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/*
* Copyright (C) 2016-2023 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include "CallFrame.h"
#include "JSCJSValue.h"
#include <wtf/Noncopyable.h>
#include <wtf/PrintStream.h>
#include <wtf/StdLibExtras.h>
#include <wtf/TZoneMalloc.h>
#include <wtf/Vector.h>
namespace JSC {
class AbstractSlotVisitor;
class CallFrame;
class CodeBlock;
class JSArray;
class JSObject;
class JSScope;
class LLIntOffsetsExtractor;
class VM;
// ShadowChicken is a log that can be used to produce a shadow stack of CHICKEN-style stack frames.
// This enables the debugger to almost always see the tail-deleted stack frames, so long as we have
// memory inside ShadowChicken to remember them.
//
// The ShadowChicken log comprises packets that have one of two shapes:
//
// Prologue Packet, which has:
// - Callee object.
// - Frame pointer.
// - Caller frame pointer.
//
// Tail Call Packet, which has just:
// - Frame pointer.
//
// Prologue Packets are placed into the log in any JS function's prologue. Tail Call Packets are
// placed into the log just before making a proper tail call. We never log returns, since that would
// require a lot of infrastructure (unwinding, multiple ways of returning, etc). We don't need to
// see the returns because the prologue packets have a frame pointer. The tail call packets tell us
// when there was a tail call, and record the FP *before* the tail call.
//
// At any time it is possible to construct a shadow stack from the log and the actual machine stack.
class ShadowChicken {
WTF_MAKE_NONCOPYABLE(ShadowChicken);
WTF_MAKE_TZONE_ALLOCATED(ShadowChicken);
public:
struct Packet {
Packet()
{
}
static constexpr unsigned unlikelyValue = 0x7a11;
static constexpr intptr_t tailMarkerValue = static_cast<intptr_t>(unlikelyValue);
static JSObject* tailMarker()
{
return std::bit_cast<JSObject*>(tailMarkerValue);
}
static JSObject* throwMarker()
{
return std::bit_cast<JSObject*>(static_cast<intptr_t>(unlikelyValue + 1));
}
static Packet prologue(JSObject* callee, CallFrame* frame, CallFrame* callerFrame, JSScope* scope)
{
Packet result;
result.callee = callee;
result.frame = frame;
result.callerFrame = callerFrame;
result.scope = scope;
return result;
}
static Packet tail(CallFrame* frame, JSValue thisValue, JSScope* scope, CodeBlock* codeBlock, CallSiteIndex callSiteIndex)
{
Packet result;
result.callee = tailMarker();
result.frame = frame;
result.thisValue = thisValue;
result.scope = scope;
result.codeBlock = codeBlock;
result.callSiteIndex = callSiteIndex;
return result;
}
static Packet throwPacket()
{
Packet result;
result.callee = throwMarker();
return result;
}
explicit operator bool() const { return !!callee; }
bool isPrologue() const { return *this && callee != tailMarker() && callee != throwMarker(); }
bool isTail() const { return *this && callee == tailMarker(); }
bool isThrow() const { return *this && callee == throwMarker(); }
void dump(PrintStream&) const;
// Only tail packets have a valid thisValue, CodeBlock*, and CallSiteIndex. We grab 'this' and CodeBlock* from non tail-deleted frames from the machine frame.
JSValue thisValue { JSValue() };
JSObject* callee { nullptr };
CallFrame* frame { nullptr };
CallFrame* callerFrame { nullptr };
JSScope* scope { nullptr };
CodeBlock* codeBlock { nullptr };
CallSiteIndex callSiteIndex;
};
struct Frame {
Frame()
{
}
Frame(JSObject* callee, CallFrame* frame, bool isTailDeleted, JSValue thisValue = JSValue(), JSScope* scope = nullptr, CodeBlock* codeBlock = nullptr, CallSiteIndex callSiteIndex = CallSiteIndex())
: callee(callee)
, frame(frame)
, thisValue(thisValue)
, scope(scope)
, codeBlock(codeBlock)
, callSiteIndex(callSiteIndex)
, isTailDeleted(isTailDeleted)
{
}
friend bool operator==(const Frame&, const Frame&) = default;
void dump(PrintStream&) const;
// FIXME: This should be able to hold the moral equivalent of StackVisitor::Frame, so that
// we can support inlining.
// https://bugs.webkit.org/show_bug.cgi?id=155686
JSObject* callee { nullptr };
CallFrame* frame { nullptr };
JSValue thisValue { JSValue() };
JSScope* scope { nullptr };
CodeBlock* codeBlock { nullptr };
CallSiteIndex callSiteIndex;
bool isTailDeleted { false };
};
ShadowChicken();
~ShadowChicken();
void log(VM& vm, CallFrame*, const Packet&);
void update(VM&, CallFrame*);
// Expects this signature: (const Frame& frame) -> bool. Return true to keep iterating. Return false to stop iterating.
// Note that this only works right with inlining disabled, but that's OK since for now we
// disable inlining when the inspector is attached. It would be easy to make this work with
// inlining, and would mostly require that we can request that StackVisitor doesn't skip tail
// frames.
template<typename Functor>
void iterate(VM&, CallFrame*, const Functor&);
void visitChildren(AbstractSlotVisitor&);
void reset();
// JIT support.
Packet* log() const { return m_log; }
unsigned logSize() const { return m_logSize; }
Packet** addressOfLogCursor() { return &m_logCursor; }
Packet* logEnd() { return m_logEnd; }
void dump(PrintStream&) const;
JS_EXPORT_PRIVATE JSArray* functionsOnStack(JSGlobalObject*, CallFrame*);
private:
friend class LLIntOffsetsExtractor;
Packet* m_log { nullptr };
unsigned m_logSize { 0 };
Packet* m_logCursor { nullptr };
Packet* m_logEnd { nullptr };
Vector<Frame> m_stack;
};
} // namespace JSC
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