linux-kernel - Re: [PATCH v3] x86/vdso: Handle clock_gettime(CLOCK

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 12 Sep 2018 16:17:26 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Florian Weimer <fweimer@...hat.com>
cc:     Andy Lutomirski <luto@...nel.org>,
        Matt Rickard <matt@...trans.com.au>,
        Stephen Boyd <sboyd@...nel.org>,
        John Stultz <john.stultz@...aro.org>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] x86/vdso: Handle clock_gettime(CLOCK_TAI) in vDSO

On Wed, 12 Sep 2018, Florian Weimer wrote:
> On 09/09/2018 10:05 PM, Thomas Gleixner wrote:
> > See the patch below. It's integrating TAI without slowing down everything
> > and it definitely does not result in indirect calls.
> > 
> > On a HSW it slows down clock_gettime() by ~0.5ns. On a SKL I get a speedup
> > by ~0.5ns. On a AMD Epyc server it's 1.2ns speedup. So it somehow depends
> > on the uarch and I also observed compiler version dependend variations.
> 
> Does this mean glibc can keep using a single vDSO entrypoint, the one we
> have today?

We have no intention to change that.

But we surely could provide separate entry points as an extra to avoid a
bunch of conditionals.

Thanks,

	tglx