On Tue, Jul 10, 2018 at 03:26:26PM -0700, Yu-cheng Yu wrote:
> diff --git a/mm/memory.c b/mm/memory.c
> index a2695dbc0418..f7c46d61eaea 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4108,7 +4108,13 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
> if (pmd_protnone(orig_pmd) && vma_is_accessible(vma))
> return do_huge_pmd_numa_page(&vmf, orig_pmd);
>
> - if (dirty && !pmd_write(orig_pmd)) {
> + /*
> + * Shadow stack trans huge PMDs are copy-on-access,
> + * so wp_huge_pmd() on them no mater if we have a
> + * write fault or not.
> + */
> + if (is_shstk_mapping(vma->vm_flags) ||
> + (dirty && !pmd_write(orig_pmd))) {
> ret = wp_huge_pmd(&vmf, orig_pmd);
> if (!(ret & VM_FAULT_FALLBACK))
> return ret;
Can't we do this (and the do_wp_page thing) by setting FAULT_FLAG_WRITE
in the arch fault handler on shadow stack faults?
