uboot 分析之 配置+编译过程

所有的注释都用 # 标示
#第一步：配置 make smdk2410_config ，从这里执行，在Makefile里面找目标##：smdk2410_config。可以自己设置这么一个目标，如mini2440_config

smdk2410_config	:	unconfig  #unconfig前面定义的有。该目标smdk_2410依赖于unconfig目标。
@$(MKCONFIG) $(@:_config=) arm arm920t smdk2410 NULL s3c24x0
#这条命令就是
#       MKCONFIG	:= $(SRCTREE)/mkconfig
#	OBJTREE		:= $(if $(BUILD_DIR),$(BUILD_DIR),$(CURDIR))
#			if函数计算OBJTREE的值，如果BUILD_DIR不为空，if函数的值就是BUILD_DIR，否则是CURDIR.
#	SRCTREE		:= $(CURDIR)	CURDIR是个环境变量。代表当前文件的目录。
#	$(@:_config=) $@是目标smdk2410_config，这里将_config 替换为空。
#	上面的命令可以替换如下
#	@$(CURDIR)/mkconfig smdk2410 arm arm920t smdk2410 NULL s3c24x0

unconfig:		#执行rm -f 命令，将以前的配置信息删除，
#配置文件：include/config.h + config.mk
#	   board/*/config.tmp board/*/*/config.tmp
#	   include/autoconf.mk include/autoconf.mk.dep
@rm -f $(obj)include/config.h $(obj)include/config.mk \
$(obj)board/*/config.tmp $(obj)board/*/*/config.tmp \
$(obj)include/autoconf.mk $(obj)include/autoconf.mk.dep

# $(obj) and (src) are defined in config.mk but here in main Makefile
# we also need them before config.mk is included which is the case for
# some targets like unconfig, clean, clobber, distclean, etc.
ifneq ($(OBJTREE),$(SRCTREE))	#如果 OBJTREE!=SRCTREE，这里人为的指定BUILD_DIR，OBJTREE=$(BUILD_DIR),CURDIR
#是个环境变量，代表当前目录
obj := $(OBJTREE)/		#这时obj 被赋值为OBJTREE
src := $(SRCTREE)/		#src也被赋值为SRCTREE.
else			#这才是没有指定BUILD_TREE编译目录时，OBJTREE=CURDIR,与SRCTREE相等，
obj :=			#obj为空
src :=			#src为空
endif
export obj src		#导出obj src

OBJTREE		:= $(if $(BUILD_DIR),$(BUILD_DIR),$(CURDIR))
SRCTREE		:= $(CURDIR)
TOPDIR		:= $(SRCTREE)
LNDIR		:= $(OBJTREE)
export	TOPDIR SRCTREE OBJTREE

MKCONFIG	:= $(SRCTREE)/mkconfig
export MKCONFIG

第二步：mkconfig文件的执行
这是一个shell脚本文件，主要功能是
1.确定开发板名称
2.创建到平台/开发板相关的头文件的连接
3.创建顶层Makefile包含的include/config.mk文件
4.创建开发板相关的头文件include/config.h
mkconfig文件的内容：
APPEND=no	# Default: Create new config file
BOARD_NAME=""	# Name to print in make output



[ "${BOARD_NAME}" ] || BOARD_NAME="$1"	#BOARD_NAME如果不为空，就不用赋值，如果为空，赋值$1.

#如果变量数目小于4或大于6，就直接退出。否则执行下面的
[ $# -lt 4 ] && exit 1
[ $# -gt 6 ] && exit 1

#打印输出下面这么一句话
echo "Configuring for ${BOARD_NAME} board..."

#
# Create link to architecture specific headers
#

cd ./include #切换到include目录下，删除asm文件，创建新的asm文件，连接指向asm-arm
rm -f asm
ln -s asm-$2 asm

#删除asm-arm920t/arch 目录，为什么？？？
rm -f asm-$2/arch

#如果$6为0 或为空，这里$6=s3c24x0
if [ -z "$6" -o "$6" = "NULL" ] ; then
ln -s ${LNPREFIX}arch-$3 asm-$2/arch
else
ln -s ${LNPREFIX}arch-$6 asm-$2/arch	#ln -s arch-s3c24x0 asm-arm920t/arch
fi


#
# Create include file for Make
#
echo "ARCH   = $2" >  config.mk		#将$2输出到并创建一个文件config.mk
echo "CPU    = $3" >> config.mk		#只是添加到文件中
echo "BOARD  = $4" >> config.mk

[ "$5" ] && [ "$5" != "NULL" ] && echo "VENDOR = $5" >> config.mk

[ "$6" ] && [ "$6" != "NULL" ] && echo "SOC    = $6" >> config.mk

#
# Create board specific header file
#
if [ "$APPEND" = "yes" ]	# Append to existing config file
then
echo >> config.h
else
> config.h		# Create new config file
fi
echo "/* Automatically generated - do not edit */" >>config.h
echo "#include " >>config.h 	#在config.h文件中包含conf#igs/$(board_name).h文件，该文件需要手动创建

exit 0

创建开发板相关的头文件:include/configs/$(board_name).h
该文件存放的是开发板的配置信息，包括两类：
1.选项，前缀为CONFIG_,
2.参数，前缀为CFG_

在mini2440.h文件里添加如下配置：
#define CONFIG_MINI2440    1
#define CONFIG_S3C2440	   1


第三步：make 命令的执行--uboot的编译连接过程

配置完后，执行make命令。
make执行中要用到哪些信息：
1.include $(OBJTREE)/include/config.mk	include目录下的config.mk文件，该文件包含ARCH,CPU,BOARD,VENDOR,SOC信息
2.include $(TOPDIR)/config.mk 	顶层目录下的config.mk文件，该文件根据上面文件中的四个变量，确定了编译器，编译选项等。

$(TOPDIR)/config.mk 的内容：
BOARDDIR = $(BOARD)	#确定了开发板名称，使用参数BOARD，这里是smdk2410，我们可以认为是mini2440

sinclude $(TOPDIR)/board/$(BOARDDIR)/config.mk	# include board specific rules

LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot.lds #本开发的连接脚本，该脚本会向后期的start_armboot函数
#传入一些参数，如__bss_start,_end,__u_boot_cmd_start,
#__u_boot_cmd_end..供C函数调用

LDFLAGS += -Bstatic -T $(LDSCRIPT) $(PLATFORM_LDFLAGS)	#连接选项

在board/mini2440/config.mk文件中，定义了TEXT_BASE = 0x33f80000.

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

OBJS  = cpu/$(CPU)/start.o  #OBJS第一个成员必须是start.o

OBJS := $(addprefix $(obj),$(OBJS))	#添加上前缀，使路径完整

LIBS  = lib_generic/libgeneric.a
LIBS += lib_generic/lzma/liblzma.a
LIBS += $(shell if [ -f board/$(VENDOR)/common/Makefile ]; then echo \	#看文件是否存在。
"board/$(VENDOR)/common/lib$(VENDOR).a"; fi)
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 fs/yaffs2/libyaffs2.a
LIBS += net/libnet.a
LIBS += disk/libdisk.a
LIBS += drivers/bios_emulator/libatibiosemu.a
LIBS += drivers/block/libblock.a
LIBS += drivers/dma/libdma.a
LIBS += drivers/hwmon/libhwmon.a
LIBS += drivers/i2c/libi2c.a
LIBS += drivers/input/libinput.a
LIBS += drivers/misc/libmisc.a
LIBS += drivers/mmc/libmmc.a
LIBS += drivers/mtd/libmtd.a
LIBS += drivers/mtd/nand/libnand.a
LIBS += drivers/mtd/nand_legacy/libnand_legacy.a
LIBS += drivers/mtd/onenand/libonenand.a
LIBS += drivers/mtd/spi/libspi_flash.a
LIBS += drivers/net/libnet.a
LIBS += drivers/net/phy/libphy.a
LIBS += drivers/net/sk98lin/libsk98lin.a
LIBS += drivers/pci/libpci.a
LIBS += drivers/pcmcia/libpcmcia.a
LIBS += drivers/spi/libspi.a

LIBS += drivers/rtc/librtc.a
LIBS += drivers/serial/libserial.a
LIBS += drivers/usb/libusb.a
LIBS += drivers/video/libvideo.a
LIBS += common/libcommon.a
LIBS += libfdt/libfdt.a
LIBS += api/libapi.a
LIBS += post/libpost.a

LIBS := $(addprefix $(obj),$(LIBS))	#也是给LIBS目标添加上完整的路径
.PHONY : $(LIBS) $(VERSION_FILE)


ALL += $(obj)u-boot.srec $(obj)u-boot.bin $(obj)System.map $(U_BOOT_NAND) $(U_BOOT_ONENAND)

all:		$(ALL)

$(obj)u-boot.hex:	$(obj)u-boot
$(OBJCOPY) ${OBJCFLAGS} -O ihex $< $@

$(obj)u-boot.srec:	$(obj)u-boot
$(OBJCOPY) -O srec $< $@

$(obj)u-boot.bin:	$(obj)u-boot
$(OBJCOPY) ${OBJCFLAGS} -O binary $< $@

$(obj)u-boot.ldr:	$(obj)u-boot
$(LDR) -T $(CONFIG_BFIN_CPU) -f -c $@ $< $(LDR_FLAGS)

$(obj)u-boot.ldr.hex:	$(obj)u-boot.ldr
$(OBJCOPY) ${OBJCFLAGS} -O ihex $< $@ -I binary

$(obj)u-boot.ldr.srec:	$(obj)u-boot.ldr
$(OBJCOPY) ${OBJCFLAGS} -O srec $< $@ -I binary

$(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.sha1:	$(obj)u-boot.bin
$(obj)tools/ubsha1 $(obj)u-boot.bin

$(obj)u-boot.dis:	$(obj)u-boot
$(OBJDUMP) -d $< > $@

$(obj)u-boot:		depend $(SUBDIRS) $(OBJS) $(LIBBOARD) $(LIBS) $(LDSCRIPT)
UNDEF_SYM=`$(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-boot

$(OBJS):	depend $(obj)include/autoconf.mk
$(MAKE) -C cpu/$(CPU) $(if $(REMOTE_BUILD),$@,$(notdir $@))
#if函数：
#如果$1为真，计算第二个参数的值，
#并将第二个参数的值作为if函数的值，如果$1为假。
#计算第三个参数的值，如果第三个参数不存在，返回空。
#notdir抽取$@的除路径外的文件名
#上面这条命令，会进入cpu/arm目录下，对OBJS中每个成员进行make,依赖的Makefile是cpu/arm/下的
#该目标OBJS的成员在前面已经添加完毕，这里对每个目标文件进行编译。
#下面LIBS也是同理


depend dep:	$(VERSION_FILE)
for dir in $(SUBDIRS) ; do $(MAKE) -C $$dir _depend ; done
#目标depend dep 依赖于VERSION_FILE
#执行一个for循环，进入目录$dir，执行make命令，产生文件 _depend
#depend文件具体是如何生成，起什么作用。

VERSION_FILE = $(obj)include/version_autogenerated.h

$(LIBS):	depend $(obj)include/autoconf.mk
$(MAKE) -C $(dir $(subst $(obj),,$@))
#dir抽取每一个文件名的路径部分，路径用空格隔开。
#subst,将$@中的每一个$(obj)用空格替换掉。
#切换到不同的路径下编译相应的库文件。

$(LIBBOARD):	depend $(LIBS) $(obj)include/autoconf.mk
$(MAKE) -C $(dir $(subst $(obj),,$@))

$(SUBDIRS):	depend $(obj)include/autoconf.mk
$(MAKE) -C $@ all

$(LDSCRIPT):	depend $(obj)include/autoconf.mk
$(MAKE) -C $(dir $@) $(notdir $@)

$(NAND_SPL):	$(VERSION_FILE)	$(obj)include/autoconf.mk
$(MAKE) -C nand_spl/board/$(BOARDDIR) all

$(U_BOOT_NAND):	$(NAND_SPL) $(obj)u-boot.bin $(obj)include/autoconf.mk
cat $(obj)nand_spl/u-boot-spl-16k.bin $(obj)u-boot.bin > $(obj)u-boot-nand.bin

$(ONENAND_IPL):	$(VERSION_FILE)	$(obj)include/autoconf.mk
$(MAKE) -C onenand_ipl/board/$(BOARDDIR) all

$(U_BOOT_ONENAND):	$(ONENAND_IPL) $(obj)u-boot.bin $(obj)include/autoconf.mk
cat $(obj)onenand_ipl/onenand-ipl-2k.bin $(obj)u-boot.bin > $(obj)u-boot-onenand.bin
cat $(obj)onenand_ipl/onenand-ipl-4k.bin $(obj)u-boot.bin > $(obj)u-boot-flexonenand.bin

$(VERSION_FILE):
@( printf '#define U_BOOT_VERSION "U-Boot %s%s"\n' "$(U_BOOT_VERSION)" \
'$(shell $(CONFIG_SHELL) $(TOPDIR)/tools/setlocalversion $(TOPDIR))' \
) > $@.tmp
@cmp -s $@ $@.tmp && rm -f $@.tmp || mv -f $@.tmp $@