Re: [PATCH bpf-next 3/3] libbpf: auto-generate list of BPF helper definitions

From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Alexei Starovoitov <ast@fb.com>
Cc: Andrii Nakryiko <andriin@fb.com>,
	"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"daniel@iogearbox.net" <daniel@iogearbox.net>,
	Kernel Team <Kernel-team@fb.com>,
	Quentin Monnet <quentin.monnet@netronome.com>
Subject: Re: [PATCH bpf-next 3/3] libbpf: auto-generate list of BPF helper definitions
Date: Sat, 5 Oct 2019 11:24:33 -0700	[thread overview]
Message-ID: <CAEf4BzZdhBTovTfv+Ar0En__RmuP6Lr=RWF2ix3uo9hZ84oHcg@mail.gmail.com> (raw)
In-Reply-To: <b0df96f6-dc41-8baf-baa3-e98da94c54b7@fb.com>

On Sat, Oct 5, 2019 at 10:10 AM Alexei Starovoitov <ast@fb.com> wrote:
>
> On 10/5/19 12:59 AM, Andrii Nakryiko wrote:
> > Get rid of list of BPF helpers in bpf_helpers.h (irony...) and
> > auto-generate it into bpf_helpers_defs.h, which is now included from
> > bpf_helpers.h.
> >
> > Suggested-by: Alexei Starovoitov<ast@fb.com>
> > Signed-off-by: Andrii Nakryiko<andriin@fb.com>
> > ---
> >   tools/lib/bpf/Makefile           |    8 +-
> >   tools/lib/bpf/bpf_helpers.h      |  264 +--
> >   tools/lib/bpf/bpf_helpers_defs.h | 2677 ++++++++++++++++++++++++++++++
> >   3 files changed, 2685 insertions(+), 264 deletions(-)
> >   create mode 100644 tools/lib/bpf/bpf_helpers_defs.h
>
> Approach looks good to me.
> imo that's better than messing with macros.
>
> Using bpf_helpers_doc.py as part of build will help man pages too.
> I think we were sloppy documenting helpers, since only Quentin
> was running that script regularly.

Yep, I agree, I had to fix few things, as well as (char *) vs (void *)
vs (__u8 *) differences were causing some extra warnings.
Please check the list of type translations whether they make sense.

>
> Only question is what is the reason to commit generated .h into git?

So originally I didn't want to depend on system UAPI headers during
Github build. But now I recalled that we do have latest UAPI synced
into Github's include/ subdir, so that's not an obstacle really. We'll
just need to re-license bpf_helpers_doc.py (I don't think Quentin will
mind) and start syncing it to Github (not a big deal at all).

There is still a benefit in having it checked in: easy to spot if
script does something wrong and double-check the changes (after
initial big commit, of course).

If you think that's not reason enough, let me know and I can drop it in v2.