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// Copyright 2020 the V8 project 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 V8_HEAP_BASE_STACK_H_
#define V8_HEAP_BASE_STACK_H_
#include <vector>
#include "src/base/macros.h"
#include "src/base/platform/platform.h"
namespace heap::base {
class StackVisitor {
public:
virtual ~StackVisitor() = default;
virtual void VisitPointer(const void* address) = 0;
};
// Abstraction over the stack. Supports handling of:
// - native stack;
// - ASAN/MSAN;
// - SafeStack: https://releases.llvm.org/10.0.0/tools/clang/docs/SafeStack.html
//
// Stacks grow down, so throughout this class "start" refers the highest
// address of the stack, and top/marker the lowest.
//
// TODO(chromium:1056170): Consider adding a component that keeps track
// of relevant GC stack regions where interesting pointers can be found.
class V8_EXPORT_PRIVATE Stack final {
public:
explicit Stack(const void* stack_start = nullptr)
: stack_start_(stack_start) {}
// Sets the start of the stack.
void SetStackStart(const void* stack_start) { stack_start_ = stack_start; }
// Returns true if |slot| is part of the stack and false otherwise.
bool IsOnStack(const void* slot) const;
// Word-aligned iteration of the stack, starting at the `stack_marker_`
// and going to the stack start. Slot values are passed on to `visitor`.
void IteratePointersUntilMarker(StackVisitor* visitor) const;
void AddStackSegment(const void* start, const void* top);
void ClearStackSegments();
// Push callee-saved registers to the stack, set the stack marker to the
// current stack top and invoke the callback.
template <typename Callback>
V8_INLINE void SetMarkerAndCallback(Callback callback) {
SetMarkerAndCallbackHelper(static_cast<void*>(&callback),
&SetMarkerAndCallbackImpl<Callback>);
}
template <typename Callback>
V8_INLINE void SetMarkerIfNeededAndCallback(Callback callback) {
if (stack_marker_ == nullptr) {
SetMarkerAndCallbackHelper(static_cast<void*>(&callback),
&SetMarkerAndCallbackImpl<Callback>);
} else {
DCHECK(IsOnCurrentStack(stack_marker_));
callback();
}
}
using IterateStackCallback = void (*)(Stack*, void*, const void*);
// This method combines SetMarkerAndCallback with IteratePointersUntilMarker.
// Callee-saved registers are pushed to the stack and then a word-aligned
// iteration of the stack is performed. Slot values are passed on to
// `visitor`. To be used for testing.
void IteratePointersForTesting(StackVisitor* visitor);
bool IsMarkerSet() const { return stack_marker_ != nullptr; }
private:
#ifdef DEBUG
static bool IsOnCurrentStack(const void* ptr);
#endif
static void IteratePointersImpl(const Stack* stack, void* argument,
const void* stack_end);
V8_NOINLINE void SetMarkerAndCallbackHelper(void* argument,
IterateStackCallback callback);
template <typename Callback>
static void SetMarkerAndCallbackImpl(Stack* stack, void* argument,
const void* stack_end) {
DCHECK_NULL(stack->stack_marker_);
stack->stack_marker_ = stack_end;
Callback* callback = static_cast<Callback*>(argument);
(*callback)();
stack->stack_marker_ = nullptr;
}
const void* stack_start_;
// Marker that signals end of the interesting stack region in which on-heap
// pointers can be found.
const void* stack_marker_ = nullptr;
// Stack segments that may also contain pointers and should be scanned.
struct StackSegments {
const void* start;
const void* top;
};
std::vector<StackSegments> inactive_stacks_;
};
} // namespace heap::base
#endif // V8_HEAP_BASE_STACK_H_
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