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Message-ID: <20240917141725.466514-20-masahiroy@kernel.org>
Date: Tue, 17 Sep 2024 23:16:47 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: linux-kbuild@...r.kernel.org
Cc: Miguel Ojeda <ojeda@...nel.org>,
rust-for-linux@...r.kernel.org,
linux-kernel@...r.kernel.org,
Nathan Chancellor <nathan@...nel.org>,
Nicolas Schier <nicolas@...sle.eu>,
Masahiro Yamada <masahiroy@...nel.org>
Subject: [PATCH 19/23] kbuild: support building external modules in a separate build directory
There has been a long-standing request to support building external
modules in a separate build directory.
This commit introduces a new environment variable, KBUILD_EXTMOD_OUTPUT,
and its shorthand Make variable, MO.
A simple usage:
$ make -C <kernel-dir> M=<module-src-dir> MO=<module-build-dir>
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---
Documentation/kbuild/kbuild.rst | 8 +++++-
Documentation/kbuild/modules.rst | 5 +++-
Makefile | 44 +++++++++++++++++++++++---------
3 files changed, 43 insertions(+), 14 deletions(-)
diff --git a/Documentation/kbuild/kbuild.rst b/Documentation/kbuild/kbuild.rst
index 716f6fb70829..66a9dc44ea28 100644
--- a/Documentation/kbuild/kbuild.rst
+++ b/Documentation/kbuild/kbuild.rst
@@ -132,12 +132,18 @@ Specify the output directory when building the kernel.
This variable can also be used to point to the kernel output directory when
building external modules using kernel build artifacts in a separate build
directory. Please note that this does NOT specify the output directory for the
-external modules themselves.
+external modules themselves. (Use KBUILD_EXTMOD_OUTPUT for that purpose.)
The output directory can also be specified using "O=...".
Setting "O=..." takes precedence over KBUILD_OUTPUT.
+KBUILD_EXTMOD_OUTPUT
+--------------------
+Specify the output directory for external modules.
+
+Setting "MO=..." takes precedence over KBUILD_EXTMOD_OUTPUT.
+
KBUILD_EXTRA_WARN
-----------------
Specify the extra build checks. The same value can be assigned by passing
diff --git a/Documentation/kbuild/modules.rst b/Documentation/kbuild/modules.rst
index 3a6e7bdc0889..03347e13eeb5 100644
--- a/Documentation/kbuild/modules.rst
+++ b/Documentation/kbuild/modules.rst
@@ -95,7 +95,7 @@ executed to make module versioning work.
of the kernel output directory if the kernel was built in a separate
build directory.)
- make -C $KDIR M=$PWD
+ make -C $KDIR M=$PWD [MO=$BUILD_DIR]
-C $KDIR
The directory that contains the kernel and relevant build
@@ -109,6 +109,9 @@ executed to make module versioning work.
directory where the external module (kbuild file) is
located.
+ MO=$BUILD_DIR
+ Speficies a separate output directory for the external module.
+
2.3 Targets
===========
diff --git a/Makefile b/Makefile
index 9fbf7ef6e394..b654baa0763a 100644
--- a/Makefile
+++ b/Makefile
@@ -134,6 +134,10 @@ ifeq ("$(origin M)", "command line")
KBUILD_EXTMOD := $(M)
endif
+ifeq ("$(origin MO)", "command line")
+ KBUILD_EXTMOD_OUTPUT := $(MO)
+endif
+
$(if $(word 2, $(KBUILD_EXTMOD)), \
$(error building multiple external modules is not supported))
@@ -187,7 +191,11 @@ ifdef KBUILD_EXTMOD
else
objtree := $(CURDIR)
endif
- output := $(KBUILD_EXTMOD)
+ output := $(or $(KBUILD_EXTMOD_OUTPUT),$(KBUILD_EXTMOD))
+ # KBUILD_EXTMOD might be a relative path. Remember its absolute path before
+ # Make changes the working directory.
+ export abs_extmodtree := $(realpath $(KBUILD_EXTMOD))
+ $(if $(abs_extmodtree),,$(error specified external module directory "$(KBUILD_EXTMOD)" does not exist))
else
objtree := .
output := $(KBUILD_OUTPUT)
@@ -246,7 +254,6 @@ else # need-sub-make
ifeq ($(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
@@ -254,22 +261,23 @@ else
else
srctree := $(abs_srctree)
endif
- building_out_of_srctree := 1
endif
ifneq ($(KBUILD_ABS_SRCTREE),)
srctree := $(abs_srctree)
endif
-VPATH :=
+export srctree
-ifeq ($(KBUILD_EXTMOD),)
-ifdef building_out_of_srctree
-VPATH := $(srctree)
-endif
-endif
+_vpath = $(or $(abs_extmodtree),$(srctree))
-export building_out_of_srctree srctree VPATH
+ifeq ($(realpath $(_vpath)),$(CURDIR))
+building_out_of_srctree :=
+VPATH :=
+else
+export building_out_of_srctree := 1
+export VPATH := $(_vpath)
+endif
# To make sure we do not include .config for any of the *config targets
# catch them early, and hand them over to scripts/kconfig/Makefile
@@ -550,7 +558,7 @@ USERINCLUDE := \
LINUXINCLUDE := \
-I$(srctree)/arch/$(SRCARCH)/include \
-I$(objtree)/arch/$(SRCARCH)/include/generated \
- $(if $(building_out_of_srctree),-I$(srctree)/include) \
+ -I$(srctree)/include \
-I$(objtree)/include \
$(USERINCLUDE)
@@ -640,6 +648,7 @@ quiet_cmd_makefile = GEN Makefile
} > Makefile
outputmakefile:
+ifeq ($(KBUILD_EXTMOD),)
@if [ -f $(srctree)/.config -o \
-d $(srctree)/include/config -o \
-d $(srctree)/arch/$(SRCARCH)/include/generated ]; then \
@@ -649,7 +658,16 @@ outputmakefile:
echo >&2 "***"; \
false; \
fi
- $(Q)ln -fsn $(srctree) source
+else
+ @if [ -f $(KBUILD_EXTMOD)/modules.order ]; then \
+ echo >&2 "***"; \
+ echo >&2 "*** The external module source tree is not clean."; \
+ echo >&2 "*** Please run 'make -C $(abs_srctree) M=$(realpath $(KBUILD_EXTMOD)) clean'"; \
+ echo >&2 "***"; \
+ false; \
+ fi
+endif
+ $(Q)ln -fsn $(_vpath) source
$(call cmd,makefile)
$(Q)test -e .gitignore || \
{ echo "# this is build directory, ignore it"; echo "*"; } > .gitignore
@@ -1926,6 +1944,8 @@ KBUILD_MODULES := 1
endif
+prepare: outputmakefile
+
# Preset locale variables to speed up the build process. Limit locale
# tweaks to this spot to avoid wrong language settings when running
# make menuconfig etc.
--
2.43.0
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