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List:       linux-api
Subject:    Re: [PATCH v8 17/40] mm: Move VM_UFFD_MINOR_BIT from 37 to 38
From:       David Hildenbrand <david () redhat ! com>
Date:       2023-03-20 10:55:27
Message-ID: da5c721e-3492-5028-2439-64875efc5a6d () redhat ! com
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On 19.03.23 01:15, 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.
> 
> Co-developed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> 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>
> ---


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

-- 
Thanks,

David / dhildenb

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