tracing/filters: Unify the regex parsing helpers

The filter code has stolen the regex parsing function from ftrace to
get the regex support.
We have duplicated this code, so factorize it in the filter area and
make it generally available, as the filter code is the most suited to
host this feature.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>

kernel/trace/trace.h

@@ -709,6 +709,13 @@ typedef int (*filter_pred_fn_t) (struct filter_pred *pred, void *event,
 
 typedef int (*regex_match_func)(char *str, struct regex *r, int len);
 
+enum regex_type {
+	MATCH_FULL,
+	MATCH_FRONT_ONLY,
+	MATCH_MIDDLE_ONLY,
+	MATCH_END_ONLY,
+};
+
 struct regex {
 	char			pattern[MAX_FILTER_STR_VAL];
 	int			len;
@@ -727,6 +734,8 @@ struct filter_pred {
 	int 			pop_n;
 };
 
+extern enum regex_type
+filter_parse_regex(char *buff, int len, char **search, int *not);
 extern void print_event_filter(struct ftrace_event_call *call,
 			       struct trace_seq *s);
 extern int apply_event_filter(struct ftrace_event_call *call,