[RFC PATCH v2 02/11] time: Add mktime64() safe version(using time64_t)

From: pang.xunlei
Date: Thu Oct 30 2014 - 07:17:05 EST


As part of addressing 2038 saftey for in-kernel uses, this patch
adds safe mktime64() using time64_t. After this patch, mktime()
should be replaced by mktime64() one by one. Eventually, mktime()
will be removed from the kernel when it has no users.

Signed-off-by: pang.xunlei <pang.xunlei@xxxxxxxxxx>
---
include/linux/time.h | 4 ++++
kernel/time/time.c | 39 +++++++++++++++++++++++++++++++++++++++
2 files changed, 43 insertions(+)

diff --git a/include/linux/time.h b/include/linux/time.h
index 8c42cf8..5c2c077 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -39,6 +39,10 @@ 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 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);
diff --git a/kernel/time/time.c b/kernel/time/time.c
index a9ae20f..f44efdb 100644
--- a/kernel/time/time.c
+++ b/kernel/time/time.c
@@ -304,6 +304,44 @@ 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.
+ * 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.
+ *
+ * [For the Julian calendar (which was used in Russia before 1917,
+ * Britain & colonies before 1752, anywhere else before 1582,
+ * and is still in use by some communities) leave out the
+ * -year/100+year/400 terms, and add 10.]
+ *
+ * This algorithm was first published by Gauss (I think).
+ *
+ * Safe version 2038 safety on 32-bit systems.
+ */
+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 ret;
+ unsigned int mon = mon0, year = year0;
+
+ /* 1..12 -> 11,12,1..10 */
+ if (0 >= (int) (mon -= 2)) {
+ mon += 12; /* Puts Feb last since it has leap day */
+ year -= 1;
+ }
+
+ ret = (year/4 - year/100 + year/400 + 367*mon/12 + day) + year*365 - 719499;
+ ret = ret*24 + hour; /* now have hours */
+ ret = ret*60 + min; /* now have minutes */
+ ret = ret*60 + sec; /* finally seconds */
+
+ return ret;
+}
+
+EXPORT_SYMBOL(mktime64);
+
/* 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.
@@ -318,6 +356,7 @@ EXPORT_SYMBOL(timespec_trunc);
* 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)
+ * TODO: [2038 safety] should be replaced by mktime64().
*/
unsigned long
mktime(const unsigned int year0, const unsigned int mon0,
--
1.7.9.5

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