Re: [PATCH 2/9] x86/cet: Add Kconfig option for user-mode shadow stack

[Andy Lutomirski]

On Thu, Jun 7, 2018 at 9:02 AM Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx> wrote:
>
> On Thu, 2018-06-07 at 08:47 -0700, Andy Lutomirski wrote:
> > On Thu, Jun 7, 2018 at 7:40 AM Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx> wrote:
> > >
> > > Introduce Kconfig option X86_INTEL_SHADOW_STACK_USER.
> > >
> > > An application has shadow stack protection when all the following are
> > > true:
> > >
> > >   (1) The kernel has X86_INTEL_SHADOW_STACK_USER enabled,
> > >   (2) The running processor supports the shadow stack,
> > >   (3) The application is built with shadow stack enabled tools & libs
> > >       and, and at runtime, all dependent shared libs can support shadow
> > >       stack.
> > >
> > > If this kernel config option is enabled, but (2) or (3) above is not
> > > true, the application runs without the shadow stack protection.
> > > Existing legacy applications will continue to work without the shadow
> > > stack protection.
> > >
> > > The user-mode shadow stack protection is only implemented for the
> > > 64-bit kernel.  Thirty-two bit applications are supported under the
> > > compatibility mode.
> > >
> >
> > The 64-bit only part seems entirely reasonable.  So please make the
> > code 64-bit only :)
>
> Yes, I will remove changes in "arch/x86/entry/entry32.S".
> We still want to support x32/ia32 in the 64-bit kernel, right?
>

Yes, I think.  But that's not in entry_32.S


>