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perf record: Don't try to find buildids in a zero sized file

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Fixing this symptom:

 [acme@mica linux-2.6-tip]$ perf record -a -f
   Fatal: Permission error - are you root?

 Bus error
 [acme@mica linux-2.6-tip]$

I.e. if for some reason no data is collected, in this case a non
root user trying to do systemwide profiling, no data will be
collected, and then we end up trying to mmap a zero sized file
and access the file header, b00m.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: <stable@kernel.org>
LKML-Reference: <1268333592-30872-1-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Arnaldo Carvalho de Melo 2010-03-11 15:53:11 -03:00 committed by Ingo Molnar
parent 639fe4b12f
commit 9f591fd76a
1 changed files with 3 additions and 0 deletions
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3
tools/perf/builtin-record.c
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@ -395,6 +395,9 @@ static int process_buildids(void)
{
u64 size = lseek(output, 0, SEEK_CUR);
if (size == 0)
return 0;
session->fd = output;
return __perf_session__process_events(session, post_processing_offset,
size - post_processing_offset,