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// Copyright 2019 The Chromium 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 "base/profiler/stack_sampler_impl.h"
#include <utility>
#include "base/logging.h"
#include "base/profiler/profile_builder.h"
#include "base/profiler/sample_metadata.h"
#include "base/profiler/stack_buffer.h"
#include "base/profiler/stack_copier.h"
#include "base/profiler/suspendable_thread_delegate.h"
#include "base/profiler/unwinder.h"
// IMPORTANT NOTE: Some functions within this implementation are invoked while
// the target thread is suspended so it must not do any allocation from the
// heap, including indirectly via use of DCHECK/CHECK or other logging
// statements. Otherwise this code can deadlock on heap locks acquired by the
// target thread before it was suspended. These functions are commented with "NO
namespace base {
StackSamplerImpl::StackSamplerImpl(std::unique_ptr<StackCopier> stack_copier,
std::unique_ptr<Unwinder> native_unwinder,
ModuleCache* module_cache,
StackSamplerTestDelegate* test_delegate)
: stack_copier_(std::move(stack_copier)),
test_delegate_(test_delegate) {}
StackSamplerImpl::~StackSamplerImpl() = default;
void StackSamplerImpl::AddAuxUnwinder(std::unique_ptr<Unwinder> unwinder) {
aux_unwinder_ = std::move(unwinder);
void StackSamplerImpl::RecordStackFrames(StackBuffer* stack_buffer,
ProfileBuilder* profile_builder) {
RegisterContext thread_context;
uintptr_t stack_top;
bool success = stack_copier_->CopyStack(stack_buffer, &stack_top,
profile_builder, &thread_context);
if (!success)
if (test_delegate_)
WalkStack(module_cache_, &thread_context, stack_top,
native_unwinder_.get(), aux_unwinder_.get()));
// static
std::vector<Frame> StackSamplerImpl::WalkStackForTesting(
ModuleCache* module_cache,
RegisterContext* thread_context,
uintptr_t stack_top,
Unwinder* native_unwinder,
Unwinder* aux_unwinder) {
return WalkStack(module_cache, thread_context, stack_top, native_unwinder,
// static
std::vector<Frame> StackSamplerImpl::WalkStack(ModuleCache* module_cache,
RegisterContext* thread_context,
uintptr_t stack_top,
Unwinder* native_unwinder,
Unwinder* aux_unwinder) {
std::vector<Frame> stack;
// Reserve enough memory for most stacks, to avoid repeated
// allocations. Approximately 99.9% of recorded stacks are 128 frames or
// fewer.
// Record the first frame from the context values.
size_t prior_stack_size;
UnwindResult result;
do {
// Choose an authoritative unwinder for the current module. Use the aux
// unwinder if it thinks it can unwind from the current frame, otherwise use
// the native unwinder.
Unwinder* unwinder =
aux_unwinder && aux_unwinder->CanUnwindFrom(&stack.back())
? aux_unwinder
: native_unwinder;
prior_stack_size = stack.size();
result =
unwinder->TryUnwind(thread_context, stack_top, module_cache, &stack);
// The native unwinder should be the only one that returns COMPLETED
// since the stack starts in native code.
DCHECK(result != UnwindResult::COMPLETED || unwinder == native_unwinder);
} while (result != UnwindResult::ABORTED &&
result != UnwindResult::COMPLETED &&
// Give up if the authoritative unwinder for the module was unable to
// unwind.
stack.size() > prior_stack_size);
return stack;
} // namespace base