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llvm-mirror/lib/Fuzzer/FuzzerLoop.cpp
Mike Aizatsky 63896f700f [sanitizers] trace buffer API to use user-allocated buffer. 
Differential Revision: https://reviews.llvm.org/D23185

llvm-svn: 277859
2016-08-05 20:09:53 +00:00

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//===- FuzzerLoop.cpp - Fuzzer's main loop --------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
// Fuzzer's main loop.
//===----------------------------------------------------------------------===//
#include "FuzzerInternal.h"
#include <algorithm>
#include <cstring>
#include <memory>
#if defined(__has_include)
#if __has_include(<sanitizer / coverage_interface.h>)
#include <sanitizer/coverage_interface.h>
#endif
#if __has_include(<sanitizer / lsan_interface.h>)
#include <sanitizer/lsan_interface.h>
#endif
#endif
#define NO_SANITIZE_MEMORY
#if defined(__has_feature)
#if __has_feature(memory_sanitizer)
#undef NO_SANITIZE_MEMORY
#define NO_SANITIZE_MEMORY __attribute__((no_sanitize_memory))
#endif
#endif
namespace fuzzer {
static const size_t kMaxUnitSizeToPrint = 256;
static const size_t TruncateMaxRuns = 1000;
thread_local bool Fuzzer::IsMyThread;
static void MissingExternalApiFunction(const char *FnName) {
Printf("ERROR: %s is not defined. Exiting.\n"
"Did you use -fsanitize-coverage=... to build your code?\n",
FnName);
exit(1);
}
#define CHECK_EXTERNAL_FUNCTION(fn) \
do { \
if (!(EF->fn)) \
MissingExternalApiFunction(#fn); \
} while (false)
// Only one Fuzzer per process.
static Fuzzer *F;
// Only one CoverageController per process should be created.
class CoverageController {
public:
explicit CoverageController(const FuzzingOptions &Options)
: Options(Options) {
if (Options.PrintNewCovPcs) {
PcBufferLen = 1 << 24;
PcBuffer = new uintptr_t[PcBufferLen];
EF->__sanitizer_set_coverage_pc_buffer(PcBuffer, PcBufferLen);
}
}
uintptr_t* pc_buffer() const { return PcBuffer; }
void Reset() {
CHECK_EXTERNAL_FUNCTION(__sanitizer_reset_coverage);
EF->__sanitizer_reset_coverage();
PcMapResetCurrent();
}
void ResetCounters() {
if (Options.UseCounters) {
EF->__sanitizer_update_counter_bitset_and_clear_counters(0);
}
}
void Prepare(Fuzzer::Coverage *C) {
if (Options.UseCounters) {
size_t NumCounters = EF->__sanitizer_get_number_of_counters();
C->CounterBitmap.resize(NumCounters);
}
}
// Records data to a maximum coverage tracker. Returns true if additional
// coverage was discovered.
bool RecordMax(Fuzzer::Coverage *C) {
bool Res = false;
uint64_t NewBlockCoverage = EF->__sanitizer_get_total_unique_coverage();
if (NewBlockCoverage > C->BlockCoverage) {
Res = true;
C->BlockCoverage = NewBlockCoverage;
}
if (Options.UseIndirCalls &&
EF->__sanitizer_get_total_unique_caller_callee_pairs) {
uint64_t NewCallerCalleeCoverage =
EF->__sanitizer_get_total_unique_caller_callee_pairs();
if (NewCallerCalleeCoverage > C->CallerCalleeCoverage) {
Res = true;
C->CallerCalleeCoverage = NewCallerCalleeCoverage;
}
}
if (Options.UseCounters) {
uint64_t CounterDelta =
EF->__sanitizer_update_counter_bitset_and_clear_counters(
C->CounterBitmap.data());
if (CounterDelta > 0) {
Res = true;
C->CounterBitmapBits += CounterDelta;
}
}
uint64_t NewPcMapBits = PcMapMergeInto(&C->PCMap);
if (NewPcMapBits > C->PcMapBits) {
Res = true;
C->PcMapBits = NewPcMapBits;
}
uint64_t NewPcBufferPos = EF->__sanitizer_get_coverage_pc_buffer_pos();
if (NewPcBufferPos > C->PcBufferPos) {
Res = true;
C->PcBufferPos = NewPcBufferPos;
}
if (NewPcBufferPos >= PcBufferLen) {
Printf("ERROR: PC buffer overflow.\n");
}
return Res;
}
private:
const FuzzingOptions Options;
uintptr_t* PcBuffer = nullptr;
size_t PcBufferLen = 0;
};
// Leak detection is expensive, so we first check if there were more mallocs
// than frees (using the sanitizer malloc hooks) and only then try to call lsan.
struct MallocFreeTracer {
void Start() {
Mallocs = 0;
Frees = 0;
}
// Returns true if there were more mallocs than frees.
bool Stop() { return Mallocs > Frees; }
std::atomic<size_t> Mallocs;
std::atomic<size_t> Frees;
};
static MallocFreeTracer AllocTracer;
void MallocHook(const volatile void *ptr, size_t size) {
AllocTracer.Mallocs++;
}
void FreeHook(const volatile void *ptr) {
AllocTracer.Frees++;
}
Fuzzer::Fuzzer(UserCallback CB, MutationDispatcher &MD, FuzzingOptions Options)
: CB(CB), MD(MD), Options(Options),
CController(new CoverageController(Options)) {
SetDeathCallback();
InitializeTraceState();
assert(!F);
F = this;
ResetCoverage();
IsMyThread = true;
if (Options.DetectLeaks && EF->__sanitizer_install_malloc_and_free_hooks)
EF->__sanitizer_install_malloc_and_free_hooks(MallocHook, FreeHook);
}
Fuzzer::~Fuzzer() { }
void Fuzzer::LazyAllocateCurrentUnitData() {
if (CurrentUnitData || Options.MaxLen == 0) return;
CurrentUnitData = new uint8_t[Options.MaxLen];
}
void Fuzzer::SetDeathCallback() {
CHECK_EXTERNAL_FUNCTION(__sanitizer_set_death_callback);
EF->__sanitizer_set_death_callback(StaticDeathCallback);
}
void Fuzzer::StaticDeathCallback() {
assert(F);
F->DeathCallback();
}
void Fuzzer::DumpCurrentUnit(const char *Prefix) {
if (!CurrentUnitData) return; // Happens when running individual inputs.
size_t UnitSize = CurrentUnitSize;
if (UnitSize <= kMaxUnitSizeToPrint) {
PrintHexArray(CurrentUnitData, UnitSize, "\n");
PrintASCII(CurrentUnitData, UnitSize, "\n");
}
WriteUnitToFileWithPrefix({CurrentUnitData, CurrentUnitData + UnitSize},
Prefix);
}
NO_SANITIZE_MEMORY
void Fuzzer::DeathCallback() {
DumpCurrentUnit("crash-");
PrintFinalStats();
}
void Fuzzer::StaticAlarmCallback() {
assert(F);
F->AlarmCallback();
}
void Fuzzer::StaticCrashSignalCallback() {
assert(F);
F->CrashCallback();
}
void Fuzzer::StaticInterruptCallback() {
assert(F);
F->InterruptCallback();
}
void Fuzzer::CrashCallback() {
Printf("==%d== ERROR: libFuzzer: deadly signal\n", GetPid());
if (EF->__sanitizer_print_stack_trace)
EF->__sanitizer_print_stack_trace();
Printf("NOTE: libFuzzer has rudimentary signal handlers.\n"
" Combine libFuzzer with AddressSanitizer or similar for better "
"crash reports.\n");
Printf("SUMMARY: libFuzzer: deadly signal\n");
DumpCurrentUnit("crash-");
PrintFinalStats();
exit(Options.ErrorExitCode);
}
void Fuzzer::InterruptCallback() {
Printf("==%d== libFuzzer: run interrupted; exiting\n", GetPid());
PrintFinalStats();
_Exit(0); // Stop right now, don't perform any at-exit actions.
}
NO_SANITIZE_MEMORY
void Fuzzer::AlarmCallback() {
assert(Options.UnitTimeoutSec > 0);
if (!InFuzzingThread()) return;
if (!CurrentUnitSize)
return; // We have not started running units yet.
size_t Seconds =
duration_cast<seconds>(system_clock::now() - UnitStartTime).count();
if (Seconds == 0)
return;
if (Options.Verbosity >= 2)
Printf("AlarmCallback %zd\n", Seconds);
if (Seconds >= (size_t)Options.UnitTimeoutSec) {
Printf("ALARM: working on the last Unit for %zd seconds\n", Seconds);
Printf(" and the timeout value is %d (use -timeout=N to change)\n",
Options.UnitTimeoutSec);
DumpCurrentUnit("timeout-");
Printf("==%d== ERROR: libFuzzer: timeout after %d seconds\n", GetPid(),
Seconds);
if (EF->__sanitizer_print_stack_trace)
EF->__sanitizer_print_stack_trace();
Printf("SUMMARY: libFuzzer: timeout\n");
PrintFinalStats();
_Exit(Options.TimeoutExitCode); // Stop right now.
}
}
void Fuzzer::RssLimitCallback() {
Printf(
"==%d== ERROR: libFuzzer: out-of-memory (used: %zdMb; limit: %zdMb)\n",
GetPid(), GetPeakRSSMb(), Options.RssLimitMb);
Printf(" To change the out-of-memory limit use -rss_limit_mb=<N>\n\n");
if (EF->__sanitizer_print_memory_profile)
EF->__sanitizer_print_memory_profile(50);
DumpCurrentUnit("oom-");
Printf("SUMMARY: libFuzzer: out-of-memory\n");
PrintFinalStats();
_Exit(Options.ErrorExitCode); // Stop right now.
}
void Fuzzer::PrintStats(const char *Where, const char *End) {
size_t ExecPerSec = execPerSec();
if (Options.OutputCSV) {
static bool csvHeaderPrinted = false;
if (!csvHeaderPrinted) {
csvHeaderPrinted = true;
Printf("runs,block_cov,bits,cc_cov,corpus,execs_per_sec,tbms,reason\n");
}
Printf("%zd,%zd,%zd,%zd,%zd,%zd,%s\n", TotalNumberOfRuns,
MaxCoverage.BlockCoverage, MaxCoverage.CounterBitmapBits,
MaxCoverage.CallerCalleeCoverage, Corpus.size(), ExecPerSec, Where);
}
if (!Options.Verbosity)
return;
Printf("#%zd\t%s", TotalNumberOfRuns, Where);
if (MaxCoverage.BlockCoverage)
Printf(" cov: %zd", MaxCoverage.BlockCoverage);
if (MaxCoverage.PcMapBits)
Printf(" path: %zd", MaxCoverage.PcMapBits);
if (auto TB = MaxCoverage.CounterBitmapBits)
Printf(" bits: %zd", TB);
if (MaxCoverage.CallerCalleeCoverage)
Printf(" indir: %zd", MaxCoverage.CallerCalleeCoverage);
Printf(" units: %zd exec/s: %zd", Corpus.size(), ExecPerSec);
Printf("%s", End);
}
void Fuzzer::PrintFinalStats() {
if (!Options.PrintFinalStats) return;
size_t ExecPerSec = execPerSec();
Printf("stat::number_of_executed_units: %zd\n", TotalNumberOfRuns);
Printf("stat::average_exec_per_sec: %zd\n", ExecPerSec);
Printf("stat::new_units_added: %zd\n", NumberOfNewUnitsAdded);
Printf("stat::slowest_unit_time_sec: %zd\n", TimeOfLongestUnitInSeconds);
Printf("stat::peak_rss_mb: %zd\n", GetPeakRSSMb());
}
size_t Fuzzer::MaxUnitSizeInCorpus() const {
size_t Res = 0;
for (auto &X : Corpus)
Res = std::max(Res, X.size());
return Res;
}
void Fuzzer::SetMaxLen(size_t MaxLen) {
assert(Options.MaxLen == 0); // Can only reset MaxLen from 0 to non-0.
assert(MaxLen);
Options.MaxLen = MaxLen;
Printf("INFO: -max_len is not provided, using %zd\n", Options.MaxLen);
}
void Fuzzer::RereadOutputCorpus(size_t MaxSize) {
if (Options.OutputCorpus.empty())
return;
std::vector<Unit> AdditionalCorpus;
ReadDirToVectorOfUnits(Options.OutputCorpus.c_str(), &AdditionalCorpus,
&EpochOfLastReadOfOutputCorpus, MaxSize);
if (Corpus.empty()) {
Corpus = AdditionalCorpus;
return;
}
if (!Options.Reload)
return;
if (Options.Verbosity >= 2)
Printf("Reload: read %zd new units.\n", AdditionalCorpus.size());
for (auto &X : AdditionalCorpus) {
if (X.size() > MaxSize)
X.resize(MaxSize);
if (UnitHashesAddedToCorpus.insert(Hash(X)).second) {
if (RunOne(X)) {
Corpus.push_back(X);
UpdateCorpusDistribution();
PrintStats("RELOAD");
}
}
}
}
void Fuzzer::ShuffleCorpus(UnitVector *V) {
std::random_shuffle(V->begin(), V->end(), MD.GetRand());
if (Options.PreferSmall)
std::stable_sort(V->begin(), V->end(), [](const Unit &A, const Unit &B) {
return A.size() < B.size();
});
}
// Tries random prefixes of corpus items.
// Prefix length is chosen according to exponential distribution
// to sample short lengths much more heavily.
void Fuzzer::TruncateUnits(std::vector<Unit> *NewCorpus) {
size_t MaxCorpusLen = 0;
for (const auto &U : Corpus)
MaxCorpusLen = std::max(MaxCorpusLen, U.size());
if (MaxCorpusLen <= 1)
return;
// 50% of exponential distribution is Log[2]/lambda.
// Choose lambda so that median is MaxCorpusLen / 2.
double Lambda = 2.0 * log(2.0) / static_cast<double>(MaxCorpusLen);
std::exponential_distribution<> Dist(Lambda);
std::vector<double> Sizes;
size_t TruncatePoints = std::max(1ul, TruncateMaxRuns / Corpus.size());
Sizes.reserve(TruncatePoints);
for (size_t I = 0; I < TruncatePoints; ++I) {
Sizes.push_back(Dist(MD.GetRand().Get_mt19937()) + 1);
}
std::sort(Sizes.begin(), Sizes.end());
for (size_t S : Sizes) {
for (const auto &U : Corpus) {
if (S < U.size() && RunOne(U.data(), S)) {
Unit U1(U.begin(), U.begin() + S);
NewCorpus->push_back(U1);
WriteToOutputCorpus(U1);
PrintStatusForNewUnit(U1);
}
}
}
PrintStats("TRUNC ");
}
void Fuzzer::ShuffleAndMinimize() {
PrintStats("READ ");
std::vector<Unit> NewCorpus;
if (Options.ShuffleAtStartUp)
ShuffleCorpus(&Corpus);
if (Options.TruncateUnits) {
ResetCoverage();
TruncateUnits(&NewCorpus);
ResetCoverage();
}
for (const auto &U : Corpus) {
bool NewCoverage = RunOne(U);
if (!Options.PruneCorpus || NewCoverage) {
NewCorpus.push_back(U);
if (Options.Verbosity >= 2)
Printf("NEW0: %zd L %zd\n", MaxCoverage.BlockCoverage, U.size());
}
TryDetectingAMemoryLeak(U.data(), U.size(),
/*DuringInitialCorpusExecution*/ true);
}
Corpus = NewCorpus;
UpdateCorpusDistribution();
for (auto &X : Corpus)
UnitHashesAddedToCorpus.insert(Hash(X));
PrintStats("INITED");
if (Corpus.empty()) {
Printf("ERROR: no interesting inputs were found. "
"Is the code instrumented for coverage? Exiting.\n");
exit(1);
}
}
bool Fuzzer::UpdateMaxCoverage() {
uintptr_t PrevPcBufferPos = MaxCoverage.PcBufferPos;
bool Res = CController->RecordMax(&MaxCoverage);
if (Options.PrintNewCovPcs && PrevPcBufferPos != MaxCoverage.PcBufferPos) {
uintptr_t* PcBuffer = CController->pc_buffer();
for (size_t I = PrevPcBufferPos; I < MaxCoverage.PcBufferPos; ++I) {
Printf("%p\n", PcBuffer[I]);
}
}
return Res;
}
bool Fuzzer::RunOne(const uint8_t *Data, size_t Size) {
TotalNumberOfRuns++;
// TODO(aizatsky): this Reset call seems to be not needed.
CController->ResetCounters();
ExecuteCallback(Data, Size);
bool Res = UpdateMaxCoverage();
auto UnitStopTime = system_clock::now();
auto TimeOfUnit =
duration_cast<seconds>(UnitStopTime - UnitStartTime).count();
if (!(TotalNumberOfRuns & (TotalNumberOfRuns - 1)) &&
secondsSinceProcessStartUp() >= 2)
PrintStats("pulse ");
if (TimeOfUnit > TimeOfLongestUnitInSeconds &&
TimeOfUnit >= Options.ReportSlowUnits) {
TimeOfLongestUnitInSeconds = TimeOfUnit;
Printf("Slowest unit: %zd s:\n", TimeOfLongestUnitInSeconds);
WriteUnitToFileWithPrefix({Data, Data + Size}, "slow-unit-");
}
return Res;
}
void Fuzzer::RunOneAndUpdateCorpus(const uint8_t *Data, size_t Size) {
if (TotalNumberOfRuns >= Options.MaxNumberOfRuns)
return;
if (RunOne(Data, Size))
ReportNewCoverage({Data, Data + Size});
}
size_t Fuzzer::GetCurrentUnitInFuzzingThead(const uint8_t **Data) const {
assert(InFuzzingThread());
*Data = CurrentUnitData;
return CurrentUnitSize;
}
void Fuzzer::ExecuteCallback(const uint8_t *Data, size_t Size) {
assert(InFuzzingThread());
LazyAllocateCurrentUnitData();
UnitStartTime = system_clock::now();
// We copy the contents of Unit into a separate heap buffer
// so that we reliably find buffer overflows in it.
std::unique_ptr<uint8_t[]> DataCopy(new uint8_t[Size]);
memcpy(DataCopy.get(), Data, Size);
if (CurrentUnitData && CurrentUnitData != Data)
memcpy(CurrentUnitData, Data, Size);
AssignTaintLabels(DataCopy.get(), Size);
CurrentUnitSize = Size;
AllocTracer.Start();
int Res = CB(DataCopy.get(), Size);
(void)Res;
HasMoreMallocsThanFrees = AllocTracer.Stop();
CurrentUnitSize = 0;
assert(Res == 0);
}
std::string Fuzzer::Coverage::DebugString() const {
std::string Result =
std::string("Coverage{") + "BlockCoverage=" +
std::to_string(BlockCoverage) + " CallerCalleeCoverage=" +
std::to_string(CallerCalleeCoverage) + " CounterBitmapBits=" +
std::to_string(CounterBitmapBits) + " PcMapBits=" +
std::to_string(PcMapBits) + "}";
return Result;
}
void Fuzzer::WriteToOutputCorpus(const Unit &U) {
if (Options.OnlyASCII)
assert(IsASCII(U));
if (Options.OutputCorpus.empty())
return;
std::string Path = DirPlusFile(Options.OutputCorpus, Hash(U));
WriteToFile(U, Path);
if (Options.Verbosity >= 2)
Printf("Written to %s\n", Path.c_str());
}
void Fuzzer::WriteUnitToFileWithPrefix(const Unit &U, const char *Prefix) {
if (!Options.SaveArtifacts)
return;
std::string Path = Options.ArtifactPrefix + Prefix + Hash(U);
if (!Options.ExactArtifactPath.empty())
Path = Options.ExactArtifactPath; // Overrides ArtifactPrefix.
WriteToFile(U, Path);
Printf("artifact_prefix='%s'; Test unit written to %s\n",
Options.ArtifactPrefix.c_str(), Path.c_str());
if (U.size() <= kMaxUnitSizeToPrint)
Printf("Base64: %s\n", Base64(U).c_str());
}
void Fuzzer::SaveCorpus() {
if (Options.OutputCorpus.empty())
return;
for (const auto &U : Corpus)
WriteToFile(U, DirPlusFile(Options.OutputCorpus, Hash(U)));
if (Options.Verbosity)
Printf("Written corpus of %zd files to %s\n", Corpus.size(),
Options.OutputCorpus.c_str());
}
void Fuzzer::PrintStatusForNewUnit(const Unit &U) {
if (!Options.PrintNEW)
return;
PrintStats("NEW ", "");
if (Options.Verbosity) {
Printf(" L: %zd ", U.size());
MD.PrintMutationSequence();
Printf("\n");
}
}
void Fuzzer::ReportNewCoverage(const Unit &U) {
Corpus.push_back(U);
UpdateCorpusDistribution();
UnitHashesAddedToCorpus.insert(Hash(U));
MD.RecordSuccessfulMutationSequence();
PrintStatusForNewUnit(U);
WriteToOutputCorpus(U);
NumberOfNewUnitsAdded++;
}
// Finds minimal number of units in 'Extra' that add coverage to 'Initial'.
// We do it by actually executing the units, sometimes more than once,
// because we may be using different coverage-like signals and the only
// common thing between them is that we can say "this unit found new stuff".
UnitVector Fuzzer::FindExtraUnits(const UnitVector &Initial,
const UnitVector &Extra) {
UnitVector Res = Extra;
size_t OldSize = Res.size();
for (int Iter = 0; Iter < 10; Iter++) {
ShuffleCorpus(&Res);
ResetCoverage();
for (auto &U : Initial)
RunOne(U);
Corpus.clear();
for (auto &U : Res)
if (RunOne(U))
Corpus.push_back(U);
char Stat[7] = "MIN ";
Stat[3] = '0' + Iter;
PrintStats(Stat);
size_t NewSize = Corpus.size();
assert(NewSize <= OldSize);
Res.swap(Corpus);
if (NewSize + 5 >= OldSize)
break;
OldSize = NewSize;
}
return Res;
}
void Fuzzer::Merge(const std::vector<std::string> &Corpora) {
if (Corpora.size() <= 1) {
Printf("Merge requires two or more corpus dirs\n");
return;
}
std::vector<std::string> ExtraCorpora(Corpora.begin() + 1, Corpora.end());
assert(Options.MaxLen > 0);
UnitVector Initial, Extra;
ReadDirToVectorOfUnits(Corpora[0].c_str(), &Initial, nullptr, Options.MaxLen);
for (auto &C : ExtraCorpora)
ReadDirToVectorOfUnits(C.c_str(), &Extra, nullptr, Options.MaxLen);
if (!Initial.empty()) {
Printf("=== Minimizing the initial corpus of %zd units\n", Initial.size());
Initial = FindExtraUnits({}, Initial);
}
Printf("=== Merging extra %zd units\n", Extra.size());
auto Res = FindExtraUnits(Initial, Extra);
for (auto &U: Res)
WriteToOutputCorpus(U);
Printf("=== Merge: written %zd units\n", Res.size());
}
// Tries detecting a memory leak on the particular input that we have just
// executed before calling this function.
void Fuzzer::TryDetectingAMemoryLeak(const uint8_t *Data, size_t Size,
bool DuringInitialCorpusExecution) {
if (!HasMoreMallocsThanFrees) return; // mallocs==frees, a leak is unlikely.
if (!Options.DetectLeaks) return;
if (!&(EF->__lsan_enable) || !&(EF->__lsan_disable) ||
!(EF->__lsan_do_recoverable_leak_check))
return; // No lsan.
// Run the target once again, but with lsan disabled so that if there is
// a real leak we do not report it twice.
EF->__lsan_disable();
RunOne(Data, Size);
EF->__lsan_enable();
if (!HasMoreMallocsThanFrees) return; // a leak is unlikely.
if (NumberOfLeakDetectionAttempts++ > 1000) {
Options.DetectLeaks = false;
Printf("INFO: libFuzzer disabled leak detection after every mutation.\n"
" Most likely the target function accumulates allocated\n"
" memory in a global state w/o actually leaking it.\n"
" If LeakSanitizer is enabled in this process it will still\n"
" run on the process shutdown.\n");
return;
}
// Now perform the actual lsan pass. This is expensive and we must ensure
// we don't call it too often.
if (EF->__lsan_do_recoverable_leak_check()) { // Leak is found, report it.
if (DuringInitialCorpusExecution)
Printf("\nINFO: a leak has been found in the initial corpus.\n\n");
Printf("INFO: to ignore leaks on libFuzzer side use -detect_leaks=0.\n\n");
CurrentUnitSize = Size;
DumpCurrentUnit("leak-");
PrintFinalStats();
_Exit(Options.ErrorExitCode); // not exit() to disable lsan further on.
}
}
void Fuzzer::MutateAndTestOne() {
LazyAllocateCurrentUnitData();
MD.StartMutationSequence();
auto &U = ChooseUnitToMutate();
assert(CurrentUnitData);
size_t Size = U.size();
assert(Size <= Options.MaxLen && "Oversized Unit");
memcpy(CurrentUnitData, U.data(), Size);
for (int i = 0; i < Options.MutateDepth; i++) {
size_t NewSize = 0;
NewSize = MD.Mutate(CurrentUnitData, Size, Options.MaxLen);
assert(NewSize > 0 && "Mutator returned empty unit");
assert(NewSize <= Options.MaxLen &&
"Mutator return overisized unit");
Size = NewSize;
if (i == 0)
StartTraceRecording();
RunOneAndUpdateCorpus(CurrentUnitData, Size);
StopTraceRecording();
TryDetectingAMemoryLeak(CurrentUnitData, Size,
/*DuringInitialCorpusExecution*/ false);
}
}
// Returns an index of random unit from the corpus to mutate.
// Hypothesis: units added to the corpus last are more likely to be interesting.
// This function gives more weight to the more recent units.
size_t Fuzzer::ChooseUnitIdxToMutate() {
size_t Idx =
static_cast<size_t>(CorpusDistribution(MD.GetRand().Get_mt19937()));
assert(Idx < Corpus.size());
return Idx;
}
void Fuzzer::ResetCoverage() {
CController->Reset();
MaxCoverage.Reset();
CController->Prepare(&MaxCoverage);
}
// Experimental search heuristic: drilling.
// - Read, shuffle, execute and minimize the corpus.
// - Choose one random unit.
// - Reset the coverage.
// - Start fuzzing as if the chosen unit was the only element of the corpus.
// - When done, reset the coverage again.
// - Merge the newly created corpus into the original one.
void Fuzzer::Drill() {
// The corpus is already read, shuffled, and minimized.
assert(!Corpus.empty());
Options.PrintNEW = false; // Don't print NEW status lines when drilling.
Unit U = ChooseUnitToMutate();
ResetCoverage();
std::vector<Unit> SavedCorpus;
SavedCorpus.swap(Corpus);
Corpus.push_back(U);
UpdateCorpusDistribution();
assert(Corpus.size() == 1);
RunOne(U);
PrintStats("DRILL ");
std::string SavedOutputCorpusPath; // Don't write new units while drilling.
SavedOutputCorpusPath.swap(Options.OutputCorpus);
Loop();
ResetCoverage();
PrintStats("REINIT");
SavedOutputCorpusPath.swap(Options.OutputCorpus);
for (auto &U : SavedCorpus)
RunOne(U);
PrintStats("MERGE ");
Options.PrintNEW = true;
size_t NumMerged = 0;
for (auto &U : Corpus) {
if (RunOne(U)) {
PrintStatusForNewUnit(U);
NumMerged++;
WriteToOutputCorpus(U);
}
}
PrintStats("MERGED");
if (NumMerged && Options.Verbosity)
Printf("Drilling discovered %zd new units\n", NumMerged);
}
void Fuzzer::Loop() {
system_clock::time_point LastCorpusReload = system_clock::now();
if (Options.DoCrossOver)
MD.SetCorpus(&Corpus);
while (true) {
auto Now = system_clock::now();
if (duration_cast<seconds>(Now - LastCorpusReload).count()) {
RereadOutputCorpus(Options.MaxLen);
LastCorpusReload = Now;
}
if (TotalNumberOfRuns >= Options.MaxNumberOfRuns)
break;
if (Options.MaxTotalTimeSec > 0 &&
secondsSinceProcessStartUp() >
static_cast<size_t>(Options.MaxTotalTimeSec))
break;
// Perform several mutations and runs.
MutateAndTestOne();
}
PrintStats("DONE ", "\n");
MD.PrintRecommendedDictionary();
}
void Fuzzer::UpdateCorpusDistribution() {
size_t N = Corpus.size();
std::vector<double> Intervals(N + 1);
std::vector<double> Weights(N);
std::iota(Intervals.begin(), Intervals.end(), 0);
std::iota(Weights.begin(), Weights.end(), 1);
CorpusDistribution = std::piecewise_constant_distribution<double>(
Intervals.begin(), Intervals.end(), Weights.begin());
}
} // namespace fuzzer
extern "C" {
size_t LLVMFuzzerMutate(uint8_t *Data, size_t Size, size_t MaxSize) {
assert(fuzzer::F);
return fuzzer::F->GetMD().DefaultMutate(Data, Size, MaxSize);
}
} // extern "C"
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