blob: 0893928bb63b59890c0aec3654c98db597147962 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
|
// 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.
#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/macros.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);
StackBuffer(size_t buffer_size);
~StackBuffer();
// Returns a kPlatformStackAlignment-aligned pointer to the stack buffer.
uintptr_t* buffer() const {
// Return the first address in the buffer aligned to
// kPlatformStackAlignment. The buffer is guaranteed to have enough space
// for size() bytes beyond this value.
return reinterpret_cast<uintptr_t*>(
(reinterpret_cast<uintptr_t>(buffer_.get()) + kPlatformStackAlignment -
1) &
~(kPlatformStackAlignment - 1));
}
// Size in bytes.
size_t size() const { return size_; }
private:
// The buffer to store the stack.
const std::unique_ptr<uint8_t[]> buffer_;
// The size in bytes of the requested buffer allocation. The actual allocation
// is larger to accommodate alignment requirements.
const size_t size_;
DISALLOW_COPY_AND_ASSIGN(StackBuffer);
};
} // namespace base
#endif // BASE_PROFILER_STACK_BUFFER_H_
|
