From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
davem@davemloft.net, daniel@iogearbox.net,
netdev@vger.kernel.org, bpf@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH bpf-next 3/6] bpf: Introduce function-by-function verification
Date: Thu, 9 Jan 2020 15:03:31 -0800 [thread overview]
Message-ID: <20200109230328.i6zuva5gqezpltwp@ast-mbp> (raw)
In-Reply-To: <87ftgpgg6p.fsf@toke.dk>
On Thu, Jan 09, 2020 at 09:57:50AM +0100, Toke Høiland-Jørgensen wrote:
>
> > As far as future plans when libbpf sees FUNC_EXTERN it will do the linking the
> > way we discussed in the other thread. The kernel will support FUNC_EXTERN when
> > we introduce dynamic libraries. A collection of bpf functions will be loaded
> > into the kernel first (like libc.so) and later programs will have FUNC_EXTERN
> > as part of their BTF to be resolved while loading. The func name to btf_id
> > resolution will be done by libbpf. The kernel verifier will do the type
> > checking on BTFs.
>
> Right, FUNC_EXTERN will be rejected by the kernel unless it's patched up
> with "target" btf_ids by libbpf before load? So it'll be
> FUNC_GLOBAL-linked functions that will be replaceable after the fact
> with the "dynamic re-linking" feature?
Right. When libbpf statically links two .o it will need to produce a combined
BTF out of these two .o. That new BTF will not have FUNC_EXTERN anymore if they
are resolved. When the kernel sees FUNC_EXTERN it's a directive for the kernel
to resolve it. BPF program with FUNC_EXTERN references would be loadable, but
not executable. Anyhow the extern work is not immediate. I don't think any of
that is necessary for dynamic re-linking.
next prev parent reply other threads:[~2020-01-09 23:03 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-08 7:25 [PATCH bpf-next 0/6] bpf: Introduce global functions Alexei Starovoitov
2020-01-08 7:25 ` [PATCH bpf-next 1/6] libbpf: Sanitize BTF_KIND_FUNC linkage Alexei Starovoitov
2020-01-08 17:35 ` Song Liu
2020-01-08 18:57 ` Yonghong Song
2020-01-08 20:12 ` Alexei Starovoitov
2020-01-08 7:25 ` [PATCH bpf-next 2/6] libbpf: Collect static vs global info about functions Alexei Starovoitov
2020-01-08 10:25 ` Toke Høiland-Jørgensen
2020-01-08 16:25 ` Yonghong Song
2020-01-09 8:50 ` Toke Høiland-Jørgensen
2020-01-08 17:57 ` Song Liu
2020-01-08 20:10 ` Alexei Starovoitov
2020-01-08 7:25 ` [PATCH bpf-next 3/6] bpf: Introduce function-by-function verification Alexei Starovoitov
2020-01-08 10:28 ` Toke Høiland-Jørgensen
2020-01-08 20:06 ` Alexei Starovoitov
2020-01-09 8:57 ` Toke Høiland-Jørgensen
2020-01-09 23:03 ` Alexei Starovoitov [this message]
2020-01-10 10:08 ` Toke Høiland-Jørgensen
2020-01-08 19:10 ` Song Liu
2020-01-08 20:20 ` Alexei Starovoitov
2020-01-08 21:24 ` Song Liu
2020-01-08 23:05 ` Alexei Starovoitov
2020-01-14 23:39 ` Stanislav Fomichev
2020-01-14 23:56 ` Andrii Nakryiko
2020-01-15 0:44 ` Stanislav Fomichev
2020-01-08 7:25 ` [PATCH bpf-next 4/6] selftests/bpf: Add fexit-to-skb test for global funcs Alexei Starovoitov
2020-01-08 19:15 ` Song Liu
2020-01-08 7:25 ` [PATCH bpf-next 5/6] selftests/bpf: Add a test for a large global function Alexei Starovoitov
2020-01-08 19:16 ` Song Liu
2020-01-08 19:17 ` Song Liu
2020-01-08 7:25 ` [PATCH bpf-next 6/6] selftests/bpf: Modify a test to check global functions Alexei Starovoitov
2020-01-08 19:18 ` Song Liu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200109230328.i6zuva5gqezpltwp@ast-mbp \
--to=alexei.starovoitov@gmail.com \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=davem@davemloft.net \
--cc=kernel-team@fb.com \
--cc=netdev@vger.kernel.org \
--cc=toke@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).