lib/Transforms/Instrumentation/SanitizerCoverage.cpp

   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 (SCK_Function)
  15 // or all blocks (SCK_BB):
  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 SCK_Edge we also split critical edges this effectively
  23 // instrumenting all edges.
  24 //
  25 // This coverage implementation provides very limited data:
  26 // it only tells if a given function (block) was ever executed. No counters.
  27 // But for many use cases this is what we need and the added slowdown small.
  28 //
  29 //===----------------------------------------------------------------------===//
  30
  31 #include "llvm/Transforms/Instrumentation.h"
  32 #include "llvm/ADT/ArrayRef.h"
  33 #include "llvm/ADT/SmallVector.h"
  34 #include "llvm/IR/CallSite.h"
  35 #include "llvm/IR/DataLayout.h"
  36 #include "llvm/IR/Function.h"
  37 #include "llvm/IR/IRBuilder.h"
  38 #include "llvm/IR/InlineAsm.h"
  39 #include "llvm/IR/LLVMContext.h"
  40 #include "llvm/IR/MDBuilder.h"
  41 #include "llvm/IR/Module.h"
  42 #include "llvm/IR/Type.h"
  43 #include "llvm/Support/CommandLine.h"
  44 #include "llvm/Support/Debug.h"
  45 #include "llvm/Support/raw_ostream.h"
  46 #include "llvm/Transforms/Scalar.h"
  47 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
  48 #include "llvm/Transforms/Utils/ModuleUtils.h"
  49
  50 using namespace llvm;
  51
  52 #define DEBUG_TYPE "sancov"
  53
  54 static const char *const kSanCovModuleInitName = "__sanitizer_cov_module_init";
  55 static const char *const kSanCovName = "__sanitizer_cov";
  56 static const char *const kSanCovWithCheckName = "__sanitizer_cov_with_check";
  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 kSanCovTraceCmp = "__sanitizer_cov_trace_cmp";
  61 static const char *const kSanCovModuleCtorName = "sancov.module_ctor";
  62 static const uint64_t    kSanCtorAndDtorPriority = 2;
  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<unsigned> ClCoverageBlockThreshold(
  71     "sanitizer-coverage-block-threshold",
  72     cl::desc("Use a callback with a guard check inside it if there are"
  73              " more than this number of blocks."),
  74     cl::Hidden, cl::init(500));
  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 static cl::opt<bool>
  83     ClExperimentalCMPTracing("sanitizer-coverage-experimental-trace-compares",
  84                              cl::desc("Experimental tracing of CMP and similar "
  85                                       "instructions"),
  86                              cl::Hidden, cl::init(false));
  87
  88 // Experimental 8-bit counters used as an additional search heuristic during
  89 // coverage-guided fuzzing.
  90 // The counters are not thread-friendly:
  91 //   - contention on these counters may cause significant slowdown;
  92 //   - the counter updates are racy and the results may be inaccurate.
  93 // They are also inaccurate due to 8-bit integer overflow.
  94 static cl::opt<bool> ClUse8bitCounters("sanitizer-coverage-8bit-counters",
  95                                        cl::desc("Experimental 8-bit counters"),
  96                                        cl::Hidden, cl::init(false));
  97
  98 namespace {
  99
 100 SanitizerCoverageOptions getOptions(int LegacyCoverageLevel) {
 101   SanitizerCoverageOptions Res;
 102   switch (LegacyCoverageLevel) {
 103   case 0:
 104     Res.CoverageType = SanitizerCoverageOptions::SCK_None;
 105     break;
 106   case 1:
 107     Res.CoverageType = SanitizerCoverageOptions::SCK_Function;
 108     break;
 109   case 2:
 110     Res.CoverageType = SanitizerCoverageOptions::SCK_BB;
 111     break;
 112   case 3:
 113     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
 114     break;
 115   case 4:
 116     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
 117     Res.IndirectCalls = true;
 118     break;
 119   }
 120   return Res;
 121 }
 122
 123 SanitizerCoverageOptions OverrideFromCL(SanitizerCoverageOptions Options) {
 124   // Sets CoverageType and IndirectCalls.
 125   SanitizerCoverageOptions CLOpts = getOptions(ClCoverageLevel);
 126   Options.CoverageType = std::max(Options.CoverageType, CLOpts.CoverageType);
 127   Options.IndirectCalls |= CLOpts.IndirectCalls;
 128   Options.TraceBB |= ClExperimentalTracing;
 129   Options.TraceCmp |= ClExperimentalCMPTracing;
 130   Options.Use8bitCounters |= ClUse8bitCounters;
 131   return Options;
 132 }
 133
 134 class SanitizerCoverageModule : public ModulePass {
 135  public:
 136   SanitizerCoverageModule(
 137       const SanitizerCoverageOptions &Options = SanitizerCoverageOptions())
 138       : ModulePass(ID), Options(OverrideFromCL(Options)) {}
 139   bool runOnModule(Module &M) override;
 140   bool runOnFunction(Function &F);
 141   static char ID;  // Pass identification, replacement for typeid
 142   const char *getPassName() const override {
 143     return "SanitizerCoverageModule";
 144   }
 145
 146  private:
 147   void InjectCoverageForIndirectCalls(Function &F,
 148                                       ArrayRef<Instruction *> IndirCalls);
 149   void InjectTraceForCmp(Function &F, ArrayRef<Instruction *> CmpTraceTargets);
 150   bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks);
 151   void SetNoSanitizeMetadata(Instruction *I);
 152   void InjectCoverageAtBlock(Function &F, BasicBlock &BB, bool UseCalls);
 153   unsigned NumberOfInstrumentedBlocks() {
 154     return SanCovFunction->getNumUses() + SanCovWithCheckFunction->getNumUses();
 155   }
 156   Function *SanCovFunction;
 157   Function *SanCovWithCheckFunction;
 158   Function *SanCovIndirCallFunction;
 159   Function *SanCovTraceEnter, *SanCovTraceBB;
 160   Function *SanCovTraceCmpFunction;
 161   InlineAsm *EmptyAsm;
 162   Type *IntptrTy, *Int64Ty;
 163   LLVMContext *C;
 164   const DataLayout *DL;
 165
 166   GlobalVariable *GuardArray;
 167   GlobalVariable *EightBitCounterArray;
 168
 169   SanitizerCoverageOptions Options;
 170 };
 171
 172 }  // namespace
 173
 174 bool SanitizerCoverageModule::runOnModule(Module &M) {
 175   if (Options.CoverageType == SanitizerCoverageOptions::SCK_None)
 176     return false;
 177   C = &(M.getContext());
 178   DL = &M.getDataLayout();
 179   IntptrTy = Type::getIntNTy(*C, DL->getPointerSizeInBits());
 180   Type *VoidTy = Type::getVoidTy(*C);
 181   IRBuilder<> IRB(*C);
 182   Type *Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
 183   Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
 184   Int64Ty = IRB.getInt64Ty();
 185
 186   SanCovFunction = checkSanitizerInterfaceFunction(
 187       M.getOrInsertFunction(kSanCovName, VoidTy, Int32PtrTy, nullptr));
 188   SanCovWithCheckFunction = checkSanitizerInterfaceFunction(
 189       M.getOrInsertFunction(kSanCovWithCheckName, VoidTy, Int32PtrTy, nullptr));
 190   SanCovIndirCallFunction =
 191       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 192           kSanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr));
 193   SanCovTraceCmpFunction =
 194       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 195           kSanCovTraceCmp, VoidTy, Int64Ty, Int64Ty, Int64Ty, nullptr));
 196
 197   // We insert an empty inline asm after cov callbacks to avoid callback merge.
 198   EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
 199                             StringRef(""), StringRef(""),
 200                             /*hasSideEffects=*/true);
 201
 202   if (Options.TraceBB) {
 203     SanCovTraceEnter = checkSanitizerInterfaceFunction(
 204         M.getOrInsertFunction(kSanCovTraceEnter, VoidTy, Int32PtrTy, nullptr));
 205     SanCovTraceBB = checkSanitizerInterfaceFunction(
 206         M.getOrInsertFunction(kSanCovTraceBB, VoidTy, Int32PtrTy, nullptr));
 207   }
 208
 209   // At this point we create a dummy array of guards because we don't
 210   // know how many elements we will need.
 211   Type *Int32Ty = IRB.getInt32Ty();
 212   Type *Int8Ty = IRB.getInt8Ty();
 213
 214   GuardArray =
 215       new GlobalVariable(M, Int32Ty, false, GlobalValue::ExternalLinkage,
 216                          nullptr, "__sancov_gen_cov_tmp");
 217   if (Options.Use8bitCounters)
 218     EightBitCounterArray =
 219         new GlobalVariable(M, Int8Ty, false, GlobalVariable::ExternalLinkage,
 220                            nullptr, "__sancov_gen_cov_tmp");
 221
 222   for (auto &F : M)
 223     runOnFunction(F);
 224
 225   auto N = NumberOfInstrumentedBlocks();
 226
 227   // Now we know how many elements we need. Create an array of guards
 228   // with one extra element at the beginning for the size.
 229   Type *Int32ArrayNTy = ArrayType::get(Int32Ty, N + 1);
 230   GlobalVariable *RealGuardArray = new GlobalVariable(
 231       M, Int32ArrayNTy, false, GlobalValue::PrivateLinkage,
 232       Constant::getNullValue(Int32ArrayNTy), "__sancov_gen_cov");
 233
 234
 235   // Replace the dummy array with the real one.
 236   GuardArray->replaceAllUsesWith(
 237       IRB.CreatePointerCast(RealGuardArray, Int32PtrTy));
 238   GuardArray->eraseFromParent();
 239
 240   GlobalVariable *RealEightBitCounterArray;
 241   if (Options.Use8bitCounters) {
 242     // Make sure the array is 16-aligned.
 243     static const int kCounterAlignment = 16;
 244     Type *Int8ArrayNTy =
 245         ArrayType::get(Int8Ty, RoundUpToAlignment(N, kCounterAlignment));
 246     RealEightBitCounterArray = new GlobalVariable(
 247         M, Int8ArrayNTy, false, GlobalValue::PrivateLinkage,
 248         Constant::getNullValue(Int8ArrayNTy), "__sancov_gen_cov_counter");
 249     RealEightBitCounterArray->setAlignment(kCounterAlignment);
 250     EightBitCounterArray->replaceAllUsesWith(
 251         IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy));
 252     EightBitCounterArray->eraseFromParent();
 253   }
 254
 255   // Create variable for module (compilation unit) name
 256   Constant *ModNameStrConst =
 257       ConstantDataArray::getString(M.getContext(), M.getName(), true);
 258   GlobalVariable *ModuleName =
 259       new GlobalVariable(M, ModNameStrConst->getType(), true,
 260                          GlobalValue::PrivateLinkage, ModNameStrConst);
 261
 262   Function *CtorFunc;
 263   std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
 264       M, kSanCovModuleCtorName, kSanCovModuleInitName,
 265       {Int32PtrTy, IntptrTy, Int8PtrTy, Int8PtrTy},
 266       {IRB.CreatePointerCast(RealGuardArray, Int32PtrTy),
 267        ConstantInt::get(IntptrTy, N),
 268        Options.Use8bitCounters
 269            ? IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy)
 270            : Constant::getNullValue(Int8PtrTy),
 271        IRB.CreatePointerCast(ModuleName, Int8PtrTy)});
 272
 273   appendToGlobalCtors(M, CtorFunc, kSanCtorAndDtorPriority);
 274
 275   return true;
 276 }
 277
 278 bool SanitizerCoverageModule::runOnFunction(Function &F) {
 279   if (F.empty()) return false;
 280   if (F.getName().find(".module_ctor") != std::string::npos)
 281     return false;  // Should not instrument sanitizer init functions.
 282   if (Options.CoverageType >= SanitizerCoverageOptions::SCK_Edge)
 283     SplitAllCriticalEdges(F);
 284   SmallVector<Instruction*, 8> IndirCalls;
 285   SmallVector<BasicBlock*, 16> AllBlocks;
 286   SmallVector<Instruction*, 8> CmpTraceTargets;
 287   for (auto &BB : F) {
 288     AllBlocks.push_back(&BB);
 289     for (auto &Inst : BB) {
 290       if (Options.IndirectCalls) {
 291         CallSite CS(&Inst);
 292         if (CS && !CS.getCalledFunction())
 293           IndirCalls.push_back(&Inst);
 294       }
 295       if (Options.TraceCmp && isa<ICmpInst>(&Inst))
 296         CmpTraceTargets.push_back(&Inst);
 297     }
 298   }
 299   InjectCoverage(F, AllBlocks);
 300   InjectCoverageForIndirectCalls(F, IndirCalls);
 301   InjectTraceForCmp(F, CmpTraceTargets);
 302   return true;
 303 }
 304
 305 bool SanitizerCoverageModule::InjectCoverage(Function &F,
 306                                              ArrayRef<BasicBlock *> AllBlocks) {
 307   switch (Options.CoverageType) {
 308   case SanitizerCoverageOptions::SCK_None:
 309     return false;
 310   case SanitizerCoverageOptions::SCK_Function:
 311     InjectCoverageAtBlock(F, F.getEntryBlock(), false);
 312     return true;
 313   default: {
 314     bool UseCalls = ClCoverageBlockThreshold < AllBlocks.size();
 315     for (auto BB : AllBlocks)
 316       InjectCoverageAtBlock(F, *BB, UseCalls);
 317     return true;
 318   }
 319   }
 320 }
 321
 322 // On every indirect call we call a run-time function
 323 // __sanitizer_cov_indir_call* with two parameters:
 324 //   - callee address,
 325 //   - global cache array that contains kCacheSize pointers (zero-initialized).
 326 //     The cache is used to speed up recording the caller-callee pairs.
 327 // The address of the caller is passed implicitly via caller PC.
 328 // kCacheSize is encoded in the name of the run-time function.
 329 void SanitizerCoverageModule::InjectCoverageForIndirectCalls(
 330     Function &F, ArrayRef<Instruction *> IndirCalls) {
 331   if (IndirCalls.empty()) return;
 332   const int kCacheSize = 16;
 333   const int kCacheAlignment = 64;  // Align for better performance.
 334   Type *Ty = ArrayType::get(IntptrTy, kCacheSize);
 335   for (auto I : IndirCalls) {
 336     IRBuilder<> IRB(I);
 337     CallSite CS(I);
 338     Value *Callee = CS.getCalledValue();
 339     if (isa<InlineAsm>(Callee)) continue;
 340     GlobalVariable *CalleeCache = new GlobalVariable(
 341         *F.getParent(), Ty, false, GlobalValue::PrivateLinkage,
 342         Constant::getNullValue(Ty), "__sancov_gen_callee_cache");
 343     CalleeCache->setAlignment(kCacheAlignment);
 344     IRB.CreateCall(SanCovIndirCallFunction,
 345                    {IRB.CreatePointerCast(Callee, IntptrTy),
 346                     IRB.CreatePointerCast(CalleeCache, IntptrTy)});
 347   }
 348 }
 349
 350 void SanitizerCoverageModule::InjectTraceForCmp(
 351     Function &F, ArrayRef<Instruction *> CmpTraceTargets) {
 352   for (auto I : CmpTraceTargets) {
 353     if (ICmpInst *ICMP = dyn_cast<ICmpInst>(I)) {
 354       IRBuilder<> IRB(ICMP);
 355       Value *A0 = ICMP->getOperand(0);
 356       Value *A1 = ICMP->getOperand(1);
 357       if (!A0->getType()->isIntegerTy()) continue;
 358       uint64_t TypeSize = DL->getTypeStoreSizeInBits(A0->getType());
 359       // __sanitizer_cov_trace_cmp((type_size << 32) | predicate, A0, A1);
 360       IRB.CreateCall(
 361           SanCovTraceCmpFunction,
 362           {ConstantInt::get(Int64Ty, (TypeSize << 32) | ICMP->getPredicate()),
 363            IRB.CreateIntCast(A0, Int64Ty, true),
 364            IRB.CreateIntCast(A1, Int64Ty, true)});
 365     }
 366   }
 367 }
 368
 369 void SanitizerCoverageModule::SetNoSanitizeMetadata(Instruction *I) {
 370   I->setMetadata(
 371       I->getParent()->getParent()->getParent()->getMDKindID("nosanitize"),
 372       MDNode::get(*C, None));
 373 }
 374
 375 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
 376                                                     bool UseCalls) {
 377   BasicBlock::iterator IP = BB.getFirstInsertionPt(), BE = BB.end();
 378   // Skip static allocas at the top of the entry block so they don't become
 379   // dynamic when we split the block.  If we used our optimized stack layout,
 380   // then there will only be one alloca and it will come first.
 381   for (; IP != BE; ++IP) {
 382     AllocaInst *AI = dyn_cast<AllocaInst>(IP);
 383     if (!AI || !AI->isStaticAlloca())
 384       break;
 385   }
 386
 387   bool IsEntryBB = &BB == &F.getEntryBlock();
 388   DebugLoc EntryLoc = IsEntryBB && IP->getDebugLoc()
 389                           ? IP->getDebugLoc().getFnDebugLoc()
 390                           : IP->getDebugLoc();
 391   IRBuilder<> IRB(IP);
 392   IRB.SetCurrentDebugLocation(EntryLoc);
 393   SmallVector<Value *, 1> Indices;
 394   Value *GuardP = IRB.CreateAdd(
 395       IRB.CreatePointerCast(GuardArray, IntptrTy),
 396       ConstantInt::get(IntptrTy, (1 + NumberOfInstrumentedBlocks()) * 4));
 397   Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
 398   GuardP = IRB.CreateIntToPtr(GuardP, Int32PtrTy);
 399   if (UseCalls) {
 400     IRB.CreateCall(SanCovWithCheckFunction, GuardP);
 401   } else {
 402     LoadInst *Load = IRB.CreateLoad(GuardP);
 403     Load->setAtomic(Monotonic);
 404     Load->setAlignment(4);
 405     SetNoSanitizeMetadata(Load);
 406     Value *Cmp = IRB.CreateICmpSGE(Constant::getNullValue(Load->getType()), Load);
 407     Instruction *Ins = SplitBlockAndInsertIfThen(
 408         Cmp, IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
 409     IRB.SetInsertPoint(Ins);
 410     IRB.SetCurrentDebugLocation(EntryLoc);
 411     // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC.
 412     IRB.CreateCall(SanCovFunction, GuardP);
 413     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
 414   }
 415
 416   if (Options.Use8bitCounters) {
 417     IRB.SetInsertPoint(IP);
 418     Value *P = IRB.CreateAdd(
 419         IRB.CreatePointerCast(EightBitCounterArray, IntptrTy),
 420         ConstantInt::get(IntptrTy, NumberOfInstrumentedBlocks() - 1));
 421     P = IRB.CreateIntToPtr(P, IRB.getInt8PtrTy());
 422     LoadInst *LI = IRB.CreateLoad(P);
 423     Value *Inc = IRB.CreateAdd(LI, ConstantInt::get(IRB.getInt8Ty(), 1));
 424     StoreInst *SI = IRB.CreateStore(Inc, P);
 425     SetNoSanitizeMetadata(LI);
 426     SetNoSanitizeMetadata(SI);
 427   }
 428
 429   if (Options.TraceBB) {
 430     // Experimental support for tracing.
 431     // Insert a callback with the same guard variable as used for coverage.
 432     IRB.SetInsertPoint(IP);
 433     IRB.CreateCall(IsEntryBB ? SanCovTraceEnter : SanCovTraceBB, GuardP);
 434   }
 435 }
 436
 437 char SanitizerCoverageModule::ID = 0;
 438 INITIALIZE_PASS(SanitizerCoverageModule, "sancov",
 439     "SanitizerCoverage: TODO."
 440     "ModulePass", false, false)
 441 ModulePass *llvm::createSanitizerCoverageModulePass(
 442     const SanitizerCoverageOptions &Options) {
 443   return new SanitizerCoverageModule(Options);
 444 }