static
void addProfileEntry(ProfileStack *aStack, ThreadProfile &aProfile, int i)
{
  // First entry has tagName 's' (start)
  // Check for magic pointer bit 1 to indicate copy
  const char* sampleLabel = aStack->mStack[i].mLabel;
  if (aStack->mStack[i].isCopyLabel()) {
    // Store the string using 1 or more 'd' (dynamic) tags
    // that will happen to the preceding tag

    aProfile.addTag(ProfileEntry('c', ""));
    // Add one to store the null termination
    size_t strLen = strlen(sampleLabel) + 1;
    for (size_t j = 0; j < strLen;) {
      // Store as many characters in the void* as the platform allows
      char text[sizeof(void*)];
      for (size_t pos = 0; pos < sizeof(void*) && j+pos < strLen; pos++) {
        text[pos] = sampleLabel[j+pos];
      }
      j += sizeof(void*)/sizeof(char);
      // Cast to *((void**) to pass the text data to a void*
      aProfile.addTag(ProfileEntry('d', *((void**)(&text[0]))));
    }
  } else {
    aProfile.addTag(ProfileEntry('c', sampleLabel));
  }
}

void TableTicker::doBacktrace(ThreadProfile &aProfile, TickSample* aSample)
{
#ifndef XP_MACOSX
  uintptr_t thread = GetThreadHandle(platform_data());
  MOZ_ASSERT(thread);
#endif
  void* pc_array[1000];
  PCArray array = {
    pc_array,
    mozilla::ArrayLength(pc_array),
    0
  };

  // Start with the current function.
  StackWalkCallback(aSample->pc, &array);

#ifdef XP_MACOSX
  pthread_t pt = GetProfiledThread(platform_data());
  void *stackEnd = reinterpret_cast<void*>(-1);
  if (pt)
    stackEnd = static_cast<char*>(pthread_get_stackaddr_np(pt));
  nsresult rv = FramePointerStackWalk(StackWalkCallback, 0, &array, reinterpret_cast<void**>(aSample->fp), stackEnd);
#else
  nsresult rv = NS_StackWalk(StackWalkCallback, 0, &array, thread);
#endif
  if (NS_SUCCEEDED(rv)) {
    aProfile.addTag(ProfileEntry('s', "(root)"));

    for (size_t i = array.count; i > 0; --i) {
      aProfile.addTag(ProfileEntry('l', (void*)array.array[i - 1]));
    }
  }
}

void TableTicker::doBacktrace(ThreadProfile &aProfile, TickSample* aSample)
{
  void *array[100];
  int count = backtrace (array, 100);

  aProfile.addTag(ProfileEntry('s', "(root)"));

  for (int i = 0; i < count; i++) {
    if( (intptr_t)array[i] == -1 ) break;
    aProfile.addTag(ProfileEntry('l', (void*)array[i]));
  }
}

static
void addProfileEntry(volatile StackEntry &entry, ThreadProfile &aProfile,
                     ProfileStack *stack, void *lastpc)
{
  int lineno = -1;

  // First entry has tagName 's' (start)
  // Check for magic pointer bit 1 to indicate copy
  const char* sampleLabel = entry.label();
  if (entry.isCopyLabel()) {
    // Store the string using 1 or more 'd' (dynamic) tags
    // that will happen to the preceding tag

    aProfile.addTag(ProfileEntry('c', ""));
    // Add one to store the null termination
    size_t strLen = strlen(sampleLabel) + 1;
    for (size_t j = 0; j < strLen;) {
      // Store as many characters in the void* as the platform allows
      char text[sizeof(void*)];
      for (size_t pos = 0; pos < sizeof(void*) && j+pos < strLen; pos++) {
        text[pos] = sampleLabel[j+pos];
      }
      j += sizeof(void*)/sizeof(char);
      // Cast to *((void**) to pass the text data to a void*
      aProfile.addTag(ProfileEntry('d', *((void**)(&text[0]))));
    }
    if (entry.js()) {
      if (!entry.pc()) {
        // The JIT only allows the top-most entry to have a NULL pc
        MOZ_ASSERT(&entry == &stack->mStack[stack->stackSize() - 1]);
        // If stack-walking was disabled, then that's just unfortunate
        if (lastpc) {
          jsbytecode *jspc = js::ProfilingGetPC(stack->mRuntime, entry.script(),
                                                lastpc);
          if (jspc) {
            lineno = JS_PCToLineNumber(NULL, entry.script(), jspc);
          }
        }
      } else {
        lineno = JS_PCToLineNumber(NULL, entry.script(), entry.pc());
      }
    } else {
      lineno = entry.line();
    }
  } else {
    aProfile.addTag(ProfileEntry('c', sampleLabel));
    lineno = entry.line();
  }
  if (lineno != -1) {
    aProfile.addTag(ProfileEntry('n', lineno));
  }
}

void TableTicker::Tick(TickSample* sample)
{
  // Marker(s) come before the sample
  ProfileStack* stack = mPrimaryThreadProfile.GetStack();
  for (int i = 0; stack->getMarker(i) != NULL; i++) {
    mPrimaryThreadProfile.addTag(ProfileEntry('m', stack->getMarker(i)));
  }
  stack->mQueueClearMarker = true;

  bool recordSample = true;
  if (mJankOnly) {
    // if we are on a different event we can discard any temporary samples
    // we've kept around
    if (sLastSampledEventGeneration != sCurrentEventGeneration) {
      // XXX: we also probably want to add an entry to the profile to help
      // distinguish which samples are part of the same event. That, or record
      // the event generation in each sample
      mPrimaryThreadProfile.erase();
    }
    sLastSampledEventGeneration = sCurrentEventGeneration;

    recordSample = false;
    // only record the events when we have a we haven't seen a tracer event for 100ms
    if (!sLastTracerEvent.IsNull()) {
      TimeDuration delta = sample->timestamp - sLastTracerEvent;
      if (delta.ToMilliseconds() > 100.0) {
          recordSample = true;
      }
    }
  }

#if defined(USE_BACKTRACE) || defined(USE_NS_STACKWALK) || defined(USE_LIBUNWIND)
  if (mUseStackWalk) {
    doBacktrace(mPrimaryThreadProfile, sample);
  } else {
    doSampleStackTrace(stack, mPrimaryThreadProfile, sample);
  }
#else
  doSampleStackTrace(stack, mPrimaryThreadProfile, sample);
#endif

  if (recordSample)
    mPrimaryThreadProfile.flush();

  if (!mJankOnly && !sLastTracerEvent.IsNull() && sample) {
    TimeDuration delta = sample->timestamp - sLastTracerEvent;
    mPrimaryThreadProfile.addTag(ProfileEntry('r', delta.ToMilliseconds()));
  }
}

static
void doSampleStackTrace(ThreadProfile &aProfile, TickSample *aSample, bool aAddLeafAddresses)
{
  NativeStack nativeStack = { nullptr, nullptr, 0, 0 };
  mergeStacksIntoProfile(aProfile, aSample, nativeStack);

#ifdef ENABLE_SPS_LEAF_DATA
  if (aSample && aAddLeafAddresses) {
    aProfile.addTag(ProfileEntry('l', (void*)aSample->pc));
#ifdef ENABLE_ARM_LR_SAVING
    aProfile.addTag(ProfileEntry('L', (void*)aSample->lr));
#endif
  }
#endif
}

static
void doSampleStackTrace(ProfileStack *aStack, ThreadProfile &aProfile, TickSample *sample)
{
  // Sample
  // 's' tag denotes the start of a sample block
  // followed by 0 or more 'c' tags.
  aProfile.addTag(ProfileEntry('s', "(root)"));
  for (mozilla::sig_safe_t i = 0;
       i < aStack->mStackPointer && i < mozilla::ArrayLength(aStack->mStack);
       i++) {
    addProfileEntry(aStack, aProfile, i);
  }
#ifdef ENABLE_SPS_LEAF_DATA
  if (sample) {
    aProfile.addTag(ProfileEntry('l', (void*)sample->pc));
#ifdef ENABLE_ARM_LR_SAVING
    aProfile.addTag(ProfileEntry('L', (void*)sample->lr));
#endif
  }
#endif
}

static
void doSampleStackTrace(ProfileStack *aStack, ThreadProfile &aProfile, TickSample *sample)
{
  // Sample
  // 's' tag denotes the start of a sample block
  // followed by 0 or more 'c' tags.
  aProfile.addTag(ProfileEntry('s', "(root)"));
  for (mozilla::sig_safe_t i = 0; i < aStack->mStackPointer; i++) {
    // First entry has tagName 's' (start)
    // Check for magic pointer bit 1 to indicate copy
    const char* sampleLabel = aStack->mStack[i].mLabel;
    if (aStack->mStack[i].isCopyLabel()) {
      // Store the string using 1 or more 'd' (dynamic) tags
      // that will happen to the preceding tag

      aProfile.addTag(ProfileEntry('c', ""));
      // Add one to store the null termination
      size_t strLen = strlen(sampleLabel) + 1;
      for (size_t j = 0; j < strLen;) {
        // Store as many characters in the void* as the platform allows
        char text[sizeof(void*)];
        for (size_t pos = 0; pos < sizeof(void*) && j+pos < strLen; pos++) {
          text[pos] = sampleLabel[j+pos];
        }
        j += sizeof(void*);
        // Take '*((void**)(&text[0]))' to pass the char[] as a single void*
        aProfile.addTag(ProfileEntry('d', *((void**)(&text[0]))));
      }
    } else {
      aProfile.addTag(ProfileEntry('c', sampleLabel));
    }
  }
#ifdef ENABLE_SPS_LEAF_DATA
  if (sample) {
    aProfile.addTag(ProfileEntry('l', (void*)sample->pc));
  }
#endif
}

void TableTicker::doNativeBacktrace(ThreadProfile &aProfile, TickSample* aSample)
{
  void *pc_array[1000];
  void *sp_array[1000];
  PCArray array = {
    pc_array,
    sp_array,
    mozilla::ArrayLength(pc_array),
    0
  };

  const mcontext_t *mcontext = &reinterpret_cast<ucontext_t *>(aSample->context)->uc_mcontext;
  mcontext_t savedContext;
  PseudoStack *pseudoStack = aProfile.GetPseudoStack();

  array.count = 0;
  // The pseudostack contains an "EnterJIT" frame whenever we enter
  // JIT code with profiling enabled; the stack pointer value points
  // the saved registers.  We use this to unwind resume unwinding
  // after encounting JIT code.
  for (uint32_t i = pseudoStack->stackSize(); i > 0; --i) {
    // The pseudostack grows towards higher indices, so we iterate
    // backwards (from callee to caller).
    volatile StackEntry &entry = pseudoStack->mStack[i - 1];
    if (!entry.js() && strcmp(entry.label(), "EnterJIT") == 0) {
      // Found JIT entry frame.  Unwind up to that point (i.e., force
      // the stack walk to stop before the block of saved registers;
      // note that it yields nondecreasing stack pointers), then restore
      // the saved state.
      uint32_t *vSP = reinterpret_cast<uint32_t*>(entry.stackAddress());

      array.count += EHABIStackWalk(*mcontext,
                                    /* stackBase = */ vSP,
                                    sp_array + array.count,
                                    pc_array + array.count,
                                    array.size - array.count);

      memset(&savedContext, 0, sizeof(savedContext));
      // See also: struct EnterJITStack in js/src/jit/arm/Trampoline-arm.cpp
      savedContext.arm_r4 = *vSP++;
      savedContext.arm_r5 = *vSP++;
      savedContext.arm_r6 = *vSP++;
      savedContext.arm_r7 = *vSP++;
      savedContext.arm_r8 = *vSP++;
      savedContext.arm_r9 = *vSP++;
      savedContext.arm_r10 = *vSP++;
      savedContext.arm_fp = *vSP++;
      savedContext.arm_lr = *vSP++;
      savedContext.arm_sp = reinterpret_cast<uint32_t>(vSP);
      savedContext.arm_pc = savedContext.arm_lr;
      mcontext = &savedContext;
    }
  }

  // Now unwind whatever's left (starting from either the last EnterJIT
  // frame or, if no EnterJIT was found, the original registers).
  array.count += EHABIStackWalk(*mcontext,
                                aProfile.GetStackTop(),
                                sp_array + array.count,
                                pc_array + array.count,
                                array.size - array.count);

  mergeNativeBacktrace(aProfile, array);
}

static
void mergeStacksIntoProfile(ThreadProfile& aProfile, TickSample* aSample, NativeStack& aNativeStack)
{
  PseudoStack* pseudoStack = aProfile.GetPseudoStack();
  volatile StackEntry *pseudoFrames = pseudoStack->mStack;
  uint32_t pseudoCount = pseudoStack->stackSize();

  // Make a copy of the JS stack into a JSFrame array. This is necessary since,
  // like the native stack, the JS stack is iterated youngest-to-oldest and we
  // need to iterate oldest-to-youngest when adding entries to aProfile.

  // Synchronous sampling reports an invalid buffer generation to
  // ProfilingFrameIterator to avoid incorrectly resetting the generation of
  // sampled JIT entries inside the JS engine. See note below concerning 'J'
  // entries.
  uint32_t startBufferGen;
  if (aSample->isSamplingCurrentThread) {
    startBufferGen = UINT32_MAX;
  } else {
    startBufferGen = aProfile.bufferGeneration();
  }
  uint32_t jsCount = 0;
#ifndef SPS_STANDALONE
  JS::ProfilingFrameIterator::Frame jsFrames[1000];
  // Only walk jit stack if profiling frame iterator is turned on.
  if (pseudoStack->mRuntime && JS::IsProfilingEnabledForRuntime(pseudoStack->mRuntime)) {
    AutoWalkJSStack autoWalkJSStack;
    const uint32_t maxFrames = mozilla::ArrayLength(jsFrames);

    if (aSample && autoWalkJSStack.walkAllowed) {
      JS::ProfilingFrameIterator::RegisterState registerState;
      registerState.pc = aSample->pc;
      registerState.sp = aSample->sp;
#ifdef ENABLE_ARM_LR_SAVING
      registerState.lr = aSample->lr;
#endif

      JS::ProfilingFrameIterator jsIter(pseudoStack->mRuntime,
                                        registerState,
                                        startBufferGen);
      for (; jsCount < maxFrames && !jsIter.done(); ++jsIter) {
        // See note below regarding 'J' entries.
        if (aSample->isSamplingCurrentThread || jsIter.isAsmJS()) {
          uint32_t extracted = jsIter.extractStack(jsFrames, jsCount, maxFrames);
          jsCount += extracted;
          if (jsCount == maxFrames)
            break;
        } else {
          mozilla::Maybe<JS::ProfilingFrameIterator::Frame> frame =
            jsIter.getPhysicalFrameWithoutLabel();
          if (frame.isSome())
            jsFrames[jsCount++] = frame.value();
        }
      }
    }
  }
#endif

  // Start the sample with a root entry.
  aProfile.addTag(ProfileEntry('s', "(root)"));

  // While the pseudo-stack array is ordered oldest-to-youngest, the JS and
  // native arrays are ordered youngest-to-oldest. We must add frames to
  // aProfile oldest-to-youngest. Thus, iterate over the pseudo-stack forwards
  // and JS and native arrays backwards. Note: this means the terminating
  // condition jsIndex and nativeIndex is being < 0.
  uint32_t pseudoIndex = 0;
  int32_t jsIndex = jsCount - 1;
  int32_t nativeIndex = aNativeStack.count - 1;

  uint8_t *lastPseudoCppStackAddr = nullptr;

  // Iterate as long as there is at least one frame remaining.
  while (pseudoIndex != pseudoCount || jsIndex >= 0 || nativeIndex >= 0) {
    // There are 1 to 3 frames available. Find and add the oldest.

    uint8_t *pseudoStackAddr = nullptr;
    uint8_t *jsStackAddr = nullptr;
    uint8_t *nativeStackAddr = nullptr;

    if (pseudoIndex != pseudoCount) {
      volatile StackEntry &pseudoFrame = pseudoFrames[pseudoIndex];

      if (pseudoFrame.isCpp())
        lastPseudoCppStackAddr = (uint8_t *) pseudoFrame.stackAddress();

#ifndef SPS_STANDALONE
      // Skip any pseudo-stack JS frames which are marked isOSR
      // Pseudostack frames are marked isOSR when the JS interpreter
      // enters a jit frame on a loop edge (via on-stack-replacement,
      // or OSR).  To avoid both the pseudoframe and jit frame being
      // recorded (and showing up twice), the interpreter marks the
      // interpreter pseudostack entry with the OSR flag to ensure that
      // it doesn't get counted.
      if (pseudoFrame.isJs() && pseudoFrame.isOSR()) {
          pseudoIndex++;
          continue;
      }
#endif

//.........这里部分代码省略.........

void GeckoSampler::doNativeBacktrace(ThreadProfile &aProfile, TickSample* aSample)
{
  const mcontext_t* mc
    = &reinterpret_cast<ucontext_t *>(aSample->context)->uc_mcontext;

  lul::UnwindRegs startRegs;
  memset(&startRegs, 0, sizeof(startRegs));

# if defined(SPS_PLAT_amd64_linux)
  startRegs.xip = lul::TaggedUWord(mc->gregs[REG_RIP]);
  startRegs.xsp = lul::TaggedUWord(mc->gregs[REG_RSP]);
  startRegs.xbp = lul::TaggedUWord(mc->gregs[REG_RBP]);
# elif defined(SPS_PLAT_arm_android)
  startRegs.r15 = lul::TaggedUWord(mc->arm_pc);
  startRegs.r14 = lul::TaggedUWord(mc->arm_lr);
  startRegs.r13 = lul::TaggedUWord(mc->arm_sp);
  startRegs.r12 = lul::TaggedUWord(mc->arm_ip);
  startRegs.r11 = lul::TaggedUWord(mc->arm_fp);
  startRegs.r7  = lul::TaggedUWord(mc->arm_r7);
# elif defined(SPS_PLAT_x86_linux) || defined(SPS_PLAT_x86_android)
  startRegs.xip = lul::TaggedUWord(mc->gregs[REG_EIP]);
  startRegs.xsp = lul::TaggedUWord(mc->gregs[REG_ESP]);
  startRegs.xbp = lul::TaggedUWord(mc->gregs[REG_EBP]);
# else
#   error "Unknown plat"
# endif

  /* Copy up to N_STACK_BYTES from rsp-REDZONE upwards, but not
     going past the stack's registered top point.  Do some basic
     sanity checks too.  This assumes that the TaggedUWord holding
     the stack pointer value is valid, but it should be, since it
     was constructed that way in the code just above. */

  lul::StackImage stackImg;

  {
#   if defined(SPS_PLAT_amd64_linux)
    uintptr_t rEDZONE_SIZE = 128;
    uintptr_t start = startRegs.xsp.Value() - rEDZONE_SIZE;
#   elif defined(SPS_PLAT_arm_android)
    uintptr_t rEDZONE_SIZE = 0;
    uintptr_t start = startRegs.r13.Value() - rEDZONE_SIZE;
#   elif defined(SPS_PLAT_x86_linux) || defined(SPS_PLAT_x86_android)
    uintptr_t rEDZONE_SIZE = 0;
    uintptr_t start = startRegs.xsp.Value() - rEDZONE_SIZE;
#   else
#     error "Unknown plat"
#   endif
    uintptr_t end   = reinterpret_cast<uintptr_t>(aProfile.GetStackTop());
    uintptr_t ws    = sizeof(void*);
    start &= ~(ws-1);
    end   &= ~(ws-1);
    uintptr_t nToCopy = 0;
    if (start < end) {
      nToCopy = end - start;
      if (nToCopy > lul::N_STACK_BYTES)
        nToCopy = lul::N_STACK_BYTES;
    }
    MOZ_ASSERT(nToCopy <= lul::N_STACK_BYTES);
    stackImg.mLen       = nToCopy;
    stackImg.mStartAvma = start;
    if (nToCopy > 0) {
      memcpy(&stackImg.mContents[0], (void*)start, nToCopy);
      (void)VALGRIND_MAKE_MEM_DEFINED(&stackImg.mContents[0], nToCopy);
    }
  }

  // The maximum number of frames that LUL will produce.  Setting it
  // too high gives a risk of it wasting a lot of time looping on
  // corrupted stacks.
  const int MAX_NATIVE_FRAMES = 256;

  size_t scannedFramesAllowed = 0;

  uintptr_t framePCs[MAX_NATIVE_FRAMES];
  uintptr_t frameSPs[MAX_NATIVE_FRAMES];
  size_t framesAvail = mozilla::ArrayLength(framePCs);
  size_t framesUsed  = 0;
  size_t scannedFramesAcquired = 0;
  sLUL->Unwind( &framePCs[0], &frameSPs[0],
                &framesUsed, &scannedFramesAcquired,
                framesAvail, scannedFramesAllowed,
                &startRegs, &stackImg );

  NativeStack nativeStack = {
    reinterpret_cast<void**>(framePCs),
    reinterpret_cast<void**>(frameSPs),
    mozilla::ArrayLength(framePCs),
    0
  };

  nativeStack.count = framesUsed;

  mergeStacksIntoProfile(aProfile, aSample, nativeStack);

  // Update stats in the LUL stats object.  Unfortunately this requires
  // three global memory operations.
  sLUL->mStats.mContext += 1;
  sLUL->mStats.mCFI     += framesUsed - 1 - scannedFramesAcquired;
  sLUL->mStats.mScanned += scannedFramesAcquired;
//.........这里部分代码省略.........