Re: [Y2038] [PATCH v4 5/8] media: v4l2-core: fix VIDIOC_DQEVENT for time64 ABI

On Tue, Nov 26, 2019 at 4:10 PM Hans Verkuil hverkuil@xs4all.nl wrote:

On 11/26/19 3:43 PM, Arnd Bergmann wrote:

...

On Mon, Nov 25, 2019 at 3:40 PM Hans Verkuil hverkuil@xs4all.nl wrote:

...

On 11/11/19 9:38 PM, Arnd Bergmann wrote:

            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;

Unfortunately this is a little uglier because it still requires the two memcpy() for the arrays, but I think it's good enough.

I agree.

Hmm, can't you do .u = ev->u ? Or is that not allowed by this syntax?

No, that doesn't work here since the two unions are considered different types despite being defined identically. It would work by giving the union a name, but that name would also become visible to user space without adding more hacks.

Arnd