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[ASan][RISCV] Teach AddressSanitizer to support indexed load/store. #160443

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Merged
merged 1 commit into from
Sep 26, 2025
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[ASan][RISCV] Teach AddressSanitizer to support indexed load/store. #160443

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9 changes: 7 additions & 2 deletions llvm/include/llvm/Analysis/InterestingMemoryOperand.h
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Original file line number Diff line number Diff line change
Expand Up @@ -32,14 +32,19 @@ class InterestingMemoryOperand {
Value *MaybeEVL;
// The Stride Value, if we're looking at a strided load/store.
Value *MaybeStride;
// The Offset Value, if we're looking at a indexed load/store. The
// offset actually means byte-offset instead of array index.
Value *MaybeByteOffset;

InterestingMemoryOperand(Instruction *I, unsigned OperandNo, bool IsWrite,
class Type *OpType, MaybeAlign Alignment,
Value *MaybeMask = nullptr,
Value *MaybeEVL = nullptr,
Value *MaybeStride = nullptr)
Value *MaybeStride = nullptr,
Value *MaybeByteOffset = nullptr)
: IsWrite(IsWrite), OpType(OpType), Alignment(Alignment),
MaybeMask(MaybeMask), MaybeEVL(MaybeEVL), MaybeStride(MaybeStride) {
MaybeMask(MaybeMask), MaybeEVL(MaybeEVL), MaybeStride(MaybeStride),
MaybeByteOffset(MaybeByteOffset) {
const DataLayout &DL = I->getDataLayout();
TypeStoreSize = DL.getTypeStoreSizeInBits(OpType);
PtrUse = &I->getOperandUse(OperandNo);
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38 changes: 38 additions & 0 deletions llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
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Expand Up @@ -2785,6 +2785,44 @@ bool RISCVTTIImpl::getTgtMemIntrinsic(IntrinsicInst *Inst,
Alignment, Mask, EVL, Stride);
return true;
}
case Intrinsic::riscv_vloxei_mask:
case Intrinsic::riscv_vluxei_mask:
case Intrinsic::riscv_vsoxei_mask:
case Intrinsic::riscv_vsuxei_mask:
HasMask = true;
[[fallthrough]];
case Intrinsic::riscv_vloxei:
case Intrinsic::riscv_vluxei:
case Intrinsic::riscv_vsoxei:
case Intrinsic::riscv_vsuxei: {
// Intrinsic interface (only listed ordered version):
// riscv_vloxei(merge, ptr, index, vl)
// riscv_vloxei_mask(merge, ptr, index, mask, vl, policy)
// riscv_vsoxei(val, ptr, index, vl)
// riscv_vsoxei_mask(val, ptr, index, mask, vl, policy)
bool IsWrite = Inst->getType()->isVoidTy();
Type *Ty = IsWrite ? Inst->getArgOperand(0)->getType() : Inst->getType();
const auto *RVVIInfo = RISCVVIntrinsicsTable::getRISCVVIntrinsicInfo(IID);
unsigned VLIndex = RVVIInfo->VLOperand;
unsigned PtrOperandNo = VLIndex - 2 - HasMask;
Value *Mask;
if (HasMask) {
Mask = Inst->getArgOperand(VLIndex - 1);
} else {
// Mask cannot be nullptr here: vector GEP produces <vscale x N x ptr>,
// and casting that to scalar i64 triggers a vector/scalar mismatch
// assertion in CreatePointerCast. Use an all-true mask so ASan lowers it
// via extractelement instead.
Type *MaskType = Ty->getWithNewType(Type::getInt1Ty(C));
Mask = ConstantInt::getTrue(MaskType);
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Why can't we use Mask = nullptr here?

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If we set Mask = nullptr, AddressSanitizer would directly call doInstrumentAddress. However, in our case the address is computed via a getelementptr

%5 = getelementptr i8, ptr %0, <vscale x 1 x i64> %4

which uses a vector index and therefore produces a VectorType of pointers. When this value is passed to CreatePointerCast, the assertion in llvm/lib/IR/Instructions.cpp is triggered because the source is a VectorType while the target IntptrTy is a scalar i64. In other words, the vector/scalar type mismatch is what causes the crash, so we cannot use nullptr here.

If we set the mask to <vscale x 1 x i1> splat (i1 true), AddressSanitizer will take the instrumentMaskedLoadOrStore path. In this case it generates

%12 = extractelement <vscale x 1 x ptr> %5, i64 %iv

to extract the element, which avoids the assertion.

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Please add this into a comment.

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Sure! Thanks for the suggestion.

}
Value *EVL = Inst->getArgOperand(VLIndex);
Value *OffsetOp = Inst->getArgOperand(PtrOperandNo + 1);
Info.InterestingOperands.emplace_back(Inst, PtrOperandNo, IsWrite, Ty,
Align(1), Mask, EVL,
/* Stride */ nullptr, OffsetOp);
return true;
}
}
return false;
}
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19 changes: 19 additions & 0 deletions llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
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Expand Up @@ -1786,6 +1786,25 @@ void AddressSanitizer::instrumentMop(ObjectSizeOffsetVisitor &ObjSizeVis,
else
NumInstrumentedReads++;

if (O.MaybeByteOffset) {
Type *Ty = Type::getInt8Ty(*C);
IRBuilder IB(O.getInsn());

Value *OffsetOp = O.MaybeByteOffset;
if (TargetTriple.isRISCV()) {
Type *OffsetTy = OffsetOp->getType();
// RVV indexed loads/stores zero-extend offset operands which are narrower
// than XLEN to XLEN.
if (OffsetTy->getScalarType()->getIntegerBitWidth() <
static_cast<unsigned>(LongSize)) {
VectorType *OrigType = cast<VectorType>(OffsetTy);
Type *ExtendTy = VectorType::get(IntptrTy, OrigType);
OffsetOp = IB.CreateZExt(OffsetOp, ExtendTy);
}
}
Addr = IB.CreateGEP(Ty, Addr, {OffsetOp});
}

unsigned Granularity = 1 << Mapping.Scale;
if (O.MaybeMask) {
instrumentMaskedLoadOrStore(this, DL, IntptrTy, O.MaybeMask, O.MaybeEVL,
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