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fix: handle NOP instructions in unexpected places (#666)
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@skylot
skylot committed May 19, 2019
1 parent 5efe4bd commit 1830c27
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Showing 9 changed files with 347 additions and 80 deletions.
43 changes: 29 additions & 14 deletions jadx-core/src/main/java/jadx/core/dex/instructions/InsnDecoder.java
View file
@@ -1,6 +1,7 @@
package jadx.core.dex.instructions;

import java.io.EOFException;
import java.util.function.Predicate;

import org.jetbrains.annotations.NotNull;
import org.slf4j.Logger;
Expand Down Expand Up @@ -598,7 +599,7 @@ private ArgType tryResolveFieldType(FieldInfo igetFld) {

private InsnNode decodeSwitch(DecodedInstruction insn, int offset, boolean packed) {
int payloadOffset = insn.getTarget();
DecodedInstruction payload = insnArr[payloadOffset];
DecodedInstruction payload = getInsnByOffsetSkipNop(insnArr, payloadOffset);
Object[] keys;
int[] targets;
if (packed) {
Expand Down Expand Up @@ -626,7 +627,7 @@ private InsnNode decodeSwitch(DecodedInstruction insn, int offset, boolean packe
}

private InsnNode fillArray(DecodedInstruction insn) {
DecodedInstruction payload = insnArr[insn.getTarget()];
DecodedInstruction payload = getInsnByOffsetSkipNop(insnArr, insn.getTarget());
return new FillArrayNode(insn.getA(), (FillArrayDataPayloadDecodedInstruction) payload);
}

Expand Down Expand Up @@ -738,7 +739,7 @@ private InsnNode insn(InsnType type, RegisterArg res, InsnArg arg) {
}

private int getMoveResultRegister(DecodedInstruction[] insnArr, int offset) {
int nextOffset = getNextInsnOffset(insnArr, offset);
int nextOffset = getNextInsnOffsetSkipNop(insnArr, offset);
if (nextOffset >= 0) {
DecodedInstruction next = insnArr[nextOffset];
int opc = next.getOpcode();
Expand All @@ -751,21 +752,35 @@ private int getMoveResultRegister(DecodedInstruction[] insnArr, int offset) {
return -1;
}

public static int getPrevInsnOffset(Object[] insnArr, int offset) {
int i = offset - 1;
while (i >= 0 && insnArr[i] == null) {
i--;
}
if (i < 0) {
return -1;
private static DecodedInstruction getInsnByOffsetSkipNop(DecodedInstruction[] insnArr, int offset) {
DecodedInstruction payload = insnArr[offset];
if (payload.getOpcode() == Opcodes.NOP) {
return insnArr[getNextInsnOffsetSkipNop(insnArr, offset)];
}
return i;
return payload;
}

public static int getNextInsnOffset(DecodedInstruction[] insnArr, int offset) {
return getNextInsnOffset(insnArr, offset, null);
}

public static int getNextInsnOffset(Object[] insnArr, int offset) {
public static int getNextInsnOffsetSkipNop(DecodedInstruction[] insnArr, int offset) {
return getNextInsnOffset(insnArr, offset, i -> i.getOpcode() == Opcodes.NOP);
}

public static int getNextInsnOffset(InsnNode[] insnArr, int offset) {
return getNextInsnOffset(insnArr, offset, null);
}

public static <T> int getNextInsnOffset(T[] insnArr, int offset, Predicate<T> skip) {
int i = offset + 1;
while (i < insnArr.length && insnArr[i] == null) {
i++;
while (i < insnArr.length) {
T insn = insnArr[i];
if (insn == null || (skip != null && skip.test(insn))) {
i++;
} else {
break;
}
}
if (i >= insnArr.length) {
return -1;
Expand Down
3 changes: 3 additions & 0 deletions jadx-core/src/main/java/jadx/core/dex/instructions/SwitchNode.java
View file
Expand Up @@ -64,6 +64,9 @@ public void initBlocks(BlockNode curBlock) {

@Override
public boolean replaceTargetBlock(BlockNode origin, BlockNode replace) {
if (targetBlocks == null) {
return false;
}
int count = 0;
int len = targetBlocks.length;
for (int i = 0; i < len; i++) {
Expand Down
50 changes: 2 additions & 48 deletions jadx-core/src/main/java/jadx/core/dex/visitors/blocksmaker/BlockProcessor.java
View file
Expand Up @@ -87,38 +87,6 @@ private static void checkForUnreachableBlocks(MethodNode mth) {
});
}

private static boolean canRemoveBlock(BlockNode block) {
return block.getInstructions().isEmpty()
&& block.isAttrStorageEmpty()
&& block.getSuccessors().size() <= 1
&& !block.getPredecessors().isEmpty();
}

private static boolean removeEmptyBlock(BlockNode block) {
if (canRemoveBlock(block)) {
if (block.getSuccessors().size() == 1) {
BlockNode successor = block.getSuccessors().get(0);
block.getPredecessors().forEach(pred -> {
pred.getSuccessors().remove(block);
BlockSplitter.connect(pred, successor);
BlockSplitter.replaceTarget(pred, block, successor);
pred.updateCleanSuccessors();
});
BlockSplitter.removeConnection(block, successor);
} else {
block.getPredecessors().forEach(pred -> {
pred.getSuccessors().remove(block);
pred.updateCleanSuccessors();
});
}
block.add(AFlag.REMOVE);
block.getSuccessors().clear();
block.getPredecessors().clear();
return true;
}
return false;
}

private static boolean deduplicateBlockInsns(BlockNode block) {
if (block.contains(AFlag.LOOP_START) || block.contains(AFlag.LOOP_END)) {
// search for same instruction at end of all predecessors blocks
Expand Down Expand Up @@ -457,7 +425,7 @@ private static boolean independentBlockTreeMod(MethodNode mth) {
}
}
for (BlockNode basicBlock : basicBlocks) {
if (removeEmptyBlock(basicBlock)) {
if (BlockSplitter.removeEmptyBlock(basicBlock)) {
changed = true;
}
}
Expand Down Expand Up @@ -631,7 +599,7 @@ private static boolean mergeHandlers(MethodNode mth, List<BlockNode> blocksForMe
ExceptionHandler excHandler = otherExcHandlerAttr.getHandler();
excHandlerAttr.getHandler().addCatchTypes(excHandler.getCatchTypes());
tryBlock.removeHandler(mth, excHandler);
detachBlock(block);
BlockSplitter.detachBlock(block);
}
return true;
}
Expand Down Expand Up @@ -734,20 +702,6 @@ private static void removeMarkedBlocks(MethodNode mth) {
});
}

private static void detachBlock(BlockNode block) {
for (BlockNode pred : block.getPredecessors()) {
pred.getSuccessors().remove(block);
pred.updateCleanSuccessors();
}
for (BlockNode successor : block.getSuccessors()) {
successor.getPredecessors().remove(block);
}
block.add(AFlag.REMOVE);
block.getInstructions().clear();
block.getPredecessors().clear();
block.getSuccessors().clear();
}

private static void clearBlocksState(MethodNode mth) {
mth.getBasicBlocks().forEach(block -> {
block.remove(AType.LOOP);
Expand Down
81 changes: 63 additions & 18 deletions jadx-core/src/main/java/jadx/core/dex/visitors/blocksmaker/BlockSplitter.java
View file
Expand Up @@ -50,13 +50,14 @@ public void visit(MethodNode mth) {

mth.initBasicBlocks();
splitBasicBlocks(mth);
initBlocksInTargetNodes(mth);

removeJumpAttr(mth);
removeInsns(mth);
removeEmptyDetachedBlocks(mth);
removeUnreachableBlocks(mth);
initBlocksInTargetNodes(mth);
mth.getBasicBlocks().removeIf(BlockSplitter::removeEmptyBlock);

removeJumpAttributes(mth.getInstructions());
mth.unloadInsnArr();
}

Expand Down Expand Up @@ -307,7 +308,7 @@ private static BlockNode getBlock(int offset, Map<Integer, BlockNode> blocksMap)
return block;
}

private void removeJumpAttr(MethodNode mth) {
private static void removeJumpAttr(MethodNode mth) {
for (BlockNode block : mth.getBasicBlocks()) {
for (InsnNode insn : block.getInstructions()) {
insn.remove(AType.JUMP);
Expand All @@ -333,44 +334,88 @@ static boolean removeEmptyDetachedBlocks(MethodNode mth) {
&& block.getSuccessors().isEmpty());
}

private void removeJumpAttributes(InsnNode[] insnArr) {
for (InsnNode insn : insnArr) {
if (insn != null && insn.contains(AType.JUMP)) {
insn.remove(AType.JUMP);
}
}
}

private void removeUnreachableBlocks(MethodNode mth) {
private static boolean removeUnreachableBlocks(MethodNode mth) {
Set<BlockNode> toRemove = new LinkedHashSet<>();
for (BlockNode block : mth.getBasicBlocks()) {
if (block.getPredecessors().isEmpty() && block != mth.getEnterBlock()) {
toRemove.add(block);
collectSuccessors(block, toRemove);
}
}
if (!toRemove.isEmpty()) {
mth.getBasicBlocks().removeIf(toRemove::contains);
if (toRemove.isEmpty()) {
return false;
}

toRemove.forEach(BlockSplitter::detachBlock);
mth.getBasicBlocks().removeAll(toRemove);
long notEmptyBlocks = toRemove.stream().filter(block -> !block.getInstructions().isEmpty()).count();
if (notEmptyBlocks != 0) {
int insnsCount = toRemove.stream().mapToInt(block -> block.getInstructions().size()).sum();
mth.addAttr(AType.COMMENTS, "JADX INFO: unreachable blocks removed: " + toRemove.size()
mth.addAttr(AType.COMMENTS, "JADX INFO: unreachable blocks removed: " + notEmptyBlocks
+ ", instructions: " + insnsCount);
}
return true;
}

private void collectSuccessors(BlockNode startBlock, Set<BlockNode> toRemove) {
static boolean removeEmptyBlock(BlockNode block) {
if (canRemoveBlock(block)) {
if (block.getSuccessors().size() == 1) {
BlockNode successor = block.getSuccessors().get(0);
block.getPredecessors().forEach(pred -> {
pred.getSuccessors().remove(block);
BlockSplitter.connect(pred, successor);
BlockSplitter.replaceTarget(pred, block, successor);
pred.updateCleanSuccessors();
});
BlockSplitter.removeConnection(block, successor);
} else {
block.getPredecessors().forEach(pred -> {
pred.getSuccessors().remove(block);
pred.updateCleanSuccessors();
});
}
block.add(AFlag.REMOVE);
block.getSuccessors().clear();
block.getPredecessors().clear();
return true;
}
return false;
}

private static boolean canRemoveBlock(BlockNode block) {
return block.getInstructions().isEmpty()
&& block.isAttrStorageEmpty()
&& block.getSuccessors().size() <= 1
&& !block.getPredecessors().isEmpty();
}

private static void collectSuccessors(BlockNode startBlock, Set<BlockNode> toRemove) {
Deque<BlockNode> stack = new ArrayDeque<>();
stack.add(startBlock);
while (!stack.isEmpty()) {
BlockNode block = stack.pop();
if (!toRemove.contains(block)) {
toRemove.add(block);
for (BlockNode successor : block.getSuccessors()) {
if (toRemove.containsAll(successor.getPredecessors())) {
stack.push(successor);
}
}
}
toRemove.add(block);

}
}

static void detachBlock(BlockNode block) {
for (BlockNode pred : block.getPredecessors()) {
pred.getSuccessors().remove(block);
pred.updateCleanSuccessors();
}
for (BlockNode successor : block.getSuccessors()) {
successor.getPredecessors().remove(block);
}
block.add(AFlag.REMOVE);
block.getInstructions().clear();
block.getPredecessors().clear();
block.getSuccessors().clear();
}
}
2 changes: 2 additions & 0 deletions jadx-core/src/main/java/jadx/core/dex/visitors/regions/ProcessTryCatchRegions.java
View file
Expand Up @@ -7,6 +7,7 @@
import java.util.Map;
import java.util.Set;

import jadx.core.dex.attributes.AFlag;
import jadx.core.dex.attributes.AType;
import jadx.core.dex.nodes.BlockNode;
import jadx.core.dex.nodes.IBranchRegion;
Expand Down Expand Up @@ -167,6 +168,7 @@ private static boolean isHandlerPath(TryCatchBlock tb, IContainer cont) {
for (ExceptionHandler h : tb.getHandlers()) {
BlockNode handlerBlock = h.getHandlerBlock();
if (handlerBlock != null
&& !handlerBlock.contains(AFlag.REMOVE)
&& RegionUtils.hasPathThroughBlock(handlerBlock, cont)) {
return true;
}
Expand Down
3 changes: 3 additions & 0 deletions jadx-core/src/main/java/jadx/core/dex/visitors/regions/RegionMaker.java
View file
Expand Up @@ -1022,6 +1022,9 @@ private void processExcHandler(MethodNode mth, ExceptionHandler handler, Set<Blo
dom = start;
stack.addExits(exits);
}
if (dom.contains(AFlag.REMOVE)) {
return;
}
BitSet domFrontier = dom.getDomFrontier();
List<BlockNode> handlerExits = BlockUtils.bitSetToBlocks(this.mth, domFrontier);
boolean inLoop = this.mth.getLoopForBlock(start) != null;
Expand Down
3 changes: 3 additions & 0 deletions jadx-core/src/main/java/jadx/core/utils/BlockUtils.java
View file
Expand Up @@ -270,6 +270,9 @@ public static BitSet blocksToBitSet(MethodNode mth, List<BlockNode> blocks) {
}

public static List<BlockNode> bitSetToBlocks(MethodNode mth, BitSet bs) {
if (bs == null) {
return Collections.emptyList();
}
int size = bs.cardinality();
if (size == 0) {
return Collections.emptyList();
Expand Down
16 changes: 16 additions & 0 deletions jadx-core/src/test/java/jadx/tests/integration/others/TestMultipleNOPs.java
View file
@@ -0,0 +1,16 @@
package jadx.tests.integration.others;

import org.junit.jupiter.api.Test;

import jadx.tests.api.SmaliTest;

public class TestMultipleNOPs extends SmaliTest {

@Test
public void test() {
disableCompilation();

// expected no errors
loadFromSmaliFiles();
}
}

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