1 //===-- SanitizerCoverage.cpp - coverage instrumentation for sanitizers ---===// 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 // 10 // Coverage instrumentation that works with AddressSanitizer 11 // and potentially with other Sanitizers. 12 // 13 // We create a Guard variable with the same linkage 14 // as the function and inject this code into the entry block (SCK_Function) 15 // or all blocks (SCK_BB): 16 // if (Guard < 0) { 17 // __sanitizer_cov(&Guard); 18 // } 19 // The accesses to Guard are atomic. The rest of the logic is 20 // in __sanitizer_cov (it's fine to call it more than once). 21 // 22 // With SCK_Edge we also split critical edges this effectively 23 // instrumenting all edges. 24 // 25 // This coverage implementation provides very limited data: 26 // it only tells if a given function (block) was ever executed. No counters. 27 // But for many use cases this is what we need and the added slowdown small. 28 // 29 //===----------------------------------------------------------------------===// 30 31 #include "llvm/Transforms/Instrumentation.h" 32 #include "llvm/ADT/ArrayRef.h" 33 #include "llvm/ADT/SmallVector.h" 34 #include "llvm/IR/CallSite.h" 35 #include "llvm/IR/DataLayout.h" 36 #include "llvm/IR/Function.h" 37 #include "llvm/IR/IRBuilder.h" 38 #include "llvm/IR/InlineAsm.h" 39 #include "llvm/IR/LLVMContext.h" 40 #include "llvm/IR/MDBuilder.h" 41 #include "llvm/IR/Module.h" 42 #include "llvm/IR/Type.h" 43 #include "llvm/Support/CommandLine.h" 44 #include "llvm/Support/Debug.h" 45 #include "llvm/Support/raw_ostream.h" 46 #include "llvm/Transforms/Scalar.h" 47 #include "llvm/Transforms/Utils/BasicBlockUtils.h" 48 #include "llvm/Transforms/Utils/ModuleUtils.h" 49 50 using namespace llvm; 51 52 #define DEBUG_TYPE "sancov" 53 54 static const char *const kSanCovModuleInitName = "__sanitizer_cov_module_init"; 55 static const char *const kSanCovName = "__sanitizer_cov"; 56 static const char *const kSanCovWithCheckName = "__sanitizer_cov_with_check"; 57 static const char *const kSanCovIndirCallName = "__sanitizer_cov_indir_call16"; 58 static const char *const kSanCovTraceEnter = "__sanitizer_cov_trace_func_enter"; 59 static const char *const kSanCovTraceBB = "__sanitizer_cov_trace_basic_block"; 60 static const char *const kSanCovTraceCmp = "__sanitizer_cov_trace_cmp"; 61 static const char *const kSanCovModuleCtorName = "sancov.module_ctor"; 62 static const uint64_t kSanCtorAndDtorPriority = 2; 63 64 static cl::opt<int> ClCoverageLevel("sanitizer-coverage-level", 65 cl::desc("Sanitizer Coverage. 0: none, 1: entry block, 2: all blocks, " 66 "3: all blocks and critical edges, " 67 "4: above plus indirect calls"), 68 cl::Hidden, cl::init(0)); 69 70 static cl::opt<unsigned> ClCoverageBlockThreshold( 71 "sanitizer-coverage-block-threshold", 72 cl::desc("Use a callback with a guard check inside it if there are" 73 " more than this number of blocks."), 74 cl::Hidden, cl::init(500)); 75 76 static cl::opt<bool> 77 ClExperimentalTracing("sanitizer-coverage-experimental-tracing", 78 cl::desc("Experimental basic-block tracing: insert " 79 "callbacks at every basic block"), 80 cl::Hidden, cl::init(false)); 81 82 static cl::opt<bool> 83 ClExperimentalCMPTracing("sanitizer-coverage-experimental-trace-compares", 84 cl::desc("Experimental tracing of CMP and similar " 85 "instructions"), 86 cl::Hidden, cl::init(false)); 87 88 // Experimental 8-bit counters used as an additional search heuristic during 89 // coverage-guided fuzzing. 90 // The counters are not thread-friendly: 91 // - contention on these counters may cause significant slowdown; 92 // - the counter updates are racy and the results may be inaccurate. 93 // They are also inaccurate due to 8-bit integer overflow. 94 static cl::opt<bool> ClUse8bitCounters("sanitizer-coverage-8bit-counters", 95 cl::desc("Experimental 8-bit counters"), 96 cl::Hidden, cl::init(false)); 97 98 namespace { 99 100 SanitizerCoverageOptions getOptions(int LegacyCoverageLevel) { 101 SanitizerCoverageOptions Res; 102 switch (LegacyCoverageLevel) { 103 case 0: 104 Res.CoverageType = SanitizerCoverageOptions::SCK_None; 105 break; 106 case 1: 107 Res.CoverageType = SanitizerCoverageOptions::SCK_Function; 108 break; 109 case 2: 110 Res.CoverageType = SanitizerCoverageOptions::SCK_BB; 111 break; 112 case 3: 113 Res.CoverageType = SanitizerCoverageOptions::SCK_Edge; 114 break; 115 case 4: 116 Res.CoverageType = SanitizerCoverageOptions::SCK_Edge; 117 Res.IndirectCalls = true; 118 break; 119 } 120 return Res; 121 } 122 123 SanitizerCoverageOptions OverrideFromCL(SanitizerCoverageOptions Options) { 124 // Sets CoverageType and IndirectCalls. 125 SanitizerCoverageOptions CLOpts = getOptions(ClCoverageLevel); 126 Options.CoverageType = std::max(Options.CoverageType, CLOpts.CoverageType); 127 Options.IndirectCalls |= CLOpts.IndirectCalls; 128 Options.TraceBB |= ClExperimentalTracing; 129 Options.TraceCmp |= ClExperimentalCMPTracing; 130 Options.Use8bitCounters |= ClUse8bitCounters; 131 return Options; 132 } 133 134 class SanitizerCoverageModule : public ModulePass { 135 public: 136 SanitizerCoverageModule( 137 const SanitizerCoverageOptions &Options = SanitizerCoverageOptions()) 138 : ModulePass(ID), Options(OverrideFromCL(Options)) {} 139 bool runOnModule(Module &M) override; 140 bool runOnFunction(Function &F); 141 static char ID; // Pass identification, replacement for typeid 142 const char *getPassName() const override { 143 return "SanitizerCoverageModule"; 144 } 145 146 private: 147 void InjectCoverageForIndirectCalls(Function &F, 148 ArrayRef<Instruction *> IndirCalls); 149 void InjectTraceForCmp(Function &F, ArrayRef<Instruction *> CmpTraceTargets); 150 bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks); 151 void SetNoSanitizeMetadata(Instruction *I); 152 void InjectCoverageAtBlock(Function &F, BasicBlock &BB, bool UseCalls); 153 unsigned NumberOfInstrumentedBlocks() { 154 return SanCovFunction->getNumUses() + SanCovWithCheckFunction->getNumUses(); 155 } 156 Function *SanCovFunction; 157 Function *SanCovWithCheckFunction; 158 Function *SanCovIndirCallFunction; 159 Function *SanCovModuleInit; 160 Function *SanCovTraceEnter, *SanCovTraceBB; 161 Function *SanCovTraceCmpFunction; 162 InlineAsm *EmptyAsm; 163 Type *IntptrTy, *Int64Ty; 164 LLVMContext *C; 165 const DataLayout *DL; 166 167 GlobalVariable *GuardArray; 168 GlobalVariable *EightBitCounterArray; 169 170 SanitizerCoverageOptions Options; 171 }; 172 173 } // namespace 174 175 bool SanitizerCoverageModule::runOnModule(Module &M) { 176 if (Options.CoverageType == SanitizerCoverageOptions::SCK_None) 177 return false; 178 C = &(M.getContext()); 179 DL = &M.getDataLayout(); 180 IntptrTy = Type::getIntNTy(*C, DL->getPointerSizeInBits()); 181 Type *VoidTy = Type::getVoidTy(*C); 182 IRBuilder<> IRB(*C); 183 Type *Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty()); 184 Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty()); 185 Int64Ty = IRB.getInt64Ty(); 186 187 Function *CtorFunc = 188 Function::Create(FunctionType::get(VoidTy, false), 189 GlobalValue::InternalLinkage, kSanCovModuleCtorName, &M); 190 ReturnInst::Create(*C, BasicBlock::Create(*C, "", CtorFunc)); 191 appendToGlobalCtors(M, CtorFunc, kSanCtorAndDtorPriority); 192 193 SanCovFunction = checkSanitizerInterfaceFunction( 194 M.getOrInsertFunction(kSanCovName, VoidTy, Int32PtrTy, nullptr)); 195 SanCovWithCheckFunction = checkSanitizerInterfaceFunction( 196 M.getOrInsertFunction(kSanCovWithCheckName, VoidTy, Int32PtrTy, nullptr)); 197 SanCovIndirCallFunction = 198 checkSanitizerInterfaceFunction(M.getOrInsertFunction( 199 kSanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr)); 200 SanCovTraceCmpFunction = 201 checkSanitizerInterfaceFunction(M.getOrInsertFunction( 202 kSanCovTraceCmp, VoidTy, Int64Ty, Int64Ty, Int64Ty, nullptr)); 203 204 SanCovModuleInit = checkSanitizerInterfaceFunction(M.getOrInsertFunction( 205 kSanCovModuleInitName, VoidTy, Int32PtrTy, IntptrTy, 206 Int8PtrTy, Int8PtrTy, nullptr)); 207 SanCovModuleInit->setLinkage(Function::ExternalLinkage); 208 // We insert an empty inline asm after cov callbacks to avoid callback merge. 209 EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false), 210 StringRef(""), StringRef(""), 211 /*hasSideEffects=*/true); 212 213 if (Options.TraceBB) { 214 SanCovTraceEnter = checkSanitizerInterfaceFunction( 215 M.getOrInsertFunction(kSanCovTraceEnter, VoidTy, Int32PtrTy, nullptr)); 216 SanCovTraceBB = checkSanitizerInterfaceFunction( 217 M.getOrInsertFunction(kSanCovTraceBB, VoidTy, Int32PtrTy, nullptr)); 218 } 219 220 // At this point we create a dummy array of guards because we don't 221 // know how many elements we will need. 222 Type *Int32Ty = IRB.getInt32Ty(); 223 Type *Int8Ty = IRB.getInt8Ty(); 224 225 GuardArray = 226 new GlobalVariable(M, Int32Ty, false, GlobalValue::ExternalLinkage, 227 nullptr, "__sancov_gen_cov_tmp"); 228 if (Options.Use8bitCounters) 229 EightBitCounterArray = 230 new GlobalVariable(M, Int8Ty, false, GlobalVariable::ExternalLinkage, 231 nullptr, "__sancov_gen_cov_tmp"); 232 233 for (auto &F : M) 234 runOnFunction(F); 235 236 auto N = NumberOfInstrumentedBlocks(); 237 238 // Now we know how many elements we need. Create an array of guards 239 // with one extra element at the beginning for the size. 240 Type *Int32ArrayNTy = ArrayType::get(Int32Ty, N + 1); 241 GlobalVariable *RealGuardArray = new GlobalVariable( 242 M, Int32ArrayNTy, false, GlobalValue::PrivateLinkage, 243 Constant::getNullValue(Int32ArrayNTy), "__sancov_gen_cov"); 244 245 246 // Replace the dummy array with the real one. 247 GuardArray->replaceAllUsesWith( 248 IRB.CreatePointerCast(RealGuardArray, Int32PtrTy)); 249 GuardArray->eraseFromParent(); 250 251 GlobalVariable *RealEightBitCounterArray; 252 if (Options.Use8bitCounters) { 253 // Make sure the array is 16-aligned. 254 static const int kCounterAlignment = 16; 255 Type *Int8ArrayNTy = 256 ArrayType::get(Int8Ty, RoundUpToAlignment(N, kCounterAlignment)); 257 RealEightBitCounterArray = new GlobalVariable( 258 M, Int8ArrayNTy, false, GlobalValue::PrivateLinkage, 259 Constant::getNullValue(Int8ArrayNTy), "__sancov_gen_cov_counter"); 260 RealEightBitCounterArray->setAlignment(kCounterAlignment); 261 EightBitCounterArray->replaceAllUsesWith( 262 IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy)); 263 EightBitCounterArray->eraseFromParent(); 264 } 265 266 // Create variable for module (compilation unit) name 267 Constant *ModNameStrConst = 268 ConstantDataArray::getString(M.getContext(), M.getName(), true); 269 GlobalVariable *ModuleName = 270 new GlobalVariable(M, ModNameStrConst->getType(), true, 271 GlobalValue::PrivateLinkage, ModNameStrConst); 272 273 // Call __sanitizer_cov_module_init 274 IRB.SetInsertPoint(CtorFunc->getEntryBlock().getTerminator()); 275 IRB.CreateCall4( 276 SanCovModuleInit, IRB.CreatePointerCast(RealGuardArray, Int32PtrTy), 277 ConstantInt::get(IntptrTy, N), 278 Options.Use8bitCounters 279 ? IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy) 280 : Constant::getNullValue(Int8PtrTy), 281 IRB.CreatePointerCast(ModuleName, Int8PtrTy)); 282 return true; 283 } 284 285 bool SanitizerCoverageModule::runOnFunction(Function &F) { 286 if (F.empty()) return false; 287 if (F.getName().find(".module_ctor") != std::string::npos) 288 return false; // Should not instrument sanitizer init functions. 289 if (Options.CoverageType >= SanitizerCoverageOptions::SCK_Edge) 290 SplitAllCriticalEdges(F); 291 SmallVector<Instruction*, 8> IndirCalls; 292 SmallVector<BasicBlock*, 16> AllBlocks; 293 SmallVector<Instruction*, 8> CmpTraceTargets; 294 for (auto &BB : F) { 295 AllBlocks.push_back(&BB); 296 for (auto &Inst : BB) { 297 if (Options.IndirectCalls) { 298 CallSite CS(&Inst); 299 if (CS && !CS.getCalledFunction()) 300 IndirCalls.push_back(&Inst); 301 } 302 if (Options.TraceCmp && isa<ICmpInst>(&Inst)) 303 CmpTraceTargets.push_back(&Inst); 304 } 305 } 306 InjectCoverage(F, AllBlocks); 307 InjectCoverageForIndirectCalls(F, IndirCalls); 308 InjectTraceForCmp(F, CmpTraceTargets); 309 return true; 310 } 311 312 bool SanitizerCoverageModule::InjectCoverage(Function &F, 313 ArrayRef<BasicBlock *> AllBlocks) { 314 switch (Options.CoverageType) { 315 case SanitizerCoverageOptions::SCK_None: 316 return false; 317 case SanitizerCoverageOptions::SCK_Function: 318 InjectCoverageAtBlock(F, F.getEntryBlock(), false); 319 return true; 320 default: { 321 bool UseCalls = ClCoverageBlockThreshold < AllBlocks.size(); 322 for (auto BB : AllBlocks) 323 InjectCoverageAtBlock(F, *BB, UseCalls); 324 return true; 325 } 326 } 327 } 328 329 // On every indirect call we call a run-time function 330 // __sanitizer_cov_indir_call* with two parameters: 331 // - callee address, 332 // - global cache array that contains kCacheSize pointers (zero-initialized). 333 // The cache is used to speed up recording the caller-callee pairs. 334 // The address of the caller is passed implicitly via caller PC. 335 // kCacheSize is encoded in the name of the run-time function. 336 void SanitizerCoverageModule::InjectCoverageForIndirectCalls( 337 Function &F, ArrayRef<Instruction *> IndirCalls) { 338 if (IndirCalls.empty()) return; 339 const int kCacheSize = 16; 340 const int kCacheAlignment = 64; // Align for better performance. 341 Type *Ty = ArrayType::get(IntptrTy, kCacheSize); 342 for (auto I : IndirCalls) { 343 IRBuilder<> IRB(I); 344 CallSite CS(I); 345 Value *Callee = CS.getCalledValue(); 346 if (isa<InlineAsm>(Callee)) continue; 347 GlobalVariable *CalleeCache = new GlobalVariable( 348 *F.getParent(), Ty, false, GlobalValue::PrivateLinkage, 349 Constant::getNullValue(Ty), "__sancov_gen_callee_cache"); 350 CalleeCache->setAlignment(kCacheAlignment); 351 IRB.CreateCall2(SanCovIndirCallFunction, 352 IRB.CreatePointerCast(Callee, IntptrTy), 353 IRB.CreatePointerCast(CalleeCache, IntptrTy)); 354 } 355 } 356 357 void SanitizerCoverageModule::InjectTraceForCmp( 358 Function &F, ArrayRef<Instruction *> CmpTraceTargets) { 359 for (auto I : CmpTraceTargets) { 360 if (ICmpInst *ICMP = dyn_cast<ICmpInst>(I)) { 361 IRBuilder<> IRB(ICMP); 362 Value *A0 = ICMP->getOperand(0); 363 Value *A1 = ICMP->getOperand(1); 364 if (!A0->getType()->isIntegerTy()) continue; 365 uint64_t TypeSize = DL->getTypeStoreSizeInBits(A0->getType()); 366 // __sanitizer_cov_trace_cmp((type_size << 32) | predicate, A0, A1); 367 IRB.CreateCall3( 368 SanCovTraceCmpFunction, 369 ConstantInt::get(Int64Ty, (TypeSize << 32) | ICMP->getPredicate()), 370 IRB.CreateIntCast(A0, Int64Ty, true), 371 IRB.CreateIntCast(A1, Int64Ty, true)); 372 } 373 } 374 } 375 376 void SanitizerCoverageModule::SetNoSanitizeMetadata(Instruction *I) { 377 I->setMetadata( 378 I->getParent()->getParent()->getParent()->getMDKindID("nosanitize"), 379 MDNode::get(*C, None)); 380 } 381 382 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB, 383 bool UseCalls) { 384 BasicBlock::iterator IP = BB.getFirstInsertionPt(), BE = BB.end(); 385 // Skip static allocas at the top of the entry block so they don't become 386 // dynamic when we split the block. If we used our optimized stack layout, 387 // then there will only be one alloca and it will come first. 388 for (; IP != BE; ++IP) { 389 AllocaInst *AI = dyn_cast<AllocaInst>(IP); 390 if (!AI || !AI->isStaticAlloca()) 391 break; 392 } 393 394 bool IsEntryBB = &BB == &F.getEntryBlock(); 395 DebugLoc EntryLoc = IsEntryBB && IP->getDebugLoc() 396 ? IP->getDebugLoc().getFnDebugLoc() 397 : IP->getDebugLoc(); 398 IRBuilder<> IRB(IP); 399 IRB.SetCurrentDebugLocation(EntryLoc); 400 SmallVector<Value *, 1> Indices; 401 Value *GuardP = IRB.CreateAdd( 402 IRB.CreatePointerCast(GuardArray, IntptrTy), 403 ConstantInt::get(IntptrTy, (1 + NumberOfInstrumentedBlocks()) * 4)); 404 Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty()); 405 GuardP = IRB.CreateIntToPtr(GuardP, Int32PtrTy); 406 if (UseCalls) { 407 IRB.CreateCall(SanCovWithCheckFunction, GuardP); 408 } else { 409 LoadInst *Load = IRB.CreateLoad(GuardP); 410 Load->setAtomic(Monotonic); 411 Load->setAlignment(4); 412 SetNoSanitizeMetadata(Load); 413 Value *Cmp = IRB.CreateICmpSGE(Constant::getNullValue(Load->getType()), Load); 414 Instruction *Ins = SplitBlockAndInsertIfThen( 415 Cmp, IP, false, MDBuilder(*C).createBranchWeights(1, 100000)); 416 IRB.SetInsertPoint(Ins); 417 IRB.SetCurrentDebugLocation(EntryLoc); 418 // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC. 419 IRB.CreateCall(SanCovFunction, GuardP); 420 IRB.CreateCall(EmptyAsm); // Avoids callback merge. 421 } 422 423 if (Options.Use8bitCounters) { 424 IRB.SetInsertPoint(IP); 425 Value *P = IRB.CreateAdd( 426 IRB.CreatePointerCast(EightBitCounterArray, IntptrTy), 427 ConstantInt::get(IntptrTy, NumberOfInstrumentedBlocks() - 1)); 428 P = IRB.CreateIntToPtr(P, IRB.getInt8PtrTy()); 429 LoadInst *LI = IRB.CreateLoad(P); 430 Value *Inc = IRB.CreateAdd(LI, ConstantInt::get(IRB.getInt8Ty(), 1)); 431 StoreInst *SI = IRB.CreateStore(Inc, P); 432 SetNoSanitizeMetadata(LI); 433 SetNoSanitizeMetadata(SI); 434 } 435 436 if (Options.TraceBB) { 437 // Experimental support for tracing. 438 // Insert a callback with the same guard variable as used for coverage. 439 IRB.SetInsertPoint(IP); 440 IRB.CreateCall(IsEntryBB ? SanCovTraceEnter : SanCovTraceBB, GuardP); 441 } 442 } 443 444 char SanitizerCoverageModule::ID = 0; 445 INITIALIZE_PASS(SanitizerCoverageModule, "sancov", 446 "SanitizerCoverage: TODO." 447 "ModulePass", false, false) 448 ModulePass *llvm::createSanitizerCoverageModulePass( 449 const SanitizerCoverageOptions &Options) { 450 return new SanitizerCoverageModule(Options); 451 } 452