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[Clang][CodeGen] Enable pointer overflow check for GCC workaround #137849

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Merged
merged 4 commits into from
May 9, 2025
Merged

[Clang][CodeGen] Enable pointer overflow check for GCC workaround #137849

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5b3a9ed
[Clang][CodeGen] Enable pointer overflow check for GCC workaround
dtcxzyw May 6, 2025
ac8207c
[Clang][CodeGen] Emit null check
dtcxzyw May 8, 2025
d4f26e6
[Clang][CodeGen] Use `NullPointerIsDefined`
dtcxzyw May 8, 2025
927eb0b
Format code
dtcxzyw May 8, 2025
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27 changes: 22 additions & 5 deletions clang/lib/CodeGen/CGExprScalar.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4169,11 +4169,28 @@ static Value *emitPointerArithmetic(CodeGenFunction &CGF,
// The index is not pointer-sized.
// The pointer type is not byte-sized.
//
if (BinaryOperator::isNullPointerArithmeticExtension(CGF.getContext(),
op.Opcode,
expr->getLHS(),
expr->getRHS()))
return CGF.Builder.CreateIntToPtr(index, pointer->getType());
// Note that we do not suppress the pointer overflow check in this case.
if (BinaryOperator::isNullPointerArithmeticExtension(
CGF.getContext(), op.Opcode, expr->getLHS(), expr->getRHS())) {
Value *Ptr = CGF.Builder.CreateIntToPtr(index, pointer->getType());
if (CGF.getLangOpts().PointerOverflowDefined ||
!CGF.SanOpts.has(SanitizerKind::PointerOverflow) ||
NullPointerIsDefined(CGF.Builder.GetInsertBlock()->getParent(),
PtrTy->getPointerAddressSpace()))
return Ptr;
// The inbounds GEP of null is valid iff the index is zero.
CodeGenFunction::SanitizerScope SanScope(&CGF);
Value *IsZeroIndex = CGF.Builder.CreateIsNull(index);
llvm::Constant *StaticArgs[] = {
CGF.EmitCheckSourceLocation(op.E->getExprLoc())};
llvm::Type *IntPtrTy = DL.getIntPtrType(PtrTy);
Value *IntPtr = llvm::Constant::getNullValue(IntPtrTy);
Value *ComputedGEP = CGF.Builder.CreateZExtOrTrunc(index, IntPtrTy);
Value *DynamicArgs[] = {IntPtr, ComputedGEP};
CGF.EmitCheck({{IsZeroIndex, SanitizerKind::SO_PointerOverflow}},
SanitizerHandler::PointerOverflow, StaticArgs, DynamicArgs);
return Ptr;
}

if (width != DL.getIndexTypeSizeInBits(PtrTy)) {
// Zero-extend or sign-extend the pointer value according to
Expand Down
21 changes: 21 additions & 0 deletions clang/test/CodeGen/catch-nullptr-and-nonzero-offset.c
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Expand Up @@ -32,6 +32,7 @@
// CHECK-SANITIZE-ANYRECOVER-DAG: @[[LINE_1500:.*]] = {{.*}}, i32 1500, i32 15 } }
// CHECK-SANITIZE-ANYRECOVER-DAG: @[[LINE_1600:.*]] = {{.*}}, i32 1600, i32 15 } }
// CHECK-SANITIZE-ANYRECOVER-DAG: @[[LINE_1700:.*]] = {{.*}}, i32 1700, i32 15 } }
// CHECK-SANITIZE-ANYRECOVER-DAG: @[[LINE_1800:.*]] = {{.*}}, i32 1800, i32 20 } }

#ifdef __cplusplus
extern "C" {
Expand Down Expand Up @@ -431,6 +432,26 @@ char *void_ptr(void *base, unsigned long offset) {
return base + offset;
}

char *constant_null_add(unsigned long offset) {
// CHECK: define{{.*}} ptr @constant_null_add(i64 noundef %[[OFFSET:.*]])
// CHECK-NEXT: [[ENTRY:.*]]:
// CHECK-NEXT: %[[OFFSET_ADDR:.*]] = alloca i64, align 8
// CHECK-NEXT: store i64 %[[OFFSET]], ptr %[[OFFSET_ADDR]], align 8
// CHECK-NEXT: %[[OFFSET_RELOADED:.*]] = load i64, ptr %[[OFFSET_ADDR]], align 8
// CHECK-NEXT: %[[ADD_PTR:.*]] = inttoptr i64 %[[OFFSET_RELOADED]] to ptr
// CHECK-SANITIZE-NEXT: %[[IS_NULL:.*]] = icmp eq i64 %[[OFFSET_RELOADED]], 0, !nosanitize
// CHECK-SANITIZE-NEXT: br i1 %[[IS_NULL]], label %[[CONT:.*]], label %[[HANDLER_POINTER_OVERFLOW:[^,]+]],{{.*}} !nosanitize
// CHECK-SANITIZE: [[HANDLER_POINTER_OVERFLOW]]:
// CHECK-SANITIZE-NORECOVER-NEXT: call void @__ubsan_handle_pointer_overflow_abort(ptr @[[LINE_1800]], i64 0, i64 %[[OFFSET_RELOADED]])
// CHECK-SANITIZE-RECOVER-NEXT: call void @__ubsan_handle_pointer_overflow(ptr @[[LINE_1800]], i64 0, i64 %[[OFFSET_RELOADED]])
// CHECK-SANITIZE-TRAP-NEXT: call void @llvm.ubsantrap(i8 19){{.*}}, !nosanitize
// CHECK-SANITIZE-UNREACHABLE-NEXT: unreachable, !nosanitize
// CHECK-SANITIZE: [[CONT]]:
// CHECK-NEXT: ret ptr %[[ADD_PTR]]
#line 1800
return (char *)0 + offset;
}

#ifdef __cplusplus
}
#endif