[PATCH] Call input_set_timestamp for events injected using uinput

Biswarup Pal
2023-04-27T00:03:46Z

Currently, uinput doesn't use the input_set_timestamp API, so any
event injected using uinput is not accurately timestamped in terms of
measuring when the actual event happened. Hence, call the
input_set_timestamp API from uinput in order to provide a more
accurate sense of time for the event. Propagate only the timestamps
which are a) positive, b) within a pre-defined offset (10 secs) from
the current time, and c) not in the future.

Signed-off-by: Biswarup Pal <biswarupp@google.com>
---
drivers/input/misc/uinput.c | 34 ++++++++++++++++++++++++++++++++++
1 file changed, 34 insertions(+)

diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c
index f2593133e524..d98212d55108 100644
--- a/drivers/input/misc/uinput.c
+++ b/drivers/input/misc/uinput.c
@@ -33,6 +33,7 @@
#define UINPUT_NAME "uinput"
#define UINPUT_BUFFER_SIZE 16
#define UINPUT_NUM_REQUESTS 16
+#define UINPUT_TIMESTAMP_ALLOWED_OFFSET_SECS 10

enum uinput_state { UIST_NEW_DEVICE, UIST_SETUP_COMPLETE, UIST_CREATED };

@@ -569,11 +570,40 @@ static int uinput_setup_device_legacy(struct uinput_device *udev,
return retval;
}

+/*
+ * Returns true if the given timestamp is valid (i.e., if all the following
+ * conditions are satisfied), false otherwise.
+ * 1) given timestamp is positive
+ * 2) it's within the allowed offset before the current time
+ * 3) it's not in the future
+ */
+static bool is_valid_timestamp(const ktime_t timestamp)
+{
+ ktime_t zero_time;
+ ktime_t current_time;
+ ktime_t min_time;
+ ktime_t offset;
+
+ zero_time = ktime_set(0, 0);
+ if (ktime_compare(zero_time, timestamp) >= 0)
+ return false;
+
+ current_time = ktime_get();
+ offset = ktime_set(UINPUT_TIMESTAMP_ALLOWED_OFFSET_SECS, 0);
+ min_time = ktime_sub(current_time, offset);
+
+ if (ktime_after(min_time, timestamp) || ktime_after(timestamp, current_time))
+ return false;
+
+ return true;
+}
+
static ssize_t uinput_inject_events(struct uinput_device *udev,
const char __user *buffer, size_t count)
{
struct input_event ev;
size_t bytes = 0;
+ ktime_t timestamp;

if (count != 0 && count < input_event_size())
return -EINVAL;
@@ -588,6 +618,10 @@ static ssize_t uinput_inject_events(struct uinput_device *udev,
if (input_event_from_user(buffer + bytes, &ev))
return -EFAULT;

+ timestamp = ktime_set(ev.input_event_sec, ev.input_event_usec * NSEC_PER_USEC);
+ if (is_valid_timestamp(timestamp))
+ input_set_timestamp(udev->dev, timestamp);
+
input_event(udev->dev, ev.type, ev.code, ev.value);
bytes += input_event_size();
cond_resched();
--
2.40.1.495.gc816e09b53d-goog