llvm/lib/Fuzzer/FuzzerLoop.cpp - toolchain/llvm-project - Gitiles

 //===- 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 <sanitizer/coverage_interface.h>
 #include <algorithm>

 namespace fuzzer {
 static const size_t kMaxUnitSizeToPrint = 4096;

 // Only one Fuzzer per process.
 static Fuzzer *F;

 Fuzzer::Fuzzer(UserSuppliedFuzzer &USF, FuzzingOptions Options)
     : USF(USF), Options(Options) {
   SetDeathCallback();
   InitializeTraceState();
   assert(!F);
   F = this;
 }

 void Fuzzer::SetDeathCallback() {
   __sanitizer_set_death_callback(StaticDeathCallback);
 }

 void Fuzzer::PrintUnitInASCIIOrTokens(const Unit &U, const char *PrintAfter) {
   if (Options.Tokens.empty()) {
     PrintASCII(U, PrintAfter);
   } else {
     auto T = SubstituteTokens(U);
     T.push_back(0);
     Printf("%s%s", T.data(), PrintAfter);
   }
 }

 void Fuzzer::StaticDeathCallback() {
   assert(F);
   F->DeathCallback();
 }

 void Fuzzer::DeathCallback() {
   Printf("DEATH:\n");
   Print(CurrentUnit, "\n");
   PrintUnitInASCIIOrTokens(CurrentUnit, "\n");
   WriteUnitToFileWithPrefix(CurrentUnit, "crash-");
 }

 void Fuzzer::StaticAlarmCallback() {
   assert(F);
   F->AlarmCallback();
 }

 void Fuzzer::AlarmCallback() {
   assert(Options.UnitTimeoutSec > 0);
   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);
     if (CurrentUnit.size() <= kMaxUnitSizeToPrint)
       Print(CurrentUnit, "\n");
     PrintUnitInASCIIOrTokens(CurrentUnit, "\n");
     WriteUnitToFileWithPrefix(CurrentUnit, "timeout-");
     exit(1);
   }
 }

 void Fuzzer::PrintStats(const char *Where, size_t Cov, const char *End) {
   if (!Options.Verbosity) return;
   size_t Seconds = secondsSinceProcessStartUp();
   size_t ExecPerSec = (Seconds ? TotalNumberOfRuns / Seconds : 0);
   Printf("#%zd\t%s cov: %zd bits: %zd units: %zd exec/s: %zd",
          TotalNumberOfRuns, Where, Cov, TotalBits(), Corpus.size(), ExecPerSec);
   if (TotalNumberOfExecutedTraceBasedMutations)
     Printf(" tbm: %zd", TotalNumberOfExecutedTraceBasedMutations);
   Printf("%s", End);
 }

 void Fuzzer::RereadOutputCorpus() {
   if (Options.OutputCorpus.empty()) return;
   std::vector<Unit> AdditionalCorpus;
   ReadDirToVectorOfUnits(Options.OutputCorpus.c_str(), &AdditionalCorpus,
                          &EpochOfLastReadOfOutputCorpus);
   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() > (size_t)Options.MaxLen)
       X.resize(Options.MaxLen);
     if (UnitHashesAddedToCorpus.insert(Hash(X)).second) {
       CurrentUnit.clear();
       CurrentUnit.insert(CurrentUnit.begin(), X.begin(), X.end());
       size_t NewCoverage = RunOne(CurrentUnit);
       if (NewCoverage) {
         Corpus.push_back(X);
         if (Options.Verbosity >= 1)
           PrintStats("RELOAD", NewCoverage);
       }
     }
   }
 }

 void Fuzzer::ShuffleAndMinimize() {
   size_t MaxCov = 0;
   bool PreferSmall = (Options.PreferSmallDuringInitialShuffle == 1 ||
                       (Options.PreferSmallDuringInitialShuffle == -1 &&
                        USF.GetRand().RandBool()));
   if (Options.Verbosity)
     Printf("PreferSmall: %d\n", PreferSmall);
   PrintStats("READ  ", 0);
   std::vector<Unit> NewCorpus;
   std::random_shuffle(Corpus.begin(), Corpus.end(), USF.GetRand());
   if (PreferSmall)
     std::stable_sort(
         Corpus.begin(), Corpus.end(),
         [](const Unit &A, const Unit &B) { return A.size() < B.size(); });
   Unit &U = CurrentUnit;
   for (const auto &C : Corpus) {
     for (size_t First = 0; First < 1; First++) {
       U.clear();
       size_t Last = std::min(First + Options.MaxLen, C.size());
       U.insert(U.begin(), C.begin() + First, C.begin() + Last);
       if (Options.OnlyASCII)
         ToASCII(U);
       size_t NewCoverage = RunOne(U);
       if (NewCoverage) {
         MaxCov = NewCoverage;
         NewCorpus.push_back(U);
         if (Options.Verbosity >= 2)
           Printf("NEW0: %zd L %zd\n", NewCoverage, U.size());
       }
     }
   }
   Corpus = NewCorpus;
   for (auto &X : Corpus)
     UnitHashesAddedToCorpus.insert(Hash(X));
   PrintStats("INITED", MaxCov);
 }

 size_t Fuzzer::RunOne(const Unit &U) {
   UnitStartTime = system_clock::now();
   TotalNumberOfRuns++;
   size_t Res = RunOneMaximizeTotalCoverage(U);
   auto UnitStopTime = system_clock::now();
   auto TimeOfUnit =
       duration_cast<seconds>(UnitStopTime - UnitStartTime).count();
   if (TimeOfUnit > TimeOfLongestUnitInSeconds &&
       TimeOfUnit >= Options.ReportSlowUnits) {
     TimeOfLongestUnitInSeconds = TimeOfUnit;
     Printf("Slowest unit: %zd s:\n", TimeOfLongestUnitInSeconds);
     if (U.size() <= kMaxUnitSizeToPrint)
       Print(U, "\n");
     WriteUnitToFileWithPrefix(U, "slow-unit-");
   }
   return Res;
 }

 void Fuzzer::RunOneAndUpdateCorpus(Unit &U) {
   if (TotalNumberOfRuns >= Options.MaxNumberOfRuns)
     return;
   if (Options.OnlyASCII)
     ToASCII(U);
   ReportNewCoverage(RunOne(U), U);
 }

 Unit Fuzzer::SubstituteTokens(const Unit &U) const {
   Unit Res;
   for (auto Idx : U) {
     if (Idx < Options.Tokens.size()) {
       std::string Token = Options.Tokens[Idx];
       Res.insert(Res.end(), Token.begin(), Token.end());
     } else {
       Res.push_back(' ');
     }
   }
   // FIXME: Apply DFSan labels.
   return Res;
 }

 void Fuzzer::ExecuteCallback(const Unit &U) {
   int Res = 0;
   if (Options.Tokens.empty()) {
     Res = USF.TargetFunction(U.data(), U.size());
   } else {
     auto T = SubstituteTokens(U);
     Res = USF.TargetFunction(T.data(), T.size());
   }
   assert(Res == 0);
 }

 size_t Fuzzer::RunOneMaximizeTotalCoverage(const Unit &U) {
   size_t NumCounters = __sanitizer_get_number_of_counters();
   if (Options.UseCounters) {
     CounterBitmap.resize(NumCounters);
     __sanitizer_update_counter_bitset_and_clear_counters(0);
   }
   size_t OldCoverage = __sanitizer_get_total_unique_coverage();
   ExecuteCallback(U);
   size_t NewCoverage = __sanitizer_get_total_unique_coverage();
   size_t NumNewBits = 0;
   if (Options.UseCounters)
     NumNewBits = __sanitizer_update_counter_bitset_and_clear_counters(
         CounterBitmap.data());

   if (!(TotalNumberOfRuns & (TotalNumberOfRuns - 1)) && Options.Verbosity)
     PrintStats("pulse ", NewCoverage);

   if (NewCoverage > OldCoverage || NumNewBits)
     return NewCoverage;
   return 0;
 }

 void Fuzzer::WriteToOutputCorpus(const Unit &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());
   assert(!Options.OnlyASCII || IsASCII(U));
 }

 void Fuzzer::WriteUnitToFileWithPrefix(const Unit &U, const char *Prefix) {
   std::string Path = Prefix + Hash(U);
   WriteToFile(U, Path);
   Printf("Test unit written to %s\n", Path.c_str());
   if (U.size() <= kMaxUnitSizeToPrint) {
     Printf("Base64: ");
     PrintFileAsBase64(Path);
   }
 }

 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::ReportNewCoverage(size_t NewCoverage, const Unit &U) {
   if (!NewCoverage) return;
   Corpus.push_back(U);
   UnitHashesAddedToCorpus.insert(Hash(U));
   PrintStats("NEW   ", NewCoverage, "");
   if (Options.Verbosity) {
     Printf(" L: %zd", U.size());
     if (U.size() < 30) {
       Printf(" ");
       PrintUnitInASCIIOrTokens(U, "\t");
       Print(U);
     }
     Printf("\n");
   }
   WriteToOutputCorpus(U);
   if (Options.ExitOnFirst)
     exit(0);
 }

 void Fuzzer::MutateAndTestOne(Unit *U) {
   for (int i = 0; i < Options.MutateDepth; i++) {
     StartTraceRecording();
     size_t Size = U->size();
     U->resize(Options.MaxLen);
     size_t NewSize = USF.Mutate(U->data(), Size, U->size());
     assert(NewSize > 0 && "Mutator returned empty unit");
     assert(NewSize <= (size_t)Options.MaxLen &&
            "Mutator return overisized unit");
     U->resize(NewSize);
     RunOneAndUpdateCorpus(*U);
     size_t NumTraceBasedMutations = StopTraceRecording();
     size_t TBMWidth =
         std::min((size_t)Options.TBMWidth, NumTraceBasedMutations);
     size_t TBMDepth =
         std::min((size_t)Options.TBMDepth, NumTraceBasedMutations);
     Unit BackUp = *U;
     for (size_t w = 0; w < TBMWidth; w++) {
       *U = BackUp;
       for (size_t d = 0; d < TBMDepth; d++) {
         TotalNumberOfExecutedTraceBasedMutations++;
         ApplyTraceBasedMutation(USF.GetRand()(NumTraceBasedMutations), U);
         RunOneAndUpdateCorpus(*U);
       }
     }
   }
 }

 void Fuzzer::Loop() {
   for (auto &U: Options.Dictionary)
     USF.GetMD().AddWordToDictionary(U.data(), U.size());

   while (true) {
     for (size_t J1 = 0; J1 < Corpus.size(); J1++) {
       SyncCorpus();
       RereadOutputCorpus();
       if (TotalNumberOfRuns >= Options.MaxNumberOfRuns)
         return;
       if (Options.MaxTotalTimeSec > 0 &&
           secondsSinceProcessStartUp() >
               static_cast<size_t>(Options.MaxTotalTimeSec))
         return;
       CurrentUnit = Corpus[J1];
       // Optionally, cross with another unit.
       if (Options.DoCrossOver && USF.GetRand().RandBool()) {
         size_t J2 = USF.GetRand()(Corpus.size());
         if (!Corpus[J1].empty() && !Corpus[J2].empty()) {
           assert(!Corpus[J2].empty());
           CurrentUnit.resize(Options.MaxLen);
           size_t NewSize = USF.CrossOver(
               Corpus[J1].data(), Corpus[J1].size(), Corpus[J2].data(),
               Corpus[J2].size(), CurrentUnit.data(), CurrentUnit.size());
           assert(NewSize > 0 && "CrossOver returned empty unit");
           assert(NewSize <= (size_t)Options.MaxLen &&
                  "CrossOver returned overisized unit");
           CurrentUnit.resize(NewSize);
         }
       }
       // Perform several mutations and runs.
       MutateAndTestOne(&CurrentUnit);
     }
   }
 }

 void Fuzzer::SyncCorpus() {
   if (Options.SyncCommand.empty() || Options.OutputCorpus.empty()) return;
   auto Now = system_clock::now();
   if (duration_cast<seconds>(Now - LastExternalSync).count() <
       Options.SyncTimeout)
     return;
   LastExternalSync = Now;
   ExecuteCommand(Options.SyncCommand + " " + Options.OutputCorpus);
 }

 }  // namespace fuzzer
	//===- 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 <sanitizer/coverage_interface.h>
	#include <algorithm>

	namespace fuzzer {
	static const size_t kMaxUnitSizeToPrint = 4096;

	// Only one Fuzzer per process.
	static Fuzzer *F;

	Fuzzer::Fuzzer(UserSuppliedFuzzer &USF, FuzzingOptions Options)
	: USF(USF), Options(Options) {
	SetDeathCallback();
	InitializeTraceState();
	assert(!F);
	F = this;
	}

	void Fuzzer::SetDeathCallback() {
	__sanitizer_set_death_callback(StaticDeathCallback);
	}

	void Fuzzer::PrintUnitInASCIIOrTokens(const Unit &U, const char *PrintAfter) {
	if (Options.Tokens.empty()) {
	PrintASCII(U, PrintAfter);
	} else {
	auto T = SubstituteTokens(U);
	T.push_back(0);
	Printf("%s%s", T.data(), PrintAfter);
	}
	}

	void Fuzzer::StaticDeathCallback() {
	assert(F);
	F->DeathCallback();
	}

	void Fuzzer::DeathCallback() {
	Printf("DEATH:\n");
	Print(CurrentUnit, "\n");
	PrintUnitInASCIIOrTokens(CurrentUnit, "\n");
	WriteUnitToFileWithPrefix(CurrentUnit, "crash-");
	}

	void Fuzzer::StaticAlarmCallback() {
	assert(F);
	F->AlarmCallback();
	}

	void Fuzzer::AlarmCallback() {
	assert(Options.UnitTimeoutSec > 0);
	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);
	if (CurrentUnit.size() <= kMaxUnitSizeToPrint)
	Print(CurrentUnit, "\n");
	PrintUnitInASCIIOrTokens(CurrentUnit, "\n");
	WriteUnitToFileWithPrefix(CurrentUnit, "timeout-");
	exit(1);
	}
	}

	void Fuzzer::PrintStats(const char Where, size_t Cov, const char End) {
	if (!Options.Verbosity) return;
	size_t Seconds = secondsSinceProcessStartUp();
	size_t ExecPerSec = (Seconds ? TotalNumberOfRuns / Seconds : 0);
	Printf("#%zd\t%s cov: %zd bits: %zd units: %zd exec/s: %zd",
	TotalNumberOfRuns, Where, Cov, TotalBits(), Corpus.size(), ExecPerSec);
	if (TotalNumberOfExecutedTraceBasedMutations)
	Printf(" tbm: %zd", TotalNumberOfExecutedTraceBasedMutations);
	Printf("%s", End);
	}

	void Fuzzer::RereadOutputCorpus() {
	if (Options.OutputCorpus.empty()) return;
	std::vector<Unit> AdditionalCorpus;
	ReadDirToVectorOfUnits(Options.OutputCorpus.c_str(), &AdditionalCorpus,
	&EpochOfLastReadOfOutputCorpus);
	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() > (size_t)Options.MaxLen)
	X.resize(Options.MaxLen);
	if (UnitHashesAddedToCorpus.insert(Hash(X)).second) {
	CurrentUnit.clear();
	CurrentUnit.insert(CurrentUnit.begin(), X.begin(), X.end());
	size_t NewCoverage = RunOne(CurrentUnit);
	if (NewCoverage) {
	Corpus.push_back(X);
	if (Options.Verbosity >= 1)
	PrintStats("RELOAD", NewCoverage);
	}
	}
	}
	}

	void Fuzzer::ShuffleAndMinimize() {
	size_t MaxCov = 0;
	bool PreferSmall = (Options.PreferSmallDuringInitialShuffle == 1 \|\|
	(Options.PreferSmallDuringInitialShuffle == -1 &&
	USF.GetRand().RandBool()));
	if (Options.Verbosity)
	Printf("PreferSmall: %d\n", PreferSmall);
	PrintStats("READ ", 0);
	std::vector<Unit> NewCorpus;
	std::random_shuffle(Corpus.begin(), Corpus.end(), USF.GetRand());
	if (PreferSmall)
	std::stable_sort(
	Corpus.begin(), Corpus.end(),
	[](const Unit &A, const Unit &B) { return A.size() < B.size(); });
	Unit &U = CurrentUnit;
	for (const auto &C : Corpus) {
	for (size_t First = 0; First < 1; First++) {
	U.clear();
	size_t Last = std::min(First + Options.MaxLen, C.size());
	U.insert(U.begin(), C.begin() + First, C.begin() + Last);
	if (Options.OnlyASCII)
	ToASCII(U);
	size_t NewCoverage = RunOne(U);
	if (NewCoverage) {
	MaxCov = NewCoverage;
	NewCorpus.push_back(U);
	if (Options.Verbosity >= 2)
	Printf("NEW0: %zd L %zd\n", NewCoverage, U.size());
	}
	}
	}
	Corpus = NewCorpus;
	for (auto &X : Corpus)
	UnitHashesAddedToCorpus.insert(Hash(X));
	PrintStats("INITED", MaxCov);
	}

	size_t Fuzzer::RunOne(const Unit &U) {
	UnitStartTime = system_clock::now();
	TotalNumberOfRuns++;
	size_t Res = RunOneMaximizeTotalCoverage(U);
	auto UnitStopTime = system_clock::now();
	auto TimeOfUnit =
	duration_cast<seconds>(UnitStopTime - UnitStartTime).count();
	if (TimeOfUnit > TimeOfLongestUnitInSeconds &&
	TimeOfUnit >= Options.ReportSlowUnits) {
	TimeOfLongestUnitInSeconds = TimeOfUnit;
	Printf("Slowest unit: %zd s:\n", TimeOfLongestUnitInSeconds);
	if (U.size() <= kMaxUnitSizeToPrint)
	Print(U, "\n");
	WriteUnitToFileWithPrefix(U, "slow-unit-");
	}
	return Res;
	}

	void Fuzzer::RunOneAndUpdateCorpus(Unit &U) {
	if (TotalNumberOfRuns >= Options.MaxNumberOfRuns)
	return;
	if (Options.OnlyASCII)
	ToASCII(U);
	ReportNewCoverage(RunOne(U), U);
	}

	Unit Fuzzer::SubstituteTokens(const Unit &U) const {
	Unit Res;
	for (auto Idx : U) {
	if (Idx < Options.Tokens.size()) {
	std::string Token = Options.Tokens[Idx];
	Res.insert(Res.end(), Token.begin(), Token.end());
	} else {
	Res.push_back(' ');
	}
	}
	// FIXME: Apply DFSan labels.
	return Res;
	}

	void Fuzzer::ExecuteCallback(const Unit &U) {
	int Res = 0;
	if (Options.Tokens.empty()) {
	Res = USF.TargetFunction(U.data(), U.size());
	} else {
	auto T = SubstituteTokens(U);
	Res = USF.TargetFunction(T.data(), T.size());
	}
	assert(Res == 0);
	}

	size_t Fuzzer::RunOneMaximizeTotalCoverage(const Unit &U) {
	size_t NumCounters = __sanitizer_get_number_of_counters();
	if (Options.UseCounters) {
	CounterBitmap.resize(NumCounters);
	__sanitizer_update_counter_bitset_and_clear_counters(0);
	}
	size_t OldCoverage = __sanitizer_get_total_unique_coverage();
	ExecuteCallback(U);
	size_t NewCoverage = __sanitizer_get_total_unique_coverage();
	size_t NumNewBits = 0;
	if (Options.UseCounters)
	NumNewBits = __sanitizer_update_counter_bitset_and_clear_counters(
	CounterBitmap.data());

	if (!(TotalNumberOfRuns & (TotalNumberOfRuns - 1)) && Options.Verbosity)
	PrintStats("pulse ", NewCoverage);

	if (NewCoverage > OldCoverage \|\| NumNewBits)
	return NewCoverage;
	return 0;
	}

	void Fuzzer::WriteToOutputCorpus(const Unit &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());
	assert(!Options.OnlyASCII \|\| IsASCII(U));
	}

	void Fuzzer::WriteUnitToFileWithPrefix(const Unit &U, const char *Prefix) {
	std::string Path = Prefix + Hash(U);
	WriteToFile(U, Path);
	Printf("Test unit written to %s\n", Path.c_str());
	if (U.size() <= kMaxUnitSizeToPrint) {
	Printf("Base64: ");
	PrintFileAsBase64(Path);
	}
	}

	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::ReportNewCoverage(size_t NewCoverage, const Unit &U) {
	if (!NewCoverage) return;
	Corpus.push_back(U);
	UnitHashesAddedToCorpus.insert(Hash(U));
	PrintStats("NEW ", NewCoverage, "");
	if (Options.Verbosity) {
	Printf(" L: %zd", U.size());
	if (U.size() < 30) {
	Printf(" ");
	PrintUnitInASCIIOrTokens(U, "\t");
	Print(U);
	}
	Printf("\n");
	}
	WriteToOutputCorpus(U);
	if (Options.ExitOnFirst)
	exit(0);
	}

	void Fuzzer::MutateAndTestOne(Unit *U) {
	for (int i = 0; i < Options.MutateDepth; i++) {
	StartTraceRecording();
	size_t Size = U->size();
	U->resize(Options.MaxLen);
	size_t NewSize = USF.Mutate(U->data(), Size, U->size());
	assert(NewSize > 0 && "Mutator returned empty unit");
	assert(NewSize <= (size_t)Options.MaxLen &&
	"Mutator return overisized unit");
	U->resize(NewSize);
	RunOneAndUpdateCorpus(*U);
	size_t NumTraceBasedMutations = StopTraceRecording();
	size_t TBMWidth =
	std::min((size_t)Options.TBMWidth, NumTraceBasedMutations);
	size_t TBMDepth =
	std::min((size_t)Options.TBMDepth, NumTraceBasedMutations);
	Unit BackUp = *U;
	for (size_t w = 0; w < TBMWidth; w++) {
	*U = BackUp;
	for (size_t d = 0; d < TBMDepth; d++) {
	TotalNumberOfExecutedTraceBasedMutations++;
	ApplyTraceBasedMutation(USF.GetRand()(NumTraceBasedMutations), U);
	RunOneAndUpdateCorpus(*U);
	}
	}
	}
	}

	void Fuzzer::Loop() {
	for (auto &U: Options.Dictionary)
	USF.GetMD().AddWordToDictionary(U.data(), U.size());

	while (true) {
	for (size_t J1 = 0; J1 < Corpus.size(); J1++) {
	SyncCorpus();
	RereadOutputCorpus();
	if (TotalNumberOfRuns >= Options.MaxNumberOfRuns)
	return;
	if (Options.MaxTotalTimeSec > 0 &&
	secondsSinceProcessStartUp() >
	static_cast<size_t>(Options.MaxTotalTimeSec))
	return;
	CurrentUnit = Corpus[J1];
	// Optionally, cross with another unit.
	if (Options.DoCrossOver && USF.GetRand().RandBool()) {
	size_t J2 = USF.GetRand()(Corpus.size());
	if (!Corpus[J1].empty() && !Corpus[J2].empty()) {
	assert(!Corpus[J2].empty());
	CurrentUnit.resize(Options.MaxLen);
	size_t NewSize = USF.CrossOver(
	Corpus[J1].data(), Corpus[J1].size(), Corpus[J2].data(),
	Corpus[J2].size(), CurrentUnit.data(), CurrentUnit.size());
	assert(NewSize > 0 && "CrossOver returned empty unit");
	assert(NewSize <= (size_t)Options.MaxLen &&
	"CrossOver returned overisized unit");
	CurrentUnit.resize(NewSize);
	}
	}
	// Perform several mutations and runs.
	MutateAndTestOne(&CurrentUnit);
	}
	}
	}

	void Fuzzer::SyncCorpus() {
	if (Options.SyncCommand.empty() \|\| Options.OutputCorpus.empty()) return;
	auto Now = system_clock::now();
	if (duration_cast<seconds>(Now - LastExternalSync).count() <
	Options.SyncTimeout)
	return;
	LastExternalSync = Now;
	ExecuteCommand(Options.SyncCommand + " " + Options.OutputCorpus);
	}

	} // namespace fuzzer