xref: /llvm-project/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp (revision 401d3693286103fd76d622ee9cd8f8a7df934bdd) 
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 SanCovTracePCGuardName =
82     "__sanitizer_cov_trace_pc_guard";
83 static const char *const SanCovTracePCGuardInitName =
84     "__sanitizer_cov_trace_pc_guard_init";
85 
86 static cl::opt<int> ClCoverageLevel(
87     "sanitizer-coverage-level",
88     cl::desc("Sanitizer Coverage. 0: none, 1: entry block, 2: all blocks, "
89              "3: all blocks and critical edges, "
90              "4: above plus indirect calls"),
91     cl::Hidden, cl::init(0));
92 
93 static cl::opt<unsigned> ClCoverageBlockThreshold(
94     "sanitizer-coverage-block-threshold",
95     cl::desc("Use a callback with a guard check inside it if there are"
96              " more than this number of blocks."),
97     cl::Hidden, cl::init(0));
98 
99 static cl::opt<bool>
100     ClExperimentalTracing("sanitizer-coverage-experimental-tracing",
101                           cl::desc("Experimental basic-block tracing: insert "
102                                    "callbacks at every basic block"),
103                           cl::Hidden, cl::init(false));
104 
105 static cl::opt<bool> ClExperimentalTracePC("sanitizer-coverage-trace-pc",
106                                            cl::desc("Experimental pc tracing"),
107                                            cl::Hidden, cl::init(false));
108 
109 static cl::opt<bool> ClTracePCGuard("sanitizer-coverage-trace-pc-guard",
110                                     cl::desc("pc tracing with a guard"),
111                                     cl::Hidden, cl::init(false));
112 
113 static cl::opt<bool>
114     ClCMPTracing("sanitizer-coverage-trace-compares",
115                  cl::desc("Tracing of CMP and similar instructions"),
116                  cl::Hidden, cl::init(false));
117 
118 static cl::opt<bool> ClDIVTracing("sanitizer-coverage-trace-divs",
119                                   cl::desc("Tracing of DIV instructions"),
120                                   cl::Hidden, cl::init(false));
121 
122 static cl::opt<bool> ClGEPTracing("sanitizer-coverage-trace-geps",
123                                   cl::desc("Tracing of GEP instructions"),
124                                   cl::Hidden, cl::init(false));
125 
126 static cl::opt<bool>
127     ClPruneBlocks("sanitizer-coverage-prune-blocks",
128                   cl::desc("Reduce the number of instrumented blocks"),
129                   cl::Hidden, cl::init(true));
130 
131 // Experimental 8-bit counters used as an additional search heuristic during
132 // coverage-guided fuzzing.
133 // The counters are not thread-friendly:
134 //   - contention on these counters may cause significant slowdown;
135 //   - the counter updates are racy and the results may be inaccurate.
136 // They are also inaccurate due to 8-bit integer overflow.
137 static cl::opt<bool> ClUse8bitCounters("sanitizer-coverage-8bit-counters",
138                                        cl::desc("Experimental 8-bit counters"),
139                                        cl::Hidden, cl::init(false));
140 
141 namespace {
142 
143 SanitizerCoverageOptions getOptions(int LegacyCoverageLevel) {
144   SanitizerCoverageOptions Res;
145   switch (LegacyCoverageLevel) {
146   case 0:
147     Res.CoverageType = SanitizerCoverageOptions::SCK_None;
148     break;
149   case 1:
150     Res.CoverageType = SanitizerCoverageOptions::SCK_Function;
151     break;
152   case 2:
153     Res.CoverageType = SanitizerCoverageOptions::SCK_BB;
154     break;
155   case 3:
156     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
157     break;
158   case 4:
159     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
160     Res.IndirectCalls = true;
161     break;
162   }
163   return Res;
164 }
165 
166 SanitizerCoverageOptions OverrideFromCL(SanitizerCoverageOptions Options) {
167   // Sets CoverageType and IndirectCalls.
168   SanitizerCoverageOptions CLOpts = getOptions(ClCoverageLevel);
169   Options.CoverageType = std::max(Options.CoverageType, CLOpts.CoverageType);
170   Options.IndirectCalls |= CLOpts.IndirectCalls;
171   Options.TraceBB |= ClExperimentalTracing;
172   Options.TraceCmp |= ClCMPTracing;
173   Options.TraceDiv |= ClDIVTracing;
174   Options.TraceGep |= ClGEPTracing;
175   Options.Use8bitCounters |= ClUse8bitCounters;
176   Options.TracePC |= ClExperimentalTracePC;
177   Options.TracePCGuard |= ClTracePCGuard;
178   return Options;
179 }
180 
181 class SanitizerCoverageModule : public ModulePass {
182 public:
183   SanitizerCoverageModule(
184       const SanitizerCoverageOptions &Options = SanitizerCoverageOptions())
185       : ModulePass(ID), Options(OverrideFromCL(Options)) {
186     initializeSanitizerCoverageModulePass(*PassRegistry::getPassRegistry());
187   }
188   bool runOnModule(Module &M) override;
189   bool runOnFunction(Function &F);
190   static char ID; // Pass identification, replacement for typeid
191   StringRef getPassName() const override { return "SanitizerCoverageModule"; }
192 
193   void getAnalysisUsage(AnalysisUsage &AU) const override {
194     AU.addRequired<DominatorTreeWrapperPass>();
195     AU.addRequired<PostDominatorTreeWrapperPass>();
196   }
197 
198 private:
199   void InjectCoverageForIndirectCalls(Function &F,
200                                       ArrayRef<Instruction *> IndirCalls);
201   void InjectTraceForCmp(Function &F, ArrayRef<Instruction *> CmpTraceTargets);
202   void InjectTraceForDiv(Function &F,
203                          ArrayRef<BinaryOperator *> DivTraceTargets);
204   void InjectTraceForGep(Function &F,
205                          ArrayRef<GetElementPtrInst *> GepTraceTargets);
206   void InjectTraceForSwitch(Function &F,
207                             ArrayRef<Instruction *> SwitchTraceTargets);
208   bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks);
209   void CreateFunctionGuardArray(size_t NumGuards, Function &F);
210   void SetNoSanitizeMetadata(Instruction *I);
211   void InjectCoverageAtBlock(Function &F, BasicBlock &BB, size_t Idx,
212                              bool UseCalls);
213   unsigned NumberOfInstrumentedBlocks() {
214     return SanCovFunction->getNumUses() +
215            SanCovWithCheckFunction->getNumUses() + SanCovTraceBB->getNumUses() +
216            SanCovTraceEnter->getNumUses();
217   }
218   StringRef getSanCovTracePCGuardSection() const;
219   StringRef getSanCovTracePCGuardSectionStart() const;
220   StringRef getSanCovTracePCGuardSectionEnd() const;
221   Function *SanCovFunction;
222   Function *SanCovWithCheckFunction;
223   Function *SanCovIndirCallFunction, *SanCovTracePCIndir;
224   Function *SanCovTraceEnter, *SanCovTraceBB, *SanCovTracePC, *SanCovTracePCGuard;
225   Function *SanCovTraceCmpFunction[4];
226   Function *SanCovTraceDivFunction[2];
227   Function *SanCovTraceGepFunction;
228   Function *SanCovTraceSwitchFunction;
229   InlineAsm *EmptyAsm;
230   Type *IntptrTy, *IntptrPtrTy, *Int64Ty, *Int64PtrTy, *Int32Ty, *Int32PtrTy;
231   Module *CurModule;
232   Triple TargetTriple;
233   LLVMContext *C;
234   const DataLayout *DL;
235 
236   GlobalVariable *GuardArray;
237   GlobalVariable *FunctionGuardArray;  // for trace-pc-guard.
238   GlobalVariable *EightBitCounterArray;
239   bool HasSancovGuardsSection;
240 
241   SanitizerCoverageOptions Options;
242 };
243 
244 } // namespace
245 
246 bool SanitizerCoverageModule::runOnModule(Module &M) {
247   if (Options.CoverageType == SanitizerCoverageOptions::SCK_None)
248     return false;
249   C = &(M.getContext());
250   DL = &M.getDataLayout();
251   CurModule = &M;
252   TargetTriple = Triple(M.getTargetTriple());
253   HasSancovGuardsSection = false;
254   IntptrTy = Type::getIntNTy(*C, DL->getPointerSizeInBits());
255   IntptrPtrTy = PointerType::getUnqual(IntptrTy);
256   Type *VoidTy = Type::getVoidTy(*C);
257   IRBuilder<> IRB(*C);
258   Type *Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
259   Int64PtrTy = PointerType::getUnqual(IRB.getInt64Ty());
260   Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
261   Int64Ty = IRB.getInt64Ty();
262   Int32Ty = IRB.getInt32Ty();
263 
264   SanCovFunction = checkSanitizerInterfaceFunction(
265       M.getOrInsertFunction(SanCovName, VoidTy, Int32PtrTy, nullptr));
266   SanCovWithCheckFunction = checkSanitizerInterfaceFunction(
267       M.getOrInsertFunction(SanCovWithCheckName, VoidTy, Int32PtrTy, nullptr));
268   SanCovTracePCIndir = checkSanitizerInterfaceFunction(
269       M.getOrInsertFunction(SanCovTracePCIndirName, VoidTy, IntptrTy, nullptr));
270   SanCovIndirCallFunction =
271       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
272           SanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr));
273   SanCovTraceCmpFunction[0] =
274       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
275           SanCovTraceCmp1, VoidTy, IRB.getInt8Ty(), IRB.getInt8Ty(), nullptr));
276   SanCovTraceCmpFunction[1] = checkSanitizerInterfaceFunction(
277       M.getOrInsertFunction(SanCovTraceCmp2, VoidTy, IRB.getInt16Ty(),
278                             IRB.getInt16Ty(), nullptr));
279   SanCovTraceCmpFunction[2] = checkSanitizerInterfaceFunction(
280       M.getOrInsertFunction(SanCovTraceCmp4, VoidTy, IRB.getInt32Ty(),
281                             IRB.getInt32Ty(), nullptr));
282   SanCovTraceCmpFunction[3] =
283       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
284           SanCovTraceCmp8, VoidTy, Int64Ty, Int64Ty, nullptr));
285 
286   SanCovTraceDivFunction[0] =
287       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
288           SanCovTraceDiv4, VoidTy, IRB.getInt32Ty(), nullptr));
289   SanCovTraceDivFunction[1] =
290       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
291           SanCovTraceDiv8, VoidTy, Int64Ty, nullptr));
292   SanCovTraceGepFunction =
293       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
294           SanCovTraceGep, VoidTy, IntptrTy, nullptr));
295   SanCovTraceSwitchFunction =
296       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
297           SanCovTraceSwitchName, VoidTy, Int64Ty, Int64PtrTy, nullptr));
298 
299   // We insert an empty inline asm after cov callbacks to avoid callback merge.
300   EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
301                             StringRef(""), StringRef(""),
302                             /*hasSideEffects=*/true);
303 
304   SanCovTracePC = checkSanitizerInterfaceFunction(
305       M.getOrInsertFunction(SanCovTracePCName, VoidTy, nullptr));
306   SanCovTracePCGuard = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
307       SanCovTracePCGuardName, VoidTy, Int32PtrTy, nullptr));
308   SanCovTraceEnter = checkSanitizerInterfaceFunction(
309       M.getOrInsertFunction(SanCovTraceEnterName, VoidTy, Int32PtrTy, nullptr));
310   SanCovTraceBB = checkSanitizerInterfaceFunction(
311       M.getOrInsertFunction(SanCovTraceBBName, VoidTy, Int32PtrTy, nullptr));
312 
313   // At this point we create a dummy array of guards because we don't
314   // know how many elements we will need.
315   Type *Int32Ty = IRB.getInt32Ty();
316   Type *Int8Ty = IRB.getInt8Ty();
317 
318   if (!Options.TracePCGuard)
319     GuardArray =
320         new GlobalVariable(M, Int32Ty, false, GlobalValue::ExternalLinkage,
321                            nullptr, "__sancov_gen_cov_tmp");
322   if (Options.Use8bitCounters)
323     EightBitCounterArray =
324         new GlobalVariable(M, Int8Ty, false, GlobalVariable::ExternalLinkage,
325                            nullptr, "__sancov_gen_cov_tmp");
326 
327   for (auto &F : M)
328     runOnFunction(F);
329 
330   auto N = NumberOfInstrumentedBlocks();
331 
332   GlobalVariable *RealGuardArray = nullptr;
333   if (!Options.TracePCGuard) {
334     // Now we know how many elements we need. Create an array of guards
335     // with one extra element at the beginning for the size.
336     Type *Int32ArrayNTy = ArrayType::get(Int32Ty, N + 1);
337     RealGuardArray = new GlobalVariable(
338         M, Int32ArrayNTy, false, GlobalValue::PrivateLinkage,
339         Constant::getNullValue(Int32ArrayNTy), "__sancov_gen_cov");
340 
341     // Replace the dummy array with the real one.
342     GuardArray->replaceAllUsesWith(
343         IRB.CreatePointerCast(RealGuardArray, Int32PtrTy));
344     GuardArray->eraseFromParent();
345   }
346 
347   GlobalVariable *RealEightBitCounterArray;
348   if (Options.Use8bitCounters) {
349     // Make sure the array is 16-aligned.
350     static const int CounterAlignment = 16;
351     Type *Int8ArrayNTy = ArrayType::get(Int8Ty, alignTo(N, CounterAlignment));
352     RealEightBitCounterArray = new GlobalVariable(
353         M, Int8ArrayNTy, false, GlobalValue::PrivateLinkage,
354         Constant::getNullValue(Int8ArrayNTy), "__sancov_gen_cov_counter");
355     RealEightBitCounterArray->setAlignment(CounterAlignment);
356     EightBitCounterArray->replaceAllUsesWith(
357         IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy));
358     EightBitCounterArray->eraseFromParent();
359   }
360 
361   // Create variable for module (compilation unit) name
362   Constant *ModNameStrConst =
363       ConstantDataArray::getString(M.getContext(), M.getName(), true);
364   GlobalVariable *ModuleName = new GlobalVariable(
365       M, ModNameStrConst->getType(), true, GlobalValue::PrivateLinkage,
366       ModNameStrConst, "__sancov_gen_modname");
367   if (Options.TracePCGuard) {
368     if (HasSancovGuardsSection) {
369       Function *CtorFunc;
370       GlobalVariable *SecStart = new GlobalVariable(
371           M, Int32PtrTy, false, GlobalVariable::ExternalLinkage, nullptr,
372           getSanCovTracePCGuardSectionStart());
373       SecStart->setVisibility(GlobalValue::HiddenVisibility);
374       GlobalVariable *SecEnd = new GlobalVariable(
375           M, Int32PtrTy, false, GlobalVariable::ExternalLinkage, nullptr,
376           getSanCovTracePCGuardSectionEnd());
377       SecEnd->setVisibility(GlobalValue::HiddenVisibility);
378 
379       std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
380           M, SanCovModuleCtorName, SanCovTracePCGuardInitName,
381           {Int32PtrTy, Int32PtrTy},
382           {IRB.CreatePointerCast(SecStart, Int32PtrTy),
383             IRB.CreatePointerCast(SecEnd, Int32PtrTy)});
384 
385       // Use comdat to dedup CtorFunc.
386       CtorFunc->setComdat(M.getOrInsertComdat(SanCovModuleCtorName));
387       appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority, CtorFunc);
388     }
389   } else if (!Options.TracePC) {
390     Function *CtorFunc;
391     std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
392         M, SanCovModuleCtorName, SanCovModuleInitName,
393         {Int32PtrTy, IntptrTy, Int8PtrTy, Int8PtrTy},
394         {IRB.CreatePointerCast(RealGuardArray, Int32PtrTy),
395          ConstantInt::get(IntptrTy, N),
396          Options.Use8bitCounters
397              ? IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy)
398              : Constant::getNullValue(Int8PtrTy),
399          IRB.CreatePointerCast(ModuleName, Int8PtrTy)});
400 
401     appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority);
402   }
403 
404   return true;
405 }
406 
407 // True if block has successors and it dominates all of them.
408 static bool isFullDominator(const BasicBlock *BB, const DominatorTree *DT) {
409   if (succ_begin(BB) == succ_end(BB))
410     return false;
411 
412   for (const BasicBlock *SUCC : make_range(succ_begin(BB), succ_end(BB))) {
413     if (!DT->dominates(BB, SUCC))
414       return false;
415   }
416 
417   return true;
418 }
419 
420 // True if block has predecessors and it postdominates all of them.
421 static bool isFullPostDominator(const BasicBlock *BB,
422                                 const PostDominatorTree *PDT) {
423   if (pred_begin(BB) == pred_end(BB))
424     return false;
425 
426   for (const BasicBlock *PRED : make_range(pred_begin(BB), pred_end(BB))) {
427     if (!PDT->dominates(BB, PRED))
428       return false;
429   }
430 
431   return true;
432 }
433 
434 static bool shouldInstrumentBlock(const Function& F, const BasicBlock *BB, const DominatorTree *DT,
435                                   const PostDominatorTree *PDT) {
436   // Don't insert coverage for unreachable blocks: we will never call
437   // __sanitizer_cov() for them, so counting them in
438   // NumberOfInstrumentedBlocks() might complicate calculation of code coverage
439   // percentage. Also, unreachable instructions frequently have no debug
440   // locations.
441   if (isa<UnreachableInst>(BB->getTerminator()))
442     return false;
443 
444   if (!ClPruneBlocks || &F.getEntryBlock() == BB)
445     return true;
446 
447   return !(isFullDominator(BB, DT) || isFullPostDominator(BB, PDT));
448 }
449 
450 bool SanitizerCoverageModule::runOnFunction(Function &F) {
451   if (F.empty())
452     return false;
453   if (F.getName().find(".module_ctor") != std::string::npos)
454     return false; // Should not instrument sanitizer init functions.
455   if (F.getName().startswith("__sanitizer_"))
456     return false;  // Don't instrument __sanitizer_* callbacks.
457   // Don't instrument MSVC CRT configuration helpers. They may run before normal
458   // initialization.
459   if (F.getName() == "__local_stdio_printf_options" ||
460       F.getName() == "__local_stdio_scanf_options")
461     return false;
462   // Don't instrument functions using SEH for now. Splitting basic blocks like
463   // we do for coverage breaks WinEHPrepare.
464   // FIXME: Remove this when SEH no longer uses landingpad pattern matching.
465   if (F.hasPersonalityFn() &&
466       isAsynchronousEHPersonality(classifyEHPersonality(F.getPersonalityFn())))
467     return false;
468   if (Options.CoverageType >= SanitizerCoverageOptions::SCK_Edge)
469     SplitAllCriticalEdges(F);
470   SmallVector<Instruction *, 8> IndirCalls;
471   SmallVector<BasicBlock *, 16> BlocksToInstrument;
472   SmallVector<Instruction *, 8> CmpTraceTargets;
473   SmallVector<Instruction *, 8> SwitchTraceTargets;
474   SmallVector<BinaryOperator *, 8> DivTraceTargets;
475   SmallVector<GetElementPtrInst *, 8> GepTraceTargets;
476 
477   const DominatorTree *DT =
478       &getAnalysis<DominatorTreeWrapperPass>(F).getDomTree();
479   const PostDominatorTree *PDT =
480       &getAnalysis<PostDominatorTreeWrapperPass>(F).getPostDomTree();
481 
482   for (auto &BB : F) {
483     if (shouldInstrumentBlock(F, &BB, DT, PDT))
484       BlocksToInstrument.push_back(&BB);
485     for (auto &Inst : BB) {
486       if (Options.IndirectCalls) {
487         CallSite CS(&Inst);
488         if (CS && !CS.getCalledFunction())
489           IndirCalls.push_back(&Inst);
490       }
491       if (Options.TraceCmp) {
492         if (isa<ICmpInst>(&Inst))
493           CmpTraceTargets.push_back(&Inst);
494         if (isa<SwitchInst>(&Inst))
495           SwitchTraceTargets.push_back(&Inst);
496       }
497       if (Options.TraceDiv)
498         if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&Inst))
499           if (BO->getOpcode() == Instruction::SDiv ||
500               BO->getOpcode() == Instruction::UDiv)
501             DivTraceTargets.push_back(BO);
502       if (Options.TraceGep)
503         if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(&Inst))
504           GepTraceTargets.push_back(GEP);
505    }
506   }
507 
508   InjectCoverage(F, BlocksToInstrument);
509   InjectCoverageForIndirectCalls(F, IndirCalls);
510   InjectTraceForCmp(F, CmpTraceTargets);
511   InjectTraceForSwitch(F, SwitchTraceTargets);
512   InjectTraceForDiv(F, DivTraceTargets);
513   InjectTraceForGep(F, GepTraceTargets);
514   return true;
515 }
516 void SanitizerCoverageModule::CreateFunctionGuardArray(size_t NumGuards,
517                                                        Function &F) {
518   if (!Options.TracePCGuard) return;
519   HasSancovGuardsSection = true;
520   ArrayType *ArrayOfInt32Ty = ArrayType::get(Int32Ty, NumGuards);
521   FunctionGuardArray = new GlobalVariable(
522       *CurModule, ArrayOfInt32Ty, false, GlobalVariable::PrivateLinkage,
523       Constant::getNullValue(ArrayOfInt32Ty), "__sancov_gen_");
524   if (auto Comdat = F.getComdat())
525     FunctionGuardArray->setComdat(Comdat);
526   FunctionGuardArray->setSection(getSanCovTracePCGuardSection());
527 }
528 
529 bool SanitizerCoverageModule::InjectCoverage(Function &F,
530                                              ArrayRef<BasicBlock *> AllBlocks) {
531   if (AllBlocks.empty()) return false;
532   switch (Options.CoverageType) {
533   case SanitizerCoverageOptions::SCK_None:
534     return false;
535   case SanitizerCoverageOptions::SCK_Function:
536     CreateFunctionGuardArray(1, F);
537     InjectCoverageAtBlock(F, F.getEntryBlock(), 0, false);
538     return true;
539   default: {
540     bool UseCalls = ClCoverageBlockThreshold < AllBlocks.size();
541     CreateFunctionGuardArray(AllBlocks.size(), F);
542     for (size_t i = 0, N = AllBlocks.size(); i < N; i++)
543       InjectCoverageAtBlock(F, *AllBlocks[i], i, UseCalls);
544     return true;
545   }
546   }
547 }
548 
549 // On every indirect call we call a run-time function
550 // __sanitizer_cov_indir_call* with two parameters:
551 //   - callee address,
552 //   - global cache array that contains CacheSize pointers (zero-initialized).
553 //     The cache is used to speed up recording the caller-callee pairs.
554 // The address of the caller is passed implicitly via caller PC.
555 // CacheSize is encoded in the name of the run-time function.
556 void SanitizerCoverageModule::InjectCoverageForIndirectCalls(
557     Function &F, ArrayRef<Instruction *> IndirCalls) {
558   if (IndirCalls.empty())
559     return;
560   const int CacheSize = 16;
561   const int CacheAlignment = 64; // Align for better performance.
562   Type *Ty = ArrayType::get(IntptrTy, CacheSize);
563   for (auto I : IndirCalls) {
564     IRBuilder<> IRB(I);
565     CallSite CS(I);
566     Value *Callee = CS.getCalledValue();
567     if (isa<InlineAsm>(Callee))
568       continue;
569     GlobalVariable *CalleeCache = new GlobalVariable(
570         *F.getParent(), Ty, false, GlobalValue::PrivateLinkage,
571         Constant::getNullValue(Ty), "__sancov_gen_callee_cache");
572     CalleeCache->setAlignment(CacheAlignment);
573     if (Options.TracePC || Options.TracePCGuard)
574       IRB.CreateCall(SanCovTracePCIndir,
575                      IRB.CreatePointerCast(Callee, IntptrTy));
576     else
577       IRB.CreateCall(SanCovIndirCallFunction,
578                      {IRB.CreatePointerCast(Callee, IntptrTy),
579                       IRB.CreatePointerCast(CalleeCache, IntptrTy)});
580   }
581 }
582 
583 // For every switch statement we insert a call:
584 // __sanitizer_cov_trace_switch(CondValue,
585 //      {NumCases, ValueSizeInBits, Case0Value, Case1Value, Case2Value, ... })
586 
587 void SanitizerCoverageModule::InjectTraceForSwitch(
588     Function &, ArrayRef<Instruction *> SwitchTraceTargets) {
589   for (auto I : SwitchTraceTargets) {
590     if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
591       IRBuilder<> IRB(I);
592       SmallVector<Constant *, 16> Initializers;
593       Value *Cond = SI->getCondition();
594       if (Cond->getType()->getScalarSizeInBits() >
595           Int64Ty->getScalarSizeInBits())
596         continue;
597       Initializers.push_back(ConstantInt::get(Int64Ty, SI->getNumCases()));
598       Initializers.push_back(
599           ConstantInt::get(Int64Ty, Cond->getType()->getScalarSizeInBits()));
600       if (Cond->getType()->getScalarSizeInBits() <
601           Int64Ty->getScalarSizeInBits())
602         Cond = IRB.CreateIntCast(Cond, Int64Ty, false);
603       for (auto It : SI->cases()) {
604         Constant *C = It.getCaseValue();
605         if (C->getType()->getScalarSizeInBits() <
606             Int64Ty->getScalarSizeInBits())
607           C = ConstantExpr::getCast(CastInst::ZExt, It.getCaseValue(), Int64Ty);
608         Initializers.push_back(C);
609       }
610       std::sort(Initializers.begin() + 2, Initializers.end(),
611                 [](const Constant *A, const Constant *B) {
612                   return cast<ConstantInt>(A)->getLimitedValue() <
613                          cast<ConstantInt>(B)->getLimitedValue();
614                 });
615       ArrayType *ArrayOfInt64Ty = ArrayType::get(Int64Ty, Initializers.size());
616       GlobalVariable *GV = new GlobalVariable(
617           *CurModule, ArrayOfInt64Ty, false, GlobalVariable::InternalLinkage,
618           ConstantArray::get(ArrayOfInt64Ty, Initializers),
619           "__sancov_gen_cov_switch_values");
620       IRB.CreateCall(SanCovTraceSwitchFunction,
621                      {Cond, IRB.CreatePointerCast(GV, Int64PtrTy)});
622     }
623   }
624 }
625 
626 void SanitizerCoverageModule::InjectTraceForDiv(
627     Function &, ArrayRef<BinaryOperator *> DivTraceTargets) {
628   for (auto BO : DivTraceTargets) {
629     IRBuilder<> IRB(BO);
630     Value *A1 = BO->getOperand(1);
631     if (isa<ConstantInt>(A1)) continue;
632     if (!A1->getType()->isIntegerTy())
633       continue;
634     uint64_t TypeSize = DL->getTypeStoreSizeInBits(A1->getType());
635     int CallbackIdx = TypeSize == 32 ? 0 :
636         TypeSize == 64 ? 1 : -1;
637     if (CallbackIdx < 0) continue;
638     auto Ty = Type::getIntNTy(*C, TypeSize);
639     IRB.CreateCall(SanCovTraceDivFunction[CallbackIdx],
640                    {IRB.CreateIntCast(A1, Ty, true)});
641   }
642 }
643 
644 void SanitizerCoverageModule::InjectTraceForGep(
645     Function &, ArrayRef<GetElementPtrInst *> GepTraceTargets) {
646   for (auto GEP : GepTraceTargets) {
647     IRBuilder<> IRB(GEP);
648     for (auto I = GEP->idx_begin(); I != GEP->idx_end(); ++I)
649       if (!isa<ConstantInt>(*I) && (*I)->getType()->isIntegerTy())
650         IRB.CreateCall(SanCovTraceGepFunction,
651                        {IRB.CreateIntCast(*I, IntptrTy, true)});
652   }
653 }
654 
655 void SanitizerCoverageModule::InjectTraceForCmp(
656     Function &, ArrayRef<Instruction *> CmpTraceTargets) {
657   for (auto I : CmpTraceTargets) {
658     if (ICmpInst *ICMP = dyn_cast<ICmpInst>(I)) {
659       IRBuilder<> IRB(ICMP);
660       Value *A0 = ICMP->getOperand(0);
661       Value *A1 = ICMP->getOperand(1);
662       if (!A0->getType()->isIntegerTy())
663         continue;
664       uint64_t TypeSize = DL->getTypeStoreSizeInBits(A0->getType());
665       int CallbackIdx = TypeSize == 8 ? 0 :
666                         TypeSize == 16 ? 1 :
667                         TypeSize == 32 ? 2 :
668                         TypeSize == 64 ? 3 : -1;
669       if (CallbackIdx < 0) continue;
670       // __sanitizer_cov_trace_cmp((type_size << 32) | predicate, A0, A1);
671       auto Ty = Type::getIntNTy(*C, TypeSize);
672       IRB.CreateCall(
673           SanCovTraceCmpFunction[CallbackIdx],
674           {IRB.CreateIntCast(A0, Ty, true), IRB.CreateIntCast(A1, Ty, true)});
675     }
676   }
677 }
678 
679 void SanitizerCoverageModule::SetNoSanitizeMetadata(Instruction *I) {
680   I->setMetadata(I->getModule()->getMDKindID("nosanitize"),
681                  MDNode::get(*C, None));
682 }
683 
684 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
685                                                     size_t Idx, bool UseCalls) {
686   BasicBlock::iterator IP = BB.getFirstInsertionPt();
687   bool IsEntryBB = &BB == &F.getEntryBlock();
688   DebugLoc EntryLoc;
689   if (IsEntryBB) {
690     if (auto SP = F.getSubprogram())
691       EntryLoc = DebugLoc::get(SP->getScopeLine(), 0, SP);
692     // Keep static allocas and llvm.localescape calls in the entry block.  Even
693     // if we aren't splitting the block, it's nice for allocas to be before
694     // calls.
695     IP = PrepareToSplitEntryBlock(BB, IP);
696   } else {
697     EntryLoc = IP->getDebugLoc();
698   }
699 
700   IRBuilder<> IRB(&*IP);
701   IRB.SetCurrentDebugLocation(EntryLoc);
702   if (Options.TracePC) {
703     IRB.CreateCall(SanCovTracePC); // gets the PC using GET_CALLER_PC.
704     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
705   } else if (Options.TracePCGuard) {
706     auto GuardPtr = IRB.CreateIntToPtr(
707         IRB.CreateAdd(IRB.CreatePointerCast(FunctionGuardArray, IntptrTy),
708                       ConstantInt::get(IntptrTy, Idx * 4)),
709         Int32PtrTy);
710     if (!UseCalls) {
711       auto GuardLoad = IRB.CreateLoad(GuardPtr);
712       GuardLoad->setAtomic(AtomicOrdering::Monotonic);
713       GuardLoad->setAlignment(8);
714       SetNoSanitizeMetadata(GuardLoad);  // Don't instrument with e.g. asan.
715       auto Cmp = IRB.CreateICmpNE(
716           GuardLoad, Constant::getNullValue(GuardLoad->getType()));
717       auto Ins = SplitBlockAndInsertIfThen(
718           Cmp, &*IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
719       IRB.SetInsertPoint(Ins);
720       IRB.SetCurrentDebugLocation(EntryLoc);
721     }
722     IRB.CreateCall(SanCovTracePCGuard, GuardPtr);
723     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
724   } else {
725     Value *GuardP = IRB.CreateAdd(
726         IRB.CreatePointerCast(GuardArray, IntptrTy),
727         ConstantInt::get(IntptrTy, (1 + NumberOfInstrumentedBlocks()) * 4));
728     GuardP = IRB.CreateIntToPtr(GuardP, Int32PtrTy);
729     if (Options.TraceBB) {
730       IRB.CreateCall(IsEntryBB ? SanCovTraceEnter : SanCovTraceBB, GuardP);
731     } else if (UseCalls) {
732       IRB.CreateCall(SanCovWithCheckFunction, GuardP);
733     } else {
734       LoadInst *Load = IRB.CreateLoad(GuardP);
735       Load->setAtomic(AtomicOrdering::Monotonic);
736       Load->setAlignment(4);
737       SetNoSanitizeMetadata(Load);
738       Value *Cmp =
739           IRB.CreateICmpSGE(Constant::getNullValue(Load->getType()), Load);
740       Instruction *Ins = SplitBlockAndInsertIfThen(
741           Cmp, &*IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
742       IRB.SetInsertPoint(Ins);
743       IRB.SetCurrentDebugLocation(EntryLoc);
744       // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC.
745       IRB.CreateCall(SanCovFunction, GuardP);
746       IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
747     }
748   }
749 
750   if (Options.Use8bitCounters) {
751     IRB.SetInsertPoint(&*IP);
752     Value *P = IRB.CreateAdd(
753         IRB.CreatePointerCast(EightBitCounterArray, IntptrTy),
754         ConstantInt::get(IntptrTy, NumberOfInstrumentedBlocks() - 1));
755     P = IRB.CreateIntToPtr(P, IRB.getInt8PtrTy());
756     LoadInst *LI = IRB.CreateLoad(P);
757     Value *Inc = IRB.CreateAdd(LI, ConstantInt::get(IRB.getInt8Ty(), 1));
758     StoreInst *SI = IRB.CreateStore(Inc, P);
759     SetNoSanitizeMetadata(LI);
760     SetNoSanitizeMetadata(SI);
761   }
762 }
763 
764 StringRef SanitizerCoverageModule::getSanCovTracePCGuardSection() const {
765   if (TargetTriple.getObjectFormat() == Triple::COFF)
766     return ".SCOV$M";
767   if (TargetTriple.isOSBinFormatMachO())
768     return "__DATA,__sancov_guards";
769   return "__sancov_guards";
770 }
771 
772 StringRef SanitizerCoverageModule::getSanCovTracePCGuardSectionStart() const {
773   if (TargetTriple.isOSBinFormatMachO())
774     return "\1section$start$__DATA$__sancov_guards";
775   return "__start___sancov_guards";
776 }
777 
778 StringRef SanitizerCoverageModule::getSanCovTracePCGuardSectionEnd() const {
779   if (TargetTriple.isOSBinFormatMachO())
780     return "\1section$end$__DATA$__sancov_guards";
781   return "__stop___sancov_guards";
782 }
783 
784 
785 char SanitizerCoverageModule::ID = 0;
786 INITIALIZE_PASS_BEGIN(SanitizerCoverageModule, "sancov",
787                       "SanitizerCoverage: TODO."
788                       "ModulePass",
789                       false, false)
790 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
791 INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)
792 INITIALIZE_PASS_END(SanitizerCoverageModule, "sancov",
793                     "SanitizerCoverage: TODO."
794                     "ModulePass",
795                     false, false)
796 ModulePass *llvm::createSanitizerCoverageModulePass(
797     const SanitizerCoverageOptions &Options) {
798   return new SanitizerCoverageModule(Options);
799 }
800