xref: /llvm-project/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp (revision 4d25ad93f3f52ca8976b4a09959135ec42d6da03) 
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 SanCovTraceCmp1 = "__sanitizer_cov_trace_cmp1";
71 static const char *const SanCovTraceCmp2 = "__sanitizer_cov_trace_cmp2";
72 static const char *const SanCovTraceCmp4 = "__sanitizer_cov_trace_cmp4";
73 static const char *const SanCovTraceCmp8 = "__sanitizer_cov_trace_cmp8";
74 static const char *const SanCovTraceDiv4 = "__sanitizer_cov_trace_div4";
75 static const char *const SanCovTraceDiv8 = "__sanitizer_cov_trace_div8";
76 static const char *const SanCovTraceGep = "__sanitizer_cov_trace_gep";
77 static const char *const SanCovTraceSwitchName = "__sanitizer_cov_trace_switch";
78 static const char *const SanCovModuleCtorName = "sancov.module_ctor";
79 static const uint64_t SanCtorAndDtorPriority = 2;
80 
81 static const char *const SanCovTracePCGuardSection = "__sancov_guards";
82 static const char *const SanCovTracePCGuardName =
83     "__sanitizer_cov_trace_pc_guard";
84 static const char *const SanCovTracePCGuardInitName =
85     "__sanitizer_cov_trace_pc_guard_init";
86 
87 static cl::opt<int> ClCoverageLevel(
88     "sanitizer-coverage-level",
89     cl::desc("Sanitizer Coverage. 0: none, 1: entry block, 2: all blocks, "
90              "3: all blocks and critical edges, "
91              "4: above plus indirect calls"),
92     cl::Hidden, cl::init(0));
93 
94 static cl::opt<unsigned> ClCoverageBlockThreshold(
95     "sanitizer-coverage-block-threshold",
96     cl::desc("Use a callback with a guard check inside it if there are"
97              " more than this number of blocks."),
98     cl::Hidden, cl::init(500));
99 
100 static cl::opt<bool>
101     ClExperimentalTracing("sanitizer-coverage-experimental-tracing",
102                           cl::desc("Experimental basic-block tracing: insert "
103                                    "callbacks at every basic block"),
104                           cl::Hidden, cl::init(false));
105 
106 static cl::opt<bool> ClExperimentalTracePC("sanitizer-coverage-trace-pc",
107                                            cl::desc("Experimental pc tracing"),
108                                            cl::Hidden, cl::init(false));
109 
110 static cl::opt<bool> ClTracePCGuard("sanitizer-coverage-trace-pc-guard",
111                                     cl::desc("pc tracing with a guard"),
112                                     cl::Hidden, cl::init(false));
113 
114 static cl::opt<bool>
115     ClCMPTracing("sanitizer-coverage-trace-compares",
116                  cl::desc("Tracing of CMP and similar instructions"),
117                  cl::Hidden, cl::init(false));
118 
119 static cl::opt<bool> ClDIVTracing("sanitizer-coverage-trace-divs",
120                                   cl::desc("Tracing of DIV instructions"),
121                                   cl::Hidden, cl::init(false));
122 
123 static cl::opt<bool> ClGEPTracing("sanitizer-coverage-trace-geps",
124                                   cl::desc("Tracing of GEP instructions"),
125                                   cl::Hidden, cl::init(false));
126 
127 static cl::opt<bool>
128     ClPruneBlocks("sanitizer-coverage-prune-blocks",
129                   cl::desc("Reduce the number of instrumented blocks"),
130                   cl::Hidden, cl::init(true));
131 
132 // Experimental 8-bit counters used as an additional search heuristic during
133 // coverage-guided fuzzing.
134 // The counters are not thread-friendly:
135 //   - contention on these counters may cause significant slowdown;
136 //   - the counter updates are racy and the results may be inaccurate.
137 // They are also inaccurate due to 8-bit integer overflow.
138 static cl::opt<bool> ClUse8bitCounters("sanitizer-coverage-8bit-counters",
139                                        cl::desc("Experimental 8-bit counters"),
140                                        cl::Hidden, cl::init(false));
141 
142 namespace {
143 
144 SanitizerCoverageOptions getOptions(int LegacyCoverageLevel) {
145   SanitizerCoverageOptions Res;
146   switch (LegacyCoverageLevel) {
147   case 0:
148     Res.CoverageType = SanitizerCoverageOptions::SCK_None;
149     break;
150   case 1:
151     Res.CoverageType = SanitizerCoverageOptions::SCK_Function;
152     break;
153   case 2:
154     Res.CoverageType = SanitizerCoverageOptions::SCK_BB;
155     break;
156   case 3:
157     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
158     break;
159   case 4:
160     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
161     Res.IndirectCalls = true;
162     break;
163   }
164   return Res;
165 }
166 
167 SanitizerCoverageOptions OverrideFromCL(SanitizerCoverageOptions Options) {
168   // Sets CoverageType and IndirectCalls.
169   SanitizerCoverageOptions CLOpts = getOptions(ClCoverageLevel);
170   Options.CoverageType = std::max(Options.CoverageType, CLOpts.CoverageType);
171   Options.IndirectCalls |= CLOpts.IndirectCalls;
172   Options.TraceBB |= ClExperimentalTracing;
173   Options.TraceCmp |= ClCMPTracing;
174   Options.TraceDiv |= ClDIVTracing;
175   Options.TraceGep |= ClGEPTracing;
176   Options.Use8bitCounters |= ClUse8bitCounters;
177   Options.TracePC |= ClExperimentalTracePC;
178   Options.TracePCGuard |= ClTracePCGuard;
179   return Options;
180 }
181 
182 class SanitizerCoverageModule : public ModulePass {
183 public:
184   SanitizerCoverageModule(
185       const SanitizerCoverageOptions &Options = SanitizerCoverageOptions())
186       : ModulePass(ID), Options(OverrideFromCL(Options)) {
187     initializeSanitizerCoverageModulePass(*PassRegistry::getPassRegistry());
188   }
189   bool runOnModule(Module &M) override;
190   bool runOnFunction(Function &F);
191   static char ID; // Pass identification, replacement for typeid
192   StringRef getPassName() const override { return "SanitizerCoverageModule"; }
193 
194   void getAnalysisUsage(AnalysisUsage &AU) const override {
195     AU.addRequired<DominatorTreeWrapperPass>();
196     AU.addRequired<PostDominatorTreeWrapperPass>();
197   }
198 
199 private:
200   void InjectCoverageForIndirectCalls(Function &F,
201                                       ArrayRef<Instruction *> IndirCalls);
202   void InjectTraceForCmp(Function &F, ArrayRef<Instruction *> CmpTraceTargets);
203   void InjectTraceForDiv(Function &F,
204                          ArrayRef<BinaryOperator *> DivTraceTargets);
205   void InjectTraceForGep(Function &F,
206                          ArrayRef<GetElementPtrInst *> GepTraceTargets);
207   void InjectTraceForSwitch(Function &F,
208                             ArrayRef<Instruction *> SwitchTraceTargets);
209   bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks);
210   void CreateFunctionGuardArray(size_t NumGuards, Function &F);
211   void SetNoSanitizeMetadata(Instruction *I);
212   void InjectCoverageAtBlock(Function &F, BasicBlock &BB, size_t Idx,
213                              bool UseCalls);
214   unsigned NumberOfInstrumentedBlocks() {
215     return SanCovFunction->getNumUses() +
216            SanCovWithCheckFunction->getNumUses() + SanCovTraceBB->getNumUses() +
217            SanCovTraceEnter->getNumUses();
218   }
219   Function *SanCovFunction;
220   Function *SanCovWithCheckFunction;
221   Function *SanCovIndirCallFunction, *SanCovTracePCIndir;
222   Function *SanCovTraceEnter, *SanCovTraceBB, *SanCovTracePC, *SanCovTracePCGuard;
223   Function *SanCovTraceCmpFunction[4];
224   Function *SanCovTraceDivFunction[2];
225   Function *SanCovTraceGepFunction;
226   Function *SanCovTraceSwitchFunction;
227   InlineAsm *EmptyAsm;
228   Type *IntptrTy, *IntptrPtrTy, *Int64Ty, *Int64PtrTy, *Int32Ty, *Int32PtrTy;
229   Module *CurModule;
230   LLVMContext *C;
231   const DataLayout *DL;
232 
233   GlobalVariable *GuardArray;
234   GlobalVariable *FunctionGuardArray;  // for trace-pc-guard.
235   GlobalVariable *EightBitCounterArray;
236   bool HasSancovGuardsSection;
237 
238   SanitizerCoverageOptions Options;
239 };
240 
241 } // namespace
242 
243 bool SanitizerCoverageModule::runOnModule(Module &M) {
244   if (Options.CoverageType == SanitizerCoverageOptions::SCK_None)
245     return false;
246   C = &(M.getContext());
247   DL = &M.getDataLayout();
248   CurModule = &M;
249   HasSancovGuardsSection = false;
250   IntptrTy = Type::getIntNTy(*C, DL->getPointerSizeInBits());
251   IntptrPtrTy = PointerType::getUnqual(IntptrTy);
252   Type *VoidTy = Type::getVoidTy(*C);
253   IRBuilder<> IRB(*C);
254   Type *Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
255   Int64PtrTy = PointerType::getUnqual(IRB.getInt64Ty());
256   Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
257   Int64Ty = IRB.getInt64Ty();
258   Int32Ty = IRB.getInt32Ty();
259 
260   SanCovFunction = checkSanitizerInterfaceFunction(
261       M.getOrInsertFunction(SanCovName, VoidTy, Int32PtrTy, nullptr));
262   SanCovWithCheckFunction = checkSanitizerInterfaceFunction(
263       M.getOrInsertFunction(SanCovWithCheckName, VoidTy, Int32PtrTy, nullptr));
264   SanCovTracePCIndir = checkSanitizerInterfaceFunction(
265       M.getOrInsertFunction(SanCovTracePCIndirName, VoidTy, IntptrTy, nullptr));
266   SanCovIndirCallFunction =
267       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
268           SanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr));
269   SanCovTraceCmpFunction[0] =
270       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
271           SanCovTraceCmp1, VoidTy, IRB.getInt8Ty(), IRB.getInt8Ty(), nullptr));
272   SanCovTraceCmpFunction[1] = checkSanitizerInterfaceFunction(
273       M.getOrInsertFunction(SanCovTraceCmp2, VoidTy, IRB.getInt16Ty(),
274                             IRB.getInt16Ty(), nullptr));
275   SanCovTraceCmpFunction[2] = checkSanitizerInterfaceFunction(
276       M.getOrInsertFunction(SanCovTraceCmp4, VoidTy, IRB.getInt32Ty(),
277                             IRB.getInt32Ty(), nullptr));
278   SanCovTraceCmpFunction[3] =
279       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
280           SanCovTraceCmp8, VoidTy, Int64Ty, Int64Ty, nullptr));
281 
282   SanCovTraceDivFunction[0] =
283       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
284           SanCovTraceDiv4, VoidTy, IRB.getInt32Ty(), nullptr));
285   SanCovTraceDivFunction[1] =
286       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
287           SanCovTraceDiv8, VoidTy, Int64Ty, nullptr));
288   SanCovTraceGepFunction =
289       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
290           SanCovTraceGep, VoidTy, IntptrTy, nullptr));
291   SanCovTraceSwitchFunction =
292       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
293           SanCovTraceSwitchName, VoidTy, Int64Ty, Int64PtrTy, nullptr));
294 
295   // We insert an empty inline asm after cov callbacks to avoid callback merge.
296   EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
297                             StringRef(""), StringRef(""),
298                             /*hasSideEffects=*/true);
299 
300   SanCovTracePC = checkSanitizerInterfaceFunction(
301       M.getOrInsertFunction(SanCovTracePCName, VoidTy, nullptr));
302   SanCovTracePCGuard = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
303       SanCovTracePCGuardName, VoidTy, Int32PtrTy, nullptr));
304   SanCovTraceEnter = checkSanitizerInterfaceFunction(
305       M.getOrInsertFunction(SanCovTraceEnterName, VoidTy, Int32PtrTy, nullptr));
306   SanCovTraceBB = checkSanitizerInterfaceFunction(
307       M.getOrInsertFunction(SanCovTraceBBName, VoidTy, Int32PtrTy, nullptr));
308 
309   // At this point we create a dummy array of guards because we don't
310   // know how many elements we will need.
311   Type *Int32Ty = IRB.getInt32Ty();
312   Type *Int8Ty = IRB.getInt8Ty();
313 
314   if (!Options.TracePCGuard)
315     GuardArray =
316         new GlobalVariable(M, Int32Ty, false, GlobalValue::ExternalLinkage,
317                            nullptr, "__sancov_gen_cov_tmp");
318   if (Options.Use8bitCounters)
319     EightBitCounterArray =
320         new GlobalVariable(M, Int8Ty, false, GlobalVariable::ExternalLinkage,
321                            nullptr, "__sancov_gen_cov_tmp");
322 
323   for (auto &F : M)
324     runOnFunction(F);
325 
326   auto N = NumberOfInstrumentedBlocks();
327 
328   GlobalVariable *RealGuardArray = nullptr;
329   if (!Options.TracePCGuard) {
330     // Now we know how many elements we need. Create an array of guards
331     // with one extra element at the beginning for the size.
332     Type *Int32ArrayNTy = ArrayType::get(Int32Ty, N + 1);
333     RealGuardArray = new GlobalVariable(
334         M, Int32ArrayNTy, false, GlobalValue::PrivateLinkage,
335         Constant::getNullValue(Int32ArrayNTy), "__sancov_gen_cov");
336 
337     // Replace the dummy array with the real one.
338     GuardArray->replaceAllUsesWith(
339         IRB.CreatePointerCast(RealGuardArray, Int32PtrTy));
340     GuardArray->eraseFromParent();
341   }
342 
343   GlobalVariable *RealEightBitCounterArray;
344   if (Options.Use8bitCounters) {
345     // Make sure the array is 16-aligned.
346     static const int CounterAlignment = 16;
347     Type *Int8ArrayNTy = ArrayType::get(Int8Ty, alignTo(N, CounterAlignment));
348     RealEightBitCounterArray = new GlobalVariable(
349         M, Int8ArrayNTy, false, GlobalValue::PrivateLinkage,
350         Constant::getNullValue(Int8ArrayNTy), "__sancov_gen_cov_counter");
351     RealEightBitCounterArray->setAlignment(CounterAlignment);
352     EightBitCounterArray->replaceAllUsesWith(
353         IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy));
354     EightBitCounterArray->eraseFromParent();
355   }
356 
357   // Create variable for module (compilation unit) name
358   Constant *ModNameStrConst =
359       ConstantDataArray::getString(M.getContext(), M.getName(), true);
360   GlobalVariable *ModuleName =
361       new GlobalVariable(M, ModNameStrConst->getType(), true,
362                          GlobalValue::PrivateLinkage, ModNameStrConst);
363   if (Options.TracePCGuard) {
364     if (HasSancovGuardsSection) {
365       Function *CtorFunc;
366       std::string SectionName(SanCovTracePCGuardSection);
367       GlobalVariable *Bounds[2];
368       const char *Prefix[2] = {"__start_", "__stop_"};
369       for (int i = 0; i < 2; i++) {
370         Bounds[i] = new GlobalVariable(M, Int32PtrTy, false,
371                                        GlobalVariable::ExternalLinkage, nullptr,
372                                        Prefix[i] + SectionName);
373         Bounds[i]->setVisibility(GlobalValue::HiddenVisibility);
374       }
375       std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
376           M, SanCovModuleCtorName, SanCovTracePCGuardInitName,
377           {Int32PtrTy, Int32PtrTy},
378           {IRB.CreatePointerCast(Bounds[0], Int32PtrTy),
379             IRB.CreatePointerCast(Bounds[1], Int32PtrTy)});
380 
381       appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority);
382     }
383   } else if (!Options.TracePC) {
384     Function *CtorFunc;
385     std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
386         M, SanCovModuleCtorName, SanCovModuleInitName,
387         {Int32PtrTy, IntptrTy, Int8PtrTy, Int8PtrTy},
388         {IRB.CreatePointerCast(RealGuardArray, Int32PtrTy),
389          ConstantInt::get(IntptrTy, N),
390          Options.Use8bitCounters
391              ? IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy)
392              : Constant::getNullValue(Int8PtrTy),
393          IRB.CreatePointerCast(ModuleName, Int8PtrTy)});
394 
395     appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority);
396   }
397 
398   return true;
399 }
400 
401 // True if block has successors and it dominates all of them.
402 static bool isFullDominator(const BasicBlock *BB, const DominatorTree *DT) {
403   if (succ_begin(BB) == succ_end(BB))
404     return false;
405 
406   for (const BasicBlock *SUCC : make_range(succ_begin(BB), succ_end(BB))) {
407     if (!DT->dominates(BB, SUCC))
408       return false;
409   }
410 
411   return true;
412 }
413 
414 // True if block has predecessors and it postdominates all of them.
415 static bool isFullPostDominator(const BasicBlock *BB,
416                                 const PostDominatorTree *PDT) {
417   if (pred_begin(BB) == pred_end(BB))
418     return false;
419 
420   for (const BasicBlock *PRED : make_range(pred_begin(BB), pred_end(BB))) {
421     if (!PDT->dominates(BB, PRED))
422       return false;
423   }
424 
425   return true;
426 }
427 
428 static bool shouldInstrumentBlock(const Function& F, const BasicBlock *BB, const DominatorTree *DT,
429                                   const PostDominatorTree *PDT) {
430   // Don't insert coverage for unreachable blocks: we will never call
431   // __sanitizer_cov() for them, so counting them in
432   // NumberOfInstrumentedBlocks() might complicate calculation of code coverage
433   // percentage. Also, unreachable instructions frequently have no debug
434   // locations.
435   if (isa<UnreachableInst>(BB->getTerminator()))
436     return false;
437 
438   if (!ClPruneBlocks || &F.getEntryBlock() == BB)
439     return true;
440 
441   return !(isFullDominator(BB, DT) || isFullPostDominator(BB, PDT));
442 }
443 
444 bool SanitizerCoverageModule::runOnFunction(Function &F) {
445   if (F.empty())
446     return false;
447   if (F.getName().find(".module_ctor") != std::string::npos)
448     return false; // Should not instrument sanitizer init functions.
449   if (F.getName().startswith("__sanitizer_"))
450     return false;  // Don't instrument __sanitizer_* callbacks.
451   // Don't instrument functions using SEH for now. Splitting basic blocks like
452   // we do for coverage breaks WinEHPrepare.
453   // FIXME: Remove this when SEH no longer uses landingpad pattern matching.
454   if (F.hasPersonalityFn() &&
455       isAsynchronousEHPersonality(classifyEHPersonality(F.getPersonalityFn())))
456     return false;
457   if (Options.CoverageType >= SanitizerCoverageOptions::SCK_Edge)
458     SplitAllCriticalEdges(F);
459   SmallVector<Instruction *, 8> IndirCalls;
460   SmallVector<BasicBlock *, 16> BlocksToInstrument;
461   SmallVector<Instruction *, 8> CmpTraceTargets;
462   SmallVector<Instruction *, 8> SwitchTraceTargets;
463   SmallVector<BinaryOperator *, 8> DivTraceTargets;
464   SmallVector<GetElementPtrInst *, 8> GepTraceTargets;
465 
466   const DominatorTree *DT =
467       &getAnalysis<DominatorTreeWrapperPass>(F).getDomTree();
468   const PostDominatorTree *PDT =
469       &getAnalysis<PostDominatorTreeWrapperPass>(F).getPostDomTree();
470 
471   for (auto &BB : F) {
472     if (shouldInstrumentBlock(F, &BB, DT, PDT))
473       BlocksToInstrument.push_back(&BB);
474     for (auto &Inst : BB) {
475       if (Options.IndirectCalls) {
476         CallSite CS(&Inst);
477         if (CS && !CS.getCalledFunction())
478           IndirCalls.push_back(&Inst);
479       }
480       if (Options.TraceCmp) {
481         if (isa<ICmpInst>(&Inst))
482           CmpTraceTargets.push_back(&Inst);
483         if (isa<SwitchInst>(&Inst))
484           SwitchTraceTargets.push_back(&Inst);
485       }
486       if (Options.TraceDiv)
487         if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&Inst))
488           if (BO->getOpcode() == Instruction::SDiv ||
489               BO->getOpcode() == Instruction::UDiv)
490             DivTraceTargets.push_back(BO);
491       if (Options.TraceGep)
492         if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(&Inst))
493           GepTraceTargets.push_back(GEP);
494    }
495   }
496 
497   InjectCoverage(F, BlocksToInstrument);
498   InjectCoverageForIndirectCalls(F, IndirCalls);
499   InjectTraceForCmp(F, CmpTraceTargets);
500   InjectTraceForSwitch(F, SwitchTraceTargets);
501   InjectTraceForDiv(F, DivTraceTargets);
502   InjectTraceForGep(F, GepTraceTargets);
503   return true;
504 }
505 void SanitizerCoverageModule::CreateFunctionGuardArray(size_t NumGuards,
506                                                        Function &F) {
507   if (!Options.TracePCGuard) return;
508   HasSancovGuardsSection = true;
509   ArrayType *ArrayOfInt32Ty = ArrayType::get(Int32Ty, NumGuards);
510   FunctionGuardArray = new GlobalVariable(
511       *CurModule, ArrayOfInt32Ty, false, GlobalVariable::PrivateLinkage,
512       Constant::getNullValue(ArrayOfInt32Ty), "__sancov_guard");
513   if (auto Comdat = F.getComdat())
514     FunctionGuardArray->setComdat(Comdat);
515   FunctionGuardArray->setSection(SanCovTracePCGuardSection);
516 }
517 
518 bool SanitizerCoverageModule::InjectCoverage(Function &F,
519                                              ArrayRef<BasicBlock *> AllBlocks) {
520   if (AllBlocks.empty()) return false;
521   switch (Options.CoverageType) {
522   case SanitizerCoverageOptions::SCK_None:
523     return false;
524   case SanitizerCoverageOptions::SCK_Function:
525     CreateFunctionGuardArray(1, F);
526     InjectCoverageAtBlock(F, F.getEntryBlock(), 0, false);
527     return true;
528   default: {
529     bool UseCalls = ClCoverageBlockThreshold < AllBlocks.size();
530     CreateFunctionGuardArray(AllBlocks.size(), F);
531     for (size_t i = 0, N = AllBlocks.size(); i < N; i++)
532       InjectCoverageAtBlock(F, *AllBlocks[i], i, UseCalls);
533     return true;
534   }
535   }
536 }
537 
538 // On every indirect call we call a run-time function
539 // __sanitizer_cov_indir_call* with two parameters:
540 //   - callee address,
541 //   - global cache array that contains CacheSize pointers (zero-initialized).
542 //     The cache is used to speed up recording the caller-callee pairs.
543 // The address of the caller is passed implicitly via caller PC.
544 // CacheSize is encoded in the name of the run-time function.
545 void SanitizerCoverageModule::InjectCoverageForIndirectCalls(
546     Function &F, ArrayRef<Instruction *> IndirCalls) {
547   if (IndirCalls.empty())
548     return;
549   const int CacheSize = 16;
550   const int CacheAlignment = 64; // Align for better performance.
551   Type *Ty = ArrayType::get(IntptrTy, CacheSize);
552   for (auto I : IndirCalls) {
553     IRBuilder<> IRB(I);
554     CallSite CS(I);
555     Value *Callee = CS.getCalledValue();
556     if (isa<InlineAsm>(Callee))
557       continue;
558     GlobalVariable *CalleeCache = new GlobalVariable(
559         *F.getParent(), Ty, false, GlobalValue::PrivateLinkage,
560         Constant::getNullValue(Ty), "__sancov_gen_callee_cache");
561     CalleeCache->setAlignment(CacheAlignment);
562     if (Options.TracePC || Options.TracePCGuard)
563       IRB.CreateCall(SanCovTracePCIndir,
564                      IRB.CreatePointerCast(Callee, IntptrTy));
565     else
566       IRB.CreateCall(SanCovIndirCallFunction,
567                      {IRB.CreatePointerCast(Callee, IntptrTy),
568                       IRB.CreatePointerCast(CalleeCache, IntptrTy)});
569   }
570 }
571 
572 // For every switch statement we insert a call:
573 // __sanitizer_cov_trace_switch(CondValue,
574 //      {NumCases, ValueSizeInBits, Case0Value, Case1Value, Case2Value, ... })
575 
576 void SanitizerCoverageModule::InjectTraceForSwitch(
577     Function &, ArrayRef<Instruction *> SwitchTraceTargets) {
578   for (auto I : SwitchTraceTargets) {
579     if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
580       IRBuilder<> IRB(I);
581       SmallVector<Constant *, 16> Initializers;
582       Value *Cond = SI->getCondition();
583       if (Cond->getType()->getScalarSizeInBits() >
584           Int64Ty->getScalarSizeInBits())
585         continue;
586       Initializers.push_back(ConstantInt::get(Int64Ty, SI->getNumCases()));
587       Initializers.push_back(
588           ConstantInt::get(Int64Ty, Cond->getType()->getScalarSizeInBits()));
589       if (Cond->getType()->getScalarSizeInBits() <
590           Int64Ty->getScalarSizeInBits())
591         Cond = IRB.CreateIntCast(Cond, Int64Ty, false);
592       for (auto It : SI->cases()) {
593         Constant *C = It.getCaseValue();
594         if (C->getType()->getScalarSizeInBits() <
595             Int64Ty->getScalarSizeInBits())
596           C = ConstantExpr::getCast(CastInst::ZExt, It.getCaseValue(), Int64Ty);
597         Initializers.push_back(C);
598       }
599       ArrayType *ArrayOfInt64Ty = ArrayType::get(Int64Ty, Initializers.size());
600       GlobalVariable *GV = new GlobalVariable(
601           *CurModule, ArrayOfInt64Ty, false, GlobalVariable::InternalLinkage,
602           ConstantArray::get(ArrayOfInt64Ty, Initializers),
603           "__sancov_gen_cov_switch_values");
604       IRB.CreateCall(SanCovTraceSwitchFunction,
605                      {Cond, IRB.CreatePointerCast(GV, Int64PtrTy)});
606     }
607   }
608 }
609 
610 void SanitizerCoverageModule::InjectTraceForDiv(
611     Function &, ArrayRef<BinaryOperator *> DivTraceTargets) {
612   for (auto BO : DivTraceTargets) {
613     IRBuilder<> IRB(BO);
614     Value *A1 = BO->getOperand(1);
615     if (isa<ConstantInt>(A1)) continue;
616     if (!A1->getType()->isIntegerTy())
617       continue;
618     uint64_t TypeSize = DL->getTypeStoreSizeInBits(A1->getType());
619     int CallbackIdx = TypeSize == 32 ? 0 :
620         TypeSize == 64 ? 1 : -1;
621     if (CallbackIdx < 0) continue;
622     auto Ty = Type::getIntNTy(*C, TypeSize);
623     IRB.CreateCall(SanCovTraceDivFunction[CallbackIdx],
624                    {IRB.CreateIntCast(A1, Ty, true)});
625   }
626 }
627 
628 void SanitizerCoverageModule::InjectTraceForGep(
629     Function &, ArrayRef<GetElementPtrInst *> GepTraceTargets) {
630   for (auto GEP : GepTraceTargets) {
631     IRBuilder<> IRB(GEP);
632     for (auto I = GEP->idx_begin(); I != GEP->idx_end(); ++I)
633       if (!isa<ConstantInt>(*I) && (*I)->getType()->isIntegerTy())
634         IRB.CreateCall(SanCovTraceGepFunction,
635                        {IRB.CreateIntCast(*I, IntptrTy, true)});
636   }
637 }
638 
639 void SanitizerCoverageModule::InjectTraceForCmp(
640     Function &, ArrayRef<Instruction *> CmpTraceTargets) {
641   for (auto I : CmpTraceTargets) {
642     if (ICmpInst *ICMP = dyn_cast<ICmpInst>(I)) {
643       IRBuilder<> IRB(ICMP);
644       Value *A0 = ICMP->getOperand(0);
645       Value *A1 = ICMP->getOperand(1);
646       if (!A0->getType()->isIntegerTy())
647         continue;
648       uint64_t TypeSize = DL->getTypeStoreSizeInBits(A0->getType());
649       int CallbackIdx = TypeSize == 8 ? 0 :
650                         TypeSize == 16 ? 1 :
651                         TypeSize == 32 ? 2 :
652                         TypeSize == 64 ? 3 : -1;
653       if (CallbackIdx < 0) continue;
654       // __sanitizer_cov_trace_cmp((type_size << 32) | predicate, A0, A1);
655       auto Ty = Type::getIntNTy(*C, TypeSize);
656       IRB.CreateCall(
657           SanCovTraceCmpFunction[CallbackIdx],
658           {IRB.CreateIntCast(A0, Ty, true), IRB.CreateIntCast(A1, Ty, true)});
659     }
660   }
661 }
662 
663 void SanitizerCoverageModule::SetNoSanitizeMetadata(Instruction *I) {
664   I->setMetadata(I->getModule()->getMDKindID("nosanitize"),
665                  MDNode::get(*C, None));
666 }
667 
668 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
669                                                     size_t Idx, bool UseCalls) {
670   BasicBlock::iterator IP = BB.getFirstInsertionPt();
671   bool IsEntryBB = &BB == &F.getEntryBlock();
672   DebugLoc EntryLoc;
673   if (IsEntryBB) {
674     if (auto SP = F.getSubprogram())
675       EntryLoc = DebugLoc::get(SP->getScopeLine(), 0, SP);
676     // Keep static allocas and llvm.localescape calls in the entry block.  Even
677     // if we aren't splitting the block, it's nice for allocas to be before
678     // calls.
679     IP = PrepareToSplitEntryBlock(BB, IP);
680   } else {
681     EntryLoc = IP->getDebugLoc();
682   }
683 
684   IRBuilder<> IRB(&*IP);
685   IRB.SetCurrentDebugLocation(EntryLoc);
686   if (Options.TracePC) {
687     IRB.CreateCall(SanCovTracePC); // gets the PC using GET_CALLER_PC.
688     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
689   } else if (Options.TracePCGuard) {
690     auto GuardPtr = IRB.CreateIntToPtr(
691         IRB.CreateAdd(IRB.CreatePointerCast(FunctionGuardArray, IntptrTy),
692                       ConstantInt::get(IntptrTy, Idx * 4)),
693         Int32PtrTy);
694     if (!UseCalls) {
695       auto GuardLoad = IRB.CreateLoad(GuardPtr);
696       GuardLoad->setAtomic(AtomicOrdering::Monotonic);
697       GuardLoad->setAlignment(8);
698       SetNoSanitizeMetadata(GuardLoad);  // Don't instrument with e.g. asan.
699       auto Cmp = IRB.CreateICmpNE(
700           GuardLoad, Constant::getNullValue(GuardLoad->getType()));
701       auto Ins = SplitBlockAndInsertIfThen(
702           Cmp, &*IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
703       IRB.SetCurrentDebugLocation(EntryLoc);
704       IRB.SetInsertPoint(Ins);
705     }
706     IRB.CreateCall(SanCovTracePCGuard, GuardPtr);
707     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
708   } else {
709     Value *GuardP = IRB.CreateAdd(
710         IRB.CreatePointerCast(GuardArray, IntptrTy),
711         ConstantInt::get(IntptrTy, (1 + NumberOfInstrumentedBlocks()) * 4));
712     GuardP = IRB.CreateIntToPtr(GuardP, Int32PtrTy);
713     if (Options.TraceBB) {
714       IRB.CreateCall(IsEntryBB ? SanCovTraceEnter : SanCovTraceBB, GuardP);
715     } else if (UseCalls) {
716       IRB.CreateCall(SanCovWithCheckFunction, GuardP);
717     } else {
718       LoadInst *Load = IRB.CreateLoad(GuardP);
719       Load->setAtomic(AtomicOrdering::Monotonic);
720       Load->setAlignment(4);
721       SetNoSanitizeMetadata(Load);
722       Value *Cmp =
723           IRB.CreateICmpSGE(Constant::getNullValue(Load->getType()), Load);
724       Instruction *Ins = SplitBlockAndInsertIfThen(
725           Cmp, &*IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
726       IRB.SetInsertPoint(Ins);
727       IRB.SetCurrentDebugLocation(EntryLoc);
728       // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC.
729       IRB.CreateCall(SanCovFunction, GuardP);
730       IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
731     }
732   }
733 
734   if (Options.Use8bitCounters) {
735     IRB.SetInsertPoint(&*IP);
736     Value *P = IRB.CreateAdd(
737         IRB.CreatePointerCast(EightBitCounterArray, IntptrTy),
738         ConstantInt::get(IntptrTy, NumberOfInstrumentedBlocks() - 1));
739     P = IRB.CreateIntToPtr(P, IRB.getInt8PtrTy());
740     LoadInst *LI = IRB.CreateLoad(P);
741     Value *Inc = IRB.CreateAdd(LI, ConstantInt::get(IRB.getInt8Ty(), 1));
742     StoreInst *SI = IRB.CreateStore(Inc, P);
743     SetNoSanitizeMetadata(LI);
744     SetNoSanitizeMetadata(SI);
745   }
746 }
747 
748 char SanitizerCoverageModule::ID = 0;
749 INITIALIZE_PASS_BEGIN(SanitizerCoverageModule, "sancov",
750                       "SanitizerCoverage: TODO."
751                       "ModulePass",
752                       false, false)
753 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
754 INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)
755 INITIALIZE_PASS_END(SanitizerCoverageModule, "sancov",
756                     "SanitizerCoverage: TODO."
757                     "ModulePass",
758                     false, false)
759 ModulePass *llvm::createSanitizerCoverageModulePass(
760     const SanitizerCoverageOptions &Options) {
761   return new SanitizerCoverageModule(Options);
762 }
763