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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 <stdint.h>
#include "base/base_export.h"
#include "base/profiler/register_context.h"
#include "base/time/time.h"
namespace base {
class StackBuffer;
class ProfileBuilder;
// StackCopier causes a thread to be suspended, copies its stack, and resumes
// the thread's execution. It's intended to provide an abstraction over stack
// copying techniques where the thread suspension is performed directly by the
// profiler thread (Windows and Mac platforms) vs. where the thread suspension
// is performed by the OS through signals (Android).
class BASE_EXPORT StackCopier {
virtual ~StackCopier();
// Copies the thread's register context into |thread_context|, the stack into
// |stack_buffer|, and the top of stack address into |stack_top|. Records
// metadata while the thread is suspended via |profile_builder|. Records
// |timestamp| at the time the stack was copied. Returns true if successful.
virtual bool CopyStack(StackBuffer* stack_buffer,
uintptr_t* stack_top,
ProfileBuilder* profile_builder,
TimeTicks* timestamp,
RegisterContext* thread_context) = 0;
// If the value at |pointer| points to the original stack, rewrite it to point
// to the corresponding location in the copied stack.
static uintptr_t RewritePointerIfInOriginalStack(
const uint8_t* original_stack_bottom,
const uintptr_t* original_stack_top,
const uint8_t* stack_copy_bottom,
uintptr_t pointer);
// Copies the stack to a buffer while rewriting possible pointers to locations
// within the stack to point to the corresponding locations in the copy. This
// is necessary to handle stack frames with dynamic stack allocation, where a
// pointer to the beginning of the dynamic allocation area is stored on the
// stack and/or in a non-volatile register.
// Eager rewriting of anything that looks like a pointer to the stack, as done
// in this function, does not adversely affect the stack unwinding. The only
// other values on the stack the unwinding depends on are return addresses,
// which should not point within the stack memory. The rewriting is guaranteed
// to catch all pointers because the stacks are guaranteed by the ABI to be
// sizeof(uintptr_t*) aligned.
// |original_stack_bottom| and |original_stack_top| are different pointer
// types due on their differing guaranteed alignments -- the bottom may only
// be 1-byte aligned while the top is aligned to double the pointer width.
// Returns a pointer to the bottom address in the copied stack. This value
// matches the alignment of |original_stack_bottom| to ensure that the stack
// contents have the same alignment as in the original stack. As a result the
// value will be different than |stack_buffer_bottom| if
// |original_stack_bottom| is not aligned to double the pointer width.
static const uint8_t* CopyStackContentsAndRewritePointers(
const uint8_t* original_stack_bottom,
const uintptr_t* original_stack_top,
int platform_stack_alignment,
uintptr_t* stack_buffer_bottom);
} // namespace base