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/Constant.h"
20 #include "llvm/IR/DataLayout.h"
21 #include "llvm/IR/DebugInfo.h"
22 #include "llvm/IR/Dominators.h"
23 #include "llvm/IR/Function.h"
24 #include "llvm/IR/GlobalVariable.h"
25 #include "llvm/IR/IRBuilder.h"
26 #include "llvm/IR/InlineAsm.h"
27 #include "llvm/IR/IntrinsicInst.h"
28 #include "llvm/IR/Intrinsics.h"
29 #include "llvm/IR/LLVMContext.h"
30 #include "llvm/IR/MDBuilder.h"
31 #include "llvm/IR/Mangler.h"
32 #include "llvm/IR/Module.h"
33 #include "llvm/IR/Type.h"
34 #include "llvm/InitializePasses.h"
35 #include "llvm/Support/CommandLine.h"
36 #include "llvm/Support/Debug.h"
37 #include "llvm/Support/SpecialCaseList.h"
38 #include "llvm/Support/VirtualFileSystem.h"
39 #include "llvm/Support/raw_ostream.h"
40 #include "llvm/Transforms/Instrumentation.h"
41 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
42 #include "llvm/Transforms/Utils/ModuleUtils.h"
43 
44 using namespace llvm;
45 
46 #define DEBUG_TYPE "sancov"
47 
48 const char SanCovTracePCIndirName[] = "__sanitizer_cov_trace_pc_indir";
49 const char SanCovTracePCName[] = "__sanitizer_cov_trace_pc";
50 const char SanCovTraceCmp1[] = "__sanitizer_cov_trace_cmp1";
51 const char SanCovTraceCmp2[] = "__sanitizer_cov_trace_cmp2";
52 const char SanCovTraceCmp4[] = "__sanitizer_cov_trace_cmp4";
53 const char SanCovTraceCmp8[] = "__sanitizer_cov_trace_cmp8";
54 const char SanCovTraceConstCmp1[] = "__sanitizer_cov_trace_const_cmp1";
55 const char SanCovTraceConstCmp2[] = "__sanitizer_cov_trace_const_cmp2";
56 const char SanCovTraceConstCmp4[] = "__sanitizer_cov_trace_const_cmp4";
57 const char SanCovTraceConstCmp8[] = "__sanitizer_cov_trace_const_cmp8";
58 const char SanCovTraceDiv4[] = "__sanitizer_cov_trace_div4";
59 const char SanCovTraceDiv8[] = "__sanitizer_cov_trace_div8";
60 const char SanCovTraceGep[] = "__sanitizer_cov_trace_gep";
61 const char SanCovTraceSwitchName[] = "__sanitizer_cov_trace_switch";
62 const char SanCovModuleCtorTracePcGuardName[] =
63     "sancov.module_ctor_trace_pc_guard";
64 const char SanCovModuleCtor8bitCountersName[] =
65     "sancov.module_ctor_8bit_counters";
66 const char SanCovModuleCtorBoolFlagName[] = "sancov.module_ctor_bool_flag";
67 static const uint64_t SanCtorAndDtorPriority = 2;
68 
69 const char SanCovTracePCGuardName[] = "__sanitizer_cov_trace_pc_guard";
70 const char SanCovTracePCGuardInitName[] = "__sanitizer_cov_trace_pc_guard_init";
71 const char SanCov8bitCountersInitName[] = "__sanitizer_cov_8bit_counters_init";
72 const char SanCovBoolFlagInitName[] = "__sanitizer_cov_bool_flag_init";
73 const char SanCovPCsInitName[] = "__sanitizer_cov_pcs_init";
74 
75 const char SanCovGuardsSectionName[] = "sancov_guards";
76 const char SanCovCountersSectionName[] = "sancov_cntrs";
77 const char SanCovBoolFlagSectionName[] = "sancov_bools";
78 const char SanCovPCsSectionName[] = "sancov_pcs";
79 
80 const char SanCovLowestStackName[] = "__sancov_lowest_stack";
81 
82 static cl::opt<int> ClCoverageLevel(
83     "sanitizer-coverage-level",
84     cl::desc("Sanitizer Coverage. 0: none, 1: entry block, 2: all blocks, "
85              "3: all blocks and critical edges"),
86     cl::Hidden, cl::init(0));
87 
88 static cl::opt<bool> ClTracePC("sanitizer-coverage-trace-pc",
89                                cl::desc("Experimental pc tracing"), cl::Hidden,
90                                cl::init(false));
91 
92 static cl::opt<bool> ClTracePCGuard("sanitizer-coverage-trace-pc-guard",
93                                     cl::desc("pc tracing with a guard"),
94                                     cl::Hidden, cl::init(false));
95 
96 // If true, we create a global variable that contains PCs of all instrumented
97 // BBs, put this global into a named section, and pass this section's bounds
98 // to __sanitizer_cov_pcs_init.
99 // This way the coverage instrumentation does not need to acquire the PCs
100 // at run-time. Works with trace-pc-guard, inline-8bit-counters, and
101 // inline-bool-flag.
102 static cl::opt<bool> ClCreatePCTable("sanitizer-coverage-pc-table",
103                                      cl::desc("create a static PC table"),
104                                      cl::Hidden, cl::init(false));
105 
106 static cl::opt<bool>
107     ClInline8bitCounters("sanitizer-coverage-inline-8bit-counters",
108                          cl::desc("increments 8-bit counter for every edge"),
109                          cl::Hidden, cl::init(false));
110 
111 static cl::opt<bool>
112     ClInlineBoolFlag("sanitizer-coverage-inline-bool-flag",
113                      cl::desc("sets a boolean flag for every edge"), cl::Hidden,
114                      cl::init(false));
115 
116 static cl::opt<bool>
117     ClCMPTracing("sanitizer-coverage-trace-compares",
118                  cl::desc("Tracing of CMP and similar instructions"),
119                  cl::Hidden, cl::init(false));
120 
121 static cl::opt<bool> ClDIVTracing("sanitizer-coverage-trace-divs",
122                                   cl::desc("Tracing of DIV instructions"),
123                                   cl::Hidden, cl::init(false));
124 
125 static cl::opt<bool> ClGEPTracing("sanitizer-coverage-trace-geps",
126                                   cl::desc("Tracing of GEP instructions"),
127                                   cl::Hidden, cl::init(false));
128 
129 static cl::opt<bool>
130     ClPruneBlocks("sanitizer-coverage-prune-blocks",
131                   cl::desc("Reduce the number of instrumented blocks"),
132                   cl::Hidden, cl::init(true));
133 
134 static cl::opt<bool> ClStackDepth("sanitizer-coverage-stack-depth",
135                                   cl::desc("max stack depth tracing"),
136                                   cl::Hidden, cl::init(false));
137 
138 namespace {
139 
140 SanitizerCoverageOptions getOptions(int LegacyCoverageLevel) {
141   SanitizerCoverageOptions Res;
142   switch (LegacyCoverageLevel) {
143   case 0:
144     Res.CoverageType = SanitizerCoverageOptions::SCK_None;
145     break;
146   case 1:
147     Res.CoverageType = SanitizerCoverageOptions::SCK_Function;
148     break;
149   case 2:
150     Res.CoverageType = SanitizerCoverageOptions::SCK_BB;
151     break;
152   case 3:
153     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
154     break;
155   case 4:
156     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
157     Res.IndirectCalls = true;
158     break;
159   }
160   return Res;
161 }
162 
163 SanitizerCoverageOptions OverrideFromCL(SanitizerCoverageOptions Options) {
164   // Sets CoverageType and IndirectCalls.
165   SanitizerCoverageOptions CLOpts = getOptions(ClCoverageLevel);
166   Options.CoverageType = std::max(Options.CoverageType, CLOpts.CoverageType);
167   Options.IndirectCalls |= CLOpts.IndirectCalls;
168   Options.TraceCmp |= ClCMPTracing;
169   Options.TraceDiv |= ClDIVTracing;
170   Options.TraceGep |= ClGEPTracing;
171   Options.TracePC |= ClTracePC;
172   Options.TracePCGuard |= ClTracePCGuard;
173   Options.Inline8bitCounters |= ClInline8bitCounters;
174   Options.InlineBoolFlag |= ClInlineBoolFlag;
175   Options.PCTable |= ClCreatePCTable;
176   Options.NoPrune |= !ClPruneBlocks;
177   Options.StackDepth |= ClStackDepth;
178   if (!Options.TracePCGuard && !Options.TracePC &&
179       !Options.Inline8bitCounters && !Options.StackDepth &&
180       !Options.InlineBoolFlag)
181     Options.TracePCGuard = true; // TracePCGuard is default.
182   return Options;
183 }
184 
185 using DomTreeCallback = function_ref<const DominatorTree *(Function &F)>;
186 using PostDomTreeCallback =
187     function_ref<const PostDominatorTree *(Function &F)>;
188 
189 class ModuleSanitizerCoverage {
190 public:
191   ModuleSanitizerCoverage(
192       const SanitizerCoverageOptions &Options = SanitizerCoverageOptions(),
193       const SpecialCaseList *Allowlist = nullptr,
194       const SpecialCaseList *Blocklist = nullptr)
195       : Options(OverrideFromCL(Options)), Allowlist(Allowlist),
196         Blocklist(Blocklist) {}
197   bool instrumentModule(Module &M, DomTreeCallback DTCallback,
198                         PostDomTreeCallback PDTCallback);
199 
200 private:
201   void instrumentFunction(Function &F, DomTreeCallback DTCallback,
202                           PostDomTreeCallback PDTCallback);
203   void InjectCoverageForIndirectCalls(Function &F,
204                                       ArrayRef<Instruction *> IndirCalls);
205   void InjectTraceForCmp(Function &F, ArrayRef<Instruction *> CmpTraceTargets);
206   void InjectTraceForDiv(Function &F,
207                          ArrayRef<BinaryOperator *> DivTraceTargets);
208   void InjectTraceForGep(Function &F,
209                          ArrayRef<GetElementPtrInst *> GepTraceTargets);
210   void InjectTraceForSwitch(Function &F,
211                             ArrayRef<Instruction *> SwitchTraceTargets);
212   bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks,
213                       bool IsLeafFunc = true);
214   GlobalVariable *CreateFunctionLocalArrayInSection(size_t NumElements,
215                                                     Function &F, Type *Ty,
216                                                     const char *Section);
217   GlobalVariable *CreatePCArray(Function &F, ArrayRef<BasicBlock *> AllBlocks);
218   void CreateFunctionLocalArrays(Function &F, ArrayRef<BasicBlock *> AllBlocks);
219   void InjectCoverageAtBlock(Function &F, BasicBlock &BB, size_t Idx,
220                              bool IsLeafFunc = true);
221   Function *CreateInitCallsForSections(Module &M, const char *CtorName,
222                                        const char *InitFunctionName, Type *Ty,
223                                        const char *Section);
224   std::pair<Value *, Value *> CreateSecStartEnd(Module &M, const char *Section,
225                                                 Type *Ty);
226 
227   void SetNoSanitizeMetadata(Instruction *I) {
228     I->setMetadata(I->getModule()->getMDKindID("nosanitize"),
229                    MDNode::get(*C, None));
230   }
231 
232   std::string getSectionName(const std::string &Section) const;
233   std::string getSectionStart(const std::string &Section) const;
234   std::string getSectionEnd(const std::string &Section) const;
235   FunctionCallee SanCovTracePCIndir;
236   FunctionCallee SanCovTracePC, SanCovTracePCGuard;
237   FunctionCallee SanCovTraceCmpFunction[4];
238   FunctionCallee SanCovTraceConstCmpFunction[4];
239   FunctionCallee SanCovTraceDivFunction[2];
240   FunctionCallee SanCovTraceGepFunction;
241   FunctionCallee SanCovTraceSwitchFunction;
242   GlobalVariable *SanCovLowestStack;
243   Type *IntptrTy, *IntptrPtrTy, *Int64Ty, *Int64PtrTy, *Int32Ty, *Int32PtrTy,
244       *Int16Ty, *Int8Ty, *Int8PtrTy, *Int1Ty, *Int1PtrTy;
245   Module *CurModule;
246   std::string CurModuleUniqueId;
247   Triple TargetTriple;
248   LLVMContext *C;
249   const DataLayout *DL;
250 
251   GlobalVariable *FunctionGuardArray;  // for trace-pc-guard.
252   GlobalVariable *Function8bitCounterArray;  // for inline-8bit-counters.
253   GlobalVariable *FunctionBoolArray;         // for inline-bool-flag.
254   GlobalVariable *FunctionPCsArray;  // for pc-table.
255   SmallVector<GlobalValue *, 20> GlobalsToAppendToUsed;
256   SmallVector<GlobalValue *, 20> GlobalsToAppendToCompilerUsed;
257 
258   SanitizerCoverageOptions Options;
259 
260   const SpecialCaseList *Allowlist;
261   const SpecialCaseList *Blocklist;
262 };
263 
264 class ModuleSanitizerCoverageLegacyPass : public ModulePass {
265 public:
266   ModuleSanitizerCoverageLegacyPass(
267       const SanitizerCoverageOptions &Options = SanitizerCoverageOptions(),
268       const std::vector<std::string> &AllowlistFiles =
269           std::vector<std::string>(),
270       const std::vector<std::string> &BlocklistFiles =
271           std::vector<std::string>())
272       : ModulePass(ID), Options(Options) {
273     if (AllowlistFiles.size() > 0)
274       Allowlist = SpecialCaseList::createOrDie(AllowlistFiles,
275                                                *vfs::getRealFileSystem());
276     if (BlocklistFiles.size() > 0)
277       Blocklist = SpecialCaseList::createOrDie(BlocklistFiles,
278                                                *vfs::getRealFileSystem());
279     initializeModuleSanitizerCoverageLegacyPassPass(
280         *PassRegistry::getPassRegistry());
281   }
282   bool runOnModule(Module &M) override {
283     ModuleSanitizerCoverage ModuleSancov(Options, Allowlist.get(),
284                                          Blocklist.get());
285     auto DTCallback = [this](Function &F) -> const DominatorTree * {
286       return &this->getAnalysis<DominatorTreeWrapperPass>(F).getDomTree();
287     };
288     auto PDTCallback = [this](Function &F) -> const PostDominatorTree * {
289       return &this->getAnalysis<PostDominatorTreeWrapperPass>(F)
290                   .getPostDomTree();
291     };
292     return ModuleSancov.instrumentModule(M, DTCallback, PDTCallback);
293   }
294 
295   static char ID; // Pass identification, replacement for typeid
296   StringRef getPassName() const override { return "ModuleSanitizerCoverage"; }
297 
298   void getAnalysisUsage(AnalysisUsage &AU) const override {
299     AU.addRequired<DominatorTreeWrapperPass>();
300     AU.addRequired<PostDominatorTreeWrapperPass>();
301   }
302 
303 private:
304   SanitizerCoverageOptions Options;
305 
306   std::unique_ptr<SpecialCaseList> Allowlist;
307   std::unique_ptr<SpecialCaseList> Blocklist;
308 };
309 
310 } // namespace
311 
312 PreservedAnalyses ModuleSanitizerCoveragePass::run(Module &M,
313                                                    ModuleAnalysisManager &MAM) {
314   ModuleSanitizerCoverage ModuleSancov(Options, Allowlist.get(),
315                                        Blocklist.get());
316   auto &FAM = MAM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
317   auto DTCallback = [&FAM](Function &F) -> const DominatorTree * {
318     return &FAM.getResult<DominatorTreeAnalysis>(F);
319   };
320   auto PDTCallback = [&FAM](Function &F) -> const PostDominatorTree * {
321     return &FAM.getResult<PostDominatorTreeAnalysis>(F);
322   };
323   if (ModuleSancov.instrumentModule(M, DTCallback, PDTCallback))
324     return PreservedAnalyses::none();
325   return PreservedAnalyses::all();
326 }
327 
328 std::pair<Value *, Value *>
329 ModuleSanitizerCoverage::CreateSecStartEnd(Module &M, const char *Section,
330                                            Type *Ty) {
331   GlobalVariable *SecStart = new GlobalVariable(
332       M, Ty->getPointerElementType(), false, GlobalVariable::ExternalLinkage,
333       nullptr, getSectionStart(Section));
334   SecStart->setVisibility(GlobalValue::HiddenVisibility);
335   GlobalVariable *SecEnd = new GlobalVariable(
336       M, Ty->getPointerElementType(), false, GlobalVariable::ExternalLinkage,
337       nullptr, getSectionEnd(Section));
338   SecEnd->setVisibility(GlobalValue::HiddenVisibility);
339   IRBuilder<> IRB(M.getContext());
340   if (!TargetTriple.isOSBinFormatCOFF())
341     return std::make_pair(SecStart, SecEnd);
342 
343   // Account for the fact that on windows-msvc __start_* symbols actually
344   // point to a uint64_t before the start of the array.
345   auto SecStartI8Ptr = IRB.CreatePointerCast(SecStart, Int8PtrTy);
346   auto GEP = IRB.CreateGEP(Int8Ty, SecStartI8Ptr,
347                            ConstantInt::get(IntptrTy, sizeof(uint64_t)));
348   return std::make_pair(IRB.CreatePointerCast(GEP, Ty), SecEnd);
349 }
350 
351 Function *ModuleSanitizerCoverage::CreateInitCallsForSections(
352     Module &M, const char *CtorName, const char *InitFunctionName, Type *Ty,
353     const char *Section) {
354   auto SecStartEnd = CreateSecStartEnd(M, Section, Ty);
355   auto SecStart = SecStartEnd.first;
356   auto SecEnd = SecStartEnd.second;
357   Function *CtorFunc;
358   std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
359       M, CtorName, InitFunctionName, {Ty, Ty}, {SecStart, SecEnd});
360   assert(CtorFunc->getName() == CtorName);
361 
362   if (TargetTriple.supportsCOMDAT()) {
363     // Use comdat to dedup CtorFunc.
364     CtorFunc->setComdat(M.getOrInsertComdat(CtorName));
365     appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority, CtorFunc);
366   } else {
367     appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority);
368   }
369 
370   if (TargetTriple.isOSBinFormatCOFF()) {
371     // In COFF files, if the contructors are set as COMDAT (they are because
372     // COFF supports COMDAT) and the linker flag /OPT:REF (strip unreferenced
373     // functions and data) is used, the constructors get stripped. To prevent
374     // this, give the constructors weak ODR linkage and ensure the linker knows
375     // to include the sancov constructor. This way the linker can deduplicate
376     // the constructors but always leave one copy.
377     CtorFunc->setLinkage(GlobalValue::WeakODRLinkage);
378     appendToUsed(M, CtorFunc);
379   }
380   return CtorFunc;
381 }
382 
383 bool ModuleSanitizerCoverage::instrumentModule(
384     Module &M, DomTreeCallback DTCallback, PostDomTreeCallback PDTCallback) {
385   if (Options.CoverageType == SanitizerCoverageOptions::SCK_None)
386     return false;
387   if (Allowlist &&
388       !Allowlist->inSection("coverage", "src", M.getSourceFileName()))
389     return false;
390   if (Blocklist &&
391       Blocklist->inSection("coverage", "src", M.getSourceFileName()))
392     return false;
393   C = &(M.getContext());
394   DL = &M.getDataLayout();
395   CurModule = &M;
396   CurModuleUniqueId = getUniqueModuleId(CurModule);
397   TargetTriple = Triple(M.getTargetTriple());
398   FunctionGuardArray = nullptr;
399   Function8bitCounterArray = nullptr;
400   FunctionBoolArray = nullptr;
401   FunctionPCsArray = nullptr;
402   IntptrTy = Type::getIntNTy(*C, DL->getPointerSizeInBits());
403   IntptrPtrTy = PointerType::getUnqual(IntptrTy);
404   Type *VoidTy = Type::getVoidTy(*C);
405   IRBuilder<> IRB(*C);
406   Int64PtrTy = PointerType::getUnqual(IRB.getInt64Ty());
407   Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
408   Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
409   Int1PtrTy = PointerType::getUnqual(IRB.getInt1Ty());
410   Int64Ty = IRB.getInt64Ty();
411   Int32Ty = IRB.getInt32Ty();
412   Int16Ty = IRB.getInt16Ty();
413   Int8Ty = IRB.getInt8Ty();
414   Int1Ty = IRB.getInt1Ty();
415 
416   SanCovTracePCIndir =
417       M.getOrInsertFunction(SanCovTracePCIndirName, VoidTy, IntptrTy);
418   // Make sure smaller parameters are zero-extended to i64 if required by the
419   // target ABI.
420   AttributeList SanCovTraceCmpZeroExtAL;
421   SanCovTraceCmpZeroExtAL =
422       SanCovTraceCmpZeroExtAL.addParamAttribute(*C, 0, Attribute::ZExt);
423   SanCovTraceCmpZeroExtAL =
424       SanCovTraceCmpZeroExtAL.addParamAttribute(*C, 1, Attribute::ZExt);
425 
426   SanCovTraceCmpFunction[0] =
427       M.getOrInsertFunction(SanCovTraceCmp1, SanCovTraceCmpZeroExtAL, VoidTy,
428                             IRB.getInt8Ty(), IRB.getInt8Ty());
429   SanCovTraceCmpFunction[1] =
430       M.getOrInsertFunction(SanCovTraceCmp2, SanCovTraceCmpZeroExtAL, VoidTy,
431                             IRB.getInt16Ty(), IRB.getInt16Ty());
432   SanCovTraceCmpFunction[2] =
433       M.getOrInsertFunction(SanCovTraceCmp4, SanCovTraceCmpZeroExtAL, VoidTy,
434                             IRB.getInt32Ty(), IRB.getInt32Ty());
435   SanCovTraceCmpFunction[3] =
436       M.getOrInsertFunction(SanCovTraceCmp8, VoidTy, Int64Ty, Int64Ty);
437 
438   SanCovTraceConstCmpFunction[0] = M.getOrInsertFunction(
439       SanCovTraceConstCmp1, SanCovTraceCmpZeroExtAL, VoidTy, Int8Ty, Int8Ty);
440   SanCovTraceConstCmpFunction[1] = M.getOrInsertFunction(
441       SanCovTraceConstCmp2, SanCovTraceCmpZeroExtAL, VoidTy, Int16Ty, Int16Ty);
442   SanCovTraceConstCmpFunction[2] = M.getOrInsertFunction(
443       SanCovTraceConstCmp4, SanCovTraceCmpZeroExtAL, VoidTy, Int32Ty, Int32Ty);
444   SanCovTraceConstCmpFunction[3] =
445       M.getOrInsertFunction(SanCovTraceConstCmp8, VoidTy, Int64Ty, Int64Ty);
446 
447   {
448     AttributeList AL;
449     AL = AL.addParamAttribute(*C, 0, Attribute::ZExt);
450     SanCovTraceDivFunction[0] =
451         M.getOrInsertFunction(SanCovTraceDiv4, AL, VoidTy, IRB.getInt32Ty());
452   }
453   SanCovTraceDivFunction[1] =
454       M.getOrInsertFunction(SanCovTraceDiv8, VoidTy, Int64Ty);
455   SanCovTraceGepFunction =
456       M.getOrInsertFunction(SanCovTraceGep, VoidTy, IntptrTy);
457   SanCovTraceSwitchFunction =
458       M.getOrInsertFunction(SanCovTraceSwitchName, VoidTy, Int64Ty, Int64PtrTy);
459 
460   Constant *SanCovLowestStackConstant =
461       M.getOrInsertGlobal(SanCovLowestStackName, IntptrTy);
462   SanCovLowestStack = dyn_cast<GlobalVariable>(SanCovLowestStackConstant);
463   if (!SanCovLowestStack) {
464     C->emitError(StringRef("'") + SanCovLowestStackName +
465                  "' should not be declared by the user");
466     return true;
467   }
468   SanCovLowestStack->setThreadLocalMode(
469       GlobalValue::ThreadLocalMode::InitialExecTLSModel);
470   if (Options.StackDepth && !SanCovLowestStack->isDeclaration())
471     SanCovLowestStack->setInitializer(Constant::getAllOnesValue(IntptrTy));
472 
473   SanCovTracePC = M.getOrInsertFunction(SanCovTracePCName, VoidTy);
474   SanCovTracePCGuard =
475       M.getOrInsertFunction(SanCovTracePCGuardName, VoidTy, Int32PtrTy);
476 
477   for (auto &F : M)
478     instrumentFunction(F, DTCallback, PDTCallback);
479 
480   Function *Ctor = nullptr;
481 
482   if (FunctionGuardArray)
483     Ctor = CreateInitCallsForSections(M, SanCovModuleCtorTracePcGuardName,
484                                       SanCovTracePCGuardInitName, Int32PtrTy,
485                                       SanCovGuardsSectionName);
486   if (Function8bitCounterArray)
487     Ctor = CreateInitCallsForSections(M, SanCovModuleCtor8bitCountersName,
488                                       SanCov8bitCountersInitName, Int8PtrTy,
489                                       SanCovCountersSectionName);
490   if (FunctionBoolArray) {
491     Ctor = CreateInitCallsForSections(M, SanCovModuleCtorBoolFlagName,
492                                       SanCovBoolFlagInitName, Int1PtrTy,
493                                       SanCovBoolFlagSectionName);
494   }
495   if (Ctor && Options.PCTable) {
496     auto SecStartEnd = CreateSecStartEnd(M, SanCovPCsSectionName, IntptrPtrTy);
497     FunctionCallee InitFunction = declareSanitizerInitFunction(
498         M, SanCovPCsInitName, {IntptrPtrTy, IntptrPtrTy});
499     IRBuilder<> IRBCtor(Ctor->getEntryBlock().getTerminator());
500     IRBCtor.CreateCall(InitFunction, {SecStartEnd.first, SecStartEnd.second});
501   }
502   appendToUsed(M, GlobalsToAppendToUsed);
503   appendToCompilerUsed(M, GlobalsToAppendToCompilerUsed);
504   return true;
505 }
506 
507 // True if block has successors and it dominates all of them.
508 static bool isFullDominator(const BasicBlock *BB, const DominatorTree *DT) {
509   if (succ_empty(BB))
510     return false;
511 
512   return llvm::all_of(successors(BB), [&](const BasicBlock *SUCC) {
513     return DT->dominates(BB, SUCC);
514   });
515 }
516 
517 // True if block has predecessors and it postdominates all of them.
518 static bool isFullPostDominator(const BasicBlock *BB,
519                                 const PostDominatorTree *PDT) {
520   if (pred_empty(BB))
521     return false;
522 
523   return llvm::all_of(predecessors(BB), [&](const BasicBlock *PRED) {
524     return PDT->dominates(BB, PRED);
525   });
526 }
527 
528 static bool shouldInstrumentBlock(const Function &F, const BasicBlock *BB,
529                                   const DominatorTree *DT,
530                                   const PostDominatorTree *PDT,
531                                   const SanitizerCoverageOptions &Options) {
532   // Don't insert coverage for blocks containing nothing but unreachable: we
533   // will never call __sanitizer_cov() for them, so counting them in
534   // NumberOfInstrumentedBlocks() might complicate calculation of code coverage
535   // percentage. Also, unreachable instructions frequently have no debug
536   // locations.
537   if (isa<UnreachableInst>(BB->getFirstNonPHIOrDbgOrLifetime()))
538     return false;
539 
540   // Don't insert coverage into blocks without a valid insertion point
541   // (catchswitch blocks).
542   if (BB->getFirstInsertionPt() == BB->end())
543     return false;
544 
545   if (Options.NoPrune || &F.getEntryBlock() == BB)
546     return true;
547 
548   if (Options.CoverageType == SanitizerCoverageOptions::SCK_Function &&
549       &F.getEntryBlock() != BB)
550     return false;
551 
552   // Do not instrument full dominators, or full post-dominators with multiple
553   // predecessors.
554   return !isFullDominator(BB, DT)
555     && !(isFullPostDominator(BB, PDT) && !BB->getSinglePredecessor());
556 }
557 
558 
559 // Returns true iff From->To is a backedge.
560 // A twist here is that we treat From->To as a backedge if
561 //   * To dominates From or
562 //   * To->UniqueSuccessor dominates From
563 static bool IsBackEdge(BasicBlock *From, BasicBlock *To,
564                        const DominatorTree *DT) {
565   if (DT->dominates(To, From))
566     return true;
567   if (auto Next = To->getUniqueSuccessor())
568     if (DT->dominates(Next, From))
569       return true;
570   return false;
571 }
572 
573 // Prunes uninteresting Cmp instrumentation:
574 //   * CMP instructions that feed into loop backedge branch.
575 //
576 // Note that Cmp pruning is controlled by the same flag as the
577 // BB pruning.
578 static bool IsInterestingCmp(ICmpInst *CMP, const DominatorTree *DT,
579                              const SanitizerCoverageOptions &Options) {
580   if (!Options.NoPrune)
581     if (CMP->hasOneUse())
582       if (auto BR = dyn_cast<BranchInst>(CMP->user_back()))
583         for (BasicBlock *B : BR->successors())
584           if (IsBackEdge(BR->getParent(), B, DT))
585             return false;
586   return true;
587 }
588 
589 void ModuleSanitizerCoverage::instrumentFunction(
590     Function &F, DomTreeCallback DTCallback, PostDomTreeCallback PDTCallback) {
591   if (F.empty())
592     return;
593   if (F.getName().find(".module_ctor") != std::string::npos)
594     return; // Should not instrument sanitizer init functions.
595   if (F.getName().startswith("__sanitizer_"))
596     return; // Don't instrument __sanitizer_* callbacks.
597   // Don't touch available_externally functions, their actual body is elewhere.
598   if (F.getLinkage() == GlobalValue::AvailableExternallyLinkage)
599     return;
600   // Don't instrument MSVC CRT configuration helpers. They may run before normal
601   // initialization.
602   if (F.getName() == "__local_stdio_printf_options" ||
603       F.getName() == "__local_stdio_scanf_options")
604     return;
605   if (isa<UnreachableInst>(F.getEntryBlock().getTerminator()))
606     return;
607   // Don't instrument functions using SEH for now. Splitting basic blocks like
608   // we do for coverage breaks WinEHPrepare.
609   // FIXME: Remove this when SEH no longer uses landingpad pattern matching.
610   if (F.hasPersonalityFn() &&
611       isAsynchronousEHPersonality(classifyEHPersonality(F.getPersonalityFn())))
612     return;
613   if (Allowlist && !Allowlist->inSection("coverage", "fun", F.getName()))
614     return;
615   if (Blocklist && Blocklist->inSection("coverage", "fun", F.getName()))
616     return;
617   if (Options.CoverageType >= SanitizerCoverageOptions::SCK_Edge)
618     SplitAllCriticalEdges(F, CriticalEdgeSplittingOptions().setIgnoreUnreachableDests());
619   SmallVector<Instruction *, 8> IndirCalls;
620   SmallVector<BasicBlock *, 16> BlocksToInstrument;
621   SmallVector<Instruction *, 8> CmpTraceTargets;
622   SmallVector<Instruction *, 8> SwitchTraceTargets;
623   SmallVector<BinaryOperator *, 8> DivTraceTargets;
624   SmallVector<GetElementPtrInst *, 8> GepTraceTargets;
625 
626   const DominatorTree *DT = DTCallback(F);
627   const PostDominatorTree *PDT = PDTCallback(F);
628   bool IsLeafFunc = true;
629 
630   for (auto &BB : F) {
631     if (shouldInstrumentBlock(F, &BB, DT, PDT, Options))
632       BlocksToInstrument.push_back(&BB);
633     for (auto &Inst : BB) {
634       if (Options.IndirectCalls) {
635         CallBase *CB = dyn_cast<CallBase>(&Inst);
636         if (CB && !CB->getCalledFunction())
637           IndirCalls.push_back(&Inst);
638       }
639       if (Options.TraceCmp) {
640         if (ICmpInst *CMP = dyn_cast<ICmpInst>(&Inst))
641           if (IsInterestingCmp(CMP, DT, Options))
642             CmpTraceTargets.push_back(&Inst);
643         if (isa<SwitchInst>(&Inst))
644           SwitchTraceTargets.push_back(&Inst);
645       }
646       if (Options.TraceDiv)
647         if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&Inst))
648           if (BO->getOpcode() == Instruction::SDiv ||
649               BO->getOpcode() == Instruction::UDiv)
650             DivTraceTargets.push_back(BO);
651       if (Options.TraceGep)
652         if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(&Inst))
653           GepTraceTargets.push_back(GEP);
654       if (Options.StackDepth)
655         if (isa<InvokeInst>(Inst) ||
656             (isa<CallInst>(Inst) && !isa<IntrinsicInst>(Inst)))
657           IsLeafFunc = false;
658     }
659   }
660 
661   InjectCoverage(F, BlocksToInstrument, IsLeafFunc);
662   InjectCoverageForIndirectCalls(F, IndirCalls);
663   InjectTraceForCmp(F, CmpTraceTargets);
664   InjectTraceForSwitch(F, SwitchTraceTargets);
665   InjectTraceForDiv(F, DivTraceTargets);
666   InjectTraceForGep(F, GepTraceTargets);
667 }
668 
669 GlobalVariable *ModuleSanitizerCoverage::CreateFunctionLocalArrayInSection(
670     size_t NumElements, Function &F, Type *Ty, const char *Section) {
671   ArrayType *ArrayTy = ArrayType::get(Ty, NumElements);
672   auto Array = new GlobalVariable(
673       *CurModule, ArrayTy, false, GlobalVariable::PrivateLinkage,
674       Constant::getNullValue(ArrayTy), "__sancov_gen_");
675 
676   if (TargetTriple.supportsCOMDAT() &&
677       (TargetTriple.isOSBinFormatELF() || !F.isInterposable()))
678     if (auto Comdat = getOrCreateFunctionComdat(F, TargetTriple))
679       Array->setComdat(Comdat);
680   Array->setSection(getSectionName(Section));
681   Array->setAlignment(Align(DL->getTypeStoreSize(Ty).getFixedSize()));
682 
683   // sancov_pcs parallels the other metadata section(s). Optimizers (e.g.
684   // GlobalOpt/ConstantMerge) may not discard sancov_pcs and the other
685   // section(s) as a unit, so we conservatively retain all unconditionally in
686   // the compiler.
687   //
688   // With comdat (COFF/ELF), the linker can guarantee the associated sections
689   // will be retained or discarded as a unit, so llvm.compiler.used is
690   // sufficient. Otherwise, conservatively make all of them retained by the
691   // linker.
692   if (Array->hasComdat())
693     GlobalsToAppendToCompilerUsed.push_back(Array);
694   else
695     GlobalsToAppendToUsed.push_back(Array);
696 
697   return Array;
698 }
699 
700 GlobalVariable *
701 ModuleSanitizerCoverage::CreatePCArray(Function &F,
702                                        ArrayRef<BasicBlock *> AllBlocks) {
703   size_t N = AllBlocks.size();
704   assert(N);
705   SmallVector<Constant *, 32> PCs;
706   IRBuilder<> IRB(&*F.getEntryBlock().getFirstInsertionPt());
707   for (size_t i = 0; i < N; i++) {
708     if (&F.getEntryBlock() == AllBlocks[i]) {
709       PCs.push_back((Constant *)IRB.CreatePointerCast(&F, IntptrPtrTy));
710       PCs.push_back((Constant *)IRB.CreateIntToPtr(
711           ConstantInt::get(IntptrTy, 1), IntptrPtrTy));
712     } else {
713       PCs.push_back((Constant *)IRB.CreatePointerCast(
714           BlockAddress::get(AllBlocks[i]), IntptrPtrTy));
715       PCs.push_back((Constant *)IRB.CreateIntToPtr(
716           ConstantInt::get(IntptrTy, 0), IntptrPtrTy));
717     }
718   }
719   auto *PCArray = CreateFunctionLocalArrayInSection(N * 2, F, IntptrPtrTy,
720                                                     SanCovPCsSectionName);
721   PCArray->setInitializer(
722       ConstantArray::get(ArrayType::get(IntptrPtrTy, N * 2), PCs));
723   PCArray->setConstant(true);
724 
725   return PCArray;
726 }
727 
728 void ModuleSanitizerCoverage::CreateFunctionLocalArrays(
729     Function &F, ArrayRef<BasicBlock *> AllBlocks) {
730   if (Options.TracePCGuard)
731     FunctionGuardArray = CreateFunctionLocalArrayInSection(
732         AllBlocks.size(), F, Int32Ty, SanCovGuardsSectionName);
733 
734   if (Options.Inline8bitCounters)
735     Function8bitCounterArray = CreateFunctionLocalArrayInSection(
736         AllBlocks.size(), F, Int8Ty, SanCovCountersSectionName);
737   if (Options.InlineBoolFlag)
738     FunctionBoolArray = CreateFunctionLocalArrayInSection(
739         AllBlocks.size(), F, Int1Ty, SanCovBoolFlagSectionName);
740 
741   if (Options.PCTable)
742     FunctionPCsArray = CreatePCArray(F, AllBlocks);
743 }
744 
745 bool ModuleSanitizerCoverage::InjectCoverage(Function &F,
746                                              ArrayRef<BasicBlock *> AllBlocks,
747                                              bool IsLeafFunc) {
748   if (AllBlocks.empty()) return false;
749   CreateFunctionLocalArrays(F, AllBlocks);
750   for (size_t i = 0, N = AllBlocks.size(); i < N; i++)
751     InjectCoverageAtBlock(F, *AllBlocks[i], i, IsLeafFunc);
752   return true;
753 }
754 
755 // On every indirect call we call a run-time function
756 // __sanitizer_cov_indir_call* with two parameters:
757 //   - callee address,
758 //   - global cache array that contains CacheSize pointers (zero-initialized).
759 //     The cache is used to speed up recording the caller-callee pairs.
760 // The address of the caller is passed implicitly via caller PC.
761 // CacheSize is encoded in the name of the run-time function.
762 void ModuleSanitizerCoverage::InjectCoverageForIndirectCalls(
763     Function &F, ArrayRef<Instruction *> IndirCalls) {
764   if (IndirCalls.empty())
765     return;
766   assert(Options.TracePC || Options.TracePCGuard ||
767          Options.Inline8bitCounters || Options.InlineBoolFlag);
768   for (auto I : IndirCalls) {
769     IRBuilder<> IRB(I);
770     CallBase &CB = cast<CallBase>(*I);
771     Value *Callee = CB.getCalledOperand();
772     if (isa<InlineAsm>(Callee))
773       continue;
774     IRB.CreateCall(SanCovTracePCIndir, IRB.CreatePointerCast(Callee, IntptrTy));
775   }
776 }
777 
778 // For every switch statement we insert a call:
779 // __sanitizer_cov_trace_switch(CondValue,
780 //      {NumCases, ValueSizeInBits, Case0Value, Case1Value, Case2Value, ... })
781 
782 void ModuleSanitizerCoverage::InjectTraceForSwitch(
783     Function &, ArrayRef<Instruction *> SwitchTraceTargets) {
784   for (auto I : SwitchTraceTargets) {
785     if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
786       IRBuilder<> IRB(I);
787       SmallVector<Constant *, 16> Initializers;
788       Value *Cond = SI->getCondition();
789       if (Cond->getType()->getScalarSizeInBits() >
790           Int64Ty->getScalarSizeInBits())
791         continue;
792       Initializers.push_back(ConstantInt::get(Int64Ty, SI->getNumCases()));
793       Initializers.push_back(
794           ConstantInt::get(Int64Ty, Cond->getType()->getScalarSizeInBits()));
795       if (Cond->getType()->getScalarSizeInBits() <
796           Int64Ty->getScalarSizeInBits())
797         Cond = IRB.CreateIntCast(Cond, Int64Ty, false);
798       for (auto It : SI->cases()) {
799         Constant *C = It.getCaseValue();
800         if (C->getType()->getScalarSizeInBits() <
801             Int64Ty->getScalarSizeInBits())
802           C = ConstantExpr::getCast(CastInst::ZExt, It.getCaseValue(), Int64Ty);
803         Initializers.push_back(C);
804       }
805       llvm::sort(drop_begin(Initializers, 2),
806                  [](const Constant *A, const Constant *B) {
807                    return cast<ConstantInt>(A)->getLimitedValue() <
808                           cast<ConstantInt>(B)->getLimitedValue();
809                  });
810       ArrayType *ArrayOfInt64Ty = ArrayType::get(Int64Ty, Initializers.size());
811       GlobalVariable *GV = new GlobalVariable(
812           *CurModule, ArrayOfInt64Ty, false, GlobalVariable::InternalLinkage,
813           ConstantArray::get(ArrayOfInt64Ty, Initializers),
814           "__sancov_gen_cov_switch_values");
815       IRB.CreateCall(SanCovTraceSwitchFunction,
816                      {Cond, IRB.CreatePointerCast(GV, Int64PtrTy)});
817     }
818   }
819 }
820 
821 void ModuleSanitizerCoverage::InjectTraceForDiv(
822     Function &, ArrayRef<BinaryOperator *> DivTraceTargets) {
823   for (auto BO : DivTraceTargets) {
824     IRBuilder<> IRB(BO);
825     Value *A1 = BO->getOperand(1);
826     if (isa<ConstantInt>(A1)) continue;
827     if (!A1->getType()->isIntegerTy())
828       continue;
829     uint64_t TypeSize = DL->getTypeStoreSizeInBits(A1->getType());
830     int CallbackIdx = TypeSize == 32 ? 0 :
831         TypeSize == 64 ? 1 : -1;
832     if (CallbackIdx < 0) continue;
833     auto Ty = Type::getIntNTy(*C, TypeSize);
834     IRB.CreateCall(SanCovTraceDivFunction[CallbackIdx],
835                    {IRB.CreateIntCast(A1, Ty, true)});
836   }
837 }
838 
839 void ModuleSanitizerCoverage::InjectTraceForGep(
840     Function &, ArrayRef<GetElementPtrInst *> GepTraceTargets) {
841   for (auto GEP : GepTraceTargets) {
842     IRBuilder<> IRB(GEP);
843     for (Use &Idx : GEP->indices())
844       if (!isa<ConstantInt>(Idx) && Idx->getType()->isIntegerTy())
845         IRB.CreateCall(SanCovTraceGepFunction,
846                        {IRB.CreateIntCast(Idx, IntptrTy, true)});
847   }
848 }
849 
850 void ModuleSanitizerCoverage::InjectTraceForCmp(
851     Function &, ArrayRef<Instruction *> CmpTraceTargets) {
852   for (auto I : CmpTraceTargets) {
853     if (ICmpInst *ICMP = dyn_cast<ICmpInst>(I)) {
854       IRBuilder<> IRB(ICMP);
855       Value *A0 = ICMP->getOperand(0);
856       Value *A1 = ICMP->getOperand(1);
857       if (!A0->getType()->isIntegerTy())
858         continue;
859       uint64_t TypeSize = DL->getTypeStoreSizeInBits(A0->getType());
860       int CallbackIdx = TypeSize == 8 ? 0 :
861                         TypeSize == 16 ? 1 :
862                         TypeSize == 32 ? 2 :
863                         TypeSize == 64 ? 3 : -1;
864       if (CallbackIdx < 0) continue;
865       // __sanitizer_cov_trace_cmp((type_size << 32) | predicate, A0, A1);
866       auto CallbackFunc = SanCovTraceCmpFunction[CallbackIdx];
867       bool FirstIsConst = isa<ConstantInt>(A0);
868       bool SecondIsConst = isa<ConstantInt>(A1);
869       // If both are const, then we don't need such a comparison.
870       if (FirstIsConst && SecondIsConst) continue;
871       // If only one is const, then make it the first callback argument.
872       if (FirstIsConst || SecondIsConst) {
873         CallbackFunc = SanCovTraceConstCmpFunction[CallbackIdx];
874         if (SecondIsConst)
875           std::swap(A0, A1);
876       }
877 
878       auto Ty = Type::getIntNTy(*C, TypeSize);
879       IRB.CreateCall(CallbackFunc, {IRB.CreateIntCast(A0, Ty, true),
880               IRB.CreateIntCast(A1, Ty, true)});
881     }
882   }
883 }
884 
885 void ModuleSanitizerCoverage::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
886                                                     size_t Idx,
887                                                     bool IsLeafFunc) {
888   BasicBlock::iterator IP = BB.getFirstInsertionPt();
889   bool IsEntryBB = &BB == &F.getEntryBlock();
890   DebugLoc EntryLoc;
891   if (IsEntryBB) {
892     if (auto SP = F.getSubprogram())
893       EntryLoc = DILocation::get(SP->getContext(), SP->getScopeLine(), 0, SP);
894     // Keep static allocas and llvm.localescape calls in the entry block.  Even
895     // if we aren't splitting the block, it's nice for allocas to be before
896     // calls.
897     IP = PrepareToSplitEntryBlock(BB, IP);
898   } else {
899     EntryLoc = IP->getDebugLoc();
900   }
901 
902   IRBuilder<> IRB(&*IP);
903   IRB.SetCurrentDebugLocation(EntryLoc);
904   if (Options.TracePC) {
905     IRB.CreateCall(SanCovTracePC)
906         ->setCannotMerge(); // gets the PC using GET_CALLER_PC.
907   }
908   if (Options.TracePCGuard) {
909     auto GuardPtr = IRB.CreateIntToPtr(
910         IRB.CreateAdd(IRB.CreatePointerCast(FunctionGuardArray, IntptrTy),
911                       ConstantInt::get(IntptrTy, Idx * 4)),
912         Int32PtrTy);
913     IRB.CreateCall(SanCovTracePCGuard, GuardPtr)->setCannotMerge();
914   }
915   if (Options.Inline8bitCounters) {
916     auto CounterPtr = IRB.CreateGEP(
917         Function8bitCounterArray->getValueType(), Function8bitCounterArray,
918         {ConstantInt::get(IntptrTy, 0), ConstantInt::get(IntptrTy, Idx)});
919     auto Load = IRB.CreateLoad(Int8Ty, CounterPtr);
920     auto Inc = IRB.CreateAdd(Load, ConstantInt::get(Int8Ty, 1));
921     auto Store = IRB.CreateStore(Inc, CounterPtr);
922     SetNoSanitizeMetadata(Load);
923     SetNoSanitizeMetadata(Store);
924   }
925   if (Options.InlineBoolFlag) {
926     auto FlagPtr = IRB.CreateGEP(
927         FunctionBoolArray->getValueType(), FunctionBoolArray,
928         {ConstantInt::get(IntptrTy, 0), ConstantInt::get(IntptrTy, Idx)});
929     auto Load = IRB.CreateLoad(Int1Ty, FlagPtr);
930     auto ThenTerm =
931         SplitBlockAndInsertIfThen(IRB.CreateIsNull(Load), &*IP, false);
932     IRBuilder<> ThenIRB(ThenTerm);
933     auto Store = ThenIRB.CreateStore(ConstantInt::getTrue(Int1Ty), FlagPtr);
934     SetNoSanitizeMetadata(Load);
935     SetNoSanitizeMetadata(Store);
936   }
937   if (Options.StackDepth && IsEntryBB && !IsLeafFunc) {
938     // Check stack depth.  If it's the deepest so far, record it.
939     Module *M = F.getParent();
940     Function *GetFrameAddr = Intrinsic::getDeclaration(
941         M, Intrinsic::frameaddress,
942         IRB.getInt8PtrTy(M->getDataLayout().getAllocaAddrSpace()));
943     auto FrameAddrPtr =
944         IRB.CreateCall(GetFrameAddr, {Constant::getNullValue(Int32Ty)});
945     auto FrameAddrInt = IRB.CreatePtrToInt(FrameAddrPtr, IntptrTy);
946     auto LowestStack = IRB.CreateLoad(IntptrTy, SanCovLowestStack);
947     auto IsStackLower = IRB.CreateICmpULT(FrameAddrInt, LowestStack);
948     auto ThenTerm = SplitBlockAndInsertIfThen(IsStackLower, &*IP, false);
949     IRBuilder<> ThenIRB(ThenTerm);
950     auto Store = ThenIRB.CreateStore(FrameAddrInt, SanCovLowestStack);
951     SetNoSanitizeMetadata(LowestStack);
952     SetNoSanitizeMetadata(Store);
953   }
954 }
955 
956 std::string
957 ModuleSanitizerCoverage::getSectionName(const std::string &Section) const {
958   if (TargetTriple.isOSBinFormatCOFF()) {
959     if (Section == SanCovCountersSectionName)
960       return ".SCOV$CM";
961     if (Section == SanCovBoolFlagSectionName)
962       return ".SCOV$BM";
963     if (Section == SanCovPCsSectionName)
964       return ".SCOVP$M";
965     return ".SCOV$GM"; // For SanCovGuardsSectionName.
966   }
967   if (TargetTriple.isOSBinFormatMachO())
968     return "__DATA,__" + Section;
969   return "__" + Section;
970 }
971 
972 std::string
973 ModuleSanitizerCoverage::getSectionStart(const std::string &Section) const {
974   if (TargetTriple.isOSBinFormatMachO())
975     return "\1section$start$__DATA$__" + Section;
976   return "__start___" + Section;
977 }
978 
979 std::string
980 ModuleSanitizerCoverage::getSectionEnd(const std::string &Section) const {
981   if (TargetTriple.isOSBinFormatMachO())
982     return "\1section$end$__DATA$__" + Section;
983   return "__stop___" + Section;
984 }
985 
986 char ModuleSanitizerCoverageLegacyPass::ID = 0;
987 INITIALIZE_PASS_BEGIN(ModuleSanitizerCoverageLegacyPass, "sancov",
988                       "Pass for instrumenting coverage on functions", false,
989                       false)
990 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
991 INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)
992 INITIALIZE_PASS_END(ModuleSanitizerCoverageLegacyPass, "sancov",
993                     "Pass for instrumenting coverage on functions", false,
994                     false)
995 ModulePass *llvm::createModuleSanitizerCoverageLegacyPassPass(
996     const SanitizerCoverageOptions &Options,
997     const std::vector<std::string> &AllowlistFiles,
998     const std::vector<std::string> &BlocklistFiles) {
999   return new ModuleSanitizerCoverageLegacyPass(Options, AllowlistFiles,
1000                                                BlocklistFiles);
1001 }
1002