linux-kernel - Re: MIPS: bug: gettimeofday syscall broken on CI20 board

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Message-ID: <3190d1a4-96c4-1843-3ae1-bae3a97af9fb@arm.com>
Date:   Tue, 26 Nov 2019 10:52:17 +0000
From:   Vincenzo Frascino <vincenzo.frascino@....com>
To:     "H. Nikolaus Schaller" <hns@...delico.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>
Cc:     linux-mips@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        MIPS Creator CI20 Development 
        <mips-creator-ci20-dev@...glegroups.com>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>
Subject: Re: MIPS: bug: gettimeofday syscall broken on CI20 board

Hi Nikolaus,

sorry for the delay in answering to your email but due to personal reasons I had
to pull off the linux development for few weeks.

On 17/11/2019 13:14, H. Nikolaus Schaller wrote:
> Hi Vincenzo,
> 

[...]

> 
> If I look at the definition of vdso_data it *is* significantly differen
> from mips_vdso_data.
> 
> What I would assume is that the struct mips_vdso_data is embossed in user
> space code and therefore using vdso_data instead is breaking API.
>

vdso_data and mips_vdso_data before are not part of the ABI hence they are not
bind by a contract with the userspace.

This means that they can change at any point and if a userspace software relies
on a specific layout of these data structures is doing something wrong.

> Please advise what I should try or check to narrow down further.
> 

I had a look at [1] line 200 and seems that the error you are seeing is
generated by:
  if (gettimeofday(&tv, NULL) == -1) { ... }

I do not have a CI20 hence I can't do the test myself: could you please write a
small application that invokes gettimeofday() as per above and report the
behavior (I am even interested in the value returned). If we can reproduce the
problem in a smaller environment it is easier to debug and get to the solution.

[1] http://users.isc.org/~each/doxygen/bind9/isc_2unix_2time_8c-source.html

> BR and thanks,
> Nikolaus Schaller
> 

Let me know.

-- 
Regards,
Vincenzo

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