本文主要是介绍Exynos4412 Uboot学习 （一）—— Uboot 编译流程分析，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
一、执行build_uboot.sh脚本
1、./build_uboot.sh POP_1GDDR
1.1、
make itop_4412_android_config_pop_1GDDR （ 进入Makefile 执行）
itop_4412_android_config_pop_1GDDR: unconfig
$(MKCONFIG) $(@:_config=) arm arm_cortexa9 smdkc210 samsung s5pc210 POP_1GDDR
(/home/hjx/work/itop-4412/iTop4412_uboot/mkconfig itop_4412_android_config_pop_1GDDR arm arm_cortexa9 smdkc210 samsung s5pc210 POP_1GDDR)a、完成创建incline/config.mk
ARCH = armCPU = arm_cortexa9BOARD = smdkc210VENDOR = samsungSOC = s5pc210CORE = POP #define CONFIG_POP_1GDDR#define CONFIG_BOARDDIR board/samsung/smdkc210#include <config_defaults.h>#include <configs/itop_4412_android.h>#include <asm/config.h>1.2.1 创建include/autoconf.mk.dep
$(obj)include/autoconf.mk.dep: $(obj)include/config.h include/common.h@$(XECHO) Generating $@ ; \set -e ; \: Generate the dependancies ; \$(CC) -x c -DDO_DEPS_ONLY -M $(HOSTCFLAGS) $(CPPFLAGS) \-MQ $(obj)include/autoconf.mk include/common.h > $@ $(obj)include/autoconf.mk.dep: $(obj)include/config.h include/common.h@$(XECHO) Generating $@ ; \set -e ; \: Generate the dependancies ; \$(CC) -x c -DDO_DEPS_ONLY -M $(HOSTCFLAGS) $(CPPFLAGS) \-MQ $(obj)include/autoconf.mk include/common.h > $@all: $(ALL)
执行u-boot.srec u-boot.bin System.map
ALL += $(obj)u-boot.srec $(obj)u-boot.bin $(obj)System.mapa、--------------------------------------------------------------------$(obj)u-boot.srec: $(obj)u-boot$(OBJCOPY) -O srec $< $@(/usr/local/arm/arm-2009q3/bin/arm-none-linux-gnueabi-objcopy -O srec u-boot u-boot.srec')b、-------------------------------------------------------------------- $(obj)u-boot.bin: $(obj)u-boot$(OBJCOPY) ${OBJCFLAGS} -O binary $< $@(/usr/local/arm/arm-2009q3/bin/arm-none-linux-gnueabi-objcopy --gap-fill=0xff -O binary u-boot u-boot.bin)@split -b 14336 u-boot.bin bl2@+make -C sdfuse_q/@./sdfuse_q/chksum@./sdfuse_q/add_padding@rm bl2a* (./sdfuse_q/chksum 执行结果生成checksum_bl2_14k.binbl2aa file size= 14336B./sdfuse_q/add_paddingbefore padding uboot.bin file size= 249988B85884 B written rm bl2a*)GEN_UBOOT = \UNDEF_SYM=`$(OBJDUMP) -x $(LIBBOARD) $(LIBS) | \sed -n -e 's/.*\($(SYM_PREFIX)__u_boot_cmd_.*\)/-u\1/p'|sort|uniq`;\cd $(LNDIR) && $(LD) $(LDFLAGS) $$UNDEF_SYM $(__OBJS) \--start-group $(__LIBS) --end-group $(PLATFORM_LIBS) \-Map u-boot.map -o u-bootc、-------------------------------------------------------------------- $(obj)u-boot: depend $(SUBDIRS) $(OBJS) $(LIBBOARD) $(LIBS) $(LDSCRIPT) $(obj)u-boot.lds$(GEN_UBOOT)d、--------------------------------------------------------------------depend dep: $(TIMESTAMP_FILE) $(VERSION_FILE) $(obj)include/autoconf.mkfor dir in $(SUBDIRS) cpu/$(CPU) $(dir $(LDSCRIPT)) ; do \$(MAKE) -C $$dir _depend ; donee、-------------------------------------------------------------------- $(OBJS): depend$(MAKE) -C cpu/$(CPU) $(if $(REMOTE_BUILD),$@,$(notdir $@))(make -C cpu/arm_cortexa9 start.o)f、--------------------------------------------------------------------$(LIBS): depend $(SUBDIRS)$(MAKE) -C $(dir $(subst $(obj),,$@)) lib_generic/lzma/liblzma.a lib_generic/lzo/liblzo.acpu/arm_cortexa9/libarm_cortexa9.a cpu/arm_cortexa9/s5pc210/libs5pc210.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 fs/yaffs2/libyaffs2.a fs/ubifs/libubifs.a net/libnet.a disk/libdisk.a drivers/bios_emulator/libatibiosemu.a drivers/block/libblock.a drivers/dma/libdma.a drivers/fpga/libfpga.a drivers/gpio/libgpio.a drivers/hwmon/libhwmon.a drivers/i2c/libi2c.a drivers/input/libinput.a drivers/misc/libmisc.a drivers/mmc/libmmc.a drivers/mtd/libmtd.a drivers/mtd/nand/libnand.a drivers/mtd/onenand/libonenand.a drivers/mtd/ubi/libubi.a drivers/mtd/spi/libspi_flash.a drivers/net/libnet.a drivers/net/phy/libphy.a drivers/pci/libpci.a drivers/pcmcia/libpcmcia.a drivers/power/libpower.a drivers/spi/libspi.a drivers/rtc/librtc.a drivers/serial/libserial.a drivers/twserial/libtws.a drivers/usb/gadget/libusb_gadget.a drivers/usb/host/libusb_host.a drivers/usb/musb/libusb_musb.a drivers/usb/phy/libusb_phy.a drivers/video/libvideo.a drivers/watchdog/libwatchdog.a common/libcommon.alibfdt/libfdt.a api/libapi.a post/libpost.a board/samsung/smdkc210/libsmdkc210.a g、--------------------------------------------------------------------$(LIBBOARD): depend $(LIBS)$(MAKE) -C $(dir $(subst $(obj),,$@))(make -C board/samsung/smdkc210/)h、--------------------------------------------------------------------$(LDSCRIPT): depend$(MAKE) -C $(dir $@) $(notdir $@)(make -C /home/hjx/work/itop-4412/iTop4412_uboot/cpu/arm_cortexa9/ u-boot.lds)i、--------------------------------------------------------------------$(obj)u-boot.lds: $(LDSCRIPT) ($(CPP) $(CPPFLAGS) $(LDPPFLAGS) -ansi -D__ASSEMBLY__ -P - <$^ >$@LDSCRIPT=/home/hjx/work/itop-4412/iTop4412_uboot/cpu/arm_cortexa9/u-boot.ldsCPPFLAGS=-g -Os -fno-common -ffixed-r8 -msoft-float -D__KERNEL__ -DTEXT_BASE=0xc3e00000 -I/home/hjx/work/itop-4412/iTop4412_uboot/include -fno-builtin -ffreestanding -nostdinc -isystem /usr/local/arm/arm-2009q3/bin/../lib/gcc/arm-none-linux-gnueabi/4.4.1/include -pipe -DCONFIG_ARM -D__ARM__ -marm -mabi=aapcs-linux -mno-thumb-interwork -march=armv7-aLDPPFLAGS=-include /home/hjx/work/itop-4412/iTop4412_uboot/include/u-boot/u-boot.lds.h/usr/local/arm/arm-2009q3/bin/arm-none-linux-gnueabi-gcc -E $(CPPFLAGS) $(LDPPFLAGS)-ansi -D__ASSEMBLY__ -P - </home/hjx/work/itop-4412/iTop4412_uboot/cpu/arm_cortexa9/u-boot.lds >u-boot.lds cp -rf checksum_bl2_14k.bin ../CodeSign4SecureBoot_POP/cp -rf u-boot.bin ../CodeSign4SecureBoot_POP/rm checksum_bl2_14k.bin cat E4412.S.BL1.SSCR.EVT1.1.bin E4412.BL2.TZ.SSCR.EVT1.1.bin all00_padding.bin u-boot.bin E4412.TZ.SSCR.EVT1.1.bin > u-boot-iTOP-4412.bin mv u-boot-iTOP-4412.bin $ ./iTop4412_uboot/rm checksum_bl2_14k.binrm u-boot.bin二、
U-Boot 还没有类似Linux一样的可视化配置界面（比如使用 make menuconfig 来配置），要手动修改配置文件 inlucde/config/<board_name>.h 来裁剪、设置U-Boot.
配置文件中有以下两类宏。1) 一类是选项（Options）,前缀为“CONFIG”，它们用于选择CPU、SOC、开发板类型，设置系统时钟、选择设备驱动等。
2）另一类是参数（Setting）,前缀为“CFG_”，它们用于设置malloc缓冲池的大小、U-Boot 下载文件时的默认加载地址、Flash的起始地址等。
三、总结 编译流程：
a -- 首先编译 cpu /$(CPU)/start.S，对于不同的CPU，还可能编译 cpu/$(CPU)下的其他文件；
b -- 然后，对于平台/开发板相关的每个目录、每个通用目录都使用它们个字的Makefile生成相应的库；
c -- 将a、b 步骤生成的.o .a文件按照 board / $(BOARDDIR)/config.mk文件中指定的代码段起始地址、board/$(BOARDDIR)/config.mk文件中指定的代码段起始地址、board/$(BOARDDIR）/U-Boot.lds链接脚本进行链接。
d -- 第c步得到的是ELF格式的U-Boot，后面的Makefile还会将它转换成二进制格式、S-Record格式。
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