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@xxxxxxxxxx>
Reviewed-by: Nicolas Schier <nicolas@xxxxxxxxx>
---
Changes in v2:
- Add -I $(src) -I $(obj) for external modules as well
- Fix a typo 'Speficies' to 'Specifies'.
Documentation/kbuild/kbuild.rst | 8 +++++++-
Documentation/kbuild/modules.rst | 8 +++++++-
Makefile | 22 +++++++++++++++++++---
scripts/Makefile.host | 8 +++-----
scripts/Makefile.lib | 2 --
5 files changed, 36 insertions(+), 12 deletions(-)
diff --git a/Documentation/kbuild/kbuild.rst b/Documentation/kbuild/kbuild.rst
index 1796b3eba37b..17c9f920f03d 100644
--- a/Documentation/kbuild/kbuild.rst
+++ b/Documentation/kbuild/kbuild.rst
@@ -137,12 +137,18 @@ 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 against a pre-built kernel 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 cd5a54d91e6d..a01f3754c7fc 100644
--- a/Documentation/kbuild/modules.rst
+++ b/Documentation/kbuild/modules.rst
@@ -66,7 +66,10 @@ Options
of the kernel output directory if the kernel was built in a separate
build directory.)
- make -C $KDIR M=$PWD
+ You can optionally pass MO= option if you want to build the modules in
+ a separate directory.
+
+ make -C $KDIR M=$PWD [MO=$BUILD_DIR]
-C $KDIR
The directory that contains the kernel and relevant build
@@ -80,6 +83,9 @@ Options
directory where the external module (kbuild file) is
located.
+ MO=$BUILD_DIR
+ Specifies a separate output directory for the external module.
+
Targets
-------
diff --git a/Makefile b/Makefile
index c7eeb10455b6..38ce19747728 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 +191,7 @@ 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.
srcroot := $(realpath $(KBUILD_EXTMOD))
@@ -555,7 +559,7 @@ USERINCLUDE := \
LINUXINCLUDE := \
-I$(srctree)/arch/$(SRCARCH)/include \
-I$(objtree)/arch/$(SRCARCH)/include/generated \
- $(if $(building_out_of_srctree),-I$(srctree)/include) \
+ -I$(srctree)/include \
-I$(objtree)/include \
$(USERINCLUDE)
@@ -645,6 +649,7 @@ quiet_cmd_makefile = GEN Makefile
} > Makefile
outputmakefile:
+ifeq ($(KBUILD_EXTMOD),)
@if [ -f $(srctree)/.config -o \
-d $(srctree)/include/config -o \
-d $(srctree)/arch/$(SRCARCH)/include/generated ]; then \
@@ -654,7 +659,16 @@ outputmakefile:
echo >&2 "***"; \
false; \
fi
- $(Q)ln -fsn $(srctree) source
+else
+ @if [ -f $(srcroot)/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 $(srcroot)) clean'"; \
+ echo >&2 "***"; \
+ false; \
+ fi
+endif
+ $(Q)ln -fsn $(srcroot) source
$(call cmd,makefile)
$(Q)test -e .gitignore || \
{ echo "# this is build directory, ignore it"; echo "*"; } > .gitignore
@@ -1940,6 +1954,8 @@ 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.
diff --git a/scripts/Makefile.host b/scripts/Makefile.host
index e01c13a588dd..c1dedf646a39 100644
--- a/scripts/Makefile.host
+++ b/scripts/Makefile.host
@@ -96,12 +96,10 @@ hostrust_flags = --out-dir $(dir $@) --emit=dep-info=$(depfile) \
$(KBUILD_HOSTRUSTFLAGS) $(HOST_EXTRARUSTFLAGS) \
$(HOSTRUSTFLAGS_$(target-stem))
-# $(objtree)/$(obj) for including generated headers from checkin source files
-ifeq ($(KBUILD_EXTMOD),)
+# $(obj) for including generated headers from checkin source files
ifdef building_out_of_srctree
-hostc_flags += -I $(objtree)/$(obj)
-hostcxx_flags += -I $(objtree)/$(obj)
-endif
+hostc_flags += -I $(obj)
+hostcxx_flags += -I $(obj)
endif
#####
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index e7859ad90224..5660dfc9ed36 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -213,13 +213,11 @@ endif
# $(src) for including checkin headers from generated source files
# $(obj) for including generated headers from checkin source files
-ifeq ($(KBUILD_EXTMOD),)
ifdef building_out_of_srctree
_c_flags += $(addprefix -I, $(src) $(obj))
_a_flags += $(addprefix -I, $(src) $(obj))
_cpp_flags += $(addprefix -I, $(src) $(obj))
endif
-endif
# If $(is-kernel-object) is 'y', this object will be linked to vmlinux or modules
is-kernel-object = $(or $(part-of-builtin),$(part-of-module))
--
2.43.0
