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      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 }
    598