xref: /llvm-project/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp (revision da718e55cf0bd5f5f2ee5e288ecd707361c46a02) 
1 //===-- SanitizerCoverage.cpp - coverage instrumentation for sanitizers ---===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // Coverage instrumentation that works with AddressSanitizer
11 // and potentially with other Sanitizers.
12 //
13 // We create a Guard variable with the same linkage
14 // as the function and inject this code into the entry block (SCK_Function)
15 // or all blocks (SCK_BB):
16 // if (Guard < 0) {
17 //    __sanitizer_cov(&Guard);
18 // }
19 // The accesses to Guard are atomic. The rest of the logic is
20 // in __sanitizer_cov (it's fine to call it more than once).
21 //
22 // With SCK_Edge we also split critical edges this effectively
23 // instrumenting all edges.
24 //
25 // This coverage implementation provides very limited data:
26 // it only tells if a given function (block) was ever executed. No counters.
27 // But for many use cases this is what we need and the added slowdown small.
28 //
29 //===----------------------------------------------------------------------===//
30 
31 #include "llvm/ADT/ArrayRef.h"
32 #include "llvm/ADT/SmallVector.h"
33 #include "llvm/Analysis/EHPersonalities.h"
34 #include "llvm/Analysis/PostDominators.h"
35 #include "llvm/IR/CFG.h"
36 #include "llvm/IR/CallSite.h"
37 #include "llvm/IR/DataLayout.h"
38 #include "llvm/IR/DebugInfo.h"
39 #include "llvm/IR/Dominators.h"
40 #include "llvm/IR/Function.h"
41 #include "llvm/IR/IRBuilder.h"
42 #include "llvm/IR/InlineAsm.h"
43 #include "llvm/IR/LLVMContext.h"
44 #include "llvm/IR/MDBuilder.h"
45 #include "llvm/IR/Module.h"
46 #include "llvm/IR/Type.h"
47 #include "llvm/Support/CommandLine.h"
48 #include "llvm/Support/Debug.h"
49 #include "llvm/Support/raw_ostream.h"
50 #include "llvm/Transforms/Instrumentation.h"
51 #include "llvm/Transforms/Scalar.h"
52 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
53 #include "llvm/Transforms/Utils/ModuleUtils.h"
54 
55 using namespace llvm;
56 
57 #define DEBUG_TYPE "sancov"
58 
59 static const char *const SanCovModuleInitName = "__sanitizer_cov_module_init";
60 static const char *const SanCovName = "__sanitizer_cov";
61 static const char *const SanCovWithCheckName = "__sanitizer_cov_with_check";
62 static const char *const SanCovIndirCallName = "__sanitizer_cov_indir_call16";
63 static const char *const SanCovTracePCIndirName =
64     "__sanitizer_cov_trace_pc_indir";
65 static const char *const SanCovTraceEnterName =
66     "__sanitizer_cov_trace_func_enter";
67 static const char *const SanCovTraceBBName =
68     "__sanitizer_cov_trace_basic_block";
69 static const char *const SanCovTracePCName = "__sanitizer_cov_trace_pc";
70 static const char *const SanCovTraceCmp1 = "__sanitizer_cov_trace_cmp1";
71 static const char *const SanCovTraceCmp2 = "__sanitizer_cov_trace_cmp2";
72 static const char *const SanCovTraceCmp4 = "__sanitizer_cov_trace_cmp4";
73 static const char *const SanCovTraceCmp8 = "__sanitizer_cov_trace_cmp8";
74 static const char *const SanCovTraceDiv4 = "__sanitizer_cov_trace_div4";
75 static const char *const SanCovTraceDiv8 = "__sanitizer_cov_trace_div8";
76 static const char *const SanCovTraceGep = "__sanitizer_cov_trace_gep";
77 static const char *const SanCovTraceSwitchName = "__sanitizer_cov_trace_switch";
78 static const char *const SanCovModuleCtorName = "sancov.module_ctor";
79 static const uint64_t SanCtorAndDtorPriority = 2;
80 
81 static const char *const SanCovTracePCGuardSection = "__sancov_guards";
82 static const char *const SanCovTracePCGuardName =
83     "__sanitizer_cov_trace_pc_guard";
84 static const char *const SanCovTracePCGuardInitName =
85     "__sanitizer_cov_trace_pc_guard_init";
86 
87 static cl::opt<int> ClCoverageLevel(
88     "sanitizer-coverage-level",
89     cl::desc("Sanitizer Coverage. 0: none, 1: entry block, 2: all blocks, "
90              "3: all blocks and critical edges, "
91              "4: above plus indirect calls"),
92     cl::Hidden, cl::init(0));
93 
94 static cl::opt<unsigned> ClCoverageBlockThreshold(
95     "sanitizer-coverage-block-threshold",
96     cl::desc("Use a callback with a guard check inside it if there are"
97              " more than this number of blocks."),
98     cl::Hidden, cl::init(500));
99 
100 static cl::opt<bool>
101     ClExperimentalTracing("sanitizer-coverage-experimental-tracing",
102                           cl::desc("Experimental basic-block tracing: insert "
103                                    "callbacks at every basic block"),
104                           cl::Hidden, cl::init(false));
105 
106 static cl::opt<bool> ClExperimentalTracePC("sanitizer-coverage-trace-pc",
107                                            cl::desc("Experimental pc tracing"),
108                                            cl::Hidden, cl::init(false));
109 
110 static cl::opt<bool> ClTracePCGuard("sanitizer-coverage-trace-pc-guard",
111                                     cl::desc("pc tracing with a guard"),
112                                     cl::Hidden, cl::init(false));
113 
114 static cl::opt<bool>
115     ClCMPTracing("sanitizer-coverage-trace-compares",
116                  cl::desc("Tracing of CMP and similar instructions"),
117                  cl::Hidden, cl::init(false));
118 
119 static cl::opt<bool> ClDIVTracing("sanitizer-coverage-trace-divs",
120                                   cl::desc("Tracing of DIV instructions"),
121                                   cl::Hidden, cl::init(false));
122 
123 static cl::opt<bool> ClGEPTracing("sanitizer-coverage-trace-geps",
124                                   cl::desc("Tracing of GEP instructions"),
125                                   cl::Hidden, cl::init(false));
126 
127 static cl::opt<bool>
128     ClPruneBlocks("sanitizer-coverage-prune-blocks",
129                   cl::desc("Reduce the number of instrumented blocks"),
130                   cl::Hidden, cl::init(true));
131 
132 // Experimental 8-bit counters used as an additional search heuristic during
133 // coverage-guided fuzzing.
134 // The counters are not thread-friendly:
135 //   - contention on these counters may cause significant slowdown;
136 //   - the counter updates are racy and the results may be inaccurate.
137 // They are also inaccurate due to 8-bit integer overflow.
138 static cl::opt<bool> ClUse8bitCounters("sanitizer-coverage-8bit-counters",
139                                        cl::desc("Experimental 8-bit counters"),
140                                        cl::Hidden, cl::init(false));
141 
142 namespace {
143 
144 SanitizerCoverageOptions getOptions(int LegacyCoverageLevel) {
145   SanitizerCoverageOptions Res;
146   switch (LegacyCoverageLevel) {
147   case 0:
148     Res.CoverageType = SanitizerCoverageOptions::SCK_None;
149     break;
150   case 1:
151     Res.CoverageType = SanitizerCoverageOptions::SCK_Function;
152     break;
153   case 2:
154     Res.CoverageType = SanitizerCoverageOptions::SCK_BB;
155     break;
156   case 3:
157     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
158     break;
159   case 4:
160     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
161     Res.IndirectCalls = true;
162     break;
163   }
164   return Res;
165 }
166 
167 SanitizerCoverageOptions OverrideFromCL(SanitizerCoverageOptions Options) {
168   // Sets CoverageType and IndirectCalls.
169   SanitizerCoverageOptions CLOpts = getOptions(ClCoverageLevel);
170   Options.CoverageType = std::max(Options.CoverageType, CLOpts.CoverageType);
171   Options.IndirectCalls |= CLOpts.IndirectCalls;
172   Options.TraceBB |= ClExperimentalTracing;
173   Options.TraceCmp |= ClCMPTracing;
174   Options.TraceDiv |= ClDIVTracing;
175   Options.TraceGep |= ClGEPTracing;
176   Options.Use8bitCounters |= ClUse8bitCounters;
177   Options.TracePC |= ClExperimentalTracePC;
178   Options.TracePCGuard |= ClTracePCGuard;
179   return Options;
180 }
181 
182 class SanitizerCoverageModule : public ModulePass {
183 public:
184   SanitizerCoverageModule(
185       const SanitizerCoverageOptions &Options = SanitizerCoverageOptions())
186       : ModulePass(ID), Options(OverrideFromCL(Options)) {
187     initializeSanitizerCoverageModulePass(*PassRegistry::getPassRegistry());
188   }
189   bool runOnModule(Module &M) override;
190   bool runOnFunction(Function &F);
191   static char ID; // Pass identification, replacement for typeid
192   const char *getPassName() const override { return "SanitizerCoverageModule"; }
193 
194   void getAnalysisUsage(AnalysisUsage &AU) const override {
195     AU.addRequired<DominatorTreeWrapperPass>();
196     AU.addRequired<PostDominatorTreeWrapperPass>();
197   }
198 
199 private:
200   void InjectCoverageForIndirectCalls(Function &F,
201                                       ArrayRef<Instruction *> IndirCalls);
202   void InjectTraceForCmp(Function &F, ArrayRef<Instruction *> CmpTraceTargets);
203   void InjectTraceForDiv(Function &F,
204                          ArrayRef<BinaryOperator *> DivTraceTargets);
205   void InjectTraceForGep(Function &F,
206                          ArrayRef<GetElementPtrInst *> GepTraceTargets);
207   void InjectTraceForSwitch(Function &F,
208                             ArrayRef<Instruction *> SwitchTraceTargets);
209   bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks);
210   void SetNoSanitizeMetadata(Instruction *I);
211   void InjectCoverageAtBlock(Function &F, BasicBlock &BB, bool UseCalls);
212   unsigned NumberOfInstrumentedBlocks() {
213     return SanCovFunction->getNumUses() +
214            SanCovWithCheckFunction->getNumUses() + SanCovTraceBB->getNumUses() +
215            SanCovTraceEnter->getNumUses();
216   }
217   Function *SanCovFunction;
218   Function *SanCovWithCheckFunction;
219   Function *SanCovIndirCallFunction, *SanCovTracePCIndir;
220   Function *SanCovTraceEnter, *SanCovTraceBB, *SanCovTracePC, *SanCovTracePCGuard;
221   Function *SanCovTraceCmpFunction[4];
222   Function *SanCovTraceDivFunction[2];
223   Function *SanCovTraceGepFunction;
224   Function *SanCovTraceSwitchFunction;
225   InlineAsm *EmptyAsm;
226   Type *IntptrTy, *Int64Ty, *Int64PtrTy;
227   Module *CurModule;
228   LLVMContext *C;
229   const DataLayout *DL;
230 
231   GlobalVariable *GuardArray;
232   GlobalVariable *EightBitCounterArray;
233 
234   SanitizerCoverageOptions Options;
235 };
236 
237 } // namespace
238 
239 bool SanitizerCoverageModule::runOnModule(Module &M) {
240   if (Options.CoverageType == SanitizerCoverageOptions::SCK_None)
241     return false;
242   C = &(M.getContext());
243   DL = &M.getDataLayout();
244   CurModule = &M;
245   IntptrTy = Type::getIntNTy(*C, DL->getPointerSizeInBits());
246   Type *VoidTy = Type::getVoidTy(*C);
247   IRBuilder<> IRB(*C);
248   Type *Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
249   Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
250   Int64PtrTy = PointerType::getUnqual(IRB.getInt64Ty());
251   Int64Ty = IRB.getInt64Ty();
252 
253   SanCovFunction = checkSanitizerInterfaceFunction(
254       M.getOrInsertFunction(SanCovName, VoidTy, Int32PtrTy, nullptr));
255   SanCovWithCheckFunction = checkSanitizerInterfaceFunction(
256       M.getOrInsertFunction(SanCovWithCheckName, VoidTy, Int32PtrTy, nullptr));
257   SanCovTracePCIndir = checkSanitizerInterfaceFunction(
258       M.getOrInsertFunction(SanCovTracePCIndirName, VoidTy, IntptrTy, nullptr));
259   SanCovIndirCallFunction =
260       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
261           SanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr));
262   SanCovTraceCmpFunction[0] =
263       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
264           SanCovTraceCmp1, VoidTy, IRB.getInt8Ty(), IRB.getInt8Ty(), nullptr));
265   SanCovTraceCmpFunction[1] = checkSanitizerInterfaceFunction(
266       M.getOrInsertFunction(SanCovTraceCmp2, VoidTy, IRB.getInt16Ty(),
267                             IRB.getInt16Ty(), nullptr));
268   SanCovTraceCmpFunction[2] = checkSanitizerInterfaceFunction(
269       M.getOrInsertFunction(SanCovTraceCmp4, VoidTy, IRB.getInt32Ty(),
270                             IRB.getInt32Ty(), nullptr));
271   SanCovTraceCmpFunction[3] =
272       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
273           SanCovTraceCmp8, VoidTy, Int64Ty, Int64Ty, nullptr));
274 
275   SanCovTraceDivFunction[0] =
276       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
277           SanCovTraceDiv4, VoidTy, IRB.getInt32Ty(), nullptr));
278   SanCovTraceDivFunction[1] =
279       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
280           SanCovTraceDiv8, VoidTy, Int64Ty, nullptr));
281   SanCovTraceGepFunction =
282       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
283           SanCovTraceGep, VoidTy, IntptrTy, nullptr));
284   SanCovTraceSwitchFunction =
285       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
286           SanCovTraceSwitchName, VoidTy, Int64Ty, Int64PtrTy, nullptr));
287 
288   // We insert an empty inline asm after cov callbacks to avoid callback merge.
289   EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
290                             StringRef(""), StringRef(""),
291                             /*hasSideEffects=*/true);
292 
293   SanCovTracePC = checkSanitizerInterfaceFunction(
294       M.getOrInsertFunction(SanCovTracePCName, VoidTy, nullptr));
295   SanCovTracePCGuard = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
296       SanCovTracePCGuardName, VoidTy, IRB.getInt8PtrTy(), nullptr));
297   SanCovTraceEnter = checkSanitizerInterfaceFunction(
298       M.getOrInsertFunction(SanCovTraceEnterName, VoidTy, Int32PtrTy, nullptr));
299   SanCovTraceBB = checkSanitizerInterfaceFunction(
300       M.getOrInsertFunction(SanCovTraceBBName, VoidTy, Int32PtrTy, nullptr));
301 
302   // At this point we create a dummy array of guards because we don't
303   // know how many elements we will need.
304   Type *Int32Ty = IRB.getInt32Ty();
305   Type *Int8Ty = IRB.getInt8Ty();
306 
307   GuardArray =
308       new GlobalVariable(M, Int32Ty, false, GlobalValue::ExternalLinkage,
309                          nullptr, "__sancov_gen_cov_tmp");
310   if (Options.Use8bitCounters)
311     EightBitCounterArray =
312         new GlobalVariable(M, Int8Ty, false, GlobalVariable::ExternalLinkage,
313                            nullptr, "__sancov_gen_cov_tmp");
314 
315   for (auto &F : M)
316     runOnFunction(F);
317 
318   auto N = NumberOfInstrumentedBlocks();
319 
320   // Now we know how many elements we need. Create an array of guards
321   // with one extra element at the beginning for the size.
322   Type *Int32ArrayNTy = ArrayType::get(Int32Ty, N + 1);
323   GlobalVariable *RealGuardArray = new GlobalVariable(
324       M, Int32ArrayNTy, false, GlobalValue::PrivateLinkage,
325       Constant::getNullValue(Int32ArrayNTy), "__sancov_gen_cov");
326 
327   // Replace the dummy array with the real one.
328   GuardArray->replaceAllUsesWith(
329       IRB.CreatePointerCast(RealGuardArray, Int32PtrTy));
330   GuardArray->eraseFromParent();
331 
332   GlobalVariable *RealEightBitCounterArray;
333   if (Options.Use8bitCounters) {
334     // Make sure the array is 16-aligned.
335     static const int CounterAlignment = 16;
336     Type *Int8ArrayNTy = ArrayType::get(Int8Ty, alignTo(N, CounterAlignment));
337     RealEightBitCounterArray = new GlobalVariable(
338         M, Int8ArrayNTy, false, GlobalValue::PrivateLinkage,
339         Constant::getNullValue(Int8ArrayNTy), "__sancov_gen_cov_counter");
340     RealEightBitCounterArray->setAlignment(CounterAlignment);
341     EightBitCounterArray->replaceAllUsesWith(
342         IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy));
343     EightBitCounterArray->eraseFromParent();
344   }
345 
346   // Create variable for module (compilation unit) name
347   Constant *ModNameStrConst =
348       ConstantDataArray::getString(M.getContext(), M.getName(), true);
349   GlobalVariable *ModuleName =
350       new GlobalVariable(M, ModNameStrConst->getType(), true,
351                          GlobalValue::PrivateLinkage, ModNameStrConst);
352   if (Options.TracePCGuard) {
353     Function *CtorFunc;
354     std::string SectionName(SanCovTracePCGuardSection);
355     auto Start =
356         new GlobalVariable(M, Int8PtrTy, false, GlobalVariable::ExternalLinkage,
357                            nullptr, "__start_" + SectionName);
358     auto Stop =
359         new GlobalVariable(M, Int8PtrTy, false, GlobalVariable::ExternalLinkage,
360                            nullptr, "__stop_" + SectionName);
361     std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
362         M, SanCovModuleCtorName, SanCovTracePCGuardInitName,
363         {Int8PtrTy, Int8PtrTy}, {IRB.CreatePointerCast(Start, Int8PtrTy),
364                                  IRB.CreatePointerCast(Stop, Int8PtrTy)});
365 
366     appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority);
367 
368   } else if (!Options.TracePC) {
369     Function *CtorFunc;
370     std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
371         M, SanCovModuleCtorName, SanCovModuleInitName,
372         {Int32PtrTy, IntptrTy, Int8PtrTy, Int8PtrTy},
373         {IRB.CreatePointerCast(RealGuardArray, Int32PtrTy),
374          ConstantInt::get(IntptrTy, N),
375          Options.Use8bitCounters
376              ? IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy)
377              : Constant::getNullValue(Int8PtrTy),
378          IRB.CreatePointerCast(ModuleName, Int8PtrTy)});
379 
380     appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority);
381   }
382 
383   return true;
384 }
385 
386 // True if block has successors and it dominates all of them.
387 static bool isFullDominator(const BasicBlock *BB, const DominatorTree *DT) {
388   if (succ_begin(BB) == succ_end(BB))
389     return false;
390 
391   for (const BasicBlock *SUCC : make_range(succ_begin(BB), succ_end(BB))) {
392     if (!DT->dominates(BB, SUCC))
393       return false;
394   }
395 
396   return true;
397 }
398 
399 // True if block has predecessors and it postdominates all of them.
400 static bool isFullPostDominator(const BasicBlock *BB,
401                                 const PostDominatorTree *PDT) {
402   if (pred_begin(BB) == pred_end(BB))
403     return false;
404 
405   for (const BasicBlock *PRED : make_range(pred_begin(BB), pred_end(BB))) {
406     if (!PDT->dominates(BB, PRED))
407       return false;
408   }
409 
410   return true;
411 }
412 
413 static bool shouldInstrumentBlock(const Function& F, const BasicBlock *BB, const DominatorTree *DT,
414                                   const PostDominatorTree *PDT) {
415   if (!ClPruneBlocks || &F.getEntryBlock() == BB)
416     return true;
417 
418   return !(isFullDominator(BB, DT) || isFullPostDominator(BB, PDT));
419 }
420 
421 bool SanitizerCoverageModule::runOnFunction(Function &F) {
422   if (F.empty())
423     return false;
424   if (F.getName().find(".module_ctor") != std::string::npos)
425     return false; // Should not instrument sanitizer init functions.
426   if (F.getName().startswith("__sanitizer_"))
427     return false;  // Don't instrument __sanitizer_* callbacks.
428   // Don't instrument functions using SEH for now. Splitting basic blocks like
429   // we do for coverage breaks WinEHPrepare.
430   // FIXME: Remove this when SEH no longer uses landingpad pattern matching.
431   if (F.hasPersonalityFn() &&
432       isAsynchronousEHPersonality(classifyEHPersonality(F.getPersonalityFn())))
433     return false;
434   if (Options.CoverageType >= SanitizerCoverageOptions::SCK_Edge)
435     SplitAllCriticalEdges(F);
436   SmallVector<Instruction *, 8> IndirCalls;
437   SmallVector<BasicBlock *, 16> BlocksToInstrument;
438   SmallVector<Instruction *, 8> CmpTraceTargets;
439   SmallVector<Instruction *, 8> SwitchTraceTargets;
440   SmallVector<BinaryOperator *, 8> DivTraceTargets;
441   SmallVector<GetElementPtrInst *, 8> GepTraceTargets;
442 
443   const DominatorTree *DT =
444       &getAnalysis<DominatorTreeWrapperPass>(F).getDomTree();
445   const PostDominatorTree *PDT =
446       &getAnalysis<PostDominatorTreeWrapperPass>(F).getPostDomTree();
447 
448   for (auto &BB : F) {
449     if (shouldInstrumentBlock(F, &BB, DT, PDT))
450       BlocksToInstrument.push_back(&BB);
451     for (auto &Inst : BB) {
452       if (Options.IndirectCalls) {
453         CallSite CS(&Inst);
454         if (CS && !CS.getCalledFunction())
455           IndirCalls.push_back(&Inst);
456       }
457       if (Options.TraceCmp) {
458         if (isa<ICmpInst>(&Inst))
459           CmpTraceTargets.push_back(&Inst);
460         if (isa<SwitchInst>(&Inst))
461           SwitchTraceTargets.push_back(&Inst);
462       }
463       if (Options.TraceDiv)
464         if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&Inst))
465           if (BO->getOpcode() == Instruction::SDiv ||
466               BO->getOpcode() == Instruction::UDiv)
467             DivTraceTargets.push_back(BO);
468       if (Options.TraceGep)
469         if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(&Inst))
470           GepTraceTargets.push_back(GEP);
471    }
472   }
473 
474   InjectCoverage(F, BlocksToInstrument);
475   InjectCoverageForIndirectCalls(F, IndirCalls);
476   InjectTraceForCmp(F, CmpTraceTargets);
477   InjectTraceForSwitch(F, SwitchTraceTargets);
478   InjectTraceForDiv(F, DivTraceTargets);
479   InjectTraceForGep(F, GepTraceTargets);
480   return true;
481 }
482 
483 bool SanitizerCoverageModule::InjectCoverage(Function &F,
484                                              ArrayRef<BasicBlock *> AllBlocks) {
485   switch (Options.CoverageType) {
486   case SanitizerCoverageOptions::SCK_None:
487     return false;
488   case SanitizerCoverageOptions::SCK_Function:
489     InjectCoverageAtBlock(F, F.getEntryBlock(), false);
490     return true;
491   default: {
492     bool UseCalls = ClCoverageBlockThreshold < AllBlocks.size();
493     for (auto BB : AllBlocks)
494       InjectCoverageAtBlock(F, *BB, UseCalls);
495     return true;
496   }
497   }
498 }
499 
500 // On every indirect call we call a run-time function
501 // __sanitizer_cov_indir_call* with two parameters:
502 //   - callee address,
503 //   - global cache array that contains CacheSize pointers (zero-initialized).
504 //     The cache is used to speed up recording the caller-callee pairs.
505 // The address of the caller is passed implicitly via caller PC.
506 // CacheSize is encoded in the name of the run-time function.
507 void SanitizerCoverageModule::InjectCoverageForIndirectCalls(
508     Function &F, ArrayRef<Instruction *> IndirCalls) {
509   if (IndirCalls.empty())
510     return;
511   const int CacheSize = 16;
512   const int CacheAlignment = 64; // Align for better performance.
513   Type *Ty = ArrayType::get(IntptrTy, CacheSize);
514   for (auto I : IndirCalls) {
515     IRBuilder<> IRB(I);
516     CallSite CS(I);
517     Value *Callee = CS.getCalledValue();
518     if (isa<InlineAsm>(Callee))
519       continue;
520     GlobalVariable *CalleeCache = new GlobalVariable(
521         *F.getParent(), Ty, false, GlobalValue::PrivateLinkage,
522         Constant::getNullValue(Ty), "__sancov_gen_callee_cache");
523     CalleeCache->setAlignment(CacheAlignment);
524     if (Options.TracePC)
525       IRB.CreateCall(SanCovTracePCIndir,
526                      IRB.CreatePointerCast(Callee, IntptrTy));
527     else
528       IRB.CreateCall(SanCovIndirCallFunction,
529                      {IRB.CreatePointerCast(Callee, IntptrTy),
530                       IRB.CreatePointerCast(CalleeCache, IntptrTy)});
531   }
532 }
533 
534 // For every switch statement we insert a call:
535 // __sanitizer_cov_trace_switch(CondValue,
536 //      {NumCases, ValueSizeInBits, Case0Value, Case1Value, Case2Value, ... })
537 
538 void SanitizerCoverageModule::InjectTraceForSwitch(
539     Function &, ArrayRef<Instruction *> SwitchTraceTargets) {
540   for (auto I : SwitchTraceTargets) {
541     if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
542       IRBuilder<> IRB(I);
543       SmallVector<Constant *, 16> Initializers;
544       Value *Cond = SI->getCondition();
545       if (Cond->getType()->getScalarSizeInBits() >
546           Int64Ty->getScalarSizeInBits())
547         continue;
548       Initializers.push_back(ConstantInt::get(Int64Ty, SI->getNumCases()));
549       Initializers.push_back(
550           ConstantInt::get(Int64Ty, Cond->getType()->getScalarSizeInBits()));
551       if (Cond->getType()->getScalarSizeInBits() <
552           Int64Ty->getScalarSizeInBits())
553         Cond = IRB.CreateIntCast(Cond, Int64Ty, false);
554       for (auto It : SI->cases()) {
555         Constant *C = It.getCaseValue();
556         if (C->getType()->getScalarSizeInBits() <
557             Int64Ty->getScalarSizeInBits())
558           C = ConstantExpr::getCast(CastInst::ZExt, It.getCaseValue(), Int64Ty);
559         Initializers.push_back(C);
560       }
561       ArrayType *ArrayOfInt64Ty = ArrayType::get(Int64Ty, Initializers.size());
562       GlobalVariable *GV = new GlobalVariable(
563           *CurModule, ArrayOfInt64Ty, false, GlobalVariable::InternalLinkage,
564           ConstantArray::get(ArrayOfInt64Ty, Initializers),
565           "__sancov_gen_cov_switch_values");
566       IRB.CreateCall(SanCovTraceSwitchFunction,
567                      {Cond, IRB.CreatePointerCast(GV, Int64PtrTy)});
568     }
569   }
570 }
571 
572 void SanitizerCoverageModule::InjectTraceForDiv(
573     Function &, ArrayRef<BinaryOperator *> DivTraceTargets) {
574   for (auto BO : DivTraceTargets) {
575     IRBuilder<> IRB(BO);
576     Value *A1 = BO->getOperand(1);
577     if (isa<ConstantInt>(A1)) continue;
578     if (!A1->getType()->isIntegerTy())
579       continue;
580     uint64_t TypeSize = DL->getTypeStoreSizeInBits(A1->getType());
581     int CallbackIdx = TypeSize == 32 ? 0 :
582         TypeSize == 64 ? 1 : -1;
583     if (CallbackIdx < 0) continue;
584     auto Ty = Type::getIntNTy(*C, TypeSize);
585     IRB.CreateCall(SanCovTraceDivFunction[CallbackIdx],
586                    {IRB.CreateIntCast(A1, Ty, true)});
587   }
588 }
589 
590 void SanitizerCoverageModule::InjectTraceForGep(
591     Function &, ArrayRef<GetElementPtrInst *> GepTraceTargets) {
592   for (auto GEP : GepTraceTargets) {
593     IRBuilder<> IRB(GEP);
594     for (auto I = GEP->idx_begin(); I != GEP->idx_end(); ++I)
595       if (!isa<ConstantInt>(*I))
596         IRB.CreateCall(SanCovTraceGepFunction,
597                        {IRB.CreateIntCast(*I, IntptrTy, true)});
598   }
599 }
600 
601 void SanitizerCoverageModule::InjectTraceForCmp(
602     Function &, ArrayRef<Instruction *> CmpTraceTargets) {
603   for (auto I : CmpTraceTargets) {
604     if (ICmpInst *ICMP = dyn_cast<ICmpInst>(I)) {
605       IRBuilder<> IRB(ICMP);
606       Value *A0 = ICMP->getOperand(0);
607       Value *A1 = ICMP->getOperand(1);
608       if (!A0->getType()->isIntegerTy())
609         continue;
610       uint64_t TypeSize = DL->getTypeStoreSizeInBits(A0->getType());
611       int CallbackIdx = TypeSize == 8 ? 0 :
612                         TypeSize == 16 ? 1 :
613                         TypeSize == 32 ? 2 :
614                         TypeSize == 64 ? 3 : -1;
615       if (CallbackIdx < 0) continue;
616       // __sanitizer_cov_trace_cmp((type_size << 32) | predicate, A0, A1);
617       auto Ty = Type::getIntNTy(*C, TypeSize);
618       IRB.CreateCall(
619           SanCovTraceCmpFunction[CallbackIdx],
620           {IRB.CreateIntCast(A0, Ty, true), IRB.CreateIntCast(A1, Ty, true)});
621     }
622   }
623 }
624 
625 void SanitizerCoverageModule::SetNoSanitizeMetadata(Instruction *I) {
626   I->setMetadata(I->getModule()->getMDKindID("nosanitize"),
627                  MDNode::get(*C, None));
628 }
629 
630 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
631                                                     bool UseCalls) {
632   // Don't insert coverage for unreachable blocks: we will never call
633   // __sanitizer_cov() for them, so counting them in
634   // NumberOfInstrumentedBlocks() might complicate calculation of code coverage
635   // percentage. Also, unreachable instructions frequently have no debug
636   // locations.
637   if (isa<UnreachableInst>(BB.getTerminator()))
638     return;
639   BasicBlock::iterator IP = BB.getFirstInsertionPt();
640 
641   bool IsEntryBB = &BB == &F.getEntryBlock();
642   DebugLoc EntryLoc;
643   if (IsEntryBB) {
644     if (auto SP = F.getSubprogram())
645       EntryLoc = DebugLoc::get(SP->getScopeLine(), 0, SP);
646     // Keep static allocas and llvm.localescape calls in the entry block.  Even
647     // if we aren't splitting the block, it's nice for allocas to be before
648     // calls.
649     IP = PrepareToSplitEntryBlock(BB, IP);
650   } else {
651     EntryLoc = IP->getDebugLoc();
652   }
653 
654   IRBuilder<> IRB(&*IP);
655   IRB.SetCurrentDebugLocation(EntryLoc);
656   Value *GuardP = IRB.CreateAdd(
657       IRB.CreatePointerCast(GuardArray, IntptrTy),
658       ConstantInt::get(IntptrTy, (1 + NumberOfInstrumentedBlocks()) * 4));
659   Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
660   GuardP = IRB.CreateIntToPtr(GuardP, Int32PtrTy);
661   if (Options.TracePC) {
662     IRB.CreateCall(SanCovTracePC); // gets the PC using GET_CALLER_PC.
663     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
664   } else if (Options.TracePCGuard) {
665     auto GuardVar = new GlobalVariable(*F.getParent(), IRB.getInt8Ty(), false,
666                                        GlobalVariable::LinkOnceODRLinkage,
667                                        Constant::getNullValue(IRB.getInt8Ty()),
668                                        "__sancov_guard." + F.getName());
669     // TODO: add debug into to GuardVar.
670     GuardVar->setSection(SanCovTracePCGuardSection);
671     auto GuardPtr = IRB.CreatePointerCast(GuardVar, IRB.getInt8PtrTy());
672     auto GuardLoad = IRB.CreateLoad(GuardPtr);
673     GuardLoad->setAtomic(AtomicOrdering::Monotonic);
674     GuardLoad->setAlignment(1);
675     SetNoSanitizeMetadata(GuardLoad);  // Don't instrument with e.g. asan.
676     auto Cmp = IRB.CreateICmpNE(
677         Constant::getAllOnesValue(GuardLoad->getType()), GuardLoad);
678     auto Ins = SplitBlockAndInsertIfThen(
679         Cmp, &*IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
680     IRB.SetCurrentDebugLocation(EntryLoc);
681     IRB.SetInsertPoint(Ins);
682     IRB.CreateCall(SanCovTracePCGuard, GuardPtr);
683     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
684   } else if (Options.TraceBB) {
685     IRB.CreateCall(IsEntryBB ? SanCovTraceEnter : SanCovTraceBB, GuardP);
686   } else if (UseCalls) {
687     IRB.CreateCall(SanCovWithCheckFunction, GuardP);
688   } else {
689     LoadInst *Load = IRB.CreateLoad(GuardP);
690     Load->setAtomic(AtomicOrdering::Monotonic);
691     Load->setAlignment(4);
692     SetNoSanitizeMetadata(Load);
693     Value *Cmp =
694         IRB.CreateICmpSGE(Constant::getNullValue(Load->getType()), Load);
695     Instruction *Ins = SplitBlockAndInsertIfThen(
696         Cmp, &*IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
697     IRB.SetInsertPoint(Ins);
698     IRB.SetCurrentDebugLocation(EntryLoc);
699     // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC.
700     IRB.CreateCall(SanCovFunction, GuardP);
701     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
702   }
703 
704   if (Options.Use8bitCounters) {
705     IRB.SetInsertPoint(&*IP);
706     Value *P = IRB.CreateAdd(
707         IRB.CreatePointerCast(EightBitCounterArray, IntptrTy),
708         ConstantInt::get(IntptrTy, NumberOfInstrumentedBlocks() - 1));
709     P = IRB.CreateIntToPtr(P, IRB.getInt8PtrTy());
710     LoadInst *LI = IRB.CreateLoad(P);
711     Value *Inc = IRB.CreateAdd(LI, ConstantInt::get(IRB.getInt8Ty(), 1));
712     StoreInst *SI = IRB.CreateStore(Inc, P);
713     SetNoSanitizeMetadata(LI);
714     SetNoSanitizeMetadata(SI);
715   }
716 }
717 
718 char SanitizerCoverageModule::ID = 0;
719 INITIALIZE_PASS_BEGIN(SanitizerCoverageModule, "sancov",
720                       "SanitizerCoverage: TODO."
721                       "ModulePass",
722                       false, false)
723 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
724 INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)
725 INITIALIZE_PASS_END(SanitizerCoverageModule, "sancov",
726                     "SanitizerCoverage: TODO."
727                     "ModulePass",
728                     false, false)
729 ModulePass *llvm::createSanitizerCoverageModulePass(
730     const SanitizerCoverageOptions &Options) {
731   return new SanitizerCoverageModule(Options);
732 }
733