linux-analyze-marginal-sizes

#!/bin/bash

#
# © Copyright 2013 by Geert Uytterhoeven <geert@linux-m68k.org>
#
# This file is subject to the terms and conditions of the GNU General Public
# License.
#

INFO=true

function usage()
{
	cat <<END

	Usage: $(basename $0) [options] [make arguments ...]

	Valid options:
		-h, --help      Display this help
		-k, --keep	Keep vmlinux and System.map for each build
		-v, --verbose   Enable verbose mode

	Make arguments are passed to make, e.g.
		CROSS_COMPILE=m68k-linux-gnu- ARCH=m68k -j 4

	CROSS_COMPILE is also extracted to call the proper size utility.
END
	exit -1
}

function extract_sizes
{
	${CROSS_COMPILE}size vmlinux > sizes || exit -1
	# Extract total
	tail -1 sizes | cut -f 4
}

function save_failure()
{
	for i in $SAVEFILES_FAILURE; do
		mv $i $i.$1;
	done
}

function save_success()
{
	for i in $SAVEFILES_SUCCESS; do
		mv $i $i.$1;
	done
}

SAVEFILES_FAILURE=".config build.log"
SAVEFILES_SUCCESS=".config build.log sizes"

for arg in $*; do
    case $arg in
    -h|--help)
	    usage
	    ;;

    -k|--keep)
	    SAVEFILES_SUCCESS="$SAVEFILES_SUCCESS vmlinux System.map"
	    ;;

    -v|--verbose)
	    INFO=echo
	    ;;

    CROSS_COMPILE=*)
	    CROSS_COMPILE=${arg#CROSS_COMPILE=}
	    # Fall through
	    ;&
    *)
	    MAKEARGS="$MAKEARGS $arg"
	    ;;
    esac
done

MAKE="make $MAKEARGS"

# Disable modules, if enabled
if grep -q '^CONFIG_MODULES=y$' .config; then
	$INFO Disabling modules
	sed -i -e 's/^CONFIG_MODULES=y$/CONFIG_MODULES=n/g' \
	       -e 's/=m$/=n/g' .config
	$MAKE olddefconfig >& /dev/null

	if grep -q '^CONFIG_MODULES=y$' .config; then
		echo CONFIG_MODULES cannot be disabled
		exit -1
	fi
fi

# Build baseline
$INFO Building baseline kernel image
rm -f vmlinux System.map
$MAKE vmlinux >& build.log || exit -1
size=$(extract_sizes)
$INFO Baseline size is $total
save_success baseline

# For all =y options
for option in $(grep '^CONFIG_.*=y$' .config.baseline | sed -e 's/=y$//g'); do
	$INFO Disabling $option
	sed -e "s/^$option=y\$/$option=n/g" < .config.baseline > .config
	$MAKE olddefconfig >& /dev/null

	if grep -q "^$option=y$" .config; then
		echo $option cannot be disabled
		continue
	fi

	rm -f vmlinux System.map
	if ! $MAKE vmlinux >& build.log; then
		echo Build with $option=n failed
		save_failure $option=n
		continue
	fi

	delta=$(($size - $(extract_sizes)))
	echo Disabling $option saves $delta bytes

	save_success $option=n
done