From: Milian Wolff <milian.wolff@kdab.com>
To: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: jolsa@kernel.org, Linux-kernel@vger.kernel.org,
linux-perf-users@vger.kernel.org
Subject: Re: [PATCH] perf util: take pgoff into account when reporting elf to libdwfl
Date: Tue, 30 Oct 2018 21:36:39 +0100 [thread overview]
Message-ID: <2799419.aVeE0VMyCs@agathebauer> (raw)
In-Reply-To: <20181029174014.GG21857@kernel.org>
[-- Attachment #1: Type: text/plain, Size: 1717 bytes --]
On Montag, 29. Oktober 2018 18:40:14 CET Arnaldo Carvalho de Melo wrote:
> Em Mon, Oct 29, 2018 at 04:26:27PM +0100, Milian Wolff escreveu:
> > On Monday, October 29, 2018 3:16:44 PM CET Milian Wolff wrote:
> > > Libdwfl parses an ELF file itself and creates mappings for the
> > > individual sections. Perf on the other hand sees raw mmap events which
> > > represent individual sections. When we encounter an address pointing
> > > into a mapping with pgoff != 0, we must take that into account and
> > > report the file at the non-offset base address.
> >
> > > This fixes unwinding with libdwfl in some cases. E.g. for a file like:
> > <snip>
> >
> > > Note that the backtrace is still stopping too early, when
> > > compared to the nice results obtained via libunwind. It's
> > > unclear so far what the reason for that is.
> >
> > The remaining issue is due to a bug in elfutils:
> >
> > https://sourceware.org/ml/elfutils-devel/2018-q4/msg00089.html
> >
> > With both patches applied, libunwind and elfutils produce the same output
> > for the above scenario.
>
> I'm updating the patch to remove:
>
> "It's unclear so far what the reason for that is."
>
> Adding:
>
> "See https://sourceware.org/ml/elfutils-devel/2018-q4/msg00089.html for
> a patch fixing that."
>
> Ok?
Yes, thanks. I figured the fix for elfutils out after I submitted the perf
patch.
> Or are you saying that that "unclear" part applies to both libunwind
> and elfutils?
No, libunwind worked fine without these patches for this specific case.
Cheers
--
Milian Wolff | milian.wolff@kdab.com | Senior Software Engineer
KDAB (Deutschland) GmbH, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt, C++ and OpenGL Experts
[-- Attachment #2: smime.p7s --]
[-- Type: application/pkcs7-signature, Size: 3826 bytes --]
next prev parent reply other threads:[~2018-10-30 20:36 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-29 14:16 [PATCH] perf util: take pgoff into account when reporting elf to libdwfl Milian Wolff
2018-10-29 14:56 ` Jiri Olsa
2018-10-29 15:26 ` Milian Wolff
2018-10-29 17:40 ` Arnaldo Carvalho de Melo
2018-10-30 20:36 ` Milian Wolff [this message]
2018-10-31 22:04 ` [tip:perf/urgent] perf unwind: Take " tip-bot for Milian Wolff
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=2799419.aVeE0VMyCs@agathebauer \
--to=milian.wolff@kdab.com \
--cc=Linux-kernel@vger.kernel.org \
--cc=acme@kernel.org \
--cc=jolsa@kernel.org \
--cc=linux-perf-users@vger.kernel.org \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.