Commit ffee0de4 authored by David Woodhouse's avatar David Woodhouse Committed by H. Peter Anvin

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

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: default avatarDavid Woodhouse <>
Link: default avatarH. Peter Anvin <>
parent 29594404
......@@ -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 := $(shell uname -m | sed -e s/i.86/x86/ -e s/x86_64/x86/ \
-e s/sun4u/sparc64/ \
-e s/arm.*/arm/ -e s/sa110/arm/ \
-e s/s390x/s390/ -e s/parisc64/parisc/ \
-e s/ppc.*/powerpc/ -e s/mips.*/mips/ \
# Select 32 or 64 bit
config 64BIT
bool "64-bit kernel" if ARCH = "x86"
default ARCH = "x86_64"
default ARCH != "i386"
Say yes to build a 64-bit kernel - formerly known as x86_64
Say no to build a 32-bit kernel - formerly known as i386
......@@ -2,7 +2,11 @@
# select defconfig based on actual architecture
ifeq ($(ARCH),x86)
ifeq ($(shell uname -m),x86_64)
KBUILD_DEFCONFIG := x86_64_defconfig
KBUILD_DEFCONFIG := i386_defconfig
# CONFIG_64BIT is not set
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