# Re: \[PATCH v8 17/40\] mm: Move VM\_UFFD\_MINOR\_BIT from 37 to 38

- From: David Hildenbrand \<hidden\>
- Date: 2023-03-20 11:01:19 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2023/03/2140183
- Thread: https://ratatoskr.run/linux-doc/2023/03/2138992/t.md

```text
On 19.03.23 01:15, Rick Edgecombe wrote:
> From: Yu-cheng Yu <redacted>
>
> The x86 Control-flow Enforcement Technology (CET) feature includes a new
> type of memory called shadow stack. This shadow stack memory has some
> unusual properties, which requires some core mm changes to function
> properly.
>
> Future patches will introduce a new VM flag VM_SHADOW_STACK that will be
> VM_HIGH_ARCH_BIT_5. VM_HIGH_ARCH_BIT_1 through VM_HIGH_ARCH_BIT_4 are
> bits 32-36, and bit 37 is the unrelated VM_UFFD_MINOR_BIT. For the sake
> of order, make all VM_HIGH_ARCH_BITs stay together by moving
> VM_UFFD_MINOR_BIT from 37 to 38. This will allow VM_SHADOW_STACK to be
> introduced as 37.
>
> Co-developed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Signed-off-by: Yu-cheng Yu <redacted>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Reviewed-by: Kees Cook <redacted>
> Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>
> Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
> Acked-by: Peter Xu <peterx@redhat.com>
> Tested-by: Pengfei Xu <redacted>
> Tested-by: John Allen <redacted>
> Tested-by: Kees Cook <redacted>
> ---


Reviewed-by: David Hildenbrand <redacted>

-- 
Thanks,

David / dhildenb

```