On Wed, Apr 01, 2020 at 06:54:44PM +0100, Catalin Marinas wrote:
On Tue, Mar 31, 2020 at 08:44:59PM +0100, Mark Brown wrote:
Compilers with branch protection support can be configured to enable it by default, it is likely that distributions will do this as part of deploying branch protection system wide. As well as the slight overhead from having some extra NOPs for unused branch protection features this can cause more serious problems when the kernel is providing pointer authentication to userspace but not built for pointer authentication itself.
With 5.7 you won't be able to configure user and kernel PAC support independently. So, I guess that's something only for prior kernel versions.
Yes, it's really for the benefit of stable at this point - hence the Cc. Going forward it's hopefully more for defensiveness than anything else, it's possible something similar might come up with some future stuff but ideally not.