mmap currently sets errno to EINVAL when it should be ENOMEM.
SUS/POSIX states that ENOMEM should be returned when:

"MAP_FIXED was specified, and the range [addr, addr + len) exceeds
that allowed for the address space of a process; or if MAP_FIXED was
not specified and there is insufficient room in the address space to
effect the mapping."

The following patch (against 2.4.17) fixes this behaviour: