1 //===- FuzzerTracePC.h - Internal header for the Fuzzer ---------*- C++ -* ===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 //===----------------------------------------------------------------------===//
11 #ifndef LLVM_FUZZER_TRACE_PC
12 #define LLVM_FUZZER_TRACE_PC
14 #include "FuzzerDefs.h"
15 #include "FuzzerDictionary.h"
16 #include "FuzzerValueBitMap.h"
19 #include <unordered_map>
23 // TableOfRecentCompares (TORC) remembers the most recently performed
24 // comparisons of type T.
25 // We record the arguments of CMP instructions in this table unconditionally
26 // because it seems cheaper this way than to compute some expensive
27 // conditions inside __sanitizer_cov_trace_cmp*.
28 // After the unit has been executed we may decide to use the contents of
29 // this table to populate a Dictionary.
30 template<class T, size_t kSizeT>
31 struct TableOfRecentCompares {
32 static const size_t kSize = kSizeT;
36 ATTRIBUTE_NO_SANITIZE_ALL
37 void Insert(size_t Idx, const T &Arg1, const T &Arg2) {
43 Pair Get(size_t I) { return Table[I % kSize]; }
48 template <size_t kSizeT>
50 static const size_t kSize = kSizeT;
51 Word MemMemWords[kSize];
54 void Add(const uint8_t *Data, size_t Size) {
55 if (Size <= 2) return;
56 Size = std::min(Size, Word::GetMaxSize());
57 size_t Idx = SimpleFastHash(Data, Size) % kSize;
58 MemMemWords[Idx].Set(Data, Size);
60 const Word &Get(size_t Idx) {
61 for (size_t i = 0; i < kSize; i++) {
62 const Word &W = MemMemWords[(Idx + i) % kSize];
63 if (W.size()) return W;
65 EmptyWord.Set(nullptr, 0);
72 void HandleInline8bitCountersInit(uint8_t *Start, uint8_t *Stop);
73 void HandlePCsInit(const uintptr_t *Start, const uintptr_t *Stop);
74 void HandleCallerCallee(uintptr_t Caller, uintptr_t Callee);
75 template <class T> void HandleCmp(uintptr_t PC, T Arg1, T Arg2);
76 size_t GetTotalPCCoverage();
77 void SetUseCounters(bool UC) { UseCounters = UC; }
78 void SetUseValueProfileMask(uint32_t VPMask) { UseValueProfileMask = VPMask; }
79 void SetPrintNewPCs(bool P) { DoPrintNewPCs = P; }
80 void SetPrintNewFuncs(size_t P) { NumPrintNewFuncs = P; }
81 void UpdateObservedPCs();
82 template <class Callback> void CollectFeatures(Callback CB) const;
85 ValueProfileMap.Reset();
87 ClearInlineCounters();
90 void ClearInlineCounters();
92 void UpdateFeatureSet(size_t CurrentElementIdx, size_t CurrentElementSize);
93 void PrintFeatureSet();
95 void PrintModuleInfo();
99 template<class CallBack>
100 void IterateCoveredFunctions(CallBack CB);
102 void AddValueForMemcmp(void *caller_pc, const void *s1, const void *s2,
103 size_t n, bool StopAtZero);
105 TableOfRecentCompares<uint32_t, 32> TORC4;
106 TableOfRecentCompares<uint64_t, 32> TORC8;
107 TableOfRecentCompares<Word, 32> TORCW;
108 MemMemTable<1024> MMT;
110 void RecordInitialStack();
111 uintptr_t GetMaxStackOffset() const;
113 template<class CallBack>
114 void ForEachObservedPC(CallBack CB) {
115 for (auto PC : ObservedPCs)
119 void SetFocusFunction(const std::string &FuncName);
120 bool ObservedFocusFunction();
122 void ProtectLazyCounters();
123 bool UnprotectLazyCounters(void *CounterPtr);
125 struct PCTableEntry {
126 uintptr_t PC, PCFlags;
129 uintptr_t PCTableEntryIdx(const PCTableEntry *TE);
130 const PCTableEntry *PCTableEntryByIdx(uintptr_t Idx);
131 static uintptr_t GetNextInstructionPc(uintptr_t PC);
132 bool PcIsFuncEntry(const PCTableEntry *TE) { return TE->PCFlags & 1; }
135 bool UseCounters = false;
136 uint32_t UseValueProfileMask = false;
137 bool DoPrintNewPCs = false;
138 size_t NumPrintNewFuncs = 0;
140 // Module represents the array of 8-bit counters split into regions
141 // such that every region, except maybe the first and the last one, is one
145 uint8_t *Start, *Stop;
151 uint8_t *Start() { return Regions[0].Start; }
152 uint8_t *Stop() { return Regions[NumRegions - 1].Stop; }
153 size_t Size() { return Stop() - Start(); }
154 size_t Idx(uint8_t *P) {
155 assert(P >= Start() && P < Stop());
160 Module Modules[4096];
161 size_t NumModules; // linker-initialized.
162 size_t NumInline8bitCounters;
164 template <class Callback>
165 void IterateCounterRegions(Callback CB) {
166 for (size_t m = 0; m < NumModules; m++)
167 for (size_t r = 0; r < Modules[m].NumRegions; r++)
168 CB(Modules[m].Regions[r]);
171 struct { const PCTableEntry *Start, *Stop; } ModulePCTable[4096];
173 size_t NumPCsInPCTables;
175 Set<const PCTableEntry*> ObservedPCs;
176 std::unordered_map<uintptr_t, uintptr_t> ObservedFuncs; // PC => Counter.
178 uint8_t *FocusFunctionCounterPtr = nullptr;
180 ValueBitMap ValueProfileMap;
181 uintptr_t InitialStack;
184 template <class Callback>
185 // void Callback(size_t FirstFeature, size_t Idx, uint8_t Value);
186 ATTRIBUTE_NO_SANITIZE_ALL
187 size_t ForEachNonZeroByte(const uint8_t *Begin, const uint8_t *End,
188 size_t FirstFeature, Callback Handle8bitCounter) {
189 typedef uintptr_t LargeType;
190 const size_t Step = sizeof(LargeType) / sizeof(uint8_t);
191 const size_t StepMask = Step - 1;
193 // Iterate by 1 byte until either the alignment boundary or the end.
194 for (; reinterpret_cast<uintptr_t>(P) & StepMask && P < End; P++)
196 Handle8bitCounter(FirstFeature, P - Begin, V);
198 // Iterate by Step bytes at a time.
199 for (; P < End; P += Step)
200 if (LargeType Bundle = *reinterpret_cast<const LargeType *>(P))
201 for (size_t I = 0; I < Step; I++, Bundle >>= 8)
202 if (uint8_t V = Bundle & 0xff)
203 Handle8bitCounter(FirstFeature, P - Begin + I, V);
205 // Iterate by 1 byte until the end.
208 Handle8bitCounter(FirstFeature, P - Begin, V);
212 // Given a non-zero Counter returns a number in the range [0,7].
214 unsigned CounterToFeature(T Counter) {
215 // Returns a feature number by placing Counters into buckets as illustrated
218 // Counter bucket: [1] [2] [3] [4-7] [8-15] [16-31] [32-127] [128+]
219 // Feature number: 0 1 2 3 4 5 6 7
221 // This is a heuristic taken from AFL (see
222 // http://lcamtuf.coredump.cx/afl/technical_details.txt).
224 // This implementation may change in the future so clients should
228 /**/ if (Counter >= 128) Bit = 7;
229 else if (Counter >= 32) Bit = 6;
230 else if (Counter >= 16) Bit = 5;
231 else if (Counter >= 8) Bit = 4;
232 else if (Counter >= 4) Bit = 3;
233 else if (Counter >= 3) Bit = 2;
234 else if (Counter >= 2) Bit = 1;
238 template <class Callback> // void Callback(size_t Feature)
239 ATTRIBUTE_NO_SANITIZE_ADDRESS
241 void TracePC::CollectFeatures(Callback HandleFeature) const {
242 auto Handle8bitCounter = [&](size_t FirstFeature,
243 size_t Idx, uint8_t Counter) {
245 HandleFeature(FirstFeature + Idx * 8 + CounterToFeature(Counter));
247 HandleFeature(FirstFeature + Idx);
250 size_t FirstFeature = 0;
252 for (size_t i = 0; i < NumModules; i++) {
253 for (size_t r = 0; r < Modules[i].NumRegions; r++) {
254 if (!Modules[i].Regions[r].Enabled) continue;
255 FirstFeature += 8 * ForEachNonZeroByte(Modules[i].Regions[r].Start,
256 Modules[i].Regions[r].Stop,
257 FirstFeature, Handle8bitCounter);
262 8 * ForEachNonZeroByte(ExtraCountersBegin(), ExtraCountersEnd(),
263 FirstFeature, Handle8bitCounter);
265 if (UseValueProfileMask) {
266 ValueProfileMap.ForEach([&](size_t Idx) {
267 HandleFeature(FirstFeature + Idx);
269 FirstFeature += ValueProfileMap.SizeInBits();
272 // Step function, grows similar to 8 * Log_2(A).
273 auto StackDepthStepFunction = [](uint32_t A) -> uint32_t {
275 uint32_t Log2 = Log(A);
276 if (Log2 < 3) return A;
278 return (Log2 + 1) * 8 + ((A >> Log2) & 7);
280 assert(StackDepthStepFunction(1024) == 64);
281 assert(StackDepthStepFunction(1024 * 4) == 80);
282 assert(StackDepthStepFunction(1024 * 1024) == 144);
284 if (auto MaxStackOffset = GetMaxStackOffset())
285 HandleFeature(FirstFeature + StackDepthStepFunction(MaxStackOffset / 8));
290 } // namespace fuzzer
292 #endif // LLVM_FUZZER_TRACE_PC