Re: [PATCH] x86/uaccess: Use pointer masking to limit uaccess speculation

[Christoph Hellwig]

On Wed, Sep 02, 2020 at 12:43:48PM +0100, Mark Rutland wrote:
> I'll see what I can do.
> 
> At first glance it looks like we might need to flesh out or refactor the
> arm64 kernel maccess routines first (since we want the user maccess
> routines to use LDTR/STTR instructions that can't access kernel memory),
> but after that I think the rest is largely mechanical.

Yes, the first thing is to implement __get_kernel_nofaul and
__put_kernel_nofault.  I think they should mostly look like the existing
non-UAO versions of get_user and put_user with a fixed address space
limit.