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/Transforms/Instrumentation.h"
  32 #include "llvm/ADT/ArrayRef.h"
  33 #include "llvm/ADT/SmallVector.h"
  34 #include "llvm/IR/CallSite.h"
  35 #include "llvm/IR/DataLayout.h"
  36 #include "llvm/IR/Function.h"
  37 #include "llvm/IR/IRBuilder.h"
  38 #include "llvm/IR/InlineAsm.h"
  39 #include "llvm/IR/LLVMContext.h"
  40 #include "llvm/IR/MDBuilder.h"
  41 #include "llvm/IR/Module.h"
  42 #include "llvm/IR/Type.h"
  43 #include "llvm/Support/CommandLine.h"
  44 #include "llvm/Support/Debug.h"
  45 #include "llvm/Support/raw_ostream.h"
  46 #include "llvm/Transforms/Scalar.h"
  47 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
  48 #include "llvm/Transforms/Utils/ModuleUtils.h"
  49
  50 using namespace llvm;
  51
  52 #define DEBUG_TYPE "sancov"
  53
  54 static const char *const kSanCovModuleInitName = "__sanitizer_cov_module_init";
  55 static const char *const kSanCovName = "__sanitizer_cov";
  56 static const char *const kSanCovWithCheckName = "__sanitizer_cov_with_check";
  57 static const char *const kSanCovIndirCallName = "__sanitizer_cov_indir_call16";
  58 static const char *const kSanCovTraceEnter = "__sanitizer_cov_trace_func_enter";
  59 static const char *const kSanCovTraceBB = "__sanitizer_cov_trace_basic_block";
  60 static const char *const kSanCovTraceCmp = "__sanitizer_cov_trace_cmp";
  61 static const char *const kSanCovModuleCtorName = "sancov.module_ctor";
  62 static const uint64_t    kSanCtorAndDtorPriority = 2;
  63
  64 static cl::opt<int> ClCoverageLevel("sanitizer-coverage-level",
  65        cl::desc("Sanitizer Coverage. 0: none, 1: entry block, 2: all blocks, "
  66                 "3: all blocks and critical edges, "
  67                 "4: above plus indirect calls"),
  68        cl::Hidden, cl::init(0));
  69
  70 static cl::opt<unsigned> ClCoverageBlockThreshold(
  71     "sanitizer-coverage-block-threshold",
  72     cl::desc("Use a callback with a guard check inside it if there are"
  73              " more than this number of blocks."),
  74     cl::Hidden, cl::init(500));
  75
  76 static cl::opt<bool>
  77     ClExperimentalTracing("sanitizer-coverage-experimental-tracing",
  78                           cl::desc("Experimental basic-block tracing: insert "
  79                                    "callbacks at every basic block"),
  80                           cl::Hidden, cl::init(false));
  81
  82 static cl::opt<bool>
  83     ClExperimentalCMPTracing("sanitizer-coverage-experimental-trace-compares",
  84                              cl::desc("Experimental tracing of CMP and similar "
  85                                       "instructions"),
  86                              cl::Hidden, cl::init(false));
  87
  88 // Experimental 8-bit counters used as an additional search heuristic during
  89 // coverage-guided fuzzing.
  90 // The counters are not thread-friendly:
  91 //   - contention on these counters may cause significant slowdown;
  92 //   - the counter updates are racy and the results may be inaccurate.
  93 // They are also inaccurate due to 8-bit integer overflow.
  94 static cl::opt<bool> ClUse8bitCounters("sanitizer-coverage-8bit-counters",
  95                                        cl::desc("Experimental 8-bit counters"),
  96                                        cl::Hidden, cl::init(false));
  97
  98 namespace {
  99
 100 SanitizerCoverageOptions getOptions(int LegacyCoverageLevel) {
 101   SanitizerCoverageOptions Res;
 102   switch (LegacyCoverageLevel) {
 103   case 0:
 104     Res.CoverageType = SanitizerCoverageOptions::SCK_None;
 105     break;
 106   case 1:
 107     Res.CoverageType = SanitizerCoverageOptions::SCK_Function;
 108     break;
 109   case 2:
 110     Res.CoverageType = SanitizerCoverageOptions::SCK_BB;
 111     break;
 112   case 3:
 113     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
 114     break;
 115   case 4:
 116     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
 117     Res.IndirectCalls = true;
 118     break;
 119   }
 120   return Res;
 121 }
 122
 123 SanitizerCoverageOptions OverrideFromCL(SanitizerCoverageOptions Options) {
 124   // Sets CoverageType and IndirectCalls.
 125   SanitizerCoverageOptions CLOpts = getOptions(ClCoverageLevel);
 126   Options.CoverageType = std::max(Options.CoverageType, CLOpts.CoverageType);
 127   Options.IndirectCalls |= CLOpts.IndirectCalls;
 128   Options.TraceBB |= ClExperimentalTracing;
 129   Options.TraceCmp |= ClExperimentalCMPTracing;
 130   Options.Use8bitCounters |= ClUse8bitCounters;
 131   return Options;
 132 }
 133
 134 class SanitizerCoverageModule : public ModulePass {
 135  public:
 136   SanitizerCoverageModule(
 137       const SanitizerCoverageOptions &Options = SanitizerCoverageOptions())
 138       : ModulePass(ID), Options(OverrideFromCL(Options)) {}
 139   bool runOnModule(Module &M) override;
 140   bool runOnFunction(Function &F);
 141   static char ID;  // Pass identification, replacement for typeid
 142   const char *getPassName() const override {
 143     return "SanitizerCoverageModule";
 144   }
 145
 146  private:
 147   void InjectCoverageForIndirectCalls(Function &F,
 148                                       ArrayRef<Instruction *> IndirCalls);
 149   void InjectTraceForCmp(Function &F, ArrayRef<Instruction *> CmpTraceTargets);
 150   bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks);
 151   void SetNoSanitizeMetadata(Instruction *I);
 152   void InjectCoverageAtBlock(Function &F, BasicBlock &BB, bool UseCalls);
 153   unsigned NumberOfInstrumentedBlocks() {
 154     return SanCovFunction->getNumUses() + SanCovWithCheckFunction->getNumUses();
 155   }
 156   Function *SanCovFunction;
 157   Function *SanCovWithCheckFunction;
 158   Function *SanCovIndirCallFunction;
 159   Function *SanCovModuleInit;
 160   Function *SanCovTraceEnter, *SanCovTraceBB;
 161   Function *SanCovTraceCmpFunction;
 162   InlineAsm *EmptyAsm;
 163   Type *IntptrTy, *Int64Ty;
 164   LLVMContext *C;
 165   const DataLayout *DL;
 166
 167   GlobalVariable *GuardArray;
 168   GlobalVariable *EightBitCounterArray;
 169
 170   SanitizerCoverageOptions Options;
 171 };
 172
 173 }  // namespace
 174
 175 bool SanitizerCoverageModule::runOnModule(Module &M) {
 176   if (Options.CoverageType == SanitizerCoverageOptions::SCK_None)
 177     return false;
 178   C = &(M.getContext());
 179   DL = &M.getDataLayout();
 180   IntptrTy = Type::getIntNTy(*C, DL->getPointerSizeInBits());
 181   Type *VoidTy = Type::getVoidTy(*C);
 182   IRBuilder<> IRB(*C);
 183   Type *Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
 184   Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
 185   Int64Ty = IRB.getInt64Ty();
 186
 187   Function *CtorFunc =
 188       Function::Create(FunctionType::get(VoidTy, false),
 189                        GlobalValue::InternalLinkage, kSanCovModuleCtorName, &M);
 190   ReturnInst::Create(*C, BasicBlock::Create(*C, "", CtorFunc));
 191   appendToGlobalCtors(M, CtorFunc, kSanCtorAndDtorPriority);
 192
 193   SanCovFunction = checkSanitizerInterfaceFunction(
 194       M.getOrInsertFunction(kSanCovName, VoidTy, Int32PtrTy, nullptr));
 195   SanCovWithCheckFunction = checkSanitizerInterfaceFunction(
 196       M.getOrInsertFunction(kSanCovWithCheckName, VoidTy, Int32PtrTy, nullptr));
 197   SanCovIndirCallFunction =
 198       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 199           kSanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr));
 200   SanCovTraceCmpFunction =
 201       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 202           kSanCovTraceCmp, VoidTy, Int64Ty, Int64Ty, Int64Ty, nullptr));
 203
 204   SanCovModuleInit = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 205       kSanCovModuleInitName, VoidTy, Int32PtrTy, IntptrTy,
 206       Int8PtrTy, Int8PtrTy, nullptr));
 207   SanCovModuleInit->setLinkage(Function::ExternalLinkage);
 208   // We insert an empty inline asm after cov callbacks to avoid callback merge.
 209   EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
 210                             StringRef(""), StringRef(""),
 211                             /*hasSideEffects=*/true);
 212
 213   if (Options.TraceBB) {
 214     SanCovTraceEnter = checkSanitizerInterfaceFunction(
 215         M.getOrInsertFunction(kSanCovTraceEnter, VoidTy, Int32PtrTy, nullptr));
 216     SanCovTraceBB = checkSanitizerInterfaceFunction(
 217         M.getOrInsertFunction(kSanCovTraceBB, VoidTy, Int32PtrTy, nullptr));
 218   }
 219
 220   // At this point we create a dummy array of guards because we don't
 221   // know how many elements we will need.
 222   Type *Int32Ty = IRB.getInt32Ty();
 223   Type *Int8Ty = IRB.getInt8Ty();
 224
 225   GuardArray =
 226       new GlobalVariable(M, Int32Ty, false, GlobalValue::ExternalLinkage,
 227                          nullptr, "__sancov_gen_cov_tmp");
 228   if (Options.Use8bitCounters)
 229     EightBitCounterArray =
 230         new GlobalVariable(M, Int8Ty, false, GlobalVariable::ExternalLinkage,
 231                            nullptr, "__sancov_gen_cov_tmp");
 232
 233   for (auto &F : M)
 234     runOnFunction(F);
 235
 236   auto N = NumberOfInstrumentedBlocks();
 237
 238   // Now we know how many elements we need. Create an array of guards
 239   // with one extra element at the beginning for the size.
 240   Type *Int32ArrayNTy = ArrayType::get(Int32Ty, N + 1);
 241   GlobalVariable *RealGuardArray = new GlobalVariable(
 242       M, Int32ArrayNTy, false, GlobalValue::PrivateLinkage,
 243       Constant::getNullValue(Int32ArrayNTy), "__sancov_gen_cov");
 244
 245
 246   // Replace the dummy array with the real one.
 247   GuardArray->replaceAllUsesWith(
 248       IRB.CreatePointerCast(RealGuardArray, Int32PtrTy));
 249   GuardArray->eraseFromParent();
 250
 251   GlobalVariable *RealEightBitCounterArray;
 252   if (Options.Use8bitCounters) {
 253     // Make sure the array is 16-aligned.
 254     static const int kCounterAlignment = 16;
 255     Type *Int8ArrayNTy =
 256         ArrayType::get(Int8Ty, RoundUpToAlignment(N, kCounterAlignment));
 257     RealEightBitCounterArray = new GlobalVariable(
 258         M, Int8ArrayNTy, false, GlobalValue::PrivateLinkage,
 259         Constant::getNullValue(Int8ArrayNTy), "__sancov_gen_cov_counter");
 260     RealEightBitCounterArray->setAlignment(kCounterAlignment);
 261     EightBitCounterArray->replaceAllUsesWith(
 262         IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy));
 263     EightBitCounterArray->eraseFromParent();
 264   }
 265
 266   // Create variable for module (compilation unit) name
 267   Constant *ModNameStrConst =
 268       ConstantDataArray::getString(M.getContext(), M.getName(), true);
 269   GlobalVariable *ModuleName =
 270       new GlobalVariable(M, ModNameStrConst->getType(), true,
 271                          GlobalValue::PrivateLinkage, ModNameStrConst);
 272
 273   // Call __sanitizer_cov_module_init
 274   IRB.SetInsertPoint(CtorFunc->getEntryBlock().getTerminator());
 275   IRB.CreateCall4(
 276       SanCovModuleInit, IRB.CreatePointerCast(RealGuardArray, Int32PtrTy),
 277       ConstantInt::get(IntptrTy, N),
 278       Options.Use8bitCounters
 279           ? IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy)
 280           : Constant::getNullValue(Int8PtrTy),
 281       IRB.CreatePointerCast(ModuleName, Int8PtrTy));
 282   return true;
 283 }
 284
 285 bool SanitizerCoverageModule::runOnFunction(Function &F) {
 286   if (F.empty()) return false;
 287   if (F.getName().find(".module_ctor") != std::string::npos)
 288     return false;  // Should not instrument sanitizer init functions.
 289   if (Options.CoverageType >= SanitizerCoverageOptions::SCK_Edge)
 290     SplitAllCriticalEdges(F);
 291   SmallVector<Instruction*, 8> IndirCalls;
 292   SmallVector<BasicBlock*, 16> AllBlocks;
 293   SmallVector<Instruction*, 8> CmpTraceTargets;
 294   for (auto &BB : F) {
 295     AllBlocks.push_back(&BB);
 296     for (auto &Inst : BB) {
 297       if (Options.IndirectCalls) {
 298         CallSite CS(&Inst);
 299         if (CS && !CS.getCalledFunction())
 300           IndirCalls.push_back(&Inst);
 301       }
 302       if (Options.TraceCmp && isa<ICmpInst>(&Inst))
 303         CmpTraceTargets.push_back(&Inst);
 304     }
 305   }
 306   InjectCoverage(F, AllBlocks);
 307   InjectCoverageForIndirectCalls(F, IndirCalls);
 308   InjectTraceForCmp(F, CmpTraceTargets);
 309   return true;
 310 }
 311
 312 bool SanitizerCoverageModule::InjectCoverage(Function &F,
 313                                              ArrayRef<BasicBlock *> AllBlocks) {
 314   switch (Options.CoverageType) {
 315   case SanitizerCoverageOptions::SCK_None:
 316     return false;
 317   case SanitizerCoverageOptions::SCK_Function:
 318     InjectCoverageAtBlock(F, F.getEntryBlock(), false);
 319     return true;
 320   default: {
 321     bool UseCalls = ClCoverageBlockThreshold < AllBlocks.size();
 322     for (auto BB : AllBlocks)
 323       InjectCoverageAtBlock(F, *BB, UseCalls);
 324     return true;
 325   }
 326   }
 327 }
 328
 329 // On every indirect call we call a run-time function
 330 // __sanitizer_cov_indir_call* with two parameters:
 331 //   - callee address,
 332 //   - global cache array that contains kCacheSize pointers (zero-initialized).
 333 //     The cache is used to speed up recording the caller-callee pairs.
 334 // The address of the caller is passed implicitly via caller PC.
 335 // kCacheSize is encoded in the name of the run-time function.
 336 void SanitizerCoverageModule::InjectCoverageForIndirectCalls(
 337     Function &F, ArrayRef<Instruction *> IndirCalls) {
 338   if (IndirCalls.empty()) return;
 339   const int kCacheSize = 16;
 340   const int kCacheAlignment = 64;  // Align for better performance.
 341   Type *Ty = ArrayType::get(IntptrTy, kCacheSize);
 342   for (auto I : IndirCalls) {
 343     IRBuilder<> IRB(I);
 344     CallSite CS(I);
 345     Value *Callee = CS.getCalledValue();
 346     if (isa<InlineAsm>(Callee)) continue;
 347     GlobalVariable *CalleeCache = new GlobalVariable(
 348         *F.getParent(), Ty, false, GlobalValue::PrivateLinkage,
 349         Constant::getNullValue(Ty), "__sancov_gen_callee_cache");
 350     CalleeCache->setAlignment(kCacheAlignment);
 351     IRB.CreateCall2(SanCovIndirCallFunction,
 352                     IRB.CreatePointerCast(Callee, IntptrTy),
 353                     IRB.CreatePointerCast(CalleeCache, IntptrTy));
 354   }
 355 }
 356
 357 void SanitizerCoverageModule::InjectTraceForCmp(
 358     Function &F, ArrayRef<Instruction *> CmpTraceTargets) {
 359   for (auto I : CmpTraceTargets) {
 360     if (ICmpInst *ICMP = dyn_cast<ICmpInst>(I)) {
 361       IRBuilder<> IRB(ICMP);
 362       Value *A0 = ICMP->getOperand(0);
 363       Value *A1 = ICMP->getOperand(1);
 364       if (!A0->getType()->isIntegerTy()) continue;
 365       uint64_t TypeSize = DL->getTypeStoreSizeInBits(A0->getType());
 366       // __sanitizer_cov_trace_cmp((type_size << 32) | predicate, A0, A1);
 367       IRB.CreateCall3(
 368           SanCovTraceCmpFunction,
 369           ConstantInt::get(Int64Ty, (TypeSize << 32) | ICMP->getPredicate()),
 370           IRB.CreateIntCast(A0, Int64Ty, true),
 371           IRB.CreateIntCast(A1, Int64Ty, true));
 372     }
 373   }
 374 }
 375
 376 void SanitizerCoverageModule::SetNoSanitizeMetadata(Instruction *I) {
 377   I->setMetadata(
 378       I->getParent()->getParent()->getParent()->getMDKindID("nosanitize"),
 379       MDNode::get(*C, None));
 380 }
 381
 382 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
 383                                                     bool UseCalls) {
 384   BasicBlock::iterator IP = BB.getFirstInsertionPt(), BE = BB.end();
 385   // Skip static allocas at the top of the entry block so they don't become
 386   // dynamic when we split the block.  If we used our optimized stack layout,
 387   // then there will only be one alloca and it will come first.
 388   for (; IP != BE; ++IP) {
 389     AllocaInst *AI = dyn_cast<AllocaInst>(IP);
 390     if (!AI || !AI->isStaticAlloca())
 391       break;
 392   }
 393
 394   bool IsEntryBB = &BB == &F.getEntryBlock();
 395   DebugLoc EntryLoc = IsEntryBB && IP->getDebugLoc()
 396                           ? IP->getDebugLoc().getFnDebugLoc()
 397                           : IP->getDebugLoc();
 398   IRBuilder<> IRB(IP);
 399   IRB.SetCurrentDebugLocation(EntryLoc);
 400   SmallVector<Value *, 1> Indices;
 401   Value *GuardP = IRB.CreateAdd(
 402       IRB.CreatePointerCast(GuardArray, IntptrTy),
 403       ConstantInt::get(IntptrTy, (1 + NumberOfInstrumentedBlocks()) * 4));
 404   Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
 405   GuardP = IRB.CreateIntToPtr(GuardP, Int32PtrTy);
 406   if (UseCalls) {
 407     IRB.CreateCall(SanCovWithCheckFunction, GuardP);
 408   } else {
 409     LoadInst *Load = IRB.CreateLoad(GuardP);
 410     Load->setAtomic(Monotonic);
 411     Load->setAlignment(4);
 412     SetNoSanitizeMetadata(Load);
 413     Value *Cmp = IRB.CreateICmpSGE(Constant::getNullValue(Load->getType()), Load);
 414     Instruction *Ins = SplitBlockAndInsertIfThen(
 415         Cmp, IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
 416     IRB.SetInsertPoint(Ins);
 417     IRB.SetCurrentDebugLocation(EntryLoc);
 418     // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC.
 419     IRB.CreateCall(SanCovFunction, GuardP);
 420     IRB.CreateCall(EmptyAsm);  // Avoids callback merge.
 421   }
 422
 423   if (Options.Use8bitCounters) {
 424     IRB.SetInsertPoint(IP);
 425     Value *P = IRB.CreateAdd(
 426         IRB.CreatePointerCast(EightBitCounterArray, IntptrTy),
 427         ConstantInt::get(IntptrTy, NumberOfInstrumentedBlocks() - 1));
 428     P = IRB.CreateIntToPtr(P, IRB.getInt8PtrTy());
 429     LoadInst *LI = IRB.CreateLoad(P);
 430     Value *Inc = IRB.CreateAdd(LI, ConstantInt::get(IRB.getInt8Ty(), 1));
 431     StoreInst *SI = IRB.CreateStore(Inc, P);
 432     SetNoSanitizeMetadata(LI);
 433     SetNoSanitizeMetadata(SI);
 434   }
 435
 436   if (Options.TraceBB) {
 437     // Experimental support for tracing.
 438     // Insert a callback with the same guard variable as used for coverage.
 439     IRB.SetInsertPoint(IP);
 440     IRB.CreateCall(IsEntryBB ? SanCovTraceEnter : SanCovTraceBB, GuardP);
 441   }
 442 }
 443
 444 char SanitizerCoverageModule::ID = 0;
 445 INITIALIZE_PASS(SanitizerCoverageModule, "sancov",
 446     "SanitizerCoverage: TODO."
 447     "ModulePass", false, false)
 448 ModulePass *llvm::createSanitizerCoverageModulePass(
 449     const SanitizerCoverageOptions &Options) {
 450   return new SanitizerCoverageModule(Options);
 451 }