linux-kernel - Re: [PATCH] x86/vsyscall: Remove CONFIG_LEGACY_VSYSCALL

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Date:   Wed, 11 May 2022 20:35:02 +0200
From:   Florian Weimer <fweimer@...hat.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     x86@...nel.org, LKML <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] x86/vsyscall: Remove CONFIG_LEGACY_VSYSCALL_EMULATE

* Andy Lutomirski:

> CONFIG_LEGACY_VSYSCALL_EMULATE is, as far as I know, only needed for the
> combined use of exotic and outdated debugging mechanisms with outdated
> binaries.  At this point, no one should be using it.  We would like to
> implement dynamic switching of vsyscalls, but this is much more
> complicated to support in EMULATE mode than XONLY mode.
>
> So let's force all the distros off of EMULATE mode.  If anyone actually
> needs it, they can set vsyscall=emulate, and we can then get away with
> refusing to support newer security models if that option is set.
>
> Cc: x86@...nel.org
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Florian Weimer <fweimer@...hat.com>
> Signed-off-by: Andy Lutomirski <luto@...nel.org>

Sounds a good idea to me.

Acked-by: Florian Weimer <fweimer@...hat.com>

Regarding the mechanics, is it customary to remove the actual code (the
EMULATE enum constant) in later commits?

Thanks,
Florian