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kbuild: save ARCH & CROSS_COMPILE when building a kernel

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When building a kernel for a different architecture
kbuild requires the user always to specify ARCH and
CROSS_COMPILE on the command-line.

We use the asm symlink to detect if user forgets to
specify the correct ARCH value - but that symlink
is about to die. And we do now want to loose this check.

This patch save the settings of ARCH and CROSS_COMPILE
in two files named:

    include/generated/kernel.arch
    include/generated/kernel.cross

The settings are saved during "make *config" time
and always read.

If user try to change the settings we error out.

This works both for plain builds and for O=...
builds.

So now you can do:
$ mkdir sparc64
$ make O=sparc64 ARCH=sparc64 CROSS_COMPILE=sparc64-linux- defconfig
$ cd sparc64
$ make

Notice that you no longer need to tell kbuild
the settings of ARCH and CROSS_COMPILE when you type make
in the output directory.

Likewise for plain builds where you do not use O=...

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Roland McGrath <roland@redhat.com>
This commit is contained in:
Sam Ravnborg 2009-09-20 12:24:55 +02:00
parent caa27b66bd
commit 575543347b
1 changed files with 44 additions and 2 deletions
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46
Makefile
View file

@ -179,9 +179,46 @@ SUBARCH := $(shell uname -m | sed -e s/i.86/i386/ -e s/sun4u/sparc64/ \
# Alternatively CROSS_COMPILE can be set in the environment.
# Default value for CROSS_COMPILE is not to prefix executables
# Note: Some architectures assign CROSS_COMPILE in their arch/*/Makefile
#
# To force ARCH and CROSS_COMPILE settings include kernel.* files
# in the kernel tree - do not patch this file.
export KBUILD_BUILDHOST := $(SUBARCH)
ARCH ?= $(SUBARCH)
CROSS_COMPILE ?=
# Kbuild save the ARCH and CROSS_COMPILE setting in kernel.* files.
# Restore these settings and check that user did not specify
# conflicting values.
saved_arch := $(shell cat include/generated/kernel.arch 2> /dev/null)
saved_cross := $(shell cat include/generated/kernel.cross 2> /dev/null)
ifneq ($(CROSS_COMPILE),)
ifneq ($(saved_cross),)
ifneq ($(CROSS_COMPILE),$(saved_cross))
$(error CROSS_COMPILE changed from \
"$(saved_cross)" to \
to "$(CROSS_COMPILE)". \
Use "make mrproper" to fix it up)
endif
endif
else
CROSS_COMPILE := $(saved_cross)
endif
ifneq ($(ARCH),)
ifneq ($(saved_arch),)
ifneq ($(saved_arch),$(ARCH))
$(error ARCH changed from \
"$(saved_arch)" to "$(ARCH)". \
Use "make mrproper" to fix it up)
endif
endif
else
ifneq ($(saved_arch),)
ARCH := $(saved_arch)
else
ARCH := $(SUBARCH)
endif
endif
# Architecture as present in compile.h
UTS_MACHINE := $(ARCH)
@ -446,6 +483,11 @@ ifeq ($(config-targets),1)
include $(srctree)/arch/$(SRCARCH)/Makefile
export KBUILD_DEFCONFIG KBUILD_KCONFIG
# save ARCH & CROSS_COMPILE settings
$(shell mkdir -p include/generated && \
echo $(ARCH) > include/generated/kernel.arch && \
echo $(CROSS_COMPILE) > include/generated/kernel.cross)
config: scripts_basic outputmakefile FORCE
$(Q)mkdir -p include/linux include/config
$(Q)$(MAKE) $(build)=scripts/kconfig $@