[PATCH v5 5/8] media: v4l2-core: fix VIDIOC_DQEVENT for time64 ABI

[Arnd Bergmann]

The v4l2_event structure contains a 'struct timespec' member that is
defined by the user space C library, creating an ABI incompatibility
when that gets updated to a 64-bit time_t.

While passing a 32-bit time_t here would be sufficient for CLOCK_MONOTONIC
timestamps, simply redefining the structure to use the kernel's
__kernel_old_timespec would not work for any library that uses a copy
of the linux/videodev2.h header file rather than including the copy from
the latest kernel headers.

This means the kernel has to be changed to handle both versions of the
structure layout on a 32-bit architecture. The easiest way to do this
is during the copy from/to user space.

Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
 drivers/media/v4l2-core/v4l2-event.c  |  5 ++++-
 drivers/media/v4l2-core/v4l2-ioctl.c  | 29 ++++++++++++++++++++++++++-
 drivers/media/v4l2-core/v4l2-subdev.c | 26 +++++++++++++++++++++++-
 include/media/v4l2-ioctl.h            | 25 +++++++++++++++++++++++
 include/uapi/linux/videodev2.h        |  4 ++++
 5 files changed, 86 insertions(+), 3 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-event.c b/drivers/media/v4l2-core/v4l2-event.c
index 9d673d113d7a..290c6b213179 100644
--- a/drivers/media/v4l2-core/v4l2-event.c
+++ b/drivers/media/v4l2-core/v4l2-event.c
@@ -27,6 +27,7 @@ static unsigned sev_pos(const struct v4l2_subscribed_event *sev, unsigned idx)
 static int __v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event)
 {
 	struct v4l2_kevent *kev;
+	struct timespec64 ts;
 	unsigned long flags;
 
 	spin_lock_irqsave(&fh->vdev->fh_lock, flags);
@@ -44,7 +45,9 @@ static int __v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event)
 
 	kev->event.pending = fh->navailable;
 	*event = kev->event;
-	event->timestamp = ns_to_timespec(kev->ts);
+	ts = ns_to_timespec64(kev->ts);
+	event->timestamp.tv_sec = ts.tv_sec;
+	event->timestamp.tv_nsec = ts.tv_nsec;
 	kev->sev->first = sev_pos(kev->sev, 1);
 	kev->sev->in_use--;
 
diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
index 2ce91f88369b..96aafb659783 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -821,7 +821,7 @@ static void v4l_print_event(const void *arg, bool write_only)
 	const struct v4l2_event *p = arg;
 	const struct v4l2_event_ctrl *c;
 
-	pr_cont("type=0x%x, pending=%u, sequence=%u, id=%u, timestamp=%lu.%9.9lu\n",
+	pr_cont("type=0x%x, pending=%u, sequence=%u, id=%u, timestamp=%llu.%9.9llu\n",
 			p->type, p->pending, p->sequence, p->id,
 			p->timestamp.tv_sec, p->timestamp.tv_nsec);
 	switch (p->type) {
@@ -3025,6 +3025,13 @@ static int check_array_args(unsigned int cmd, void *parg, size_t *array_size,
 
 static unsigned int video_translate_cmd(unsigned int cmd)
 {
+	switch (cmd) {
+#ifdef CONFIG_COMPAT_32BIT_TIME
+	case VIDIOC_DQEVENT_TIME32:
+		return VIDIOC_DQEVENT;
+#endif
+	}
+
 	return cmd;
 }
 
@@ -3074,6 +3081,26 @@ static int video_put_user(void __user *arg, void *parg, unsigned int cmd)
 		return 0;
 
 	switch (cmd) {
+#ifdef CONFIG_COMPAT_32BIT_TIME
+	case VIDIOC_DQEVENT_TIME32: {
+		struct v4l2_event *ev = parg;
+		struct v4l2_event_time32 ev32 = {
+			.type		= ev->type,
+			.pending	= ev->pending,
+			.sequence	= ev->sequence,
+			.timestamp.tv_sec  = ev->timestamp.tv_sec,
+			.timestamp.tv_nsec = ev->timestamp.tv_nsec,
+			.id		= ev->id,
+		};
+
+		memcpy(&ev32.u, &ev->u, sizeof(ev->u));
+		memcpy(&ev32.reserved, &ev->reserved, sizeof(ev->reserved));
+
+		if (copy_to_user(arg, &ev32, sizeof(ev32)))
+			return -EFAULT;
+		break;
+	}
+#endif
 	default:
 		/*  Copy results into user buffer  */
 		if (copy_to_user(arg, parg, _IOC_SIZE(cmd)))
diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 9e987c0f840e..de926e311348 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -331,8 +331,8 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 	struct v4l2_fh *vfh = file->private_data;
 #if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
 	struct v4l2_subdev_fh *subdev_fh = to_v4l2_subdev_fh(vfh);
-	int rval;
 #endif
+	int rval;
 
 	switch (cmd) {
 	case VIDIOC_QUERYCTRL:
@@ -392,6 +392,30 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 
 		return v4l2_event_dequeue(vfh, arg, file->f_flags & O_NONBLOCK);
 
+	case VIDIOC_DQEVENT_TIME32: {
+		struct v4l2_event_time32 *ev32 = arg;
+		struct v4l2_event ev;
+
+		if (!(sd->flags & V4L2_SUBDEV_FL_HAS_EVENTS))
+			return -ENOIOCTLCMD;
+
+		rval = v4l2_event_dequeue(vfh, &ev, file->f_flags & O_NONBLOCK);
+
+		*ev32 = (struct v4l2_event_time32) {
+			.type		= ev.type,
+			.pending	= ev.pending,
+			.sequence	= ev.sequence,
+			.timestamp.tv_sec  = ev.timestamp.tv_sec,
+			.timestamp.tv_nsec = ev.timestamp.tv_nsec,
+			.id		= ev.id,
+		};
+
+		memcpy(&ev32->u, &ev.u, sizeof(ev.u));
+		memcpy(&ev32->reserved, &ev.reserved, sizeof(ev.reserved));
+
+		return rval;
+	}
+
 	case VIDIOC_SUBSCRIBE_EVENT:
 		return v4l2_subdev_call(sd, core, subscribe_event, vfh, arg);
 
diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h
index 4bba65a59d46..05c1ec93a911 100644
--- a/include/media/v4l2-ioctl.h
+++ b/include/media/v4l2-ioctl.h
@@ -724,4 +724,29 @@ long int video_usercopy(struct file *file, unsigned int cmd,
 long int video_ioctl2(struct file *file,
 		      unsigned int cmd, unsigned long int arg);
 
+/*
+ * The user space interpretation of the 'v4l2_event' differs
+ * based on the 'time_t' definition on 32-bit architectures, so
+ * the kernel has to handle both.
+ * This is the old version for 32-bit architectures.
+ */
+struct v4l2_event_time32 {
+	__u32				type;
+	union {
+		struct v4l2_event_vsync		vsync;
+		struct v4l2_event_ctrl		ctrl;
+		struct v4l2_event_frame_sync	frame_sync;
+		struct v4l2_event_src_change	src_change;
+		struct v4l2_event_motion_det	motion_det;
+		__u8				data[64];
+	} u;
+	__u32				pending;
+	__u32				sequence;
+	struct old_timespec32		timestamp;
+	__u32				id;
+	__u32				reserved[8];
+};
+
+#define	VIDIOC_DQEVENT_TIME32	 _IOR('V', 89, struct v4l2_event_time32)
+
 #endif /* _V4L2_IOCTL_H */
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 6ef4a5b787a4..caf156d45842 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -2341,7 +2341,11 @@ struct v4l2_event {
 	} u;
 	__u32				pending;
 	__u32				sequence;
+#ifdef __KERNEL__
+	struct __kernel_timespec	timestamp;
+#else
 	struct timespec			timestamp;
+#endif
 	__u32				id;
 	__u32				reserved[8];
 };
-- 
2.20.0