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// ASM: a very small and fast Java bytecode manipulation framework
// Copyright (c) 2000-2011 INRIA, France Telecom
// 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.
// 3. Neither the name of the copyright holders nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT OWNER 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.
package org.objectweb.asm.tree.analysis;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;
import org.objectweb.asm.tree.AbstractInsnNode;
import org.objectweb.asm.tree.IincInsnNode;
import org.objectweb.asm.tree.InsnList;
import org.objectweb.asm.tree.JumpInsnNode;
import org.objectweb.asm.tree.LabelNode;
import org.objectweb.asm.tree.LookupSwitchInsnNode;
import org.objectweb.asm.tree.MethodNode;
import org.objectweb.asm.tree.TableSwitchInsnNode;
import org.objectweb.asm.tree.TryCatchBlockNode;
import org.objectweb.asm.tree.VarInsnNode;
/**
* A semantic bytecode analyzer. This class does not fully check that JSR and RET instructions
* are valid.
*
* @param type of the Value used for the analysis.
* @author Eric Bruneton
*/
public class Analyzer implements Opcodes {
/** The interpreter to use to symbolically interpret the bytecode instructions. */
private final Interpreter interpreter;
/** The instructions of the currently analyzed method. */
private InsnList insnList;
/** The size of {@link #insnList}. */
private int insnListSize;
/** The exception handlers of the currently analyzed method (one list per instruction index). */
private List[] handlers;
/** The execution stack frames of the currently analyzed method (one per instruction index). */
private Frame[] frames;
/** The subroutines of the currently analyzed method (one per instruction index). */
private Subroutine[] subroutines;
/** The instructions that remain to process (one boolean per instruction index). */
private boolean[] inInstructionsToProcess;
/** The indices of the instructions that remain to process in the currently analyzed method. */
private int[] instructionsToProcess;
/** The number of instructions that remain to process in the currently analyzed method. */
private int numInstructionsToProcess;
/**
* Constructs a new {@link Analyzer}.
*
* @param interpreter the interpreter to use to symbolically interpret the bytecode instructions.
*/
public Analyzer(final Interpreter interpreter) {
this.interpreter = interpreter;
}
/**
* Analyzes the given method.
*
* @param owner the internal name of the class to which 'method' belongs.
* @param method the method to be analyzed.
* @return the symbolic state of the execution stack frame at each bytecode instruction of the
* method. The size of the returned array is equal to the number of instructions (and labels)
* of the method. A given frame is null if and only if the corresponding instruction
* cannot be reached (dead code).
* @throws AnalyzerException if a problem occurs during the analysis.
*/
@SuppressWarnings("unchecked")
public Frame[] analyze(final String owner, final MethodNode method) throws AnalyzerException {
if ((method.access & (ACC_ABSTRACT | ACC_NATIVE)) != 0) {
frames = (Frame[]) new Frame[0];
return frames;
}
insnList = method.instructions;
insnListSize = insnList.size();
handlers = (List[]) new List[insnListSize];
frames = (Frame[]) new Frame[insnListSize];
subroutines = new Subroutine[insnListSize];
inInstructionsToProcess = new boolean[insnListSize];
instructionsToProcess = new int[insnListSize];
numInstructionsToProcess = 0;
// For each exception handler, and each instruction within its range, record in 'handlers' the
// fact that execution can flow from this instruction to the exception handler.
for (int i = 0; i < method.tryCatchBlocks.size(); ++i) {
TryCatchBlockNode tryCatchBlock = method.tryCatchBlocks.get(i);
int startIndex = insnList.indexOf(tryCatchBlock.start);
int endIndex = insnList.indexOf(tryCatchBlock.end);
for (int j = startIndex; j < endIndex; ++j) {
List insnHandlers = handlers[j];
if (insnHandlers == null) {
insnHandlers = new ArrayList();
handlers[j] = insnHandlers;
}
insnHandlers.add(tryCatchBlock);
}
}
// For each instruction, compute the subroutine to which it belongs.
// Follow the main 'subroutine', and collect the jsr instructions to nested subroutines.
Subroutine main = new Subroutine(null, method.maxLocals, null);
List jsrInsns = new ArrayList();
findSubroutine(0, main, jsrInsns);
// Follow the nested subroutines, and collect their own nested subroutines, until all
// subroutines are found.
Map jsrSubroutines = new HashMap();
while (!jsrInsns.isEmpty()) {
JumpInsnNode jsrInsn = (JumpInsnNode) jsrInsns.remove(0);
Subroutine subroutine = jsrSubroutines.get(jsrInsn.label);
if (subroutine == null) {
subroutine = new Subroutine(jsrInsn.label, method.maxLocals, jsrInsn);
jsrSubroutines.put(jsrInsn.label, subroutine);
findSubroutine(insnList.indexOf(jsrInsn.label), subroutine, jsrInsns);
} else {
subroutine.callers.add(jsrInsn);
}
}
// Clear the main 'subroutine', which is not a real subroutine (and was used only as an
// intermediate step above to find the real ones).
for (int i = 0; i < insnListSize; ++i) {
if (subroutines[i] != null && subroutines[i].start == null) {
subroutines[i] = null;
}
}
// Initializes the data structures for the control flow analysis.
Frame currentFrame = computeInitialFrame(owner, method);
merge(0, currentFrame, null);
init(owner, method);
// Control flow analysis.
while (numInstructionsToProcess > 0) {
// Get and remove one instruction from the list of instructions to process.
int insnIndex = instructionsToProcess[--numInstructionsToProcess];
Frame oldFrame = frames[insnIndex];
Subroutine subroutine = subroutines[insnIndex];
inInstructionsToProcess[insnIndex] = false;
// Simulate the execution of this instruction.
AbstractInsnNode insnNode = null;
try {
insnNode = method.instructions.get(insnIndex);
int insnOpcode = insnNode.getOpcode();
int insnType = insnNode.getType();
if (insnType == AbstractInsnNode.LABEL
|| insnType == AbstractInsnNode.LINE
|| insnType == AbstractInsnNode.FRAME) {
merge(insnIndex + 1, oldFrame, subroutine);
newControlFlowEdge(insnIndex, insnIndex + 1);
} else {
currentFrame.init(oldFrame).execute(insnNode, interpreter);
subroutine = subroutine == null ? null : new Subroutine(subroutine);
if (insnNode instanceof JumpInsnNode) {
JumpInsnNode jumpInsn = (JumpInsnNode) insnNode;
if (insnOpcode != GOTO && insnOpcode != JSR) {
merge(insnIndex + 1, currentFrame, subroutine);
newControlFlowEdge(insnIndex, insnIndex + 1);
}
int jumpInsnIndex = insnList.indexOf(jumpInsn.label);
if (insnOpcode == JSR) {
merge(
jumpInsnIndex,
currentFrame,
new Subroutine(jumpInsn.label, method.maxLocals, jumpInsn));
} else {
merge(jumpInsnIndex, currentFrame, subroutine);
}
newControlFlowEdge(insnIndex, jumpInsnIndex);
} else if (insnNode instanceof LookupSwitchInsnNode) {
LookupSwitchInsnNode lookupSwitchInsn = (LookupSwitchInsnNode) insnNode;
int targetInsnIndex = insnList.indexOf(lookupSwitchInsn.dflt);
merge(targetInsnIndex, currentFrame, subroutine);
newControlFlowEdge(insnIndex, targetInsnIndex);
for (int i = 0; i < lookupSwitchInsn.labels.size(); ++i) {
targetInsnIndex = insnList.indexOf(lookupSwitchInsn.labels.get(i));
merge(targetInsnIndex, currentFrame, subroutine);
newControlFlowEdge(insnIndex, targetInsnIndex);
}
} else if (insnNode instanceof TableSwitchInsnNode) {
TableSwitchInsnNode tableSwitchInsn = (TableSwitchInsnNode) insnNode;
int targetInsnIndex = insnList.indexOf(tableSwitchInsn.dflt);
merge(targetInsnIndex, currentFrame, subroutine);
newControlFlowEdge(insnIndex, targetInsnIndex);
for (int i = 0; i < tableSwitchInsn.labels.size(); ++i) {
targetInsnIndex = insnList.indexOf(tableSwitchInsn.labels.get(i));
merge(targetInsnIndex, currentFrame, subroutine);
newControlFlowEdge(insnIndex, targetInsnIndex);
}
} else if (insnOpcode == RET) {
if (subroutine == null) {
throw new AnalyzerException(insnNode, "RET instruction outside of a sub routine");
}
for (int i = 0; i < subroutine.callers.size(); ++i) {
JumpInsnNode caller = subroutine.callers.get(i);
int jsrInsnIndex = insnList.indexOf(caller);
if (frames[jsrInsnIndex] != null) {
merge(
jsrInsnIndex + 1,
frames[jsrInsnIndex],
currentFrame,
subroutines[jsrInsnIndex],
subroutine.localsUsed);
newControlFlowEdge(insnIndex, jsrInsnIndex + 1);
}
}
} else if (insnOpcode != ATHROW && (insnOpcode < IRETURN || insnOpcode > RETURN)) {
if (subroutine != null) {
if (insnNode instanceof VarInsnNode) {
int var = ((VarInsnNode) insnNode).var;
subroutine.localsUsed[var] = true;
if (insnOpcode == LLOAD
|| insnOpcode == DLOAD
|| insnOpcode == LSTORE
|| insnOpcode == DSTORE) {
subroutine.localsUsed[var + 1] = true;
}
} else if (insnNode instanceof IincInsnNode) {
int var = ((IincInsnNode) insnNode).var;
subroutine.localsUsed[var] = true;
}
}
merge(insnIndex + 1, currentFrame, subroutine);
newControlFlowEdge(insnIndex, insnIndex + 1);
}
}
List insnHandlers = handlers[insnIndex];
if (insnHandlers != null) {
for (int i = 0; i < insnHandlers.size(); ++i) {
TryCatchBlockNode tryCatchBlock = insnHandlers.get(i);
Type catchType;
if (tryCatchBlock.type == null) {
catchType = Type.getObjectType("java/lang/Throwable");
} else {
catchType = Type.getObjectType(tryCatchBlock.type);
}
if (newControlFlowExceptionEdge(insnIndex, tryCatchBlock)) {
Frame handler = new Frame(oldFrame);
handler.clearStack();
handler.push(interpreter.newValue(catchType));
merge(insnList.indexOf(tryCatchBlock.handler), handler, subroutine);
}
}
}
} catch (AnalyzerException e) {
throw new AnalyzerException(
e.node, "Error at instruction " + insnIndex + ": " + e.getMessage(), e);
} catch (Exception e) {
throw new AnalyzerException(
insnNode, "Error at instruction " + insnIndex + ": " + e.getMessage(), e);
}
}
return frames;
}
/**
* Follows the control flow graph of the currently analyzed method, starting at the given
* instruction index, and stores a copy of the given subroutine in {@link #subroutines} for each
* encountered instruction. Jumps to nested subroutines are not followed: instead, the
* corresponding instructions are put in the given list.
*
* @param insnIndex an instruction index.
* @param subroutine a subroutine.
* @param jsrInsns where the jsr instructions for nested subroutines must be put.
* @throws AnalyzerException if the control flow graph can fall off the end of the code.
*/
private void findSubroutine(
final int insnIndex, final Subroutine subroutine, final List jsrInsns)
throws AnalyzerException {
int currentInsnIndex = insnIndex;
while (true) {
if (currentInsnIndex < 0 || currentInsnIndex >= insnListSize) {
throw new AnalyzerException(null, "Execution can fall off the end of the code");
}
if (subroutines[currentInsnIndex] != null) {
return;
}
subroutines[currentInsnIndex] = new Subroutine(subroutine);
AbstractInsnNode currentInsn = insnList.get(currentInsnIndex);
// Call findSubroutine recursively on the normal successors of currentInsn.
if (currentInsn instanceof JumpInsnNode) {
if (currentInsn.getOpcode() == JSR) {
// Do not follow a jsr, it leads to another subroutine!
jsrInsns.add(currentInsn);
} else {
JumpInsnNode jumpInsn = (JumpInsnNode) currentInsn;
findSubroutine(insnList.indexOf(jumpInsn.label), subroutine, jsrInsns);
}
} else if (currentInsn instanceof TableSwitchInsnNode) {
TableSwitchInsnNode tableSwitchInsn = (TableSwitchInsnNode) currentInsn;
findSubroutine(insnList.indexOf(tableSwitchInsn.dflt), subroutine, jsrInsns);
for (int i = tableSwitchInsn.labels.size() - 1; i >= 0; --i) {
LabelNode l = tableSwitchInsn.labels.get(i);
findSubroutine(insnList.indexOf(l), subroutine, jsrInsns);
}
} else if (currentInsn instanceof LookupSwitchInsnNode) {
LookupSwitchInsnNode lookupSwitchInsn = (LookupSwitchInsnNode) currentInsn;
findSubroutine(insnList.indexOf(lookupSwitchInsn.dflt), subroutine, jsrInsns);
for (int i = lookupSwitchInsn.labels.size() - 1; i >= 0; --i) {
LabelNode l = lookupSwitchInsn.labels.get(i);
findSubroutine(insnList.indexOf(l), subroutine, jsrInsns);
}
}
// Call findSubroutine recursively on the exception handler successors of currentInsn.
List insnHandlers = handlers[currentInsnIndex];
if (insnHandlers != null) {
for (int i = 0; i < insnHandlers.size(); ++i) {
TryCatchBlockNode tryCatchBlock = insnHandlers.get(i);
findSubroutine(insnList.indexOf(tryCatchBlock.handler), subroutine, jsrInsns);
}
}
// If currentInsn does not fall through to the next instruction, return.
switch (currentInsn.getOpcode()) {
case GOTO:
case RET:
case TABLESWITCH:
case LOOKUPSWITCH:
case IRETURN:
case LRETURN:
case FRETURN:
case DRETURN:
case ARETURN:
case RETURN:
case ATHROW:
return;
default:
break;
}
currentInsnIndex++;
}
}
/**
* Computes the initial execution stack frame of the given method.
*
* @param owner the internal name of the class to which 'method' belongs.
* @param method the method to be analyzed.
* @return the initial execution stack frame of the 'method'.
*/
private Frame computeInitialFrame(final String owner, final MethodNode method) {
Frame frame = newFrame(method.maxLocals, method.maxStack);
int currentLocal = 0;
if ((method.access & ACC_STATIC) == 0) {
Type ownerType = Type.getObjectType(owner);
frame.setLocal(currentLocal++, interpreter.newValue(ownerType));
}
Type[] argumentTypes = Type.getArgumentTypes(method.desc);
for (int i = 0; i < argumentTypes.length; ++i) {
frame.setLocal(currentLocal++, interpreter.newValue(argumentTypes[i]));
if (argumentTypes[i].getSize() == 2) {
frame.setLocal(currentLocal++, interpreter.newValue(null));
}
}
while (currentLocal < method.maxLocals) {
frame.setLocal(currentLocal++, interpreter.newValue(null));
}
frame.setReturn(interpreter.newValue(Type.getReturnType(method.desc)));
return frame;
}
/**
* Returns the symbolic execution stack frame for each instruction of the last analyzed method.
*
* @return the symbolic state of the execution stack frame at each bytecode instruction of the
* method. The size of the returned array is equal to the number of instructions (and labels)
* of the method. A given frame is null if the corresponding instruction cannot be
* reached, or if an error occured during the analysis of the method.
*/
public Frame[] getFrames() {
return frames;
}
/**
* Returns the exception handlers for the given instruction.
*
* @param insnIndex the index of an instruction of the last analyzed method.
* @return a list of {@link TryCatchBlockNode} objects.
*/
public List getHandlers(final int insnIndex) {
return handlers[insnIndex];
}
/**
* Initializes this analyzer. This method is called just before the execution of control flow
* analysis loop in #analyze. The default implementation of this method does nothing.
*
* @param owner the internal name of the class to which the method belongs.
* @param method the method to be analyzed.
* @throws AnalyzerException if a problem occurs.
*/
protected void init(final String owner, final MethodNode method) throws AnalyzerException {
// Nothing to do.
}
/**
* Constructs a new frame with the given size.
*
* @param nLocals the maximum number of local variables of the frame.
* @param nStack the maximum stack size of the frame.
* @return the created frame.
*/
protected Frame newFrame(final int nLocals, final int nStack) {
return new Frame(nLocals, nStack);
}
/**
* Constructs a copy of the given frame.
*
* @param frame a frame.
* @return the created frame.
*/
protected Frame newFrame(final Frame frame) {
return new Frame(frame);
}
/**
* Creates a control flow graph edge. The default implementation of this method does nothing. It
* can be overriden in order to construct the control flow graph of a method (this method is
* called by the {@link #analyze} method during its visit of the method's code).
*
* @param insnIndex an instruction index.
* @param successorIndex index of a successor instruction.
*/
protected void newControlFlowEdge(final int insnIndex, final int successorIndex) {
// Nothing to do.
}
/**
* Creates a control flow graph edge corresponding to an exception handler. The default
* implementation of this method does nothing. It can be overridden in order to construct the
* control flow graph of a method (this method is called by the {@link #analyze} method during its
* visit of the method's code).
*
* @param insnIndex an instruction index.
* @param successorIndex index of a successor instruction.
* @return true if this edge must be considered in the data flow analysis performed by this
* analyzer, or false otherwise. The default implementation of this method always returns
* true.
*/
protected boolean newControlFlowExceptionEdge(final int insnIndex, final int successorIndex) {
return true;
}
/**
* Creates a control flow graph edge corresponding to an exception handler. The default
* implementation of this method delegates to {@link #newControlFlowExceptionEdge(int, int)}. It
* can be overridden in order to construct the control flow graph of a method (this method is
* called by the {@link #analyze} method during its visit of the method's code).
*
* @param insnIndex an instruction index.
* @param tryCatchBlock TryCatchBlockNode corresponding to this edge.
* @return true if this edge must be considered in the data flow analysis performed by this
* analyzer, or false otherwise. The default implementation of this method delegates to {@link
* #newControlFlowExceptionEdge(int, int)}.
*/
protected boolean newControlFlowExceptionEdge(
final int insnIndex, final TryCatchBlockNode tryCatchBlock) {
return newControlFlowExceptionEdge(insnIndex, insnList.indexOf(tryCatchBlock.handler));
}
// -----------------------------------------------------------------------------------------------
/**
* Merges the given frame and subroutine into the frame and subroutines at the given instruction
* index. If the frame or the subroutine at the given instruction index changes as a result of
* this merge, the instruction index is added to the list of instructions to process (if it is not
* already the case).
*
* @param insnIndex an instruction index.
* @param frame a frame. This frame is left unchanged by this method.
* @param subroutine a subroutine. This subroutine is left unchanged by this method.
* @throws AnalyzerException if the frames have incompatible sizes.
*/
private void merge(final int insnIndex, final Frame frame, final Subroutine subroutine)
throws AnalyzerException {
boolean changed;
Frame oldFrame = frames[insnIndex];
if (oldFrame == null) {
frames[insnIndex] = newFrame(frame);
changed = true;
} else {
changed = oldFrame.merge(frame, interpreter);
}
Subroutine oldSubroutine = subroutines[insnIndex];
if (oldSubroutine == null) {
if (subroutine != null) {
subroutines[insnIndex] = new Subroutine(subroutine);
changed = true;
}
} else {
if (subroutine != null) {
changed |= oldSubroutine.merge(subroutine);
}
}
if (changed && !inInstructionsToProcess[insnIndex]) {
inInstructionsToProcess[insnIndex] = true;
instructionsToProcess[numInstructionsToProcess++] = insnIndex;
}
}
/**
* Merges the given frame and subroutine into the frame and subroutines at the given instruction
* index (case of a RET instruction). If the frame or the subroutine at the given instruction
* index changes as a result of this merge, the instruction index is added to the list of
* instructions to process (if it is not already the case).
*
* @param insnIndex the index of an instruction immediately following a jsr instruction.
* @param frameBeforeJsr the execution stack frame before the jsr instruction. This frame is
* merged into 'frameAfterRet'.
* @param frameAfterRet the execution stack frame after a ret instruction of the subroutine. This
* frame is merged into the frame at 'insnIndex' (after it has itself been merge with
* 'frameBeforeJsr').
* @param subroutineBeforeJsr if the jsr is itself part of a subroutine (case of nested
* subroutine), the subroutine it belongs to.
* @param localsUsed the local variables read or written in the subroutine.
* @throws AnalyzerException if the frames have incompatible sizes.
*/
private void merge(
final int insnIndex,
final Frame frameBeforeJsr,
final Frame frameAfterRet,
final Subroutine subroutineBeforeJsr,
final boolean[] localsUsed)
throws AnalyzerException {
frameAfterRet.merge(frameBeforeJsr, localsUsed);
boolean changed;
Frame oldFrame = frames[insnIndex];
if (oldFrame == null) {
frames[insnIndex] = newFrame(frameAfterRet);
changed = true;
} else {
changed = oldFrame.merge(frameAfterRet, interpreter);
}
Subroutine oldSubroutine = subroutines[insnIndex];
if (oldSubroutine != null && subroutineBeforeJsr != null) {
changed |= oldSubroutine.merge(subroutineBeforeJsr);
}
if (changed && !inInstructionsToProcess[insnIndex]) {
inInstructionsToProcess[insnIndex] = true;
instructionsToProcess[numInstructionsToProcess++] = insnIndex;
}
}
}
