1 files changed, 294 insertions, 0 deletions
diff --git a/lib/Transforms/Instrumentation/SanitizerCoverage.cpp b/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
new file mode 100644
index 0000000..f882072
--- /dev/null
+++ b/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
@@ -0,0 +1,294 @@
+//===-- 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 boolean variable with the same linkage
+// as the function and inject this code into the entry block (CoverageLevel=1)
+// or all blocks (CoverageLevel>=2):
+// if (*Guard) {
+//    __sanitizer_cov();
+//    *Guard = 1;
+// }
+// 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 CoverageLevel>=3 we also split critical edges this effectively
+// instrumenting all edges.
+//
+// CoverageLevel>=4 add indirect call profiling implented as a function call.
+//
+// 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/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 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 kSanCovModuleCtorName = "sancov.module_ctor";
+static const uint64_t    kSanCtorAndDtorPriority = 1;
+
+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<int> ClCoverageBlockThreshold(
+    "sanitizer-coverage-block-threshold",
+    cl::desc("Add coverage instrumentation only to the entry block if there "
+             "are more than this number of blocks."),
+    cl::Hidden, cl::init(1500));
+
+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));
+
+namespace {
+
+class SanitizerCoverageModule : public ModulePass {
+ public:
+   SanitizerCoverageModule(int CoverageLevel = 0)
+       : ModulePass(ID),
+         CoverageLevel(std::max(CoverageLevel, (int)ClCoverageLevel)) {}
+  bool runOnModule(Module &M) override;
+  bool runOnFunction(Function &F);
+  static char ID;  // Pass identification, replacement for typeid
+  const char *getPassName() const override {
+    return "SanitizerCoverageModule";
+  }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.addRequired<DataLayoutPass>();
+  }
+
+ private:
+  void InjectCoverageForIndirectCalls(Function &F,
+                                      ArrayRef<Instruction *> IndirCalls);
+  bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks,
+                      ArrayRef<Instruction *> IndirCalls);
+  bool InjectTracing(Function &F, ArrayRef<BasicBlock *> AllBlocks);
+  void InjectCoverageAtBlock(Function &F, BasicBlock &BB);
+  Function *SanCovFunction;
+  Function *SanCovIndirCallFunction;
+  Function *SanCovModuleInit;
+  Function *SanCovTraceEnter, *SanCovTraceBB;
+  Type *IntptrTy;
+  LLVMContext *C;
+
+  int CoverageLevel;
+};
+
+}  // namespace
+
+static Function *checkInterfaceFunction(Constant *FuncOrBitcast) {
+  if (Function *F = dyn_cast<Function>(FuncOrBitcast))
+     return F;
+  std::string Err;
+  raw_string_ostream Stream(Err);
+  Stream << "SanitizerCoverage interface function redefined: "
+         << *FuncOrBitcast;
+  report_fatal_error(Err);
+}
+
+bool SanitizerCoverageModule::runOnModule(Module &M) {
+  if (!CoverageLevel) return false;
+  C = &(M.getContext());
+  DataLayoutPass *DLP = &getAnalysis<DataLayoutPass>();
+  IntptrTy = Type::getIntNTy(*C, DLP->getDataLayout().getPointerSizeInBits());
+  Type *VoidTy = Type::getVoidTy(*C);
+
+  Function *CtorFunc =
+      Function::Create(FunctionType::get(VoidTy, false),
+                       GlobalValue::InternalLinkage, kSanCovModuleCtorName, &M);
+  ReturnInst::Create(*C, BasicBlock::Create(*C, "", CtorFunc));
+  appendToGlobalCtors(M, CtorFunc, kSanCtorAndDtorPriority);
+
+  SanCovFunction =
+      checkInterfaceFunction(M.getOrInsertFunction(kSanCovName, VoidTy, nullptr));
+  SanCovIndirCallFunction = checkInterfaceFunction(M.getOrInsertFunction(
+      kSanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr));
+  SanCovModuleInit = checkInterfaceFunction(M.getOrInsertFunction(
+      kSanCovModuleInitName, Type::getVoidTy(*C), IntptrTy, nullptr));
+  SanCovModuleInit->setLinkage(Function::ExternalLinkage);
+
+  if (ClExperimentalTracing) {
+    SanCovTraceEnter = checkInterfaceFunction(
+        M.getOrInsertFunction(kSanCovTraceEnter, VoidTy, IntptrTy, nullptr));
+    SanCovTraceBB = checkInterfaceFunction(
+        M.getOrInsertFunction(kSanCovTraceBB, VoidTy, IntptrTy, nullptr));
+  }
+
+  for (auto &F : M)
+    runOnFunction(F);
+
+  IRBuilder<> IRB(CtorFunc->getEntryBlock().getTerminator());
+  IRB.CreateCall(SanCovModuleInit,
+                 ConstantInt::get(IntptrTy, SanCovFunction->getNumUses()));
+  return true;
+}
+
+bool SanitizerCoverageModule::runOnFunction(Function &F) {
+  if (F.empty()) return false;
+  // For now instrument only functions that will also be asan-instrumented.
+  if (!F.hasFnAttribute(Attribute::SanitizeAddress))
+    return false;
+  if (CoverageLevel >= 3)
+    SplitAllCriticalEdges(F, this);
+  SmallVector<Instruction*, 8> IndirCalls;
+  SmallVector<BasicBlock*, 16> AllBlocks;
+  for (auto &BB : F) {
+    AllBlocks.push_back(&BB);
+    if (CoverageLevel >= 4)
+      for (auto &Inst : BB) {
+        CallSite CS(&Inst);
+        if (CS && !CS.getCalledFunction())
+          IndirCalls.push_back(&Inst);
+      }
+  }
+  InjectCoverage(F, AllBlocks, IndirCalls);
+  InjectTracing(F, AllBlocks);
+  return true;
+}
+
+// Experimental support for tracing.
+// Basicaly, insert a callback at the beginning of every basic block.
+// Every callback gets a pointer to a uniqie global for internal storage.
+bool SanitizerCoverageModule::InjectTracing(Function &F,
+                                            ArrayRef<BasicBlock *> AllBlocks) {
+  if (!ClExperimentalTracing) return false;
+  Type *Ty = ArrayType::get(IntptrTy, 1);  // May need to use more words later.
+  for (auto BB : AllBlocks) {
+    IRBuilder<> IRB(BB->getFirstInsertionPt());
+    GlobalVariable *TraceCache = new GlobalVariable(
+        *F.getParent(), Ty, false, GlobalValue::PrivateLinkage,
+        Constant::getNullValue(Ty), "__sancov_gen_trace_cache");
+    IRB.CreateCall(&F.getEntryBlock() == BB ? SanCovTraceEnter : SanCovTraceBB,
+                   IRB.CreatePointerCast(TraceCache, IntptrTy));
+  }
+  return true;
+}
+
+bool
+SanitizerCoverageModule::InjectCoverage(Function &F,
+                                        ArrayRef<BasicBlock *> AllBlocks,
+                                        ArrayRef<Instruction *> IndirCalls) {
+  if (!CoverageLevel) return false;
+
+  if (CoverageLevel == 1 ||
+      (unsigned)ClCoverageBlockThreshold < AllBlocks.size()) {
+    InjectCoverageAtBlock(F, F.getEntryBlock());
+  } else {
+    for (auto BB : AllBlocks)
+      InjectCoverageAtBlock(F, *BB);
+  }
+  InjectCoverageForIndirectCalls(F, IndirCalls);
+  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 (dyn_cast<InlineAsm>(Callee)) continue;
+    GlobalVariable *CalleeCache = new GlobalVariable(
+        *F.getParent(), Ty, false, GlobalValue::PrivateLinkage,
+        Constant::getNullValue(Ty), "__sancov_gen_callee_cache");
+    CalleeCache->setAlignment(kCacheAlignment);
+    IRB.CreateCall2(SanCovIndirCallFunction,
+                    IRB.CreatePointerCast(Callee, IntptrTy),
+                    IRB.CreatePointerCast(CalleeCache, IntptrTy));
+  }
+}
+
+void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F,
+                                                    BasicBlock &BB) {
+  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;
+  }
+
+  DebugLoc EntryLoc = &BB == &F.getEntryBlock()
+                          ? IP->getDebugLoc().getFnDebugLoc(*C)
+                          : IP->getDebugLoc();
+  IRBuilder<> IRB(IP);
+  IRB.SetCurrentDebugLocation(EntryLoc);
+  Type *Int8Ty = IRB.getInt8Ty();
+  GlobalVariable *Guard = new GlobalVariable(
+      *F.getParent(), Int8Ty, false, GlobalValue::PrivateLinkage,
+      Constant::getNullValue(Int8Ty), "__sancov_gen_cov_" + F.getName());
+  LoadInst *Load = IRB.CreateLoad(Guard);
+  Load->setAtomic(Monotonic);
+  Load->setAlignment(1);
+  Value *Cmp = IRB.CreateICmpEQ(Constant::getNullValue(Int8Ty), 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);
+  StoreInst *Store = IRB.CreateStore(ConstantInt::get(Int8Ty, 1), Guard);
+  Store->setAtomic(Monotonic);
+  Store->setAlignment(1);
+}
+
+char SanitizerCoverageModule::ID = 0;
+INITIALIZE_PASS(SanitizerCoverageModule, "sancov",
+    "SanitizerCoverage: TODO."
+    "ModulePass", false, false)
+ModulePass *llvm::createSanitizerCoverageModulePass(int CoverageLevel) {
+  return new SanitizerCoverageModule(CoverageLevel);
+}