diff --git Makefile Makefile
index 7674e608b6bd..5165c7f3cae7 100644
--- Makefile
+++ Makefile
@@ -167,18 +167,6 @@ META_TGT_WHITELIST+= \
 	tinderbox toolchain \
 	toolchains universe world worlds xdev xdev-build
 
-# Likewise for AUTO_OBJ.  Many targets do not need object directories created
-# for each visited directory.  Only when things are being built are they
-# needed.  Having AUTO_OBJ disabled in a build target is fine as it should
-# fallback to running 'make obj' as needed.  If a target is not in this list
-# then it is ran with MK_AUTO_OBJ=no in environment.
-# 'showconfig' is in the list to avoid forcing MK_AUTO_OBJ=no for it.
-AUTO_OBJ_TGT_WHITELIST+= \
-	_* all all-man build* depend everything *toolchain* includes \
-	libraries obj objlink showconfig tags xdev xdev-build native-xtools \
-	stage* create-packages* real-packages sign-packages package-pkg \
-	tinderbox universe* kernel kernels world worlds bmake
-
 .ORDER: buildworld installworld
 .ORDER: buildworld distrib-dirs
 .ORDER: buildworld distribution
@@ -245,7 +233,7 @@ SUB_MAKE= ${MAKE} -m ${.CURDIR}/share/mk
 .endif
 
 _MAKE=	PATH=${PATH} MAKE_CMD="${MAKE}" ${SUB_MAKE} -f Makefile.inc1 \
-	TARGET=${_TARGET} TARGET_ARCH=${_TARGET_ARCH}
+	TARGET=${_TARGET} TARGET_ARCH=${_TARGET_ARCH} ${_MAKEARGS}
 
 .if defined(MK_META_MODE) && ${MK_META_MODE} == "yes"
 # Only allow meta mode for the whitelisted targets.  See META_TGT_WHITELIST
@@ -276,21 +264,6 @@ MK_META_MODE= no
 .endif	# ${MK_META_MODE} == yes
 .endif	# defined(MK_META_MODE) && ${MK_META_MODE} == yes
 
-# Only allow AUTO_OBJ for the whitelisted targets.  See AUTO_OBJ_TGT_WHITELIST
-# above.  MK_AUTO_OBJ not checked here for "yes" as it may not yet be enabled
-# since it is opportunistic.
-.if empty(.MAKEOVERRIDES:MMK_AUTO_OBJ)
-.for _tgt in ${AUTO_OBJ_TGT_WHITELIST}
-.if make(${_tgt})
-_CAN_USE_AUTO_OBJ?= yes
-.endif
-.endfor
-.if !defined(_CAN_USE_AUTO_OBJ)
-_MAKE+=	MK_AUTO_OBJ=no
-MK_AUTO_OBJ= no
-.endif
-.endif	# empty(.MAKEOVERRIDES:MMK_AUTO_OBJ)
-
 # Guess target architecture from target type, and vice versa, based on
 # historic FreeBSD practice of tending to have TARGET == TARGET_ARCH
 # expanding to TARGET == TARGET_CPUARCH in recent times, with known
diff --git Makefile.inc.sys Makefile.inc.sys
new file mode 100644
index 000000000000..30eff1e6a3c4
--- /dev/null
+++ Makefile.inc.sys
@@ -0,0 +1,41 @@
+# $FreeBSD$
+#
+# This is included very early from share/mk/src.sys.env.mk, after
+# /etc/src-env.conf but before /etc/make.conf, /etc/src.conf, or OBJDIR
+# handling.
+# - It is not safe to use .OBJDIR/OBJTOP/OBJROOT here.
+# - __ENV_ONLY_OPTIONS have been parsed by now except for opporutunistic
+#   MK_AUTO_OBJ.
+#
+
+# For AUTO_OBJ many targets do not need object directories created at top-level
+# for each visited directory.  Only when things are being built are they
+# needed.  Having AUTO_OBJ disabled in a build target is fine as it should
+# fallback to running 'make obj' as needed.  If a target is not in this list
+# then it is ran with MK_AUTO_OBJ=no in environment.
+# 'showconfig' is in the list to avoid forcing MK_AUTO_OBJ=no for it.
+AUTO_OBJ_TGT_WHITELIST+= \
+	_* all all-man build* depend everything *toolchain* includes \
+	libraries obj objlink showconfig tags xdev xdev-build native-xtools \
+	stage* create-packages* real-packages sign-packages package-pkg \
+	tinderbox universe* kernel kernels world worlds bmake
+
+# Only allow AUTO_OBJ for the whitelisted targets.  See AUTO_OBJ_TGT_WHITELIST
+# above.  MK_AUTO_OBJ not checked here for "yes" as it may not yet be enabled
+# since it is opportunistic.
+.if empty(.MAKEOVERRIDES:MMK_AUTO_OBJ)
+.for _tgt in ${AUTO_OBJ_TGT_WHITELIST}
+.if make(${_tgt})
+_CAN_USE_AUTO_OBJ?= yes
+.endif
+.endfor
+.if !defined(_CAN_USE_AUTO_OBJ)
+_MAKEARGS+=		MK_AUTO_OBJ=no
+MK_AUTO_OBJ=		no
+# This will prevent src.sys.obj.mk from opportunistically enabling AUTO_OBJ
+# in this make execution and for sub-makes.  For all of these targets we
+# just want to read any existing OBJDIR but we don't care if we can create
+# or write to them.
+.MAKEOVERRIDES+=	MK_AUTO_OBJ
+.endif
+.endif	# empty(.MAKEOVERRIDES:MMK_AUTO_OBJ)
diff --git share/mk/src.sys.env.mk share/mk/src.sys.env.mk
index b100c2ad1429..9c131b2dfe58 100644
--- share/mk/src.sys.env.mk
+++ share/mk/src.sys.env.mk
@@ -44,4 +44,7 @@ MAKESYSPATH:=	${.PARSEDIR:tA}
 .export MAKESYSPATH
 .endif
 
+.if ${RELDIR:U} == "." && ${.MAKE.LEVEL} == 0
+.sinclude "${.CURDIR}/Makefile.inc.sys"
+.endif
 .include <src.sys.obj.mk>
diff --git share/mk/src.sys.obj.mk share/mk/src.sys.obj.mk
index fe15717d4f05..d3d2a32dcb36 100644
--- share/mk/src.sys.obj.mk
+++ share/mk/src.sys.obj.mk
@@ -19,6 +19,12 @@
 #  TARGET.TARGET_ARCH added in as it assumes that MAKEOBJDIRPREFIX is
 #  nested in the existing OBJTOP with TARGET.TARGET_ARCH in it.
 #
+#  The expected OBJDIR is stored in __objdir for auto.obj.mk to use.
+#
+#  AUTO_OBJ is opportunistically enabled if the computed .OBJDIR is writable
+#  by the current user.  Some top-level targets disable this behavior in
+#  Makefile.inc.sys.
+#
 
 _default_makeobjdirprefix?=	/usr/obj
 _default_makeobjdir=	$${.CURDIR:S,^$${SRCTOP},$${OBJTOP},}