TLS register access trapping failure on Orion

["Jonathan A. Kollasch" <jakllsch%kollasch.net@localhost>]

I'm running a recent -current evbarm on my Marvell Orion box (HP MV2120).
All pthreaded processes segfault due to __lwp_getprivate_fast() returning
a NULL pointer.  Further debugging shows that netbsd:cp15_trapper() never
executes.

AFAICT Linux doesn't attempt to rely on unprivileged mrc/mrc trapping on
pre-ARMv6.

Is there a plausible reason as to why this doesn't work?

        Jonathan Kollasch