Function vm_map_lookup_entry

freebsd/vm/vm_map.c:1560–1632

* vm_map_lookup_entry: [ internal use only ] * * Finds the map entry containing (or * immediately preceding) the specified address * in the given map; the entry is returned * in the "entry" parameter. The boolean * result indicates whether the address is * actually contained in the map. */

 *	actually contained in the map.
 */
boolean_t
vm_map_lookup_entry(
	vm_map_t map,
	vm_offset_t address,
	vm_map_entry_t *entry)	/* OUT */
{
	vm_map_entry_t cur, header, lbound, ubound;
	boolean_t locked;

	/*
	 * If the map is empty, then the map entry immediately preceding
	 * "address" is the map's header.
	 */
	header = &map->header;
	cur = map->root;
	if (cur == NULL) {
		*entry = header;
		return (FALSE);
	}
	if (address >= cur->start && cur->end > address) {
		*entry = cur;
		return (TRUE);
	}
	if ((locked = vm_map_locked(map)) ||
	    sx_try_upgrade(&map->lock)) {
		/*
		 * Splay requires a write lock on the map.  However, it only
		 * restructures the binary search tree; it does not otherwise
		 * change the map.  Thus, the map's timestamp need not change
		 * on a temporary upgrade.
		 */
		cur = vm_map_splay(map, address);
		if (!locked) {
			VM_MAP_UNLOCK_CONSISTENT(map);
			sx_downgrade(&map->lock);
		}

		/*
		 * If "address" is contained within a map entry, the new root
		 * is that map entry.  Otherwise, the new root is a map entry
		 * immediately before or after "address".
		 */
		if (address < cur->start) {
			*entry = header;
			return (FALSE);
		}
		*entry = cur;
		return (address < cur->end);
	}
	/*
	 * Since the map is only locked for read access, perform a
	 * standard binary search tree lookup for "address".
	 */
	lbound = ubound = header;
	for (;;) {
		if (address < cur->start) {
			ubound = cur;
			cur = cur->left;