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

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Date:	Thu, 09 Jul 2015 17:02:47 +0800
From:	Bamvor Zhang Jian <bamvor.zhangjian@...aro.org>
To:	John Stultz <john.stultz@...aro.org>
CC:	Arnd Bergmann <arnd@...db.de>,
	Thomas Gleixner <tglx@...utronix.de>, y2038@...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

Hi, John

On 07/09/2015 04:09 AM, John Stultz wrote:
> 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.
I add this ifdef because I got compile failure on arm platform. This
file do not include the <linux/compat.h> directly. And in arm64,
compat.h is included implicitily.
So, I am not sure what I should do here. Include <linux/compat.h> in
this file directly or add a this check at the beginning of this file?

#ifndef is_compat_task
#define is_compat_task() (0)
#endif

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

regards

bamvor
>
> thanks
> -john
>
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