Re: [PATCH bpf-next v1 2/2] selftests/bpf: Test resolve_btfids arena argument suffixes

["Kumar Kartikeya Dwivedi" <memxor@gmail.com>]

On Sun Aug 9, 2026 at 11:57 AM CEST, bot+bpf-ci wrote:
>> diff --git a/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c b/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
>> index 732cfed35e1c..9bd84fe32b89 100644
>> --- a/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
>> +++ b/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
>> @@ -15,6 +15,7 @@
>>  #define DECL_TAG_FASTCALL "bpf_fastcall"
>>  #define DECL_TAG_KFUNC "bpf_kfunc"
>>  #define TYPE_ATTR_ARENA "address_space(1)"
>> +#define ARENA_ARG(n) (1U << (n))
>
> This isn't a bug, but ARENA_ARG(n) is zero-based while the KF_ARENA_ARGn
> flags it sits next to are one-based, so the same argument is spelled two
> different ways inside a single table row.
>
> For example, '{ "kfunc_d", -1, KF_ARENA_ARG2, ARENA_ARG(1), false }'
> means KF_ARENA_ARG2 and ARENA_ARG(1) refer to the same parameter.
>
> Would a name like ARENA_ARG_IDX(n), or a short comment noting that
> ARENA_ARG(0) corresponds to KF_ARENA_ARG1, help keep the two columns
> from drifting?
>

I think it's ok, we might drop the other flag soon anyhow.

> [ ... ]
>
>> @@ -49,13 +50,18 @@ struct kfunc_symbol {
>>  	const char	*name;
>>  	s32		 id;
>>  	u32		 flags;
>> +	u32		 arena_args;
>> +	bool		 arena_ret;
>>  };
>>
>>  static struct kfunc_symbol kfunc_symbols[] = {
>> -	{ "kfunc_a", -1, 0 },
>> -	{ "kfunc_b", -1, KF_FASTCALL },
>> -	{ "kfunc_c", -1, KF_ARENA_RET | KF_ARENA_ARG1 | KF_ARENA_ARG2 },
>> -	{ "kfunc_d", -1, KF_ARENA_ARG2 },
>> +	{ "kfunc_a", -1, 0, 0, false },
>> +	{ "kfunc_b", -1, KF_FASTCALL, 0, false },
>> +	{ "kfunc_c", -1, KF_ARENA_RET | KF_ARENA_ARG1 | KF_ARENA_ARG2,
>> +	  ARENA_ARG(0) | ARENA_ARG(1), true },
>> +	{ "kfunc_d", -1, KF_ARENA_ARG2, ARENA_ARG(1), false },
>> +	{ "kfunc_e", -1, 0, ARENA_ARG(0) | ARENA_ARG(1) | ARENA_ARG(2) |
>> +	  ARENA_ARG(3) | ARENA_ARG(4), false },
>>  };
>
> This isn't a bug, but the new arena_ret field duplicates information
> that the existing flags field already carries.
>
> resolve_btfids only ever arena-tags a return value from KF_ARENA_RET:
>
> tools/bpf/resolve_btfids/main.c:add_arena_tagged_proto() {
>     ...
>     if (kfunc->flags & KF_ARENA_RET)
>         /* tag return */
>     ...
> }
>
> There is no return-position suffix mechanism, so arena_ret is exactly
> !!(flags & KF_ARENA_RET) for every row and the old expression it
> replaced was already correct.
>
> Since only KF_ARENA_RET drives return tagging, could the return
> assertion keep using !!(flags & KF_ARENA_RET) instead of the new
> arena_ret field?
>

I found this more clear, but am fine with reworking in any direction.

> [ ... ]
>
>
> ---
> 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/31305217088