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    Subject[tip:x86/build] x86: Default to ARCH= x86 to avoid overriding CONFIG_64BIT
    Commit-ID:  ffee0de411fd4f74f3b788892eeb075abbf26c52
    Gitweb: http://git.kernel.org/tip/ffee0de411fd4f74f3b788892eeb075abbf26c52
    Author: David Woodhouse <dwmw2@infradead.org>
    AuthorDate: Thu, 20 Dec 2012 21:51:55 +0000
    Committer: H. Peter Anvin <hpa@linux.intel.com>
    CommitDate: Thu, 20 Dec 2012 14:37:18 -0800

    x86: Default to ARCH=x86 to avoid overriding CONFIG_64BIT

    It is easy to waste a bunch of time when one takes a 32-bit .config
    from a test machine and try to build it on a faster 64-bit system, and
    its existing setting of CONFIG_64BIT=n gets *changed* to match the
    build host. Similarly, if one has an existing build tree it is easy
    to trash an entire build tree that way.

    This is because the default setting for $ARCH when discovered from
    'uname' is one of the legacy pre-x86-merge values (i386 or x86_64),
    which effectively force the setting of CONFIG_64BIT to match. We should
    default to ARCH=x86 instead, finally completing the merge that we
    started so long ago.

    This patch preserves the behaviour of the legacy ARCH settings for commands
    such as:

    make ARCH=x86_64 randconfig
    make ARCH=i386 randconfig

    ... since making the value of CONFIG_64BIT actually random in that situation
    is not desirable.

    In time, perhaps we can retire this legacy use of the old ARCH= values.
    We already have a way to override values for *any* config option, using
    $KCONFIG_ALLCONFIG, so it could be argued that we don't necessarily need
    to keep ARCH={i386,x86_64} around as a special case just for overriding
    CONFIG_64BIT.

    We'd probably at least want to add a way to override config options from
    the command line ('make CONFIG_FOO=y oldconfig') before we talk about doing
    that though.

    Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
    Link: http://lkml.kernel.org/r/1356040315.3198.51.camel@shinybook.infradead.org
    Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
    ---
    Makefile | 3 ++-
    arch/x86/Kconfig | 2 +-
    arch/x86/Makefile | 4 ++++
    arch/x86/configs/i386_defconfig | 1 +
    4 files changed, 8 insertions(+), 2 deletions(-)

    diff --git a/Makefile b/Makefile
    index 540f7b2..9a07340 100644
    --- a/Makefile
    +++ b/Makefile
    @@ -165,7 +165,8 @@ export srctree objtree VPATH
    # then ARCH is assigned, getting whatever value it gets normally, and
    # SUBARCH is subsequently ignored.

    -SUBARCH := $(shell uname -m | sed -e s/i.86/i386/ -e s/sun4u/sparc64/ \
    +SUBARCH := $(shell uname -m | sed -e s/i.86/x86/ -e s/x86_64/x86/ \
    + -e s/sun4u/sparc64/ \
    -e s/arm.*/arm/ -e s/sa110/arm/ \
    -e s/s390x/s390/ -e s/parisc64/parisc/ \
    -e s/ppc.*/powerpc/ -e s/mips.*/mips/ \
    diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
    index 46c3bff..9084c7b 100644
    --- a/arch/x86/Kconfig
    +++ b/arch/x86/Kconfig
    @@ -1,7 +1,7 @@
    # Select 32 or 64 bit
    config 64BIT
    bool "64-bit kernel" if ARCH = "x86"
    - default ARCH = "x86_64"
    + default ARCH != "i386"
    ---help---
    Say yes to build a 64-bit kernel - formerly known as x86_64
    Say no to build a 32-bit kernel - formerly known as i386
    diff --git a/arch/x86/Makefile b/arch/x86/Makefile
    index 05afcca..fa981ca 100644
    --- a/arch/x86/Makefile
    +++ b/arch/x86/Makefile
    @@ -2,7 +2,11 @@

    # select defconfig based on actual architecture
    ifeq ($(ARCH),x86)
    + ifeq ($(shell uname -m),x86_64)
    + KBUILD_DEFCONFIG := x86_64_defconfig
    + else
    KBUILD_DEFCONFIG := i386_defconfig
    + endif
    else
    KBUILD_DEFCONFIG := $(ARCH)_defconfig
    endif
    diff --git a/arch/x86/configs/i386_defconfig b/arch/x86/configs/i386_defconfig
    index 5598547..9444708 100644
    --- a/arch/x86/configs/i386_defconfig
    +++ b/arch/x86/configs/i386_defconfig
    @@ -1,3 +1,4 @@
    +# CONFIG_64BIT is not set
    CONFIG_EXPERIMENTAL=y
    # CONFIG_LOCALVERSION_AUTO is not set
    CONFIG_SYSVIPC=y

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