tracing: Require all trace events to have a TRACE_SYSTEM

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.

Link: https://lkml.kernel.org/r/1690568452-46553-2-git-send-email-akaher@vmware.com
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Ajay Kaher <akaher@vmware.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 578f1f7d49a61a2a3f9a3fc4a67cb292c7b764da..3ecc41f6acd96039f29d8f9f22840d7a1254e50b 100644 (file)
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -2420,14 +2420,15 @@ 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);