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/*
* Copyright (C) 2016 Yusuke Suzuki <utatane.tea@gmail.com>
* Copyright (C) 2016 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. AND ITS CONTRIBUTORS ``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 ITS 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 "BytecodeGraph.h"
#include "Bytecodes.h"
#include "Opcode.h"
#include "UnlinkedCodeBlock.h"
#include <wtf/Insertion.h>
namespace JSC {
// BytecodeRewriter offers the ability to insert and remove the bytecodes including jump operations.
//
// We use the original bytecode offsets as labels. When you emit some jumps, you can specify the jump target by
// using the original bytecode offsets. These bytecode offsets are later converted appropriate values by the
// rewriter. And we also use the labels to represents the position the new bytecodes inserted.
//
// | [bytecode] | [bytecode] |
// offsets A B C
//
// We can use the above "A", "B", and "C" offsets as labels. And the rewriter has the ability to insert bytecode fragments
// before and after the label. For example, if you insert the fragment after "B", the layout becomes like this.
//
// | [bytecode] | [fragment] [bytecode] |
// offsets A B C
//
// And even if you remove some original bytecodes, the offset remains as labels. For example, when you remove the A's bytecode,
// the layout becomes like this.
//
// | | [bytecode] |
// offsets A B C
//
// And still you can insert fragments before and after "A".
//
// | [fragment] | [bytecode] |
// offsets A B C
//
// We can insert bytecode fragments "Before" and "After" the labels. This inserted position, either "Before" and "After",
// has effect when the label is involved with jumps. For example, when you have jump to the position "B",
//
// | [bytecode] | [bytecode] |
// offsets A B C
// ^
// jump to here.
//
// and you insert the bytecode before/after "B",
//
// | [bytecode] [before] | [after] [bytecode] |
// offsets A B C
// ^
// jump to here.
//
// as you can see, the execution jumping into "B" does not execute [before] code.
class BytecodeRewriter {
WTF_MAKE_NONCOPYABLE(BytecodeRewriter);
public:
enum class Position : int8_t {
EntryPoint = -2,
Before = -1,
LabelPoint = 0,
After = 1,
OriginalBytecodePoint = 2,
};
enum class IncludeBranch : uint8_t {
No = 0,
Yes = 1,
};
struct InsertionPoint {
int bytecodeOffset;
Position position;
InsertionPoint(int offset, Position pos)
: bytecodeOffset(offset)
, position(pos)
{
}
bool operator<(const InsertionPoint& other) const
{
if (bytecodeOffset == other.bytecodeOffset)
return position < other.position;
return bytecodeOffset < other.bytecodeOffset;
}
bool operator==(const InsertionPoint& other) const
{
return bytecodeOffset == other.bytecodeOffset && position == other.position;
}
};
private:
struct Insertion {
enum class Type : uint8_t { Insert = 0, Remove = 1, };
size_t length() const
{
if (type == Type::Remove)
return removeLength;
return instructions.size();
}
InsertionPoint index;
Type type;
IncludeBranch includeBranch;
size_t removeLength;
Vector<UnlinkedInstruction> instructions;
};
public:
class Fragment {
WTF_MAKE_NONCOPYABLE(Fragment);
public:
Fragment(Vector<UnlinkedInstruction>& fragment, IncludeBranch& includeBranch)
: m_fragment(fragment)
, m_includeBranch(includeBranch)
{
}
template<class... Args>
void appendInstruction(OpcodeID opcodeID, Args... args)
{
if (isBranch(opcodeID))
m_includeBranch = IncludeBranch::Yes;
UnlinkedInstruction instructions[sizeof...(args) + 1] = {
UnlinkedInstruction(opcodeID),
UnlinkedInstruction(args)...
};
m_fragment.append(instructions, sizeof...(args) + 1);
}
private:
Vector<UnlinkedInstruction>& m_fragment;
IncludeBranch& m_includeBranch;
};
BytecodeRewriter(BytecodeGraph<UnlinkedCodeBlock>& graph)
: m_graph(graph)
{
}
template<class Function>
void insertFragmentBefore(unsigned bytecodeOffset, Function function)
{
IncludeBranch includeBranch = IncludeBranch::No;
Vector<UnlinkedInstruction> instructions;
Fragment fragment(instructions, includeBranch);
function(fragment);
insertImpl(InsertionPoint(bytecodeOffset, Position::Before), includeBranch, WTFMove(instructions));
}
template<class Function>
void insertFragmentAfter(unsigned bytecodeOffset, Function function)
{
IncludeBranch includeBranch = IncludeBranch::No;
Vector<UnlinkedInstruction> instructions;
Fragment fragment(instructions, includeBranch);
function(fragment);
insertImpl(InsertionPoint(bytecodeOffset, Position::After), includeBranch, WTFMove(instructions));
}
void removeBytecode(unsigned bytecodeOffset)
{
m_insertions.append(Insertion { InsertionPoint(bytecodeOffset, Position::OriginalBytecodePoint), Insertion::Type::Remove, IncludeBranch::No, opcodeLength(m_graph.instructions()[bytecodeOffset].u.opcode), { } });
}
void execute();
BytecodeGraph<UnlinkedCodeBlock>& graph() { return m_graph; }
int adjustAbsoluteOffset(int absoluteOffset)
{
return adjustJumpTarget(InsertionPoint(0, Position::EntryPoint), InsertionPoint(absoluteOffset, Position::LabelPoint));
}
int adjustJumpTarget(int originalBytecodeOffset, int originalJumpTarget)
{
return adjustJumpTarget(InsertionPoint(originalBytecodeOffset, Position::LabelPoint), InsertionPoint(originalJumpTarget, Position::LabelPoint));
}
private:
void insertImpl(InsertionPoint, IncludeBranch, Vector<UnlinkedInstruction>&& fragment);
friend class UnlinkedCodeBlock;
void applyModification();
void adjustJumpTargetsInFragment(unsigned finalOffset, Insertion&);
int adjustJumpTarget(InsertionPoint startPoint, InsertionPoint jumpTargetPoint);
template<typename Iterator> int calculateDifference(Iterator begin, Iterator end);
BytecodeGraph<UnlinkedCodeBlock>& m_graph;
Vector<Insertion, 8> m_insertions;
};
template<typename Iterator>
inline int BytecodeRewriter::calculateDifference(Iterator begin, Iterator end)
{
int result = 0;
for (; begin != end; ++begin) {
if (begin->type == Insertion::Type::Remove)
result -= begin->length();
else
result += begin->length();
}
return result;
}
} // namespace JSC
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