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 "$$BASH" ]; then echo $$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 := $(O)
endif
endif
第二种方式
ifneq ($(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)) OBJTREE
BUILD_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
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
# $(CPPFLAGS) sets -g, which causes gcc to pass a suitable -g
# option to the assembler.
AFLAGS_DEBUG :=
# turn jbsr into jsr for m68k
ifeq ($(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="\"$${smap}\"" \
-c common/system_map.c -o $(obj)common/system_map.o
$(GEN_UBOOT) $(obj)common/system_map.o
endif
$(OBJS):
depend
$(MAKE) -C $(CPUDIR) $(if $(REMOTE_BUILD),$@,$(notdir $@))
$(LIBS):
depend $(SUBDIRS)
$(MAKE) -C $(dir $(subst $(obj),,$@))
$(LIBBOARD):
depend $(LIBS)
$(MAKE) -C $(dir $(subst $(obj),,$@))
$(SUBDIRS):
depend
$(MAKE) -C $@ all
$(LDSCRIPT):
depend
$(MAKE) -C $(dir $@) $(notdir $@)
$(obj)u-boot.lds: $(LDSCRIPT)
$(CPP) $(CPPFLAGS) $(LDPPFLAGS) -ansi -D__ASSEMBLY__ -P - <$^ >$@
$(NAND_SPL):
$(TIMESTAMP_FILE) $(VERSION_FILE) $(obj)include/autoconf.mk
$(MAKE) -C nand_spl/board/$(BOARDDIR) all
$(U_BOOT_NAND):
$(NAND_SPL) $(obj)u-boot.bin
cat $(obj)nand_spl/u-boot-spl-16k.bin $(obj)u-boot.bin > $(obj)u-boot-nand.bin
$(ONENAND_IPL):
$(TIMESTAMP_FILE) $(VERSION_FILE) $(obj)include/autoconf.mk
$(MAKE) -C onenand_ipl/board/$(BOARDDIR) all
$(U_BOOT_ONENAND):
$(ONENAND_IPL) $(obj)u-boot.bin
cat $(ONENAND_BIN) $(obj)u-boot.bin > $(obj)u-boot-onenand.bin
$(VERSION_FILE):
@( printf '#define U_BOOT_VERSION "U-Boot %s%s"\n' "$(U_BOOT_VERSION)" \
'$(shell $(TOPDIR)/tools/setlocalversion $(TOPDIR))' ) > [email protected]
$(TIMESTAMP_FILE):
@date +'#define U_BOOT_DATE "%b %d %C%y"' > $@
@date +'#define U_BOOT_TIME "%T"' >> $@
gdbtools:
$(MAKE) -C tools/gdb all || exit 1
updater:
$(MAKE) -C tools/updater all || exit 1
env:
$(MAKE) -C tools/env all MTD_VERSION=${MTD_VERSION} || exit 1
# Explicitly make _depend in subdirs containing multiple targets to prevent
# parallel sub-makes creating .depend files simultaneously.
depend dep: $(TIMESTAMP_FILE) $(VERSION_FILE) $(obj)include/autoconf.mk
for dir in $(SUBDIRS) $(CPUDIR) $(dir $(LDSCRIPT)) ; do \
$(MAKE) -C $$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 > [email protected] && \
mv [email protected] $@
#########################################################################
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
#include
#include
***********************************************************************************************************************
#!/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
#
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
fi
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
fi
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
fi
if [ "$2" = "arm" ] ; then
rm -f asm/proc
ln -s ${LNPREFIX}proc-armv asm/proc
创建proc链接
fi
#
#
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/$4
fi
#
#
Create board specific header file 创建config.h文件
#
if [ "$APPEND" = "yes" ]
# Append to existing config file
then
echo >> config.h
else
> config.h
# Create new config file
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
#include
#include
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 "+$$F-%Y-%m-%d-%T.tar.gz"` $$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。