Messages in this thread | | | Date | Fri, 14 Oct 2022 17:32:38 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2 16/39] x86/mm: Update maybe_mkwrite() for shadow stack |
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On Thu, Sep 29, 2022 at 03:29:13PM -0700, Rick Edgecombe wrote:
> diff --git a/include/linux/mm.h b/include/linux/mm.h > index 8cd413c5a329..fef14ab3abcb 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -981,13 +981,25 @@ void free_compound_page(struct page *page); > * servicing faults for write access. In the normal case, do always want > * pte_mkwrite. But get_user_pages can cause write faults for mappings > * that do not have writing enabled, when used by access_process_vm. > + * > + * If a vma is shadow stack (a type of writable memory), mark the pte shadow > + * stack. > */ > +#ifndef maybe_mkwrite > static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma) > { > - if (likely(vma->vm_flags & VM_WRITE)) > + if (!(vma->vm_flags & VM_WRITE)) > + goto out; > + > + if (vma->vm_flags & VM_SHADOW_STACK) > + pte = pte_mkwrite_shstk(pte); > + else > pte = pte_mkwrite(pte); > + > +out: > return pte; > } > +#endif
Why the #ifndef guard? There is no other implementation, nor does this patch introduce one.
Also, wouldn't it be simpler to write it like:
static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma) { if (!(vma->vm_flags & VM_WRITE)) return pte;
if (vma->vm_flags & VM_SHADOW_STACK) return pte_mkwrite_shstk(pte);
return pte_mkwrite(pte); }
? (idem for the pmd version etc..)
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