Theoretically it's possible. Just keep all memory in the first 4GB. Load all pointers from 32bit locations and do 32bit arithmetic on them, they should get 0-ex

Theoretically it's possible. Just keep all memory in the first 4GB. Load all pointers from 32bit locations and do 32bit arithmetic on them, they should get 0-extended for loads and stores. With the correct linker scripts this could be done in user space (modulo calling dynamically linked libraries).