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1 //===- FuzzerTraceState.cpp - Trace-based fuzzer mutator ------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 // This file implements a mutation algorithm based on instruction traces and
10 // on taint analysis feedback from DFSan.
11 //
12 // Instruction traces are special hooks inserted by the compiler around
13 // interesting instructions. Currently supported traces:
14 //   * __sanitizer_cov_trace_cmp -- inserted before every ICMP instruction,
15 //    receives the type, size and arguments of ICMP.
16 //
17 // Every time a traced event is intercepted we analyse the data involved
18 // in the event and suggest a mutation for future executions.
19 // For example if 4 bytes of data that derive from input bytes {4,5,6,7}
20 // are compared with a constant 12345,
21 // we try to insert 12345, 12344, 12346 into bytes
22 // {4,5,6,7} of the next fuzzed inputs.
23 //
24 // The fuzzer can work only with the traces, or with both traces and DFSan.
25 //
26 // DataFlowSanitizer (DFSan) is a tool for
27 // generalised dynamic data flow (taint) analysis:
28 // http://clang.llvm.org/docs/DataFlowSanitizer.html .
29 //
30 // The approach with DFSan-based fuzzing has some similarity to
31 // "Taint-based Directed Whitebox Fuzzing"
32 // by Vijay Ganesh & Tim Leek & Martin Rinard:
33 // http://dspace.mit.edu/openaccess-disseminate/1721.1/59320,
34 // but it uses a full blown LLVM IR taint analysis and separate instrumentation
35 // to analyze all of the "attack points" at once.
36 //
37 // Workflow with DFSan:
38 //   * lib/Fuzzer/Fuzzer*.cpp is compiled w/o any instrumentation.
39 //   * The code under test is compiled with DFSan *and* with instruction traces.
40 //   * Every call to HOOK(a,b) is replaced by DFSan with
41 //     __dfsw_HOOK(a, b, label(a), label(b)) so that __dfsw_HOOK
42 //     gets all the taint labels for the arguments.
43 //   * At the Fuzzer startup we assign a unique DFSan label
44 //     to every byte of the input string (Fuzzer::CurrentUnit) so that for any
45 //     chunk of data we know which input bytes it has derived from.
46 //   * The __dfsw_* functions (implemented in this file) record the
47 //     parameters (i.e. the application data and the corresponding taint labels)
48 //     in a global state.
49 //   * Fuzzer::ApplyTraceBasedMutation() tries to use the data recorded
50 //     by __dfsw_* hooks to guide the fuzzing towards new application states.
51 //
52 // Parts of this code will not function when DFSan is not linked in.
53 // Instead of using ifdefs and thus requiring a separate build of lib/Fuzzer
54 // we redeclare the dfsan_* interface functions as weak and check if they
55 // are nullptr before calling.
56 // If this approach proves to be useful we may add attribute(weak) to the
57 // dfsan declarations in dfsan_interface.h
58 //
59 // This module is in the "proof of concept" stage.
60 // It is capable of solving only the simplest puzzles
61 // like test/dfsan/DFSanSimpleCmpTest.cpp.
62 //===----------------------------------------------------------------------===//
63 
64 /* Example of manual usage (-fsanitize=dataflow is optional):
65 (
66   cd $LLVM/lib/Fuzzer/
67   clang  -fPIC -c -g -O2 -std=c++11 Fuzzer*.cpp
68   clang++ -O0 -std=c++11 -fsanitize-coverage=edge,trace-cmp \
69     -fsanitize=dataflow \
70     test/SimpleCmpTest.cpp Fuzzer*.o
71   ./a.out -use_traces=1
72 )
73 */
74 
75 #include "FuzzerDFSan.h"
76 #include "FuzzerInternal.h"
77 
78 #include <algorithm>
79 #include <cstring>
80 #include <unordered_map>
81 
82 #if !LLVM_FUZZER_SUPPORTS_DFSAN
83 // Stubs for dfsan for platforms where dfsan does not exist and weak
84 // functions don't work.
85 extern "C" {
dfsan_create_label(const char * desc,void * userdata)86 dfsan_label dfsan_create_label(const char *desc, void *userdata) { return 0; }
dfsan_set_label(dfsan_label label,void * addr,size_t size)87 void dfsan_set_label(dfsan_label label, void *addr, size_t size) {}
dfsan_add_label(dfsan_label label,void * addr,size_t size)88 void dfsan_add_label(dfsan_label label, void *addr, size_t size) {}
dfsan_get_label_info(dfsan_label label)89 const struct dfsan_label_info *dfsan_get_label_info(dfsan_label label) {
90   return nullptr;
91 }
dfsan_read_label(const void * addr,size_t size)92 dfsan_label dfsan_read_label(const void *addr, size_t size) { return 0; }
93 }  // extern "C"
94 #endif  // !LLVM_FUZZER_SUPPORTS_DFSAN
95 
96 namespace fuzzer {
97 
98 // These values are copied from include/llvm/IR/InstrTypes.h.
99 // We do not include the LLVM headers here to remain independent.
100 // If these values ever change, an assertion in ComputeCmp will fail.
101 enum Predicate {
102   ICMP_EQ = 32,  ///< equal
103   ICMP_NE = 33,  ///< not equal
104   ICMP_UGT = 34, ///< unsigned greater than
105   ICMP_UGE = 35, ///< unsigned greater or equal
106   ICMP_ULT = 36, ///< unsigned less than
107   ICMP_ULE = 37, ///< unsigned less or equal
108   ICMP_SGT = 38, ///< signed greater than
109   ICMP_SGE = 39, ///< signed greater or equal
110   ICMP_SLT = 40, ///< signed less than
111   ICMP_SLE = 41, ///< signed less or equal
112 };
113 
114 template <class U, class S>
ComputeCmp(size_t CmpType,U Arg1,U Arg2)115 bool ComputeCmp(size_t CmpType, U Arg1, U Arg2) {
116   switch(CmpType) {
117     case ICMP_EQ : return Arg1 == Arg2;
118     case ICMP_NE : return Arg1 != Arg2;
119     case ICMP_UGT: return Arg1 > Arg2;
120     case ICMP_UGE: return Arg1 >= Arg2;
121     case ICMP_ULT: return Arg1 < Arg2;
122     case ICMP_ULE: return Arg1 <= Arg2;
123     case ICMP_SGT: return (S)Arg1 > (S)Arg2;
124     case ICMP_SGE: return (S)Arg1 >= (S)Arg2;
125     case ICMP_SLT: return (S)Arg1 < (S)Arg2;
126     case ICMP_SLE: return (S)Arg1 <= (S)Arg2;
127     default: assert(0 && "unsupported CmpType");
128   }
129   return false;
130 }
131 
ComputeCmp(size_t CmpSize,size_t CmpType,uint64_t Arg1,uint64_t Arg2)132 static bool ComputeCmp(size_t CmpSize, size_t CmpType, uint64_t Arg1,
133                        uint64_t Arg2) {
134   if (CmpSize == 8) return ComputeCmp<uint64_t, int64_t>(CmpType, Arg1, Arg2);
135   if (CmpSize == 4) return ComputeCmp<uint32_t, int32_t>(CmpType, Arg1, Arg2);
136   if (CmpSize == 2) return ComputeCmp<uint16_t, int16_t>(CmpType, Arg1, Arg2);
137   if (CmpSize == 1) return ComputeCmp<uint8_t, int8_t>(CmpType, Arg1, Arg2);
138   // Other size, ==
139   if (CmpType == ICMP_EQ) return Arg1 == Arg2;
140   // assert(0 && "unsupported cmp and type size combination");
141   return true;
142 }
143 
144 // As a simplification we use the range of input bytes instead of a set of input
145 // bytes.
146 struct LabelRange {
147   uint16_t Beg, End;  // Range is [Beg, End), thus Beg==End is an empty range.
148 
LabelRangefuzzer::LabelRange149   LabelRange(uint16_t Beg = 0, uint16_t End = 0) : Beg(Beg), End(End) {}
150 
Joinfuzzer::LabelRange151   static LabelRange Join(LabelRange LR1, LabelRange LR2) {
152     if (LR1.Beg == LR1.End) return LR2;
153     if (LR2.Beg == LR2.End) return LR1;
154     return {std::min(LR1.Beg, LR2.Beg), std::max(LR1.End, LR2.End)};
155   }
Joinfuzzer::LabelRange156   LabelRange &Join(LabelRange LR) {
157     return *this = Join(*this, LR);
158   }
Singletonfuzzer::LabelRange159   static LabelRange Singleton(const dfsan_label_info *LI) {
160     uint16_t Idx = (uint16_t)(uintptr_t)LI->userdata;
161     assert(Idx > 0);
162     return {(uint16_t)(Idx - 1), Idx};
163   }
164 };
165 
166 // For now, very simple: put Size bytes of Data at position Pos.
167 struct TraceBasedMutation {
168   size_t Pos;
169   size_t Size;
170   uint64_t Data;
171 };
172 
173 class TraceState {
174  public:
TraceState(const Fuzzer::FuzzingOptions & Options,const Unit & CurrentUnit)175    TraceState(const Fuzzer::FuzzingOptions &Options, const Unit &CurrentUnit)
176        : Options(Options), CurrentUnit(CurrentUnit) {}
177 
178   LabelRange GetLabelRange(dfsan_label L);
179   void DFSanCmpCallback(uintptr_t PC, size_t CmpSize, size_t CmpType,
180                         uint64_t Arg1, uint64_t Arg2, dfsan_label L1,
181                         dfsan_label L2);
182   void DFSanSwitchCallback(uint64_t PC, size_t ValSizeInBits, uint64_t Val,
183                            size_t NumCases, uint64_t *Cases, dfsan_label L);
184   void TraceCmpCallback(uintptr_t PC, size_t CmpSize, size_t CmpType,
185                         uint64_t Arg1, uint64_t Arg2);
186 
187   void TraceSwitchCallback(uintptr_t PC, size_t ValSizeInBits, uint64_t Val,
188                            size_t NumCases, uint64_t *Cases);
189   int TryToAddDesiredData(uint64_t PresentData, uint64_t DesiredData,
190                            size_t DataSize);
191 
StartTraceRecording()192   void StartTraceRecording() {
193     if (!Options.UseTraces) return;
194     RecordingTraces = true;
195     Mutations.clear();
196   }
197 
StopTraceRecording(FuzzerRandomBase & Rand)198   size_t StopTraceRecording(FuzzerRandomBase &Rand) {
199     RecordingTraces = false;
200     return Mutations.size();
201   }
202 
203   void ApplyTraceBasedMutation(size_t Idx, fuzzer::Unit *U);
204 
205  private:
IsTwoByteData(uint64_t Data)206   bool IsTwoByteData(uint64_t Data) {
207     int64_t Signed = static_cast<int64_t>(Data);
208     Signed >>= 16;
209     return Signed == 0 || Signed == -1L;
210   }
211   bool RecordingTraces = false;
212   std::vector<TraceBasedMutation> Mutations;
213   LabelRange LabelRanges[1 << (sizeof(dfsan_label) * 8)];
214   const Fuzzer::FuzzingOptions &Options;
215   const Unit &CurrentUnit;
216 };
217 
GetLabelRange(dfsan_label L)218 LabelRange TraceState::GetLabelRange(dfsan_label L) {
219   LabelRange &LR = LabelRanges[L];
220   if (LR.Beg < LR.End || L == 0)
221     return LR;
222   const dfsan_label_info *LI = dfsan_get_label_info(L);
223   if (LI->l1 || LI->l2)
224     return LR = LabelRange::Join(GetLabelRange(LI->l1), GetLabelRange(LI->l2));
225   return LR = LabelRange::Singleton(LI);
226 }
227 
ApplyTraceBasedMutation(size_t Idx,fuzzer::Unit * U)228 void TraceState::ApplyTraceBasedMutation(size_t Idx, fuzzer::Unit *U) {
229   assert(Idx < Mutations.size());
230   auto &M = Mutations[Idx];
231   if (Options.Verbosity >= 3)
232     Printf("TBM %zd %zd %zd\n", M.Pos, M.Size, M.Data);
233   if (M.Pos + M.Size > U->size()) return;
234   memcpy(U->data() + M.Pos, &M.Data, M.Size);
235 }
236 
DFSanCmpCallback(uintptr_t PC,size_t CmpSize,size_t CmpType,uint64_t Arg1,uint64_t Arg2,dfsan_label L1,dfsan_label L2)237 void TraceState::DFSanCmpCallback(uintptr_t PC, size_t CmpSize, size_t CmpType,
238                                   uint64_t Arg1, uint64_t Arg2, dfsan_label L1,
239                                   dfsan_label L2) {
240   assert(ReallyHaveDFSan());
241   if (!RecordingTraces) return;
242   if (L1 == 0 && L2 == 0)
243     return;  // Not actionable.
244   if (L1 != 0 && L2 != 0)
245     return;  // Probably still actionable.
246   bool Res = ComputeCmp(CmpSize, CmpType, Arg1, Arg2);
247   uint64_t Data = L1 ? Arg2 : Arg1;
248   LabelRange LR = L1 ? GetLabelRange(L1) : GetLabelRange(L2);
249 
250   for (size_t Pos = LR.Beg; Pos + CmpSize <= LR.End; Pos++) {
251     Mutations.push_back({Pos, CmpSize, Data});
252     Mutations.push_back({Pos, CmpSize, Data + 1});
253     Mutations.push_back({Pos, CmpSize, Data - 1});
254   }
255 
256   if (CmpSize > LR.End - LR.Beg)
257     Mutations.push_back({LR.Beg, (unsigned)(LR.End - LR.Beg), Data});
258 
259 
260   if (Options.Verbosity >= 3)
261     Printf("DFSanCmpCallback: PC %lx S %zd T %zd A1 %llx A2 %llx R %d L1 %d L2 "
262            "%d MU %zd\n",
263            PC, CmpSize, CmpType, Arg1, Arg2, Res, L1, L2, Mutations.size());
264 }
265 
DFSanSwitchCallback(uint64_t PC,size_t ValSizeInBits,uint64_t Val,size_t NumCases,uint64_t * Cases,dfsan_label L)266 void TraceState::DFSanSwitchCallback(uint64_t PC, size_t ValSizeInBits,
267                                      uint64_t Val, size_t NumCases,
268                                      uint64_t *Cases, dfsan_label L) {
269   assert(ReallyHaveDFSan());
270   if (!RecordingTraces) return;
271   if (!L) return;  // Not actionable.
272   LabelRange LR = GetLabelRange(L);
273   size_t ValSize = ValSizeInBits / 8;
274   bool TryShort = IsTwoByteData(Val);
275   for (size_t i = 0; i < NumCases; i++)
276     TryShort &= IsTwoByteData(Cases[i]);
277 
278   for (size_t Pos = LR.Beg; Pos + ValSize <= LR.End; Pos++)
279     for (size_t i = 0; i < NumCases; i++)
280       Mutations.push_back({Pos, ValSize, Cases[i]});
281 
282   if (TryShort)
283     for (size_t Pos = LR.Beg; Pos + 2 <= LR.End; Pos++)
284       for (size_t i = 0; i < NumCases; i++)
285         Mutations.push_back({Pos, 2, Cases[i]});
286 
287   if (Options.Verbosity >= 3)
288     Printf("DFSanSwitchCallback: PC %lx Val %zd SZ %zd # %zd L %d: {%d, %d} "
289            "TryShort %d\n",
290            PC, Val, ValSize, NumCases, L, LR.Beg, LR.End, TryShort);
291 }
292 
TryToAddDesiredData(uint64_t PresentData,uint64_t DesiredData,size_t DataSize)293 int TraceState::TryToAddDesiredData(uint64_t PresentData, uint64_t DesiredData,
294                                     size_t DataSize) {
295   int Res = 0;
296   const uint8_t *Beg = CurrentUnit.data();
297   const uint8_t *End = Beg + CurrentUnit.size();
298   for (const uint8_t *Cur = Beg; Cur < End; Cur++) {
299     Cur = (uint8_t *)memmem(Cur, End - Cur, &PresentData, DataSize);
300     if (!Cur)
301       break;
302     size_t Pos = Cur - Beg;
303     assert(Pos < CurrentUnit.size());
304     if (Mutations.size() > 100000U) return Res;  // Just in case.
305     Mutations.push_back({Pos, DataSize, DesiredData});
306     Mutations.push_back({Pos, DataSize, DesiredData + 1});
307     Mutations.push_back({Pos, DataSize, DesiredData - 1});
308     Res++;
309   }
310   return Res;
311 }
312 
TraceCmpCallback(uintptr_t PC,size_t CmpSize,size_t CmpType,uint64_t Arg1,uint64_t Arg2)313 void TraceState::TraceCmpCallback(uintptr_t PC, size_t CmpSize, size_t CmpType,
314                                   uint64_t Arg1, uint64_t Arg2) {
315   if (!RecordingTraces) return;
316   int Added = 0;
317   if (Options.Verbosity >= 3)
318     Printf("TraceCmp %zd/%zd: %p %zd %zd\n", CmpSize, CmpType, PC, Arg1, Arg2);
319   Added += TryToAddDesiredData(Arg1, Arg2, CmpSize);
320   Added += TryToAddDesiredData(Arg2, Arg1, CmpSize);
321   if (!Added && CmpSize == 4 && IsTwoByteData(Arg1) && IsTwoByteData(Arg2)) {
322     Added += TryToAddDesiredData(Arg1, Arg2, 2);
323     Added += TryToAddDesiredData(Arg2, Arg1, 2);
324   }
325 }
326 
TraceSwitchCallback(uintptr_t PC,size_t ValSizeInBits,uint64_t Val,size_t NumCases,uint64_t * Cases)327 void TraceState::TraceSwitchCallback(uintptr_t PC, size_t ValSizeInBits,
328                                      uint64_t Val, size_t NumCases,
329                                      uint64_t *Cases) {
330   if (!RecordingTraces) return;
331   size_t ValSize = ValSizeInBits / 8;
332   bool TryShort = IsTwoByteData(Val);
333   for (size_t i = 0; i < NumCases; i++)
334     TryShort &= IsTwoByteData(Cases[i]);
335 
336   if (Options.Verbosity >= 3)
337     Printf("TraceSwitch: %p %zd # %zd; TryShort %d\n", PC, Val, NumCases,
338            TryShort);
339 
340   for (size_t i = 0; i < NumCases; i++) {
341     TryToAddDesiredData(Val, Cases[i], ValSize);
342     if (TryShort)
343       TryToAddDesiredData(Val, Cases[i], 2);
344   }
345 
346 }
347 
348 static TraceState *TS;
349 
StartTraceRecording()350 void Fuzzer::StartTraceRecording() {
351   if (!TS) return;
352   if (ReallyHaveDFSan())
353     for (size_t i = 0; i < static_cast<size_t>(Options.MaxLen); i++)
354       dfsan_set_label(i + 1, &CurrentUnit[i], 1);
355   TS->StartTraceRecording();
356 }
357 
StopTraceRecording()358 size_t Fuzzer::StopTraceRecording() {
359   if (!TS) return 0;
360   return TS->StopTraceRecording(USF.GetRand());
361 }
362 
ApplyTraceBasedMutation(size_t Idx,Unit * U)363 void Fuzzer::ApplyTraceBasedMutation(size_t Idx, Unit *U) {
364   assert(TS);
365   TS->ApplyTraceBasedMutation(Idx, U);
366 }
367 
InitializeTraceState()368 void Fuzzer::InitializeTraceState() {
369   if (!Options.UseTraces) return;
370   TS = new TraceState(Options, CurrentUnit);
371   CurrentUnit.resize(Options.MaxLen);
372   // The rest really requires DFSan.
373   if (!ReallyHaveDFSan()) return;
374   for (size_t i = 0; i < static_cast<size_t>(Options.MaxLen); i++) {
375     dfsan_label L = dfsan_create_label("input", (void*)(i + 1));
376     // We assume that no one else has called dfsan_create_label before.
377     if (L != i + 1) {
378       Printf("DFSan labels are not starting from 1, exiting\n");
379       exit(1);
380     }
381   }
382 }
383 
InternalStrnlen(const char * S,size_t MaxLen)384 static size_t InternalStrnlen(const char *S, size_t MaxLen) {
385   size_t Len = 0;
386   for (; Len < MaxLen && S[Len]; Len++) {}
387   return Len;
388 }
389 
390 }  // namespace fuzzer
391 
392 using fuzzer::TS;
393 
394 extern "C" {
__dfsw___sanitizer_cov_trace_cmp(uint64_t SizeAndType,uint64_t Arg1,uint64_t Arg2,dfsan_label L0,dfsan_label L1,dfsan_label L2)395 void __dfsw___sanitizer_cov_trace_cmp(uint64_t SizeAndType, uint64_t Arg1,
396                                       uint64_t Arg2, dfsan_label L0,
397                                       dfsan_label L1, dfsan_label L2) {
398   if (!TS) return;
399   assert(L0 == 0);
400   uintptr_t PC = reinterpret_cast<uintptr_t>(__builtin_return_address(0));
401   uint64_t CmpSize = (SizeAndType >> 32) / 8;
402   uint64_t Type = (SizeAndType << 32) >> 32;
403   TS->DFSanCmpCallback(PC, CmpSize, Type, Arg1, Arg2, L1, L2);
404 }
405 
__dfsw___sanitizer_cov_trace_switch(uint64_t Val,uint64_t * Cases,dfsan_label L1,dfsan_label L2)406 void __dfsw___sanitizer_cov_trace_switch(uint64_t Val, uint64_t *Cases,
407                                          dfsan_label L1, dfsan_label L2) {
408   if (!TS) return;
409   uintptr_t PC = reinterpret_cast<uintptr_t>(__builtin_return_address(0));
410   TS->DFSanSwitchCallback(PC, Cases[1], Val, Cases[0], Cases+2, L1);
411 }
412 
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)413 void dfsan_weak_hook_memcmp(void *caller_pc, const void *s1, const void *s2,
414                             size_t n, dfsan_label s1_label,
415                             dfsan_label s2_label, dfsan_label n_label) {
416   if (!TS) return;
417   uintptr_t PC = reinterpret_cast<uintptr_t>(caller_pc);
418   uint64_t S1 = 0, S2 = 0;
419   // Simplification: handle only first 8 bytes.
420   memcpy(&S1, s1, std::min(n, sizeof(S1)));
421   memcpy(&S2, s2, std::min(n, sizeof(S2)));
422   dfsan_label L1 = dfsan_read_label(s1, n);
423   dfsan_label L2 = dfsan_read_label(s2, n);
424   TS->DFSanCmpCallback(PC, n, fuzzer::ICMP_EQ, S1, S2, L1, L2);
425 }
426 
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)427 void dfsan_weak_hook_strncmp(void *caller_pc, const char *s1, const char *s2,
428                              size_t n, dfsan_label s1_label,
429                              dfsan_label s2_label, dfsan_label n_label) {
430   if (!TS) return;
431   uintptr_t PC = reinterpret_cast<uintptr_t>(caller_pc);
432   uint64_t S1 = 0, S2 = 0;
433   n = std::min(n, fuzzer::InternalStrnlen(s1, n));
434   n = std::min(n, fuzzer::InternalStrnlen(s2, n));
435   // Simplification: handle only first 8 bytes.
436   memcpy(&S1, s1, std::min(n, sizeof(S1)));
437   memcpy(&S2, s2, std::min(n, sizeof(S2)));
438   dfsan_label L1 = dfsan_read_label(s1, n);
439   dfsan_label L2 = dfsan_read_label(s2, n);
440   TS->DFSanCmpCallback(PC, n, fuzzer::ICMP_EQ, S1, S2, L1, L2);
441 }
442 
dfsan_weak_hook_strcmp(void * caller_pc,const char * s1,const char * s2,dfsan_label s1_label,dfsan_label s2_label)443 void dfsan_weak_hook_strcmp(void *caller_pc, const char *s1, const char *s2,
444                             dfsan_label s1_label, dfsan_label s2_label) {
445   if (!TS) return;
446   uintptr_t PC = reinterpret_cast<uintptr_t>(caller_pc);
447   uint64_t S1 = 0, S2 = 0;
448   size_t Len1 = strlen(s1);
449   size_t Len2 = strlen(s2);
450   size_t N = std::min(Len1, Len2);
451   if (N <= 1) return;  // Not interesting.
452   // Simplification: handle only first 8 bytes.
453   memcpy(&S1, s1, std::min(N, sizeof(S1)));
454   memcpy(&S2, s2, std::min(N, sizeof(S2)));
455   dfsan_label L1 = dfsan_read_label(s1, Len1);
456   dfsan_label L2 = dfsan_read_label(s2, Len2);
457   TS->DFSanCmpCallback(PC, N, fuzzer::ICMP_EQ, S1, S2, L1, L2);
458 }
459 
__sanitizer_weak_hook_memcmp(void * caller_pc,const void * s1,const void * s2,size_t n)460 void __sanitizer_weak_hook_memcmp(void *caller_pc, const void *s1,
461                                   const void *s2, size_t n) {
462   if (!TS) return;
463   uintptr_t PC = reinterpret_cast<uintptr_t>(caller_pc);
464   uint64_t S1 = 0, S2 = 0;
465   // Simplification: handle only first 8 bytes.
466   memcpy(&S1, s1, std::min(n, sizeof(S1)));
467   memcpy(&S2, s2, std::min(n, sizeof(S2)));
468   TS->TraceCmpCallback(PC, n, fuzzer::ICMP_EQ, S1, S2);
469 }
470 
__sanitizer_weak_hook_strncmp(void * caller_pc,const char * s1,const char * s2,size_t n)471 void __sanitizer_weak_hook_strncmp(void *caller_pc, const char *s1,
472                                    const char *s2, size_t n) {
473   if (!TS) return;
474   uintptr_t PC = reinterpret_cast<uintptr_t>(caller_pc);
475   uint64_t S1 = 0, S2 = 0;
476   size_t Len1 = fuzzer::InternalStrnlen(s1, n);
477   size_t Len2 = fuzzer::InternalStrnlen(s2, n);
478   n = std::min(n, Len1);
479   n = std::min(n, Len2);
480   if (n <= 1) return;  // Not interesting.
481   // Simplification: handle only first 8 bytes.
482   memcpy(&S1, s1, std::min(n, sizeof(S1)));
483   memcpy(&S2, s2, std::min(n, sizeof(S2)));
484   TS->TraceCmpCallback(PC, n, fuzzer::ICMP_EQ, S1, S2);
485 }
486 
__sanitizer_weak_hook_strcmp(void * caller_pc,const char * s1,const char * s2)487 void __sanitizer_weak_hook_strcmp(void *caller_pc, const char *s1,
488                                    const char *s2) {
489   if (!TS) return;
490   uintptr_t PC = reinterpret_cast<uintptr_t>(caller_pc);
491   uint64_t S1 = 0, S2 = 0;
492   size_t Len1 = strlen(s1);
493   size_t Len2 = strlen(s2);
494   size_t N = std::min(Len1, Len2);
495   if (N <= 1) return;  // Not interesting.
496   // Simplification: handle only first 8 bytes.
497   memcpy(&S1, s1, std::min(N, sizeof(S1)));
498   memcpy(&S2, s2, std::min(N, sizeof(S2)));
499   TS->TraceCmpCallback(PC, N, fuzzer::ICMP_EQ, S1, S2);
500 }
501 
502 __attribute__((visibility("default")))
__sanitizer_cov_trace_cmp(uint64_t SizeAndType,uint64_t Arg1,uint64_t Arg2)503 void __sanitizer_cov_trace_cmp(uint64_t SizeAndType, uint64_t Arg1,
504                                uint64_t Arg2) {
505   if (!TS) return;
506   uintptr_t PC = reinterpret_cast<uintptr_t>(__builtin_return_address(0));
507   uint64_t CmpSize = (SizeAndType >> 32) / 8;
508   uint64_t Type = (SizeAndType << 32) >> 32;
509   TS->TraceCmpCallback(PC, CmpSize, Type, Arg1, Arg2);
510 }
511 
512 __attribute__((visibility("default")))
__sanitizer_cov_trace_switch(uint64_t Val,uint64_t * Cases)513 void __sanitizer_cov_trace_switch(uint64_t Val, uint64_t *Cases) {
514   if (!TS) return;
515   uintptr_t PC = reinterpret_cast<uintptr_t>(__builtin_return_address(0));
516   TS->TraceSwitchCallback(PC, Cases[1], Val, Cases[0], Cases + 2);
517 }
518 
519 }  // extern "C"
520