Use the space freed up by sparc and zaurus to import LLVM.

ok hackroom@

1 files changed, 604 insertions, 0 deletions

diff --git a/gnu/llvm/lib/Fuzzer/FuzzerTraceState.cpp b/gnu/llvm/lib/Fuzzer/FuzzerTraceState.cpp
new file mode 100644
index 00000000000..b2006fa3aa4
--- /dev/null
+++ b/gnu/llvm/lib/Fuzzer/FuzzerTraceState.cpp
@@ -0,0 +1,604 @@
+//===- 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.
+//
+// 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/SimpleCmpTest.cpp Fuzzer*.o
+  ./a.out -use_traces=1
+)
+*/
+
+#include "FuzzerDFSan.h"
+#include "FuzzerInternal.h"
+
+#include <algorithm>
+#include <cstring>
+#include <thread>
+#include <map>
+
+#if !LLVM_FUZZER_SUPPORTS_DFSAN
+// Stubs for dfsan for platforms where dfsan does not exist and weak
+// functions don't work.
+extern "C" {
+dfsan_label dfsan_create_label(const char *desc, void *userdata) { return 0; }
+void dfsan_set_label(dfsan_label label, void *addr, size_t size) {}
+void dfsan_add_label(dfsan_label label, void *addr, size_t size) {}
+const struct dfsan_label_info *dfsan_get_label_info(dfsan_label label) {
+  return nullptr;
+}
+dfsan_label dfsan_read_label(const void *addr, size_t size) { return 0; }
+}  // extern "C"
+#endif  // !LLVM_FUZZER_SUPPORTS_DFSAN
+
+namespace fuzzer {
+
+// 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};
+  }
+};
+
+// For now, very simple: put Size bytes of Data at position Pos.
+struct TraceBasedMutation {
+  static const size_t kMaxSize = 28;
+  uint32_t Pos : 24;
+  uint32_t Size : 8;
+  uint8_t  Data[kMaxSize];
+};
+
+const size_t TraceBasedMutation::kMaxSize;
+
+class TraceState {
+ public:
+  TraceState(UserSuppliedFuzzer &USF,
+             const Fuzzer::FuzzingOptions &Options, const Unit &CurrentUnit)
+       : USF(USF), Options(Options), CurrentUnit(CurrentUnit) {
+    // Current trace collection is not thread-friendly and it probably
+    // does not have to be such, but at least we should not crash in presence
+    // of threads. So, just ignore all traces coming from all threads but one.
+    IsMyThread = true;
+  }
+
+  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 DFSanMemcmpCallback(size_t CmpSize, const uint8_t *Data1,
+                           const uint8_t *Data2, 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 TraceMemcmpCallback(size_t CmpSize, const uint8_t *Data1,
+                           const uint8_t *Data2);
+
+  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);
+  int TryToAddDesiredData(const uint8_t *PresentData,
+                          const uint8_t *DesiredData, size_t DataSize);
+
+  void StartTraceRecording() {
+    if (!Options.UseTraces) return;
+    RecordingTraces = true;
+    NumMutations = 0;
+    USF.GetMD().ClearAutoDictionary();
+  }
+
+  void StopTraceRecording() {
+    if (!RecordingTraces) return;
+    RecordingTraces = false;
+    for (size_t i = 0; i < NumMutations; i++) {
+      auto &M = Mutations[i];
+      Unit U(M.Data, M.Data + M.Size);
+      if (Options.Verbosity >= 2) {
+        AutoDictUnitCounts[U]++;
+        AutoDictAdds++;
+        if ((AutoDictAdds & (AutoDictAdds - 1)) == 0) {
+          typedef std::pair<size_t, Unit> CU;
+          std::vector<CU> CountedUnits;
+          for (auto &I : AutoDictUnitCounts)
+            CountedUnits.push_back(std::make_pair(I.second, I.first));
+          std::sort(CountedUnits.begin(), CountedUnits.end(),
+                    [](const CU &a, const CU &b) { return a.first > b.first; });
+          Printf("AutoDict:\n");
+          for (auto &I : CountedUnits) {
+            Printf("   %zd ", I.first);
+            PrintASCII(I.second);
+            Printf("\n");
+          }
+        }
+      }
+      USF.GetMD().AddWordToAutoDictionary(U, M.Pos);
+    }
+  }
+
+  void AddMutation(uint32_t Pos, uint32_t Size, const uint8_t *Data) {
+    if (NumMutations >= kMaxMutations) return;
+    assert(Size <= TraceBasedMutation::kMaxSize);
+    auto &M = Mutations[NumMutations++];
+    M.Pos = Pos;
+    M.Size = Size;
+    memcpy(M.Data, Data, Size);
+  }
+
+  void AddMutation(uint32_t Pos, uint32_t Size, uint64_t Data) {
+    assert(Size <= sizeof(Data));
+    AddMutation(Pos, Size, reinterpret_cast<uint8_t*>(&Data));
+  }
+
+ private:
+  bool IsTwoByteData(uint64_t Data) {
+    int64_t Signed = static_cast<int64_t>(Data);
+    Signed >>= 16;
+    return Signed == 0 || Signed == -1L;
+  }
+  bool RecordingTraces = false;
+  static const size_t kMaxMutations = 1 << 16;
+  size_t NumMutations;
+  TraceBasedMutation Mutations[kMaxMutations];
+  LabelRange LabelRanges[1 << (sizeof(dfsan_label) * 8)];
+  UserSuppliedFuzzer &USF;
+  const Fuzzer::FuzzingOptions &Options;
+  const Unit &CurrentUnit;
+  std::map<Unit, size_t> AutoDictUnitCounts;
+  size_t AutoDictAdds = 0;
+  static thread_local bool IsMyThread;
+};
+
+thread_local bool TraceState::IsMyThread;
+
+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::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 || !IsMyThread) 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++) {
+    AddMutation(Pos, CmpSize, Data);
+    AddMutation(Pos, CmpSize, Data + 1);
+    AddMutation(Pos, CmpSize, Data - 1);
+  }
+
+  if (CmpSize > LR.End - LR.Beg)
+    AddMutation(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, NumMutations);
+}
+
+void TraceState::DFSanMemcmpCallback(size_t CmpSize, const uint8_t *Data1,
+                                     const uint8_t *Data2, dfsan_label L1,
+                                     dfsan_label L2) {
+
+  assert(ReallyHaveDFSan());
+  if (!RecordingTraces || !IsMyThread) return;
+  if (L1 == 0 && L2 == 0)
+    return;  // Not actionable.
+  if (L1 != 0 && L2 != 0)
+    return;  // Probably still actionable.
+
+  const uint8_t *Data = L1 ? Data2 : Data1;
+  LabelRange LR = L1 ? GetLabelRange(L1) : GetLabelRange(L2);
+  for (size_t Pos = LR.Beg; Pos + CmpSize <= LR.End; Pos++) {
+    AddMutation(Pos, CmpSize, Data);
+    if (Options.Verbosity >= 3)
+      Printf("DFSanMemcmpCallback: Pos %d Size %d\n", Pos, CmpSize);
+  }
+}
+
+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 || !IsMyThread) 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++)
+      AddMutation(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++)
+        AddMutation(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++) {
+    Cur = (uint8_t *)memmem(Cur, End - Cur, &PresentData, DataSize);
+    if (!Cur)
+      break;
+    size_t Pos = Cur - Beg;
+    assert(Pos < CurrentUnit.size());
+    AddMutation(Pos, DataSize, DesiredData);
+    AddMutation(Pos, DataSize, DesiredData + 1);
+    AddMutation(Pos, DataSize, DesiredData - 1);
+    Res++;
+  }
+  return Res;
+}
+
+int TraceState::TryToAddDesiredData(const uint8_t *PresentData,
+                                    const uint8_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++) {
+    Cur = (uint8_t *)memmem(Cur, End - Cur, PresentData, DataSize);
+    if (!Cur)
+      break;
+    size_t Pos = Cur - Beg;
+    assert(Pos < CurrentUnit.size());
+    AddMutation(Pos, DataSize, DesiredData);
+    Res++;
+  }
+  return Res;
+}
+
+void TraceState::TraceCmpCallback(uintptr_t PC, size_t CmpSize, size_t CmpType,
+                                  uint64_t Arg1, uint64_t Arg2) {
+  if (!RecordingTraces || !IsMyThread) return;
+  if ((CmpType == ICMP_EQ || CmpType == ICMP_NE) && Arg1 == Arg2)
+    return;  // No reason to mutate.
+  int Added = 0;
+  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);
+  }
+  if (Options.Verbosity >= 3 && Added)
+    Printf("TraceCmp %zd/%zd: %p %zd %zd\n", CmpSize, CmpType, PC, Arg1, Arg2);
+}
+
+void TraceState::TraceMemcmpCallback(size_t CmpSize, const uint8_t *Data1,
+                                     const uint8_t *Data2) {
+  if (!RecordingTraces || !IsMyThread) return;
+  CmpSize = std::min(CmpSize, TraceBasedMutation::kMaxSize);
+  int Added2 = TryToAddDesiredData(Data1, Data2, CmpSize);
+  int Added1 = TryToAddDesiredData(Data2, Data1, CmpSize);
+  if ((Added1 || Added2) && Options.Verbosity >= 3) {
+    Printf("MemCmp Added %d%d: ", Added1, Added2);
+    if (Added1) PrintASCII(Data1, CmpSize);
+    if (Added2) PrintASCII(Data2, CmpSize);
+    Printf("\n");
+  }
+}
+
+void TraceState::TraceSwitchCallback(uintptr_t PC, size_t ValSizeInBits,
+                                     uint64_t Val, size_t NumCases,
+                                     uint64_t *Cases) {
+  if (!RecordingTraces || !IsMyThread) 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();
+}
+
+void Fuzzer::StopTraceRecording() {
+  if (!TS) return;
+  TS->StopTraceRecording();
+}
+
+void Fuzzer::InitializeTraceState() {
+  if (!Options.UseTraces) return;
+  TS = new TraceState(USF, 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;
+  dfsan_label L1 = dfsan_read_label(s1, n);
+  dfsan_label L2 = dfsan_read_label(s2, n);
+  TS->DFSanMemcmpCallback(n, reinterpret_cast<const uint8_t *>(s1),
+                          reinterpret_cast<const uint8_t *>(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;
+  n = std::min(n, fuzzer::InternalStrnlen(s1, n));
+  n = std::min(n, fuzzer::InternalStrnlen(s2, n));
+  dfsan_label L1 = dfsan_read_label(s1, n);
+  dfsan_label L2 = dfsan_read_label(s2, n);
+  TS->DFSanMemcmpCallback(n, reinterpret_cast<const uint8_t *>(s1),
+                          reinterpret_cast<const uint8_t *>(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;
+  size_t Len1 = strlen(s1);
+  size_t Len2 = strlen(s2);
+  size_t N = std::min(Len1, Len2);
+  if (N <= 1) return;  // Not interesting.
+  dfsan_label L1 = dfsan_read_label(s1, Len1);
+  dfsan_label L2 = dfsan_read_label(s2, Len2);
+  TS->DFSanMemcmpCallback(N, reinterpret_cast<const uint8_t *>(s1),
+                          reinterpret_cast<const uint8_t *>(s2), L1, L2);
+}
+
+// We may need to avoid defining weak hooks to stay compatible with older clang.
+#ifndef LLVM_FUZZER_DEFINES_SANITIZER_WEAK_HOOOKS
+# define LLVM_FUZZER_DEFINES_SANITIZER_WEAK_HOOOKS 1
+#endif
+
+#if LLVM_FUZZER_DEFINES_SANITIZER_WEAK_HOOOKS
+void __sanitizer_weak_hook_memcmp(void *caller_pc, const void *s1,
+                                  const void *s2, size_t n, int result) {
+  if (!TS) return;
+  if (result == 0) return;  // No reason to mutate.
+  if (n <= 1) return;  // Not interesting.
+  TS->TraceMemcmpCallback(n, reinterpret_cast<const uint8_t *>(s1),
+                          reinterpret_cast<const uint8_t *>(s2));
+}
+
+void __sanitizer_weak_hook_strncmp(void *caller_pc, const char *s1,
+                                   const char *s2, size_t n, int result) {
+  if (!TS) return;
+  if (result == 0) return;  // No reason to mutate.
+  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.
+  TS->TraceMemcmpCallback(n, reinterpret_cast<const uint8_t *>(s1),
+                          reinterpret_cast<const uint8_t *>(s2));
+}
+
+void __sanitizer_weak_hook_strcmp(void *caller_pc, const char *s1,
+                                   const char *s2, int result) {
+  if (!TS) return;
+  if (result == 0) return;  // No reason to mutate.
+  size_t Len1 = strlen(s1);
+  size_t Len2 = strlen(s2);
+  size_t N = std::min(Len1, Len2);
+  if (N <= 1) return;  // Not interesting.
+  TS->TraceMemcmpCallback(N, reinterpret_cast<const uint8_t *>(s1),
+                          reinterpret_cast<const uint8_t *>(s2));
+}
+
+#endif  // LLVM_FUZZER_DEFINES_SANITIZER_WEAK_HOOOKS
+
+__attribute__((visibility("default")))
+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);
+}
+
+__attribute__((visibility("default")))
+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"