u-boot Makefile完全解读

编译u-boot的步骤：

#make XX_config XX表示某个cpu体系

#make 生成我们需要的u-boot.bin

具体可参考u-boot文件中的README。

1.设置版本

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

以上定义了版本的变量U_BOOT_VERSION。

2.获取主机类型和主机系统

HOSTARCH := $(shell uname -m | \ 执行shell命令 uname -m 查看主机类型

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命令进行替换，比如将i386替换成i.86，并将结果放入变量HOSTARCH 。

HOSTOS := $(shell uname -s | tr '[:upper:]' '[:lower:]' | \

sed -e 's/cygwin.*/cygwin/')

uname -s 查看主机操作系统，tr '[:upper:]' '[:lower:]'将所有大写变小写，然后假如有cygwin，替换成cygwin.*，并将结果放入变量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)

选择/bin/bash

export HOSTARCH HOSTOS SHELL

导出变量HOSTARCH HOSTOS SHELL

LC_ALL=C

export LC_ALL

# Deal with colliding definitions from tcsh etc.

VENDOR=

变量为空

#########################################################################

# 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 生成一个目标文件来分开外面的文件夹，支持两种方式：

1）将 0= 加到make命令行如：

make 0=/tmp/build all

2) 通过设置全局环境变量BUILD_DIR如：

export BUILD_DIR=/tmp/build

make

第二种方式也可以用MAKEFILE脚本

export BUILD_DIR=/tmp/build

./MAKEALL

通过第一种方式会覆盖环境变量 BUILD_DIR

如果没有显式指定使用哪种方式，编译脚本会自动进行本地编译，目标文件被存放在当前文件夹里

3.获取BUILD_DIR，并定义源码，目标文件等目录

第一种方式

ifdef O

ifeq ("$(origin O)", "command line")

BUILD_DIR := $(O)

endif

第二种方式

ifneq ($(BUILD_DIR),)

saved-output := $(BUILD_DIR)

# Attempt to create a output directory. 创建输出目录

$(shell [ -d ${BUILD_DIR} ] || mkdir -p ${BUILD_DIR})

# Verify if it was successful. 验证目录是否创建成功

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变量不为空，OBJTREE = BUILD_DIR，否则OBJTREE = CURDIR

SRCTREE := $(CURDIR)

TOPDIR := $(SRCTREE)

LNDIR := $(OBJTREE)

export TOPDIR SRCTREE OBJTREE

导出环境变量 TOPDIR SRCTREE OBJTREE

4.定义MKCONFIG等环境变量

MKCONFIG := $(SRCTREE)/mkconfig 指向一个脚本，即顶层目录的mkconfig

export MKCONFIG

导出环境变量 MKCONFIG

ifneq ($(OBJTREE),$(SRCTREE))

REMOTE_BUILD := 1

export REMOTE_BUILD

endif

导出环境变量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 不导出CDPATH

#########################################################################

代码已修改，原来是根据目标体系结构选择交叉编译器。

# 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

导出ARCH CPU BOARD VENDOR SOC

5.指定交叉编译器前缀

# set default to nothing for native builds

ifeq ($(HOSTARCH),$(ARCH))

CROSS_COMPILE ?=arm-eabi-

endif

设置交叉编译器

6.包含config.mk文件

# load other configuration

include $(TOPDIR)/config.mk 将config.mk包含进来

以下是config.mk的相关内容并分析：

*****************************************************************************************************************

定义相关目录

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 =

#########################################################################

#定义交叉编译链工具

# 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

定义AR选项ARFLAGS，调试选项DBGFLAGS，优化选项OPTFLAGS

预处理选项CPPFLAGS，C编译器选项CFLAGS，连接选项LDFLAGS

#########################################################################

包含体系，开发板，CPU特定的规则文件

# 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 指定特定板子的镜像连接时的内存基地址

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

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

# $(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

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

#########################################################################

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

#########################################################################

指定编译规则

# 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要生成的目标文件

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

设置目标文件，start.o要放在第一个。

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)) 变量OBJS加前缀obj。

8.需要的库文件

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)) 加前缀

.PHONY : $(LIBS) $(TIMESTAMP_FILE) $(VERSION_FILE)

设置LIBS TIMESTAMP_FILE VERSION_FILE为伪目标

LIBBOARD = board/$(BOARDDIR)/lib$(BOARD).a

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

# Add GCC lib 添加GCC库，并导出

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 += \ 设置cpp变量

-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) 从NAND启动u-boot，设置变量NAND_SPL ，U_BOOT_NAND

NAND_SPL = nand_spl

U_BOOT_NAND = $(obj)u-boot-nand.bin

endif

ifeq ($(CONFIG_ONENAND_U_BOOT),y) 从ONENAND启动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.最终生成的各种镜像文件，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)

这里是最关键的：生成u-boot的ELF文件镜像。

$(obj)u-boot.lds定义了连接时各个目标文件是如何组织的。

***********************************************************************************************************

GUN编译过的段，最基本的三个段是RO，RW，ZI （rodata，data，bss）

分别是代码段，数据段，归零段，就是全局变量的那段

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); 调整对齐格式的

.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出错

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

删除相关配置文件，主要是$(obj)include/config.h $(obj)include/config.mk

%: %_config

$(MAKE)

9.各CPU体系匹配

#########################################################################

## 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 先调用unconfig删除配置文件，然后执行mkconfig

@$(MKCONFIG) $(@:_config=) arm arm_cortexa8 devkit8500 timll omap3 $(@就是omap3_devkit8500_config，而$(@:_config=)就是将_config替换为空，也就是删掉_config。即上面的命令实际上是./mkconfig omap3_devkit8500 arm arm_cortexa8 devkit8500 timll omap3

mkconfig主要做了以下三件事：

a.在include文件夹下建立相应的文件夹软连接

比如ls -s asm-arm arm

b.生成/include/config.mk，其内容为：

ARCH = arm

CPU = arm_cortexa8

BOARD = devkit8500

VENDOR = timll

SOC = omap3

c.生成/include/config.h，其内容为：

#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]

APPEND=no # Default: Create new config file

BOARD_NAME="" # Name to print in make output

TARGETS=""

while [ $# -gt 0 ] ; do 解析传递参数 $# 所有参数，详情请进

case "$1" in

--) shift ; break ;; shift是剩余参数向左移动一个位置并$#的值减一

-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" 获取平台名称

[ $# -lt 4 ] && exit 1

[ $# -gt 6 ] && exit 1

if [ "${ARCH}" -a "${ARCH}" != "$2" ]; then 处理第二个参数

echo "Failed: \$ARCH=${ARCH}, should be '$2' for ${BOARD_NAME}" 1>&2

exit 1

echo "Configuring for ${BOARD_NAME} board..."

# Create link to architecture specific headers 创建include的链接

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 创建asm链接

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

rm -f asm/arch

if [ -z "$6" -o "$6" = "NULL" ] ; then 创建arch链接

ln -s ${LNPREFIX}arch-$3 asm/arch

else

ln -s ${LNPREFIX}arch-$6 asm/arch

if [ "$2" = "arm" ] ; then

rm -f asm/proc

ln -s ${LNPREFIX}proc-armv asm/proc创建proc链接

# Create include file for Make 创建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

# Create board specific header file 创建config.h文件

if [ "$APPEND" = "yes" ] # Append to existing config file

then

echo >> config.h

else

> config.h# Create new config file

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: 删除所有中间生成文件、配置文件、目标文件

@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.清除中间生成文件、目标文件等

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: 打包备份

F=`basename $(TOPDIR)` ; cd .. ; \

gtar --force-local -zcvf `date "+

F−

概括一下

1.执行make XX_config传入ARCH，CPU，BOARD，SOC参数

2.mkconfig根据参数将include头文件夹相应的头文件夹连接好，生成config.h。

3.执行make分别调用各子目录的makefile 生成所有的obj文件和obj库文件*.a.

4.连接所有目标文件，生成镜像。

转自： http://blog.csdn.net/williamwang2013/article/details/8858943

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