Function vm_map_inherit

freebsd/vm/vm_map.c:3146–3197

* vm_map_inherit: * * Sets the inheritance of the specified address * range in the target map. Inheritance * affects how the map will be shared with * child maps at the time of vmspace_fork. */

 *	child maps at the time of vmspace_fork.
 */
int
vm_map_inherit(vm_map_t map, vm_offset_t start, vm_offset_t end,
	       vm_inherit_t new_inheritance)
{
	vm_map_entry_t entry, lentry, prev_entry, start_entry;
	int rv;

	switch (new_inheritance) {
	case VM_INHERIT_NONE:
	case VM_INHERIT_COPY:
	case VM_INHERIT_SHARE:
	case VM_INHERIT_ZERO:
		break;
	default:
		return (KERN_INVALID_ARGUMENT);
	}
	if (start == end)
		return (KERN_SUCCESS);
	vm_map_lock(map);
	VM_MAP_RANGE_CHECK(map, start, end);
	rv = vm_map_lookup_clip_start(map, start, &start_entry, &prev_entry);
	if (rv != KERN_SUCCESS)
		goto unlock;
	if (vm_map_lookup_entry(map, end - 1, &lentry)) {
		rv = vm_map_clip_end(map, lentry, end);
		if (rv != KERN_SUCCESS)
			goto unlock;
	}
	if (new_inheritance == VM_INHERIT_COPY) {
		for (entry = start_entry; entry->start < end;
		    prev_entry = entry, entry = vm_map_entry_succ(entry)) {
			if ((entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK)
			    != 0) {
				rv = KERN_INVALID_ARGUMENT;
				goto unlock;
			}
		}
	}
	for (entry = start_entry; entry->start < end; prev_entry = entry,
	    entry = vm_map_entry_succ(entry)) {
		KASSERT(entry->end <= end, ("non-clipped entry %p end %jx %jx",
		    entry, (uintmax_t)entry->end, (uintmax_t)end));
		if ((entry->eflags & MAP_ENTRY_GUARD) == 0 ||
		    new_inheritance != VM_INHERIT_ZERO)
			entry->inheritance = new_inheritance;
		vm_map_try_merge_entries(map, prev_entry, entry);
	}
	vm_map_try_merge_entries(map, prev_entry, entry);
unlock:
	vm_map_unlock(map);
	return (rv);
}

/*
 *	vm_map_entry_in_transition: