Re: [patch 05/16] mm: Allow special mappings with user access cleared

[Peter Zijlstra]

On Tue, Dec 12, 2017 at 10:00:08AM -0800, Andy Lutomirski wrote:
> On Tue, Dec 12, 2017 at 9:32 AM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> > From: Peter Zijstra <peterz@xxxxxxxxxxxxx>
> >
> > In order to create VMAs that are not accessible to userspace create a new
> > VM_NOUSER flag. This can be used in conjunction with
> > install_special_mapping() to inject 'kernel' data into the userspace map.
> >
> > Similar to how arch_vm_get_page_prot() allows adding _PAGE_flags to
> > pgprot_t, introduce arch_vm_get_page_prot_excl() which masks
> > _PAGE_flags from pgprot_t and use this to implement VM_NOUSER for x86.
> 
> How does this interact with get_user_pages(), etc?

gup would find the page. These patches do in fact rely on that through
the populate things.