linux-kernel - Re: [RFC PATCH v2 1/4] y2038: add 64bit time_t support in timeval for 32bit architecture

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Message-ID: <CALAqxLU0XnQfmPLOVqRtv0z_jU6kDFdK6rkfBNh11Ri-q5gPqw@mail.gmail.com>
Date:	Wed, 8 Jul 2015 13:09:55 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Bamvor Zhang Jian <bamvor.zhangjian@...aro.org>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Thomas Gleixner <tglx@...utronix.de>, y2039@...ts.linaro.org,
	lkml <linux-kernel@...r.kernel.org>,
	Baolin Wang <baolin.wang@...aro.org>
Subject: Re: [RFC PATCH v2 1/4] y2038: add 64bit time_t support in timeval for
 32bit architecture

On Mon, Jun 29, 2015 at 7:23 AM, Bamvor Zhang Jian
<bamvor.zhangjian@...aro.org> wrote:
> +int get_timeval64(struct timeval64 *tv,
> +                  const struct __kernel_timeval __user *utv)
> +{
> +       struct __kernel_timeval ktv;
> +       int ret;
> +
> +       ret = copy_from_user(&ktv, utv, sizeof(ktv));
> +       if (ret)
> +               return -EFAULT;
> +
> +       tv->tv_sec = ktv.tv_sec;
> +       if (!IS_ENABLED(CONFIG_64BIT)
> +#ifdef CONFIG_COMPAT
> +          || is_compat_task()
> +#endif

These sorts of ifdefs are to be avoided inside of functions.

Instead, it seems is_compat_task() should be defined to 0 in the
!CONFIG_COMPAT case, so you can avoid the ifdefs and the compiler can
still optimize it out.

Otherwise this looks similar to a patch Baolin (cc'ed) has been working on.

thanks
-john
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