tracing: Make trace_get_fields() global

trace_get_fields() is the only way to read tracepoint fields at
run time, as their fields are defined at compile-time with macros.
Make this function visible to all users and it will be used by
trace event injection code to calculate the size of a tracepoint
entry.
Link: http://lkml.kernel.org/r/20190525165802.25944-4-xiyou.wangcong@gmail.com

Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

include/linux/trace_events.h

@@ -318,6 +318,14 @@ trace_event_name(struct trace_event_call *call)
 		return call->name;
 }
 
+static inline struct list_head *
+trace_get_fields(struct trace_event_call *event_call)
+{
+	if (!event_call->class->get_fields)
+		return &event_call->class->fields;
+	return event_call->class->get_fields(event_call);
+}
+
 struct trace_array;
 struct trace_subsystem_dir;
 

kernel/trace/trace_events.c

@@ -70,14 +70,6 @@ static int system_refcount_dec(struct event_subsystem *system)
 #define while_for_each_event_file()		\
 	}
 
-static struct list_head *
-trace_get_fields(struct trace_event_call *event_call)
-{
-	if (!event_call->class->get_fields)
-		return &event_call->class->fields;
-	return event_call->class->get_fields(event_call);
-}
-
 static struct ftrace_event_field *
 __find_event_field(struct list_head *head, char *name)
 {