一、分析配置过程(make 100ask24x0_config)
1.执行make 100ask24x0_config配置uboot时,就相当于执行下面红框中的话。
MKCONFIG := $(SRCTREE)/mkconfig/*源文件所在的目录下面找mkconfig*/100ask24x0_config : unconfig @$(MKCONFIG) $(@:_config=) arm arm920t 100ask24x0 NULL s3c24x0/*$,@表示目标是100ask24x0_config, 执行的时候100ask24x0_config替换_config=*/mkconfig 100ask24x0 arm arm920t 100ask24x0 NULL s3c24x0/*执行配置命令就相当于执行这句话*/
2.在目录下找到mkconfig 文件。
/*分析命令传入的参数是否有 -- -a 等。*/while [ $# -gt 0 ] ; docase "$1" in --) shift ; break ;;-a) shift ; APPEND=yes ;;-n) shift ; BOARD_NAME="${1%%_config}" ; shift ;;*) break ;; esac done/*BOARD_NAME是否定义,定义就执行第一句,否则第二句*//*linux脚本中 $表示参数*//*mkconfig 100ask24x0 arm arm920t 100ask24x0 NULL s3c24x0*//* $0 $1 $2 $3 $4 $5 $6*//*执行完下面这句话,相当于 BOARD_NAME = 100ask24x0 */[ "${BOARD_NAME}" ] || BOARD_NAME="$1"/*判断参数的个数,小于4个或者大于6个就退出*/[ $# -lt 4 ] && exit 1[ $# -gt 6 ] && exit 1/*打印这句话*/echo "Configuring for ${BOARD_NAME} board..."/*SRCTREE OBJTREE 两个区是否相等*//*打开makefile文件,可以看到 OBJTREE := $(if $(BUILD_DIR),$(BUILD_DIR),$(CURDIR))是否定义BUILD_DIR,定义的话OBJTREE = BUILD_DIR,否则 OBJTREE = CURDIR。文件中没有定义,所以OBJTREE = CURDIR SRCTREE := $(CURDIR)*//*条件不成立*/if [ "$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 asmelse cd ./include rm -f asm/*ln -s asm-arm asm 建立一个指向asm-arm架构的链接文件*/ ln -s asm-$2 asm fi/*删除 -f asm-$2(arm)/arch*/rm -f asm-$2/arch/*如果第六个参数为空或者为NULL就会执行下面一句话,显然不满足*/if [ -z "$6" -o "$6" = "NULL" ] ; then ln -s ${LNPREFIX}arch-$3 asm-$2/arch/*下面这句话相当于执行 ln -s arch-s3c24x0 asm-arm/arch*//*建立一个指向arch-s3c24x0的链接文件arch*/else ln -s ${LNPREFIX}arch-$6 asm-$2/arch/*如果 "$2" = "arm"相等*//*建立一个一个指向proc-armv的链接文件proc*/if [ "$2" = "arm" ] ; then rm -f asm-$2/proc ln -s ${LNPREFIX}proc-armv asm-$2/proc fi/*生成一个config.mk配置文件,>表示新建一个文件。>>表示把内容追加过去*//*执行完三条语句后,config.mk为下面的内容*//*ARCH=arm CPU = arm920t BOARD = 100ask24x0*/## Create include file for Make# echo "ARCH = $2" > config.mkecho "CPU = $3" >> config.mk echo "BOARD = $4" >> config.mk/*第五个参数存在并且不为NULL,再增加一项内容"VENDOR = $5"。显然不成立*/[ "$5" ] && [ "$5" != "NULL" ] && echo "VENDOR = $5" >> config.mk/*第六个参数存在并且不为NULL,再增加一项内容"SOC= $6" 成立 *//*config.mk中内容*//*ARCH=arm CPU = arm920t BOARD = 100ask24x0 SOC =s3c24x0*/[ "$6" ] && [ "$6" != "NULL" ] && echo "SOC = $6" >> config.mk/*APPEND 不成立*/## Create board specific header file#if [ "$APPEND" = "yes" ] # Append to existing config filethen echo >> config.h/*新建一个config.h*/else> config.h # Create new config file fi/*把信息追加到config.h*//*config.h内容*//* Automatically generated - do not edit *//*#include <configs/100ask24x0.h>*/echo "/* Automatically generated - do not edit */" >>config.h echo "#include <configs/$1.h>" >>config.h
二、编译过程(make命令)
分析makefile
/*包含include 下的config.mk。文件内容如上*/include $(OBJTREE)/include/config.mk/*如果是arm架构,编译工具链arm-linux-*/ifeq ($(ARCH),arm)CROSS_COMPILE = arm-linux-endif/*CPU=arm920t*/OBJS = cpu/$(CPU)/start.o/*BOARD=BOARDDIR=100ask24x0,CPU=arm920t*/LIBS = lib_generic/libgeneric.a LIBS += board/$(BOARDDIR)/lib$(BOARD).a LIBS += cpu/$(CPU)/lib$(CPU).a/*make的时候,如果不指定目标,就是生成all目标*//*all依赖于ALL*//*目的是要生成u-boot.bin*/ALL = $(obj)u-boot.srec $(obj)u-boot.bin $(obj)System.map $(U_BOOT_NAND)all: $(ALL)/*u-boot.bin依赖于u-boot*//*u-boot.bin二进制文件 u-boot elf格式*/$(obj)u-boot.bin: $(obj)u-boot $(OBJCOPY) ${OBJCFLAGS} -O binary $< $@/*u-boot又依赖于下面的文件*/$(obj)u-boot: depend version $(SUBDIRS) $(OBJS) $(LIBS) $(LDSCRIPT) UNDEF_SYM=`$(OBJDUMP) -x $(LIBS) |sed -n -e 's/.*\(__u_boot_cmd_.*\)/-u\1/p'|sort|uniq`;\ cd $(LNDIR) && $(LD) $(LDFLAGS) $$UNDEF_SYM $(__OBJS) \ --start-group $(__LIBS) --end-group $(PLATFORM_LIBS) \ -Map u-boot.map -o u-boot
三、分析结论
1.程序执行的第一个文件 cpu/arm920t/start.s
2.链接地址的定义:board/100ask24x0/u-boot.lds +0x33f80000(config.mk中定义的0x33f80000,修改TEXT_BASE=0x33f80000可以重新定义uboot的起始地址)