[perf tool] record failure with 3.14-rc4

[perf tool] record failure with 3.14-rc4

[Will Deacon]

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?

Will

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

[Jiri Olsa]

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