[2]real210 uboot_Makefile编译过程分析

上篇文章地址:http://www.jyguagua.com/?p=1042
1:继续上次的分析，编译uboot需要执行如下两条命令：

make smdkv210single_config
make

make smdkv210single_config在上文已经具体分析过了,这里不再分析,本篇重点分析make命令执行之后的结构

2:打开Makefile,我们逐行向下分析,我只贴出重要部分的内容,讲解也在其中注释中:

#查看include目录下是否有config.mk,上一篇博文我们讲了,这个include目录下是生成了config.mk文件的
#内容如下:

#ARCH = arm
#CPU = s5pc11x
#BOARD = smdkc110
#VENDOR = samsung
#SOC = s5pc110

ifeq ($(obj)include/config.mk,$(wildcard $(obj)include/config.mk))

# load ARCH, BOARD, and CPU configuration
# 加载include/config.mk文件
include $(obj)include/config.mk
#将各个变量添加到环境变量里
export ARCH CPU BOARD VENDOR SOC

...

#这里定义了我们的arm平台的交叉编译链
ifeq ($(ARCH),arm)
CROSS_COMPILE = arm-linux-
...

#第一个目标文件
OBJS = cpu/$(CPU)/start.o
...

#加载编译所需要的一些库文件
LIBS = lib_generic/libgeneric.a
LIBS += $(shell if [ -f board/$(VENDOR)/common/Makefile ]; then echo \
"board/$(VENDOR)/common/lib$(VENDOR).a"; fi)
LIBS += cpu/$(CPU)/lib$(CPU).a
ifdef SOC
LIBS += cpu/$(CPU)/$(SOC)/lib$(SOC).a
endif
ifeq ($(CPU),ixp)
LIBS += cpu/ixp/npe/libnpe.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 += 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
....
#我们编译默认从这里开始,我们需要生成u-boot.bin,所以我们看下面u-boot.bin的依赖
ALL += $(obj)u-boot.srec $(obj)u-boot.bin $(obj)System.map $(U_BOOT_NAND) $(U_BOOT_ONENAND) $(obj)u-boot.dis
...
...
#默认make命令从这里开始执行
all: $(ALL)
...
$(obj)u-boot.hex: $(obj)u-boot
$(OBJCOPY) ${OBJCFLAGS} -O ihex $< $@

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

#u-boot.bin依赖u-boot,我们再看u-boot依赖哪里,接着向下分析 
$(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 $< > $@

#我们发现u-boot依赖后面这些内容 
$(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

...
#对各个子目录下的obj,lib文件进行编译
$(OBJS): depend $(obj)include/autoconf.mk
$(MAKE) -C cpu/$(CPU) $(if $(REMOTE_BUILD),$@,$(notdir $@))

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

...

3:上述过程我们分析到了uboot编译的命令如下:

$(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

这一堆命令暂时看不懂,那就先不管具体是怎么样的,暂时不管,可以先编译下,看最后编译输出的内容,然后再倒推去分析,执行make,在最后,我们发现如下:

make[1]: Leaving directory `/root/uboot_smdkv210-8-18/board/samsung/smdkc110'
make -C /root/uboot_smdkv210-8-18/board/samsung/smdkc110/ u-boot.lds
make[1]: Entering directory `/root/uboot_smdkv210-8-18/board/samsung/smdkc110'
make[1]: Nothing to be done for `u-boot.lds'.
make[1]: Leaving directory `/root/uboot_smdkv210-8-18/board/samsung/smdkc110'
UNDEF_SYM=`arm-linux-objdump -x board/samsung/smdkc110/libsmdkc110.a lib_generic/libgeneric.a cpu/s5pc11x/libs5pc11x.a cpu/s5pc11x/s5pc110/libs5pc110.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 drivers/bios_emulator/libatibiosemu.a drivers/block/libblock.a drivers/dma/libdma.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/nand_legacy/libnand_legacy.a drivers/mtd/onenand/libonenand.a drivers/mtd/ubi/libubi.a drivers/mtd/spi/libspi_flash.a drivers/net/libnet.a drivers/net/sk98lin/libsk98lin.a drivers/pci/libpci.a drivers/pcmcia/libpcmcia.a drivers/spi/libspi.a drivers/rtc/librtc.a drivers/serial/libserial.a drivers/usb/libusb.a drivers/video/libvideo.a common/libcommon.a libfdt/libfdt.a api/libapi.a post/libpost.a | \
sed -n -e 's/.*\(__u_boot_cmd_.*\)/-u\1/p'|sort|uniq`;\
cd /root/uboot_smdkv210-8-18 && arm-linux-ld -Bstatic -T /root/uboot_smdkv210-8-18/board/samsung/smdkc110/u-boot.lds -Ttext 0xc3e00000 $UNDEF_SYM cpu/s5pc11x/start.o \
--start-group lib_generic/libgeneric.a cpu/s5pc11x/libs5pc11x.a cpu/s5pc11x/s5pc110/libs5pc110.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 drivers/bios_emulator/libatibiosemu.a drivers/block/libblock.a drivers/dma/libdma.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/nand_legacy/libnand_legacy.a drivers/mtd/onenand/libonenand.a drivers/mtd/ubi/libubi.a drivers/mtd/spi/libspi_flash.a drivers/net/libnet.a drivers/net/sk98lin/libsk98lin.a drivers/pci/libpci.a drivers/pcmcia/libpcmcia.a drivers/spi/libspi.a drivers/rtc/librtc.a drivers/serial/libserial.a drivers/usb/libusb.a drivers/video/libvideo.a common/libcommon.a libfdt/libfdt.a api/libapi.a post/libpost.a board/samsung/smdkc110/libsmdkc110.a --end-group -L /usr/src/arm-2009q3/bin/../lib/gcc/arm-none-linux-gnueabi/4.4.1 -lgcc \
-Map u-boot.map -o u-boot
arm-linux-objcopy --gap-fill=0xff -O srec u-boot u-boot.srec
arm-linux-objcopy --gap-fill=0xff -O binary u-boot u-boot.bin
arm-linux-objdump -d u-boot > u-boot.dis

,根据上面的显示,我们发现最后一部分跟makefile是匹配的,我们可以看到编译的命令具体是什么,我们这个时候可以反推下编译中的命令意思,比如:

cd $(LNDIR) && $(LD) $(LDFLAGS) $$UNDEF_SYM $(__OBJS) \
--start-group $(__LIBS) --end-group $(PLATFORM_LIBS) \
-Map u-boot.map -o u-boot

中的红色部分,这些具体是什么,其实都可以在上面的那堆编译命令行里找到了,比如:

$(LNDIR) = /root/uboot_smdkv210-8-18

$(LD) =  arm-linux-ld

$(LDFLAGS) = -Bstatic -T /root/uboot_smdkv210-8-18/board/samsung/smdkc110/u-boot.lds -Ttext 0xc3e00000

...具体这些在哪些文件里面呢?我们可以通过对uboot源码进行grep分析,可以清楚的看到这些定义在哪个地方,比如我们搜索$(LDFLAGS) 这个定义:

[root@localhost uboot_smdkv210-8-18]# grep "LDFLAGS" * nR
avr32_config.mk:PLATFORM_LDFLAGS += --relax
config.mk:PLATFORM_LDFLAGS =
config.mk:LDFLAGS += -Bstatic -T $(LDSCRIPT) $(PLATFORM_LDFLAGS)
config.mk:LDFLAGS += -Ttext $(TEXT_BASE)
m68k_config.mk:PLATFORM_LDFLAGS += -n
Makefile: cd $(LNDIR) && $(LD) $(LDFLAGS) $$UNDEF_SYM $(__OBJS) \
mips_config.mk:# LDFLAGS_vmlinux += -G 0 -static -n -nostdlib
mips_config.mk:PLATFORM_LDFLAGS += -G 0 -static -n -nostdlib
ppc_config.mk:PLATFORM_LDFLAGS += -n

然后我们可以继续找LDSCRIPT,如下:

[root@localhost uboot_smdkv210-8-18]#grep "LDSCRIPT" * nR
CHANGELOG: Makefile: add target for $(LDSCRIPT)
CHANGELOG: If the $(LDSCRIPT) does not exist (normally it's board/$(BOARD)/u-boot.lds),
CHANGELOG-before-U-Boot-1.1.5: - allow LDSCRIPT override and OBJCFLAGS initialization: change to
CHANGELOG-before-U-Boot-1.1.5: linker script, selected via the LDSCRIPT, make variable, and to
config.mk:ifndef LDSCRIPT
config.mk:#LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot.lds.debug
config.mk:LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot-nand.lds
config.mk:LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot.lds
config.mk:LDFLAGS += -Bstatic -T $(LDSCRIPT) $(PLATFORM_LDFLAGS)
Makefile:$(obj)u-boot: depend $(SUBDIRS) $(OBJS) $(LIBBOARD) $(LIBS) $(LDSCRIPT)
Makefile:$(LDSCRIPT): depend $(obj)include/autoconf.mk

然后我们接着找BOARDDIR:

[root@localhost uboot_smdkv210-8-18]# grep "BOARDDIR" * nR 
CHANGELOG: $(TOPDIR)/board/$(BOARDDIR)/config.tmp
CHANGELOG: $(OBJTREE)/board/$(BOARDDIR)/config.tmp
config.mk:BOARDDIR = $(VENDOR)/$(BOARD)
config.mk:BOARDDIR = $(BOARD)
config.mk:sinclude $(TOPDIR)/board/$(BOARDDIR)/config.mk # include board specific rules
config.mk:#LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot.lds.debug
config.mk:LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot-nand.lds
config.mk:LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot.lds
Makefile:LIBBOARD = board/$(BOARDDIR)/lib$(BOARD).a
Makefile: $(MAKE) -C nand_spl/board/$(BOARDDIR) all
Makefile:# $(MAKE) -C onenand_ipl/board/$(BOARDDIR) all
Makefile:TAG_SUBDIRS += lib_generic board/$(BOARDDIR)

然后这个脚本的地址便是:uboot_smdkv210-8-18/board/samsung/smdkc110/u-boot.lds

然后就这样向下分析,我们便可以知道的更多了,通过这个编译之后链接,我们发现第一个是从cpu/s5pc11x/start.o开始链接的,那么第一个文件也就是cpu/s5pc11x/start.S这个文件了,具体uboot的详细引导启动过程,下次有时间再说.

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