Re: [PATCH v2 3/4] input: Deprecate real timestamps beyond year 2106

Arnd Bergmann
2016-10-28T15:45:26Z

On Friday, October 28, 2016 8:19:46 AM CEST Deepa Dinamani wrote:
> On Fri, Oct 28, 2016 at 5:43 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> > On Monday, October 17, 2016 8:27:32 PM CEST Deepa Dinamani wrote:
> >> @@ -55,24 +60,24 @@ struct ff_effect_compat {
> >>
> >> static inline size_t input_event_size(void)
> >> {
> >> - return (in_compat_syscall() && !COMPAT_USE_64BIT_TIME) ?
> >> - sizeof(struct input_event_compat) : sizeof(struct input_event);
> >> + return in_compat_syscall() ? sizeof(struct raw_input_event_compat) :
> >> + sizeof(struct raw_input_event);
> >> }
> >
> > I think the COMPAT_USE_64BIT_TIME check has to stay here,
> > it's needed for x32 mode on x86-64.
>
> There is no time_t anymore in the raw_input_event structure.
> The struct uses __kernel_ulong_t type.
> This should take care of x32 support.

I don't think it does.

> From this cover letter:
> https://www.spinics.net/lists/linux-arch/msg16356.html
>
> I see that that the __kernel types were introduced to address the ABI
> issues for x32.

This is a variation of the problem we are trying to solve for
the other architectures in your patch set:

On x32, the kernel uses produces a structure with the 64-bit
layout, using __u64 tv_sec, to match the current user space
that has 64-bit __kernel_ulong_t and 64-bit time_t, but
in_compat_syscall() also returns 'true' here, as this is
mostly a 32-bit ABI (time_t being one of the exceptions).

ARnd