linux-kernel - Re: [perf tool] record failure with 3.14-rc4

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Date:	Mon, 24 Feb 2014 18:36:40 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Will Deacon <will.deacon@....com>
Cc:	adrian.hunter@...el.com, acme@...hat.com, a.p.zijlstra@...llo.nl,
	linux-kernel@...r.kernel.org
Subject: Re: [perf tool] record failure with 3.14-rc4

On Mon, Feb 24, 2014 at 05:24:41PM +0000, Will Deacon wrote:
> Hi guys,
> 
> If I try to run perf record as a non-root user, I end up with the following
> (unhelpful) error:
> 
>   $ perf record -e cycles ls
>   [...]
>   Not enough memory for reading perf file header
> 
> This is because the addresses in /proc/kallsyms always read as 0x0 when
> viewed by a non-privileged user, causing kallsyms__get_function_start to
> return 0x0 in args.start. machine__create_kernel_maps then treats this as
> an error an returns -1 to perf_session__create_kernel_maps, causing
> perf_session__new to fail and perf to exit.
> 
> The perf tool code in 3.13 is perfectly happy creating maps at 0x0, but I
> can see this has changed quite substantially in the recent merge window.
> 
> Any ideas? We could fix kallsyms__get_function_start to return < 0 on
> failure then fix the checks in the callers. Adrian?
hi,
not sure it's related, but i sent out rfc some time ago
for similar bad error messages:
  http://marc.info/?l=linux-kernel&m=138572558210216&w=2

maybe it could be updated for your case as well,
I'll try to check deeply later

jirka
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