uboot-Makefile分析(2)

Makefile分析

截取Makefile中主要代码分析：
Makefile：

# load ARCH, BOARD, and CPU configurationinclude $(OBJTREE)/include/config.mk  //包含配置生成的config.mkexportARCH CPU BOARD VENDOR SOCifeq ($(ARCH),arm)//arm架构就用arm-linux-CROSS_COMPILE = arm-linux-endifOBJS  = cpu/$(CPU)/start.o   //目标文件start.o 来源于start.S

/*下面是各种文件夹下目标文件打包起来的库*/

LIBS  = lib_generic/libgeneric.aLIBS += board/$(BOARDDIR)/lib$(BOARD).aLIBS += cpu/$(CPU)/lib$(CPU).aifdef SOCLIBS += cpu/$(CPU)/$(SOC)/lib$(SOC).aendifLIBS += lib_$(ARCH)/lib$(ARCH).aLIBS += fs/cramfs/libcramfs.a fs/fat/libfat.a fs/fdos/libfdos.a fs/jffs2/libjffs2.a \fs/reiserfs/libreiserfs.a fs/ext2/libext2fs.aLIBS += net/libnet.aLIBS += disk/libdisk.aLIBS += rtc/librtc.aLIBS += dtt/libdtt.aLIBS += drivers/libdrivers.aLIBS += drivers/nand/libnand.aLIBS += drivers/nand_legacy/libnand_legacy.aLIBS += drivers/usb/libusb.aLIBS += drivers/sk98lin/libsk98lin.aLIBS += common/libcommon.aLIBS += $(BOARDLIBS)LIBS := $(addprefix $(obj),$(LIBS)).PHONY : $(LIBS)

/*执行make时，目标为ALL，依赖于$(obj)u-boot.bin $(obj)*/
ALL = $(obj)u-boot.srec $(obj)u-boot.bin $(obj)System.map $(U_BOOT_NAND)

all:$(ALL)$(obj)u-boot.hex:$(obj)u-boot$(OBJCOPY) ${OBJCFLAGS} -O ihex $< $@$(obj)u-boot.srec:$(obj)u-boot$(OBJCOPY) ${OBJCFLAGS} -O srec $< $@/*$(obj)u-boot.bin 依赖于 $(obj)u-boot（elf）*/$(obj)u-boot.bin:$(obj)u-boot$(OBJCOPY) ${OBJCFLAGS} -O binary $< $@//elf=》bin$(obj)u-boot.img:$(obj)u-boot.bin./tools/mkimage -A $(ARCH) -T firmware -C none \-a $(TEXT_BASE) -e 0 \-n $(shell sed -n -e 's/.*U_BOOT_VERSION//p' $(VERSION_FILE) | \sed -e 's/"[ ]*$$/ for $(BOARD) board"/') \-d $< $@$(obj)u-boot.dis:$(obj)u-boot  //反汇编文件$(OBJDUMP) -d $< > $@

/*生成$(obj)u-boot 需执行以下命令*/

$(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

来自make之后的产物：
/*通过make得到的最后命令，其等价于上面的看不懂的命令*/

UNDEF_SYM=`arm-linux-objdump -x lib_generic/libgeneric.a board/100ask24x0/lib100ask24x0.a cpu/arm920t/libarm920t.a cpu/arm920t/s3c24x0/libs3c24x0.a lib_arm/libarm.a fs/cramfs/libcramfs.a fs/fat/libfat.a fs/fdos/libfdos.a fs/jffs2/libjffs2.a fs/reiserfs/libreiserfs.a fs/ext2/libext2fs.a net/libnet.a disk/libdisk.a rtc/librtc.a dtt/libdtt.a drivers/libdrivers.a drivers/nand/libnand.a drivers/nand_legacy/libnand_legacy.a drivers/usb/libusb.a drivers/sk98lin/libsk98lin.a common/libcommon.a |sed  -n -e 's/.*\(__u_boot_cmd_.*\)/-u\1/p'|sort|uniq`;\cd /home/neo/linux/u-boot-1.1.6_jz2440 && arm-linux-ld -Bstatic -T /home/neo/linux/u-boot-1.1.6_jz2440/board/100ask24x0/u-boot.lds -Ttext 0x33F80000  \//连接脚本和允许地址$UNDEF_SYM cpu/arm920t/start.o \  //第一个文件 --start-group lib_generic/libgeneric.a board/100ask24x0/lib100ask24x0.a cpu/arm920t/libarm920t.a cpu/arm920t/s3c24x0/libs3c24x0.a lib_arm/libarm.a fs/cramfs/libcramfs.a fs/fat/libfat.a fs/fdos/libfdos.a fs/jffs2/libjffs2.a fs/reiserfs/libreiserfs.a fs/ext2/libext2fs.a net/libnet.a disk/libdisk.a rtc/librtc.a dtt/libdtt.a drivers/libdrivers.a drivers/nand/libnand.a drivers/nand_legacy/libnand_legacy.a drivers/usb/libusb.a drivers/sk98lin/libsk98lin.a common/libcommon.a --end-group -L /usr/local/arm/3.4.5/gcc-3.4.5-glibc-2.3.6/bin/../lib/gcc/arm-linux/3.4.5 -lgcc \ -Map u-boot.map -o u-boot

脚本文件u-boot.lds：

SECTIONS{. = 0x00000000;. = ALIGN(4);.text      :{  cpu/arm920t/start.o(.text)//start.s的代码段          board/100ask24x0/boot_init.o (.text)  //boot_init.s 的代码段  *(.text)                              //其他文件的所有代码段}. = ALIGN(4);.rodata : { *(.rodata) }. = ALIGN(4);.data : { *(.data) }. = ALIGN(4);.got : { *(.got) }. = .;__u_boot_cmd_start = .;        /*专门用来存放命令结构体的段*/.u_boot_cmd : { *(.u_boot_cmd) }__u_boot_cmd_end = .;. = ALIGN(4);__bss_start = .;.bss : { *(.bss) }_end = .;}

总结：
1.u-boot的第一个文件是cpu/arm920t/start.s
        2. 链接脚本为board/100ask24x0/u-boot.lds,运行地址为： 0x00000000+0x33F80000
3.0x33F80000这个值怎么来的：grep "0x33F80000" * -nR 

     显然运行地址是在 board/100ask24x0/config.mk 文件中定义的，以后若想修改运行地址，只需要修改相应处就可以了。