Re: [PATCH bpf-next v6 06/10] bpf: Add verifier support for 16-byte returns in R0:R2

On 8/16/26 10:17 PM, [email protected] wrote:
>> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
>> index 5b9d767895c9..2ae7cb9b30f2 100644
>> --- a/kernel/bpf/btf.c
>> +++ b/kernel/bpf/btf.c
>> @@ -7684,6 +7684,12 @@ static int btf_check_func_type_match(struct bpf_verifier_log *log,
>>   			btf_type_str(t2), fn2);
>>   		return -EINVAL;
>>   	}
>> +	if (btf_type_has_size(t1) && (t1->size > 8 || t2->size > 8)) {
>> +		bpf_log(log,
>> +			"Return type of %s() has size %u while %s() has size %u, and a size above 8 bytes cannot be replaced\n",
>> +			fn1, t1->size, fn2, t2->size);
>> +		return -EINVAL;
>> +	}
> This isn't a bug, but since this check fires on the absolute size rather
> than on a mismatch, the message can end up reading "has size 16 while g()
> has size 16". Would it be clearer to state which side exceeds 8 bytes
> instead of using the "X while Y" mismatch phrasing the neighbouring
> diagnostics use?

Okay, I see. Maybe
  "Return type of %s() has size %u and of %s() size %u, and a size above 8 bytes cannot be replaced\n"
?
I guess the intention is to explicitly mention which function exceeds 8 bytes.
User should be able to know this by checking original func and freplace prog?

>
>
> ---
> 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/31995069373