[PATCH V2] tracing: Don't display trigger file for events that can't be enabled

[Chunyu Hu]

Currently register function of the event 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 regisgter
function except events/ftrace/function.) can't be enabled
at all, and an oops will be hit when setting up trigger
for those events, so just not showing them is an easy way
to avoid the oops.

Signed-off-by: Chunyu Hu <chuhu@xxxxxxxxxx>
---
 kernel/trace/trace_events.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index da1eeb6..b2eef30 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -2138,8 +2138,13 @@ event_create_dir(struct dentry *parent, struct trace_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);
 
 #ifdef CONFIG_HIST_TRIGGERS
 	trace_create_file("hist", 0444, file->dir, file,
-- 
1.8.3.1