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// Copyright 2012 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// This module contains the platform-specific code. This make the rest of the
// code less dependent on operating system, compilers and runtime libraries.
// This module does specifically not deal with differences between different
// processor architecture.
// The platform classes have the same definition for all platforms. The
// implementation for a particular platform is put in platform_<os>.cc.
// The build system then uses the implementation for the target platform.
// This design has been chosen because it is simple and fast. Alternatively,
// the platform dependent classes could have been implemented using abstract
// superclasses with virtual methods and having specializations for each
// platform. This design was rejected because it was more complicated and
// slower. It would require factory methods for selecting the right
// implementation and the overhead of virtual methods for performance
// sensitive like mutex locking/unlocking.
#include <cstdarg>
#include <string>
#include <vector>
#include "src/base/base-export.h"
#include "src/base/build_config.h"
#include "src/base/compiler-specific.h"
#include "src/base/platform/mutex.h"
#include "src/base/platform/semaphore.h"
#if V8_OS_QNX
#include "src/base/qnx-math.h"
namespace v8 {
namespace base {
// ----------------------------------------------------------------------------
// Fast TLS support
#ifndef V8_NO_FAST_TLS
V8_INLINE intptr_t InternalGetExistingThreadLocal(intptr_t index);
inline intptr_t InternalGetExistingThreadLocal(intptr_t index) {
const intptr_t kTibInlineTlsOffset = 0xE10;
const intptr_t kTibExtraTlsOffset = 0xF94;
const intptr_t kMaxInlineSlots = 64;
const intptr_t kMaxSlots = kMaxInlineSlots + 1024;
const intptr_t kSystemPointerSize = sizeof(void*);
DCHECK(0 <= index && index < kMaxSlots);
if (index < kMaxInlineSlots) {
return static_cast<intptr_t>(
__readfsdword(kTibInlineTlsOffset + kSystemPointerSize * index));
intptr_t extra = static_cast<intptr_t>(__readfsdword(kTibExtraTlsOffset));
DCHECK_NE(extra, 0);
return *reinterpret_cast<intptr_t*>(extra + kSystemPointerSize *
(index - kMaxInlineSlots));
#elif defined(__APPLE__) && (V8_HOST_ARCH_IA32 || V8_HOST_ARCH_X64)
extern V8_BASE_EXPORT intptr_t kMacTlsBaseOffset;
V8_INLINE intptr_t InternalGetExistingThreadLocal(intptr_t index);
inline intptr_t InternalGetExistingThreadLocal(intptr_t index) {
intptr_t result;
asm("movl %%gs:(%1,%2,4), %0;"
:"=r"(result) // Output must be a writable register.
:"r"(kMacTlsBaseOffset), "r"(index));
asm("movq %%gs:(%1,%2,8), %0;"
:"r"(kMacTlsBaseOffset), "r"(index));
return result;
#endif // V8_NO_FAST_TLS
class PageAllocator;
class TimezoneCache;
// ----------------------------------------------------------------------------
// OS
// This class has static methods for the different platform specific
// functions. Add methods here to cope with differences between the
// supported platforms.
// Initialize the OS class.
// - hard_abort: If true, OS::Abort() will crash instead of aborting.
// - gc_fake_mmap: Name of the file for fake gc mmap used in ll_prof.
static void Initialize(bool hard_abort, const char* const gc_fake_mmap);
// Returns the accumulated user time for thread. This routine
// can be used for profiling. The implementation should
// strive for high-precision timer resolution, preferable
// micro-second resolution.
static int GetUserTime(uint32_t* secs, uint32_t* usecs);
// Returns current time as the number of milliseconds since
// 00:00:00 UTC, January 1, 1970.
static double TimeCurrentMillis();
static TimezoneCache* CreateTimezoneCache();
// Returns last OS error.
static int GetLastError();
static FILE* FOpen(const char* path, const char* mode);
static bool Remove(const char* path);
static char DirectorySeparator();
static bool isDirectorySeparator(const char ch);
// Opens a temporary file, the file is auto removed on close.
static FILE* OpenTemporaryFile();
// Log file open mode is platform-dependent due to line ends issues.
static const char* const LogFileOpenMode;
// Print output to console. This is mostly used for debugging output.
// On platforms that has standard terminal output, the output
// should go to stdout.
static PRINTF_FORMAT(1, 2) void Print(const char* format, ...);
static PRINTF_FORMAT(1, 0) void VPrint(const char* format, va_list args);
// Print output to a file. This is mostly used for debugging output.
static PRINTF_FORMAT(2, 3) void FPrint(FILE* out, const char* format, ...);
static PRINTF_FORMAT(2, 0) void VFPrint(FILE* out, const char* format,
va_list args);
// Print error output to console. This is mostly used for error message
// output. On platforms that has standard terminal output, the output
// should go to stderr.
static PRINTF_FORMAT(1, 2) void PrintError(const char* format, ...);
static PRINTF_FORMAT(1, 0) void VPrintError(const char* format, va_list args);
// Memory permissions. These should be kept in sync with the ones in
// v8::PageAllocator.
enum class MemoryPermission {
// TODO(hpayer): Remove this flag. Memory should never be rwx.
static bool HasLazyCommits();
// Sleep for a specified time interval.
static void Sleep(TimeDelta interval);
// Abort the current process.
[[noreturn]] static void Abort();
// Debug break.
static void DebugBreak();
// Walk the stack.
static const int kStackWalkError = -1;
static const int kStackWalkMaxNameLen = 256;
static const int kStackWalkMaxTextLen = 256;
struct StackFrame {
void* address;
char text[kStackWalkMaxTextLen];
class V8_BASE_EXPORT MemoryMappedFile {
enum class FileMode { kReadOnly, kReadWrite };
virtual ~MemoryMappedFile() = default;
virtual void* memory() const = 0;
virtual size_t size() const = 0;
static MemoryMappedFile* open(const char* name,
FileMode mode = FileMode::kReadWrite);
static MemoryMappedFile* create(const char* name, size_t size,
void* initial);
// Safe formatting print. Ensures that str is always null-terminated.
// Returns the number of chars written, or -1 if output was truncated.
static PRINTF_FORMAT(3, 4) int SNPrintF(char* str, int length,
const char* format, ...);
static PRINTF_FORMAT(3, 0) int VSNPrintF(char* str, int length,
const char* format, va_list args);
static void StrNCpy(char* dest, int length, const char* src, size_t n);
// Support for the profiler. Can do nothing, in which case ticks
// occurring in shared libraries will not be properly accounted for.
struct SharedLibraryAddress {
SharedLibraryAddress(const std::string& library_path, uintptr_t start,
uintptr_t end)
: library_path(library_path), start(start), end(end), aslr_slide(0) {}
SharedLibraryAddress(const std::string& library_path, uintptr_t start,
uintptr_t end, intptr_t aslr_slide)
: library_path(library_path),
aslr_slide(aslr_slide) {}
std::string library_path;
uintptr_t start;
uintptr_t end;
intptr_t aslr_slide;
static std::vector<SharedLibraryAddress> GetSharedLibraryAddresses();
// Support for the profiler. Notifies the external profiling
// process that a code moving garbage collection starts. Can do
// nothing, in which case the code objects must not move (e.g., by
// using --never-compact) if accurate profiling is desired.
static void SignalCodeMovingGC();
// Support runtime detection of whether the hard float option of the
// EABI is used.
static bool ArmUsingHardFloat();
// Returns the activation frame alignment constraint or zero if
// the platform doesn't care. Guaranteed to be a power of two.
static int ActivationFrameAlignment();
static int GetCurrentProcessId();
static int GetCurrentThreadId();
static void AdjustSchedulingParams();
static void ExitProcess(int exit_code);
// These classes use the private memory management API below.
friend class MemoryMappedFile;
friend class PosixMemoryMappedFile;
friend class v8::base::PageAllocator;
static size_t AllocatePageSize();
static size_t CommitPageSize();
static void SetRandomMmapSeed(int64_t seed);
static void* GetRandomMmapAddr();
V8_WARN_UNUSED_RESULT static void* Allocate(void* address, size_t size,
size_t alignment,
MemoryPermission access);
V8_WARN_UNUSED_RESULT static bool Free(void* address, const size_t size);
V8_WARN_UNUSED_RESULT static bool Release(void* address, size_t size);
V8_WARN_UNUSED_RESULT static bool SetPermissions(void* address, size_t size,
MemoryPermission access);
V8_WARN_UNUSED_RESULT static bool DiscardSystemPages(void* address,
size_t size);
static const int msPerSecond = 1000;
static const char* GetGCFakeMMapFile();
#if (defined(_WIN32) || defined(_WIN64))
V8_BASE_EXPORT void EnsureConsoleOutputWin32();
#endif // (defined(_WIN32) || defined(_WIN64))
inline void EnsureConsoleOutput() {
#if (defined(_WIN32) || defined(_WIN64))
// Windows requires extra calls to send assert output to the console
// rather than a dialog box.
#endif // (defined(_WIN32) || defined(_WIN64))
// ----------------------------------------------------------------------------
// Thread
// Thread objects are used for creating and running threads. When the start()
// method is called the new thread starts running the run() method in the new
// thread. The Thread object should not be deallocated before the thread has
// terminated.
class V8_BASE_EXPORT Thread {
// Opaque data type for thread-local storage keys.
using LocalStorageKey = SbThreadLocalKey;
using LocalStorageKey = int32_t;
class Options {
Options() : name_("v8:<unknown>"), stack_size_(0) {}
explicit Options(const char* name, int stack_size = 0)
: name_(name), stack_size_(stack_size) {}
const char* name() const { return name_; }
int stack_size() const { return stack_size_; }
const char* name_;
int stack_size_;
// Create new thread.
explicit Thread(const Options& options);
virtual ~Thread();
// Start new thread by calling the Run() method on the new thread.
void Start();
// Start new thread and wait until Run() method is called on the new thread.
void StartSynchronously() {
start_semaphore_ = new Semaphore(0);
delete start_semaphore_;
start_semaphore_ = nullptr;
// Wait until thread terminates.
void Join();
inline const char* name() const {
return name_;
// Abstract method for run handler.
virtual void Run() = 0;
// Thread-local storage.
static LocalStorageKey CreateThreadLocalKey();
static void DeleteThreadLocalKey(LocalStorageKey key);
static void* GetThreadLocal(LocalStorageKey key);
static int GetThreadLocalInt(LocalStorageKey key) {
return static_cast<int>(reinterpret_cast<intptr_t>(GetThreadLocal(key)));
static void SetThreadLocal(LocalStorageKey key, void* value);
static void SetThreadLocalInt(LocalStorageKey key, int value) {
SetThreadLocal(key, reinterpret_cast<void*>(static_cast<intptr_t>(value)));
static bool HasThreadLocal(LocalStorageKey key) {
return GetThreadLocal(key) != nullptr;
static inline void* GetExistingThreadLocal(LocalStorageKey key) {
void* result = reinterpret_cast<void*>(
DCHECK(result == GetThreadLocal(key));
return result;
static inline void* GetExistingThreadLocal(LocalStorageKey key) {
return GetThreadLocal(key);
// The thread name length is limited to 16 based on Linux's implementation of
// prctl().
static const int kMaxThreadNameLength = 16;
class PlatformData;
PlatformData* data() { return data_; }
void NotifyStartedAndRun() {
if (start_semaphore_) start_semaphore_->Signal();
void set_name(const char* name);
PlatformData* data_;
char name_[kMaxThreadNameLength];
int stack_size_;
Semaphore* start_semaphore_;
} // namespace base
} // namespace v8