Re: [PATCH v3] powerpc, pkey: make protection key 0 less special

On Tue, May 08, 2018 at 07:03:36PM +0200, Michal Suchánek wrote:

How is the application denied setting the permissions on key 0 if it
can program the register directly?

There is a UAMOR register. The userspace can change the permissions of a
given key; by modifying the bits in AMOR register, only if the kernel
has set the corresponding bit in the UAMOR register.  For key-0 the
kernel does not set the corresponding UAMOR bit.

RP