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 boolean variable with the same linkage 14 // as the function and inject this code into the entry block (CoverageLevel=1) 15 // or all blocks (CoverageLevel>=2): 16 // if (*Guard) { 17 // __sanitizer_cov(); 18 // *Guard = 1; 19 // } 20 // The accesses to Guard are atomic. The rest of the logic is 21 // in __sanitizer_cov (it's fine to call it more than once). 22 // 23 // With CoverageLevel>=3 we also split critical edges this effectively 24 // instrumenting all edges. 25 // 26 // CoverageLevel>=4 add indirect call profiling implented as a function call. 27 // 28 // This coverage implementation provides very limited data: 29 // it only tells if a given function (block) was ever executed. No counters. 30 // But for many use cases this is what we need and the added slowdown small. 31 // 32 //===----------------------------------------------------------------------===// 33 34 #include "llvm/Transforms/Instrumentation.h" 35 #include "llvm/ADT/ArrayRef.h" 36 #include "llvm/ADT/SmallVector.h" 37 #include "llvm/IR/CallSite.h" 38 #include "llvm/IR/DataLayout.h" 39 #include "llvm/IR/Function.h" 40 #include "llvm/IR/IRBuilder.h" 41 #include "llvm/IR/LLVMContext.h" 42 #include "llvm/IR/MDBuilder.h" 43 #include "llvm/IR/Module.h" 44 #include "llvm/IR/Type.h" 45 #include "llvm/Support/CommandLine.h" 46 #include "llvm/Support/Debug.h" 47 #include "llvm/Support/raw_ostream.h" 48 #include "llvm/Transforms/Scalar.h" 49 #include "llvm/Transforms/Utils/BasicBlockUtils.h" 50 #include "llvm/Transforms/Utils/ModuleUtils.h" 51 52 using namespace llvm; 53 54 #define DEBUG_TYPE "sancov" 55 56 static const char *const kSanCovModuleInitName = "__sanitizer_cov_module_init"; 57 static const char *const kSanCovName = "__sanitizer_cov"; 58 static const char *const kSanCovIndirCallName = "__sanitizer_cov_indir_call16"; 59 static const char *const kSanCovModuleCtorName = "sancov.module_ctor"; 60 static const uint64_t kSanCtorAndDtorPriority = 1; 61 62 static cl::opt<int> ClCoverageLevel("sanitizer-coverage-level", 63 cl::desc("Sanitizer Coverage. 0: none, 1: entry block, 2: all blocks, " 64 "3: all blocks and critical edges, " 65 "4: above plus indirect calls"), 66 cl::Hidden, cl::init(0)); 67 68 static cl::opt<int> ClCoverageBlockThreshold( 69 "sanitizer-coverage-block-threshold", 70 cl::desc("Add coverage instrumentation only to the entry block if there " 71 "are more than this number of blocks."), 72 cl::Hidden, cl::init(1500)); 73 74 namespace { 75 76 class SanitizerCoverageModule : public ModulePass { 77 public: 78 SanitizerCoverageModule(int CoverageLevel = 0) 79 : ModulePass(ID), 80 CoverageLevel(std::max(CoverageLevel, (int)ClCoverageLevel)) { 81 initializeBreakCriticalEdgesPass(*PassRegistry::getPassRegistry()); 82 } 83 bool runOnModule(Module &M) override; 84 bool runOnFunction(Function &F); 85 static char ID; // Pass identification, replacement for typeid 86 const char *getPassName() const override { 87 return "SanitizerCoverageModule"; 88 } 89 90 void getAnalysisUsage(AnalysisUsage &AU) const override { 91 if (CoverageLevel >= 3) 92 AU.addRequiredID(BreakCriticalEdgesID); 93 AU.addRequired<DataLayoutPass>(); 94 } 95 96 private: 97 void InjectCoverageForIndirectCalls(Function &F, 98 ArrayRef<Instruction *> IndirCalls); 99 bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks, 100 ArrayRef<Instruction *> IndirCalls); 101 void InjectCoverageAtBlock(Function &F, BasicBlock &BB); 102 Function *SanCovFunction; 103 Function *SanCovIndirCallFunction; 104 Function *SanCovModuleInit; 105 Type *IntptrTy; 106 LLVMContext *C; 107 108 int CoverageLevel; 109 }; 110 111 } // namespace 112 113 static Function *checkInterfaceFunction(Constant *FuncOrBitcast) { 114 if (Function *F = dyn_cast<Function>(FuncOrBitcast)) 115 return F; 116 std::string Err; 117 raw_string_ostream Stream(Err); 118 Stream << "SanitizerCoverage interface function redefined: " 119 << *FuncOrBitcast; 120 report_fatal_error(Err); 121 } 122 123 bool SanitizerCoverageModule::runOnModule(Module &M) { 124 if (!CoverageLevel) return false; 125 C = &(M.getContext()); 126 DataLayoutPass *DLP = &getAnalysis<DataLayoutPass>(); 127 IntptrTy = Type::getIntNTy(*C, DLP->getDataLayout().getPointerSizeInBits()); 128 Type *VoidTy = Type::getVoidTy(*C); 129 130 Function *CtorFunc = 131 Function::Create(FunctionType::get(VoidTy, false), 132 GlobalValue::InternalLinkage, kSanCovModuleCtorName, &M); 133 ReturnInst::Create(*C, BasicBlock::Create(*C, "", CtorFunc)); 134 appendToGlobalCtors(M, CtorFunc, kSanCtorAndDtorPriority); 135 136 SanCovFunction = 137 checkInterfaceFunction(M.getOrInsertFunction(kSanCovName, VoidTy, nullptr)); 138 SanCovIndirCallFunction = checkInterfaceFunction(M.getOrInsertFunction( 139 kSanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr)); 140 SanCovModuleInit = checkInterfaceFunction(M.getOrInsertFunction( 141 kSanCovModuleInitName, Type::getVoidTy(*C), IntptrTy, nullptr)); 142 SanCovModuleInit->setLinkage(Function::ExternalLinkage); 143 144 for (auto &F : M) 145 runOnFunction(F); 146 147 IRBuilder<> IRB(CtorFunc->getEntryBlock().getTerminator()); 148 IRB.CreateCall(SanCovModuleInit, 149 ConstantInt::get(IntptrTy, SanCovFunction->getNumUses())); 150 return true; 151 } 152 153 bool SanitizerCoverageModule::runOnFunction(Function &F) { 154 if (F.empty()) return false; 155 // For now instrument only functions that will also be asan-instrumented. 156 if (!F.hasFnAttribute(Attribute::SanitizeAddress)) 157 return false; 158 SmallVector<Instruction*, 8> IndirCalls; 159 SmallVector<BasicBlock*, 16> AllBlocks; 160 for (auto &BB : F) { 161 AllBlocks.push_back(&BB); 162 if (CoverageLevel >= 4) 163 for (auto &Inst : BB) { 164 CallSite CS(&Inst); 165 if (CS && !CS.getCalledFunction()) 166 IndirCalls.push_back(&Inst); 167 } 168 } 169 InjectCoverage(F, AllBlocks, IndirCalls); 170 return true; 171 } 172 173 bool 174 SanitizerCoverageModule::InjectCoverage(Function &F, 175 ArrayRef<BasicBlock *> AllBlocks, 176 ArrayRef<Instruction *> IndirCalls) { 177 if (!CoverageLevel) return false; 178 179 if (CoverageLevel == 1 || 180 (unsigned)ClCoverageBlockThreshold < AllBlocks.size()) { 181 InjectCoverageAtBlock(F, F.getEntryBlock()); 182 } else { 183 for (auto BB : AllBlocks) 184 InjectCoverageAtBlock(F, *BB); 185 } 186 InjectCoverageForIndirectCalls(F, IndirCalls); 187 return true; 188 } 189 190 // On every indirect call we call a run-time function 191 // __sanitizer_cov_indir_call* with two parameters: 192 // - callee address, 193 // - global cache array that contains kCacheSize pointers (zero-initialized). 194 // The cache is used to speed up recording the caller-callee pairs. 195 // The address of the caller is passed implicitly via caller PC. 196 // kCacheSize is encoded in the name of the run-time function. 197 void SanitizerCoverageModule::InjectCoverageForIndirectCalls( 198 Function &F, ArrayRef<Instruction *> IndirCalls) { 199 if (IndirCalls.empty()) return; 200 const int kCacheSize = 16; 201 const int kCacheAlignment = 64; // Align for better performance. 202 Type *Ty = ArrayType::get(IntptrTy, kCacheSize); 203 for (auto I : IndirCalls) { 204 IRBuilder<> IRB(I); 205 CallSite CS(I); 206 Value *Callee = CS.getCalledValue(); 207 if (dyn_cast<InlineAsm>(Callee)) continue; 208 GlobalVariable *CalleeCache = new GlobalVariable( 209 *F.getParent(), Ty, false, GlobalValue::PrivateLinkage, 210 Constant::getNullValue(Ty), "__sancov_gen_callee_cache"); 211 CalleeCache->setAlignment(kCacheAlignment); 212 IRB.CreateCall2(SanCovIndirCallFunction, 213 IRB.CreatePointerCast(Callee, IntptrTy), 214 IRB.CreatePointerCast(CalleeCache, IntptrTy)); 215 } 216 } 217 218 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, 219 BasicBlock &BB) { 220 BasicBlock::iterator IP = BB.getFirstInsertionPt(), BE = BB.end(); 221 // Skip static allocas at the top of the entry block so they don't become 222 // dynamic when we split the block. If we used our optimized stack layout, 223 // then there will only be one alloca and it will come first. 224 for (; IP != BE; ++IP) { 225 AllocaInst *AI = dyn_cast<AllocaInst>(IP); 226 if (!AI || !AI->isStaticAlloca()) 227 break; 228 } 229 230 DebugLoc EntryLoc = &BB == &F.getEntryBlock() 231 ? IP->getDebugLoc().getFnDebugLoc(*C) 232 : IP->getDebugLoc(); 233 IRBuilder<> IRB(IP); 234 IRB.SetCurrentDebugLocation(EntryLoc); 235 Type *Int8Ty = IRB.getInt8Ty(); 236 GlobalVariable *Guard = new GlobalVariable( 237 *F.getParent(), Int8Ty, false, GlobalValue::PrivateLinkage, 238 Constant::getNullValue(Int8Ty), "__sancov_gen_cov_" + F.getName()); 239 LoadInst *Load = IRB.CreateLoad(Guard); 240 Load->setAtomic(Monotonic); 241 Load->setAlignment(1); 242 Value *Cmp = IRB.CreateICmpEQ(Constant::getNullValue(Int8Ty), Load); 243 Instruction *Ins = SplitBlockAndInsertIfThen( 244 Cmp, IP, false, MDBuilder(*C).createBranchWeights(1, 100000)); 245 IRB.SetInsertPoint(Ins); 246 IRB.SetCurrentDebugLocation(EntryLoc); 247 // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC. 248 IRB.CreateCall(SanCovFunction); 249 StoreInst *Store = IRB.CreateStore(ConstantInt::get(Int8Ty, 1), Guard); 250 Store->setAtomic(Monotonic); 251 Store->setAlignment(1); 252 } 253 254 char SanitizerCoverageModule::ID = 0; 255 INITIALIZE_PASS(SanitizerCoverageModule, "sancov", 256 "SanitizerCoverage: TODO." 257 "ModulePass", false, false) 258 ModulePass *llvm::createSanitizerCoverageModulePass(int CoverageLevel) { 259 return new SanitizerCoverageModule(CoverageLevel); 260 } 261