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
55using namespace llvm;
56
57#define DEBUG_TYPE "sancov"
58
59static const char *const SanCovModuleInitName = "__sanitizer_cov_module_init";
60static const char *const SanCovName = "__sanitizer_cov";
61static const char *const SanCovWithCheckName = "__sanitizer_cov_with_check";
62static const char *const SanCovIndirCallName = "__sanitizer_cov_indir_call16";
63static const char *const SanCovTracePCIndirName =
64    "__sanitizer_cov_trace_pc_indir";
65static const char *const SanCovTraceEnterName =
66    "__sanitizer_cov_trace_func_enter";
67static const char *const SanCovTraceBBName =
68    "__sanitizer_cov_trace_basic_block";
69static const char *const SanCovTracePCName = "__sanitizer_cov_trace_pc";
70static const char *const SanCovTraceCmpName = "__sanitizer_cov_trace_cmp";
71static const char *const SanCovTraceSwitchName = "__sanitizer_cov_trace_switch";
72static const char *const SanCovModuleCtorName = "sancov.module_ctor";
73static const uint64_t SanCtorAndDtorPriority = 2;
74
75static cl::opt<int> ClCoverageLevel(
76    "sanitizer-coverage-level",
77    cl::desc("Sanitizer Coverage. 0: none, 1: entry block, 2: all blocks, "
78             "3: all blocks and critical edges, "
79             "4: above plus indirect calls"),
80    cl::Hidden, cl::init(0));
81
82static cl::opt<unsigned> ClCoverageBlockThreshold(
83    "sanitizer-coverage-block-threshold",
84    cl::desc("Use a callback with a guard check inside it if there are"
85             " more than this number of blocks."),
86    cl::Hidden, cl::init(500));
87
88static cl::opt<bool>
89    ClExperimentalTracing("sanitizer-coverage-experimental-tracing",
90                          cl::desc("Experimental basic-block tracing: insert "
91                                   "callbacks at every basic block"),
92                          cl::Hidden, cl::init(false));
93
94static cl::opt<bool> ClExperimentalTracePC("sanitizer-coverage-trace-pc",
95                                           cl::desc("Experimental pc tracing"),
96                                           cl::Hidden, cl::init(false));
97
98static cl::opt<bool>
99    ClExperimentalCMPTracing("sanitizer-coverage-experimental-trace-compares",
100                             cl::desc("Experimental tracing of CMP and similar "
101                                      "instructions"),
102                             cl::Hidden, cl::init(false));
103
104static cl::opt<bool>
105    ClPruneBlocks("sanitizer-coverage-prune-blocks",
106                  cl::desc("Reduce the number of instrumented blocks"),
107                  cl::Hidden, cl::init(true));
108
109// Experimental 8-bit counters used as an additional search heuristic during
110// coverage-guided fuzzing.
111// The counters are not thread-friendly:
112//   - contention on these counters may cause significant slowdown;
113//   - the counter updates are racy and the results may be inaccurate.
114// They are also inaccurate due to 8-bit integer overflow.
115static cl::opt<bool> ClUse8bitCounters("sanitizer-coverage-8bit-counters",
116                                       cl::desc("Experimental 8-bit counters"),
117                                       cl::Hidden, cl::init(false));
118
119namespace {
120
121SanitizerCoverageOptions getOptions(int LegacyCoverageLevel) {
122  SanitizerCoverageOptions Res;
123  switch (LegacyCoverageLevel) {
124  case 0:
125    Res.CoverageType = SanitizerCoverageOptions::SCK_None;
126    break;
127  case 1:
128    Res.CoverageType = SanitizerCoverageOptions::SCK_Function;
129    break;
130  case 2:
131    Res.CoverageType = SanitizerCoverageOptions::SCK_BB;
132    break;
133  case 3:
134    Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
135    break;
136  case 4:
137    Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
138    Res.IndirectCalls = true;
139    break;
140  }
141  return Res;
142}
143
144SanitizerCoverageOptions OverrideFromCL(SanitizerCoverageOptions Options) {
145  // Sets CoverageType and IndirectCalls.
146  SanitizerCoverageOptions CLOpts = getOptions(ClCoverageLevel);
147  Options.CoverageType = std::max(Options.CoverageType, CLOpts.CoverageType);
148  Options.IndirectCalls |= CLOpts.IndirectCalls;
149  Options.TraceBB |= ClExperimentalTracing;
150  Options.TraceCmp |= ClExperimentalCMPTracing;
151  Options.Use8bitCounters |= ClUse8bitCounters;
152  Options.TracePC |= ClExperimentalTracePC;
153  return Options;
154}
155
156class SanitizerCoverageModule : public ModulePass {
157public:
158  SanitizerCoverageModule(
159      const SanitizerCoverageOptions &Options = SanitizerCoverageOptions())
160      : ModulePass(ID), Options(OverrideFromCL(Options)) {
161    initializeSanitizerCoverageModulePass(*PassRegistry::getPassRegistry());
162  }
163  bool runOnModule(Module &M) override;
164  bool runOnFunction(Function &F);
165  static char ID; // Pass identification, replacement for typeid
166  const char *getPassName() const override { return "SanitizerCoverageModule"; }
167
168  void getAnalysisUsage(AnalysisUsage &AU) const override {
169    AU.addRequired<DominatorTreeWrapperPass>();
170    AU.addRequired<PostDominatorTreeWrapperPass>();
171  }
172
173private:
174  void InjectCoverageForIndirectCalls(Function &F,
175                                      ArrayRef<Instruction *> IndirCalls);
176  void InjectTraceForCmp(Function &F, ArrayRef<Instruction *> CmpTraceTargets);
177  void InjectTraceForSwitch(Function &F,
178                            ArrayRef<Instruction *> SwitchTraceTargets);
179  bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks);
180  void SetNoSanitizeMetadata(Instruction *I);
181  void InjectCoverageAtBlock(Function &F, BasicBlock &BB, bool UseCalls);
182  unsigned NumberOfInstrumentedBlocks() {
183    return SanCovFunction->getNumUses() +
184           SanCovWithCheckFunction->getNumUses() + SanCovTraceBB->getNumUses() +
185           SanCovTraceEnter->getNumUses();
186  }
187  Function *SanCovFunction;
188  Function *SanCovWithCheckFunction;
189  Function *SanCovIndirCallFunction, *SanCovTracePCIndir;
190  Function *SanCovTraceEnter, *SanCovTraceBB, *SanCovTracePC;
191  Function *SanCovTraceCmpFunction;
192  Function *SanCovTraceSwitchFunction;
193  InlineAsm *EmptyAsm;
194  Type *IntptrTy, *Int64Ty, *Int64PtrTy;
195  Module *CurModule;
196  LLVMContext *C;
197  const DataLayout *DL;
198
199  GlobalVariable *GuardArray;
200  GlobalVariable *EightBitCounterArray;
201
202  SanitizerCoverageOptions Options;
203};
204
205} // namespace
206
207bool SanitizerCoverageModule::runOnModule(Module &M) {
208  if (Options.CoverageType == SanitizerCoverageOptions::SCK_None)
209    return false;
210  C = &(M.getContext());
211  DL = &M.getDataLayout();
212  CurModule = &M;
213  IntptrTy = Type::getIntNTy(*C, DL->getPointerSizeInBits());
214  Type *VoidTy = Type::getVoidTy(*C);
215  IRBuilder<> IRB(*C);
216  Type *Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
217  Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
218  Int64PtrTy = PointerType::getUnqual(IRB.getInt64Ty());
219  Int64Ty = IRB.getInt64Ty();
220
221  SanCovFunction = checkSanitizerInterfaceFunction(
222      M.getOrInsertFunction(SanCovName, VoidTy, Int32PtrTy, nullptr));
223  SanCovWithCheckFunction = checkSanitizerInterfaceFunction(
224      M.getOrInsertFunction(SanCovWithCheckName, VoidTy, Int32PtrTy, nullptr));
225  SanCovTracePCIndir = checkSanitizerInterfaceFunction(
226      M.getOrInsertFunction(SanCovTracePCIndirName, VoidTy, IntptrTy, nullptr));
227  SanCovIndirCallFunction =
228      checkSanitizerInterfaceFunction(M.getOrInsertFunction(
229          SanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr));
230  SanCovTraceCmpFunction =
231      checkSanitizerInterfaceFunction(M.getOrInsertFunction(
232          SanCovTraceCmpName, VoidTy, Int64Ty, Int64Ty, Int64Ty, nullptr));
233  SanCovTraceSwitchFunction =
234      checkSanitizerInterfaceFunction(M.getOrInsertFunction(
235          SanCovTraceSwitchName, VoidTy, Int64Ty, Int64PtrTy, nullptr));
236
237  // We insert an empty inline asm after cov callbacks to avoid callback merge.
238  EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
239                            StringRef(""), StringRef(""),
240                            /*hasSideEffects=*/true);
241
242  SanCovTracePC = checkSanitizerInterfaceFunction(
243      M.getOrInsertFunction(SanCovTracePCName, VoidTy, nullptr));
244  SanCovTraceEnter = checkSanitizerInterfaceFunction(
245      M.getOrInsertFunction(SanCovTraceEnterName, VoidTy, Int32PtrTy, nullptr));
246  SanCovTraceBB = checkSanitizerInterfaceFunction(
247      M.getOrInsertFunction(SanCovTraceBBName, VoidTy, Int32PtrTy, nullptr));
248
249  // At this point we create a dummy array of guards because we don't
250  // know how many elements we will need.
251  Type *Int32Ty = IRB.getInt32Ty();
252  Type *Int8Ty = IRB.getInt8Ty();
253
254  GuardArray =
255      new GlobalVariable(M, Int32Ty, false, GlobalValue::ExternalLinkage,
256                         nullptr, "__sancov_gen_cov_tmp");
257  if (Options.Use8bitCounters)
258    EightBitCounterArray =
259        new GlobalVariable(M, Int8Ty, false, GlobalVariable::ExternalLinkage,
260                           nullptr, "__sancov_gen_cov_tmp");
261
262  for (auto &F : M)
263    runOnFunction(F);
264
265  auto N = NumberOfInstrumentedBlocks();
266
267  // Now we know how many elements we need. Create an array of guards
268  // with one extra element at the beginning for the size.
269  Type *Int32ArrayNTy = ArrayType::get(Int32Ty, N + 1);
270  GlobalVariable *RealGuardArray = new GlobalVariable(
271      M, Int32ArrayNTy, false, GlobalValue::PrivateLinkage,
272      Constant::getNullValue(Int32ArrayNTy), "__sancov_gen_cov");
273
274  // Replace the dummy array with the real one.
275  GuardArray->replaceAllUsesWith(
276      IRB.CreatePointerCast(RealGuardArray, Int32PtrTy));
277  GuardArray->eraseFromParent();
278
279  GlobalVariable *RealEightBitCounterArray;
280  if (Options.Use8bitCounters) {
281    // Make sure the array is 16-aligned.
282    static const int CounterAlignment = 16;
283    Type *Int8ArrayNTy = ArrayType::get(Int8Ty, alignTo(N, CounterAlignment));
284    RealEightBitCounterArray = new GlobalVariable(
285        M, Int8ArrayNTy, false, GlobalValue::PrivateLinkage,
286        Constant::getNullValue(Int8ArrayNTy), "__sancov_gen_cov_counter");
287    RealEightBitCounterArray->setAlignment(CounterAlignment);
288    EightBitCounterArray->replaceAllUsesWith(
289        IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy));
290    EightBitCounterArray->eraseFromParent();
291  }
292
293  // Create variable for module (compilation unit) name
294  Constant *ModNameStrConst =
295      ConstantDataArray::getString(M.getContext(), M.getName(), true);
296  GlobalVariable *ModuleName =
297      new GlobalVariable(M, ModNameStrConst->getType(), true,
298                         GlobalValue::PrivateLinkage, ModNameStrConst);
299
300  if (!Options.TracePC) {
301    Function *CtorFunc;
302    std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
303        M, SanCovModuleCtorName, SanCovModuleInitName,
304        {Int32PtrTy, IntptrTy, Int8PtrTy, Int8PtrTy},
305        {IRB.CreatePointerCast(RealGuardArray, Int32PtrTy),
306         ConstantInt::get(IntptrTy, N),
307         Options.Use8bitCounters
308             ? IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy)
309             : Constant::getNullValue(Int8PtrTy),
310         IRB.CreatePointerCast(ModuleName, Int8PtrTy)});
311
312    appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority);
313  }
314
315  return true;
316}
317
318// True if block has successors and it dominates all of them.
319static bool isFullDominator(const BasicBlock *BB, const DominatorTree *DT) {
320  if (succ_begin(BB) == succ_end(BB))
321    return false;
322
323  for (const BasicBlock *SUCC : make_range(succ_begin(BB), succ_end(BB))) {
324    if (!DT->dominates(BB, SUCC))
325      return false;
326  }
327
328  return true;
329}
330
331// True if block has predecessors and it postdominates all of them.
332static bool isFullPostDominator(const BasicBlock *BB,
333                                const PostDominatorTree *PDT) {
334  if (pred_begin(BB) == pred_end(BB))
335    return false;
336
337  for (const BasicBlock *PRED : make_range(pred_begin(BB), pred_end(BB))) {
338    if (!PDT->dominates(BB, PRED))
339      return false;
340  }
341
342  return true;
343}
344
345static bool shouldInstrumentBlock(const Function& F, const BasicBlock *BB, const DominatorTree *DT,
346                                  const PostDominatorTree *PDT) {
347  if (!ClPruneBlocks || &F.getEntryBlock() == BB)
348    return true;
349
350  return !(isFullDominator(BB, DT) || isFullPostDominator(BB, PDT));
351}
352
353bool SanitizerCoverageModule::runOnFunction(Function &F) {
354  if (F.empty())
355    return false;
356  if (F.getName().find(".module_ctor") != std::string::npos)
357    return false; // Should not instrument sanitizer init functions.
358  // Don't instrument functions using SEH for now. Splitting basic blocks like
359  // we do for coverage breaks WinEHPrepare.
360  // FIXME: Remove this when SEH no longer uses landingpad pattern matching.
361  if (F.hasPersonalityFn() &&
362      isAsynchronousEHPersonality(classifyEHPersonality(F.getPersonalityFn())))
363    return false;
364  if (Options.CoverageType >= SanitizerCoverageOptions::SCK_Edge)
365    SplitAllCriticalEdges(F);
366  SmallVector<Instruction *, 8> IndirCalls;
367  SmallVector<BasicBlock *, 16> BlocksToInstrument;
368  SmallVector<Instruction *, 8> CmpTraceTargets;
369  SmallVector<Instruction *, 8> SwitchTraceTargets;
370
371  const DominatorTree *DT =
372      &getAnalysis<DominatorTreeWrapperPass>(F).getDomTree();
373  const PostDominatorTree *PDT =
374      &getAnalysis<PostDominatorTreeWrapperPass>(F).getPostDomTree();
375
376  for (auto &BB : F) {
377    if (shouldInstrumentBlock(F, &BB, DT, PDT))
378      BlocksToInstrument.push_back(&BB);
379    for (auto &Inst : BB) {
380      if (Options.IndirectCalls) {
381        CallSite CS(&Inst);
382        if (CS && !CS.getCalledFunction())
383          IndirCalls.push_back(&Inst);
384      }
385      if (Options.TraceCmp) {
386        if (isa<ICmpInst>(&Inst))
387          CmpTraceTargets.push_back(&Inst);
388        if (isa<SwitchInst>(&Inst))
389          SwitchTraceTargets.push_back(&Inst);
390      }
391    }
392  }
393
394  InjectCoverage(F, BlocksToInstrument);
395  InjectCoverageForIndirectCalls(F, IndirCalls);
396  InjectTraceForCmp(F, CmpTraceTargets);
397  InjectTraceForSwitch(F, SwitchTraceTargets);
398  return true;
399}
400
401bool SanitizerCoverageModule::InjectCoverage(Function &F,
402                                             ArrayRef<BasicBlock *> AllBlocks) {
403  switch (Options.CoverageType) {
404  case SanitizerCoverageOptions::SCK_None:
405    return false;
406  case SanitizerCoverageOptions::SCK_Function:
407    InjectCoverageAtBlock(F, F.getEntryBlock(), false);
408    return true;
409  default: {
410    bool UseCalls = ClCoverageBlockThreshold < AllBlocks.size();
411    for (auto BB : AllBlocks)
412      InjectCoverageAtBlock(F, *BB, UseCalls);
413    return true;
414  }
415  }
416}
417
418// On every indirect call we call a run-time function
419// __sanitizer_cov_indir_call* with two parameters:
420//   - callee address,
421//   - global cache array that contains CacheSize pointers (zero-initialized).
422//     The cache is used to speed up recording the caller-callee pairs.
423// The address of the caller is passed implicitly via caller PC.
424// CacheSize is encoded in the name of the run-time function.
425void SanitizerCoverageModule::InjectCoverageForIndirectCalls(
426    Function &F, ArrayRef<Instruction *> IndirCalls) {
427  if (IndirCalls.empty())
428    return;
429  const int CacheSize = 16;
430  const int CacheAlignment = 64; // Align for better performance.
431  Type *Ty = ArrayType::get(IntptrTy, CacheSize);
432  for (auto I : IndirCalls) {
433    IRBuilder<> IRB(I);
434    CallSite CS(I);
435    Value *Callee = CS.getCalledValue();
436    if (isa<InlineAsm>(Callee))
437      continue;
438    GlobalVariable *CalleeCache = new GlobalVariable(
439        *F.getParent(), Ty, false, GlobalValue::PrivateLinkage,
440        Constant::getNullValue(Ty), "__sancov_gen_callee_cache");
441    CalleeCache->setAlignment(CacheAlignment);
442    if (Options.TracePC)
443      IRB.CreateCall(SanCovTracePCIndir,
444                     IRB.CreatePointerCast(Callee, IntptrTy));
445    else
446      IRB.CreateCall(SanCovIndirCallFunction,
447                     {IRB.CreatePointerCast(Callee, IntptrTy),
448                      IRB.CreatePointerCast(CalleeCache, IntptrTy)});
449  }
450}
451
452// For every switch statement we insert a call:
453// __sanitizer_cov_trace_switch(CondValue,
454//      {NumCases, ValueSizeInBits, Case0Value, Case1Value, Case2Value, ... })
455
456void SanitizerCoverageModule::InjectTraceForSwitch(
457    Function &, ArrayRef<Instruction *> SwitchTraceTargets) {
458  for (auto I : SwitchTraceTargets) {
459    if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
460      IRBuilder<> IRB(I);
461      SmallVector<Constant *, 16> Initializers;
462      Value *Cond = SI->getCondition();
463      if (Cond->getType()->getScalarSizeInBits() >
464          Int64Ty->getScalarSizeInBits())
465        continue;
466      Initializers.push_back(ConstantInt::get(Int64Ty, SI->getNumCases()));
467      Initializers.push_back(
468          ConstantInt::get(Int64Ty, Cond->getType()->getScalarSizeInBits()));
469      if (Cond->getType()->getScalarSizeInBits() <
470          Int64Ty->getScalarSizeInBits())
471        Cond = IRB.CreateIntCast(Cond, Int64Ty, false);
472      for (auto It : SI->cases()) {
473        Constant *C = It.getCaseValue();
474        if (C->getType()->getScalarSizeInBits() <
475            Int64Ty->getScalarSizeInBits())
476          C = ConstantExpr::getCast(CastInst::ZExt, It.getCaseValue(), Int64Ty);
477        Initializers.push_back(C);
478      }
479      ArrayType *ArrayOfInt64Ty = ArrayType::get(Int64Ty, Initializers.size());
480      GlobalVariable *GV = new GlobalVariable(
481          *CurModule, ArrayOfInt64Ty, false, GlobalVariable::InternalLinkage,
482          ConstantArray::get(ArrayOfInt64Ty, Initializers),
483          "__sancov_gen_cov_switch_values");
484      IRB.CreateCall(SanCovTraceSwitchFunction,
485                     {Cond, IRB.CreatePointerCast(GV, Int64PtrTy)});
486    }
487  }
488}
489
490void SanitizerCoverageModule::InjectTraceForCmp(
491    Function &, ArrayRef<Instruction *> CmpTraceTargets) {
492  for (auto I : CmpTraceTargets) {
493    if (ICmpInst *ICMP = dyn_cast<ICmpInst>(I)) {
494      IRBuilder<> IRB(ICMP);
495      Value *A0 = ICMP->getOperand(0);
496      Value *A1 = ICMP->getOperand(1);
497      if (!A0->getType()->isIntegerTy())
498        continue;
499      uint64_t TypeSize = DL->getTypeStoreSizeInBits(A0->getType());
500      // __sanitizer_cov_trace_cmp((type_size << 32) | predicate, A0, A1);
501      IRB.CreateCall(
502          SanCovTraceCmpFunction,
503          {ConstantInt::get(Int64Ty, (TypeSize << 32) | ICMP->getPredicate()),
504           IRB.CreateIntCast(A0, Int64Ty, true),
505           IRB.CreateIntCast(A1, Int64Ty, true)});
506    }
507  }
508}
509
510void SanitizerCoverageModule::SetNoSanitizeMetadata(Instruction *I) {
511  I->setMetadata(I->getModule()->getMDKindID("nosanitize"),
512                 MDNode::get(*C, None));
513}
514
515void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
516                                                    bool UseCalls) {
517  // Don't insert coverage for unreachable blocks: we will never call
518  // __sanitizer_cov() for them, so counting them in
519  // NumberOfInstrumentedBlocks() might complicate calculation of code coverage
520  // percentage. Also, unreachable instructions frequently have no debug
521  // locations.
522  if (isa<UnreachableInst>(BB.getTerminator()))
523    return;
524  BasicBlock::iterator IP = BB.getFirstInsertionPt();
525
526  bool IsEntryBB = &BB == &F.getEntryBlock();
527  DebugLoc EntryLoc;
528  if (IsEntryBB) {
529    if (auto SP = F.getSubprogram())
530      EntryLoc = DebugLoc::get(SP->getScopeLine(), 0, SP);
531    // Keep static allocas and llvm.localescape calls in the entry block.  Even
532    // if we aren't splitting the block, it's nice for allocas to be before
533    // calls.
534    IP = PrepareToSplitEntryBlock(BB, IP);
535  } else {
536    EntryLoc = IP->getDebugLoc();
537  }
538
539  IRBuilder<> IRB(&*IP);
540  IRB.SetCurrentDebugLocation(EntryLoc);
541  Value *GuardP = IRB.CreateAdd(
542      IRB.CreatePointerCast(GuardArray, IntptrTy),
543      ConstantInt::get(IntptrTy, (1 + NumberOfInstrumentedBlocks()) * 4));
544  Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
545  GuardP = IRB.CreateIntToPtr(GuardP, Int32PtrTy);
546  if (Options.TracePC) {
547    IRB.CreateCall(SanCovTracePC); // gets the PC using GET_CALLER_PC.
548    IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
549  } else if (Options.TraceBB) {
550    IRB.CreateCall(IsEntryBB ? SanCovTraceEnter : SanCovTraceBB, GuardP);
551  } else if (UseCalls) {
552    IRB.CreateCall(SanCovWithCheckFunction, GuardP);
553  } else {
554    LoadInst *Load = IRB.CreateLoad(GuardP);
555    Load->setAtomic(AtomicOrdering::Monotonic);
556    Load->setAlignment(4);
557    SetNoSanitizeMetadata(Load);
558    Value *Cmp =
559        IRB.CreateICmpSGE(Constant::getNullValue(Load->getType()), Load);
560    Instruction *Ins = SplitBlockAndInsertIfThen(
561        Cmp, &*IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
562    IRB.SetInsertPoint(Ins);
563    IRB.SetCurrentDebugLocation(EntryLoc);
564    // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC.
565    IRB.CreateCall(SanCovFunction, GuardP);
566    IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
567  }
568
569  if (Options.Use8bitCounters) {
570    IRB.SetInsertPoint(&*IP);
571    Value *P = IRB.CreateAdd(
572        IRB.CreatePointerCast(EightBitCounterArray, IntptrTy),
573        ConstantInt::get(IntptrTy, NumberOfInstrumentedBlocks() - 1));
574    P = IRB.CreateIntToPtr(P, IRB.getInt8PtrTy());
575    LoadInst *LI = IRB.CreateLoad(P);
576    Value *Inc = IRB.CreateAdd(LI, ConstantInt::get(IRB.getInt8Ty(), 1));
577    StoreInst *SI = IRB.CreateStore(Inc, P);
578    SetNoSanitizeMetadata(LI);
579    SetNoSanitizeMetadata(SI);
580  }
581}
582
583char SanitizerCoverageModule::ID = 0;
584INITIALIZE_PASS_BEGIN(SanitizerCoverageModule, "sancov",
585                      "SanitizerCoverage: TODO."
586                      "ModulePass",
587                      false, false)
588INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
589INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)
590INITIALIZE_PASS_END(SanitizerCoverageModule, "sancov",
591                    "SanitizerCoverage: TODO."
592                    "ModulePass",
593                    false, false)
594ModulePass *llvm::createSanitizerCoverageModulePass(
595    const SanitizerCoverageOptions &Options) {
596  return new SanitizerCoverageModule(Options);
597}
598