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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,
bool wasm_stack_switching = false)
: stack_start_(stack_start),
wasm_stack_switching_(wasm_stack_switching) {}
// Sets the start of the stack.
void SetStackStart(const void* stack_start, bool wasm_stack_switching) {
stack_start_ = stack_start;
wasm_stack_switching_ = wasm_stack_switching;
}
// Returns true if |slot| is part of the stack and false otherwise.
bool IsOnStack(const void* slot) const;
// Word-aligned iteration of the stack. Callee-saved registers are pushed to
// the stack before iterating pointers. Slot values are passed on to
// `visitor`.
void IteratePointers(StackVisitor* visitor) const;
// Word-aligned iteration of the stack, starting at the `stack_marker_`. Slot
// values are passed on to `visitor`. This is intended to be used with
// verifiers that only visit a subset of the stack of IteratePointers().
//
// **Ignores:**
// - Callee-saved registers.
// - SafeStack.
void IteratePointersUntilMarker(StackVisitor* visitor) const;
void AddStackSegment(const void* start, const void* top);
void ClearStackSegments();
// This method should be inlined, to set the marker at the current frame's
// stack top.
V8_INLINE void SetMarkerToCurrentStackPosition() {
stack_marker_ = v8::base::Stack::GetCurrentStackPosition();
}
private:
#ifdef DEBUG
static bool IsOnCurrentStack(const void* ptr);
#endif
static void IteratePointersImpl(const Stack* stack, StackVisitor* visitor,
const void* stack_end);
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_;
// TODO(v8:13493): This is for suppressing the check that we are in the
// correct stack, in the case of WASM stack switching. It will be removed as
// soon as context saving becomes compatible with stack switching.
bool wasm_stack_switching_;
// 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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