This patch makes kernel cross-compilation little bit easier. After initial configuration no special environment variables are required because default ARCH is saved in .config file:
# make ARCH=arm defconfig # make menuconfig # make To solve chicken and egg problem ARCH is read directly from config file. Signed-off-by: Konstantin Khlebnikov <[email protected]> --- Documentation/kbuild/makefiles.txt | 3 ++- Makefile | 15 ++++++++++----- 2 files changed, 12 insertions(+), 6 deletions(-) diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt index 764f599..92cf95b 100644 --- a/Documentation/kbuild/makefiles.txt +++ b/Documentation/kbuild/makefiles.txt @@ -1365,7 +1365,8 @@ The top Makefile exports the following variables: "arm", or "sparc". Some kbuild Makefiles test $(ARCH) to determine which files to compile. - By default, the top Makefile sets $(ARCH) to be the same as the + By default $(ARCH) is set by option CONFIG_ARCH in .config, + default for it is set by top Makefile to be the same as the host system architecture. For a cross build, a user may override the value of $(ARCH) on the command line: diff --git a/Makefile b/Makefile index 2893d7f..f648405 100644 --- a/Makefile +++ b/Makefile @@ -220,6 +220,8 @@ VPATH := $(srctree)$(if $(KBUILD_EXTMOD),:$(KBUILD_EXTMOD)) export srctree objtree VPATH +KCONFIG_CONFIG ?= .config +export KCONFIG_CONFIG # SUBARCH tells the usermode build what the underlying arch is. That is set # first, and if a usermode build is happening, the "ARCH=um" on the command @@ -242,7 +244,14 @@ SUBARCH := $(shell uname -m | sed -e s/i.86/x86/ -e s/x86_64/x86/ \ # ARCH can be set during invocation of make: # make ARCH=ia64 # Another way is to have ARCH set in the environment. -# The default ARCH is the host where make is executed. +# Usually default value is saved in .config as CONFIG_ARCH. +# If this option is undefined or config file does not exist +# ARCH is set to the host where make is executed. +ifndef ARCH + ARCH := $(shell $(srctree)/scripts/config \ + --file $(KBUILD_OUTPUT)$(KCONFIG_CONFIG) \ + --if-undef "$(SUBARCH)" --state "ARCH") +endif # CROSS_COMPILE specify the prefix used for all executables used # during compilation. Only gcc and related bin-utils executables @@ -254,7 +263,6 @@ SUBARCH := $(shell uname -m | sed -e s/i.86/x86/ -e s/x86_64/x86/ \ # "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 -ARCH ?= $(SUBARCH) CROSS_COMPILE ?= $(CONFIG_CROSS_COMPILE:"%"=%) # Architecture as present in compile.h @@ -293,9 +301,6 @@ endif # Where to locate arch specific headers hdr-arch := $(SRCARCH) -KCONFIG_CONFIG ?= .config -export KCONFIG_CONFIG - # SHELL used by kbuild CONFIG_SHELL := $(shell if [ -x "$$BASH" ]; then echo $$BASH; \ else if [ -x /bin/bash ]; then echo /bin/bash; \ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
