1 //===- FuzzerDataFlowTrace.cpp - DataFlowTrace ---*- C++ -* ===// 2 // 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 6 // 7 //===----------------------------------------------------------------------===// 8 // fuzzer::DataFlowTrace 9 //===----------------------------------------------------------------------===// 10 11 #include "FuzzerDataFlowTrace.h" 12 13 #include "FuzzerCommand.h" 14 #include "FuzzerIO.h" 15 #include "FuzzerRandom.h" 16 #include "FuzzerSHA1.h" 17 #include "FuzzerUtil.h" 18 19 #include <cstdlib> 20 #include <fstream> 21 #include <numeric> 22 #include <queue> 23 #include <sstream> 24 #include <string> 25 #include <unordered_map> 26 #include <unordered_set> 27 #include <vector> 28 29 namespace fuzzer { 30 static const char *kFunctionsTxt = "functions.txt"; 31 32 bool BlockCoverage::AppendCoverage(const std::string &S) { 33 std::stringstream SS(S); 34 return AppendCoverage(SS); 35 } 36 37 // Coverage lines have this form: 38 // CN X Y Z T 39 // where N is the number of the function, T is the total number of instrumented 40 // BBs, and X,Y,Z, if present, are the indecies of covered BB. 41 // BB #0, which is the entry block, is not explicitly listed. 42 bool BlockCoverage::AppendCoverage(std::istream &IN) { 43 std::string L; 44 while (std::getline(IN, L, '\n')) { 45 if (L.empty()) 46 continue; 47 std::stringstream SS(L.c_str() + 1); 48 size_t FunctionId = 0; 49 SS >> FunctionId; 50 if (L[0] == 'F') { 51 FunctionsWithDFT.insert(FunctionId); 52 continue; 53 } 54 if (L[0] != 'C') continue; 55 Vector<uint32_t> CoveredBlocks; 56 while (true) { 57 uint32_t BB = 0; 58 SS >> BB; 59 if (!SS) break; 60 CoveredBlocks.push_back(BB); 61 } 62 if (CoveredBlocks.empty()) return false; 63 uint32_t NumBlocks = CoveredBlocks.back(); 64 CoveredBlocks.pop_back(); 65 for (auto BB : CoveredBlocks) 66 if (BB >= NumBlocks) return false; 67 auto It = Functions.find(FunctionId); 68 auto &Counters = 69 It == Functions.end() 70 ? Functions.insert({FunctionId, Vector<uint32_t>(NumBlocks)}) 71 .first->second 72 : It->second; 73 74 if (Counters.size() != NumBlocks) return false; // wrong number of blocks. 75 76 Counters[0]++; 77 for (auto BB : CoveredBlocks) 78 Counters[BB]++; 79 } 80 return true; 81 } 82 83 // Assign weights to each function. 84 // General principles: 85 // * any uncovered function gets weight 0. 86 // * a function with lots of uncovered blocks gets bigger weight. 87 // * a function with a less frequently executed code gets bigger weight. 88 Vector<double> BlockCoverage::FunctionWeights(size_t NumFunctions) const { 89 Vector<double> Res(NumFunctions); 90 for (auto It : Functions) { 91 auto FunctionID = It.first; 92 auto Counters = It.second; 93 assert(FunctionID < NumFunctions); 94 auto &Weight = Res[FunctionID]; 95 // Give higher weight if the function has a DFT. 96 Weight = FunctionsWithDFT.count(FunctionID) ? 1000. : 1; 97 // Give higher weight to functions with less frequently seen basic blocks. 98 Weight /= SmallestNonZeroCounter(Counters); 99 // Give higher weight to functions with the most uncovered basic blocks. 100 Weight *= NumberOfUncoveredBlocks(Counters) + 1; 101 } 102 return Res; 103 } 104 105 void DataFlowTrace::ReadCoverage(const std::string &DirPath) { 106 Vector<SizedFile> Files; 107 GetSizedFilesFromDir(DirPath, &Files); 108 for (auto &SF : Files) { 109 auto Name = Basename(SF.File); 110 if (Name == kFunctionsTxt) continue; 111 if (!CorporaHashes.count(Name)) continue; 112 std::ifstream IF(SF.File); 113 Coverage.AppendCoverage(IF); 114 } 115 } 116 117 static void DFTStringAppendToVector(Vector<uint8_t> *DFT, 118 const std::string &DFTString) { 119 assert(DFT->size() == DFTString.size()); 120 for (size_t I = 0, Len = DFT->size(); I < Len; I++) 121 (*DFT)[I] = DFTString[I] == '1'; 122 } 123 124 // converts a string of '0' and '1' into a Vector<uint8_t> 125 static Vector<uint8_t> DFTStringToVector(const std::string &DFTString) { 126 Vector<uint8_t> DFT(DFTString.size()); 127 DFTStringAppendToVector(&DFT, DFTString); 128 return DFT; 129 } 130 131 static bool ParseError(const char *Err, const std::string &Line) { 132 Printf("DataFlowTrace: parse error: %s: Line: %s\n", Err, Line.c_str()); 133 return false; 134 } 135 136 // TODO(metzman): replace std::string with std::string_view for 137 // better performance. Need to figure our how to use string_view on Windows. 138 static bool ParseDFTLine(const std::string &Line, size_t *FunctionNum, 139 std::string *DFTString) { 140 if (!Line.empty() && Line[0] != 'F') 141 return false; // Ignore coverage. 142 size_t SpacePos = Line.find(' '); 143 if (SpacePos == std::string::npos) 144 return ParseError("no space in the trace line", Line); 145 if (Line.empty() || Line[0] != 'F') 146 return ParseError("the trace line doesn't start with 'F'", Line); 147 *FunctionNum = std::atol(Line.c_str() + 1); 148 const char *Beg = Line.c_str() + SpacePos + 1; 149 const char *End = Line.c_str() + Line.size(); 150 assert(Beg < End); 151 size_t Len = End - Beg; 152 for (size_t I = 0; I < Len; I++) { 153 if (Beg[I] != '0' && Beg[I] != '1') 154 return ParseError("the trace should contain only 0 or 1", Line); 155 } 156 *DFTString = Beg; 157 return true; 158 } 159 160 bool DataFlowTrace::Init(const std::string &DirPath, std::string *FocusFunction, 161 Vector<SizedFile> &CorporaFiles, Random &Rand) { 162 if (DirPath.empty()) return false; 163 Printf("INFO: DataFlowTrace: reading from '%s'\n", DirPath.c_str()); 164 Vector<SizedFile> Files; 165 GetSizedFilesFromDir(DirPath, &Files); 166 std::string L; 167 size_t FocusFuncIdx = SIZE_MAX; 168 Vector<std::string> FunctionNames; 169 170 // Collect the hashes of the corpus files. 171 for (auto &SF : CorporaFiles) 172 CorporaHashes.insert(Hash(FileToVector(SF.File))); 173 174 // Read functions.txt 175 std::ifstream IF(DirPlusFile(DirPath, kFunctionsTxt)); 176 size_t NumFunctions = 0; 177 while (std::getline(IF, L, '\n')) { 178 FunctionNames.push_back(L); 179 NumFunctions++; 180 if (*FocusFunction == L) 181 FocusFuncIdx = NumFunctions - 1; 182 } 183 if (!NumFunctions) 184 return false; 185 186 if (*FocusFunction == "auto") { 187 // AUTOFOCUS works like this: 188 // * reads the coverage data from the DFT files. 189 // * assigns weights to functions based on coverage. 190 // * chooses a random function according to the weights. 191 ReadCoverage(DirPath); 192 auto Weights = Coverage.FunctionWeights(NumFunctions); 193 Vector<double> Intervals(NumFunctions + 1); 194 std::iota(Intervals.begin(), Intervals.end(), 0); 195 auto Distribution = std::piecewise_constant_distribution<double>( 196 Intervals.begin(), Intervals.end(), Weights.begin()); 197 FocusFuncIdx = static_cast<size_t>(Distribution(Rand)); 198 *FocusFunction = FunctionNames[FocusFuncIdx]; 199 assert(FocusFuncIdx < NumFunctions); 200 Printf("INFO: AUTOFOCUS: %zd %s\n", FocusFuncIdx, 201 FunctionNames[FocusFuncIdx].c_str()); 202 for (size_t i = 0; i < NumFunctions; i++) { 203 if (!Weights[i]) continue; 204 Printf(" [%zd] W %g\tBB-tot %u\tBB-cov %u\tEntryFreq %u:\t%s\n", i, 205 Weights[i], Coverage.GetNumberOfBlocks(i), 206 Coverage.GetNumberOfCoveredBlocks(i), Coverage.GetCounter(i, 0), 207 FunctionNames[i].c_str()); 208 } 209 } 210 211 if (!NumFunctions || FocusFuncIdx == SIZE_MAX || Files.size() <= 1) 212 return false; 213 214 // Read traces. 215 size_t NumTraceFiles = 0; 216 size_t NumTracesWithFocusFunction = 0; 217 for (auto &SF : Files) { 218 auto Name = Basename(SF.File); 219 if (Name == kFunctionsTxt) continue; 220 if (!CorporaHashes.count(Name)) continue; // not in the corpus. 221 NumTraceFiles++; 222 // Printf("=== %s\n", Name.c_str()); 223 std::ifstream IF(SF.File); 224 while (std::getline(IF, L, '\n')) { 225 size_t FunctionNum = 0; 226 std::string DFTString; 227 if (ParseDFTLine(L, &FunctionNum, &DFTString) && 228 FunctionNum == FocusFuncIdx) { 229 NumTracesWithFocusFunction++; 230 231 if (FunctionNum >= NumFunctions) 232 return ParseError("N is greater than the number of functions", L); 233 Traces[Name] = DFTStringToVector(DFTString); 234 // Print just a few small traces. 235 if (NumTracesWithFocusFunction <= 3 && DFTString.size() <= 16) 236 Printf("%s => |%s|\n", Name.c_str(), std::string(DFTString).c_str()); 237 break; // No need to parse the following lines. 238 } 239 } 240 } 241 Printf("INFO: DataFlowTrace: %zd trace files, %zd functions, " 242 "%zd traces with focus function\n", 243 NumTraceFiles, NumFunctions, NumTracesWithFocusFunction); 244 return NumTraceFiles > 0; 245 } 246 247 int CollectDataFlow(const std::string &DFTBinary, const std::string &DirPath, 248 const Vector<SizedFile> &CorporaFiles) { 249 Printf("INFO: collecting data flow: bin: %s dir: %s files: %zd\n", 250 DFTBinary.c_str(), DirPath.c_str(), CorporaFiles.size()); 251 if (CorporaFiles.empty()) { 252 Printf("ERROR: can't collect data flow without corpus provided."); 253 return 1; 254 } 255 256 static char DFSanEnv[] = "DFSAN_OPTIONS=fast16labels=1:warn_unimplemented=0"; 257 putenv(DFSanEnv); 258 MkDir(DirPath); 259 for (auto &F : CorporaFiles) { 260 // For every input F we need to collect the data flow and the coverage. 261 // Data flow collection may fail if we request too many DFSan tags at once. 262 // So, we start from requesting all tags in range [0,Size) and if that fails 263 // we then request tags in [0,Size/2) and [Size/2, Size), and so on. 264 // Function number => DFT. 265 auto OutPath = DirPlusFile(DirPath, Hash(FileToVector(F.File))); 266 std::unordered_map<size_t, Vector<uint8_t>> DFTMap; 267 std::unordered_set<std::string> Cov; 268 Command Cmd; 269 Cmd.addArgument(DFTBinary); 270 Cmd.addArgument(F.File); 271 Cmd.addArgument(OutPath); 272 Printf("CMD: %s\n", Cmd.toString().c_str()); 273 ExecuteCommand(Cmd); 274 } 275 // Write functions.txt if it's currently empty or doesn't exist. 276 auto FunctionsTxtPath = DirPlusFile(DirPath, kFunctionsTxt); 277 if (FileToString(FunctionsTxtPath).empty()) { 278 Command Cmd; 279 Cmd.addArgument(DFTBinary); 280 Cmd.setOutputFile(FunctionsTxtPath); 281 ExecuteCommand(Cmd); 282 } 283 return 0; 284 } 285 286 } // namespace fuzzer 287