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ProGuard is a free shrinker, optimizer, obfuscator, and preverifier for Java bytecode
/*
* ProGuard -- shrinking, optimization, obfuscation, and preverification
* of Java bytecode.
*
* Copyright (c) 2002-2021 Guardsquare NV
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package proguard.optimize.info;
import proguard.classfile.*;
import proguard.classfile.attribute.*;
import proguard.classfile.attribute.visitor.AttributeVisitor;
import proguard.classfile.constant.*;
import proguard.classfile.constant.visitor.ConstantVisitor;
import proguard.classfile.editor.ClassEstimates;
import proguard.classfile.instruction.*;
import proguard.classfile.instruction.visitor.InstructionVisitor;
import proguard.classfile.util.*;
import proguard.evaluation.*;
import proguard.evaluation.value.*;
import proguard.optimize.evaluation.*;
import proguard.util.ArrayUtil;
/**
* This AttributeVisitor can tell whether reference parameters and instances
* are escaping, are modified, or are returned.
*
* @see ParameterEscapeMarker
* @author Eric Lafortune
*/
public class ReferenceEscapeChecker
implements AttributeVisitor,
InstructionVisitor,
ConstantVisitor
{
//*
private static final boolean DEBUG = false;
/*/
private static boolean DEBUG = System.getProperty("rec") != null;
//*/
private boolean[] instanceEscaping = new boolean[ClassEstimates.TYPICAL_CODE_LENGTH];
private boolean[] instanceReturned = new boolean[ClassEstimates.TYPICAL_CODE_LENGTH];
private boolean[] instanceModified = new boolean[ClassEstimates.TYPICAL_CODE_LENGTH];
private boolean[] externalInstance = new boolean[ClassEstimates.TYPICAL_CODE_LENGTH];
// private boolean[] exceptionEscaping = new boolean[ClassEstimates.TYPICAL_CODE_LENGTH];
// private boolean[] exceptionReturned = new boolean[ClassEstimates.TYPICAL_CODE_LENGTH];
// private boolean[] exceptionModified = new boolean[ClassEstimates.TYPICAL_CODE_LENGTH];
private final PartialEvaluator partialEvaluator;
private final boolean runPartialEvaluator;
// Parameters and values for visitor methods.
private Method referencingMethod;
private int referencingOffset;
private int referencingPopCount;
/**
* Creates a new ReferenceEscapeChecker.
*/
public ReferenceEscapeChecker()
{
this(new ReferenceTracingValueFactory(new BasicValueFactory()));
}
/**
* Creates a new ReferenceEscapeChecker. This private constructor gets around
* the constraint that it's not allowed to add statements before calling
* 'this'.
*/
private ReferenceEscapeChecker(ReferenceTracingValueFactory referenceTracingValueFactory)
{
this(new PartialEvaluator(referenceTracingValueFactory,
new ParameterTracingInvocationUnit(new BasicInvocationUnit(referenceTracingValueFactory)),
true,
referenceTracingValueFactory),
true);
}
/**
* Creates a new ReferenceEscapeChecker.
* @param partialEvaluator the evaluator to be used for the analysis.
* @param runPartialEvaluator specifies whether to run this evaluator on
* every code attribute that is visited.
*/
public ReferenceEscapeChecker(PartialEvaluator partialEvaluator,
boolean runPartialEvaluator)
{
this.partialEvaluator = partialEvaluator;
this.runPartialEvaluator = runPartialEvaluator;
}
/**
* Returns whether the instance created or retrieved at the specified
* instruction offset is escaping.
*/
public boolean isInstanceEscaping(int instructionOffset)
{
return instanceEscaping[instructionOffset];
}
/**
* Returns whether the instance created or retrieved at the specified
* instruction offset is being returned.
*/
public boolean isInstanceReturned(int instructionOffset)
{
return instanceReturned[instructionOffset];
}
/**
* Returns whether the instance created or retrieved at the specified
* instruction offset is being modified.
*/
public boolean isInstanceModified(int instructionOffset)
{
return instanceModified[instructionOffset];
}
/**
* Returns whether the instance created or retrieved at the specified
* instruction offset is external to this method and its invoked methods.
*/
public boolean isInstanceExternal(int instructionOffset)
{
return externalInstance[instructionOffset];
}
// Implementations for AttributeVisitor.
public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}
public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute)
{
// Evaluate the method.
if (runPartialEvaluator)
{
partialEvaluator.visitCodeAttribute(clazz, method, codeAttribute);
}
int codeLength = codeAttribute.u4codeLength;
// Initialize the global arrays.
instanceEscaping = ArrayUtil.ensureArraySize(instanceEscaping, codeLength, false);
instanceReturned = ArrayUtil.ensureArraySize(instanceReturned, codeLength, false);
instanceModified = ArrayUtil.ensureArraySize(instanceModified, codeLength, false);
externalInstance = ArrayUtil.ensureArraySize(externalInstance, codeLength, false);
// Mark the parameters and instances that are escaping from the code.
codeAttribute.instructionsAccept(clazz, method, partialEvaluator.tracedInstructionFilter(this));
if (DEBUG)
{
System.out.println();
System.out.println("ReferenceEscapeChecker: ["+clazz.getName()+"."+method.getName(clazz)+method.getDescriptor(clazz)+"]");
for (int index = 0; index < codeLength; index++)
{
if (partialEvaluator.isInstruction(index))
{
System.out.println(" " +
(instanceEscaping[index] ? 'E' : '.') +
(instanceReturned[index] ? 'R' : '.') +
(instanceModified[index] ? 'M' : '.') +
(externalInstance[index] ? 'X' : '.') +
' ' +
InstructionFactory.create(codeAttribute.code, index).toString(index));
}
}
}
}
// Implementations for InstructionVisitor.
public void visitAnyInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, Instruction instruction) {}
public void visitSimpleInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, SimpleInstruction simpleInstruction)
{
switch (simpleInstruction.opcode)
{
case Instruction.OP_AASTORE:
// Mark array reference values whose element is modified.
markModifiedReferenceValues(offset,
simpleInstruction.stackPopCount(clazz) - 1);
// Mark reference values that are put in the array.
markEscapingReferenceValues(offset, 0);
break;
case Instruction.OP_IASTORE:
case Instruction.OP_LASTORE:
case Instruction.OP_FASTORE:
case Instruction.OP_DASTORE:
case Instruction.OP_BASTORE:
case Instruction.OP_CASTORE:
case Instruction.OP_SASTORE:
// Mark array reference values whose element is modified.
markModifiedReferenceValues(offset,
simpleInstruction.stackPopCount(clazz) - 1);
break;
case Instruction.OP_ARETURN:
// Mark the returned reference values.
markReturnedReferenceValues(offset, 0);
break;
case Instruction.OP_ATHROW:
// Mark the escaping reference values.
markEscapingReferenceValues(offset, 0);
break;
}
}
public void visitConstantInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, ConstantInstruction constantInstruction)
{
switch (constantInstruction.opcode)
{
case Instruction.OP_GETSTATIC:
case Instruction.OP_GETFIELD:
// Mark external reference values.
markExternalReferenceValue(offset);
break;
case Instruction.OP_PUTSTATIC:
// Mark reference values that are put in the field.
markEscapingReferenceValues(offset, 0);
break;
case Instruction.OP_PUTFIELD:
// Mark reference reference values whose field is modified.
markModifiedReferenceValues(offset,
constantInstruction.stackPopCount(clazz) - 1);
// Mark reference values that are put in the field.
markEscapingReferenceValues(offset, 0);
break;
case Instruction.OP_INVOKEVIRTUAL:
case Instruction.OP_INVOKESPECIAL:
case Instruction.OP_INVOKESTATIC:
case Instruction.OP_INVOKEINTERFACE:
// Mark reference reference values that are modified as parameters
// of the invoked method.
// Mark reference values that are escaping as parameters
// of the invoked method.
// Mark escaped reference reference values in the invoked method.
referencingMethod = method;
referencingOffset = offset;
referencingPopCount = constantInstruction.stackPopCount(clazz);
clazz.constantPoolEntryAccept(constantInstruction.constantIndex, this);
break;
}
}
// Implementations for ConstantVisitor.
public void visitAnyConstant(Clazz clazz, Constant constant) {}
public void visitFieldrefConstant(Clazz clazz, FieldrefConstant fieldrefConstant)
{
clazz.constantPoolEntryAccept(fieldrefConstant.u2classIndex, this);
}
public void visitAnyMethodrefConstant(Clazz clazz, AnyMethodrefConstant anyMethodrefConstant)
{
Method referencedMethod = (Method)anyMethodrefConstant.referencedMethod;
// Mark reference reference values that are passed to the method.
for (int index = 0; index < referencingPopCount; index++)
{
int stackEntryIndex = referencingPopCount - index - 1;
TracedStack stackBefore = partialEvaluator.getStackBefore(referencingOffset);
Value stackEntry = stackBefore.getTop(stackEntryIndex);
if (stackEntry.computationalType() == Value.TYPE_REFERENCE)
{
// Is the parameter escaping from the referenced method?
if (referencedMethod == null ||
ParameterEscapeMarker.isParameterEscaping(referencedMethod, index))
{
markEscapingReferenceValues(referencingOffset,
stackEntryIndex);
}
// Is the parameter being modified in the referenced method?
if (referencedMethod == null ||
ParameterEscapeMarker.isParameterModified(referencedMethod, index))
{
markModifiedReferenceValues(referencingOffset,
stackEntryIndex);
}
}
}
// Is the return value from the referenced method external?
String returnType =
ClassUtil.internalMethodReturnType(anyMethodrefConstant.getType(clazz));
if (referencedMethod == null ||
((ClassUtil.isInternalClassType(returnType) ||
ClassUtil.isInternalArrayType(returnType)) &&
ParameterEscapeMarker.returnsExternalValues(referencedMethod)))
{
markExternalReferenceValue(referencingOffset);
}
}
// Small utility methods.
/**
* Marks the producing offsets of the specified stack entry at the given
* instruction offset.
*/
private void markEscapingReferenceValues(int instructionOffset,
int stackEntryIndex)
{
TracedStack stackBefore = partialEvaluator.getStackBefore(instructionOffset);
Value stackEntry = stackBefore.getTop(stackEntryIndex);
if (stackEntry.computationalType() == Value.TYPE_REFERENCE)
{
ReferenceValue referenceValue = stackEntry.referenceValue();
// The null reference value may not have a trace value.
if (referenceValue.isNull() != Value.ALWAYS)
{
markEscapingReferenceValues(referenceValue);
}
}
}
/**
* Marks the producing offsets of the given traced reference value.
*/
private void markEscapingReferenceValues(ReferenceValue referenceValue)
{
TracedReferenceValue tracedReferenceValue = (TracedReferenceValue)referenceValue;
InstructionOffsetValue instructionOffsetValue = tracedReferenceValue.getTraceValue().instructionOffsetValue();
int parameterCount = instructionOffsetValue.instructionOffsetCount();
for (int index = 0; index < parameterCount; index++)
{
if (!instructionOffsetValue.isMethodParameter(index))
{
instanceEscaping[instructionOffsetValue.instructionOffset(index)] = true;
}
}
}
/**
* Marks the producing offsets of the specified stack entry at the given
* instruction offset.
*/
private void markReturnedReferenceValues(int instructionOffset,
int stackEntryIndex)
{
TracedStack stackBefore = partialEvaluator.getStackBefore(instructionOffset);
ReferenceValue referenceValue = stackBefore.getTop(stackEntryIndex).referenceValue();
// The null reference value may not have a trace value.
if (referenceValue.isNull() != Value.ALWAYS)
{
markReturnedReferenceValues(referenceValue);
}
}
/**
* Marks the producing offsets of the given traced reference value.
*/
private void markReturnedReferenceValues(ReferenceValue referenceValue)
{
TracedReferenceValue tracedReferenceValue = (TracedReferenceValue)referenceValue;
InstructionOffsetValue instructionOffsetValue = tracedReferenceValue.getTraceValue().instructionOffsetValue();
int parameterCount = instructionOffsetValue.instructionOffsetCount();
for (int index = 0; index < parameterCount; index++)
{
if (!instructionOffsetValue.isMethodParameter(index))
{
instanceReturned[instructionOffsetValue.instructionOffset(index)] = true;
}
}
}
/**
* Marks the producing offsets of the specified stack entry at the given
* instruction offset.
*/
private void markModifiedReferenceValues(int instructionOffset,
int stackEntryIndex)
{
TracedStack stackBefore = partialEvaluator.getStackBefore(instructionOffset);
ReferenceValue referenceValue = stackBefore.getTop(stackEntryIndex).referenceValue();
// The null reference value may not have a trace value.
if (referenceValue.isNull() != Value.ALWAYS)
{
markModifiedReferenceValues(referenceValue);
}
}
/**
* Marks the producing offsets of the given traced reference value.
*/
private void markModifiedReferenceValues(ReferenceValue referenceValue)
{
TracedReferenceValue tracedReferenceValue = (TracedReferenceValue)referenceValue;
InstructionOffsetValue instructionOffsetValue = tracedReferenceValue.getTraceValue().instructionOffsetValue();
int parameterCount = instructionOffsetValue.instructionOffsetCount();
for (int index = 0; index < parameterCount; index++)
{
if (!instructionOffsetValue.isMethodParameter(index))
{
instanceModified[instructionOffsetValue.instructionOffset(index)] = true;
}
}
}
/**
* Marks the producing offsets of the specified stack entry at the given
* instruction offset.
*/
private void markExternalReferenceValue(int offset)
{
externalInstance[offset] = true;
}
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