perf util: Improve error checking for time percent input

The command line like 'perf report --stdio --time 1abc%/1' could be
accepted by perf. It looks not very good.

This patch uses strtod() to replace original atof() and check the entire
string. Now for the same command line, it would return error message
"Invalid time string".

root@skl:/tmp# perf report --stdio --time 1abc%/1
Invalid time string

Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Reviewed-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1515596433-24653-4-git-send-email-yao.jin@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/time-utils.c

@@ -116,7 +116,8 @@ int perf_time__parse_str(struct perf_time_interval *ptime, const char *ostr)
 
 static int parse_percent(double *pcnt, char *str)
 {
-	char *c;
+	char *c, *endptr;
+	double d;
 
 	c = strchr(str, '%');
 	if (c)
@@ -124,8 +125,11 @@ static int parse_percent(double *pcnt, char *str)
 	else
 		return -1;
 
-	*pcnt = atof(str) / 100.0;
+	d = strtod(str, &endptr);
+	if (endptr != str + strlen(str))
+		return -1;
 
+	*pcnt = d / 100.0;
 	return 0;
 }