tracing: Allow whitespace to surround hist trigger filter

The existing code only allows for one space before and after the 'if'
specifying the filter for a hist trigger.  Add code to make that more
permissive as far as whitespace goes.  Specifically, we want to allow
spaces in the trigger itself now that we have additional syntax
(onmatch/onmax) where spaces are more natural e.g. spaces after commas
in param lists.

Link: http://lkml.kernel.org/r/1053090c3c308d4f431accdeb59dff4b511d4554.1516069914.git.tom.zanussi@linux.intel.com

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace_events_hist.c

@@ -5162,7 +5162,7 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
 	struct synth_event *se;
 	const char *se_name;
 	bool remove = false;
-	char *trigger;
+	char *trigger, *p;
 	int ret = 0;
 
 	if (!param)
@@ -5171,10 +5171,37 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
 	if (glob[0] == '!')
 		remove = true;
 
-	/* separate the trigger from the filter (k:v [if filter]) */
-	trigger = strsep(&param, " \t");
-	if (!trigger)
-		return -EINVAL;
+	/*
+	 * separate the trigger from the filter (k:v [if filter])
+	 * allowing for whitespace in the trigger
+	 */
+	p = trigger = param;
+	do {
+		p = strstr(p, "if");
+		if (!p)
+			break;
+		if (p == param)
+			return -EINVAL;
+		if (*(p - 1) != ' ' && *(p - 1) != '\t') {
+			p++;
+			continue;
+		}
+		if (p >= param + strlen(param) - strlen("if") - 1)
+			return -EINVAL;
+		if (*(p + strlen("if")) != ' ' && *(p + strlen("if")) != '\t') {
+			p++;
+			continue;
+		}
+		break;
+	} while (p);
+
+	if (!p)
+		param = NULL;
+	else {
+		*(p - 1) = '\0';
+		param = strstrip(p);
+		trigger = strstrip(trigger);
+	}
 
 	attrs = parse_hist_trigger_attrs(trigger);
 	if (IS_ERR(attrs))