lib/Transforms/Instrumentation/SanitizerCoverage.cpp

   1 //===-- SanitizerCoverage.cpp - coverage instrumentation for sanitizers ---===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // Coverage instrumentation done on LLVM IR level, works with Sanitizers.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/ADT/ArrayRef.h"
  14 #include "llvm/ADT/SmallVector.h"
  15 #include "llvm/Analysis/EHPersonalities.h"
  16 #include "llvm/Analysis/PostDominators.h"
  17 #include "llvm/IR/CFG.h"
  18 #include "llvm/IR/CallSite.h"
  19 #include "llvm/IR/Constant.h"
  20 #include "llvm/IR/DataLayout.h"
  21 #include "llvm/IR/DebugInfo.h"
  22 #include "llvm/IR/Dominators.h"
  23 #include "llvm/IR/Function.h"
  24 #include "llvm/IR/GlobalVariable.h"
  25 #include "llvm/IR/IRBuilder.h"
  26 #include "llvm/IR/InlineAsm.h"
  27 #include "llvm/IR/IntrinsicInst.h"
  28 #include "llvm/IR/Intrinsics.h"
  29 #include "llvm/IR/LLVMContext.h"
  30 #include "llvm/IR/MDBuilder.h"
  31 #include "llvm/IR/Mangler.h"
  32 #include "llvm/IR/Module.h"
  33 #include "llvm/IR/Type.h"
  34 #include "llvm/Support/CommandLine.h"
  35 #include "llvm/Support/Debug.h"
  36 #include "llvm/Support/raw_ostream.h"
  37 #include "llvm/Transforms/Instrumentation.h"
  38 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
  39 #include "llvm/Transforms/Utils/ModuleUtils.h"
  40
  41 using namespace llvm;
  42
  43 #define DEBUG_TYPE "sancov"
  44
  45 static const char *const SanCovTracePCIndirName =
  46     "__sanitizer_cov_trace_pc_indir";
  47 static const char *const SanCovTracePCName = "__sanitizer_cov_trace_pc";
  48 static const char *const SanCovTraceCmp1 = "__sanitizer_cov_trace_cmp1";
  49 static const char *const SanCovTraceCmp2 = "__sanitizer_cov_trace_cmp2";
  50 static const char *const SanCovTraceCmp4 = "__sanitizer_cov_trace_cmp4";
  51 static const char *const SanCovTraceCmp8 = "__sanitizer_cov_trace_cmp8";
  52 static const char *const SanCovTraceConstCmp1 =
  53     "__sanitizer_cov_trace_const_cmp1";
  54 static const char *const SanCovTraceConstCmp2 =
  55     "__sanitizer_cov_trace_const_cmp2";
  56 static const char *const SanCovTraceConstCmp4 =
  57     "__sanitizer_cov_trace_const_cmp4";
  58 static const char *const SanCovTraceConstCmp8 =
  59     "__sanitizer_cov_trace_const_cmp8";
  60 static const char *const SanCovTraceDiv4 = "__sanitizer_cov_trace_div4";
  61 static const char *const SanCovTraceDiv8 = "__sanitizer_cov_trace_div8";
  62 static const char *const SanCovTraceGep = "__sanitizer_cov_trace_gep";
  63 static const char *const SanCovTraceSwitchName = "__sanitizer_cov_trace_switch";
  64 static const char *const SanCovModuleCtorName = "sancov.module_ctor";
  65 static const uint64_t SanCtorAndDtorPriority = 2;
  66
  67 static const char *const SanCovTracePCGuardName =
  68     "__sanitizer_cov_trace_pc_guard";
  69 static const char *const SanCovTracePCGuardInitName =
  70     "__sanitizer_cov_trace_pc_guard_init";
  71 static const char *const SanCov8bitCountersInitName =
  72     "__sanitizer_cov_8bit_counters_init";
  73 static const char *const SanCovPCsInitName = "__sanitizer_cov_pcs_init";
  74
  75 static const char *const SanCovGuardsSectionName = "sancov_guards";
  76 static const char *const SanCovCountersSectionName = "sancov_cntrs";
  77 static const char *const SanCovPCsSectionName = "sancov_pcs";
  78
  79 static const char *const SanCovLowestStackName = "__sancov_lowest_stack";
  80
  81 static cl::opt<int> ClCoverageLevel(
  82     "sanitizer-coverage-level",
  83     cl::desc("Sanitizer Coverage. 0: none, 1: entry block, 2: all blocks, "
  84              "3: all blocks and critical edges"),
  85     cl::Hidden, cl::init(0));
  86
  87 static cl::opt<bool> ClTracePC("sanitizer-coverage-trace-pc",
  88                                cl::desc("Experimental pc tracing"), cl::Hidden,
  89                                cl::init(false));
  90
  91 static cl::opt<bool> ClTracePCGuard("sanitizer-coverage-trace-pc-guard",
  92                                     cl::desc("pc tracing with a guard"),
  93                                     cl::Hidden, cl::init(false));
  94
  95 // If true, we create a global variable that contains PCs of all instrumented
  96 // BBs, put this global into a named section, and pass this section's bounds
  97 // to __sanitizer_cov_pcs_init.
  98 // This way the coverage instrumentation does not need to acquire the PCs
  99 // at run-time. Works with trace-pc-guard and inline-8bit-counters.
 100 static cl::opt<bool> ClCreatePCTable("sanitizer-coverage-pc-table",
 101                                      cl::desc("create a static PC table"),
 102                                      cl::Hidden, cl::init(false));
 103
 104 static cl::opt<bool>
 105     ClInline8bitCounters("sanitizer-coverage-inline-8bit-counters",
 106                          cl::desc("increments 8-bit counter for every edge"),
 107                          cl::Hidden, cl::init(false));
 108
 109 static cl::opt<bool>
 110     ClCMPTracing("sanitizer-coverage-trace-compares",
 111                  cl::desc("Tracing of CMP and similar instructions"),
 112                  cl::Hidden, cl::init(false));
 113
 114 static cl::opt<bool> ClDIVTracing("sanitizer-coverage-trace-divs",
 115                                   cl::desc("Tracing of DIV instructions"),
 116                                   cl::Hidden, cl::init(false));
 117
 118 static cl::opt<bool> ClGEPTracing("sanitizer-coverage-trace-geps",
 119                                   cl::desc("Tracing of GEP instructions"),
 120                                   cl::Hidden, cl::init(false));
 121
 122 static cl::opt<bool>
 123     ClPruneBlocks("sanitizer-coverage-prune-blocks",
 124                   cl::desc("Reduce the number of instrumented blocks"),
 125                   cl::Hidden, cl::init(true));
 126
 127 static cl::opt<bool> ClStackDepth("sanitizer-coverage-stack-depth",
 128                                   cl::desc("max stack depth tracing"),
 129                                   cl::Hidden, cl::init(false));
 130
 131 namespace {
 132
 133 SanitizerCoverageOptions getOptions(int LegacyCoverageLevel) {
 134   SanitizerCoverageOptions Res;
 135   switch (LegacyCoverageLevel) {
 136   case 0:
 137     Res.CoverageType = SanitizerCoverageOptions::SCK_None;
 138     break;
 139   case 1:
 140     Res.CoverageType = SanitizerCoverageOptions::SCK_Function;
 141     break;
 142   case 2:
 143     Res.CoverageType = SanitizerCoverageOptions::SCK_BB;
 144     break;
 145   case 3:
 146     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
 147     break;
 148   case 4:
 149     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
 150     Res.IndirectCalls = true;
 151     break;
 152   }
 153   return Res;
 154 }
 155
 156 SanitizerCoverageOptions OverrideFromCL(SanitizerCoverageOptions Options) {
 157   // Sets CoverageType and IndirectCalls.
 158   SanitizerCoverageOptions CLOpts = getOptions(ClCoverageLevel);
 159   Options.CoverageType = std::max(Options.CoverageType, CLOpts.CoverageType);
 160   Options.IndirectCalls |= CLOpts.IndirectCalls;
 161   Options.TraceCmp |= ClCMPTracing;
 162   Options.TraceDiv |= ClDIVTracing;
 163   Options.TraceGep |= ClGEPTracing;
 164   Options.TracePC |= ClTracePC;
 165   Options.TracePCGuard |= ClTracePCGuard;
 166   Options.Inline8bitCounters |= ClInline8bitCounters;
 167   Options.PCTable |= ClCreatePCTable;
 168   Options.NoPrune |= !ClPruneBlocks;
 169   Options.StackDepth |= ClStackDepth;
 170   if (!Options.TracePCGuard && !Options.TracePC &&
 171       !Options.Inline8bitCounters && !Options.StackDepth)
 172     Options.TracePCGuard = true; // TracePCGuard is default.
 173   return Options;
 174 }
 175
 176 class SanitizerCoverageModule : public ModulePass {
 177 public:
 178   SanitizerCoverageModule(
 179       const SanitizerCoverageOptions &Options = SanitizerCoverageOptions())
 180       : ModulePass(ID), Options(OverrideFromCL(Options)) {
 181     initializeSanitizerCoverageModulePass(*PassRegistry::getPassRegistry());
 182   }
 183   bool runOnModule(Module &M) override;
 184   bool runOnFunction(Function &F);
 185   static char ID; // Pass identification, replacement for typeid
 186   StringRef getPassName() const override { return "SanitizerCoverageModule"; }
 187
 188   void getAnalysisUsage(AnalysisUsage &AU) const override {
 189     AU.addRequired<DominatorTreeWrapperPass>();
 190     AU.addRequired<PostDominatorTreeWrapperPass>();
 191   }
 192
 193 private:
 194   void InjectCoverageForIndirectCalls(Function &F,
 195                                       ArrayRef<Instruction *> IndirCalls);
 196   void InjectTraceForCmp(Function &F, ArrayRef<Instruction *> CmpTraceTargets);
 197   void InjectTraceForDiv(Function &F,
 198                          ArrayRef<BinaryOperator *> DivTraceTargets);
 199   void InjectTraceForGep(Function &F,
 200                          ArrayRef<GetElementPtrInst *> GepTraceTargets);
 201   void InjectTraceForSwitch(Function &F,
 202                             ArrayRef<Instruction *> SwitchTraceTargets);
 203   bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks,
 204                       bool IsLeafFunc = true);
 205   GlobalVariable *CreateFunctionLocalArrayInSection(size_t NumElements,
 206                                                     Function &F, Type *Ty,
 207                                                     const char *Section);
 208   GlobalVariable *CreatePCArray(Function &F, ArrayRef<BasicBlock *> AllBlocks);
 209   void CreateFunctionLocalArrays(Function &F, ArrayRef<BasicBlock *> AllBlocks);
 210   void InjectCoverageAtBlock(Function &F, BasicBlock &BB, size_t Idx,
 211                              bool IsLeafFunc = true);
 212   Function *CreateInitCallsForSections(Module &M, const char *InitFunctionName,
 213                                        Type *Ty, const char *Section);
 214   std::pair<Value *, Value *> CreateSecStartEnd(Module &M, const char *Section,
 215                                                 Type *Ty);
 216
 217   void SetNoSanitizeMetadata(Instruction *I) {
 218     I->setMetadata(I->getModule()->getMDKindID("nosanitize"),
 219                    MDNode::get(*C, None));
 220   }
 221
 222   std::string getSectionName(const std::string &Section) const;
 223   std::string getSectionStart(const std::string &Section) const;
 224   std::string getSectionEnd(const std::string &Section) const;
 225   FunctionCallee SanCovTracePCIndir;
 226   FunctionCallee SanCovTracePC, SanCovTracePCGuard;
 227   FunctionCallee SanCovTraceCmpFunction[4];
 228   FunctionCallee SanCovTraceConstCmpFunction[4];
 229   FunctionCallee SanCovTraceDivFunction[2];
 230   FunctionCallee SanCovTraceGepFunction;
 231   FunctionCallee SanCovTraceSwitchFunction;
 232   GlobalVariable *SanCovLowestStack;
 233   InlineAsm *EmptyAsm;
 234   Type *IntptrTy, *IntptrPtrTy, *Int64Ty, *Int64PtrTy, *Int32Ty, *Int32PtrTy,
 235       *Int16Ty, *Int8Ty, *Int8PtrTy;
 236   Module *CurModule;
 237   std::string CurModuleUniqueId;
 238   Triple TargetTriple;
 239   LLVMContext *C;
 240   const DataLayout *DL;
 241
 242   GlobalVariable *FunctionGuardArray;  // for trace-pc-guard.
 243   GlobalVariable *Function8bitCounterArray;  // for inline-8bit-counters.
 244   GlobalVariable *FunctionPCsArray;  // for pc-table.
 245   SmallVector<GlobalValue *, 20> GlobalsToAppendToUsed;
 246   SmallVector<GlobalValue *, 20> GlobalsToAppendToCompilerUsed;
 247
 248   SanitizerCoverageOptions Options;
 249 };
 250
 251 } // namespace
 252
 253 std::pair<Value *, Value *>
 254 SanitizerCoverageModule::CreateSecStartEnd(Module &M, const char *Section,
 255                                            Type *Ty) {
 256   GlobalVariable *SecStart =
 257       new GlobalVariable(M, Ty, false, GlobalVariable::ExternalLinkage, nullptr,
 258                          getSectionStart(Section));
 259   SecStart->setVisibility(GlobalValue::HiddenVisibility);
 260   GlobalVariable *SecEnd =
 261       new GlobalVariable(M, Ty, false, GlobalVariable::ExternalLinkage,
 262                          nullptr, getSectionEnd(Section));
 263   SecEnd->setVisibility(GlobalValue::HiddenVisibility);
 264   IRBuilder<> IRB(M.getContext());
 265   Value *SecEndPtr = IRB.CreatePointerCast(SecEnd, Ty);
 266   if (!TargetTriple.isOSBinFormatCOFF())
 267     return std::make_pair(IRB.CreatePointerCast(SecStart, Ty), SecEndPtr);
 268
 269   // Account for the fact that on windows-msvc __start_* symbols actually
 270   // point to a uint64_t before the start of the array.
 271   auto SecStartI8Ptr = IRB.CreatePointerCast(SecStart, Int8PtrTy);
 272   auto GEP = IRB.CreateGEP(Int8Ty, SecStartI8Ptr,
 273                            ConstantInt::get(IntptrTy, sizeof(uint64_t)));
 274   return std::make_pair(IRB.CreatePointerCast(GEP, Ty), SecEndPtr);
 275 }
 276
 277 Function *SanitizerCoverageModule::CreateInitCallsForSections(
 278     Module &M, const char *InitFunctionName, Type *Ty,
 279     const char *Section) {
 280   auto SecStartEnd = CreateSecStartEnd(M, Section, Ty);
 281   auto SecStart = SecStartEnd.first;
 282   auto SecEnd = SecStartEnd.second;
 283   Function *CtorFunc;
 284   std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
 285       M, SanCovModuleCtorName, InitFunctionName, {Ty, Ty}, {SecStart, SecEnd});
 286
 287   if (TargetTriple.supportsCOMDAT()) {
 288     // Use comdat to dedup CtorFunc.
 289     CtorFunc->setComdat(M.getOrInsertComdat(SanCovModuleCtorName));
 290     appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority, CtorFunc);
 291   } else {
 292     appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority);
 293   }
 294
 295   if (TargetTriple.isOSBinFormatCOFF()) {
 296     // In COFF files, if the contructors are set as COMDAT (they are because
 297     // COFF supports COMDAT) and the linker flag /OPT:REF (strip unreferenced
 298     // functions and data) is used, the constructors get stripped. To prevent
 299     // this, give the constructors weak ODR linkage and ensure the linker knows
 300     // to include the sancov constructor. This way the linker can deduplicate
 301     // the constructors but always leave one copy.
 302     CtorFunc->setLinkage(GlobalValue::WeakODRLinkage);
 303     appendToUsed(M, CtorFunc);
 304   }
 305   return CtorFunc;
 306 }
 307
 308 bool SanitizerCoverageModule::runOnModule(Module &M) {
 309   if (Options.CoverageType == SanitizerCoverageOptions::SCK_None)
 310     return false;
 311   C = &(M.getContext());
 312   DL = &M.getDataLayout();
 313   CurModule = &M;
 314   CurModuleUniqueId = getUniqueModuleId(CurModule);
 315   TargetTriple = Triple(M.getTargetTriple());
 316   FunctionGuardArray = nullptr;
 317   Function8bitCounterArray = nullptr;
 318   FunctionPCsArray = nullptr;
 319   IntptrTy = Type::getIntNTy(*C, DL->getPointerSizeInBits());
 320   IntptrPtrTy = PointerType::getUnqual(IntptrTy);
 321   Type *VoidTy = Type::getVoidTy(*C);
 322   IRBuilder<> IRB(*C);
 323   Int64PtrTy = PointerType::getUnqual(IRB.getInt64Ty());
 324   Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
 325   Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
 326   Int64Ty = IRB.getInt64Ty();
 327   Int32Ty = IRB.getInt32Ty();
 328   Int16Ty = IRB.getInt16Ty();
 329   Int8Ty = IRB.getInt8Ty();
 330
 331   SanCovTracePCIndir =
 332       M.getOrInsertFunction(SanCovTracePCIndirName, VoidTy, IntptrTy);
 333   // Make sure smaller parameters are zero-extended to i64 as required by the
 334   // x86_64 ABI.
 335   AttributeList SanCovTraceCmpZeroExtAL;
 336   if (TargetTriple.getArch() == Triple::x86_64) {
 337     SanCovTraceCmpZeroExtAL =
 338         SanCovTraceCmpZeroExtAL.addParamAttribute(*C, 0, Attribute::ZExt);
 339     SanCovTraceCmpZeroExtAL =
 340         SanCovTraceCmpZeroExtAL.addParamAttribute(*C, 1, Attribute::ZExt);
 341   }
 342
 343   SanCovTraceCmpFunction[0] =
 344       M.getOrInsertFunction(SanCovTraceCmp1, SanCovTraceCmpZeroExtAL, VoidTy,
 345                             IRB.getInt8Ty(), IRB.getInt8Ty());
 346   SanCovTraceCmpFunction[1] =
 347       M.getOrInsertFunction(SanCovTraceCmp2, SanCovTraceCmpZeroExtAL, VoidTy,
 348                             IRB.getInt16Ty(), IRB.getInt16Ty());
 349   SanCovTraceCmpFunction[2] =
 350       M.getOrInsertFunction(SanCovTraceCmp4, SanCovTraceCmpZeroExtAL, VoidTy,
 351                             IRB.getInt32Ty(), IRB.getInt32Ty());
 352   SanCovTraceCmpFunction[3] =
 353       M.getOrInsertFunction(SanCovTraceCmp8, VoidTy, Int64Ty, Int64Ty);
 354
 355   SanCovTraceConstCmpFunction[0] = M.getOrInsertFunction(
 356       SanCovTraceConstCmp1, SanCovTraceCmpZeroExtAL, VoidTy, Int8Ty, Int8Ty);
 357   SanCovTraceConstCmpFunction[1] = M.getOrInsertFunction(
 358       SanCovTraceConstCmp2, SanCovTraceCmpZeroExtAL, VoidTy, Int16Ty, Int16Ty);
 359   SanCovTraceConstCmpFunction[2] = M.getOrInsertFunction(
 360       SanCovTraceConstCmp4, SanCovTraceCmpZeroExtAL, VoidTy, Int32Ty, Int32Ty);
 361   SanCovTraceConstCmpFunction[3] =
 362       M.getOrInsertFunction(SanCovTraceConstCmp8, VoidTy, Int64Ty, Int64Ty);
 363
 364   {
 365     AttributeList AL;
 366     if (TargetTriple.getArch() == Triple::x86_64)
 367       AL = AL.addParamAttribute(*C, 0, Attribute::ZExt);
 368     SanCovTraceDivFunction[0] =
 369         M.getOrInsertFunction(SanCovTraceDiv4, AL, VoidTy, IRB.getInt32Ty());
 370   }
 371   SanCovTraceDivFunction[1] =
 372       M.getOrInsertFunction(SanCovTraceDiv8, VoidTy, Int64Ty);
 373   SanCovTraceGepFunction =
 374       M.getOrInsertFunction(SanCovTraceGep, VoidTy, IntptrTy);
 375   SanCovTraceSwitchFunction =
 376       M.getOrInsertFunction(SanCovTraceSwitchName, VoidTy, Int64Ty, Int64PtrTy);
 377
 378   Constant *SanCovLowestStackConstant =
 379       M.getOrInsertGlobal(SanCovLowestStackName, IntptrTy);
 380   SanCovLowestStack = dyn_cast<GlobalVariable>(SanCovLowestStackConstant);
 381   if (!SanCovLowestStack) {
 382     C->emitError(StringRef("'") + SanCovLowestStackName +
 383                  "' should not be declared by the user");
 384     return true;
 385   }
 386   SanCovLowestStack->setThreadLocalMode(
 387       GlobalValue::ThreadLocalMode::InitialExecTLSModel);
 388   if (Options.StackDepth && !SanCovLowestStack->isDeclaration())
 389     SanCovLowestStack->setInitializer(Constant::getAllOnesValue(IntptrTy));
 390
 391   // We insert an empty inline asm after cov callbacks to avoid callback merge.
 392   EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
 393                             StringRef(""), StringRef(""),
 394                             /*hasSideEffects=*/true);
 395
 396   SanCovTracePC = M.getOrInsertFunction(SanCovTracePCName, VoidTy);
 397   SanCovTracePCGuard =
 398       M.getOrInsertFunction(SanCovTracePCGuardName, VoidTy, Int32PtrTy);
 399
 400   for (auto &F : M)
 401     runOnFunction(F);
 402
 403   Function *Ctor = nullptr;
 404
 405   if (FunctionGuardArray)
 406     Ctor = CreateInitCallsForSections(M, SanCovTracePCGuardInitName, Int32PtrTy,
 407                                       SanCovGuardsSectionName);
 408   if (Function8bitCounterArray)
 409     Ctor = CreateInitCallsForSections(M, SanCov8bitCountersInitName, Int8PtrTy,
 410                                       SanCovCountersSectionName);
 411   if (Ctor && Options.PCTable) {
 412     auto SecStartEnd = CreateSecStartEnd(M, SanCovPCsSectionName, IntptrPtrTy);
 413     FunctionCallee InitFunction = declareSanitizerInitFunction(
 414         M, SanCovPCsInitName, {IntptrPtrTy, IntptrPtrTy});
 415     IRBuilder<> IRBCtor(Ctor->getEntryBlock().getTerminator());
 416     IRBCtor.CreateCall(InitFunction, {SecStartEnd.first, SecStartEnd.second});
 417   }
 418   // We don't reference these arrays directly in any of our runtime functions,
 419   // so we need to prevent them from being dead stripped.
 420   if (TargetTriple.isOSBinFormatMachO())
 421     appendToUsed(M, GlobalsToAppendToUsed);
 422   appendToCompilerUsed(M, GlobalsToAppendToCompilerUsed);
 423   return true;
 424 }
 425
 426 // True if block has successors and it dominates all of them.
 427 static bool isFullDominator(const BasicBlock *BB, const DominatorTree *DT) {
 428   if (succ_begin(BB) == succ_end(BB))
 429     return false;
 430
 431   for (const BasicBlock *SUCC : make_range(succ_begin(BB), succ_end(BB))) {
 432     if (!DT->dominates(BB, SUCC))
 433       return false;
 434   }
 435
 436   return true;
 437 }
 438
 439 // True if block has predecessors and it postdominates all of them.
 440 static bool isFullPostDominator(const BasicBlock *BB,
 441                                 const PostDominatorTree *PDT) {
 442   if (pred_begin(BB) == pred_end(BB))
 443     return false;
 444
 445   for (const BasicBlock *PRED : make_range(pred_begin(BB), pred_end(BB))) {
 446     if (!PDT->dominates(BB, PRED))
 447       return false;
 448   }
 449
 450   return true;
 451 }
 452
 453 static bool shouldInstrumentBlock(const Function &F, const BasicBlock *BB,
 454                                   const DominatorTree *DT,
 455                                   const PostDominatorTree *PDT,
 456                                   const SanitizerCoverageOptions &Options) {
 457   // Don't insert coverage for unreachable blocks: we will never call
 458   // __sanitizer_cov() for them, so counting them in
 459   // NumberOfInstrumentedBlocks() might complicate calculation of code coverage
 460   // percentage. Also, unreachable instructions frequently have no debug
 461   // locations.
 462   if (isa<UnreachableInst>(BB->getTerminator()))
 463     return false;
 464
 465   // Don't insert coverage into blocks without a valid insertion point
 466   // (catchswitch blocks).
 467   if (BB->getFirstInsertionPt() == BB->end())
 468     return false;
 469
 470   if (Options.NoPrune || &F.getEntryBlock() == BB)
 471     return true;
 472
 473   if (Options.CoverageType == SanitizerCoverageOptions::SCK_Function &&
 474       &F.getEntryBlock() != BB)
 475     return false;
 476
 477   // Do not instrument full dominators, or full post-dominators with multiple
 478   // predecessors.
 479   return !isFullDominator(BB, DT)
 480     && !(isFullPostDominator(BB, PDT) && !BB->getSinglePredecessor());
 481 }
 482
 483
 484 // Returns true iff From->To is a backedge.
 485 // A twist here is that we treat From->To as a backedge if
 486 //   * To dominates From or
 487 //   * To->UniqueSuccessor dominates From
 488 static bool IsBackEdge(BasicBlock *From, BasicBlock *To,
 489                        const DominatorTree *DT) {
 490   if (DT->dominates(To, From))
 491     return true;
 492   if (auto Next = To->getUniqueSuccessor())
 493     if (DT->dominates(Next, From))
 494       return true;
 495   return false;
 496 }
 497
 498 // Prunes uninteresting Cmp instrumentation:
 499 //   * CMP instructions that feed into loop backedge branch.
 500 //
 501 // Note that Cmp pruning is controlled by the same flag as the
 502 // BB pruning.
 503 static bool IsInterestingCmp(ICmpInst *CMP, const DominatorTree *DT,
 504                              const SanitizerCoverageOptions &Options) {
 505   if (!Options.NoPrune)
 506     if (CMP->hasOneUse())
 507       if (auto BR = dyn_cast<BranchInst>(CMP->user_back()))
 508         for (BasicBlock *B : BR->successors())
 509           if (IsBackEdge(BR->getParent(), B, DT))
 510             return false;
 511   return true;
 512 }
 513
 514 bool SanitizerCoverageModule::runOnFunction(Function &F) {
 515   if (F.empty())
 516     return false;
 517   if (F.getName().find(".module_ctor") != std::string::npos)
 518     return false; // Should not instrument sanitizer init functions.
 519   if (F.getName().startswith("__sanitizer_"))
 520     return false;  // Don't instrument __sanitizer_* callbacks.
 521   // Don't touch available_externally functions, their actual body is elewhere.
 522   if (F.getLinkage() == GlobalValue::AvailableExternallyLinkage)
 523     return false;
 524   // Don't instrument MSVC CRT configuration helpers. They may run before normal
 525   // initialization.
 526   if (F.getName() == "__local_stdio_printf_options" ||
 527       F.getName() == "__local_stdio_scanf_options")
 528     return false;
 529   if (isa<UnreachableInst>(F.getEntryBlock().getTerminator()))
 530     return false;
 531   // Don't instrument functions using SEH for now. Splitting basic blocks like
 532   // we do for coverage breaks WinEHPrepare.
 533   // FIXME: Remove this when SEH no longer uses landingpad pattern matching.
 534   if (F.hasPersonalityFn() &&
 535       isAsynchronousEHPersonality(classifyEHPersonality(F.getPersonalityFn())))
 536     return false;
 537   if (Options.CoverageType >= SanitizerCoverageOptions::SCK_Edge)
 538     SplitAllCriticalEdges(F);
 539   SmallVector<Instruction *, 8> IndirCalls;
 540   SmallVector<BasicBlock *, 16> BlocksToInstrument;
 541   SmallVector<Instruction *, 8> CmpTraceTargets;
 542   SmallVector<Instruction *, 8> SwitchTraceTargets;
 543   SmallVector<BinaryOperator *, 8> DivTraceTargets;
 544   SmallVector<GetElementPtrInst *, 8> GepTraceTargets;
 545
 546   const DominatorTree *DT =
 547       &getAnalysis<DominatorTreeWrapperPass>(F).getDomTree();
 548   const PostDominatorTree *PDT =
 549       &getAnalysis<PostDominatorTreeWrapperPass>(F).getPostDomTree();
 550   bool IsLeafFunc = true;
 551
 552   for (auto &BB : F) {
 553     if (shouldInstrumentBlock(F, &BB, DT, PDT, Options))
 554       BlocksToInstrument.push_back(&BB);
 555     for (auto &Inst : BB) {
 556       if (Options.IndirectCalls) {
 557         CallSite CS(&Inst);
 558         if (CS && !CS.getCalledFunction())
 559           IndirCalls.push_back(&Inst);
 560       }
 561       if (Options.TraceCmp) {
 562         if (ICmpInst *CMP = dyn_cast<ICmpInst>(&Inst))
 563           if (IsInterestingCmp(CMP, DT, Options))
 564             CmpTraceTargets.push_back(&Inst);
 565         if (isa<SwitchInst>(&Inst))
 566           SwitchTraceTargets.push_back(&Inst);
 567       }
 568       if (Options.TraceDiv)
 569         if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&Inst))
 570           if (BO->getOpcode() == Instruction::SDiv ||
 571               BO->getOpcode() == Instruction::UDiv)
 572             DivTraceTargets.push_back(BO);
 573       if (Options.TraceGep)
 574         if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(&Inst))
 575           GepTraceTargets.push_back(GEP);
 576       if (Options.StackDepth)
 577         if (isa<InvokeInst>(Inst) ||
 578             (isa<CallInst>(Inst) && !isa<IntrinsicInst>(Inst)))
 579           IsLeafFunc = false;
 580     }
 581   }
 582
 583   InjectCoverage(F, BlocksToInstrument, IsLeafFunc);
 584   InjectCoverageForIndirectCalls(F, IndirCalls);
 585   InjectTraceForCmp(F, CmpTraceTargets);
 586   InjectTraceForSwitch(F, SwitchTraceTargets);
 587   InjectTraceForDiv(F, DivTraceTargets);
 588   InjectTraceForGep(F, GepTraceTargets);
 589   return true;
 590 }
 591
 592 GlobalVariable *SanitizerCoverageModule::CreateFunctionLocalArrayInSection(
 593     size_t NumElements, Function &F, Type *Ty, const char *Section) {
 594   ArrayType *ArrayTy = ArrayType::get(Ty, NumElements);
 595   auto Array = new GlobalVariable(
 596       *CurModule, ArrayTy, false, GlobalVariable::PrivateLinkage,
 597       Constant::getNullValue(ArrayTy), "__sancov_gen_");
 598
 599   if (TargetTriple.supportsCOMDAT() && !F.isInterposable())
 600     if (auto Comdat =
 601             GetOrCreateFunctionComdat(F, TargetTriple, CurModuleUniqueId))
 602       Array->setComdat(Comdat);
 603   Array->setSection(getSectionName(Section));
 604   Array->setAlignment(Ty->isPointerTy() ? DL->getPointerSize()
 605                                         : Ty->getPrimitiveSizeInBits() / 8);
 606   GlobalsToAppendToUsed.push_back(Array);
 607   GlobalsToAppendToCompilerUsed.push_back(Array);
 608   MDNode *MD = MDNode::get(F.getContext(), ValueAsMetadata::get(&F));
 609   Array->addMetadata(LLVMContext::MD_associated, *MD);
 610
 611   return Array;
 612 }
 613
 614 GlobalVariable *
 615 SanitizerCoverageModule::CreatePCArray(Function &F,
 616                                        ArrayRef<BasicBlock *> AllBlocks) {
 617   size_t N = AllBlocks.size();
 618   assert(N);
 619   SmallVector<Constant *, 32> PCs;
 620   IRBuilder<> IRB(&*F.getEntryBlock().getFirstInsertionPt());
 621   for (size_t i = 0; i < N; i++) {
 622     if (&F.getEntryBlock() == AllBlocks[i]) {
 623       PCs.push_back((Constant *)IRB.CreatePointerCast(&F, IntptrPtrTy));
 624       PCs.push_back((Constant *)IRB.CreateIntToPtr(
 625           ConstantInt::get(IntptrTy, 1), IntptrPtrTy));
 626     } else {
 627       PCs.push_back((Constant *)IRB.CreatePointerCast(
 628           BlockAddress::get(AllBlocks[i]), IntptrPtrTy));
 629       PCs.push_back((Constant *)IRB.CreateIntToPtr(
 630           ConstantInt::get(IntptrTy, 0), IntptrPtrTy));
 631     }
 632   }
 633   auto *PCArray = CreateFunctionLocalArrayInSection(N * 2, F, IntptrPtrTy,
 634                                                     SanCovPCsSectionName);
 635   PCArray->setInitializer(
 636       ConstantArray::get(ArrayType::get(IntptrPtrTy, N * 2), PCs));
 637   PCArray->setConstant(true);
 638
 639   return PCArray;
 640 }
 641
 642 void SanitizerCoverageModule::CreateFunctionLocalArrays(
 643     Function &F, ArrayRef<BasicBlock *> AllBlocks) {
 644   if (Options.TracePCGuard)
 645     FunctionGuardArray = CreateFunctionLocalArrayInSection(
 646         AllBlocks.size(), F, Int32Ty, SanCovGuardsSectionName);
 647
 648   if (Options.Inline8bitCounters)
 649     Function8bitCounterArray = CreateFunctionLocalArrayInSection(
 650         AllBlocks.size(), F, Int8Ty, SanCovCountersSectionName);
 651
 652   if (Options.PCTable)
 653     FunctionPCsArray = CreatePCArray(F, AllBlocks);
 654 }
 655
 656 bool SanitizerCoverageModule::InjectCoverage(Function &F,
 657                                              ArrayRef<BasicBlock *> AllBlocks,
 658                                              bool IsLeafFunc) {
 659   if (AllBlocks.empty()) return false;
 660   CreateFunctionLocalArrays(F, AllBlocks);
 661   for (size_t i = 0, N = AllBlocks.size(); i < N; i++)
 662     InjectCoverageAtBlock(F, *AllBlocks[i], i, IsLeafFunc);
 663   return true;
 664 }
 665
 666 // On every indirect call we call a run-time function
 667 // __sanitizer_cov_indir_call* with two parameters:
 668 //   - callee address,
 669 //   - global cache array that contains CacheSize pointers (zero-initialized).
 670 //     The cache is used to speed up recording the caller-callee pairs.
 671 // The address of the caller is passed implicitly via caller PC.
 672 // CacheSize is encoded in the name of the run-time function.
 673 void SanitizerCoverageModule::InjectCoverageForIndirectCalls(
 674     Function &F, ArrayRef<Instruction *> IndirCalls) {
 675   if (IndirCalls.empty())
 676     return;
 677   assert(Options.TracePC || Options.TracePCGuard || Options.Inline8bitCounters);
 678   for (auto I : IndirCalls) {
 679     IRBuilder<> IRB(I);
 680     CallSite CS(I);
 681     Value *Callee = CS.getCalledValue();
 682     if (isa<InlineAsm>(Callee))
 683       continue;
 684     IRB.CreateCall(SanCovTracePCIndir, IRB.CreatePointerCast(Callee, IntptrTy));
 685   }
 686 }
 687
 688 // For every switch statement we insert a call:
 689 // __sanitizer_cov_trace_switch(CondValue,
 690 //      {NumCases, ValueSizeInBits, Case0Value, Case1Value, Case2Value, ... })
 691
 692 void SanitizerCoverageModule::InjectTraceForSwitch(
 693     Function &, ArrayRef<Instruction *> SwitchTraceTargets) {
 694   for (auto I : SwitchTraceTargets) {
 695     if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
 696       IRBuilder<> IRB(I);
 697       SmallVector<Constant *, 16> Initializers;
 698       Value *Cond = SI->getCondition();
 699       if (Cond->getType()->getScalarSizeInBits() >
 700           Int64Ty->getScalarSizeInBits())
 701         continue;
 702       Initializers.push_back(ConstantInt::get(Int64Ty, SI->getNumCases()));
 703       Initializers.push_back(
 704           ConstantInt::get(Int64Ty, Cond->getType()->getScalarSizeInBits()));
 705       if (Cond->getType()->getScalarSizeInBits() <
 706           Int64Ty->getScalarSizeInBits())
 707         Cond = IRB.CreateIntCast(Cond, Int64Ty, false);
 708       for (auto It : SI->cases()) {
 709         Constant *C = It.getCaseValue();
 710         if (C->getType()->getScalarSizeInBits() <
 711             Int64Ty->getScalarSizeInBits())
 712           C = ConstantExpr::getCast(CastInst::ZExt, It.getCaseValue(), Int64Ty);
 713         Initializers.push_back(C);
 714       }
 715       llvm::sort(Initializers.begin() + 2, Initializers.end(),
 716                  [](const Constant *A, const Constant *B) {
 717                    return cast<ConstantInt>(A)->getLimitedValue() <
 718                           cast<ConstantInt>(B)->getLimitedValue();
 719                  });
 720       ArrayType *ArrayOfInt64Ty = ArrayType::get(Int64Ty, Initializers.size());
 721       GlobalVariable *GV = new GlobalVariable(
 722           *CurModule, ArrayOfInt64Ty, false, GlobalVariable::InternalLinkage,
 723           ConstantArray::get(ArrayOfInt64Ty, Initializers),
 724           "__sancov_gen_cov_switch_values");
 725       IRB.CreateCall(SanCovTraceSwitchFunction,
 726                      {Cond, IRB.CreatePointerCast(GV, Int64PtrTy)});
 727     }
 728   }
 729 }
 730
 731 void SanitizerCoverageModule::InjectTraceForDiv(
 732     Function &, ArrayRef<BinaryOperator *> DivTraceTargets) {
 733   for (auto BO : DivTraceTargets) {
 734     IRBuilder<> IRB(BO);
 735     Value *A1 = BO->getOperand(1);
 736     if (isa<ConstantInt>(A1)) continue;
 737     if (!A1->getType()->isIntegerTy())
 738       continue;
 739     uint64_t TypeSize = DL->getTypeStoreSizeInBits(A1->getType());
 740     int CallbackIdx = TypeSize == 32 ? 0 :
 741         TypeSize == 64 ? 1 : -1;
 742     if (CallbackIdx < 0) continue;
 743     auto Ty = Type::getIntNTy(*C, TypeSize);
 744     IRB.CreateCall(SanCovTraceDivFunction[CallbackIdx],
 745                    {IRB.CreateIntCast(A1, Ty, true)});
 746   }
 747 }
 748
 749 void SanitizerCoverageModule::InjectTraceForGep(
 750     Function &, ArrayRef<GetElementPtrInst *> GepTraceTargets) {
 751   for (auto GEP : GepTraceTargets) {
 752     IRBuilder<> IRB(GEP);
 753     for (auto I = GEP->idx_begin(); I != GEP->idx_end(); ++I)
 754       if (!isa<ConstantInt>(*I) && (*I)->getType()->isIntegerTy())
 755         IRB.CreateCall(SanCovTraceGepFunction,
 756                        {IRB.CreateIntCast(*I, IntptrTy, true)});
 757   }
 758 }
 759
 760 void SanitizerCoverageModule::InjectTraceForCmp(
 761     Function &, ArrayRef<Instruction *> CmpTraceTargets) {
 762   for (auto I : CmpTraceTargets) {
 763     if (ICmpInst *ICMP = dyn_cast<ICmpInst>(I)) {
 764       IRBuilder<> IRB(ICMP);
 765       Value *A0 = ICMP->getOperand(0);
 766       Value *A1 = ICMP->getOperand(1);
 767       if (!A0->getType()->isIntegerTy())
 768         continue;
 769       uint64_t TypeSize = DL->getTypeStoreSizeInBits(A0->getType());
 770       int CallbackIdx = TypeSize == 8 ? 0 :
 771                         TypeSize == 16 ? 1 :
 772                         TypeSize == 32 ? 2 :
 773                         TypeSize == 64 ? 3 : -1;
 774       if (CallbackIdx < 0) continue;
 775       // __sanitizer_cov_trace_cmp((type_size << 32) | predicate, A0, A1);
 776       auto CallbackFunc = SanCovTraceCmpFunction[CallbackIdx];
 777       bool FirstIsConst = isa<ConstantInt>(A0);
 778       bool SecondIsConst = isa<ConstantInt>(A1);
 779       // If both are const, then we don't need such a comparison.
 780       if (FirstIsConst && SecondIsConst) continue;
 781       // If only one is const, then make it the first callback argument.
 782       if (FirstIsConst || SecondIsConst) {
 783         CallbackFunc = SanCovTraceConstCmpFunction[CallbackIdx];
 784         if (SecondIsConst)
 785           std::swap(A0, A1);
 786       }
 787
 788       auto Ty = Type::getIntNTy(*C, TypeSize);
 789       IRB.CreateCall(CallbackFunc, {IRB.CreateIntCast(A0, Ty, true),
 790               IRB.CreateIntCast(A1, Ty, true)});
 791     }
 792   }
 793 }
 794
 795 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
 796                                                     size_t Idx,
 797                                                     bool IsLeafFunc) {
 798   BasicBlock::iterator IP = BB.getFirstInsertionPt();
 799   bool IsEntryBB = &BB == &F.getEntryBlock();
 800   DebugLoc EntryLoc;
 801   if (IsEntryBB) {
 802     if (auto SP = F.getSubprogram())
 803       EntryLoc = DebugLoc::get(SP->getScopeLine(), 0, SP);
 804     // Keep static allocas and llvm.localescape calls in the entry block.  Even
 805     // if we aren't splitting the block, it's nice for allocas to be before
 806     // calls.
 807     IP = PrepareToSplitEntryBlock(BB, IP);
 808   } else {
 809     EntryLoc = IP->getDebugLoc();
 810   }
 811
 812   IRBuilder<> IRB(&*IP);
 813   IRB.SetCurrentDebugLocation(EntryLoc);
 814   if (Options.TracePC) {
 815     IRB.CreateCall(SanCovTracePC); // gets the PC using GET_CALLER_PC.
 816     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
 817   }
 818   if (Options.TracePCGuard) {
 819     auto GuardPtr = IRB.CreateIntToPtr(
 820         IRB.CreateAdd(IRB.CreatePointerCast(FunctionGuardArray, IntptrTy),
 821                       ConstantInt::get(IntptrTy, Idx * 4)),
 822         Int32PtrTy);
 823     IRB.CreateCall(SanCovTracePCGuard, GuardPtr);
 824     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
 825   }
 826   if (Options.Inline8bitCounters) {
 827     auto CounterPtr = IRB.CreateGEP(
 828         Function8bitCounterArray->getValueType(), Function8bitCounterArray,
 829         {ConstantInt::get(IntptrTy, 0), ConstantInt::get(IntptrTy, Idx)});
 830     auto Load = IRB.CreateLoad(Int8Ty, CounterPtr);
 831     auto Inc = IRB.CreateAdd(Load, ConstantInt::get(Int8Ty, 1));
 832     auto Store = IRB.CreateStore(Inc, CounterPtr);
 833     SetNoSanitizeMetadata(Load);
 834     SetNoSanitizeMetadata(Store);
 835   }
 836   if (Options.StackDepth && IsEntryBB && !IsLeafFunc) {
 837     // Check stack depth.  If it's the deepest so far, record it.
 838     Function *GetFrameAddr =
 839         Intrinsic::getDeclaration(F.getParent(), Intrinsic::frameaddress);
 840     auto FrameAddrPtr =
 841         IRB.CreateCall(GetFrameAddr, {Constant::getNullValue(Int32Ty)});
 842     auto FrameAddrInt = IRB.CreatePtrToInt(FrameAddrPtr, IntptrTy);
 843     auto LowestStack = IRB.CreateLoad(IntptrTy, SanCovLowestStack);
 844     auto IsStackLower = IRB.CreateICmpULT(FrameAddrInt, LowestStack);
 845     auto ThenTerm = SplitBlockAndInsertIfThen(IsStackLower, &*IP, false);
 846     IRBuilder<> ThenIRB(ThenTerm);
 847     auto Store = ThenIRB.CreateStore(FrameAddrInt, SanCovLowestStack);
 848     SetNoSanitizeMetadata(LowestStack);
 849     SetNoSanitizeMetadata(Store);
 850   }
 851 }
 852
 853 std::string
 854 SanitizerCoverageModule::getSectionName(const std::string &Section) const {
 855   if (TargetTriple.isOSBinFormatCOFF()) {
 856     if (Section == SanCovCountersSectionName)
 857       return ".SCOV$CM";
 858     if (Section == SanCovPCsSectionName)
 859       return ".SCOVP$M";
 860     return ".SCOV$GM"; // For SanCovGuardsSectionName.
 861   }
 862   if (TargetTriple.isOSBinFormatMachO())
 863     return "__DATA,__" + Section;
 864   return "__" + Section;
 865 }
 866
 867 std::string
 868 SanitizerCoverageModule::getSectionStart(const std::string &Section) const {
 869   if (TargetTriple.isOSBinFormatMachO())
 870     return "\1section$start$__DATA$__" + Section;
 871   return "__start___" + Section;
 872 }
 873
 874 std::string
 875 SanitizerCoverageModule::getSectionEnd(const std::string &Section) const {
 876   if (TargetTriple.isOSBinFormatMachO())
 877     return "\1section$end$__DATA$__" + Section;
 878   return "__stop___" + Section;
 879 }
 880
 881
 882 char SanitizerCoverageModule::ID = 0;
 883 INITIALIZE_PASS_BEGIN(SanitizerCoverageModule, "sancov",
 884                       "SanitizerCoverage: TODO."
 885                       "ModulePass",
 886                       false, false)
 887 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
 888 INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)
 889 INITIALIZE_PASS_END(SanitizerCoverageModule, "sancov",
 890                     "SanitizerCoverage: TODO."
 891                     "ModulePass",
 892                     false, false)
 893 ModulePass *llvm::createSanitizerCoverageModulePass(
 894     const SanitizerCoverageOptions &Options) {
 895   return new SanitizerCoverageModule(Options);
 896 }