On Tue, Nov 07, 2017 at 09:15:21AM +0100, Florian Weimer wrote:

MAP_FIXED is near-impossible to use correctly.  I hope you don't expect
applications to do that.  If you want address-based opt in, it should work
without MAP_FIXED.  Sure, in obscure cases, applications might still see
out-of-range addresses, but I expected a full opt-out based on RLIMIT_AS
would be sufficient for them.

Just use mmap(-1), without MAP_FIXED to get full address space.

-- 
 Kirill A. Shutemov