編譯u-boot的步驟： #make XX_config? ? XX表示某個cpu體系 #make ?生成我們需要的u-boot.bin 具體可參考u-boot文件中的README。
1.設(shè)置版本 VERSION = 2010 PATCHLEVEL = 06 SUBLEVEL = EXTRAVERSION = -rc1 ifneq "$(SUBLEVEL)" "" U_BOOT_VERSION = $(VERSION).$(PATCHLEVEL).$(SUBLEVEL)$(EXTRAVERSION) else U_BOOT_VERSION = $(VERSION).$(PATCHLEVEL)$(EXTRAVERSION) endif TIMESTAMP_FILE = $(obj)include/timestamp_autogenerated.h VERSION_FILE = $(obj)include/version_autogenerated.h 以上定義了版本的變量U_BOOT_VERSION。
2.獲取主機類型和主機系統(tǒng) HOSTARCH := $(shell uname -m | \????? ??執(zhí)行shell命令 ?uname -m 查看主機類型 sed -e s/i.86/i386/ \ ?? ?-e s/sun4u/sparc64/ \ ?? ?-e s/arm.*/arm/ \ ?? ?-e s/sa110/arm/ \ ?? ?-e s/ppc64/powerpc/ \ ?? ?-e s/ppc/powerpc/ \ ?? ?-e s/macppc/powerpc/) sed -e命令進行替換，比如將i386替換成i.86，并將結(jié)果放入變量HOSTARCH?。
HOSTOS := $(shell uname -s | tr '[:upper:]' '[:lower:]' | \ ?? ?sed -e 's/cygwin.*/cygwin/') uname -s 查看主機操作系統(tǒng)，tr '[:upper:]' '[:lower:]'將所有大寫變小寫，然后假如有cygwin，替換成cygwin.*，并將結(jié)果放入變量HOSTOS?
# Set shell to bash if possible, otherwise fall back to sh SHELL := $(shell if [ -x " BASH"];thenecho BASH; \ else if [ -x /bin/bash ]; then echo /bin/bash; \ else echo sh; fi; fi) 選擇/bin/bash
export HOSTARCH HOSTOS SHELL 導(dǎo)出變量HOSTARCH HOSTOS SHELL
LC_ALL=C export LC_ALL
# Deal with colliding definitions from tcsh etc. VENDOR= 變量為空 ######################################################################### # Allow for silent builds ifeq (,$(findstring s,$(MAKEFLAGS))) XECHO = echo else XECHO = : endif
######################################################################### # # U-boot build supports producing a object files to the separate external # directory. Two use cases are supported: # # 1) Add O= to the make command line # 'make O=/tmp/build all' # # 2) Set environement variable BUILD_DIR to point to the desired location # 'export BUILD_DIR=/tmp/build' # 'make' # # The second approach can also be used with a MAKEALL script # 'export BUILD_DIR=/tmp/build' # './MAKEALL' # # Command line 'O=' setting overrides BUILD_DIR environent variable. # # When none of the above methods is used the local build is performed and # the object files are placed in the source directory. # U-boot 生成一個目標文件來分開外面的文件夾，支持兩種方式： ?1）將 0= 加到make命令行如：? ?make 0=/tmp/build all ?2) 通過設(shè)置全局環(huán)境變量BUILD_DIR如：? ?export BUILD_DIR=/tmp/build ? ?make? 第二種方式也可以用MAKEFILE腳本 ?export BUILD_DIR=/tmp/build? ?./MAKEALL 通過第一種方式會覆蓋環(huán)境變量 BUILD_DIR? ?如果沒有顯式指定使用哪種方式，編譯腳本會自動進行本地編譯，目標文件被存放在當前文件夾里
3.獲取BUILD_DIR，并定義源碼，目標文件等目錄 第一種方式 ifdef O ifeq ("$(origin O)", "command line") BUILD_DIR := $(O) endif endif 第二種方式 ifneq ($(BUILD_DIR),) saved-output := $(BUILD_DIR)
# Attempt to create a output directory.?創(chuàng)建輸出目錄 $(shell [ -d ${BUILD_DIR} ] || mkdir -p ${BUILD_DIR})
# Verify if it was successful.? ??驗證目錄是否創(chuàng)建成功 BUILD_DIR := $(shell cd $(BUILD_DIR) && /bin/pwd) $(if $(BUILD_DIR),,$(error output directory "$(saved-output)" does not exist)) endif # ifneq ($(BUILD_DIR),)
OBJTREE := $(if $(BUILD_DIR),$(BUILD_DIR),$(CURDIR))?OBJTREEBUILD_DIR變量不為空，OBJTREE = BUILD_DIR，否則OBJTREE = CURDIR SRCTREE := $(CURDIR) TOPDIR := $(SRCTREE) LNDIR := $(OBJTREE) export TOPDIR SRCTREE OBJTREE 導(dǎo)出環(huán)境變量?TOPDIR SRCTREE OBJTREE
4.定義MKCONFIG等環(huán)境變量 MKCONFIG := $(SRCTREE)/mkconfig? ??指向一個腳本，即頂層目錄的mkconfig export MKCONFIG 導(dǎo)出環(huán)境變量 ?MKCONFIG
ifneq ($(OBJTREE),$(SRCTREE)) REMOTE_BUILD := 1 export REMOTE_BUILD endif 導(dǎo)出環(huán)境變量REMOTE_BUILD=1
# $(obj) and (src) are defined in config.mk but here in main Makefile # we also need them before config.mk is included which is the case for # some targets like unconfig, clean, clobber, distclean, etc. ifneq ($(OBJTREE),$(SRCTREE)) obj := $(OBJTREE)/ src := $(SRCTREE)/ else obj := src := endif export obj src
# Make sure CDPATH settings don't interfere unexport CDPATH????不導(dǎo)出CDPATH
######################################################################### 代碼已修改，原來是根據(jù)目標體系結(jié)構(gòu)選擇交叉編譯器。 # The "tools" are needed early, so put this first # Don't include stuff already done in $(LIBS) SUBDIRS = tools \ ??examples/standalone \ ??examples/api
.PHONY : $(SUBDIRS)
ifeq ($(obj)include/config.mk,$(wildcard $(obj)include/config.mk))
# Include autoconf.mk before config.mk so that the config options are available # to all top level build files. ?We need the dummy all: target to prevent the # dependency target in autoconf.mk.dep from being the default. all: sinclude $(obj)include/autoconf.mk.dep sinclude $(obj)include/autoconf.mk
# load ARCH, BOARD, and CPU configuration include $(obj)include/config.mk export ARCH CPU BOARD VENDOR SOC 導(dǎo)出ARCH CPU BOARD VENDOR SOC
5.指定交叉編譯器前綴 # set default to nothing for native builds ifeq ($(HOSTARCH),$(ARCH)) CROSS_COMPILE ?=arm-eabi- endif 設(shè)置交叉編譯器
6.包含config.mk文件 # load other configuration include $(TOPDIR)/config.mk????將config.mk包含進來 以下是config.mk的相關(guān)內(nèi)容并分析： ***************************************************************************************************************** 定義相關(guān)目錄 ifneq ($(OBJTREE),$(SRCTREE)) ifeq ($(CURDIR),$(SRCTREE)) dir := else dir := $(subst $(SRCTREE)/,,$(CURDIR)) endif
obj := $(if $(dir),$(OBJTREE)/$(dir)/,$(OBJTREE)/) src := $(if $(dir),$(SRCTREE)/$(dir)/,$(SRCTREE)/)
$(shell mkdir -p $(obj)) else obj := src := endif
# clean the slate ... PLATFORM_RELFLAGS = PLATFORM_CPPFLAGS = PLATFORM_LDFLAGS =
######################################################################### #定義交叉編譯鏈工具 # Option checker (courtesy linux kernel) to ensure # only supported compiler options are used # cc-option = $(shell if $(CC) $(CFLAGS) $(1) -S -o /dev/null -xc /dev/null \ > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)
# # Include the make variables (CC, etc...) # AS = $(CROSS_COMPILE)as LD = $(CROSS_COMPILE)ld CC = $(CROSS_COMPILE)gcc CPP = $(CC) -E AR = $(CROSS_COMPILE)ar NM = $(CROSS_COMPILE)nm LDR = $(CROSS_COMPILE)ldr STRIP = $(CROSS_COMPILE)strip OBJCOPY = $(CROSS_COMPILE)objcopy OBJDUMP = $(CROSS_COMPILE)objdump RANLIB = $(CROSS_COMPILE)RANLIB 定義AR選項ARFLAGS，調(diào)試選項DBGFLAGS，優(yōu)化選項OPTFLAGS 預(yù)處理選項CPPFLAGS，C編譯器選項CFLAGS，連接選項LDFLAGS ######################################################################### 包含體系，開發(fā)板，CPU特定的規(guī)則文件 # Load generated board configuration sinclude $(OBJTREE)/include/autoconf.mk
# Some architecture config.mk files need to know what CPUDIR is set to, # so calculate CPUDIR before including ARCH/SOC/CPU config.mk files. # Check if arch/$ARCH/cpu/$CPU exists, otherwise assume arch/$ARCH/cpu contains # CPU-specific code. CPUDIR=arch/$(ARCH)/cpu/$(CPU) ifneq ($(SRCTREE)/$(CPUDIR),$(wildcard $(SRCTREE)/$(CPUDIR))) CPUDIR=arch/$(ARCH)/cpu endif
sinclude $(TOPDIR)/arch/$(ARCH)/config.mk ?# include architecture dependend rules sinclude $(TOPDIR)/$(CPUDIR)/config.mk ?# include ?CPU specific rules
ifdef SOC sinclude $(TOPDIR)/$(CPUDIR)/$(SOC)/config.mk ?# include ?SoC specific rules endif ifdef VENDOR BOARDDIR = $(VENDOR)/$(BOARD) else BOARDDIR = $(BOARD) endif ifdef BOARD????指定特定板子的鏡像連接時的內(nèi)存基地址 sinclude $(TOPDIR)/board/$(BOARDDIR)/config.mk# include board specific rules endif
#########################################################################
ifneq (,$(findstring s,$(MAKEFLAGS))) ARFLAGS = cr else ARFLAGS = crv endif RELFLAGS= $(PLATFORM_RELFLAGS) DBGFLAGS= -g # -DDEBUG OPTFLAGS= -Os #-fomit-frame-pointer ifndef LDSCRIPT #LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot.lds.debug ifeq ($(CONFIG_NAND_U_BOOT),y) LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot-nand.lds else LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot.lds endif endif OBJCFLAGS += --gap-fill=0xff
gccincdir := $(shell $(CC) -print-file-name=include)
CPPFLAGS := $(DBGFLAGS) $(OPTFLAGS) $(RELFLAGS)\ -D__KERNEL__ ifneq ($(TEXT_BASE),) CPPFLAGS += -DTEXT_BASE=$(TEXT_BASE) endif
ifneq ($(RESET_VECTOR_ADDRESS),) CPPFLAGS += -DRESET_VECTOR_ADDRESS=$(RESET_VECTOR_ADDRESS) endif
ifneq ($(OBJTREE),$(SRCTREE)) CPPFLAGS += -I$(OBJTREE)/include2 -I$(OBJTREE)/include endif
CPPFLAGS += -I$(TOPDIR)/include CPPFLAGS += -fno-builtin -ffreestanding -nostdinc\ -isystem $(gccincdir) -pipe $(PLATFORM_CPPFLAGS)
ifdef BUILD_TAG CFLAGS := $(CPPFLAGS) -Wall -Wstrict-prototypes \ -DBUILD_TAG='"$(BUILD_TAG)"' else CFLAGS := $(CPPFLAGS) -Wall -Wstrict-prototypes endif
CFLAGS += $(call cc-option,-fno-stack-protector)
# avoid trigraph warnings while parsing pci.h (produced by NIOS gcc-2.9) # this option have to be placed behind -Wall -- that's why it is here ifeq ($(ARCH),nios) ifeq ($(findstring 2.9,$(shell $(CC) --version)),2.9) CFLAGS := $(CPPFLAGS) -Wall -Wno-trigraphs endif endif
# $(CPPFLAGS) sets -g, which causes gcc to pass a suitable -g<format> # option to the assembler. AFLAGS_DEBUG :=
# turn jbsr into jsr for m68k ifeq ($(ARCH),m68k) ifeq ($(findstring 3.4,$(shell $(CC) --version)),3.4) AFLAGS_DEBUG := -Wa,-gstabs,-S endif endif
AFLAGS := $(AFLAGS_DEBUG) -D__ASSEMBLY__ $(CPPFLAGS)
LDFLAGS += -Bstatic -T $(obj)u-boot.lds $(PLATFORM_LDFLAGS) ifneq ($(TEXT_BASE),)? ??指定起始地址TEXT_BASE LDFLAGS += -Ttext $(TEXT_BASE) endif
# Location of a usable BFD library, where we define "usable" as # "built for ${HOST}, supports ${TARGET}". ?Sensible values are # - When cross-compiling: the root of the cross-environment # - Linux/ppc (native): /usr # - NetBSD/ppc (native): you lose ... (must extract these from the # ? binutils build directory, plus the native and U-Boot include # ? files don't like each other) # # So far, this is used only by tools/gdb/Makefile.
ifeq ($(HOSTOS),darwin) BFD_ROOT_DIR = /usr/local/tools else ifeq ($(HOSTARCH),$(ARCH)) # native BFD_ROOT_DIR = /usr else #BFD_ROOT_DIR = /LinuxPPC/CDK# Linux/i386 #BFD_ROOT_DIR = /usr/pkg/cross# NetBSD/i386 BFD_ROOT_DIR = /opt/powerpc endif endif
#########################################################################
export HOSTCC HOSTCFLAGS HOSTLDFLAGS PEDCFLAGS HOSTSTRIP CROSS_COMPILE \ AS LD CC CPP AR NM STRIP OBJCOPY OBJDUMP MAKE export TEXT_BASE PLATFORM_CPPFLAGS PLATFORM_RELFLAGS CPPFLAGS CFLAGS AFLAGS
######################################################################### 指定編譯規(guī)則 # Allow boards to use custom optimize flags on a per dir/file basis BCURDIR = $(subst $(SRCTREE)/,,$(CURDIR:$(obj)%=%)) $(obj)%.s: %.S $(CPP) $(AFLAGS) $(AFLAGS_$(BCURDIR)/$(@F)) $(AFLAGS_$(BCURDIR)) \ -o $@ $< $(obj)%.o: %.S $(CC) ?$(AFLAGS) $(AFLAGS_$(BCURDIR)/$(@F)) $(AFLAGS_$(BCURDIR)) \ -o $@ $< -c $(obj)%.o: %.c $(CC) ?$(CFLAGS) $(CFLAGS_$(BCURDIR)/$(@F)) $(CFLAGS_$(BCURDIR)) \ -o $@ $< -c $(obj)%.i: %.c $(CPP) $(CFLAGS) $(CFLAGS_$(BCURDIR)/$(@F)) $(CFLAGS_$(BCURDIR)) \ -o $@ $< -c $(obj)%.s: %.c $(CC) ?$(CFLAGS) $(CFLAGS_$(BCURDIR)/$(@F)) $(CFLAGS_$(BCURDIR)) \ -o $@ $< -c -S
*****************************************************************************************************************
重新回到Makefile ######################################################################### 7.u-boot要生成的目標文件 # U-Boot objects....order is important (i.e. start must be first) 設(shè)置目標文件，start.o要放在第一個。 OBJS ?= $(CPUDIR)/start.o ifeq ($(CPU),i386) 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))????變量OBJS加前綴obj。
8.需要的庫文件 LIBS ?= lib/libgeneric.a LIBS += lib/lzma/liblzma.a LIBS += lib/lzo/liblzo.a LIBS += $(shell if [ -f board/$(VENDOR)/common/Makefile ]; then echo \ "board/$(VENDOR)/common/lib$(VENDOR).a"; fi) LIBS += $(CPUDIR)/lib$(CPU).a ifdef SOC LIBS += $(CPUDIR)/$(SOC)/lib$(SOC).a endif ifeq ($(CPU),ixp) LIBS += arch/arm/cpu/ixp/npe/libnpe.a endif LIBS += arch/$(ARCH)/lib/lib$(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 \ fs/ubifs/libubifs.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/fpga/libfpga.a LIBS += drivers/gpio/libgpio.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/onenand/libonenand.a LIBS += drivers/mtd/ubi/libubi.a LIBS += drivers/mtd/spi/libspi_flash.a LIBS += drivers/net/libnet.a LIBS += drivers/net/phy/libphy.a LIBS += drivers/pci/libpci.a LIBS += drivers/pcmcia/libpcmcia.a LIBS += drivers/power/libpower.a LIBS += drivers/spi/libspi.a ifeq ($(CPU),mpc83xx) LIBS += drivers/qe/qe.a endif ifeq ($(CPU),mpc85xx) LIBS += drivers/qe/qe.a LIBS += arch/powerpc/cpu/mpc8xxx/ddr/libddr.a LIBS += arch/powerpc/cpu/mpc8xxx/lib8xxx.a endif ifeq ($(CPU),mpc86xx) LIBS += arch/powerpc/cpu/mpc8xxx/ddr/libddr.a LIBS += arch/powerpc/cpu/mpc8xxx/lib8xxx.a endif LIBS += drivers/rtc/librtc.a LIBS += drivers/serial/libserial.a LIBS += drivers/twserial/libtws.a LIBS += drivers/usb/gadget/libusb_gadget.a LIBS += drivers/usb/host/libusb_host.a LIBS += drivers/usb/musb/libusb_musb.a LIBS += drivers/usb/phy/libusb_phy.a LIBS += drivers/video/libvideo.a LIBS += drivers/watchdog/libwatchdog.a LIBS += common/libcommon.a LIBS += lib/libfdt/libfdt.a LIBS += api/libapi.a LIBS += post/libpost.a
LIBS := $(addprefix $(obj),$(LIBS))? ??加前綴 .PHONY : $(LIBS) $(TIMESTAMP_FILE) $(VERSION_FILE) 設(shè)置LIBS ?TIMESTAMP_FILE ?VERSION_FILE為偽目標
LIBBOARD = board/$(BOARDDIR)/lib$(BOARD).a LIBBOARD := $(addprefix $(obj),$(LIBBOARD))
# Add GCC lib? ??添加GCC庫，并導(dǎo)出 ifdef USE_PRIVATE_LIBGCC ifeq ("$(USE_PRIVATE_LIBGCC)", "yes") PLATFORM_LIBGCC = -L $(OBJTREE)/arch/$(ARCH)/lib -lgcc 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
# Special flags for CPP when processing the linker script. # Pass the version down so we can handle backwards compatibility # on the fly. LDPPFLAGS += \????????設(shè)置cpp變量 -include $(TOPDIR)/include/u-boot/u-boot.lds.h \ $(shell $(LD) --version | \ ??sed -ne 's/GNU ld version?[0?9][0?9]?\.[0?9][0?9]?.*/-DLD_MAJOR=\1 -DLD_MINOR=\2/p')
ifeq ($(CONFIG_NAND_U_BOOT),y)? ??從NAND啟動u-boot，設(shè)置變量NAND_SPL?，U_BOOT_NAND? NAND_SPL = nand_spl U_BOOT_NAND = $(obj)u-boot-nand.bin endif
ifeq ($(CONFIG_ONENAND_U_BOOT),y)? ???從ONENAND啟動u-boot ONENAND_IPL = onenand_ipl U_BOOT_ONENAND = $(obj)u-boot-onenand.bin ONENAND_BIN ?= $(obj)onenand_ipl/onenand-ipl-2k.bin endif
__OBJS := $(subst $(obj),,$(OBJS)) ?去掉OBJS中的$(obj) __LIBS := $(subst $(obj),,$(LIBS)) $(subst $(obj),,$(LIBBOARD)) ?去掉LIBS和LIBBOARD?中的$(obj)
######################################################################### ######################################################################### 9.最終生成的各種鏡像文件，主要是u-boot.sre，u-boot.bin，System.map # 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 $(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 $(CREATE_LDR_ENV) $(LDR) -T $(CONFIG_BFIN_CPU) -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 $(obj)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/"[?]*$$/ for $(BOARD) board"/') \ -d $< $@
$(obj)u-boot.imx: ? ? ? $(obj)u-boot.bin $(obj)tools/mkimage -n $(IMX_CONFIG) -T imximage \ -e $(TEXT_BASE) -d $< $@
$(obj)u-boot.kwb: ? ? ? $(obj)u-boot.bin $(obj)tools/mkimage -n $(KWD_CONFIG) -T kwbimage \ -a $(TEXT_BASE) -e $(TEXT_BASE) -d $< $@
$(obj)u-boot.sha1: $(obj)u-boot.bin $(obj)tools/ubsha1 $(obj)u-boot.bin
$(obj)u-boot.dis: $(obj)u-boot $(OBJDUMP) -d $< > $@
GEN_UBOOT?= \ UNDEF_SYM=`$(OBJDUMP) -x $(LIBBOARD) $(LIBS) | \ sed ?-n -e 's/.*$(SYM_PREFIX)__u_boot_cmd_.*/-u\1/p'|sort|uniq`;\ cd $(LNDIR) && $(LD) $(LDFLAGS) $$UNDEF_SYM $(__OBJS) \ --start-group $(__LIBS) --end-group $(PLATFORM_LIBS) \ -Map u-boot.map -o u-boot $(obj)u-boot: depend $(SUBDIRS) $(OBJS) $(LIBBOARD) $(LIBS) $(LDSCRIPT) $(obj)u-boot.lds $(GEN_UBOOT) 這里是最關(guān)鍵的：生成u-boot的ELF文件鏡像。 $(obj)u-boot.lds定義了連接時各個目標文件是如何組織的。 *********************************************************************************************************** GUN編譯過的段，最基本的三個段是RO，RW，ZI （rodata，data，bss） 分別是代碼段， 數(shù)據(jù)段，?歸零段，就是全局變量的那段 ?? OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm") OUTPUT_ARCH(arm) ENTRY(_start) SECTIONS { . = 0x00000000;
. = ALIGN(4); .text ?:????????.text的基地址由LDFLAGS中-Ttext $(TEXT_BASE)指定 { arch/arm/cpu/arm_cortexa8/start.o(.text) *(.text) }
. = ALIGN(4);? ??調(diào)整對齊格式的 .rodata : { *(SORT_BY_ALIGNMENT(SORT_BY_NAME(.rodata*))) }
. = ALIGN(4); .data : { *(.data) }
. = ALIGN(4); .got : { *(.got) }
__u_boot_cmd_start = .; .u_boot_cmd : { *(.u_boot_cmd) } __u_boot_cmd_end = .;
. = ALIGN(4); __bss_start = .; .bss : { *(.bss) } _end = .; } ***********************************************************************************************************

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
$(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) $(LDPPFLAGS) -ansi -D__ASSEMBLY__ -P - <$^ >$@
$(NAND_SPL): $(TIMESTAMP_FILE) $(VERSION_FILE) $(obj)include/autoconf.mk $(MAKE) -C nand_spl/board/$(BOARDDIR) all
$(U_BOOT_NAND): $(NAND_SPL) $(obj)u-boot.bin cat $(obj)nand_spl/u-boot-spl-16k.bin $(obj)u-boot.bin > $(obj)u-boot-nand.bin
$(ONENAND_IPL): $(TIMESTAMP_FILE) $(VERSION_FILE) $(obj)include/autoconf.mk $(MAKE) -C onenand_ipl/board/$(BOARDDIR) all
$(U_BOOT_ONENAND): $(ONENAND_IPL) $(obj)u-boot.bin cat $(ONENAND_BIN) $(obj)u-boot.bin > $(obj)u-boot-onenand.bin
$(VERSION_FILE): @( printf '#define U_BOOT_VERSION "U-Boot %s%s"\n' "$(U_BOOT_VERSION)" \ ?'$(shell $(TOPDIR)/tools/setlocalversion $(TOPDIR))' ) > $@.tmp @cmp -s $@ $@.tmp && rm -f $@.tmp || mv -f $@.tmp $@
$(TIMESTAMP_FILE): @date +'#define U_BOOT_DATE "%b %d %C%y"' > $@ @date +'#define U_BOOT_TIME "%T"' >> $@
gdbtools: $(MAKE) -C tools/gdb all || exit 1
updater: $(MAKE) -C tools/updater all || exit 1
env: $(MAKE) -C tools/env all MTD_VERSION=${MTD_VERSION} || exit 1
# Explicitly make _depend in subdirs containing multiple targets to prevent # parallel sub-makes creating .depend files simultaneously. depend dep: $(TIMESTAMP_FILE) $(VERSION_FILE) $(obj)include/autoconf.mk for dir in $(SUBDIRS) $(CPUDIR) $(dir $(LDSCRIPT)) ; do \ $(MAKE) -C $$dir _depend ; done
TAG_SUBDIRS = $(SUBDIRS) TAG_SUBDIRS += $(dir $(__LIBS)) TAG_SUBDIRS += include
tags ctags: ctags -w -o $(obj)ctags `find $(TAG_SUBDIRS) \ -name '*.[chS]' -print`
etags: etags -a -o $(obj)etags `find $(TAG_SUBDIRS) \ -name '*.[chS]' -print` cscope: find $(TAG_SUBDIRS) -name '*.[chS]' -print > cscope.files cscope -b -q -k
SYSTEM_MAP = \ $(NM) $1 | \ grep -v 'compiled\|\.o$$\|[aUw]\|\.\.ng$$\|LASH[RL]DI' | \ LC_ALL=C sort $(obj)System.map: $(obj)u-boot @$(call SYSTEM_MAP,$<) > $(obj)System.map
# # Auto-generate the autoconf.mk file (which is included by all makefiles) # # This target actually generates 2 files; autoconf.mk and autoconf.mk.dep. # the dep file is only include in this top level makefile to determine when # to regenerate the autoconf.mk file. $(obj)include/autoconf.mk.dep: $(obj)include/config.h include/common.h @$(XECHO) Generating $@ ; \ set -e ; \ : Generate the dependancies ; \ $(CC) -x c -DDO_DEPS_ONLY -M $(HOSTCFLAGS) $(CPPFLAGS) \ -MQ $(obj)include/autoconf.mk include/common.h > $@
$(obj)include/autoconf.mk: $(obj)include/config.h @$(XECHO) Generating $@ ; \ set -e ; \ : Extract the config macros ; \ $(CPP) $(CFLAGS) -DDO_DEPS_ONLY -dM include/common.h | \ sed -n -f tools/scripts/define2mk.sed > $@.tmp && \ mv $@.tmp $@
######################################################################### else # !config.mk all $(obj)u-boot.hex $(obj)u-boot.srec $(obj)u-boot.bin \ $(obj)u-boot.img $(obj)u-boot.dis $(obj)u-boot \ $(filter-out tools,$(SUBDIRS)) $(TIMESTAMP_FILE) $(VERSION_FILE) gdbtools \ updater env depend dep tags ctags etags cscope $(obj)System.map: @echo "System not configured - see README" >&2 @ exit 1 配置config.mk出錯 tools: $(MAKE) -C tools tools-all: $(MAKE) -C tools HOST_TOOLS_ALL=y endif # config.mk
.PHONY : CHANGELOG CHANGELOG: git log --no-merges U-Boot-1_1_5.. | \ unexpand -a | sed -e 's/\s\s*$$//' > $@
include/license.h: tools/bin2header COPYING ?cat COPYING | gzip -9 -c | ./tools/bin2header license_gzip > include/license.h #########################################################################
unconfig: @rm -f $(obj)include/config.h $(obj)include/config.mk \ $(obj)board/*/config.tmp $(obj)board/*/*/config.tmp \ $(obj)include/autoconf.mk $(obj)include/autoconf.mk.dep 刪除相關(guān)配置文件，主要是$(obj)include/config.h $(obj)include/config.mk %: %_config $(MAKE)
9.各CPU體系匹配 ######################################################################### ## ARM CORTEX Systems #########################################################################
am3517_evm_config : unconfig????? ?? @$(MKCONFIG) $(@:_config=) arm arm_cortexa8 am3517evm logicpd omap3
devkit8000_config : unconfig @$(MKCONFIG) $(@:_config=) arm arm_cortexa8 devkit8000 timll omap3
omap3_devkit8500_config : ? unconfig????? ??先調(diào)用unconfig刪除配置文件，然后執(zhí)行mkconfig @$(MKCONFIG) $(@:_config=) arm arm_cortexa8 devkit8500 timll omap3? ??$(@就是omap3_devkit8500_config，而$(@:_config=)就是將_config替換為空，也就是刪掉_config。即上面的命令實際上是./mkconfig?omap3_devkit8500?arm arm_cortexa8 devkit8500 timll omap3
mkconfig主要做了以下三件事： a.在include文件夾下建立相應(yīng)的文件夾軟連接 比如ls -s asm-arm?? ? arm
b.生成/include/config.mk，其內(nèi)容為： ARCH ? = arm CPU ? ?= arm_cortexa8 BOARD ?= devkit8500 VENDOR = timll SOC ? ?= omap3
c.生成/include/config.h，其內(nèi)容為： #define CONFIG_BOARDDIR board/timll/devkit8500 #include <config_defaults.h> #include <configs/omap3_devkit8500.h> #include <asm/config.h>
*********************************************************************************************************************** #!/bin/sh -e
# Script to create header files and links to configure # U-Boot for a specific board. # # Parameters: ?Target ?Architecture ?CPU ?Board [VENDOR] [SOC] # # (C) 2002-2006 DENX Software Engineering, Wolfgang Denk <wd@denx.de> #
APPEND=no # Default: Create new config file BOARD_NAME="" # Name to print in make output TARGETS=""
while [ $# -gt 0 ] ; do????? ??解析傳遞參數(shù) ?$#?所有參數(shù)，詳情請進 case "$1" in --) shift ; break ;;????? ??shift是剩余參數(shù)向左移動一個位置并$#的值減一 -a) shift ; APPEND=yes ;; -n) shift ; BOARD_NAME="${1%%_config}" ; shift ;; -t) shift ; TARGETS="`echo $1 | sed 's:_: :g'` ${TARGETS}" ; shift ;; *) ?break ;; esac done
[ "${BOARD_NAME}" ] || BOARD_NAME="$1"? ??獲取平臺名稱
[ $# -lt 4 ] && exit 1 [ $# -gt 6 ] && exit 1
if [ "${ARCH}" -a "${ARCH}" != "$2" ]; then? ??處理第二個參數(shù) echo "Failed: \$ARCH=${ARCH}, should be '$2' for ${BOARD_NAME}" 1>&2 exit 1 fi
echo "Configuring for ${BOARD_NAME} board..."
# #?Create link to architecture specific headers 創(chuàng)建include的鏈接 # if [ "$SRCTREE" != "$OBJTREE" ] ; then mkdir -p ${OBJTREE}/include mkdir -p ${OBJTREE}/include2 cd ${OBJTREE}/include2 rm -f asm ln -s ${SRCTREE}/arch/$2/include/asm asm? ?創(chuàng)建asm鏈接 LNPREFIX=${SRCTREE}/arch/$2/include/asm/ cd ../include rm -f asm ln -s ${SRCTREE}/arch/$2/include/asm asm else cd ./include rm -f asm ln -s ../arch/$2/include/asm asm fi
rm -f asm/arch
if [ -z "$6" -o "$6" = "NULL" ] ; then ?創(chuàng)建arch鏈接 ln -s ${LNPREFIX}arch-$3 asm/arch else ln -s ${LNPREFIX}arch-$6 asm/arch fi
if [ "$2" = "arm" ] ; then rm -f asm/proc ln -s ${LNPREFIX}proc-armv asm/proc創(chuàng)建proc鏈接 fi
# #?Create include file for Make??創(chuàng)建config.mk文件 # echo "ARCH ? = $2" > ?config.mk echo "CPU ? ?= $3" >> config.mk echo "BOARD ?= $4" >> config.mk
[ "$5" ] && [ "$5" != "NULL" ] && echo "VENDOR = $5" >> config.mk
[ "$6" ] && [ "$6" != "NULL" ] && echo "SOC ? ?= $6" >> config.mk
# Assign board directory to BOARDIR variable if [ -z "$5" -o "$5" = "NULL" ] ; then BOARDDIR=$4 else BOARDDIR=$5/$4 fi
# #?Create board specific header file ?創(chuàng)建config.h文件 # if [ "$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
for i in ${TARGETS} ; do echo "#define CONFIG_MK_${i} 1" >>config.h ; done
cat << EOF >> config.h #define CONFIG_BOARDDIR board/$BOARDDIR #include <config_defaults.h> #include <configs/$1.h> #include <asm/config.h> EOF
exit 0 *************************************************************************************************************************************
clean:????? ??刪除所有中間生成文件、配置文件、目標文件 @rm -f $(obj)examples/standalone/82559_eeprom??\ ?? ? ? $(obj)examples/standalone/atmel_df_pow2??\ ?? ? ? $(obj)examples/standalone/eepro100_eeprom??\ ?? ? ? $(obj)examples/standalone/hello_world??\ ?? ? ? $(obj)examples/standalone/interrupt??\ ?? ? ? $(obj)examples/standalone/mem_to_mem_idma2intr??\ ?? ? ? $(obj)examples/standalone/sched??\ ?? ? ? $(obj)examples/standalone/smc91111_eeprom??\ ?? ? ? $(obj)examples/standalone/test_burst??\ ?? ? ? $(obj)examples/standalone/timer @rm -f $(obj)examples/api/demo{,.bin} @rm -f $(obj)tools/bmp_logo?? $(obj)tools/easylogo/easylogo ?\ ?? ? ? $(obj)tools/env/{fw_printenv,fw_setenv}??\ ?? ? ? $(obj)tools/envcrc??\ ?? ? ? $(obj)tools/gdb/{astest,gdbcont,gdbsend}??\ ?? ? ? $(obj)tools/gen_eth_addr ? ?$(obj)tools/img2srec??\ ?? ? ? $(obj)tools/mkimage?? $(obj)tools/mpc86x_clk??\ ?? ? ? $(obj)tools/ncb?? $(obj)tools/ubsha1 @rm -f $(obj)board/cray/L1/{bootscript.c,bootscript.image}??\ ?? ? ? $(obj)board/netstar/{eeprom,crcek,crcit,*.srec,*.bin}??\ ?? ? ? $(obj)board/trab/trab_fkt ? $(obj)board/voiceblue/eeprom ? \ ?? ? ? $(obj)board/armltd/{integratorap,integratorcp}/u-boot.lds ?\ ?? ? ? $(obj)arch/blackfin/lib/u-boot.lds??\ ?? ? ? $(obj)u-boot.lds??\ ?? ? ? $(obj)arch/blackfin/cpu/bootrom-asm-offsets.[chs] @rm -f $(obj)include/bmp_logo.h @rm -f $(obj)nand_spl/{u-boot.lds,u-boot-spl,u-boot-spl.map,System.map} @rm -f $(obj)onenand_ipl/onenand-{ipl,ipl.bin,ipl.map} @rm -f $(ONENAND_BIN) @rm -f $(obj)onenand_ipl/u-boot.lds @rm -f $(TIMESTAMP_FILE) $(VERSION_FILE) @find $(OBJTREE) -type f \ \( -name 'core' -o -name '*.bak' -o -name '*~' \ -o -name '*.o'-o -name '*.a' -o -name '*.exe'\) -print \ | xargs rm -f
10.清除中間生成文件、目標文件等 clobber: clean @find $(OBJTREE) -type f \( -name .depend \ -o -name '*.srec' -o -name '*.bin' -o -name u-boot.img \) \ -print0 \ | xargs -0 rm -f @rm -f $(OBJS) $(obj)*.bak $(obj)ctags $(obj)etags $(obj)TAGS \ $(obj)cscope.* $(obj)*.*~ @rm -f $(obj)u-boot $(obj)u-boot.map $(obj)u-boot.hex $(ALL) @rm -f $(obj)u-boot.kwb @rm -f $(obj)u-boot.imx @rm -f $(obj)tools/{env/crc32.c,inca-swap-bytes} @rm -f $(obj)arch/powerpc/cpu/mpc824x/bedbug_603e.c @rm -f $(obj)include/asm/proc $(obj)include/asm/arch $(obj)include/asm @[ ! -d $(obj)nand_spl ] || find $(obj)nand_spl -name "*" -type l -print | xargs rm -f @[ ! -d $(obj)onenand_ipl ] || find $(obj)onenand_ipl -name "*" -type l -print | xargs rm -f
ifeq ($(OBJTREE),$(SRCTREE)) mrproper \ distclean: clobber unconfig else mrproper \ distclean: clobber unconfig rm -rf $(obj)* endif
backup:? ??打包備份 F=`basename $(TOPDIR)` ; cd .. ; \ gtar --force-local -zcvf `date "+ F? F
概括一下 1.執(zhí)行make XX_config傳入ARCH，CPU，BOARD，SOC參數(shù) 2.mkconfig根據(jù)參數(shù)將include頭文件夾相應(yīng)的頭文件夾連接好，生成config.h。 3.執(zhí)行make分別調(diào)用各子目錄的makefile 生成所有的obj文件和obj庫文件*.a. ?

4.連接所有目標文件，生成鏡像。

轉(zhuǎn)自： ?http://blog.csdn.net/williamwang2013/article/details/8858943

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