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 kSanCovIndirCallName = "__sanitizer_cov_indir_call16"; 59 static const char *const kSanCovTraceEnter = "__sanitizer_cov_trace_func_enter"; 60 static const char *const kSanCovTraceBB = "__sanitizer_cov_trace_basic_block"; 61 static const char *const kSanCovModuleCtorName = "sancov.module_ctor"; 62 static const uint64_t kSanCtorAndDtorPriority = 1; 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<int> ClCoverageBlockThreshold( 71 "sanitizer-coverage-block-threshold", 72 cl::desc("Add coverage instrumentation only to the entry block if there " 73 "are more than this number of blocks."), 74 cl::Hidden, cl::init(1500)); 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 namespace { 83 84 class SanitizerCoverageModule : public ModulePass { 85 public: 86 SanitizerCoverageModule(int CoverageLevel = 0) 87 : ModulePass(ID), 88 CoverageLevel(std::max(CoverageLevel, (int)ClCoverageLevel)) {} 89 bool runOnModule(Module &M) override; 90 bool runOnFunction(Function &F); 91 static char ID; // Pass identification, replacement for typeid 92 const char *getPassName() const override { 93 return "SanitizerCoverageModule"; 94 } 95 96 void getAnalysisUsage(AnalysisUsage &AU) const override { 97 AU.addRequired<DataLayoutPass>(); 98 } 99 100 private: 101 void InjectCoverageForIndirectCalls(Function &F, 102 ArrayRef<Instruction *> IndirCalls); 103 bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks, 104 ArrayRef<Instruction *> IndirCalls); 105 bool InjectTracing(Function &F, ArrayRef<BasicBlock *> AllBlocks); 106 void InjectCoverageAtBlock(Function &F, BasicBlock &BB); 107 Function *SanCovFunction; 108 Function *SanCovIndirCallFunction; 109 Function *SanCovModuleInit; 110 Function *SanCovTraceEnter, *SanCovTraceBB; 111 InlineAsm *EmptyAsm; 112 Type *IntptrTy; 113 LLVMContext *C; 114 115 SmallVector<Constant *, 16> Guards; 116 117 int CoverageLevel; 118 }; 119 120 } // namespace 121 122 static Function *checkInterfaceFunction(Constant *FuncOrBitcast) { 123 if (Function *F = dyn_cast<Function>(FuncOrBitcast)) 124 return F; 125 std::string Err; 126 raw_string_ostream Stream(Err); 127 Stream << "SanitizerCoverage interface function redefined: " 128 << *FuncOrBitcast; 129 report_fatal_error(Err); 130 } 131 132 bool SanitizerCoverageModule::runOnModule(Module &M) { 133 if (!CoverageLevel) return false; 134 C = &(M.getContext()); 135 DataLayoutPass *DLP = &getAnalysis<DataLayoutPass>(); 136 IntptrTy = Type::getIntNTy(*C, DLP->getDataLayout().getPointerSizeInBits()); 137 Type *VoidTy = Type::getVoidTy(*C); 138 IRBuilder<> IRB(*C); 139 Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty()); 140 Type *Int32PtrPtrTy = PointerType::getUnqual(Int32PtrTy); 141 142 Function *CtorFunc = 143 Function::Create(FunctionType::get(VoidTy, false), 144 GlobalValue::InternalLinkage, kSanCovModuleCtorName, &M); 145 ReturnInst::Create(*C, BasicBlock::Create(*C, "", CtorFunc)); 146 appendToGlobalCtors(M, CtorFunc, kSanCtorAndDtorPriority); 147 148 SanCovFunction = checkInterfaceFunction( 149 M.getOrInsertFunction(kSanCovName, VoidTy, Int32PtrTy, nullptr)); 150 SanCovIndirCallFunction = checkInterfaceFunction(M.getOrInsertFunction( 151 kSanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr)); 152 SanCovModuleInit = checkInterfaceFunction( 153 M.getOrInsertFunction(kSanCovModuleInitName, Type::getVoidTy(*C), 154 Int32PtrPtrTy, IntptrTy, nullptr)); 155 SanCovModuleInit->setLinkage(Function::ExternalLinkage); 156 // We insert an empty inline asm after cov callbacks to avoid callback merge. 157 EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false), 158 StringRef(""), StringRef(""), 159 /*hasSideEffects=*/true); 160 161 if (ClExperimentalTracing) { 162 SanCovTraceEnter = checkInterfaceFunction( 163 M.getOrInsertFunction(kSanCovTraceEnter, VoidTy, IntptrTy, nullptr)); 164 SanCovTraceBB = checkInterfaceFunction( 165 M.getOrInsertFunction(kSanCovTraceBB, VoidTy, IntptrTy, nullptr)); 166 } 167 168 for (auto &F : M) 169 runOnFunction(F); 170 171 ArrayType *ArrayOfInt32PtrTy = ArrayType::get(Int32PtrTy, Guards.size()); 172 IRB.SetInsertPoint(CtorFunc->getEntryBlock().getTerminator()); 173 GlobalVariable *AllGuards = new GlobalVariable( 174 M, ArrayOfInt32PtrTy, false, GlobalVariable::InternalLinkage, 175 ConstantArray::get(ArrayOfInt32PtrTy, Guards), ""); 176 assert(SanCovFunction->getNumUses() == Guards.size()); 177 IRB.CreateCall2(SanCovModuleInit, 178 IRB.CreatePointerCast(AllGuards, Int32PtrPtrTy), 179 ConstantInt::get(IntptrTy, Guards.size())); 180 return true; 181 } 182 183 bool SanitizerCoverageModule::runOnFunction(Function &F) { 184 if (F.empty()) return false; 185 if (F.getName().find(".module_ctor") != std::string::npos) 186 return false; // Should not instrument sanitizer init functions. 187 if (CoverageLevel >= 3) 188 SplitAllCriticalEdges(F, this); 189 SmallVector<Instruction*, 8> IndirCalls; 190 SmallVector<BasicBlock*, 16> AllBlocks; 191 for (auto &BB : F) { 192 AllBlocks.push_back(&BB); 193 if (CoverageLevel >= 4) 194 for (auto &Inst : BB) { 195 CallSite CS(&Inst); 196 if (CS && !CS.getCalledFunction()) 197 IndirCalls.push_back(&Inst); 198 } 199 } 200 InjectCoverage(F, AllBlocks, IndirCalls); 201 InjectTracing(F, AllBlocks); 202 return true; 203 } 204 205 // Experimental support for tracing. 206 // Basicaly, insert a callback at the beginning of every basic block. 207 // Every callback gets a pointer to a uniqie global for internal storage. 208 bool SanitizerCoverageModule::InjectTracing(Function &F, 209 ArrayRef<BasicBlock *> AllBlocks) { 210 if (!ClExperimentalTracing) return false; 211 Type *Ty = ArrayType::get(IntptrTy, 1); // May need to use more words later. 212 for (auto BB : AllBlocks) { 213 IRBuilder<> IRB(BB->getFirstInsertionPt()); 214 GlobalVariable *TraceCache = new GlobalVariable( 215 *F.getParent(), Ty, false, GlobalValue::PrivateLinkage, 216 Constant::getNullValue(Ty), "__sancov_gen_trace_cache"); 217 IRB.CreateCall(&F.getEntryBlock() == BB ? SanCovTraceEnter : SanCovTraceBB, 218 IRB.CreatePointerCast(TraceCache, IntptrTy)); 219 } 220 return true; 221 } 222 223 bool 224 SanitizerCoverageModule::InjectCoverage(Function &F, 225 ArrayRef<BasicBlock *> AllBlocks, 226 ArrayRef<Instruction *> IndirCalls) { 227 if (!CoverageLevel) return false; 228 229 if (CoverageLevel == 1 || 230 (unsigned)ClCoverageBlockThreshold < AllBlocks.size()) { 231 InjectCoverageAtBlock(F, F.getEntryBlock()); 232 } else { 233 for (auto BB : AllBlocks) 234 InjectCoverageAtBlock(F, *BB); 235 } 236 InjectCoverageForIndirectCalls(F, IndirCalls); 237 return true; 238 } 239 240 // On every indirect call we call a run-time function 241 // __sanitizer_cov_indir_call* with two parameters: 242 // - callee address, 243 // - global cache array that contains kCacheSize pointers (zero-initialized). 244 // The cache is used to speed up recording the caller-callee pairs. 245 // The address of the caller is passed implicitly via caller PC. 246 // kCacheSize is encoded in the name of the run-time function. 247 void SanitizerCoverageModule::InjectCoverageForIndirectCalls( 248 Function &F, ArrayRef<Instruction *> IndirCalls) { 249 if (IndirCalls.empty()) return; 250 const int kCacheSize = 16; 251 const int kCacheAlignment = 64; // Align for better performance. 252 Type *Ty = ArrayType::get(IntptrTy, kCacheSize); 253 for (auto I : IndirCalls) { 254 IRBuilder<> IRB(I); 255 CallSite CS(I); 256 Value *Callee = CS.getCalledValue(); 257 if (dyn_cast<InlineAsm>(Callee)) continue; 258 GlobalVariable *CalleeCache = new GlobalVariable( 259 *F.getParent(), Ty, false, GlobalValue::PrivateLinkage, 260 Constant::getNullValue(Ty), "__sancov_gen_callee_cache"); 261 CalleeCache->setAlignment(kCacheAlignment); 262 IRB.CreateCall2(SanCovIndirCallFunction, 263 IRB.CreatePointerCast(Callee, IntptrTy), 264 IRB.CreatePointerCast(CalleeCache, IntptrTy)); 265 } 266 } 267 268 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, 269 BasicBlock &BB) { 270 BasicBlock::iterator IP = BB.getFirstInsertionPt(), BE = BB.end(); 271 // Skip static allocas at the top of the entry block so they don't become 272 // dynamic when we split the block. If we used our optimized stack layout, 273 // then there will only be one alloca and it will come first. 274 for (; IP != BE; ++IP) { 275 AllocaInst *AI = dyn_cast<AllocaInst>(IP); 276 if (!AI || !AI->isStaticAlloca()) 277 break; 278 } 279 280 DebugLoc EntryLoc = &BB == &F.getEntryBlock() 281 ? IP->getDebugLoc().getFnDebugLoc(*C) 282 : IP->getDebugLoc(); 283 IRBuilder<> IRB(IP); 284 IRB.SetCurrentDebugLocation(EntryLoc); 285 Type *Int32Ty = IRB.getInt32Ty(); 286 GlobalVariable *Guard = new GlobalVariable( 287 *F.getParent(), Int32Ty, false, GlobalValue::PrivateLinkage, 288 Constant::getNullValue(Int32Ty), "__sancov_gen_cov_" + F.getName()); 289 LoadInst *Load = IRB.CreateLoad(Guard); 290 Load->setAtomic(Monotonic); 291 Load->setAlignment(4); 292 Load->setMetadata(F.getParent()->getMDKindID("nosanitize"), 293 MDNode::get(*C, None)); 294 Value *Cmp = IRB.CreateICmpSGE(Constant::getNullValue(Int32Ty), Load); 295 Instruction *Ins = SplitBlockAndInsertIfThen( 296 Cmp, IP, false, MDBuilder(*C).createBranchWeights(1, 100000)); 297 IRB.SetInsertPoint(Ins); 298 IRB.SetCurrentDebugLocation(EntryLoc); 299 // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC. 300 IRB.CreateCall(SanCovFunction, Guard); 301 IRB.CreateCall(EmptyAsm); // Avoids callback merge. 302 Guards.push_back(Guard); // Save the guard for later. 303 } 304 305 char SanitizerCoverageModule::ID = 0; 306 INITIALIZE_PASS(SanitizerCoverageModule, "sancov", 307 "SanitizerCoverage: TODO." 308 "ModulePass", false, false) 309 ModulePass *llvm::createSanitizerCoverageModulePass(int CoverageLevel) { 310 return new SanitizerCoverageModule(CoverageLevel); 311 } 312