Re: [PATCH v12 8/8] x86: Disallow vsyscall emulation when CET is enabled

[H.J. Lu]

On Fri, Sep 18, 2020 at 2:00 PM Pavel Machek <pavel@xxxxxx> wrote:
>
> On Fri 2020-09-18 12:32:57, Dave Hansen wrote:
> > On 9/18/20 12:23 PM, Yu-cheng Yu wrote:
> > > Emulation of the legacy vsyscall page is required by some programs
> > > built before 2013.  Newer programs after 2013 don't use it.
> > > Disable vsyscall emulation when Control-flow Enforcement (CET) is
> > > enabled to enhance security.
> >
> > How does this "enhance security"?
> >
> > What is the connection between vsyscall emulation and CET?
>
> Boom.
>
> We don't break compatibility by default, and you should not tell
> people to enable CET by default if you plan to do this.
>

Nothing will be broken.   CET enabled applications don't use/need
vsyscall emulation.

-- 
H.J.