linux-kernel - Re: [PATCH v2 0/4] kselftest: Extend vDSO tests

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Date:   Tue, 5 May 2020 16:04:13 +0100
From:   Vincenzo Frascino <vincenzo.frascino@....com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>, Shuah Khan <shuah@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH v2 0/4] kselftest: Extend vDSO tests

Hi Arnd,

On 5/5/20 3:50 PM, Arnd Bergmann wrote:
> On Wed, Apr 29, 2020 at 1:34 PM Vincenzo Frascino
> <vincenzo.frascino@....com> wrote:
>>
>> This series extends the kselftests for the vDSO library making sure: that
>> they compile correctly on non x86 platforms, that they can be cross
>> compiled and introducing new tests that verify the correctness of the
>> library.
>>
>> The so extended vDSO kselftests have been verified on all the platforms
>> supported by the unified vDSO library [1].
>>
>> The only new patch that this series introduces is the first one, patch 2 and
>> patch 3 have already been reviewed in past as part of other series [2] [3].
>>
>> [1] https://lore.kernel.org/lkml/20190621095252.32307-1-vincenzo.frascino@arm.com
>> [2] https://lore.kernel.org/lkml/20190621095252.32307-26-vincenzo.frascino@arm.com
>> [3] https://lore.kernel.org/lkml/20190523112116.19233-4-vincenzo.frascino@arm.com
> 
> Hi Vincenzo,
> 
> Not sure if you are aware of the recent bug report about clock_gettime64()
> returning invalid times on some arm32 kernels:
> https://github.com/raspberrypi/linux/issues/3579
> 

No, I was not aware of the problem. There has been no mention on the arm list
(unless I missed it). I can try to have a look at it as soon as I get some time.

> Regardless of when that gets fixed or by whom, I wonder if kselftest should
> also check for consistency, i.e. call both the vdso and the syscall version of
> clock_gettime() and clock_gettime64() and check that the results are always
> in sequence.
> 

The test #4 partially does that: it calls syscall-vdso-syscall and verifies that
the sequencing is correct. I reused the x86 code for that. I could extend it to
clock_gettime64() and make sure it builds on all the platforms.

>       Arnd
> 

-- 
Regards,
Vincenzo