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fix: replace recursive analysis algorithms with iterations to avoid S…
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…tackOverflow on big methods (#441)
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@skylot
skylot committed Feb 14, 2019
1 parent 8c7140d commit 710245d
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Showing 4 changed files with 117 additions and 52 deletions.
31 changes: 24 additions & 7 deletions jadx-core/src/main/java/jadx/core/dex/visitors/blocksmaker/BlockProcessor.java
View file
Expand Up @@ -3,7 +3,9 @@
import java.util.ArrayList;
import java.util.BitSet;
import java.util.Collections;
import java.util.Deque;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

import org.slf4j.Logger;
Expand All @@ -25,7 +27,6 @@
import jadx.core.dex.trycatch.TryCatchBlock;
import jadx.core.dex.visitors.AbstractVisitor;
import jadx.core.utils.BlockUtils;
import jadx.core.utils.exceptions.JadxOverflowException;
import jadx.core.utils.exceptions.JadxRuntimeException;

import static jadx.core.dex.visitors.blocksmaker.BlockSplitter.connect;
Expand Down Expand Up @@ -220,7 +221,12 @@ private static void computeDominators(MethodNode mth) {
markLoops(mth);

// clear self dominance
basicBlocks.forEach(block -> block.getDoms().clear(block.getId()));
basicBlocks.forEach(block -> {
block.getDoms().clear(block.getId());
if (block.getDoms().isEmpty()) {
block.setDoms(EMPTY);
}
});

// calculate immediate dominators
for (BlockNode block : basicBlocks) {
Expand Down Expand Up @@ -253,11 +259,20 @@ private static void computeDominanceFrontier(MethodNode mth) {
for (BlockNode exit : mth.getExitBlocks()) {
exit.setDomFrontier(EMPTY);
}
for (BlockNode block : mth.getBasicBlocks()) {
List<BlockNode> domSortedBlocks = new ArrayList<>(mth.getBasicBlocks().size());
Deque<BlockNode> stack = new LinkedList<>();
stack.push(mth.getEnterBlock());
while (!stack.isEmpty()) {
BlockNode node = stack.pop();
for (BlockNode dominated : node.getDominatesOn()) {
stack.push(dominated);
}
domSortedBlocks.add(node);
}
Collections.reverse(domSortedBlocks);
for (BlockNode block : domSortedBlocks) {
try {
computeBlockDF(mth, block);
} catch (StackOverflowError e) {
throw new JadxOverflowException("Failed compute block dominance frontier");
} catch (Exception e) {
throw new JadxRuntimeException("Failed compute block dominance frontier", e);
}
Expand All @@ -268,7 +283,6 @@ private static void computeBlockDF(MethodNode mth, BlockNode block) {
if (block.getDomFrontier() != null) {
return;
}
block.getDominatesOn().forEach(domBlock -> computeBlockDF(mth, domBlock));
List<BlockNode> blocks = mth.getBasicBlocks();
BitSet domFrontier = null;
for (BlockNode s : block.getSuccessors()) {
Expand All @@ -281,6 +295,9 @@ private static void computeBlockDF(MethodNode mth, BlockNode block) {
}
for (BlockNode c : block.getDominatesOn()) {
BitSet frontier = c.getDomFrontier();
if (frontier == null) {
throw new JadxRuntimeException("Dominance frontier not calculated for dominated block: " + c + ", from: " + block);
}
for (int p = frontier.nextSetBit(0); p >= 0; p = frontier.nextSetBit(p + 1)) {
if (blocks.get(p).getIDom() != block) {
if (domFrontier == null) {
Expand All @@ -290,7 +307,7 @@ private static void computeBlockDF(MethodNode mth, BlockNode block) {
}
}
}
if (domFrontier == null || domFrontier.cardinality() == 0) {
if (domFrontier == null || domFrontier.isEmpty()) {
domFrontier = EMPTY;
}
block.setDomFrontier(domFrontier);
Expand Down
23 changes: 11 additions & 12 deletions jadx-core/src/main/java/jadx/core/dex/visitors/ssa/LiveVarAnalysis.java
View file
Expand Up @@ -80,35 +80,34 @@ private void fillBasicBlockInfo() {
private void processLiveInfo() {
int bbCount = mth.getBasicBlocks().size();
int regsCount = mth.getRegsCount();
BitSet[] liveIn = initBitSetArray(bbCount, regsCount);
BitSet[] liveInBlocks = initBitSetArray(bbCount, regsCount);
List<BlockNode> blocks = mth.getBasicBlocks();
int blocksSize = blocks.size();
int blocksCount = blocks.size();
int iterationsLimit = blocksCount * 10;
boolean changed;
int k = 0;
do {
changed = false;
for (int i = 0; i < blocksSize; i++) {
BlockNode block = blocks.get(i);
for (BlockNode block : blocks) {
int blockId = block.getId();
BitSet prevIn = liveIn[blockId];
BitSet prevIn = liveInBlocks[blockId];
BitSet newIn = new BitSet(regsCount);
List<BlockNode> successors = block.getSuccessors();
for (int s = 0, successorsSize = successors.size(); s < successorsSize; s++) {
newIn.or(liveIn[successors.get(s).getId()]);
for (BlockNode successor : block.getSuccessors()) {
newIn.or(liveInBlocks[successor.getId()]);
}
newIn.andNot(defs[blockId]);
newIn.or(uses[blockId]);
if (!prevIn.equals(newIn)) {
changed = true;
liveIn[blockId] = newIn;
liveInBlocks[blockId] = newIn;
}
}
if (k++ > 1000) {
throw new JadxRuntimeException("Live variable analysis reach iterations limit");
if (k++ > iterationsLimit) {
throw new JadxRuntimeException("Live variable analysis reach iterations limit, blocks count: " + blocksCount);
}
} while (changed);

this.liveIn = liveIn;
this.liveIn = liveInBlocks;
}

private static BitSet[] initBitSetArray(int length, int bitsCount) {
Expand Down
59 changes: 59 additions & 0 deletions jadx-core/src/main/java/jadx/core/dex/visitors/ssa/RenameState.java
View file
@@ -0,0 +1,59 @@
package jadx.core.dex.visitors.ssa;

import java.util.Arrays;

import jadx.core.dex.instructions.args.RegisterArg;
import jadx.core.dex.instructions.args.SSAVar;
import jadx.core.dex.nodes.BlockNode;
import jadx.core.dex.nodes.MethodNode;

final class RenameState {
private final MethodNode mth;
private final BlockNode block;
private final SSAVar[] vars;
private final int[] versions;

public static RenameState init(MethodNode mth) {
int regsCount = mth.getRegsCount();
RenameState state = new RenameState(
mth,
mth.getEnterBlock(),
new SSAVar[regsCount],
new int[regsCount]
);
for (RegisterArg arg : mth.getArguments(true)) {
state.startVar(arg);
}
return state;
}

public static RenameState copyFrom(RenameState state, BlockNode block) {
return new RenameState(
state.mth,
block,
Arrays.copyOf(state.vars, state.vars.length),
state.versions
);
}

private RenameState(MethodNode mth, BlockNode block, SSAVar[] vars, int[] versions) {
this.mth = mth;
this.block = block;
this.vars = vars;
this.versions = versions;
}

public BlockNode getBlock() {
return block;
}

public SSAVar getVar(int regNum) {
return vars[regNum];
}

public void startVar(RegisterArg regArg) {
int regNum = regArg.getRegNum();
int version = versions[regNum]++;
vars[regNum] = mth.makeNewSVar(regNum, version, regArg);
}
}
56 changes: 23 additions & 33 deletions jadx-core/src/main/java/jadx/core/dex/visitors/ssa/SSATransform.java
View file
@@ -1,7 +1,6 @@
package jadx.core.dex.visitors.ssa;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.BitSet;
import java.util.Deque;
import java.util.Iterator;
Expand Down Expand Up @@ -120,35 +119,31 @@ private static void renameVariables(MethodNode mth) {
if (!mth.getSVars().isEmpty()) {
throw new JadxRuntimeException("SSA rename variables already executed");
}
int regsCount = mth.getRegsCount();
SSAVar[] vars = new SSAVar[regsCount];
int[] versions = new int[regsCount];
// init method arguments
for (RegisterArg arg : mth.getArguments(true)) {
int regNum = arg.getRegNum();
vars[regNum] = newSSAVar(mth, versions, arg, regNum);
}
BlockNode enterBlock = mth.getEnterBlock();
initPhiInEnterBlock(vars, enterBlock);
renameVar(mth, vars, versions, enterBlock);
}
RenameState initState = RenameState.init(mth);
initPhiInEnterBlock(initState);

private static SSAVar newSSAVar(MethodNode mth, int[] versions, RegisterArg arg, int regNum) {
int version = versions[regNum]++;
return mth.makeNewSVar(regNum, version, arg);
Deque<RenameState> stack = new LinkedList<>();
stack.push(initState);
while (!stack.isEmpty()) {
RenameState state = stack.pop();
renameVarsInBlock(state);
for (BlockNode dominated : state.getBlock().getDominatesOn()) {
stack.push(RenameState.copyFrom(state, dominated));
}
}
}

private static void initPhiInEnterBlock(SSAVar[] vars, BlockNode enterBlock) {
PhiListAttr phiList = enterBlock.get(AType.PHI_LIST);
private static void initPhiInEnterBlock(RenameState initState) {
PhiListAttr phiList = initState.getBlock().get(AType.PHI_LIST);
if (phiList != null) {
for (PhiInsn phiInsn : phiList.getList()) {
bindPhiArg(vars, enterBlock, phiInsn);
bindPhiArg(initState, phiInsn);
}
}
}

private static void renameVar(MethodNode mth, SSAVar[] vars, int[] vers, BlockNode block) {
SSAVar[] inputVars = Arrays.copyOf(vars, vars.length);
private static void renameVarsInBlock(RenameState state) {
BlockNode block = state.getBlock();
for (InsnNode insn : block.getInstructions()) {
if (insn.getType() != InsnType.PHI) {
for (InsnArg arg : insn.getArguments()) {
Expand All @@ -157,18 +152,17 @@ private static void renameVar(MethodNode mth, SSAVar[] vars, int[] vers, BlockNo
}
RegisterArg reg = (RegisterArg) arg;
int regNum = reg.getRegNum();
SSAVar var = vars[regNum];
SSAVar var = state.getVar(regNum);
if (var == null) {
throw new JadxRuntimeException("Not initialized variable reg: " + regNum
+ ", insn: " + insn + ", block:" + block + ", method: " + mth);
+ ", insn: " + insn + ", block:" + block);
}
var.use(reg);
}
}
RegisterArg result = insn.getResult();
if (result != null) {
int regNum = result.getRegNum();
vars[regNum] = newSSAVar(mth, vers, result, regNum);
state.startVar(result);
}
}
for (BlockNode s : block.getSuccessors()) {
Expand All @@ -177,22 +171,18 @@ private static void renameVar(MethodNode mth, SSAVar[] vars, int[] vers, BlockNo
continue;
}
for (PhiInsn phiInsn : phiList.getList()) {
bindPhiArg(vars, block, phiInsn);
bindPhiArg(state, phiInsn);
}
}
for (BlockNode domOn : block.getDominatesOn()) {
renameVar(mth, vars, vers, domOn);
}
System.arraycopy(inputVars, 0, vars, 0, vars.length);
}

private static void bindPhiArg(SSAVar[] vars, BlockNode block, PhiInsn phiInsn) {
private static void bindPhiArg(RenameState state, PhiInsn phiInsn) {
int regNum = phiInsn.getResult().getRegNum();
SSAVar var = vars[regNum];
SSAVar var = state.getVar(regNum);
if (var == null) {
return;
}
RegisterArg arg = phiInsn.bindArg(block);
RegisterArg arg = phiInsn.bindArg(state.getBlock());
var.use(arg);
var.setUsedInPhi(phiInsn);
}
Expand Down

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