dwarves.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>, Jiri Olsa <jolsa@kernel.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	dwarves@vger.kernel.org, bpf <bpf@vger.kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Andrii Nakryiko <andriin@fb.com>, Yonghong Song <yhs@fb.com>,
	Hao Luo <haoluo@google.com>
Subject: Re: [RFC/PATCH 3/3] btf_encoder: Func generation fix
Date: Thu, 12 Nov 2020 16:30:42 -0800	[thread overview]
Message-ID: <CAEf4BzZhRPVf=qVU7vVrtVaJzvBmsWL3hHYySKczMrrO-1Xotw@mail.gmail.com> (raw)
In-Reply-To: <CAADnVQKUYFE0vE3XZB0FPNMxw_+BNpOLJ37QJ+CxLbssDPHFdw@mail.gmail.com>

On Thu, Nov 12, 2020 at 4:19 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Thu, Nov 12, 2020 at 4:08 PM Andrii Nakryiko
> <andrii.nakryiko@gmail.com> wrote:
> >
> > So I looked at your vmlinux image. I think we should just keep
> > everything mostly as it it right now (without changes in this patch),
> > but add just two simple checks:
> >
> > 1. Skip if fn->declaration (ignore correctly marked func declarations)
> > 2. Skip if DW_AT_inline: 1 (ignore inlined functions).
> >
> > I'd keep the named arguments check as is, I think it's helpful. 1)
> > will skip stuff that's explicitly marked as declaration. 2) inline
> > check will partially mitigate dropping of fn->external check (and we
> > can't really attach to inlined functions).
>
> I thought DW_AT_inline is an indication that the function was marked "inline"
> in C code. That doesn't mean that the function was actually inlined.
> So I don't think pahole should check that bit.

According to DWARF spec, there are 4 possible values:

DW_INL_not_inlined = 0            Not declared inline nor inlined by
the compiler
DW_INL_inlined = 1                Not declared inline but inlined by
the compiler
DW_INL_declared_not_inlined = 2   Declared inline but not inlined by
the compiler
DW_INL_declared_inlined = 3       Declared inline and inlined by the compiler

So DW_INL_inlined is supposed to be added to functions that are not
marked inline, but were nevertheless inlined. I saw this for one of
vfs_getattr entries in DWARF, which clearly is not marked inline.

But also that DWARF entry had proper args with names, so it would work
fine as well. I don't know, with DWARF it's always some guessing game.
Let's leave DW_AT_inline alone for now.

Important part is skipping declarations (when they are marked as
such), though I'm not claiming it will solve the problem completely...
:)

  reply	other threads:[~2020-11-13  0:30 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-12 15:05 [RFC 0/3] btf_encoder: Fix functions BTF data generation Jiri Olsa
2020-11-12 15:05 ` [RFC/PATCH 1/3] btf_encoder: Generate also .init functions Jiri Olsa
2020-11-12 19:37   ` Andrii Nakryiko
2020-11-12 15:05 ` [RFC/PATCH 2/3] btf_encoder: Put function generation code to generate_func Jiri Olsa
2020-11-12 19:39   ` Andrii Nakryiko
2020-11-12 15:05 ` [RFC/PATCH 3/3] btf_encoder: Func generation fix Jiri Olsa
2020-11-12 19:54   ` Andrii Nakryiko
2020-11-12 21:14     ` Jiri Olsa
2020-11-13  0:08       ` Andrii Nakryiko
2020-11-13  0:18         ` Alexei Starovoitov
2020-11-13  0:30           ` Andrii Nakryiko [this message]
2020-11-13  1:00             ` Yonghong Song
2020-11-13  1:12               ` Andrii Nakryiko
2020-11-13 10:59         ` Jiri Olsa
2020-11-13 11:52           ` Arnaldo Carvalho de Melo

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='CAEf4BzZhRPVf=qVU7vVrtVaJzvBmsWL3hHYySKczMrrO-1Xotw@mail.gmail.com' \
    --to=andrii.nakryiko@gmail.com \
    --cc=acme@kernel.org \
    --cc=alexei.starovoitov@gmail.com \
    --cc=andriin@fb.com \
    --cc=ast@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=dwarves@vger.kernel.org \
    --cc=haoluo@google.com \
    --cc=jolsa@kernel.org \
    --cc=jolsa@redhat.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).