mirror of
https://github.com/klzgrad/naiveproxy.git
synced 2025-02-21 09:23:18 +03:00
72 lines
2.6 KiB
C++
72 lines
2.6 KiB
C++
// Copyright 2019 The Chromium Authors
|
|
// Use of this source code is governed by a BSD-style license that can be
|
|
// found in the LICENSE file.
|
|
|
|
#ifndef BASE_PROFILER_STACK_BUFFER_H_
|
|
#define BASE_PROFILER_STACK_BUFFER_H_
|
|
|
|
#include <stddef.h>
|
|
#include <stdint.h>
|
|
#include <memory>
|
|
|
|
#include "base/base_export.h"
|
|
#include "base/memory/aligned_memory.h"
|
|
#include "build/build_config.h"
|
|
|
|
namespace base {
|
|
|
|
// This class contains a buffer for stack copies that can be shared across
|
|
// multiple instances of StackSampler.
|
|
class BASE_EXPORT StackBuffer {
|
|
public:
|
|
// The expected alignment of the stack on the current platform. Windows and
|
|
// System V AMD64 ABIs on x86, x64, and ARM require the stack to be aligned
|
|
// to twice the pointer size. Excepted from this requirement is code setting
|
|
// up the stack during function calls (between pushing the return address
|
|
// and the end of the function prologue). The profiler will sometimes
|
|
// encounter this exceptional case for leaf frames.
|
|
static constexpr size_t kPlatformStackAlignment = 2 * sizeof(uintptr_t);
|
|
|
|
explicit StackBuffer(size_t buffer_size);
|
|
|
|
StackBuffer(const StackBuffer&) = delete;
|
|
StackBuffer& operator=(const StackBuffer&) = delete;
|
|
|
|
~StackBuffer();
|
|
|
|
// Returns a kPlatformStackAlignment-aligned pointer to the stack buffer.
|
|
uintptr_t* buffer() const {
|
|
// Aligned during allocation.
|
|
return buffer_.get();
|
|
}
|
|
|
|
// Size in bytes.
|
|
size_t size() const { return size_; }
|
|
|
|
#if BUILDFLAG(IS_CHROMEOS)
|
|
// Tell the kernel that we no longer need the data currently in the upper
|
|
// parts of the buffer and that the kernel may discard it to free up space.
|
|
// Specifically, the bytes from |(uint8_t*)buffer + retained_bytes| to the
|
|
// end of the buffer may be discarded, while the bytes from |buffer| to
|
|
// |(uint8_t*)buffer + retained_bytes - 1| will not be affected.
|
|
// The program can still write to that part of the buffer, but should not read
|
|
// from that part of buffer until after the next write. (The contents of that
|
|
// part of the buffer are undefined.)
|
|
// After calling this function, there may be a page fault on the next write to
|
|
// that area, so it should only be called when parts of the buffer were
|
|
// written to and will probably not be written to again soon.
|
|
void MarkUpperBufferContentsAsUnneeded(size_t retained_bytes);
|
|
#endif
|
|
|
|
private:
|
|
// The size in bytes of the requested buffer allocation.
|
|
const size_t size_;
|
|
|
|
// The buffer to store the stack. Already aligned.
|
|
const std::unique_ptr<uintptr_t, AlignedFreeDeleter> buffer_;
|
|
};
|
|
|
|
} // namespace base
|
|
|
|
#endif // BASE_PROFILER_STACK_BUFFER_H_
|