U-boot编译过程

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本文介绍U-Boot编译过程中的关键步骤，包括修改Makefile文件、添加配置文件及生成配置文件等内容。通过具体实例展示了如何为特定硬件平台配置U-Boot。

1，Makefile

在编译U-Boot时，首先执行的就是顶层的Makefile文件，通过顶层的Makefile文件去调用各层子目录下的Makefile文件，最后完成编译。

第一步：修改Makefile

ARCH=arm

CROSS_COMPILE = arm-linux-

2）添加配置文件

zbatp6410_nand_config-ram256 :  unconfig
	@$(MKCONFIG) zbatp6410 arm s3c64xx zbatp6410 samsung s3c6410 NAND ram256

其中unconfig定义如下：

unconfig:
 @rm -f $(obj)include/config.h $(obj)include/config.mk \
  $(obj)board/*/config.tmp $(obj)board/*/*/config.tmp

MKCONFIG定义如下：

 MKCONFIG := $(SRCTREE)/mkconfig

第二步：make zbatp6410_nand_config-ram256，等价于执行了以下语句./mkconfig zbatp6410 arm s3c64xx zbatp6410 samsung s3c6410 NAND ram256执行完改语句后会在include目录下生成config.h和config.mk文件

mkconfig文件

#!/bin/sh -e

# Script to create header files and links to configure
# U-Boot for a specific board.
#
# Parameters:  Target  Architecture  CPU  Board [VENDOR] [SOC]
#
# (C) 2002-2006 DENX Software Engineering, Wolfgang Denk <wd@denx.de>
#

APPEND=no	# Default: Create new config file
BOARD_NAME=""	# Name to print in make output

while [ $# -gt 0 ] ; do
	case "$1" in
	--) shift ; break ;;
	-a) shift ; APPEND=yes ;;
	-n) shift ; BOARD_NAME="${1%%_config}" ; shift ;;
	*)  break ;;
	esac
done

[ "${BOARD_NAME}" ] || BOARD_NAME="$1"

[ $# -lt 4 ] && exit 1
[ $# -gt 8 ] && exit 1

echo "Configuring for ${BOARD_NAME} board which boot from $7 $8..."

#
# Create link to architecture specific headers
#
if [ "$SRCTREE" != "$OBJTREE" ] ; then
	mkdir -p ${OBJTREE}/include
	mkdir -p ${OBJTREE}/include2
	cd ${OBJTREE}/include2
	rm -f asm
	ln -s ${SRCTREE}/include/asm-$2 asm
	LNPREFIX="../../include2/asm/"
	cd ../include
	rm -rf asm-$2
	rm -f asm
	mkdir asm-$2
	ln -s asm-$2 asm
else
	cd ./include
	rm -f asm
	ln -s asm-$2 asm
fi

rm -f asm-$2/arch

if [ -z "$6" -o "$6" = "NULL" ] ; then
	ln -s ${LNPREFIX}arch-$3 asm-$2/arch
else
	ln -s ${LNPREFIX}arch-$6 asm-$2/arch
fi

# create link for s3c24xx SoC
if [ "$3" = "s3c24xx" ] ; then
	rm -f regs.h
	ln -s $6.h regs.h
	rm -f asm-$2/arch
	ln -s arch-$3 asm-$2/arch
fi

# create link for s3c64xx SoC
if [ "$3" = "s3c64xx" ] ; then
	rm -f regs.h
	ln -s $6.h regs.h
	rm -f asm-$2/arch
	ln -s arch-$3 asm-$2/arch
fi

if [ "$2" = "arm" ] ; then
	rm -f asm-$2/proc
	ln -s ${LNPREFIX}proc-armv asm-$2/proc
fi

# create link for s3c64xx-mp SoC
if [ "$3" = "s3c64xx-mp" ] ; then
	rm -f regs.h
	ln -s $6.h regs.h
	rm -f asm-$2/arch
	ln -s arch-$3 asm-$2/arch
fi

#
# Create include file for Make
#
echo "ARCH   = $2" >  config.mk
echo "CPU    = $3" >> config.mk
echo "BOARD  = $4" >> config.mk

[ "$5" ] && [ "$5" != "NULL" ] && echo "VENDOR = $5" >> config.mk

[ "$6" ] && [ "$6" != "NULL" ] && echo "SOC    = $6" >> config.mk

#
# Create board specific header file
#
if [ "$APPEND" = "yes" ]	# Append to existing config file
then
	echo >> config.h
else
	> config.h		# Create new config file
fi
echo "/* Automatically generated - do not edit */" >>config.h
case $7 in
SD)
	echo "#define FRIENDLYARM_BOOT_MEDIA_SD"   >> config.h
	;;
NAND)
	echo "#define FRIENDLYARM_BOOT_MEDIA_NAND" >> config.h
	;;
*)
	;;
esac
case $8 in
ram128)
	echo "#define FRIENDLYARM_BOOT_RAM128" >> config.h
	;;
ram256)
	echo "#define FRIENDLYARM_BOOT_RAM256" >> config.h
	;;
*)
	;;
esac
echo "#include <configs/$1.h>" >>config.h

exit 0

第三步：make执行完成后直接生成u-boot.bin文件