Index: share/mk/bsd.port.mk
===================================================================
--- share/mk/bsd.port.mk
+++ share/mk/bsd.port.mk
@@ -1,6 +1,20 @@
 # $FreeBSD$
 
-PORTSDIR?=	/usr/ports
+.if !defined(PORTSDIR)
+PORTSDIR!=	while :; do						\
+			curdir=`pwd`;					\
+			if [ -f "Mk/bsd.port.mk" ]; then		\
+				echo $$curdir;				\
+				break;					\
+			fi;						\
+			if [ "$$curdir" = "/" ]; then			\
+				echo "/usr/ports";			\
+				break;					\
+			fi;						\
+			cd ..;						\
+		done
+.endif
+
 BSDPORTMK?=	${PORTSDIR}/Mk/bsd.port.mk
 
 # Needed to keep bsd.own.mk from reading in /etc/src.conf