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[libFuzzer] when a single mutation fails try a few more times with other mutations before returning un-mutated data 

llvm-svn: 246828
This commit is contained in:
Kostya Serebryany 2015-09-04 00:40:29 +00:00
parent 419d79189f
commit b2e9897644
1 changed files with 14 additions and 7 deletions
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19
llvm/lib/Fuzzer/FuzzerMutate.cpp
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@ -71,7 +71,7 @@ size_t MutationDispatcher::Mutate_ShuffleBytes(uint8_t *Data, size_t Size,
size_t MutationDispatcher::Mutate_EraseByte(uint8_t *Data, size_t Size,
size_t MaxSize) {
assert(Size);
if (Size == 1) return Size;
if (Size == 1) return 0;
size_t Idx = Rand(Size);
// Erase Data[Idx].
memmove(Data + Idx, Data + Idx + 1, Size - Idx - 1);
@ -80,7 +80,7 @@ size_t MutationDispatcher::Mutate_EraseByte(uint8_t *Data, size_t Size,
size_t MutationDispatcher::Mutate_InsertByte(uint8_t *Data, size_t Size,
size_t MaxSize) {
if (Size == MaxSize) return Size;
if (Size == MaxSize) return 0;
size_t Idx = Rand(Size + 1);
// Insert new value at Data[Idx].
memmove(Data + Idx + 1, Data + Idx, Size - Idx);
@ -106,9 +106,10 @@ size_t MutationDispatcher::Mutate_AddWordFromDictionary(uint8_t *Data,
size_t Size,
size_t MaxSize) {
auto &D = MDImpl->Dictionary;
if (D.empty()) return Size; // FIXME: indicate failure.
assert(!D.empty());
if (D.empty()) return 0;
const Unit &Word = D[Rand(D.size())];
if (Size + Word.size() > MaxSize) return Size;
if (Size + Word.size() > MaxSize) return 0;
size_t Idx = Rand(Size + 1);
memmove(Data + Idx + Word.size(), Data + Idx, Size - Idx);
memcpy(Data + Idx, Word.data(), Word.size());
@ -125,9 +126,15 @@ size_t MutationDispatcher::Mutate(uint8_t *Data, size_t Size, size_t MaxSize) {
return MaxSize;
}
assert(Size > 0);
// Some mutations may fail (e.g. can't insert more bytes if Size == MaxSize),
// in which case they will return 0.
// Try several times before returning un-mutated data.
for (int Iter = 0; Iter < 10; Iter++) {
size_t MutatorIdx = Rand(MDImpl->Mutators.size());
Size = (this->*(MDImpl->Mutators[MutatorIdx]))(Data, Size, MaxSize);
assert(Size > 0);
size_t NewSize =
(this->*(MDImpl->Mutators[MutatorIdx]))(Data, Size, MaxSize);
if (NewSize) return NewSize;
}
return Size;
}