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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 <stdarg.h>
#include <string>
#include <vector>
#include "src/base/build_config.h"
#include "src/base/platform/mutex.h"
#include "src/base/platform/semaphore.h"
#ifdef __sun
# ifndef signbit
namespace std {
int signbit(double x);
# endif
#if V8_OS_QNX
#include "src/base/qnx-math.h"
// Microsoft Visual C++ specific stuff.
#include "src/base/win32-headers.h"
#include "src/base/win32-math.h"
int strncasecmp(const char* s1, const char* s2, int n);
// Visual C++ 2013 and higher implement this function.
#if (_MSC_VER < 1800)
inline int lrint(double flt) {
int intgr;
__asm {
fld flt
fistp intgr
intgr = static_cast<int>(flt + 0.5);
if ((intgr & 1) != 0 && intgr - flt == 0.5) {
// If the number is halfway between two integers, round to the even one.
return intgr;
#endif // _MSC_VER < 1800
#endif // V8_LIBC_MSVCRT
namespace v8 {
namespace base {
// ----------------------------------------------------------------------------
// Fast TLS support
#ifndef V8_NO_FAST_TLS
#if defined(_MSC_VER) && (V8_HOST_ARCH_IA32)
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 kPointerSize = sizeof(void*);
DCHECK(0 <= index && index < kMaxSlots);
if (index < kMaxInlineSlots) {
return static_cast<intptr_t>(__readfsdword(kTibInlineTlsOffset +
kPointerSize * index));
intptr_t extra = static_cast<intptr_t>(__readfsdword(kTibExtraTlsOffset));
DCHECK(extra != 0);
return *reinterpret_cast<intptr_t*>(extra +
kPointerSize * (index - kMaxInlineSlots));
#elif defined(__APPLE__) && (V8_HOST_ARCH_IA32 || V8_HOST_ARCH_X64)
extern intptr_t kMacTlsBaseOffset;
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 TimezoneCache;
// ----------------------------------------------------------------------------
// OS
// This class has static methods for the different platform specific
// functions. Add methods here to cope with differences between the
// supported platforms.
class OS {
// Initialize the OS class.
// - random_seed: Used for the GetRandomMmapAddress() if non-zero.
// - 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(int64_t random_seed,
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();
static void DisposeTimezoneCache(TimezoneCache* cache);
static void ClearTimezoneCache(TimezoneCache* cache);
// Returns a string identifying the current time zone. The
// timestamp is used for determining if DST is in effect.
static const char* LocalTimezone(double time, TimezoneCache* cache);
// Returns the local time offset in milliseconds east of UTC without
// taking daylight savings time into account.
static double LocalTimeOffset(TimezoneCache* cache);
// Returns the daylight savings offset for the given time.
static double DaylightSavingsOffset(double time, TimezoneCache* cache);
// Returns last OS error.
static int GetLastError();
static FILE* FOpen(const char* path, const char* mode);
static bool Remove(const char* path);
// 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 void Print(const char* format, ...);
static void VPrint(const char* format, va_list args);
// Print output to a file. This is mostly used for debugging output.
static void FPrint(FILE* out, const char* format, ...);
static 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 void PrintError(const char* format, ...);
static void VPrintError(const char* format, va_list args);
// Allocate/Free memory used by JS heap. Pages are readable/writable, but
// they are not guaranteed to be executable unless 'executable' is true.
// Returns the address of allocated memory, or NULL if failed.
static void* Allocate(const size_t requested,
size_t* allocated,
bool is_executable);
static void Free(void* address, const size_t size);
// This is the granularity at which the ProtectCode(...) call can set page
// permissions.
static intptr_t CommitPageSize();
// Mark code segments non-writable.
static void ProtectCode(void* address, const size_t size);
// Assign memory as a guard page so that access will cause an exception.
static void Guard(void* address, const size_t size);
// Generate a random address to be used for hinting mmap().
static void* GetRandomMmapAddr();
// Get the Alignment guaranteed by Allocate().
static size_t AllocateAlignment();
// Sleep for a number of milliseconds.
static void Sleep(const int milliseconds);
// Abort the current process.
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 MemoryMappedFile {
static MemoryMappedFile* open(const char* name);
static MemoryMappedFile* create(const char* name, int size, void* initial);
virtual ~MemoryMappedFile() { }
virtual void* memory() = 0;
virtual int size() = 0;
// Safe formatting print. Ensures that str is always null-terminated.
// Returns the number of chars written, or -1 if output was truncated.
static int SNPrintF(char* str, int length, const char* format, ...);
static int VSNPrintF(char* str,
int length,
const char* format,
va_list args);
static char* StrChr(char* str, int c);
static void StrNCpy(char* dest, int length, const char* src, size_t n);
// Support for the profiler. Can do nothing, in which case ticks
// occuring in shared libraries will not be properly accounted for.
struct SharedLibraryAddress {
const std::string& library_path, uintptr_t start, uintptr_t end)
: library_path(library_path), start(start), end(end) {}
std::string library_path;
uintptr_t start;
uintptr_t end;
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();
// Returns the number of processors online.
static int NumberOfProcessorsOnline();
// The total amount of physical memory available on the current system.
static uint64_t TotalPhysicalMemory();
// Maximum size of the virtual memory. 0 means there is no artificial
// limit.
static intptr_t MaxVirtualMemory();
// Returns the double constant NAN
static double nan_value();
// 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 const int msPerSecond = 1000;
static const char* GetGCFakeMMapFile();
// Represents and controls an area of reserved memory.
// Control of the reserved memory can be assigned to another VirtualMemory
// object by assignment or copy-contructing. This removes the reserved memory
// from the original object.
class VirtualMemory {
// Empty VirtualMemory object, controlling no reserved memory.
// Reserves virtual memory with size.
explicit VirtualMemory(size_t size);
// Reserves virtual memory containing an area of the given size that
// is aligned per alignment. This may not be at the position returned
// by address().
VirtualMemory(size_t size, size_t alignment);
// Releases the reserved memory, if any, controlled by this VirtualMemory
// object.
// Returns whether the memory has been reserved.
bool IsReserved();
// Initialize or resets an embedded VirtualMemory object.
void Reset();
// Returns the start address of the reserved memory.
// If the memory was reserved with an alignment, this address is not
// necessarily aligned. The user might need to round it up to a multiple of
// the alignment to get the start of the aligned block.
void* address() {
return address_;
// Returns the size of the reserved memory. The returned value is only
// meaningful when IsReserved() returns true.
// If the memory was reserved with an alignment, this size may be larger
// than the requested size.
size_t size() { return size_; }
// Commits real memory. Returns whether the operation succeeded.
bool Commit(void* address, size_t size, bool is_executable);
// Uncommit real memory. Returns whether the operation succeeded.
bool Uncommit(void* address, size_t size);
// Creates a single guard page at the given address.
bool Guard(void* address);
void Release() {
// Notice: Order is important here. The VirtualMemory object might live
// inside the allocated region.
void* address = address_;
size_t size = size_;
bool result = ReleaseRegion(address, size);
// Assign control of the reserved region to a different VirtualMemory object.
// The old object is no longer functional (IsReserved() returns false).
void TakeControl(VirtualMemory* from) {
address_ = from->address_;
size_ = from->size_;
static void* ReserveRegion(size_t size);
static bool CommitRegion(void* base, size_t size, bool is_executable);
static bool UncommitRegion(void* base, size_t size);
// Must be called with a base pointer that has been returned by ReserveRegion
// and the same size it was reserved with.
static bool ReleaseRegion(void* base, size_t size);
// Returns true if OS performs lazy commits, i.e. the memory allocation call
// defers actual physical memory allocation till the first memory access.
// Otherwise returns false.
static bool HasLazyCommits();
void* address_; // Start address of the virtual memory.
size_t size_; // Size of the virtual memory.
// ----------------------------------------------------------------------------
// 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 Thread {
// Opaque data type for thread-local storage keys.
typedef int32_t LocalStorageKey;
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_ = NULL;
// 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) != NULL;
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);
// A hint to the scheduler to let another thread run.
static void YieldCPU();
// 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 v8::base