diff --git a/share/mk/bsd.subdir.mk b/share/mk/bsd.subdir.mk
index 8ca237f6b40a..4a95b5dce031 100644
--- a/share/mk/bsd.subdir.mk
+++ b/share/mk/bsd.subdir.mk
@@ -1,5 +1,5 @@
 #	from: @(#)bsd.subdir.mk	5.9 (Berkeley) 2/1/91
-#	$Id: bsd.subdir.mk,v 1.21 1998/03/23 14:58:29 eivind Exp $
+#	$Id: bsd.subdir.mk,v 1.22 1998/03/26 16:02:44 eivind Exp $
 #
 # The include file <bsd.subdir.mk> contains the default targets
 # for building subdirectories. It has the same seven targets
@@ -20,6 +20,13 @@
 #		Each of the targets will execute the same target in the
 #		subdirectories.
 #
+# SUBDIR_CHANGE A directory-tree that contains overrides for
+#               corresponding build subdirs.
+#		Each override is a file containing one subdirname per line:
+#                  'subdirlist'  is a pure override
+#		   'subdirdrop'  drops directories from the build
+#		   'subdiradd'   adds directories to the build
+#
 # +++ targets +++
 #
 #	distribute:
@@ -34,18 +41,37 @@
 
 .MAIN: all
 
+.if defined(SUBDIR_CHANGE) && !empty(SUBDIR_CHANGE) && \
+	exists(${SUBDIR_CHANGE}/${DIRPRFX}/subdirlist)
+SUBDIR!=cat ${SUBDIR_CHANGE}/${DIRPRFX}/subdirlist
+.endif
+
+.if defined(SUBDIR_CHANGE) && !empty(SUBDIR_CHANGE) && \
+	exists(${SUBDIR_CHANGE}/${DIRPRFX}/subdirlist)
+_SUBDIR_EXTRA!=cat ${SUBDIR_CHANGE}/${DIRPRFX}/subdiradd
+.endif
+
 _SUBDIRUSE: .USE
-	@for entry in ${SUBDIR}; do \
-		(if test -d ${.CURDIR}/$${entry}.${MACHINE}; then \
-			${ECHODIR} "===> ${DIRPRFX}$${entry}.${MACHINE}"; \
-			edir=$${entry}.${MACHINE}; \
-			cd ${.CURDIR}/$${edir}; \
-		else \
-			${ECHODIR} "===> ${DIRPRFX}$$entry"; \
-			edir=$${entry}; \
-			cd ${.CURDIR}/$${edir}; \
-		fi; \
-		${MAKE} ${.TARGET:realinstall=install} DIRPRFX=${DIRPRFX}$$edir/); \
+	@for entry in ${SUBDIR} ${_SUBDIR_EXTRA}; do \
+		(if ! (test -f ${SUBDIR_CHANGE}/${DIRPRFX}/subdirdrop && \
+			grep -w $${entry} \
+			    ${SUBDIR_CHANGE}/${DIRPRFX}/subdirdrop \
+				> /dev/null); then \
+			if test -d ${.CURDIR}/$${entry}.${MACHINE}; then \
+				${ECHODIR} \
+				    "===> ${DIRPRFX}$${entry}.${MACHINE}"; \
+				edir=$${entry}.${MACHINE}; \
+				cd ${.CURDIR}/$${edir}; \
+			else \
+				${ECHODIR} "===> ${DIRPRFX}$$entry"; \
+				edir=$${entry}; \
+				cd ${.CURDIR}/$${edir}; \
+			fi; \
+			${MAKE} ${.TARGET:realinstall=install} \
+				SUBDIR_CHANGE=${SUBDIR_CHANGE} \
+				DIRPRFX=${DIRPRFX}$$edir/; \
+			fi; \
+		); \
 	done
 
 ${SUBDIR}::