Re: [PATCH bpf v2 0/2] bpf: add _impl suffix for kfuncs with implicit args

[Ihor Solodrai <ihor.solodrai@linux.dev>]

On 11/4/25 11:29 AM, Andrii Nakryiko wrote:
> On Tue, Nov 4, 2025 at 9:23 AM Ihor Solodrai <ihor.solodrai@linux.dev> wrote:
>>
>> On 11/4/25 7:29 AM, Mykyta Yatsenko wrote:
>>> We’re introducing support for implicit kfunc arguments and need to
>>> rename new kfuncs to comply with the naming convention.
>>> This new feature, will for each kfunc of the form:
>>>
>>> `bpf_foo_impl(args..., aux__prog)`
>>>
>>> generate a public BTF type:
>>>
>>> `bpf_foo(args...)`
>>>
>>> and the verifier will resolve calls to bpf_foo() to bpf_foo_impl(),
>>> supplying a valid struct bpf_prog_aux via aux__prog.
>>
>> Hi Mykyta, thank you for submitting this.
>>
>> The explanation in this cover is inaccurate. There were a few
>> discussions, and the "implicit" feature is in active development, so
>> it is confusing... Let me try to elaborate.
>>
>> [...]
>> 
>>> The implicit-arg mechanism is not in tree yet, so callers must switch to
>>> the *_impl names for now. Once the new mechanism lands, the plain
>>> names (without _impl) will be reintroduced as BTF-visible entry points
>>> and will resolve to the _impl versions automatically.
>>>
> 
> TBH, it looks like both Mykyta's and Ihor's descriptions are a little
> bit too detailed and are more concerned with details of the upcoming
> feature.
> 
> What's important with these fixes is that we are fixing deviation from
> the previously established "_impl" suffix naming convention for these
> kfuncs that accept verifier-provided bpf_prog_aux arguments. Following
> uniform convention will allow for transparent backwards compatibility
> with the upcoming KF_IMPLICIT_ARGS feature, so this patch set aims to
> fix current deviation from the convention so as to eliminate
> unnecessary backwards incompatibility breakage in the future.
> 
> WDYT?

I agree. For this patches we didn't have to go into the details, but that
has already happened :)

> 
>>> Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
>>> ---
>>> Changes in v1:
>>> - Split commit into 2
>>> - Rebase on the correct branch
>>> - Link to v1: https://lore.kernel.org/all/20251103232319.122965-1-mykyta.yatsenko5@gmail.com/
>>>
>>> ---
>>> Mykyta Yatsenko (2):
>>>       bpf:add _impl suffix for bpf_task_work_schedule* kfuncs
>>>       bpf:add _impl suffix for bpf_stream_vprintk() kfunc
>>>
>>>  kernel/bpf/helpers.c                               | 26 +++++++++++---------
>>>  kernel/bpf/stream.c                                |  3 ++-
>>>  kernel/bpf/verifier.c                              | 12 +++++-----
>>>  tools/bpf/bpftool/Documentation/bpftool-prog.rst   |  2 +-
>>>  tools/lib/bpf/bpf_helpers.h                        | 28 +++++++++++-----------
>>>  tools/testing/selftests/bpf/progs/stream_fail.c    |  6 ++---
>>>  tools/testing/selftests/bpf/progs/task_work.c      |  6 ++---
>>>  tools/testing/selftests/bpf/progs/task_work_fail.c |  8 +++----
>>>  .../testing/selftests/bpf/progs/task_work_stress.c |  4 ++--
>>>  9 files changed, 50 insertions(+), 45 deletions(-)
>>> ---
>>> base-commit: 6146a0f1dfae5d37442a9ddcba012add260bceb0
>>> change-id: 20251104-implv2-d6c4be255026
>>>
>>> Best regards,
>>