Index: share/mk/kmod.opts.mk
===================================================================
--- /dev/null
+++ share/mk/kmod.opts.mk
@@ -0,0 +1,20 @@
+# $FreeBSD$
+
+# Search for kernel source tree in standard places.
+.if empty(KERNBUILDDIR)
+.if !defined(SYSDIR)
+.for _dir in ${SRCTOP:D${SRCTOP}/sys} \
+    ${.CURDIR}/../.. ${.CURDIR}/../../.. ${.CURDIR}/../../../.. \
+    ${.CURDIR}/../../../../.. /sys /usr/src/sys
+.if !defined(SYSDIR) && exists(${_dir}/kern/) && exists(${_dir}/conf/kmod.opts.mk)
+SYSDIR=	${_dir:tA}
+.endif
+.endfor
+.endif
+.if !defined(SYSDIR) || !exists(${SYSDIR}/kern/) || \
+    !exists(${SYSDIR}/conf/kmod.opts.mk)
+.error Unable to locate the kernel source tree. Set SYSDIR to override.
+.endif
+.endif
+
+.include "${SYSDIR}/conf/kmod.opts.mk"
Index: sys/conf/kmod.mk
===================================================================
--- sys/conf/kmod.mk
+++ sys/conf/kmod.mk
@@ -73,12 +73,7 @@
 KMODISLOADED?=	/sbin/kldstat -q -n
 OBJCOPY?=	objcopy
 
-.include <bsd.init.mk>
-# Grab all the options for a kernel build. For backwards compat, we need to
-# do this after bsd.own.mk.
-.include "kern.opts.mk"
-.include <bsd.compiler.mk>
-.include "config.mk"
+.include "kmod.opts.mk"
 
 # Search for kernel source tree in standard places.
 .if empty(KERNBUILDDIR)
Index: sys/conf/kmod.opts.mk
===================================================================
--- /dev/null
+++ sys/conf/kmod.opts.mk
@@ -0,0 +1,16 @@
+# $FreeBSD$
+#
+# Handle options (KERN_OPTS) for kernel module options.  This can be included earlier in a kmod Makefile
+# to allow KERN_OPTS to control SRCS, etc.
+
+.if !target(__<kmod.opts.mk>__)
+__<kmod.opts.mk>__:
+
+.include <bsd.init.mk>
+# Grab all the options for a kernel build. For backwards compat, we need to
+# do this after bsd.own.mk.
+.include "kern.opts.mk"
+.include <bsd.compiler.mk>
+.include "config.mk"
+
+.endif #  !target(__<kmod.opts.mk>__)