[cpu-profiler] Add parameter to filter profiles by v8::Context

Adds support to the CPU profiler for scraping the incumbent contexts of
V8 stack frames. While it is generally unsafe to access heap objects
during a profiling interrupt, the native context is uniquely usable due
to being guaranteed an alive root on the stack, as well as its slots
being immutable after context creation.

Change-Id: I2c3149c1302b74d2f13aa99d1fdd0cf006e0f9d1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1580020
Commit-Queue: Andrew Comminos <acomminos@fb.com>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Alexei Filippov <alph@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63258}

include/v8-profiler.h

@@ -26,6 +26,10 @@ struct CpuProfileDeoptFrame {
   size_t position;
 };
 
+namespace internal {
+class CpuProfile;
+}  // namespace internal
+
 }  // namespace v8
 
 #ifdef V8_OS_WIN
@@ -94,6 +98,10 @@ struct V8_EXPORT TickSample {
    *                                register state rather than the one provided
    *                                with |state| argument. Otherwise the method
    *                                will use provided register |state| as is.
+   * \param contexts If set, contexts[i] will be set to the address of the
+   *                 incumbent native context associated with frames[i]. It
+   *                 should be large enough to hold |frames_limit| frame
+   *                 contexts.
    * \note GetStackSample is thread and signal safe and should only be called
    *                      when the JS thread is paused or interrupted.
    *                      Otherwise the behavior is undefined.
@@ -102,7 +110,8 @@ struct V8_EXPORT TickSample {
                              RecordCEntryFrame record_c_entry_frame,
                              void** frames, size_t frames_limit,
                              v8::SampleInfo* sample_info,
-                             bool use_simulator_reg_state = true);
+                             bool use_simulator_reg_state = true,
+                             void** contexts = nullptr);
   StateTag state;  // The state of the VM.
   void* pc;        // Instruction pointer.
   union {
@@ -112,6 +121,8 @@ struct V8_EXPORT TickSample {
   static const unsigned kMaxFramesCountLog2 = 8;
   static const unsigned kMaxFramesCount = (1 << kMaxFramesCountLog2) - 1;
   void* stack[kMaxFramesCount];                 // Call stack.
+  void* contexts[kMaxFramesCount];  // Stack of associated native contexts.
+  void* top_context = nullptr;      // Address of the incumbent native context.
   unsigned frames_count : kMaxFramesCountLog2;  // Number of captured frames.
   bool has_external_callback : 1;
   bool update_stats : 1;  // Whether the sample should update aggregated stats.
@@ -337,21 +348,25 @@ class V8_EXPORT CpuProfilingOptions {
    *                             zero, the sampling interval will be equal to
    *                             the profiler's sampling interval.
    */
-  CpuProfilingOptions(CpuProfilingMode mode = kLeafNodeLineNumbers,
-                      unsigned max_samples = kNoSampleLimit,
-                      int sampling_interval_us = 0)
-      : mode_(mode),
-        max_samples_(max_samples),
-        sampling_interval_us_(sampling_interval_us) {}
+  CpuProfilingOptions(
+      CpuProfilingMode mode = kLeafNodeLineNumbers,
+      unsigned max_samples = kNoSampleLimit, int sampling_interval_us = 0,
+      MaybeLocal<Context> filter_context = MaybeLocal<Context>());
 
   CpuProfilingMode mode() const { return mode_; }
   unsigned max_samples() const { return max_samples_; }
   int sampling_interval_us() const { return sampling_interval_us_; }
 
  private:
+  friend class internal::CpuProfile;
+
+  bool has_filter_context() const { return !filter_context_.IsEmpty(); }
+  void* raw_filter_context() const;
+
   CpuProfilingMode mode_;
   unsigned max_samples_;
   int sampling_interval_us_;
+  CopyablePersistentTraits<Context>::CopyablePersistent filter_context_;
 };
 
 /**

include/v8.h

@@ -1968,6 +1968,7 @@ struct SampleInfo {
   StateTag vm_state;              // Current VM state.
   void* external_callback_entry;  // External callback address if VM is
                                   // executing an external callback.
+  void* top_context;              // Incumbent native context address.
 };
 
 struct MemoryRange {

src/api/api.cc

@@ -9845,6 +9845,27 @@ CpuProfiler* CpuProfiler::New(Isolate* isolate,
       reinterpret_cast<i::Isolate*>(isolate), naming_mode, logging_mode));
 }
 
+CpuProfilingOptions::CpuProfilingOptions(CpuProfilingMode mode,
+                                         unsigned max_samples,
+                                         int sampling_interval_us,
+                                         MaybeLocal<Context> filter_context)
+    : mode_(mode),
+      max_samples_(max_samples),
+      sampling_interval_us_(sampling_interval_us) {
+  if (!filter_context.IsEmpty()) {
+    Local<Context> local_filter_context = filter_context.ToLocalChecked();
+    filter_context_.Reset(local_filter_context->GetIsolate(),
+                          local_filter_context);
+  }
+}
+
+void* CpuProfilingOptions::raw_filter_context() const {
+  return reinterpret_cast<void*>(
+      i::Context::cast(*Utils::OpenPersistent(filter_context_))
+          .native_context()
+          .address());
+}
+
 void CpuProfiler::Dispose() { delete reinterpret_cast<i::CpuProfiler*>(this); }
 
 // static

src/api/api.h

@@ -251,9 +251,9 @@ class Utils {
   template <class From, class To>
   static inline Local<To> Convert(v8::internal::Handle<From> obj);
 
-  template <class T>
+  template <class T, class M>
   static inline v8::internal::Handle<v8::internal::Object> OpenPersistent(
-      const v8::Persistent<T>& persistent) {
+      const v8::Persistent<T, M>& persistent) {
     return v8::internal::Handle<v8::internal::Object>(
         reinterpret_cast<v8::internal::Address*>(persistent.val_));
   }

src/execution/frames.cc

@@ -270,6 +270,7 @@ SafeStackFrameIterator::SafeStackFrameIterator(Isolate* isolate, Address pc,
       low_bound_(sp),
       high_bound_(js_entry_sp),
       top_frame_type_(StackFrame::NONE),
+      top_context_address_(kNullAddress),
       external_callback_scope_(isolate->external_callback_scope()),
       top_link_register_(lr) {
   StackFrame::State state;
@@ -342,6 +343,13 @@ SafeStackFrameIterator::SafeStackFrameIterator(Isolate* isolate, Address pc,
       if (type != StackFrame::INTERPRETED) {
         advance_frame = true;
       }
+      MSAN_MEMORY_IS_INITIALIZED(
+          fp + CommonFrameConstants::kContextOrFrameTypeOffset,
+          kSystemPointerSize);
+      Address type_or_context_address =
+          Memory<Address>(fp + CommonFrameConstants::kContextOrFrameTypeOffset);
+      if (!StackFrame::IsTypeMarker(type_or_context_address))
+        top_context_address_ = type_or_context_address;
     } else {
       // Mark the frame as OPTIMIZED if we cannot determine its type.
       // We chose OPTIMIZED rather than INTERPRETED because it's closer to

src/execution/frames.h

@@ -1285,6 +1285,7 @@ class SafeStackFrameIterator : public StackFrameIteratorBase {
   void Advance();
 
   StackFrame::Type top_frame_type() const { return top_frame_type_; }
+  Address top_context_address() const { return top_context_address_; }
 
  private:
   void AdvanceOneFrame();
@@ -1308,6 +1309,7 @@ class SafeStackFrameIterator : public StackFrameIteratorBase {
   const Address low_bound_;
   const Address high_bound_;
   StackFrame::Type top_frame_type_;
+  Address top_context_address_;
   ExternalCallbackScope* external_callback_scope_;
   Address top_link_register_;
 };

src/heap/heap.cc

@@ -2923,6 +2923,9 @@ void Heap::OnMoveEvent(HeapObject target, HeapObject source,
   if (target.IsSharedFunctionInfo()) {
     LOG_CODE_EVENT(isolate_, SharedFunctionInfoMoveEvent(source.address(),
                                                          target.address()));
+  } else if (target.IsNativeContext()) {
+    PROFILE(isolate_,
+            NativeContextMoveEvent(source.address(), target.address()));
   }
 
   if (FLAG_verify_predictable) {

src/logging/code-events.h

@@ -89,6 +89,7 @@ class CodeEventListener {
   virtual void RegExpCodeCreateEvent(AbstractCode code, String source) = 0;
   virtual void CodeMoveEvent(AbstractCode from, AbstractCode to) = 0;
   virtual void SharedFunctionInfoMoveEvent(Address from, Address to) = 0;
+  virtual void NativeContextMoveEvent(Address from, Address to) = 0;
   virtual void CodeMovingGCEvent() = 0;
   virtual void CodeDisableOptEvent(AbstractCode code,
                                    SharedFunctionInfo shared) = 0;
@@ -164,6 +165,9 @@ class CodeEventDispatcher {
   void SharedFunctionInfoMoveEvent(Address from, Address to) {
     CODE_EVENT_DISPATCH(SharedFunctionInfoMoveEvent(from, to));
   }
+  void NativeContextMoveEvent(Address from, Address to) {
+    CODE_EVENT_DISPATCH(NativeContextMoveEvent(from, to));
+  }
   void CodeMovingGCEvent() { CODE_EVENT_DISPATCH(CodeMovingGCEvent()); }
   void CodeDisableOptEvent(AbstractCode code, SharedFunctionInfo shared) {
     CODE_EVENT_DISPATCH(CodeDisableOptEvent(code, shared));

src/logging/log.h

@@ -216,6 +216,8 @@ class Logger : public CodeEventListener {
 
   void SharedFunctionInfoMoveEvent(Address from, Address to) override;
 
+  void NativeContextMoveEvent(Address from, Address to) override {}
+
   void CodeNameEvent(Address addr, int pos, const char* code_name);
 
   void CodeDeoptEvent(Code code, DeoptimizeKind kind, Address pc,
@@ -401,6 +403,7 @@ class V8_EXPORT_PRIVATE CodeEventLogger : public CodeEventListener {
   void GetterCallbackEvent(Name name, Address entry_point) override {}
   void SetterCallbackEvent(Name name, Address entry_point) override {}
   void SharedFunctionInfoMoveEvent(Address from, Address to) override {}
+  void NativeContextMoveEvent(Address from, Address to) override {}
   void CodeMovingGCEvent() override {}
   void CodeDeoptEvent(Code code, DeoptimizeKind kind, Address pc,
                       int fp_to_sp_delta) override {}
@@ -453,6 +456,7 @@ class ExternalCodeEventListener : public CodeEventListener {
   void GetterCallbackEvent(Name name, Address entry_point) override {}
   void SetterCallbackEvent(Name name, Address entry_point) override {}
   void SharedFunctionInfoMoveEvent(Address from, Address to) override {}
+  void NativeContextMoveEvent(Address from, Address to) override {}
   void CodeMoveEvent(AbstractCode from, AbstractCode to) override {}
   void CodeDisableOptEvent(AbstractCode code,
                            SharedFunctionInfo shared) override {}

src/profiler/cpu-profiler.cc

@@ -161,7 +161,14 @@ void ProfilerEventsProcessor::StopSynchronously() {
 bool ProfilerEventsProcessor::ProcessCodeEvent() {
   CodeEventsContainer record;
   if (events_buffer_.Dequeue(&record)) {
-    code_observer_->CodeEventHandlerInternal(record);
+    if (record.generic.type == CodeEventRecord::NATIVE_CONTEXT_MOVE) {
+      NativeContextMoveEventRecord& nc_record =
+          record.NativeContextMoveEventRecord_;
+      generator_->UpdateNativeContextAddress(nc_record.from_address,
+                                             nc_record.to_address);
+    } else {
+      code_observer_->CodeEventHandlerInternal(record);
+    }
     last_processed_code_event_id_ = record.generic.order;
     return true;
   }
@@ -174,6 +181,7 @@ void ProfilerEventsProcessor::CodeEventHandler(
     case CodeEventRecord::CODE_CREATION:
     case CodeEventRecord::CODE_MOVE:
     case CodeEventRecord::CODE_DISABLE_OPT:
+    case CodeEventRecord::NATIVE_CONTEXT_MOVE:
       Enqueue(evt_rec);
       break;
     case CodeEventRecord::CODE_DEOPT: {

src/profiler/cpu-profiler.h

@@ -13,6 +13,7 @@
 #include "src/base/platform/mutex.h"
 #include "src/base/platform/time.h"
 #include "src/execution/isolate.h"
+#include "src/handles/maybe-handles.h"
 #include "src/libsampler/sampler.h"
 #include "src/profiler/circular-queue.h"
 #include "src/profiler/profiler-listener.h"
@@ -30,21 +31,21 @@ class CpuProfile;
 class CpuProfilesCollection;
 class ProfileGenerator;
 
-#define CODE_EVENTS_TYPE_LIST(V)                         \
-  V(CODE_CREATION, CodeCreateEventRecord)                \
-  V(CODE_MOVE, CodeMoveEventRecord)                      \
-  V(CODE_DISABLE_OPT, CodeDisableOptEventRecord)         \
-  V(CODE_DEOPT, CodeDeoptEventRecord)                    \
+#define CODE_EVENTS_TYPE_LIST(V)                 \
+  V(CODE_CREATION, CodeCreateEventRecord)        \
+  V(CODE_MOVE, CodeMoveEventRecord)              \
+  V(CODE_DISABLE_OPT, CodeDisableOptEventRecord) \
+  V(CODE_DEOPT, CodeDeoptEventRecord)            \
   V(REPORT_BUILTIN, ReportBuiltinEventRecord)
 
+#define VM_EVENTS_TYPE_LIST(V) \
+  CODE_EVENTS_TYPE_LIST(V)     \
+  V(NATIVE_CONTEXT_MOVE, NativeContextMoveEventRecord)
 
 class CodeEventRecord {
  public:
 #define DECLARE_TYPE(type, ignore) type,
-  enum Type {
-    NONE = 0,
-    CODE_EVENTS_TYPE_LIST(DECLARE_TYPE)
-  };
+  enum Type { NONE = 0, VM_EVENTS_TYPE_LIST(DECLARE_TYPE) };
 #undef DECLARE_TYPE
 
   Type type;
@@ -102,6 +103,12 @@ class ReportBuiltinEventRecord : public CodeEventRecord {
   V8_INLINE void UpdateCodeMap(CodeMap* code_map);
 };
 
+// Signals that a native context's address has changed.
+class NativeContextMoveEventRecord : public CodeEventRecord {
+ public:
+  Address from_address;
+  Address to_address;
+};
 
 class TickSampleEventRecord {
  public:
@@ -124,7 +131,7 @@ class CodeEventsContainer {
   union  {
     CodeEventRecord generic;
 #define DECLARE_CLASS(ignore, type) type type##_;
-    CODE_EVENTS_TYPE_LIST(DECLARE_CLASS)
+    VM_EVENTS_TYPE_LIST(DECLARE_CLASS)
 #undef DECLARE_CLASS
   };
 };
@@ -293,6 +300,7 @@ class V8_EXPORT_PRIVATE CpuProfiler {
   void CollectSample();
   void StartProfiling(const char* title, CpuProfilingOptions options = {});
   void StartProfiling(String title, CpuProfilingOptions options = {});
+
   CpuProfile* StopProfiling(const char* title);
   CpuProfile* StopProfiling(String title);
   int GetProfilesCount();

src/profiler/profile-generator.cc

@@ -412,16 +412,18 @@ ProfileNode* ProfileTree::AddPathFromEnd(const std::vector<CodeEntry*>& path,
 
 ProfileNode* ProfileTree::AddPathFromEnd(const ProfileStackTrace& path,
                                          int src_line, bool update_stats,
-                                         ProfilingMode mode) {
+                                         ProfilingMode mode,
+                                         ContextFilter* context_filter) {
   ProfileNode* node = root_;
   CodeEntry* last_entry = nullptr;
   int parent_line_number = v8::CpuProfileNode::kNoLineNumberInfo;
   for (auto it = path.rbegin(); it != path.rend(); ++it) {
-    if ((*it).code_entry == nullptr) continue;
-    last_entry = (*it).code_entry;
-    node = node->FindOrAddChild((*it).code_entry, parent_line_number);
+    if (it->entry.code_entry == nullptr) continue;
+    if (context_filter && !context_filter->Accept(*it)) continue;
+    last_entry = (*it).entry.code_entry;
+    node = node->FindOrAddChild((*it).entry.code_entry, parent_line_number);
     parent_line_number = mode == ProfilingMode::kCallerLineNumbers
-                             ? (*it).line_number
+                             ? (*it).entry.line_number
                              : v8::CpuProfileNode::kNoLineNumberInfo;
   }
   if (last_entry && last_entry->has_deopt_info()) {
@@ -436,7 +438,6 @@ ProfileNode* ProfileTree::AddPathFromEnd(const ProfileStackTrace& path,
   return node;
 }
 
-
 class Position {
  public:
   explicit Position(ProfileNode* node)
@@ -478,6 +479,21 @@ void ProfileTree::TraverseDepthFirst(Callback* callback) {
   }
 }
 
+bool ContextFilter::Accept(const ProfileStackFrame& frame) {
+  // If a frame should always be included in profiles (e.g. metadata frames),
+  // skip the context check.
+  if (!frame.filterable) return true;
+
+  // Strip heap object tag from frame.
+  return (frame.native_context & ~kHeapObjectTag) == native_context_address_;
+}
+
+void ContextFilter::OnMoveEvent(Address from_address, Address to_address) {
+  if (native_context_address() != from_address) return;
+
+  set_native_context_address(to_address);
+}
+
 using v8::tracing::TracedValue;
 
 std::atomic<uint32_t> CpuProfile::last_id_;
@@ -496,6 +512,13 @@ CpuProfile::CpuProfile(CpuProfiler* profiler, const char* title,
                    (start_time_ - base::TimeTicks()).InMicroseconds());
   TRACE_EVENT_SAMPLE_WITH_ID1(TRACE_DISABLED_BY_DEFAULT("v8.cpu_profiler"),
                               "Profile", id_, "data", std::move(value));
+
+  if (options_.has_filter_context()) {
+    DisallowHeapAllocation no_gc;
+    i::Address raw_filter_context =
+        reinterpret_cast<i::Address>(options_.raw_filter_context());
+    context_filter_ = base::make_unique<ContextFilter>(raw_filter_context);
+  }
 }
 
 bool CpuProfile::CheckSubsample(base::TimeDelta source_sampling_interval) {
@@ -520,11 +543,11 @@ void CpuProfile::AddPath(base::TimeTicks timestamp,
                          bool update_stats, base::TimeDelta sampling_interval) {
   if (!CheckSubsample(sampling_interval)) return;
 
-  ProfileNode* top_frame_node =
-      top_down_.AddPathFromEnd(path, src_line, update_stats, options_.mode());
+  ProfileNode* top_frame_node = top_down_.AddPathFromEnd(
+      path, src_line, update_stats, options_.mode(), context_filter_.get());
 
   bool should_record_sample =
-      !timestamp.IsNull() &&
+      !timestamp.IsNull() && timestamp >= start_time_ &&
       (options_.max_samples() == CpuProfilingOptions::kNoSampleLimit ||
        samples_.size() < options_.max_samples());
 
@@ -623,6 +646,8 @@ void CpuProfile::StreamPendingTraceEvents() {
 
 void CpuProfile::FinishProfile() {
   end_time_ = base::TimeTicks::HighResolutionNow();
+  // Stop tracking context movements after profiling stops.
+  context_filter_ = nullptr;
   StreamPendingTraceEvents();
   auto value = TracedValue::Create();
   value->SetDouble("endTime", (end_time_ - base::TimeTicks()).InMicroseconds());
@@ -833,6 +858,17 @@ void CpuProfilesCollection::AddPathToCurrentProfiles(
   current_profiles_semaphore_.Signal();
 }
 
+void CpuProfilesCollection::UpdateNativeContextAddressForCurrentProfiles(
+    Address from, Address to) {
+  current_profiles_semaphore_.Wait();
+  for (const std::unique_ptr<CpuProfile>& profile : current_profiles_) {
+    if (auto* context_filter = profile->context_filter()) {
+      context_filter->OnMoveEvent(from, to);
+    }
+  }
+  current_profiles_semaphore_.Signal();
+}
+
 ProfileGenerator::ProfileGenerator(CpuProfilesCollection* profiles,
                                    CodeMap* code_map)
     : profiles_(profiles), code_map_(code_map) {}
@@ -857,9 +893,11 @@ void ProfileGenerator::RecordTickSample(const TickSample& sample) {
       // Don't use PC when in external callback code, as it can point
       // inside a callback's code, and we will erroneously report
       // that a callback calls itself.
-      stack_trace.push_back(
-          {FindEntry(reinterpret_cast<Address>(sample.external_callback_entry)),
-           no_line_info});
+      stack_trace.push_back({{FindEntry(reinterpret_cast<Address>(
+                                  sample.external_callback_entry)),
+                              no_line_info},
+                             reinterpret_cast<Address>(sample.top_context),
+                             true});
     } else {
       Address attributed_pc = reinterpret_cast<Address>(sample.pc);
       CodeEntry* pc_entry = FindEntry(attributed_pc);
@@ -883,7 +921,9 @@ void ProfileGenerator::RecordTickSample(const TickSample& sample) {
           src_line = pc_entry->line_number();
         }
         src_line_not_found = false;
-        stack_trace.push_back({pc_entry, src_line});
+        stack_trace.push_back({{pc_entry, src_line},
+                               reinterpret_cast<Address>(sample.top_context),
+                               true});
 
         if (pc_entry->builtin_id() == Builtins::kFunctionPrototypeApply ||
             pc_entry->builtin_id() == Builtins::kFunctionPrototypeCall) {
@@ -895,7 +935,9 @@ void ProfileGenerator::RecordTickSample(const TickSample& sample) {
           // 'unresolved' entry.
           if (!sample.has_external_callback) {
             stack_trace.push_back(
-                {CodeEntry::unresolved_entry(), no_line_info});
+                {{CodeEntry::unresolved_entry(), no_line_info},
+                 kNullAddress,
+                 true});
           }
         }
       }
@@ -903,6 +945,7 @@ void ProfileGenerator::RecordTickSample(const TickSample& sample) {
 
     for (unsigned i = 0; i < sample.frames_count; ++i) {
       Address stack_pos = reinterpret_cast<Address>(sample.stack[i]);
+      Address native_context = reinterpret_cast<Address>(sample.contexts[i]);
       CodeEntry* entry = FindEntry(stack_pos);
       int line_number = no_line_info;
       if (entry) {
@@ -914,8 +957,13 @@ void ProfileGenerator::RecordTickSample(const TickSample& sample) {
             entry->GetInlineStack(pc_offset);
         if (inline_stack) {
           int most_inlined_frame_line_number = entry->GetSourceLine(pc_offset);
-          stack_trace.insert(stack_trace.end(), inline_stack->begin(),
-                             inline_stack->end());
+          for (auto entry : *inline_stack) {
+            // Set the native context of inlined frames to be equal to that of
+            // their parent. This is safe, as functions cannot inline themselves
+            // into a parent from another native context.
+            stack_trace.push_back({entry, native_context, true});
+          }
+
           // This is a bit of a messy hack. The line number for the most-inlined
           // frame (the function at the end of the chain of function calls) has
           // the wrong line number in inline_stack. The actual line number in
@@ -925,7 +973,7 @@ void ProfileGenerator::RecordTickSample(const TickSample& sample) {
           // inlining_id.
           DCHECK(!inline_stack->empty());
           size_t index = stack_trace.size() - inline_stack->size();
-          stack_trace[index].line_number = most_inlined_frame_line_number;
+          stack_trace[index].entry.line_number = most_inlined_frame_line_number;
         }
         // Skip unresolved frames (e.g. internal frame) and get source line of
         // the first JS caller.
@@ -944,21 +992,22 @@ void ProfileGenerator::RecordTickSample(const TickSample& sample) {
         // so we use it instead of pushing entry to stack_trace.
         if (inline_stack) continue;
       }
-      stack_trace.push_back({entry, line_number});
+      stack_trace.push_back({{entry, line_number}, native_context, true});
     }
   }
 
   if (FLAG_prof_browser_mode) {
     bool no_symbolized_entries = true;
     for (auto e : stack_trace) {
-      if (e.code_entry != nullptr) {
+      if (e.entry.code_entry != nullptr) {
         no_symbolized_entries = false;
         break;
       }
     }
     // If no frames were symbolized, put the VM state entry in.
     if (no_symbolized_entries) {
-      stack_trace.push_back({EntryForVMState(sample.state), no_line_info});
+      stack_trace.push_back(
+          {{EntryForVMState(sample.state), no_line_info}, kNullAddress, false});
     }
   }
 
@@ -967,6 +1016,10 @@ void ProfileGenerator::RecordTickSample(const TickSample& sample) {
                                       sample.sampling_interval);
 }
 
+void ProfileGenerator::UpdateNativeContextAddress(Address from, Address to) {
+  profiles_->UpdateNativeContextAddressForCurrentProfiles(from, to);
+}
+
 CodeEntry* ProfileGenerator::EntryForVMState(StateTag tag) {
   switch (tag) {
     case GC:

src/profiler/profile-generator.h

@@ -234,7 +234,36 @@ struct CodeEntryAndLineNumber {
   int line_number;
 };
 
-using ProfileStackTrace = std::vector<CodeEntryAndLineNumber>;
+struct ProfileStackFrame {
+  CodeEntryAndLineNumber entry;
+  Address native_context;
+  bool filterable;  // If true, the frame should be filtered by context (if a
+                    // filter is present).
+};
+
+typedef std::vector<ProfileStackFrame> ProfileStackTrace;
+
+// Filters stack frames from sources other than a target native context.
+class ContextFilter {
+ public:
+  explicit ContextFilter(Address native_context_address)
+      : native_context_address_(native_context_address) {}
+
+  // Returns true if the stack frame passes a context check.
+  bool Accept(const ProfileStackFrame&);
+
+  // Invoked when a native context has changed address.
+  void OnMoveEvent(Address from_address, Address to_address);
+
+  // Update the context's tracked address based on VM-thread events.
+  void set_native_context_address(Address address) {
+    native_context_address_ = address;
+  }
+  Address native_context_address() const { return native_context_address_; }
+
+ private:
+  Address native_context_address_;
+};
 
 class ProfileTree;
 
@@ -321,7 +350,8 @@ class V8_EXPORT_PRIVATE ProfileTree {
       const ProfileStackTrace& path,
       int src_line = v8::CpuProfileNode::kNoLineNumberInfo,
       bool update_stats = true,
-      ProfilingMode mode = ProfilingMode::kLeafNodeLineNumbers);
+      ProfilingMode mode = ProfilingMode::kLeafNodeLineNumbers,
+      ContextFilter* context_filter = nullptr);
   ProfileNode* root() const { return root_; }
   unsigned next_node_id() { return next_node_id_++; }
   unsigned GetFunctionId(const ProfileNode* node);
@@ -389,6 +419,7 @@ class CpuProfile {
   base::TimeTicks start_time() const { return start_time_; }
   base::TimeTicks end_time() const { return end_time_; }
   CpuProfiler* cpu_profiler() const { return profiler_; }
+  ContextFilter* context_filter() const { return context_filter_.get(); }
 
   void UpdateTicksScale();
 
@@ -399,6 +430,7 @@ class CpuProfile {
 
   const char* title_;
   const CpuProfilingOptions options_;
+  std::unique_ptr<ContextFilter> context_filter_;
   base::TimeTicks start_time_;
   base::TimeTicks end_time_;
   std::deque<SampleInfo> samples_;
@@ -477,6 +509,9 @@ class V8_EXPORT_PRIVATE CpuProfilesCollection {
                                 bool update_stats,
                                 base::TimeDelta sampling_interval);
 
+  // Called from profile generator thread.
+  void UpdateNativeContextAddressForCurrentProfiles(Address from, Address to);
+
   // Limits the number of profiles that can be simultaneously collected.
   static const int kMaxSimultaneousProfiles = 100;
 
@@ -498,6 +533,8 @@ class V8_EXPORT_PRIVATE ProfileGenerator {
 
   void RecordTickSample(const TickSample& sample);
 
+  void UpdateNativeContextAddress(Address from, Address to);
+
   CodeMap* code_map() { return code_map_; }
 
  private:

src/profiler/profiler-listener.cc

@@ -177,8 +177,7 @@ void ProfilerListener::CodeCreateEvent(CodeEventListener::LogEventsAndTags tag,
           CodeEntry* cached_entry = GetOrInsertCachedEntry(
               &cached_inline_entries, std::move(inline_entry));
 
-          inline_stack.push_back(
-              CodeEntryAndLineNumber{cached_entry, line_number});
+          inline_stack.push_back({cached_entry, line_number});
         }
         DCHECK(!inline_stack.empty());
         inline_stacks.emplace(inlining_id, std::move(inline_stack));
@@ -280,6 +279,13 @@ void ProfilerListener::SetterCallbackEvent(Name name, Address entry_point) {
   DispatchCodeEvent(evt_rec);
 }
 
+void ProfilerListener::NativeContextMoveEvent(Address from, Address to) {
+  CodeEventsContainer evt_rec(CodeEventRecord::NATIVE_CONTEXT_MOVE);
+  evt_rec.NativeContextMoveEventRecord_.from_address = from;
+  evt_rec.NativeContextMoveEventRecord_.to_address = to;
+  DispatchCodeEvent(evt_rec);
+}
+
 Name ProfilerListener::InferScriptName(Name name, SharedFunctionInfo info) {
   if (name.IsString() && String::cast(name).length()) return name;
   if (!info.script().IsScript()) return name;

src/profiler/profiler-listener.h

@@ -55,6 +55,7 @@ class V8_EXPORT_PRIVATE ProfilerListener : public CodeEventListener {
   void RegExpCodeCreateEvent(AbstractCode code, String source) override;
   void SetterCallbackEvent(Name name, Address entry_point) override;
   void SharedFunctionInfoMoveEvent(Address from, Address to) override {}
+  void NativeContextMoveEvent(Address from, Address to) override;
 
   const char* GetName(Name name) {
     return function_and_resource_names_.GetName(name);

src/profiler/tick-sample.cc

@@ -147,6 +147,42 @@ bool SimulatorHelper::FillRegisters(Isolate* isolate,
 }
 #endif  // USE_SIMULATOR
 
+// Attempts to safely dereference the address of a native context at a given
+// context's address. Returns kNullAddress on failure, in the event that the
+// context is in an inconsistent state.
+Address ScrapeNativeContextAddress(Heap* heap, Address context_address) {
+  DCHECK_EQ(heap->gc_state(), Heap::NOT_IN_GC);
+
+  if (!HAS_STRONG_HEAP_OBJECT_TAG(context_address)) return kNullAddress;
+
+  if (heap->memory_allocator()->IsOutsideAllocatedSpace(context_address))
+    return kNullAddress;
+
+  // Note that once a native context has been assigned to a context, the slot
+  // is no longer mutated except during pointer updates / evictions. Since
+  // pointer updates exclusively occur on the main thread, and we don't record
+  // TickSamples when the main thread's VM state is GC, the only other
+  // situation where the address here would be invalid is if it's being
+  // reassigned -- which isn't possible.
+  int native_context_offset =
+      i::Context::SlotOffset(i::Context::NATIVE_CONTEXT_INDEX);
+  i::Address native_context_slot_address =
+      context_address + native_context_offset;
+
+  // By the prior hypothesis, the indirect native context address should always
+  // be valid.
+  if (heap->memory_allocator()->IsOutsideAllocatedSpace(
+          native_context_slot_address)) {
+    DCHECK(false);
+    return kNullAddress;
+  }
+
+  i::ObjectSlot native_context_slot(native_context_slot_address);
+  i::Object native_context = native_context_slot.Relaxed_Load();
+
+  return native_context.ptr();
+}
+
 }  // namespace
 }  // namespace internal
 
@@ -162,7 +198,8 @@ DISABLE_ASAN void TickSample::Init(Isolate* v8_isolate,
   SampleInfo info;
   RegisterState regs = reg_state;
   if (!GetStackSample(v8_isolate, &regs, record_c_entry_frame, stack,
-                      kMaxFramesCount, &info, use_simulator_reg_state)) {
+                      kMaxFramesCount, &info, use_simulator_reg_state,
+                      contexts)) {
     // It is executing JS but failed to collect a stack trace.
     // Mark the sample as spoiled.
     pc = nullptr;
@@ -173,6 +210,7 @@ DISABLE_ASAN void TickSample::Init(Isolate* v8_isolate,
   pc = regs.pc;
   frames_count = static_cast<unsigned>(info.frames_count);
   has_external_callback = info.external_callback_entry != nullptr;
+  top_context = info.top_context;
   if (has_external_callback) {
     external_callback_entry = info.external_callback_entry;
   } else if (frames_count) {
@@ -197,11 +235,12 @@ bool TickSample::GetStackSample(Isolate* v8_isolate, RegisterState* regs,
                                 RecordCEntryFrame record_c_entry_frame,
                                 void** frames, size_t frames_limit,
                                 v8::SampleInfo* sample_info,
-                                bool use_simulator_reg_state) {
+                                bool use_simulator_reg_state, void** contexts) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(v8_isolate);
   sample_info->frames_count = 0;
   sample_info->vm_state = isolate->current_vm_state();
   sample_info->external_callback_entry = nullptr;
+  sample_info->top_context = nullptr;
   if (sample_info->vm_state == GC) return true;
 
   i::Address js_entry_sp = isolate->js_entry_sp();
@@ -229,7 +268,7 @@ bool TickSample::GetStackSample(Isolate* v8_isolate, RegisterState* regs,
   i::ExternalCallbackScope* scope = isolate->external_callback_scope();
   i::Address handler = i::Isolate::handler(isolate->thread_local_top());
   // If there is a handler on top of the external callback scope then
-  // we have already entrered JavaScript again and the external callback
+  // we have already entered JavaScript again and the external callback
   // is not the top function.
   if (scope && scope->scope_address() < handler) {
     i::Address* external_callback_entry_ptr =
@@ -245,23 +284,62 @@ bool TickSample::GetStackSample(Isolate* v8_isolate, RegisterState* regs,
                                reinterpret_cast<i::Address>(regs->sp),
                                reinterpret_cast<i::Address>(regs->lr),
                                js_entry_sp);
+
+  i::Address top_context_address = it.top_context_address();
+  if (top_context_address != i::kNullAddress) {
+    sample_info->top_context = reinterpret_cast<void*>(
+        i::ScrapeNativeContextAddress(isolate->heap(), top_context_address));
+  } else {
+    sample_info->top_context = nullptr;
+  }
+
   if (it.done()) return true;
 
   size_t i = 0;
   if (record_c_entry_frame == kIncludeCEntryFrame &&
       (it.top_frame_type() == internal::StackFrame::EXIT ||
        it.top_frame_type() == internal::StackFrame::BUILTIN_EXIT)) {
-    frames[i++] = reinterpret_cast<void*>(isolate->c_function());
+    frames[i] = reinterpret_cast<void*>(isolate->c_function());
+    if (contexts) contexts[i] = sample_info->top_context;
+    i++;
   }
+
+  // If we couldn't get a context address from the top frame due to execution
+  // being in a callback, borrow it from the next context on the stack.
+  bool borrows_top_context = it.top_frame_type() == i::StackFrame::EXIT ||
+                             it.top_frame_type() == i::StackFrame::BUILTIN_EXIT;
+
   i::RuntimeCallTimer* timer =
       isolate->counters()->runtime_call_stats()->current_timer();
   for (; !it.done() && i < frames_limit; it.Advance()) {
     while (timer && reinterpret_cast<i::Address>(timer) < it.frame()->fp() &&
            i < frames_limit) {
+      if (contexts) contexts[i] = nullptr;
       frames[i++] = reinterpret_cast<void*>(timer->counter());
       timer = timer->parent();
     }
     if (i == frames_limit) break;
+
+    // Attempt to read the native context associated with the frame from the
+    // heap for standard frames.
+    if (it.frame()->is_standard() && (contexts || borrows_top_context)) {
+      i::Address context_address = base::Memory<i::Address>(
+          it.frame()->fp() + i::StandardFrameConstants::kContextOffset);
+      i::Address native_context_address =
+          i::ScrapeNativeContextAddress(isolate->heap(), context_address);
+      if (contexts)
+        contexts[i] = reinterpret_cast<void*>(native_context_address);
+
+      if (borrows_top_context) {
+        DCHECK(!sample_info->top_context);
+        sample_info->top_context =
+            reinterpret_cast<void*>(native_context_address);
+      }
+    } else if (contexts) {
+      contexts[i] = nullptr;
+    }
+    borrows_top_context = false;
+
     if (it.frame()->is_interpreted()) {
       // For interpreted frames use the bytecode array pointer as the pc.
       i::InterpretedFrame* frame =

src/runtime/runtime-test.cc

@@ -1305,6 +1305,7 @@ RUNTIME_FUNCTION(Runtime_EnableCodeLoggingForTesting) {
     void RegExpCodeCreateEvent(AbstractCode code, String source) final {}
     void CodeMoveEvent(AbstractCode from, AbstractCode to) final {}
     void SharedFunctionInfoMoveEvent(Address from, Address to) final {}
+    void NativeContextMoveEvent(Address from, Address to) final {}
     void CodeMovingGCEvent() final {}
     void CodeDisableOptEvent(AbstractCode code,
                              SharedFunctionInfo shared) final {}

test/cctest/test-cpu-profiler.cc

@@ -37,6 +37,7 @@
 #include "src/base/platform/platform.h"
 #include "src/codegen/source-position-table.h"
 #include "src/deoptimizer/deoptimizer.h"
+#include "src/heap/spaces.h"
 #include "src/libplatform/default-platform.h"
 #include "src/logging/log.h"
 #include "src/objects/objects-inl.h"
@@ -45,6 +46,7 @@
 #include "src/profiler/tracing-cpu-profiler.h"
 #include "src/utils/utils.h"
 #include "test/cctest/cctest.h"
+#include "test/cctest/heap/heap-utils.h"
 #include "test/cctest/profiler-extension.h"
 
 #include "include/libplatform/v8-tracing.h"
@@ -456,7 +458,8 @@ class ProfilerHelper {
       v8::Local<v8::Function> function, v8::Local<v8::Value> argv[], int argc,
       unsigned min_js_samples = 0, unsigned min_external_samples = 0,
       ProfilingMode mode = ProfilingMode::kLeafNodeLineNumbers,
-      unsigned max_samples = CpuProfilingOptions::kNoSampleLimit);
+      unsigned max_samples = v8::CpuProfilingOptions::kNoSampleLimit,
+      v8::Local<v8::Context> context = v8::Local<v8::Context>());
 
   v8::CpuProfiler* profiler() { return profiler_; }
 
@@ -469,11 +472,12 @@ v8::CpuProfile* ProfilerHelper::Run(v8::Local<v8::Function> function,
                                     v8::Local<v8::Value> argv[], int argc,
                                     unsigned min_js_samples,
                                     unsigned min_external_samples,
-                                    ProfilingMode mode, unsigned max_samples) {
+                                    ProfilingMode mode, unsigned max_samples,
+                                    v8::Local<v8::Context> context) {
   v8::Local<v8::String> profile_name = v8_str("my_profile");
 
   profiler_->SetSamplingInterval(100);
-  profiler_->StartProfiling(profile_name, {mode, max_samples});
+  profiler_->StartProfiling(profile_name, {mode, max_samples, 0, context});
 
   v8::internal::CpuProfiler* iprofiler =
       reinterpret_cast<v8::internal::CpuProfiler*>(profiler_);
@@ -481,6 +485,7 @@ v8::CpuProfile* ProfilerHelper::Run(v8::Local<v8::Function> function,
       reinterpret_cast<i::SamplingEventsProcessor*>(iprofiler->processor())
           ->sampler();
   sampler->StartCountingSamples();
+
   do {
     function->Call(context_, context_->Global(), argc, argv).ToLocalChecked();
   } while (sampler->js_sample_count() < min_js_samples ||
@@ -1825,7 +1830,7 @@ TEST(Inlining2) {
   v8::Local<v8::String> profile_name = v8_str("inlining");
   profiler->StartProfiling(
       profile_name,
-      CpuProfilingOptions{v8::CpuProfilingMode::kCallerLineNumbers});
+      v8::CpuProfilingOptions{v8::CpuProfilingMode::kCallerLineNumbers});
 
   v8::Local<v8::Value> args[] = {
       v8::Integer::New(env->GetIsolate(), 50000 * load_factor)};
@@ -3467,6 +3472,140 @@ TEST(Bug9151StaleCodeEntries) {
   CHECK(callback);
 }
 
+// Tests that functions from other contexts aren't recorded when filtering for
+// another context.
+TEST(ContextIsolation) {
+  i::FLAG_allow_natives_syntax = true;
+  LocalContext execution_env;
+  i::HandleScope scope(CcTest::i_isolate());
+
+  // Install CollectSample callback for more deterministic sampling.
+  v8::Local<v8::FunctionTemplate> func_template = v8::FunctionTemplate::New(
+      execution_env.local()->GetIsolate(), CallCollectSample);
+  v8::Local<v8::Function> func =
+      func_template->GetFunction(execution_env.local()).ToLocalChecked();
+  func->SetName(v8_str("CallCollectSample"));
+  execution_env->Global()
+      ->Set(execution_env.local(), v8_str("CallCollectSample"), func)
+      .FromJust();
+
+  ProfilerHelper helper(execution_env.local());
+  CompileRun(R"(
+    function optimized() {
+      CallCollectSample();
+    }
+
+    function unoptimized() {
+      CallCollectSample();
+    }
+
+    function start() {
+      // Test optimized functions
+      %PrepareFunctionForOptimization(optimized);
+      optimized();
+      optimized();
+      %OptimizeFunctionOnNextCall(optimized);
+      optimized();
+
+      // Test unoptimized functions
+      %NeverOptimizeFunction(unoptimized);
+      unoptimized();
+
+      // Test callback
+      CallCollectSample();
+    }
+  )");
+  v8::Local<v8::Function> function =
+      GetFunction(execution_env.local(), "start");
+
+  v8::CpuProfile* same_context_profile = helper.Run(
+      function, nullptr, 0, 0, 0, v8::CpuProfilingMode::kLeafNodeLineNumbers,
+      v8::CpuProfilingOptions::kNoSampleLimit, execution_env.local());
+  const v8::CpuProfileNode* root = same_context_profile->GetTopDownRoot();
+  const v8::CpuProfileNode* start_node = FindChild(root, "start");
+  CHECK(start_node);
+  const v8::CpuProfileNode* optimized_node = FindChild(start_node, "optimized");
+  CHECK(optimized_node);
+  const v8::CpuProfileNode* unoptimized_node =
+      FindChild(start_node, "unoptimized");
+  CHECK(unoptimized_node);
+  const v8::CpuProfileNode* callback_node =
+      FindChild(start_node, "CallCollectSample");
+  CHECK(callback_node);
+
+  {
+    LocalContext filter_env;
+    v8::CpuProfile* diff_context_profile = helper.Run(
+        function, nullptr, 0, 0, 0, v8::CpuProfilingMode::kLeafNodeLineNumbers,
+        v8::CpuProfilingOptions::kNoSampleLimit, filter_env.local());
+    const v8::CpuProfileNode* diff_root =
+        diff_context_profile->GetTopDownRoot();
+    // Ensure that no children were recorded (including callbacks, builtins).
+    CHECK(!FindChild(diff_root, "start"));
+  }
+}
+
+// Tests that when a native context that's being filtered is moved, we continue
+// to track its execution.
+TEST(ContextFilterMovedNativeContext) {
+  i::FLAG_allow_natives_syntax = true;
+  i::FLAG_manual_evacuation_candidates_selection = true;
+  LocalContext env;
+  i::HandleScope scope(CcTest::i_isolate());
+
+  {
+    // Install CollectSample callback for more deterministic sampling.
+    v8::Local<v8::FunctionTemplate> sample_func_template =
+        v8::FunctionTemplate::New(env.local()->GetIsolate(), CallCollectSample);
+    v8::Local<v8::Function> sample_func =
+        sample_func_template->GetFunction(env.local()).ToLocalChecked();
+    sample_func->SetName(v8_str("CallCollectSample"));
+    env->Global()
+        ->Set(env.local(), v8_str("CallCollectSample"), sample_func)
+        .FromJust();
+
+    // Install a function that triggers the native context to be moved.
+    v8::Local<v8::FunctionTemplate> move_func_template =
+        v8::FunctionTemplate::New(
+            env.local()->GetIsolate(),
+            [](const v8::FunctionCallbackInfo<v8::Value>& info) {
+              i::Isolate* isolate =
+                  reinterpret_cast<i::Isolate*>(info.GetIsolate());
+              i::heap::ForceEvacuationCandidate(
+                  i::Page::FromHeapObject(isolate->raw_native_context()));
+              CcTest::CollectAllGarbage();
+            });
+    v8::Local<v8::Function> move_func =
+        move_func_template->GetFunction(env.local()).ToLocalChecked();
+    move_func->SetName(v8_str("ForceNativeContextMove"));
+    env->Global()
+        ->Set(env.local(), v8_str("ForceNativeContextMove"), move_func)
+        .FromJust();
+
+    ProfilerHelper helper(env.local());
+    CompileRun(R"(
+      function start() {
+        ForceNativeContextMove();
+        CallCollectSample();
+      }
+    )");
+    v8::Local<v8::Function> function = GetFunction(env.local(), "start");
+
+    v8::CpuProfile* profile = helper.Run(
+        function, nullptr, 0, 0, 0, v8::CpuProfilingMode::kLeafNodeLineNumbers,
+        v8::CpuProfilingOptions::kNoSampleLimit, env.local());
+    const v8::CpuProfileNode* root = profile->GetTopDownRoot();
+    const v8::CpuProfileNode* start_node = FindChild(root, "start");
+    CHECK(start_node);
+
+    // Verify that after moving the native context, CallCollectSample is still
+    // recorded.
+    const v8::CpuProfileNode* callback_node =
+        FindChild(start_node, "CallCollectSample");
+    CHECK(callback_node);
+  }
+}
+
 enum class EntryCountMode { kAll, kOnlyInlined };
 
 // Count the number of unique source positions.

test/cctest/test-profile-generator.cc

@@ -200,7 +200,9 @@ TEST(ProfileTreeAddPathFromEndWithLineNumbers) {
   ProfileTree tree(CcTest::i_isolate());
   ProfileTreeTestHelper helper(&tree);
 
-  ProfileStackTrace path = {{&c, 5}, {&b, 3}, {&a, 1}};
+  ProfileStackTrace path = {{{&c, 5}, kNullAddress, false},
+                            {{&b, 3}, kNullAddress, false},
+                            {{&a, 1}, kNullAddress, false}};
   tree.AddPathFromEnd(path, v8::CpuProfileNode::kNoLineNumberInfo, true,
                       v8::CpuProfilingMode::kCallerLineNumbers);