U-BOOT主MAKEFILE代码

#
# (C) Copyright 2000-2006
# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
#
# See file CREDITS for list of people who contributed to this
# project.
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License as
# published by the Free Software Foundatio; either version 2 of
# the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston,
# MA 02111-1307 USA
#

VERSION = 1
PATCHLEVEL = 1
SUBLEVEL = 6
EXTRAVERSION =
U_BOOT_VERSION = $(VERSION).$(PATCHLEVEL).$(SUBLEVEL)$(EXTRAVERSION)
VERSION_FILE = $(obj)include/version_autogenerated.h

HOSTARCH := $(shell uname -m | /
 sed -e s/i.86/i386/ /
     -e s/sun4u/sparc64/ /
     -e s/arm.*/arm/ /
     -e s/sa110/arm/ /
     -e s/powerpc/ppc/ /
     -e s/macppc/ppc/)

HOSTOS := $(shell uname -s | tr '[:upper:]' '[:lower:]' | /
     sed -e 's//(cygwin/).*/cygwin/')

export HOSTARCH HOSTOS

# Deal with colliding definitions from tcsh etc.
VENDOR=

#########################################################################
#
# 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 //如果定义了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,LNDIR存放生成文件的目录，SRCTREE,TOPDIR目录存放源代码的目录
OBJTREE  := $(if $(BUILD_DIR),$(BUILD_DIR),$(CURDIR))
SRCTREE  := $(CURDIR)
TOPDIR  := $(SRCTREE)
LNDIR  := $(OBJTREE)
export TOPDIR SRCTREE OBJTREE

#MKCONFIG指向顶层目录的MKCONFIG脚本
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

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

#包含include/config.mk,相当于MAKEFILE中定义了三个变量ARCH ,BOARD ,CPU
ifeq ($(OBJTREE)/include/config.mk,$(wildcard $(OBJTREE)/include/config.mk))

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

#以下是指定交叉编译器
ifndef CROSS_COMPILE
ifeq ($(HOSTARCH),ppc)
CROSS_COMPILE =
else
ifeq ($(ARCH),ppc)
CROSS_COMPILE = powerpc-linux-
endif
ifeq ($(ARCH),arm)
CROSS_COMPILE = arm-linux-
endif
ifeq ($(ARCH),i386)
ifeq ($(HOSTARCH),i386)
CROSS_COMPILE =
else
CROSS_COMPILE = i386-linux-
endif
endif
ifeq ($(ARCH),mips)
CROSS_COMPILE = mips_4KC-
endif
ifeq ($(ARCH),nios)
CROSS_COMPILE = nios-elf-
endif
ifeq ($(ARCH),nios2)
CROSS_COMPILE = nios2-elf-
endif
ifeq ($(ARCH),m68k)
CROSS_COMPILE = m68k-elf-
endif
ifeq ($(ARCH),microblaze)
CROSS_COMPILE = mb-
endif
ifeq ($(ARCH),blackfin)
CROSS_COMPILE = bfin-elf-
endif
ifeq ($(ARCH),avr32)
CROSS_COMPILE = avr32-
endif
endif
endif

export CROSS_COMPILE

#包含顶层目录下的config.mk，这个文件里面主要定义了交叉编译器及选项和编译规则
# load other configuration
include $(TOPDIR)/config.mk

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

OBJS  = cpu/$(CPU)/start.o //顺序很重要，start.o一定放到最前面
ifeq ($(CPU),i386)
OBJS += cpu/$(CPU)/start16.o
OBJS += cpu/$(CPU)/reset.o
endif
ifeq ($(CPU),ppc4xx)
OBJS += cpu/$(CPU)/resetvec.o
endif
ifeq ($(CPU),mpc83xx)
OBJS += cpu/$(CPU)/resetvec.o
endif
ifeq ($(CPU),mpc85xx)
OBJS += cpu/$(CPU)/resetvec.o
endif
ifeq ($(CPU),mpc86xx)
OBJS += cpu/$(CPU)/resetvec.o
endif
ifeq ($(CPU),bf533)
OBJS += cpu/$(CPU)/start1.o cpu/$(CPU)/interrupt.o cpu/$(CPU)/cache.o
OBJS += cpu/$(CPU)/cplbhdlr.o cpu/$(CPU)/cplbmgr.o cpu/$(CPU)/flush.o
endif

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

需要的库文件：

LIBS  = lib_generic/libgeneric.a
LIBS += board/$(BOARDDIR)/lib$(BOARD).a
LIBS += cpu/$(CPU)/lib$(CPU).a
ifdef SOC
LIBS += cpu/$(CPU)/$(SOC)/lib$(SOC).a
endif
LIBS += lib_$(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
LIBS += net/libnet.a
LIBS += disk/libdisk.a
LIBS += rtc/librtc.a
LIBS += dtt/libdtt.a
LIBS += drivers/libdrivers.a
LIBS += drivers/nand/libnand.a
LIBS += drivers/nand_legacy/libnand_legacy.a
LIBS += drivers/usb/libusb.a
LIBS += drivers/sk98lin/libsk98lin.a
LIBS += common/libcommon.a
LIBS += $(BOARDLIBS)

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

#根据上面的include/config.mk文件定义的ARCH、CPU、BOARD、SOC这些变量。
#硬件平台依赖的目录文件可以根据这些定义来确定。
#SMDK2410平台相关目录及对应生成的库文件如下。
 #   board/smdk2410/        ：库文件board/smdk2410/libsmdk2410.a
 #  cpu/arm920t/              ：库文件cpu/arm920t/libarm920t.a
 # cpu/arm920t/s3c24x0/ :  库文件cpu/arm920t/s3c24x0/libs3c24x0.a
 # lib_arm/                     : 库文件lib_arm/libarm.a
 #include/asm-arm/       :下面两个是头文件。
 #include/configs/smdk2410.h

 

# Add GCC lib
PLATFORM_LIBS += -L $(shell dirname `$(CC) $(CFLAGS) -print-libgcc-file-name`) -lgcc -lc -L/usr/local/arm/4.3.2/arm-none-linux-gnueabi/libc/armv4t/usr/lib

# The "tools" are needed early, so put this first
# Don't include stuff already done in $(LIBS)
@执行tools ,examples ,post,post/cpu 子目录下面的make文件
SUBDIRS = tools /
   examples /
   post /
   post/cpu
.PHONY : $(SUBDIRS)

ifeq ($(CONFIG_NAND_U_BOOT),y)
NAND_SPL = nand_spl
U_BOOT_NAND = $(obj)u-boot-nand.bin
endif

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

#########################################################################
#########################################################################
#最终生成的各种镜像文件：

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

all:  $(ALL)

$(obj)u-boot.hex: $(obj)u-boot
  $(OBJCOPY) ${OBJCFLAGS} -O ihex $< $@

$(obj)u-boot.srec: $(obj)u-boot
  $(OBJCOPY) ${OBJCFLAGS} -O srec $< $@

$(obj)u-boot.bin: $(obj)u-boot
  $(OBJCOPY) ${OBJCFLAGS} -O binary $< $@

$(obj)u-boot.img: $(obj)u-boot.bin
  ./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.dis: $(obj)u-boot
  $(OBJDUMP) -d $< > $@

$(obj)u-boot:  depend version $(SUBDIRS) $(OBJS) $(LIBS) $(LDSCRIPT)
  UNDEF_SYM=`$(OBJDUMP) -x $(LIBS) |sed  -n -e 's/.*/(__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

$(OBJS): @即cpu/start.o 
 echo $(OBJS) 
  $(MAKE) -C cpu/$(CPU) $(if $(REMOTE_BUILD),$@,$(notdir $@))

$(LIBS): @依赖目标$(LIBS)，这个目标太多，都是每个子目录的库文件*.a ，通过执行相应子目录下的make来完成：
  $(MAKE) -C $(dir $(subst $(obj),,$@))

usb:
 $(MAKE) -C drivers/usb

$(SUBDIRS): @伪目标SUBDIRS: 执行tools ,examples ,post,post/cpu 子目录下面的make文件。
  $(MAKE) -C $@ all

$(NAND_SPL): version
  $(MAKE) -C nand_spl/board/$(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

分析一下最关键的u-boot ELF文件镜像的生成：(详细见MAKEFILE篇)

version: @依赖目标version：生成版本信息到版本文件VERSION_FILE中
  @echo -n "#define U_BOOT_VERSION /"U-Boot " > $(VERSION_FILE); /
  echo -n "$(U_BOOT_VERSION)" >> $(VERSION_FILE); /
  echo -n $(shell $(CONFIG_SHELL) $(TOPDIR)/tools/setlocalversion /
    $(TOPDIR)) >> $(VERSION_FILE); /
  echo "/"" >> $(VERSION_FILE)

gdbtools:
  $(MAKE) -C tools/gdb all || exit 1

updater:
  $(MAKE) -C tools/updater all || exit 1

env:
  $(MAKE) -C tools/env all || exit 1

depend dep: @依赖目标depend :生成各个子目录的.depend文件，.depend列出每个目标文件的依赖文件。
  @生成方法，调用每个子目录的make _depend。
  for dir in $(SUBDIRS) ; do $(MAKE) -C $$dir _depend ; done

tags ctags:
  ctags -w -o $(OBJTREE)/ctags `find $(SUBDIRS) include /
    lib_generic board/$(BOARDDIR) cpu/$(CPU) lib_$(ARCH) /
    fs/cramfs fs/fat fs/fdos fs/jffs2 /
    net disk rtc dtt drivers drivers/sk98lin common /
   /( -name CVS -prune /) -o /( -name '*.[ch]' -print /)`

etags:
  etags -a -o $(OBJTREE)/etags `find $(SUBDIRS) include /
    lib_generic board/$(BOARDDIR) cpu/$(CPU) lib_$(ARCH) /
    fs/cramfs fs/fat fs/fdos fs/jffs2 /
    net disk rtc dtt drivers drivers/sk98lin common /
   /( -name CVS -prune /) -o /( -name '*.[ch]' -print /)`

$(obj)System.map: $(obj)u-boot
  @$(NM) $< | /
  grep -v '/(compiled/)/|/(/.o$$/)/|/( [aUw] /)/|/(/./.ng$$/)/|/(LASH[RL]DI/)' | /
  sort > $(obj)System.map

#########################################################################
else
all $(obj)u-boot.hex $(obj)u-boot.srec $(obj)u-boot.bin /
$(obj)u-boot.img $(obj)u-boot.dis $(obj)u-boot /
$(SUBDIRS) version gdbtools updater env depend /
dep tags ctags etags $(obj)System.map:
 @echo "System not configured - see README" >&2
 @ exit 1
endif

.PHONY : CHANGELOG
CHANGELOG:
 git log --no-merges U-Boot-1_1_5.. | /
 unexpand -a | sed -e 's//s/s*$$//' > $@