xref: /llvm-project/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp (revision 06694d0a2f487c5fc59dd8e2d76366d97598abfb) 
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, *IntptrPtrTy, *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   IntptrPtrTy = PointerType::getUnqual(IntptrTy);
247   Type *VoidTy = Type::getVoidTy(*C);
248   IRBuilder<> IRB(*C);
249   Type *Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
250   Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
251   Int64PtrTy = PointerType::getUnqual(IRB.getInt64Ty());
252   Int64Ty = IRB.getInt64Ty();
253 
254   SanCovFunction = checkSanitizerInterfaceFunction(
255       M.getOrInsertFunction(SanCovName, VoidTy, Int32PtrTy, nullptr));
256   SanCovWithCheckFunction = checkSanitizerInterfaceFunction(
257       M.getOrInsertFunction(SanCovWithCheckName, VoidTy, Int32PtrTy, nullptr));
258   SanCovTracePCIndir = checkSanitizerInterfaceFunction(
259       M.getOrInsertFunction(SanCovTracePCIndirName, VoidTy, IntptrTy, nullptr));
260   SanCovIndirCallFunction =
261       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
262           SanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr));
263   SanCovTraceCmpFunction[0] =
264       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
265           SanCovTraceCmp1, VoidTy, IRB.getInt8Ty(), IRB.getInt8Ty(), nullptr));
266   SanCovTraceCmpFunction[1] = checkSanitizerInterfaceFunction(
267       M.getOrInsertFunction(SanCovTraceCmp2, VoidTy, IRB.getInt16Ty(),
268                             IRB.getInt16Ty(), nullptr));
269   SanCovTraceCmpFunction[2] = checkSanitizerInterfaceFunction(
270       M.getOrInsertFunction(SanCovTraceCmp4, VoidTy, IRB.getInt32Ty(),
271                             IRB.getInt32Ty(), nullptr));
272   SanCovTraceCmpFunction[3] =
273       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
274           SanCovTraceCmp8, VoidTy, Int64Ty, Int64Ty, nullptr));
275 
276   SanCovTraceDivFunction[0] =
277       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
278           SanCovTraceDiv4, VoidTy, IRB.getInt32Ty(), nullptr));
279   SanCovTraceDivFunction[1] =
280       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
281           SanCovTraceDiv8, VoidTy, Int64Ty, nullptr));
282   SanCovTraceGepFunction =
283       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
284           SanCovTraceGep, VoidTy, IntptrTy, nullptr));
285   SanCovTraceSwitchFunction =
286       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
287           SanCovTraceSwitchName, VoidTy, Int64Ty, Int64PtrTy, nullptr));
288 
289   // We insert an empty inline asm after cov callbacks to avoid callback merge.
290   EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
291                             StringRef(""), StringRef(""),
292                             /*hasSideEffects=*/true);
293 
294   SanCovTracePC = checkSanitizerInterfaceFunction(
295       M.getOrInsertFunction(SanCovTracePCName, VoidTy, nullptr));
296   SanCovTracePCGuard = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
297       SanCovTracePCGuardName, VoidTy, IntptrPtrTy, nullptr));
298   SanCovTraceEnter = checkSanitizerInterfaceFunction(
299       M.getOrInsertFunction(SanCovTraceEnterName, VoidTy, Int32PtrTy, nullptr));
300   SanCovTraceBB = checkSanitizerInterfaceFunction(
301       M.getOrInsertFunction(SanCovTraceBBName, VoidTy, Int32PtrTy, nullptr));
302 
303   // At this point we create a dummy array of guards because we don't
304   // know how many elements we will need.
305   Type *Int32Ty = IRB.getInt32Ty();
306   Type *Int8Ty = IRB.getInt8Ty();
307 
308   GuardArray =
309       new GlobalVariable(M, Int32Ty, false, GlobalValue::ExternalLinkage,
310                          nullptr, "__sancov_gen_cov_tmp");
311   if (Options.Use8bitCounters)
312     EightBitCounterArray =
313         new GlobalVariable(M, Int8Ty, false, GlobalVariable::ExternalLinkage,
314                            nullptr, "__sancov_gen_cov_tmp");
315 
316   for (auto &F : M)
317     runOnFunction(F);
318 
319   auto N = NumberOfInstrumentedBlocks();
320 
321   // Now we know how many elements we need. Create an array of guards
322   // with one extra element at the beginning for the size.
323   Type *Int32ArrayNTy = ArrayType::get(Int32Ty, N + 1);
324   GlobalVariable *RealGuardArray = new GlobalVariable(
325       M, Int32ArrayNTy, false, GlobalValue::PrivateLinkage,
326       Constant::getNullValue(Int32ArrayNTy), "__sancov_gen_cov");
327 
328   // Replace the dummy array with the real one.
329   GuardArray->replaceAllUsesWith(
330       IRB.CreatePointerCast(RealGuardArray, Int32PtrTy));
331   GuardArray->eraseFromParent();
332 
333   GlobalVariable *RealEightBitCounterArray;
334   if (Options.Use8bitCounters) {
335     // Make sure the array is 16-aligned.
336     static const int CounterAlignment = 16;
337     Type *Int8ArrayNTy = ArrayType::get(Int8Ty, alignTo(N, CounterAlignment));
338     RealEightBitCounterArray = new GlobalVariable(
339         M, Int8ArrayNTy, false, GlobalValue::PrivateLinkage,
340         Constant::getNullValue(Int8ArrayNTy), "__sancov_gen_cov_counter");
341     RealEightBitCounterArray->setAlignment(CounterAlignment);
342     EightBitCounterArray->replaceAllUsesWith(
343         IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy));
344     EightBitCounterArray->eraseFromParent();
345   }
346 
347   // Create variable for module (compilation unit) name
348   Constant *ModNameStrConst =
349       ConstantDataArray::getString(M.getContext(), M.getName(), true);
350   GlobalVariable *ModuleName =
351       new GlobalVariable(M, ModNameStrConst->getType(), true,
352                          GlobalValue::PrivateLinkage, ModNameStrConst);
353   if (Options.TracePCGuard) {
354     Function *CtorFunc;
355     std::string SectionName(SanCovTracePCGuardSection);
356     GlobalVariable *Bounds[2];
357     const char *Prefix[2] = {"__start_", "__stop_"};
358     for (int i = 0; i < 2; i++) {
359       Bounds[i] = new GlobalVariable(M, IntptrPtrTy, false,
360                                      GlobalVariable::ExternalLinkage, nullptr,
361                                      Prefix[i] + SectionName);
362       Bounds[i]->setVisibility(GlobalValue::HiddenVisibility);
363     }
364     std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
365         M, SanCovModuleCtorName, SanCovTracePCGuardInitName,
366         {IntptrPtrTy, IntptrPtrTy},
367         {IRB.CreatePointerCast(Bounds[0], IntptrPtrTy),
368          IRB.CreatePointerCast(Bounds[1], IntptrPtrTy)});
369 
370     appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority);
371 
372   } else if (!Options.TracePC) {
373     Function *CtorFunc;
374     std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
375         M, SanCovModuleCtorName, SanCovModuleInitName,
376         {Int32PtrTy, IntptrTy, Int8PtrTy, Int8PtrTy},
377         {IRB.CreatePointerCast(RealGuardArray, Int32PtrTy),
378          ConstantInt::get(IntptrTy, N),
379          Options.Use8bitCounters
380              ? IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy)
381              : Constant::getNullValue(Int8PtrTy),
382          IRB.CreatePointerCast(ModuleName, Int8PtrTy)});
383 
384     appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority);
385   }
386 
387   return true;
388 }
389 
390 // True if block has successors and it dominates all of them.
391 static bool isFullDominator(const BasicBlock *BB, const DominatorTree *DT) {
392   if (succ_begin(BB) == succ_end(BB))
393     return false;
394 
395   for (const BasicBlock *SUCC : make_range(succ_begin(BB), succ_end(BB))) {
396     if (!DT->dominates(BB, SUCC))
397       return false;
398   }
399 
400   return true;
401 }
402 
403 // True if block has predecessors and it postdominates all of them.
404 static bool isFullPostDominator(const BasicBlock *BB,
405                                 const PostDominatorTree *PDT) {
406   if (pred_begin(BB) == pred_end(BB))
407     return false;
408 
409   for (const BasicBlock *PRED : make_range(pred_begin(BB), pred_end(BB))) {
410     if (!PDT->dominates(BB, PRED))
411       return false;
412   }
413 
414   return true;
415 }
416 
417 static bool shouldInstrumentBlock(const Function& F, const BasicBlock *BB, const DominatorTree *DT,
418                                   const PostDominatorTree *PDT) {
419   if (!ClPruneBlocks || &F.getEntryBlock() == BB)
420     return true;
421 
422   return !(isFullDominator(BB, DT) || isFullPostDominator(BB, PDT));
423 }
424 
425 bool SanitizerCoverageModule::runOnFunction(Function &F) {
426   if (F.empty())
427     return false;
428   if (F.getName().find(".module_ctor") != std::string::npos)
429     return false; // Should not instrument sanitizer init functions.
430   if (F.getName().startswith("__sanitizer_"))
431     return false;  // Don't instrument __sanitizer_* callbacks.
432   // Don't instrument functions using SEH for now. Splitting basic blocks like
433   // we do for coverage breaks WinEHPrepare.
434   // FIXME: Remove this when SEH no longer uses landingpad pattern matching.
435   if (F.hasPersonalityFn() &&
436       isAsynchronousEHPersonality(classifyEHPersonality(F.getPersonalityFn())))
437     return false;
438   if (Options.CoverageType >= SanitizerCoverageOptions::SCK_Edge)
439     SplitAllCriticalEdges(F);
440   SmallVector<Instruction *, 8> IndirCalls;
441   SmallVector<BasicBlock *, 16> BlocksToInstrument;
442   SmallVector<Instruction *, 8> CmpTraceTargets;
443   SmallVector<Instruction *, 8> SwitchTraceTargets;
444   SmallVector<BinaryOperator *, 8> DivTraceTargets;
445   SmallVector<GetElementPtrInst *, 8> GepTraceTargets;
446 
447   const DominatorTree *DT =
448       &getAnalysis<DominatorTreeWrapperPass>(F).getDomTree();
449   const PostDominatorTree *PDT =
450       &getAnalysis<PostDominatorTreeWrapperPass>(F).getPostDomTree();
451 
452   for (auto &BB : F) {
453     if (shouldInstrumentBlock(F, &BB, DT, PDT))
454       BlocksToInstrument.push_back(&BB);
455     for (auto &Inst : BB) {
456       if (Options.IndirectCalls) {
457         CallSite CS(&Inst);
458         if (CS && !CS.getCalledFunction())
459           IndirCalls.push_back(&Inst);
460       }
461       if (Options.TraceCmp) {
462         if (isa<ICmpInst>(&Inst))
463           CmpTraceTargets.push_back(&Inst);
464         if (isa<SwitchInst>(&Inst))
465           SwitchTraceTargets.push_back(&Inst);
466       }
467       if (Options.TraceDiv)
468         if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&Inst))
469           if (BO->getOpcode() == Instruction::SDiv ||
470               BO->getOpcode() == Instruction::UDiv)
471             DivTraceTargets.push_back(BO);
472       if (Options.TraceGep)
473         if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(&Inst))
474           GepTraceTargets.push_back(GEP);
475    }
476   }
477 
478   InjectCoverage(F, BlocksToInstrument);
479   InjectCoverageForIndirectCalls(F, IndirCalls);
480   InjectTraceForCmp(F, CmpTraceTargets);
481   InjectTraceForSwitch(F, SwitchTraceTargets);
482   InjectTraceForDiv(F, DivTraceTargets);
483   InjectTraceForGep(F, GepTraceTargets);
484   return true;
485 }
486 
487 bool SanitizerCoverageModule::InjectCoverage(Function &F,
488                                              ArrayRef<BasicBlock *> AllBlocks) {
489   switch (Options.CoverageType) {
490   case SanitizerCoverageOptions::SCK_None:
491     return false;
492   case SanitizerCoverageOptions::SCK_Function:
493     InjectCoverageAtBlock(F, F.getEntryBlock(), false);
494     return true;
495   default: {
496     bool UseCalls = ClCoverageBlockThreshold < AllBlocks.size();
497     for (auto BB : AllBlocks)
498       InjectCoverageAtBlock(F, *BB, UseCalls);
499     return true;
500   }
501   }
502 }
503 
504 // On every indirect call we call a run-time function
505 // __sanitizer_cov_indir_call* with two parameters:
506 //   - callee address,
507 //   - global cache array that contains CacheSize pointers (zero-initialized).
508 //     The cache is used to speed up recording the caller-callee pairs.
509 // The address of the caller is passed implicitly via caller PC.
510 // CacheSize is encoded in the name of the run-time function.
511 void SanitizerCoverageModule::InjectCoverageForIndirectCalls(
512     Function &F, ArrayRef<Instruction *> IndirCalls) {
513   if (IndirCalls.empty())
514     return;
515   const int CacheSize = 16;
516   const int CacheAlignment = 64; // Align for better performance.
517   Type *Ty = ArrayType::get(IntptrTy, CacheSize);
518   for (auto I : IndirCalls) {
519     IRBuilder<> IRB(I);
520     CallSite CS(I);
521     Value *Callee = CS.getCalledValue();
522     if (isa<InlineAsm>(Callee))
523       continue;
524     GlobalVariable *CalleeCache = new GlobalVariable(
525         *F.getParent(), Ty, false, GlobalValue::PrivateLinkage,
526         Constant::getNullValue(Ty), "__sancov_gen_callee_cache");
527     CalleeCache->setAlignment(CacheAlignment);
528     if (Options.TracePC || Options.TracePCGuard)
529       IRB.CreateCall(SanCovTracePCIndir,
530                      IRB.CreatePointerCast(Callee, IntptrTy));
531     else
532       IRB.CreateCall(SanCovIndirCallFunction,
533                      {IRB.CreatePointerCast(Callee, IntptrTy),
534                       IRB.CreatePointerCast(CalleeCache, IntptrTy)});
535   }
536 }
537 
538 // For every switch statement we insert a call:
539 // __sanitizer_cov_trace_switch(CondValue,
540 //      {NumCases, ValueSizeInBits, Case0Value, Case1Value, Case2Value, ... })
541 
542 void SanitizerCoverageModule::InjectTraceForSwitch(
543     Function &, ArrayRef<Instruction *> SwitchTraceTargets) {
544   for (auto I : SwitchTraceTargets) {
545     if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
546       IRBuilder<> IRB(I);
547       SmallVector<Constant *, 16> Initializers;
548       Value *Cond = SI->getCondition();
549       if (Cond->getType()->getScalarSizeInBits() >
550           Int64Ty->getScalarSizeInBits())
551         continue;
552       Initializers.push_back(ConstantInt::get(Int64Ty, SI->getNumCases()));
553       Initializers.push_back(
554           ConstantInt::get(Int64Ty, Cond->getType()->getScalarSizeInBits()));
555       if (Cond->getType()->getScalarSizeInBits() <
556           Int64Ty->getScalarSizeInBits())
557         Cond = IRB.CreateIntCast(Cond, Int64Ty, false);
558       for (auto It : SI->cases()) {
559         Constant *C = It.getCaseValue();
560         if (C->getType()->getScalarSizeInBits() <
561             Int64Ty->getScalarSizeInBits())
562           C = ConstantExpr::getCast(CastInst::ZExt, It.getCaseValue(), Int64Ty);
563         Initializers.push_back(C);
564       }
565       ArrayType *ArrayOfInt64Ty = ArrayType::get(Int64Ty, Initializers.size());
566       GlobalVariable *GV = new GlobalVariable(
567           *CurModule, ArrayOfInt64Ty, false, GlobalVariable::InternalLinkage,
568           ConstantArray::get(ArrayOfInt64Ty, Initializers),
569           "__sancov_gen_cov_switch_values");
570       IRB.CreateCall(SanCovTraceSwitchFunction,
571                      {Cond, IRB.CreatePointerCast(GV, Int64PtrTy)});
572     }
573   }
574 }
575 
576 void SanitizerCoverageModule::InjectTraceForDiv(
577     Function &, ArrayRef<BinaryOperator *> DivTraceTargets) {
578   for (auto BO : DivTraceTargets) {
579     IRBuilder<> IRB(BO);
580     Value *A1 = BO->getOperand(1);
581     if (isa<ConstantInt>(A1)) continue;
582     if (!A1->getType()->isIntegerTy())
583       continue;
584     uint64_t TypeSize = DL->getTypeStoreSizeInBits(A1->getType());
585     int CallbackIdx = TypeSize == 32 ? 0 :
586         TypeSize == 64 ? 1 : -1;
587     if (CallbackIdx < 0) continue;
588     auto Ty = Type::getIntNTy(*C, TypeSize);
589     IRB.CreateCall(SanCovTraceDivFunction[CallbackIdx],
590                    {IRB.CreateIntCast(A1, Ty, true)});
591   }
592 }
593 
594 void SanitizerCoverageModule::InjectTraceForGep(
595     Function &, ArrayRef<GetElementPtrInst *> GepTraceTargets) {
596   for (auto GEP : GepTraceTargets) {
597     IRBuilder<> IRB(GEP);
598     for (auto I = GEP->idx_begin(); I != GEP->idx_end(); ++I)
599       if (!isa<ConstantInt>(*I))
600         IRB.CreateCall(SanCovTraceGepFunction,
601                        {IRB.CreateIntCast(*I, IntptrTy, true)});
602   }
603 }
604 
605 void SanitizerCoverageModule::InjectTraceForCmp(
606     Function &, ArrayRef<Instruction *> CmpTraceTargets) {
607   for (auto I : CmpTraceTargets) {
608     if (ICmpInst *ICMP = dyn_cast<ICmpInst>(I)) {
609       IRBuilder<> IRB(ICMP);
610       Value *A0 = ICMP->getOperand(0);
611       Value *A1 = ICMP->getOperand(1);
612       if (!A0->getType()->isIntegerTy())
613         continue;
614       uint64_t TypeSize = DL->getTypeStoreSizeInBits(A0->getType());
615       int CallbackIdx = TypeSize == 8 ? 0 :
616                         TypeSize == 16 ? 1 :
617                         TypeSize == 32 ? 2 :
618                         TypeSize == 64 ? 3 : -1;
619       if (CallbackIdx < 0) continue;
620       // __sanitizer_cov_trace_cmp((type_size << 32) | predicate, A0, A1);
621       auto Ty = Type::getIntNTy(*C, TypeSize);
622       IRB.CreateCall(
623           SanCovTraceCmpFunction[CallbackIdx],
624           {IRB.CreateIntCast(A0, Ty, true), IRB.CreateIntCast(A1, Ty, true)});
625     }
626   }
627 }
628 
629 void SanitizerCoverageModule::SetNoSanitizeMetadata(Instruction *I) {
630   I->setMetadata(I->getModule()->getMDKindID("nosanitize"),
631                  MDNode::get(*C, None));
632 }
633 
634 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
635                                                     bool UseCalls) {
636   // Don't insert coverage for unreachable blocks: we will never call
637   // __sanitizer_cov() for them, so counting them in
638   // NumberOfInstrumentedBlocks() might complicate calculation of code coverage
639   // percentage. Also, unreachable instructions frequently have no debug
640   // locations.
641   if (isa<UnreachableInst>(BB.getTerminator()))
642     return;
643   BasicBlock::iterator IP = BB.getFirstInsertionPt();
644 
645   bool IsEntryBB = &BB == &F.getEntryBlock();
646   DebugLoc EntryLoc;
647   if (IsEntryBB) {
648     if (auto SP = F.getSubprogram())
649       EntryLoc = DebugLoc::get(SP->getScopeLine(), 0, SP);
650     // Keep static allocas and llvm.localescape calls in the entry block.  Even
651     // if we aren't splitting the block, it's nice for allocas to be before
652     // calls.
653     IP = PrepareToSplitEntryBlock(BB, IP);
654   } else {
655     EntryLoc = IP->getDebugLoc();
656   }
657 
658   IRBuilder<> IRB(&*IP);
659   IRB.SetCurrentDebugLocation(EntryLoc);
660   Value *GuardP = IRB.CreateAdd(
661       IRB.CreatePointerCast(GuardArray, IntptrTy),
662       ConstantInt::get(IntptrTy, (1 + NumberOfInstrumentedBlocks()) * 4));
663   Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
664   GuardP = IRB.CreateIntToPtr(GuardP, Int32PtrTy);
665   if (Options.TracePC) {
666     IRB.CreateCall(SanCovTracePC); // gets the PC using GET_CALLER_PC.
667     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
668   } else if (Options.TracePCGuard) {
669     auto GuardVar = new GlobalVariable(
670         *F.getParent(), Int64Ty, false, GlobalVariable::LinkOnceODRLinkage,
671         Constant::getNullValue(Int64Ty), "__sancov_guard." + F.getName());
672     if (auto Comdat = F.getComdat())
673       GuardVar->setComdat(Comdat);
674     // TODO: add debug into to GuardVar.
675     GuardVar->setSection(SanCovTracePCGuardSection);
676     auto GuardPtr = IRB.CreatePointerCast(GuardVar, IntptrPtrTy);
677     if (!UseCalls) {
678       auto GuardLoad = IRB.CreateLoad(GuardPtr);
679       GuardLoad->setAtomic(AtomicOrdering::Monotonic);
680       GuardLoad->setAlignment(8);
681       SetNoSanitizeMetadata(GuardLoad);  // Don't instrument with e.g. asan.
682       auto Cmp = IRB.CreateICmpNE(
683           GuardLoad, Constant::getNullValue(GuardLoad->getType()));
684       auto Ins = SplitBlockAndInsertIfThen(
685           Cmp, &*IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
686       IRB.SetCurrentDebugLocation(EntryLoc);
687       IRB.SetInsertPoint(Ins);
688     }
689     IRB.CreateCall(SanCovTracePCGuard, GuardPtr);
690     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
691   } else if (Options.TraceBB) {
692     IRB.CreateCall(IsEntryBB ? SanCovTraceEnter : SanCovTraceBB, GuardP);
693   } else if (UseCalls) {
694     IRB.CreateCall(SanCovWithCheckFunction, GuardP);
695   } else {
696     LoadInst *Load = IRB.CreateLoad(GuardP);
697     Load->setAtomic(AtomicOrdering::Monotonic);
698     Load->setAlignment(4);
699     SetNoSanitizeMetadata(Load);
700     Value *Cmp =
701         IRB.CreateICmpSGE(Constant::getNullValue(Load->getType()), Load);
702     Instruction *Ins = SplitBlockAndInsertIfThen(
703         Cmp, &*IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
704     IRB.SetInsertPoint(Ins);
705     IRB.SetCurrentDebugLocation(EntryLoc);
706     // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC.
707     IRB.CreateCall(SanCovFunction, GuardP);
708     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
709   }
710 
711   if (Options.Use8bitCounters) {
712     IRB.SetInsertPoint(&*IP);
713     Value *P = IRB.CreateAdd(
714         IRB.CreatePointerCast(EightBitCounterArray, IntptrTy),
715         ConstantInt::get(IntptrTy, NumberOfInstrumentedBlocks() - 1));
716     P = IRB.CreateIntToPtr(P, IRB.getInt8PtrTy());
717     LoadInst *LI = IRB.CreateLoad(P);
718     Value *Inc = IRB.CreateAdd(LI, ConstantInt::get(IRB.getInt8Ty(), 1));
719     StoreInst *SI = IRB.CreateStore(Inc, P);
720     SetNoSanitizeMetadata(LI);
721     SetNoSanitizeMetadata(SI);
722   }
723 }
724 
725 char SanitizerCoverageModule::ID = 0;
726 INITIALIZE_PASS_BEGIN(SanitizerCoverageModule, "sancov",
727                       "SanitizerCoverage: TODO."
728                       "ModulePass",
729                       false, false)
730 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
731 INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)
732 INITIALIZE_PASS_END(SanitizerCoverageModule, "sancov",
733                     "SanitizerCoverage: TODO."
734                     "ModulePass",
735                     false, false)
736 ModulePass *llvm::createSanitizerCoverageModulePass(
737     const SanitizerCoverageOptions &Options) {
738   return new SanitizerCoverageModule(Options);
739 }
740