linux-kernel - [tip: x86/shstk] mm: Move VM_UFFD_MINOR

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Date:   Mon, 20 Mar 2023 16:39:26 -0000
From:   "tip-bot2 for Yu-cheng Yu" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Yu-cheng Yu" <yu-cheng.yu@...el.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Borislav Petkov (AMD)" <bp@...en8.de>,
        Kees Cook <keescook@...omium.org>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        "Mike Rapoport (IBM)" <rppt@...nel.org>,
        Peter Xu <peterx@...hat.com>,
        Pengfei Xu <pengfei.xu@...el.com>,
        John Allen <john.allen@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/shstk] mm: Move VM_UFFD_MINOR_BIT from 37 to 38

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@...el.com>
AuthorDate:    Sat, 18 Mar 2023 17:15:12 -07:00
Committer:     Dave Hansen <dave.hansen@...ux.intel.com>
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@...el.com>
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Reviewed-by: Borislav Petkov (AMD) <bp@...en8.de>
Reviewed-by: Kees Cook <keescook@...omium.org>
Reviewed-by: Axel Rasmussen <axelrasmussen@...gle.com>
Acked-by: Mike Rapoport (IBM) <rppt@...nel.org>
Acked-by: Peter Xu <peterx@...hat.com>
Tested-by: Pengfei Xu <pengfei.xu@...el.com>
Tested-by: John Allen <john.allen@....com>
Tested-by: Kees Cook <keescook@...omium.org>
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