最近看Omapl138UBOOT主Makefile的一些整理

如下：

VERSION = 2012

PATCHLEVEL = 04

SUBLEVEL = 01

EXTRAVERSION =

ifneq “$(SUBLEVEL)” “”

U_BOOT_VERSION =
$ (VERSION).$ (PATCHLEVEL).$ (SUBLEVEL)$(EXTRAVERSION)

else

U_BOOT_VERSION =
$ (VERSION).$ (PATCHLEVEL)$(EXTRAVERSION)

endif

TIMESTAMP_FILE =
$(obj)include/generated/timestamp_autogenerated.h

VERSION_FILE =
$(obj)include/generated/version_autogenerated.h

变量名	含义
U_BOOT_VERSION	2012.04.01
TIMESTAMP_FILE	include/generated/timestamp_autogenerated.h
VERSION_FILE	include/generated/version_autogenerated.h

HOSTARCH := $(shell uname -m | \

       sed
-e s/i.86/x86/ \

           -e s/sun4u/sparc64/ \

           -e s/arm.*/arm/ \

           -e s/sa110/arm/ \

           -e s/ppc64/powerpc/ \

           -e s/ppc/powerpc/ \

           -e s/macppc/powerpc/\

           -e s/sh.*/sh/)


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

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

    “sed
–e”表示后面跟的是一串命令脚本，而表达式“s/abc/def/”表示要从标准输入中，查找到内容为“abc”的，然后替换成“def”。其中“abc”表达式用可以使用“.”作为通配符。

       命令“uname –m”将输出主机CPU的体系架构类型。作者的电脑使用Intel Core2系列的CPU，因此“uname –m”输出“i686”。 “i686”可以匹配命令“sed -e
s/i.86/x86/”中的“i.86”，因此在作者的机器上执行Makefile，HOSTARCH将被设置成“x86” 。

“uname
–s”输出主机内核名字，作者使用Linux发行版Ubuntu10.04，因此“uname –s”结果是“Linux”。“tr
'[:upper:]' '[:lower:]'”作用是将标准输入中的所有大写字母转换为响应的小写字母。因此执行结果是将HOSTOS 设置为“linux”。

# Set shell to bash if possible, otherwise
fall back to sh

SHELL := $(shell if [ -x "$$BASH"
]; then echo $$BASH; \

       else
if [ -x /bin/bash ]; then echo /bin/bash; \

       else
echo sh; fi; fi)

 

export    HOSTARCH
HOSTOS SHELL

 

# Deal with colliding definitions from tcsh
etc.

VENDOR=

 

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

# Allow for silent builds

ifeq (,$(findstring s,$(MAKEFLAGS)))

XECHO = echo

else

XECHO = :

endif

#因为没有定义MAKEFLAGS，所以XECHO=echo

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

#

# 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.

#

 

ifdef O

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

BUILD_DIR := $(O)

endif

endif

 

ifneq ($(BUILD_DIR),)

saved-output := $(BUILD_DIR)

 

# Attempt to create a output directory.

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

 

# Verify if it was successful.

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))

SPLTREE        :=
$(OBJTREE)/spl

SRCTREE        :=
$(CURDIR)

TOPDIR         :=
$(SRCTREE)

LNDIR            :=
$(OBJTREE)

export    TOPDIR
SRCTREE OBJTREE SPLTREE

 

MKCONFIG   :=
$(SRCTREE)/mkconfig

export MKCONFIG

 

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

REMOTE_BUILD    := 1

export REMOTE_BUILD

endif

 

# $(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

   CURDIR变量指示Make当前的工作目录，由于当前Make在U-Boot顶层目录执行Makefile，因此CURDIR此时就是U-Boot顶层目录。

   执行完上面的代码后， SRCTREE，src变量就是U-Boot代码顶层目录，而OBJTREE，obj变量就是输出目录，若没有定义BUILD_DIR环境变量，则SRCTREE，src变量与OBJTREE，obj变量都是U-Boot源代码目录。而MKCONFIG则表示U-Boot根目录下的mkconfig脚本。

变量	含义
OBJTREE	Omapl138/uboot
SPLTREE	Omapl138/uboot/spl
SRCTREE	Omapl138/uboot
TOPDIR	Omapl138/uboot
LNDDIR	Omapl138/uboot
src	Omapl138/uboot
obj	Omapl138/uboot
MKCONFIG	Omapl138/uboot/mkconfig

# Make sure CDPATH settings don't interfere

unexport
CDPATH

 

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

 

# The "tools" are needed early,
so put this first

# Don't include stuff already done in
$(LIBS)

# The "examples" conditionally
depend on U-Boot (say, when USE_PRIVATE_LIBGCC

# is "yes"), so compile examples
after U-Boot is compiled.

SUBDIR_TOOLS = tools

SUBDIR_EXAMPLES = examples/standalone
examples/api

SUBDIRS = $(SUBDIR_TOOLS)

 

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

 

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

当makefile中有两个相同目标的时候，会执行后一个目标。因为后一个目标会重载前一个。如果你 执行make的时候没有带任何其他目标。单独的一个make。可以避免以autoconf.mk.dep里面的include/autoconf.mk作为错误目标。如果你执行make的时候带了目标。这个all:有不有都无所谓。

ifndef CONFIG_SANDBOX

SUBDIRS += $(SUBDIR_EXAMPLES)

endif

 

# load ARCH, BOARD, and CPU configuration

include $(obj)include/config.mk

export    ARCH
CPU BOARD VENDOR SOC

#包含include/config.mk文件，这个文件是在makexxx_config过程中产生的

# set default to nothing for native builds

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

CROSS_COMPILE ?=

endif

#HOSTARCH是x86的，目标是arm的，所以不执行

这个CROSS_COMPILE是通过命令行引入的，make CROSS_COMPILE=arm-none-linux-gnueabi-

# load other configuration

include $(TOPDIR)/config.mk

#包含Omapl138/uboot/mkconfig

# If board code explicitly specified
LDSCRIPT or CONFIG_SYS_LDSCRIPT, use

# that (or fail if absent).  Otherwise, search for a linker script in a

# standard location.

 

LDSCRIPT_MAKEFILE_DIR = $(dir $(LDSCRIPT))

#用等号赋值的变量是递归方式扩展的变量。变量定义时，变量值中对其他变量的引用不会被替换展开；

#而是变量在引用它的地方替换展开的同时，它所引用的其它变量才会被一同替换展开。

#其优点是：

#这种类型变量在定义时，可以引用其它的之前没有定义的变量（可能在后续部分定义，或者是通过make的命令行选项传递的变量）。

#LDSCRIPT变量就是后面才定义的

ifndef LDSCRIPT

       #LDSCRIPT
:= $(TOPDIR)/board/$(BOARDDIR)/u-boot.lds.debug

       ifdef
CONFIG_SYS_LDSCRIPT

       #没有定义

              #
need to strip off double quotes

              LDSCRIPT
:= $(subst ",,$(CONFIG_SYS_LDSCRIPT))

#如果定义了CONFIG_SYS_LDSCRIPT，将CONFIG_SYS_LDSCRIPT代表的字符串去掉双引号后赋值给LDSCRIPT变量

       endif

endif

 

# If there is no specified link script, we
look in a number of places for it

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)),)

              LDSCRIPT
:= $(TOPDIR)/arch/$(ARCH)/cpu/u-boot.lds

              #
We don't expect a Makefile here

              LDSCRIPT_MAKEFILE_DIR
=

       endif

       ifeq
($(wildcard $(LDSCRIPT)),)

$(error could not find linker script)

       endif

endif

在config.mk中有如下定义：

BOARDDIR =$ (VENDDOR)/$( BOARD)

CPUDIR=arch/$ (ARCH)/cpu/$(CPU)

ifneq
($ (SRCTREE)/$ (CPUDIR),$ (wildcard $ (SRCTREE)/$ (CPUDIR)))

CPUDIR= arch/$(ARCH)/cpu

结合boards.cfg中的定义：

变量名	定义
ARCH	arm
CPU	arm926ejs
BOARD name	da8xxevm
Vendor	davinci
SOC	davinci

综上：

BOARDDIR=davinci/da8xxevm/

CPUDIF=arch/arm/cpu/arm926ejs

#注释写的很明确，如果没有用CONFIG_SYS_LDSCRIPT指定LDSCRIPT，那么就在几个地方搜

#第一个地方:如果CONFIG_NAND_U_BOOT是y，就用u-boot-nand.lds但是这里没有这个定义

#第一个地方没找到，就找第二个地方:uboot/board/davinci /da8xxevm这个目录没有u-boot.lds文件

#第二个地方没找到，就找第三个地方:其中CPUDIR是在顶层的config.mk中定义的，在arch/arm/cpu/arm926ejs中找这个目录也没有

#第三个地方没找到，就找第四个地方:arch/arm/cpu/u-boot.lds，这里就找到了！！！！

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

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

 

OBJS 
= $(CPUDIR)/start.o

OBJS    =arch/arm/cpu/arm926ejs/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

均不满足

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

OBJS:=arch/arm/cpu/arm926ejs/start.o 

 

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)

#-f表示该文件为常规文件，经查该文件不存在

LIBS += $(CPUDIR)/lib$(CPU).o

LIBS+= arch/arm/cpu/arm926ejs/libarm926ejs.o

ifdef SOC

LIBS += $(CPUDIR)/$(SOC)/lib$(SOC).o

LIBS+=
arch/arm/cpu/arm926ejs/davinci/libdavinci.o

endif

ifeq ($(CPU),ixp)

LIBS += arch/arm/cpu/ixp/npe/libnpe.o

endif

ifeq ($(CONFIG_OF_EMBED),y)

LIBS += dts/libdts.o

endif

LIBS += arch/$(ARCH)/lib/lib$(ARCH).o

LIBS+= arch/arm/libarm.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/ddr/libddr.o

LIBS += arch/powerpc/cpu/mpc8xxx/lib8xxx.o

endif

ifeq ($(CPU),mpc85xx)

LIBS += drivers/qe/libqe.o

LIBS += drivers/net/fm/libfm.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

ifeq ($(CONFIG_GENERIC_LPC_TPM),y)

LIBS += drivers/tpm/libtpm.o

endif

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/usb/ulpi/libusb_ulpi.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

 

ifneq
($(CONFIG_AM33XX)$(CONFIG_OMAP34XX)$(CONFIG_OMAP44XX)$(CONFIG_OMAP54XX),)

LIBS +=
$(CPUDIR)/omap-common/libomap-common.o

endif

 

ifeq ($(SOC),mx5)

LIBS +=
$(CPUDIR)/imx-common/libimx-common.o

endif

ifeq ($(SOC),mx6)

LIBS +=
$(CPUDIR)/imx-common/libimx-common.o

endif

 

ifeq ($(SOC),s5pc1xx)

LIBS +=
$(CPUDIR)/s5p-common/libs5p-common.o

endif

ifeq ($(SOC),exynos)

LIBS +=
$(CPUDIR)/s5p-common/libs5p-common.o

endif

 

LIBS := $(addprefix $(obj),$(sort $(LIBS)))

.PHONY : $(LIBS)

 

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

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

#为LIBBOARD增加前缀，board/davinci/da8xxevm/libda8xxevm.o

 

# 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

#dirname 命令读取指定路径名删除最后一个“/”（斜杠）及其后面的字符，保留其他部分，并写结果到标准输出。如果最后一个“/”后无字符，dirname
命令使用倒数第二个“/”，并忽略其后的所有字符。

CFLGS:=$(CPPFLAGS) -Wall
-Wstrict-prototypes

1）USE_PRIVATE_LIBGCC = yes，从 /arch/arm/lib 中获得 libgcc.a

2）USE_PRIVATE_LIBGCC = path+file，从 指定的路径获得 libgcc.a

3）如果没有配置USE_PRIVATE_LIBGCC，就从工具链 libgcc路径获得。

我们这里没有定义用户私有GCC库，所以执行ifdef的else分支

PLATFORM_LIBGCC
= -L $ (shell dirname $(CC) $(CFLAGS) -print-libgcc-file-name) -lgcc

CC和CFLAGS都是make的隐含变量，CC表示C语言编译器，缺省为：‘cc’。cflags表示执行CC时的命令行参数

但是在这里并不是使用“cc”这个编译器，在顶层的config.mk文件中我们可以找到关于$ (CC)和$(CFLAGS)的定义，如下：

dirname
$(CC) $(CFLAGS) -print-libgcc-file-name取得交叉编译器的libgcc.a的绝对路径

CC =
$(CROSS_COMPILE)gcc // CROSS_COMPILE = arm-none-linux-gnueabi-

                                                    //所以这里：CC = arm-none-linux-gnueabi-gcc

# 没有定义BUILD_TAG，执行else分支,赋值CFLAGS  

ifdef BUILD_TAG  

CFLAGS := $(CPPFLAGS) -Wall -Wstrict-prototypes \  

    -DBUILD_TAG='"$(BUILD_TAG)"'  

else  

CFLAGS := $(CPPFLAGS) -Wall -Wstrict-prototypes  

endif  

  

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

# 利用call函数，使得$1=cc-option ,$2=-fno-stack-protector  

# CFLAGS_SSP= $1$2 = -fno-stack-protector,然后把CFLAGS_SSP  

# 追加给CFLAGS  

CFLAGS_SSP := $(call cc-option,-fno-stack-protector)  

# ARFLAGS = $(error update your Makefile to use cmd_link_o_target and not AR)  

# RELFLAGS=$(PLATFORM_RELFLAGS)=-fno-common -ffixed-r8 -msoft-float  

# DBGFLAGS = -g  

# OPTFLAGS = -Os  

# OBJCFLAGS = --gap-fill=0xff  

# gccincdir = $(shell $(CC) -print-file-name=include)=交叉工具链include目录在宿# 主机中的位置CPPFLAGS = -g -Os -fno-common -ffixed-r8 -msoft-float -D__KERNEL__  

ARFLAGS = $(error update your Makefile to use cmd_link_o_target and not AR)  

RELFLAGS= $(PLATFORM_RELFLAGS)  

DBGFLAGS= -g  # -DDEBUG  

OPTFLAGS= -Os # -fomit-frame-pointer  

  

OBJCFLAGS += --gap-fill=0xff  

  

gccincdir := $(shell $(CC) -print-file-name=include)  

  

CPPFLAGS := $(DBGFLAGS) $(OPTFLAGS) $(RELFLAGS)     \  

    -D__KERNEL__  

  

# Enable garbage collection of un-used sections for SPL  

ifeq ($(CONFIG_SPL_BUILD),y)  

CPPFLAGS += -ffunction-sections -fdata-sections  

LDFLAGS_FINAL += --gc-sections  

endif  

 －L

表示：编译程序按照－L指定的路进去寻找库文件，一般的在-L的后面可以一次用-l指定多个库文件。

-lgcc 代表链接器将连接GCC的支持库libgcc.a  

 

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 += \

       -include
$(TOPDIR)/include/u-boot/u-boot.lds.h \

       -DCPUDIR=$(CPUDIR)
\

       $(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))

 

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

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

 

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

 

# Always append ALL so that arch
config.mk's can add custom ones

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

 

ALL-$(CONFIG_NAND_U_BOOT) +=
$(obj)u-boot-nand.bin

ALL-$(CONFIG_ONENAND_U_BOOT) +=
$(obj)u-boot-onenand.bin

ONENAND_BIN ?=
$(obj)onenand_ipl/onenand-ipl-2k.bin

ALL-$(CONFIG_SPL) +=
$(obj)spl/u-boot-spl.bin

ALL-$(CONFIG_OF_SEPARATE) +=
$(obj)u-boot.dtb $(obj)u-boot-dtb.bin

 

all:          $(ALL-y)
$(SUBDIR_EXAMPLES)

 

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

              $(MAKE)
-C dts binary

              mv
$(obj)dts/dt.dtb $@

 

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

              cat
$^ >$@

 

$(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 \

              -O
u-boot -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 $< > $@

 

$(obj)u-boot.ubl:       $(obj)spl/u-boot-spl.bin
$(obj)u-boot.bin

              $(OBJCOPY)
${OBJCFLAGS} --pad-to=$(PAD_TO) -O binary $(obj)spl/u-boot-spl
$(obj)spl/u-boot-spl-pad.bin

              cat
$(obj)spl/u-boot-spl-pad.bin $(obj)u-boot.bin > $(obj)u-boot-ubl.bin

              $(obj)tools/mkimage
-n $(UBL_CONFIG) -T ublimage \

              -e
$(CONFIG_SYS_TEXT_BASE) -d $(obj)u-boot-ubl.bin $(obj)u-boot.ubl

              rm
$(obj)u-boot-ubl.bin

              rm
$(obj)spl/u-boot-spl-pad.bin

$(obj)u-boot.ais:       $(obj)spl/u-boot-spl.bin
$(obj)u-boot.bin

              $(obj)tools/mkimage -s -n
/dev/null -T aisimage \

                     -e $(CONFIG_SPL_TEXT_BASE)
\

                     -d $(obj)spl/u-boot-spl.bin
\

                     $(obj)spl/u-boot-spl.ais

              $(OBJCOPY) ${OBJCFLAGS} -I binary
\

                     --pad-to=$(CONFIG_SPL_MAX_SIZE)
-O binary \

                     $(obj)spl/u-boot-spl.ais
$(obj)spl/u-boot-spl-pad.ais

              cat $(obj)spl/u-boot-spl-pad.ais
$(obj)u-boot.bin > \

                     $(obj)u-boot.ais

u-boot.ais的编译依赖u-boot-spl.bin，u-boot.bin等文件

$(obj)u-boot.sb:       $(obj)u-boot.bin
$(obj)spl/u-boot-spl.bin

              elftosb
-zdf imx28 -c $(TOPDIR)/board/$(BOARDDIR)/u-boot.bd \

                     -o
$(obj)u-boot.sb

 

ifeq ($(CONFIG_SANDBOX),y)

GEN_UBOOT = \

              cd
$(LNDIR) && $(CC) $(SYMS) -T $(obj)u-boot.lds \

                     -Wl,--start-group
$(__LIBS) -Wl,--end-group \

                     $(PLATFORM_LIBS)
-Wl,-Map -Wl,u-boot.map -o u-boot

else

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

endif

$(obj)u-boot: depend \

              $(SUBDIR_TOOLS)
$(OBJS) $(LIBBOARD) $(LIBS) $(LDSCRIPT) $(obj)u-boot.lds

              $(GEN_UBOOT)

u-boot.ais的编译依赖u-boot-spl.bin，u-boot.bin等文件

$(obj)u-boot.sb:       $(obj)u-boot.bin
$(obj)spl/u-boot-spl.bin

              elftosb
-zdf imx28 -c $(TOPDIR)/board/$(BOARDDIR)/u-boot.bd \

                     -o
$(obj)u-boot.sb

 

ifeq ($(CONFIG_SANDBOX),y)

GEN_UBOOT = \

              cd
$(LNDIR) && $(CC) $(SYMS) -T $(obj)u-boot.lds \

                     -Wl,--start-group
$(__LIBS) -Wl,--end-group \

                     $(PLATFORM_LIBS)
-Wl,-Map -Wl,u-boot.map -o u-boot

else

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

endif

$(obj)u-boot: depend \

              $(SUBDIR_TOOLS)
$(OBJS) $(LIBBOARD) $(LIBS) $(LDSCRIPT) $(obj)u-boot.lds

              $(GEN_UBOOT)

#all依赖于$(ALL) 最终生成镜像文件,注意各种依赖关系。

重点分析一下“u-boot.bin”， u-boot.bin的依赖关系是这样的：$(obj)u-boot.bin - > $(obj)u-boot - >

depend
$(SUBDIRS) $(OBJS) $(LIBBOARD) $(LIBS) $(LDSCRIPT) $(obj)u-boot.lds

先来看看GEN_UBOOT变量的具体内容：

（1） $(OBJDUMP)

在顶层目录的config.mk（$(TOPDIR)/config.mk ）文件中我们可以找到该变量的定义：

OBJDUMP =
$(CROSS_COMPILE)objdump

命令行中定义了 CROSS_COMPILE=arm-none-linux-gnueabi-，所以

OBJDUMP =arm- none-linux-gnueabi
-objdump

（2） $(LIBBOARD)

LIBBOARD在Makefile中有定义。如下：

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

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

展开后得到的结果是：

LIBBOARD =
$(obj)board/davinci/da8xxevm/libda8xxevm.o

（3）$(LIBS)

这个变量是添加库了（在Makefile中定义的），内容比较多，如下：

LIBS =
lib_generic/libgeneric.a

LIBS +=
lib_generic/lzma/liblzma.a

LIBS +=
lib_generic/lzo/liblzo.a

LIBS += $(shellif[-fboard/$(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 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 += cpu/mpc8xxx/ddr/libddr.a

LIBS +=
cpu/mpc8xxx/lib8xxx.a

endif

ifeq ($(CPU),mpc86xx)

LIBS +=
cpu/mpc8xxx/ddr/libddr.a

LIBS +=
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

LBS +=
drivers/usb/phy/libusb_phy.a

LIBS +=
drivers/video/libvideo.a

LIBS += drivers/watchdog/libwatchdog.a

LIBS +=
common/libcommon.a

LIBS += libfdt/libfdt.a

LIBS += api/libapi.a

LIBS += post/libpost.a

从这些添加进来的这些库的文件名，大概可以知道这些库的用途了，包含了cup的配置、drivers驱动程序、api等，这里就不列出了。

（3）$(SYM_PREFIX)

没有定义这个变量，

（4） $(LNDIR)

LNDIR := $(OBJTREE) ，前面分析知道 OBJTREE就是顶层目录了。

（5） $(LD)

在config.mk中有定义

LD =

$(CROSS_COMPILE)ld

 结果为：  LD = arm-none-linux-gnueabi-ld

咱们可以用type命令查看一下“ arm-linux-ld”命令在哪里：

（6）$(LDFLAGS)、$(LDFLAGS_$(@F))

  在config.mk中有定义  ：

  LDFLAGS
+=$(PLATFORM_LDFLAGS)

LDFLAGS_FINAL += -Bstatic  

  

# 设置U-boot的链接选项  

LDFLAGS_u-boot += -T $(obj)u-boot.lds $(LDFLAGS_FINAL)  

ifneq ($(CONFIG_SYS_TEXT_BASE),)  

LDFLAGS_u-boot += -Ttext $(CONFIG_SYS_TEXT_BASE)  

endif  

  

# 设置U-boot的链接选项，当uboot是采用spl时的情况  

LDFLAGS_u-boot-spl += -T $(obj)u-boot-spl.lds $(LDFLAGS_FINAL)  

ifneq ($(CONFIG_SPL_TEXT_BASE),)  

LDFLAGS_u-boot-spl += -Ttext $(CONFIG_SPL_TEXT_BASE)  

endif  



（7） $(__OBJS)和 $(__LIBS)

  在config.mk中有定义  ：

  __OBJS :=
$(subst $(obj),,$(OBJS))

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

    

    subst函数的使用规则：

    $(subst from,to,text)

    在文本‘text’中使用‘to’替换每一处‘from’。

 

 结果就是：将变量OBJS内容里的$(obj)替换成空，然后赋给 __OBJS

     
                

（8）$(PLATFORM_LIBS)

   
PLATFORM_LIBS在Makefile中定义为：

   
PLATFORM_LIBS += $(PLATFORM_LIBGCC)

 

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
$(SUBDIR_TOOLS)

              $(MAKE)
-C $(dir $(subst $(obj),,$@))

 

$(LIBBOARD): depend $(LIBS)

              $(MAKE)
-C $(dir $(subst $(obj),,$@))

 

$(SUBDIRS):   depend

              $(MAKE)
-C $@ all

 

$(SUBDIR_EXAMPLES): $(obj)u-boot

 

$(LDSCRIPT):  depend

              $(MAKE)
-C $(dir $@) $(notdir $@)

 

$(obj)u-boot.lds: $(LDSCRIPT)

              $(CPP)
$(CPPFLAGS) $(LDPPFLAGS) -ansi -D__ASSEMBLY__ -P - <$^ >$@

 



#CPP=$(CC)
-E=$(CORSS_COMPILE)gcc -E=arm-none-linux-gnueabi-gcc -E

# LDPPFLAGS += \

       -include $(TOPDIR)/include/u-boot/u-boot.lds.h \具体的位置是/include/u-boot/u-boot.lds.h

       -DCPUDIR=$(CPUDIR) \

       $(shell $(LD) --version | \

         sed -ne 's/GNU ld
version \([0-9][0-9]*\)\.\([0-9][0-9]*\).*/-DLD_MAJOR=\1 -DLD_MINOR=\2/p')

默认变量“ CPP”  :C
程序的预处理器（输出是标准输出设备）。默认命令是“$(CC) –E”。

-Dmacro：定义宏macro,宏的内容定义为字符串`1'. 这里

-D__ASSEMBLY__ 相当于  #define __ASSEMBLY__   ‘1’
。-D 是选项，__ASSEMBLY__ 相当于一个宏。