arm64 mrs and system registers

Hi

I've been looking at this bugzilla item

https://bugs.kde.org/show_bug.cgi?id=392146

Is there any difference between Linux and FreeBSD when it comes to what 
registers and fields are exposed by the kernel (see comment 17 in the 
link above).

I did have a poke around the kernel code but it's a bit hard to tell 
exactly which of the access macros are being used, without exhaustively 
grepping for them one by one.

A+
Paul