[tip: x86/shstk] mm: Move VM_UFFD_MINOR_BIT from 37 to 38

[tip-bot2 for Yu-cheng Yu]

The following commit has been merged into the x86/shstk branch of tip:

Commit-ID:     5b541538cd8c86cb3a8f7a049a0b4a4ff1bd462b
Gitweb:        https://git.kernel.org/tip/5b541538cd8c86cb3a8f7a049a0b4a4ff1bd462b
Author:        Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
AuthorDate:    Sat, 18 Mar 2023 17:15:12 -07:00
Committer:     Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
CommitterDate: Mon, 20 Mar 2023 09:01:09 -07:00

mm: Move VM_UFFD_MINOR_BIT from 37 to 38

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@xxxxxxxxx>
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Acked-by: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
Acked-by: Peter Xu <peterx@xxxxxxxxxx>
Tested-by: Pengfei Xu <pengfei.xu@xxxxxxxxx>
Tested-by: John Allen <john.allen@xxxxxxx>
Tested-by: Kees Cook <keescook@xxxxxxxxxxxx>
Link: https://lore.kernel.org/all/20230319001535.23210-18-rick.p.edgecombe%40intel.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 af65244..a1b31ca 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -377,7 +377,7 @@ 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