75 lines
2.9 KiB
C++
75 lines
2.9 KiB
C++
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// 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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#include "base/profiler/stack_copier.h"
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#include "base/compiler_specific.h"
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namespace base {
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StackCopier::~StackCopier() = default;
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// static
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uintptr_t StackCopier::RewritePointerIfInOriginalStack(
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const uint8_t* original_stack_bottom,
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const uintptr_t* original_stack_top,
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const uint8_t* stack_copy_bottom,
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uintptr_t pointer) {
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auto original_stack_bottom_uint =
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reinterpret_cast<uintptr_t>(original_stack_bottom);
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auto original_stack_top_uint =
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reinterpret_cast<uintptr_t>(original_stack_top);
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auto stack_copy_bottom_uint = reinterpret_cast<uintptr_t>(stack_copy_bottom);
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if (pointer < original_stack_bottom_uint ||
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pointer >= original_stack_top_uint)
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return pointer;
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return stack_copy_bottom_uint + (pointer - original_stack_bottom_uint);
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}
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// static
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NO_SANITIZE("address")
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const uint8_t* StackCopier::CopyStackContentsAndRewritePointers(
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const uint8_t* original_stack_bottom,
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const uintptr_t* original_stack_top,
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int platform_stack_alignment,
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uintptr_t* stack_buffer_bottom) {
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const uint8_t* byte_src = original_stack_bottom;
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// The first address in the stack with pointer alignment. Pointer-aligned
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// values from this point to the end of the stack are possibly rewritten using
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// RewritePointerIfInOriginalStack(). Bytes before this cannot be a pointer
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// because they occupy less space than a pointer would.
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const uint8_t* first_aligned_address = reinterpret_cast<uint8_t*>(
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(reinterpret_cast<uintptr_t>(byte_src) + sizeof(uintptr_t) - 1) &
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~(sizeof(uintptr_t) - 1));
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// The stack copy bottom, which is offset from |stack_buffer_bottom| by the
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// same alignment as in the original stack. This guarantees identical
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// alignment between values in the original stack and the copy. This uses the
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// platform stack alignment rather than pointer alignment so that the stack
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// copy is aligned to platform expectations.
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uint8_t* stack_copy_bottom =
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reinterpret_cast<uint8_t*>(stack_buffer_bottom) +
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(reinterpret_cast<uintptr_t>(byte_src) & (platform_stack_alignment - 1));
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uint8_t* byte_dst = stack_copy_bottom;
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// Copy bytes verbatim up to the first aligned address.
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for (; byte_src < first_aligned_address; ++byte_src, ++byte_dst)
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*byte_dst = *byte_src;
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// Copy the remaining stack by pointer-sized values, rewriting anything that
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// looks like a pointer into the stack.
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const uintptr_t* src = reinterpret_cast<const uintptr_t*>(byte_src);
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uintptr_t* dst = reinterpret_cast<uintptr_t*>(byte_dst);
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for (; src < original_stack_top; ++src, ++dst) {
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*dst = RewritePointerIfInOriginalStack(
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original_stack_bottom, original_stack_top, stack_copy_bottom, *src);
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}
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return stack_copy_bottom;
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}
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} // namespace base
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