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

 //===- FuzzerTraceState.cpp - Trace-based fuzzer mutator ------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 // This file implements a mutation algorithm based on instruction traces and
 // on taint analysis feedback from DFSan.
 //
 // Instruction traces are special hooks inserted by the compiler around
 // interesting instructions. Currently supported traces:
 //   * __sanitizer_cov_trace_cmp -- inserted before every ICMP instruction,
 //    receives the type, size and arguments of ICMP.
 //
 // Every time a traced event is intercepted we analyse the data involved
 // in the event and suggest a mutation for future executions.
 // For example if 4 bytes of data that derive from input bytes {4,5,6,7}
 // are compared with a constant 12345,
 // we try to insert 12345, 12344, 12346 into bytes
 // {4,5,6,7} of the next fuzzed inputs.
 //
 // The fuzzer can work only with the traces, or with both traces and DFSan.
 //
 // DataFlowSanitizer (DFSan) is a tool for
 // generalised dynamic data flow (taint) analysis:
 // http://clang.llvm.org/docs/DataFlowSanitizer.html .
 //
 // The approach with DFSan-based fuzzing has some similarity to
 // "Taint-based Directed Whitebox Fuzzing"
 // by Vijay Ganesh & Tim Leek & Martin Rinard:
 // http://dspace.mit.edu/openaccess-disseminate/1721.1/59320,
 // but it uses a full blown LLVM IR taint analysis and separate instrumentation
 // to analyze all of the "attack points" at once.
 //
 // Workflow with DFSan:
 //   * lib/Fuzzer/Fuzzer*.cpp is compiled w/o any instrumentation.
 //   * The code under test is compiled with DFSan *and* with instruction traces.
 //   * Every call to HOOK(a,b) is replaced by DFSan with
 //     __dfsw_HOOK(a, b, label(a), label(b)) so that __dfsw_HOOK
 //     gets all the taint labels for the arguments.
 //   * At the Fuzzer startup we assign a unique DFSan label
 //     to every byte of the input string (Fuzzer::CurrentUnit) so that for any
 //     chunk of data we know which input bytes it has derived from.
 //   * The __dfsw_* functions (implemented in this file) record the
 //     parameters (i.e. the application data and the corresponding taint labels)
 //     in a global state.
 //   * Fuzzer::ApplyTraceBasedMutation() tries to use the data recorded
 //     by __dfsw_* hooks to guide the fuzzing towards new application states.
 //
 // Parts of this code will not function when DFSan is not linked in.
 // Instead of using ifdefs and thus requiring a separate build of lib/Fuzzer
 // we redeclare the dfsan_* interface functions as weak and check if they
 // are nullptr before calling.
 // If this approach proves to be useful we may add attribute(weak) to the
 // dfsan declarations in dfsan_interface.h
 //
 // This module is in the "proof of concept" stage.
 // It is capable of solving only the simplest puzzles
 // like test/dfsan/DFSanSimpleCmpTest.cpp.
 //===----------------------------------------------------------------------===//

 /* Example of manual usage (-fsanitize=dataflow is optional):
 (
   cd $LLVM/lib/Fuzzer/
   clang  -fPIC -c -g -O2 -std=c++11 Fuzzer*.cpp
   clang++ -O0 -std=c++11 -fsanitize-coverage=edge,trace-cmp \
     -fsanitize=dataflow \
     test/dfsan/DFSanSimpleCmpTest.cpp Fuzzer*.o
   ./a.out
 )
 */

 #include "FuzzerInternal.h"
 #include <sanitizer/dfsan_interface.h>

 #include <algorithm>
 #include <cstring>
 #include <unordered_map>

 extern "C" {
 __attribute__((weak))
 dfsan_label dfsan_create_label(const char *desc, void *userdata);
 __attribute__((weak))
 void dfsan_set_label(dfsan_label label, void *addr, size_t size);
 __attribute__((weak))
 void dfsan_add_label(dfsan_label label, void *addr, size_t size);
 __attribute__((weak))
 const struct dfsan_label_info *dfsan_get_label_info(dfsan_label label);
 __attribute__((weak))
 dfsan_label dfsan_read_label(const void *addr, size_t size);
 }  // extern "C"

 namespace fuzzer {

 static bool ReallyHaveDFSan() {
   return &dfsan_create_label != nullptr;
 }

 // These values are copied from include/llvm/IR/InstrTypes.h.
 // We do not include the LLVM headers here to remain independent.
 // If these values ever change, an assertion in ComputeCmp will fail.
 enum Predicate {
   ICMP_EQ = 32,  ///< equal
   ICMP_NE = 33,  ///< not equal
   ICMP_UGT = 34, ///< unsigned greater than
   ICMP_UGE = 35, ///< unsigned greater or equal
   ICMP_ULT = 36, ///< unsigned less than
   ICMP_ULE = 37, ///< unsigned less or equal
   ICMP_SGT = 38, ///< signed greater than
   ICMP_SGE = 39, ///< signed greater or equal
   ICMP_SLT = 40, ///< signed less than
   ICMP_SLE = 41, ///< signed less or equal
 };

 template <class U, class S>
 bool ComputeCmp(size_t CmpType, U Arg1, U Arg2) {
   switch(CmpType) {
     case ICMP_EQ : return Arg1 == Arg2;
     case ICMP_NE : return Arg1 != Arg2;
     case ICMP_UGT: return Arg1 > Arg2;
     case ICMP_UGE: return Arg1 >= Arg2;
     case ICMP_ULT: return Arg1 < Arg2;
     case ICMP_ULE: return Arg1 <= Arg2;
     case ICMP_SGT: return (S)Arg1 > (S)Arg2;
     case ICMP_SGE: return (S)Arg1 >= (S)Arg2;
     case ICMP_SLT: return (S)Arg1 < (S)Arg2;
     case ICMP_SLE: return (S)Arg1 <= (S)Arg2;
     default: assert(0 && "unsupported CmpType");
   }
   return false;
 }

 static bool ComputeCmp(size_t CmpSize, size_t CmpType, uint64_t Arg1,
                        uint64_t Arg2) {
   if (CmpSize == 8) return ComputeCmp<uint64_t, int64_t>(CmpType, Arg1, Arg2);
   if (CmpSize == 4) return ComputeCmp<uint32_t, int32_t>(CmpType, Arg1, Arg2);
   if (CmpSize == 2) return ComputeCmp<uint16_t, int16_t>(CmpType, Arg1, Arg2);
   if (CmpSize == 1) return ComputeCmp<uint8_t, int8_t>(CmpType, Arg1, Arg2);
   // Other size, ==
   if (CmpType == ICMP_EQ) return Arg1 == Arg2;
   // assert(0 && "unsupported cmp and type size combination");
   return true;
 }

 // As a simplification we use the range of input bytes instead of a set of input
 // bytes.
 struct LabelRange {
   uint16_t Beg, End;  // Range is [Beg, End), thus Beg==End is an empty range.

   LabelRange(uint16_t Beg = 0, uint16_t End = 0) : Beg(Beg), End(End) {}

   static LabelRange Join(LabelRange LR1, LabelRange LR2) {
     if (LR1.Beg == LR1.End) return LR2;
     if (LR2.Beg == LR2.End) return LR1;
     return {std::min(LR1.Beg, LR2.Beg), std::max(LR1.End, LR2.End)};
   }
   LabelRange &Join(LabelRange LR) {
     return *this = Join(*this, LR);
   }
   static LabelRange Singleton(const dfsan_label_info *LI) {
     uint16_t Idx = (uint16_t)(uintptr_t)LI->userdata;
     assert(Idx > 0);
     return {(uint16_t)(Idx - 1), Idx};
   }
 };

 // A passport for a CMP site. We want to keep track of where the given CMP is
 // and how many times it is evaluated to true or false.
 struct CmpSitePassport {
   uintptr_t PC;
   size_t Counter[2];

   bool IsInterestingCmpTarget() {
     static const size_t kRareEnough = 50;
     size_t C0 = Counter[0];
     size_t C1 = Counter[1];
     return C0 > kRareEnough * (C1 + 1) || C1 > kRareEnough * (C0 + 1);
   }
 };

 // For now, just keep a simple imprecise hash table PC => CmpSitePassport.
 // Potentially, will need to have a compiler support to have a precise mapping
 // and also thread-safety.
 struct CmpSitePassportTable {
   static const size_t kSize = 99991;  // Prime.
   CmpSitePassport Passports[kSize];

   CmpSitePassport *GetPassport(uintptr_t PC) {
     uintptr_t Idx = PC & kSize;
     CmpSitePassport *Res = &Passports[Idx];
     if (Res->PC == 0)  // Not thread safe.
       Res->PC = PC;
     return Res->PC == PC ? Res : nullptr;
   }
 };

 static CmpSitePassportTable CSPTable;  // Zero initialized.

 // For now, very simple: put Size bytes of Data at position Pos.
 struct TraceBasedMutation {
   size_t Pos;
   size_t Size;
   uint64_t Data;
 };

 class TraceState {
  public:
    TraceState(const Fuzzer::FuzzingOptions &Options, const Unit &CurrentUnit)
        : Options(Options), CurrentUnit(CurrentUnit) {}

   LabelRange GetLabelRange(dfsan_label L);
   void DFSanCmpCallback(uintptr_t PC, size_t CmpSize, size_t CmpType,
                         uint64_t Arg1, uint64_t Arg2, dfsan_label L1,
                         dfsan_label L2);
   void DFSanSwitchCallback(uint64_t PC, size_t ValSizeInBits, uint64_t Val,
                            size_t NumCases, uint64_t *Cases, dfsan_label L);
   void TraceCmpCallback(uintptr_t PC, size_t CmpSize, size_t CmpType, uint64_t Arg1,
                         uint64_t Arg2);

   void TraceSwitchCallback(uintptr_t PC, size_t ValSizeInBits, uint64_t Val,
                            size_t NumCases, uint64_t *Cases);
   int TryToAddDesiredData(uint64_t PresentData, uint64_t DesiredData,
                            size_t DataSize);

   void StartTraceRecording() {
     if (!Options.UseTraces) return;
     RecordingTraces = true;
     Mutations.clear();
   }

   size_t StopTraceRecording(FuzzerRandomBase &Rand) {
     RecordingTraces = false;
     return Mutations.size();
   }

   void ApplyTraceBasedMutation(size_t Idx, fuzzer::Unit *U);

  private:
   bool IsTwoByteData(uint64_t Data) {
     int64_t Signed = static_cast<int64_t>(Data);
     Signed >>= 16;
     return Signed == 0 || Signed == -1L;
   }
   bool RecordingTraces = false;
   std::vector<TraceBasedMutation> Mutations;
   LabelRange LabelRanges[1 << (sizeof(dfsan_label) * 8)] = {};
   const Fuzzer::FuzzingOptions &Options;
   const Unit &CurrentUnit;
 };

 LabelRange TraceState::GetLabelRange(dfsan_label L) {
   LabelRange &LR = LabelRanges[L];
   if (LR.Beg < LR.End || L == 0)
     return LR;
   const dfsan_label_info *LI = dfsan_get_label_info(L);
   if (LI->l1 || LI->l2)
     return LR = LabelRange::Join(GetLabelRange(LI->l1), GetLabelRange(LI->l2));
   return LR = LabelRange::Singleton(LI);
 }

 void TraceState::ApplyTraceBasedMutation(size_t Idx, fuzzer::Unit *U) {
   assert(Idx < Mutations.size());
   auto &M = Mutations[Idx];
   if (Options.Verbosity >= 3)
     Printf("TBM %zd %zd %zd\n", M.Pos, M.Size, M.Data);
   if (M.Pos + M.Size > U->size()) return;
   memcpy(U->data() + M.Pos, &M.Data, M.Size);
 }

 void TraceState::DFSanCmpCallback(uintptr_t PC, size_t CmpSize, size_t CmpType,
                                   uint64_t Arg1, uint64_t Arg2, dfsan_label L1,
                                   dfsan_label L2) {
   assert(ReallyHaveDFSan());
   if (!RecordingTraces) return;
   if (L1 == 0 && L2 == 0)
     return;  // Not actionable.
   if (L1 != 0 && L2 != 0)
     return;  // Probably still actionable.
   bool Res = ComputeCmp(CmpSize, CmpType, Arg1, Arg2);
   uint64_t Data = L1 ? Arg2 : Arg1;
   LabelRange LR = L1 ? GetLabelRange(L1) : GetLabelRange(L2);

   for (size_t Pos = LR.Beg; Pos + CmpSize <= LR.End; Pos++) {
     Mutations.push_back({Pos, CmpSize, Data});
     Mutations.push_back({Pos, CmpSize, Data + 1});
     Mutations.push_back({Pos, CmpSize, Data - 1});
   }

   if (CmpSize > LR.End - LR.Beg)
     Mutations.push_back({LR.Beg, (unsigned)(LR.End - LR.Beg), Data});


   if (Options.Verbosity >= 3)
     Printf("DFSanCmpCallback: PC %lx S %zd T %zd A1 %llx A2 %llx R %d L1 %d L2 "
            "%d MU %zd\n",
            PC, CmpSize, CmpType, Arg1, Arg2, Res, L1, L2, Mutations.size());
 }

 void TraceState::DFSanSwitchCallback(uint64_t PC, size_t ValSizeInBits,
                                      uint64_t Val, size_t NumCases,
                                      uint64_t *Cases, dfsan_label L) {
   assert(ReallyHaveDFSan());
   if (!RecordingTraces) return;
   if (!L) return;  // Not actionable.
   LabelRange LR = GetLabelRange(L);
   size_t ValSize = ValSizeInBits / 8;
   bool TryShort = IsTwoByteData(Val);
   for (size_t i = 0; i < NumCases; i++)
     TryShort &= IsTwoByteData(Cases[i]);

   for (size_t Pos = LR.Beg; Pos + ValSize <= LR.End; Pos++)
     for (size_t i = 0; i < NumCases; i++)
       Mutations.push_back({Pos, ValSize, Cases[i]});

   if (TryShort)
     for (size_t Pos = LR.Beg; Pos + 2 <= LR.End; Pos++)
       for (size_t i = 0; i < NumCases; i++)
         Mutations.push_back({Pos, 2, Cases[i]});

   if (Options.Verbosity >= 3)
     Printf("DFSanSwitchCallback: PC %lx Val %zd SZ %zd # %zd L %d: {%d, %d} "
            "TryShort %d\n",
            PC, Val, ValSize, NumCases, L, LR.Beg, LR.End, TryShort);
 }

 int TraceState::TryToAddDesiredData(uint64_t PresentData, uint64_t DesiredData,
                                     size_t DataSize) {
   int Res = 0;
   const uint8_t *Beg = CurrentUnit.data();
   const uint8_t *End = Beg + CurrentUnit.size();
   for (const uint8_t *Cur = Beg; Cur < End; Cur += DataSize) {
     Cur = (uint8_t *)memmem(Cur, End - Cur, &PresentData, DataSize);
     if (!Cur)
       break;
     size_t Pos = Cur - Beg;
     assert(Pos < CurrentUnit.size());
     if (Mutations.size() > 100000U) return Res;  // Just in case.
     Mutations.push_back({Pos, DataSize, DesiredData});
     Mutations.push_back({Pos, DataSize, DesiredData + 1});
     Mutations.push_back({Pos, DataSize, DesiredData - 1});
     Cur += DataSize;
     Res++;
   }
   return Res;
 }

 void TraceState::TraceCmpCallback(uintptr_t PC, size_t CmpSize, size_t CmpType, uint64_t Arg1,
                         uint64_t Arg2) {
   if (!RecordingTraces) return;
   int Added = 0;
   CmpSitePassport *CSP = CSPTable.GetPassport(PC);
   if (!CSP) return;
   CSP->Counter[ComputeCmp(CmpSize, CmpType, Arg1, Arg2)]++;
   size_t C0 = CSP->Counter[0];
   size_t C1 = CSP->Counter[1];
   // FIXME: is this a good idea or a bad?
   // if (!CSP->IsInterestingCmpTarget())
   //  return;
   if (Options.Verbosity >= 3)
     Printf("TraceCmp: %p %zd/%zd; %zd %zd\n", CSP->PC, C0, C1, Arg1, Arg2);
   Added += TryToAddDesiredData(Arg1, Arg2, CmpSize);
   Added += TryToAddDesiredData(Arg2, Arg1, CmpSize);
   if (!Added && CmpSize == 4 && IsTwoByteData(Arg1) && IsTwoByteData(Arg2)) {
     Added += TryToAddDesiredData(Arg1, Arg2, 2);
     Added += TryToAddDesiredData(Arg2, Arg1, 2);
   }
 }

 void TraceState::TraceSwitchCallback(uintptr_t PC, size_t ValSizeInBits,
                                      uint64_t Val, size_t NumCases,
                                      uint64_t *Cases) {
   if (!RecordingTraces) return;
   size_t ValSize = ValSizeInBits / 8;
   bool TryShort = IsTwoByteData(Val);
   for (size_t i = 0; i < NumCases; i++)
     TryShort &= IsTwoByteData(Cases[i]);

   if (Options.Verbosity >= 3)
     Printf("TraceSwitch: %p %zd # %zd; TryShort %d\n", PC, Val, NumCases,
            TryShort);

   for (size_t i = 0; i < NumCases; i++) {
     TryToAddDesiredData(Val, Cases[i], ValSize);
     if (TryShort)
       TryToAddDesiredData(Val, Cases[i], 2);
   }

 }

 static TraceState *TS;

 void Fuzzer::StartTraceRecording() {
   if (!TS) return;
   if (ReallyHaveDFSan())
     for (size_t i = 0; i < static_cast<size_t>(Options.MaxLen); i++)
       dfsan_set_label(i + 1, &CurrentUnit[i], 1);
   TS->StartTraceRecording();
 }

 size_t Fuzzer::StopTraceRecording() {
   if (!TS) return 0;
   return TS->StopTraceRecording(USF.GetRand());
 }

 void Fuzzer::ApplyTraceBasedMutation(size_t Idx, Unit *U) {
   assert(TS);
   TS->ApplyTraceBasedMutation(Idx, U);
 }

 void Fuzzer::InitializeTraceState() {
   if (!Options.UseTraces) return;
   TS = new TraceState(Options, CurrentUnit);
   CurrentUnit.resize(Options.MaxLen);
   // The rest really requires DFSan.
   if (!ReallyHaveDFSan()) return;
   for (size_t i = 0; i < static_cast<size_t>(Options.MaxLen); i++) {
     dfsan_label L = dfsan_create_label("input", (void*)(i + 1));
     // We assume that no one else has called dfsan_create_label before.
     if (L != i + 1) {
       Printf("DFSan labels are not starting from 1, exiting\n");
       exit(1);
     }
   }
 }

 static size_t InternalStrnlen(const char *S, size_t MaxLen) {
   size_t Len = 0;
   for (; Len < MaxLen && S[Len]; Len++) {}
   return Len;
 }

 }  // namespace fuzzer

 using fuzzer::TS;

 extern "C" {
 void __dfsw___sanitizer_cov_trace_cmp(uint64_t SizeAndType, uint64_t Arg1,
                                       uint64_t Arg2, dfsan_label L0,
                                       dfsan_label L1, dfsan_label L2) {
   if (!TS) return;
   assert(L0 == 0);
   uintptr_t PC = reinterpret_cast<uintptr_t>(__builtin_return_address(0));
   uint64_t CmpSize = (SizeAndType >> 32) / 8;
   uint64_t Type = (SizeAndType << 32) >> 32;
   TS->DFSanCmpCallback(PC, CmpSize, Type, Arg1, Arg2, L1, L2);
 }

 void __dfsw___sanitizer_cov_trace_switch(uint64_t Val, uint64_t *Cases,
                                          dfsan_label L1, dfsan_label L2) {
   if (!TS) return;
   uintptr_t PC = reinterpret_cast<uintptr_t>(__builtin_return_address(0));
   TS->DFSanSwitchCallback(PC, Cases[1], Val, Cases[0], Cases+2, L1);
 }

 void dfsan_weak_hook_memcmp(void *caller_pc, const void *s1, const void *s2,
                             size_t n, dfsan_label s1_label,
                             dfsan_label s2_label, dfsan_label n_label) {
   if (!TS) return;
   uintptr_t PC = reinterpret_cast<uintptr_t>(caller_pc);
   uint64_t S1 = 0, S2 = 0;
   // Simplification: handle only first 8 bytes.
   memcpy(&S1, s1, std::min(n, sizeof(S1)));
   memcpy(&S2, s2, std::min(n, sizeof(S2)));
   dfsan_label L1 = dfsan_read_label(s1, n);
   dfsan_label L2 = dfsan_read_label(s2, n);
   TS->DFSanCmpCallback(PC, n, fuzzer::ICMP_EQ, S1, S2, L1, L2);
 }

 void dfsan_weak_hook_strncmp(void *caller_pc, const char *s1, const char *s2,
                              size_t n, dfsan_label s1_label,
                              dfsan_label s2_label, dfsan_label n_label) {
   if (!TS) return;
   uintptr_t PC = reinterpret_cast<uintptr_t>(caller_pc);
   uint64_t S1 = 0, S2 = 0;
   n = std::min(n, fuzzer::InternalStrnlen(s1, n));
   n = std::min(n, fuzzer::InternalStrnlen(s2, n));
   // Simplification: handle only first 8 bytes.
   memcpy(&S1, s1, std::min(n, sizeof(S1)));
   memcpy(&S2, s2, std::min(n, sizeof(S2)));
   dfsan_label L1 = dfsan_read_label(s1, n);
   dfsan_label L2 = dfsan_read_label(s2, n);
   TS->DFSanCmpCallback(PC, n, fuzzer::ICMP_EQ, S1, S2, L1, L2);
 }

 void dfsan_weak_hook_strcmp(void *caller_pc, const char *s1, const char *s2,
                             dfsan_label s1_label, dfsan_label s2_label) {
   if (!TS) return;
   uintptr_t PC = reinterpret_cast<uintptr_t>(caller_pc);
   uint64_t S1 = 0, S2 = 0;
   size_t Len1 = strlen(s1);
   size_t Len2 = strlen(s2);
   size_t N = std::min(Len1, Len2);
   if (N <= 1) return;  // Not interesting.
   // Simplification: handle only first 8 bytes.
   memcpy(&S1, s1, std::min(N, sizeof(S1)));
   memcpy(&S2, s2, std::min(N, sizeof(S2)));
   dfsan_label L1 = dfsan_read_label(s1, Len1);
   dfsan_label L2 = dfsan_read_label(s2, Len2);
   TS->DFSanCmpCallback(PC, N, fuzzer::ICMP_EQ, S1, S2, L1, L2);
 }

 void __sanitizer_weak_hook_memcmp(void *caller_pc, const void *s1,
                                   const void *s2, size_t n) {
   if (!TS) return;
   uintptr_t PC = reinterpret_cast<uintptr_t>(caller_pc);
   uint64_t S1 = 0, S2 = 0;
   // Simplification: handle only first 8 bytes.
   memcpy(&S1, s1, std::min(n, sizeof(S1)));
   memcpy(&S2, s2, std::min(n, sizeof(S2)));
   TS->TraceCmpCallback(PC, n, fuzzer::ICMP_EQ, S1, S2);
 }

 void __sanitizer_weak_hook_strncmp(void *caller_pc, const char *s1,
                                    const char *s2, size_t n) {
   if (!TS) return;
   uintptr_t PC = reinterpret_cast<uintptr_t>(caller_pc);
   uint64_t S1 = 0, S2 = 0;
   size_t Len1 = fuzzer::InternalStrnlen(s1, n);
   size_t Len2 = fuzzer::InternalStrnlen(s2, n);
   n = std::min(n, Len1);
   n = std::min(n, Len2);
   if (n <= 1) return;  // Not interesting.
   // Simplification: handle only first 8 bytes.
   memcpy(&S1, s1, std::min(n, sizeof(S1)));
   memcpy(&S2, s2, std::min(n, sizeof(S2)));
   TS->TraceCmpCallback(PC, n, fuzzer::ICMP_EQ, S1, S2);
 }

 void __sanitizer_weak_hook_strcmp(void *caller_pc, const char *s1,
                                    const char *s2) {
   if (!TS) return;
   uintptr_t PC = reinterpret_cast<uintptr_t>(caller_pc);
   uint64_t S1 = 0, S2 = 0;
   size_t Len1 = strlen(s1);
   size_t Len2 = strlen(s2);
   size_t N = std::min(Len1, Len2);
   if (N <= 1) return;  // Not interesting.
   // Simplification: handle only first 8 bytes.
   memcpy(&S1, s1, std::min(N, sizeof(S1)));
   memcpy(&S2, s2, std::min(N, sizeof(S2)));
   TS->TraceCmpCallback(PC, N, fuzzer::ICMP_EQ, S1, S2);
 }


 void __sanitizer_cov_trace_cmp(uint64_t SizeAndType, uint64_t Arg1,
                                uint64_t Arg2) {
   if (!TS) return;
   uintptr_t PC = reinterpret_cast<uintptr_t>(__builtin_return_address(0));
   uint64_t CmpSize = (SizeAndType >> 32) / 8;
   uint64_t Type = (SizeAndType << 32) >> 32;
   TS->TraceCmpCallback(PC, CmpSize, Type, Arg1, Arg2);
 }

 void __sanitizer_cov_trace_switch(uint64_t Val, uint64_t *Cases) {
   if (!TS) return;
   uintptr_t PC = reinterpret_cast<uintptr_t>(__builtin_return_address(0));
   TS->TraceSwitchCallback(PC, Cases[1], Val, Cases[0], Cases + 2);
 }

 }  // extern "C"
	//===- FuzzerTraceState.cpp - Trace-based fuzzer mutator ------------------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	// This file implements a mutation algorithm based on instruction traces and
	// on taint analysis feedback from DFSan.
	//
	// Instruction traces are special hooks inserted by the compiler around
	// interesting instructions. Currently supported traces:
	// * __sanitizer_cov_trace_cmp -- inserted before every ICMP instruction,
	// receives the type, size and arguments of ICMP.
	//
	// Every time a traced event is intercepted we analyse the data involved
	// in the event and suggest a mutation for future executions.
	// For example if 4 bytes of data that derive from input bytes {4,5,6,7}
	// are compared with a constant 12345,
	// we try to insert 12345, 12344, 12346 into bytes
	// {4,5,6,7} of the next fuzzed inputs.
	//
	// The fuzzer can work only with the traces, or with both traces and DFSan.
	//
	// DataFlowSanitizer (DFSan) is a tool for
	// generalised dynamic data flow (taint) analysis:
	// http://clang.llvm.org/docs/DataFlowSanitizer.html .
	//
	// The approach with DFSan-based fuzzing has some similarity to
	// "Taint-based Directed Whitebox Fuzzing"
	// by Vijay Ganesh & Tim Leek & Martin Rinard:
	// http://dspace.mit.edu/openaccess-disseminate/1721.1/59320,
	// but it uses a full blown LLVM IR taint analysis and separate instrumentation
	// to analyze all of the "attack points" at once.
	//
	// Workflow with DFSan:
	// * lib/Fuzzer/Fuzzer*.cpp is compiled w/o any instrumentation.
	// * The code under test is compiled with DFSan and with instruction traces.
	// * Every call to HOOK(a,b) is replaced by DFSan with
	// __dfsw_HOOK(a, b, label(a), label(b)) so that __dfsw_HOOK
	// gets all the taint labels for the arguments.
	// * At the Fuzzer startup we assign a unique DFSan label
	// to every byte of the input string (Fuzzer::CurrentUnit) so that for any
	// chunk of data we know which input bytes it has derived from.
	// * The __dfsw_* functions (implemented in this file) record the
	// parameters (i.e. the application data and the corresponding taint labels)
	// in a global state.
	// * Fuzzer::ApplyTraceBasedMutation() tries to use the data recorded
	// by __dfsw_* hooks to guide the fuzzing towards new application states.
	//
	// Parts of this code will not function when DFSan is not linked in.
	// Instead of using ifdefs and thus requiring a separate build of lib/Fuzzer
	// we redeclare the dfsan_* interface functions as weak and check if they
	// are nullptr before calling.
	// If this approach proves to be useful we may add attribute(weak) to the
	// dfsan declarations in dfsan_interface.h
	//
	// This module is in the "proof of concept" stage.
	// It is capable of solving only the simplest puzzles
	// like test/dfsan/DFSanSimpleCmpTest.cpp.
	//===----------------------------------------------------------------------===//

	/* Example of manual usage (-fsanitize=dataflow is optional):
	(
	cd $LLVM/lib/Fuzzer/
	clang -fPIC -c -g -O2 -std=c++11 Fuzzer*.cpp
	clang++ -O0 -std=c++11 -fsanitize-coverage=edge,trace-cmp \
	-fsanitize=dataflow \
	test/dfsan/DFSanSimpleCmpTest.cpp Fuzzer*.o
	./a.out
	)
	*/

	#include "FuzzerInternal.h"
	#include <sanitizer/dfsan_interface.h>

	#include <algorithm>
	#include <cstring>
	#include <unordered_map>

	extern "C" {
	__attribute__((weak))
	dfsan_label dfsan_create_label(const char desc, void userdata);
	__attribute__((weak))
	void dfsan_set_label(dfsan_label label, void *addr, size_t size);
	__attribute__((weak))
	void dfsan_add_label(dfsan_label label, void *addr, size_t size);
	__attribute__((weak))
	const struct dfsan_label_info *dfsan_get_label_info(dfsan_label label);
	__attribute__((weak))
	dfsan_label dfsan_read_label(const void *addr, size_t size);
	} // extern "C"

	namespace fuzzer {

	static bool ReallyHaveDFSan() {
	return &dfsan_create_label != nullptr;
	}

	// These values are copied from include/llvm/IR/InstrTypes.h.
	// We do not include the LLVM headers here to remain independent.
	// If these values ever change, an assertion in ComputeCmp will fail.
	enum Predicate {
	ICMP_EQ = 32, ///< equal
	ICMP_NE = 33, ///< not equal
	ICMP_UGT = 34, ///< unsigned greater than
	ICMP_UGE = 35, ///< unsigned greater or equal
	ICMP_ULT = 36, ///< unsigned less than
	ICMP_ULE = 37, ///< unsigned less or equal
	ICMP_SGT = 38, ///< signed greater than
	ICMP_SGE = 39, ///< signed greater or equal
	ICMP_SLT = 40, ///< signed less than
	ICMP_SLE = 41, ///< signed less or equal
	};

	template <class U, class S>
	bool ComputeCmp(size_t CmpType, U Arg1, U Arg2) {
	switch(CmpType) {
	case ICMP_EQ : return Arg1 == Arg2;
	case ICMP_NE : return Arg1 != Arg2;
	case ICMP_UGT: return Arg1 > Arg2;
	case ICMP_UGE: return Arg1 >= Arg2;
	case ICMP_ULT: return Arg1 < Arg2;
	case ICMP_ULE: return Arg1 <= Arg2;
	case ICMP_SGT: return (S)Arg1 > (S)Arg2;
	case ICMP_SGE: return (S)Arg1 >= (S)Arg2;
	case ICMP_SLT: return (S)Arg1 < (S)Arg2;
	case ICMP_SLE: return (S)Arg1 <= (S)Arg2;
	default: assert(0 && "unsupported CmpType");
	}
	return false;
	}

	static bool ComputeCmp(size_t CmpSize, size_t CmpType, uint64_t Arg1,
	uint64_t Arg2) {
	if (CmpSize == 8) return ComputeCmp<uint64_t, int64_t>(CmpType, Arg1, Arg2);
	if (CmpSize == 4) return ComputeCmp<uint32_t, int32_t>(CmpType, Arg1, Arg2);
	if (CmpSize == 2) return ComputeCmp<uint16_t, int16_t>(CmpType, Arg1, Arg2);
	if (CmpSize == 1) return ComputeCmp<uint8_t, int8_t>(CmpType, Arg1, Arg2);
	// Other size, ==
	if (CmpType == ICMP_EQ) return Arg1 == Arg2;
	// assert(0 && "unsupported cmp and type size combination");
	return true;
	}

	// As a simplification we use the range of input bytes instead of a set of input
	// bytes.
	struct LabelRange {
	uint16_t Beg, End; // Range is [Beg, End), thus Beg==End is an empty range.

	LabelRange(uint16_t Beg = 0, uint16_t End = 0) : Beg(Beg), End(End) {}

	static LabelRange Join(LabelRange LR1, LabelRange LR2) {
	if (LR1.Beg == LR1.End) return LR2;
	if (LR2.Beg == LR2.End) return LR1;
	return {std::min(LR1.Beg, LR2.Beg), std::max(LR1.End, LR2.End)};
	}
	LabelRange &Join(LabelRange LR) {
	return this = Join(this, LR);
	}
	static LabelRange Singleton(const dfsan_label_info *LI) {
	uint16_t Idx = (uint16_t)(uintptr_t)LI->userdata;
	assert(Idx > 0);
	return {(uint16_t)(Idx - 1), Idx};
	}
	};

	// A passport for a CMP site. We want to keep track of where the given CMP is
	// and how many times it is evaluated to true or false.
	struct CmpSitePassport {
	uintptr_t PC;
	size_t Counter[2];

	bool IsInterestingCmpTarget() {
	static const size_t kRareEnough = 50;
	size_t C0 = Counter[0];
	size_t C1 = Counter[1];
	return C0 > kRareEnough * (C1 + 1) \|\| C1 > kRareEnough * (C0 + 1);
	}
	};

	// For now, just keep a simple imprecise hash table PC => CmpSitePassport.
	// Potentially, will need to have a compiler support to have a precise mapping
	// and also thread-safety.
	struct CmpSitePassportTable {
	static const size_t kSize = 99991; // Prime.
	CmpSitePassport Passports[kSize];

	CmpSitePassport *GetPassport(uintptr_t PC) {
	uintptr_t Idx = PC & kSize;
	CmpSitePassport *Res = &Passports[Idx];
	if (Res->PC == 0) // Not thread safe.
	Res->PC = PC;
	return Res->PC == PC ? Res : nullptr;
	}
	};

	static CmpSitePassportTable CSPTable; // Zero initialized.

	// For now, very simple: put Size bytes of Data at position Pos.
	struct TraceBasedMutation {
	size_t Pos;
	size_t Size;
	uint64_t Data;
	};

	class TraceState {
	public:
	TraceState(const Fuzzer::FuzzingOptions &Options, const Unit &CurrentUnit)
	: Options(Options), CurrentUnit(CurrentUnit) {}

	LabelRange GetLabelRange(dfsan_label L);
	void DFSanCmpCallback(uintptr_t PC, size_t CmpSize, size_t CmpType,
	uint64_t Arg1, uint64_t Arg2, dfsan_label L1,
	dfsan_label L2);
	void DFSanSwitchCallback(uint64_t PC, size_t ValSizeInBits, uint64_t Val,
	size_t NumCases, uint64_t *Cases, dfsan_label L);
	void TraceCmpCallback(uintptr_t PC, size_t CmpSize, size_t CmpType, uint64_t Arg1,
	uint64_t Arg2);

	void TraceSwitchCallback(uintptr_t PC, size_t ValSizeInBits, uint64_t Val,
	size_t NumCases, uint64_t *Cases);
	int TryToAddDesiredData(uint64_t PresentData, uint64_t DesiredData,
	size_t DataSize);

	void StartTraceRecording() {
	if (!Options.UseTraces) return;
	RecordingTraces = true;
	Mutations.clear();
	}

	size_t StopTraceRecording(FuzzerRandomBase &Rand) {
	RecordingTraces = false;
	return Mutations.size();
	}

	void ApplyTraceBasedMutation(size_t Idx, fuzzer::Unit *U);

	private:
	bool IsTwoByteData(uint64_t Data) {
	int64_t Signed = static_cast<int64_t>(Data);
	Signed >>= 16;
	return Signed == 0 \|\| Signed == -1L;
	}
	bool RecordingTraces = false;
	std::vector<TraceBasedMutation> Mutations;
	LabelRange LabelRanges[1 << (sizeof(dfsan_label) * 8)] = {};
	const Fuzzer::FuzzingOptions &Options;
	const Unit &CurrentUnit;
	};

	LabelRange TraceState::GetLabelRange(dfsan_label L) {
	LabelRange &LR = LabelRanges[L];
	if (LR.Beg < LR.End \|\| L == 0)
	return LR;
	const dfsan_label_info *LI = dfsan_get_label_info(L);
	if (LI->l1 \|\| LI->l2)
	return LR = LabelRange::Join(GetLabelRange(LI->l1), GetLabelRange(LI->l2));
	return LR = LabelRange::Singleton(LI);
	}

	void TraceState::ApplyTraceBasedMutation(size_t Idx, fuzzer::Unit *U) {
	assert(Idx < Mutations.size());
	auto &M = Mutations[Idx];
	if (Options.Verbosity >= 3)
	Printf("TBM %zd %zd %zd\n", M.Pos, M.Size, M.Data);
	if (M.Pos + M.Size > U->size()) return;
	memcpy(U->data() + M.Pos, &M.Data, M.Size);
	}

	void TraceState::DFSanCmpCallback(uintptr_t PC, size_t CmpSize, size_t CmpType,
	uint64_t Arg1, uint64_t Arg2, dfsan_label L1,
	dfsan_label L2) {
	assert(ReallyHaveDFSan());
	if (!RecordingTraces) return;
	if (L1 == 0 && L2 == 0)
	return; // Not actionable.
	if (L1 != 0 && L2 != 0)
	return; // Probably still actionable.
	bool Res = ComputeCmp(CmpSize, CmpType, Arg1, Arg2);
	uint64_t Data = L1 ? Arg2 : Arg1;
	LabelRange LR = L1 ? GetLabelRange(L1) : GetLabelRange(L2);

	for (size_t Pos = LR.Beg; Pos + CmpSize <= LR.End; Pos++) {
	Mutations.push_back({Pos, CmpSize, Data});
	Mutations.push_back({Pos, CmpSize, Data + 1});
	Mutations.push_back({Pos, CmpSize, Data - 1});
	}

	if (CmpSize > LR.End - LR.Beg)
	Mutations.push_back({LR.Beg, (unsigned)(LR.End - LR.Beg), Data});


	if (Options.Verbosity >= 3)
	Printf("DFSanCmpCallback: PC %lx S %zd T %zd A1 %llx A2 %llx R %d L1 %d L2 "
	"%d MU %zd\n",
	PC, CmpSize, CmpType, Arg1, Arg2, Res, L1, L2, Mutations.size());
	}

	void TraceState::DFSanSwitchCallback(uint64_t PC, size_t ValSizeInBits,
	uint64_t Val, size_t NumCases,
	uint64_t *Cases, dfsan_label L) {
	assert(ReallyHaveDFSan());
	if (!RecordingTraces) return;
	if (!L) return; // Not actionable.
	LabelRange LR = GetLabelRange(L);
	size_t ValSize = ValSizeInBits / 8;
	bool TryShort = IsTwoByteData(Val);
	for (size_t i = 0; i < NumCases; i++)
	TryShort &= IsTwoByteData(Cases[i]);

	for (size_t Pos = LR.Beg; Pos + ValSize <= LR.End; Pos++)
	for (size_t i = 0; i < NumCases; i++)
	Mutations.push_back({Pos, ValSize, Cases[i]});

	if (TryShort)
	for (size_t Pos = LR.Beg; Pos + 2 <= LR.End; Pos++)
	for (size_t i = 0; i < NumCases; i++)
	Mutations.push_back({Pos, 2, Cases[i]});

	if (Options.Verbosity >= 3)
	Printf("DFSanSwitchCallback: PC %lx Val %zd SZ %zd # %zd L %d: {%d, %d} "
	"TryShort %d\n",
	PC, Val, ValSize, NumCases, L, LR.Beg, LR.End, TryShort);
	}

	int TraceState::TryToAddDesiredData(uint64_t PresentData, uint64_t DesiredData,
	size_t DataSize) {
	int Res = 0;
	const uint8_t *Beg = CurrentUnit.data();
	const uint8_t *End = Beg + CurrentUnit.size();
	for (const uint8_t *Cur = Beg; Cur < End; Cur += DataSize) {
	Cur = (uint8_t *)memmem(Cur, End - Cur, &PresentData, DataSize);
	if (!Cur)
	break;
	size_t Pos = Cur - Beg;
	assert(Pos < CurrentUnit.size());
	if (Mutations.size() > 100000U) return Res; // Just in case.
	Mutations.push_back({Pos, DataSize, DesiredData});
	Mutations.push_back({Pos, DataSize, DesiredData + 1});
	Mutations.push_back({Pos, DataSize, DesiredData - 1});
	Cur += DataSize;
	Res++;
	}
	return Res;
	}

	void TraceState::TraceCmpCallback(uintptr_t PC, size_t CmpSize, size_t CmpType, uint64_t Arg1,
	uint64_t Arg2) {
	if (!RecordingTraces) return;
	int Added = 0;
	CmpSitePassport *CSP = CSPTable.GetPassport(PC);
	if (!CSP) return;
	CSP->Counter[ComputeCmp(CmpSize, CmpType, Arg1, Arg2)]++;
	size_t C0 = CSP->Counter[0];
	size_t C1 = CSP->Counter[1];
	// FIXME: is this a good idea or a bad?
	// if (!CSP->IsInterestingCmpTarget())
	// return;
	if (Options.Verbosity >= 3)
	Printf("TraceCmp: %p %zd/%zd; %zd %zd\n", CSP->PC, C0, C1, Arg1, Arg2);
	Added += TryToAddDesiredData(Arg1, Arg2, CmpSize);
	Added += TryToAddDesiredData(Arg2, Arg1, CmpSize);
	if (!Added && CmpSize == 4 && IsTwoByteData(Arg1) && IsTwoByteData(Arg2)) {
	Added += TryToAddDesiredData(Arg1, Arg2, 2);
	Added += TryToAddDesiredData(Arg2, Arg1, 2);
	}
	}

	void TraceState::TraceSwitchCallback(uintptr_t PC, size_t ValSizeInBits,
	uint64_t Val, size_t NumCases,
	uint64_t *Cases) {
	if (!RecordingTraces) return;
	size_t ValSize = ValSizeInBits / 8;
	bool TryShort = IsTwoByteData(Val);
	for (size_t i = 0; i < NumCases; i++)
	TryShort &= IsTwoByteData(Cases[i]);

	if (Options.Verbosity >= 3)
	Printf("TraceSwitch: %p %zd # %zd; TryShort %d\n", PC, Val, NumCases,
	TryShort);

	for (size_t i = 0; i < NumCases; i++) {
	TryToAddDesiredData(Val, Cases[i], ValSize);
	if (TryShort)
	TryToAddDesiredData(Val, Cases[i], 2);
	}

	}

	static TraceState *TS;

	void Fuzzer::StartTraceRecording() {
	if (!TS) return;
	if (ReallyHaveDFSan())
	for (size_t i = 0; i < static_cast<size_t>(Options.MaxLen); i++)
	dfsan_set_label(i + 1, &CurrentUnit[i], 1);
	TS->StartTraceRecording();
	}

	size_t Fuzzer::StopTraceRecording() {
	if (!TS) return 0;
	return TS->StopTraceRecording(USF.GetRand());
	}

	void Fuzzer::ApplyTraceBasedMutation(size_t Idx, Unit *U) {
	assert(TS);
	TS->ApplyTraceBasedMutation(Idx, U);
	}

	void Fuzzer::InitializeTraceState() {
	if (!Options.UseTraces) return;
	TS = new TraceState(Options, CurrentUnit);
	CurrentUnit.resize(Options.MaxLen);
	// The rest really requires DFSan.
	if (!ReallyHaveDFSan()) return;
	for (size_t i = 0; i < static_cast<size_t>(Options.MaxLen); i++) {
	dfsan_label L = dfsan_create_label("input", (void*)(i + 1));
	// We assume that no one else has called dfsan_create_label before.
	if (L != i + 1) {
	Printf("DFSan labels are not starting from 1, exiting\n");
	exit(1);
	}
	}
	}

	static size_t InternalStrnlen(const char *S, size_t MaxLen) {
	size_t Len = 0;
	for (; Len < MaxLen && S[Len]; Len++) {}
	return Len;
	}

	} // namespace fuzzer

	using fuzzer::TS;

	extern "C" {
	void __dfsw___sanitizer_cov_trace_cmp(uint64_t SizeAndType, uint64_t Arg1,
	uint64_t Arg2, dfsan_label L0,
	dfsan_label L1, dfsan_label L2) {
	if (!TS) return;
	assert(L0 == 0);
	uintptr_t PC = reinterpret_cast<uintptr_t>(__builtin_return_address(0));
	uint64_t CmpSize = (SizeAndType >> 32) / 8;
	uint64_t Type = (SizeAndType << 32) >> 32;
	TS->DFSanCmpCallback(PC, CmpSize, Type, Arg1, Arg2, L1, L2);
	}

	void __dfsw___sanitizer_cov_trace_switch(uint64_t Val, uint64_t *Cases,
	dfsan_label L1, dfsan_label L2) {
	if (!TS) return;
	uintptr_t PC = reinterpret_cast<uintptr_t>(__builtin_return_address(0));
	TS->DFSanSwitchCallback(PC, Cases[1], Val, Cases[0], Cases+2, L1);
	}

	void dfsan_weak_hook_memcmp(void caller_pc, const void s1, const void *s2,
	size_t n, dfsan_label s1_label,
	dfsan_label s2_label, dfsan_label n_label) {
	if (!TS) return;
	uintptr_t PC = reinterpret_cast<uintptr_t>(caller_pc);
	uint64_t S1 = 0, S2 = 0;
	// Simplification: handle only first 8 bytes.
	memcpy(&S1, s1, std::min(n, sizeof(S1)));
	memcpy(&S2, s2, std::min(n, sizeof(S2)));
	dfsan_label L1 = dfsan_read_label(s1, n);
	dfsan_label L2 = dfsan_read_label(s2, n);
	TS->DFSanCmpCallback(PC, n, fuzzer::ICMP_EQ, S1, S2, L1, L2);
	}

	void dfsan_weak_hook_strncmp(void caller_pc, const char s1, const char *s2,
	size_t n, dfsan_label s1_label,
	dfsan_label s2_label, dfsan_label n_label) {
	if (!TS) return;
	uintptr_t PC = reinterpret_cast<uintptr_t>(caller_pc);
	uint64_t S1 = 0, S2 = 0;
	n = std::min(n, fuzzer::InternalStrnlen(s1, n));
	n = std::min(n, fuzzer::InternalStrnlen(s2, n));
	// Simplification: handle only first 8 bytes.
	memcpy(&S1, s1, std::min(n, sizeof(S1)));
	memcpy(&S2, s2, std::min(n, sizeof(S2)));
	dfsan_label L1 = dfsan_read_label(s1, n);
	dfsan_label L2 = dfsan_read_label(s2, n);
	TS->DFSanCmpCallback(PC, n, fuzzer::ICMP_EQ, S1, S2, L1, L2);
	}

	void dfsan_weak_hook_strcmp(void caller_pc, const char s1, const char *s2,
	dfsan_label s1_label, dfsan_label s2_label) {
	if (!TS) return;
	uintptr_t PC = reinterpret_cast<uintptr_t>(caller_pc);
	uint64_t S1 = 0, S2 = 0;
	size_t Len1 = strlen(s1);
	size_t Len2 = strlen(s2);
	size_t N = std::min(Len1, Len2);
	if (N <= 1) return; // Not interesting.
	// Simplification: handle only first 8 bytes.
	memcpy(&S1, s1, std::min(N, sizeof(S1)));
	memcpy(&S2, s2, std::min(N, sizeof(S2)));
	dfsan_label L1 = dfsan_read_label(s1, Len1);
	dfsan_label L2 = dfsan_read_label(s2, Len2);
	TS->DFSanCmpCallback(PC, N, fuzzer::ICMP_EQ, S1, S2, L1, L2);
	}

	void __sanitizer_weak_hook_memcmp(void caller_pc, const void s1,
	const void *s2, size_t n) {
	if (!TS) return;
	uintptr_t PC = reinterpret_cast<uintptr_t>(caller_pc);
	uint64_t S1 = 0, S2 = 0;
	// Simplification: handle only first 8 bytes.
	memcpy(&S1, s1, std::min(n, sizeof(S1)));
	memcpy(&S2, s2, std::min(n, sizeof(S2)));
	TS->TraceCmpCallback(PC, n, fuzzer::ICMP_EQ, S1, S2);
	}

	void __sanitizer_weak_hook_strncmp(void caller_pc, const char s1,
	const char *s2, size_t n) {
	if (!TS) return;
	uintptr_t PC = reinterpret_cast<uintptr_t>(caller_pc);
	uint64_t S1 = 0, S2 = 0;
	size_t Len1 = fuzzer::InternalStrnlen(s1, n);
	size_t Len2 = fuzzer::InternalStrnlen(s2, n);
	n = std::min(n, Len1);
	n = std::min(n, Len2);
	if (n <= 1) return; // Not interesting.
	// Simplification: handle only first 8 bytes.
	memcpy(&S1, s1, std::min(n, sizeof(S1)));
	memcpy(&S2, s2, std::min(n, sizeof(S2)));
	TS->TraceCmpCallback(PC, n, fuzzer::ICMP_EQ, S1, S2);
	}

	void __sanitizer_weak_hook_strcmp(void caller_pc, const char s1,
	const char *s2) {
	if (!TS) return;
	uintptr_t PC = reinterpret_cast<uintptr_t>(caller_pc);
	uint64_t S1 = 0, S2 = 0;
	size_t Len1 = strlen(s1);
	size_t Len2 = strlen(s2);
	size_t N = std::min(Len1, Len2);
	if (N <= 1) return; // Not interesting.
	// Simplification: handle only first 8 bytes.
	memcpy(&S1, s1, std::min(N, sizeof(S1)));
	memcpy(&S2, s2, std::min(N, sizeof(S2)));
	TS->TraceCmpCallback(PC, N, fuzzer::ICMP_EQ, S1, S2);
	}


	void __sanitizer_cov_trace_cmp(uint64_t SizeAndType, uint64_t Arg1,
	uint64_t Arg2) {
	if (!TS) return;
	uintptr_t PC = reinterpret_cast<uintptr_t>(__builtin_return_address(0));
	uint64_t CmpSize = (SizeAndType >> 32) / 8;
	uint64_t Type = (SizeAndType << 32) >> 32;
	TS->TraceCmpCallback(PC, CmpSize, Type, Arg1, Arg2);
	}

	void __sanitizer_cov_trace_switch(uint64_t Val, uint64_t *Cases) {
	if (!TS) return;
	uintptr_t PC = reinterpret_cast<uintptr_t>(__builtin_return_address(0));
	TS->TraceSwitchCallback(PC, Cases[1], Val, Cases[0], Cases + 2);
	}

	} // extern "C"