On Sat, Sep 19, 2009 at 04:48:23PM -0700, Roland McGrath wrote:
> > Another approach would be to ask kbuild for
> > this information so we do not expose various filenames to the
> > outer world.
>
> For shell scripts and makefiles, running a command like make and retrieving
> its output via pipe is de rigueur. But for some other programs it might be
> substantially less hassle to just read plain files. That's what I was
> thinking, anyway. (I only really think that $ARCH is something that anyone
> would want to fetch before they'd run make anyway, and I guess $SUBARCH in
> the case of ARCH=um, but not $CROSS_COMPILE.)
>
> > This is analogous to the way we ask for
> > kernelrelease and kernelversion these days.
>
> Except that include/config/kernel.release is there for all to see (when
> referring to /lib/modules/.../build directory, e.g.), so perhaps some
> people are in fact using that.
So when I move that file to include/generated I will break users script silently - sigh.
Revised patch following your guidelines below.
Does this look better to you?
Sam
commit 575543347b5baed0ca927cb90ba8807396fe9cc9
Author: Sam Ravnborg <sam@xxxxxxxxxxxx>
Date: Sun Sep 20 12:24:55 2009 +0200
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: Sam Ravnborg <sam@xxxxxxxxxxxx>
Cc: Roland McGrath <roland@xxxxxxxxxx>
diff --git a/Makefile b/Makefile
index 305d005..a45b0a2 100644
--- a/Makefile
+++ b/Makefile
@@ -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 $@
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