Input: extend usable life of event timestamps to 2106 on 32 bit systems

The input events use struct timeval to store event time, unfortunately
this structure is not y2038 safe and is being replaced in kernel with
y2038 safe structures.

Because of ABI concerns we can not change the size or the layout of
structure input_event, so we opt to re-interpreting the 'seconds' part
of timestamp as an unsigned value, effectively doubling the range of
values, to year 2106.

Newer glibc that has support for 32 bit applications to use 64 bit
time_t supplies __USE_TIME_BITS64 define [1], that we can use to present
the userspace with updated input_event layout. The updated layout will
cause the compile time breakage, alerting applications and distributions
maintainers to the issue. Existing 32 binaries will continue working
without any changes until 2038.

Ultimately userspace applications should switch to using monotonic or
boot time clocks, as realtime clock is not very well suited for input
event timestamps as it can go backwards (see a80b83b7b8 "Input: evdev -
add CLOCK_BOOTTIME support" by by John Stultz). With monotonic clock the
practical range of reported times will always fit into the pair of 32
bit values, as we do not expect any system to stay up for a hundred
years without a single reboot.

[1] https://sourceware.org/glibc/wiki/Y2038ProofnessDesign

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Acked-by: Peter Hutterer <peter.hutterer@who-t.net>
Patchwork-Id: 10148083
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

1 files changed, 13 insertions, 7 deletions

diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index 925571475005..116088fc3621 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -135,10 +135,7 @@ static void __evdev_flush_queue(struct evdev_client *client, unsigned int type)
 			continue;
 		} else if (head != i) {
 			/* move entry to fill the gap */
-			client->buffer[head].time = ev->time;
-			client->buffer[head].type = ev->type;
-			client->buffer[head].code = ev->code;
-			client->buffer[head].value = ev->value;
+			client->buffer[head] = *ev;
 		}
 
 		num++;
@@ -157,6 +154,7 @@ static void __evdev_queue_syn_dropped(struct evdev_client *client)
 {
 	struct input_event ev;
 	ktime_t time;
+	struct timespec64 ts;
 
 	time = client->clk_type == EV_CLK_REAL ?
 			ktime_get_real() :
@@ -164,7 +162,9 @@ static void __evdev_queue_syn_dropped(struct evdev_client *client)
 				ktime_get() :
 				ktime_get_boottime();
 
-	ev.time = ktime_to_timeval(time);
+	ts = ktime_to_timespec64(time);
+	ev.input_event_sec = ts.tv_sec;
+	ev.input_event_usec = ts.tv_nsec / NSEC_PER_USEC;
 	ev.type = EV_SYN;
 	ev.code = SYN_DROPPED;
 	ev.value = 0;
@@ -241,7 +241,10 @@ static void __pass_event(struct evdev_client *client,
 		 */
 		client->tail = (client->head - 2) & (client->bufsize - 1);
 
-		client->buffer[client->tail].time = event->time;
+		client->buffer[client->tail].input_event_sec =
+						event->input_event_sec;
+		client->buffer[client->tail].input_event_usec =
+						event->input_event_usec;
 		client->buffer[client->tail].type = EV_SYN;
 		client->buffer[client->tail].code = SYN_DROPPED;
 		client->buffer[client->tail].value = 0;
@@ -262,12 +265,15 @@ static void evdev_pass_values(struct evdev_client *client,
 	struct evdev *evdev = client->evdev;
 	const struct input_value *v;
 	struct input_event event;
+	struct timespec64 ts;
 	bool wakeup = false;
 
 	if (client->revoked)
 		return;
 
-	event.time = ktime_to_timeval(ev_time[client->clk_type]);
+	ts = ktime_to_timespec64(ev_time[client->clk_type]);
+	event.input_event_sec = ts.tv_sec;
+	event.input_event_usec = ts.tv_nsec / NSEC_PER_USEC;
 
 	/* Interrupts are disabled, just acquire the lock. */
 	spin_lock(&client->buffer_lock);