Split TickSample and Sampler.

src/profiler/tick-sample.cc

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/profiler/tick-sample.h"
+
+#include "src/frames-inl.h"
+#include "src/vm-state-inl.h"
+
+
+namespace v8 {
+namespace internal {
+
+namespace {
+
+bool IsSamePage(byte* ptr1, byte* ptr2) {
+  const uint32_t kPageSize = 4096;
+  uintptr_t mask = ~static_cast<uintptr_t>(kPageSize - 1);
+  return (reinterpret_cast<uintptr_t>(ptr1) & mask) ==
+         (reinterpret_cast<uintptr_t>(ptr2) & mask);
+}
+
+
+// Check if the code at specified address could potentially be a
+// frame setup code.
+bool IsNoFrameRegion(Address address) {
+  struct Pattern {
+    int bytes_count;
+    byte bytes[8];
+    int offsets[4];
+  };
+  byte* pc = reinterpret_cast<byte*>(address);
+  static Pattern patterns[] = {
+#if V8_HOST_ARCH_IA32
+    // push %ebp
+    // mov %esp,%ebp
+    {3, {0x55, 0x89, 0xe5}, {0, 1, -1}},
+    // pop %ebp
+    // ret N
+    {2, {0x5d, 0xc2}, {0, 1, -1}},
+    // pop %ebp
+    // ret
+    {2, {0x5d, 0xc3}, {0, 1, -1}},
+#elif V8_HOST_ARCH_X64
+    // pushq %rbp
+    // movq %rsp,%rbp
+    {4, {0x55, 0x48, 0x89, 0xe5}, {0, 1, -1}},
+    // popq %rbp
+    // ret N
+    {2, {0x5d, 0xc2}, {0, 1, -1}},
+    // popq %rbp
+    // ret
+    {2, {0x5d, 0xc3}, {0, 1, -1}},
+#endif
+    {0, {}, {}}
+  };
+  for (Pattern* pattern = patterns; pattern->bytes_count; ++pattern) {
+    for (int* offset_ptr = pattern->offsets; *offset_ptr != -1; ++offset_ptr) {
+      int offset = *offset_ptr;
+      if (!offset || IsSamePage(pc, pc - offset)) {
+        MSAN_MEMORY_IS_INITIALIZED(pc - offset, pattern->bytes_count);
+        if (!memcmp(pc - offset, pattern->bytes, pattern->bytes_count))
+          return true;
+      } else {
+        // It is not safe to examine bytes on another page as it might not be
+        // allocated thus causing a SEGFAULT.
+        // Check the pattern part that's on the same page and
+        // pessimistically assume it could be the entire pattern match.
+        MSAN_MEMORY_IS_INITIALIZED(pc, pattern->bytes_count - offset);
+        if (!memcmp(pc, pattern->bytes + offset, pattern->bytes_count - offset))
+          return true;
+      }
+    }
+  }
+  return false;
+}
+
+}  // namespace
+
+
+//
+// StackTracer implementation
+//
+DISABLE_ASAN void TickSample::Init(Isolate* isolate,
+                                   const v8::RegisterState& regs,
+                                   RecordCEntryFrame record_c_entry_frame,
+                                   bool update_stats) {
+  timestamp = base::TimeTicks::HighResolutionNow();
+  pc = reinterpret_cast<Address>(regs.pc);
+  state = isolate->current_vm_state();
+  this->update_stats = update_stats;
+
+  // Avoid collecting traces while doing GC.
+  if (state == GC) return;
+
+  Address js_entry_sp = isolate->js_entry_sp();
+  if (js_entry_sp == 0) return;  // Not executing JS now.
+
+  if (pc && IsNoFrameRegion(pc)) {
+    // Can't collect stack. Mark the sample as spoiled.
+    timestamp = base::TimeTicks();
+    pc = 0;
+    return;
+  }
+
+  ExternalCallbackScope* scope = isolate->external_callback_scope();
+  Address handler = 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
+  // is not the top function.
+  if (scope && scope->scope_address() < handler) {
+    external_callback_entry = *scope->callback_entrypoint_address();
+    has_external_callback = true;
+  } else {
+    // sp register may point at an arbitrary place in memory, make
+    // sure MSAN doesn't complain about it.
+    MSAN_MEMORY_IS_INITIALIZED(regs.sp, sizeof(Address));
+    // Sample potential return address value for frameless invocation of
+    // stubs (we'll figure out later, if this value makes sense).
+    tos = Memory::Address_at(reinterpret_cast<Address>(regs.sp));
+    has_external_callback = false;
+  }
+
+  SafeStackFrameIterator it(isolate, reinterpret_cast<Address>(regs.fp),
+                            reinterpret_cast<Address>(regs.sp), js_entry_sp);
+  top_frame_type = it.top_frame_type();
+
+  SampleInfo info;
+  GetStackSample(isolate, regs, record_c_entry_frame,
+                 reinterpret_cast<void**>(&stack[0]), kMaxFramesCount, &info);
+  frames_count = static_cast<unsigned>(info.frames_count);
+  if (!frames_count) {
+    // It is executing JS but failed to collect a stack trace.
+    // Mark the sample as spoiled.
+    timestamp = base::TimeTicks();
+    pc = 0;
+  }
+}
+
+
+void TickSample::GetStackSample(Isolate* isolate, const v8::RegisterState& regs,
+                                RecordCEntryFrame record_c_entry_frame,
+                                void** frames, size_t frames_limit,
+                                v8::SampleInfo* sample_info) {
+  sample_info->frames_count = 0;
+  sample_info->vm_state = isolate->current_vm_state();
+  if (sample_info->vm_state == GC) return;
+
+  Address js_entry_sp = isolate->js_entry_sp();
+  if (js_entry_sp == 0) return;  // Not executing JS now.
+
+  SafeStackFrameIterator it(isolate, reinterpret_cast<Address>(regs.fp),
+                            reinterpret_cast<Address>(regs.sp), js_entry_sp);
+  size_t i = 0;
+  if (record_c_entry_frame == kIncludeCEntryFrame && !it.done() &&
+      it.top_frame_type() == StackFrame::EXIT) {
+    frames[i++] = isolate->c_function();
+  }
+  while (!it.done() && i < frames_limit) {
+    if (it.frame()->is_interpreted()) {
+      // For interpreted frames use the bytecode array pointer as the pc.
+      InterpretedFrame* frame = static_cast<InterpretedFrame*>(it.frame());
+      // Since the sampler can interrupt execution at any point the
+      // bytecode_array might be garbage, so don't dereference it.
+      Address bytecode_array =
+          reinterpret_cast<Address>(frame->GetBytecodeArray()) - kHeapObjectTag;
+      frames[i++] = bytecode_array + BytecodeArray::kHeaderSize +
+                    frame->GetBytecodeOffset();
+    } else {
+      frames[i++] = it.frame()->pc();
+    }
+    it.Advance();
+  }
+  sample_info->frames_count = i;
+}
+
+
+}  // namespace internal
+}  // namespace v8