linux-kernel - Re: [RFC] perf tools: Filter out hidden symbols from labels

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Message-ID: <20190117132612.GI11922@kernel.org>
Date:   Thu, 17 Jan 2019 10:26:13 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Nick Clifton <nickc@...hat.com>
Cc:     Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Michael Petlan <mpetlan@...hat.com>,
        Masami Hiramatsu <mhiramat@...nel.org>, kernel-team@....com
Subject: Re: [RFC] perf tools: Filter out hidden symbols from labels

Em Thu, Jan 17, 2019 at 10:25:24AM +0000, Nick Clifton escreveu:
> Hi Arnaldo,
> 
> >>> Humm, is -fno-omit-frame-pointer there by any chance? :-)
> 
> > Would be interestint to have that info, as we could hint the user that
> > backtraces should be done with something else than '--call-graph fp' :-)
> 
> OK, well I have added the feature to annobin 8.67, now in Fedora
> rawhide.  Unfortunately it will take a while before the information
> actually gets into binaries, since the new data is only recorded
> when a package is rebuilt.  So basically you are looking at Fedora 30
> at the earliest.

That is not a problem, I have containers for rawhide, so I can just go
ahead and do a podman pull + build, build some binary, and then add the
feature, the warning will get into effect when that note is found and
userspace callchains are used without DWARF info for such binaries.
 
> If you want to see the plugin in action, build something on a rawhide
> system (or a mock chroot) using the gcc command line option -fplugin=annobin.

Right, that is what I'll do as soon as I get the time.

> (Make sure that you have annobin-8.67 installed).  Then once the binary 
> is built run "readelf --wide --notes <file> | grep omit" to see the 
> omit-frame-pointer notes.

Thanks for the hints, I'll get you CCed when I get to work on this.

- Arnaldo