linux-kernel - Re: 3.10-rc6 "perf test" seems unhappy

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Date:	Wed, 26 Jun 2013 19:09:32 +0530
From:	Prabhat Kumar Ravi <prabhatravi09@...il.com>
To:	Andy Green <andy.green@...aro.org>
Cc:	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: Re: 3.10-rc6 "perf test" seems unhappy

Hi,

On Wed, Jun 26, 2013 at 4:39 PM, Andy Green <andy.green@...aro.org> wrote:
> Hi -
>
> Running perf test on 3.10-rc6 gives some unexpected behaviours.
>
> This is on a dual Cortex A9 board with perf userland cross-built from
> same tree as the kernel.
>
> root@...-eb:~# perf test
>  1: vmlinux symtab matches kallsyms                        : FAILED!

> I started tracing the first failure... it stops because it can't find
> "_stext" in /proc/kallsyms.  But it is there
>
> root@...-eb:~# cat /proc/kallsyms | grep _stext
> 800081c0 T _stext
>

>
> The others may be due to missing some config somewhere.
>
> Any ideas what I am (or perf is) doing wrong?
>

I Think your Perf test is failing at dso__find_symbol_by_name
where in perf test we have something like:

        kallsyms_map = machine__kernel_map(&kallsyms, type);

        sym = map__find_symbol_by_name(kallsyms_map, ref_reloc_sym.name, NULL);
        if (sym == NULL) {
                pr_debug("dso__find_symbol_by_name ");
                goto out;
        }

Here sym is search for "_stext" which is NULL here so perf test fails here only,

Here _stext having same address as some other, like

c00081c0 T asm_do_IRQ
c00081c0 T _stext
c00081c0 T __exception_text_start

Function call is like this:
machine__load_kallsyms
--> dso__load_kallsyms
    --> symbols__fixup_duplicate

So, it getting deleted, I think we should disable symbols__fixup_duplicate.

- Prabhat
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