uboot 2011-06 之makefile 分析（二）

接着uboot分析一，回到顶层的makefile文件，在上次的分析中已经提到执行了make xxx_config，那么下一步就是执行make了

make会读取整个的makefile文件，找到第一个要生成的目标作为自己的终极目标。

all:
sinclude $(obj)include/autoconf.mk.dep
sinclude $(obj)include/autoconf.mk

# load ARCH, BOARD, and CPU configuration
include $(obj)include/config.mk
export	ARCH CPU BOARD VENDOR SOC

可以看到all是最后的终极目标：

sinclude 和include的区别在于sinclude 当包含的文件不存在时，不会因为文件不存在导致错误而退出编译，然后包含执行make xxx_config自动生成的include/config.mk文件，导出  ARCH CPU BOARD VENDOR SOC 几个变量的值。

# set default to nothing for native builds
ifeq ($(HOSTARCH),$(ARCH))
CROSS_COMPILE ?=
endif

$HOSTARCH的值为x86，而ARCH是arm，显然不同，CROSS_COMPILE 是指定交叉编译器的，这里是不会用到的，

# load other configuration
include $(TOPDIR)/config.mk

包含顶层目录的config.mk文件

ifndef LDSCRIPT
	#LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot.lds.debug
	ifdef CONFIG_SYS_LDSCRIPT
		# need to strip off double quotes
		LDSCRIPT := $(subst ",,$(CONFIG_SYS_LDSCRIPT))
	endif
endif

LDSCRIPT是未定义的，而CONFIG_SYS_LDSCRIPT也是未定义的，什么也不干。

ifndef LDSCRIPT
	ifeq ($(CONFIG_NAND_U_BOOT),y)
		LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot-nand.lds
		ifeq ($(wildcard $(LDSCRIPT)),)
			LDSCRIPT := $(TOPDIR)/$(CPUDIR)/u-boot-nand.lds
		endif
	endif
	ifeq ($(wildcard $(LDSCRIPT)),)
		LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot.lds
	endif
	ifeq ($(wildcard $(LDSCRIPT)),)
		LDSCRIPT := $(TOPDIR)/$(CPUDIR)/u-boot.lds
	endif
	ifeq ($(wildcard $(LDSCRIPT)),)
$(error could not find linker script)
	endif
endif

其实最后的 LDSCRIPT := $(TOPDIR)/$(CPUDIR)/u-boot.lds，其实LDSCRIPT  = arch/arm/cpu/armv7/u-boot.lds

OBJS  = $(CPUDIR)/start.o
ifeq ($(CPU),x86)
OBJS += $(CPUDIR)/start16.o
OBJS += $(CPUDIR)/resetvec.o
endif
ifeq ($(CPU),ppc4xx)
OBJS += $(CPUDIR)/resetvec.o
endif
ifeq ($(CPU),mpc85xx)
OBJS += $(CPUDIR)/resetvec.o
endif

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

CPUDIR在顶层的config.mk文件中定义，OBJS = arch/arm/cpu/armv7/start.o,，然后在OBJS 加前缀，此时，$obj 在config.mk文件中定义,

LIBS  = lib/libgeneric.o
LIBS += lib/lzma/liblzma.o
LIBS += lib/lzo/liblzo.o
LIBS += lib/zlib/libz.o
LIBS += $(shell if [ -f board/$(VENDOR)/common/Makefile ]; then echo \
	"board/$(VENDOR)/common/lib$(VENDOR).o"; fi)
LIBS += $(CPUDIR)/lib$(CPU).o
ifdef SOC
LIBS += $(CPUDIR)/$(SOC)/lib$(SOC).o
endif
ifeq ($(CPU),ixp)
LIBS += arch/arm/cpu/ixp/npe/libnpe.o
endif
LIBS += arch/$(ARCH)/lib/lib$(ARCH).o
LIBS += fs/cramfs/libcramfs.o fs/fat/libfat.o fs/fdos/libfdos.o fs/jffs2/libjffs2.o \
	fs/reiserfs/libreiserfs.o fs/ext2/libext2fs.o fs/yaffs2/libyaffs2.o \
	fs/ubifs/libubifs.o
LIBS += net/libnet.o
LIBS += disk/libdisk.o
LIBS += drivers/bios_emulator/libatibiosemu.o
LIBS += drivers/block/libblock.o
LIBS += drivers/dma/libdma.o
LIBS += drivers/fpga/libfpga.o
LIBS += drivers/gpio/libgpio.o
LIBS += drivers/hwmon/libhwmon.o
LIBS += drivers/i2c/libi2c.o
LIBS += drivers/input/libinput.o
LIBS += drivers/misc/libmisc.o
LIBS += drivers/mmc/libmmc.o
LIBS += drivers/mtd/libmtd.o
LIBS += drivers/mtd/nand/libnand.o
LIBS += drivers/mtd/onenand/libonenand.o
LIBS += drivers/mtd/ubi/libubi.o
LIBS += drivers/mtd/spi/libspi_flash.o
LIBS += drivers/net/libnet.o
LIBS += drivers/net/phy/libphy.o
LIBS += drivers/pci/libpci.o
LIBS += drivers/pcmcia/libpcmcia.o
LIBS += drivers/power/libpower.o
LIBS += drivers/spi/libspi.o
ifeq ($(CPU),mpc83xx)
LIBS += drivers/qe/libqe.o
LIBS += arch/powerpc/cpu/mpc8xxx/lib8xxx.o
endif
ifeq ($(CPU),mpc85xx)
LIBS += drivers/qe/libqe.o
LIBS += arch/powerpc/cpu/mpc8xxx/ddr/libddr.o
LIBS += arch/powerpc/cpu/mpc8xxx/lib8xxx.o
endif
ifeq ($(CPU),mpc86xx)
LIBS += arch/powerpc/cpu/mpc8xxx/ddr/libddr.o
LIBS += arch/powerpc/cpu/mpc8xxx/lib8xxx.o
endif
LIBS += drivers/rtc/librtc.o
LIBS += drivers/serial/libserial.o
LIBS += drivers/twserial/libtws.o
LIBS += drivers/usb/eth/libusb_eth.o
LIBS += drivers/usb/gadget/libusb_gadget.o
LIBS += drivers/usb/host/libusb_host.o
LIBS += drivers/usb/musb/libusb_musb.o
LIBS += drivers/usb/phy/libusb_phy.o
LIBS += drivers/video/libvideo.o
LIBS += drivers/watchdog/libwatchdog.o
LIBS += common/libcommon.o
LIBS += lib/libfdt/libfdt.o
LIBS += api/libapi.o
LIBS += post/libpost.o

ifeq ($(SOC),omap3)
LIBS += $(CPUDIR)/omap-common/libomap-common.o
endif
ifeq ($(SOC),omap4)
LIBS += $(CPUDIR)/omap-common/libomap-common.o
endif

ifeq ($(SOC),s5pc1xx)
LIBS += $(CPUDIR)/s5p-common/libs5p-common.o
endif
ifeq ($(SOC),s5pc2xx)
LIBS += $(CPUDIR)/s5p-common/libs5p-common.o
endif

LIBS := $(addprefix $(obj),$(sort $(LIBS)))
.PHONY : $(LIBS) $(TIMESTAMP_FILE)

加了一堆基本的库文件和根据所选的CPU的类型选择性的加载了一些库文件。

LIBBOARD = board/$(BOARDDIR)/lib$(BOARD).o
LIBBOARD := $(addprefix $(obj),$(LIBBOARD))


# Add GCC lib
ifdef USE_PRIVATE_LIBGCC
ifeq ("$(USE_PRIVATE_LIBGCC)", "yes")
PLATFORM_LIBGCC = $(OBJTREE)/arch/$(ARCH)/lib/libgcc.o
else
PLATFORM_LIBGCC = -L $(USE_PRIVATE_LIBGCC) -lgcc
endif
else
PLATFORM_LIBGCC = -L $(shell dirname `$(CC) $(CFLAGS) -print-libgcc-file-name`) -lgcc
endif
PLATFORM_LIBS += $(PLATFORM_LIBGCC)
export PLATFORM_LIBS

用sourceinsight搜索了一下 USE_PRIVATE_LIBGCC 

根本没有定义，PLATFORM_LIBGCC = -L $(shell dirname `$(CC) $(CFLAGS) -print-libgcc-file-name`) -lgcc

PLATFORM_LIBS += $(PLATFORM_LIBGCC)

# Special flags for CPP when processing the linker script.
# Pass the version down so we can handle backwards compatibility
# on the fly.
LDPPFLAGS += \
	-include $(TOPDIR)/include/u-boot/u-boot.lds.h \
	$(shell $(LD) --version | \
	  sed -ne 's/GNU ld version \([0-9][0-9]*\)\.\([0-9][0-9]*\).*/-DLD_MAJOR=\1 -DLD_MINOR=\2/p')

__OBJS := $(subst $(obj),,$(OBJS))
__LIBS := $(subst $(obj),,$(LIBS)) $(subst $(obj),,$(LIBBOARD))

看一下英文注释就知道怎么回事，不解释了。

ifneq ($(CONFIG_BOARD_SIZE_LIMIT),)
BOARD_SIZE_CHECK = \
	@actual=`wc -c $@ | awk '{print $$1}'`; \
	limit=$(CONFIG_BOARD_SIZE_LIMIT); \
	if test $$actual -gt $$limit; then \
		echo "$@ exceeds file size limit:"; \
		echo "  limit:  $$limit bytes"; \
		echo "  actual: $$actual bytes"; \
		echo "  excess: $$((actual - limit)) bytes"; \
		exit 1; \
	fi
else
BOARD_SIZE_CHECK =
endif

首先看CONFIG_BOARD_SIZE_LIMIT是否被定义了（是否定义了，在autoconf.mk文件中查看，它的意思是规定了文件大小的上限），如果没定义，BOARD_SIZE_CHECK为空，如果定义了，就比较目标文件的实际大小与他的上限大小（CONFIG_BOARD_SIZE_LIMIT的值），如果前者大于后者，就退出，如前者小于后者，则继续执行（摘抄别人的）

# Always append ALL so that arch config.mk's can add custom ones
ALL += $(obj)u-boot.srec $(obj)u-boot.bin $(obj)System.map

ifeq ($(CONFIG_NAND_U_BOOT),y)
ALL += $(obj)u-boot-nand.bin
endif

ifeq ($(CONFIG_ONENAND_U_BOOT),y)
ALL += $(obj)u-boot-onenand.bin
ONENAND_BIN ?= $(obj)onenand_ipl/onenand-ipl-2k.bin
endif

ifeq ($(CONFIG_MMC_U_BOOT),y)
ALL += $(obj)mmc_spl/u-boot-mmc-spl.bin
endif

会判断CONFIG_NAND_U_BOOT，CONFIG_ONENAND_U_BOOT，CONFIG_MMC_U_BOOT是不是被定义y了，选择性的添加一些bin文件。后面一节将讲到这些CONFIG属性在哪儿定义的。

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 $< $@
		$(BOARD_SIZE_CHECK)

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

$(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
		$(obj)tools/mkimage -A $(ARCH) -T firmware -C none \
		-a $(CONFIG_SYS_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.imx:       $(obj)u-boot.bin
		$(obj)tools/mkimage -n  $(CONFIG_IMX_CONFIG) -T imximage \
		-e $(CONFIG_SYS_TEXT_BASE) -d $< $@

$(obj)u-boot.kwb:       $(obj)u-boot.bin
		$(obj)tools/mkimage -n $(CONFIG_SYS_KWD_CONFIG) -T kwbimage \
		-a $(CONFIG_SYS_TEXT_BASE) -e $(CONFIG_SYS_TEXT_BASE) -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 $< > $@

定义了一堆的依赖关系，真正重要的是$(obj)u-boot.bin和$(obj)u-boot，可以看到很多都依赖这个文件。 $(obj)u-boot.bin是依赖于

$(obj)u-boot.bin:$(obj)u-boot

$(OBJCOPY) ${OBJCFLAGS} -O binary $< $@
$(BOARD_SIZE_CHECK)       

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) $(LDFLAGS_$(@F)) $$UNDEF_SYM $(__OBJS) \
			--start-group $(__LIBS) --end-group $(PLATFORM_LIBS) \
			-Map u-boot.map -o u-boot
$(obj)u-boot:	depend \
		$(SUBDIRS) $(OBJS) $(LIBBOARD) $(LIBS) $(LDSCRIPT) $(obj)u-boot.lds
		$(GEN_UBOOT)

ifeq ($(CONFIG_KALLSYMS),y)
		smap=`$(call SYSTEM_MAP,u-boot) | \
			awk '$$2 ~ /[tTwW]/ {printf $$1 $$3 "\\\\000"}'` ; \
		$(CC) $(CFLAGS) -DSYSTEM_MAP="\"$${smap}\"" \
			-c common/system_map.c -o $(obj)common/system_map.o
		$(GEN_UBOOT) $(obj)common/system_map.o
endif

出来第一位主人公了，即 $(obj)u-boot，这个家伙依赖了好多变量，咱们往下看代码，依次展开来看：

$(OBJS):	depend
		$(MAKE) -C $(CPUDIR) $(if $(REMOTE_BUILD),$@,$(notdir $@))

$(LIBS):	depend $(SUBDIRS)
		$(MAKE) -C $(dir $(subst $(obj),,$@))

$(LIBBOARD):	depend $(LIBS)
		$(MAKE) -C $(dir $(subst $(obj),,$@))

$(SUBDIRS):	depend
		$(MAKE) -C $@ all

$(LDSCRIPT):	depend
		$(MAKE) -C $(dir $@) $(notdir $@)

$(obj)u-boot.lds: $(LDSCRIPT)
		$(CPP) $(CPPFLAGS) $(LDPPFLAGS) -ansi -D__ASSEMBLY__ -P - <$^ >$@

激动人心的时刻到了，开始编译了，刚才$(u-boot)依赖的这个多变量依次展开并按照其各自的命令生成。其实现在uboot.bin文件已经生成了。

下一节将结合具体的编译来重复讲述关于上述的许多没有讲完整的地方。