From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: "linuxppc-dev@ozlabs.org" <linuxppc-dev@ozlabs.org>
Subject: Re: C vdso
Date: Thu, 24 Sep 2020 15:17:19 +0200 [thread overview]
Message-ID: <cc532aa8-a9e0-a105-b7b1-ee8d723b7ed6@csgroup.eu> (raw)
In-Reply-To: <87r1r0oa4o.fsf@mpe.ellerman.id.au>
Hi Michael
Le 17/09/2020 à 14:33, Michael Ellerman a écrit :
> Hi Christophe,
>
> Christophe Leroy <christophe.leroy@csgroup.eu> writes:
>> Hi Michael,
>>
>> What is the status with the generic C vdso merge ?
>> In some mail, you mentionned having difficulties getting it working on
>> ppc64, any progress ? What's the problem ? Can I help ?
>
> Yeah sorry I was hoping to get time to work on it but haven't been able
> to.
>
> It's causing crashes on ppc64 ie. big endian.
>
>
> As you can see from the instruction dump we have jumped into the weeds somewhere.
>
> We also had the report from the kbuild robot about rela.opd being
> discarded, which I think is indicative of a bigger problem. ie. we don't
> process relocations for the VDSO, but opds require relocations (they
> contain an absolute pointer).
>
> I thought we could get away with that, because the VDSO entry points
> aren't proper functions (so they don't have opds), and I didn't think
> we'd be calling via function pointers in the VDSO code (which would
> require opds). But seems something is not working right.
>
> Sorry I haven't got back to you with those details. Things are a bit of
> a mess inside IBM at the moment (always?), and I've been trying to get
> everything done before I take a holiday next week.
>
Can you tell what defconfig you are using ? I have been able to setup a
full glibc PPC64 cross compilation chain and been able to test it under
QEMU with success, using Nathan's vdsotest tool.
I tested with both ppc64_defconfig and pseries_defconfig.
The only problem I got is with getcpu, which segfaults but both before
and after applying my series, so I guess this is unrelated.
Not sure we can pay too much attention to the exact measurement as it is
a ppc64 QEMU running on a x86 Linux which is running in a Virtual Box on
a x86 windows Laptop, but at least it works:
Without the series:
clock-getres-monotonic: vdso: 389 nsec/call
clock-gettime-monotonic: vdso: 781 nsec/call
clock-getres-monotonic-coarse: vdso: 13715 nsec/call
clock-gettime-monotonic-coarse: vdso: 312 nsec/call
clock-getres-monotonic-raw: vdso: 13589 nsec/call
clock-getres-tai: vdso: 13827 nsec/call
clock-gettime-tai: vdso: 14846 nsec/call
clock-getres-boottime: vdso: 13596 nsec/call
clock-gettime-boottime: vdso: 14758 nsec/call
clock-getres-realtime: vdso: 327 nsec/call
clock-gettime-realtime: vdso: 717 nsec/call
clock-getres-realtime-coarse: vdso: 14102 nsec/call
clock-gettime-realtime-coarse: vdso: 299 nsec/call
gettimeofday: vdso: 771 nsec/call
With the series:
clock-getres-monotonic: vdso: 350 nsec/call
clock-gettime-monotonic: vdso: 726 nsec/call
clock-getres-monotonic-coarse: vdso: 356 nsec/call
clock-gettime-monotonic-coarse: vdso: 423 nsec/call
clock-getres-monotonic-raw: vdso: 349 nsec/call
clock-getres-tai: vdso: 419 nsec/call
clock-gettime-tai: vdso: 724 nsec/call
clock-getres-boottime: vdso: 352 nsec/call
clock-gettime-boottime: vdso: 752 nsec/call
clock-getres-realtime: vdso: 351 nsec/call
clock-gettime-realtime: vdso: 733 nsec/call
clock-getres-realtime-coarse: vdso: 356 nsec/call
clock-gettime-realtime-coarse: vdso: 367 nsec/call
gettimeofday: vdso: 796 nsec/call
Thanks
Christophe
next parent reply other threads:[~2020-09-24 13:20 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200916165516.Horde.uocmo3irPb7BMg__NUSqRA9@messagerie.si.c-s.fr>
[not found] ` <87r1r0oa4o.fsf@mpe.ellerman.id.au>
2020-09-24 13:17 ` Christophe Leroy [this message]
2020-10-23 6:28 ` C vdso Christophe Leroy
2020-10-23 13:24 ` Michael Ellerman
2020-10-24 10:07 ` Michael Ellerman
2020-10-24 11:16 ` Christophe Leroy
2020-11-03 18:11 ` Christophe Leroy
2020-11-03 18:13 ` Christophe Leroy
2020-11-24 10:11 ` Christophe Leroy
2020-11-25 2:04 ` Michael Ellerman
2020-11-25 9:21 ` Christophe Leroy
2020-11-25 12:22 ` Michael Ellerman
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