I think you just need to set the _ptr field the same as the _base.

I've been poking at netbsd for a couple weekends so far on a sun3
running mach, and it's been pretty easy to get things to work.
So far I've built the netbsd versions of: gcc, gas, gld; ld.so and
shared libc (just for giggles, I can't actually do anything with them yet);
config.new and the kernel (with a few hacks to make it link, like
an empty swtch() function).  The kernel gets as far as you'd expect
given the lack of device drivers, so it seems pretty happy.
I haven't been able to try the nfsmounting-the-root-filesystem
thang yet for lack of a second machine at home.

Anyway, the sun3_mach binaries that I made will likely work ok under
sunos, I could make them available if you'd like.

-Chuck

------------------------------------------------------------------------------