Messages in this thread | | | Date | Wed, 11 Jul 2018 11:06:56 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC PATCH v2 13/27] mm: Handle shadow stack page fault |
| |
On Tue, Jul 10, 2018 at 04:06:25PM -0700, Dave Hansen wrote: > On 07/10/2018 03:26 PM, Yu-cheng Yu wrote: > > + if (is_shstk_mapping(vma->vm_flags)) > > + entry = pte_mkdirty_shstk(entry); > > + else > > + entry = pte_mkdirty(entry); > > + > > + entry = maybe_mkwrite(entry, vma); > > if (ptep_set_access_flags(vma, vmf->address, vmf->pte, entry, 1)) > > update_mmu_cache(vma, vmf->address, vmf->pte); > > pte_unmap_unlock(vmf->pte, vmf->ptl); > > @@ -2526,7 +2532,11 @@ static int wp_page_copy(struct vm_fault *vmf) > > } > > flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte)); > > entry = mk_pte(new_page, vma->vm_page_prot); > > - entry = maybe_mkwrite(pte_mkdirty(entry), vma); > > + if (is_shstk_mapping(vma->vm_flags)) > > + entry = pte_mkdirty_shstk(entry); > > + else > > + entry = pte_mkdirty(entry); > > + entry = maybe_mkwrite(entry, vma); > > Do we want to lift this hunk of code and put it elsewhere? Maybe: > > entry = pte_set_vma_features(entry, vma); > > and then: > > pte_t pte_set_vma_features(pte_t entry, struct vm_area_struct) > { > /* > * Shadow stack PTEs are always dirty and always > * writable. They have a different encoding for > * this than normal PTEs, though. > */ > if (is_shstk_mapping(vma->vm_flags)) > entry = pte_mkdirty_shstk(entry); > else > entry = pte_mkdirty(entry); > > entry = maybe_mkwrite(entry, vma); > > return entry; > }
Yes, that wants a helper like that. Not sold on the name, but whatever.
Is there any way we can hide all the shadow stack magic in arch code?
| |