xref: /llvm-project/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp (revision 5652f35817f07b16f8b3856d594cc42f4d7ee29c)
1 //===-- SanitizerCoverage.cpp - coverage instrumentation for sanitizers ---===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // Coverage instrumentation done on LLVM IR level, works with Sanitizers.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/Transforms/Instrumentation/SanitizerCoverage.h"
14 #include "llvm/ADT/ArrayRef.h"
15 #include "llvm/ADT/SmallVector.h"
16 #include "llvm/Analysis/EHPersonalities.h"
17 #include "llvm/Analysis/PostDominators.h"
18 #include "llvm/IR/CFG.h"
19 #include "llvm/IR/CallSite.h"
20 #include "llvm/IR/Constant.h"
21 #include "llvm/IR/DataLayout.h"
22 #include "llvm/IR/DebugInfo.h"
23 #include "llvm/IR/Dominators.h"
24 #include "llvm/IR/Function.h"
25 #include "llvm/IR/GlobalVariable.h"
26 #include "llvm/IR/IRBuilder.h"
27 #include "llvm/IR/InlineAsm.h"
28 #include "llvm/IR/IntrinsicInst.h"
29 #include "llvm/IR/Intrinsics.h"
30 #include "llvm/IR/LLVMContext.h"
31 #include "llvm/IR/MDBuilder.h"
32 #include "llvm/IR/Mangler.h"
33 #include "llvm/IR/Module.h"
34 #include "llvm/IR/Type.h"
35 #include "llvm/Support/CommandLine.h"
36 #include "llvm/Support/Debug.h"
37 #include "llvm/Support/raw_ostream.h"
38 #include "llvm/Transforms/Instrumentation.h"
39 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
40 #include "llvm/Transforms/Utils/ModuleUtils.h"
41 
42 using namespace llvm;
43 
44 #define DEBUG_TYPE "sancov"
45 
46 static const char *const SanCovTracePCIndirName =
47     "__sanitizer_cov_trace_pc_indir";
48 static const char *const SanCovTracePCName = "__sanitizer_cov_trace_pc";
49 static const char *const SanCovTraceCmp1 = "__sanitizer_cov_trace_cmp1";
50 static const char *const SanCovTraceCmp2 = "__sanitizer_cov_trace_cmp2";
51 static const char *const SanCovTraceCmp4 = "__sanitizer_cov_trace_cmp4";
52 static const char *const SanCovTraceCmp8 = "__sanitizer_cov_trace_cmp8";
53 static const char *const SanCovTraceConstCmp1 =
54     "__sanitizer_cov_trace_const_cmp1";
55 static const char *const SanCovTraceConstCmp2 =
56     "__sanitizer_cov_trace_const_cmp2";
57 static const char *const SanCovTraceConstCmp4 =
58     "__sanitizer_cov_trace_const_cmp4";
59 static const char *const SanCovTraceConstCmp8 =
60     "__sanitizer_cov_trace_const_cmp8";
61 static const char *const SanCovTraceDiv4 = "__sanitizer_cov_trace_div4";
62 static const char *const SanCovTraceDiv8 = "__sanitizer_cov_trace_div8";
63 static const char *const SanCovTraceGep = "__sanitizer_cov_trace_gep";
64 static const char *const SanCovTraceSwitchName = "__sanitizer_cov_trace_switch";
65 static const char *const SanCovModuleCtorTracePcGuardName =
66     "sancov.module_ctor_trace_pc_guard";
67 static const char *const SanCovModuleCtor8bitCountersName =
68     "sancov.module_ctor_8bit_counters";
69 static const uint64_t SanCtorAndDtorPriority = 2;
70 
71 static const char *const SanCovTracePCGuardName =
72     "__sanitizer_cov_trace_pc_guard";
73 static const char *const SanCovTracePCGuardInitName =
74     "__sanitizer_cov_trace_pc_guard_init";
75 static const char *const SanCov8bitCountersInitName =
76     "__sanitizer_cov_8bit_counters_init";
77 static const char *const SanCovPCsInitName = "__sanitizer_cov_pcs_init";
78 
79 static const char *const SanCovGuardsSectionName = "sancov_guards";
80 static const char *const SanCovCountersSectionName = "sancov_cntrs";
81 static const char *const SanCovPCsSectionName = "sancov_pcs";
82 
83 static const char *const SanCovLowestStackName = "__sancov_lowest_stack";
84 
85 static cl::opt<int> ClCoverageLevel(
86     "sanitizer-coverage-level",
87     cl::desc("Sanitizer Coverage. 0: none, 1: entry block, 2: all blocks, "
88              "3: all blocks and critical edges"),
89     cl::Hidden, cl::init(0));
90 
91 static cl::opt<bool> ClTracePC("sanitizer-coverage-trace-pc",
92                                cl::desc("Experimental pc tracing"), cl::Hidden,
93                                cl::init(false));
94 
95 static cl::opt<bool> ClTracePCGuard("sanitizer-coverage-trace-pc-guard",
96                                     cl::desc("pc tracing with a guard"),
97                                     cl::Hidden, cl::init(false));
98 
99 // If true, we create a global variable that contains PCs of all instrumented
100 // BBs, put this global into a named section, and pass this section's bounds
101 // to __sanitizer_cov_pcs_init.
102 // This way the coverage instrumentation does not need to acquire the PCs
103 // at run-time. Works with trace-pc-guard and inline-8bit-counters.
104 static cl::opt<bool> ClCreatePCTable("sanitizer-coverage-pc-table",
105                                      cl::desc("create a static PC table"),
106                                      cl::Hidden, cl::init(false));
107 
108 static cl::opt<bool>
109     ClInline8bitCounters("sanitizer-coverage-inline-8bit-counters",
110                          cl::desc("increments 8-bit counter for every edge"),
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 static cl::opt<bool> ClStackDepth("sanitizer-coverage-stack-depth",
132                                   cl::desc("max stack depth tracing"),
133                                   cl::Hidden, cl::init(false));
134 
135 namespace {
136 
137 SanitizerCoverageOptions getOptions(int LegacyCoverageLevel) {
138   SanitizerCoverageOptions Res;
139   switch (LegacyCoverageLevel) {
140   case 0:
141     Res.CoverageType = SanitizerCoverageOptions::SCK_None;
142     break;
143   case 1:
144     Res.CoverageType = SanitizerCoverageOptions::SCK_Function;
145     break;
146   case 2:
147     Res.CoverageType = SanitizerCoverageOptions::SCK_BB;
148     break;
149   case 3:
150     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
151     break;
152   case 4:
153     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
154     Res.IndirectCalls = true;
155     break;
156   }
157   return Res;
158 }
159 
160 SanitizerCoverageOptions OverrideFromCL(SanitizerCoverageOptions Options) {
161   // Sets CoverageType and IndirectCalls.
162   SanitizerCoverageOptions CLOpts = getOptions(ClCoverageLevel);
163   Options.CoverageType = std::max(Options.CoverageType, CLOpts.CoverageType);
164   Options.IndirectCalls |= CLOpts.IndirectCalls;
165   Options.TraceCmp |= ClCMPTracing;
166   Options.TraceDiv |= ClDIVTracing;
167   Options.TraceGep |= ClGEPTracing;
168   Options.TracePC |= ClTracePC;
169   Options.TracePCGuard |= ClTracePCGuard;
170   Options.Inline8bitCounters |= ClInline8bitCounters;
171   Options.PCTable |= ClCreatePCTable;
172   Options.NoPrune |= !ClPruneBlocks;
173   Options.StackDepth |= ClStackDepth;
174   if (!Options.TracePCGuard && !Options.TracePC &&
175       !Options.Inline8bitCounters && !Options.StackDepth)
176     Options.TracePCGuard = true; // TracePCGuard is default.
177   return Options;
178 }
179 
180 bool canInstrumentWithSancov(const Function &F) {
181   if (F.empty())
182     return false;
183   if (F.getName().find(".module_ctor") != std::string::npos)
184     return false; // Should not instrument sanitizer init functions.
185   if (F.getName().startswith("__sanitizer_"))
186     return false; // Don't instrument __sanitizer_* callbacks.
187   // Don't touch available_externally functions, their actual body is elewhere.
188   if (F.getLinkage() == GlobalValue::AvailableExternallyLinkage)
189     return false;
190   // Don't instrument MSVC CRT configuration helpers. They may run before normal
191   // initialization.
192   if (F.getName() == "__local_stdio_printf_options" ||
193       F.getName() == "__local_stdio_scanf_options")
194     return false;
195   if (isa<UnreachableInst>(F.getEntryBlock().getTerminator()))
196     return false;
197   // Don't instrument functions using SEH for now. Splitting basic blocks like
198   // we do for coverage breaks WinEHPrepare.
199   // FIXME: Remove this when SEH no longer uses landingpad pattern matching.
200   if (F.hasPersonalityFn() &&
201       isAsynchronousEHPersonality(classifyEHPersonality(F.getPersonalityFn())))
202     return false;
203   return true;
204 }
205 
206 std::string getSectionStartImpl(const Triple &TargetTriple,
207                                 const std::string &Section) {
208   if (TargetTriple.isOSBinFormatMachO())
209     return "\1section$start$__DATA$__" + Section;
210   return "__start___" + Section;
211 }
212 
213 std::string getSectionEndImpl(const Triple &TargetTriple,
214                               const std::string &Section) {
215   if (TargetTriple.isOSBinFormatMachO())
216     return "\1section$end$__DATA$__" + Section;
217   return "__stop___" + Section;
218 }
219 
220 /// This is a class for instrumenting the module to add calls to initializing
221 /// the trace PC guards and 8bit counter globals. This should only be done
222 /// though if there is at least one function that can be instrumented with
223 /// Sancov.
224 class ModuleSanitizerCoverage {
225 public:
226   ModuleSanitizerCoverage(const SanitizerCoverageOptions &Options)
227       : Options(OverrideFromCL(Options)) {}
228 
229   bool instrumentModule(Module &M) {
230     if (Options.CoverageType == SanitizerCoverageOptions::SCK_None)
231       return false;
232 
233     Function *Ctor = nullptr;
234     LLVMContext *C = &(M.getContext());
235     const DataLayout *DL = &M.getDataLayout();
236     TargetTriple = Triple(M.getTargetTriple());
237     IntptrTy = Type::getIntNTy(*C, DL->getPointerSizeInBits());
238     Type *IntptrPtrTy = PointerType::getUnqual(IntptrTy);
239     IRBuilder<> IRB(*C);
240     Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
241     Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
242     Int8Ty = IRB.getInt8Ty();
243 
244     // Check that the __sancov_lowest_stack marker does not already exist.
245     Constant *SanCovLowestStackConstant =
246         M.getOrInsertGlobal(SanCovLowestStackName, IntptrTy);
247     GlobalVariable *SanCovLowestStack =
248         dyn_cast<GlobalVariable>(SanCovLowestStackConstant);
249     if (!SanCovLowestStack) {
250       C->emitError(StringRef("'") + SanCovLowestStackName +
251                    "' should not be declared by the user");
252       return true;
253     }
254 
255     // We want to emit guard init calls if the module contains a function that
256     // we can instrument with SanitizerCoverage. We ignore any functions that
257     // were inserted by SanitizerCoverage and get the result from the analysis
258     // that checks for a valid function that the analysis may have run over.
259     if (!llvm::any_of(
260             M, [](const Function &F) { return canInstrumentWithSancov(F); }))
261       return false;
262 
263     // Emit the init calls.
264     if (Options.TracePCGuard)
265       Ctor = CreateInitCallsForSections(M, SanCovModuleCtorTracePcGuardName,
266                                         SanCovTracePCGuardInitName, Int32PtrTy,
267                                         SanCovGuardsSectionName);
268     if (Options.Inline8bitCounters)
269       Ctor = CreateInitCallsForSections(M, SanCovModuleCtor8bitCountersName,
270                                         SanCov8bitCountersInitName, Int8PtrTy,
271                                         SanCovCountersSectionName);
272     if (Ctor && Options.PCTable) {
273       auto SecStartEnd =
274           CreateSecStartEnd(M, SanCovPCsSectionName, IntptrPtrTy);
275       FunctionCallee InitFunction = declareSanitizerInitFunction(
276           M, SanCovPCsInitName, {IntptrPtrTy, IntptrPtrTy});
277       IRBuilder<> IRBCtor(Ctor->getEntryBlock().getTerminator());
278       IRBCtor.CreateCall(InitFunction, {SecStartEnd.first, SecStartEnd.second});
279     }
280     return Ctor;
281   }
282 
283 private:
284   Function *CreateInitCallsForSections(Module &M, const char *CtorName,
285                                        const char *InitFunctionName, Type *Ty,
286                                        const char *Section);
287   std::pair<Value *, Value *> CreateSecStartEnd(Module &M, const char *Section,
288                                                 Type *Ty);
289   std::string getSectionStart(const std::string &Section) const {
290     return getSectionStartImpl(TargetTriple, Section);
291   }
292   std::string getSectionEnd(const std::string &Section) const {
293     return getSectionEndImpl(TargetTriple, Section);
294   }
295 
296   SanitizerCoverageOptions Options;
297   Triple TargetTriple;
298   Type *IntptrTy, *Int8PtrTy, *Int8Ty;
299 };
300 
301 class ModuleSanitizerCoverageLegacyPass : public ModulePass {
302 public:
303   static char ID;
304 
305   ModuleSanitizerCoverageLegacyPass(
306       SanitizerCoverageOptions Options = SanitizerCoverageOptions())
307       : ModulePass(ID), Options(Options) {
308     initializeModuleSanitizerCoverageLegacyPassPass(
309         *PassRegistry::getPassRegistry());
310   }
311 
312   bool runOnModule(Module &M) override {
313     ModuleSanitizerCoverage ModuleSancov(Options);
314     return ModuleSancov.instrumentModule(M);
315   };
316 
317   StringRef getPassName() const override {
318     return "ModuleSanitizerCoverageLegacyPass";
319   }
320 
321 private:
322   SanitizerCoverageOptions Options;
323 };
324 
325 char ModuleSanitizerCoverageLegacyPass::ID = 0;
326 
327 class SanitizerCoverage {
328 public:
329   SanitizerCoverage(Function &F, const SanitizerCoverageOptions &Options)
330       : CurModule(F.getParent()), Options(OverrideFromCL(Options)) {
331     initializeModule(*F.getParent());
332   }
333 
334   ~SanitizerCoverage() { finalizeModule(*CurModule); }
335 
336   bool instrumentFunction(Function &F, const DominatorTree *DT,
337                           const PostDominatorTree *PDT);
338 
339 private:
340   void initializeModule(Module &M);
341   void finalizeModule(Module &M);
342   void InjectCoverageForIndirectCalls(Function &F,
343                                       ArrayRef<Instruction *> IndirCalls);
344   void InjectTraceForCmp(Function &F, ArrayRef<Instruction *> CmpTraceTargets);
345   void InjectTraceForDiv(Function &F,
346                          ArrayRef<BinaryOperator *> DivTraceTargets);
347   void InjectTraceForGep(Function &F,
348                          ArrayRef<GetElementPtrInst *> GepTraceTargets);
349   void InjectTraceForSwitch(Function &F,
350                             ArrayRef<Instruction *> SwitchTraceTargets);
351   bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks,
352                       bool IsLeafFunc = true);
353   GlobalVariable *CreateFunctionLocalArrayInSection(size_t NumElements,
354                                                     Function &F, Type *Ty,
355                                                     const char *Section);
356   GlobalVariable *CreatePCArray(Function &F, ArrayRef<BasicBlock *> AllBlocks);
357   void CreateFunctionLocalArrays(Function &F, ArrayRef<BasicBlock *> AllBlocks);
358   void InjectCoverageAtBlock(Function &F, BasicBlock &BB, size_t Idx,
359                              bool IsLeafFunc = true);
360 
361   void SetNoSanitizeMetadata(Instruction *I) {
362     I->setMetadata(I->getModule()->getMDKindID("nosanitize"),
363                    MDNode::get(*C, None));
364   }
365 
366   std::string getSectionName(const std::string &Section) const;
367   std::string getSectionStart(const std::string &Section) const;
368   std::string getSectionEnd(const std::string &Section) const;
369   FunctionCallee SanCovTracePCIndir;
370   FunctionCallee SanCovTracePC, SanCovTracePCGuard;
371   FunctionCallee SanCovTraceCmpFunction[4];
372   FunctionCallee SanCovTraceConstCmpFunction[4];
373   FunctionCallee SanCovTraceDivFunction[2];
374   FunctionCallee SanCovTraceGepFunction;
375   FunctionCallee SanCovTraceSwitchFunction;
376   GlobalVariable *SanCovLowestStack;
377   InlineAsm *EmptyAsm;
378   Type *IntptrTy, *IntptrPtrTy, *Int64Ty, *Int64PtrTy, *Int32Ty, *Int32PtrTy,
379       *Int16Ty, *Int8Ty, *Int8PtrTy;
380   Module *CurModule;
381   std::string CurModuleUniqueId;
382   Triple TargetTriple;
383   LLVMContext *C;
384   const DataLayout *DL;
385 
386   GlobalVariable *FunctionGuardArray;  // for trace-pc-guard.
387   GlobalVariable *Function8bitCounterArray;  // for inline-8bit-counters.
388   GlobalVariable *FunctionPCsArray;  // for pc-table.
389   SmallVector<GlobalValue *, 20> GlobalsToAppendToUsed;
390   SmallVector<GlobalValue *, 20> GlobalsToAppendToCompilerUsed;
391 
392   SanitizerCoverageOptions Options;
393 };
394 
395 class SanitizerCoverageLegacyPass : public FunctionPass {
396 public:
397   static char ID; // Pass identification, replacement for typeid
398 
399   SanitizerCoverageLegacyPass(
400       SanitizerCoverageOptions Options = SanitizerCoverageOptions())
401       : FunctionPass(ID), Options(Options) {
402     initializeSanitizerCoverageLegacyPassPass(*PassRegistry::getPassRegistry());
403   }
404 
405   bool runOnFunction(Function &F) override {
406     const DominatorTree *DT =
407         &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
408     const PostDominatorTree *PDT =
409         &getAnalysis<PostDominatorTreeWrapperPass>().getPostDomTree();
410     SanitizerCoverage Sancov(F, Options);
411     return Sancov.instrumentFunction(F, DT, PDT);
412   }
413 
414   StringRef getPassName() const override {
415     return "SanitizerCoverageLegacyPass";
416   }
417 
418   void getAnalysisUsage(AnalysisUsage &AU) const override {
419     // Make the module sancov pass required by this pass so that it runs when
420     // -sancov is passed.
421     AU.addRequired<ModuleSanitizerCoverageLegacyPass>();
422     AU.addRequired<DominatorTreeWrapperPass>();
423     AU.addRequired<PostDominatorTreeWrapperPass>();
424   }
425 
426 private:
427   SanitizerCoverageOptions Options;
428 };
429 
430 } // namespace
431 
432 PreservedAnalyses SanitizerCoveragePass::run(Function &F,
433                                              FunctionAnalysisManager &AM) {
434   const DominatorTree *DT = &AM.getResult<DominatorTreeAnalysis>(F);
435   const PostDominatorTree *PDT = &AM.getResult<PostDominatorTreeAnalysis>(F);
436   SanitizerCoverage Sancov(F, Options);
437   if (Sancov.instrumentFunction(F, DT, PDT))
438     return PreservedAnalyses::none();
439   return PreservedAnalyses::all();
440 }
441 
442 PreservedAnalyses ModuleSanitizerCoveragePass::run(Module &M,
443                                                    ModuleAnalysisManager &AM) {
444   ModuleSanitizerCoverage ModuleSancov(Options);
445   if (ModuleSancov.instrumentModule(M))
446     return PreservedAnalyses::none();
447   return PreservedAnalyses::all();
448 }
449 
450 std::pair<Value *, Value *>
451 ModuleSanitizerCoverage::CreateSecStartEnd(Module &M, const char *Section,
452                                            Type *Ty) {
453   GlobalVariable *SecStart =
454       new GlobalVariable(M, Ty, false, GlobalVariable::ExternalLinkage, nullptr,
455                          getSectionStart(Section));
456   SecStart->setVisibility(GlobalValue::HiddenVisibility);
457   GlobalVariable *SecEnd =
458       new GlobalVariable(M, Ty, false, GlobalVariable::ExternalLinkage,
459                          nullptr, getSectionEnd(Section));
460   SecEnd->setVisibility(GlobalValue::HiddenVisibility);
461 
462   IRBuilder<> IRB(M.getContext());
463   Value *SecEndPtr = IRB.CreatePointerCast(SecEnd, Ty);
464   if (!TargetTriple.isOSBinFormatCOFF())
465     return std::make_pair(IRB.CreatePointerCast(SecStart, Ty), SecEndPtr);
466 
467   // Account for the fact that on windows-msvc __start_* symbols actually
468   // point to a uint64_t before the start of the array.
469   auto SecStartI8Ptr = IRB.CreatePointerCast(SecStart, Int8PtrTy);
470   auto GEP = IRB.CreateGEP(Int8Ty, SecStartI8Ptr,
471                            ConstantInt::get(IntptrTy, sizeof(uint64_t)));
472   return std::make_pair(IRB.CreatePointerCast(GEP, Ty), SecEndPtr);
473 }
474 
475 Function *ModuleSanitizerCoverage::CreateInitCallsForSections(
476     Module &M, const char *CtorName, const char *InitFunctionName, Type *Ty,
477     const char *Section) {
478   auto SecStartEnd = CreateSecStartEnd(M, Section, Ty);
479   auto SecStart = SecStartEnd.first;
480   auto SecEnd = SecStartEnd.second;
481   Function *CtorFunc;
482   std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
483       M, CtorName, InitFunctionName, {Ty, Ty}, {SecStart, SecEnd});
484   assert(CtorFunc->getName() == CtorName);
485 
486   if (TargetTriple.supportsCOMDAT()) {
487     // Use comdat to dedup CtorFunc.
488     CtorFunc->setComdat(M.getOrInsertComdat(CtorName));
489     appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority, CtorFunc);
490   } else {
491     appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority);
492   }
493 
494   if (TargetTriple.isOSBinFormatCOFF()) {
495     // In COFF files, if the contructors are set as COMDAT (they are because
496     // COFF supports COMDAT) and the linker flag /OPT:REF (strip unreferenced
497     // functions and data) is used, the constructors get stripped. To prevent
498     // this, give the constructors weak ODR linkage and ensure the linker knows
499     // to include the sancov constructor. This way the linker can deduplicate
500     // the constructors but always leave one copy.
501     CtorFunc->setLinkage(GlobalValue::WeakODRLinkage);
502     appendToUsed(M, CtorFunc);
503   }
504   return CtorFunc;
505 }
506 
507 void SanitizerCoverage::initializeModule(Module &M) {
508   if (Options.CoverageType == SanitizerCoverageOptions::SCK_None)
509     return;
510   C = &(M.getContext());
511   DL = &M.getDataLayout();
512   CurModuleUniqueId = getUniqueModuleId(CurModule);
513   TargetTriple = Triple(M.getTargetTriple());
514   FunctionGuardArray = nullptr;
515   Function8bitCounterArray = nullptr;
516   FunctionPCsArray = nullptr;
517   IntptrTy = Type::getIntNTy(*C, DL->getPointerSizeInBits());
518   IntptrPtrTy = PointerType::getUnqual(IntptrTy);
519   Type *VoidTy = Type::getVoidTy(*C);
520   IRBuilder<> IRB(*C);
521   Int64PtrTy = PointerType::getUnqual(IRB.getInt64Ty());
522   Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
523   Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
524   Int64Ty = IRB.getInt64Ty();
525   Int32Ty = IRB.getInt32Ty();
526   Int16Ty = IRB.getInt16Ty();
527   Int8Ty = IRB.getInt8Ty();
528 
529   SanCovTracePCIndir =
530       M.getOrInsertFunction(SanCovTracePCIndirName, VoidTy, IntptrTy);
531   // Make sure smaller parameters are zero-extended to i64 as required by the
532   // x86_64 ABI.
533   AttributeList SanCovTraceCmpZeroExtAL;
534   if (TargetTriple.getArch() == Triple::x86_64) {
535     SanCovTraceCmpZeroExtAL =
536         SanCovTraceCmpZeroExtAL.addParamAttribute(*C, 0, Attribute::ZExt);
537     SanCovTraceCmpZeroExtAL =
538         SanCovTraceCmpZeroExtAL.addParamAttribute(*C, 1, Attribute::ZExt);
539   }
540 
541   SanCovTraceCmpFunction[0] =
542       M.getOrInsertFunction(SanCovTraceCmp1, SanCovTraceCmpZeroExtAL, VoidTy,
543                             IRB.getInt8Ty(), IRB.getInt8Ty());
544   SanCovTraceCmpFunction[1] =
545       M.getOrInsertFunction(SanCovTraceCmp2, SanCovTraceCmpZeroExtAL, VoidTy,
546                             IRB.getInt16Ty(), IRB.getInt16Ty());
547   SanCovTraceCmpFunction[2] =
548       M.getOrInsertFunction(SanCovTraceCmp4, SanCovTraceCmpZeroExtAL, VoidTy,
549                             IRB.getInt32Ty(), IRB.getInt32Ty());
550   SanCovTraceCmpFunction[3] =
551       M.getOrInsertFunction(SanCovTraceCmp8, VoidTy, Int64Ty, Int64Ty);
552 
553   SanCovTraceConstCmpFunction[0] = M.getOrInsertFunction(
554       SanCovTraceConstCmp1, SanCovTraceCmpZeroExtAL, VoidTy, Int8Ty, Int8Ty);
555   SanCovTraceConstCmpFunction[1] = M.getOrInsertFunction(
556       SanCovTraceConstCmp2, SanCovTraceCmpZeroExtAL, VoidTy, Int16Ty, Int16Ty);
557   SanCovTraceConstCmpFunction[2] = M.getOrInsertFunction(
558       SanCovTraceConstCmp4, SanCovTraceCmpZeroExtAL, VoidTy, Int32Ty, Int32Ty);
559   SanCovTraceConstCmpFunction[3] =
560       M.getOrInsertFunction(SanCovTraceConstCmp8, VoidTy, Int64Ty, Int64Ty);
561 
562   {
563     AttributeList AL;
564     if (TargetTriple.getArch() == Triple::x86_64)
565       AL = AL.addParamAttribute(*C, 0, Attribute::ZExt);
566     SanCovTraceDivFunction[0] =
567         M.getOrInsertFunction(SanCovTraceDiv4, AL, VoidTy, IRB.getInt32Ty());
568   }
569   SanCovTraceDivFunction[1] =
570       M.getOrInsertFunction(SanCovTraceDiv8, VoidTy, Int64Ty);
571   SanCovTraceGepFunction =
572       M.getOrInsertFunction(SanCovTraceGep, VoidTy, IntptrTy);
573   SanCovTraceSwitchFunction =
574       M.getOrInsertFunction(SanCovTraceSwitchName, VoidTy, Int64Ty, Int64PtrTy);
575 
576   Constant *SanCovLowestStackConstant =
577       M.getOrInsertGlobal(SanCovLowestStackName, IntptrTy);
578   SanCovLowestStack = dyn_cast<GlobalVariable>(SanCovLowestStackConstant);
579   SanCovLowestStack->setThreadLocalMode(
580       GlobalValue::ThreadLocalMode::InitialExecTLSModel);
581   if (Options.StackDepth && !SanCovLowestStack->isDeclaration())
582     SanCovLowestStack->setInitializer(Constant::getAllOnesValue(IntptrTy));
583 
584   // We insert an empty inline asm after cov callbacks to avoid callback merge.
585   EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
586                             StringRef(""), StringRef(""),
587                             /*hasSideEffects=*/true);
588 
589   SanCovTracePC = M.getOrInsertFunction(SanCovTracePCName, VoidTy);
590   SanCovTracePCGuard =
591       M.getOrInsertFunction(SanCovTracePCGuardName, VoidTy, Int32PtrTy);
592 }
593 
594 void SanitizerCoverage::finalizeModule(Module &M) {
595   // We don't reference these arrays directly in any of our runtime functions,
596   // so we need to prevent them from being dead stripped.
597   if (TargetTriple.isOSBinFormatMachO())
598     appendToUsed(M, GlobalsToAppendToUsed);
599   appendToCompilerUsed(M, GlobalsToAppendToCompilerUsed);
600 }
601 
602 // True if block has successors and it dominates all of them.
603 static bool isFullDominator(const BasicBlock *BB, const DominatorTree *DT) {
604   if (succ_begin(BB) == succ_end(BB))
605     return false;
606 
607   for (const BasicBlock *SUCC : make_range(succ_begin(BB), succ_end(BB))) {
608     if (!DT->dominates(BB, SUCC))
609       return false;
610   }
611 
612   return true;
613 }
614 
615 // True if block has predecessors and it postdominates all of them.
616 static bool isFullPostDominator(const BasicBlock *BB,
617                                 const PostDominatorTree *PDT) {
618   if (pred_begin(BB) == pred_end(BB))
619     return false;
620 
621   for (const BasicBlock *PRED : make_range(pred_begin(BB), pred_end(BB))) {
622     if (!PDT->dominates(BB, PRED))
623       return false;
624   }
625 
626   return true;
627 }
628 
629 static bool shouldInstrumentBlock(const Function &F, const BasicBlock *BB,
630                                   const DominatorTree *DT,
631                                   const PostDominatorTree *PDT,
632                                   const SanitizerCoverageOptions &Options) {
633   // Don't insert coverage for blocks containing nothing but unreachable: we
634   // will never call __sanitizer_cov() for them, so counting them in
635   // NumberOfInstrumentedBlocks() might complicate calculation of code coverage
636   // percentage. Also, unreachable instructions frequently have no debug
637   // locations.
638   if (isa<UnreachableInst>(BB->getFirstNonPHIOrDbgOrLifetime()))
639     return false;
640 
641   // Don't insert coverage into blocks without a valid insertion point
642   // (catchswitch blocks).
643   if (BB->getFirstInsertionPt() == BB->end())
644     return false;
645 
646   if (Options.NoPrune || &F.getEntryBlock() == BB)
647     return true;
648 
649   if (Options.CoverageType == SanitizerCoverageOptions::SCK_Function &&
650       &F.getEntryBlock() != BB)
651     return false;
652 
653   // Do not instrument full dominators, or full post-dominators with multiple
654   // predecessors.
655   return !isFullDominator(BB, DT)
656     && !(isFullPostDominator(BB, PDT) && !BB->getSinglePredecessor());
657 }
658 
659 
660 // Returns true iff From->To is a backedge.
661 // A twist here is that we treat From->To as a backedge if
662 //   * To dominates From or
663 //   * To->UniqueSuccessor dominates From
664 static bool IsBackEdge(BasicBlock *From, BasicBlock *To,
665                        const DominatorTree *DT) {
666   if (DT->dominates(To, From))
667     return true;
668   if (auto Next = To->getUniqueSuccessor())
669     if (DT->dominates(Next, From))
670       return true;
671   return false;
672 }
673 
674 // Prunes uninteresting Cmp instrumentation:
675 //   * CMP instructions that feed into loop backedge branch.
676 //
677 // Note that Cmp pruning is controlled by the same flag as the
678 // BB pruning.
679 static bool IsInterestingCmp(ICmpInst *CMP, const DominatorTree *DT,
680                              const SanitizerCoverageOptions &Options) {
681   if (!Options.NoPrune)
682     if (CMP->hasOneUse())
683       if (auto BR = dyn_cast<BranchInst>(CMP->user_back()))
684         for (BasicBlock *B : BR->successors())
685           if (IsBackEdge(BR->getParent(), B, DT))
686             return false;
687   return true;
688 }
689 
690 bool SanitizerCoverage::instrumentFunction(Function &F, const DominatorTree *DT,
691                                            const PostDominatorTree *PDT) {
692   if (Options.CoverageType == SanitizerCoverageOptions::SCK_None)
693     return false;
694   if (!canInstrumentWithSancov(F))
695     return false;
696   if (Options.CoverageType >= SanitizerCoverageOptions::SCK_Edge)
697     SplitAllCriticalEdges(F, CriticalEdgeSplittingOptions().setIgnoreUnreachableDests());
698   SmallVector<Instruction *, 8> IndirCalls;
699   SmallVector<BasicBlock *, 16> BlocksToInstrument;
700   SmallVector<Instruction *, 8> CmpTraceTargets;
701   SmallVector<Instruction *, 8> SwitchTraceTargets;
702   SmallVector<BinaryOperator *, 8> DivTraceTargets;
703   SmallVector<GetElementPtrInst *, 8> GepTraceTargets;
704 
705   bool IsLeafFunc = true;
706 
707   for (auto &BB : F) {
708     if (shouldInstrumentBlock(F, &BB, DT, PDT, Options))
709       BlocksToInstrument.push_back(&BB);
710     for (auto &Inst : BB) {
711       if (Options.IndirectCalls) {
712         CallSite CS(&Inst);
713         if (CS && !CS.getCalledFunction())
714           IndirCalls.push_back(&Inst);
715       }
716       if (Options.TraceCmp) {
717         if (ICmpInst *CMP = dyn_cast<ICmpInst>(&Inst))
718           if (IsInterestingCmp(CMP, DT, Options))
719             CmpTraceTargets.push_back(&Inst);
720         if (isa<SwitchInst>(&Inst))
721           SwitchTraceTargets.push_back(&Inst);
722       }
723       if (Options.TraceDiv)
724         if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&Inst))
725           if (BO->getOpcode() == Instruction::SDiv ||
726               BO->getOpcode() == Instruction::UDiv)
727             DivTraceTargets.push_back(BO);
728       if (Options.TraceGep)
729         if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(&Inst))
730           GepTraceTargets.push_back(GEP);
731       if (Options.StackDepth)
732         if (isa<InvokeInst>(Inst) ||
733             (isa<CallInst>(Inst) && !isa<IntrinsicInst>(Inst)))
734           IsLeafFunc = false;
735     }
736   }
737 
738   InjectCoverage(F, BlocksToInstrument, IsLeafFunc);
739   InjectCoverageForIndirectCalls(F, IndirCalls);
740   InjectTraceForCmp(F, CmpTraceTargets);
741   InjectTraceForSwitch(F, SwitchTraceTargets);
742   InjectTraceForDiv(F, DivTraceTargets);
743   InjectTraceForGep(F, GepTraceTargets);
744   return true;
745 }
746 
747 GlobalVariable *SanitizerCoverage::CreateFunctionLocalArrayInSection(
748     size_t NumElements, Function &F, Type *Ty, const char *Section) {
749   ArrayType *ArrayTy = ArrayType::get(Ty, NumElements);
750   auto Array = new GlobalVariable(
751       *CurModule, ArrayTy, false, GlobalVariable::PrivateLinkage,
752       Constant::getNullValue(ArrayTy), "__sancov_gen_");
753 
754   if (TargetTriple.supportsCOMDAT() && !F.isInterposable())
755     if (auto Comdat =
756             GetOrCreateFunctionComdat(F, TargetTriple, CurModuleUniqueId))
757       Array->setComdat(Comdat);
758   Array->setSection(getSectionName(Section));
759   Array->setAlignment(Ty->isPointerTy() ? DL->getPointerSize()
760                                         : Ty->getPrimitiveSizeInBits() / 8);
761   GlobalsToAppendToUsed.push_back(Array);
762   GlobalsToAppendToCompilerUsed.push_back(Array);
763   MDNode *MD = MDNode::get(F.getContext(), ValueAsMetadata::get(&F));
764   Array->addMetadata(LLVMContext::MD_associated, *MD);
765 
766   return Array;
767 }
768 
769 GlobalVariable *
770 SanitizerCoverage::CreatePCArray(Function &F,
771                                  ArrayRef<BasicBlock *> AllBlocks) {
772   size_t N = AllBlocks.size();
773   assert(N);
774   SmallVector<Constant *, 32> PCs;
775   IRBuilder<> IRB(&*F.getEntryBlock().getFirstInsertionPt());
776   for (size_t i = 0; i < N; i++) {
777     if (&F.getEntryBlock() == AllBlocks[i]) {
778       PCs.push_back((Constant *)IRB.CreatePointerCast(&F, IntptrPtrTy));
779       PCs.push_back((Constant *)IRB.CreateIntToPtr(
780           ConstantInt::get(IntptrTy, 1), IntptrPtrTy));
781     } else {
782       PCs.push_back((Constant *)IRB.CreatePointerCast(
783           BlockAddress::get(AllBlocks[i]), IntptrPtrTy));
784       PCs.push_back((Constant *)IRB.CreateIntToPtr(
785           ConstantInt::get(IntptrTy, 0), IntptrPtrTy));
786     }
787   }
788   auto *PCArray = CreateFunctionLocalArrayInSection(N * 2, F, IntptrPtrTy,
789                                                     SanCovPCsSectionName);
790   PCArray->setInitializer(
791       ConstantArray::get(ArrayType::get(IntptrPtrTy, N * 2), PCs));
792   PCArray->setConstant(true);
793 
794   return PCArray;
795 }
796 
797 void SanitizerCoverage::CreateFunctionLocalArrays(
798     Function &F, ArrayRef<BasicBlock *> AllBlocks) {
799   if (Options.TracePCGuard)
800     FunctionGuardArray = CreateFunctionLocalArrayInSection(
801         AllBlocks.size(), F, Int32Ty, SanCovGuardsSectionName);
802 
803   if (Options.Inline8bitCounters)
804     Function8bitCounterArray = CreateFunctionLocalArrayInSection(
805         AllBlocks.size(), F, Int8Ty, SanCovCountersSectionName);
806 
807   if (Options.PCTable)
808     FunctionPCsArray = CreatePCArray(F, AllBlocks);
809 }
810 
811 bool SanitizerCoverage::InjectCoverage(Function &F,
812                                        ArrayRef<BasicBlock *> AllBlocks,
813                                        bool IsLeafFunc) {
814   if (AllBlocks.empty()) return false;
815   CreateFunctionLocalArrays(F, AllBlocks);
816   for (size_t i = 0, N = AllBlocks.size(); i < N; i++)
817     InjectCoverageAtBlock(F, *AllBlocks[i], i, IsLeafFunc);
818   return true;
819 }
820 
821 // On every indirect call we call a run-time function
822 // __sanitizer_cov_indir_call* with two parameters:
823 //   - callee address,
824 //   - global cache array that contains CacheSize pointers (zero-initialized).
825 //     The cache is used to speed up recording the caller-callee pairs.
826 // The address of the caller is passed implicitly via caller PC.
827 // CacheSize is encoded in the name of the run-time function.
828 void SanitizerCoverage::InjectCoverageForIndirectCalls(
829     Function &F, ArrayRef<Instruction *> IndirCalls) {
830   if (IndirCalls.empty())
831     return;
832   assert(Options.TracePC || Options.TracePCGuard || Options.Inline8bitCounters);
833   for (auto I : IndirCalls) {
834     IRBuilder<> IRB(I);
835     CallSite CS(I);
836     Value *Callee = CS.getCalledValue();
837     if (isa<InlineAsm>(Callee))
838       continue;
839     IRB.CreateCall(SanCovTracePCIndir, IRB.CreatePointerCast(Callee, IntptrTy));
840   }
841 }
842 
843 // For every switch statement we insert a call:
844 // __sanitizer_cov_trace_switch(CondValue,
845 //      {NumCases, ValueSizeInBits, Case0Value, Case1Value, Case2Value, ... })
846 
847 void SanitizerCoverage::InjectTraceForSwitch(
848     Function &, ArrayRef<Instruction *> SwitchTraceTargets) {
849   for (auto I : SwitchTraceTargets) {
850     if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
851       IRBuilder<> IRB(I);
852       SmallVector<Constant *, 16> Initializers;
853       Value *Cond = SI->getCondition();
854       if (Cond->getType()->getScalarSizeInBits() >
855           Int64Ty->getScalarSizeInBits())
856         continue;
857       Initializers.push_back(ConstantInt::get(Int64Ty, SI->getNumCases()));
858       Initializers.push_back(
859           ConstantInt::get(Int64Ty, Cond->getType()->getScalarSizeInBits()));
860       if (Cond->getType()->getScalarSizeInBits() <
861           Int64Ty->getScalarSizeInBits())
862         Cond = IRB.CreateIntCast(Cond, Int64Ty, false);
863       for (auto It : SI->cases()) {
864         Constant *C = It.getCaseValue();
865         if (C->getType()->getScalarSizeInBits() <
866             Int64Ty->getScalarSizeInBits())
867           C = ConstantExpr::getCast(CastInst::ZExt, It.getCaseValue(), Int64Ty);
868         Initializers.push_back(C);
869       }
870       llvm::sort(Initializers.begin() + 2, Initializers.end(),
871                  [](const Constant *A, const Constant *B) {
872                    return cast<ConstantInt>(A)->getLimitedValue() <
873                           cast<ConstantInt>(B)->getLimitedValue();
874                  });
875       ArrayType *ArrayOfInt64Ty = ArrayType::get(Int64Ty, Initializers.size());
876       GlobalVariable *GV = new GlobalVariable(
877           *CurModule, ArrayOfInt64Ty, false, GlobalVariable::InternalLinkage,
878           ConstantArray::get(ArrayOfInt64Ty, Initializers),
879           "__sancov_gen_cov_switch_values");
880       IRB.CreateCall(SanCovTraceSwitchFunction,
881                      {Cond, IRB.CreatePointerCast(GV, Int64PtrTy)});
882     }
883   }
884 }
885 
886 void SanitizerCoverage::InjectTraceForDiv(
887     Function &, ArrayRef<BinaryOperator *> DivTraceTargets) {
888   for (auto BO : DivTraceTargets) {
889     IRBuilder<> IRB(BO);
890     Value *A1 = BO->getOperand(1);
891     if (isa<ConstantInt>(A1)) continue;
892     if (!A1->getType()->isIntegerTy())
893       continue;
894     uint64_t TypeSize = DL->getTypeStoreSizeInBits(A1->getType());
895     int CallbackIdx = TypeSize == 32 ? 0 :
896         TypeSize == 64 ? 1 : -1;
897     if (CallbackIdx < 0) continue;
898     auto Ty = Type::getIntNTy(*C, TypeSize);
899     IRB.CreateCall(SanCovTraceDivFunction[CallbackIdx],
900                    {IRB.CreateIntCast(A1, Ty, true)});
901   }
902 }
903 
904 void SanitizerCoverage::InjectTraceForGep(
905     Function &, ArrayRef<GetElementPtrInst *> GepTraceTargets) {
906   for (auto GEP : GepTraceTargets) {
907     IRBuilder<> IRB(GEP);
908     for (auto I = GEP->idx_begin(); I != GEP->idx_end(); ++I)
909       if (!isa<ConstantInt>(*I) && (*I)->getType()->isIntegerTy())
910         IRB.CreateCall(SanCovTraceGepFunction,
911                        {IRB.CreateIntCast(*I, IntptrTy, true)});
912   }
913 }
914 
915 void SanitizerCoverage::InjectTraceForCmp(
916     Function &, ArrayRef<Instruction *> CmpTraceTargets) {
917   for (auto I : CmpTraceTargets) {
918     if (ICmpInst *ICMP = dyn_cast<ICmpInst>(I)) {
919       IRBuilder<> IRB(ICMP);
920       Value *A0 = ICMP->getOperand(0);
921       Value *A1 = ICMP->getOperand(1);
922       if (!A0->getType()->isIntegerTy())
923         continue;
924       uint64_t TypeSize = DL->getTypeStoreSizeInBits(A0->getType());
925       int CallbackIdx = TypeSize == 8 ? 0 :
926                         TypeSize == 16 ? 1 :
927                         TypeSize == 32 ? 2 :
928                         TypeSize == 64 ? 3 : -1;
929       if (CallbackIdx < 0) continue;
930       // __sanitizer_cov_trace_cmp((type_size << 32) | predicate, A0, A1);
931       auto CallbackFunc = SanCovTraceCmpFunction[CallbackIdx];
932       bool FirstIsConst = isa<ConstantInt>(A0);
933       bool SecondIsConst = isa<ConstantInt>(A1);
934       // If both are const, then we don't need such a comparison.
935       if (FirstIsConst && SecondIsConst) continue;
936       // If only one is const, then make it the first callback argument.
937       if (FirstIsConst || SecondIsConst) {
938         CallbackFunc = SanCovTraceConstCmpFunction[CallbackIdx];
939         if (SecondIsConst)
940           std::swap(A0, A1);
941       }
942 
943       auto Ty = Type::getIntNTy(*C, TypeSize);
944       IRB.CreateCall(CallbackFunc, {IRB.CreateIntCast(A0, Ty, true),
945               IRB.CreateIntCast(A1, Ty, true)});
946     }
947   }
948 }
949 
950 void SanitizerCoverage::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
951                                               size_t Idx, bool IsLeafFunc) {
952   BasicBlock::iterator IP = BB.getFirstInsertionPt();
953   bool IsEntryBB = &BB == &F.getEntryBlock();
954   DebugLoc EntryLoc;
955   if (IsEntryBB) {
956     if (auto SP = F.getSubprogram())
957       EntryLoc = DebugLoc::get(SP->getScopeLine(), 0, SP);
958     // Keep static allocas and llvm.localescape calls in the entry block.  Even
959     // if we aren't splitting the block, it's nice for allocas to be before
960     // calls.
961     IP = PrepareToSplitEntryBlock(BB, IP);
962   } else {
963     EntryLoc = IP->getDebugLoc();
964   }
965 
966   IRBuilder<> IRB(&*IP);
967   IRB.SetCurrentDebugLocation(EntryLoc);
968   if (Options.TracePC) {
969     IRB.CreateCall(SanCovTracePC); // gets the PC using GET_CALLER_PC.
970     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
971   }
972   if (Options.TracePCGuard) {
973     auto GuardPtr = IRB.CreateIntToPtr(
974         IRB.CreateAdd(IRB.CreatePointerCast(FunctionGuardArray, IntptrTy),
975                       ConstantInt::get(IntptrTy, Idx * 4)),
976         Int32PtrTy);
977     IRB.CreateCall(SanCovTracePCGuard, GuardPtr);
978     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
979   }
980   if (Options.Inline8bitCounters) {
981     auto CounterPtr = IRB.CreateGEP(
982         Function8bitCounterArray->getValueType(), Function8bitCounterArray,
983         {ConstantInt::get(IntptrTy, 0), ConstantInt::get(IntptrTy, Idx)});
984     auto Load = IRB.CreateLoad(Int8Ty, CounterPtr);
985     auto Inc = IRB.CreateAdd(Load, ConstantInt::get(Int8Ty, 1));
986     auto Store = IRB.CreateStore(Inc, CounterPtr);
987     SetNoSanitizeMetadata(Load);
988     SetNoSanitizeMetadata(Store);
989   }
990   if (Options.StackDepth && IsEntryBB && !IsLeafFunc) {
991     // Check stack depth.  If it's the deepest so far, record it.
992     Function *GetFrameAddr =
993         Intrinsic::getDeclaration(F.getParent(), Intrinsic::frameaddress);
994     auto FrameAddrPtr =
995         IRB.CreateCall(GetFrameAddr, {Constant::getNullValue(Int32Ty)});
996     auto FrameAddrInt = IRB.CreatePtrToInt(FrameAddrPtr, IntptrTy);
997     auto LowestStack = IRB.CreateLoad(IntptrTy, SanCovLowestStack);
998     auto IsStackLower = IRB.CreateICmpULT(FrameAddrInt, LowestStack);
999     auto ThenTerm = SplitBlockAndInsertIfThen(IsStackLower, &*IP, false);
1000     IRBuilder<> ThenIRB(ThenTerm);
1001     auto Store = ThenIRB.CreateStore(FrameAddrInt, SanCovLowestStack);
1002     SetNoSanitizeMetadata(LowestStack);
1003     SetNoSanitizeMetadata(Store);
1004   }
1005 }
1006 
1007 std::string
1008 SanitizerCoverage::getSectionName(const std::string &Section) const {
1009   if (TargetTriple.isOSBinFormatCOFF()) {
1010     if (Section == SanCovCountersSectionName)
1011       return ".SCOV$CM";
1012     if (Section == SanCovPCsSectionName)
1013       return ".SCOVP$M";
1014     return ".SCOV$GM"; // For SanCovGuardsSectionName.
1015   }
1016   if (TargetTriple.isOSBinFormatMachO())
1017     return "__DATA,__" + Section;
1018   return "__" + Section;
1019 }
1020 
1021 std::string
1022 SanitizerCoverage::getSectionStart(const std::string &Section) const {
1023   return getSectionStartImpl(TargetTriple, Section);
1024 }
1025 
1026 std::string SanitizerCoverage::getSectionEnd(const std::string &Section) const {
1027   return getSectionEndImpl(TargetTriple, Section);
1028 }
1029 
1030 INITIALIZE_PASS(ModuleSanitizerCoverageLegacyPass, "module-sancov",
1031                 "Pass for inserting sancov top-level initialization calls",
1032                 false, false)
1033 
1034 char SanitizerCoverageLegacyPass::ID = 0;
1035 INITIALIZE_PASS_BEGIN(SanitizerCoverageLegacyPass, "sancov",
1036                       "Pass for instrumenting coverage on functions", false,
1037                       false)
1038 INITIALIZE_PASS_DEPENDENCY(ModuleSanitizerCoverageLegacyPass)
1039 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
1040 INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)
1041 INITIALIZE_PASS_END(SanitizerCoverageLegacyPass, "sancov",
1042                     "Pass for instrumenting coverage on functions", false,
1043                     false)
1044 FunctionPass *llvm::createSanitizerCoverageLegacyPassPass(
1045     const SanitizerCoverageOptions &Options) {
1046   return new SanitizerCoverageLegacyPass(Options);
1047 }
1048 ModulePass *llvm::createModuleSanitizerCoverageLegacyPassPass(
1049     const SanitizerCoverageOptions &Options) {
1050   return new ModuleSanitizerCoverageLegacyPass(Options);
1051 }
1052