1 files changed, 63 insertions, 5 deletions

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 2dc0646258ae..6a931852082f 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -417,7 +417,8 @@ EXPORT_SYMBOL_GPL(pvclock_gtod_unregister_notifier);
  */
 static inline void tk_update_ktime_data(struct timekeeper *tk)
 {
-	s64 nsec;
+	u64 seconds;
+	u32 nsec;
 
 	/*
 	 * The xtime based monotonic readout is:
@@ -426,13 +427,22 @@ static inline void tk_update_ktime_data(struct timekeeper *tk)
 	 *	nsec = base_mono + now();
 	 * ==> base_mono = (xtime_sec + wtm_sec) * 1e9 + wtm_nsec
 	 */
-	nsec = (s64)(tk->xtime_sec + tk->wall_to_monotonic.tv_sec);
-	nsec *= NSEC_PER_SEC;
-	nsec += tk->wall_to_monotonic.tv_nsec;
-	tk->tkr.base_mono = ns_to_ktime(nsec);
+	seconds = (u64)(tk->xtime_sec + tk->wall_to_monotonic.tv_sec);
+	nsec = (u32) tk->wall_to_monotonic.tv_nsec;
+	tk->tkr.base_mono = ns_to_ktime(seconds * NSEC_PER_SEC + nsec);
 
 	/* Update the monotonic raw base */
 	tk->base_raw = timespec64_to_ktime(tk->raw_time);
+
+	/*
+	 * The sum of the nanoseconds portions of xtime and
+	 * wall_to_monotonic can be greater/equal one second. Take
+	 * this into account before updating tk->ktime_sec.
+	 */
+	nsec += (u32)(tk->tkr.xtime_nsec >> tk->tkr.shift);
+	if (nsec >= NSEC_PER_SEC)
+		seconds++;
+	tk->ktime_sec = seconds;
 }
 
 /* must hold timekeeper_lock */
@@ -648,6 +658,54 @@ void ktime_get_ts64(struct timespec64 *ts)
 }
 EXPORT_SYMBOL_GPL(ktime_get_ts64);
 
+/**
+ * ktime_get_seconds - Get the seconds portion of CLOCK_MONOTONIC
+ *
+ * Returns the seconds portion of CLOCK_MONOTONIC with a single non
+ * serialized read. tk->ktime_sec is of type 'unsigned long' so this
+ * works on both 32 and 64 bit systems. On 32 bit systems the readout
+ * covers ~136 years of uptime which should be enough to prevent
+ * premature wrap arounds.
+ */
+time64_t ktime_get_seconds(void)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+
+	WARN_ON(timekeeping_suspended);
+	return tk->ktime_sec;
+}
+EXPORT_SYMBOL_GPL(ktime_get_seconds);
+
+/**
+ * ktime_get_real_seconds - Get the seconds portion of CLOCK_REALTIME
+ *
+ * Returns the wall clock seconds since 1970. This replaces the
+ * get_seconds() interface which is not y2038 safe on 32bit systems.
+ *
+ * For 64bit systems the fast access to tk->xtime_sec is preserved. On
+ * 32bit systems the access must be protected with the sequence
+ * counter to provide "atomic" access to the 64bit tk->xtime_sec
+ * value.
+ */
+time64_t ktime_get_real_seconds(void)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	time64_t seconds;
+	unsigned int seq;
+
+	if (IS_ENABLED(CONFIG_64BIT))
+		return tk->xtime_sec;
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+		seconds = tk->xtime_sec;
+
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	return seconds;
+}
+EXPORT_SYMBOL_GPL(ktime_get_real_seconds);
+
 #ifdef CONFIG_NTP_PPS
 
 /**