lib/Transforms/Instrumentation/AddressSanitizer.cpp

//===-- AddressSanitizer.cpp - memory error detector ------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file is a part of AddressSanitizer, an address sanity checker.
// Details of the algorithm:
//  http://code.google.com/p/address-sanitizer/wiki/AddressSanitizerAlgorithm
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "asan"

#include "FunctionBlackList.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Function.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/LLVMContext.h"
#include "llvm/Module.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/DataTypes.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/IRBuilder.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/system_error.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Transforms/Instrumentation.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
#include "llvm/Type.h"

#include <string>
#include <algorithm>

using namespace llvm;

static const uint64_t kDefaultShadowScale = 3;
static const uint64_t kDefaultShadowOffset32 = 1ULL << 29;
static const uint64_t kDefaultShadowOffset64 = 1ULL << 44;

static const size_t kMaxStackMallocSize = 1 << 16;  // 64K
static const uintptr_t kCurrentStackFrameMagic = 0x41B58AB3;
static const uintptr_t kRetiredStackFrameMagic = 0x45E0360E;

static const char *kAsanModuleCtorName = "asan.module_ctor";
static const char *kAsanModuleDtorName = "asan.module_dtor";
static const int   kAsanCtorAndCtorPriority = 1;
static const char *kAsanReportErrorTemplate = "__asan_report_";
static const char *kAsanRegisterGlobalsName = "__asan_register_globals";
static const char *kAsanUnregisterGlobalsName = "__asan_unregister_globals";
static const char *kAsanInitName = "__asan_init";
static const char *kAsanHandleNoReturnName = "__asan_handle_no_return";
static const char *kAsanMappingOffsetName = "__asan_mapping_offset";
static const char *kAsanMappingScaleName = "__asan_mapping_scale";
static const char *kAsanStackMallocName = "__asan_stack_malloc";
static const char *kAsanStackFreeName = "__asan_stack_free";

static const int kAsanStackLeftRedzoneMagic = 0xf1;
static const int kAsanStackMidRedzoneMagic = 0xf2;
static const int kAsanStackRightRedzoneMagic = 0xf3;
static const int kAsanStackPartialRedzoneMagic = 0xf4;

// Command-line flags.

// This flag may need to be replaced with -f[no-]asan-reads.
static cl::opt<bool> ClInstrumentReads("asan-instrument-reads",
       cl::desc("instrument read instructions"), cl::Hidden, cl::init(true));
static cl::opt<bool> ClInstrumentWrites("asan-instrument-writes",
       cl::desc("instrument write instructions"), cl::Hidden, cl::init(true));
// This flag may need to be replaced with -f[no]asan-stack.
static cl::opt<bool> ClStack("asan-stack",
       cl::desc("Handle stack memory"), cl::Hidden, cl::init(true));
// This flag may need to be replaced with -f[no]asan-use-after-return.
static cl::opt<bool> ClUseAfterReturn("asan-use-after-return",
       cl::desc("Check return-after-free"), cl::Hidden, cl::init(false));
// This flag may need to be replaced with -f[no]asan-globals.
static cl::opt<bool> ClGlobals("asan-globals",
       cl::desc("Handle global objects"), cl::Hidden, cl::init(true));
static cl::opt<bool> ClMemIntrin("asan-memintrin",
       cl::desc("Handle memset/memcpy/memmove"), cl::Hidden, cl::init(true));
// This flag may need to be replaced with -fasan-blacklist.
static cl::opt<std::string>  ClBlackListFile("asan-blacklist",
       cl::desc("File containing the list of functions to ignore "
                "during instrumentation"), cl::Hidden);

// These flags allow to change the shadow mapping.
// The shadow mapping looks like
//    Shadow = (Mem >> scale) + (1 << offset_log)
static cl::opt<int> ClMappingScale("asan-mapping-scale",
       cl::desc("scale of asan shadow mapping"), cl::Hidden, cl::init(0));
static cl::opt<int> ClMappingOffsetLog("asan-mapping-offset-log",
       cl::desc("offset of asan shadow mapping"), cl::Hidden, cl::init(-1));

// Optimization flags. Not user visible, used mostly for testing
// and benchmarking the tool.
static cl::opt<bool> ClOpt("asan-opt",
       cl::desc("Optimize instrumentation"), cl::Hidden, cl::init(true));
static cl::opt<bool> ClOptSameTemp("asan-opt-same-temp",
       cl::desc("Instrument the same temp just once"), cl::Hidden,
       cl::init(true));
static cl::opt<bool> ClOptGlobals("asan-opt-globals",
       cl::desc("Don't instrument scalar globals"), cl::Hidden, cl::init(true));

// Debug flags.
static cl::opt<int> ClDebug("asan-debug", cl::desc("debug"), cl::Hidden,
                            cl::init(0));
static cl::opt<int> ClDebugStack("asan-debug-stack", cl::desc("debug stack"),
                                 cl::Hidden, cl::init(0));
static cl::opt<std::string> ClDebugFunc("asan-debug-func",
                                        cl::Hidden, cl::desc("Debug func"));
static cl::opt<int> ClDebugMin("asan-debug-min", cl::desc("Debug min inst"),
                               cl::Hidden, cl::init(-1));
static cl::opt<int> ClDebugMax("asan-debug-max", cl::desc("Debug man inst"),
                               cl::Hidden, cl::init(-1));

namespace {

/// AddressSanitizer: instrument the code in module to find memory bugs.
struct AddressSanitizer : public ModulePass {
  AddressSanitizer();
  virtual const char *getPassName() const;
  void instrumentMop(Instruction *I);
  void instrumentAddress(Instruction *OrigIns, IRBuilder<> &IRB,
                         Value *Addr, uint32_t TypeSize, bool IsWrite);
  Instruction *generateCrashCode(IRBuilder<> &IRB, Value *Addr,
                                 bool IsWrite, uint32_t TypeSize);
  bool instrumentMemIntrinsic(MemIntrinsic *MI);
  void instrumentMemIntrinsicParam(Instruction *OrigIns, Value *Addr,
                                  Value *Size,
                                   Instruction *InsertBefore, bool IsWrite);
  Value *memToShadow(Value *Shadow, IRBuilder<> &IRB);
  bool handleFunction(Module &M, Function &F);
  bool maybeInsertAsanInitAtFunctionEntry(Function &F);
  bool poisonStackInFunction(Module &M, Function &F);
  virtual bool runOnModule(Module &M);
  bool insertGlobalRedzones(Module &M);
  BranchInst *splitBlockAndInsertIfThen(Instruction *SplitBefore, Value *Cmp);
  static char ID;  // Pass identification, replacement for typeid

 private:

  uint64_t getAllocaSizeInBytes(AllocaInst *AI) {
    Type *Ty = AI->getAllocatedType();
    uint64_t SizeInBytes = TD->getTypeAllocSize(Ty);
    return SizeInBytes;
  }
  uint64_t getAlignedSize(uint64_t SizeInBytes) {
    return ((SizeInBytes + RedzoneSize - 1)
            / RedzoneSize) * RedzoneSize;
  }
  uint64_t getAlignedAllocaSize(AllocaInst *AI) {
    uint64_t SizeInBytes = getAllocaSizeInBytes(AI);
    return getAlignedSize(SizeInBytes);
  }

  void PoisonStack(const ArrayRef<AllocaInst*> &AllocaVec, IRBuilder<> IRB,
                   Value *ShadowBase, bool DoPoison);
  bool LooksLikeCodeInBug11395(Instruction *I);

  Module      *CurrentModule;
  LLVMContext *C;
  TargetData *TD;
  uint64_t MappingOffset;
  int MappingScale;
  size_t RedzoneSize;
  int LongSize;
  Type *IntptrTy;
  Type *IntptrPtrTy;
  Function *AsanCtorFunction;
  Function *AsanInitFunction;
  Instruction *CtorInsertBefore;
  OwningPtr<FunctionBlackList> BL;
};
}  // namespace

char AddressSanitizer::ID = 0;
INITIALIZE_PASS(AddressSanitizer, "asan",
    "AddressSanitizer: detects use-after-free and out-of-bounds bugs.",
    false, false)
AddressSanitizer::AddressSanitizer() : ModulePass(ID) { }
ModulePass *llvm::createAddressSanitizerPass() {
  return new AddressSanitizer();
}

const char *AddressSanitizer::getPassName() const {
  return "AddressSanitizer";
}

// Create a constant for Str so that we can pass it to the run-time lib.
static GlobalVariable *createPrivateGlobalForString(Module &M, StringRef Str) {
  Constant *StrConst = ConstantDataArray::getString(M.getContext(), Str);
  return new GlobalVariable(M, StrConst->getType(), true,
                            GlobalValue::PrivateLinkage, StrConst, "");
}

// Split the basic block and insert an if-then code.
// Before:
//   Head
//   SplitBefore
//   Tail
// After:
//   Head
//   if (Cmp)
//     NewBasicBlock
//   SplitBefore
//   Tail
//
// Returns the NewBasicBlock's terminator.
BranchInst *AddressSanitizer::splitBlockAndInsertIfThen(
    Instruction *SplitBefore, Value *Cmp) {
  BasicBlock *Head = SplitBefore->getParent();
  BasicBlock *Tail = Head->splitBasicBlock(SplitBefore);
  TerminatorInst *HeadOldTerm = Head->getTerminator();
  BasicBlock *NewBasicBlock =
      BasicBlock::Create(*C, "", Head->getParent());
  BranchInst *HeadNewTerm = BranchInst::Create(/*ifTrue*/NewBasicBlock,
                                               /*ifFalse*/Tail,
                                               Cmp);
  ReplaceInstWithInst(HeadOldTerm, HeadNewTerm);

  BranchInst *CheckTerm = BranchInst::Create(Tail, NewBasicBlock);
  return CheckTerm;
}

Value *AddressSanitizer::memToShadow(Value *Shadow, IRBuilder<> &IRB) {
  // Shadow >> scale
  Shadow = IRB.CreateLShr(Shadow, MappingScale);
  if (MappingOffset == 0)
    return Shadow;
  // (Shadow >> scale) | offset
  return IRB.CreateOr(Shadow, ConstantInt::get(IntptrTy,
                                               MappingOffset));
}

void AddressSanitizer::instrumentMemIntrinsicParam(Instruction *OrigIns,
    Value *Addr, Value *Size, Instruction *InsertBefore, bool IsWrite) {
  // Check the first byte.
  {
    IRBuilder<> IRB(InsertBefore);
    instrumentAddress(OrigIns, IRB, Addr, 8, IsWrite);
  }
  // Check the last byte.
  {
    IRBuilder<> IRB(InsertBefore);
    Value *SizeMinusOne = IRB.CreateSub(
        Size, ConstantInt::get(Size->getType(), 1));
    SizeMinusOne = IRB.CreateIntCast(SizeMinusOne, IntptrTy, false);
    Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy);
    Value *AddrPlusSizeMinisOne = IRB.CreateAdd(AddrLong, SizeMinusOne);
    instrumentAddress(OrigIns, IRB, AddrPlusSizeMinisOne, 8, IsWrite);
  }
}

// Instrument memset/memmove/memcpy
bool AddressSanitizer::instrumentMemIntrinsic(MemIntrinsic *MI) {
  Value *Dst = MI->getDest();
  MemTransferInst *MemTran = dyn_cast<MemTransferInst>(MI);
  Value *Src = MemTran ? MemTran->getSource() : NULL;
  Value *Length = MI->getLength();

  Constant *ConstLength = dyn_cast<Constant>(Length);
  Instruction *InsertBefore = MI;
  if (ConstLength) {
    if (ConstLength->isNullValue()) return false;
  } else {
    // The size is not a constant so it could be zero -- check at run-time.
    IRBuilder<> IRB(InsertBefore);

    Value *Cmp = IRB.CreateICmpNE(Length,
                                   Constant::getNullValue(Length->getType()));
    InsertBefore = splitBlockAndInsertIfThen(InsertBefore, Cmp);
  }

  instrumentMemIntrinsicParam(MI, Dst, Length, InsertBefore, true);
  if (Src)
    instrumentMemIntrinsicParam(MI, Src, Length, InsertBefore, false);
  return true;
}

static Value *getLDSTOperand(Instruction *I) {
  if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
    return LI->getPointerOperand();
  }
  return cast<StoreInst>(*I).getPointerOperand();
}

void AddressSanitizer::instrumentMop(Instruction *I) {
  int IsWrite = isa<StoreInst>(*I);
  Value *Addr = getLDSTOperand(I);
  if (ClOpt && ClOptGlobals && isa<GlobalVariable>(Addr)) {
    // We are accessing a global scalar variable. Nothing to catch here.
    return;
  }
  Type *OrigPtrTy = Addr->getType();
  Type *OrigTy = cast<PointerType>(OrigPtrTy)->getElementType();

  assert(OrigTy->isSized());
  uint32_t TypeSize = TD->getTypeStoreSizeInBits(OrigTy);

  if (TypeSize != 8  && TypeSize != 16 &&
      TypeSize != 32 && TypeSize != 64 && TypeSize != 128) {
    // Ignore all unusual sizes.
    return;
  }

  IRBuilder<> IRB(I);
  instrumentAddress(I, IRB, Addr, TypeSize, IsWrite);
}

Instruction *AddressSanitizer::generateCrashCode(
    IRBuilder<> &IRB, Value *Addr, bool IsWrite, uint32_t TypeSize) {
  // IsWrite and TypeSize are encoded in the function name.
  std::string FunctionName = std::string(kAsanReportErrorTemplate) +
      (IsWrite ? "store" : "load") + itostr(TypeSize / 8);
  Value *ReportWarningFunc = CurrentModule->getOrInsertFunction(
      FunctionName, IRB.getVoidTy(), IntptrTy, NULL);
  CallInst *Call = IRB.CreateCall(ReportWarningFunc, Addr);
  Call->setDoesNotReturn();
  return Call;
}

void AddressSanitizer::instrumentAddress(Instruction *OrigIns,
                                         IRBuilder<> &IRB, Value *Addr,
                                         uint32_t TypeSize, bool IsWrite) {
  Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy);

  Type *ShadowTy  = IntegerType::get(
      *C, std::max(8U, TypeSize >> MappingScale));
  Type *ShadowPtrTy = PointerType::get(ShadowTy, 0);
  Value *ShadowPtr = memToShadow(AddrLong, IRB);
  Value *CmpVal = Constant::getNullValue(ShadowTy);
  Value *ShadowValue = IRB.CreateLoad(
      IRB.CreateIntToPtr(ShadowPtr, ShadowPtrTy));

  Value *Cmp = IRB.CreateICmpNE(ShadowValue, CmpVal);

  Instruction *CheckTerm = splitBlockAndInsertIfThen(
      cast<Instruction>(Cmp)->getNextNode(), Cmp);
  IRBuilder<> IRB2(CheckTerm);

  size_t Granularity = 1 << MappingScale;
  if (TypeSize < 8 * Granularity) {
    // Addr & (Granularity - 1)
    Value *Lower3Bits = IRB2.CreateAnd(
        AddrLong, ConstantInt::get(IntptrTy, Granularity - 1));
    // (Addr & (Granularity - 1)) + size - 1
    Value *LastAccessedByte = IRB2.CreateAdd(
        Lower3Bits, ConstantInt::get(IntptrTy, TypeSize / 8 - 1));
    // (uint8_t) ((Addr & (Granularity-1)) + size - 1)
    LastAccessedByte = IRB2.CreateIntCast(
        LastAccessedByte, IRB.getInt8Ty(), false);
    // ((uint8_t) ((Addr & (Granularity-1)) + size - 1)) >= ShadowValue
    Value *Cmp2 = IRB2.CreateICmpSGE(LastAccessedByte, ShadowValue);

    CheckTerm = splitBlockAndInsertIfThen(CheckTerm, Cmp2);
  }

  IRBuilder<> IRB1(CheckTerm);
  Instruction *Crash = generateCrashCode(IRB1, AddrLong, IsWrite, TypeSize);
  Crash->setDebugLoc(OrigIns->getDebugLoc());
  ReplaceInstWithInst(CheckTerm, new UnreachableInst(*C));
}

// This function replaces all global variables with new variables that have
// trailing redzones. It also creates a function that poisons
// redzones and inserts this function into llvm.global_ctors.
bool AddressSanitizer::insertGlobalRedzones(Module &M) {
  SmallVector<GlobalVariable *, 16> GlobalsToChange;

  for (Module::GlobalListType::iterator G = M.getGlobalList().begin(),
       E = M.getGlobalList().end(); G != E; ++G) {
    Type *Ty = cast<PointerType>(G->getType())->getElementType();
    DEBUG(dbgs() << "GLOBAL: " << *G);

    if (!Ty->isSized()) continue;
    if (!G->hasInitializer()) continue;
    // Touch only those globals that will not be defined in other modules.
    // Don't handle ODR type linkages since other modules may be built w/o asan.
    if (G->getLinkage() != GlobalVariable::ExternalLinkage &&
        G->getLinkage() != GlobalVariable::PrivateLinkage &&
        G->getLinkage() != GlobalVariable::InternalLinkage)
      continue;
    // Two problems with thread-locals:
    //   - The address of the main thread's copy can't be computed at link-time.
    //   - Need to poison all copies, not just the main thread's one.
    if (G->isThreadLocal())
      continue;
    // For now, just ignore this Alloca if the alignment is large.
    if (G->getAlignment() > RedzoneSize) continue;

    // Ignore all the globals with the names starting with "\01L_OBJC_".
    // Many of those are put into the .cstring section. The linker compresses
    // that section by removing the spare \0s after the string terminator, so
    // our redzones get broken.
    if ((G->getName().find("\01L_OBJC_") == 0) ||
        (G->getName().find("\01l_OBJC_") == 0)) {
      DEBUG(dbgs() << "Ignoring \\01L_OBJC_* global: " << *G);
      continue;
    }

    if (G->hasSection()) {
      StringRef Section(G->getSection());
      // Ignore the globals from the __OBJC section. The ObjC runtime assumes
      // those conform to /usr/lib/objc/runtime.h, so we can't add redzones to
      // them.
      if ((Section.find("__OBJC,") == 0) ||
          (Section.find("__DATA, __objc_") == 0)) {
        DEBUG(dbgs() << "Ignoring ObjC runtime global: " << *G);
        continue;
      }
      // See http://code.google.com/p/address-sanitizer/issues/detail?id=32
      // Constant CFString instances are compiled in the following way:
      //  -- the string buffer is emitted into
      //     __TEXT,__cstring,cstring_literals
      //  -- the constant NSConstantString structure referencing that buffer
      //     is placed into __DATA,__cfstring
      // Therefore there's no point in placing redzones into __DATA,__cfstring.
      // Moreover, it causes the linker to crash on OS X 10.7
      if (Section.find("__DATA,__cfstring") == 0) {
        DEBUG(dbgs() << "Ignoring CFString: " << *G);
        continue;
      }
    }

    GlobalsToChange.push_back(G);
  }

  size_t n = GlobalsToChange.size();
  if (n == 0) return false;

  // A global is described by a structure
  //   size_t beg;
  //   size_t size;
  //   size_t size_with_redzone;
  //   const char *name;
  // We initialize an array of such structures and pass it to a run-time call.
  StructType *GlobalStructTy = StructType::get(IntptrTy, IntptrTy,
                                               IntptrTy, IntptrTy, NULL);
  SmallVector<Constant *, 16> Initializers(n);

  IRBuilder<> IRB(CtorInsertBefore);

  for (size_t i = 0; i < n; i++) {
    GlobalVariable *G = GlobalsToChange[i];
    PointerType *PtrTy = cast<PointerType>(G->getType());
    Type *Ty = PtrTy->getElementType();
    uint64_t SizeInBytes = TD->getTypeAllocSize(Ty);
    uint64_t RightRedzoneSize = RedzoneSize +
        (RedzoneSize - (SizeInBytes % RedzoneSize));
    Type *RightRedZoneTy = ArrayType::get(IRB.getInt8Ty(), RightRedzoneSize);

    StructType *NewTy = StructType::get(Ty, RightRedZoneTy, NULL);
    Constant *NewInitializer = ConstantStruct::get(
        NewTy, G->getInitializer(),
        Constant::getNullValue(RightRedZoneTy), NULL);

    SmallString<2048> DescriptionOfGlobal = G->getName();
    DescriptionOfGlobal += " (";
    DescriptionOfGlobal += M.getModuleIdentifier();
    DescriptionOfGlobal += ")";
    GlobalVariable *Name = createPrivateGlobalForString(M, DescriptionOfGlobal);

    // Create a new global variable with enough space for a redzone.
    GlobalVariable *NewGlobal = new GlobalVariable(
        M, NewTy, G->isConstant(), G->getLinkage(),
        NewInitializer, "", G, G->isThreadLocal());
    NewGlobal->copyAttributesFrom(G);
    NewGlobal->setAlignment(RedzoneSize);

    Value *Indices2[2];
    Indices2[0] = IRB.getInt32(0);
    Indices2[1] = IRB.getInt32(0);

    G->replaceAllUsesWith(
        ConstantExpr::getGetElementPtr(NewGlobal, Indices2, true));
    NewGlobal->takeName(G);
    G->eraseFromParent();

    Initializers[i] = ConstantStruct::get(
        GlobalStructTy,
        ConstantExpr::getPointerCast(NewGlobal, IntptrTy),
        ConstantInt::get(IntptrTy, SizeInBytes),
        ConstantInt::get(IntptrTy, SizeInBytes + RightRedzoneSize),
        ConstantExpr::getPointerCast(Name, IntptrTy),
        NULL);
    DEBUG(dbgs() << "NEW GLOBAL:\n" << *NewGlobal);
  }

  ArrayType *ArrayOfGlobalStructTy = ArrayType::get(GlobalStructTy, n);
  GlobalVariable *AllGlobals = new GlobalVariable(
      M, ArrayOfGlobalStructTy, false, GlobalVariable::PrivateLinkage,
      ConstantArray::get(ArrayOfGlobalStructTy, Initializers), "");

  Function *AsanRegisterGlobals = cast<Function>(M.getOrInsertFunction(
      kAsanRegisterGlobalsName, IRB.getVoidTy(), IntptrTy, IntptrTy, NULL));
  AsanRegisterGlobals->setLinkage(Function::ExternalLinkage);

  IRB.CreateCall2(AsanRegisterGlobals,
                  IRB.CreatePointerCast(AllGlobals, IntptrTy),
                  ConstantInt::get(IntptrTy, n));

  // We also need to unregister globals at the end, e.g. when a shared library
  // gets closed.
  Function *AsanDtorFunction = Function::Create(
      FunctionType::get(Type::getVoidTy(*C), false),
      GlobalValue::InternalLinkage, kAsanModuleDtorName, &M);
  BasicBlock *AsanDtorBB = BasicBlock::Create(*C, "", AsanDtorFunction);
  IRBuilder<> IRB_Dtor(ReturnInst::Create(*C, AsanDtorBB));
  Function *AsanUnregisterGlobals = cast<Function>(M.getOrInsertFunction(
      kAsanUnregisterGlobalsName, IRB.getVoidTy(), IntptrTy, IntptrTy, NULL));
  AsanUnregisterGlobals->setLinkage(Function::ExternalLinkage);

  IRB_Dtor.CreateCall2(AsanUnregisterGlobals,
                       IRB.CreatePointerCast(AllGlobals, IntptrTy),
                       ConstantInt::get(IntptrTy, n));
  appendToGlobalDtors(M, AsanDtorFunction, kAsanCtorAndCtorPriority);

  DEBUG(dbgs() << M);
  return true;
}

// virtual
bool AddressSanitizer::runOnModule(Module &M) {
  // Initialize the private fields. No one has accessed them before.
  TD = getAnalysisIfAvailable<TargetData>();
  if (!TD)
    return false;
  BL.reset(new FunctionBlackList(ClBlackListFile));

  CurrentModule = &M;
  C = &(M.getContext());
  LongSize = TD->getPointerSizeInBits();
  IntptrTy = Type::getIntNTy(*C, LongSize);
  IntptrPtrTy = PointerType::get(IntptrTy, 0);

  AsanCtorFunction = Function::Create(
      FunctionType::get(Type::getVoidTy(*C), false),
      GlobalValue::InternalLinkage, kAsanModuleCtorName, &M);
  BasicBlock *AsanCtorBB = BasicBlock::Create(*C, "", AsanCtorFunction);
  CtorInsertBefore = ReturnInst::Create(*C, AsanCtorBB);

  // call __asan_init in the module ctor.
  IRBuilder<> IRB(CtorInsertBefore);
  AsanInitFunction = cast<Function>(
      M.getOrInsertFunction(kAsanInitName, IRB.getVoidTy(), NULL));
  AsanInitFunction->setLinkage(Function::ExternalLinkage);
  IRB.CreateCall(AsanInitFunction);

  MappingOffset = LongSize == 32
      ? kDefaultShadowOffset32 : kDefaultShadowOffset64;
  if (ClMappingOffsetLog >= 0) {
    if (ClMappingOffsetLog == 0) {
      // special case
      MappingOffset = 0;
    } else {
      MappingOffset = 1ULL << ClMappingOffsetLog;
    }
  }
  MappingScale = kDefaultShadowScale;
  if (ClMappingScale) {
    MappingScale = ClMappingScale;
  }
  // Redzone used for stack and globals is at least 32 bytes.
  // For scales 6 and 7, the redzone has to be 64 and 128 bytes respectively.
  RedzoneSize = std::max(32, (int)(1 << MappingScale));

  bool Res = false;

  if (ClGlobals)
    Res |= insertGlobalRedzones(M);

  if (ClMappingOffsetLog >= 0) {
    // Tell the run-time the current values of mapping offset and scale.
    GlobalValue *asan_mapping_offset =
        new GlobalVariable(M, IntptrTy, true, GlobalValue::LinkOnceODRLinkage,
                       ConstantInt::get(IntptrTy, MappingOffset),
                       kAsanMappingOffsetName);
    // Read the global, otherwise it may be optimized away.
    IRB.CreateLoad(asan_mapping_offset, true);
  }
  if (ClMappingScale) {
    GlobalValue *asan_mapping_scale =
        new GlobalVariable(M, IntptrTy, true, GlobalValue::LinkOnceODRLinkage,
                           ConstantInt::get(IntptrTy, MappingScale),
                           kAsanMappingScaleName);
    // Read the global, otherwise it may be optimized away.
    IRB.CreateLoad(asan_mapping_scale, true);
  }


  for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
    if (F->isDeclaration()) continue;
    Res |= handleFunction(M, *F);
  }

  appendToGlobalCtors(M, AsanCtorFunction, kAsanCtorAndCtorPriority);

  return Res;
}

bool AddressSanitizer::maybeInsertAsanInitAtFunctionEntry(Function &F) {
  // For each NSObject descendant having a +load method, this method is invoked
  // by the ObjC runtime before any of the static constructors is called.
  // Therefore we need to instrument such methods with a call to __asan_init
  // at the beginning in order to initialize our runtime before any access to
  // the shadow memory.
  // We cannot just ignore these methods, because they may call other
  // instrumented functions.
  if (F.getName().find(" load]") != std::string::npos) {
    IRBuilder<> IRB(F.begin()->begin());
    IRB.CreateCall(AsanInitFunction);
    return true;
  }
  return false;
}

bool AddressSanitizer::handleFunction(Module &M, Function &F) {
  if (BL->isIn(F)) return false;
  if (&F == AsanCtorFunction) return false;

  // If needed, insert __asan_init before checking for AddressSafety attr.
  maybeInsertAsanInitAtFunctionEntry(F);

  if (!F.hasFnAttr(Attribute::AddressSafety)) return false;

  if (!ClDebugFunc.empty() && ClDebugFunc != F.getName())
    return false;
  // We want to instrument every address only once per basic block
  // (unless there are calls between uses).
  SmallSet<Value*, 16> TempsToInstrument;
  SmallVector<Instruction*, 16> ToInstrument;
  SmallVector<Instruction*, 8> NoReturnCalls;

  // Fill the set of memory operations to instrument.
  for (Function::iterator FI = F.begin(), FE = F.end();
       FI != FE; ++FI) {
    TempsToInstrument.clear();
    for (BasicBlock::iterator BI = FI->begin(), BE = FI->end();
         BI != BE; ++BI) {
      if (LooksLikeCodeInBug11395(BI)) return false;
      if ((isa<LoadInst>(BI) && ClInstrumentReads) ||
          (isa<StoreInst>(BI) && ClInstrumentWrites)) {
        Value *Addr = getLDSTOperand(BI);
        if (ClOpt && ClOptSameTemp) {
          if (!TempsToInstrument.insert(Addr))
            continue;  // We've seen this temp in the current BB.
        }
      } else if (isa<MemIntrinsic>(BI) && ClMemIntrin) {
        // ok, take it.
      } else {
        if (CallInst *CI = dyn_cast<CallInst>(BI)) {
          // A call inside BB.
          TempsToInstrument.clear();
          if (CI->doesNotReturn()) {
            NoReturnCalls.push_back(CI);
          }
        }
        continue;
      }
      ToInstrument.push_back(BI);
    }
  }

  // Instrument.
  int NumInstrumented = 0;
  for (size_t i = 0, n = ToInstrument.size(); i != n; i++) {
    Instruction *Inst = ToInstrument[i];
    if (ClDebugMin < 0 || ClDebugMax < 0 ||
        (NumInstrumented >= ClDebugMin && NumInstrumented <= ClDebugMax)) {
      if (isa<StoreInst>(Inst) || isa<LoadInst>(Inst))
        instrumentMop(Inst);
      else
        instrumentMemIntrinsic(cast<MemIntrinsic>(Inst));
    }
    NumInstrumented++;
  }

  DEBUG(dbgs() << F);

  bool ChangedStack = poisonStackInFunction(M, F);

  // We must unpoison the stack before every NoReturn call (throw, _exit, etc).
  // See e.g. http://code.google.com/p/address-sanitizer/issues/detail?id=37
  for (size_t i = 0, n = NoReturnCalls.size(); i != n; i++) {
    Instruction *CI = NoReturnCalls[i];
    IRBuilder<> IRB(CI);
    IRB.CreateCall(M.getOrInsertFunction(kAsanHandleNoReturnName,
                                         IRB.getVoidTy(), NULL));
  }

  return NumInstrumented > 0 || ChangedStack || !NoReturnCalls.empty();
}

static uint64_t ValueForPoison(uint64_t PoisonByte, size_t ShadowRedzoneSize) {
  if (ShadowRedzoneSize == 1) return PoisonByte;
  if (ShadowRedzoneSize == 2) return (PoisonByte << 8) + PoisonByte;
  if (ShadowRedzoneSize == 4)
    return (PoisonByte << 24) + (PoisonByte << 16) +
        (PoisonByte << 8) + (PoisonByte);
  llvm_unreachable("ShadowRedzoneSize is either 1, 2 or 4");
}

static void PoisonShadowPartialRightRedzone(uint8_t *Shadow,
                                            size_t Size,
                                            size_t RedzoneSize,
                                            size_t ShadowGranularity,
                                            uint8_t Magic) {
  for (size_t i = 0; i < RedzoneSize;
       i+= ShadowGranularity, Shadow++) {
    if (i + ShadowGranularity <= Size) {
      *Shadow = 0;  // fully addressable
    } else if (i >= Size) {
      *Shadow = Magic;  // unaddressable
    } else {
      *Shadow = Size - i;  // first Size-i bytes are addressable
    }
  }
}

void AddressSanitizer::PoisonStack(const ArrayRef<AllocaInst*> &AllocaVec,
                                   IRBuilder<> IRB,
                                   Value *ShadowBase, bool DoPoison) {
  size_t ShadowRZSize = RedzoneSize >> MappingScale;
  assert(ShadowRZSize >= 1 && ShadowRZSize <= 4);
  Type *RZTy = Type::getIntNTy(*C, ShadowRZSize * 8);
  Type *RZPtrTy = PointerType::get(RZTy, 0);

  Value *PoisonLeft  = ConstantInt::get(RZTy,
    ValueForPoison(DoPoison ? kAsanStackLeftRedzoneMagic : 0LL, ShadowRZSize));
  Value *PoisonMid   = ConstantInt::get(RZTy,
    ValueForPoison(DoPoison ? kAsanStackMidRedzoneMagic : 0LL, ShadowRZSize));
  Value *PoisonRight = ConstantInt::get(RZTy,
    ValueForPoison(DoPoison ? kAsanStackRightRedzoneMagic : 0LL, ShadowRZSize));

  // poison the first red zone.
  IRB.CreateStore(PoisonLeft, IRB.CreateIntToPtr(ShadowBase, RZPtrTy));

  // poison all other red zones.
  uint64_t Pos = RedzoneSize;
  for (size_t i = 0, n = AllocaVec.size(); i < n; i++) {
    AllocaInst *AI = AllocaVec[i];
    uint64_t SizeInBytes = getAllocaSizeInBytes(AI);
    uint64_t AlignedSize = getAlignedAllocaSize(AI);
    assert(AlignedSize - SizeInBytes < RedzoneSize);
    Value *Ptr = NULL;

    Pos += AlignedSize;

    assert(ShadowBase->getType() == IntptrTy);
    if (SizeInBytes < AlignedSize) {
      // Poison the partial redzone at right
      Ptr = IRB.CreateAdd(
          ShadowBase, ConstantInt::get(IntptrTy,
                                       (Pos >> MappingScale) - ShadowRZSize));
      size_t AddressableBytes = RedzoneSize - (AlignedSize - SizeInBytes);
      uint32_t Poison = 0;
      if (DoPoison) {
        PoisonShadowPartialRightRedzone((uint8_t*)&Poison, AddressableBytes,
                                        RedzoneSize,
                                        1ULL << MappingScale,
                                        kAsanStackPartialRedzoneMagic);
      }
      Value *PartialPoison = ConstantInt::get(RZTy, Poison);
      IRB.CreateStore(PartialPoison, IRB.CreateIntToPtr(Ptr, RZPtrTy));
    }

    // Poison the full redzone at right.
    Ptr = IRB.CreateAdd(ShadowBase,
                        ConstantInt::get(IntptrTy, Pos >> MappingScale));
    Value *Poison = i == AllocaVec.size() - 1 ? PoisonRight : PoisonMid;
    IRB.CreateStore(Poison, IRB.CreateIntToPtr(Ptr, RZPtrTy));

    Pos += RedzoneSize;
  }
}

// Workaround for bug 11395: we don't want to instrument stack in functions
// with large assembly blobs (32-bit only), otherwise reg alloc may crash.
// FIXME: remove once the bug 11395 is fixed.
bool AddressSanitizer::LooksLikeCodeInBug11395(Instruction *I) {
  if (LongSize != 32) return false;
  CallInst *CI = dyn_cast<CallInst>(I);
  if (!CI || !CI->isInlineAsm()) return false;
  if (CI->getNumArgOperands() <= 5) return false;
  // We have inline assembly with quite a few arguments.
  return true;
}

// Find all static Alloca instructions and put
// poisoned red zones around all of them.
// Then unpoison everything back before the function returns.
//
// Stack poisoning does not play well with exception handling.
// When an exception is thrown, we essentially bypass the code
// that unpoisones the stack. This is why the run-time library has
// to intercept __cxa_throw (as well as longjmp, etc) and unpoison the entire
// stack in the interceptor. This however does not work inside the
// actual function which catches the exception. Most likely because the
// compiler hoists the load of the shadow value somewhere too high.
// This causes asan to report a non-existing bug on 453.povray.
// It sounds like an LLVM bug.
bool AddressSanitizer::poisonStackInFunction(Module &M, Function &F) {
  if (!ClStack) return false;
  SmallVector<AllocaInst*, 16> AllocaVec;
  SmallVector<Instruction*, 8> RetVec;
  uint64_t TotalSize = 0;

  // Filter out Alloca instructions we want (and can) handle.
  // Collect Ret instructions.
  for (Function::iterator FI = F.begin(), FE = F.end();
       FI != FE; ++FI) {
    BasicBlock &BB = *FI;
    for (BasicBlock::iterator BI = BB.begin(), BE = BB.end();
         BI != BE; ++BI) {
      if (isa<ReturnInst>(BI)) {
          RetVec.push_back(BI);
          continue;
      }

      AllocaInst *AI = dyn_cast<AllocaInst>(BI);
      if (!AI) continue;
      if (AI->isArrayAllocation()) continue;
      if (!AI->isStaticAlloca()) continue;
      if (!AI->getAllocatedType()->isSized()) continue;
      if (AI->getAlignment() > RedzoneSize) continue;
      AllocaVec.push_back(AI);
      uint64_t AlignedSize =  getAlignedAllocaSize(AI);
      TotalSize += AlignedSize;
    }
  }

  if (AllocaVec.empty()) return false;

  uint64_t LocalStackSize = TotalSize + (AllocaVec.size() + 1) * RedzoneSize;

  bool DoStackMalloc = ClUseAfterReturn
      && LocalStackSize <= kMaxStackMallocSize;

  Instruction *InsBefore = AllocaVec[0];
  IRBuilder<> IRB(InsBefore);


  Type *ByteArrayTy = ArrayType::get(IRB.getInt8Ty(), LocalStackSize);
  AllocaInst *MyAlloca =
      new AllocaInst(ByteArrayTy, "MyAlloca", InsBefore);
  MyAlloca->setAlignment(RedzoneSize);
  assert(MyAlloca->isStaticAlloca());
  Value *OrigStackBase = IRB.CreatePointerCast(MyAlloca, IntptrTy);
  Value *LocalStackBase = OrigStackBase;

  if (DoStackMalloc) {
    Value *AsanStackMallocFunc = M.getOrInsertFunction(
        kAsanStackMallocName, IntptrTy, IntptrTy, IntptrTy, NULL);
    LocalStackBase = IRB.CreateCall2(AsanStackMallocFunc,
        ConstantInt::get(IntptrTy, LocalStackSize), OrigStackBase);
  }

  // This string will be parsed by the run-time (DescribeStackAddress).
  SmallString<2048> StackDescriptionStorage;
  raw_svector_ostream StackDescription(StackDescriptionStorage);
  StackDescription << F.getName() << " " << AllocaVec.size() << " ";

  uint64_t Pos = RedzoneSize;
  // Replace Alloca instructions with base+offset.
  for (size_t i = 0, n = AllocaVec.size(); i < n; i++) {
    AllocaInst *AI = AllocaVec[i];
    uint64_t SizeInBytes = getAllocaSizeInBytes(AI);
    StringRef Name = AI->getName();
    StackDescription << Pos << " " << SizeInBytes << " "
                     << Name.size() << " " << Name << " ";
    uint64_t AlignedSize = getAlignedAllocaSize(AI);
    assert((AlignedSize % RedzoneSize) == 0);
    AI->replaceAllUsesWith(
        IRB.CreateIntToPtr(
            IRB.CreateAdd(LocalStackBase, ConstantInt::get(IntptrTy, Pos)),
            AI->getType()));
    Pos += AlignedSize + RedzoneSize;
  }
  assert(Pos == LocalStackSize);

  // Write the Magic value and the frame description constant to the redzone.
  Value *BasePlus0 = IRB.CreateIntToPtr(LocalStackBase, IntptrPtrTy);
  IRB.CreateStore(ConstantInt::get(IntptrTy, kCurrentStackFrameMagic),
                  BasePlus0);
  Value *BasePlus1 = IRB.CreateAdd(LocalStackBase,
                                   ConstantInt::get(IntptrTy, LongSize/8));
  BasePlus1 = IRB.CreateIntToPtr(BasePlus1, IntptrPtrTy);
  Value *Description = IRB.CreatePointerCast(
      createPrivateGlobalForString(M, StackDescription.str()),
      IntptrTy);
  IRB.CreateStore(Description, BasePlus1);

  // Poison the stack redzones at the entry.
  Value *ShadowBase = memToShadow(LocalStackBase, IRB);
  PoisonStack(ArrayRef<AllocaInst*>(AllocaVec), IRB, ShadowBase, true);

  Value *AsanStackFreeFunc = NULL;
  if (DoStackMalloc) {
    AsanStackFreeFunc = M.getOrInsertFunction(
        kAsanStackFreeName, IRB.getVoidTy(),
        IntptrTy, IntptrTy, IntptrTy, NULL);
  }

  // Unpoison the stack before all ret instructions.
  for (size_t i = 0, n = RetVec.size(); i < n; i++) {
    Instruction *Ret = RetVec[i];
    IRBuilder<> IRBRet(Ret);

    // Mark the current frame as retired.
    IRBRet.CreateStore(ConstantInt::get(IntptrTy, kRetiredStackFrameMagic),
                       BasePlus0);
    // Unpoison the stack.
    PoisonStack(ArrayRef<AllocaInst*>(AllocaVec), IRBRet, ShadowBase, false);

    if (DoStackMalloc) {
      IRBRet.CreateCall3(AsanStackFreeFunc, LocalStackBase,
                         ConstantInt::get(IntptrTy, LocalStackSize),
                         OrigStackBase);
    }
  }

  if (ClDebugStack) {
    DEBUG(dbgs() << F);
  }

  return true;
}