Re: [PATCH v4 0/6] Micro-optimize vclock_gettime

From: Ingo Molnar
Date: Tue May 17 2011 - 04:00:56 EST

* Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:

> > see if I can persuade Uli to take accept a glibc patch to stop calling it
> > in future static glibc versions.
> How wide spread is this in reality on 64bit systems ?
> IOW, what's the damage if we take a trap and emulate it in the most painful
> way we can come up with ?

Well, how does that differ from having the real syscall instruction there? How
are we going to filter real (old-)glibc calls from exploits?

If it can be filtered in a meaningful way then we should just do that and
perhaps offer a (default enabled) .config COMPAT_VDSO_EMU=y switch to turn the
emulation off.

That way we keep the ABI and also have a way out for users who *really* need
this to work in a performant way.


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