contrib/llvm/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/ADT/ArrayRef.h"
  32 #include "llvm/ADT/SmallVector.h"
  33 #include "llvm/Analysis/EHPersonalities.h"
  34 #include "llvm/Analysis/PostDominators.h"
  35 #include "llvm/IR/CFG.h"
  36 #include "llvm/IR/CallSite.h"
  37 #include "llvm/IR/DataLayout.h"
  38 #include "llvm/IR/DebugInfo.h"
  39 #include "llvm/IR/Dominators.h"
  40 #include "llvm/IR/Function.h"
  41 #include "llvm/IR/IRBuilder.h"
  42 #include "llvm/IR/InlineAsm.h"
  43 #include "llvm/IR/LLVMContext.h"
  44 #include "llvm/IR/MDBuilder.h"
  45 #include "llvm/IR/Module.h"
  46 #include "llvm/IR/Type.h"
  47 #include "llvm/Support/CommandLine.h"
  48 #include "llvm/Support/Debug.h"
  49 #include "llvm/Support/raw_ostream.h"
  50 #include "llvm/Transforms/Instrumentation.h"
  51 #include "llvm/Transforms/Scalar.h"
  52 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
  53 #include "llvm/Transforms/Utils/ModuleUtils.h"
  54
  55 using namespace llvm;
  56
  57 #define DEBUG_TYPE "sancov"
  58
  59 static const char *const SanCovModuleInitName = "__sanitizer_cov_module_init";
  60 static const char *const SanCovName = "__sanitizer_cov";
  61 static const char *const SanCovWithCheckName = "__sanitizer_cov_with_check";
  62 static const char *const SanCovIndirCallName = "__sanitizer_cov_indir_call16";
  63 static const char *const SanCovTracePCIndirName =
  64     "__sanitizer_cov_trace_pc_indir";
  65 static const char *const SanCovTraceEnterName =
  66     "__sanitizer_cov_trace_func_enter";
  67 static const char *const SanCovTraceBBName =
  68     "__sanitizer_cov_trace_basic_block";
  69 static const char *const SanCovTracePCName = "__sanitizer_cov_trace_pc";
  70 static const char *const SanCovTraceCmpName = "__sanitizer_cov_trace_cmp";
  71 static const char *const SanCovTraceSwitchName = "__sanitizer_cov_trace_switch";
  72 static const char *const SanCovModuleCtorName = "sancov.module_ctor";
  73 static const uint64_t SanCtorAndDtorPriority = 2;
  74
  75 static cl::opt<int> ClCoverageLevel(
  76     "sanitizer-coverage-level",
  77     cl::desc("Sanitizer Coverage. 0: none, 1: entry block, 2: all blocks, "
  78              "3: all blocks and critical edges, "
  79              "4: above plus indirect calls"),
  80     cl::Hidden, cl::init(0));
  81
  82 static cl::opt<unsigned> ClCoverageBlockThreshold(
  83     "sanitizer-coverage-block-threshold",
  84     cl::desc("Use a callback with a guard check inside it if there are"
  85              " more than this number of blocks."),
  86     cl::Hidden, cl::init(500));
  87
  88 static cl::opt<bool>
  89     ClExperimentalTracing("sanitizer-coverage-experimental-tracing",
  90                           cl::desc("Experimental basic-block tracing: insert "
  91                                    "callbacks at every basic block"),
  92                           cl::Hidden, cl::init(false));
  93
  94 static cl::opt<bool> ClExperimentalTracePC("sanitizer-coverage-trace-pc",
  95                                            cl::desc("Experimental pc tracing"),
  96                                            cl::Hidden, cl::init(false));
  97
  98 static cl::opt<bool>
  99     ClExperimentalCMPTracing("sanitizer-coverage-experimental-trace-compares",
 100                              cl::desc("Experimental tracing of CMP and similar "
 101                                       "instructions"),
 102                              cl::Hidden, cl::init(false));
 103
 104 static cl::opt<bool>
 105     ClPruneBlocks("sanitizer-coverage-prune-blocks",
 106                   cl::desc("Reduce the number of instrumented blocks"),
 107                   cl::Hidden, cl::init(true));
 108
 109 // Experimental 8-bit counters used as an additional search heuristic during
 110 // coverage-guided fuzzing.
 111 // The counters are not thread-friendly:
 112 //   - contention on these counters may cause significant slowdown;
 113 //   - the counter updates are racy and the results may be inaccurate.
 114 // They are also inaccurate due to 8-bit integer overflow.
 115 static cl::opt<bool> ClUse8bitCounters("sanitizer-coverage-8bit-counters",
 116                                        cl::desc("Experimental 8-bit counters"),
 117                                        cl::Hidden, cl::init(false));
 118
 119 namespace {
 120
 121 SanitizerCoverageOptions getOptions(int LegacyCoverageLevel) {
 122   SanitizerCoverageOptions Res;
 123   switch (LegacyCoverageLevel) {
 124   case 0:
 125     Res.CoverageType = SanitizerCoverageOptions::SCK_None;
 126     break;
 127   case 1:
 128     Res.CoverageType = SanitizerCoverageOptions::SCK_Function;
 129     break;
 130   case 2:
 131     Res.CoverageType = SanitizerCoverageOptions::SCK_BB;
 132     break;
 133   case 3:
 134     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
 135     break;
 136   case 4:
 137     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
 138     Res.IndirectCalls = true;
 139     break;
 140   }
 141   return Res;
 142 }
 143
 144 SanitizerCoverageOptions OverrideFromCL(SanitizerCoverageOptions Options) {
 145   // Sets CoverageType and IndirectCalls.
 146   SanitizerCoverageOptions CLOpts = getOptions(ClCoverageLevel);
 147   Options.CoverageType = std::max(Options.CoverageType, CLOpts.CoverageType);
 148   Options.IndirectCalls |= CLOpts.IndirectCalls;
 149   Options.TraceBB |= ClExperimentalTracing;
 150   Options.TraceCmp |= ClExperimentalCMPTracing;
 151   Options.Use8bitCounters |= ClUse8bitCounters;
 152   Options.TracePC |= ClExperimentalTracePC;
 153   return Options;
 154 }
 155
 156 class SanitizerCoverageModule : public ModulePass {
 157 public:
 158   SanitizerCoverageModule(
 159       const SanitizerCoverageOptions &Options = SanitizerCoverageOptions())
 160       : ModulePass(ID), Options(OverrideFromCL(Options)) {
 161     initializeSanitizerCoverageModulePass(*PassRegistry::getPassRegistry());
 162   }
 163   bool runOnModule(Module &M) override;
 164   bool runOnFunction(Function &F);
 165   static char ID; // Pass identification, replacement for typeid
 166   const char *getPassName() const override { return "SanitizerCoverageModule"; }
 167
 168   void getAnalysisUsage(AnalysisUsage &AU) const override {
 169     AU.addRequired<DominatorTreeWrapperPass>();
 170     AU.addRequired<PostDominatorTreeWrapperPass>();
 171   }
 172
 173 private:
 174   void InjectCoverageForIndirectCalls(Function &F,
 175                                       ArrayRef<Instruction *> IndirCalls);
 176   void InjectTraceForCmp(Function &F, ArrayRef<Instruction *> CmpTraceTargets);
 177   void InjectTraceForSwitch(Function &F,
 178                             ArrayRef<Instruction *> SwitchTraceTargets);
 179   bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks);
 180   void SetNoSanitizeMetadata(Instruction *I);
 181   void InjectCoverageAtBlock(Function &F, BasicBlock &BB, bool UseCalls);
 182   unsigned NumberOfInstrumentedBlocks() {
 183     return SanCovFunction->getNumUses() +
 184            SanCovWithCheckFunction->getNumUses() + SanCovTraceBB->getNumUses() +
 185            SanCovTraceEnter->getNumUses();
 186   }
 187   Function *SanCovFunction;
 188   Function *SanCovWithCheckFunction;
 189   Function *SanCovIndirCallFunction, *SanCovTracePCIndir;
 190   Function *SanCovTraceEnter, *SanCovTraceBB, *SanCovTracePC;
 191   Function *SanCovTraceCmpFunction;
 192   Function *SanCovTraceSwitchFunction;
 193   InlineAsm *EmptyAsm;
 194   Type *IntptrTy, *Int64Ty, *Int64PtrTy;
 195   Module *CurModule;
 196   LLVMContext *C;
 197   const DataLayout *DL;
 198
 199   GlobalVariable *GuardArray;
 200   GlobalVariable *EightBitCounterArray;
 201
 202   SanitizerCoverageOptions Options;
 203 };
 204
 205 } // namespace
 206
 207 bool SanitizerCoverageModule::runOnModule(Module &M) {
 208   if (Options.CoverageType == SanitizerCoverageOptions::SCK_None)
 209     return false;
 210   C = &(M.getContext());
 211   DL = &M.getDataLayout();
 212   CurModule = &M;
 213   IntptrTy = Type::getIntNTy(*C, DL->getPointerSizeInBits());
 214   Type *VoidTy = Type::getVoidTy(*C);
 215   IRBuilder<> IRB(*C);
 216   Type *Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
 217   Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
 218   Int64PtrTy = PointerType::getUnqual(IRB.getInt64Ty());
 219   Int64Ty = IRB.getInt64Ty();
 220
 221   SanCovFunction = checkSanitizerInterfaceFunction(
 222       M.getOrInsertFunction(SanCovName, VoidTy, Int32PtrTy, nullptr));
 223   SanCovWithCheckFunction = checkSanitizerInterfaceFunction(
 224       M.getOrInsertFunction(SanCovWithCheckName, VoidTy, Int32PtrTy, nullptr));
 225   SanCovTracePCIndir = checkSanitizerInterfaceFunction(
 226       M.getOrInsertFunction(SanCovTracePCIndirName, VoidTy, IntptrTy, nullptr));
 227   SanCovIndirCallFunction =
 228       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 229           SanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr));
 230   SanCovTraceCmpFunction =
 231       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 232           SanCovTraceCmpName, VoidTy, Int64Ty, Int64Ty, Int64Ty, nullptr));
 233   SanCovTraceSwitchFunction =
 234       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 235           SanCovTraceSwitchName, VoidTy, Int64Ty, Int64PtrTy, nullptr));
 236
 237   // We insert an empty inline asm after cov callbacks to avoid callback merge.
 238   EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
 239                             StringRef(""), StringRef(""),
 240                             /*hasSideEffects=*/true);
 241
 242   SanCovTracePC = checkSanitizerInterfaceFunction(
 243       M.getOrInsertFunction(SanCovTracePCName, VoidTy, nullptr));
 244   SanCovTraceEnter = checkSanitizerInterfaceFunction(
 245       M.getOrInsertFunction(SanCovTraceEnterName, VoidTy, Int32PtrTy, nullptr));
 246   SanCovTraceBB = checkSanitizerInterfaceFunction(
 247       M.getOrInsertFunction(SanCovTraceBBName, VoidTy, Int32PtrTy, nullptr));
 248
 249   // At this point we create a dummy array of guards because we don't
 250   // know how many elements we will need.
 251   Type *Int32Ty = IRB.getInt32Ty();
 252   Type *Int8Ty = IRB.getInt8Ty();
 253
 254   GuardArray =
 255       new GlobalVariable(M, Int32Ty, false, GlobalValue::ExternalLinkage,
 256                          nullptr, "__sancov_gen_cov_tmp");
 257   if (Options.Use8bitCounters)
 258     EightBitCounterArray =
 259         new GlobalVariable(M, Int8Ty, false, GlobalVariable::ExternalLinkage,
 260                            nullptr, "__sancov_gen_cov_tmp");
 261
 262   for (auto &F : M)
 263     runOnFunction(F);
 264
 265   auto N = NumberOfInstrumentedBlocks();
 266
 267   // Now we know how many elements we need. Create an array of guards
 268   // with one extra element at the beginning for the size.
 269   Type *Int32ArrayNTy = ArrayType::get(Int32Ty, N + 1);
 270   GlobalVariable *RealGuardArray = new GlobalVariable(
 271       M, Int32ArrayNTy, false, GlobalValue::PrivateLinkage,
 272       Constant::getNullValue(Int32ArrayNTy), "__sancov_gen_cov");
 273
 274   // Replace the dummy array with the real one.
 275   GuardArray->replaceAllUsesWith(
 276       IRB.CreatePointerCast(RealGuardArray, Int32PtrTy));
 277   GuardArray->eraseFromParent();
 278
 279   GlobalVariable *RealEightBitCounterArray;
 280   if (Options.Use8bitCounters) {
 281     // Make sure the array is 16-aligned.
 282     static const int CounterAlignment = 16;
 283     Type *Int8ArrayNTy = ArrayType::get(Int8Ty, alignTo(N, CounterAlignment));
 284     RealEightBitCounterArray = new GlobalVariable(
 285         M, Int8ArrayNTy, false, GlobalValue::PrivateLinkage,
 286         Constant::getNullValue(Int8ArrayNTy), "__sancov_gen_cov_counter");
 287     RealEightBitCounterArray->setAlignment(CounterAlignment);
 288     EightBitCounterArray->replaceAllUsesWith(
 289         IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy));
 290     EightBitCounterArray->eraseFromParent();
 291   }
 292
 293   // Create variable for module (compilation unit) name
 294   Constant *ModNameStrConst =
 295       ConstantDataArray::getString(M.getContext(), M.getName(), true);
 296   GlobalVariable *ModuleName =
 297       new GlobalVariable(M, ModNameStrConst->getType(), true,
 298                          GlobalValue::PrivateLinkage, ModNameStrConst);
 299
 300   if (!Options.TracePC) {
 301     Function *CtorFunc;
 302     std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
 303         M, SanCovModuleCtorName, SanCovModuleInitName,
 304         {Int32PtrTy, IntptrTy, Int8PtrTy, Int8PtrTy},
 305         {IRB.CreatePointerCast(RealGuardArray, Int32PtrTy),
 306          ConstantInt::get(IntptrTy, N),
 307          Options.Use8bitCounters
 308              ? IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy)
 309              : Constant::getNullValue(Int8PtrTy),
 310          IRB.CreatePointerCast(ModuleName, Int8PtrTy)});
 311
 312     appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority);
 313   }
 314
 315   return true;
 316 }
 317
 318 // True if block has successors and it dominates all of them.
 319 static bool isFullDominator(const BasicBlock *BB, const DominatorTree *DT) {
 320   if (succ_begin(BB) == succ_end(BB))
 321     return false;
 322
 323   for (const BasicBlock *SUCC : make_range(succ_begin(BB), succ_end(BB))) {
 324     if (!DT->dominates(BB, SUCC))
 325       return false;
 326   }
 327
 328   return true;
 329 }
 330
 331 // True if block has predecessors and it postdominates all of them.
 332 static bool isFullPostDominator(const BasicBlock *BB,
 333                                 const PostDominatorTree *PDT) {
 334   if (pred_begin(BB) == pred_end(BB))
 335     return false;
 336
 337   for (const BasicBlock *PRED : make_range(pred_begin(BB), pred_end(BB))) {
 338     if (!PDT->dominates(BB, PRED))
 339       return false;
 340   }
 341
 342   return true;
 343 }
 344
 345 static bool shouldInstrumentBlock(const Function& F, const BasicBlock *BB, const DominatorTree *DT,
 346                                   const PostDominatorTree *PDT) {
 347   if (!ClPruneBlocks || &F.getEntryBlock() == BB)
 348     return true;
 349
 350   return !(isFullDominator(BB, DT) || isFullPostDominator(BB, PDT));
 351 }
 352
 353 bool SanitizerCoverageModule::runOnFunction(Function &F) {
 354   if (F.empty())
 355     return false;
 356   if (F.getName().find(".module_ctor") != std::string::npos)
 357     return false; // Should not instrument sanitizer init functions.
 358   // Don't instrument functions using SEH for now. Splitting basic blocks like
 359   // we do for coverage breaks WinEHPrepare.
 360   // FIXME: Remove this when SEH no longer uses landingpad pattern matching.
 361   if (F.hasPersonalityFn() &&
 362       isAsynchronousEHPersonality(classifyEHPersonality(F.getPersonalityFn())))
 363     return false;
 364   if (Options.CoverageType >= SanitizerCoverageOptions::SCK_Edge)
 365     SplitAllCriticalEdges(F);
 366   SmallVector<Instruction *, 8> IndirCalls;
 367   SmallVector<BasicBlock *, 16> BlocksToInstrument;
 368   SmallVector<Instruction *, 8> CmpTraceTargets;
 369   SmallVector<Instruction *, 8> SwitchTraceTargets;
 370
 371   const DominatorTree *DT =
 372       &getAnalysis<DominatorTreeWrapperPass>(F).getDomTree();
 373   const PostDominatorTree *PDT =
 374       &getAnalysis<PostDominatorTreeWrapperPass>(F).getPostDomTree();
 375
 376   for (auto &BB : F) {
 377     if (shouldInstrumentBlock(F, &BB, DT, PDT))
 378       BlocksToInstrument.push_back(&BB);
 379     for (auto &Inst : BB) {
 380       if (Options.IndirectCalls) {
 381         CallSite CS(&Inst);
 382         if (CS && !CS.getCalledFunction())
 383           IndirCalls.push_back(&Inst);
 384       }
 385       if (Options.TraceCmp) {
 386         if (isa<ICmpInst>(&Inst))
 387           CmpTraceTargets.push_back(&Inst);
 388         if (isa<SwitchInst>(&Inst))
 389           SwitchTraceTargets.push_back(&Inst);
 390       }
 391     }
 392   }
 393
 394   InjectCoverage(F, BlocksToInstrument);
 395   InjectCoverageForIndirectCalls(F, IndirCalls);
 396   InjectTraceForCmp(F, CmpTraceTargets);
 397   InjectTraceForSwitch(F, SwitchTraceTargets);
 398   return true;
 399 }
 400
 401 bool SanitizerCoverageModule::InjectCoverage(Function &F,
 402                                              ArrayRef<BasicBlock *> AllBlocks) {
 403   switch (Options.CoverageType) {
 404   case SanitizerCoverageOptions::SCK_None:
 405     return false;
 406   case SanitizerCoverageOptions::SCK_Function:
 407     InjectCoverageAtBlock(F, F.getEntryBlock(), false);
 408     return true;
 409   default: {
 410     bool UseCalls = ClCoverageBlockThreshold < AllBlocks.size();
 411     for (auto BB : AllBlocks)
 412       InjectCoverageAtBlock(F, *BB, UseCalls);
 413     return true;
 414   }
 415   }
 416 }
 417
 418 // On every indirect call we call a run-time function
 419 // __sanitizer_cov_indir_call* with two parameters:
 420 //   - callee address,
 421 //   - global cache array that contains CacheSize pointers (zero-initialized).
 422 //     The cache is used to speed up recording the caller-callee pairs.
 423 // The address of the caller is passed implicitly via caller PC.
 424 // CacheSize is encoded in the name of the run-time function.
 425 void SanitizerCoverageModule::InjectCoverageForIndirectCalls(
 426     Function &F, ArrayRef<Instruction *> IndirCalls) {
 427   if (IndirCalls.empty())
 428     return;
 429   const int CacheSize = 16;
 430   const int CacheAlignment = 64; // Align for better performance.
 431   Type *Ty = ArrayType::get(IntptrTy, CacheSize);
 432   for (auto I : IndirCalls) {
 433     IRBuilder<> IRB(I);
 434     CallSite CS(I);
 435     Value *Callee = CS.getCalledValue();
 436     if (isa<InlineAsm>(Callee))
 437       continue;
 438     GlobalVariable *CalleeCache = new GlobalVariable(
 439         *F.getParent(), Ty, false, GlobalValue::PrivateLinkage,
 440         Constant::getNullValue(Ty), "__sancov_gen_callee_cache");
 441     CalleeCache->setAlignment(CacheAlignment);
 442     if (Options.TracePC)
 443       IRB.CreateCall(SanCovTracePCIndir,
 444                      IRB.CreatePointerCast(Callee, IntptrTy));
 445     else
 446       IRB.CreateCall(SanCovIndirCallFunction,
 447                      {IRB.CreatePointerCast(Callee, IntptrTy),
 448                       IRB.CreatePointerCast(CalleeCache, IntptrTy)});
 449   }
 450 }
 451
 452 // For every switch statement we insert a call:
 453 // __sanitizer_cov_trace_switch(CondValue,
 454 //      {NumCases, ValueSizeInBits, Case0Value, Case1Value, Case2Value, ... })
 455
 456 void SanitizerCoverageModule::InjectTraceForSwitch(
 457     Function &, ArrayRef<Instruction *> SwitchTraceTargets) {
 458   for (auto I : SwitchTraceTargets) {
 459     if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
 460       IRBuilder<> IRB(I);
 461       SmallVector<Constant *, 16> Initializers;
 462       Value *Cond = SI->getCondition();
 463       if (Cond->getType()->getScalarSizeInBits() >
 464           Int64Ty->getScalarSizeInBits())
 465         continue;
 466       Initializers.push_back(ConstantInt::get(Int64Ty, SI->getNumCases()));
 467       Initializers.push_back(
 468           ConstantInt::get(Int64Ty, Cond->getType()->getScalarSizeInBits()));
 469       if (Cond->getType()->getScalarSizeInBits() <
 470           Int64Ty->getScalarSizeInBits())
 471         Cond = IRB.CreateIntCast(Cond, Int64Ty, false);
 472       for (auto It : SI->cases()) {
 473         Constant *C = It.getCaseValue();
 474         if (C->getType()->getScalarSizeInBits() <
 475             Int64Ty->getScalarSizeInBits())
 476           C = ConstantExpr::getCast(CastInst::ZExt, It.getCaseValue(), Int64Ty);
 477         Initializers.push_back(C);
 478       }
 479       ArrayType *ArrayOfInt64Ty = ArrayType::get(Int64Ty, Initializers.size());
 480       GlobalVariable *GV = new GlobalVariable(
 481           *CurModule, ArrayOfInt64Ty, false, GlobalVariable::InternalLinkage,
 482           ConstantArray::get(ArrayOfInt64Ty, Initializers),
 483           "__sancov_gen_cov_switch_values");
 484       IRB.CreateCall(SanCovTraceSwitchFunction,
 485                      {Cond, IRB.CreatePointerCast(GV, Int64PtrTy)});
 486     }
 487   }
 488 }
 489
 490 void SanitizerCoverageModule::InjectTraceForCmp(
 491     Function &, ArrayRef<Instruction *> CmpTraceTargets) {
 492   for (auto I : CmpTraceTargets) {
 493     if (ICmpInst *ICMP = dyn_cast<ICmpInst>(I)) {
 494       IRBuilder<> IRB(ICMP);
 495       Value *A0 = ICMP->getOperand(0);
 496       Value *A1 = ICMP->getOperand(1);
 497       if (!A0->getType()->isIntegerTy())
 498         continue;
 499       uint64_t TypeSize = DL->getTypeStoreSizeInBits(A0->getType());
 500       // __sanitizer_cov_trace_cmp((type_size << 32) | predicate, A0, A1);
 501       IRB.CreateCall(
 502           SanCovTraceCmpFunction,
 503           {ConstantInt::get(Int64Ty, (TypeSize << 32) | ICMP->getPredicate()),
 504            IRB.CreateIntCast(A0, Int64Ty, true),
 505            IRB.CreateIntCast(A1, Int64Ty, true)});
 506     }
 507   }
 508 }
 509
 510 void SanitizerCoverageModule::SetNoSanitizeMetadata(Instruction *I) {
 511   I->setMetadata(I->getModule()->getMDKindID("nosanitize"),
 512                  MDNode::get(*C, None));
 513 }
 514
 515 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
 516                                                     bool UseCalls) {
 517   // Don't insert coverage for unreachable blocks: we will never call
 518   // __sanitizer_cov() for them, so counting them in
 519   // NumberOfInstrumentedBlocks() might complicate calculation of code coverage
 520   // percentage. Also, unreachable instructions frequently have no debug
 521   // locations.
 522   if (isa<UnreachableInst>(BB.getTerminator()))
 523     return;
 524   BasicBlock::iterator IP = BB.getFirstInsertionPt();
 525
 526   bool IsEntryBB = &BB == &F.getEntryBlock();
 527   DebugLoc EntryLoc;
 528   if (IsEntryBB) {
 529     if (auto SP = F.getSubprogram())
 530       EntryLoc = DebugLoc::get(SP->getScopeLine(), 0, SP);
 531     // Keep static allocas and llvm.localescape calls in the entry block.  Even
 532     // if we aren't splitting the block, it's nice for allocas to be before
 533     // calls.
 534     IP = PrepareToSplitEntryBlock(BB, IP);
 535   } else {
 536     EntryLoc = IP->getDebugLoc();
 537   }
 538
 539   IRBuilder<> IRB(&*IP);
 540   IRB.SetCurrentDebugLocation(EntryLoc);
 541   Value *GuardP = IRB.CreateAdd(
 542       IRB.CreatePointerCast(GuardArray, IntptrTy),
 543       ConstantInt::get(IntptrTy, (1 + NumberOfInstrumentedBlocks()) * 4));
 544   Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
 545   GuardP = IRB.CreateIntToPtr(GuardP, Int32PtrTy);
 546   if (Options.TracePC) {
 547     IRB.CreateCall(SanCovTracePC); // gets the PC using GET_CALLER_PC.
 548     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
 549   } else if (Options.TraceBB) {
 550     IRB.CreateCall(IsEntryBB ? SanCovTraceEnter : SanCovTraceBB, GuardP);
 551   } else if (UseCalls) {
 552     IRB.CreateCall(SanCovWithCheckFunction, GuardP);
 553   } else {
 554     LoadInst *Load = IRB.CreateLoad(GuardP);
 555     Load->setAtomic(AtomicOrdering::Monotonic);
 556     Load->setAlignment(4);
 557     SetNoSanitizeMetadata(Load);
 558     Value *Cmp =
 559         IRB.CreateICmpSGE(Constant::getNullValue(Load->getType()), Load);
 560     Instruction *Ins = SplitBlockAndInsertIfThen(
 561         Cmp, &*IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
 562     IRB.SetInsertPoint(Ins);
 563     IRB.SetCurrentDebugLocation(EntryLoc);
 564     // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC.
 565     IRB.CreateCall(SanCovFunction, GuardP);
 566     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
 567   }
 568
 569   if (Options.Use8bitCounters) {
 570     IRB.SetInsertPoint(&*IP);
 571     Value *P = IRB.CreateAdd(
 572         IRB.CreatePointerCast(EightBitCounterArray, IntptrTy),
 573         ConstantInt::get(IntptrTy, NumberOfInstrumentedBlocks() - 1));
 574     P = IRB.CreateIntToPtr(P, IRB.getInt8PtrTy());
 575     LoadInst *LI = IRB.CreateLoad(P);
 576     Value *Inc = IRB.CreateAdd(LI, ConstantInt::get(IRB.getInt8Ty(), 1));
 577     StoreInst *SI = IRB.CreateStore(Inc, P);
 578     SetNoSanitizeMetadata(LI);
 579     SetNoSanitizeMetadata(SI);
 580   }
 581 }
 582
 583 char SanitizerCoverageModule::ID = 0;
 584 INITIALIZE_PASS_BEGIN(SanitizerCoverageModule, "sancov",
 585                       "SanitizerCoverage: TODO."
 586                       "ModulePass",
 587                       false, false)
 588 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
 589 INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)
 590 INITIALIZE_PASS_END(SanitizerCoverageModule, "sancov",
 591                     "SanitizerCoverage: TODO."
 592                     "ModulePass",
 593                     false, false)
 594 ModulePass *llvm::createSanitizerCoverageModulePass(
 595     const SanitizerCoverageOptions &Options) {
 596   return new SanitizerCoverageModule(Options);
 597 }