linux-kernel - Re: [RFC] propagating symtab load errors. was: Re: [GIT PULL 00/20] perf/core improvements and fixes

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Message-ID: <20150324131656.GD5337@krava.brq.redhat.com>
Date:	Tue, 24 Mar 2015 14:16:56 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	linux-kernel@...r.kernel.org,
	Adrian Hunter <adrian.hunter@...el.com>,
	Andi Kleen <ak@...ux.intel.com>, Borislav Petkov <bp@...e.de>,
	David Ahern <david.ahern@...cle.com>,
	Don Zickus <dzickus@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	He Kuang <hekuang@...wei.com>,
	"H . Peter Anvin" <hpa@...or.com>, Kaixu Xia <xiakaixu@...wei.com>,
	Kan Liang <kan.liang@...el.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Naohiro Aota <naota@...sp.net>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>,
	"Suzuki K . Poulose" <suzuki.poulose@....com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC] propagating symtab load errors. was: Re: [GIT PULL 00/20]
 perf/core improvements and fixes

On Mon, Mar 23, 2015 at 07:18:37PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Tue, Mar 10, 2015 at 11:03:31AM +0100, Ingo Molnar escreveu:
> > So I got this error today:
> > 
> >                     ┌─Warning:───────────────────────────┐
> >                     │The vmlinux file can't be used.     │
> >                     │Kernel samples will not be resolved.│
> >                     │                                    │
> >                     │                                    │
> >                     │Press any key...                    │
> >                     └────────────────────────────────────┘
> > ... and sadly perf is being passive-aggressive again: being negative 
> > but refusing to say why! :-)
> > 
> > Is there a way to figure out why it did not like the vmlinux?
> 
> So, we need some infrastructure for that, i.e. a strerror like routine
> like we have for other classes, because there are lots of things that
> can go wrong while loading a file: ELF error, decompression stuff, you
> name it, so, with the patch below it ends up as:
> 
> 
> # perf top --vmlinux /dev/null
> 
>            ┌─Warning:───────────────────────────────────────────┐
>            │The /tmp/passwd file can't be used: Invalid ELF file│
>            │Kernel samples will not be resolved.                │
>            │                                                    │
>            │                                                    │
>            │Press any key...                                    │
>            └────────────────────────────────────────────────────┘
> 
> 
> Basically save the errno, that may be an elf_errno (in this case I just came up
> with a DSO_LOAD_ERRNO__INVALID_ELF), an errno or some other error that needs
> propagating.
> 
> Just a heads up, I'll polish it a bit more before submitting, sounds OK?
> 
> Jiri, Namhyung, this would go down to the decompression code, etc.
> 
> Right now some of this can be obtained via the pr_debug calls, but that is too
> ä passive aggressive, and we don't want to do the error report syncronously,
> this is up for the tools/UI used, so saving it and providing a strerror routine
> looks sane, right?

right, DSO_LOAD_ERRNO__DECOMPRESSION_FAILURE seems ok

jirka
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