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2 different implementations

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This commit is contained in:
van Hauser
2019-06-27 15:43:51 +02:00
parent 45be91ff48
commit aa4fc44a80
1 changed files with 34 additions and 19 deletions
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53
llvm_mode/afl-llvm-pass.so.cc
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@ -119,7 +119,6 @@ bool AFLCoverage::runOnModule(Module &M) {
}
char* neverZero_counters_str = getenv("AFL_NZERO_COUNTS");
bool enable_neverZero_counters = neverZero_counters_str && '1' == *neverZero_counters_str;
/* Get globals for the SHM region and the previous location. Note that
__afl_prev_loc is thread-local. */
@ -230,16 +229,16 @@ bool AFLCoverage::runOnModule(Module &M) {
LoadInst *MapPtr = IRB.CreateLoad(AFLMapPtr);
MapPtr->setMetadata(M.getMDKindID("nosanitize"), MDNode::get(C, None));
Value *MapPtrIdx =
IRB.CreateGEP(MapPtr, IRB.CreateXor(PrevLocCasted, CurLoc));
Value *MapPtrIdx = IRB.CreateGEP(MapPtr, IRB.CreateXor(PrevLocCasted, CurLoc));
/* Update bitmap */
LoadInst *Counter = IRB.CreateLoad(MapPtrIdx);
Counter->setMetadata(M.getMDKindID("nosanitize"), MDNode::get(C, None));
Value *Incr;
if (enable_neverZero_counters) {
Value *Incr = IRB.CreateAdd(Counter, ConstantInt::get(Int8Ty, 1));
if (neverZero_counters_str != NULL) {
/* hexcoder: Realize a counter that skips zero during overflow.
* Once this counter reaches its maximum value, it next increments to 1
*
@ -249,27 +248,43 @@ bool AFLCoverage::runOnModule(Module &M) {
* Counter + 1 -> {Counter, OverflowFlag}
* Counter + OverflowFlag -> Counter
*/
CallInst *AddOv = IRB.CreateBinaryIntrinsic(Intrinsic::uadd_with_overflow,
Counter, ConstantInt::get(Int8Ty, 1));
// Solution #1 - creates
//mov dl,BYTE PTR [rsi+rdi*1]
//mov ecx,edx
//add cl,0x1
//adc dl,0x1
/*
CallInst *AddOv = IRB.CreateBinaryIntrinsic(Intrinsic::uadd_with_overflow, Counter, ConstantInt::get(Int8Ty, 1));
AddOv->setMetadata(M.getMDKindID("nosanitize"), MDNode::get(C, None));
Value *SumWithOverflowBit = AddOv;
Incr = IRB.CreateAdd(
IRB.CreateExtractValue(SumWithOverflowBit, 0), /* sum */
IRB.CreateZExt( /* convert from one bit type to 8 bits type */
IRB.CreateExtractValue(SumWithOverflowBit, 1) /* overflow */
, Int8Ty));
} else {
/* standard AFL behavior: wrapping counters */
Incr = IRB.CreateAdd(Counter, ConstantInt::get(Int8Ty, 1));
Incr = IRB.CreateAdd(IRB.CreateExtractValue(SumWithOverflowBit, 0), // sum
IRB.CreateZExt( // convert from one bit type to 8 bits type
IRB.CreateExtractValue(SumWithOverflowBit, 1), // overflow
Int8Ty));
*/
// Solution #2 - creates the same code as #1
///*
auto cf = IRB.CreateICmpULT(Incr, ConstantInt::get(Int8Ty, 1));
Incr = IRB.CreateAdd(Incr, cf);
//*/
// Solution #3 - creates
//mov cl,BYTE PTR [rsi+rdx*1]
//add cl,0x1
//cmp cl,0x1
//adc cl,0x0
/*
auto cf = IRB.CreateICmpEQ(Incr, ConstantInt::get(Int8Ty, 0));
Incr = IRB.CreateAdd(Incr, cf);
*/
}
IRB.CreateStore(Incr, MapPtrIdx)
->setMetadata(M.getMDKindID("nosanitize"), MDNode::get(C, None));
IRB.CreateStore(Incr, MapPtrIdx)->setMetadata(M.getMDKindID("nosanitize"), MDNode::get(C, None));
/* Set prev_loc to cur_loc >> 1 */
StoreInst *Store =
IRB.CreateStore(ConstantInt::get(Int32Ty, cur_loc >> 1), AFLPrevLoc);
StoreInst *Store = IRB.CreateStore(ConstantInt::get(Int32Ty, cur_loc >> 1), AFLPrevLoc);
Store->setMetadata(M.getMDKindID("nosanitize"), MDNode::get(C, None));
inst_blocks++;