equivalent of MAP_32BIT

[Justin Cormack <justin%specialbusservice.com@localhost>]

I have been informed that there might be an undocumented ability to
get mmap to return addresses in the lower 4G of address space on a 64
bit machine by passing ~(unsigned)0 as the first parameter (or
(1<<31)-1 for 2GB). Is this correct? Or is it possibley to use
netbsd32_mmap()? Linux and some other OSs support a MAP_32BIT flag to
achieve this, looking for a way to port some code to NetBSD that
requires this.

Thanks

Justin