u-boot 统述

定义 arm-elf格式文件的布局。

$(TOPDIR)/board/$(BOARDDIR)/u-boot.lds

OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")

/*OUTPUT_FORMAT("elf32-arm", "elf32-arm", "elf32-arm")*/

OUTPUT_ARCH(arm)

ENTRY(_start)

SECTIONS

{

. = 0x00000000;

. = ALIGN(4);

.text :

{

cpu/arm920t/start.o (.text) －－> 可以看出整个程序的入口是start.S的源码

board/open24x0/boot_init.o (.text)

*(.text)

}

...

...

}

Config.mk

LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot.lds

sinclude $(TOPDIR)/$(ARCH)_config.mk # include architecture dependend rules

sinclude $(TOPDIR)/cpu/$(CPU)/config.mk # include CPU specific rules

sinclude $(TOPDIR)/cpu/$(CPU)/$(SOC)/config.mk # include SoC specific rules

sinclude $(TOPDIR)/board/$(BOARDDIR)/config.mk

Makefile

include $(TOPDIR)/config.mk

1. Makefile分析
   VERSION_FILE = $(obj)include/version_autogenerated.h

HOSTARCH=i386

HOSTOS=linux

MKCONFIG := $(SRCTREE)/mkconfig

include $(OBJTREE)/include/config.mk # make xxx_config后内容为配置的内容

export ARCH CPU BOARD VENDOR SOC

CROSS_COMPILE = arm-linux-

include $(TOPDIR)/config.mk

# U-Boot objects....order is important (i.e. start must be first)

OBJS = cpu/$(CPU)/start.o

LIBS = lib_generic/libgeneric.a

LIBS += board/$(BOARDDIR)/lib$(BOARD).a

LIBS += cpu/$(CPU)/lib$(CPU).a

ifdef SOC

LIBS += cpu/$(CPU)/$(SOC)/lib$(SOC).a

endif

LIBS += lib_$(ARCH)/lib$(ARCH).a

LIBS += fs/cramfs/libcramfs.a fs/fat/libfat.a fs/fdos/libfdos.a
fs/jffs2/libjffs2.a fs/reiserfs/libreiserfs.a fs/ext2/libext2fs.a

LIBS += net/libnet.a

LIBS += disk/libdisk.a

LIBS += rtc/librtc.a

LIBS += dtt/libdtt.a

LIBS += drivers/libdrivers.a

LIBS += drivers/nand/libnand.a

LIBS += drivers/nand_legacy/libnand_legacy.a

LIBS += drivers/usb/libusb.a

LIBS += drivers/sk98lin/libsk98lin.a

LIBS += common/libcommon.a

LIBS += $(BOARDLIBS)

LIBS := $(addprefix $(obj),$(LIBS))

xxx_config: unconfig

@echo "#define CONFIG_CPU" >>include/config.h

@echo "#define CONFIG_BOARD" >>include/config.h

@$(MKCONFIG) $(@:_config=) ARCH CPU BOARD VENDOR SOC

@sed -i "s,^TEXT_BASE = .*,TEXT_BASE = (内存的高端地址-足够的运行空间),g" $(obj)board/VENDOR/BOARD/config.mk

@echo "... configured for VENDOR Logic BOARD board"

1. 使用 make xxx_config的时候生成了

   1. include/asm include/asm-arm

   2. include/asm/arch include/asm-arm/arch- CPU

   3. include/config.h

   4. include/config.mk

再次使用Make的时候，Makefile中包含的各项配置文件已经有了