Re: [PATCH] x86/vsyscall: Remove CONFIG_LEGACY_VSYSCALL_EMULATE

[Andy Lutomirski]

On Wed, May 11, 2022, at 11:35 AM, Florian Weimer wrote:
> * 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 combined use of exotic and outdated debugging mechanisms with outdated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@xxxxxxxxxx
>> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
>> Cc: Florian Weimer <fweimer@xxxxxxxxxx>
>> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
>
> Sounds a good idea to me.
>
> Acked-by: Florian Weimer <fweimer@xxxxxxxxxx>
>
> Regarding the mechanics, is it customary to remove the actual code (the
> EMULATE enum constant) in later commits?
>

Might be several versions later. This patch intentionally still supports booting with vsyscall=emulate.