u boot啟動之Makefile結構分析

先進行配置命令：

make	smdk2410_config

在makefile檔案中：

smdk2410_config	:	unconfig
@$(mkconfig) $(@:_config=
) arm arm920t smdk2410 null s3c24x0

因此mkconfig檔案中會傳入如下引數：

#parameters:  	target  	architecture 	 cpu     	 board        [vendor]    	 [soc]
mkconfig smdk2410 arm arm920t smdk2410 null s3c24x0
$0 $1 $2 $3 $4 $5 $6

arch   = arm
cpu = arm920t
board = smdk2410
soc = s3c24x0

/* automatically generated - do not edit */ #include

"

編譯命令：

make

分析頂層makefile：

# load arch, board, and cpu configuration
include $(objtree)
/include/config.mk
export arch cpu board vendor soc..
.ifeq ($(arch)
,arm)
/* arch = arm */
cross_compile = arm-linux-
endif..
.objs = cpu/$(cpu)
/start.o /* cpu = arm920t */..
.libs = lib_generic/libgeneric.a
libs +
= board/$(boarddir)
/lib$(board)
.a /* board = smdk2410 */
libs +
= cpu/$(cpu)
/lib$(cpu)
.a /* cpu = arm920t */..
.all = $(obj)u-boot.srec $(obj)u-boot.bin $(obj)system.map $(u_boot_nand)
all: $(all)..
.$(obj)u-boot.bin: $(obj)u-boot /* 該u-boot為elf格式，u-boot.bin是二進位制格式 */
$(objcopy) $
-o binary $< $@..
.$(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

執行make命令，得到：

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 /work/system/u-boot- 1.1.6 && arm-linux-ld -bstatic -t /work/system/u-boot- 1.1.6 /board/ 100ask24x0/u-boot.lds -ttext 0x33f80000 $undef_sym cpu/arm920t/start.o \ --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/ 4.3.2 /bin/.. /lib/gcc/arm-none-linux-gnueabi/ 4.3.2 /armv4t -lgcc \

-map u-boot.map -o u-boot

text_base = 0x33f80000

/* 若要改變u-boot放的位置，可以改這個位址 */

而該ldflags在頂層目錄的config.mk中定義：

config.mk:
189:ldflags +
=-bstatic -t $(ldscript)
-ttext $(text_base) $(platform_ldflags)

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