When locating the anonymous memory region for a vm_map with ASLR
enabled, we try to keep the slid base address aligned on a superpage
boundary to minimize pagetable fragmentation and maximize the potential
usage of superpage mappings. We can't (portably) do this if superpages
have been disabled by loader tunable and pagesizes is 0, and it
would be less beneficial in that case anyway.
Reported by: firstname.lastname@example.org
MFC after: 1 week