From: "Björn Töpel" <bjorn@kernel.org>
To: Jiri Olsa <olsajiri@gmail.com>
Cc: Chen Zhongjin <chenzhongjin@huawei.com>,
Steven Rostedt <rostedt@goodmis.org>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Ingo Molnar <mingo@redhat.com>, bpf <bpf@vger.kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
LKML <linux-kernel@vger.kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [RFC] ftrace: Add support to keep some functions out of ftrace
Date: Mon, 15 Aug 2022 14:19:52 +0200 [thread overview]
Message-ID: <CAJ+HfNhir0HcNYi5PediR=O39nAKUCptbxLDsNsQd-nUQNt=aQ@mail.gmail.com> (raw)
In-Reply-To: <YvouGQzlOhb88SM/@krava>
On Mon, 15 Aug 2022 at 13:29, Jiri Olsa <olsajiri@gmail.com> wrote:
>
> On Mon, Aug 15, 2022 at 01:01:06PM +0200, Björn Töpel wrote:
> > On Mon, 15 Aug 2022 at 10:04, Jiri Olsa <olsajiri@gmail.com> wrote:
> > [...]
> > > > > >
> > > > > > Today, objtool has also got involved, and added an "--mcount" option
> > > > > > that will create the section too.
> > > > > I overlooked that objtool is involved as well,
> > > > > will check on that
> > > >
> > > > objtool --mcount option only involves mcount_loc generation (see
> > > > annotate_call_site) and other validation check call destination directly
> > > > (see is_fentry_call).
> > > >
> > > > Some simply removing --mcount option dose work for this.
> > > >
> > > >
> > > > Another question, it seems we can export and use DEFINE_BPF_DISPATCHER out
> > > > of kernel, does that means we should add NO_MCOUNT_FILES for these single
> > > > uages as well?
> > >
> > > yes, cc-ing Björn to make sure it's valid use case for dispatcher
> > >
> >
> > Hmm, could you expand a bit on how this would work?
>
> the goal here is to remove bpf_dispatcher_<FUNC>_func functions from
> ftrace, because it's updated by dispatcher code with bpf_arch_text_poke,
> but it's also visible and attachable to ftrace.. and will cause problems
> when these 2 updates will race
>
> question was if DEFINE_BPF_DISPATCHER can be used in kernel module,
> which would bring another realm of problems ;-)
>
Oh, now I follow. AFAIK there is only one flavor of BPF dispatcher in
use, and that's the XDP dispatcher, which does not reside in module
code, but is typically *called* by module code.
A module could define a BPF dispatcher, but it wouldn't be able to
update it, since bpf_arch_text_poke() does not support poking in
modules.
Björn
next prev parent reply other threads:[~2022-08-15 12:20 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-22 11:08 [RFC] ftrace: Add support to keep some functions out of ftrace Jiri Olsa
2022-07-22 11:26 ` Steven Rostedt
2022-07-22 16:04 ` Alexei Starovoitov
2022-07-22 16:08 ` Steven Rostedt
2022-07-22 16:25 ` Steven Rostedt
2022-07-22 16:53 ` Alexei Starovoitov
2022-07-22 17:14 ` Steven Rostedt
2022-07-22 21:05 ` Jiri Olsa
2022-07-22 21:41 ` Steven Rostedt
2022-07-23 3:53 ` Steven Rostedt
2022-07-23 3:56 ` Steven Rostedt
2022-07-25 7:00 ` Jiri Olsa
2022-07-23 21:39 ` Jiri Olsa
2022-08-12 21:18 ` Jiri Olsa
2022-08-12 21:50 ` Steven Rostedt
2022-08-13 19:02 ` Steven Rostedt
2022-08-14 11:32 ` Steven Rostedt
2022-08-14 15:22 ` Jiri Olsa
2022-08-15 2:07 ` Chen Zhongjin
2022-08-15 8:04 ` Jiri Olsa
2022-08-15 11:01 ` Björn Töpel
2022-08-15 11:29 ` Jiri Olsa
2022-08-15 12:19 ` Björn Töpel [this message]
2022-08-15 12:30 ` Björn Töpel
2022-08-15 8:03 ` Peter Zijlstra
2022-08-15 9:44 ` Jiri Olsa
2022-08-15 12:37 ` Peter Zijlstra
2022-08-15 14:25 ` Alexei Starovoitov
2022-08-15 14:33 ` Peter Zijlstra
2022-08-15 14:45 ` Alexei Starovoitov
2022-08-15 15:02 ` Peter Zijlstra
2022-08-15 15:17 ` Alexei Starovoitov
2022-08-15 15:28 ` Peter Zijlstra
2022-08-15 15:35 ` Alexei Starovoitov
2022-08-15 15:44 ` Steven Rostedt
2022-08-15 15:53 ` Alexei Starovoitov
2022-08-15 16:13 ` Steven Rostedt
2022-08-15 15:48 ` Peter Zijlstra
2022-08-16 6:56 ` Jiri Olsa
2022-08-17 9:29 ` Jiri Olsa
2022-08-17 16:57 ` Alexei Starovoitov
2022-08-17 19:39 ` Jiri Olsa
2022-08-15 15:41 ` Peter Zijlstra
2022-08-15 15:49 ` Alexei Starovoitov
2022-08-15 16:08 ` Steven Rostedt
2022-08-18 20:27 ` Jiri Olsa
2022-08-18 20:50 ` Steven Rostedt
2022-08-18 21:00 ` Alexei Starovoitov
2022-08-18 21:05 ` Steven Rostedt
2022-08-18 21:32 ` Jiri Olsa
2022-08-19 11:45 ` Jiri Olsa
2022-08-23 17:23 ` Alexei Starovoitov
2022-08-26 8:00 ` Jiri Olsa
2022-08-18 21:14 ` Jiri Olsa
2022-08-15 15:32 ` Steven Rostedt
2022-07-22 16:26 ` Jiri Olsa
2022-07-22 16:37 ` Steven Rostedt
2022-07-22 16:54 ` Alexei Starovoitov
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='CAJ+HfNhir0HcNYi5PediR=O39nAKUCptbxLDsNsQd-nUQNt=aQ@mail.gmail.com' \
--to=bjorn@kernel.org \
--cc=alexei.starovoitov@gmail.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=chenzhongjin@huawei.com \
--cc=daniel@iogearbox.net \
--cc=haoluo@google.com \
--cc=john.fastabend@gmail.com \
--cc=jpoimboe@redhat.com \
--cc=kafai@fb.com \
--cc=kpsingh@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=olsajiri@gmail.com \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--cc=sdf@google.com \
--cc=songliubraving@fb.com \
--cc=yhs@fb.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).