Change in coreboot[master]: lib/rtc: Add sanity check for time and date

[Patrick Georgi (Code Review)]

Patrick Georgi has submitted this change. ( https://review.coreboot.org/c/coreboot/+/54913 )

Change subject: lib/rtc: Add sanity check for time and date
......................................................................

lib/rtc: Add sanity check for time and date

Add a function to check sanity of a given RTC date and time.
Invalid values in terms of overrun ranges of the registers can lead to
strange issues in the OS.

Change-Id: I0a381d445c894eee4f82b50fe86dad22cc587605
Signed-off-by: Werner Zeh 
Reviewed-on: https://review.coreboot.org/c/coreboot/+/54913
Tested-by: build bot (Jenkins) 
Reviewed-by: Arthur Heymans 
Reviewed-by: Paul Menzel 
---
M src/include/rtc.h
M src/lib/rtc.c
2 files changed, 17 insertions(+), 0 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Paul Menzel: Looks good to me, but someone else must approve
  Arthur Heymans: Looks good to me, approved

diff --git a/src/include/rtc.h b/src/include/rtc.h
index 0a38074..6d562f7 100644
--- a/src/include/rtc.h
+++ b/src/include/rtc.h
@@ -21,5 +21,6 @@
 int rtc_to_tm(int tim, struct rtc_time *tm);
 unsigned long rtc_mktime(const struct rtc_time *tm);
 void rtc_display(const struct rtc_time *tm);
+int rtc_invalid(const struct rtc_time *tm);

#endif /* _RTC_H_ */
diff --git a/src/lib/rtc.c b/src/lib/rtc.c
index c5fffa0..d151480 100644
--- a/src/lib/rtc.c
+++ b/src/lib/rtc.c
@@ -121,3 +121,19 @@
           (tm->wday < 0 || tm->wday > 6) ? "unknown " : weekdays[tm->wday],
           tm->hour,  tm->min,  tm->sec);
 }
+
+static int rtc_month_days(unsigned int month, unsigned int year)
+{
+	int month_days[12] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
+
+	return month_days[month] + (LEAP_YEAR(year) && month == 2);
+}
+
+int rtc_invalid(const struct rtc_time *tm)
+{
+	if (tm->sec > 59 || tm->min > 59 || tm->hour > 23 || tm->mon == 0 || tm->mon > 12 ||
+	    tm->year < 1970 || tm->mday > rtc_month_days(tm->mon - 1, tm->year))
+		return 1;
+	else
+		return 0;
+}