tracing: Don't display trigger file for events that can't be enabled

[ Upstream commit 854145e0a8e9a05f7366d240e2f99d9c1ca6d6dd ]

Currently register functions for events will be called
through the 'reg' field of event class directly without
any check when seting up triggers.

Triggers for events that don't support register through
debug fs (events under events/ftrace are for trace-cmd to
read event format, and most of them don't have a register
function except events/ftrace/functionx) can't be enabled
at all, and an oops will be hit when setting up trigger
for those events, so just not creating them is an easy way
to avoid the oops.

Link: http://lkml.kernel.org/r/1462275274-3911-1-git-send-email-chuhu@redhat.com
Cc: stable@vger.kernel.org # 3.14+
Fixes: 85f2b08268c01 ("tracing: Add basic event trigger framework")
Signed-off-by: Chunyu Hu <chuhu@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index b6cd1b653e21068adfdea6aecfe9bac02761d7f6..51c47bc832d4709b6e2cfcf29cb53876bca80bba 100644 (file)
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1584,8 +1584,13 @@ event_create_dir(struct dentry *parent, struct ftrace_event_file *file)
        trace_create_file("filter", 0644, file->dir, file,
                          &ftrace_event_filter_fops);
 
-       trace_create_file("trigger", 0644, file->dir, file,
-                         &event_trigger_fops);
+       /*
+        * Only event directories that can be enabled should have
+        * triggers.
+        */
+       if (!(call->flags & TRACE_EVENT_FL_IGNORE_ENABLE))
+               trace_create_file("trigger", 0644, file->dir, file,
+                                 &event_trigger_fops);
 
        trace_create_file("format", 0444, file->dir, call,
                          &ftrace_event_format_fops);