linux-kernel - Re: [PATCH 0/3] x86_64: Tidy up vsyscall emulation and make it optional

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Date:	Tue, 28 Oct 2014 10:46:33 -0700
From:	josh@...htriplett.org
To:	Andy Lutomirski <luto@...capital.net>
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org, mingo@...nel.org
Subject: Re: [PATCH 0/3] x86_64: Tidy up vsyscall emulation and make it
 optional

On Tue, Oct 28, 2014 at 10:22:25AM -0700, Andy Lutomirski wrote:
> Now that arch/x86/kernel/vsyscall_64.c contains only vsyscall
> emulation code, clean it up and make it optional.
> 
> Patch 1 makes vsyscall=none work be a bit more self-consistent: it
> actually removes the fake vsyscall page instead of just segfaulting
> anyone who tries to use it.
> 
> Patch 2 is pure cosmetic cleanup.
> 
> Patch 3 is the meat: it lets vsyscall emulation be configured out.
> The config option to disable it is hidden under CONFIG_EXPERT, since
> it will break legacy code.
> 
> Note that, last I checked, current userspace is unlikely to work if
> the vDSO *and* vsyscalls are off.  Take it up with the glibc
> maintainers.
> 
> This applies on top of tip/x86/vdso.
> 
> Andy Lutomirski (3):
>   x86_64,vsyscall: Turn vsyscalls all the way off when vsyscall=none
>   x86_64,vsyscall: Rewrite comment and clean up headers in vsyscall code
>   x86_64,vsyscall: Make vsyscall emulation configurable

Nice!

For patches 1 and 2:
Reviewed-by: Josh Triplett <josh@...htriplett.org>

For patch 3, I responded with a possible minor improvement, but with or
without that:
Reviewed-by: Josh Triplett <josh@...htriplett.org>

I assume these should go through tip/x86/vdso as well?

Also, any plans to do something similar for vsyscall_gtod.c?

- Josh Triplett
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