Messages in this thread Patch in this message | | | From | Rick Edgecombe <> | Subject | [PATCH v4 14/39] mm: Move VM_UFFD_MINOR_BIT from 37 to 38 | Date | Fri, 2 Dec 2022 16:35:41 -0800 |
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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.
Tested-by: Pengfei Xu <pengfei.xu@intel.com> Tested-by: John Allen <john.allen@amd.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Peter Xu <peterx@redhat.com> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> Reviewed-by: Axel Rasmussen <axelrasmussen@google.com> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> Cc: Peter Xu <peterx@redhat.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> --- 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 bfac5a166cb8..9ae6bc38d0b7 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -354,7 +354,7 @@ 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 -- 2.17.1
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