[PATCH] kbuild: Allow scripts/* to be cross compiled

[Mark Brown <broonie@kernel.org>]

From: John Rigby <john.rigby@linaro.org>

Cross compiling the binaries in scripts/* is not possible
because various makefiles assume that $(obj)/whatever is
executable on the build host.

This patch introduces a new variable called KBUILD_SCRIPTROOT
that points to script/binaries to use while cross compiling.

Usage:

Build scripts for the build host:
	make O=path/to/buildhost/buildscripts \
		silentoldconfig prepare scripts
Then cross build script for target:
	make O=path/to/target/buildscripts \
		HOSTCC=$CROSS_COMPILE \
		KBUILD_SCRIPTROOT=path/to/buildhost/buildscripts
		silentoldconfig prepare scripts

This patch does not use KBUILD_SCRIPTROOT for all script invocations
it only redefines the following if KBUILD_SCRIPTROOT is defined.

scripts/Makefile.build
	scripts/basic/fixdep --> $(KBUILD_SCRIPTROOT)/scripts/basic/fixdep

scripts/kconfig/Makefile
	$(obj)/conf --> $(KBUILD_SCRIPTROOT)/scripts/kconfig/conf

scripts/mod/Makefile
	$(obj)mk_elfconfig --> $(KBUILD_SCRIPTROOT)/scripts/mod/mk_elfconfig

Signed-off-by: John Rigby <john.rigby@linaro.org>
Signed-off-by: Mark Brown <broonie@linaro.org>
---
 scripts/Kbuild.include   |  6 +++++-
 scripts/Makefile.build   |  6 +++++-
 scripts/kconfig/Makefile | 30 ++++++++++++++++++------------
 scripts/mod/Makefile     | 10 ++++++++--
 4 files changed, 36 insertions(+), 16 deletions(-)

diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 547e15d..09aa90c 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -222,11 +222,15 @@ if_changed = $(if $(strip $(any-prereq) $(arg-check)),                       \
 	$(echo-cmd) $(cmd_$(1));                                             \
 	echo 'cmd_$@ := $(make-cmd)' > $(dot-target).cmd)
 
+ifeq ($(KBUILD_SCRIPTROOT),)
+KBUILD_SCRIPTROOT=.
+endif
+
 # Execute the command and also postprocess generated .d dependencies file.
 if_changed_dep = $(if $(strip $(any-prereq) $(arg-check) ),                  \
 	@set -e;                                                             \
 	$(echo-cmd) $(cmd_$(1));                                             \
-	scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).tmp;\
+	$(KBUILD_SCRIPTROOT)/scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).tmp;\
 	rm -f $(depfile);                                                    \
 	mv -f $(dot-target).tmp $(dot-target).cmd)
 
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index d5d859c..de35192 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -291,13 +291,17 @@ cmd_record_mcount = 						\
 	fi;
 endif
 
+ifeq ($(KBUILD_SCRIPTROOT),)
+KBUILD_SCRIPTROOT=.
+endif
+
 define rule_cc_o_c
 	$(call echo-cmd,checksrc) $(cmd_checksrc)			  \
 	$(call echo-cmd,cc_o_c) $(cmd_cc_o_c);				  \
 	$(cmd_modversions)						  \
 	$(call echo-cmd,record_mcount)					  \
 	$(cmd_record_mcount)						  \
-	scripts/basic/fixdep $(depfile) $@ '$(call make-cmd,cc_o_c)' >    \
+	$(KBUILD_SCRIPTROOT)/scripts/basic/fixdep $(depfile) $@ '$(call make-cmd,cc_o_c)' >    \
 	                                              $(dot-target).tmp;  \
 	rm -f $(depfile);						  \
 	mv -f $(dot-target).tmp $(dot-target).cmd
diff --git a/scripts/kconfig/Makefile b/scripts/kconfig/Makefile
index 844bc9d..c58f912 100644
--- a/scripts/kconfig/Makefile
+++ b/scripts/kconfig/Makefile
@@ -14,6 +14,12 @@ endif
 # We need this, in case the user has it in its environment
 unexport CONFIG_
 
+ifdef KBUILD_SCRIPTROOT
+CONF = $(KBUILD_SCRIPTROOT)/scripts/kconfig/conf
+else
+CONF = $(obj)/conf
+endif
+
 xconfig: $(obj)/qconf
 	$< $(Kconfig)
 
@@ -23,31 +29,31 @@ gconfig: $(obj)/gconf
 menuconfig: $(obj)/mconf
 	$< $(Kconfig)
 
-config: $(obj)/conf
+config: $(CONF)
 	$< --oldaskconfig $(Kconfig)
 
 nconfig: $(obj)/nconf
 	$< $(Kconfig)
 
-oldconfig: $(obj)/conf
+oldconfig: $(CONF)
 	$< --$@ $(Kconfig)
 
-silentoldconfig: $(obj)/conf
+silentoldconfig: $(CONF)
 	$(Q)mkdir -p include/generated
 	$< --$@ $(Kconfig)
 
-localyesconfig localmodconfig: $(obj)/streamline_config.pl $(obj)/conf
+localyesconfig localmodconfig: $(obj)/streamline_config.pl $(CONF)
 	$(Q)mkdir -p include/generated
 	$(Q)perl $< --$@ $(srctree) $(Kconfig) > .tmp.config
 	$(Q)if [ -f .config ]; then 					\
 			cmp -s .tmp.config .config ||			\
 			(mv -f .config .config.old.1;			\
 			 mv -f .tmp.config .config;			\
-			 $(obj)/conf --silentoldconfig $(Kconfig);	\
+			 $(CONF) --silentoldconfig $(Kconfig);	\
 			 mv -f .config.old.1 .config.old)		\
 	else								\
 			mv -f .tmp.config .config;			\
-			$(obj)/conf --silentoldconfig $(Kconfig);	\
+			$(CONF) --silentoldconfig $(Kconfig);	\
 	fi
 	$(Q)rm -f .tmp.config
 
@@ -76,24 +82,24 @@ update-po-config: $(obj)/kxgettext $(obj)/gconf.glade.h
 
 PHONY += allnoconfig allyesconfig allmodconfig alldefconfig randconfig
 
-allnoconfig allyesconfig allmodconfig alldefconfig randconfig: $(obj)/conf
+allnoconfig allyesconfig allmodconfig alldefconfig randconfig: $(CONF)
 	$< --$@ $(Kconfig)
 
 PHONY += listnewconfig olddefconfig oldnoconfig savedefconfig defconfig
 
-listnewconfig olddefconfig: $(obj)/conf
+listnewconfig olddefconfig: $(CONF)
 	$< --$@ $(Kconfig)
 
 # oldnoconfig is an alias of olddefconfig, because people already are dependent
 # on its behavior(sets new symbols to their default value but not 'n') with the
 # counter-intuitive name.
-oldnoconfig: $(obj)/conf
+oldnoconfig: $(CONF)
 	$< --olddefconfig $(Kconfig)
 
-savedefconfig: $(obj)/conf
+savedefconfig: $(CONF)
 	$< --$@=defconfig $(Kconfig)
 
-defconfig: $(obj)/conf
+defconfig: $(CONF)
 ifeq ($(KBUILD_DEFCONFIG),)
 	$< --defconfig $(Kconfig)
 else
@@ -101,7 +107,7 @@ else
 	$(Q)$< --defconfig=arch/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG) $(Kconfig)
 endif
 
-%_defconfig: $(obj)/conf
+%_defconfig: $(CONF)
 	$(Q)$< --defconfig=arch/$(SRCARCH)/configs/$@ $(Kconfig)
 
 # Help text used by make help
diff --git a/scripts/mod/Makefile b/scripts/mod/Makefile
index c11212f..8967d55 100644
--- a/scripts/mod/Makefile
+++ b/scripts/mod/Makefile
@@ -1,6 +1,12 @@
 hostprogs-y	:= modpost mk_elfconfig
 always		:= $(hostprogs-y) empty.o
 
+ifdef KBUILD_SCRIPTROOT
+MKELFCONFIG = $(KBUILD_SCRIPTROOT)/scripts/mod/mk_elfconfig
+else
+MKELFCONFIG = $(obj)/mk_elfconfig
+endif
+
 modpost-objs	:= modpost.o file2alias.o sumversion.o
 
 devicetable-offsets-file := devicetable-offsets.h
@@ -40,9 +46,9 @@ $(obj)/modpost.o $(obj)/file2alias.o $(obj)/sumversion.o: $(obj)/elfconfig.h
 $(obj)/file2alias.o: $(obj)/$(devicetable-offsets-file)
 
 quiet_cmd_elfconfig = MKELF   $@
-      cmd_elfconfig = $(obj)/mk_elfconfig < $< > $@
+      cmd_elfconfig = $(MKELFCONFIG) < $< > $@
 
-$(obj)/elfconfig.h: $(obj)/empty.o $(obj)/mk_elfconfig FORCE
+$(obj)/elfconfig.h: $(obj)/empty.o $(MKELFCONFIG) FORCE
 	$(call if_changed,elfconfig)
 
 targets += elfconfig.h
-- 
1.8.4.rc1