Linux 内核裁剪的自动化方法

随着广泛地获得使用并被移植到不同的平台，Linux 内核源代码正在越来越大，比如, Linux 2.6.28 中， 文件数有 25282 个，大小有350M。
对于某一个平台，真正需要的的文件其实不到 10%, 为了提高研发效率，我们应当删除或者暂时删除那些永远也不会用到的文件， 比如，可以使内核的文件数缩减到5000， 从而节约拷贝、查找等的时间，提高研发效率。

本文提出一种高效、干净的进行内核裁剪的办法。

以往，我们是通过手工删除某些目录来完成这个任务的。手工删除的缺点有：
花时间，每次裁剪都要花 1 – 2 天， 才能将文件数目删除到 5000 以下。
不够干净。 内核代码的 Makefile 以及 Kconfig 配置文件彼此的依赖性比较大， 即使某个目录下的功能不被使用，直接删除也会导致编译出错， 从而，不得不修改相应的 Makefile 以及 Kconfig 才能使编译通过。 这留下一下隐患。 恢复困难。 根据2）的描述，在我们对外发布完整版本而需要将以前删除、修改的文件复原时，需要使用比较工具，仔细地比对，才能完整恢复， 这也非常花时间。
 
在经历了手工操作的痛苦之后，我们提出了一种自动化的方法。具体为：
只删除文件，不删除目录，保留 Makefile 及 Kconfig
使用时，只需要填充一个配置表，其中，可以指定：
删除某个文件， 比如：drivers/macintosh/adbhid.c
删除某个目录下的匹配文件, 比如：include/asm-arm/hardware/*.h
删除某个目录及其子目录下的匹配文件，比如：drivers/block/#.c
删除某个目录及其子目录下的适合删除文件, 比如：arch/alpha/##
脚本会根据配置表，将相关的文件移动到一备份目录，并保持原有的目录结构
需要恢复时，只需要将备份目录下的文件拷贝到原来的目录，既可。
 
优点如下：
配置文件一次指定，可反复使用， 对同一内核，不需要更改就可以再次运行。对不同内核，只要稍作修改(内核的目录结构不怎么变化)，既可复用。
配置文件指定后，裁剪及备份内核的操作可以在几秒内完成，大大提高的效率。
由于我们只删除 *.c, *.h, *.txt 等文件，而不删除编译相关的配置文件，裁剪后的内核特别干净，不会影响编译。打外部 patch 也特别容易。
需要对外发布版本时，可以直接运行 restore.sh 脚本，瞬间完成。
由于操作的可反复性，我们可以不断优化裁剪列表，得到最小内核。最大程度地提高研发效率。
 
以下为例子配置文件：
############################################################
####################     README      #######################
############################################################
#here to specify which files(unused in your project) to move
#you can specify a relative directory with file name followed
#you can specify
# *.c to mean all c files below the dir
# #.c to mean all c files below the dir and subdir
# ## to mean all files of known type below the dir and subdir
#
# Example:
# drivers/macintosh/adbhid.c
# drivers/dio/*.c
# drivers/block/#.c
# drivers/dio/##
############################################################
##################*kernel version: 2.6.25###################
############################################################
############################################################
########################### arch/###########################
############################################################
arch/alpha/##
arch/avr32/##
arch/blackfin/##
arch/cris/##
arch/frv/##
arch/h8300/##
arch/ia64/##
arch/m32r/##
arch/m68k/##
arch/m68knommu/##
arch/mips/##
arch/mn10300/##
arch/parisc/##
arch/powerpc/##
arch/ppc/##
arch/s390/##
arch/sh/##
arch/sparc/##
arch/sparc64/##
arch/v850/##
arch/x86/##
arch/xtensa/##
############################################################
########################### arch/arm########################
############################################################
arch/arm/mach-s3c2442/##
arch/arm/mach-imx/##
arch/arm/mach-s3c2440/##
arch/arm/mach-omap2/##
arch/arm/mach-clps711x/##
arch/arm/mach-s3c2443/##
arch/arm/plat-iop/##
arch/arm/mach-davinci/##
arch/arm/mach-ixp2000/##
arch/arm/mach-iop13xx/##
arch/arm/mach-integrator/##
arch/arm/mach-iop33x/##
arch/arm/plat-s3c24xx/##
arch/arm/plat-s3c/##
arch/arm/plat-omap/##
arch/arm/mach-sa1100/##
arch/arm/mach-omap1/##
arch/arm/mach-aaec2000/##
arch/arm/mach-ixp23xx/##
arch/arm/mach-mx3/##
arch/arm/mach-l7200/##
arch/arm/mach-ixp4xx/##
arch/arm/mach-at91/##
arch/arm/mach-clps7500/##
arch/arm/mach-rpc/##
arch/arm/mach-s3c2400/##
arch/arm/plat-mxc/##
arch/arm/mach-iop32x/##
arch/arm/mach-footbridge/##
arch/arm/mach-h720x/##
arch/arm/mach-ep93xx/##
arch/arm/mach-ebsa110/##
arch/arm/mach-realview/##
arch/arm/mach-s3c2412/##
arch/arm/mach-ns9xxx/##
arch/arm/mach-orion/##
arch/arm/mach-shark/##
arch/arm/mach-netx/##
arch/arm/mach-pnx4008/##
arch/arm/mach-s3c2410/##
arch/arm/mach-lh7a40x/##
arch/arm/mach-ks8695/##
arch/arm/mach-versatile/##
arch/arm/mach-msm/##
############################################################
########################### Documetation####################
############################################################
Documentation/##
############################################################
########################### drivers ########################
############################################################
drivers/acorn/##
drivers/acpi/##
drivers/amba/##
drivers/ata/##
drivers/atm/##
drivers/auxdisplay/##
drivers/cdrom/##
drivers/dca/##
drivers/dio/##
drivers/edac/##
drivers/eisa/##
drivers/ide/##
drivers/ieee1394/##
drivers/infiniband/##
drivers/isdn/##
drivers/macintosh/##
drivers/mca/##
drivers/md/##
drivers/memstick/##
drivers/nubus/##
drivers/of/##
drivers/parisc/##
drivers/parport/##
drivers/pci/##
drivers/pcmcia/##
drivers/pnp/##
drivers/ps3/##
drivers/rapidio/##
drivers/s390/##
drivers/sbus/##
drivers/sh/##
drivers/sn/##
drivers/ssb/##
drivers/telephony/##
drivers/thermal/##
drivers/w1/##
drivers/xen/##
drivers/zorro/##
############################################################
######################### drivers/char #####################
############################################################
drivers/char/agp/##
drivers/char/mwave/##
drivers/char/pcmcia/##
drivers/char/rio/##
drivers/char/drm/##
############################################################
######################### drivers/net ######################
############################################################
drivers/net/appletalk/##
drivers/net/ibm_emac/##
drivers/net/ibm_newemac/##
drivers/net/ixp2000/##
drivers/net/pcmcia/##
drivers/net/tokenring/##
############################################################
######################### drivers/scsi #####################
############################################################
drivers/scsi/aic7xxx/##
drivers/scsi/aic7xxx_old/##
drivers/scsi/aic94xx/##
drivers/scsi/lpfc/##
drivers/scsi/pcmcia/##
drivers/scsi/qla2xxx/##
drivers/scsi/qla4xxx/##
drivers/scsi/sym53c8xx_2/##
############################################################
######################### drivers/media ####################
############################################################
drivers/media/dvb/##
############################################################
######################### drivers/media/video ##############
############################################################
drivers/media/video/bt8xx/##
drivers/media/video/cpia2/##
drivers/media/video/cx23885/##
drivers/media/video/cx25840/##
drivers/media/video/em28xx/##
drivers/media/video/ivtv/##
drivers/media/video/pvrusb2/##
drivers/media/video/saa7134/##
drivers/media/video/sn9c102/##
drivers/media/video/zc0301/##
############################################################
########################### fs #############################
############################################################
fs/9p/##
fs/afs/##
fs/adfs/##
fs/affs/##
fs/bfs/##
fs/befs/##
fs/coda/##
fs/dlm/##
fs/ext2/##
fs/ext3/##
fs/ext4/##
fs/freevxfs/##
fs/gfs2/##
fs/hfs/##
fs/hfsplus/##
fs/hpfs/##
fs/isofs/##
fs/jbd/##
fs/jbd2/##
fs/jfs/##
fs/minix/##
fs/ntfs/##
fs/ncpfs/##
fs/ocfs2/##
fs/qnx4/##
fs/udf/##
fs/ufs/##
#fs/xfs/##
############################################################
######################## include ###########################
############################################################
include/acpi/##
include/asm-alpha/##
include/asm-avr32/##
include/asm-blackfin/##
include/asm-cris/##
include/asm-frv/##
include/asm-h8300/##
include/asm-ia64/##
include/asm-m32r/##
include/asm-m68k/##
include/asm-m68knommu/##
include/asm-mips/##
include/asm-mn10300/##
include/asm-parisc/##
include/asm-powerpc/##
include/asm-ppc/##
include/asm-s390/##
include/asm-sh/##
include/asm-sparc/##
include/asm-sparc64/##
include/asm-um/##
include/asm-v850/##
#include/asm-x86/##
include/asm-xtensa/##
include/pcmcia/##
############################################################
##################### include/asm-arm ######################
############################################################
include/asm-arm/arch-ks8695/##
include/asm-arm/arch-iop33x/##
include/asm-arm/arch-mxc/##
include/asm-arm/arch-iop32x/##
include/asm-arm/arch-ep93xx/##
include/asm-arm/arch-h720x/##
include/asm-arm/arch-iop13xx/##
include/asm-arm/arch-ns9xxx/##
include/asm-arm/arch-ebsa285/##
include/asm-arm/arch-orion/##
include/asm-arm/arch-ixp2000/##
include/asm-arm/arch-s3c2400/##
include/asm-arm/arch-msm/##
include/asm-arm/arch-ixp4xx/##
include/asm-arm/arch-lh7a40x/##
include/asm-arm/arch-ebsa110/##
include/asm-arm/arch-netx/##
include/asm-arm/arch-imx/##
include/asm-arm/arch-ixp23xx/##
include/asm-arm/arch-davinci/##
include/asm-arm/arch-sa1100/##
include/asm-arm/plat-s3c24xx/##
include/asm-arm/plat-s3c/##
include/asm-arm/arch-l7200/##
include/asm-arm/arch-versatile/##
include/asm-arm/arch-clps711x/##
include/asm-arm/arch-aaec2000/##
include/asm-arm/arch-cl7500/#.h
include/asm-arm/arch-pnx4008/##
include/asm-arm/arch-integrator/##
include/asm-arm/arch-at91/##
include/asm-arm/arch-shark/##
include/asm-arm/arch-rpc/##
include/asm-arm/arch-s3c2410/##
include/asm-arm/arch-realview/##
############################################################
########################### net/###########################
############################################################
net/ax25/##
net/can/##
net/decnet/##
net/ipv6/##
net/x25/##
############################################################
########################### sound/###########################
############################################################
sound/aoa/##
sound/isa/##
sound/mips/##
sound/oss/##
sound/parisc/##
sound/pci/##
sound/pcmcia/##
sound/ppc/##
sound/sh/##
sound/sparc/##

以下为备份脚本：

#! /bin/bash
#name: move.sh
#function: move unused files from kernel to make size smaller
#set -x
function usage()
{
              echo "Usage:" $0 "filename"
              echo " filename is the file that includes files to be deleted"
              echo " if not provided, filename default to to_delete_files"
}
if [ $# -ne "1" ]; then
              INPUT_FILE="to_cutoff_files"
              echo inputfile default to $INPUT_FILE
else
              if [ $1 = "-h" ]; then
                            usage
                            exit 0
              fi
              INPUT_FILE=$1
fi
BASE_ORIG=`cd ..; pwd`/
BASE_NEW=`cd files; pwd`/
FILES_LIST=.${INPUT_FILE}_detailed
rm -f ${FILES_LIST}
#echo "restore files"
#cp -a files/* ../ 2>/dev/null
#rm -rf files/* 2> /dev/null
echo "generate detailed file list..."
cat $INPUT_FILE | grep -v '^#' | while read LINE
do
              if [ ! -z $LINE ]; then
                            if [ `expr index $LINE "##"` != "0" ]; then
                                          DIR_ORIG=${BASE_ORIG}${LINE}
                                          DIR_ORIG=${DIR_ORIG%/*}
                                          find $DIR_ORIG -name *.h  >> ${FILES_LIST}
                                          find $DIR_ORIG -name *.c  >> ${FILES_LIST}
                                          find $DIR_ORIG -name *.S  >> ${FILES_LIST}
                                          find $DIR_ORIG -name *.txt  >> ${FILES_LIST}
                                          find $DIR_ORIG -name *_defconfig  >> ${FILES_LIST}
                            elif [ `expr index $LINE "#"` != "0" ]; then
                                          DIR_ORIG=${BASE_ORIG}${LINE}
                                          DIR_ORIG=${DIR_ORIG%/*}
                                          FILE_EXT=${LINE##*.}
                                          find $DIR_ORIG -name *.${FILE_EXT}  >> ${FILES_LIST}
                            elif [ `expr index $LINE "*"` != "0" ]; then
                                          DIR_ORIG=${BASE_ORIG}${LINE}
                                          DIR_ORIG=${DIR_ORIG%/*}
                                          FILE_EXT=${LINE##*.}
                                          find $DIR_ORIG -name *.${FILE_EXT} -maxdepth 1 >> ${FILES_LIST}
                            else
                                          echo $BASE_ORIG$LINE >> ${FILES_LIST}
                            fi
              fi
done
echo "move files..."
INPUT_FILE=${FILES_LIST}
cat $INPUT_FILE 2>/dev/null | grep -v '^#' | while read LINE
do
              if [ ! $LINE == "" ]; then
                            FILE_ORIG=${LINE}
                            LINE2=${LINE#$BASE_ORIG}
                            FILE_NEW=${BASE_NEW}${LINE2}
                            DIR_NEW=${FILE_NEW%/*}
                            if [ ! -d $DIR_NEW ]; then
                                          mkdir -p $DIR_NEW
                            fi
                            if [ -f $FILE_ORIG ]; then
                                          mv -f $FILE_ORIG $DIR_NEW
                            fi
              fi
done

以下为恢复脚本：

#! /bin/bash
cp -a files/* ../
rm -rf files/*