perf symbols: Cache /proc/kallsyms files by build-id

So that when we don't have a vmlinux handy we can store the
kallsyms for later use by 'perf report'.

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>
LKML-Reference: <1263501006-14185-3-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index 24ec5be..0e9820a 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -245,7 +245,7 @@
 	 */
 	struct process_symbol_args args = { .name = symbol_name, };
 
-	if (kallsyms__parse(&args, find_symbol_cb) <= 0)
+	if (kallsyms__parse("/proc/kallsyms", &args, find_symbol_cb) <= 0)
 		return -ENOENT;
 
 	size = snprintf(ev.mmap.filename, sizeof(ev.mmap.filename),