Re: [PATCH v5 18/39] mm: Handle faultless write upgrades for shstk

Edgecombe, Rick P
2023-02-01T17:33:57Z

On Wed, 2023-02-01 at 10:03 +0100, David Hildenbrand wrote:
> >
> > The other problem is that one of NULL passers is not for kernel
> > memory.
> > huge_pte_mkwrite() calls pte_mkwrite(). Shadow stack memory can't
> > be
> > created with MAP_HUGETLB, so it is not needed. Using
> > pte_mkwrite_kernel() would look weird in this case, but making
> > huge_pte_mkwrite() take a VMA would be for no reason. Maybe making
> > huge_pte_mkwrite() take a VMA is the better of those two options.
> > Or
> > keep the NULL semantics... Any thoughts?
>
> Well, the reason would be consistency. From a core-mm point of view
> it
> makes sense to handle this all consistency, even if the single user
> (x86) wouldn't strictly require it right now.
>
> I'd just pass in the VMA and call it a day :)

Ok, I'll give it a spin.