Add an owner check to opening perf.data files and a switch to
silence it.

Because perf-report/perf-annotate are binary parsers reading
another users' perf.data file could be a security risk if the
file were explicitly engineered to trigger bugs in the parser
(we hope of course there are non such bugs, but you never
know).
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <20090819092023.896648538@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>