time: add get_timespec64 and put_timespec64

Add helper functions to convert between struct timespec64 and
struct timespec at userspace boundaries.

This is a preparatory patch to use timespec64 as the basic type
internally in the kernel as timespec is not y2038 safe on 32 bit systems.
The patch helps the cause by containing all data conversions at the
userspace boundaries within these functions.
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

include/linux/compat.h

@@ -164,6 +164,8 @@ extern int compat_get_timespec(struct timespec *, const void __user *);
 extern int compat_put_timespec(const struct timespec *, void __user *);
 extern int compat_get_timeval(struct timeval *, const void __user *);
 extern int compat_put_timeval(const struct timeval *, void __user *);
+extern int compat_get_timespec64(struct timespec64 *, const void __user *);
+extern int compat_put_timespec64(const struct timespec64 *, void __user *);
 
 /*
  * This function convert a timespec if necessary and returns a *user

include/linux/time.h

@@ -8,6 +8,11 @@
 
 extern struct timezone sys_tz;
 
+int get_timespec64(struct timespec64 *ts,
+		const struct timespec __user *uts);
+int put_timespec64(const struct timespec64 *ts,
+		struct timespec __user *uts);
+
 #define TIME_T_MAX	(time_t)((1UL << ((sizeof(time_t) << 3) - 1)) - 1)
 
 static inline int timespec_equal(const struct timespec *a,

kernel/compat.c

@@ -120,6 +120,50 @@ static int __compat_put_timespec(const struct timespec *ts, struct compat_timesp
 			__put_user(ts->tv_nsec, &cts->tv_nsec)) ? -EFAULT : 0;
 }
 
+static int __compat_get_timespec64(struct timespec64 *ts64,
+				   const struct compat_timespec __user *cts)
+{
+	struct compat_timespec ts;
+	int ret;
+
+	ret = copy_from_user(&ts, cts, sizeof(ts));
+	if (ret)
+		return -EFAULT;
+
+	ts64->tv_sec = ts.tv_sec;
+	ts64->tv_nsec = ts.tv_nsec;
+
+	return 0;
+}
+
+static int __compat_put_timespec64(const struct timespec64 *ts64,
+				   struct compat_timespec __user *cts)
+{
+	struct compat_timespec ts = {
+		.tv_sec = ts64->tv_sec,
+		.tv_nsec = ts64->tv_nsec
+	};
+	return copy_to_user(cts, &ts, sizeof(ts)) ? -EFAULT : 0;
+}
+
+int compat_get_timespec64(struct timespec64 *ts, const void __user *uts)
+{
+	if (COMPAT_USE_64BIT_TIME)
+		return copy_from_user(ts, uts, sizeof(*ts)) ? -EFAULT : 0;
+	else
+		return __compat_get_timespec64(ts, uts);
+}
+EXPORT_SYMBOL_GPL(compat_get_timespec64);
+
+int compat_put_timespec64(const struct timespec64 *ts, void __user *uts)
+{
+	if (COMPAT_USE_64BIT_TIME)
+		return copy_to_user(uts, ts, sizeof(*ts)) ? -EFAULT : 0;
+	else
+		return __compat_put_timespec64(ts, uts);
+}
+EXPORT_SYMBOL_GPL(compat_put_timespec64);
+
 int compat_get_timeval(struct timeval *tv, const void __user *utv)
 {
 	if (COMPAT_USE_64BIT_TIME)

kernel/time/time.c

@@ -890,3 +890,31 @@ struct timespec64 timespec64_add_safe(const struct timespec64 lhs,
 
 	return res;
 }
+
+int get_timespec64(struct timespec64 *ts,
+		   const struct timespec __user *uts)
+{
+	struct timespec kts;
+	int ret;
+
+	ret = copy_from_user(&kts, uts, sizeof(kts));
+	if (ret)
+		return -EFAULT;
+
+	ts->tv_sec = kts.tv_sec;
+	ts->tv_nsec = kts.tv_nsec;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(get_timespec64);
+
+int put_timespec64(const struct timespec64 *ts,
+		   struct timespec __user *uts)
+{
+	struct timespec kts = {
+		.tv_sec = ts->tv_sec,
+		.tv_nsec = ts->tv_nsec
+	};
+	return copy_to_user(uts, &kts, sizeof(kts)) ? -EFAULT : 0;
+}
+EXPORT_SYMBOL_GPL(put_timespec64);