Re: [PATCH v2] x86/fpu: Allow PKRU to be (once again) written by ptrace.

On 8/3/22 20:16, Kyle Huey wrote:

When management of the PKRU register was moved away from XSTATE, emulation of PKRU's existence in XSTATE was added for APIs that read XSTATE, but not for APIs that write XSTATE. This can be seen by running gdb and executing `p $pkru`, `set $pkru = 42`, and `p $pkru`. On affected kernels (5.14+) the write to the PKRU register (which gdb performs through ptrace) is ignored.

Do you happen to have a reproducer for this sitting around? I'd love to get an addition to the pkeys selftest/ in place to make sure we don't break this again. PKRU is a very special snowflake.