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...
:)
next prev parent 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
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