time: Provide y2038 safe do_settimeofday() replacement

The kernel uses 32-bit signed value(time_t) for seconds elapsed
1970-01-01:00:00:00, thus it will overflow at 2038-01-19 03:14:08
on 32-bit systems. This is widely known as the y2038 problem.

As part of addressing "y2038 problem" for in-kernel uses, this patch
adds safe do_settimeofday64() using timespec64.

After this patch, do_settimeofday() is deprecated and all its call
sites will be fixed using do_settimeofday64(), after that it can be
removed.

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

include/linux/timekeeping.h

@@ -10,7 +10,7 @@ extern int timekeeping_suspended;
  * Get and set timeofday
  */
 extern void do_gettimeofday(struct timeval *tv);
-extern int do_settimeofday(const struct timespec *tv);
+extern int do_settimeofday64(const struct timespec64 *ts);
 extern int do_sys_settimeofday(const struct timespec *tv,
 			       const struct timezone *tz);
 
@@ -33,6 +33,14 @@ extern int __getnstimeofday64(struct timespec64 *tv);
 extern void getnstimeofday64(struct timespec64 *tv);
 
 #if BITS_PER_LONG == 64
+/**
+ * Deprecated. Use do_settimeofday64().
+ */
+static inline int do_settimeofday(const struct timespec *ts)
+{
+	return do_settimeofday64(ts);
+}
+
 static inline int __getnstimeofday(struct timespec *ts)
 {
 	return __getnstimeofday64(ts);
@@ -54,6 +62,17 @@ static inline void ktime_get_real_ts(struct timespec *ts)
 }
 
 #else
+/**
+ * Deprecated. Use do_settimeofday64().
+ */
+static inline int do_settimeofday(const struct timespec *ts)
+{
+	struct timespec64 ts64;
+
+	ts64 = timespec_to_timespec64(*ts);
+	return do_settimeofday64(&ts64);
+}
+
 static inline int __getnstimeofday(struct timespec *ts)
 {
 	struct timespec64 ts64;

kernel/time/timekeeping.c

@@ -703,18 +703,18 @@ void do_gettimeofday(struct timeval *tv)
 EXPORT_SYMBOL(do_gettimeofday);
 
 /**
- * do_settimeofday - Sets the time of day
- * @tv:		pointer to the timespec variable containing the new time
+ * do_settimeofday64 - Sets the time of day.
+ * @ts:     pointer to the timespec64 variable containing the new time
  *
  * Sets the time of day to the new time and update NTP and notify hrtimers
  */
-int do_settimeofday(const struct timespec *tv)
+int do_settimeofday64(const struct timespec64 *ts)
 {
 	struct timekeeper *tk = &tk_core.timekeeper;
-	struct timespec64 ts_delta, xt, tmp;
+	struct timespec64 ts_delta, xt;
 	unsigned long flags;
 
-	if (!timespec_valid_strict(tv))
+	if (!timespec64_valid_strict(ts))
 		return -EINVAL;
 
 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
@@ -723,13 +723,12 @@ int do_settimeofday(const struct timespec *tv)
 	timekeeping_forward_now(tk);
 
 	xt = tk_xtime(tk);
-	ts_delta.tv_sec = tv->tv_sec - xt.tv_sec;
-	ts_delta.tv_nsec = tv->tv_nsec - xt.tv_nsec;
+	ts_delta.tv_sec = ts->tv_sec - xt.tv_sec;
+	ts_delta.tv_nsec = ts->tv_nsec - xt.tv_nsec;
 
 	tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, ts_delta));
 
-	tmp = timespec_to_timespec64(*tv);
-	tk_set_xtime(tk, &tmp);
+	tk_set_xtime(tk, ts);
 
 	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
 
@@ -741,7 +740,7 @@ int do_settimeofday(const struct timespec *tv)
 
 	return 0;
 }
-EXPORT_SYMBOL(do_settimeofday);
+EXPORT_SYMBOL(do_settimeofday64);
 
 /**
  * timekeeping_inject_offset - Adds or subtracts from the current time.