tracing/filters: Provide basic regex support

This patch provides basic support for regular expressions in filters.

It supports the following types of regexp:

- *match_beginning
- *match_middle*
- match_end*
- !don't match

Example:
	cd /debug/tracing/events/bkl/lock_kernel
	echo 'file == "*reiserfs*"' > filter
	echo 1 > enable

           gedit-4941  [000]   457.735437: lock_kernel: depth: 0, fs/reiserfs/namei.c:334 reiserfs_lookup()
     sync_supers-227   [001]   461.379985: lock_kernel: depth: 0, fs/reiserfs/super.c:69 reiserfs_sync_fs()
     sync_supers-227   [000]   461.383096: lock_kernel: depth: 0, fs/reiserfs/journal.c:1069 flush_commit_list()
      reiserfs/1-1369  [001]   461.479885: lock_kernel: depth: 0, fs/reiserfs/journal.c:3509 flush_async_commits()

Every string is now handled as a regexp in the filter framework, which
helps to factorize the code for handling both simple strings and
regexp comparisons.

(The regexp parsing code has been wildly cherry picked from ftrace.c
written by Steve.)

v2: Simplify the whole and drop the filter_regex file

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

@@ -702,20 +702,29 @@ struct event_subsystem {
 };
 
 struct filter_pred;
+struct regex;
 
 typedef int (*filter_pred_fn_t) (struct filter_pred *pred, void *event,
 				 int val1, int val2);
 
+typedef int (*regex_match_func)(char *str, struct regex *r, int len);
+
+struct regex {
+	char			pattern[MAX_FILTER_STR_VAL];
+	int			len;
+	int			field_len;
+	regex_match_func	match;
+};
+
 struct filter_pred {
-	filter_pred_fn_t fn;
-	u64 val;
-	char str_val[MAX_FILTER_STR_VAL];
-	int str_len;
-	char *field_name;
-	int offset;
-	int not;
-	int op;
-	int pop_n;
+	filter_pred_fn_t 	fn;
+	u64 			val;
+	struct regex		regex;
+	char 			*field_name;
+	int 			offset;
+	int 			not;
+	int 			op;
+	int 			pop_n;
 };
 
 extern void print_event_filter(struct ftrace_event_call *call,