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+//===-- SanitizerCoverage.cpp - coverage instrumentation for sanitizers ---===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Coverage instrumentation that works with AddressSanitizer
+// and potentially with other Sanitizers.
+//
+// We create a Guard variable with the same linkage
+// as the function and inject this code into the entry block (SCK_Function)
+// or all blocks (SCK_BB):
+// if (Guard < 0) {
+// __sanitizer_cov(&Guard);
+// }
+// The accesses to Guard are atomic. The rest of the logic is
+// in __sanitizer_cov (it's fine to call it more than once).
+//
+// With SCK_Edge we also split critical edges this effectively
+// instrumenting all edges.
+//
+// This coverage implementation provides very limited data:
+// it only tells if a given function (block) was ever executed. No counters.
+// But for many use cases this is what we need and the added slowdown small.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Instrumentation.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/IR/CallSite.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/InlineAsm.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/MDBuilder.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Type.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "sancov"
+
+static const char *const kSanCovModuleInitName = "__sanitizer_cov_module_init";
+static const char *const kSanCovName = "__sanitizer_cov";
+static const char *const kSanCovWithCheckName = "__sanitizer_cov_with_check";
+static const char *const kSanCovIndirCallName = "__sanitizer_cov_indir_call16";
+static const char *const kSanCovTraceEnter = "__sanitizer_cov_trace_func_enter";
+static const char *const kSanCovTraceBB = "__sanitizer_cov_trace_basic_block";
+static const char *const kSanCovTraceCmp = "__sanitizer_cov_trace_cmp";
+static const char *const kSanCovModuleCtorName = "sancov.module_ctor";
+static const uint64_t kSanCtorAndDtorPriority = 2;
+
+static cl::opt<int> ClCoverageLevel("sanitizer-coverage-level",
+ cl::desc("Sanitizer Coverage. 0: none, 1: entry block, 2: all blocks, "
+ "3: all blocks and critical edges, "
+ "4: above plus indirect calls"),
+ cl::Hidden, cl::init(0));
+
+static cl::opt<unsigned> ClCoverageBlockThreshold(
+ "sanitizer-coverage-block-threshold",
+ cl::desc("Use a callback with a guard check inside it if there are"
+ " more than this number of blocks."),
+ cl::Hidden, cl::init(500));
+
+static cl::opt<bool>
+ ClExperimentalTracing("sanitizer-coverage-experimental-tracing",
+ cl::desc("Experimental basic-block tracing: insert "
+ "callbacks at every basic block"),
+ cl::Hidden, cl::init(false));
+
+static cl::opt<bool>
+ ClExperimentalCMPTracing("sanitizer-coverage-experimental-trace-compares",
+ cl::desc("Experimental tracing of CMP and similar "
+ "instructions"),
+ cl::Hidden, cl::init(false));
+
+// Experimental 8-bit counters used as an additional search heuristic during
+// coverage-guided fuzzing.
+// The counters are not thread-friendly:
+// - contention on these counters may cause significant slowdown;
+// - the counter updates are racy and the results may be inaccurate.
+// They are also inaccurate due to 8-bit integer overflow.
+static cl::opt<bool> ClUse8bitCounters("sanitizer-coverage-8bit-counters",
+ cl::desc("Experimental 8-bit counters"),
+ cl::Hidden, cl::init(false));
+
+namespace {
+
+SanitizerCoverageOptions getOptions(int LegacyCoverageLevel) {
+ SanitizerCoverageOptions Res;
+ switch (LegacyCoverageLevel) {
+ case 0:
+ Res.CoverageType = SanitizerCoverageOptions::SCK_None;
+ break;
+ case 1:
+ Res.CoverageType = SanitizerCoverageOptions::SCK_Function;
+ break;
+ case 2:
+ Res.CoverageType = SanitizerCoverageOptions::SCK_BB;
+ break;
+ case 3:
+ Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
+ break;
+ case 4:
+ Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
+ Res.IndirectCalls = true;
+ break;
+ }
+ return Res;
+}
+
+SanitizerCoverageOptions OverrideFromCL(SanitizerCoverageOptions Options) {
+ // Sets CoverageType and IndirectCalls.
+ SanitizerCoverageOptions CLOpts = getOptions(ClCoverageLevel);
+ Options.CoverageType = std::max(Options.CoverageType, CLOpts.CoverageType);
+ Options.IndirectCalls |= CLOpts.IndirectCalls;
+ Options.TraceBB |= ClExperimentalTracing;
+ Options.TraceCmp |= ClExperimentalCMPTracing;
+ Options.Use8bitCounters |= ClUse8bitCounters;
+ return Options;
+}
+
+class SanitizerCoverageModule : public ModulePass {
+ public:
+ SanitizerCoverageModule(
+ const SanitizerCoverageOptions &Options = SanitizerCoverageOptions())
+ : ModulePass(ID), Options(OverrideFromCL(Options)) {}
+ bool runOnModule(Module &M) override;
+ bool runOnFunction(Function &F);
+ static char ID; // Pass identification, replacement for typeid
+ const char *getPassName() const override {
+ return "SanitizerCoverageModule";
+ }
+
+ private:
+ void InjectCoverageForIndirectCalls(Function &F,
+ ArrayRef<Instruction *> IndirCalls);
+ void InjectTraceForCmp(Function &F, ArrayRef<Instruction *> CmpTraceTargets);
+ bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks);
+ void SetNoSanitizeMetadata(Instruction *I);
+ void InjectCoverageAtBlock(Function &F, BasicBlock &BB, bool UseCalls);
+ unsigned NumberOfInstrumentedBlocks() {
+ return SanCovFunction->getNumUses() + SanCovWithCheckFunction->getNumUses();
+ }
+ Function *SanCovFunction;
+ Function *SanCovWithCheckFunction;
+ Function *SanCovIndirCallFunction;
+ Function *SanCovTraceEnter, *SanCovTraceBB;
+ Function *SanCovTraceCmpFunction;
+ InlineAsm *EmptyAsm;
+ Type *IntptrTy, *Int64Ty;
+ LLVMContext *C;
+ const DataLayout *DL;
+
+ GlobalVariable *GuardArray;
+ GlobalVariable *EightBitCounterArray;
+
+ SanitizerCoverageOptions Options;
+};
+
+} // namespace
+
+bool SanitizerCoverageModule::runOnModule(Module &M) {
+ if (Options.CoverageType == SanitizerCoverageOptions::SCK_None)
+ return false;
+ C = &(M.getContext());
+ DL = &M.getDataLayout();
+ IntptrTy = Type::getIntNTy(*C, DL->getPointerSizeInBits());
+ Type *VoidTy = Type::getVoidTy(*C);
+ IRBuilder<> IRB(*C);
+ Type *Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
+ Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
+ Int64Ty = IRB.getInt64Ty();
+
+ SanCovFunction = checkSanitizerInterfaceFunction(
+ M.getOrInsertFunction(kSanCovName, VoidTy, Int32PtrTy, nullptr));
+ SanCovWithCheckFunction = checkSanitizerInterfaceFunction(
+ M.getOrInsertFunction(kSanCovWithCheckName, VoidTy, Int32PtrTy, nullptr));
+ SanCovIndirCallFunction =
+ checkSanitizerInterfaceFunction(M.getOrInsertFunction(
+ kSanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr));
+ SanCovTraceCmpFunction =
+ checkSanitizerInterfaceFunction(M.getOrInsertFunction(
+ kSanCovTraceCmp, VoidTy, Int64Ty, Int64Ty, Int64Ty, nullptr));
+
+ // We insert an empty inline asm after cov callbacks to avoid callback merge.
+ EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
+ StringRef(""), StringRef(""),
+ /*hasSideEffects=*/true);
+
+ if (Options.TraceBB) {
+ SanCovTraceEnter = checkSanitizerInterfaceFunction(
+ M.getOrInsertFunction(kSanCovTraceEnter, VoidTy, Int32PtrTy, nullptr));
+ SanCovTraceBB = checkSanitizerInterfaceFunction(
+ M.getOrInsertFunction(kSanCovTraceBB, VoidTy, Int32PtrTy, nullptr));
+ }
+
+ // At this point we create a dummy array of guards because we don't
+ // know how many elements we will need.
+ Type *Int32Ty = IRB.getInt32Ty();
+ Type *Int8Ty = IRB.getInt8Ty();
+
+ GuardArray =
+ new GlobalVariable(M, Int32Ty, false, GlobalValue::ExternalLinkage,
+ nullptr, "__sancov_gen_cov_tmp");
+ if (Options.Use8bitCounters)
+ EightBitCounterArray =
+ new GlobalVariable(M, Int8Ty, false, GlobalVariable::ExternalLinkage,
+ nullptr, "__sancov_gen_cov_tmp");
+
+ for (auto &F : M)
+ runOnFunction(F);
+
+ auto N = NumberOfInstrumentedBlocks();
+
+ // Now we know how many elements we need. Create an array of guards
+ // with one extra element at the beginning for the size.
+ Type *Int32ArrayNTy = ArrayType::get(Int32Ty, N + 1);
+ GlobalVariable *RealGuardArray = new GlobalVariable(
+ M, Int32ArrayNTy, false, GlobalValue::PrivateLinkage,
+ Constant::getNullValue(Int32ArrayNTy), "__sancov_gen_cov");
+
+
+ // Replace the dummy array with the real one.
+ GuardArray->replaceAllUsesWith(
+ IRB.CreatePointerCast(RealGuardArray, Int32PtrTy));
+ GuardArray->eraseFromParent();
+
+ GlobalVariable *RealEightBitCounterArray;
+ if (Options.Use8bitCounters) {
+ // Make sure the array is 16-aligned.
+ static const int kCounterAlignment = 16;
+ Type *Int8ArrayNTy =
+ ArrayType::get(Int8Ty, RoundUpToAlignment(N, kCounterAlignment));
+ RealEightBitCounterArray = new GlobalVariable(
+ M, Int8ArrayNTy, false, GlobalValue::PrivateLinkage,
+ Constant::getNullValue(Int8ArrayNTy), "__sancov_gen_cov_counter");
+ RealEightBitCounterArray->setAlignment(kCounterAlignment);
+ EightBitCounterArray->replaceAllUsesWith(
+ IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy));
+ EightBitCounterArray->eraseFromParent();
+ }
+
+ // Create variable for module (compilation unit) name
+ Constant *ModNameStrConst =
+ ConstantDataArray::getString(M.getContext(), M.getName(), true);
+ GlobalVariable *ModuleName =
+ new GlobalVariable(M, ModNameStrConst->getType(), true,
+ GlobalValue::PrivateLinkage, ModNameStrConst);
+
+ Function *CtorFunc;
+ std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
+ M, kSanCovModuleCtorName, kSanCovModuleInitName,
+ {Int32PtrTy, IntptrTy, Int8PtrTy, Int8PtrTy},
+ {IRB.CreatePointerCast(RealGuardArray, Int32PtrTy),
+ ConstantInt::get(IntptrTy, N),
+ Options.Use8bitCounters
+ ? IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy)
+ : Constant::getNullValue(Int8PtrTy),
+ IRB.CreatePointerCast(ModuleName, Int8PtrTy)});
+
+ appendToGlobalCtors(M, CtorFunc, kSanCtorAndDtorPriority);
+
+ return true;
+}
+
+bool SanitizerCoverageModule::runOnFunction(Function &F) {
+ if (F.empty()) return false;
+ if (F.getName().find(".module_ctor") != std::string::npos)
+ return false; // Should not instrument sanitizer init functions.
+ if (Options.CoverageType >= SanitizerCoverageOptions::SCK_Edge)
+ SplitAllCriticalEdges(F);
+ SmallVector<Instruction*, 8> IndirCalls;
+ SmallVector<BasicBlock*, 16> AllBlocks;
+ SmallVector<Instruction*, 8> CmpTraceTargets;
+ for (auto &BB : F) {
+ AllBlocks.push_back(&BB);
+ for (auto &Inst : BB) {
+ if (Options.IndirectCalls) {
+ CallSite CS(&Inst);
+ if (CS && !CS.getCalledFunction())
+ IndirCalls.push_back(&Inst);
+ }
+ if (Options.TraceCmp && isa<ICmpInst>(&Inst))
+ CmpTraceTargets.push_back(&Inst);
+ }
+ }
+ InjectCoverage(F, AllBlocks);
+ InjectCoverageForIndirectCalls(F, IndirCalls);
+ InjectTraceForCmp(F, CmpTraceTargets);
+ return true;
+}
+
+bool SanitizerCoverageModule::InjectCoverage(Function &F,
+ ArrayRef<BasicBlock *> AllBlocks) {
+ switch (Options.CoverageType) {
+ case SanitizerCoverageOptions::SCK_None:
+ return false;
+ case SanitizerCoverageOptions::SCK_Function:
+ InjectCoverageAtBlock(F, F.getEntryBlock(), false);
+ return true;
+ default: {
+ bool UseCalls = ClCoverageBlockThreshold < AllBlocks.size();
+ for (auto BB : AllBlocks)
+ InjectCoverageAtBlock(F, *BB, UseCalls);
+ return true;
+ }
+ }
+}
+
+// On every indirect call we call a run-time function
+// __sanitizer_cov_indir_call* with two parameters:
+// - callee address,
+// - global cache array that contains kCacheSize pointers (zero-initialized).
+// The cache is used to speed up recording the caller-callee pairs.
+// The address of the caller is passed implicitly via caller PC.
+// kCacheSize is encoded in the name of the run-time function.
+void SanitizerCoverageModule::InjectCoverageForIndirectCalls(
+ Function &F, ArrayRef<Instruction *> IndirCalls) {
+ if (IndirCalls.empty()) return;
+ const int kCacheSize = 16;
+ const int kCacheAlignment = 64; // Align for better performance.
+ Type *Ty = ArrayType::get(IntptrTy, kCacheSize);
+ for (auto I : IndirCalls) {
+ IRBuilder<> IRB(I);
+ CallSite CS(I);
+ Value *Callee = CS.getCalledValue();
+ if (isa<InlineAsm>(Callee)) continue;
+ GlobalVariable *CalleeCache = new GlobalVariable(
+ *F.getParent(), Ty, false, GlobalValue::PrivateLinkage,
+ Constant::getNullValue(Ty), "__sancov_gen_callee_cache");
+ CalleeCache->setAlignment(kCacheAlignment);
+ IRB.CreateCall(SanCovIndirCallFunction,
+ {IRB.CreatePointerCast(Callee, IntptrTy),
+ IRB.CreatePointerCast(CalleeCache, IntptrTy)});
+ }
+}
+
+void SanitizerCoverageModule::InjectTraceForCmp(
+ Function &F, ArrayRef<Instruction *> CmpTraceTargets) {
+ for (auto I : CmpTraceTargets) {
+ if (ICmpInst *ICMP = dyn_cast<ICmpInst>(I)) {
+ IRBuilder<> IRB(ICMP);
+ Value *A0 = ICMP->getOperand(0);
+ Value *A1 = ICMP->getOperand(1);
+ if (!A0->getType()->isIntegerTy()) continue;
+ uint64_t TypeSize = DL->getTypeStoreSizeInBits(A0->getType());
+ // __sanitizer_cov_trace_cmp((type_size << 32) | predicate, A0, A1);
+ IRB.CreateCall(
+ SanCovTraceCmpFunction,
+ {ConstantInt::get(Int64Ty, (TypeSize << 32) | ICMP->getPredicate()),
+ IRB.CreateIntCast(A0, Int64Ty, true),
+ IRB.CreateIntCast(A1, Int64Ty, true)});
+ }
+ }
+}
+
+void SanitizerCoverageModule::SetNoSanitizeMetadata(Instruction *I) {
+ I->setMetadata(
+ I->getParent()->getParent()->getParent()->getMDKindID("nosanitize"),
+ MDNode::get(*C, None));
+}
+
+void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
+ bool UseCalls) {
+ BasicBlock::iterator IP = BB.getFirstInsertionPt(), BE = BB.end();
+ // Skip static allocas at the top of the entry block so they don't become
+ // dynamic when we split the block. If we used our optimized stack layout,
+ // then there will only be one alloca and it will come first.
+ for (; IP != BE; ++IP) {
+ AllocaInst *AI = dyn_cast<AllocaInst>(IP);
+ if (!AI || !AI->isStaticAlloca())
+ break;
+ }
+
+ bool IsEntryBB = &BB == &F.getEntryBlock();
+ DebugLoc EntryLoc = IsEntryBB && IP->getDebugLoc()
+ ? IP->getDebugLoc().getFnDebugLoc()
+ : IP->getDebugLoc();
+ IRBuilder<> IRB(IP);
+ IRB.SetCurrentDebugLocation(EntryLoc);
+ SmallVector<Value *, 1> Indices;
+ Value *GuardP = IRB.CreateAdd(
+ IRB.CreatePointerCast(GuardArray, IntptrTy),
+ ConstantInt::get(IntptrTy, (1 + NumberOfInstrumentedBlocks()) * 4));
+ Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
+ GuardP = IRB.CreateIntToPtr(GuardP, Int32PtrTy);
+ if (UseCalls) {
+ IRB.CreateCall(SanCovWithCheckFunction, GuardP);
+ } else {
+ LoadInst *Load = IRB.CreateLoad(GuardP);
+ Load->setAtomic(Monotonic);
+ Load->setAlignment(4);
+ SetNoSanitizeMetadata(Load);
+ Value *Cmp = IRB.CreateICmpSGE(Constant::getNullValue(Load->getType()), Load);
+ Instruction *Ins = SplitBlockAndInsertIfThen(
+ Cmp, IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
+ IRB.SetInsertPoint(Ins);
+ IRB.SetCurrentDebugLocation(EntryLoc);
+ // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC.
+ IRB.CreateCall(SanCovFunction, GuardP);
+ IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
+ }
+
+ if (Options.Use8bitCounters) {
+ IRB.SetInsertPoint(IP);
+ Value *P = IRB.CreateAdd(
+ IRB.CreatePointerCast(EightBitCounterArray, IntptrTy),
+ ConstantInt::get(IntptrTy, NumberOfInstrumentedBlocks() - 1));
+ P = IRB.CreateIntToPtr(P, IRB.getInt8PtrTy());
+ LoadInst *LI = IRB.CreateLoad(P);
+ Value *Inc = IRB.CreateAdd(LI, ConstantInt::get(IRB.getInt8Ty(), 1));
+ StoreInst *SI = IRB.CreateStore(Inc, P);
+ SetNoSanitizeMetadata(LI);
+ SetNoSanitizeMetadata(SI);
+ }
+
+ if (Options.TraceBB) {
+ // Experimental support for tracing.
+ // Insert a callback with the same guard variable as used for coverage.
+ IRB.SetInsertPoint(IP);
+ IRB.CreateCall(IsEntryBB ? SanCovTraceEnter : SanCovTraceBB, GuardP);
+ }
+}
+
+char SanitizerCoverageModule::ID = 0;
+INITIALIZE_PASS(SanitizerCoverageModule, "sancov",
+ "SanitizerCoverage: TODO."
+ "ModulePass", false, false)
+ModulePass *llvm::createSanitizerCoverageModulePass(
+ const SanitizerCoverageOptions &Options) {
+ return new SanitizerCoverageModule(Options);
+}
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