linux-kernel - Re: [PATCH 0/3] perf: Fix perf probe for Fedora34 glibc update

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Date:   Tue, 6 Jul 2021 14:51:50 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Namhyung Kim <namhyung@...il.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Stefan Liebler <stli@...ux.ibm.com>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/3] perf: Fix perf probe for Fedora34 glibc update

On Mon, 5 Jul 2021 13:48:04 -0700
Namhyung Kim <namhyung@...il.com> wrote:

> On Sat, Jul 3, 2021 at 8:36 AM Masami Hiramatsu <mhiramat@...nel.org> wrote:
> >
> > Hi Arnaldo,
> >
> > Here is a series of patches to fix the perf-probe error against the
> > Fedora34 glibc update, which moves most of symbols from .symtab to
> > .dynsym. The key is that the "most of" symbols moved, but it still
> > have some PLT symbols in .symtab. Thus the perf symbol-elf failes to
> > decode symbols.
> 
> Do you know what's the rationale of the move?
> Is it a change from glibc or Fedora?

I don't know, but it seems that this happens when updating glibc package,
the version is same but revision is different. Also, in the Ubuntu, I saw
all symbols has been moved to .dynsym in older glibc.
Thus I guess that this depends on the build option or configuration.
Might Fedora change the packaging script?

Thank you,

> 
> Thanks,
> Namhyung
> 
> 
> >
> > Here is the original report from Thomas about this issue.
> >
> >  https://lore.kernel.org/linux-perf-users/f6752514-eaf9-371e-f81b-0d9e41ebae0c@linux.ibm.com/
> >
> > Thank you,
> >
> > ---
> >
> > Masami Hiramatsu (3):
> >       perf-probe: Fix debuginfo__new() to enable build-id based debuginfo
> >       perf symbol-elf: Decode dynsym even if symtab exists
> >       perf probe: Do not show @plt function by default
> >
> >
> >  tools/perf/builtin-probe.c     |    2 -
> >  tools/perf/util/probe-finder.c |    5 ++
> >  tools/perf/util/symbol-elf.c   |   82 ++++++++++++++++++++++++++--------------
> >  3 files changed, 60 insertions(+), 29 deletions(-)
> >
> > --
> > Masami Hiramatsu (Linaro) <mhiramat@...nel.org>


-- 
Masami Hiramatsu <mhiramat@...nel.org>