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DateMon, 20 Jul 2009 12:01:57 +0200
FromSam Ravnborg <>
Subject[PATCH] kbuild: save ARCH & CROSS_COMPILE when building a kernel
I have tested this locally - but it would
be good if someone with different habits than me try it
out before it hits -next.

So far it works for me.

Last time I tries this it failed in strange ways in different setups.
But I think I have addressed this by postponing the settings to *config
time _after_ including the arch specific makefile.

This patch is a prerequisite for a small serie of patches to clean up
how we handle generated files.

Sam


From 9e27e311540fbe0c31d9cdfe731ad60a54ad1202 Mon Sep 17 00:00:00 2001
From: Sam Ravnborg <sam@ravnborg.org>
Date: Mon, 20 Jul 2009 11:49:54 +0200
Subject: [PATCH] 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 a file named ".kbuild".
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>
---
Makefile | 36 ++++++++++++++++++++++++++++++++++--
1 files changed, 34 insertions(+), 2 deletions(-)
diff --git a/Makefile b/Makefile
index 79957b3..3c95e76 100644
--- a/Makefile
+++ b/Makefile
@@ -179,9 +179,36 @@ 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 .kbuild
+# in the kernel tree - do not patch this file.
export KBUILD_BUILDHOST := $(SUBARCH)
-ARCH ?= $(SUBARCH)
-CROSS_COMPILE ?=
+
+# Kbuild save the ARCH and CROSS_COMPILE setting in .kbuild
+# Restore these settings and check that user did not specify
+# conflicting values.
+ifneq ($(wildcard .kbuild),)
+ -include .kbuild
+ ifneq ($(CROSS_COMPILE),)
+ ifneq ($(CROSS_COMPILE),$(KBUILD_CROSS_COMPILE))
+ $(error CROSS_COMPILE changed from \
+ "$(KBUILD_CROSS_COMPILE)" to \
+ to "$(CROSS_COMPILE)". \
+ Use "make mrproper" to fix it up)
+ endif
+ endif
+ ifneq ($(ARCH),)
+ ifneq ($(KBUILD_ARCH),$(ARCH))
+ $(error ARCH changed from \
+ "$(KBUILD_ARCH)" to "$(ARCH)". \
+ Use "make mrproper" to fix it up)
+ endif
+ endif
+ CROSS_COMPILE := $(KBUILD_CROSS_COMPILE)
+ ARCH := $(KBUILD_ARCH)
+else
+ ARCH ?= $(SUBARCH)
+endif

# Architecture as present in compile.h
UTS_MACHINE := $(ARCH)
@@ -444,6 +471,10 @@ ifeq ($(config-targets),1)
include $(srctree)/arch/$(SRCARCH)/Makefile
export KBUILD_DEFCONFIG KBUILD_KCONFIG

+# save ARCH & CROSS_COMPILE settings
+$(shell (echo KBUILD_ARCH := $(ARCH) && \
+ echo KBUILD_CROSS_COMPILE := $(CROSS_COMPILE)) > .kbuild)
+
config: scripts_basic outputmakefile FORCE
$(Q)mkdir -p include/linux include/config
$(Q)$(MAKE) $(build)=scripts/kconfig $@
@@ -1195,6 +1226,7 @@ CLEAN_FILES += vmlinux System.map \
# Directories & files removed with 'make mrproper'
MRPROPER_DIRS += include/config include2 usr/include include/generated
MRPROPER_FILES += .config .config.old include/asm .version .old_version \
+ .kbuild \
include/linux/autoconf.h include/linux/version.h \
include/linux/utsrelease.h \
include/linux/bounds.h include/asm*/asm-offsets.h \
--
1.6.2.5


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