do not silently fall-back to kallsyms.

Reported-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: rostedt@goodmis.org
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
LKML-Reference: <1253697658.11461.36.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Þ