The vm_map_lookup function attempts to find the
.Vt vm_object , page index and protection, for the given virtual address vaddr, in the map var_map, assuming a page fault of the type fault_type had occurred.
Return values are guaranteed until vm_map_lookup_done is called to release the lock.
The function vm_map_lookup acquires a read-lock on the map *var_map, but does not release it. The caller should invoke vm_map_lookup_done in order to release this lock.
The vm_map_lookup function returns KERN_SUCCESS, and sets the *object, *pindex, *out_prot, and *out_entry arguments appropriately for the hypothetical page fault.