Re: [PATCH bpf-next 02/12] bpf: Add verifier support for 16-byte returns in R0:R2

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

On 7/8/26 2:17 PM, bot+bpf-ci@kernel.org wrote:
>> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
>> index 3f34ce1a3107d..03ffb5f839fa0 100644
>> --- a/kernel/bpf/verifier.c
>> +++ b/kernel/bpf/verifier.c
>> @@ -424,6 +424,35 @@ static bool subprog_returns_void(struct bpf_verifier_env *env, int subprog)
>>   	return btf_type_is_void(type);
>>   }
>>
>> +static bool bpf_ret_reg_pair(struct bpf_verifier_env *env, int subprog)
>> +{
>> +	const struct btf_type *type, *func, *func_proto;
>> +	const struct btf *btf = env->prog->aux->btf;
>> +	u32 btf_id;
>> +
>> +	if (!btf || !env->prog->aux->func_info)
>> +		return false;
>> +
>> +	btf_id = env->prog->aux->func_info[subprog].type_id;
>> +
>> +	func = btf_type_by_id(btf, btf_id);
>> +	if (!func)
>> +		return false;
>> +
>> +	func_proto = btf_type_by_id(btf, func->type);
>> +	if (!func_proto)
>> +		return false;
>> +
>> +	type = btf_type_skip_modifiers(btf, func_proto->type, NULL);
>> +	if (!type)
>> +		return false;
>> +
>> +	if (btf_type_is_struct(type) || btf_type_is_scalar(type))
>> +		return type->size > 8 && type->size <= 16;
>> +
>> +	return false;
>> +}
> This isn't a bug, but could bpf_ret_reg_pair() and subprog_returns_void()
> share a helper for the func_info -> func -> func_proto -> return type walk?
>
> Both functions repeat the same ~8 line sequence:
>
> subprog_returns_void():
> 	btf_id = env->prog->aux->func_info[subprog].type_id;
> 	func = btf_type_by_id(btf, btf_id);
> 	if (!func)
> 		return false;
> 	func_proto = btf_type_by_id(btf, func->type);
> 	if (!func_proto)
> 		return false;
> 	type = btf_type_skip_modifiers(btf, func_proto->type, NULL);
>
> They only differ in the final predicate: subprog_returns_void() checks
> btf_type_is_void(type), while bpf_ret_reg_pair() checks the struct/scalar
> size.
>
> [ ... ]

Indeed, I think this probably worthwhile to factor a new helper.

>
>
> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
>
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/28973410219