ftrace/kprobe: Show the maxactive number on kprobe_events

Show maxactive parameter on kprobe_events.
This allows user to save the current configuration and
restore it without losing maxactive parameter.

Link: http://lkml.kernel.org/r/[email protected]
Link: http://lkml.kernel.org/r/158503528846.22706.5549974121212526020.stgit@devnote2

Cc: [email protected]
Fixes: 696ced4 ("tracing/kprobes: expose maxactive for kretprobe in kprobe_events")
Reported-by: Taeung Song <[email protected]>
Signed-off-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>

Author: mhiramat

kernel/trace/trace_kprobe.c

@@ -1078,6 +1078,8 @@ static int trace_kprobe_show(struct seq_file *m, struct dyn_event *ev)
 	int i;
 
 	seq_putc(m, trace_kprobe_is_return(tk) ? 'r' : 'p');
+	if (trace_kprobe_is_return(tk) && tk->rp.maxactive)
+		seq_printf(m, "%d", tk->rp.maxactive);
 	seq_printf(m, ":%s/%s", trace_probe_group_name(&tk->tp),
 				trace_probe_name(&tk->tp));