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/*
* Copyright (C) 2014 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package dexfuzz.program.mutators;
import dexfuzz.Log;
import dexfuzz.MutationStats;
import dexfuzz.program.MInsn;
import dexfuzz.program.MutatableCode;
import dexfuzz.program.Mutation;
import dexfuzz.rawdex.formats.ContainsVRegs;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
public class VRegChanger extends CodeMutator {
/**
* Every CodeMutator has an AssociatedMutation, representing the
* mutation that this CodeMutator can perform, to allow separate
* generateMutation() and applyMutation() phases, allowing serialization.
*/
public static class AssociatedMutation extends Mutation {
public int vregInsnIdx;
public int mutatingVreg;
public int newVregValue;
@Override
public String getString() {
StringBuilder builder = new StringBuilder();
builder.append(vregInsnIdx).append(" ");
builder.append(mutatingVreg).append(" ");
builder.append(newVregValue);
return builder.toString();
}
@Override
public void parseString(String[] elements) {
vregInsnIdx = Integer.parseInt(elements[2]);
mutatingVreg = Integer.parseInt(elements[3]);
newVregValue = Integer.parseInt(elements[4]);
}
}
// The following two methods are here for the benefit of MutationSerializer,
// so it can create a CodeMutator and get the correct associated Mutation, as it
// reads in mutations from a dump of mutations.
@Override
public Mutation getNewMutation() {
return new AssociatedMutation();
}
public VRegChanger() { }
public VRegChanger(Random rng, MutationStats stats, List<Mutation> mutations) {
super(rng, stats, mutations);
likelihood = 60;
}
// A cache that should only exist between generateMutation() and applyMutation(),
// or be created at the start of applyMutation(), if we're reading in mutations from
// a file.
private List<MInsn> vregInsns = null;
private void generateCachedVRegInsns(MutatableCode mutatableCode) {
if (vregInsns != null) {
return;
}
vregInsns = new ArrayList<MInsn>();
for (MInsn mInsn : mutatableCode.getInstructions()) {
if (mInsn.insn.info.format instanceof ContainsVRegs) {
vregInsns.add(mInsn);
}
}
}
@Override
protected boolean canMutate(MutatableCode mutatableCode) {
if (mutatableCode.registersSize < 2) {
Log.debug("Impossible to change vregs in a method with fewer than 2 registers.");
return false;
}
for (MInsn mInsn : mutatableCode.getInstructions()) {
if (mInsn.insn.info.format instanceof ContainsVRegs) {
return true;
}
}
return false;
}
@Override
protected Mutation generateMutation(MutatableCode mutatableCode) {
generateCachedVRegInsns(mutatableCode);
// Pick a random vreg instruction.
int vregInsnIdx = rng.nextInt(vregInsns.size());
MInsn vregInsn = vregInsns.get(vregInsnIdx);
// Get the number of VRegs this instruction uses.
int numVregs = ((ContainsVRegs)vregInsn.insn.info.format).getVRegCount();
// Pick which vreg to mutate.
int mutatingVreg = rng.nextInt(numVregs);
// Find the old index.
int oldVregValue = 0;
switch (mutatingVreg) {
case 0:
oldVregValue = (int) vregInsn.insn.vregA;
break;
case 1:
oldVregValue = (int) vregInsn.insn.vregB;
break;
case 2:
oldVregValue = (int) vregInsn.insn.vregC;
break;
default:
Log.errorAndQuit("Invalid number of vregs reported by a Format.");
}
// Search for a new vreg value.
int newVregValue = oldVregValue;
while (newVregValue == oldVregValue) {
newVregValue = rng.nextInt(mutatableCode.registersSize);
}
AssociatedMutation mutation = new AssociatedMutation();
mutation.setup(this.getClass(), mutatableCode);
mutation.vregInsnIdx = vregInsnIdx;
mutation.mutatingVreg = mutatingVreg;
mutation.newVregValue = newVregValue;
return mutation;
}
@Override
protected void applyMutation(Mutation uncastMutation) {
// Cast the Mutation to our AssociatedMutation, so we can access its fields.
AssociatedMutation mutation = (AssociatedMutation) uncastMutation;
MutatableCode mutatableCode = mutation.mutatableCode;
generateCachedVRegInsns(mutatableCode);
MInsn vregInsn = vregInsns.get(mutation.vregInsnIdx);
// Remember what the instruction used to look like.
String oldInsnString = vregInsn.toString();
int oldVregValue = 0;
String vregId = "A";
switch (mutation.mutatingVreg) {
case 0:
oldVregValue = (int) vregInsn.insn.vregA;
vregInsn.insn.vregA = (long) mutation.newVregValue;
break;
case 1:
oldVregValue = (int) vregInsn.insn.vregB;
vregInsn.insn.vregB = (long) mutation.newVregValue;
vregId = "B";
break;
case 2:
oldVregValue = (int) vregInsn.insn.vregC;
vregInsn.insn.vregC = (long) mutation.newVregValue;
vregId = "C";
break;
default:
Log.errorAndQuit("Invalid number of vregs specified in a VRegChanger mutation.");
}
Log.info("In " + oldInsnString + " changed v" + vregId + ": v" + oldVregValue
+ " to v" + mutation.newVregValue);
stats.incrementStat("Changed a virtual register");
// Clear cache.
vregInsns = null;
}
}
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