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(&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 CoverageLevel>=3 we also split critical edges this effectively 23 // instrumenting all edges. 24 // 25 // CoverageLevel>=4 add indirect call profiling implented as a function call. 26 // 27 // This coverage implementation provides very limited data: 28 // it only tells if a given function (block) was ever executed. No counters. 29 // But for many use cases this is what we need and the added slowdown small. 30 // 31 //===----------------------------------------------------------------------===// 32 33 #include "llvm/Transforms/Instrumentation.h" 34 #include "llvm/ADT/ArrayRef.h" 35 #include "llvm/ADT/SmallVector.h" 36 #include "llvm/IR/CallSite.h" 37 #include "llvm/IR/DataLayout.h" 38 #include "llvm/IR/Function.h" 39 #include "llvm/IR/IRBuilder.h" 40 #include "llvm/IR/LLVMContext.h" 41 #include "llvm/IR/MDBuilder.h" 42 #include "llvm/IR/Module.h" 43 #include "llvm/IR/Type.h" 44 #include "llvm/Support/CommandLine.h" 45 #include "llvm/Support/Debug.h" 46 #include "llvm/Support/raw_ostream.h" 47 #include "llvm/Transforms/Scalar.h" 48 #include "llvm/Transforms/Utils/BasicBlockUtils.h" 49 #include "llvm/Transforms/Utils/ModuleUtils.h" 50 51 using namespace llvm; 52 53 #define DEBUG_TYPE "sancov" 54 55 static const char *const kSanCovModuleInitName = "__sanitizer_cov_module_init"; 56 static const char *const kSanCovName = "__sanitizer_cov"; 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 kSanCovModuleCtorName = "sancov.module_ctor"; 61 static const uint64_t kSanCtorAndDtorPriority = 1; 62 63 static cl::opt<int> ClCoverageLevel("sanitizer-coverage-level", 64 cl::desc("Sanitizer Coverage. 0: none, 1: entry block, 2: all blocks, " 65 "3: all blocks and critical edges, " 66 "4: above plus indirect calls"), 67 cl::Hidden, cl::init(0)); 68 69 static cl::opt<int> ClCoverageBlockThreshold( 70 "sanitizer-coverage-block-threshold", 71 cl::desc("Add coverage instrumentation only to the entry block if there " 72 "are more than this number of blocks."), 73 cl::Hidden, cl::init(1500)); 74 75 static cl::opt<bool> 76 ClExperimentalTracing("sanitizer-coverage-experimental-tracing", 77 cl::desc("Experimental basic-block tracing: insert " 78 "callbacks at every basic block"), 79 cl::Hidden, cl::init(false)); 80 81 namespace { 82 83 class SanitizerCoverageModule : public ModulePass { 84 public: 85 SanitizerCoverageModule(int CoverageLevel = 0) 86 : ModulePass(ID), 87 CoverageLevel(std::max(CoverageLevel, (int)ClCoverageLevel)) {} 88 bool runOnModule(Module &M) override; 89 bool runOnFunction(Function &F); 90 static char ID; // Pass identification, replacement for typeid 91 const char *getPassName() const override { 92 return "SanitizerCoverageModule"; 93 } 94 95 void getAnalysisUsage(AnalysisUsage &AU) const override { 96 AU.addRequired<DataLayoutPass>(); 97 } 98 99 private: 100 void InjectCoverageForIndirectCalls(Function &F, 101 ArrayRef<Instruction *> IndirCalls); 102 bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks, 103 ArrayRef<Instruction *> IndirCalls); 104 bool InjectTracing(Function &F, ArrayRef<BasicBlock *> AllBlocks); 105 void InjectCoverageAtBlock(Function &F, BasicBlock &BB); 106 Function *SanCovFunction; 107 Function *SanCovIndirCallFunction; 108 Function *SanCovModuleInit; 109 Function *SanCovTraceEnter, *SanCovTraceBB; 110 Type *IntptrTy; 111 LLVMContext *C; 112 113 int CoverageLevel; 114 }; 115 116 } // namespace 117 118 static Function *checkInterfaceFunction(Constant *FuncOrBitcast) { 119 if (Function *F = dyn_cast<Function>(FuncOrBitcast)) 120 return F; 121 std::string Err; 122 raw_string_ostream Stream(Err); 123 Stream << "SanitizerCoverage interface function redefined: " 124 << *FuncOrBitcast; 125 report_fatal_error(Err); 126 } 127 128 bool SanitizerCoverageModule::runOnModule(Module &M) { 129 if (!CoverageLevel) return false; 130 C = &(M.getContext()); 131 DataLayoutPass *DLP = &getAnalysis<DataLayoutPass>(); 132 IntptrTy = Type::getIntNTy(*C, DLP->getDataLayout().getPointerSizeInBits()); 133 Type *VoidTy = Type::getVoidTy(*C); 134 IRBuilder<> IRB(*C); 135 136 Function *CtorFunc = 137 Function::Create(FunctionType::get(VoidTy, false), 138 GlobalValue::InternalLinkage, kSanCovModuleCtorName, &M); 139 ReturnInst::Create(*C, BasicBlock::Create(*C, "", CtorFunc)); 140 appendToGlobalCtors(M, CtorFunc, kSanCtorAndDtorPriority); 141 142 SanCovFunction = checkInterfaceFunction( 143 M.getOrInsertFunction(kSanCovName, VoidTy, IRB.getInt8PtrTy(), nullptr)); 144 SanCovIndirCallFunction = checkInterfaceFunction(M.getOrInsertFunction( 145 kSanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr)); 146 SanCovModuleInit = checkInterfaceFunction(M.getOrInsertFunction( 147 kSanCovModuleInitName, Type::getVoidTy(*C), IntptrTy, nullptr)); 148 SanCovModuleInit->setLinkage(Function::ExternalLinkage); 149 150 if (ClExperimentalTracing) { 151 SanCovTraceEnter = checkInterfaceFunction( 152 M.getOrInsertFunction(kSanCovTraceEnter, VoidTy, IntptrTy, nullptr)); 153 SanCovTraceBB = checkInterfaceFunction( 154 M.getOrInsertFunction(kSanCovTraceBB, VoidTy, IntptrTy, nullptr)); 155 } 156 157 for (auto &F : M) 158 runOnFunction(F); 159 160 IRB.SetInsertPoint(CtorFunc->getEntryBlock().getTerminator()); 161 IRB.CreateCall(SanCovModuleInit, 162 ConstantInt::get(IntptrTy, SanCovFunction->getNumUses())); 163 return true; 164 } 165 166 bool SanitizerCoverageModule::runOnFunction(Function &F) { 167 if (F.empty()) return false; 168 // For now instrument only functions that will also be asan-instrumented. 169 if (!F.hasFnAttribute(Attribute::SanitizeAddress) && 170 !F.hasFnAttribute(Attribute::SanitizeMemory)) 171 return false; 172 if (CoverageLevel >= 3) 173 SplitAllCriticalEdges(F, this); 174 SmallVector<Instruction*, 8> IndirCalls; 175 SmallVector<BasicBlock*, 16> AllBlocks; 176 for (auto &BB : F) { 177 AllBlocks.push_back(&BB); 178 if (CoverageLevel >= 4) 179 for (auto &Inst : BB) { 180 CallSite CS(&Inst); 181 if (CS && !CS.getCalledFunction()) 182 IndirCalls.push_back(&Inst); 183 } 184 } 185 InjectCoverage(F, AllBlocks, IndirCalls); 186 InjectTracing(F, AllBlocks); 187 return true; 188 } 189 190 // Experimental support for tracing. 191 // Basicaly, insert a callback at the beginning of every basic block. 192 // Every callback gets a pointer to a uniqie global for internal storage. 193 bool SanitizerCoverageModule::InjectTracing(Function &F, 194 ArrayRef<BasicBlock *> AllBlocks) { 195 if (!ClExperimentalTracing) return false; 196 Type *Ty = ArrayType::get(IntptrTy, 1); // May need to use more words later. 197 for (auto BB : AllBlocks) { 198 IRBuilder<> IRB(BB->getFirstInsertionPt()); 199 GlobalVariable *TraceCache = new GlobalVariable( 200 *F.getParent(), Ty, false, GlobalValue::PrivateLinkage, 201 Constant::getNullValue(Ty), "__sancov_gen_trace_cache"); 202 IRB.CreateCall(&F.getEntryBlock() == BB ? SanCovTraceEnter : SanCovTraceBB, 203 IRB.CreatePointerCast(TraceCache, IntptrTy)); 204 } 205 return true; 206 } 207 208 bool 209 SanitizerCoverageModule::InjectCoverage(Function &F, 210 ArrayRef<BasicBlock *> AllBlocks, 211 ArrayRef<Instruction *> IndirCalls) { 212 if (!CoverageLevel) return false; 213 214 if (CoverageLevel == 1 || 215 (unsigned)ClCoverageBlockThreshold < AllBlocks.size()) { 216 InjectCoverageAtBlock(F, F.getEntryBlock()); 217 } else { 218 for (auto BB : AllBlocks) 219 InjectCoverageAtBlock(F, *BB); 220 } 221 InjectCoverageForIndirectCalls(F, IndirCalls); 222 return true; 223 } 224 225 // On every indirect call we call a run-time function 226 // __sanitizer_cov_indir_call* with two parameters: 227 // - callee address, 228 // - global cache array that contains kCacheSize pointers (zero-initialized). 229 // The cache is used to speed up recording the caller-callee pairs. 230 // The address of the caller is passed implicitly via caller PC. 231 // kCacheSize is encoded in the name of the run-time function. 232 void SanitizerCoverageModule::InjectCoverageForIndirectCalls( 233 Function &F, ArrayRef<Instruction *> IndirCalls) { 234 if (IndirCalls.empty()) return; 235 const int kCacheSize = 16; 236 const int kCacheAlignment = 64; // Align for better performance. 237 Type *Ty = ArrayType::get(IntptrTy, kCacheSize); 238 for (auto I : IndirCalls) { 239 IRBuilder<> IRB(I); 240 CallSite CS(I); 241 Value *Callee = CS.getCalledValue(); 242 if (dyn_cast<InlineAsm>(Callee)) continue; 243 GlobalVariable *CalleeCache = new GlobalVariable( 244 *F.getParent(), Ty, false, GlobalValue::PrivateLinkage, 245 Constant::getNullValue(Ty), "__sancov_gen_callee_cache"); 246 CalleeCache->setAlignment(kCacheAlignment); 247 IRB.CreateCall2(SanCovIndirCallFunction, 248 IRB.CreatePointerCast(Callee, IntptrTy), 249 IRB.CreatePointerCast(CalleeCache, IntptrTy)); 250 } 251 } 252 253 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, 254 BasicBlock &BB) { 255 BasicBlock::iterator IP = BB.getFirstInsertionPt(), BE = BB.end(); 256 // Skip static allocas at the top of the entry block so they don't become 257 // dynamic when we split the block. If we used our optimized stack layout, 258 // then there will only be one alloca and it will come first. 259 for (; IP != BE; ++IP) { 260 AllocaInst *AI = dyn_cast<AllocaInst>(IP); 261 if (!AI || !AI->isStaticAlloca()) 262 break; 263 } 264 265 DebugLoc EntryLoc = &BB == &F.getEntryBlock() 266 ? IP->getDebugLoc().getFnDebugLoc(*C) 267 : IP->getDebugLoc(); 268 IRBuilder<> IRB(IP); 269 IRB.SetCurrentDebugLocation(EntryLoc); 270 Type *Int8Ty = IRB.getInt8Ty(); 271 GlobalVariable *Guard = new GlobalVariable( 272 *F.getParent(), Int8Ty, false, GlobalValue::PrivateLinkage, 273 Constant::getNullValue(Int8Ty), "__sancov_gen_cov_" + F.getName()); 274 LoadInst *Load = IRB.CreateLoad(Guard); 275 Load->setAtomic(Monotonic); 276 Load->setAlignment(1); 277 Load->setMetadata(F.getParent()->getMDKindID("nosanitize"), 278 MDNode::get(*C, ArrayRef<llvm::Value *>())); 279 Value *Cmp = IRB.CreateICmpEQ(Constant::getNullValue(Int8Ty), Load); 280 Instruction *Ins = SplitBlockAndInsertIfThen( 281 Cmp, IP, false, MDBuilder(*C).createBranchWeights(1, 100000)); 282 IRB.SetInsertPoint(Ins); 283 IRB.SetCurrentDebugLocation(EntryLoc); 284 // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC. 285 IRB.CreateCall(SanCovFunction, Guard); 286 } 287 288 char SanitizerCoverageModule::ID = 0; 289 INITIALIZE_PASS(SanitizerCoverageModule, "sancov", 290 "SanitizerCoverage: TODO." 291 "ModulePass", false, false) 292 ModulePass *llvm::createSanitizerCoverageModulePass(int CoverageLevel) { 293 return new SanitizerCoverageModule(CoverageLevel); 294 } 295