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 (CoverageLevel=1) 15 // or all blocks (CoverageLevel>=2): 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 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/InlineAsm.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 kSanCovWithCheckName = "__sanitizer_cov_with_check"; 59 static const char *const kSanCovIndirCallName = "__sanitizer_cov_indir_call16"; 60 static const char *const kSanCovTraceEnter = "__sanitizer_cov_trace_func_enter"; 61 static const char *const kSanCovTraceBB = "__sanitizer_cov_trace_basic_block"; 62 static const char *const kSanCovModuleCtorName = "sancov.module_ctor"; 63 static const uint64_t kSanCtorAndDtorPriority = 2; 64 65 static cl::opt<int> ClCoverageLevel("sanitizer-coverage-level", 66 cl::desc("Sanitizer Coverage. 0: none, 1: entry block, 2: all blocks, " 67 "3: all blocks and critical edges, " 68 "4: above plus indirect calls"), 69 cl::Hidden, cl::init(0)); 70 71 static cl::opt<unsigned> ClCoverageBlockThreshold( 72 "sanitizer-coverage-block-threshold", 73 cl::desc("Use a callback with a guard check inside it if there are" 74 " more than this number of blocks."), 75 cl::Hidden, cl::init(1000)); 76 77 static cl::opt<bool> 78 ClExperimentalTracing("sanitizer-coverage-experimental-tracing", 79 cl::desc("Experimental basic-block tracing: insert " 80 "callbacks at every basic block"), 81 cl::Hidden, cl::init(false)); 82 83 namespace { 84 85 class SanitizerCoverageModule : public ModulePass { 86 public: 87 SanitizerCoverageModule(int CoverageLevel = 0) 88 : ModulePass(ID), 89 CoverageLevel(std::max(CoverageLevel, (int)ClCoverageLevel)) {} 90 bool runOnModule(Module &M) override; 91 bool runOnFunction(Function &F); 92 static char ID; // Pass identification, replacement for typeid 93 const char *getPassName() const override { 94 return "SanitizerCoverageModule"; 95 } 96 97 void getAnalysisUsage(AnalysisUsage &AU) const override { 98 AU.addRequired<DataLayoutPass>(); 99 } 100 101 private: 102 void InjectCoverageForIndirectCalls(Function &F, 103 ArrayRef<Instruction *> IndirCalls); 104 bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks, 105 ArrayRef<Instruction *> IndirCalls); 106 void InjectCoverageAtBlock(Function &F, BasicBlock &BB, bool UseCalls); 107 Function *SanCovFunction; 108 Function *SanCovWithCheckFunction; 109 Function *SanCovIndirCallFunction; 110 Function *SanCovModuleInit; 111 Function *SanCovTraceEnter, *SanCovTraceBB; 112 InlineAsm *EmptyAsm; 113 Type *IntptrTy; 114 LLVMContext *C; 115 116 GlobalVariable *GuardArray; 117 118 int CoverageLevel; 119 }; 120 121 } // namespace 122 123 static Function *checkInterfaceFunction(Constant *FuncOrBitcast) { 124 if (Function *F = dyn_cast<Function>(FuncOrBitcast)) 125 return F; 126 std::string Err; 127 raw_string_ostream Stream(Err); 128 Stream << "SanitizerCoverage interface function redefined: " 129 << *FuncOrBitcast; 130 report_fatal_error(Err); 131 } 132 133 bool SanitizerCoverageModule::runOnModule(Module &M) { 134 if (!CoverageLevel) return false; 135 C = &(M.getContext()); 136 DataLayoutPass *DLP = &getAnalysis<DataLayoutPass>(); 137 IntptrTy = Type::getIntNTy(*C, DLP->getDataLayout().getPointerSizeInBits()); 138 Type *VoidTy = Type::getVoidTy(*C); 139 IRBuilder<> IRB(*C); 140 Type *Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty()); 141 Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty()); 142 143 Function *CtorFunc = 144 Function::Create(FunctionType::get(VoidTy, false), 145 GlobalValue::InternalLinkage, kSanCovModuleCtorName, &M); 146 ReturnInst::Create(*C, BasicBlock::Create(*C, "", CtorFunc)); 147 appendToGlobalCtors(M, CtorFunc, kSanCtorAndDtorPriority); 148 149 SanCovFunction = checkInterfaceFunction( 150 M.getOrInsertFunction(kSanCovName, VoidTy, Int32PtrTy, nullptr)); 151 SanCovWithCheckFunction = checkInterfaceFunction( 152 M.getOrInsertFunction(kSanCovWithCheckName, VoidTy, Int32PtrTy, nullptr)); 153 SanCovIndirCallFunction = checkInterfaceFunction(M.getOrInsertFunction( 154 kSanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr)); 155 SanCovModuleInit = checkInterfaceFunction( 156 M.getOrInsertFunction(kSanCovModuleInitName, Type::getVoidTy(*C), 157 Int32PtrTy, IntptrTy, Int8PtrTy, nullptr)); 158 SanCovModuleInit->setLinkage(Function::ExternalLinkage); 159 // We insert an empty inline asm after cov callbacks to avoid callback merge. 160 EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false), 161 StringRef(""), StringRef(""), 162 /*hasSideEffects=*/true); 163 164 if (ClExperimentalTracing) { 165 SanCovTraceEnter = checkInterfaceFunction( 166 M.getOrInsertFunction(kSanCovTraceEnter, VoidTy, Int32PtrTy, nullptr)); 167 SanCovTraceBB = checkInterfaceFunction( 168 M.getOrInsertFunction(kSanCovTraceBB, VoidTy, Int32PtrTy, nullptr)); 169 } 170 171 // At this point we create a dummy array of guards because we don't 172 // know how many elements we will need. 173 Type *Int32Ty = IRB.getInt32Ty(); 174 GuardArray = 175 new GlobalVariable(M, Int32Ty, false, GlobalValue::ExternalLinkage, 176 nullptr, "__sancov_gen_cov_tmp"); 177 178 for (auto &F : M) 179 runOnFunction(F); 180 181 // Now we know how many elements we need. Create an array of guards 182 // with one extra element at the beginning for the size. 183 Type *Int32ArrayNTy = 184 ArrayType::get(Int32Ty, SanCovFunction->getNumUses() + 1); 185 GlobalVariable *RealGuardArray = new GlobalVariable( 186 M, Int32ArrayNTy, false, GlobalValue::PrivateLinkage, 187 Constant::getNullValue(Int32ArrayNTy), "__sancov_gen_cov"); 188 189 // Replace the dummy array with the real one. 190 GuardArray->replaceAllUsesWith( 191 IRB.CreatePointerCast(RealGuardArray, Int32PtrTy)); 192 GuardArray->eraseFromParent(); 193 194 // Create variable for module (compilation unit) name 195 Constant *ModNameStrConst = 196 ConstantDataArray::getString(M.getContext(), M.getName(), true); 197 GlobalVariable *ModuleName = 198 new GlobalVariable(M, ModNameStrConst->getType(), true, 199 GlobalValue::PrivateLinkage, ModNameStrConst); 200 201 // Call __sanitizer_cov_module_init 202 IRB.SetInsertPoint(CtorFunc->getEntryBlock().getTerminator()); 203 IRB.CreateCall3(SanCovModuleInit, 204 IRB.CreatePointerCast(RealGuardArray, Int32PtrTy), 205 ConstantInt::get(IntptrTy, SanCovFunction->getNumUses()), 206 IRB.CreatePointerCast(ModuleName, Int8PtrTy)); 207 return true; 208 } 209 210 bool SanitizerCoverageModule::runOnFunction(Function &F) { 211 if (F.empty()) return false; 212 if (F.getName().find(".module_ctor") != std::string::npos) 213 return false; // Should not instrument sanitizer init functions. 214 if (CoverageLevel >= 3) 215 SplitAllCriticalEdges(F); 216 SmallVector<Instruction*, 8> IndirCalls; 217 SmallVector<BasicBlock*, 16> AllBlocks; 218 for (auto &BB : F) { 219 AllBlocks.push_back(&BB); 220 if (CoverageLevel >= 4) 221 for (auto &Inst : BB) { 222 CallSite CS(&Inst); 223 if (CS && !CS.getCalledFunction()) 224 IndirCalls.push_back(&Inst); 225 } 226 } 227 InjectCoverage(F, AllBlocks, IndirCalls); 228 return true; 229 } 230 231 bool 232 SanitizerCoverageModule::InjectCoverage(Function &F, 233 ArrayRef<BasicBlock *> AllBlocks, 234 ArrayRef<Instruction *> IndirCalls) { 235 if (!CoverageLevel) return false; 236 237 if (CoverageLevel == 1) { 238 InjectCoverageAtBlock(F, F.getEntryBlock(), false); 239 } else { 240 for (auto BB : AllBlocks) 241 InjectCoverageAtBlock(F, *BB, 242 ClCoverageBlockThreshold < AllBlocks.size()); 243 } 244 InjectCoverageForIndirectCalls(F, IndirCalls); 245 return true; 246 } 247 248 // On every indirect call we call a run-time function 249 // __sanitizer_cov_indir_call* with two parameters: 250 // - callee address, 251 // - global cache array that contains kCacheSize pointers (zero-initialized). 252 // The cache is used to speed up recording the caller-callee pairs. 253 // The address of the caller is passed implicitly via caller PC. 254 // kCacheSize is encoded in the name of the run-time function. 255 void SanitizerCoverageModule::InjectCoverageForIndirectCalls( 256 Function &F, ArrayRef<Instruction *> IndirCalls) { 257 if (IndirCalls.empty()) return; 258 const int kCacheSize = 16; 259 const int kCacheAlignment = 64; // Align for better performance. 260 Type *Ty = ArrayType::get(IntptrTy, kCacheSize); 261 for (auto I : IndirCalls) { 262 IRBuilder<> IRB(I); 263 CallSite CS(I); 264 Value *Callee = CS.getCalledValue(); 265 if (dyn_cast<InlineAsm>(Callee)) continue; 266 GlobalVariable *CalleeCache = new GlobalVariable( 267 *F.getParent(), Ty, false, GlobalValue::PrivateLinkage, 268 Constant::getNullValue(Ty), "__sancov_gen_callee_cache"); 269 CalleeCache->setAlignment(kCacheAlignment); 270 IRB.CreateCall2(SanCovIndirCallFunction, 271 IRB.CreatePointerCast(Callee, IntptrTy), 272 IRB.CreatePointerCast(CalleeCache, IntptrTy)); 273 } 274 } 275 276 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB, 277 bool UseCalls) { 278 BasicBlock::iterator IP = BB.getFirstInsertionPt(), BE = BB.end(); 279 // Skip static allocas at the top of the entry block so they don't become 280 // dynamic when we split the block. If we used our optimized stack layout, 281 // then there will only be one alloca and it will come first. 282 for (; IP != BE; ++IP) { 283 AllocaInst *AI = dyn_cast<AllocaInst>(IP); 284 if (!AI || !AI->isStaticAlloca()) 285 break; 286 } 287 288 bool IsEntryBB = &BB == &F.getEntryBlock(); 289 DebugLoc EntryLoc = 290 IsEntryBB ? IP->getDebugLoc().getFnDebugLoc(*C) : IP->getDebugLoc(); 291 IRBuilder<> IRB(IP); 292 IRB.SetCurrentDebugLocation(EntryLoc); 293 SmallVector<Value *, 1> Indices; 294 Value *GuardP = IRB.CreateAdd( 295 IRB.CreatePointerCast(GuardArray, IntptrTy), 296 ConstantInt::get(IntptrTy, (1 + SanCovFunction->getNumUses()) * 4)); 297 Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty()); 298 GuardP = IRB.CreateIntToPtr(GuardP, Int32PtrTy); 299 if (UseCalls) { 300 IRB.CreateCall(SanCovWithCheckFunction, GuardP); 301 } else { 302 LoadInst *Load = IRB.CreateLoad(GuardP); 303 Load->setAtomic(Monotonic); 304 Load->setAlignment(4); 305 Load->setMetadata(F.getParent()->getMDKindID("nosanitize"), 306 MDNode::get(*C, None)); 307 Value *Cmp = IRB.CreateICmpSGE(Constant::getNullValue(Load->getType()), Load); 308 Instruction *Ins = SplitBlockAndInsertIfThen( 309 Cmp, IP, false, MDBuilder(*C).createBranchWeights(1, 100000)); 310 IRB.SetInsertPoint(Ins); 311 IRB.SetCurrentDebugLocation(EntryLoc); 312 // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC. 313 IRB.CreateCall(SanCovFunction, GuardP); 314 IRB.CreateCall(EmptyAsm); // Avoids callback merge. 315 } 316 317 if (ClExperimentalTracing) { 318 // Experimental support for tracing. 319 // Insert a callback with the same guard variable as used for coverage. 320 IRB.SetInsertPoint(IP); 321 IRB.CreateCall(IsEntryBB ? SanCovTraceEnter : SanCovTraceBB, GuardP); 322 } 323 } 324 325 char SanitizerCoverageModule::ID = 0; 326 INITIALIZE_PASS(SanitizerCoverageModule, "sancov", 327 "SanitizerCoverage: TODO." 328 "ModulePass", false, false) 329 ModulePass *llvm::createSanitizerCoverageModulePass(int CoverageLevel) { 330 return new SanitizerCoverageModule(CoverageLevel); 331 } 332