os_map_memory
extern int os_map_memory(void *virt, int fd, unsigned long long off,
err = os_map_memory((void *) virt, fd, offset, len, r, w, x);
err = os_map_memory((void *) reserve_end, physmem_fd, reserve,
return os_map_memory((void *)virt, phys_fd, offset, len,