Re: [RFC PATCH v9 06/27] mm: Introduce VM_SHSTK for Shadow Stack memory

Dave Hansen
2020-02-26T18:08:00Z

On 2/5/20 10:19 AM, Yu-cheng Yu wrote:
> A Shadow Stack (SHSTK) PTE must be read-only and have _PAGE_DIRTY set.
> However, read-only and Dirty PTEs also exist for copy-on-write (COW) pages.
> These two cases are handled differently for page faults and a new VM flag
> is necessary for tracking SHSTK VMAs.
>
> v9:
> - Add VM_SHSTK case to arch_vma_name().
> - Revise the commit log to explain why a new VM flag is needed.

To be honest, a flag is not strictly *needed*. It is certainly
convenient and straightforward, but it's far from being truly necessary.