1 files changed, 49 insertions, 33 deletions
diff --git a/Makefile b/Makefile
index cf1d55560ae289..2718d2037f5e69 100644
--- a/Makefile
+++ b/Makefile
@@ -180,7 +180,24 @@ ifeq ("$(origin O)", "command line")
   KBUILD_OUTPUT := $(O)
 endif
 
-output := $(KBUILD_OUTPUT)
+ifdef KBUILD_EXTMOD
+    ifdef KBUILD_OUTPUT
+        objtree := $(realpath $(KBUILD_OUTPUT))
+        $(if $(objtree),,$(error specified kernel directory "$(KBUILD_OUTPUT)" does not exist))
+    else
+        objtree := $(CURDIR)
+    endif
+    output := $(KBUILD_EXTMOD)
+    # KBUILD_EXTMOD might be a relative path. Remember its absolute path before
+    # Make changes the working directory.
+    srcroot := $(realpath $(KBUILD_EXTMOD))
+    $(if $(srcroot),,$(error specified external module directory "$(KBUILD_EXTMOD)" does not exist))
+else
+    objtree := .
+    output := $(KBUILD_OUTPUT)
+endif
+
+export objtree srcroot
 
 # Do we want to change the working directory?
 ifneq ($(output),)
@@ -230,36 +247,34 @@ else # need-sub-make
 
 # We process the rest of the Makefile if this is the final invocation of make
 
-ifeq ($(abs_srctree),$(CURDIR))
-        # building in the source tree
-        srctree := .
-	building_out_of_srctree :=
-else
-        ifeq ($(abs_srctree)/,$(dir $(CURDIR)))
-                # building in a subdirectory of the source tree
-                srctree := ..
-        else
-                srctree := $(abs_srctree)
-        endif
-	building_out_of_srctree := 1
+ifndef KBUILD_EXTMOD
+srcroot := $(abs_srctree)
 endif
 
-ifneq ($(KBUILD_ABS_SRCTREE),)
-srctree := $(abs_srctree)
+ifeq ($(srcroot),$(CURDIR))
+building_out_of_srctree :=
+else
+export building_out_of_srctree := 1
 endif
 
-objtree		:= .
+ifdef KBUILD_ABS_SRCTREE
+    # Do nothing. Use the absolute path.
+else ifeq ($(srcroot),$(CURDIR))
+    # Building in the source.
+    srcroot := .
+else ifeq ($(srcroot)/,$(dir $(CURDIR)))
+    # Building in a subdirectory of the source.
+    srcroot := ..
+endif
 
-VPATH		:=
+export srctree := $(if $(KBUILD_EXTMOD),$(abs_srctree),$(srcroot))
 
-ifeq ($(KBUILD_EXTMOD),)
 ifdef building_out_of_srctree
-VPATH		:= $(srctree)
-endif
+export VPATH := $(srcroot)
+else
+VPATH :=
 endif
 
-export building_out_of_srctree srctree objtree VPATH
-
 # To make sure we do not include .config for any of the *config targets
 # catch them early, and hand them over to scripts/kconfig/Makefile
 # It is allowed to specify more targets when calling make, including
@@ -540,7 +555,7 @@ USERINCLUDE    := \
 LINUXINCLUDE    := \
 		-I$(srctree)/arch/$(SRCARCH)/include \
 		-I$(objtree)/arch/$(SRCARCH)/include/generated \
-		$(if $(building_out_of_srctree),-I$(srctree)/include) \
+		-I$(srctree)/include \
 		-I$(objtree)/include \
 		$(USERINCLUDE)
 
@@ -711,7 +726,7 @@ endif
 # in addition to whatever we do anyway.
 # Just "make" or "make all" shall build modules as well
 
-ifneq ($(filter all modules nsdeps %compile_commands.json clang-%,$(MAKECMDGOALS)),)
+ifneq ($(filter all modules nsdeps compile_commands.json clang-%,$(MAKECMDGOALS)),)
   KBUILD_MODULES := 1
 endif
 
@@ -1107,7 +1122,7 @@ export MODLIB
 
 PHONY += prepare0
 
-export extmod_prefix = $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/)
+export extmod_prefix =
 export MODORDER := $(extmod_prefix)modules.order
 export MODULES_NSDEPS := $(extmod_prefix)modules.nsdeps
 
@@ -1799,14 +1814,10 @@ filechk_kernel.release = echo $(KERNELRELEASE)
 KBUILD_BUILTIN :=
 KBUILD_MODULES := 1
 
-build-dir := $(KBUILD_EXTMOD)
+build-dir := .
 
-compile_commands.json: $(extmod_prefix)compile_commands.json
-PHONY += compile_commands.json
-
-clean-dirs := $(KBUILD_EXTMOD)
-clean: private rm-files := $(KBUILD_EXTMOD)/Module.symvers $(KBUILD_EXTMOD)/modules.nsdeps \
-	$(KBUILD_EXTMOD)/compile_commands.json
+clean-dirs := .
+clean: private rm-files := Module.symvers modules.nsdeps compile_commands.json
 
 PHONY += prepare
 # now expand this into a simple variable to reduce the cost of shell evaluations
@@ -1948,7 +1959,7 @@ $(clean-dirs):
 
 clean: $(clean-dirs)
 	$(call cmd,rmfiles)
-	@find $(or $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE) \
+	@find . $(RCS_FIND_IGNORE) \
 		\( -name '*.[aios]' -o -name '*.rsi' -o -name '*.ko' -o -name '.*.cmd' \
 		-o -name '*.ko.*' \
 		-o -name '*.dtb' -o -name '*.dtbo' \
@@ -1981,7 +1992,12 @@ tags TAGS cscope gtags: FORCE
 PHONY += rust-analyzer
 rust-analyzer:
 	+$(Q)$(CONFIG_SHELL) $(srctree)/scripts/rust_is_available.sh
+ifdef KBUILD_EXTMOD
+# FIXME: external modules must not descend into a sub-directory of the kernel
+	$(Q)$(MAKE) $(build)=$(objtree)/rust src=$(srctree)/rust $@
+else
 	$(Q)$(MAKE) $(build)=rust $@
+endif
 
 # Script to generate missing namespace dependencies
 # ---------------------------------------------------------------------------