specific probe function did not specify it. It picks the same address
as mmap() does for a non-fixed map at address 0. See also the comment
around a similar line of code in vm/vm_mmap.c.
it's text or data; use the entry point instead (this solves some trouble
with ELF executables with strange permissions)
* Incorporate some fixes from r_friedl@informatik.uni-kl.de sent to
netbsd-bugs a while ago
