On 5/21/2021 3:25 PM, Axel Rasmussen wrote:

This seems reasonable to me. The particular bit used isn't so
important from my perspective. I can't think of a way this would break
backward compatibility or such. So:

Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>

Thanks!

Yu-cheng

On Fri, May 21, 2021 at 3:13 PM Yu-cheng Yu [off-list ref] wrote:

quoted

To introduce VM_SHADOW_STACK as VM_HIGH_ARCH_BIT (37), and make all
VM_HIGH_ARCH_BITs stay together, move VM_UFFD_MINOR_BIT from 37 to 38.

Signed-off-by: Yu-cheng Yu <redacted>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Mike Kravetz <redacted>
---
  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 c274f75efcf9..923f89b9f1b5 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h

@@ -373,7 +373,7 @@ 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
--

2.21.0