Re: [PATCH v28 16/32] x86/mm: Update maybe_mkwrite() for shadow stack

Borislav Petkov
2021-08-16T17:03:27Z

On Thu, Jul 22, 2021 at 01:52:03PM -0700, Yu-cheng Yu wrote:
> diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
> index 3364fe62b903..ba449d12ec32 100644
> --- a/arch/x86/mm/pgtable.c
> +++ b/arch/x86/mm/pgtable.c
> @@ -610,6 +610,26 @@ int pmdp_clear_flush_young(struct vm_area_struct *vma,
> }
> #endif
>
> +pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
> +{
> + if (likely(vma->vm_flags & VM_WRITE))
> + pte = pte_mkwrite(pte);
> + else if (likely(vma->vm_flags & VM_SHADOW_STACK))
> + pte = pte_mkwrite_shstk(pte);
> + return pte;
> +}
> +
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
> +{
> + if (likely(vma->vm_flags & VM_WRITE))
> + pmd = pmd_mkwrite(pmd);
> + else if (likely(vma->vm_flags & VM_SHADOW_STACK))
> + pmd = pmd_mkwrite_shstk(pmd);

What are all those likely()ies here for?

--
Regards/Gruss,
Boris.