1 files changed, 469 insertions, 0 deletions
diff --git a/tools/profiler/public/PseudoStack.h b/tools/profiler/public/PseudoStack.h
new file mode 100644
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+++ b/tools/profiler/public/PseudoStack.h
@@ -0,0 +1,469 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef PROFILER_PSEUDO_STACK_H_
+#define PROFILER_PSEUDO_STACK_H_
+
+#include "mozilla/ArrayUtils.h"
+#include <stdint.h>
+#include "js/ProfilingStack.h"
+#include <stdlib.h>
+#include "mozilla/Atomics.h"
+#ifndef SPS_STANDALONE
+#include "nsISupportsImpl.h"
+#endif
+
+/* we duplicate this code here to avoid header dependencies
+ * which make it more difficult to include in other places */
+#if defined(_M_X64) || defined(__x86_64__)
+#define V8_HOST_ARCH_X64 1
+#elif defined(_M_IX86) || defined(__i386__) || defined(__i386)
+#define V8_HOST_ARCH_IA32 1
+#elif defined(__ARMEL__)
+#define V8_HOST_ARCH_ARM 1
+#else
+#warning Please add support for your architecture in chromium_types.h
+#endif
+
+// STORE_SEQUENCER: Because signals can interrupt our profile modification
+//                  we need to make stores are not re-ordered by the compiler
+//                  or hardware to make sure the profile is consistent at
+//                  every point the signal can fire.
+#ifdef V8_HOST_ARCH_ARM
+// TODO Is there something cheaper that will prevent
+//      memory stores from being reordered
+
+typedef void (*LinuxKernelMemoryBarrierFunc)(void);
+LinuxKernelMemoryBarrierFunc pLinuxKernelMemoryBarrier __attribute__((weak)) =
+    (LinuxKernelMemoryBarrierFunc) 0xffff0fa0;
+
+# define STORE_SEQUENCER() pLinuxKernelMemoryBarrier()
+#elif defined(V8_HOST_ARCH_IA32) || defined(V8_HOST_ARCH_X64)
+# if defined(_MSC_VER)
+#  include <intrin.h>
+#  define STORE_SEQUENCER() _ReadWriteBarrier();
+# elif defined(__INTEL_COMPILER)
+#  define STORE_SEQUENCER() __memory_barrier();
+# elif __GNUC__
+#  define STORE_SEQUENCER() asm volatile("" ::: "memory");
+# else
+#  error "Memory clobber not supported for your compiler."
+# endif
+#else
+# error "Memory clobber not supported for your platform."
+#endif
+
+// We can't include <algorithm> because it causes issues on OS X, so we use
+// our own min function.
+static inline uint32_t sMin(uint32_t l, uint32_t r) {
+  return l < r ? l : r;
+}
+
+// A stack entry exists to allow the JS engine to inform SPS of the current
+// backtrace, but also to instrument particular points in C++ in case stack
+// walking is not available on the platform we are running on.
+//
+// Each entry has a descriptive string, a relevant stack address, and some extra
+// information the JS engine might want to inform SPS of. This class inherits
+// from the JS engine's version of the entry to ensure that the size and layout
+// of the two representations are consistent.
+class StackEntry : public js::ProfileEntry
+{
+};
+
+class ProfilerMarkerPayload;
+template<typename T>
+class ProfilerLinkedList;
+class SpliceableJSONWriter;
+class UniqueStacks;
+
+class ProfilerMarker {
+  friend class ProfilerLinkedList<ProfilerMarker>;
+public:
+  explicit ProfilerMarker(const char* aMarkerName,
+                          ProfilerMarkerPayload* aPayload = nullptr,
+                          double aTime = 0);
+
+  ~ProfilerMarker();
+
+  const char* GetMarkerName() const {
+    return mMarkerName;
+  }
+
+  void StreamJSON(SpliceableJSONWriter& aWriter, UniqueStacks& aUniqueStacks) const;
+
+  void SetGeneration(uint32_t aGenID);
+
+  bool HasExpired(uint32_t aGenID) const {
+    return mGenID + 2 <= aGenID;
+  }
+
+  double GetTime() const;
+
+private:
+  char* mMarkerName;
+  ProfilerMarkerPayload* mPayload;
+  ProfilerMarker* mNext;
+  double mTime;
+  uint32_t mGenID;
+};
+
+template<typename T>
+class ProfilerLinkedList {
+public:
+  ProfilerLinkedList()
+    : mHead(nullptr)
+    , mTail(nullptr)
+  {}
+
+  void insert(T* elem)
+  {
+    if (!mTail) {
+      mHead = elem;
+      mTail = elem;
+    } else {
+      mTail->mNext = elem;
+      mTail = elem;
+    }
+    elem->mNext = nullptr;
+  }
+
+  T* popHead()
+  {
+    if (!mHead) {
+      MOZ_ASSERT(false);
+      return nullptr;
+    }
+
+    T* head = mHead;
+
+    mHead = head->mNext;
+    if (!mHead) {
+      mTail = nullptr;
+    }
+
+    return head;
+  }
+
+  const T* peek() {
+    return mHead;
+  }
+
+private:
+  T* mHead;
+  T* mTail;
+};
+
+typedef ProfilerLinkedList<ProfilerMarker> ProfilerMarkerLinkedList;
+
+template<typename T>
+class ProfilerSignalSafeLinkedList {
+public:
+  ProfilerSignalSafeLinkedList()
+    : mSignalLock(false)
+  {}
+
+  ~ProfilerSignalSafeLinkedList()
+  {
+    if (mSignalLock) {
+      // Some thread is modifying the list. We should only be released on that
+      // thread.
+      abort();
+    }
+
+    while (mList.peek()) {
+      delete mList.popHead();
+    }
+  }
+
+  // Insert an item into the list.
+  // Must only be called from the owning thread.
+  // Must not be called while the list from accessList() is being accessed.
+  // In the profiler, we ensure that by interrupting the profiled thread
+  // (which is the one that owns this list and calls insert() on it) until
+  // we're done reading the list from the signal handler.
+  void insert(T* aElement) {
+    MOZ_ASSERT(aElement);
+
+    mSignalLock = true;
+    STORE_SEQUENCER();
+
+    mList.insert(aElement);
+
+    STORE_SEQUENCER();
+    mSignalLock = false;
+  }
+
+  // Called within signal, from any thread, possibly while insert() is in the
+  // middle of modifying the list (on the owning thread). Will return null if
+  // that is the case.
+  // Function must be reentrant.
+  ProfilerLinkedList<T>* accessList()
+  {
+    if (mSignalLock) {
+      return nullptr;
+    }
+    return &mList;
+  }
+
+private:
+  ProfilerLinkedList<T> mList;
+
+  // If this is set, then it's not safe to read the list because its contents
+  // are being changed.
+  volatile bool mSignalLock;
+};
+
+// Stub eventMarker function for js-engine event generation.
+void ProfilerJSEventMarker(const char *event);
+
+// the PseudoStack members are read by signal
+// handlers, so the mutation of them needs to be signal-safe.
+struct PseudoStack
+{
+public:
+  // Create a new PseudoStack and acquire a reference to it.
+  static PseudoStack *create()
+  {
+    return new PseudoStack();
+  }
+
+  // This is called on every profiler restart. Put things that should happen at that time here.
+  void reinitializeOnResume() {
+    // This is needed to cause an initial sample to be taken from sleeping threads. Otherwise sleeping
+    // threads would not have any samples to copy forward while sleeping.
+    mSleepId++;
+  }
+
+  void addMarker(const char* aMarkerStr, ProfilerMarkerPayload* aPayload, double aTime)
+  {
+    ProfilerMarker* marker = new ProfilerMarker(aMarkerStr, aPayload, aTime);
+    mPendingMarkers.insert(marker);
+  }
+
+  // called within signal. Function must be reentrant
+  ProfilerMarkerLinkedList* getPendingMarkers()
+  {
+    // The profiled thread is interrupted, so we can access the list safely.
+    // Unless the profiled thread was in the middle of changing the list when
+    // we interrupted it - in that case, accessList() will return null.
+    return mPendingMarkers.accessList();
+  }
+
+  void push(const char *aName, js::ProfileEntry::Category aCategory, uint32_t line)
+  {
+    push(aName, aCategory, nullptr, false, line);
+  }
+
+  void push(const char *aName, js::ProfileEntry::Category aCategory,
+    void *aStackAddress, bool aCopy, uint32_t line)
+  {
+    if (size_t(mStackPointer) >= mozilla::ArrayLength(mStack)) {
+      mStackPointer++;
+      return;
+    }
+
+    // In order to ensure this object is kept alive while it is
+    // active, we acquire a reference at the outermost push.  This is
+    // released by the corresponding pop.
+    if (mStackPointer == 0) {
+      ref();
+    }
+
+    volatile StackEntry &entry = mStack[mStackPointer];
+
+    // Make sure we increment the pointer after the name has
+    // been written such that mStack is always consistent.
+    entry.initCppFrame(aStackAddress, line);
+    entry.setLabel(aName);
+    MOZ_ASSERT(entry.flags() == js::ProfileEntry::IS_CPP_ENTRY);
+    entry.setCategory(aCategory);
+
+    // Track if mLabel needs a copy.
+    if (aCopy)
+      entry.setFlag(js::ProfileEntry::FRAME_LABEL_COPY);
+    else
+      entry.unsetFlag(js::ProfileEntry::FRAME_LABEL_COPY);
+
+    // Prevent the optimizer from re-ordering these instructions
+    STORE_SEQUENCER();
+    mStackPointer++;
+  }
+
+  // Pop the stack.  If the stack is empty and all other references to
+  // this PseudoStack have been dropped, then the PseudoStack is
+  // deleted and "false" is returned.  Otherwise "true" is returned.
+  bool popAndMaybeDelete()
+  {
+    mStackPointer--;
+    if (mStackPointer == 0) {
+      // Release our self-owned reference count.  See 'push'.
+      deref();
+      return false;
+    } else {
+      return true;
+    }
+  }
+  bool isEmpty()
+  {
+    return mStackPointer == 0;
+  }
+  uint32_t stackSize() const
+  {
+    return sMin(mStackPointer, mozilla::sig_safe_t(mozilla::ArrayLength(mStack)));
+  }
+
+  void sampleContext(JSContext* context) {
+#ifndef SPS_STANDALONE
+    if (mContext && !context) {
+      // On JS shut down, flush the current buffer as stringifying JIT samples
+      // requires a live JSContext.
+      flushSamplerOnJSShutdown();
+    }
+
+    mContext = context;
+
+    if (!context) {
+      return;
+    }
+
+    static_assert(sizeof(mStack[0]) == sizeof(js::ProfileEntry),
+                  "mStack must be binary compatible with js::ProfileEntry.");
+    js::SetContextProfilingStack(context,
+                                 (js::ProfileEntry*) mStack,
+                                 (uint32_t*) &mStackPointer,
+                                 (uint32_t) mozilla::ArrayLength(mStack));
+    if (mStartJSSampling)
+      enableJSSampling();
+#endif
+  }
+#ifndef SPS_STANDALONE
+  void enableJSSampling() {
+    if (mContext) {
+      js::EnableContextProfilingStack(mContext, true);
+      js::RegisterContextProfilingEventMarker(mContext, &ProfilerJSEventMarker);
+      mStartJSSampling = false;
+    } else {
+      mStartJSSampling = true;
+    }
+  }
+  void jsOperationCallback() {
+    if (mStartJSSampling)
+      enableJSSampling();
+  }
+  void disableJSSampling() {
+    mStartJSSampling = false;
+    if (mContext)
+      js::EnableContextProfilingStack(mContext, false);
+  }
+#endif
+
+  // Keep a list of active checkpoints
+  StackEntry volatile mStack[1024];
+ private:
+
+  // A PseudoStack can only be created via the "create" method.
+  PseudoStack()
+    : mStackPointer(0)
+    , mSleepId(0)
+    , mSleepIdObserved(0)
+    , mSleeping(false)
+    , mRefCnt(1)
+#ifndef SPS_STANDALONE
+    , mContext(nullptr)
+#endif
+    , mStartJSSampling(false)
+    , mPrivacyMode(false)
+  {
+    MOZ_COUNT_CTOR(PseudoStack);
+  }
+
+  // A PseudoStack can only be deleted via deref.
+  ~PseudoStack() {
+    MOZ_COUNT_DTOR(PseudoStack);
+    if (mStackPointer != 0) {
+      // We're releasing the pseudostack while it's still in use.
+      // The label macros keep a non ref counted reference to the
+      // stack to avoid a TLS. If these are not all cleared we will
+      // get a use-after-free so better to crash now.
+      abort();
+    }
+  }
+
+  // No copying.
+  PseudoStack(const PseudoStack&) = delete;
+  void operator=(const PseudoStack&) = delete;
+
+  void flushSamplerOnJSShutdown();
+
+  // Keep a list of pending markers that must be moved
+  // to the circular buffer
+  ProfilerSignalSafeLinkedList<ProfilerMarker> mPendingMarkers;
+  // This may exceed the length of mStack, so instead use the stackSize() method
+  // to determine the number of valid samples in mStack
+  mozilla::sig_safe_t mStackPointer;
+  // Incremented at every sleep/wake up of the thread
+  int mSleepId;
+  // Previous id observed. If this is not the same as mSleepId, this thread is not sleeping in the same place any more
+  mozilla::Atomic<int> mSleepIdObserved;
+  // Keeps tack of whether the thread is sleeping or not (1 when sleeping 0 when awake)
+  mozilla::Atomic<int> mSleeping;
+  // This class is reference counted because it must be kept alive by
+  // the ThreadInfo, by the reference from tlsPseudoStack, and by the
+  // current thread when callbacks are in progress.
+  mozilla::Atomic<int> mRefCnt;
+
+ public:
+#ifndef SPS_STANDALONE
+  // The context which is being sampled
+  JSContext *mContext;
+#endif
+  // Start JS Profiling when possible
+  bool mStartJSSampling;
+  bool mPrivacyMode;
+
+  enum SleepState {NOT_SLEEPING, SLEEPING_FIRST, SLEEPING_AGAIN};
+
+  // The first time this is called per sleep cycle we return SLEEPING_FIRST
+  // and any other subsequent call within the same sleep cycle we return SLEEPING_AGAIN
+  SleepState observeSleeping() {
+    if (mSleeping != 0) {
+      if (mSleepIdObserved == mSleepId) {
+        return SLEEPING_AGAIN;
+      } else {
+        mSleepIdObserved = mSleepId;
+        return SLEEPING_FIRST;
+      }
+    } else {
+      return NOT_SLEEPING;
+    }
+  }
+
+
+  // Call this whenever the current thread sleeps or wakes up
+  // Calling setSleeping with the same value twice in a row is an error
+  void setSleeping(int sleeping) {
+    MOZ_ASSERT(mSleeping != sleeping);
+    mSleepId++;
+    mSleeping = sleeping;
+  }
+
+  bool isSleeping() {
+    return !!mSleeping;
+  }
+
+  void ref() {
+    ++mRefCnt;
+  }
+
+  void deref() {
+    int newValue = --mRefCnt;
+    if (newValue == 0) {
+      delete this;
+    }
+  }
+};
+
+#endif