contrib/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp

   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   StringRef 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 CreateFunctionGuardArray(size_t NumGuards, Function &F);
 211   void SetNoSanitizeMetadata(Instruction *I);
 212   void InjectCoverageAtBlock(Function &F, BasicBlock &BB, size_t Idx,
 213                              bool UseCalls);
 214   unsigned NumberOfInstrumentedBlocks() {
 215     return SanCovFunction->getNumUses() +
 216            SanCovWithCheckFunction->getNumUses() + SanCovTraceBB->getNumUses() +
 217            SanCovTraceEnter->getNumUses();
 218   }
 219   Function *SanCovFunction;
 220   Function *SanCovWithCheckFunction;
 221   Function *SanCovIndirCallFunction, *SanCovTracePCIndir;
 222   Function *SanCovTraceEnter, *SanCovTraceBB, *SanCovTracePC, *SanCovTracePCGuard;
 223   Function *SanCovTraceCmpFunction[4];
 224   Function *SanCovTraceDivFunction[2];
 225   Function *SanCovTraceGepFunction;
 226   Function *SanCovTraceSwitchFunction;
 227   InlineAsm *EmptyAsm;
 228   Type *IntptrTy, *IntptrPtrTy, *Int64Ty, *Int64PtrTy, *Int32Ty, *Int32PtrTy;
 229   Module *CurModule;
 230   LLVMContext *C;
 231   const DataLayout *DL;
 232
 233   GlobalVariable *GuardArray;
 234   GlobalVariable *FunctionGuardArray;  // for trace-pc-guard.
 235   GlobalVariable *EightBitCounterArray;
 236   bool HasSancovGuardsSection;
 237
 238   SanitizerCoverageOptions Options;
 239 };
 240
 241 } // namespace
 242
 243 bool SanitizerCoverageModule::runOnModule(Module &M) {
 244   if (Options.CoverageType == SanitizerCoverageOptions::SCK_None)
 245     return false;
 246   C = &(M.getContext());
 247   DL = &M.getDataLayout();
 248   CurModule = &M;
 249   HasSancovGuardsSection = false;
 250   IntptrTy = Type::getIntNTy(*C, DL->getPointerSizeInBits());
 251   IntptrPtrTy = PointerType::getUnqual(IntptrTy);
 252   Type *VoidTy = Type::getVoidTy(*C);
 253   IRBuilder<> IRB(*C);
 254   Type *Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
 255   Int64PtrTy = PointerType::getUnqual(IRB.getInt64Ty());
 256   Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
 257   Int64Ty = IRB.getInt64Ty();
 258   Int32Ty = IRB.getInt32Ty();
 259
 260   SanCovFunction = checkSanitizerInterfaceFunction(
 261       M.getOrInsertFunction(SanCovName, VoidTy, Int32PtrTy, nullptr));
 262   SanCovWithCheckFunction = checkSanitizerInterfaceFunction(
 263       M.getOrInsertFunction(SanCovWithCheckName, VoidTy, Int32PtrTy, nullptr));
 264   SanCovTracePCIndir = checkSanitizerInterfaceFunction(
 265       M.getOrInsertFunction(SanCovTracePCIndirName, VoidTy, IntptrTy, nullptr));
 266   SanCovIndirCallFunction =
 267       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 268           SanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr));
 269   SanCovTraceCmpFunction[0] =
 270       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 271           SanCovTraceCmp1, VoidTy, IRB.getInt8Ty(), IRB.getInt8Ty(), nullptr));
 272   SanCovTraceCmpFunction[1] = checkSanitizerInterfaceFunction(
 273       M.getOrInsertFunction(SanCovTraceCmp2, VoidTy, IRB.getInt16Ty(),
 274                             IRB.getInt16Ty(), nullptr));
 275   SanCovTraceCmpFunction[2] = checkSanitizerInterfaceFunction(
 276       M.getOrInsertFunction(SanCovTraceCmp4, VoidTy, IRB.getInt32Ty(),
 277                             IRB.getInt32Ty(), nullptr));
 278   SanCovTraceCmpFunction[3] =
 279       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 280           SanCovTraceCmp8, VoidTy, Int64Ty, Int64Ty, nullptr));
 281
 282   SanCovTraceDivFunction[0] =
 283       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 284           SanCovTraceDiv4, VoidTy, IRB.getInt32Ty(), nullptr));
 285   SanCovTraceDivFunction[1] =
 286       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 287           SanCovTraceDiv8, VoidTy, Int64Ty, nullptr));
 288   SanCovTraceGepFunction =
 289       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 290           SanCovTraceGep, VoidTy, IntptrTy, nullptr));
 291   SanCovTraceSwitchFunction =
 292       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 293           SanCovTraceSwitchName, VoidTy, Int64Ty, Int64PtrTy, nullptr));
 294
 295   // We insert an empty inline asm after cov callbacks to avoid callback merge.
 296   EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
 297                             StringRef(""), StringRef(""),
 298                             /*hasSideEffects=*/true);
 299
 300   SanCovTracePC = checkSanitizerInterfaceFunction(
 301       M.getOrInsertFunction(SanCovTracePCName, VoidTy, nullptr));
 302   SanCovTracePCGuard = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 303       SanCovTracePCGuardName, VoidTy, Int32PtrTy, nullptr));
 304   SanCovTraceEnter = checkSanitizerInterfaceFunction(
 305       M.getOrInsertFunction(SanCovTraceEnterName, VoidTy, Int32PtrTy, nullptr));
 306   SanCovTraceBB = checkSanitizerInterfaceFunction(
 307       M.getOrInsertFunction(SanCovTraceBBName, VoidTy, Int32PtrTy, nullptr));
 308
 309   // At this point we create a dummy array of guards because we don't
 310   // know how many elements we will need.
 311   Type *Int32Ty = IRB.getInt32Ty();
 312   Type *Int8Ty = IRB.getInt8Ty();
 313
 314   if (!Options.TracePCGuard)
 315     GuardArray =
 316         new GlobalVariable(M, Int32Ty, false, GlobalValue::ExternalLinkage,
 317                            nullptr, "__sancov_gen_cov_tmp");
 318   if (Options.Use8bitCounters)
 319     EightBitCounterArray =
 320         new GlobalVariable(M, Int8Ty, false, GlobalVariable::ExternalLinkage,
 321                            nullptr, "__sancov_gen_cov_tmp");
 322
 323   for (auto &F : M)
 324     runOnFunction(F);
 325
 326   auto N = NumberOfInstrumentedBlocks();
 327
 328   GlobalVariable *RealGuardArray = nullptr;
 329   if (!Options.TracePCGuard) {
 330     // Now we know how many elements we need. Create an array of guards
 331     // with one extra element at the beginning for the size.
 332     Type *Int32ArrayNTy = ArrayType::get(Int32Ty, N + 1);
 333     RealGuardArray = new GlobalVariable(
 334         M, Int32ArrayNTy, false, GlobalValue::PrivateLinkage,
 335         Constant::getNullValue(Int32ArrayNTy), "__sancov_gen_cov");
 336
 337     // Replace the dummy array with the real one.
 338     GuardArray->replaceAllUsesWith(
 339         IRB.CreatePointerCast(RealGuardArray, Int32PtrTy));
 340     GuardArray->eraseFromParent();
 341   }
 342
 343   GlobalVariable *RealEightBitCounterArray;
 344   if (Options.Use8bitCounters) {
 345     // Make sure the array is 16-aligned.
 346     static const int CounterAlignment = 16;
 347     Type *Int8ArrayNTy = ArrayType::get(Int8Ty, alignTo(N, CounterAlignment));
 348     RealEightBitCounterArray = new GlobalVariable(
 349         M, Int8ArrayNTy, false, GlobalValue::PrivateLinkage,
 350         Constant::getNullValue(Int8ArrayNTy), "__sancov_gen_cov_counter");
 351     RealEightBitCounterArray->setAlignment(CounterAlignment);
 352     EightBitCounterArray->replaceAllUsesWith(
 353         IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy));
 354     EightBitCounterArray->eraseFromParent();
 355   }
 356
 357   // Create variable for module (compilation unit) name
 358   Constant *ModNameStrConst =
 359       ConstantDataArray::getString(M.getContext(), M.getName(), true);
 360   GlobalVariable *ModuleName = new GlobalVariable(
 361       M, ModNameStrConst->getType(), true, GlobalValue::PrivateLinkage,
 362       ModNameStrConst, "__sancov_gen_modname");
 363   if (Options.TracePCGuard) {
 364     if (HasSancovGuardsSection) {
 365       Function *CtorFunc;
 366       std::string SectionName(SanCovTracePCGuardSection);
 367       GlobalVariable *Bounds[2];
 368       const char *Prefix[2] = {"__start_", "__stop_"};
 369       for (int i = 0; i < 2; i++) {
 370         Bounds[i] = new GlobalVariable(M, Int32PtrTy, false,
 371                                        GlobalVariable::ExternalLinkage, nullptr,
 372                                        Prefix[i] + SectionName);
 373         Bounds[i]->setVisibility(GlobalValue::HiddenVisibility);
 374       }
 375       std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
 376           M, SanCovModuleCtorName, SanCovTracePCGuardInitName,
 377           {Int32PtrTy, Int32PtrTy},
 378           {IRB.CreatePointerCast(Bounds[0], Int32PtrTy),
 379             IRB.CreatePointerCast(Bounds[1], Int32PtrTy)});
 380
 381       appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority);
 382     }
 383   } else if (!Options.TracePC) {
 384     Function *CtorFunc;
 385     std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
 386         M, SanCovModuleCtorName, SanCovModuleInitName,
 387         {Int32PtrTy, IntptrTy, Int8PtrTy, Int8PtrTy},
 388         {IRB.CreatePointerCast(RealGuardArray, Int32PtrTy),
 389          ConstantInt::get(IntptrTy, N),
 390          Options.Use8bitCounters
 391              ? IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy)
 392              : Constant::getNullValue(Int8PtrTy),
 393          IRB.CreatePointerCast(ModuleName, Int8PtrTy)});
 394
 395     appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority);
 396   }
 397
 398   return true;
 399 }
 400
 401 // True if block has successors and it dominates all of them.
 402 static bool isFullDominator(const BasicBlock *BB, const DominatorTree *DT) {
 403   if (succ_begin(BB) == succ_end(BB))
 404     return false;
 405
 406   for (const BasicBlock *SUCC : make_range(succ_begin(BB), succ_end(BB))) {
 407     if (!DT->dominates(BB, SUCC))
 408       return false;
 409   }
 410
 411   return true;
 412 }
 413
 414 // True if block has predecessors and it postdominates all of them.
 415 static bool isFullPostDominator(const BasicBlock *BB,
 416                                 const PostDominatorTree *PDT) {
 417   if (pred_begin(BB) == pred_end(BB))
 418     return false;
 419
 420   for (const BasicBlock *PRED : make_range(pred_begin(BB), pred_end(BB))) {
 421     if (!PDT->dominates(BB, PRED))
 422       return false;
 423   }
 424
 425   return true;
 426 }
 427
 428 static bool shouldInstrumentBlock(const Function& F, const BasicBlock *BB, const DominatorTree *DT,
 429                                   const PostDominatorTree *PDT) {
 430   // Don't insert coverage for unreachable blocks: we will never call
 431   // __sanitizer_cov() for them, so counting them in
 432   // NumberOfInstrumentedBlocks() might complicate calculation of code coverage
 433   // percentage. Also, unreachable instructions frequently have no debug
 434   // locations.
 435   if (isa<UnreachableInst>(BB->getTerminator()))
 436     return false;
 437
 438   if (!ClPruneBlocks || &F.getEntryBlock() == BB)
 439     return true;
 440
 441   return !(isFullDominator(BB, DT) || isFullPostDominator(BB, PDT));
 442 }
 443
 444 bool SanitizerCoverageModule::runOnFunction(Function &F) {
 445   if (F.empty())
 446     return false;
 447   if (F.getName().find(".module_ctor") != std::string::npos)
 448     return false; // Should not instrument sanitizer init functions.
 449   if (F.getName().startswith("__sanitizer_"))
 450     return false;  // Don't instrument __sanitizer_* callbacks.
 451   // Don't instrument MSVC CRT configuration helpers. They may run before normal
 452   // initialization.
 453   if (F.getName() == "__local_stdio_printf_options" ||
 454       F.getName() == "__local_stdio_scanf_options")
 455     return false;
 456   // Don't instrument functions using SEH for now. Splitting basic blocks like
 457   // we do for coverage breaks WinEHPrepare.
 458   // FIXME: Remove this when SEH no longer uses landingpad pattern matching.
 459   if (F.hasPersonalityFn() &&
 460       isAsynchronousEHPersonality(classifyEHPersonality(F.getPersonalityFn())))
 461     return false;
 462   if (Options.CoverageType >= SanitizerCoverageOptions::SCK_Edge)
 463     SplitAllCriticalEdges(F);
 464   SmallVector<Instruction *, 8> IndirCalls;
 465   SmallVector<BasicBlock *, 16> BlocksToInstrument;
 466   SmallVector<Instruction *, 8> CmpTraceTargets;
 467   SmallVector<Instruction *, 8> SwitchTraceTargets;
 468   SmallVector<BinaryOperator *, 8> DivTraceTargets;
 469   SmallVector<GetElementPtrInst *, 8> GepTraceTargets;
 470
 471   const DominatorTree *DT =
 472       &getAnalysis<DominatorTreeWrapperPass>(F).getDomTree();
 473   const PostDominatorTree *PDT =
 474       &getAnalysis<PostDominatorTreeWrapperPass>(F).getPostDomTree();
 475
 476   for (auto &BB : F) {
 477     if (shouldInstrumentBlock(F, &BB, DT, PDT))
 478       BlocksToInstrument.push_back(&BB);
 479     for (auto &Inst : BB) {
 480       if (Options.IndirectCalls) {
 481         CallSite CS(&Inst);
 482         if (CS && !CS.getCalledFunction())
 483           IndirCalls.push_back(&Inst);
 484       }
 485       if (Options.TraceCmp) {
 486         if (isa<ICmpInst>(&Inst))
 487           CmpTraceTargets.push_back(&Inst);
 488         if (isa<SwitchInst>(&Inst))
 489           SwitchTraceTargets.push_back(&Inst);
 490       }
 491       if (Options.TraceDiv)
 492         if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&Inst))
 493           if (BO->getOpcode() == Instruction::SDiv ||
 494               BO->getOpcode() == Instruction::UDiv)
 495             DivTraceTargets.push_back(BO);
 496       if (Options.TraceGep)
 497         if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(&Inst))
 498           GepTraceTargets.push_back(GEP);
 499    }
 500   }
 501
 502   InjectCoverage(F, BlocksToInstrument);
 503   InjectCoverageForIndirectCalls(F, IndirCalls);
 504   InjectTraceForCmp(F, CmpTraceTargets);
 505   InjectTraceForSwitch(F, SwitchTraceTargets);
 506   InjectTraceForDiv(F, DivTraceTargets);
 507   InjectTraceForGep(F, GepTraceTargets);
 508   return true;
 509 }
 510 void SanitizerCoverageModule::CreateFunctionGuardArray(size_t NumGuards,
 511                                                        Function &F) {
 512   if (!Options.TracePCGuard) return;
 513   HasSancovGuardsSection = true;
 514   ArrayType *ArrayOfInt32Ty = ArrayType::get(Int32Ty, NumGuards);
 515   FunctionGuardArray = new GlobalVariable(
 516       *CurModule, ArrayOfInt32Ty, false, GlobalVariable::PrivateLinkage,
 517       Constant::getNullValue(ArrayOfInt32Ty), "__sancov_gen_");
 518   if (auto Comdat = F.getComdat())
 519     FunctionGuardArray->setComdat(Comdat);
 520   FunctionGuardArray->setSection(SanCovTracePCGuardSection);
 521 }
 522
 523 bool SanitizerCoverageModule::InjectCoverage(Function &F,
 524                                              ArrayRef<BasicBlock *> AllBlocks) {
 525   if (AllBlocks.empty()) return false;
 526   switch (Options.CoverageType) {
 527   case SanitizerCoverageOptions::SCK_None:
 528     return false;
 529   case SanitizerCoverageOptions::SCK_Function:
 530     CreateFunctionGuardArray(1, F);
 531     InjectCoverageAtBlock(F, F.getEntryBlock(), 0, false);
 532     return true;
 533   default: {
 534     bool UseCalls = ClCoverageBlockThreshold < AllBlocks.size();
 535     CreateFunctionGuardArray(AllBlocks.size(), F);
 536     for (size_t i = 0, N = AllBlocks.size(); i < N; i++)
 537       InjectCoverageAtBlock(F, *AllBlocks[i], i, UseCalls);
 538     return true;
 539   }
 540   }
 541 }
 542
 543 // On every indirect call we call a run-time function
 544 // __sanitizer_cov_indir_call* with two parameters:
 545 //   - callee address,
 546 //   - global cache array that contains CacheSize pointers (zero-initialized).
 547 //     The cache is used to speed up recording the caller-callee pairs.
 548 // The address of the caller is passed implicitly via caller PC.
 549 // CacheSize is encoded in the name of the run-time function.
 550 void SanitizerCoverageModule::InjectCoverageForIndirectCalls(
 551     Function &F, ArrayRef<Instruction *> IndirCalls) {
 552   if (IndirCalls.empty())
 553     return;
 554   const int CacheSize = 16;
 555   const int CacheAlignment = 64; // Align for better performance.
 556   Type *Ty = ArrayType::get(IntptrTy, CacheSize);
 557   for (auto I : IndirCalls) {
 558     IRBuilder<> IRB(I);
 559     CallSite CS(I);
 560     Value *Callee = CS.getCalledValue();
 561     if (isa<InlineAsm>(Callee))
 562       continue;
 563     GlobalVariable *CalleeCache = new GlobalVariable(
 564         *F.getParent(), Ty, false, GlobalValue::PrivateLinkage,
 565         Constant::getNullValue(Ty), "__sancov_gen_callee_cache");
 566     CalleeCache->setAlignment(CacheAlignment);
 567     if (Options.TracePC || Options.TracePCGuard)
 568       IRB.CreateCall(SanCovTracePCIndir,
 569                      IRB.CreatePointerCast(Callee, IntptrTy));
 570     else
 571       IRB.CreateCall(SanCovIndirCallFunction,
 572                      {IRB.CreatePointerCast(Callee, IntptrTy),
 573                       IRB.CreatePointerCast(CalleeCache, IntptrTy)});
 574   }
 575 }
 576
 577 // For every switch statement we insert a call:
 578 // __sanitizer_cov_trace_switch(CondValue,
 579 //      {NumCases, ValueSizeInBits, Case0Value, Case1Value, Case2Value, ... })
 580
 581 void SanitizerCoverageModule::InjectTraceForSwitch(
 582     Function &, ArrayRef<Instruction *> SwitchTraceTargets) {
 583   for (auto I : SwitchTraceTargets) {
 584     if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
 585       IRBuilder<> IRB(I);
 586       SmallVector<Constant *, 16> Initializers;
 587       Value *Cond = SI->getCondition();
 588       if (Cond->getType()->getScalarSizeInBits() >
 589           Int64Ty->getScalarSizeInBits())
 590         continue;
 591       Initializers.push_back(ConstantInt::get(Int64Ty, SI->getNumCases()));
 592       Initializers.push_back(
 593           ConstantInt::get(Int64Ty, Cond->getType()->getScalarSizeInBits()));
 594       if (Cond->getType()->getScalarSizeInBits() <
 595           Int64Ty->getScalarSizeInBits())
 596         Cond = IRB.CreateIntCast(Cond, Int64Ty, false);
 597       for (auto It : SI->cases()) {
 598         Constant *C = It.getCaseValue();
 599         if (C->getType()->getScalarSizeInBits() <
 600             Int64Ty->getScalarSizeInBits())
 601           C = ConstantExpr::getCast(CastInst::ZExt, It.getCaseValue(), Int64Ty);
 602         Initializers.push_back(C);
 603       }
 604       std::sort(Initializers.begin() + 2, Initializers.end(),
 605                 [](const Constant *A, const Constant *B) {
 606                   return cast<ConstantInt>(A)->getLimitedValue() <
 607                          cast<ConstantInt>(B)->getLimitedValue();
 608                 });
 609       ArrayType *ArrayOfInt64Ty = ArrayType::get(Int64Ty, Initializers.size());
 610       GlobalVariable *GV = new GlobalVariable(
 611           *CurModule, ArrayOfInt64Ty, false, GlobalVariable::InternalLinkage,
 612           ConstantArray::get(ArrayOfInt64Ty, Initializers),
 613           "__sancov_gen_cov_switch_values");
 614       IRB.CreateCall(SanCovTraceSwitchFunction,
 615                      {Cond, IRB.CreatePointerCast(GV, Int64PtrTy)});
 616     }
 617   }
 618 }
 619
 620 void SanitizerCoverageModule::InjectTraceForDiv(
 621     Function &, ArrayRef<BinaryOperator *> DivTraceTargets) {
 622   for (auto BO : DivTraceTargets) {
 623     IRBuilder<> IRB(BO);
 624     Value *A1 = BO->getOperand(1);
 625     if (isa<ConstantInt>(A1)) continue;
 626     if (!A1->getType()->isIntegerTy())
 627       continue;
 628     uint64_t TypeSize = DL->getTypeStoreSizeInBits(A1->getType());
 629     int CallbackIdx = TypeSize == 32 ? 0 :
 630         TypeSize == 64 ? 1 : -1;
 631     if (CallbackIdx < 0) continue;
 632     auto Ty = Type::getIntNTy(*C, TypeSize);
 633     IRB.CreateCall(SanCovTraceDivFunction[CallbackIdx],
 634                    {IRB.CreateIntCast(A1, Ty, true)});
 635   }
 636 }
 637
 638 void SanitizerCoverageModule::InjectTraceForGep(
 639     Function &, ArrayRef<GetElementPtrInst *> GepTraceTargets) {
 640   for (auto GEP : GepTraceTargets) {
 641     IRBuilder<> IRB(GEP);
 642     for (auto I = GEP->idx_begin(); I != GEP->idx_end(); ++I)
 643       if (!isa<ConstantInt>(*I) && (*I)->getType()->isIntegerTy())
 644         IRB.CreateCall(SanCovTraceGepFunction,
 645                        {IRB.CreateIntCast(*I, IntptrTy, true)});
 646   }
 647 }
 648
 649 void SanitizerCoverageModule::InjectTraceForCmp(
 650     Function &, ArrayRef<Instruction *> CmpTraceTargets) {
 651   for (auto I : CmpTraceTargets) {
 652     if (ICmpInst *ICMP = dyn_cast<ICmpInst>(I)) {
 653       IRBuilder<> IRB(ICMP);
 654       Value *A0 = ICMP->getOperand(0);
 655       Value *A1 = ICMP->getOperand(1);
 656       if (!A0->getType()->isIntegerTy())
 657         continue;
 658       uint64_t TypeSize = DL->getTypeStoreSizeInBits(A0->getType());
 659       int CallbackIdx = TypeSize == 8 ? 0 :
 660                         TypeSize == 16 ? 1 :
 661                         TypeSize == 32 ? 2 :
 662                         TypeSize == 64 ? 3 : -1;
 663       if (CallbackIdx < 0) continue;
 664       // __sanitizer_cov_trace_cmp((type_size << 32) | predicate, A0, A1);
 665       auto Ty = Type::getIntNTy(*C, TypeSize);
 666       IRB.CreateCall(
 667           SanCovTraceCmpFunction[CallbackIdx],
 668           {IRB.CreateIntCast(A0, Ty, true), IRB.CreateIntCast(A1, Ty, true)});
 669     }
 670   }
 671 }
 672
 673 void SanitizerCoverageModule::SetNoSanitizeMetadata(Instruction *I) {
 674   I->setMetadata(I->getModule()->getMDKindID("nosanitize"),
 675                  MDNode::get(*C, None));
 676 }
 677
 678 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
 679                                                     size_t Idx, bool UseCalls) {
 680   BasicBlock::iterator IP = BB.getFirstInsertionPt();
 681   bool IsEntryBB = &BB == &F.getEntryBlock();
 682   DebugLoc EntryLoc;
 683   if (IsEntryBB) {
 684     if (auto SP = F.getSubprogram())
 685       EntryLoc = DebugLoc::get(SP->getScopeLine(), 0, SP);
 686     // Keep static allocas and llvm.localescape calls in the entry block.  Even
 687     // if we aren't splitting the block, it's nice for allocas to be before
 688     // calls.
 689     IP = PrepareToSplitEntryBlock(BB, IP);
 690   } else {
 691     EntryLoc = IP->getDebugLoc();
 692   }
 693
 694   IRBuilder<> IRB(&*IP);
 695   IRB.SetCurrentDebugLocation(EntryLoc);
 696   if (Options.TracePC) {
 697     IRB.CreateCall(SanCovTracePC); // gets the PC using GET_CALLER_PC.
 698     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
 699   } else if (Options.TracePCGuard) {
 700     auto GuardPtr = IRB.CreateIntToPtr(
 701         IRB.CreateAdd(IRB.CreatePointerCast(FunctionGuardArray, IntptrTy),
 702                       ConstantInt::get(IntptrTy, Idx * 4)),
 703         Int32PtrTy);
 704     if (!UseCalls) {
 705       auto GuardLoad = IRB.CreateLoad(GuardPtr);
 706       GuardLoad->setAtomic(AtomicOrdering::Monotonic);
 707       GuardLoad->setAlignment(8);
 708       SetNoSanitizeMetadata(GuardLoad);  // Don't instrument with e.g. asan.
 709       auto Cmp = IRB.CreateICmpNE(
 710           GuardLoad, Constant::getNullValue(GuardLoad->getType()));
 711       auto Ins = SplitBlockAndInsertIfThen(
 712           Cmp, &*IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
 713       IRB.SetInsertPoint(Ins);
 714       IRB.SetCurrentDebugLocation(EntryLoc);
 715     }
 716     IRB.CreateCall(SanCovTracePCGuard, GuardPtr);
 717     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
 718   } else {
 719     Value *GuardP = IRB.CreateAdd(
 720         IRB.CreatePointerCast(GuardArray, IntptrTy),
 721         ConstantInt::get(IntptrTy, (1 + NumberOfInstrumentedBlocks()) * 4));
 722     GuardP = IRB.CreateIntToPtr(GuardP, Int32PtrTy);
 723     if (Options.TraceBB) {
 724       IRB.CreateCall(IsEntryBB ? SanCovTraceEnter : SanCovTraceBB, GuardP);
 725     } else if (UseCalls) {
 726       IRB.CreateCall(SanCovWithCheckFunction, GuardP);
 727     } else {
 728       LoadInst *Load = IRB.CreateLoad(GuardP);
 729       Load->setAtomic(AtomicOrdering::Monotonic);
 730       Load->setAlignment(4);
 731       SetNoSanitizeMetadata(Load);
 732       Value *Cmp =
 733           IRB.CreateICmpSGE(Constant::getNullValue(Load->getType()), Load);
 734       Instruction *Ins = SplitBlockAndInsertIfThen(
 735           Cmp, &*IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
 736       IRB.SetInsertPoint(Ins);
 737       IRB.SetCurrentDebugLocation(EntryLoc);
 738       // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC.
 739       IRB.CreateCall(SanCovFunction, GuardP);
 740       IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
 741     }
 742   }
 743
 744   if (Options.Use8bitCounters) {
 745     IRB.SetInsertPoint(&*IP);
 746     Value *P = IRB.CreateAdd(
 747         IRB.CreatePointerCast(EightBitCounterArray, IntptrTy),
 748         ConstantInt::get(IntptrTy, NumberOfInstrumentedBlocks() - 1));
 749     P = IRB.CreateIntToPtr(P, IRB.getInt8PtrTy());
 750     LoadInst *LI = IRB.CreateLoad(P);
 751     Value *Inc = IRB.CreateAdd(LI, ConstantInt::get(IRB.getInt8Ty(), 1));
 752     StoreInst *SI = IRB.CreateStore(Inc, P);
 753     SetNoSanitizeMetadata(LI);
 754     SetNoSanitizeMetadata(SI);
 755   }
 756 }
 757
 758 char SanitizerCoverageModule::ID = 0;
 759 INITIALIZE_PASS_BEGIN(SanitizerCoverageModule, "sancov",
 760                       "SanitizerCoverage: TODO."
 761                       "ModulePass",
 762                       false, false)
 763 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
 764 INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)
 765 INITIALIZE_PASS_END(SanitizerCoverageModule, "sancov",
 766                     "SanitizerCoverage: TODO."
 767                     "ModulePass",
 768                     false, false)
 769 ModulePass *llvm::createSanitizerCoverageModulePass(
 770     const SanitizerCoverageOptions &Options) {
 771   return new SanitizerCoverageModule(Options);
 772 }