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59 lines
1.9 KiB
C++
59 lines
1.9 KiB
C++
// Copyright 2019 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_PROFILER_STACK_BUFFER_H_
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#define BASE_PROFILER_STACK_BUFFER_H_
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#include <stddef.h>
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#include <stdint.h>
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#include <memory>
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#include "base/base_export.h"
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#include "base/macros.h"
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namespace base {
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// This class contains a buffer for stack copies that can be shared across
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// multiple instances of StackSampler.
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class BASE_EXPORT StackBuffer {
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public:
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// The expected alignment of the stack on the current platform. Windows and
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// System V AMD64 ABIs on x86, x64, and ARM require the stack to be aligned
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// to twice the pointer size. Excepted from this requirement is code setting
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// up the stack during function calls (between pushing the return address
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// and the end of the function prologue). The profiler will sometimes
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// encounter this exceptional case for leaf frames.
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static constexpr size_t kPlatformStackAlignment = 2 * sizeof(uintptr_t);
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StackBuffer(size_t buffer_size);
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~StackBuffer();
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// Returns a kPlatformStackAlignment-aligned pointer to the stack buffer.
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uintptr_t* buffer() const {
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// Return the first address in the buffer aligned to
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// kPlatformStackAlignment. The buffer is guaranteed to have enough space
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// for size() bytes beyond this value.
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return reinterpret_cast<uintptr_t*>(
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(reinterpret_cast<uintptr_t>(buffer_.get()) + kPlatformStackAlignment -
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1) &
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~(kPlatformStackAlignment - 1));
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}
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// Size in bytes.
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size_t size() const { return size_; }
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private:
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// The buffer to store the stack.
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const std::unique_ptr<uint8_t[]> buffer_;
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// The size in bytes of the requested buffer allocation. The actual allocation
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// is larger to accommodate alignment requirements.
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const size_t size_;
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DISALLOW_COPY_AND_ASSIGN(StackBuffer);
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};
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} // namespace base
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#endif // BASE_PROFILER_STACK_BUFFER_H_
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