tracing/filters: operand can be negative

This should be a bug:

 # cat format
 name: foo_bar
 ID: 71
 format:
	 ...
         field:int bar;  offset:24;      size:4;
 # echo 'bar < 0' > filter
 # echo 'bar < -1' > filter
 bash: echo: write error: Invalid argument

[ Impact: fix to allow negative operand in filer expr ]
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A35B8DF.60400@cn.fujitsu.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

kernel/trace/trace_events_filter.c

@@ -546,6 +546,7 @@ static int filter_add_pred(struct filter_parse_state *ps,
 	filter_pred_fn_t fn;
 	unsigned long long val;
 	int string_type;
+	int ret;
 
 	pred->fn = filter_pred_none;
 
@@ -581,7 +582,11 @@ static int filter_add_pred(struct filter_parse_state *ps,
 			pred->not = 1;
 		return filter_add_pred_fn(ps, call, pred, fn);
 	} else {
-		if (strict_strtoull(pred->str_val, 0, &val)) {
+		if (field->is_signed)
+			ret = strict_strtoll(pred->str_val, 0, &val);
+		else
+			ret = strict_strtoull(pred->str_val, 0, &val);
+		if (ret) {
 			parse_error(ps, FILT_ERR_ILLEGAL_INTVAL, 0);
 			return -EINVAL;
 		}