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

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Message-ID: <CABeXuvro53b_h-L80idmB9G9U=WcdxHekCij4GYx7eVqxWVeNQ@mail.gmail.com>
Date:   Fri, 28 Oct 2016 14:39:35 -0700
From:   Deepa Dinamani <deepa.kernel@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
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

>> >> @@ -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).

Yes, I missed this.

in_compat_syscall() is true for x32, this would mean we end up here
even if it is a x32 syscall.
But, wouldn't it be better to use in_x32_syscall() here since there is
no timeval any more?

Thanks,
Deepa