linux-kernel - Re: [PATCH v6 19/36] nds32: VDSO support

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Date:   Tue, 6 Feb 2018 09:48:17 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Vincent Chen <deanbo422@...il.com>
Cc:     Greentime Hu <green.hu@...il.com>,
        Greentime <greentime@...estech.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <marc.zyngier@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Networking <netdev@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        David Howells <dhowells@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        linux-serial@...r.kernel.org,
        Geert Uytterhoeven <geert.uytterhoeven@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Mark Rutland <mark.rutland@....com>, Greg KH <greg@...ah.com>,
        Guo Ren <ren_guo@...ky.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        David Miller <davem@...emloft.net>,
        Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Stafford Horne <shorne@...il.com>,
        Vincent Chen <vincentc@...estech.com>
Subject: Re: [PATCH v6 19/36] nds32: VDSO support

On Tue, Feb 6, 2018 at 8:41 AM, Vincent Chen <deanbo422@...il.com> wrote:
> 2018-01-18 18:28 GMT+08:00 Arnd Bergmann <arnd@...db.de>:
>> On Mon, Jan 15, 2018 at 6:53 AM, Greentime Hu <green.hu@...il.com> wrote:
>>> From: Greentime Hu <greentime@...estech.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@...estech.com>
>>> Signed-off-by: Greentime Hu <greentime@...estech.com>
>>
>> Acked-by: Arnd Bergmann <arnd@...db.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