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

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Date:   Fri, 28 Oct 2016 17:45:20 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Deepa Dinamani <deepa.kernel@...il.com>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-input@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        y2038 Mailman List <y2038@...ts.linaro.org>
Subject: Re: [PATCH v2 3/4] input: Deprecate real timestamps beyond year 2106

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@...db.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