Re: [PATCH dwarves v1 0/3] btf_encoder: support for BPF magic kernel functions

[Eduard Zingerman <eddyz87@gmail.com>]

On Tue, 2025-11-04 at 14:25 -0800, Ihor Solodrai wrote:
> On 11/4/25 12:59 PM, Alan Maguire wrote:
> > On 29/10/2025 19:02, Ihor Solodrai wrote:
> > > This series implements BTF encoding of BPF kernel functions marked
> > > with KF_MAGIC_ARGS flag in pahole.
> > > 
> > > The kfunc flag indicates that the arguments of a kfunc with __magic
> > > suffix are implicitly set by the verifier, and so pahole must emit two
> > > functions to BTF:
> > >   * kfunc_impl() with the arguments matching kernel declaration
> > >   * kfunc() with __magic arguments omitted
> > > 
> > > For more details see relevant patch series for BPF:
> > > "bpf: magic kernel functions"
> > > 
> > > This series is built upon KF_IMPLICIT_PROG_AUX_ARG support [1],
> > > although the approach changed signifcantly to call it a v2.
> > > 
> > > [1] https://lore.kernel.org/dwarves/20250924211512.1287298-1-ihor.solodrai@linux.dev/
> > > 
> > > Ihor Solodrai (3):
> > >   btf_encoder: refactor btf_encoder__add_func_proto
> > >   btf_encoder: factor out btf_encoder__add_bpf_kfunc()
> > >   btf_encoder: support kfuncs with KF_MAGIC_ARGS flag
> > > 
> > >  btf_encoder.c | 292 ++++++++++++++++++++++++++++++++++++++------------
> > >  1 file changed, 222 insertions(+), 70 deletions(-)
> > > 
> > 
> > seems like we could potentially pull in patches 1 and 2 as cleanups
> > prior to handling the KF_MAGIC/IMPLICIT change; would that be worthwhile?
> > 
> 
> Hi Alan.
> 
> Feel free to merge in the refactoring patches if you think they are
> useful. No objections.

Hi Alan, Ihor,

If you thinking about merging patch #1, please consider my comment:

  > > +static int32_t btf_encoder__add_func_proto_for_state(struct btf_encoder *encoder, struct btf_encoder_func_state *state)

  > You can get rid of the `encoder` parameter here.
  > See https://github.com/acmel/dwarves/commit/080d1f27ae71e30c269a1e26e85bb86c3683f195 .

I sound a bit like a broken record, sorry.

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