198     srcroot := $(realpath $(KBUILD_EXTMOD))  macro
199     $(if $(srcroot),,$(error specified external module directory "$(KBUILD_EXTMOD)" does not exist))
205 export objtree srcroot
256 srcroot := $(abs_srctree)  macro
259 ifeq ($(srcroot),$(CURDIR))
267 else ifeq ($(srcroot),$(CURDIR))
269     srcroot := .  macro
270 else ifeq ($(srcroot)/,$(dir $(CURDIR)))
272     srcroot := ..  macro
275 export srctree := $(if $(KBUILD_EXTMOD),$(abs_srctree),$(srcroot))
278 export VPATH := $(srcroot)
683 	@if [ -f $(srcroot)/modules.order ]; then \
691 	$(Q)ln -fsn $(srcroot) source
1071 KBUILD_CPPFLAGS += $(call cc-option,-fmacro-prefix-map=$(srcroot)/=)