Re: [PATCH bpf-next 09/12] selftests/bpf: Add C tests for 16-byte returns in R0:R2

[Yonghong Song <yonghong.song@linux.dev>]

On 7/8/26 1:24 PM, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Low] Unconditional use of `__int128` in `bpf_testmod` breaks compilation on 32-bit host architectures.
> --
>
> --- Patch [9]: [PATCH bpf-next 09/12] selftests/bpf: Add C tests for 16-byte returns in R0:R2 ---
> commit 5ed3844739f04c920bb1c37cdf474501b3ca9fef
> Author: Yonghong Song <yonghong.song@linux.dev>
>
> selftests/bpf: Add C tests for 16-byte returns in R0:R2
>
> This commit adds selftests to exercise 16-byte return values passed in the
> R0:R2 register pair. The tests include an __int128 return, a 16-byte struct
> return, and a 16-byte union return.
>
> [ ... ]
>
>> diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
>> --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
>> +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
> [ ... ]
>
>> @@ -825,6 +825,18 @@ __bpf_kfunc int bpf_kfunc_call_test5(u8 a, u16 b, u32 c)
>>   	return 0;
>>   }
>>   
>> +__bpf_kfunc __int128 bpf_kfunc_call_test_i128(u64 a, u64 b)
>> +{
>> +	return ((__int128)a << 64) | b;
>> +}
> [Severity: Low]
> Will this unconditional use of __int128 break the build on 32-bit host
> architectures?
>
> The __int128 type is a compiler extension that is typically only available
> on 64-bit systems.
>
> [ ... ]
>
>> @@ -1358,6 +1370,8 @@ BTF_ID_FLAGS(func, bpf_kfunc_call_test2)
>>   BTF_ID_FLAGS(func, bpf_kfunc_call_test3)
>>   BTF_ID_FLAGS(func, bpf_kfunc_call_test4)
>>   BTF_ID_FLAGS(func, bpf_kfunc_call_test5)
>> +BTF_ID_FLAGS(func, bpf_kfunc_call_test_i128)
> [Severity: Low]
> If bpf_kfunc_call_test_i128 needs to be conditionally excluded for 32-bit
> builds to fix the issue above, should this BTF ID registration also be
> conditionally excluded to prevent a missing symbol error during the build?
>
> [ ... ]
>
>> diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
>> --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
>> +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
> [ ... ]
>
>> @@ -118,6 +127,8 @@ int bpf_kfunc_call_test2(struct sock *sk, __u32 a, __u32 b) __ksym;
>>   struct sock *bpf_kfunc_call_test3(struct sock *sk) __ksym;
>>   long bpf_kfunc_call_test4(signed char a, short b, int c, long d) __ksym;
>>   int bpf_kfunc_call_test5(__u8 a, __u16 b, __u32 c) __ksym;
>> +__int128 bpf_kfunc_call_test_i128(__u64 a, __u64 b) __ksym;
> [Severity: Low]
> Does this declaration also need to be guarded for 64-bit architectures,
> so that including this header doesn't fail on 32-bit host compilers?

We may need to guard with __SIZEOF_INT128__ in selftests. But current CI all supports 64bit,
so I am not sure whether we should do it or not.