1 //===- FuzzerLoop.cpp - Fuzzer's main loop --------------------------------===//
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's main loop.
10 //===----------------------------------------------------------------------===//
11
12 #include "FuzzerInternal.h"
13 #include <algorithm>
14
15 #if defined(__has_include)
16 # if __has_include(<sanitizer/coverage_interface.h>)
17 # include <sanitizer/coverage_interface.h>
18 # endif
19 #endif
20
21 extern "C" {
22 // Re-declare some of the sanitizer functions as "weak" so that
23 // libFuzzer can be linked w/o the sanitizers and sanitizer-coverage
24 // (in which case it will complain at start-up time).
25 __attribute__((weak)) void __sanitizer_print_stack_trace();
26 __attribute__((weak)) void __sanitizer_reset_coverage();
27 __attribute__((weak)) size_t __sanitizer_get_total_unique_caller_callee_pairs();
28 __attribute__((weak)) size_t __sanitizer_get_total_unique_coverage();
29 __attribute__((weak))
30 void __sanitizer_set_death_callback(void (*callback)(void));
31 __attribute__((weak)) size_t __sanitizer_get_number_of_counters();
32 __attribute__((weak))
33 uintptr_t __sanitizer_update_counter_bitset_and_clear_counters(uint8_t *bitset);
34 }
35
36 namespace fuzzer {
37 static const size_t kMaxUnitSizeToPrint = 256;
38
MissingWeakApiFunction(const char * FnName)39 static void MissingWeakApiFunction(const char *FnName) {
40 Printf("ERROR: %s is not defined. Exiting.\n"
41 "Did you use -fsanitize-coverage=... to build your code?\n", FnName);
42 exit(1);
43 }
44
45 #define CHECK_WEAK_API_FUNCTION(fn) \
46 do { \
47 if (!fn) \
48 MissingWeakApiFunction(#fn); \
49 } while (false)
50
51 // Only one Fuzzer per process.
52 static Fuzzer *F;
53
Fuzzer(UserSuppliedFuzzer & USF,FuzzingOptions Options)54 Fuzzer::Fuzzer(UserSuppliedFuzzer &USF, FuzzingOptions Options)
55 : USF(USF), Options(Options) {
56 SetDeathCallback();
57 InitializeTraceState();
58 assert(!F);
59 F = this;
60 }
61
SetDeathCallback()62 void Fuzzer::SetDeathCallback() {
63 CHECK_WEAK_API_FUNCTION(__sanitizer_set_death_callback);
64 __sanitizer_set_death_callback(StaticDeathCallback);
65 }
66
PrintUnitInASCII(const Unit & U,const char * PrintAfter)67 void Fuzzer::PrintUnitInASCII(const Unit &U, const char *PrintAfter) {
68 PrintASCII(U, PrintAfter);
69 }
70
StaticDeathCallback()71 void Fuzzer::StaticDeathCallback() {
72 assert(F);
73 F->DeathCallback();
74 }
75
DeathCallback()76 void Fuzzer::DeathCallback() {
77 Printf("DEATH:\n");
78 if (CurrentUnit.size() <= kMaxUnitSizeToPrint) {
79 Print(CurrentUnit, "\n");
80 PrintUnitInASCII(CurrentUnit, "\n");
81 }
82 WriteUnitToFileWithPrefix(CurrentUnit, "crash-");
83 }
84
StaticAlarmCallback()85 void Fuzzer::StaticAlarmCallback() {
86 assert(F);
87 F->AlarmCallback();
88 }
89
AlarmCallback()90 void Fuzzer::AlarmCallback() {
91 assert(Options.UnitTimeoutSec > 0);
92 size_t Seconds =
93 duration_cast<seconds>(system_clock::now() - UnitStartTime).count();
94 if (Seconds == 0) return;
95 if (Options.Verbosity >= 2)
96 Printf("AlarmCallback %zd\n", Seconds);
97 if (Seconds >= (size_t)Options.UnitTimeoutSec) {
98 Printf("ALARM: working on the last Unit for %zd seconds\n", Seconds);
99 Printf(" and the timeout value is %d (use -timeout=N to change)\n",
100 Options.UnitTimeoutSec);
101 if (CurrentUnit.size() <= kMaxUnitSizeToPrint) {
102 Print(CurrentUnit, "\n");
103 PrintUnitInASCII(CurrentUnit, "\n");
104 }
105 WriteUnitToFileWithPrefix(CurrentUnit, "timeout-");
106 Printf("==%d== ERROR: libFuzzer: timeout after %d seconds\n", GetPid(),
107 Seconds);
108 if (__sanitizer_print_stack_trace)
109 __sanitizer_print_stack_trace();
110 Printf("SUMMARY: libFuzzer: timeout\n");
111 exit(1);
112 }
113 }
114
PrintStats(const char * Where,const char * End)115 void Fuzzer::PrintStats(const char *Where, const char *End) {
116 size_t Seconds = secondsSinceProcessStartUp();
117 size_t ExecPerSec = (Seconds ? TotalNumberOfRuns / Seconds : 0);
118
119 if (Options.OutputCSV) {
120 static bool csvHeaderPrinted = false;
121 if (!csvHeaderPrinted) {
122 csvHeaderPrinted = true;
123 Printf("runs,block_cov,bits,cc_cov,corpus,execs_per_sec,tbms,reason\n");
124 }
125 Printf("%zd,%zd,%zd,%zd,%zd,%zd,%zd,%s\n", TotalNumberOfRuns,
126 LastRecordedBlockCoverage, TotalBits(),
127 LastRecordedCallerCalleeCoverage, Corpus.size(), ExecPerSec,
128 TotalNumberOfExecutedTraceBasedMutations, Where);
129 }
130
131 if (!Options.Verbosity)
132 return;
133 Printf("#%zd\t%s", TotalNumberOfRuns, Where);
134 if (LastRecordedBlockCoverage)
135 Printf(" cov: %zd", LastRecordedBlockCoverage);
136 if (auto TB = TotalBits())
137 Printf(" bits: %zd", TB);
138 if (LastRecordedCallerCalleeCoverage)
139 Printf(" indir: %zd", LastRecordedCallerCalleeCoverage);
140 Printf(" units: %zd exec/s: %zd", Corpus.size(), ExecPerSec);
141 if (TotalNumberOfExecutedTraceBasedMutations)
142 Printf(" tbm: %zd", TotalNumberOfExecutedTraceBasedMutations);
143 Printf("%s", End);
144 }
145
RereadOutputCorpus()146 void Fuzzer::RereadOutputCorpus() {
147 if (Options.OutputCorpus.empty()) return;
148 std::vector<Unit> AdditionalCorpus;
149 ReadDirToVectorOfUnits(Options.OutputCorpus.c_str(), &AdditionalCorpus,
150 &EpochOfLastReadOfOutputCorpus);
151 if (Corpus.empty()) {
152 Corpus = AdditionalCorpus;
153 return;
154 }
155 if (!Options.Reload) return;
156 if (Options.Verbosity >= 2)
157 Printf("Reload: read %zd new units.\n", AdditionalCorpus.size());
158 for (auto &X : AdditionalCorpus) {
159 if (X.size() > (size_t)Options.MaxLen)
160 X.resize(Options.MaxLen);
161 if (UnitHashesAddedToCorpus.insert(Hash(X)).second) {
162 CurrentUnit.clear();
163 CurrentUnit.insert(CurrentUnit.begin(), X.begin(), X.end());
164 if (RunOne(CurrentUnit)) {
165 Corpus.push_back(X);
166 PrintStats("RELOAD");
167 }
168 }
169 }
170 }
171
ShuffleAndMinimize()172 void Fuzzer::ShuffleAndMinimize() {
173 bool PreferSmall = (Options.PreferSmallDuringInitialShuffle == 1 ||
174 (Options.PreferSmallDuringInitialShuffle == -1 &&
175 USF.GetRand().RandBool()));
176 if (Options.Verbosity)
177 Printf("PreferSmall: %d\n", PreferSmall);
178 PrintStats("READ ");
179 std::vector<Unit> NewCorpus;
180 if (Options.ShuffleAtStartUp) {
181 std::random_shuffle(Corpus.begin(), Corpus.end(), USF.GetRand());
182 if (PreferSmall)
183 std::stable_sort(
184 Corpus.begin(), Corpus.end(),
185 [](const Unit &A, const Unit &B) { return A.size() < B.size(); });
186 }
187 Unit &U = CurrentUnit;
188 for (const auto &C : Corpus) {
189 for (size_t First = 0; First < 1; First++) {
190 U.clear();
191 size_t Last = std::min(First + Options.MaxLen, C.size());
192 U.insert(U.begin(), C.begin() + First, C.begin() + Last);
193 if (Options.OnlyASCII)
194 ToASCII(U);
195 if (RunOne(U)) {
196 NewCorpus.push_back(U);
197 if (Options.Verbosity >= 2)
198 Printf("NEW0: %zd L %zd\n", LastRecordedBlockCoverage, U.size());
199 }
200 }
201 }
202 Corpus = NewCorpus;
203 for (auto &X : Corpus)
204 UnitHashesAddedToCorpus.insert(Hash(X));
205 PrintStats("INITED");
206 }
207
RunOne(const Unit & U)208 bool Fuzzer::RunOne(const Unit &U) {
209 UnitStartTime = system_clock::now();
210 TotalNumberOfRuns++;
211
212 PrepareCoverageBeforeRun();
213 ExecuteCallback(U);
214 bool Res = CheckCoverageAfterRun();
215
216 auto UnitStopTime = system_clock::now();
217 auto TimeOfUnit =
218 duration_cast<seconds>(UnitStopTime - UnitStartTime).count();
219 if (!(TotalNumberOfRuns & (TotalNumberOfRuns - 1)) &&
220 secondsSinceProcessStartUp() >= 2)
221 PrintStats("pulse ");
222 if (TimeOfUnit > TimeOfLongestUnitInSeconds &&
223 TimeOfUnit >= Options.ReportSlowUnits) {
224 TimeOfLongestUnitInSeconds = TimeOfUnit;
225 Printf("Slowest unit: %zd s:\n", TimeOfLongestUnitInSeconds);
226 WriteUnitToFileWithPrefix(U, "slow-unit-");
227 }
228 return Res;
229 }
230
RunOneAndUpdateCorpus(Unit & U)231 void Fuzzer::RunOneAndUpdateCorpus(Unit &U) {
232 if (TotalNumberOfRuns >= Options.MaxNumberOfRuns)
233 return;
234 if (Options.OnlyASCII)
235 ToASCII(U);
236 if (RunOne(U))
237 ReportNewCoverage(U);
238 }
239
ExecuteCallback(const Unit & U)240 void Fuzzer::ExecuteCallback(const Unit &U) {
241 const uint8_t *Data = U.data();
242 uint8_t EmptyData;
243 if (!Data)
244 Data = &EmptyData;
245 int Res = USF.TargetFunction(Data, U.size());
246 (void)Res;
247 assert(Res == 0);
248 }
249
RecordBlockCoverage()250 size_t Fuzzer::RecordBlockCoverage() {
251 CHECK_WEAK_API_FUNCTION(__sanitizer_get_total_unique_coverage);
252 return LastRecordedBlockCoverage = __sanitizer_get_total_unique_coverage();
253 }
254
RecordCallerCalleeCoverage()255 size_t Fuzzer::RecordCallerCalleeCoverage() {
256 if (!Options.UseIndirCalls)
257 return 0;
258 if (!__sanitizer_get_total_unique_caller_callee_pairs)
259 return 0;
260 return LastRecordedCallerCalleeCoverage =
261 __sanitizer_get_total_unique_caller_callee_pairs();
262 }
263
PrepareCoverageBeforeRun()264 void Fuzzer::PrepareCoverageBeforeRun() {
265 if (Options.UseCounters) {
266 size_t NumCounters = __sanitizer_get_number_of_counters();
267 CounterBitmap.resize(NumCounters);
268 __sanitizer_update_counter_bitset_and_clear_counters(0);
269 }
270 RecordBlockCoverage();
271 RecordCallerCalleeCoverage();
272 }
273
CheckCoverageAfterRun()274 bool Fuzzer::CheckCoverageAfterRun() {
275 size_t OldCoverage = LastRecordedBlockCoverage;
276 size_t NewCoverage = RecordBlockCoverage();
277 size_t OldCallerCalleeCoverage = LastRecordedCallerCalleeCoverage;
278 size_t NewCallerCalleeCoverage = RecordCallerCalleeCoverage();
279 size_t NumNewBits = 0;
280 if (Options.UseCounters)
281 NumNewBits = __sanitizer_update_counter_bitset_and_clear_counters(
282 CounterBitmap.data());
283 return NewCoverage > OldCoverage ||
284 NewCallerCalleeCoverage > OldCallerCalleeCoverage || NumNewBits;
285 }
286
WriteToOutputCorpus(const Unit & U)287 void Fuzzer::WriteToOutputCorpus(const Unit &U) {
288 if (Options.OutputCorpus.empty()) return;
289 std::string Path = DirPlusFile(Options.OutputCorpus, Hash(U));
290 WriteToFile(U, Path);
291 if (Options.Verbosity >= 2)
292 Printf("Written to %s\n", Path.c_str());
293 assert(!Options.OnlyASCII || IsASCII(U));
294 }
295
WriteUnitToFileWithPrefix(const Unit & U,const char * Prefix)296 void Fuzzer::WriteUnitToFileWithPrefix(const Unit &U, const char *Prefix) {
297 if (!Options.SaveArtifacts)
298 return;
299 std::string Path = Options.ArtifactPrefix + Prefix + Hash(U);
300 if (!Options.ExactArtifactPath.empty())
301 Path = Options.ExactArtifactPath; // Overrides ArtifactPrefix.
302 WriteToFile(U, Path);
303 Printf("artifact_prefix='%s'; Test unit written to %s\n",
304 Options.ArtifactPrefix.c_str(), Path.c_str());
305 if (U.size() <= kMaxUnitSizeToPrint)
306 Printf("Base64: %s\n", Base64(U).c_str());
307 }
308
SaveCorpus()309 void Fuzzer::SaveCorpus() {
310 if (Options.OutputCorpus.empty()) return;
311 for (const auto &U : Corpus)
312 WriteToFile(U, DirPlusFile(Options.OutputCorpus, Hash(U)));
313 if (Options.Verbosity)
314 Printf("Written corpus of %zd files to %s\n", Corpus.size(),
315 Options.OutputCorpus.c_str());
316 }
317
PrintStatusForNewUnit(const Unit & U)318 void Fuzzer::PrintStatusForNewUnit(const Unit &U) {
319 if (!Options.PrintNEW)
320 return;
321 PrintStats("NEW ", "");
322 if (Options.Verbosity) {
323 Printf(" L: %zd ", U.size());
324 USF.PrintMutationSequence();
325 Printf("\n");
326 }
327 }
328
ReportNewCoverage(const Unit & U)329 void Fuzzer::ReportNewCoverage(const Unit &U) {
330 Corpus.push_back(U);
331 UnitHashesAddedToCorpus.insert(Hash(U));
332 PrintStatusForNewUnit(U);
333 WriteToOutputCorpus(U);
334 if (Options.ExitOnFirst)
335 exit(0);
336 }
337
Merge(const std::vector<std::string> & Corpora)338 void Fuzzer::Merge(const std::vector<std::string> &Corpora) {
339 if (Corpora.size() <= 1) {
340 Printf("Merge requires two or more corpus dirs\n");
341 return;
342 }
343 auto InitialCorpusDir = Corpora[0];
344 ReadDir(InitialCorpusDir, nullptr);
345 Printf("Merge: running the initial corpus '%s' of %d units\n",
346 InitialCorpusDir.c_str(), Corpus.size());
347 for (auto &U : Corpus)
348 RunOne(U);
349
350 std::vector<std::string> ExtraCorpora(Corpora.begin() + 1, Corpora.end());
351
352 size_t NumTried = 0;
353 size_t NumMerged = 0;
354 for (auto &C : ExtraCorpora) {
355 Corpus.clear();
356 ReadDir(C, nullptr);
357 Printf("Merge: merging the extra corpus '%s' of %zd units\n", C.c_str(),
358 Corpus.size());
359 for (auto &U : Corpus) {
360 NumTried++;
361 if (RunOne(U)) {
362 WriteToOutputCorpus(U);
363 NumMerged++;
364 }
365 }
366 }
367 Printf("Merge: written %zd out of %zd units\n", NumMerged, NumTried);
368 }
369
MutateAndTestOne()370 void Fuzzer::MutateAndTestOne() {
371 auto &U = CurrentUnit;
372 USF.StartMutationSequence();
373
374 U = ChooseUnitToMutate();
375
376 for (int i = 0; i < Options.MutateDepth; i++) {
377 StartTraceRecording();
378 size_t Size = U.size();
379 U.resize(Options.MaxLen);
380 size_t NewSize = USF.Mutate(U.data(), Size, U.size());
381 assert(NewSize > 0 && "Mutator returned empty unit");
382 assert(NewSize <= (size_t)Options.MaxLen &&
383 "Mutator return overisized unit");
384 U.resize(NewSize);
385 RunOneAndUpdateCorpus(U);
386 size_t NumTraceBasedMutations = StopTraceRecording();
387 size_t TBMWidth =
388 std::min((size_t)Options.TBMWidth, NumTraceBasedMutations);
389 size_t TBMDepth =
390 std::min((size_t)Options.TBMDepth, NumTraceBasedMutations);
391 Unit BackUp = U;
392 for (size_t w = 0; w < TBMWidth; w++) {
393 U = BackUp;
394 for (size_t d = 0; d < TBMDepth; d++) {
395 TotalNumberOfExecutedTraceBasedMutations++;
396 ApplyTraceBasedMutation(USF.GetRand()(NumTraceBasedMutations), &U);
397 RunOneAndUpdateCorpus(U);
398 }
399 }
400 }
401 }
402
403 // Returns an index of random unit from the corpus to mutate.
404 // Hypothesis: units added to the corpus last are more likely to be interesting.
405 // This function gives more wieght to the more recent units.
ChooseUnitIdxToMutate()406 size_t Fuzzer::ChooseUnitIdxToMutate() {
407 size_t N = Corpus.size();
408 size_t Total = (N + 1) * N / 2;
409 size_t R = USF.GetRand()(Total);
410 size_t IdxBeg = 0, IdxEnd = N;
411 // Binary search.
412 while (IdxEnd - IdxBeg >= 2) {
413 size_t Idx = IdxBeg + (IdxEnd - IdxBeg) / 2;
414 if (R > (Idx + 1) * Idx / 2)
415 IdxBeg = Idx;
416 else
417 IdxEnd = Idx;
418 }
419 assert(IdxBeg < N);
420 return IdxBeg;
421 }
422
423 // Experimental search heuristic: drilling.
424 // - Read, shuffle, execute and minimize the corpus.
425 // - Choose one random unit.
426 // - Reset the coverage.
427 // - Start fuzzing as if the chosen unit was the only element of the corpus.
428 // - When done, reset the coverage again.
429 // - Merge the newly created corpus into the original one.
Drill()430 void Fuzzer::Drill() {
431 // The corpus is already read, shuffled, and minimized.
432 assert(!Corpus.empty());
433 Options.PrintNEW = false; // Don't print NEW status lines when drilling.
434
435 Unit U = ChooseUnitToMutate();
436
437 CHECK_WEAK_API_FUNCTION(__sanitizer_reset_coverage);
438 __sanitizer_reset_coverage();
439
440 std::vector<Unit> SavedCorpus;
441 SavedCorpus.swap(Corpus);
442 Corpus.push_back(U);
443 assert(Corpus.size() == 1);
444 RunOne(U);
445 PrintStats("DRILL ");
446 std::string SavedOutputCorpusPath; // Don't write new units while drilling.
447 SavedOutputCorpusPath.swap(Options.OutputCorpus);
448 Loop();
449
450 __sanitizer_reset_coverage();
451
452 PrintStats("REINIT");
453 SavedOutputCorpusPath.swap(Options.OutputCorpus);
454 for (auto &U : SavedCorpus)
455 RunOne(U);
456 PrintStats("MERGE ");
457 Options.PrintNEW = true;
458 size_t NumMerged = 0;
459 for (auto &U : Corpus) {
460 if (RunOne(U)) {
461 PrintStatusForNewUnit(U);
462 NumMerged++;
463 WriteToOutputCorpus(U);
464 }
465 }
466 PrintStats("MERGED");
467 if (NumMerged && Options.Verbosity)
468 Printf("Drilling discovered %zd new units\n", NumMerged);
469 }
470
Loop()471 void Fuzzer::Loop() {
472 system_clock::time_point LastCorpusReload = system_clock::now();
473 if (Options.DoCrossOver)
474 USF.SetCorpus(&Corpus);
475 while (true) {
476 SyncCorpus();
477 auto Now = system_clock::now();
478 if (duration_cast<seconds>(Now - LastCorpusReload).count()) {
479 RereadOutputCorpus();
480 LastCorpusReload = Now;
481 }
482 if (TotalNumberOfRuns >= Options.MaxNumberOfRuns)
483 break;
484 if (Options.MaxTotalTimeSec > 0 &&
485 secondsSinceProcessStartUp() >
486 static_cast<size_t>(Options.MaxTotalTimeSec))
487 break;
488 // Perform several mutations and runs.
489 MutateAndTestOne();
490 }
491
492 PrintStats("DONE ", "\n");
493 }
494
SyncCorpus()495 void Fuzzer::SyncCorpus() {
496 if (Options.SyncCommand.empty() || Options.OutputCorpus.empty()) return;
497 auto Now = system_clock::now();
498 if (duration_cast<seconds>(Now - LastExternalSync).count() <
499 Options.SyncTimeout)
500 return;
501 LastExternalSync = Now;
502 ExecuteCommand(Options.SyncCommand + " " + Options.OutputCorpus);
503 }
504
505 } // namespace fuzzer
506