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llvm-project/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp

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//===- HWAddressSanitizer.cpp - detector of uninitialized reads -------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
/// \file
/// This file is a part of HWAddressSanitizer, an address sanity checker
/// based on tagged addressing.
//===----------------------------------------------------------------------===//
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Triple.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/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/InstVisitor.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/Pass.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Instrumentation.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
#include "llvm/Transforms/Utils/PromoteMemToReg.h"
using namespace llvm;
#define DEBUG_TYPE "hwasan"
static const char *const kHwasanModuleCtorName = "hwasan.module_ctor";
static const char *const kHwasanInitName = "__hwasan_init";
static const char *const 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 uint64_t kDynamicShadowSentinel =
std::numeric_limits<uint64_t>::max();
static const unsigned kPointerTagShift = 56;
static cl::opt<std::string> ClMemoryAccessCallbackPrefix(
"hwasan-memory-access-callback-prefix",
cl::desc("Prefix for memory access callbacks"), cl::Hidden,
cl::init("__hwasan_"));
static cl::opt<bool>
ClInstrumentWithCalls("hwasan-instrument-with-calls",
cl::desc("instrument reads and writes with callbacks"),
cl::Hidden, cl::init(false));
static cl::opt<bool> ClInstrumentReads("hwasan-instrument-reads",
cl::desc("instrument read instructions"),
cl::Hidden, cl::init(true));
static cl::opt<bool> ClInstrumentWrites(
"hwasan-instrument-writes", cl::desc("instrument write instructions"),
cl::Hidden, cl::init(true));
static cl::opt<bool> ClInstrumentAtomics(
"hwasan-instrument-atomics",
cl::desc("instrument atomic instructions (rmw, cmpxchg)"), cl::Hidden,
cl::init(true));
static cl::opt<bool> ClRecover(
"hwasan-recover",
cl::desc("Enable recovery mode (continue-after-error)."),
cl::Hidden, cl::init(false));
static cl::opt<bool> ClInstrumentStack("hwasan-instrument-stack",
cl::desc("instrument stack (allocas)"),
cl::Hidden, cl::init(true));
static cl::opt<bool> ClGenerateTagsWithCalls(
"hwasan-generate-tags-with-calls",
cl::desc("generate new tags with runtime library calls"), cl::Hidden,
cl::init(false));
static cl::opt<int> ClMatchAllTag(
"hwasan-match-all-tag",
cl::desc("don't report bad accesses via pointers with this tag"),
cl::Hidden, cl::init(-1));
static cl::opt<bool> ClEnableKhwasan(
"hwasan-kernel",
cl::desc("Enable KernelHWAddressSanitizer instrumentation"),
cl::Hidden, cl::init(false));
// 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<unsigned long long> ClMappingOffset(
"hwasan-mapping-offset",
cl::desc("HWASan shadow mapping offset [EXPERIMENTAL]"), cl::Hidden,
cl::init(0));
namespace {
/// An instrumentation pass implementing detection of addressability bugs
/// using tagged pointers.
class HWAddressSanitizer : public FunctionPass {
public:
// Pass identification, replacement for typeid.
static char ID;
explicit HWAddressSanitizer(bool CompileKernel = false, bool Recover = false)
: FunctionPass(ID) {
this->Recover = ClRecover.getNumOccurrences() > 0 ? ClRecover : Recover;
this->CompileKernel = ClEnableKhwasan.getNumOccurrences() > 0 ?
ClEnableKhwasan : CompileKernel;
}
StringRef getPassName() const override { return "HWAddressSanitizer"; }
bool runOnFunction(Function &F) override;
bool doInitialization(Module &M) override;
void initializeCallbacks(Module &M);
void maybeInsertDynamicShadowAtFunctionEntry(Function &F);
void untagPointerOperand(Instruction *I, Value *Addr);
Value *memToShadow(Value *Shadow, Type *Ty, IRBuilder<> &IRB);
void instrumentMemAccessInline(Value *PtrLong, bool IsWrite,
unsigned AccessSizeIndex,
Instruction *InsertBefore);
bool instrumentMemAccess(Instruction *I);
Value *isInterestingMemoryAccess(Instruction *I, bool *IsWrite,
uint64_t *TypeSize, unsigned *Alignment,
Value **MaybeMask);
bool isInterestingAlloca(const AllocaInst &AI);
bool tagAlloca(IRBuilder<> &IRB, AllocaInst *AI, Value *Tag);
Value *tagPointer(IRBuilder<> &IRB, Type *Ty, Value *PtrLong, Value *Tag);
Value *untagPointer(IRBuilder<> &IRB, Value *PtrLong);
bool instrumentStack(SmallVectorImpl<AllocaInst *> &Allocas,
SmallVectorImpl<Instruction *> &RetVec);
Value *getNextTagWithCall(IRBuilder<> &IRB);
Value *getStackBaseTag(IRBuilder<> &IRB);
Value *getAllocaTag(IRBuilder<> &IRB, Value *StackTag, AllocaInst *AI,
unsigned AllocaNo);
Value *getUARTag(IRBuilder<> &IRB, Value *StackTag);
private:
LLVMContext *C;
Triple TargetTriple;
/// This struct defines the shadow mapping using the rule:
/// shadow = (mem >> Scale) + Offset.
/// If InGlobal is true, then
/// extern char __hwasan_shadow[];
/// shadow = (mem >> Scale) + &__hwasan_shadow
struct ShadowMapping {
int Scale;
uint64_t Offset;
bool InGlobal;
void init(Triple &TargetTriple);
unsigned getAllocaAlignment() const { return 1U << Scale; }
};
ShadowMapping Mapping;
Type *IntptrTy;
Type *Int8Ty;
bool CompileKernel;
bool Recover;
Function *HwasanCtorFunction;
Function *HwasanMemoryAccessCallback[2][kNumberOfAccessSizes];
Function *HwasanMemoryAccessCallbackSized[2];
Function *HwasanTagMemoryFunc;
Function *HwasanGenerateTagFunc;
Constant *ShadowGlobal;
Value *LocalDynamicShadow = nullptr;
};
} // end anonymous namespace
char HWAddressSanitizer::ID = 0;
INITIALIZE_PASS_BEGIN(
HWAddressSanitizer, "hwasan",
"HWAddressSanitizer: detect memory bugs using tagged addressing.", false,
false)
INITIALIZE_PASS_END(
HWAddressSanitizer, "hwasan",
"HWAddressSanitizer: detect memory bugs using tagged addressing.", false,
false)
FunctionPass *llvm::createHWAddressSanitizerPass(bool CompileKernel,
bool Recover) {
assert(!CompileKernel || Recover);
return new HWAddressSanitizer(CompileKernel, Recover);
}
/// Module-level initialization.
///
/// inserts a call to __hwasan_init to the module's constructor list.
bool HWAddressSanitizer::doInitialization(Module &M) {
LLVM_DEBUG(dbgs() << "Init " << M.getName() << "\n");
auto &DL = M.getDataLayout();
TargetTriple = Triple(M.getTargetTriple());
Mapping.init(TargetTriple);
C = &(M.getContext());
IRBuilder<> IRB(*C);
IntptrTy = IRB.getIntPtrTy(DL);
Int8Ty = IRB.getInt8Ty();
HwasanCtorFunction = nullptr;
if (!CompileKernel) {
std::tie(HwasanCtorFunction, std::ignore) =
createSanitizerCtorAndInitFunctions(M, kHwasanModuleCtorName,
kHwasanInitName,
/*InitArgTypes=*/{},
/*InitArgs=*/{});
appendToGlobalCtors(M, HwasanCtorFunction, 0);
}
return true;
}
void HWAddressSanitizer::initializeCallbacks(Module &M) {
IRBuilder<> IRB(*C);
for (size_t AccessIsWrite = 0; AccessIsWrite <= 1; AccessIsWrite++) {
const std::string TypeStr = AccessIsWrite ? "store" : "load";
const std::string EndingStr = Recover ? "_noabort" : "";
HwasanMemoryAccessCallbackSized[AccessIsWrite] =
checkSanitizerInterfaceFunction(M.getOrInsertFunction(
ClMemoryAccessCallbackPrefix + TypeStr + "N" + EndingStr,
FunctionType::get(IRB.getVoidTy(), {IntptrTy, IntptrTy}, false)));
for (size_t AccessSizeIndex = 0; AccessSizeIndex < kNumberOfAccessSizes;
AccessSizeIndex++) {
HwasanMemoryAccessCallback[AccessIsWrite][AccessSizeIndex] =
checkSanitizerInterfaceFunction(M.getOrInsertFunction(
ClMemoryAccessCallbackPrefix + TypeStr +
itostr(1ULL << AccessSizeIndex) + EndingStr,
FunctionType::get(IRB.getVoidTy(), {IntptrTy}, false)));
}
}
HwasanTagMemoryFunc = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
"__hwasan_tag_memory", IRB.getVoidTy(), IntptrTy, Int8Ty, IntptrTy));
HwasanGenerateTagFunc = checkSanitizerInterfaceFunction(
M.getOrInsertFunction("__hwasan_generate_tag", Int8Ty));
if (Mapping.InGlobal)
ShadowGlobal = M.getOrInsertGlobal("__hwasan_shadow",
ArrayType::get(IRB.getInt8Ty(), 0));
}
void HWAddressSanitizer::maybeInsertDynamicShadowAtFunctionEntry(Function &F) {
// Generate code only when dynamic addressing is needed.
if (Mapping.Offset != kDynamicShadowSentinel)
return;
IRBuilder<> IRB(&F.front().front());
if (Mapping.InGlobal) {
// An empty inline asm with input reg == output reg.
// An opaque pointer-to-int cast, basically.
InlineAsm *Asm = InlineAsm::get(
FunctionType::get(IntptrTy, {ShadowGlobal->getType()}, false),
StringRef(""), StringRef("=r,0"),
/*hasSideEffects=*/false);
LocalDynamicShadow = IRB.CreateCall(Asm, {ShadowGlobal}, ".hwasan.shadow");
} else {
Value *GlobalDynamicAddress = F.getParent()->getOrInsertGlobal(
kHwasanShadowMemoryDynamicAddress, IntptrTy);
LocalDynamicShadow = IRB.CreateLoad(GlobalDynamicAddress);
}
}
Value *HWAddressSanitizer::isInterestingMemoryAccess(Instruction *I,
bool *IsWrite,
uint64_t *TypeSize,
unsigned *Alignment,
Value **MaybeMask) {
// Skip memory accesses inserted by another instrumentation.
if (I->getMetadata("nosanitize")) return nullptr;
// Do not instrument the load fetching the dynamic shadow address.
if (LocalDynamicShadow == I)
return nullptr;
Value *PtrOperand = nullptr;
const DataLayout &DL = I->getModule()->getDataLayout();
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
if (!ClInstrumentReads) return nullptr;
*IsWrite = false;
*TypeSize = DL.getTypeStoreSizeInBits(LI->getType());
*Alignment = LI->getAlignment();
PtrOperand = LI->getPointerOperand();
} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
if (!ClInstrumentWrites) return nullptr;
*IsWrite = true;
*TypeSize = DL.getTypeStoreSizeInBits(SI->getValueOperand()->getType());
*Alignment = SI->getAlignment();
PtrOperand = SI->getPointerOperand();
} else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(I)) {
if (!ClInstrumentAtomics) return nullptr;
*IsWrite = true;
*TypeSize = DL.getTypeStoreSizeInBits(RMW->getValOperand()->getType());
*Alignment = 0;
PtrOperand = RMW->getPointerOperand();
} else if (AtomicCmpXchgInst *XCHG = dyn_cast<AtomicCmpXchgInst>(I)) {
if (!ClInstrumentAtomics) return nullptr;
*IsWrite = true;
*TypeSize = DL.getTypeStoreSizeInBits(XCHG->getCompareOperand()->getType());
*Alignment = 0;
PtrOperand = XCHG->getPointerOperand();
}
if (PtrOperand) {
// Do not instrument accesses from different address spaces; we cannot deal
// with them.
Type *PtrTy = cast<PointerType>(PtrOperand->getType()->getScalarType());
if (PtrTy->getPointerAddressSpace() != 0)
return nullptr;
// 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 (PtrOperand->isSwiftError())
return nullptr;
}
return PtrOperand;
}
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 = countTrailingZeros(TypeSize / 8);
assert(Res < kNumberOfAccessSizes);
return Res;
}
void HWAddressSanitizer::untagPointerOperand(Instruction *I, Value *Addr) {
if (TargetTriple.isAArch64())
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, Type *Ty, IRBuilder<> &IRB) {
// Mem >> Scale
Value *Shadow = IRB.CreateLShr(Mem, Mapping.Scale);
if (Mapping.Offset == 0)
return Shadow;
// (Mem >> Scale) + Offset
Value *ShadowBase;
if (LocalDynamicShadow)
ShadowBase = LocalDynamicShadow;
else
ShadowBase = ConstantInt::get(Ty, Mapping.Offset);
return IRB.CreateAdd(Shadow, ShadowBase);
}
void HWAddressSanitizer::instrumentMemAccessInline(Value *PtrLong, bool IsWrite,
unsigned AccessSizeIndex,
Instruction *InsertBefore) {
IRBuilder<> IRB(InsertBefore);
Value *PtrTag = IRB.CreateTrunc(IRB.CreateLShr(PtrLong, kPointerTagShift),
IRB.getInt8Ty());
Value *AddrLong = untagPointer(IRB, PtrLong);
Value *ShadowLong = memToShadow(AddrLong, PtrLong->getType(), IRB);
Value *MemTag =
IRB.CreateLoad(IRB.CreateIntToPtr(ShadowLong, IRB.getInt8PtrTy()));
Value *TagMismatch = IRB.CreateICmpNE(PtrTag, MemTag);
int matchAllTag = ClMatchAllTag.getNumOccurrences() > 0 ?
ClMatchAllTag : (CompileKernel ? 0xFF : -1);
if (matchAllTag != -1) {
Value *TagNotIgnored = IRB.CreateICmpNE(PtrTag,
ConstantInt::get(PtrTag->getType(), matchAllTag));
TagMismatch = IRB.CreateAnd(TagMismatch, TagNotIgnored);
}
TerminatorInst *CheckTerm =
SplitBlockAndInsertIfThen(TagMismatch, InsertBefore, !Recover,
MDBuilder(*C).createBranchWeights(1, 100000));
IRB.SetInsertPoint(CheckTerm);
const int64_t AccessInfo = Recover * 0x20 + IsWrite * 0x10 + AccessSizeIndex;
InlineAsm *Asm;
switch (TargetTriple.getArch()) {
case Triple::x86_64:
// The signal handler will find the data address in rdi.
Asm = InlineAsm::get(
FunctionType::get(IRB.getVoidTy(), {PtrLong->getType()}, false),
"int3\nnopl " + itostr(0x40 + AccessInfo) + "(%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(IRB.getVoidTy(), {PtrLong->getType()}, false),
"brk #" + itostr(0x900 + AccessInfo),
"{x0}",
/*hasSideEffects=*/true);
break;
default:
report_fatal_error("unsupported architecture");
}
IRB.CreateCall(Asm, PtrLong);
}
bool HWAddressSanitizer::instrumentMemAccess(Instruction *I) {
LLVM_DEBUG(dbgs() << "Instrumenting: " << *I << "\n");
bool IsWrite = false;
unsigned Alignment = 0;
uint64_t TypeSize = 0;
Value *MaybeMask = nullptr;
Value *Addr =
isInterestingMemoryAccess(I, &IsWrite, &TypeSize, &Alignment, &MaybeMask);
if (!Addr)
return false;
if (MaybeMask)
return false; //FIXME
IRBuilder<> IRB(I);
Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy);
if (isPowerOf2_64(TypeSize) &&
(TypeSize / 8 <= (1UL << (kNumberOfAccessSizes - 1))) &&
(Alignment >= (1UL << Mapping.Scale) || Alignment == 0 ||
Alignment >= TypeSize / 8)) {
size_t AccessSizeIndex = TypeSizeToSizeIndex(TypeSize);
if (ClInstrumentWithCalls) {
IRB.CreateCall(HwasanMemoryAccessCallback[IsWrite][AccessSizeIndex],
AddrLong);
} else {
instrumentMemAccessInline(AddrLong, IsWrite, AccessSizeIndex, I);
}
} else {
IRB.CreateCall(HwasanMemoryAccessCallbackSized[IsWrite],
{AddrLong, ConstantInt::get(IntptrTy, TypeSize / 8)});
}
untagPointerOperand(I, Addr);
return true;
}
static uint64_t getAllocaSizeInBytes(const AllocaInst &AI) {
uint64_t ArraySize = 1;
if (AI.isArrayAllocation()) {
const ConstantInt *CI = dyn_cast<ConstantInt>(AI.getArraySize());
assert(CI && "non-constant array size");
ArraySize = CI->getZExtValue();
}
Type *Ty = AI.getAllocatedType();
uint64_t SizeInBytes = AI.getModule()->getDataLayout().getTypeAllocSize(Ty);
return SizeInBytes * ArraySize;
}
bool HWAddressSanitizer::tagAlloca(IRBuilder<> &IRB, AllocaInst *AI,
Value *Tag) {
size_t Size = (getAllocaSizeInBytes(*AI) + Mapping.getAllocaAlignment() - 1) &
~(Mapping.getAllocaAlignment() - 1);
Value *JustTag = IRB.CreateTrunc(Tag, IRB.getInt8Ty());
if (ClInstrumentWithCalls) {
IRB.CreateCall(HwasanTagMemoryFunc,
{IRB.CreatePointerCast(AI, IntptrTy), JustTag,
ConstantInt::get(IntptrTy, Size)});
} else {
size_t ShadowSize = Size >> Mapping.Scale;
Value *ShadowPtr = IRB.CreateIntToPtr(
memToShadow(IRB.CreatePointerCast(AI, IntptrTy), AI->getType(), IRB),
IRB.getInt8PtrTy());
// 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.
IRB.CreateMemSet(ShadowPtr, JustTag, ShadowSize, /*Align=*/1);
}
return true;
}
static unsigned RetagMask(unsigned AllocaNo) {
// 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.
static unsigned FastMasks[] = {
0, 1, 2, 3, 4, 6, 7, 8, 12, 14, 15, 16, 24,
28, 30, 31, 32, 48, 56, 60, 62, 63, 64, 96, 112, 120,
124, 126, 127, 128, 192, 224, 240, 248, 252, 254};
return FastMasks[AllocaNo % (sizeof(FastMasks) / sizeof(FastMasks[0]))];
}
Value *HWAddressSanitizer::getNextTagWithCall(IRBuilder<> &IRB) {
return IRB.CreateZExt(IRB.CreateCall(HwasanGenerateTagFunc), IntptrTy);
}
Value *HWAddressSanitizer::getStackBaseTag(IRBuilder<> &IRB) {
if (ClGenerateTagsWithCalls)
return nullptr;
// FIXME: use addressofreturnaddress (but implement it in aarch64 backend
// first).
Module *M = IRB.GetInsertBlock()->getParent()->getParent();
auto GetStackPointerFn =
Intrinsic::getDeclaration(M, Intrinsic::frameaddress);
Value *StackPointer = IRB.CreateCall(
GetStackPointerFn, {Constant::getNullValue(IRB.getInt32Ty())});
// 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 *StackPointerLong = IRB.CreatePointerCast(StackPointer, IntptrTy);
Value *StackTag =
IRB.CreateXor(StackPointerLong, IRB.CreateLShr(StackPointerLong, 20),
"hwasan.stack.base.tag");
return StackTag;
}
Value *HWAddressSanitizer::getAllocaTag(IRBuilder<> &IRB, Value *StackTag,
AllocaInst *AI, unsigned AllocaNo) {
if (ClGenerateTagsWithCalls)
return getNextTagWithCall(IRB);
return IRB.CreateXor(StackTag,
ConstantInt::get(IntptrTy, RetagMask(AllocaNo)));
}
Value *HWAddressSanitizer::getUARTag(IRBuilder<> &IRB, Value *StackTag) {
if (ClGenerateTagsWithCalls)
return getNextTagWithCall(IRB);
return IRB.CreateXor(StackTag, ConstantInt::get(IntptrTy, 0xFFU));
}
// Add a tag to an address.
Value *HWAddressSanitizer::tagPointer(IRBuilder<> &IRB, Type *Ty,
Value *PtrLong, Value *Tag) {
Value *TaggedPtrLong;
if (CompileKernel) {
// Kernel addresses have 0xFF in the most significant byte.
Value *ShiftedTag = IRB.CreateOr(
IRB.CreateShl(Tag, kPointerTagShift),
ConstantInt::get(IntptrTy, (1ULL << kPointerTagShift) - 1));
TaggedPtrLong = IRB.CreateAnd(PtrLong, ShiftedTag);
} else {
// Userspace can simply do OR (tag << 56);
Value *ShiftedTag = IRB.CreateShl(Tag, kPointerTagShift);
TaggedPtrLong = IRB.CreateOr(PtrLong, ShiftedTag);
}
return IRB.CreateIntToPtr(TaggedPtrLong, Ty);
}
// Remove tag from an address.
Value *HWAddressSanitizer::untagPointer(IRBuilder<> &IRB, Value *PtrLong) {
Value *UntaggedPtrLong;
if (CompileKernel) {
// Kernel addresses have 0xFF in the most significant byte.
UntaggedPtrLong = IRB.CreateOr(PtrLong,
ConstantInt::get(PtrLong->getType(), 0xFFULL << kPointerTagShift));
} else {
// Userspace addresses have 0x00.
UntaggedPtrLong = IRB.CreateAnd(PtrLong,
ConstantInt::get(PtrLong->getType(), ~(0xFFULL << kPointerTagShift)));
}
return UntaggedPtrLong;
}
bool HWAddressSanitizer::instrumentStack(
SmallVectorImpl<AllocaInst *> &Allocas,
SmallVectorImpl<Instruction *> &RetVec) {
Function *F = Allocas[0]->getParent()->getParent();
Instruction *InsertPt = &*F->getEntryBlock().begin();
IRBuilder<> IRB(InsertPt);
Value *StackTag = getStackBaseTag(IRB);
// 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.
for (unsigned N = 0; N < Allocas.size(); ++N) {
auto *AI = Allocas[N];
IRB.SetInsertPoint(AI->getNextNode());
// Replace uses of the alloca with tagged address.
Value *Tag = getAllocaTag(IRB, StackTag, AI, N);
Value *AILong = IRB.CreatePointerCast(AI, IntptrTy);
Value *Replacement = tagPointer(IRB, AI->getType(), AILong, Tag);
std::string Name =
AI->hasName() ? AI->getName().str() : "alloca." + itostr(N);
Replacement->setName(Name + ".hwasan");
for (auto UI = AI->use_begin(), UE = AI->use_end(); UI != UE;) {
Use &U = *UI++;
if (U.getUser() != AILong)
U.set(Replacement);
}
tagAlloca(IRB, AI, Tag);
for (auto RI : RetVec) {
IRB.SetInsertPoint(RI);
// Re-tag alloca memory with the special UAR tag.
Value *Tag = getUARTag(IRB, StackTag);
tagAlloca(IRB, AI, Tag);
}
}
return true;
}
bool HWAddressSanitizer::isInterestingAlloca(const AllocaInst &AI) {
return (AI.getAllocatedType()->isSized() &&
// FIXME: instrument dynamic allocas, too
AI.isStaticAlloca() &&
// alloca() may be called with 0 size, ignore it.
getAllocaSizeInBytes(AI) > 0 &&
// We are only interested in allocas not promotable to registers.
// Promotable allocas are common under -O0.
!isAllocaPromotable(&AI) &&
// inalloca allocas are not treated as static, and we don't want
// dynamic alloca instrumentation for them as well.
!AI.isUsedWithInAlloca() &&
// swifterror allocas are register promoted by ISel
!AI.isSwiftError());
}
bool HWAddressSanitizer::runOnFunction(Function &F) {
if (&F == HwasanCtorFunction)
return false;
if (!F.hasFnAttribute(Attribute::SanitizeHWAddress))
return false;
LLVM_DEBUG(dbgs() << "Function: " << F.getName() << "\n");
initializeCallbacks(*F.getParent());
assert(!LocalDynamicShadow);
maybeInsertDynamicShadowAtFunctionEntry(F);
bool Changed = false;
SmallVector<Instruction*, 16> ToInstrument;
SmallVector<AllocaInst*, 8> AllocasToInstrument;
SmallVector<Instruction*, 8> RetVec;
for (auto &BB : F) {
for (auto &Inst : BB) {
if (ClInstrumentStack)
if (AllocaInst *AI = dyn_cast<AllocaInst>(&Inst)) {
// Realign all allocas. We don't want small uninteresting allocas to
// hide in instrumented alloca's padding.
if (AI->getAlignment() < Mapping.getAllocaAlignment())
AI->setAlignment(Mapping.getAllocaAlignment());
// Instrument some of them.
if (isInterestingAlloca(*AI))
AllocasToInstrument.push_back(AI);
continue;
}
if (isa<ReturnInst>(Inst) || isa<ResumeInst>(Inst) ||
isa<CleanupReturnInst>(Inst))
RetVec.push_back(&Inst);
Value *MaybeMask = nullptr;
bool IsWrite;
unsigned Alignment;
uint64_t TypeSize;
Value *Addr = isInterestingMemoryAccess(&Inst, &IsWrite, &TypeSize,
&Alignment, &MaybeMask);
if (Addr || isa<MemIntrinsic>(Inst))
ToInstrument.push_back(&Inst);
}
}
if (!AllocasToInstrument.empty())
Changed |= instrumentStack(AllocasToInstrument, RetVec);
for (auto Inst : ToInstrument)
Changed |= instrumentMemAccess(Inst);
LocalDynamicShadow = nullptr;
return Changed;
}
void HWAddressSanitizer::ShadowMapping::init(Triple &TargetTriple) {
const bool IsAndroid = TargetTriple.isAndroid();
const bool IsAndroidWithIfuncSupport =
IsAndroid && !TargetTriple.isAndroidVersionLT(21);
Scale = kDefaultShadowScale;
if (ClEnableKhwasan || ClInstrumentWithCalls || !IsAndroidWithIfuncSupport)
Offset = 0;
else
Offset = kDynamicShadowSentinel;
if (ClMappingOffset.getNumOccurrences() > 0)
Offset = ClMappingOffset;
InGlobal = IsAndroidWithIfuncSupport;
}
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