Fix MSAN error on arm64 bot.

The main fix is to mark stack memory the SafeStackFrameIterator
accesses as initialied.

Drive-by: Make sure we bail out when the simulator is in the
process of updating FP/SP registers.

BUG=v8:5156

Review-Url: https://codereview.chromium.org/2104763002
Cr-Commit-Position: refs/heads/master@{#37315}

src/api.cc

@@ -7550,7 +7550,12 @@ void Isolate::GetStackSample(const RegisterState& state, void** frames,
   regs.pc = state.pc;
   regs.sp = state.sp;
   regs.fp = state.fp;
-  i::SimulatorHelper::FillRegisters(isolate, &regs);
+  if (!i::SimulatorHelper::FillRegisters(isolate, &regs)) {
+    sample_info->frames_count = 0;
+    sample_info->vm_state = OTHER;
+    sample_info->external_callback_entry = nullptr;
+    return;
+  }
 #else
   const RegisterState& regs = state;
 #endif

src/frames.cc

@@ -304,7 +304,8 @@ bool SafeStackFrameIterator::IsValidExitFrame(Address fp) const {
   if (!IsValidStackAddress(sp)) return false;
   StackFrame::State state;
   ExitFrame::FillState(fp, sp, &state);
-  return *state.pc_address != NULL;
+  MSAN_MEMORY_IS_INITIALIZED(state.pc_address, sizeof(state.pc_address));
+  return *state.pc_address != nullptr;
 }
 
 
@@ -414,11 +415,9 @@ StackFrame::Type StackFrame::ComputeType(const StackFrameIteratorBase* iterator,
                                          State* state) {
   DCHECK(state->fp != NULL);
 
-#if defined(USE_SIMULATOR)
   MSAN_MEMORY_IS_INITIALIZED(
       state->fp + CommonFrameConstants::kContextOrFrameTypeOffset,
       kPointerSize);
-#endif
   Object* marker = Memory::Object_at(
       state->fp + CommonFrameConstants::kContextOrFrameTypeOffset);
   if (!iterator->can_access_heap_objects_) {
@@ -427,10 +426,8 @@ StackFrame::Type StackFrame::ComputeType(const StackFrameIteratorBase* iterator,
     // the VM with a signal at any arbitrary instruction, with essentially
     // anything on the stack. So basically none of these checks are 100%
     // reliable.
-#if defined(USE_SIMULATOR)
     MSAN_MEMORY_IS_INITIALIZED(
         state->fp + StandardFrameConstants::kFunctionOffset, kPointerSize);
-#endif
     Object* maybe_function =
         Memory::Object_at(state->fp + StandardFrameConstants::kFunctionOffset);
     if (!marker->IsSmi()) {
@@ -607,9 +604,7 @@ StackFrame::Type ExitFrame::GetStateForFramePointer(Address fp, State* state) {
 }
 
 Address ExitFrame::ComputeStackPointer(Address fp) {
-#if defined(USE_SIMULATOR)
   MSAN_MEMORY_IS_INITIALIZED(fp + ExitFrameConstants::kSPOffset, kPointerSize);
-#endif
   return Memory::Address_at(fp + ExitFrameConstants::kSPOffset);
 }
 

src/log.cc

@@ -647,8 +647,9 @@ class Ticker: public sampler::Sampler {
     v8::Isolate* v8_isolate = isolate();
     Isolate* isolate = reinterpret_cast<Isolate*>(v8_isolate);
 #if defined(USE_SIMULATOR)
-    SimulatorHelper::FillRegisters(isolate,
-                                   const_cast<v8::RegisterState*>(&state));
+    if (!SimulatorHelper::FillRegisters(isolate,
+                                        const_cast<v8::RegisterState*>(&state)))
+      return;
 #endif
     TickSample* sample = isolate->cpu_profiler()->StartTickSample();
     TickSample sample_obj;

src/profiler/tick-sample.cc

@@ -125,7 +125,8 @@ bool TickSample::GetStackSample(Isolate* isolate, const v8::RegisterState& regs,
   if (sample_info->vm_state == GC) return true;
 
   Address js_entry_sp = isolate->js_entry_sp();
-  if (js_entry_sp == 0) return true;  // Not executing JS now.
+  if (js_entry_sp == nullptr) return true;  // Not executing JS now.
+  DCHECK(regs.sp);
 
   if (regs.pc && IsNoFrameRegion(static_cast<Address>(regs.pc))) {
     // Can't collect stack.