diff mbox series

[v7,17/41] mm: Move VM_UFFD_MINOR_BIT from 37 to 38

Message ID 20230227222957.24501-18-rick.p.edgecombe@intel.com
State New
Headers
Series Shadow stacks for userspace |

Commit Message

Edgecombe, Rick P Feb. 27, 2023, 10:29 p.m. UTC 
  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>
Tested-by: Kees Cook <keescook@chromium.org>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
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 mbox series

Patch

diff --git a/include/linux/mm.h b/include/linux/mm.h
index af652444fbba..a1b31caae013 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