Arnd Bergmann writes:

Well, the point I made earlier ist that the native ppc32 path should
behave the same way as the compat ppc32 path. If we keep ppc_select
in one way or another, we should also have a compat wrapper for that,
right?

No - we have other old system calls that don't exist at all on a
64-bit kernel but do on a 32-bit kernel.  We decided a long time ago
that there was no point supporting really ancient 32-bit userland code
on a 64-bit kernel.  That doesn't mean we need to rip out the support
from the 32-bit kernel.

Paul.