perf probe: Check whether debugfs path is correct

Check whether the debugfs path is correct before executing
a command, because perf-probe depends on debugfs.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Jason Baron <jbaron@redhat.com>
Cc: K.Prasad <prasad@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: systemtap <systemtap@sources.redhat.com>
Cc: DLE <dle-develop@lists.sourceforge.net>
LKML-Reference: <20091216222400.14459.48162.stgit@dhcp-100-2-132.bos.redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/builtin-probe.c

@@ -38,6 +38,7 @@
 #include "util/strlist.h"
 #include "util/event.h"
 #include "util/debug.h"
+#include "util/debugfs.h"
 #include "util/symbol.h"
 #include "util/thread.h"
 #include "util/session.h"
@@ -205,6 +206,9 @@ int cmd_probe(int argc, const char **argv, const char *prefix __used)
 	if ((!session.nr_probe && !session.dellist && !session.list_events))
 		usage_with_options(probe_usage, options);
 
+	if (debugfs_valid_mountpoint(debugfs_path) < 0)
+		die("Failed to find debugfs path.");
+
 	if (session.list_events) {
 		if (session.nr_probe != 0 || session.dellist) {
 			pr_warning("  Error: Don't use --list with"