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Commit 57554334 authored by Sam Ravnborg's avatar Sam Ravnborg
Browse files

kbuild: save ARCH & CROSS_COMPILE when building a kernel 



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: default avatarSam Ravnborg <sam@ravnborg.org>
Cc: Roland McGrath <roland@redhat.com>
parent caa27b66

Makefile

+44 −2
Original line number Diff line number Diff line
@@ -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 $@