From mboxrd@z Thu Jan  1 00:00:00 1970
From: Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH v6 19/36] nds32: VDSO support
Date: Tue, 6 Feb 2018 09:48:17 +0100
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To: Vincent Chen <deanbo422@gmail.com>
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On Tue, Feb 6, 2018 at 8:41 AM, Vincent Chen <deanbo422@gmail.com> wrote:
> 2018-01-18 18:28 GMT+08:00 Arnd Bergmann <arnd@arndb.de>:
>> On Mon, Jan 15, 2018 at 6:53 AM, Greentime Hu <green.hu@gmail.com> wrote:
>>> From: Greentime Hu <greentime@andestech.com>
>>>
>>> This patch adds VDSO support. The VDSO code is currently used for
>>> sys_rt_sigreturn() and optimised gettimeofday() (using the SoC timer counter).
>>>
>>> Signed-off-by: Vincent Chen <vincentc@andestech.com>
>>> Signed-off-by: Greentime Hu <greentime@andestech.com>
>>
>> Acked-by: Arnd Bergmann <arnd@arndb.de>
>
> Dear Arnd Bergmann:
>
> We find a small bug here which make LTP 20170929 clock_getres01
> fail. The bug is in __vdso_clock_getres() function. When argument res
> is NULL, -EFAULT error code is returned now. But, the returned
> value is 0 for SyS_clock_getres under the same conditions.
> Therefore, testcase thinks it is a bug.
>
> I will modify the code as below and add it in the next version patch
> if you think it is OK.
>
> @@ -209,7 +209,7 @@ static notrace int clock_getres_fallback( ...
>  {
>          if (res == NULL)
> -                return -EFAULT;
> +                return 0;
>

Ok. I don't know why that is the expected behavior (clock_getres
with a NULL argument makes little sense), but I can see that it
matches the regular syscall implementation.

      Arnd