Reject times in the first year that can be represented by the clock to catch

RTC clocks that aren't battery powered.

ok deraadt@, millert@, visa@, tom@

1 files changed, 9 insertions, 1 deletions

diff --git a/sys/dev/fdt/sxirtc.c b/sys/dev/fdt/sxirtc.c
index fd61fc043ee..1bc5a689372 100644
--- a/sys/dev/fdt/sxirtc.c
+++ b/sys/dev/fdt/sxirtc.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: sxirtc.c,v 1.1 2017/01/21 08:26:49 patrick Exp $	*/
+/*	$OpenBSD: sxirtc.c,v 1.2 2017/03/27 14:03:19 kettenis Exp $	*/
 /*
  * Copyright (c) 2008 Mark Kettenis
  * Copyright (c) 2013 Artturi Alm
@@ -152,6 +152,14 @@ sxirtc_gettime(todr_chip_handle_t handle, struct timeval *tv)
 	    dt.dt_mon > 12 || dt.dt_mon == 0)
 		return 1;
 
+	/*
+	 * Reject the first year that can be represented by the clock.
+	 * This avoids reporting a bogus time if the RTC isn't battery
+	 * powered.
+	 */
+	if (dt.dt_year == sc->base_year)
+		return 1;
+
 	tv->tv_sec = clock_ymdhms_to_secs(&dt);
 	tv->tv_usec = 0;
 	return 0;