[PATCH v4 01/10] tracing: Require all trace events to have a TRACE_SYSTEM

[Ajay Kaher <akaher@vmware.com>]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

The creation of the trace event directory requires that a TRACE_SYSTEM is
defined that the trace event directory is added within the system it was
defined in.

The code handled the case where a TRACE_SYSTEM was not added, and would
then add the event at the events directory. But nothing should be doing
this. This code also prevents the implementation of creating dynamic
dentrys for the eventfs system.

As this path has never been hit on correct code, remove it. If it does get
hit, issues a WARN_ON_ONCE() and return ENODEV.

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Ajay Kaher <akaher@vmware.com>
---
 kernel/trace/trace_events.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 57e539d47989..12ed71428939 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -2426,14 +2426,15 @@ event_create_dir(struct dentry *parent, struct trace_event_file *file)
 
 	/*
 	 * If the trace point header did not define TRACE_SYSTEM
-	 * then the system would be called "TRACE_SYSTEM".
+	 * then the system would be called "TRACE_SYSTEM". This should
+	 * never happen.
 	 */
-	if (strcmp(call->class->system, TRACE_SYSTEM) != 0) {
-		d_events = event_subsystem_dir(tr, call->class->system, file, parent);
-		if (!d_events)
-			return -ENOMEM;
-	} else
-		d_events = parent;
+	if (WARN_ON_ONCE(strcmp(call->class->system, TRACE_SYSTEM) == 0))
+		return -ENODEV;
+
+	d_events = event_subsystem_dir(tr, call->class->system, file, parent);
+	if (!d_events)
+		return -ENOMEM;
 
 	name = trace_event_name(call);
 	file->dir = tracefs_create_dir(name, d_events);
-- 
2.39.0