time: Provide y2038 safe mktime() replacement

As part of addressing "y2038 problem" for in-kernel uses, this
patch adds safe mktime64() using time64_t.

After this patch, mktime() is deprecated and all its call sites
will be fixed using mktime64(), after that it can be removed.

Signed-off-by: pang.xunlei <pang.xunlei@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>

2 files changed, 22 insertions, 15 deletions

diff --git a/include/linux/time.h b/include/linux/time.h
index 8c42cf8d2444..203c2ad40d71 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -39,9 +39,20 @@ static inline int timeval_compare(const struct timeval *lhs, const struct timeva
         return lhs->tv_usec - rhs->tv_usec;
 }
 
-extern 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);
+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);
+
+/**
+ * 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)
+{
+        return mktime64(year, mon, day, hour, min, sec);
+}
 
 extern void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec);
 
diff --git a/kernel/time/time.c b/kernel/time/time.c
index a9ae20fb0b11..65015ff2f07c 100644
--- a/kernel/time/time.c
+++ b/kernel/time/time.c
@@ -304,7 +304,9 @@ struct timespec timespec_trunc(struct timespec t, unsigned gran)
 }
 EXPORT_SYMBOL(timespec_trunc);
 
-/* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
+/*
+ * mktime64 - Converts date to seconds.
+ * Converts Gregorian date to seconds since 1970-01-01 00:00:00.
  * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
  * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
  *
@@ -314,15 +316,10 @@ EXPORT_SYMBOL(timespec_trunc);
  * -year/100+year/400 terms, and add 10.]
  *
  * This algorithm was first published by Gauss (I think).
- *
- * WARNING: this function will overflow on 2106-02-07 06:28:16 on
- * machines where long is 32-bit! (However, as time_t is signed, we
- * will already get problems at other places on 2038-01-19 03:14:08)
  */
-unsigned long
-mktime(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(const unsigned int year0, const unsigned int mon0,
+                const unsigned int day, const unsigned int hour,
+                const unsigned int min, const unsigned int sec)
 {
         unsigned int mon = mon0, year = year0;
 
@@ -332,15 +329,14 @@ mktime(const unsigned int year0, const unsigned int mon0,
                 year -= 1;
         }
 
-        return ((((unsigned long)
+        return ((((time64_t)
                   (year/4 - year/100 + year/400 + 367*mon/12 + day) +
                   year*365 - 719499
             )*24 + hour /* now have hours */
           )*60 + min /* now have minutes */
         )*60 + sec; /* finally seconds */
 }
-
-EXPORT_SYMBOL(mktime);
+EXPORT_SYMBOL(mktime64);
 
 /**
  * set_normalized_timespec - set timespec sec and nsec parts and normalize