HWAddressSanitizer.cpp

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//===- HWAddressSanitizer.cpp - memory access error detector --------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
/// \file
/// This file is a part of HWAddressSanitizer, an address basic correctness
/// checker based on tagged addressing.
//===----------------------------------------------------------------------===//
 
#include "llvm/Transforms/Instrumentation/HWAddressSanitizer.h"
#include "InstrumentationOptions.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/DomTreeUpdater.h"
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/Analysis/PostDominators.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/Analysis/StackSafetyAnalysis.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MD5.h"
#include "llvm/Support/RandomNumberGenerator.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/TargetParser/Triple.h"
#include "llvm/Transforms/Instrumentation/AddressSanitizerCommon.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Instrumentation.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/MemoryTaggingSupport.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
#include "llvm/Transforms/Utils/PromoteMemToReg.h"
#include <optional>
#include <random>
 
using namespace llvm;
 
#define DEBUG_TYPE "hwasan"
 
const char kHwasanModuleCtorName[] = "hwasan.module_ctor";
const char kHwasanNoteName[] = "hwasan.note";
const char kHwasanInitName[] = "__hwasan_init";
const char kHwasanPersonalityThunkName[] = "__hwasan_personality_thunk";
 
const char kHwasanShadowMemoryDynamicAddress[] =
    "__hwasan_shadow_memory_dynamic_address";
 
// Accesses sizes are powers of two: 1, 2, 4, 8, 16.
static const size_t kNumberOfAccessSizes = 5;
 
static const size_t kDefaultShadowScale = 4;
 
static const unsigned kShadowBaseAlignment = 32;
 
namespace {
enum class OffsetKind {
  kFixed = 0,
  kGlobal,
  kIfunc,
  kTls,
};
}
 
// These flags allow to change the shadow mapping and control how shadow memory
// is accessed. The shadow mapping looks like:
//    Shadow = (Mem >> scale) + offset
 
static cl::opt<uint64_t>
    ClMappingOffset("hwasan-mapping-offset",
                    cl::desc("HWASan shadow mapping offset [EXPERIMENTAL]"),
                    cl::Hidden);
 
static cl::opt<OffsetKind> ClMappingOffsetDynamic(
    "hwasan-mapping-offset-dynamic",
    cl::desc("HWASan shadow mapping dynamic offset location"), cl::Hidden,
    cl::values(clEnumValN(OffsetKind::kGlobal, "global", "Use global"),
               clEnumValN(OffsetKind::kIfunc, "ifunc", "Use ifunc global"),
               clEnumValN(OffsetKind::kTls, "tls", "Use TLS")));
 
STATISTIC(NumTotalFuncs, "Number of total funcs");
STATISTIC(NumInstrumentedFuncs, "Number of instrumented funcs");
STATISTIC(NumNoProfileSummaryFuncs, "Number of funcs without PS");
 
namespace {
 
bool shouldUsePageAliases(const InstrumentationOptions &Opts,
                          const Triple &TargetTriple) {
  return Opts.hwasan_experimental_use_page_aliases &&
         TargetTriple.getArch() == Triple::x86_64;
}
 
bool shouldInstrumentStack(const InstrumentationOptions &Opts,
                           const Triple &TargetTriple) {
  return !shouldUsePageAliases(Opts, TargetTriple) &&
         Opts.hwasan_instrument_stack;
}
 
bool shouldInstrumentWithCalls(const InstrumentationOptions &Opts,
                               const Triple &TargetTriple) {
  return valueOr(Opts.hwasan_instrument_with_calls,
                 TargetTriple.getArch() == Triple::x86_64);
}
 
bool mightUseStackSafetyAnalysis(const InstrumentationOptions &Opts,
                                 bool DisableOptimization) {
  return valueOr(Opts.hwasan_use_stack_safety, !DisableOptimization);
}
 
bool shouldUseStackSafetyAnalysis(const InstrumentationOptions &Opts,
                                  const Triple &TargetTriple,
                                  bool DisableOptimization) {
  return shouldInstrumentStack(Opts, TargetTriple) &&
         mightUseStackSafetyAnalysis(Opts, DisableOptimization);
}
 
bool shouldDetectUseAfterScope(const InstrumentationOptions &Opts,
                               const Triple &TargetTriple) {
  return Opts.hwasan_use_after_scope &&
         shouldInstrumentStack(Opts, TargetTriple);
}
 
/// An instrumentation pass implementing detection of addressability bugs
/// using tagged pointers.
class HWAddressSanitizer {
public:
  HWAddressSanitizer(const InstrumentationOptions &Opts, Module &M,
                     bool CompileKernel, bool Recover,
                     const StackSafetyGlobalInfo *SSI)
      : Opts(Opts), M(M), SSI(SSI) {
    this->Recover = valueOr(Opts.hwasan_recover, Recover);
    this->CompileKernel = valueOr(Opts.hwasan_kernel, CompileKernel);
    this->Rng = Opts.hwasan_random_rate ? M.createRNG(DEBUG_TYPE) : nullptr;
 
    initializeModule();
  }
 
  void sanitizeFunction(Function &F, FunctionAnalysisManager &FAM);
 
private:
  struct ShadowTagCheckInfo {
    Instruction *TagMismatchTerm = nullptr;
    Value *PtrLong = nullptr;
    Value *AddrLong = nullptr;
    Value *PtrTag = nullptr;
    Value *MemTag = nullptr;
  };
 
  bool selectiveInstrumentationShouldSkip(Function &F,
                                          FunctionAnalysisManager &FAM) const;
  void initializeModule();
  void createHwasanCtorComdat();
  void createHwasanNote();
 
  void initializeCallbacks(Module &M);
 
  Value *getOpaqueNoopCast(IRBuilder<> &IRB, Value *Val);
 
  Value *getDynamicShadowIfunc(IRBuilder<> &IRB);
  Value *getShadowNonTls(IRBuilder<> &IRB);
 
  void untagPointerOperand(Instruction *I, Value *Addr);
  Value *memToShadow(Value *Shadow, IRBuilder<> &IRB);
 
  int64_t getAccessInfo(bool IsWrite, unsigned AccessSizeIndex);
  ShadowTagCheckInfo insertShadowTagCheck(Value *Ptr, Instruction *InsertBefore,
                                          DomTreeUpdater &DTU, LoopInfo *LI);
  void instrumentMemAccessOutline(Value *Ptr, bool IsWrite,
                                  unsigned AccessSizeIndex,
                                  Instruction *InsertBefore,
                                  DomTreeUpdater &DTU, LoopInfo *LI);
  void instrumentMemAccessInline(Value *Ptr, bool IsWrite,
                                 unsigned AccessSizeIndex,
                                 Instruction *InsertBefore, DomTreeUpdater &DTU,
                                 LoopInfo *LI);
  bool ignoreMemIntrinsic(OptimizationRemarkEmitter &ORE, MemIntrinsic *MI);
  void instrumentMemIntrinsic(MemIntrinsic *MI);
  bool instrumentMemAccess(InterestingMemoryOperand &O, DomTreeUpdater &DTU,
                           LoopInfo *LI, const DataLayout &DL);
  bool ignoreAccessWithoutRemark(Instruction *Inst, Value *Ptr);
  bool ignoreAccess(OptimizationRemarkEmitter &ORE, Instruction *Inst,
                    Value *Ptr);
 
  void getInterestingMemoryOperands(
      OptimizationRemarkEmitter &ORE, Instruction *I,
      const TargetLibraryInfo &TLI,
      SmallVectorImpl<InterestingMemoryOperand> &Interesting);
 
  void tagAlloca(IRBuilder<> &IRB, AllocaInst *AI, Value *Tag, size_t Size);
  Value *tagPointer(IRBuilder<> &IRB, Type *Ty, Value *PtrLong, Value *Tag);
  Value *untagPointer(IRBuilder<> &IRB, Value *PtrLong);
  void instrumentStack(OptimizationRemarkEmitter &ORE, memtag::StackInfo &Info,
                       Value *StackTag, Value *UARTag, const DominatorTree &DT,
                       const PostDominatorTree &PDT, const LoopInfo &LI);
  void instrumentLandingPads(SmallVectorImpl<Instruction *> &RetVec);
  Value *getNextTagWithCall(IRBuilder<> &IRB);
  Value *getStackBaseTag(IRBuilder<> &IRB);
  Value *getAllocaTag(IRBuilder<> &IRB, Value *StackTag, unsigned AllocaNo);
  Value *getUARTag(IRBuilder<> &IRB);
 
  Value *getHwasanThreadSlotPtr(IRBuilder<> &IRB);
  Value *applyTagMask(IRBuilder<> &IRB, Value *OldTag);
  unsigned retagMask(unsigned AllocaNo);
 
  void emitPrologue(IRBuilder<> &IRB, bool WithFrameRecord);
 
  void instrumentGlobal(GlobalVariable *GV, uint8_t Tag);
  void instrumentGlobals();
 
  Value *getCachedFP(IRBuilder<> &IRB);
  Value *getFrameRecordInfo(IRBuilder<> &IRB);
 
  void instrumentPersonalityFunctions();
 
  const InstrumentationOptions &Opts;
  LLVMContext *C;
  Module &M;
  const StackSafetyGlobalInfo *SSI;
  Triple TargetTriple;
  std::unique_ptr<RandomNumberGenerator> Rng;
 
  /// This struct defines the shadow mapping using the rule:
  /// If `kFixed`, then
  ///   shadow = (mem >> Scale) + Offset.
  /// If `kGlobal`, then
  ///   extern char* __hwasan_shadow_memory_dynamic_address;
  ///   shadow = (mem >> Scale) + __hwasan_shadow_memory_dynamic_address
  /// If `kIfunc`, then
  ///   extern char __hwasan_shadow[];
  ///   shadow = (mem >> Scale) + &__hwasan_shadow
  /// If `kTls`, then
  ///   extern char *__hwasan_tls;
  ///   shadow = (mem>>Scale) + align_up(__hwasan_shadow, kShadowBaseAlignment)
  ///
  /// If WithFrameRecord is true, then __hwasan_tls will be used to access the
  /// ring buffer for storing stack allocations on targets that support it.
  class ShadowMapping {
    OffsetKind Kind;
    uint64_t Offset;
    uint8_t Scale;
    bool WithFrameRecord;
 
    void SetFixed(uint64_t O) {
      Kind = OffsetKind::kFixed;
      Offset = O;
    }
 
  public:
    void init(const InstrumentationOptions &Opts, Triple &TargetTriple,
              bool InstrumentWithCalls, bool CompileKernel);
    Align getObjectAlignment() const { return Align::fromLog2(Scale); }
    bool isInGlobal() const { return Kind == OffsetKind::kGlobal; }
    bool isInIfunc() const { return Kind == OffsetKind::kIfunc; }
    bool isInTls() const { return Kind == OffsetKind::kTls; }
    bool isFixed() const { return Kind == OffsetKind::kFixed; }
    uint8_t scale() const { return Scale; };
    uint64_t offset() const {
      assert(isFixed());
      return Offset;
    };
    bool withFrameRecord() const { return WithFrameRecord; };
  };
 
  ShadowMapping Mapping;
 
  Type *VoidTy = Type::getVoidTy(M.getContext());
  Type *IntptrTy = M.getDataLayout().getIntPtrType(M.getContext());
  PointerType *PtrTy = PointerType::getUnqual(M.getContext());
  Type *Int8Ty = Type::getInt8Ty(M.getContext());
  Type *Int32Ty = Type::getInt32Ty(M.getContext());
  Type *Int64Ty = Type::getInt64Ty(M.getContext());
 
  bool CompileKernel;
  bool Recover;
  bool OutlinedChecks;
  bool InlineFastPath;
  bool UseShortGranules;
  bool InstrumentLandingPads;
  bool InstrumentWithCalls;
  bool InstrumentStack;
  bool InstrumentGlobals;
  bool DetectUseAfterScope;
  bool UsePageAliases;
  bool UseMatchAllCallback;
 
  std::optional<uint8_t> MatchAllTag;
 
  unsigned PointerTagShift;
  uint64_t TagMaskByte;
 
  Function *HwasanCtorFunction;
 
  FunctionCallee HwasanMemoryAccessCallback[2][kNumberOfAccessSizes];
  FunctionCallee HwasanMemoryAccessCallbackSized[2];
 
  FunctionCallee HwasanMemmove, HwasanMemcpy, HwasanMemset;
  FunctionCallee HwasanHandleVfork;
 
  FunctionCallee HwasanTagMemoryFunc;
  FunctionCallee HwasanGenerateTagFunc;
  FunctionCallee HwasanRecordFrameRecordFunc;
 
  Constant *ShadowGlobal;
 
  Value *ShadowBase = nullptr;
  Value *StackBaseTag = nullptr;
  Value *CachedFP = nullptr;
  GlobalValue *ThreadPtrGlobal = nullptr;
};
 
} // end anonymous namespace
 
PreservedAnalyses HWAddressSanitizerPass::run(Module &M,
                                              ModuleAnalysisManager &MAM) {
  // Return early if nosanitize_hwaddress module flag is present for the module.
  if (checkIfAlreadyInstrumented(M, "nosanitize_hwaddress"))
    return PreservedAnalyses::all();
  const StackSafetyGlobalInfo *SSI = nullptr;
  const Triple &TargetTriple = M.getTargetTriple();
  const InstrumentationOptions &Opts = InstrumentationOptions::Global;
  if (shouldUseStackSafetyAnalysis(Opts, TargetTriple,
                                   Options.DisableOptimization))
    SSI = &MAM.getResult<StackSafetyGlobalAnalysis>(M);
 
  HWAddressSanitizer HWASan(Opts, M, Options.CompileKernel, Options.Recover,
                            SSI);
  auto &FAM = MAM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
  for (Function &F : M)
    HWASan.sanitizeFunction(F, FAM);
 
  PreservedAnalyses PA = PreservedAnalyses::none();
  // DominatorTreeAnalysis, PostDominatorTreeAnalysis, and LoopAnalysis
  // are incrementally updated throughout this pass whenever
  // SplitBlockAndInsertIfThen is called.
  PA.preserve<DominatorTreeAnalysis>();
  PA.preserve<PostDominatorTreeAnalysis>();
  PA.preserve<LoopAnalysis>();
  // GlobalsAA is considered stateless and does not get invalidated unless
  // explicitly invalidated; PreservedAnalyses::none() is not enough. Sanitizers
  // make changes that require GlobalsAA to be invalidated.
  PA.abandon<GlobalsAA>();
  return PA;
}
void HWAddressSanitizerPass::printPipeline(
    raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) {
  static_cast<PassInfoMixin<HWAddressSanitizerPass> *>(this)->printPipeline(
      OS, MapClassName2PassName);
  OS << '<';
  if (Options.CompileKernel)
    OS << "kernel;";
  if (Options.Recover)
    OS << "recover";
  OS << '>';
}
 
void HWAddressSanitizer::createHwasanNote() {
  // Create a note that contains pointers to the list of global
  // descriptors. Adding a note to the output file will cause the linker to
  // create a PT_NOTE program header pointing to the note that we can use to
  // find the descriptor list starting from the program headers. A function
  // provided by the runtime initializes the shadow memory for the globals by
  // accessing the descriptor list via the note. The dynamic loader needs to
  // call this function whenever a library is loaded.
  //
  // The reason why we use a note for this instead of a more conventional
  // approach of having a global constructor pass a descriptor list pointer to
  // the runtime is because of an order of initialization problem. With
  // constructors we can encounter the following problematic scenario:
  //
  // 1) library A depends on library B and also interposes one of B's symbols
  // 2) B's constructors are called before A's (as required for correctness)
  // 3) during construction, B accesses one of its "own" globals (actually
  //    interposed by A) and triggers a HWASAN failure due to the initialization
  //    for A not having happened yet
  //
  // Even without interposition it is possible to run into similar situations in
  // cases where two libraries mutually depend on each other.
  //
  // We only need one note per binary, so put everything for the note in a
  // comdat. This needs to be a comdat with an .init_array section to prevent
  // newer versions of lld from discarding the note.
  //
  // Create the note even if we aren't instrumenting globals. This ensures that
  // binaries linked from object files with both instrumented and
  // non-instrumented globals will end up with a note, even if a comdat from an
  // object file with non-instrumented globals is selected. The note is harmless
  // if the runtime doesn't support it, since it will just be ignored.
  Comdat *NoteComdat = M.getOrInsertComdat(kHwasanModuleCtorName);
 
  Type *Int8Arr0Ty = ArrayType::get(Int8Ty, 0);
  auto *Start =
      new GlobalVariable(M, Int8Arr0Ty, true, GlobalVariable::ExternalLinkage,
                         nullptr, "__start_hwasan_globals");
  Start->setVisibility(GlobalValue::HiddenVisibility);
  auto *Stop =
      new GlobalVariable(M, Int8Arr0Ty, true, GlobalVariable::ExternalLinkage,
                         nullptr, "__stop_hwasan_globals");
  Stop->setVisibility(GlobalValue::HiddenVisibility);
 
  // Null-terminated so actually 8 bytes, which are required in order to align
  // the note properly.
  auto *Name = ConstantDataArray::get(*C, "LLVM\0\0\0");
 
  auto *NoteTy = StructType::get(Int32Ty, Int32Ty, Int32Ty, Name->getType(),
                                 Int32Ty, Int32Ty);
  auto *Note =
      new GlobalVariable(M, NoteTy, /*isConstant=*/true,
                         GlobalValue::PrivateLinkage, nullptr, kHwasanNoteName);
  Note->setSection(".note.hwasan.globals");
  Note->setComdat(NoteComdat);
  Note->setAlignment(Align(4));
 
  // The pointers in the note need to be relative so that the note ends up being
  // placed in rodata, which is the standard location for notes.
  auto CreateRelPtr = [&](Constant *Ptr) {
    return ConstantExpr::getTrunc(
        ConstantExpr::getSub(ConstantExpr::getPtrToInt(Ptr, Int64Ty),
                             ConstantExpr::getPtrToInt(Note, Int64Ty)),
        Int32Ty);
  };
  Note->setInitializer(ConstantStruct::getAnon(
      {ConstantInt::get(Int32Ty, 8),                           // n_namesz
       ConstantInt::get(Int32Ty, 8),                           // n_descsz
       ConstantInt::get(Int32Ty, ELF::NT_LLVM_HWASAN_GLOBALS), // n_type
       Name, CreateRelPtr(Start), CreateRelPtr(Stop)}));
  appendToCompilerUsed(M, Note);
 
  // Create a zero-length global in hwasan_globals so that the linker will
  // always create start and stop symbols.
  auto *Dummy = new GlobalVariable(
      M, Int8Arr0Ty, /*isConstantGlobal*/ true, GlobalVariable::PrivateLinkage,
      Constant::getNullValue(Int8Arr0Ty), "hwasan.dummy.global");
  Dummy->setSection("hwasan_globals");
  Dummy->setComdat(NoteComdat);
  Dummy->setMetadata(LLVMContext::MD_associated,
                     MDNode::get(*C, ValueAsMetadata::get(Note)));
  appendToCompilerUsed(M, Dummy);
}
 
void HWAddressSanitizer::createHwasanCtorComdat() {
  std::tie(HwasanCtorFunction, std::ignore) =
      getOrCreateSanitizerCtorAndInitFunctions(
          M, kHwasanModuleCtorName, kHwasanInitName,
          /*InitArgTypes=*/{},
          /*InitArgs=*/{},
          // This callback is invoked when the functions are created the first
          // time. Hook them into the global ctors list in that case:
          [&](Function *Ctor, FunctionCallee) {
            Comdat *CtorComdat = M.getOrInsertComdat(kHwasanModuleCtorName);
            Ctor->setComdat(CtorComdat);
            appendToGlobalCtors(M, Ctor, 0, Ctor);
          });
 
  // Do not create .note.hwasan.globals for static binaries, as it is only
  // needed for instrumenting globals from dynamic libraries. In static
  // binaries, the global variables section can be accessed directly via the
  // __start_hwasan_globals and __stop_hwasan_globals symbols inserted by the
  // linker.
  if (!Opts.hwasan_static_linking)
    createHwasanNote();
}
 
/// Module-level initialization.
///
/// inserts a call to __hwasan_init to the module's constructor list.
void HWAddressSanitizer::initializeModule() {
  LLVM_DEBUG(dbgs() << "Init " << M.getName() << "\n");
  TargetTriple = M.getTargetTriple();
 
  // HWASan may do short granule checks on function arguments read from the
  // argument memory (last byte of the granule), which invalidates writeonly.
  for (Function &F : M.functions())
    removeASanIncompatibleFnAttributes(F, /*ReadsArgMem=*/true);
 
  // x86_64 currently has two modes:
  // - Intel LAM (default)
  // - pointer aliasing (heap only)
  bool IsX86_64 = TargetTriple.getArch() == Triple::x86_64;
  UsePageAliases = shouldUsePageAliases(Opts, TargetTriple);
  InstrumentWithCalls = shouldInstrumentWithCalls(Opts, TargetTriple);
  InstrumentStack = shouldInstrumentStack(Opts, TargetTriple);
  DetectUseAfterScope = shouldDetectUseAfterScope(Opts, TargetTriple);
  PointerTagShift = IsX86_64 ? 57 : 56;
  TagMaskByte = IsX86_64 ? 0x3F : 0xFF;
  if (Opts.hwasan_tag_bits) {
    if (TagMaskByte < 4)
      reportFatalUsageError(
          "need more than 4 bits of tag to have non-short-granule tags");
    TagMaskByte &= (1ULL << Opts.hwasan_tag_bits) - 1;
  }
 
  Mapping.init(Opts, TargetTriple, InstrumentWithCalls, CompileKernel);
 
  C = &(M.getContext());
  IRBuilder<> IRB(M);
 
  HwasanCtorFunction = nullptr;
 
  // Older versions of Android do not have the required runtime support for
  // short granules, global or personality function instrumentation. On other
  // platforms we currently require using the latest version of the runtime.
  bool NewRuntime =
      !TargetTriple.isAndroid() || !TargetTriple.isAndroidVersionLT(30);
 
  UseShortGranules = valueOr(Opts.hwasan_use_short_granules, NewRuntime);
  OutlinedChecks = (TargetTriple.isAArch64() || TargetTriple.isRISCV64()) &&
                   TargetTriple.isOSBinFormatELF() &&
                   !valueOr(Opts.hwasan_inline_all_checks, Recover);
 
  // These platforms may prefer less inlining to reduce binary size.
  InlineFastPath =
      valueOr(Opts.hwasan_inline_fast_path_checks,
              !(TargetTriple.isAndroid() || TargetTriple.isOSFuchsia()));
 
  if (Opts.hwasan_match_all_tag) {
    if (*Opts.hwasan_match_all_tag != -1) {
      MatchAllTag = *Opts.hwasan_match_all_tag & 0xFF;
    }
  } else if (CompileKernel) {
    MatchAllTag = 0xFF;
  }
  UseMatchAllCallback = !CompileKernel && MatchAllTag.has_value();
 
  // If we don't have personality function support, fall back to landing pads.
  InstrumentLandingPads =
      valueOr(Opts.hwasan_instrument_landing_pads, !NewRuntime);
 
  InstrumentGlobals = !CompileKernel && !UsePageAliases &&
                      valueOr(Opts.hwasan_globals, NewRuntime);
 
  if (!CompileKernel) {
    if (InstrumentGlobals)
      instrumentGlobals();
 
    createHwasanCtorComdat();
 
    bool InstrumentPersonalityFunctions =
        valueOr(Opts.hwasan_instrument_personality_functions, NewRuntime);
    if (InstrumentPersonalityFunctions)
      instrumentPersonalityFunctions();
  }
 
  if (!TargetTriple.isAndroid()) {
    ThreadPtrGlobal = M.getOrInsertGlobal("__hwasan_tls", IntptrTy, [&] {
      auto *GV = new GlobalVariable(M, IntptrTy, /*isConstant=*/false,
                                    GlobalValue::ExternalLinkage, nullptr,
                                    "__hwasan_tls", nullptr,
                                    GlobalVariable::InitialExecTLSModel);
      appendToCompilerUsed(M, GV);
      return GV;
    });
  }
}
 
void HWAddressSanitizer::initializeCallbacks(Module &M) {
  IRBuilder<> IRB(M);
  const std::string MatchAllStr = UseMatchAllCallback ? "_match_all" : "";
  FunctionType *HwasanMemoryAccessCallbackSizedFnTy,
      *HwasanMemoryAccessCallbackFnTy, *HwasanMemTransferFnTy,
      *HwasanMemsetFnTy;
  if (UseMatchAllCallback) {
    HwasanMemoryAccessCallbackSizedFnTy =
        FunctionType::get(VoidTy, {IntptrTy, IntptrTy, Int8Ty}, false);
    HwasanMemoryAccessCallbackFnTy =
        FunctionType::get(VoidTy, {IntptrTy, Int8Ty}, false);
    HwasanMemTransferFnTy =
        FunctionType::get(PtrTy, {PtrTy, PtrTy, IntptrTy, Int8Ty}, false);
    HwasanMemsetFnTy =
        FunctionType::get(PtrTy, {PtrTy, Int32Ty, IntptrTy, Int8Ty}, false);
  } else {
    HwasanMemoryAccessCallbackSizedFnTy =
        FunctionType::get(VoidTy, {IntptrTy, IntptrTy}, false);
    HwasanMemoryAccessCallbackFnTy =
        FunctionType::get(VoidTy, {IntptrTy}, false);
    HwasanMemTransferFnTy =
        FunctionType::get(PtrTy, {PtrTy, PtrTy, IntptrTy}, false);
    HwasanMemsetFnTy =
        FunctionType::get(PtrTy, {PtrTy, Int32Ty, IntptrTy}, false);
  }
 
  for (size_t AccessIsWrite = 0; AccessIsWrite <= 1; AccessIsWrite++) {
    const std::string TypeStr = AccessIsWrite ? "store" : "load";
    const std::string EndingStr = Recover ? "_noabort" : "";
 
    HwasanMemoryAccessCallbackSized[AccessIsWrite] =
        M.getOrInsertFunction((Opts.hwasan_memory_access_callback_prefix +
                               TypeStr + "N" + MatchAllStr + EndingStr)
                                  .str(),
                              HwasanMemoryAccessCallbackSizedFnTy);
 
    for (size_t AccessSizeIndex = 0; AccessSizeIndex < kNumberOfAccessSizes;
         AccessSizeIndex++) {
      HwasanMemoryAccessCallback[AccessIsWrite][AccessSizeIndex] =
          M.getOrInsertFunction((Opts.hwasan_memory_access_callback_prefix +
                                 TypeStr + itostr(1ULL << AccessSizeIndex) +
                                 MatchAllStr + EndingStr)
                                    .str(),
                                HwasanMemoryAccessCallbackFnTy);
    }
  }
 
  const std::string MemIntrinCallbackPrefix =
      (CompileKernel && !Opts.hwasan_kernel_mem_intrinsic_prefix)
          ? std::string("")
          : Opts.hwasan_memory_access_callback_prefix.str();
 
  HwasanMemmove = M.getOrInsertFunction(
      MemIntrinCallbackPrefix + "memmove" + MatchAllStr, HwasanMemTransferFnTy);
  HwasanMemcpy = M.getOrInsertFunction(
      MemIntrinCallbackPrefix + "memcpy" + MatchAllStr, HwasanMemTransferFnTy);
  HwasanMemset = M.getOrInsertFunction(
      MemIntrinCallbackPrefix + "memset" + MatchAllStr, HwasanMemsetFnTy);
 
  HwasanTagMemoryFunc = M.getOrInsertFunction("__hwasan_tag_memory", VoidTy,
                                              PtrTy, Int8Ty, IntptrTy);
  HwasanGenerateTagFunc =
      M.getOrInsertFunction("__hwasan_generate_tag", Int8Ty);
 
  HwasanRecordFrameRecordFunc =
      M.getOrInsertFunction("__hwasan_add_frame_record", VoidTy, Int64Ty);
 
  ShadowGlobal =
      M.getOrInsertGlobal("__hwasan_shadow", ArrayType::get(Int8Ty, 0));
 
  HwasanHandleVfork =
      M.getOrInsertFunction("__hwasan_handle_vfork", VoidTy, IntptrTy);
}
 
Value *HWAddressSanitizer::getOpaqueNoopCast(IRBuilder<> &IRB, Value *Val) {
  // An empty inline asm with input reg == output reg.
  // An opaque no-op cast, basically.
  // This prevents code bloat as a result of rematerializing trivial definitions
  // such as constants or global addresses at every load and store.
  InlineAsm *Asm =
      InlineAsm::get(FunctionType::get(PtrTy, {Val->getType()}, false),
                     StringRef(""), StringRef("=r,0"),
                     /*hasSideEffects=*/false);
  return IRB.CreateCall(Asm, {Val}, ".hwasan.shadow");
}
 
Value *HWAddressSanitizer::getDynamicShadowIfunc(IRBuilder<> &IRB) {
  return getOpaqueNoopCast(IRB, ShadowGlobal);
}
 
Value *HWAddressSanitizer::getShadowNonTls(IRBuilder<> &IRB) {
  if (Mapping.isFixed()) {
    return getOpaqueNoopCast(
        IRB, ConstantExpr::getIntToPtr(
                 ConstantInt::get(IntptrTy, Mapping.offset()), PtrTy));
  }
 
  if (Mapping.isInIfunc())
    return getDynamicShadowIfunc(IRB);
 
  Value *GlobalDynamicAddress = IRB.getModule()->getOrInsertGlobal(
      kHwasanShadowMemoryDynamicAddress, PtrTy);
  return IRB.CreateLoad(PtrTy, GlobalDynamicAddress);
}
 
bool HWAddressSanitizer::ignoreAccessWithoutRemark(Instruction *Inst,
                                                   Value *Ptr) {
  // Do not instrument accesses from different address spaces; we cannot deal
  // with them.
  Type *PtrTy = cast<PointerType>(Ptr->getType()->getScalarType());
  if (PtrTy->getPointerAddressSpace() != 0)
    return true;
 
  // Ignore swifterror addresses.
  // swifterror memory addresses are mem2reg promoted by instruction
  // selection. As such they cannot have regular uses like an instrumentation
  // function and it makes no sense to track them as memory.
  if (Ptr->isSwiftError())
    return true;
 
  if (findAllocaForValue(Ptr)) {
    if (!InstrumentStack)
      return true;
    if (SSI && SSI->stackAccessIsSafe(*Inst))
      return true;
  }
 
  if (isa<GlobalVariable>(getUnderlyingObject(Ptr))) {
    if (!InstrumentGlobals)
      return true;
    // TODO: Optimize inbound global accesses, like Asan `instrumentMop`.
  }
 
  return false;
}
 
bool HWAddressSanitizer::ignoreAccess(OptimizationRemarkEmitter &ORE,
                                      Instruction *Inst, Value *Ptr) {
  bool Ignored = ignoreAccessWithoutRemark(Inst, Ptr);
  if (Ignored) {
    ORE.emit(
        [&]() { return OptimizationRemark(DEBUG_TYPE, "ignoreAccess", Inst); });
  } else {
    ORE.emit([&]() {
      return OptimizationRemarkMissed(DEBUG_TYPE, "ignoreAccess", Inst);
    });
  }
  return Ignored;
}
 
void HWAddressSanitizer::getInterestingMemoryOperands(
    OptimizationRemarkEmitter &ORE, Instruction *I,
    const TargetLibraryInfo &TLI,
    SmallVectorImpl<InterestingMemoryOperand> &Interesting) {
  // Skip memory accesses inserted by another instrumentation.
  if (I->hasMetadata(LLVMContext::MD_nosanitize))
    return;
 
  // Do not instrument the load fetching the dynamic shadow address.
  if (ShadowBase == I)
    return;
 
  if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
    if (!Opts.hwasan_instrument_reads ||
        ignoreAccess(ORE, I, LI->getPointerOperand()))
      return;
    Interesting.emplace_back(I, LI->getPointerOperandIndex(), false,
                             LI->getType(), LI->getAlign());
  } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
    if (!Opts.hwasan_instrument_writes ||
        ignoreAccess(ORE, I, SI->getPointerOperand()))
      return;
    Interesting.emplace_back(I, SI->getPointerOperandIndex(), true,
                             SI->getValueOperand()->getType(), SI->getAlign());
  } else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(I)) {
    if (!Opts.hwasan_instrument_atomics ||
        ignoreAccess(ORE, I, RMW->getPointerOperand()))
      return;
    Interesting.emplace_back(I, RMW->getPointerOperandIndex(), true,
                             RMW->getValOperand()->getType(), std::nullopt);
  } else if (AtomicCmpXchgInst *XCHG = dyn_cast<AtomicCmpXchgInst>(I)) {
    if (!Opts.hwasan_instrument_atomics ||
        ignoreAccess(ORE, I, XCHG->getPointerOperand()))
      return;
    Interesting.emplace_back(I, XCHG->getPointerOperandIndex(), true,
                             XCHG->getCompareOperand()->getType(),
                             std::nullopt);
  } else if (auto *CI = dyn_cast<CallInst>(I)) {
    for (unsigned ArgNo = 0; ArgNo < CI->arg_size(); ArgNo++) {
      if (!Opts.hwasan_instrument_byval || !CI->isByValArgument(ArgNo) ||
          ignoreAccess(ORE, I, CI->getArgOperand(ArgNo)))
        continue;
      Type *Ty = CI->getParamByValType(ArgNo);
      Interesting.emplace_back(I, ArgNo, false, Ty, Align(1));
    }
    maybeMarkSanitizerLibraryCallNoBuiltin(CI, &TLI);
  }
}
 
static unsigned getPointerOperandIndex(Instruction *I) {
  if (LoadInst *LI = dyn_cast<LoadInst>(I))
    return LI->getPointerOperandIndex();
  if (StoreInst *SI = dyn_cast<StoreInst>(I))
    return SI->getPointerOperandIndex();
  if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(I))
    return RMW->getPointerOperandIndex();
  if (AtomicCmpXchgInst *XCHG = dyn_cast<AtomicCmpXchgInst>(I))
    return XCHG->getPointerOperandIndex();
  report_fatal_error("Unexpected instruction");
  return -1;
}
 
static size_t TypeSizeToSizeIndex(uint32_t TypeSize) {
  size_t Res = llvm::countr_zero(TypeSize / 8);
  assert(Res < kNumberOfAccessSizes);
  return Res;
}
 
void HWAddressSanitizer::untagPointerOperand(Instruction *I, Value *Addr) {
  if (TargetTriple.isAArch64() || TargetTriple.getArch() == Triple::x86_64 ||
      TargetTriple.isRISCV64())
    return;
 
  IRBuilder<> IRB(I);
  Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy);
  Value *UntaggedPtr =
      IRB.CreateIntToPtr(untagPointer(IRB, AddrLong), Addr->getType());
  I->setOperand(getPointerOperandIndex(I), UntaggedPtr);
}
 
Value *HWAddressSanitizer::memToShadow(Value *Mem, IRBuilder<> &IRB) {
  // Mem >> Scale
  Value *Shadow = IRB.CreateLShr(Mem, Mapping.scale());
  if (Mapping.isFixed() && Mapping.offset() == 0)
    return IRB.CreateIntToPtr(Shadow, PtrTy);
  // (Mem >> Scale) + Offset
  return IRB.CreatePtrAdd(ShadowBase, Shadow);
}
 
int64_t HWAddressSanitizer::getAccessInfo(bool IsWrite,
                                          unsigned AccessSizeIndex) {
  return (CompileKernel << HWASanAccessInfo::CompileKernelShift) |
         (MatchAllTag.has_value() << HWASanAccessInfo::HasMatchAllShift) |
         (MatchAllTag.value_or(0) << HWASanAccessInfo::MatchAllShift) |
         (Recover << HWASanAccessInfo::RecoverShift) |
         (IsWrite << HWASanAccessInfo::IsWriteShift) |
         (AccessSizeIndex << HWASanAccessInfo::AccessSizeShift);
}
 
HWAddressSanitizer::ShadowTagCheckInfo
HWAddressSanitizer::insertShadowTagCheck(Value *Ptr, Instruction *InsertBefore,
                                         DomTreeUpdater &DTU, LoopInfo *LI) {
  ShadowTagCheckInfo R;
 
  IRBuilder<> IRB(InsertBefore);
 
  R.PtrLong = IRB.CreatePointerCast(Ptr, IntptrTy);
  R.PtrTag =
      IRB.CreateTrunc(IRB.CreateLShr(R.PtrLong, PointerTagShift), Int8Ty);
  R.AddrLong = untagPointer(IRB, R.PtrLong);
  Value *Shadow = memToShadow(R.AddrLong, IRB);
  R.MemTag = IRB.CreateLoad(Int8Ty, Shadow);
  Value *TagMismatch = IRB.CreateICmpNE(R.PtrTag, R.MemTag);
 
  if (MatchAllTag.has_value()) {
    Value *TagNotIgnored = IRB.CreateICmpNE(
        R.PtrTag, ConstantInt::get(R.PtrTag->getType(), *MatchAllTag));
    TagMismatch = IRB.CreateAnd(TagMismatch, TagNotIgnored);
  }
 
  R.TagMismatchTerm = SplitBlockAndInsertIfThen(
      TagMismatch, InsertBefore, false,
      MDBuilder(*C).createUnlikelyBranchWeights(), &DTU, LI);
 
  return R;
}
 
void HWAddressSanitizer::instrumentMemAccessOutline(Value *Ptr, bool IsWrite,
                                                    unsigned AccessSizeIndex,
                                                    Instruction *InsertBefore,
                                                    DomTreeUpdater &DTU,
                                                    LoopInfo *LI) {
  assert(!UsePageAliases);
  const int64_t AccessInfo = getAccessInfo(IsWrite, AccessSizeIndex);
 
  if (InlineFastPath)
    InsertBefore =
        insertShadowTagCheck(Ptr, InsertBefore, DTU, LI).TagMismatchTerm;
 
  IRBuilder<> IRB(InsertBefore);
  bool UseFixedShadowIntrinsic = false;
  // The memaccess fixed shadow intrinsic is only supported on AArch64,
  // which allows a 16-bit immediate to be left-shifted by 32.
  // Since kShadowBaseAlignment == 32, and Linux by default will not
  // mmap above 48-bits, practically any valid shadow offset is
  // representable.
  // In particular, an offset of 4TB (1024 << 32) is representable, and
  // ought to be good enough for anybody.
  if (TargetTriple.isAArch64() && Mapping.isFixed()) {
    uint16_t OffsetShifted = Mapping.offset() >> 32;
    UseFixedShadowIntrinsic =
        static_cast<uint64_t>(OffsetShifted) << 32 == Mapping.offset();
  }
 
  if (UseFixedShadowIntrinsic) {
    IRB.CreateIntrinsic(
        UseShortGranules
            ? Intrinsic::hwasan_check_memaccess_shortgranules_fixedshadow
            : Intrinsic::hwasan_check_memaccess_fixedshadow,
        {Ptr, ConstantInt::get(Int32Ty, AccessInfo),
         ConstantInt::get(Int64Ty, Mapping.offset())});
  } else {
    IRB.CreateIntrinsic(
        UseShortGranules ? Intrinsic::hwasan_check_memaccess_shortgranules
                         : Intrinsic::hwasan_check_memaccess,
        {ShadowBase, Ptr, ConstantInt::get(Int32Ty, AccessInfo)});
  }
}
 
void HWAddressSanitizer::instrumentMemAccessInline(Value *Ptr, bool IsWrite,
                                                   unsigned AccessSizeIndex,
                                                   Instruction *InsertBefore,
                                                   DomTreeUpdater &DTU,
                                                   LoopInfo *LI) {
  assert(!UsePageAliases);
  const int64_t AccessInfo = getAccessInfo(IsWrite, AccessSizeIndex);
 
  ShadowTagCheckInfo TCI = insertShadowTagCheck(Ptr, InsertBefore, DTU, LI);
 
  IRBuilder<> IRB(TCI.TagMismatchTerm);
  Value *OutOfShortGranuleTagRange =
      IRB.CreateICmpUGT(TCI.MemTag, ConstantInt::get(Int8Ty, 15));
  Instruction *CheckFailTerm = SplitBlockAndInsertIfThen(
      OutOfShortGranuleTagRange, TCI.TagMismatchTerm, !Recover,
      MDBuilder(*C).createUnlikelyBranchWeights(), &DTU, LI);
 
  IRB.SetInsertPoint(TCI.TagMismatchTerm);
  Value *PtrLowBits = IRB.CreateTrunc(IRB.CreateAnd(TCI.PtrLong, 15), Int8Ty);
  PtrLowBits = IRB.CreateAdd(
      PtrLowBits, ConstantInt::get(Int8Ty, (1 << AccessSizeIndex) - 1));
  Value *PtrLowBitsOOB = IRB.CreateICmpUGE(PtrLowBits, TCI.MemTag);
  SplitBlockAndInsertIfThen(PtrLowBitsOOB, TCI.TagMismatchTerm, false,
                            MDBuilder(*C).createUnlikelyBranchWeights(), &DTU,
                            LI, CheckFailTerm->getParent());
 
  IRB.SetInsertPoint(TCI.TagMismatchTerm);
  Value *InlineTagAddr = IRB.CreateOr(TCI.AddrLong, 15);
  InlineTagAddr = IRB.CreateIntToPtr(InlineTagAddr, PtrTy);
  Value *InlineTag = IRB.CreateLoad(Int8Ty, InlineTagAddr);
  Value *InlineTagMismatch = IRB.CreateICmpNE(TCI.PtrTag, InlineTag);
  SplitBlockAndInsertIfThen(InlineTagMismatch, TCI.TagMismatchTerm, false,
                            MDBuilder(*C).createUnlikelyBranchWeights(), &DTU,
                            LI, CheckFailTerm->getParent());
 
  IRB.SetInsertPoint(CheckFailTerm);
  InlineAsm *Asm;
  switch (TargetTriple.getArch()) {
  case Triple::x86_64:
    // The signal handler will find the data address in rdi.
    Asm = InlineAsm::get(
        FunctionType::get(VoidTy, {TCI.PtrLong->getType()}, false),
        "int3\nnopl " +
            itostr(0x40 + (AccessInfo & HWASanAccessInfo::RuntimeMask)) +
            "(%rax)",
        "{rdi}",
        /*hasSideEffects=*/true);
    break;
  case Triple::aarch64:
  case Triple::aarch64_be:
    // The signal handler will find the data address in x0.
    Asm = InlineAsm::get(
        FunctionType::get(VoidTy, {TCI.PtrLong->getType()}, false),
        "brk #" + itostr(0x900 + (AccessInfo & HWASanAccessInfo::RuntimeMask)),
        "{x0}",
        /*hasSideEffects=*/true);
    break;
  case Triple::riscv64:
    // The signal handler will find the data address in x10.
    Asm = InlineAsm::get(
        FunctionType::get(VoidTy, {TCI.PtrLong->getType()}, false),
        "ebreak\naddiw x0, x11, " +
            itostr(0x40 + (AccessInfo & HWASanAccessInfo::RuntimeMask)),
        "{x10}",
        /*hasSideEffects=*/true);
    break;
  default:
    report_fatal_error("unsupported architecture");
  }
  IRB.CreateCall(Asm, TCI.PtrLong);
  if (Recover)
    cast<UncondBrInst>(CheckFailTerm)
        ->setSuccessor(TCI.TagMismatchTerm->getParent());
}
 
bool HWAddressSanitizer::ignoreMemIntrinsic(OptimizationRemarkEmitter &ORE,
                                            MemIntrinsic *MI) {
  if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) {
    return (!Opts.hwasan_instrument_writes ||
            ignoreAccess(ORE, MTI, MTI->getDest())) &&
           (!Opts.hwasan_instrument_reads ||
            ignoreAccess(ORE, MTI, MTI->getSource()));
  }
  if (isa<MemSetInst>(MI))
    return !Opts.hwasan_instrument_writes ||
           ignoreAccess(ORE, MI, MI->getDest());
  return false;
}
 
void HWAddressSanitizer::instrumentMemIntrinsic(MemIntrinsic *MI) {
  IRBuilder<> IRB(MI);
  if (isa<MemTransferInst>(MI)) {
    SmallVector<Value *, 4> Args{
        MI->getOperand(0), MI->getOperand(1),
        IRB.CreateIntCast(MI->getOperand(2), IntptrTy, false)};
 
    if (UseMatchAllCallback)
      Args.emplace_back(ConstantInt::get(Int8Ty, *MatchAllTag));
    IRB.CreateCall(isa<MemMoveInst>(MI) ? HwasanMemmove : HwasanMemcpy, Args);
  } else if (isa<MemSetInst>(MI)) {
    SmallVector<Value *, 4> Args{
        MI->getOperand(0),
        IRB.CreateIntCast(MI->getOperand(1), IRB.getInt32Ty(), false),
        IRB.CreateIntCast(MI->getOperand(2), IntptrTy, false)};
    if (UseMatchAllCallback)
      Args.emplace_back(ConstantInt::get(Int8Ty, *MatchAllTag));
    IRB.CreateCall(HwasanMemset, Args);
  }
  MI->eraseFromParent();
}
 
bool HWAddressSanitizer::instrumentMemAccess(InterestingMemoryOperand &O,
                                             DomTreeUpdater &DTU, LoopInfo *LI,
                                             const DataLayout &DL) {
  Value *Addr = O.getPtr();
 
  LLVM_DEBUG(dbgs() << "Instrumenting: " << O.getInsn() << "\n");
 
  // If the pointer is statically known to be zero, the tag check will pass
  // since:
  // 1) it has a zero tag
  // 2) the shadow memory corresponding to address 0 is initialized to zero and
  //    never updated.
  // We can therefore elide the tag check.
  llvm::KnownBits Known(DL.getPointerTypeSizeInBits(Addr->getType()));
  llvm::computeKnownBits(Addr, Known, DL);
  if (Known.isZero())
    return false;
 
  if (O.MaybeMask)
    return false; // FIXME
 
  IRBuilder<> IRB(O.getInsn());
  if (!O.TypeStoreSize.isScalable() && isPowerOf2_64(O.TypeStoreSize) &&
      (O.TypeStoreSize / 8 <= (1ULL << (kNumberOfAccessSizes - 1))) &&
      (!O.Alignment || *O.Alignment >= Mapping.getObjectAlignment() ||
       *O.Alignment >= O.TypeStoreSize / 8)) {
    size_t AccessSizeIndex = TypeSizeToSizeIndex(O.TypeStoreSize);
    if (InstrumentWithCalls) {
      SmallVector<Value *, 2> Args{IRB.CreatePointerCast(Addr, IntptrTy)};
      if (UseMatchAllCallback)
        Args.emplace_back(ConstantInt::get(Int8Ty, *MatchAllTag));
      IRB.CreateCall(HwasanMemoryAccessCallback[O.IsWrite][AccessSizeIndex],
                     Args);
    } else if (OutlinedChecks) {
      instrumentMemAccessOutline(Addr, O.IsWrite, AccessSizeIndex, O.getInsn(),
                                 DTU, LI);
    } else {
      instrumentMemAccessInline(Addr, O.IsWrite, AccessSizeIndex, O.getInsn(),
                                DTU, LI);
    }
  } else {
    SmallVector<Value *, 3> Args{
        IRB.CreatePointerCast(Addr, IntptrTy),
        IRB.CreateUDiv(IRB.CreateTypeSize(IntptrTy, O.TypeStoreSize),
                       ConstantInt::get(IntptrTy, 8))};
    if (UseMatchAllCallback)
      Args.emplace_back(ConstantInt::get(Int8Ty, *MatchAllTag));
    IRB.CreateCall(HwasanMemoryAccessCallbackSized[O.IsWrite], Args);
  }
  untagPointerOperand(O.getInsn(), Addr);
 
  return true;
}
 
void HWAddressSanitizer::tagAlloca(IRBuilder<> &IRB, AllocaInst *AI, Value *Tag,
                                   size_t Size) {
  size_t AlignedSize = alignTo(Size, Mapping.getObjectAlignment());
  if (!UseShortGranules)
    Size = AlignedSize;
 
  Tag = IRB.CreateTrunc(Tag, Int8Ty);
  if (InstrumentWithCalls) {
    IRB.CreateCall(HwasanTagMemoryFunc,
                   {IRB.CreatePointerCast(AI, PtrTy), Tag,
                    ConstantInt::get(IntptrTy, AlignedSize)});
  } else {
    size_t ShadowSize = Size >> Mapping.scale();
    Value *AddrLong = untagPointer(IRB, IRB.CreatePointerCast(AI, IntptrTy));
    Value *ShadowPtr = memToShadow(AddrLong, IRB);
    // If this memset is not inlined, it will be intercepted in the hwasan
    // runtime library. That's OK, because the interceptor skips the checks if
    // the address is in the shadow region.
    // FIXME: the interceptor is not as fast as real memset. Consider lowering
    // llvm.memset right here into either a sequence of stores, or a call to
    // hwasan_tag_memory.
    if (ShadowSize)
      IRB.CreateMemSet(ShadowPtr, Tag, ShadowSize, Align(1));
    if (Size != AlignedSize) {
      const uint8_t SizeRemainder = Size % Mapping.getObjectAlignment().value();
      IRB.CreateStore(ConstantInt::get(Int8Ty, SizeRemainder),
                      IRB.CreateConstGEP1_32(Int8Ty, ShadowPtr, ShadowSize));
      IRB.CreateStore(
          Tag, IRB.CreateConstGEP1_32(Int8Ty, IRB.CreatePointerCast(AI, PtrTy),
                                      AlignedSize - 1));
    }
  }
}
 
unsigned HWAddressSanitizer::retagMask(unsigned AllocaNo) {
  if (TargetTriple.getArch() == Triple::x86_64)
    return AllocaNo & TagMaskByte;
 
  // A list of 8-bit numbers that have at most one run of non-zero bits.
  // x = x ^ (mask << 56) can be encoded as a single armv8 instruction for these
  // masks.
  // The list does not include the value 255, which is used for UAR.
  //
  // Because we are more likely to use earlier elements of this list than later
  // ones, it is sorted in increasing order of probability of collision with a
  // mask allocated (temporally) nearby. The program that generated this list
  // can be found at:
  // https://github.com/google/sanitizers/blob/master/hwaddress-sanitizer/sort_masks.py
  static const unsigned FastMasks[] = {
      0,   128, 64, 192, 32,  96,  224, 112, 240, 48, 16,  120,
      248, 56,  24, 8,   124, 252, 60,  28,  12,  4,  126, 254,
      62,  30,  14, 6,   2,   127, 63,  31,  15,  7,  3,   1};
  return FastMasks[AllocaNo % std::size(FastMasks)];
}
 
Value *HWAddressSanitizer::applyTagMask(IRBuilder<> &IRB, Value *OldTag) {
  if (TagMaskByte == 0xFF)
    return OldTag; // No need to clear the tag byte.
  return IRB.CreateAnd(OldTag,
                       ConstantInt::get(OldTag->getType(), TagMaskByte));
}
 
Value *HWAddressSanitizer::getNextTagWithCall(IRBuilder<> &IRB) {
  return IRB.CreateZExt(IRB.CreateCall(HwasanGenerateTagFunc), IntptrTy);
}
 
Value *HWAddressSanitizer::getStackBaseTag(IRBuilder<> &IRB) {
  if (Opts.hwasan_generate_tags_with_calls)
    return nullptr;
  if (StackBaseTag)
    return StackBaseTag;
  // Extract some entropy from the stack pointer for the tags.
  // Take bits 20..28 (ASLR entropy) and xor with bits 0..8 (these differ
  // between functions).
  Value *FramePointerLong = getCachedFP(IRB);
  Value *StackTag =
      applyTagMask(IRB, IRB.CreateXor(FramePointerLong,
                                      IRB.CreateLShr(FramePointerLong, 20)));
  StackTag->setName("hwasan.stack.base.tag");
  return StackTag;
}
 
Value *HWAddressSanitizer::getAllocaTag(IRBuilder<> &IRB, Value *StackTag,
                                        unsigned AllocaNo) {
  if (Opts.hwasan_generate_tags_with_calls)
    return getNextTagWithCall(IRB);
  return IRB.CreateXor(
      StackTag, ConstantInt::get(StackTag->getType(), retagMask(AllocaNo)));
}
 
Value *HWAddressSanitizer::getUARTag(IRBuilder<> &IRB) {
  Value *FramePointerLong = getCachedFP(IRB);
  Value *UARTag =
      applyTagMask(IRB, IRB.CreateLShr(FramePointerLong, PointerTagShift));
 
  UARTag->setName("hwasan.uar.tag");
  return UARTag;
}
 
// Add a tag to an address.
Value *HWAddressSanitizer::tagPointer(IRBuilder<> &IRB, Type *Ty,
                                      Value *PtrLong, Value *Tag) {
  assert(!UsePageAliases);
  Value *TaggedPtrLong;
  if (CompileKernel) {
    // Kernel addresses have 0xFF in the most significant byte.
    Value *ShiftedTag =
        IRB.CreateOr(IRB.CreateShl(Tag, PointerTagShift),
                     ConstantInt::get(IntptrTy, (1ULL << PointerTagShift) - 1));
    TaggedPtrLong = IRB.CreateAnd(PtrLong, ShiftedTag);
  } else {
    // Userspace can simply do OR (tag << PointerTagShift);
    Value *ShiftedTag = IRB.CreateShl(Tag, PointerTagShift);
    TaggedPtrLong = IRB.CreateOr(PtrLong, ShiftedTag);
  }
  return IRB.CreateIntToPtr(TaggedPtrLong, Ty);
}
 
// Remove tag from an address.
Value *HWAddressSanitizer::untagPointer(IRBuilder<> &IRB, Value *PtrLong) {
  assert(!UsePageAliases);
  Value *UntaggedPtrLong;
  if (CompileKernel) {
    // Kernel addresses have 0xFF in the most significant byte.
    UntaggedPtrLong =
        IRB.CreateOr(PtrLong, ConstantInt::get(PtrLong->getType(),
                                               TagMaskByte << PointerTagShift));
  } else {
    // Userspace addresses have 0x00.
    UntaggedPtrLong = IRB.CreateAnd(
        PtrLong, ConstantInt::get(PtrLong->getType(),
                                  ~(TagMaskByte << PointerTagShift)));
  }
  return UntaggedPtrLong;
}
 
Value *HWAddressSanitizer::getHwasanThreadSlotPtr(IRBuilder<> &IRB) {
  // Android provides a fixed TLS slot for sanitizers. See TLS_SLOT_SANITIZER
  // in Bionic's libc/platform/bionic/tls_defines.h.
  constexpr int SanitizerSlot = 6;
  if (TargetTriple.isAArch64() && TargetTriple.isAndroid())
    return memtag::getAndroidSlotPtr(IRB, SanitizerSlot);
  return ThreadPtrGlobal;
}
 
Value *HWAddressSanitizer::getCachedFP(IRBuilder<> &IRB) {
  if (!CachedFP)
    CachedFP = memtag::getFP(IRB);
  return CachedFP;
}
 
Value *HWAddressSanitizer::getFrameRecordInfo(IRBuilder<> &IRB) {
  // Prepare ring buffer data.
  Value *PC = memtag::getPC(TargetTriple, IRB);
  Value *FP = getCachedFP(IRB);
 
  // Mix FP and PC.
  // Assumptions:
  // PC is 0x0000PPPPPPPPPPPP  (48 bits are meaningful, others are zero)
  // FP is 0xfffffffffffFFFF0  (4 lower bits are zero)
  // We only really need ~20 lower non-zero bits (FFFF), so we mix like this:
  //       0xFFFFPPPPPPPPPPPP
  //
  // FP works because in AArch64FrameLowering::getFrameIndexReference, we
  // prefer FP-relative offsets for functions compiled with HWASan.
  FP = IRB.CreateShl(FP, 44);
  return IRB.CreateOr(PC, FP);
}
 
void HWAddressSanitizer::emitPrologue(IRBuilder<> &IRB, bool WithFrameRecord) {
  if (!Mapping.isInTls())
    ShadowBase = getShadowNonTls(IRB);
  else if (!WithFrameRecord && TargetTriple.isAndroid())
    ShadowBase = getDynamicShadowIfunc(IRB);
 
  if (!WithFrameRecord && ShadowBase)
    return;
 
  Value *SlotPtr = nullptr;
  Value *ThreadLong = nullptr;
  Value *ThreadLongMaybeUntagged = nullptr;
 
  auto getThreadLongMaybeUntagged = [&]() {
    if (!SlotPtr)
      SlotPtr = getHwasanThreadSlotPtr(IRB);
    if (!ThreadLong)
      ThreadLong = IRB.CreateLoad(IntptrTy, SlotPtr);
    // Extract the address field from ThreadLong. Unnecessary on AArch64 with
    // TBI.
    return TargetTriple.isAArch64() ? ThreadLong
                                    : untagPointer(IRB, ThreadLong);
  };
 
  if (WithFrameRecord) {
    switch (Opts.hwasan_record_stack_history) {
    case RecordStackHistoryMode::libcall: {
      // Emit a runtime call into hwasan rather than emitting instructions for
      // recording stack history.
      Value *FrameRecordInfo = getFrameRecordInfo(IRB);
      IRB.CreateCall(HwasanRecordFrameRecordFunc, {FrameRecordInfo});
      break;
    }
    case RecordStackHistoryMode::instr: {
      ThreadLongMaybeUntagged = getThreadLongMaybeUntagged();
 
      StackBaseTag = IRB.CreateAShr(ThreadLong, 3);
 
      // Store data to ring buffer.
      Value *FrameRecordInfo = getFrameRecordInfo(IRB);
      Value *RecordPtr =
          IRB.CreateIntToPtr(ThreadLongMaybeUntagged, IRB.getPtrTy(0));
      IRB.CreateStore(FrameRecordInfo, RecordPtr);
 
      IRB.CreateStore(memtag::incrementThreadLong(IRB, ThreadLong, 8), SlotPtr);
      break;
    }
    case RecordStackHistoryMode::none: {
      llvm_unreachable(
          "A stack history recording mode should've been selected.");
    }
    }
  }
 
  if (!ShadowBase) {
    if (!ThreadLongMaybeUntagged)
      ThreadLongMaybeUntagged = getThreadLongMaybeUntagged();
 
    // Get shadow base address by aligning RecordPtr up.
    // Note: this is not correct if the pointer is already aligned.
    // Runtime library will make sure this never happens.
    ShadowBase = IRB.CreateAdd(
        IRB.CreateOr(
            ThreadLongMaybeUntagged,
            ConstantInt::get(IntptrTy, (1ULL << kShadowBaseAlignment) - 1)),
        ConstantInt::get(IntptrTy, 1), "hwasan.shadow");
    ShadowBase = IRB.CreateIntToPtr(ShadowBase, PtrTy);
  }
}
 
void HWAddressSanitizer::instrumentLandingPads(
    SmallVectorImpl<Instruction *> &LandingPadVec) {
  for (auto *LP : LandingPadVec) {
    IRBuilder<> IRB(LP->getNextNode());
    IRB.CreateCall(
        HwasanHandleVfork,
        {memtag::readRegister(
            IRB, (TargetTriple.getArch() == Triple::x86_64) ? "rsp" : "sp")});
  }
}
 
void HWAddressSanitizer::instrumentStack(OptimizationRemarkEmitter &ORE,
                                         memtag::StackInfo &SInfo,
                                         Value *StackTag, Value *UARTag,
                                         const DominatorTree &DT,
                                         const PostDominatorTree &PDT,
                                         const LoopInfo &LI) {
  // Ideally, we want to calculate tagged stack base pointer, and rewrite all
  // alloca addresses using that. Unfortunately, offsets are not known yet
  // (unless we use ASan-style mega-alloca). Instead we keep the base tag in a
  // temp, shift-OR it into each alloca address and xor with the retag mask.
  // This generates one extra instruction per alloca use.
  unsigned int I = 0;
 
  for (auto &KV : SInfo.AllocasToInstrument) {
    auto N = I++;
    auto *AI = KV.first;
    memtag::AllocaInfo &Info = KV.second;
    IRBuilder<> IRB(AI->getNextNode());
 
    // Replace uses of the alloca with tagged address.
    Value *Tag = getAllocaTag(IRB, StackTag, N);
    Value *AILong = IRB.CreatePointerCast(AI, IntptrTy);
    Value *AINoTagLong = untagPointer(IRB, AILong);
    Value *Replacement = tagPointer(IRB, AI->getType(), AINoTagLong, Tag);
    std::string Name =
        AI->hasName() ? AI->getName().str() : "alloca." + itostr(N);
    Replacement->setName(Name + ".hwasan");
 
    size_t Size = memtag::getAllocaSizeInBytes(*AI);
    size_t AlignedSize = alignTo(Size, Mapping.getObjectAlignment());
 
    AI->replaceUsesWithIf(Replacement, [AILong](const Use &U) {
      auto *User = U.getUser();
      return User != AILong && !isa<LifetimeIntrinsic>(User);
    });
 
    memtag::annotateDebugRecords(Info, retagMask(N));
 
    auto TagStarts = [&]() {
      for (IntrinsicInst *Start : Info.LifetimeStart) {
        IRB.SetInsertPoint(Start->getNextNode());
        tagAlloca(IRB, AI, Tag, Size);
      }
    };
    auto TagEnd = [&](Instruction *Node) {
      IRB.SetInsertPoint(Node);
      // When untagging, use the `AlignedSize` because we need to set the tags
      // for the entire alloca to original. If we used `Size` here, we would
      // keep the last granule tagged, and store zero in the last byte of the
      // last granule, due to how short granules are implemented.
      tagAlloca(IRB, AI, UARTag, AlignedSize);
    };
    auto EraseLifetimes = [&]() {
      for (auto &II : Info.LifetimeStart)
        II->eraseFromParent();
      for (auto &II : Info.LifetimeEnd)
        II->eraseFromParent();
    };
    // Calls to functions that may return twice (e.g. setjmp) confuse the
    // postdominator analysis, and will leave us to keep memory tagged after
    // function return. Work around this by always untagging at every return
    // statement if return_twice functions are called.
    if (DetectUseAfterScope && !SInfo.CallsReturnTwice &&
        memtag::isSupportedLifetime(Info, &DT, &LI)) {
      TagStarts();
      memtag::forAllReachableExits(DT, PDT, LI, Info, SInfo.RetVec, TagEnd);
      ORE.emit([&]() {
        return OptimizationRemark(DEBUG_TYPE, "supportedLifetime", AI);
      });
    } else if (DetectUseAfterScope && Opts.hwasan_strict_use_after_scope) {
      // SInfo.CallsReturnTwice || !isStandardLifetime
      ORE.emit([&]() {
        return OptimizationRemarkMissed(DEBUG_TYPE, "supportedLifetime", AI);
      });
 
      tagAlloca(IRB, AI, Tag, Size);
      TagStarts();
      for_each(Info.LifetimeEnd, TagEnd);
      for_each(SInfo.RetVec, TagEnd);
      EraseLifetimes();
    } else {
      tagAlloca(IRB, AI, Tag, Size);
      for_each(SInfo.RetVec, TagEnd);
      EraseLifetimes();
    }
    memtag::alignAndPadAlloca(Info, Mapping.getObjectAlignment());
  }
}
 
static void emitRemark(const Function &F, OptimizationRemarkEmitter &ORE,
                       bool Skip) {
  if (Skip) {
    ORE.emit([&]() {
      return OptimizationRemark(DEBUG_TYPE, "Skip", &F)
             << "Skipped: F=" << ore::NV("Function", &F);
    });
  } else {
    ORE.emit([&]() {
      return OptimizationRemarkMissed(DEBUG_TYPE, "Sanitize", &F)
             << "Sanitized: F=" << ore::NV("Function", &F);
    });
  }
}
 
bool HWAddressSanitizer::selectiveInstrumentationShouldSkip(
    Function &F, FunctionAnalysisManager &FAM) const {
  auto SkipHot = [&]() {
    if (!Opts.hwasan_percentile_cutoff_hot)
      return false;
    auto &MAMProxy = FAM.getResult<ModuleAnalysisManagerFunctionProxy>(F);
    ProfileSummaryInfo *PSI =
        MAMProxy.getCachedResult<ProfileSummaryAnalysis>(*F.getParent());
    if (!PSI || !PSI->hasProfileSummary()) {
      ++NumNoProfileSummaryFuncs;
      return false;
    }
    return PSI->isFunctionHotInCallGraphNthPercentile(
        *Opts.hwasan_percentile_cutoff_hot, &F,
        FAM.getResult<BlockFrequencyAnalysis>(F));
  };
 
  auto SkipRandom = [&]() {
    if (!Opts.hwasan_random_rate)
      return false;
    std::bernoulli_distribution D(*Opts.hwasan_random_rate);
    return !D(*Rng);
  };
 
  bool Skip = SkipRandom() || SkipHot();
  emitRemark(F, FAM.getResult<OptimizationRemarkEmitterAnalysis>(F), Skip);
  return Skip;
}
 
void HWAddressSanitizer::sanitizeFunction(Function &F,
                                          FunctionAnalysisManager &FAM) {
  if (&F == HwasanCtorFunction)
    return;
 
  // Do not apply any instrumentation for naked functions.
  if (F.hasFnAttribute(Attribute::Naked))
    return;
 
  if (!F.hasFnAttribute(Attribute::SanitizeHWAddress))
    return;
 
  if (F.empty())
    return;
 
  if (F.isPresplitCoroutine())
    return;
 
  NumTotalFuncs++;
 
  OptimizationRemarkEmitter &ORE =
      FAM.getResult<OptimizationRemarkEmitterAnalysis>(F);
 
  if (selectiveInstrumentationShouldSkip(F, FAM))
    return;
 
  NumInstrumentedFuncs++;
 
  LLVM_DEBUG(dbgs() << "Function: " << F.getName() << "\n");
 
  SmallVector<InterestingMemoryOperand, 16> OperandsToInstrument;
  SmallVector<MemIntrinsic *, 16> IntrinToInstrument;
  SmallVector<Instruction *, 8> LandingPadVec;
  const TargetLibraryInfo &TLI = FAM.getResult<TargetLibraryAnalysis>(F);
 
  memtag::StackInfoBuilder SIB(SSI, DEBUG_TYPE);
  for (auto &Inst : instructions(F)) {
    if (InstrumentStack) {
      SIB.visit(ORE, Inst);
    }
 
    if (InstrumentLandingPads && isa<LandingPadInst>(Inst))
      LandingPadVec.push_back(&Inst);
 
    getInterestingMemoryOperands(ORE, &Inst, TLI, OperandsToInstrument);
 
    if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(&Inst))
      if (!ignoreMemIntrinsic(ORE, MI))
        IntrinToInstrument.push_back(MI);
  }
 
  memtag::StackInfo &SInfo = SIB.get();
 
  initializeCallbacks(*F.getParent());
 
  if (!LandingPadVec.empty())
    instrumentLandingPads(LandingPadVec);
 
  if (SInfo.AllocasToInstrument.empty() && F.hasPersonalityFn() &&
      F.getPersonalityFn()->getName() == kHwasanPersonalityThunkName) {
    // __hwasan_personality_thunk is a no-op for functions without an
    // instrumented stack, so we can drop it.
    F.setPersonalityFn(nullptr);
  }
 
  if (SInfo.AllocasToInstrument.empty() && OperandsToInstrument.empty() &&
      IntrinToInstrument.empty())
    return;
 
  assert(!ShadowBase);
 
  BasicBlock::iterator InsertPt = F.getEntryBlock().begin();
  IRBuilder<> EntryIRB(InsertPt);
  emitPrologue(EntryIRB,
               /*WithFrameRecord*/ Opts.hwasan_record_stack_history !=
                       RecordStackHistoryMode::none &&
                   Mapping.withFrameRecord() &&
                   !SInfo.AllocasToInstrument.empty());
 
  if (!SInfo.AllocasToInstrument.empty()) {
    const DominatorTree &DT = FAM.getResult<DominatorTreeAnalysis>(F);
    const PostDominatorTree &PDT = FAM.getResult<PostDominatorTreeAnalysis>(F);
    const LoopInfo &LI = FAM.getResult<LoopAnalysis>(F);
    Value *StackTag = getStackBaseTag(EntryIRB);
    Value *UARTag = getUARTag(EntryIRB);
    instrumentStack(ORE, SInfo, StackTag, UARTag, DT, PDT, LI);
  }
 
  // If we split the entry block, move any allocas that were originally in the
  // entry block back into the entry block so that they aren't treated as
  // dynamic allocas.
  if (EntryIRB.GetInsertBlock() != &F.getEntryBlock()) {
    InsertPt = F.getEntryBlock().begin();
    for (Instruction &I :
         llvm::make_early_inc_range(*EntryIRB.GetInsertBlock())) {
      if (auto *AI = dyn_cast<AllocaInst>(&I))
        if (isa<ConstantInt>(AI->getArraySize()))
          I.moveBefore(F.getEntryBlock(), InsertPt);
    }
  }
 
  DominatorTree *DT = FAM.getCachedResult<DominatorTreeAnalysis>(F);
  PostDominatorTree *PDT = FAM.getCachedResult<PostDominatorTreeAnalysis>(F);
  LoopInfo *LI = FAM.getCachedResult<LoopAnalysis>(F);
  DomTreeUpdater DTU(DT, PDT, DomTreeUpdater::UpdateStrategy::Lazy);
  const DataLayout &DL = F.getDataLayout();
  for (auto &Operand : OperandsToInstrument)
    instrumentMemAccess(Operand, DTU, LI, DL);
  DTU.flush();
 
  if (Opts.hwasan_instrument_mem_intrinsics && !IntrinToInstrument.empty()) {
    for (auto *Inst : IntrinToInstrument)
      instrumentMemIntrinsic(Inst);
  }
 
  ShadowBase = nullptr;
  StackBaseTag = nullptr;
  CachedFP = nullptr;
}
 
void HWAddressSanitizer::instrumentGlobal(GlobalVariable *GV, uint8_t Tag) {
  assert(!UsePageAliases);
  Constant *Initializer = GV->getInitializer();
  uint64_t SizeInBytes =
      M.getDataLayout().getTypeAllocSize(Initializer->getType());
  uint64_t NewSize = alignTo(SizeInBytes, Mapping.getObjectAlignment());
  if (SizeInBytes != NewSize) {
    // Pad the initializer out to the next multiple of 16 bytes and add the
    // required short granule tag.
    std::vector<uint8_t> Init(NewSize - SizeInBytes, 0);
    Init.back() = Tag;
    Constant *Padding = ConstantDataArray::get(*C, Init);
    Initializer = ConstantStruct::getAnon({Initializer, Padding});
  }
 
  auto *NewGV = new GlobalVariable(M, Initializer->getType(), GV->isConstant(),
                                   GlobalValue::ExternalLinkage, Initializer,
                                   GV->getName() + ".hwasan");
  NewGV->copyAttributesFrom(GV);
  NewGV->setLinkage(GlobalValue::PrivateLinkage);
  NewGV->copyMetadata(GV, 0);
  NewGV->setAlignment(
      std::max(GV->getAlign().valueOrOne(), Mapping.getObjectAlignment()));
 
  // It is invalid to ICF two globals that have different tags. In the case
  // where the size of the global is a multiple of the tag granularity the
  // contents of the globals may be the same but the tags (i.e. symbol values)
  // may be different, and the symbols are not considered during ICF. In the
  // case where the size is not a multiple of the granularity, the short granule
  // tags would discriminate two globals with different tags, but there would
  // otherwise be nothing stopping such a global from being incorrectly ICF'd
  // with an uninstrumented (i.e. tag 0) global that happened to have the short
  // granule tag in the last byte.
  NewGV->setUnnamedAddr(GlobalValue::UnnamedAddr::None);
 
  // Descriptor format (assuming little-endian):
  // bytes 0-3: relative address of global
  // bytes 4-6: size of global (16MB ought to be enough for anyone, but in case
  // it isn't, we create multiple descriptors)
  // byte 7: tag
  auto *DescriptorTy = StructType::get(Int32Ty, Int32Ty);
  const uint64_t MaxDescriptorSize = 0xfffff0;
  for (uint64_t DescriptorPos = 0; DescriptorPos < SizeInBytes;
       DescriptorPos += MaxDescriptorSize) {
    auto *Descriptor =
        new GlobalVariable(M, DescriptorTy, true, GlobalValue::PrivateLinkage,
                           nullptr, GV->getName() + ".hwasan.descriptor");
    auto *GVRelPtr = ConstantExpr::getTrunc(
        ConstantExpr::getAdd(
            ConstantExpr::getSub(
                ConstantExpr::getPtrToInt(NewGV, Int64Ty),
                ConstantExpr::getPtrToInt(Descriptor, Int64Ty)),
            ConstantInt::get(Int64Ty, DescriptorPos)),
        Int32Ty);
    uint32_t Size = std::min(SizeInBytes - DescriptorPos, MaxDescriptorSize);
    auto *SizeAndTag = ConstantInt::get(Int32Ty, Size | (uint32_t(Tag) << 24));
    Descriptor->setComdat(NewGV->getComdat());
    Descriptor->setInitializer(ConstantStruct::getAnon({GVRelPtr, SizeAndTag}));
    Descriptor->setSection("hwasan_globals");
    Descriptor->setMetadata(LLVMContext::MD_associated,
                            MDNode::get(*C, ValueAsMetadata::get(NewGV)));
    appendToCompilerUsed(M, Descriptor);
  }
 
  Constant *Aliasee = ConstantExpr::getIntToPtr(
      ConstantExpr::getAdd(
          ConstantExpr::getPtrToInt(NewGV, Int64Ty),
          ConstantInt::get(Int64Ty, uint64_t(Tag) << PointerTagShift)),
      GV->getType());
  auto *Alias = GlobalAlias::create(GV->getValueType(), GV->getAddressSpace(),
                                    GV->getLinkage(), "", Aliasee, &M);
  Alias->setVisibility(GV->getVisibility());
  Alias->takeName(GV);
  GV->replaceAllUsesWith(Alias);
  GV->eraseFromParent();
}
 
void HWAddressSanitizer::instrumentGlobals() {
  std::vector<GlobalVariable *> Globals;
  for (GlobalVariable &GV : M.globals()) {
    if (GV.hasSanitizerMetadata() && GV.getSanitizerMetadata().NoHWAddress)
      continue;
 
    if (GV.isDeclarationForLinker() || GV.getName().starts_with("llvm.") ||
        GV.isThreadLocal())
      continue;
 
    // Common symbols can't have aliases point to them, so they can't be tagged.
    if (GV.hasCommonLinkage())
      continue;
 
    if (Opts.hwasan_all_globals) {
      // Avoid instrumenting intrinsic global variables.
      if (GV.getSection() == "llvm.metadata")
        continue;
    } else {
      // Globals with custom sections may be used in __start_/__stop_
      // enumeration, which would be broken both by adding tags and potentially
      // by the extra padding/alignment that we insert.
      if (GV.hasSection())
        continue;
    }
 
    Globals.push_back(&GV);
  }
 
  MD5 Hasher;
  Hasher.update(M.getSourceFileName());
  MD5::MD5Result Hash;
  Hasher.final(Hash);
  uint8_t Tag = Hash[0];
 
  assert(TagMaskByte >= 16);
 
  for (GlobalVariable *GV : Globals) {
    // Don't allow globals to be tagged with something that looks like a
    // short-granule tag, otherwise we lose inter-granule overflow detection, as
    // the fast path shadow-vs-address check succeeds.
    if (Tag < 16 || Tag > TagMaskByte)
      Tag = 16;
    instrumentGlobal(GV, Tag++);
  }
}
 
void HWAddressSanitizer::instrumentPersonalityFunctions() {
  // We need to untag stack frames as we unwind past them. That is the job of
  // the personality function wrapper, which either wraps an existing
  // personality function or acts as a personality function on its own. Each
  // function that has a personality function or that can be unwound past has
  // its personality function changed to a thunk that calls the personality
  // function wrapper in the runtime.
  MapVector<Constant *, std::vector<Function *>> PersonalityFns;
  for (Function &F : M) {
    if (F.isDeclaration() || !F.hasFnAttribute(Attribute::SanitizeHWAddress))
      continue;
 
    if (F.hasPersonalityFn()) {
      PersonalityFns[F.getPersonalityFn()->stripPointerCasts()].push_back(&F);
    } else if (!F.hasFnAttribute(Attribute::NoUnwind)) {
      PersonalityFns[nullptr].push_back(&F);
    }
  }
 
  if (PersonalityFns.empty())
    return;
 
  FunctionCallee HwasanPersonalityWrapper = M.getOrInsertFunction(
      "__hwasan_personality_wrapper", Int32Ty, Int32Ty, Int32Ty, Int64Ty, PtrTy,
      PtrTy, PtrTy, PtrTy, PtrTy);
  FunctionCallee UnwindGetGR = M.getOrInsertFunction("_Unwind_GetGR", VoidTy);
  FunctionCallee UnwindGetCFA = M.getOrInsertFunction("_Unwind_GetCFA", VoidTy);
 
  for (auto &P : PersonalityFns) {
    std::string ThunkName = kHwasanPersonalityThunkName;
    if (P.first)
      ThunkName += ("." + P.first->getName()).str();
    FunctionType *ThunkFnTy = FunctionType::get(
        Int32Ty, {Int32Ty, Int32Ty, Int64Ty, PtrTy, PtrTy}, false);
    bool IsLocal = P.first && (!isa<GlobalValue>(P.first) ||
                               cast<GlobalValue>(P.first)->hasLocalLinkage());
    auto *ThunkFn = Function::Create(ThunkFnTy,
                                     IsLocal ? GlobalValue::InternalLinkage
                                             : GlobalValue::LinkOnceODRLinkage,
                                     ThunkName, &M);
    // TODO: think about other attributes as well.
    if (any_of(P.second, [](const Function *F) {
          return F->hasFnAttribute("branch-target-enforcement");
        })) {
      ThunkFn->addFnAttr("branch-target-enforcement");
    }
    if (!IsLocal) {
      ThunkFn->setVisibility(GlobalValue::HiddenVisibility);
      ThunkFn->setComdat(M.getOrInsertComdat(ThunkName));
    }
 
    auto *BB = BasicBlock::Create(*C, "entry", ThunkFn);
    IRBuilder<> IRB(BB);
    CallInst *WrapperCall = IRB.CreateCall(
        HwasanPersonalityWrapper,
        {ThunkFn->getArg(0), ThunkFn->getArg(1), ThunkFn->getArg(2),
         ThunkFn->getArg(3), ThunkFn->getArg(4),
         P.first ? P.first : Constant::getNullValue(PtrTy),
         UnwindGetGR.getCallee(), UnwindGetCFA.getCallee()});
    WrapperCall->setTailCall();
    IRB.CreateRet(WrapperCall);
 
    for (Function *F : P.second)
      F->setPersonalityFn(ThunkFn);
  }
}
 
void HWAddressSanitizer::ShadowMapping::init(const InstrumentationOptions &Opts,
                                             Triple &TargetTriple,
                                             bool InstrumentWithCalls,
                                             bool CompileKernel) {
  // Start with defaults.
  Scale = kDefaultShadowScale;
  Kind = OffsetKind::kTls;
  WithFrameRecord = true;
 
  // Tune for the target.
  if (TargetTriple.isOSFuchsia()) {
    // Fuchsia is always PIE, which means that the beginning of the address
    // space is always available.
    Kind = OffsetKind::kGlobal;
  } else if (CompileKernel || InstrumentWithCalls) {
    SetFixed(0);
    WithFrameRecord = false;
  }
 
  WithFrameRecord = valueOr(Opts.hwasan_with_frame_record, WithFrameRecord);
 
  // Apply the last of ClMappingOffset and ClMappingOffsetDynamic.
  if (ClMappingOffsetDynamic.getNumOccurrences())
    Kind = ClMappingOffsetDynamic;
  if (ClMappingOffset.getNumOccurrences() > 0 &&
      !(ClMappingOffsetDynamic.getNumOccurrences() > 0 &&
        ClMappingOffsetDynamic.getPosition() > ClMappingOffset.getPosition())) {
    SetFixed(ClMappingOffset);
  }
}