text: // Copyright 2012 the V8 project authors. All rights reserved.
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  //       notice, this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above
  //       copyright notice, this list of conditions and the following
  //       disclaimer in the documentation and/or other materials provided
  //       with the distribution.
  //     * Neither the name of Google Inc. nor the names of its
  //       contributors may be used to endorse or promote products derived
  //       from this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  // Platform specific code for OpenBSD and NetBSD goes here. For the POSIX
  // comaptible parts the implementation is in platform-posix.cc.
  
  #include <pthread.h>
  #include <semaphore.h>
  #include <signal.h>
  #include <sys/time.h>
  #include <sys/resource.h>
  #include <sys/syscall.h>
  #include <sys/types.h>
  #include <stdlib.h>
  
  #include <sys/types.h>  // mmap & munmap
  #include <sys/mman.h>   // mmap & munmap
  #include <sys/stat.h>   // open
  #include <fcntl.h>      // open
  #include <unistd.h>     // sysconf
  #include <execinfo.h>   // backtrace, backtrace_symbols
  #include <strings.h>    // index
  #include <errno.h>
  #include <stdarg.h>
  
  #undef MAP_TYPE
  
  #include "v8.h"
  
  #include "platform-posix.h"
  #include "platform.h"
  #include "v8threads.h"
  #include "vm-state-inl.h"
  
  
  namespace v8 {
  namespace internal {
  
  // 0 is never a valid thread id on Linux and OpenBSD since tids and pids share a
  // name space and pid 0 is reserved (see man 2 kill).
  static const pthread_t kNoThread = (pthread_t) 0;
  
  
  double ceiling(double x) {
    return ceil(x);
  }
  
  
  static Mutex* limit_mutex = NULL;
  
  
  static void* GetRandomMmapAddr() {
    Isolate* isolate = Isolate::UncheckedCurrent();
    // Note that the current isolate isn't set up in a call path via
    // CpuFeatures::Probe. We don't care about randomization in this case because
    // the code page is immediately freed.
    if (isolate != NULL) {
  #ifdef V8_TARGET_ARCH_X64
      uint64_t rnd1 = V8::RandomPrivate(isolate);
      uint64_t rnd2 = V8::RandomPrivate(isolate);
      uint64_t raw_addr = (rnd1 << 32) ^ rnd2;
      // Currently available CPUs have 48 bits of virtual addressing.  Truncate
      // the hint address to 46 bits to give the kernel a fighting chance of
      // fulfilling our placement request.
      raw_addr &= V8_UINT64_C(0x3ffffffff000);
  #else
      uint32_t raw_addr = V8::RandomPrivate(isolate);
      // The range 0x20000000 - 0x60000000 is relatively unpopulated across a
      // variety of ASLR modes (PAE kernel, NX compat mode, etc).
      raw_addr &= 0x3ffff000;
      raw_addr += 0x20000000;
  #endif
      return reinterpret_cast<void*>(raw_addr);
    }
    return NULL;
  }
  
  
  void OS::PostSetUp() {
    POSIXPostSetUp();
  }
  
  
  uint64_t OS::CpuFeaturesImpliedByPlatform() {
    return 0;
  }
  
  
  int OS::ActivationFrameAlignment() {
    // With gcc 4.4 the tree vectorization optimizer can generate code
    // that requires 16 byte alignment such as movdqa on x86.
    return 16;
  }
  
  
  void OS::ReleaseStore(volatile AtomicWord* ptr, AtomicWord value) {
    __asm__ __volatile__("" : : : "memory");
    // An x86 store acts as a release barrier.
    *ptr = value;
  }
  
  
  const char* OS::LocalTimezone(double time) {
    if (isnan(time)) return "";
    time_t tv = static_cast<time_t>(floor(time/msPerSecond));
    struct tm* t = localtime(&tv);
    if (NULL == t) return "";
    return t->tm_zone;
  }
  
  
  double OS::LocalTimeOffset() {
    time_t tv = time(NULL);
    struct tm* t = localtime(&tv);
    // tm_gmtoff includes any daylight savings offset, so subtract it.
    return static_cast<double>(t->tm_gmtoff * msPerSecond -
                               (t->tm_isdst > 0 ? 3600 * msPerSecond : 0));
  }
  
  
  // We keep the lowest and highest addresses mapped as a quick way of
  // determining that pointers are outside the heap (used mostly in assertions
  // and verification).  The estimate is conservative, i.e., not all addresses in
  // 'allocated' space are actually allocated to our heap.  The range is
  // [lowest, highest), inclusive on the low and and exclusive on the high end.
  static void* lowest_ever_allocated = reinterpret_cast<void*>(-1);
  static void* highest_ever_allocated = reinterpret_cast<void*>(0);
  
  
  static void UpdateAllocatedSpaceLimits(void* address, int size) {
    ASSERT(limit_mutex != NULL);
    ScopedLock lock(limit_mutex);
  
    lowest_ever_allocated = Min(lowest_ever_allocated, address);
    highest_ever_allocated =
        Max(highest_ever_allocated,
            reinterpret_cast<void*>(reinterpret_cast<char*>(address) + size));
  }
  
  
  bool OS::IsOutsideAllocatedSpace(void* address) {
    return address < lowest_ever_allocated || address >= highest_ever_allocated;
  }
  
  
  size_t OS::AllocateAlignment() {
    return sysconf(_SC_PAGESIZE);
  }
  
  
  void* OS::Allocate(const size_t requested,
                     size_t* allocated,
                     bool is_executable) {
    const size_t msize = RoundUp(requested, AllocateAlignment());
    int prot = PROT_READ | PROT_WRITE | (is_executable ? PROT_EXEC : 0);
    void* addr = GetRandomMmapAddr();
    void* mbase = mmap(addr, msize, prot, MAP_PRIVATE | MAP_ANON, -1, 0);
    if (mbase == MAP_FAILED) {
      LOG(i::Isolate::Current(),
          StringEvent("OS::Allocate", "mmap failed"));
      return NULL;
    }
    *allocated = msize;
    UpdateAllocatedSpaceLimits(mbase, msize);
    return mbase;
  }
  
  
  void OS::Free(void* address, const size_t size) {
    // TODO(1240712): munmap has a return value which is ignored here.
    int result = munmap(address, size);
    USE(result);
    ASSERT(result == 0);
  }
  
  
  void OS::Sleep(int milliseconds) {
    unsigned int ms = static_cast<unsigned int>(milliseconds);
    usleep(1000 * ms);
  }
  
  
  void OS::Abort() {
    // Redirect to std abort to signal abnormal program termination.
    abort();
  }
  
  
  void OS::DebugBreak() {
    asm("int $3");
  }
  
  
  class PosixMemoryMappedFile : public OS::MemoryMappedFile {
   public:
    PosixMemoryMappedFile(FILE* file, void* memory, int size)
      : file_(file), memory_(memory), size_(size) { }
    virtual ~PosixMemoryMappedFile();
    virtual void* memory() { return memory_; }
    virtual int size() { return size_; }
   private:
    FILE* file_;
    void* memory_;
    int size_;
  };
  
  
  OS::MemoryMappedFile* OS::MemoryMappedFile::open(const char* name) {
    FILE* file = fopen(name, "r+");
    if (file == NULL) return NULL;
  
    fseek(file, 0, SEEK_END);
    int size = ftell(file);
  
    void* memory =
        mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, fileno(file), 0);
    return new PosixMemoryMappedFile(file, memory, size);
  }
  
  
  OS::MemoryMappedFile* OS::MemoryMappedFile::create(const char* name, int size,
      void* initial) {
    FILE* file = fopen(name, "w+");
    if (file == NULL) return NULL;
    int result = fwrite(initial, size, 1, file);
    if (result < 1) {
      fclose(file);
      return NULL;
    }
    void* memory =
        mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, fileno(file), 0);
    return new PosixMemoryMappedFile(file, memory, size);
  }
  
  
  PosixMemoryMappedFile::~PosixMemoryMappedFile() {
    if (memory_) OS::Free(memory_, size_);
    fclose(file_);
  }
  
  
  void OS::LogSharedLibraryAddresses() {
    // This function assumes that the layout of the file is as follows:
    // hex_start_addr-hex_end_addr rwxp <unused data> [binary_file_name]
    // If we encounter an unexpected situation we abort scanning further entries.
    FILE* fp = fopen("/proc/self/maps", "r");
    if (fp == NULL) return;
  
    // Allocate enough room to be able to store a full file name.
    const int kLibNameLen = FILENAME_MAX + 1;
    char* lib_name = reinterpret_cast<char*>(malloc(kLibNameLen));
  
    i::Isolate* isolate = ISOLATE;
    // This loop will terminate once the scanning hits an EOF.
    while (true) {
      uintptr_t start, end;
      char attr_r, attr_w, attr_x, attr_p;
      // Parse the addresses and permission bits at the beginning of the line.
      if (fscanf(fp, "%" V8PRIxPTR "-%" V8PRIxPTR, &start, &end) != 2) break;
      if (fscanf(fp, " %c%c%c%c", &attr_r, &attr_w, &attr_x, &attr_p) != 4) break;
  
      int c;
      if (attr_r == 'r' && attr_w != 'w' && attr_x == 'x') {
        // Found a read-only executable entry. Skip characters until we reach
        // the beginning of the filename or the end of the line.
        do {
          c = getc(fp);
        } while ((c != EOF) && (c != '\n') && (c != '/'));
        if (c == EOF) break;  // EOF: Was unexpected, just exit.
  
        // Process the filename if found.
        if (c == '/') {
          ungetc(c, fp);  // Push the '/' back into the stream to be read below.
  
          // Read to the end of the line. Exit if the read fails.
          if (fgets(lib_name, kLibNameLen, fp) == NULL) break;
  
          // Drop the newline character read by fgets. We do not need to check
          // for a zero-length string because we know that we at least read the
          // '/' character.
          lib_name[strlen(lib_name) - 1] = '\0';
        } else {
          // No library name found, just record the raw address range.
          snprintf(lib_name, kLibNameLen,
                   "%08" V8PRIxPTR "-%08" V8PRIxPTR, start, end);
        }
        LOG(isolate, SharedLibraryEvent(lib_name, start, end));
      } else {
        // Entry not describing executable data. Skip to end of line to set up
        // reading the next entry.
        do {
          c = getc(fp);
        } while ((c != EOF) && (c != '\n'));
        if (c == EOF) break;
      }
    }
    free(lib_name);
    fclose(fp);
  }
  
  
  void OS::SignalCodeMovingGC() {
    // Support for ll_prof.py.
    //
    // The Linux profiler built into the kernel logs all mmap's with
    // PROT_EXEC so that analysis tools can properly attribute ticks. We
    // do a mmap with a name known by ll_prof.py and immediately munmap
    // it. This injects a GC marker into the stream of events generated
    // by the kernel and allows us to synchronize V8 code log and the
    // kernel log.
    int size = sysconf(_SC_PAGESIZE);
    FILE* f = fopen(FLAG_gc_fake_mmap, "w+");
    void* addr = mmap(NULL, size, PROT_READ | PROT_EXEC, MAP_PRIVATE,
                      fileno(f), 0);
    ASSERT(addr != MAP_FAILED);
    OS::Free(addr, size);
    fclose(f);
  }
  
  
  int OS::StackWalk(Vector<OS::StackFrame> frames) {
    // backtrace is a glibc extension.
    int frames_size = frames.length();
    ScopedVector<void*> addresses(frames_size);
  
    int frames_count = backtrace(addresses.start(), frames_size);
  
    char** symbols = backtrace_symbols(addresses.start(), frames_count);
    if (symbols == NULL) {
      return kStackWalkError;
    }
  
    for (int i = 0; i < frames_count; i++) {
      frames[i].address = addresses[i];
      // Format a text representation of the frame based on the information
      // available.
      SNPrintF(MutableCStrVector(frames[i].text, kStackWalkMaxTextLen),
               "%s",
               symbols[i]);
      // Make sure line termination is in place.
      frames[i].text[kStackWalkMaxTextLen - 1] = '\0';
    }
  
    free(symbols);
  
    return frames_count;
  }
  
  
  // Constants used for mmap.
  static const int kMmapFd = -1;
  static const int kMmapFdOffset = 0;
  
  VirtualMemory::VirtualMemory() : address_(NULL), size_(0) { }
  
  VirtualMemory::VirtualMemory(size_t size) {
    address_ = ReserveRegion(size);
    size_ = size;
  }
  
  
  VirtualMemory::VirtualMemory(size_t size, size_t alignment)
      : address_(NULL), size_(0) {
    ASSERT(IsAligned(alignment, static_cast<intptr_t>(OS::AllocateAlignment())));
    size_t request_size = RoundUp(size + alignment,
                                  static_cast<intptr_t>(OS::AllocateAlignment()));
    void* reservation = mmap(GetRandomMmapAddr(),
                             request_size,
                             PROT_NONE,
                             MAP_PRIVATE | MAP_ANON | MAP_NORESERVE,
                             kMmapFd,
                             kMmapFdOffset);
    if (reservation == MAP_FAILED) return;
  
    Address base = static_cast<Address>(reservation);
    Address aligned_base = RoundUp(base, alignment);
    ASSERT_LE(base, aligned_base);
  
    // Unmap extra memory reserved before and after the desired block.
    if (aligned_base != base) {
      size_t prefix_size = static_cast<size_t>(aligned_base - base);
      OS::Free(base, prefix_size);
      request_size -= prefix_size;
    }
  
    size_t aligned_size = RoundUp(size, OS::AllocateAlignment());
    ASSERT_LE(aligned_size, request_size);
  
    if (aligned_size != request_size) {
      size_t suffix_size = request_size - aligned_size;
      OS::Free(aligned_base + aligned_size, suffix_size);
      request_size -= suffix_size;
    }
  
    ASSERT(aligned_size == request_size);
  
    address_ = static_cast<void*>(aligned_base);
    size_ = aligned_size;
  }
  
  
  VirtualMemory::~VirtualMemory() {
    if (IsReserved()) {
      bool result = ReleaseRegion(address(), size());
      ASSERT(result);
      USE(result);
    }
  }
  
  
  bool VirtualMemory::IsReserved() {
    return address_ != NULL;
  }
  
  
  void VirtualMemory::Reset() {
    address_ = NULL;
    size_ = 0;
  }
  
  
  bool VirtualMemory::Commit(void* address, size_t size, bool is_executable) {
    return CommitRegion(address, size, is_executable);
  }
  
  
  bool VirtualMemory::Uncommit(void* address, size_t size) {
    return UncommitRegion(address, size);
  }
  
  
  bool VirtualMemory::Guard(void* address) {
    OS::Guard(address, OS::CommitPageSize());
    return true;
  }
  
  
  void* VirtualMemory::ReserveRegion(size_t size) {
    void* result = mmap(GetRandomMmapAddr(),
                        size,
                        PROT_NONE,
                        MAP_PRIVATE | MAP_ANON | MAP_NORESERVE,
                        kMmapFd,
                        kMmapFdOffset);
  
    if (result == MAP_FAILED) return NULL;
  
    return result;
  }
  
  
  bool VirtualMemory::CommitRegion(void* base, size_t size, bool is_executable) {
    int prot = PROT_READ | PROT_WRITE | (is_executable ? PROT_EXEC : 0);
    if (MAP_FAILED == mmap(base,
                           size,
                           prot,
                           MAP_PRIVATE | MAP_ANON | MAP_FIXED,
                           kMmapFd,
                           kMmapFdOffset)) {
      return false;
    }
  
    UpdateAllocatedSpaceLimits(base, size);
    return true;
  }
  
  
  bool VirtualMemory::UncommitRegion(void* base, size_t size) {
    return mmap(base,
                size,
                PROT_NONE,
                MAP_PRIVATE | MAP_ANON | MAP_NORESERVE | MAP_FIXED,
                kMmapFd,
                kMmapFdOffset) != MAP_FAILED;
  }
  
  
  bool VirtualMemory::ReleaseRegion(void* base, size_t size) {
    return munmap(base, size) == 0;
  }
  
  
  bool VirtualMemory::HasLazyCommits() {
    // TODO(alph): implement for the platform.
    return false;
  }
  
  
  class Thread::PlatformData : public Malloced {
   public:
    PlatformData() : thread_(kNoThread) {}
  
    pthread_t thread_;  // Thread handle for pthread.
  };
  
  Thread::Thread(const Options& options)
      : data_(new PlatformData()),
        stack_size_(options.stack_size()) {
    set_name(options.name());
  }
  
  
  Thread::~Thread() {
    delete data_;
  }
  
  
  static void* ThreadEntry(void* arg) {
    Thread* thread = reinterpret_cast<Thread*>(arg);
    // This is also initialized by the first argument to pthread_create() but we
    // don't know which thread will run first (the original thread or the new
    // one) so we initialize it here too.
  #ifdef PR_SET_NAME
    prctl(PR_SET_NAME,
          reinterpret_cast<unsigned long>(thread->name()),  // NOLINT
          0, 0, 0);
  #endif
    thread->data()->thread_ = pthread_self();
    ASSERT(thread->data()->thread_ != kNoThread);
    thread->Run();
    return NULL;
  }
  
  
  void Thread::set_name(const char* name) {
    strncpy(name_, name, sizeof(name_));
    name_[sizeof(name_) - 1] = '\0';
  }
  
  
  void Thread::Start() {
    pthread_attr_t* attr_ptr = NULL;
    pthread_attr_t attr;
    if (stack_size_ > 0) {
      pthread_attr_init(&attr);
      pthread_attr_setstacksize(&attr, static_cast<size_t>(stack_size_));
      attr_ptr = &attr;
    }
    pthread_create(&data_->thread_, attr_ptr, ThreadEntry, this);
    ASSERT(data_->thread_ != kNoThread);
  }
  
  
  void Thread::Join() {
    pthread_join(data_->thread_, NULL);
  }
  
  
  Thread::LocalStorageKey Thread::CreateThreadLocalKey() {
    pthread_key_t key;
    int result = pthread_key_create(&key, NULL);
    USE(result);
    ASSERT(result == 0);
    return static_cast<LocalStorageKey>(key);
  }
  
  
  void Thread::DeleteThreadLocalKey(LocalStorageKey key) {
    pthread_key_t pthread_key = static_cast<pthread_key_t>(key);
    int result = pthread_key_delete(pthread_key);
    USE(result);
    ASSERT(result == 0);
  }
  
  
  void* Thread::GetThreadLocal(LocalStorageKey key) {
    pthread_key_t pthread_key = static_cast<pthread_key_t>(key);
    return pthread_getspecific(pthread_key);
  }
  
  
  void Thread::SetThreadLocal(LocalStorageKey key, void* value) {
    pthread_key_t pthread_key = static_cast<pthread_key_t>(key);
    pthread_setspecific(pthread_key, value);
  }
  
  
  void Thread::YieldCPU() {
    sched_yield();
  }
  
  
  class OpenBSDMutex : public Mutex {
   public:
    OpenBSDMutex() {
      pthread_mutexattr_t attrs;
      int result = pthread_mutexattr_init(&attrs);
      ASSERT(result == 0);
      result = pthread_mutexattr_settype(&attrs, PTHREAD_MUTEX_RECURSIVE);
      ASSERT(result == 0);
      result = pthread_mutex_init(&mutex_, &attrs);
      ASSERT(result == 0);
      USE(result);
    }
  
    virtual ~OpenBSDMutex() { pthread_mutex_destroy(&mutex_); }
  
    virtual int Lock() {
      int result = pthread_mutex_lock(&mutex_);
      return result;
    }
  
    virtual int Unlock() {
      int result = pthread_mutex_unlock(&mutex_);
      return result;
    }
  
    virtual bool TryLock() {
      int result = pthread_mutex_trylock(&mutex_);
      // Return false if the lock is busy and locking failed.
      if (result == EBUSY) {
        return false;
      }
      ASSERT(result == 0);  // Verify no other errors.
      return true;
    }
  
   private:
    pthread_mutex_t mutex_;   // Pthread mutex for POSIX platforms.
  };
  
  
  Mutex* OS::CreateMutex() {
    return new OpenBSDMutex();
  }
  
  
  class OpenBSDSemaphore : public Semaphore {
   public:
    explicit OpenBSDSemaphore(int count) {  sem_init(&sem_, 0, count); }
    virtual ~OpenBSDSemaphore() { sem_destroy(&sem_); }
  
    virtual void Wait();
    virtual bool Wait(int timeout);
    virtual void Signal() { sem_post(&sem_); }
   private:
    sem_t sem_;
  };
  
  
  void OpenBSDSemaphore::Wait() {
    while (true) {
      int result = sem_wait(&sem_);
      if (result == 0) return;  // Successfully got semaphore.
      CHECK(result == -1 && errno == EINTR);  // Signal caused spurious wakeup.
    }
  }
  
  
  #ifndef TIMEVAL_TO_TIMESPEC
  #define TIMEVAL_TO_TIMESPEC(tv, ts) do {                            \
      (ts)->tv_sec = (tv)->tv_sec;                                    \
      (ts)->tv_nsec = (tv)->tv_usec * 1000;                           \
  } while (false)
  #endif
  
  
  bool OpenBSDSemaphore::Wait(int timeout) {
    const long kOneSecondMicros = 1000000;  // NOLINT
  
    // Split timeout into second and nanosecond parts.
    struct timeval delta;
    delta.tv_usec = timeout % kOneSecondMicros;
    delta.tv_sec = timeout / kOneSecondMicros;
  
    struct timeval current_time;
    // Get the current time.
    if (gettimeofday(&current_time, NULL) == -1) {
      return false;
    }
  
    // Calculate time for end of timeout.
    struct timeval end_time;
    timeradd(&current_time, &delta, &end_time);
  
    struct timespec ts;
    TIMEVAL_TO_TIMESPEC(&end_time, &ts);
  
    int to = ts.tv_sec;
  
    while (true) {
      int result = sem_trywait(&sem_);
      if (result == 0) return true;  // Successfully got semaphore.
      if (!to) return false;  // Timeout.
      CHECK(result == -1 && errno == EINTR);  // Signal caused spurious wakeup.
      usleep(ts.tv_nsec / 1000);
      to--;
    }
  }
  
  Semaphore* OS::CreateSemaphore(int count) {
    return new OpenBSDSemaphore(count);
  }
  
  
  static pthread_t GetThreadID() {
    return pthread_self();
  }
  
  static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
    USE(info);
    if (signal != SIGPROF) return;
    Isolate* isolate = Isolate::UncheckedCurrent();
    if (isolate == NULL || !isolate->IsInitialized() || !isolate->IsInUse()) {
      // We require a fully initialized and entered isolate.
      return;
    }
    if (v8::Locker::IsActive() &&
        !isolate->thread_manager()->IsLockedByCurrentThread()) {
      return;
    }
  
    Sampler* sampler = isolate->logger()->sampler();
    if (sampler == NULL || !sampler->IsActive()) return;
  
    TickSample sample_obj;
    TickSample* sample = CpuProfiler::TickSampleEvent(isolate);
    if (sample == NULL) sample = &sample_obj;
  
    // Extracting the sample from the context is extremely machine dependent.
    sample->state = isolate->current_vm_state();
    ucontext_t* ucontext = reinterpret_cast<ucontext_t*>(context);
  #ifdef __NetBSD__
    mcontext_t& mcontext = ucontext->uc_mcontext;
  #if V8_HOST_ARCH_IA32
    sample->pc = reinterpret_cast<Address>(mcontext.__gregs[_REG_EIP]);
    sample->sp = reinterpret_cast<Address>(mcontext.__gregs[_REG_ESP]);
    sample->fp = reinterpret_cast<Address>(mcontext.__gregs[_REG_EBP]);
  #elif V8_HOST_ARCH_X64
    sample->pc = reinterpret_cast<Address>(mcontext.__gregs[_REG_RIP]);
    sample->sp = reinterpret_cast<Address>(mcontext.__gregs[_REG_RSP]);
    sample->fp = reinterpret_cast<Address>(mcontext.__gregs[_REG_RBP]);
  #endif  // V8_HOST_ARCH
  #else  // OpenBSD
  #if V8_HOST_ARCH_IA32
    sample->pc = reinterpret_cast<Address>(ucontext->sc_eip);
    sample->sp = reinterpret_cast<Address>(ucontext->sc_esp);
    sample->fp = reinterpret_cast<Address>(ucontext->sc_ebp);
  #elif V8_HOST_ARCH_X64
    sample->pc = reinterpret_cast<Address>(ucontext->sc_rip);
    sample->sp = reinterpret_cast<Address>(ucontext->sc_rsp);
    sample->fp = reinterpret_cast<Address>(ucontext->sc_rbp);
  #endif  // V8_HOST_ARCH
  #endif  // __NetBSD__
    sampler->SampleStack(sample);
    sampler->Tick(sample);
  }
  
  
  class Sampler::PlatformData : public Malloced {
   public:
    PlatformData() : vm_tid_(GetThreadID()) {}
  
    pthread_t vm_tid() const { return vm_tid_; }
  
   private:
    pthread_t vm_tid_;
  };
  
  
  class SignalSender : public Thread {
   public:
    static const int kSignalSenderStackSize = 64 * KB;
  
    explicit SignalSender(int interval)
        : Thread(Thread::Options("SignalSender", kSignalSenderStackSize)),
          vm_tgid_(getpid()),
          interval_(interval) {}
  
    static void SetUp() { if (!mutex_) mutex_ = OS::CreateMutex(); }
    static void TearDown() { delete mutex_; }
  
    static void InstallSignalHandler() {
      struct sigaction sa;
      sa.sa_sigaction = ProfilerSignalHandler;
      sigemptyset(&sa.sa_mask);
      sa.sa_flags = SA_RESTART | SA_SIGINFO;
      signal_handler_installed_ =
          (sigaction(SIGPROF, &sa, &old_signal_handler_) == 0);
    }
  
    static void RestoreSignalHandler() {
      if (signal_handler_installed_) {
        sigaction(SIGPROF, &old_signal_handler_, 0);
        signal_handler_installed_ = false;
      }
    }
  
    static void AddActiveSampler(Sampler* sampler) {
      ScopedLock lock(mutex_);
      SamplerRegistry::AddActiveSampler(sampler);
      if (instance_ == NULL) {
        // Start a thread that will send SIGPROF signal to VM threads,
        // when CPU profiling will be enabled.
        instance_ = new SignalSender(sampler->interval());
        instance_->Start();
      } else {
        ASSERT(instance_->interval_ == sampler->interval());
      }
    }
  
    static void RemoveActiveSampler(Sampler* sampler) {
      ScopedLock lock(mutex_);
      SamplerRegistry::RemoveActiveSampler(sampler);
      if (SamplerRegistry::GetState() == SamplerRegistry::HAS_NO_SAMPLERS) {
        RuntimeProfiler::StopRuntimeProfilerThreadBeforeShutdown(instance_);
        delete instance_;
        instance_ = NULL;
        RestoreSignalHandler();
      }
    }
  
    // Implement Thread::Run().
    virtual void Run() {
      SamplerRegistry::State state;
      while ((state = SamplerRegistry::GetState()) !=
             SamplerRegistry::HAS_NO_SAMPLERS) {
        // When CPU profiling is enabled both JavaScript and C++ code is
        // profiled. We must not suspend.
        if (state == SamplerRegistry::HAS_CPU_PROFILING_SAMPLERS) {
          if (!signal_handler_installed_) InstallSignalHandler();
          SamplerRegistry::IterateActiveSamplers(&DoCpuProfile, this);
        } else {
          if (signal_handler_installed_) RestoreSignalHandler();
          if (rate_limiter_.SuspendIfNecessary()) continue;
        }
        Sleep();  // TODO(svenpanne) Figure out if OS:Sleep(interval_) is enough.
      }
    }
  
    static void DoCpuProfile(Sampler* sampler, void* raw_sender) {
      if (!sampler->IsProfiling()) return;
      SignalSender* sender = reinterpret_cast<SignalSender*>(raw_sender);
      sender->SendProfilingSignal(sampler->platform_data()->vm_tid());
    }
  
    void SendProfilingSignal(pthread_t tid) {
      if (!signal_handler_installed_) return;
      pthread_kill(tid, SIGPROF);
    }
  
    void Sleep() {
      // Convert ms to us and subtract 100 us to compensate delays
      // occuring during signal delivery.
      useconds_t interval = interval_ * 1000 - 100;
      int result = usleep(interval);
  #ifdef DEBUG
      if (result != 0 && errno != EINTR) {
        fprintf(stderr,
                "SignalSender usleep error; interval = %u, errno = %d\n",
                interval,
                errno);
        ASSERT(result == 0 || errno == EINTR);
      }
  #endif
      USE(result);
    }
  
    const int vm_tgid_;
    const int interval_;
    RuntimeProfilerRateLimiter rate_limiter_;
  
    // Protects the process wide state below.
    static Mutex* mutex_;
    static SignalSender* instance_;
    static bool signal_handler_installed_;
    static struct sigaction old_signal_handler_;
  
   private:
    DISALLOW_COPY_AND_ASSIGN(SignalSender);
  };
  
  
  Mutex* SignalSender::mutex_ = NULL;
  SignalSender* SignalSender::instance_ = NULL;
  struct sigaction SignalSender::old_signal_handler_;
  bool SignalSender::signal_handler_installed_ = false;
  
  
  void OS::SetUp() {
    // Seed the random number generator. We preserve microsecond resolution.
    uint64_t seed = Ticks() ^ (getpid() << 16);
    srandom(static_cast<unsigned int>(seed));
    limit_mutex = CreateMutex();
    SignalSender::SetUp();
  }
  
  
  void OS::TearDown() {
    SignalSender::TearDown();
    delete limit_mutex;
  }
  
  
  Sampler::Sampler(Isolate* isolate, int interval)
      : isolate_(isolate),
        interval_(interval),
        profiling_(false),
        active_(false),
        samples_taken_(0) {
    data_ = new PlatformData;
  }
  
  
  Sampler::~Sampler() {
    ASSERT(!IsActive());
    delete data_;
  }
  
  
  void Sampler::Start() {
    ASSERT(!IsActive());
    SetActive(true);
    SignalSender::AddActiveSampler(this);
  }
  
  
  void Sampler::Stop() {
    ASSERT(IsActive());
    SignalSender::RemoveActiveSampler(this);
    SetActive(false);
  }
  
  
  } }  // namespace v8::internal
  