tracing: Don't show dynamic string internals in synthetic event description

For synthetic event dynamic fields, the type contains "__data_loc",
which is basically an internal part of the type which is only meant to
be displayed in the format, not in the event description itself, which
is confusing to users since they can't use __data_loc on the
command-line to define an event field, which printing it would lead
them to believe.

So filter it out from the description, while leaving it in the type.

Link: https://lkml.kernel.org/r/b3b7baf7813298a5ede4ff02e2e837b91c05a724.1602598160.git.zanussi@kernel.org

Reported-by: Masami Hiramatsu <mhiramat@kernel.org>
Tested-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Author: Tom Zanussi

kernel/trace/trace_events_synth.c

@@ -1867,14 +1867,22 @@ static int __synth_event_show(struct seq_file *m, struct synth_event *event)
 {
 	struct synth_field *field;
 	unsigned int i;
+	char *type, *t;
 
 	seq_printf(m, "%s\t", event->name);
 
 	for (i = 0; i < event->n_fields; i++) {
 		field = event->fields[i];
 
+		type = field->type;
+		t = strstr(type, "__data_loc");
+		if (t) { /* __data_loc belongs in format but not event desc */
+			t += sizeof("__data_loc");
+			type = t;
+		}
+
 		/* parameter values */
-		seq_printf(m, "%s %s%s", field->type, field->name,
+		seq_printf(m, "%s %s%s", type, field->name,
 			   i == event->n_fields - 1 ? "" : "; ");
 	}