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

Yu, Yu-cheng
2021-08-17T18:36:36Z

On 8/16/2021 10:03 AM, Borislav Petkov wrote:
> 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?
>

I will remove those.

Thanks,
Yu-cheng