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