[patch 11/18] kconfig CROSS_COMPILE option

[patch 11/18] kconfig CROSS_COMPILE option

[akpm]

From: Roland McGrath <roland@redhat.com>

This adds CROSS_COMPILE as a kconfig string so you can store it in
.config.  Then you can use plain "make" in the configured kernel build
directory to do the right cross compilation without setting the
command-line or environment variable every time.

With this, you can set up different build directories for different kernel
configurations, whether native or cross-builds, and then use the simple:

	make -C /build/dir M=module-source-dir

idiom to build modules for any given target kernel, indicating which one
by nothing but the build directory chosen.

I tried a version that defaults the string with env="CROSS_COMPILE" so
that in a "make oldconfig" with CROSS_COMPILE in the environment you can
just hit return to store the way you're building it.  But the kconfig
prompt for strings doesn't give you any way to say you want an empty
string instead of the default, so I punted that.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 Makefile     |    4 +++-
 init/Kconfig |    8 ++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff -puN Makefile~kconfig-cross_compile-option Makefile
--- a/Makefile~kconfig-cross_compile-option
+++ a/Makefile
@@ -177,11 +177,13 @@ SUBARCH := $(shell uname -m | sed -e s/i
 # CROSS_COMPILE can be set on the command line
 # make CROSS_COMPILE=ia64-linux-
 # Alternatively CROSS_COMPILE can be set in the environment.
+# A third alternative is to store a setting in .config so that plain
+# "make" in the configured kernel build directory always uses that.
 # Default value for CROSS_COMPILE is not to prefix executables
 # Note: Some architectures assign CROSS_COMPILE in their arch/*/Makefile
 export KBUILD_BUILDHOST := $(SUBARCH)
 ARCH		?= $(SUBARCH)
-CROSS_COMPILE	?=
+CROSS_COMPILE	?= $(CONFIG_CROSS_COMPILE:"%"=%)
 
 # Architecture as present in compile.h
 UTS_MACHINE 	:= $(ARCH)
diff -puN init/Kconfig~kconfig-cross_compile-option init/Kconfig
--- a/init/Kconfig~kconfig-cross_compile-option
+++ a/init/Kconfig
@@ -76,6 +76,14 @@ config INIT_ENV_ARG_LIMIT
 	  variables passed to init from the kernel command line.
 
 
+config CROSS_COMPILE
+	string "Cross-compiler tool prefix"
+	help
+	  Same as running 'make CROSS_COMPILE=prefix-' but stored for
+	  default make runs in this kernel build directory.  You don't
+	  need to set this unless you want the configured kernel build
+	  directory to select the cross-compiler automatically.
+
 config LOCALVERSION
 	string "Local version - append to kernel release"
 	help
_

Re: [patch 11/18] kconfig CROSS_COMPILE option

[Sam Ravnborg]

On Fri, Sep 18, 2009 at 12:49:30PM -0700, akpm@linux-foundation.org wrote:
> From: Roland McGrath <roland@redhat.com>
> 
> This adds CROSS_COMPILE as a kconfig string so you can store it in
> .config.  Then you can use plain "make" in the configured kernel build
> directory to do the right cross compilation without setting the
> command-line or environment variable every time.
> 
> With this, you can set up different build directories for different kernel
> configurations, whether native or cross-builds, and then use the simple:
> 
> 	make -C /build/dir M=module-source-dir
> 
> idiom to build modules for any given target kernel, indicating which one
> by nothing but the build directory chosen.
> 
> I tried a version that defaults the string with env="CROSS_COMPILE" so
> that in a "make oldconfig" with CROSS_COMPILE in the environment you can
> just hit return to store the way you're building it.  But the kconfig
> prompt for strings doesn't give you any way to say you want an empty
> string instead of the default, so I punted that.
> 
> Signed-off-by: Roland McGrath <roland@redhat.com>
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>


I had queued this patch (but for various reasons it had
not hit -next - sigh).
It does not save/restore SUBARCH - but that should
be doable too.

For my testing it works and we save both ARCH and CROSS_COMPILE.

	Sam

commit 07d291e7ad3bff028e7a452e5c2ad66dfdeef146
Author: Sam Ravnborg <sam@ravnborg.org>
Date:   Mon Jul 20 11:49:54 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 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>

diff --git a/Makefile b/Makefile
index 305d005..d46f688 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 	:= $(ARCH)
@@ -446,6 +473,10 @@ ifeq ($(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 $@
@@ -1197,6 +1228,7 @@ 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     \

Re: [patch 11/18] kconfig CROSS_COMPILE option

[Roland McGrath]

Cool.  I had done a hack locally to save ARCH in a different way, but
had not gotten around to finishing it up to submit.  My tack was to
write an include/config/kernel.arch file analogous to kernel.release,
and then use that.  It was about the same as yours I guess, but without
all the fancy sanity checks.  

One thing I'd thought to do in "finishing it up" was to write just the
$ARCH string alone to kernel.arch (then needing a kernel.subarch too)
rather than a makefile fragment.  My thinking is that any scripty things
that would like to look at a given build dir (as in the installed
/lib/modules/foo/build in kernel-devel packages) would like to extract
the arch name as well as the kernel release string, and not necessarily
do it by running make or parsing makeish assignment lines.


Thanks,
Roland

Re: [patch 11/18] kconfig CROSS_COMPILE option

[Sam Ravnborg]

On Sat, Sep 19, 2009 at 05:19:50AM -0700, Roland McGrath wrote:
> 
> One thing I'd thought to do in "finishing it up" was to write just the
> $ARCH string alone to kernel.arch (then needing a kernel.subarch too)
> rather than a makefile fragment.  My thinking is that any scripty things
> that would like to look at a given build dir (as in the installed
> /lib/modules/foo/build in kernel-devel packages) would like to extract
> the arch name as well as the kernel release string, and not necessarily
> do it by running make or parsing makeish assignment lines.

Another approach would be to ask kbuild for
this information so we do not expose various filenames to the
outer world.

Somthing like this:

diff --git a/Makefile b/Makefile
index c41035a..8f488c9 100644
--- a/Makefile
+++ b/Makefile
@@ -1528,6 +1523,12 @@ kernelrelease:
 kernelversion:
 	@echo $(KERNELVERSION)
 
+kernelarch:
+	@echo $(ARCH)
+
+kernelsubarch:
+	@echo $(SUBARCH)
+
 # Single targets
 # ---------------------------------------------------------------------------
 # Single targets are compatible with:

This is analogous to the way we ask for
kernelrelease and kernelversion these days.

	Sam

Re: [patch 11/18] kconfig CROSS_COMPILE option

[Roland McGrath]

> 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.


Thanks,
Roland

Re: [patch 11/18] kconfig CROSS_COMPILE option

[Sam Ravnborg]

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@ravnborg.org>
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@ravnborg.org>
    Cc: Roland McGrath <roland@redhat.com>

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 $@

Re: [patch 11/18] kconfig CROSS_COMPILE option

[Roland McGrath]

> So when I move that file to include/generated I will break users script
> silently - sigh.

It's a possibility.  If so, they will probably have a far easier time
handling a simple change in the location of the file than an entirely
new scheme where there is no simple file that contains the same string.

> Revised patch following your guidelines below.
> Does this look better to you?

Yes, I like it!  I wonder if we might want to treat SUBARCH the same
way, though.  I'm not sure that matters except for the ARCH=um case,
but there I have the impression it has exactly the same utility as
$ARCH otherwise, so it makes sense to me to treat it similarly.


Thanks,
Roland

Re: [patch 11/18] kconfig CROSS_COMPILE option

[Pavel Machek]

Hi!

> > > 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?

Well.. having that option in .config, so it can be easily transported
between trees (as proposed originally) would be even nicer, but I
guess this is better than nothing.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

[patch 11/18] kconfig CROSS_COMPILE option

[akpm]

From: Roland McGrath <roland@redhat.com>

This adds CROSS_COMPILE as a kconfig string so you can store it in
.config.  Then you can use plain "make" in the configured kernel build
directory to do the right cross compilation without setting the
command-line or environment variable every time.

With this, you can set up different build directories for different kernel
configurations, whether native or cross-builds, and then use the simple:

	make -C /build/dir M=module-source-dir

idiom to build modules for any given target kernel, indicating which one
by nothing but the build directory chosen.

I tried a version that defaults the string with env="CROSS_COMPILE" so
that in a "make oldconfig" with CROSS_COMPILE in the environment you can
just hit return to store the way you're building it.  But the kconfig
prompt for strings doesn't give you any way to say you want an empty
string instead of the default, so I punted that.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 Makefile     |    4 +++-
 init/Kconfig |    8 ++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff -puN Makefile~kconfig-cross_compile-option Makefile
--- a/Makefile~kconfig-cross_compile-option
+++ a/Makefile
@@ -177,11 +177,13 @@ SUBARCH := $(shell uname -m | sed -e s/i
 # CROSS_COMPILE can be set on the command line
 # make CROSS_COMPILE=ia64-linux-
 # Alternatively CROSS_COMPILE can be set in the environment.
+# A third alternative is to store a setting in .config so that plain
+# "make" in the configured kernel build directory always uses that.
 # Default value for CROSS_COMPILE is not to prefix executables
 # Note: Some architectures assign CROSS_COMPILE in their arch/*/Makefile
 export KBUILD_BUILDHOST := $(SUBARCH)
 ARCH		?= $(SUBARCH)
-CROSS_COMPILE	?=
+CROSS_COMPILE	?= $(CONFIG_CROSS_COMPILE:"%"=%)
 
 # Architecture as present in compile.h
 UTS_MACHINE 	:= $(ARCH)
diff -puN init/Kconfig~kconfig-cross_compile-option init/Kconfig
--- a/init/Kconfig~kconfig-cross_compile-option
+++ a/init/Kconfig
@@ -76,6 +76,14 @@ config INIT_ENV_ARG_LIMIT
 	  variables passed to init from the kernel command line.
 
 
+config CROSS_COMPILE
+	string "Cross-compiler tool prefix"
+	help
+	  Same as running 'make CROSS_COMPILE=prefix-' but stored for
+	  default make runs in this kernel build directory.  You don't
+	  need to set this unless you want the configured kernel build
+	  directory to select the cross-compiler automatically.
+
 config LOCALVERSION
 	string "Local version - append to kernel release"
 	help
_