time for the current
  //     thread.
  static bool supports_vtime();
  static bool enable_vtime();
  static bool vtime_enabled();
  static double elapsedVTime();

  // Return current local time in a string (YYYY-MM-DD HH:MM:SS).
  // It is MT safe, but not async-safe, as reading time zone
  // information may require a lock on some platforms.
  static char*      local_time_string(char *buf, size_t buflen);
  static struct tm* localtime_pd     (const time_t* clock, struct tm*  res);
  // Fill in buffer with current local time as an ISO-8601 string.
  // E.g., YYYY-MM-DDThh:mm:ss.mmm+zzzz.
  // Returns buffer, or NULL if it failed.
  static char* iso8601_time(char* buffer, size_t buffer_length);

  // Interface for detecting multiprocessor system
  static inline bool is_MP() {
    // During bootstrap if _processor_count is not yet initialized
    // we claim to be MP as that is safest. If any platform has a
    // stub generator that might be triggered in this phase and for
    // which being declared MP when in fact not, is a problem - then
    // the bootstrap routine for the stub generator needs to check
    // the processor count directly and leave the bootstrap routine
    // in place until called after initialization has ocurred.
    return (_processor_count != 1) || AssumeMP;
  }
  static julong available_memory();
  static julong physical_memory();
  static bool has_allocatable_memory_limit(julong* limit);
  static bool is_server_class_machine();

  // number of CPUs
  static int processor_count() {
    return _processor_count;
  }
  static void set_processor_count(int count) { _processor_count = count; }

  // Returns the number of CPUs this process is currently allowed to run on.
  // Note that on some OSes this can change dynamically.
  static int active_processor_count();

  // Bind processes to processors.
  //     This is a two step procedure:
  //     first you generate a distribution of processes to processors,
  //     then you bind processes according to that distribution.
  // Compute a distribution for number of processes to processors.
  //    Stores the processor id's into the distribution array argument.
  //    Returns true if it worked, false if it didn't.
  static bool distribute_processes(uint length, uint* distribution);
  // Binds the current process to a processor.
  //    Returns true if it worked, false if it didn't.
  static bool bind_to_processor(uint processor_id);

  // Give a name to the current thread.
  static void set_native_thread_name(const char *name);

  // Interface for stack banging (predetect possible stack overflow for
  // exception processing)  There are guard pages, and above that shadow
  // pages for stack overflow checking.
  static bool uses_stack_guard_pages();
  static bool allocate_stack_guard_pages();
  static void bang_stack_shadow_pages();
  static bool stack_shadow_pages_available(Thread *thread, methodHandle method);

  // OS interface to Virtual Memory

  // Return the default page size.
  static int    vm_page_size();

  // Returns the page size to use for a region of memory.
  // region_size / min_pages will always be greater than or equal to the
  // returned value. The returned value will divide region_size.
  static size_t page_size_for_region_aligned(size_t region_size, size_t min_pages);

  // Returns the page size to use for a region of memory.
  // region_size / min_pages will always be greater than or equal to the
  // returned value. The returned value might not divide region_size.
  static size_t page_size_for_region_unaligned(size_t region_size, size_t min_pages);

  // Return the largest page size that can be used
  static size_t max_page_size() {
    // The _page_sizes array is sorted in descending order.
    return _page_sizes[0];
  }

  // Methods for tracing page sizes returned by the above method; enabled by
  // TracePageSizes.  The region_{min,max}_size parameters should be the values
  // passed to page_size_for_region() and page_size should be the result of that
  // call.  The (optional) base and size parameters should come from the
  // ReservedSpace base() and size() methods.
  static void trace_page_sizes(const char* str, const size_t* page_sizes,
                               int count) PRODUCT_RETURN;
  static void trace_page_sizes(const char* str, const size_t region_min_size,
                               const size_t region_max_size,
                               const size_t page_size,
                               const char* base = NULL,
                               const size_t size = 0) PRODUCT_RETURN;

  static int    vm_allocation_granularity();
  static char*  reserve_memory(size_t bytes, char* addr = 0,
                               size_t alignment_hint = 0);
  static char*  reserve_memory(size_t bytes, char* addr,
                               size_t alignment_hint, MEMFLAGS flags);
  static char*  reserve_memory_aligned(size_t size, size_t alignment);
  static char*  attempt_reserve_memory_at(size_t bytes, char* addr);
  static void   split_reserved_memory(char *base, size_t size,
                                      size_t split, bool realloc);
  static bool   commit_memory(char* addr, size_t bytes, bool executable);
  static bool   commit_memory(char* addr, size_t size, size_t alignment_hint,
                              bool executable);
  // Same as commit_memory() that either succeeds or calls
  // vm_exit_out_of_memory() with the specified mesg.
  static void   commit_memory_or_exit(char* addr, size_t bytes,
                                      bool executable, const char* mesg);
  static void   commit_memory_or_exit(char* addr, size_t size,
                                      size_t alignment_hint,
                                      bool executable, const char* mesg);
  static bool   uncommit_memory(char* addr, size_t bytes);
  static bool   release_memory(char* addr, size_t bytes);

  // Touch memory pages that cover the memory range from start to end (exclusive)
  // to make the OS back the memory range with actual memory.
  // Current implementation may not touch the last page if unaligned addresses
  // are passed.
  static void   pretouch_memory(char* start, char* end);

  enum ProtType { MEM_PROT_NONE, MEM_PROT_READ, MEM_PROT_RW, MEM_PROT_RWX };
  static bool   protect_memory(char* addr, size_t bytes, ProtType prot,
                               bool is_committed = true);

  static bool   guard_memory(char* addr, size_t bytes);
  static bool   unguard_memory(char* addr, size_t bytes);
  static bool   create_stack_guard_pages(char* addr, size_t bytes);
  static bool   pd_create_stack_guard_pages(char* addr, size_t bytes);
  static bool   remove_stack_guard_pages(char* addr, size_t bytes);

  static char*  map_memory(int fd, const char* file_name, size_t file_offset,
                           char *addr, size_t bytes, bool read_only = false,
                           bool allow_exec = false);
  static char*  remap_memory(int fd, const char* file_name, size_t file_offset,
                             char *addr, size_t bytes, bool read_only,
                             bool allow_exec);
  static bool   unmap_memory(char *addr, size_t bytes);
  static void   free_memory(char *addr, size_t bytes, size_t alignment_hint);
  static void   realign_memory(char *addr, size_t bytes, size_t alignment_hint);

  // NUMA-specific interface
  static bool   numa_has_static_binding();
  static bool   numa_has_group_homing();
  static void   numa_make_local(char *addr, size_t bytes, int lgrp_hint);
  static void   numa_make_global(char *addr, size_t bytes);
  static size_t numa_get_groups_num();
  static size_t numa_get_leaf_groups(int *ids, size_t size);
  static bool   numa_topology_changed();
  static int    numa_get_group_id();

  // Page manipulation
  struct page_info {
    size_t size;
    int lgrp_id;
  };
  static bool   get_page_info(char *start, page_info* info);
  static char*  scan_pages(char *start, char* end, page_info* page_expected, page_info* page_found);

  static char*  non_memory_address_word();
  // reserve, commit and pin the entire memory region
  static char*  reserve_memory_special(size_t size, size_t alignment,
                                       char* addr, bool executable);
  static bool   release_memory_special(char* addr, size_t bytes);
  static void   large_page_init();
  static size_t large_page_size();
  static bool   can_commit_large_page_memory();
  static bool   can_execute_large_page_memory();

  // OS interface to polling page
  static address get_polling_page()             { return _polling_page; }
  static void    set_polling_page(address page) { _polling_page = page; }
  static bool    is_poll_address(address addr)  { return addr >= _polling_page && addr < (_polling_page + os::vm_page_size()); }
  static void    make_polling_page_unreadable();
  static void    make_polling_page_readable();

  // Routines used to serialize the thread state without using membars
  static void    serialize_thread_states();

  // Since we write to the serialize page from every thread, we
  // want stores to be on unique cache lines whenever possible
  // in order to minimize CPU cross talk.  We pre-compute the
  // amount to shift the thread* to make this offset unique to
  // each thread.
  static int     get_serialize_page_shift_count() {
    return SerializePageShiftCount;
  }

  static void     set_serialize_page_mask(uintptr_t mask) {
    _serialize_page_mask = mask;
  }

  static unsigned int  get_serialize_page_mask() {
    return _serialize_page_mask;
  }

  static void    set_memory_serialize_page(address page);

  static address get_memory_serialize_page() {
    return (address)_mem_serialize_page;
  }

  static inline void write_memory_serialize_page(JavaThread *thread) {
    uintptr_t page_offset = ((uintptr_t)thread >>
                            get_serialize_page_shift_count()) &
                            get_serialize_page_mask();
    *(volatile int32_t *)((uintptr_t)_mem_serialize_page+page_offset) = 1;
  }

  static bool    is_memory_serialize_page(JavaThread *thread, address addr) {
    if (UseMembar) return false;
    // Previously this function calculated the exact address of this
    // thread's serialize page, and checked if the faulting address
    // was equal.  However, some platforms mask off faulting addresses
    // to the page size, so now we just check that the address is
    // within the page.  This makes the thread argument unnecessary,
    // but we retain the NULL check to preserve existing behavior.
    if (thread == NULL) return false;
    address page = (address) _mem_serialize_page;
    return addr >= page && addr < (page + os::vm_page_size());
  }

  static void block_on_serialize_page_trap();

  // threads

  enum ThreadType {
    vm_thread,
    cgc_thread,        // Concurrent GC thread
    pgc_thread,        // Parallel GC thread
    java_thread,
    compiler_thread,
    watcher_thread,
    os_thread
  };

  static bool create_thread(Thread* thread,
                            ThreadType thr_type,
                            size_t stack_size = 0);
  static bool create_main_thread(JavaThread* thread);
  static bool create_attached_thread(JavaThread* thread);
  static void pd_start_thread(Thread* thread);
  static void start_thread(Thread* thread);

  static void initialize_thread(Thread* thr);
  static void free_thread(OSThread* osthread);

  // thread id on Linux/64bit is 64bit, on Windows and Solaris, it's 32bit
  static intx current_thread_id();
  static int current_process_id();
  static int sleep(Thread* thread, jlong ms, bool interruptable);
  // Short standalone OS sleep suitable for slow path spin loop.
  // Ignores Thread.interrupt() (so keep it short).
  // ms = 0, will sleep for the least amount of time allowed by the OS.
  static void naked_short_sleep(jlong ms);
  static void infinite_sleep(); // never returns, use with CAUTION
  static void naked_yield () ;
  static OSReturn set_priority(Thread* thread, ThreadPriority priority);
  static OSReturn get_priority(const Thread* const thread, ThreadPriority& priority);

  static void interrupt(Thread* thread);
  static bool is_interrupted(Thread* thread, bool clear_interrupted);

  static int pd_self_suspend_thread(Thread* thread);

  static ExtendedPC fetch_frame_from_context(void* ucVoid, intptr_t** sp, intptr_t** fp);
  static frame      fetch_frame_from_context(void* ucVoid);

  static ExtendedPC get_thread_pc(Thread *thread);
  static void breakpoint();

  static address current_stack_pointer();
  static address current_stack_base();
  static size_t current_stack_size();

  static void verify_stack_alignment() PRODUCT_RETURN;

  static int message_box(const char* title, const char* message);
  static char* do_you_want_to_debug(const char* message);

  // run cmd in a separate process and return its exit code; or -1 on failures
  static int fork_and_exec(char *cmd);

  // Call ::exit() on all platforms but Windows
  static void exit(int num);

  // Terminate the VM, but don't exit the process
  static void shutdown();

  // Terminate with an error.  Default is to generate a core file on platforms
  // that support such things.  This calls shutdown() and then aborts.
  static void abort(bool dump_core, void *siginfo, void *context);
  static void abort(bool dump_core = true);

  // Die immediately, no exit hook, no abort hook, no cleanup.
  static void die();

  // File i/o operations
  static const int default_file_open_flags();
  static int open(const char *path, int oflag, int mode);
  static FILE* open(int fd, const char* mode);
  static int close(int fd);
  static jlong lseek(int fd, jlong offset, int whence);
  static char* native_path(char *path);
  static int ftruncate(int fd, jlong length);
  static int fsync(int fd);
  static int available(int fd, jlong *bytes);

  //File i/o operations

  static size_t read(int fd, void *buf, unsigned int nBytes);
  static size_t read_at(int fd, void *buf, unsigned int nBytes, jlong offset);
  static size_t restartable_read(int fd, void *buf, unsigned int nBytes);
  static size_t write(int fd, const void *buf, unsigned int nBytes);

  // Reading directories.
  static DIR*           opendir(const char* dirname);
  static int            readdir_buf_size(const char *path);
  static struct dirent* readdir(DIR* dirp, dirent* dbuf);
  static int            closedir(DIR* dirp);

  // Dynamic library extension
  static const char*    dll_file_extension();

  static const char*    get_temp_directory();
  static const char*    get_current_directory(char *buf, size_t buflen);

  // Builds a platform-specific full library path given a ld path and lib name
  // Returns true if buffer contains full path to existing file, false otherwise
  static bool           dll_build_name(char* buffer, size_t size,
                                       const char* pathname, const char* fname);

  // Symbol lookup, find nearest function name; basically it implements
  // dladdr() for all platforms. Name of the nearest function is copied
  // to buf. Distance from its base address is optionally returned as offset.
  // If function name is not found, buf[0] is set to '\0' and offset is
  // set to -1 (if offset is non-NULL).
  static bool dll_address_to_function_name(address addr, char* buf,
                                           int buflen, int* offset,
                                           bool demangle = true);

  // Locate DLL/DSO. On success, full path of the library is copied to
  // buf, and offset is optionally set to be the distance between addr
  // and the library's base address. On failure, buf[0] is set to '\0'
  // and offset is set to -1 (if offset is non-NULL).
  static bool dll_address_to_library_name(address addr, char* buf,
                                          int buflen, int* offset);

  // Find out whether the pc is in the static code for jvm.dll/libjvm.so.
  static bool address_is_in_vm(address addr);

  // Loads .dll/.so and
  // in case of error it checks if .dll/.so was built for the
  // same architecture as HotSpot is running on
  static void* dll_load(const char *name, char *ebuf, int ebuflen);

  // lookup symbol in a shared library
  static void* dll_lookup(void* handle, const char* name);

  // Unload library
  static void  dll_unload(void *lib);

  // Callback for loaded module information
  // Input parameters:
  //    char*     module_file_name,
  //    address   module_base_addr,
  //    address   module_top_addr,
  //    void*     param
  typedef int (*LoadedModulesCallbackFunc)(const char *, address, address, void *);

  static int get_loaded_modules_info(LoadedModulesCallbackFunc callback, void *param);

  // Return the handle of this process
  static void* get_default_process_handle();

  // Check for static linked agent library
  static bool find_builtin_agent(AgentLibrary *agent_lib, const char *syms[],
                                 size_t syms_len);

  // Find agent entry point
  static void *find_agent_function(AgentLibrary *agent_lib, bool check_lib,
                                   const char *syms[], size_t syms_len);

  // Print out system information; they are called by fatal error handler.
  // Output format may be different on different platforms.
  static void print_os_info(outputStream* st);
  static void print_os_info_brief(outputStream* st);
  static void print_cpu_info(outputStream* st, char* buf, size_t buflen);
  static void pd_print_cpu_info(outputStream* st, char* buf, size_t buflen);
  static void print_summary_info(outputStream* st, char* buf, size_t buflen);
  static void print_memory_info(outputStream* st);
  static void print_dll_info(outputStream* st);
  static void print_environment_variables(outputStream* st, const char** env_list);
  static void print_context(outputStream* st, void* context);
  static void print_register_info(outputStream* st, void* context);
  static void print_siginfo(outputStream* st, void* siginfo);
  static void print_signal_handlers(outputStream* st, char* buf, size_t buflen);
  static void print_date_and_time(outputStream* st, char* buf, size_t buflen);

  static void print_location(outputStream* st, intptr_t x, bool verbose = false);
  static size_t lasterror(char *buf, size_t len);
  static int get_last_error();

  // Determines whether the calling process is being debugged by a user-mode debugger.
  static bool is_debugger_attached();

  // wait for a key press if PauseAtExit is set
  static void wait_for_keypress_at_exit(void);

  // The following two functions are used by fatal error handler to trace
  // native (C) frames. They are not part of frame.hpp/frame.cpp because
  // frame.hpp/cpp assume thread is JavaThread, and also because different
  // OS/compiler may have different convention or provide different API to
  // walk C frames.
  //
  // We don't attempt to become a debugger, so we only follow frames if that
  // does not require a lookup in the unwind table, which is part of the binary
  // file but may be unsafe to read after a fatal error. So on x86, we can
  // only walk stack if %ebp is used as frame pointer; on ia64, it's not
  // possible to walk C stack without having the unwind table.
  static bool is_first_C_frame(frame *fr);
  static frame get_sender_for_C_frame(frame *fr);

  // return current frame. pc() and sp() are set to NULL on failure.
  static frame      current_frame();

  static void print_hex_dump(outputStream* st, address start, address end, int unitsize);

  // returns a string to describe the exception/signal;
  // returns NULL if exception_code is not an OS exception/signal.
  static const char* exception_name(int exception_code, char* buf, size_t buflen);

  // Returns native Java library, loads if necessary
  static void*    native_java_library();

  // Fills in path to jvm.dll/libjvm.so (used by the Disassembler)
  static void     jvm_path(char *buf, jint buflen);

  // Returns true if we are running in a headless jre.
  static bool     is_headless_jre();

  // JNI names
  static void     print_jni_name_prefix_on(outputStream* st, int args_size);
  static void     print_jni_name_suffix_on(outputStream* st, int args_size);

  // Init os specific system properties values
  static void init_system_properties_values();

  // IO operations, non-JVM_ version.
  static int stat(const char* path, struct stat* sbuf);
  static bool dir_is_empty(const char* path);

  // IO operations on binary files
  static int create_binary_file(const char* path, bool rewrite_existing);
  static jlong current_file_offset(int fd);
  static jlong seek_to_file_offset(int fd, jlong offset);

  // Thread Local Storage
  static int   allocate_thread_local_storage();
  static void  thread_local_storage_at_put(int index, void* value);
  static void* thread_local_storage_at(int index);
  static void  free_thread_local_storage(int index);

  // Retrieve native stack frames.
  // Parameter:
  //   stack:  an array to storage stack pointers.
  //   frames: size of above array.
  //   toSkip: number of stack frames to skip at the beginning.
  // Return: number of stack frames captured.
  static int get_native_stack(address* stack, int size, int toSkip = 0);

  // General allocation (must be MT-safe)
  static void* malloc  (size_t size, MEMFLAGS flags, const NativeCallStack& stack);
  static void* malloc  (size_t size, MEMFLAGS flags);
  static void* realloc (void *memblock, size_t size, MEMFLAGS flag, const NativeCallStack& stack);
  static void* realloc (void *memblock, size_t size, MEMFLAGS flag);

  static void  free    (void *memblock);
  static bool  check_heap(bool force = false);      // verify C heap integrity
  static char* strdup(const char *, MEMFLAGS flags = mtInternal);  // Like strdup
  // Like strdup, but exit VM when strdup() returns NULL
  static char* strdup_check_oom(const char*, MEMFLAGS flags = mtInternal);

#ifndef PRODUCT
  static julong num_mallocs;         // # of calls to malloc/realloc
  static julong alloc_bytes;         // # of bytes allocated
  static julong num_frees;           // # of calls to free
  static julong free_bytes;          // # of bytes freed
#endif

  // SocketInterface (ex HPI SocketInterface )
  static int socket(int domain, int type, int protocol);
  static int socket_close(int fd);
  static int recv(int fd, char* buf, size_t nBytes, uint flags);
  static int send(int fd, char* buf, size_t nBytes, uint flags);
  static int raw_send(int fd, char* buf, size_t nBytes, uint flags);
  static int connect(int fd, struct sockaddr* him, socklen_t len);
  static struct hostent* get_host_by_name(char* name);

  // Support for signals (see JVM_RaiseSignal, JVM_RegisterSignal)
  static void  signal_init();
  static void  signal_init_pd();
  static void  signal_notify(int signal_number);
  static void* signal(int signal_number, void* handler);
  static void  signal_raise(int signal_number);
  static int   signal_wait();
  static int   signal_lookup();
  static void* user_handler();
  static void  terminate_signal_thread();
  static int   sigexitnum_pd();

  // random number generation
  static long random();                    // return 32bit pseudorandom number
  static void init_random(long initval);   // initialize random sequence

  // Structured OS Exception support
  static void os_exception_wrapper(java_call_t f, JavaValue* value, methodHandle* method, JavaCallArguments* args, Thread* thread);

  // On Posix compatible OS it will simply check core dump limits while on Windows
  // it will check if dump file can be created. Check or prepare a core dump to be
  // taken at a later point in the same thread in os::abort(). Use the caller
  // provided buffer as a scratch buffer. The status message which will be written
  // into the error log either is file location or a short error message, depending
  // on the checking result.
  static void check_dump_limit(char* buffer, size_t bufferSize);

  // Get the default path to the core file
  // Returns the length of the string
  static int get_core_path(char* buffer, size_t bufferSize);

  // JVMTI & JVM monitoring and management support
  // The thread_cpu_time() and current_thread_cpu_time() are only
  // supported if is_thread_cpu_time_supported() returns true.
  // They are not supported on Solaris T1.

  // Thread CPU Time - return the fast estimate on a platform
  // On Solaris - call gethrvtime (fast) - user time only
  // On Linux   - fast clock_gettime where available - user+sys
  //            - otherwise: very slow /proc fs - user+sys
  // On Windows - GetThreadTimes - user+sys
  static jlong current_thread_cpu_time();
  static jlong thread_cpu_time(Thread* t);

  // Thread CPU Time with user_sys_cpu_time parameter.
  //
  // If user_sys_cpu_time is true, user+sys time is returned.
  // Otherwise, only user time is returned
  static jlong current_thread_cpu_time(bool user_sys_cpu_time);
  static jlong thread_cpu_time(Thread* t, bool user_sys_cpu_time);

  // Return a bunch of info about the timers.
  // Note that the returned info for these two functions may be different
  // on some platforms
  static void current_thread_cpu_time_info(jvmtiTimerInfo *info_ptr);
  static void thread_cpu_time_info(jvmtiTimerInfo *info_ptr);

  static bool is_thread_cpu_time_supported();

  // System loadavg support.  Returns -1 if load average cannot be obtained.
  static int loadavg(double loadavg[], int nelem);

  // Hook for os specific jvm options that we don't want to abort on seeing
  static bool obsolete_option(const JavaVMOption *option);

  // Amount beyond the callee frame size that we bang the stack.
  static int extra_bang_size_in_bytes();

  // Extensions
#include "runtime/os_ext.hpp"

 public:
  class CrashProtectionCallback : public StackObj {
  public:
    virtual void call() = 0;
  };

  // Platform dependent stuff
#ifdef TARGET_OS_FAMILY_linux
# include "os_linux.hpp"
# include "os_posix.hpp"
#endif
#ifdef TARGET_OS_FAMILY_solaris
# include "os_solaris.hpp"
# include "os_posix.hpp"
#endif
#ifdef TARGET_OS_FAMILY_windows
# include "os_windows.hpp"
#endif
#ifdef TARGET_OS_FAMILY_aix
# include "os_aix.hpp"
# include "os_posix.hpp"
#endif
#ifdef TARGET_OS_FAMILY_bsd
# include "os_posix.hpp"
# include "os_bsd.hpp"
#endif
#ifdef TARGET_OS_ARCH_linux_x86
# include "os_linux_x86.hpp"
#endif
#ifdef TARGET_OS_ARCH_linux_sparc
# include "os_linux_sparc.hpp"
#endif
#ifdef TARGET_OS_ARCH_linux_zero
# include "os_linux_zero.hpp"
#endif
#ifdef TARGET_OS_ARCH_solaris_x86
# include "os_solaris_x86.hpp"
#endif
#ifdef TARGET_OS_ARCH_solaris_sparc
# include "os_solaris_sparc.hpp"
#endif
#ifdef TARGET_OS_ARCH_windows_x86
# include "os_windows_x86.hpp"
#endif
#ifdef TARGET_OS_ARCH_linux_arm
# include "os_linux_arm.hpp"
#endif
#ifdef TARGET_OS_ARCH_linux_ppc
# include "os_linux_ppc.hpp"
#endif
#ifdef TARGET_OS_ARCH_aix_ppc
# include "os_aix_ppc.hpp"
#endif
#ifdef TARGET_OS_ARCH_linux_aarch64
# include "os_linux_aarch64.hpp"
#endif
#ifdef TARGET_OS_ARCH_bsd_x86
# include "os_bsd_x86.hpp"
#endif
#ifdef TARGET_OS_ARCH_bsd_zero
# include "os_bsd_zero.hpp"
#endif

#ifndef OS_NATIVE_THREAD_CREATION_FAILED_MSG
#define OS_NATIVE_THREAD_CREATION_FAILED_MSG "unable to create native thread: possibly out of memory or process/resource limits reached"
#endif

 public:
#ifndef PLATFORM_PRINT_NATIVE_STACK
  // No platform-specific code for printing the native stack.
  static bool platform_print_native_stack(outputStream* st, void* context,
                                          char *buf, int buf_size) {
    return false;
  }
#endif

  // debugging support (mostly used by debug.cpp but also fatal error handler)
  static bool find(address pc, outputStream* st = tty); // OS specific function to make sense out of an address

  static bool dont_yield();                     // when true, JVM_Yield() is nop
  static void print_statistics();

  // Thread priority helpers (implemented in OS-specific part)
  static OSReturn set_native_priority(Thread* thread, int native_prio);
  static OSReturn get_native_priority(const Thread* const thread, int* priority_ptr);
  static int java_to_os_priority[CriticalPriority + 1];
  // Hint to the underlying OS that a task switch would not be good.
  // Void return because it's a hint and can fail.
  static void hint_no_preempt();
  static const char* native_thread_creation_failed_msg() {
    return OS_NATIVE_THREAD_CREATION_FAILED_MSG;
  }

  // Used at creation if requested by the diagnostic flag PauseAtStartup.
  // Causes the VM to wait until an external stimulus has been applied
  // (for Unix, that stimulus is a signal, for Windows, an external
  // ResumeThread call)
  static void pause();

  // Builds a platform dependent Agent_OnLoad_<libname> function name
  // which is used to find statically linked in agents.
  static char*  build_agent_function_name(const char *sym, const char *cname,
                                          bool is_absolute_path);

  class SuspendedThreadTaskContext {
  public:
    SuspendedThreadTaskContext(Thread* thread, void *ucontext) : _thread(thread), _ucontext(ucontext) {}
    Thread* thread() const { return _thread; }
    void* ucontext() const { return _ucontext; }
  private:
    Thread* _thread;
    void* _ucontext;
  };

  class SuspendedThreadTask {
  public:
    SuspendedThreadTask(Thread* thread) : _thread(thread), _done(false) {}
    virtual ~SuspendedThreadTask() {}
    void run();
    bool is_done() { return _done; }
    virtual void do_task(const SuspendedThreadTaskContext& context) = 0;
  protected:
  private:
    void internal_do_task();
    Thread* _thread;
    bool _done;
  };

#ifndef TARGET_OS_FAMILY_windows
  // Suspend/resume support
  // Protocol:
  //
  // a thread starts in SR_RUNNING
  //
  // SR_RUNNING can go to
  //   * SR_SUSPEND_REQUEST when the WatcherThread wants to suspend it
  // SR_SUSPEND_REQUEST can go to
  //   * SR_RUNNING if WatcherThread decides it waited for SR_SUSPENDED too long (timeout)
  //   * SR_SUSPENDED if the stopped thread receives the signal and switches state
  // SR_SUSPENDED can go to
  //   * SR_WAKEUP_REQUEST when the WatcherThread has done the work and wants to resume
  // SR_WAKEUP_REQUEST can go to
  //   * SR_RUNNING when the stopped thread receives the signal
  //   * SR_WAKEUP_REQUEST on timeout (resend the signal and try again)
  class SuspendResume {
   public:
    enum State {
      SR_RUNNING,
      SR_SUSPEND_REQUEST,
      SR_SUSPENDED,
      SR_WAKEUP_REQUEST
    };

  private:
    volatile State _state;

  private:
    /* try to switch state from state "from" to state "to"
     * returns the state set after the method is complete
     */
    State switch_state(State from, State to);

  public:
    SuspendResume() : _state(SR_RUNNING) { }

    State state() const { return _state; }

    State request_suspend() {
      return switch_state(SR_RUNNING, SR_SUSPEND_REQUEST);
    }

    State cancel_suspend() {
      return switch_state(SR_SUSPEND_REQUEST, SR_RUNNING);
    }

    State suspended() {
      return switch_state(SR_SUSPEND_REQUEST, SR_SUSPENDED);
    }

    State request_wakeup() {
      return switch_state(SR_SUSPENDED, SR_WAKEUP_REQUEST);
    }

    State running() {
      return switch_state(SR_WAKEUP_REQUEST, SR_RUNNING);
    }

    bool is_running() const {
      return _state == SR_RUNNING;
    }

    bool is_suspend_request() const {
      return _state == SR_SUSPEND_REQUEST;
    }

    bool is_suspended() const {
      return _state == SR_SUSPENDED;
    }
  };
#endif


 protected:
  static long _rand_seed;                   // seed for random number generator
  static int _processor_count;              // number of processors

  static char* format_boot_path(const char* format_string,
                                const char* home,
                                int home_len,
                                char fileSep,
                                char pathSep);
  static bool set_boot_path(char fileSep, char pathSep);
  static char** split_path(const char* path, int* n);

};

// Note that "PAUSE" is almost always used with synchronization
// so arguably we should provide Atomic::SpinPause() instead
// of the global SpinPause() with C linkage.
// It'd also be eligible for inlining on many platforms.

extern "C" int SpinPause();

#endif // SHARE_VM_RUNTIME_OS_HPP