1 //===- FuzzerTracePC.h - Internal header for the Fuzzer ---------*- C++ -* ===//
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 // fuzzer::TracePC
10 //===----------------------------------------------------------------------===//
11
12 #ifndef LLVM_FUZZER_TRACE_PC
13 #define LLVM_FUZZER_TRACE_PC
14
15 #include "FuzzerDefs.h"
16 #include "FuzzerDictionary.h"
17 #include "FuzzerValueBitMap.h"
18
19 #include <set>
20 #include <unordered_map>
21
22 namespace fuzzer {
23
24 // TableOfRecentCompares (TORC) remembers the most recently performed
25 // comparisons of type T.
26 // We record the arguments of CMP instructions in this table unconditionally
27 // because it seems cheaper this way than to compute some expensive
28 // conditions inside __sanitizer_cov_trace_cmp*.
29 // After the unit has been executed we may decide to use the contents of
30 // this table to populate a Dictionary.
31 template<class T, size_t kSizeT>
32 struct TableOfRecentCompares {
33 static const size_t kSize = kSizeT;
34 struct Pair {
35 T A, B;
36 };
37 ATTRIBUTE_NO_SANITIZE_ALL
InsertTableOfRecentCompares38 void Insert(size_t Idx, const T &Arg1, const T &Arg2) {
39 Idx = Idx % kSize;
40 Table[Idx].A = Arg1;
41 Table[Idx].B = Arg2;
42 }
43
GetTableOfRecentCompares44 Pair Get(size_t I) { return Table[I % kSize]; }
45
46 Pair Table[kSize];
47 };
48
49 template <size_t kSizeT>
50 struct MemMemTable {
51 static const size_t kSize = kSizeT;
52 Word MemMemWords[kSize];
53 Word EmptyWord;
54
AddMemMemTable55 void Add(const uint8_t *Data, size_t Size) {
56 if (Size <= 2) return;
57 Size = std::min(Size, Word::GetMaxSize());
58 size_t Idx = SimpleFastHash(Data, Size) % kSize;
59 MemMemWords[Idx].Set(Data, Size);
60 }
GetMemMemTable61 const Word &Get(size_t Idx) {
62 for (size_t i = 0; i < kSize; i++) {
63 const Word &W = MemMemWords[(Idx + i) % kSize];
64 if (W.size()) return W;
65 }
66 EmptyWord.Set(nullptr, 0);
67 return EmptyWord;
68 }
69 };
70
71 class TracePC {
72 public:
73 static const size_t kNumPCs = 1 << 21;
74 // How many bits of PC are used from __sanitizer_cov_trace_pc.
75 static const size_t kTracePcBits = 18;
76
77 void HandleInit(uint32_t *Start, uint32_t *Stop);
78 void HandleInline8bitCountersInit(uint8_t *Start, uint8_t *Stop);
79 void HandlePCsInit(const uintptr_t *Start, const uintptr_t *Stop);
80 void HandleCallerCallee(uintptr_t Caller, uintptr_t Callee);
81 template <class T> void HandleCmp(uintptr_t PC, T Arg1, T Arg2);
82 size_t GetTotalPCCoverage();
SetUseCounters(bool UC)83 void SetUseCounters(bool UC) { UseCounters = UC; }
SetUseValueProfileMask(uint32_t VPMask)84 void SetUseValueProfileMask(uint32_t VPMask) { UseValueProfileMask = VPMask; }
SetPrintNewPCs(bool P)85 void SetPrintNewPCs(bool P) { DoPrintNewPCs = P; }
SetPrintNewFuncs(size_t P)86 void SetPrintNewFuncs(size_t P) { NumPrintNewFuncs = P; }
87 void UpdateObservedPCs();
88 template <class Callback> void CollectFeatures(Callback CB) const;
89
ResetMaps()90 void ResetMaps() {
91 ValueProfileMap.Reset();
92 if (NumModules)
93 memset(Counters(), 0, GetNumPCs());
94 ClearExtraCounters();
95 ClearInlineCounters();
96 }
97
98 void ClearInlineCounters();
99
100 void UpdateFeatureSet(size_t CurrentElementIdx, size_t CurrentElementSize);
101 void PrintFeatureSet();
102
103 void PrintModuleInfo();
104
105 void PrintCoverage();
106 void DumpCoverage();
107
108 template<class CallBack>
109 void IterateCoveredFunctions(CallBack CB);
110
111 void AddValueForMemcmp(void *caller_pc, const void *s1, const void *s2,
112 size_t n, bool StopAtZero);
113
114 TableOfRecentCompares<uint32_t, 32> TORC4;
115 TableOfRecentCompares<uint64_t, 32> TORC8;
116 TableOfRecentCompares<Word, 32> TORCW;
117 MemMemTable<1024> MMT;
118
GetNumPCs()119 size_t GetNumPCs() const {
120 return NumGuards == 0 ? (1 << kTracePcBits) : Min(kNumPCs, NumGuards + 1);
121 }
GetPC(size_t Idx)122 uintptr_t GetPC(size_t Idx) {
123 assert(Idx < GetNumPCs());
124 return PCs()[Idx];
125 }
126
127 void RecordInitialStack();
128 uintptr_t GetMaxStackOffset() const;
129
130 template<class CallBack>
ForEachObservedPC(CallBack CB)131 void ForEachObservedPC(CallBack CB) {
132 for (auto PC : ObservedPCs)
133 CB(PC);
134 }
135
136 void SetFocusFunction(const std::string &FuncName);
137 bool ObservedFocusFunction();
138
139 private:
140 bool UseCounters = false;
141 uint32_t UseValueProfileMask = false;
142 bool DoPrintNewPCs = false;
143 size_t NumPrintNewFuncs = 0;
144
145 struct Module {
146 uint32_t *Start, *Stop;
147 };
148
149 Module Modules[4096];
150 size_t NumModules; // linker-initialized.
151 size_t NumGuards; // linker-initialized.
152
153 struct { uint8_t *Start, *Stop; } ModuleCounters[4096];
154 size_t NumModulesWithInline8bitCounters; // linker-initialized.
155 size_t NumInline8bitCounters;
156
157 struct PCTableEntry {
158 uintptr_t PC, PCFlags;
159 };
160
161 struct { const PCTableEntry *Start, *Stop; } ModulePCTable[4096];
162 size_t NumPCTables;
163 size_t NumPCsInPCTables;
164
165 uint8_t *Counters() const;
166 uintptr_t *PCs() const;
167
168 Set<uintptr_t> ObservedPCs;
169 std::unordered_map<uintptr_t, uintptr_t> ObservedFuncs; // PC => Counter.
170
171 std::pair<size_t, size_t> FocusFunction = {-1, -1}; // Module and PC IDs.
172
173 ValueBitMap ValueProfileMap;
174 uintptr_t InitialStack;
175 };
176
177 template <class Callback>
178 // void Callback(size_t FirstFeature, size_t Idx, uint8_t Value);
179 ATTRIBUTE_NO_SANITIZE_ALL
ForEachNonZeroByte(const uint8_t * Begin,const uint8_t * End,size_t FirstFeature,Callback Handle8bitCounter)180 void ForEachNonZeroByte(const uint8_t *Begin, const uint8_t *End,
181 size_t FirstFeature, Callback Handle8bitCounter) {
182 typedef uintptr_t LargeType;
183 const size_t Step = sizeof(LargeType) / sizeof(uint8_t);
184 const size_t StepMask = Step - 1;
185 auto P = Begin;
186 // Iterate by 1 byte until either the alignment boundary or the end.
187 for (; reinterpret_cast<uintptr_t>(P) & StepMask && P < End; P++)
188 if (uint8_t V = *P)
189 Handle8bitCounter(FirstFeature, P - Begin, V);
190
191 // Iterate by Step bytes at a time.
192 for (; P < End; P += Step)
193 if (LargeType Bundle = *reinterpret_cast<const LargeType *>(P))
194 for (size_t I = 0; I < Step; I++, Bundle >>= 8)
195 if (uint8_t V = Bundle & 0xff)
196 Handle8bitCounter(FirstFeature, P - Begin + I, V);
197
198 // Iterate by 1 byte until the end.
199 for (; P < End; P++)
200 if (uint8_t V = *P)
201 Handle8bitCounter(FirstFeature, P - Begin, V);
202 }
203
204 // Given a non-zero Counter returns a number in the range [0,7].
205 template<class T>
CounterToFeature(T Counter)206 unsigned CounterToFeature(T Counter) {
207 // Returns a feature number by placing Counters into buckets as illustrated
208 // below.
209 //
210 // Counter bucket: [1] [2] [3] [4-7] [8-15] [16-31] [32-127] [128+]
211 // Feature number: 0 1 2 3 4 5 6 7
212 //
213 // This is a heuristic taken from AFL (see
214 // http://lcamtuf.coredump.cx/afl/technical_details.txt).
215 //
216 // This implementation may change in the future so clients should
217 // not rely on it.
218 assert(Counter);
219 unsigned Bit = 0;
220 /**/ if (Counter >= 128) Bit = 7;
221 else if (Counter >= 32) Bit = 6;
222 else if (Counter >= 16) Bit = 5;
223 else if (Counter >= 8) Bit = 4;
224 else if (Counter >= 4) Bit = 3;
225 else if (Counter >= 3) Bit = 2;
226 else if (Counter >= 2) Bit = 1;
227 return Bit;
228 }
229
230 template <class Callback> // void Callback(size_t Feature)
231 ATTRIBUTE_NO_SANITIZE_ADDRESS
232 __attribute__((noinline))
CollectFeatures(Callback HandleFeature)233 void TracePC::CollectFeatures(Callback HandleFeature) const {
234 uint8_t *Counters = this->Counters();
235 size_t N = GetNumPCs();
236 auto Handle8bitCounter = [&](size_t FirstFeature,
237 size_t Idx, uint8_t Counter) {
238 if (UseCounters)
239 HandleFeature(FirstFeature + Idx * 8 + CounterToFeature(Counter));
240 else
241 HandleFeature(FirstFeature + Idx);
242 };
243
244 size_t FirstFeature = 0;
245
246 if (!NumInline8bitCounters) {
247 ForEachNonZeroByte(Counters, Counters + N, FirstFeature, Handle8bitCounter);
248 FirstFeature += N * 8;
249 }
250
251 if (NumInline8bitCounters) {
252 for (size_t i = 0; i < NumModulesWithInline8bitCounters; i++) {
253 ForEachNonZeroByte(ModuleCounters[i].Start, ModuleCounters[i].Stop,
254 FirstFeature, Handle8bitCounter);
255 FirstFeature += 8 * (ModuleCounters[i].Stop - ModuleCounters[i].Start);
256 }
257 }
258
259 ForEachNonZeroByte(ExtraCountersBegin(), ExtraCountersEnd(), FirstFeature,
260 Handle8bitCounter);
261 FirstFeature += (ExtraCountersEnd() - ExtraCountersBegin()) * 8;
262
263 if (UseValueProfileMask) {
264 ValueProfileMap.ForEach([&](size_t Idx) {
265 HandleFeature(FirstFeature + Idx);
266 });
267 FirstFeature += ValueProfileMap.SizeInBits();
268 }
269
270 // Step function, grows similar to 8 * Log_2(A).
271 auto StackDepthStepFunction = [](uint32_t A) -> uint32_t {
272 if (!A) return A;
273 uint32_t Log2 = Log(A);
274 if (Log2 < 3) return A;
275 Log2 -= 3;
276 return (Log2 + 1) * 8 + ((A >> Log2) & 7);
277 };
278 assert(StackDepthStepFunction(1024) == 64);
279 assert(StackDepthStepFunction(1024 * 4) == 80);
280 assert(StackDepthStepFunction(1024 * 1024) == 144);
281
282 if (auto MaxStackOffset = GetMaxStackOffset())
283 HandleFeature(FirstFeature + StackDepthStepFunction(MaxStackOffset / 8));
284 }
285
286 extern TracePC TPC;
287
288 } // namespace fuzzer
289
290 #endif // LLVM_FUZZER_TRACE_PC
291