From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jiri Olsa <jolsa@kernel.org>, Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andriin@fb.com>, Yonghong Song <yhs@fb.com>,
netdev@vger.kernel.org, bpf@vger.kernel.org,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>
Subject: Re: [PATCHv6 bpf] bpf: Move iterator functions into special init section
Date: Wed, 11 Nov 2020 09:37:38 -0300 [thread overview]
Message-ID: <20201111123738.GE355344@kernel.org> (raw)
In-Reply-To: <2a71a0b4-b5de-e9fb-bacc-3636e16245c5@iogearbox.net>
Em Wed, Nov 11, 2020 at 12:26:29PM +0100, Daniel Borkmann escreveu:
> On 11/10/20 4:40 PM, Jiri Olsa wrote:
> > With upcoming changes to pahole, that change the way how and
> > which kernel functions are stored in BTF data, we need a way
> > to recognize iterator functions.
> >
> > Iterator functions need to be in BTF data, but have no real
> > body and are currently placed in .init.text section, so they
> > are freed after kernel init and are filtered out of BTF data
> > because of that.
> >
> > The solution is to place these functions under new section:
> > .init.bpf.preserve_type
> >
> > And add 2 new symbols to mark that area:
> > __init_bpf_preserve_type_begin
> > __init_bpf_preserve_type_end
> >
> > The code in pahole responsible for picking up the functions will
> > be able to recognize functions from this section and add them to
> > the BTF data and filter out all other .init.text functions.
> >
> > Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
> > Suggested-by: Yonghong Song <yhs@fb.com>
> > Signed-off-by: Jiri Olsa <jolsa@redhat.com>
>
> LGTM, applied, thanks! Also added a reference to the pahole commit
Applied to what branch? I'm trying to test it now :-)
- Arnaldo
> to the commit log so that this info doesn't get lost in the void
> plus carried over prior Acks given nothing changed logically in the
> patch.
>
> P.s.: I've been wondering whether we also need to align the begin/end
> symbols via ALIGN_FUNCTION() in case ld might realign to a different
> boundary on later passes but this seems neither the case for .init.text
> right now, likely since it doesn't matter for kallsyms data in our
> particular case.
--
- Arnaldo
next prev parent reply other threads:[~2020-11-11 12:37 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-10 15:40 [PATCHv6 bpf] bpf: Move iterator functions into special init section Jiri Olsa
2020-11-11 11:26 ` Daniel Borkmann
2020-11-11 11:51 ` Jiri Olsa
2020-11-11 12:37 ` Arnaldo Carvalho de Melo [this message]
2020-11-11 12:38 ` Arnaldo Carvalho de Melo
2020-11-11 20:09 ` Alexei Starovoitov
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