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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/Transforms/Instrumentation.h"
32 #include "llvm/ADT/ArrayRef.h"
33 #include "llvm/ADT/SmallVector.h"
34 #include "llvm/Analysis/EHPersonalities.h"
35 #include "llvm/IR/CallSite.h"
36 #include "llvm/IR/DataLayout.h"
37 #include "llvm/IR/DebugInfo.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 kSanCovWithCheckName = "__sanitizer_cov_with_check";
59 static const char *const kSanCovIndirCallName = "__sanitizer_cov_indir_call16";
60 static const char *const kSanCovTraceEnter = "__sanitizer_cov_trace_func_enter";
61 static const char *const kSanCovTraceBB = "__sanitizer_cov_trace_basic_block";
62 static const char *const kSanCovTraceCmp = "__sanitizer_cov_trace_cmp";
63 static const char *const kSanCovTraceSwitch = "__sanitizer_cov_trace_switch";
64 static const char *const kSanCovModuleCtorName = "sancov.module_ctor";
65 static const uint64_t    kSanCtorAndDtorPriority = 2;
66 
67 static cl::opt<int> ClCoverageLevel("sanitizer-coverage-level",
68        cl::desc("Sanitizer Coverage. 0: none, 1: entry block, 2: all blocks, "
69                 "3: all blocks and critical edges, "
70                 "4: above plus indirect calls"),
71        cl::Hidden, cl::init(0));
72 
73 static cl::opt<unsigned> ClCoverageBlockThreshold(
74     "sanitizer-coverage-block-threshold",
75     cl::desc("Use a callback with a guard check inside it if there are"
76              " more than this number of blocks."),
77     cl::Hidden, cl::init(500));
78 
79 static cl::opt<bool>
80     ClExperimentalTracing("sanitizer-coverage-experimental-tracing",
81                           cl::desc("Experimental basic-block tracing: insert "
82                                    "callbacks at every basic block"),
83                           cl::Hidden, cl::init(false));
84 
85 static cl::opt<bool>
86     ClExperimentalCMPTracing("sanitizer-coverage-experimental-trace-compares",
87                              cl::desc("Experimental tracing of CMP and similar "
88                                       "instructions"),
89                              cl::Hidden, cl::init(false));
90 
91 // Experimental 8-bit counters used as an additional search heuristic during
92 // coverage-guided fuzzing.
93 // The counters are not thread-friendly:
94 //   - contention on these counters may cause significant slowdown;
95 //   - the counter updates are racy and the results may be inaccurate.
96 // They are also inaccurate due to 8-bit integer overflow.
97 static cl::opt<bool> ClUse8bitCounters("sanitizer-coverage-8bit-counters",
98                                        cl::desc("Experimental 8-bit counters"),
99                                        cl::Hidden, cl::init(false));
100 
101 namespace {
102 
getOptions(int LegacyCoverageLevel)103 SanitizerCoverageOptions getOptions(int LegacyCoverageLevel) {
104   SanitizerCoverageOptions Res;
105   switch (LegacyCoverageLevel) {
106   case 0:
107     Res.CoverageType = SanitizerCoverageOptions::SCK_None;
108     break;
109   case 1:
110     Res.CoverageType = SanitizerCoverageOptions::SCK_Function;
111     break;
112   case 2:
113     Res.CoverageType = SanitizerCoverageOptions::SCK_BB;
114     break;
115   case 3:
116     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
117     break;
118   case 4:
119     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
120     Res.IndirectCalls = true;
121     break;
122   }
123   return Res;
124 }
125 
OverrideFromCL(SanitizerCoverageOptions Options)126 SanitizerCoverageOptions OverrideFromCL(SanitizerCoverageOptions Options) {
127   // Sets CoverageType and IndirectCalls.
128   SanitizerCoverageOptions CLOpts = getOptions(ClCoverageLevel);
129   Options.CoverageType = std::max(Options.CoverageType, CLOpts.CoverageType);
130   Options.IndirectCalls |= CLOpts.IndirectCalls;
131   Options.TraceBB |= ClExperimentalTracing;
132   Options.TraceCmp |= ClExperimentalCMPTracing;
133   Options.Use8bitCounters |= ClUse8bitCounters;
134   return Options;
135 }
136 
137 class SanitizerCoverageModule : public ModulePass {
138  public:
SanitizerCoverageModule(const SanitizerCoverageOptions & Options=SanitizerCoverageOptions ())139   SanitizerCoverageModule(
140       const SanitizerCoverageOptions &Options = SanitizerCoverageOptions())
141       : ModulePass(ID), Options(OverrideFromCL(Options)) {}
142   bool runOnModule(Module &M) override;
143   bool runOnFunction(Function &F);
144   static char ID;  // Pass identification, replacement for typeid
getPassName() const145   const char *getPassName() const override {
146     return "SanitizerCoverageModule";
147   }
148 
149  private:
150   void InjectCoverageForIndirectCalls(Function &F,
151                                       ArrayRef<Instruction *> IndirCalls);
152   void InjectTraceForCmp(Function &F, ArrayRef<Instruction *> CmpTraceTargets);
153   void InjectTraceForSwitch(Function &F,
154                             ArrayRef<Instruction *> SwitchTraceTargets);
155   bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks);
156   void SetNoSanitizeMetadata(Instruction *I);
157   void InjectCoverageAtBlock(Function &F, BasicBlock &BB, bool UseCalls);
NumberOfInstrumentedBlocks()158   unsigned NumberOfInstrumentedBlocks() {
159     return SanCovFunction->getNumUses() +
160            SanCovWithCheckFunction->getNumUses() + SanCovTraceBB->getNumUses() +
161            SanCovTraceEnter->getNumUses();
162   }
163   Function *SanCovFunction;
164   Function *SanCovWithCheckFunction;
165   Function *SanCovIndirCallFunction;
166   Function *SanCovTraceEnter, *SanCovTraceBB;
167   Function *SanCovTraceCmpFunction;
168   Function *SanCovTraceSwitchFunction;
169   InlineAsm *EmptyAsm;
170   Type *IntptrTy, *Int64Ty, *Int64PtrTy;
171   Module *CurModule;
172   LLVMContext *C;
173   const DataLayout *DL;
174 
175   GlobalVariable *GuardArray;
176   GlobalVariable *EightBitCounterArray;
177 
178   SanitizerCoverageOptions Options;
179 };
180 
181 }  // namespace
182 
runOnModule(Module & M)183 bool SanitizerCoverageModule::runOnModule(Module &M) {
184   if (Options.CoverageType == SanitizerCoverageOptions::SCK_None)
185     return false;
186   C = &(M.getContext());
187   DL = &M.getDataLayout();
188   CurModule = &M;
189   IntptrTy = Type::getIntNTy(*C, DL->getPointerSizeInBits());
190   Type *VoidTy = Type::getVoidTy(*C);
191   IRBuilder<> IRB(*C);
192   Type *Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
193   Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
194   Int64PtrTy = PointerType::getUnqual(IRB.getInt64Ty());
195   Int64Ty = IRB.getInt64Ty();
196 
197   SanCovFunction = checkSanitizerInterfaceFunction(
198       M.getOrInsertFunction(kSanCovName, VoidTy, Int32PtrTy, nullptr));
199   SanCovWithCheckFunction = checkSanitizerInterfaceFunction(
200       M.getOrInsertFunction(kSanCovWithCheckName, VoidTy, Int32PtrTy, nullptr));
201   SanCovIndirCallFunction =
202       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
203           kSanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr));
204   SanCovTraceCmpFunction =
205       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
206           kSanCovTraceCmp, VoidTy, Int64Ty, Int64Ty, Int64Ty, nullptr));
207   SanCovTraceSwitchFunction =
208       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
209           kSanCovTraceSwitch, VoidTy, Int64Ty, Int64PtrTy, nullptr));
210 
211   // We insert an empty inline asm after cov callbacks to avoid callback merge.
212   EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
213                             StringRef(""), StringRef(""),
214                             /*hasSideEffects=*/true);
215 
216   SanCovTraceEnter = checkSanitizerInterfaceFunction(
217       M.getOrInsertFunction(kSanCovTraceEnter, VoidTy, Int32PtrTy, nullptr));
218   SanCovTraceBB = checkSanitizerInterfaceFunction(
219       M.getOrInsertFunction(kSanCovTraceBB, VoidTy, Int32PtrTy, nullptr));
220 
221   // At this point we create a dummy array of guards because we don't
222   // know how many elements we will need.
223   Type *Int32Ty = IRB.getInt32Ty();
224   Type *Int8Ty = IRB.getInt8Ty();
225 
226   GuardArray =
227       new GlobalVariable(M, Int32Ty, false, GlobalValue::ExternalLinkage,
228                          nullptr, "__sancov_gen_cov_tmp");
229   if (Options.Use8bitCounters)
230     EightBitCounterArray =
231         new GlobalVariable(M, Int8Ty, false, GlobalVariable::ExternalLinkage,
232                            nullptr, "__sancov_gen_cov_tmp");
233 
234   for (auto &F : M)
235     runOnFunction(F);
236 
237   auto N = NumberOfInstrumentedBlocks();
238 
239   // Now we know how many elements we need. Create an array of guards
240   // with one extra element at the beginning for the size.
241   Type *Int32ArrayNTy = ArrayType::get(Int32Ty, N + 1);
242   GlobalVariable *RealGuardArray = new GlobalVariable(
243       M, Int32ArrayNTy, false, GlobalValue::PrivateLinkage,
244       Constant::getNullValue(Int32ArrayNTy), "__sancov_gen_cov");
245 
246 
247   // Replace the dummy array with the real one.
248   GuardArray->replaceAllUsesWith(
249       IRB.CreatePointerCast(RealGuardArray, Int32PtrTy));
250   GuardArray->eraseFromParent();
251 
252   GlobalVariable *RealEightBitCounterArray;
253   if (Options.Use8bitCounters) {
254     // Make sure the array is 16-aligned.
255     static const int kCounterAlignment = 16;
256     Type *Int8ArrayNTy =
257         ArrayType::get(Int8Ty, RoundUpToAlignment(N, kCounterAlignment));
258     RealEightBitCounterArray = new GlobalVariable(
259         M, Int8ArrayNTy, false, GlobalValue::PrivateLinkage,
260         Constant::getNullValue(Int8ArrayNTy), "__sancov_gen_cov_counter");
261     RealEightBitCounterArray->setAlignment(kCounterAlignment);
262     EightBitCounterArray->replaceAllUsesWith(
263         IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy));
264     EightBitCounterArray->eraseFromParent();
265   }
266 
267   // Create variable for module (compilation unit) name
268   Constant *ModNameStrConst =
269       ConstantDataArray::getString(M.getContext(), M.getName(), true);
270   GlobalVariable *ModuleName =
271       new GlobalVariable(M, ModNameStrConst->getType(), true,
272                          GlobalValue::PrivateLinkage, ModNameStrConst);
273 
274   Function *CtorFunc;
275   std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
276       M, kSanCovModuleCtorName, kSanCovModuleInitName,
277       {Int32PtrTy, IntptrTy, Int8PtrTy, Int8PtrTy},
278       {IRB.CreatePointerCast(RealGuardArray, Int32PtrTy),
279        ConstantInt::get(IntptrTy, N),
280        Options.Use8bitCounters
281            ? IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy)
282            : Constant::getNullValue(Int8PtrTy),
283        IRB.CreatePointerCast(ModuleName, Int8PtrTy)});
284 
285   appendToGlobalCtors(M, CtorFunc, kSanCtorAndDtorPriority);
286 
287   return true;
288 }
289 
runOnFunction(Function & F)290 bool SanitizerCoverageModule::runOnFunction(Function &F) {
291   if (F.empty()) return false;
292   if (F.getName().find(".module_ctor") != std::string::npos)
293     return false;  // Should not instrument sanitizer init functions.
294   // Don't instrument functions using SEH for now. Splitting basic blocks like
295   // we do for coverage breaks WinEHPrepare.
296   // FIXME: Remove this when SEH no longer uses landingpad pattern matching.
297   if (F.hasPersonalityFn() &&
298       isAsynchronousEHPersonality(classifyEHPersonality(F.getPersonalityFn())))
299     return false;
300   if (Options.CoverageType >= SanitizerCoverageOptions::SCK_Edge)
301     SplitAllCriticalEdges(F);
302   SmallVector<Instruction*, 8> IndirCalls;
303   SmallVector<BasicBlock*, 16> AllBlocks;
304   SmallVector<Instruction*, 8> CmpTraceTargets;
305   SmallVector<Instruction*, 8> SwitchTraceTargets;
306   for (auto &BB : F) {
307     AllBlocks.push_back(&BB);
308     for (auto &Inst : BB) {
309       if (Options.IndirectCalls) {
310         CallSite CS(&Inst);
311         if (CS && !CS.getCalledFunction())
312           IndirCalls.push_back(&Inst);
313       }
314       if (Options.TraceCmp) {
315         if (isa<ICmpInst>(&Inst))
316           CmpTraceTargets.push_back(&Inst);
317         if (isa<SwitchInst>(&Inst))
318           SwitchTraceTargets.push_back(&Inst);
319       }
320     }
321   }
322   InjectCoverage(F, AllBlocks);
323   InjectCoverageForIndirectCalls(F, IndirCalls);
324   InjectTraceForCmp(F, CmpTraceTargets);
325   InjectTraceForSwitch(F, SwitchTraceTargets);
326   return true;
327 }
328 
InjectCoverage(Function & F,ArrayRef<BasicBlock * > AllBlocks)329 bool SanitizerCoverageModule::InjectCoverage(Function &F,
330                                              ArrayRef<BasicBlock *> AllBlocks) {
331   switch (Options.CoverageType) {
332   case SanitizerCoverageOptions::SCK_None:
333     return false;
334   case SanitizerCoverageOptions::SCK_Function:
335     InjectCoverageAtBlock(F, F.getEntryBlock(), false);
336     return true;
337   default: {
338     bool UseCalls = ClCoverageBlockThreshold < AllBlocks.size();
339     for (auto BB : AllBlocks)
340       InjectCoverageAtBlock(F, *BB, UseCalls);
341     return true;
342   }
343   }
344 }
345 
346 // On every indirect call we call a run-time function
347 // __sanitizer_cov_indir_call* with two parameters:
348 //   - callee address,
349 //   - global cache array that contains kCacheSize pointers (zero-initialized).
350 //     The cache is used to speed up recording the caller-callee pairs.
351 // The address of the caller is passed implicitly via caller PC.
352 // kCacheSize is encoded in the name of the run-time function.
InjectCoverageForIndirectCalls(Function & F,ArrayRef<Instruction * > IndirCalls)353 void SanitizerCoverageModule::InjectCoverageForIndirectCalls(
354     Function &F, ArrayRef<Instruction *> IndirCalls) {
355   if (IndirCalls.empty()) return;
356   const int kCacheSize = 16;
357   const int kCacheAlignment = 64;  // Align for better performance.
358   Type *Ty = ArrayType::get(IntptrTy, kCacheSize);
359   for (auto I : IndirCalls) {
360     IRBuilder<> IRB(I);
361     CallSite CS(I);
362     Value *Callee = CS.getCalledValue();
363     if (isa<InlineAsm>(Callee)) continue;
364     GlobalVariable *CalleeCache = new GlobalVariable(
365         *F.getParent(), Ty, false, GlobalValue::PrivateLinkage,
366         Constant::getNullValue(Ty), "__sancov_gen_callee_cache");
367     CalleeCache->setAlignment(kCacheAlignment);
368     IRB.CreateCall(SanCovIndirCallFunction,
369                    {IRB.CreatePointerCast(Callee, IntptrTy),
370                     IRB.CreatePointerCast(CalleeCache, IntptrTy)});
371   }
372 }
373 
374 // For every switch statement we insert a call:
375 // __sanitizer_cov_trace_switch(CondValue,
376 //      {NumCases, ValueSizeInBits, Case0Value, Case1Value, Case2Value, ... })
377 
InjectTraceForSwitch(Function & F,ArrayRef<Instruction * > SwitchTraceTargets)378 void SanitizerCoverageModule::InjectTraceForSwitch(
379     Function &F, ArrayRef<Instruction *> SwitchTraceTargets) {
380   for (auto I : SwitchTraceTargets) {
381     if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
382       IRBuilder<> IRB(I);
383       SmallVector<Constant *, 16> Initializers;
384       Value *Cond = SI->getCondition();
385       if (Cond->getType()->getScalarSizeInBits() >
386           Int64Ty->getScalarSizeInBits())
387         continue;
388       Initializers.push_back(ConstantInt::get(Int64Ty, SI->getNumCases()));
389       Initializers.push_back(
390           ConstantInt::get(Int64Ty, Cond->getType()->getScalarSizeInBits()));
391       if (Cond->getType()->getScalarSizeInBits() <
392           Int64Ty->getScalarSizeInBits())
393         Cond = IRB.CreateIntCast(Cond, Int64Ty, false);
394       for (auto It: SI->cases()) {
395         Constant *C = It.getCaseValue();
396         if (C->getType()->getScalarSizeInBits() <
397             Int64Ty->getScalarSizeInBits())
398           C = ConstantExpr::getCast(CastInst::ZExt, It.getCaseValue(), Int64Ty);
399         Initializers.push_back(C);
400       }
401       ArrayType *ArrayOfInt64Ty = ArrayType::get(Int64Ty, Initializers.size());
402       GlobalVariable *GV = new GlobalVariable(
403           *CurModule, ArrayOfInt64Ty, false, GlobalVariable::InternalLinkage,
404           ConstantArray::get(ArrayOfInt64Ty, Initializers),
405           "__sancov_gen_cov_switch_values");
406       IRB.CreateCall(SanCovTraceSwitchFunction,
407                      {Cond, IRB.CreatePointerCast(GV, Int64PtrTy)});
408     }
409   }
410 }
411 
412 
InjectTraceForCmp(Function & F,ArrayRef<Instruction * > CmpTraceTargets)413 void SanitizerCoverageModule::InjectTraceForCmp(
414     Function &F, ArrayRef<Instruction *> CmpTraceTargets) {
415   for (auto I : CmpTraceTargets) {
416     if (ICmpInst *ICMP = dyn_cast<ICmpInst>(I)) {
417       IRBuilder<> IRB(ICMP);
418       Value *A0 = ICMP->getOperand(0);
419       Value *A1 = ICMP->getOperand(1);
420       if (!A0->getType()->isIntegerTy()) continue;
421       uint64_t TypeSize = DL->getTypeStoreSizeInBits(A0->getType());
422       // __sanitizer_cov_trace_cmp((type_size << 32) | predicate, A0, A1);
423       IRB.CreateCall(
424           SanCovTraceCmpFunction,
425           {ConstantInt::get(Int64Ty, (TypeSize << 32) | ICMP->getPredicate()),
426            IRB.CreateIntCast(A0, Int64Ty, true),
427            IRB.CreateIntCast(A1, Int64Ty, true)});
428     }
429   }
430 }
431 
SetNoSanitizeMetadata(Instruction * I)432 void SanitizerCoverageModule::SetNoSanitizeMetadata(Instruction *I) {
433   I->setMetadata(
434       I->getModule()->getMDKindID("nosanitize"), MDNode::get(*C, None));
435 }
436 
InjectCoverageAtBlock(Function & F,BasicBlock & BB,bool UseCalls)437 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
438                                                     bool UseCalls) {
439   // Don't insert coverage for unreachable blocks: we will never call
440   // __sanitizer_cov() for them, so counting them in
441   // NumberOfInstrumentedBlocks() might complicate calculation of code coverage
442   // percentage. Also, unreachable instructions frequently have no debug
443   // locations.
444   if (isa<UnreachableInst>(BB.getTerminator()))
445     return;
446   BasicBlock::iterator IP = BB.getFirstInsertionPt();
447 
448   bool IsEntryBB = &BB == &F.getEntryBlock();
449   DebugLoc EntryLoc;
450   if (IsEntryBB) {
451     if (auto SP = getDISubprogram(&F))
452       EntryLoc = DebugLoc::get(SP->getScopeLine(), 0, SP);
453     // Keep static allocas and llvm.localescape calls in the entry block.  Even
454     // if we aren't splitting the block, it's nice for allocas to be before
455     // calls.
456     IP = PrepareToSplitEntryBlock(BB, IP);
457   } else {
458     EntryLoc = IP->getDebugLoc();
459   }
460 
461   IRBuilder<> IRB(&*IP);
462   IRB.SetCurrentDebugLocation(EntryLoc);
463   Value *GuardP = IRB.CreateAdd(
464       IRB.CreatePointerCast(GuardArray, IntptrTy),
465       ConstantInt::get(IntptrTy, (1 + NumberOfInstrumentedBlocks()) * 4));
466   Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
467   GuardP = IRB.CreateIntToPtr(GuardP, Int32PtrTy);
468   if (Options.TraceBB) {
469     IRB.CreateCall(IsEntryBB ? SanCovTraceEnter : SanCovTraceBB, GuardP);
470   } else if (UseCalls) {
471     IRB.CreateCall(SanCovWithCheckFunction, GuardP);
472   } else {
473     LoadInst *Load = IRB.CreateLoad(GuardP);
474     Load->setAtomic(Monotonic);
475     Load->setAlignment(4);
476     SetNoSanitizeMetadata(Load);
477     Value *Cmp = IRB.CreateICmpSGE(Constant::getNullValue(Load->getType()), Load);
478     Instruction *Ins = SplitBlockAndInsertIfThen(
479         Cmp, &*IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
480     IRB.SetInsertPoint(Ins);
481     IRB.SetCurrentDebugLocation(EntryLoc);
482     // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC.
483     IRB.CreateCall(SanCovFunction, GuardP);
484     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
485   }
486 
487   if (Options.Use8bitCounters) {
488     IRB.SetInsertPoint(&*IP);
489     Value *P = IRB.CreateAdd(
490         IRB.CreatePointerCast(EightBitCounterArray, IntptrTy),
491         ConstantInt::get(IntptrTy, NumberOfInstrumentedBlocks() - 1));
492     P = IRB.CreateIntToPtr(P, IRB.getInt8PtrTy());
493     LoadInst *LI = IRB.CreateLoad(P);
494     Value *Inc = IRB.CreateAdd(LI, ConstantInt::get(IRB.getInt8Ty(), 1));
495     StoreInst *SI = IRB.CreateStore(Inc, P);
496     SetNoSanitizeMetadata(LI);
497     SetNoSanitizeMetadata(SI);
498   }
499 }
500 
501 char SanitizerCoverageModule::ID = 0;
502 INITIALIZE_PASS(SanitizerCoverageModule, "sancov",
503     "SanitizerCoverage: TODO."
504     "ModulePass", false, false)
createSanitizerCoverageModulePass(const SanitizerCoverageOptions & Options)505 ModulePass *llvm::createSanitizerCoverageModulePass(
506     const SanitizerCoverageOptions &Options) {
507   return new SanitizerCoverageModule(Options);
508 }
509