[PATCH 2/5] Handle leap seconds in mktime64()

[David Howells <dhowells@redhat.com>]

Handle leap seconds in mktime64() - where the seconds parameter is the
value 60 - by treating it the same as 59.

This facility will be used by the X.509 parser.  Doing it in mktime64()
makes the policy common to the whole kernel and easier to find.

Whilst we're at it, remove the const markers from all the parameters since
they don't really achieve anything and we do need to alter the sec
parameter.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: John Stultz <john.stultz@linaro.org>
cc: Arnd Bergmann <arnd@arndb.de>
cc: stable@vger.kernel.org
---

 include/linux/time.h |   13 ++++++-------
 kernel/time/time.c   |   14 +++++++++++---
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/include/linux/time.h b/include/linux/time.h
index beebe3a02d43..35384f0c0aa2 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -39,17 +39,16 @@ static inline int timeval_compare(const struct timeval *lhs, const struct timeva
 	return lhs->tv_usec - rhs->tv_usec;
 }
 
-extern time64_t mktime64(const unsigned int year, const unsigned int mon,
-			const unsigned int day, const unsigned int hour,
-			const unsigned int min, const unsigned int sec);
+extern time64_t mktime64(unsigned int year, unsigned int mon,
+			 unsigned int day, unsigned int hour,
+			 unsigned int min, unsigned int sec);
 
 /**
  * Deprecated. Use mktime64().
  */
-static inline unsigned long mktime(const unsigned int year,
-			const unsigned int mon, const unsigned int day,
-			const unsigned int hour, const unsigned int min,
-			const unsigned int sec)
+static inline unsigned long mktime(unsigned int year, unsigned int mon,
+				   unsigned int day, unsigned int hour,
+				   unsigned int min, unsigned int sec)
 {
 	return mktime64(year, mon, day, hour, min, sec);
 }
diff --git a/kernel/time/time.c b/kernel/time/time.c
index 86751c68e08d..1858b10602f5 100644
--- a/kernel/time/time.c
+++ b/kernel/time/time.c
@@ -322,10 +322,14 @@ EXPORT_SYMBOL(timespec_trunc);
  * -year/100+year/400 terms, and add 10.]
  *
  * This algorithm was first published by Gauss (I think).
+ *
+ * A leap second can be indicated by calling this function with sec as
+ * 60 (allowable under ISO 8601).  The leap second is treated the same
+ * as the preceding second since they don't exist in UNIX time.
  */
-time64_t mktime64(const unsigned int year0, const unsigned int mon0,
-		const unsigned int day, const unsigned int hour,
-		const unsigned int min, const unsigned int sec)
+time64_t mktime64(unsigned int year0, unsigned int mon0,
+		  unsigned int day, unsigned int hour,
+		  unsigned int min, unsigned int sec)
 {
 	unsigned int mon = mon0, year = year0;
 
@@ -335,6 +339,10 @@ time64_t mktime64(const unsigned int year0, const unsigned int mon0,
 		year -= 1;
 	}
 
+	/* Handle leap seconds */
+	if (sec == 60)
+		sec = 59;
+
 	return ((((time64_t)
 		  (year/4 - year/100 + year/400 + 367*mon/12 + day) +
 		  year*365 - 719499