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SubjectRe: [PATCH v9 05/42] mm: Move VM_UFFD_MINOR_BIT from 37 to 38
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On 13.06.23 02:10, Rick Edgecombe wrote:
> From: Yu-cheng Yu <yu-cheng.yu@intel.com>
>
> 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.
>
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
> Co-developed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> 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 <pengfei.xu@intel.com>
> Tested-by: John Allen <john.allen@amd.com>
> Tested-by: Kees Cook <keescook@chromium.org>
> ---
> include/linux/mm.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 9ec20cbb20c1..6f52c1e7c640 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -370,7 +370,7 @@ extern unsigned int kobjsize(const void *objp);
> #endif
>
> #ifdef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
> -# define VM_UFFD_MINOR_BIT 37
> +# define VM_UFFD_MINOR_BIT 38
> # define VM_UFFD_MINOR BIT(VM_UFFD_MINOR_BIT) /* UFFD minor faults */
> #else /* !CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */
> # define VM_UFFD_MINOR VM_NONE

Reviewed-by: David Hildenbrand <david@redhat.com>

--
Cheers,

David / dhildenb

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