[PATCH v4 3/3] kselftest: Extend vDSO selftest to clock_getres

[Christophe Leroy]

Le 04/06/2019 à 15:32, Vincenzo Frascino a écrit :
> Hi Christophe,
> 
> On 04/06/2019 14:16, Christophe Leroy wrote:
>> Hi Vincenzo
>>
>> Le 28/05/2019 à 13:57, Vincenzo Frascino a écrit :
>>> Hi Michael,
>>>
>>> thank you for your reply.
>>>
>>> On 28/05/2019 07:19, Michael Ellerman wrote:
>>>> Vincenzo Frascino <vincenzo.frascino at arm.com> writes:
>>>>
>>>>> The current version of the multiarch vDSO selftest verifies only
>>>>> gettimeofday.
>>>>>
>>>>> Extend the vDSO selftest to clock_getres, to verify that the
>>>>> syscall and the vDSO library function return the same information.
>>>>>
>>>>> The extension has been used to verify the hrtimer_resoltion fix.
>>>>
>>>> This is passing for me even without patch 1 applied, shouldn't it fail
>>>> without the fix? What am I missing?
>>>>
>>>
>>> This is correct, because during the refactoring process I missed an "n" :)
>>>
>>> if·((x.tv_sec·!=·y.tv_sec)·||·(x.tv_sec·!=·y.tv_sec))
>>>
>>> Should be:
>>>
>>> if·((x.tv_sec·!=·y.tv_sec)·||·(x.tv_nsec·!=·y.tv_nsec))
>>>
>>> My mistake, I am going to fix the test and re-post v5 of this set.
>>>
>>> Without my patch if you pass "highres=off" to the kernel (as a command line
>>> parameter) it leads to a broken implementation of clock_getres since the value
>>> of CLOCK_REALTIME_RES does not change at runtime.
>>>
>>> Expected result (with highres=off):
>>>
>>> # uname -r
>>> 5.2.0-rc2
>>> # ./vdso_clock_getres
>>> clock_id: CLOCK_REALTIME [FAIL]
>>> clock_id: CLOCK_BOOTTIME [PASS]
>>> clock_id: CLOCK_TAI [PASS]
>>> clock_id: CLOCK_REALTIME_COARSE [PASS]
>>> clock_id: CLOCK_MONOTONIC [FAIL]
>>> clock_id: CLOCK_MONOTONIC_RAW [PASS]
>>> clock_id: CLOCK_MONOTONIC_COARSE [PASS]
>>>
>>> The reason of this behavior is that the only clocks supported by getres on
>>> powerpc are CLOCK_REALTIME and CLOCK_MONOTONIC, the rest on the clocks use
>>> always syscalls.
>>
>> vdso64 is supposed to implement CLOCK_{REALTIME/MONOTONIC}_COARSE, so I
>> guess it should fail for them too ?
>>
>> Or is your test done on vdso32 ?
>>
> 
> Based on what I can see in kernel/vdso64 in 5.2-rc3:
> 
> /*
>   * Exact prototype of clock_getres()
>   *
>   * int __kernel_clock_getres(clockid_t clock_id, struct timespec *res);
>   *
>   */
> V_FUNCTION_BEGIN(__kernel_clock_getres)
>    .cfi_startproc
> 	/* Check for supported clock IDs */
> 	cmpwi	cr0,r3,CLOCK_REALTIME
> 	cmpwi	cr1,r3,CLOCK_MONOTONIC
> 	cror	cr0*4+eq,cr0*4+eq,cr1*4+eq
> 	bne	cr0,99f
> 
> 	li	r3,0
> 	cmpldi	cr0,r4,0
> 	crclr	cr0*4+so
> 	beqlr
> 	lis	r5,CLOCK_REALTIME_RES at h
> 	ori	r5,r5,CLOCK_REALTIME_RES at l
> 	std	r3,TSPC64_TV_SEC(r4)
> 	std	r5,TSPC64_TV_NSEC(r4)
> 	blr
> 
> 	/*
> 	 * syscall fallback
> 	 */
> 99:
> 	li	r0,__NR_clock_getres
> 	sc
> 	blr
>    .cfi_endproc
> V_FUNCTION_END(__kernel_clock_getres)
> 
> it does not seem so for what concerns vdso64. I did run again the test both on
> ppc and ppc64 qemu instances and the result is the same to what I reported in
> this thread.
> 
> Am I missing something?

I was thinking about 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5c929885f1bb 
but apparently clock_getres() was left aside. Should we do something 
about it ?

Christophe

> 
>> Christophe
>>
>>>
>>>> # uname -r
>>>> 5.2.0-rc2-gcc-8.2.0
>>>>
>>>> # ./vdso_clock_getres
>>>> clock_id: CLOCK_REALTIME [PASS]
>>>> clock_id: CLOCK_BOOTTIME [PASS]
>>>> clock_id: CLOCK_TAI [PASS]
>>>> clock_id: CLOCK_REALTIME_COARSE [PASS]
>>>> clock_id: CLOCK_MONOTONIC [PASS]
>>>> clock_id: CLOCK_MONOTONIC_RAW [PASS]
>>>> clock_id: CLOCK_MONOTONIC_COARSE [PASS]
>>>>
>>>> cheers
>>>>
>>>>> Cc: Shuah Khan <shuah at kernel.org>
>>>>> Signed-off-by: Vincenzo Frascino <vincenzo.frascino at arm.com>
>>>>> ---
>>>>>
>>>>> Note: This patch is independent from the others in this series, hence it
>>>>> can be merged singularly by the kselftest maintainers.
>>>>>
>>>>>    tools/testing/selftests/vDSO/Makefile         |   2 +
>>>>>    .../selftests/vDSO/vdso_clock_getres.c        | 124 ++++++++++++++++++
>>>>>    2 files changed, 126 insertions(+)
>>>>>    create mode 100644 tools/testing/selftests/vDSO/vdso_clock_getres.c
>>>
>