linux 顶层Makefile执行的流程

原文地址：linux 顶层Makefile执行的流程作者：天涯孤舟

1、make menuconfig

# *DOCUMENTATION*

# To see a list of typical targets execute "make help"

# More info can be located in ./README

# Comments in this file are targeted only to the developer, donot

# expect to learn how to build the kernel reading this file.

# Do not:

# o use make's built-in rules and variables

# (thisincreases performance and avoids hard-to-debug behaviour);

# o print "Entering directory ...";

MAKEFLAGS += -rR --no-print-directory

#-r禁止使用build-in规则

#--no-print-directory是:不要再屏幕上打印"Entering directory.."

#记住变量SHELL,MAKEFLAGS在整个make的执行过程中

#始终被自动的传递给所有的子make

# We are using a recursive build, so we need to do a littlethinking

# to get the ordering right.

#

# Most importantly: sub-Makefiles should only ever modify filesin

# their own directory. If in some directory we have a dependencyon

# a file in another dir (which doesn't happen often, but it'soften

# unavoidable when linking the built-in.o targets which finy

# turn into vmlinux), we will call a sub make in that other dir,and

# after that we are sure that everything which is in that otherdir

# is now up to date.

#

# The only cases where we need to modify files which haveglobal

# effects are thus separated out and done before therecursive

# descending is started. They are now explicitly listed asthe

# prepare rule.

# To put more focus on warnings, be less verbose asdefault

# Use 'make V=1' to see the full commands

ifdef V #v=1

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

KBUILD_VERBOSE = $(V) #把V的值作为KBUILD_VERBOSE的值

endif

endif

ifndef KBUILD_VERBOSE #即默认我们是不回显的

#回显即在命令执行前显示要执行的命令

KBUILD_VERBOSE = 0

endif

#函数origin并不操作变量的值，只是告诉你你的这个变量是哪里来的。

# 语法是： $(origin <variable>;)#origin函数的返回值有：

#"undefined"从来没有定义过、“default”是一个默认的定义、“

#"environment"是一个环境变量、

#"file"这个变量被定义在Makefile中

#"command line"这个变量是被命令行定义的

#"override"是被override指示符重新定义的

#"automatic"是一个命令运行中的自动化变量

# Call a source code checker (by default, "sparse") as part ofthe

# C compilation.调用一个静态分析工具作为c编译器的

#部分

# Use 'make C=1' to enable checking of only re-compiledfiles.

# Use 'make C=2' to enable checking of *all* source files,regardless

# of whether they are re-compiled or not.

#

# See the file "Documentation/sparse.txt" for more details,including

# where to get the "sparse" utility.

ifdef C

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

KBUILD_CHECKSRC = $(C)

endif

endif

ifndef KBUILD_CHECKSRC

KBUILD_CHECKSRC = 0

endif

#用M来指定外部模块的目录

# Use make M=dir to specify directory of external module tobuild

# Old syntax make ... SUBDIRS=$PWD is still supported

# Setting the environment variable KBUILD_EXTMOD takeprecedence

#识别这里是定义一个外部模块吗??

#当我们定义了M变量或者SUBDIRS时表示编译一个外部模块

# “?=”操作符

#条件赋值的赋值操作符。被称为条件赋值是因为：只有此变量在之前没有赋值的情况下才会对这个变量进行赋值。例如：

FOO ?= bar

#其等价于：

ifeq ($(origin FOO), undefined)

FOO = bar

endif

#含义是：如果变量“FOO”在没有定义过，就给它赋值“bar”。否则不改变它的值。

ifdef SUBDIRS

KBUILD_EXTMOD ?= $(SUBDIRS) #?=为条件赋值操作符仅仅在变量还

#还没有定义的情况下有效

endif

ifdef M

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

在使用“:=”

定义变量时，变量值中对另外变量的引用或者函数的引用在定义时被展开（对变量进行替换）

而=是在使用时才进行替换

举例：

CFLAGS = $(include_dirs)-O

include_dirs = -Ifoo -Ibar

“CFLAGS”会在命令中被展开为“-Ifoo -Ibar-O”

CFLAGS := $(include_dirs)-O

include_dirs := -Ifoo-Ibar

由于在变量“include_dirs”的定义出现在“CFLAGS”定义之后。因此在“CFLAGS”的定义中，

“include_dirs”的值为空。“CFLAGS”的值为“-O”而不是“-Ifoo -Ibar-O”。

KBUILD_EXTMOD := $(M)

endif

endif

# kbuild supports saving output files in a separatedirectory.

# To locate output files in a separate directory two syntaxes aresupported.

# In both cases the working directory must be the root of thekernel src.

# 1) O=

# Use "make O=dir/to/store/output/files/"

#

# 2) Set KBUILD_OUTPUT

# Set the environment variable KBUILD_OUTPUT to point to thedirectory

# where the output files shall be placed.

# export KBUILD_OUTPUT=dir/to/store/output/files/

# make

#

# The O= assignment takes precedence over the KBUILD_OUTPUTenvironment

# variable.

# KBUILD_SRC is set on invocation of make in OBJ directory

# KBUILD_SRC is not intended to be used by the regular user (fornow)

###################make的最开始###################

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

ifeq ($(KBUILD_SRC),)#如果KBUILD_SRC没有定义则进入下面一层即首次进入

#时一般都需要两次进入顶层Makefile

#若定义了则不为空直接跳入下一步

# OK, Make called in directory where kernel src resides

# Do we want to locate output files in a separate directory?

ifdefO #把输出文件放在不同的文件夹内

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

KBUILD_OUTPUT := $(O) #用于指定我们的输出文件的输出目录

endif

endif

# That's our default target when none is given on the commandline

PHONY := _all

_all:

# Cancel implicit rules on top Makefile取消隐式推倒规则

$(CURDIR)/Makefile Makefile: ; #remake 操作查看当前目录Makefile是否为最新

#CURDIR值为当前的内核源码目录current
dir

#为GNU
make使用的变量,CURDIR设置当前工作目录的路径名

ifneq ($(KBUILD_OUTPUT),) #如果输出目录不为空即设置了输出目录则检测

# Invoke a second make in the output directory, passing relevantvariables

# check that the output directory actually exists

saved-output := $(KBUILD_OUTPUT)

KBUILD_OUTPUT := $(shell cd $(KBUILD_OUTPUT)&&/bin/pwd) #这里是测试此目录是否

#存在,若存在则赋给K
BUILD_OUTPUT

$(if $(KBUILD_OUTPUT),,/ #这里的<then-part>为空即表示输出目录不存在

$(error output directory "$(saved-output)" does notexist)) #使用了error函数

#这里的if函数语法为:if<condition>,<then-part>

#或者是if<condition>,<thenpart>,<else-part>

#make的环境变量叫MAKECMDGOALS 这个变量中会存放你所指定的

#终极目标的列表，如果在命令行上，你没有指定目标，

#那么，这个变量是空值。

PHONY += $(MAKECMDGOALS) sub-make

#将任何在命令行中给出的目标放入变量MAKECMDGOALS

#这里filter-out是返回$(MAKECMDGOALS)中除了Makefile _allsub-make以外的

#其他文件; 匹配模式的过滤掉，留下不匹配的

$(filter-out _all sub-make $(CURDIR)/Makefile, $(MAKECMDGOALS))_all: sub-make

$(Q)@:

#这里仅仅只是取消回显没有别的意思

#如果要执行的命令行以字符“@”开始，则make在执行时这个命令就不会被回显。

#$(KBUILD_VERBOSE:1=)为变量替换，如果为1就替换为空

#if KBUILD_VERBOSE = 1 or KBUILD_VERBOSE is NULL

#then

#$(MAKE) -C $(KBUILD_OUTPUT) //回显

#else

#@ $(MAKE) -C $(KBUILD_OUTPUT)//即不回显

#endif

sub-make: FORCE

$(if $(KBUILD_VERBOSE:1=),@)$(MAKE) -C $(KBUILD_OUTPUT)/ #KBUILD_OUTPUT==dir前面测试了

KBUILD_SRC=$(CURDIR) /

KBUILD_EXTMOD="$(KBUILD_EXTMOD)" -f$(CURDIR)/Makefile/ #

$(filter-out _allsub-make,$(MAKECMDGOALS)) #这里是表示要生成的目标

#make
-C dir KBUILD_SRC=`pwd` KBUILD_EXTMOD="" -f `pwd`/Makefile[Targets]

#这里表示再次执行Makefile 但此时我们的KBUILD

#此时再次执行完make后skip-makefile := 1从而

# Leave processing to above invocation ofmake结束子make返回根目录的make

skip-makefile := 1

endif # ifneq ($(KBUILD_OUTPUT),)这里是ifneq

endif # ifeq ($(KBUILD_SRC),)#这里是ifeq的结束处

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

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

ifeq($(skip-makefile),) #如果为空则开始分类执行!!!!!!

#endif #
skip-makefile在1813行处结束最大的ifeq结构

# If building an external module we do not care about the all:rule

# but instead _all depend on modules

PHONY +=all #声明一个伪目标all

ifeq ($(KBUILD_EXTMOD),) #如果外部模块定义为空则_all依赖于all

_all:all

else

_all:modules #否则依赖于modules

endif

srctree := $(if$(KBUILD_SRC),$(KBUILD_SRC),$(CURDIR)) #看KBUILD_SRC是否为空, #设置源码目录

TOPDIR :=$(srctree) #顶层目录

# FIXME - TOPDIR is obsolete, use srctree/objtree

objtree :=$(CURDIR) #CURDIR为make的默认环境变量

src :=$(srctree) #源文件的目录也设置为当前目录

obj :=$(objtree) #目标文件的输出目录设置当前目录

VPATH := $(srctree)$(if$(KBUILD_EXTMOD),:$(KBUILD_EXTMOD))

#这里是说当前目录找不到源文件时的搜索目录

export srctree objtree VPATHTOPDIR

#export用于要将指定变量输出给子make，

# SUBARCH tells the usermode build what the underlying archis. That is set

# first, and if a usermode build is happening, the "ARCH=um" on thecommand

# line overrides the setting of ARCH below. If anative build is happening,

# then ARCH is assigned, getting whatever value it gets normally,and

# SUBARCH is subsequently ignored.

#这里是获取cpu的具体型号存在变量SUBARCH中

#sed -e s表示替换,这里表示出现i.86的用i386替换

#出现sun4u的用sparc64替换

#一般写成sed -e 's/i.86/i386' 用''括起来

SUBARCH := $(shell uname -m | sed -e s/i.86/i386/ -es/sun4u/sparc64/ /

-e s/arm.*/arm/ -e s/sa110/arm/ /

-e s/s390x/s390/ -e s/parisc64/parisc/ /

-e s/ppc.*/powerpc/ -e s/mips.*/mips/ /

-e s/sh.*/sh/ )

# Cross compiling and selecting different set ofgcc/bin-utils

#---------------------------------------------------------------------------

#

# When performing cross compilation for other architectures ARCHshall be set

# to the target architecture. (See archMakefile

export KBUILD_BUILDHOST := $(SUBARCH) #这里是把宿主机的cpu结构导出到

#KBUILD_BUILDHOST变量,并传入子make

ARCH ?=$(SUBARCH)

# 设置变量 ARCH 的方法有两种，

# 一：在命令行中 如： make ARCH=ia64 ；

# 二：设置环境变量，在环境变量中默认

#的 ARCH 的值是执行 make 的 cpu 架构

# "?="表示为ARCH 条件赋值如果ARCH前面没有赋值则这里赋值

#成功,否则不重新赋值

CROSS_COMPILE ?= #交叉编译工具的设置在嵌入式系统

#经常要修改此处设置交叉编译器的路径

# Architecture as present in compile.h

UTS_MACHINE := $(ARCH)

SRCARCH := $(ARCH)

# Additional ARCH settings for x86

ifeq ($(ARCH),i386)

SRCARCH := x86

endif

ifeq ($(ARCH),x86_64)

SRCARCH := x86

endif

KCONFIG_CONFIG ?= .config #这里是生成的配置文件

# SHELL used by kbuild 这里shel中的if [-x file ]测试file是否可执行

CONFIG_SHELL := $(shell if [ -x "$$BASH" ]; then echo $$BASH;/

else if [ -x /bin/bash ]; thenecho /bin/bash; /

else echo sh; fi ; fi)

HOSTCC = gcc

HOSTCXX = g++

HOSTCFLAGS = -Wall-Wstrict-prototypes -O2 -fomit-frame-pointer

HOSTCXXFLAGS = -O2

# Decide whether to build built-in, modular, or both.

# Normally, just do built-in.

KBUILD_MODULES :=

KBUILD_BUILTIN := 1

# If we have only "make modules", don't compilebuilt-in objects.编译内置对象

# When we're building modules with modversions, weneed to consider

# the built-in objects during the descend as well,in order to

# make sure the checksums are up to date before werecord them.

#如果执行”make modules”则这里在这里重新处理KBUILD_BUILTIN :=1

ifeq ($(MAKECMDGOALS),modules)

KBUILD_BUILTIN := $(if$(CONFIG_MODVERSIONS),1)

endif

# If we have "make<whatever> modules", compilemodules

# in addition to whatever we do anyway.

# Just "make" or "make all" shall build modules aswell

#如果执行"make all","make _all","make modules","make"中任一个命令

#则在这里重新处理KBUILD_MODULES

ifneq ($(filter all _allmodules,$(MAKECMDGOALS)),)#filter过滤出指定的字符串

#这里表示如果不为空则编译模块

KBUILD_MODULES := 1

endif

ifeq ($(MAKECMDGOALS),)

KBUILD_MODULES := 1

endif

export KBUILD_MODULES KBUILD_BUILTIN

#导出变量给子make

export KBUILD_CHECKSRC KBUILD_SRC KBUILD_EXTMOD

# Beautify output 格式化的回显控制

#---------------------------------------------------------------------------

#

# Normally, we echo the whole command before executing it. Bymaking

# that echo $($(quiet)$(cmd)), we now have the possibility toset

# $(quiet) to choose other forms of output instead, e.g.

#

# quiet_cmd_cc_o_c = Compiling $(RELDIR)/$@

# cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<

#

# If $(quiet) is empty, the whole command will beprinted.表示如果为空则完全回显

# If it is set to "quiet_", only the short version will be printed.$(quiet)=quiet_表示只有版本显示

# If it is set to "silent_", nothing will be printed at all,since如果$(quiet)=silent表示完全不回显

# the variable $(silent_cmd_cc_o_c) doesn't exist.

#

# A simple variant is to prefix commands with $(Q) - that'suseful..$(Q)用作前缀,如果$(Q)=@表示

# for commands that shall be hidden in non-verbosemode. 不回显,为空表示回显

#

# $(Q)ln $@ :<

#

# If KBUILD_VERBOSE equals 0 then the above command will behidden.

# If KBUILD_VERBOSE equals 1 then the above command isdisplayed.

ifeq ($(KBUILD_VERBOSE),1) #这里就是定义是否要回显

quiet =

Q= #不以@开头表示回显

else

quiet=quiet_

Q =@ #这里以@开头表示不回显

endif

# If the user is running make -s (silent mode), suppress echoingof

# commands

ifneq ($(findstring s,$(MAKEFLAGS)),)

#如果MAKEFLAGS中带了-s表示完全不要回显

quiet=silent_

endif

export quiet Q KBUILD_VERBOSE #导出子make

# Look for make include files relative to root of kernel src

MAKEFLAGS += --include-dir=$(srctree)

# We need some generic definitions (do not try to remake thefile).

$(srctree)/scripts/Kbuild.include: ;

#这里执行remake操作请看GNU make 流程

include $(srctree)/scripts/Kbuild.include #这里是文件包含

#Kbuild.include 这里定义了大量通用的函数和变量

#重点!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

# Make variables (CC, etc...)

#这里是设置编译连接的默认程序,都是变量赋值操作

AS = $(CROSS_COMPILE)as

LD = $(CROSS_COMPILE)ld

CC = $(CROSS_COMPILE)gcc

CPP = $(CC) -E

AR = $(CROSS_COMPILE)ar

NM = $(CROSS_COMPILE)nm

STRIP =$(CROSS_COMPILE)strip

OBJCOPY =$(CROSS_COMPILE)objcopy

OBJDUMP =$(CROSS_COMPILE)objdump

AWK = awk

GENKSYMS = scripts/genksyms/genksyms

DEPMOD = /sbin/depmod

KALLSYMS = scripts/kallsyms

PERL = perl

CHECK = sparse #默认的字符串检查

CHECKFLAGS := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ -Wbitwise$(CF)

MODFLAGS = -DMODULE

CFLAGS_MODULE =$(MODFLAGS)

AFLAGS_MODULE =$(MODFLAGS)

LDFLAGS_MODULE =

CFLAGS_KERNEL =

AFLAGS_KERNEL =

# Use LINUXINCLUDE when you must reference the include/directory.

# Needed to be compatible with the O= option

LINUXINCLUDE := -Iinclude /

$(if $(KBUILD_SRC),-Iinclude2 -I$(srctree)/include) /

-include include/linux/autoconf.h

KBUILD_CPPFLAGS := -D__KERNEL__ $(LINUXINCLUDE)

KBUILD_CFLAGS := -Wall-Wundef -Wstrict-prototypes -Wno-trigraphs /

-fno-strict-aliasing -fno-common /

-Werror-implicit-function-declaration

KBUILD_AFLAGS :=-D__ASSEMBLY__

# Read KERNELRELEASE from include/config/kernel.release (if itexists)

KERNELRELEASE = $(shell cat include/config/kernel.release2> /dev/null)#

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

export VERSION PATCHLEVEL SUBLEVEL KERNELRELEASEKERNELVERSION

export ARCH SRCARCH CONFIG_SHELL HOSTCC HOSTCFLAGS CROSS_COMPILE ASLD CC

export CPP AR NM STRIP OBJCOPY OBJDUMP MAKE AWK GENKSYMS PERLUTS_MACHINE

export HOSTCXX HOSTCXXFLAGS LDFLAGS_MODULE CHECK CHECKFLAGS

export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGSLDFLAGS

export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE

export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE

# When compiling out-of-tree modules, put MODVERDIR in themodule

# tree rather than in the kernel tree. The kernel tree might

# even be read-only.

export MODVERDIR := $(if $(KBUILD_EXTMOD),$(firstword$(KBUILD_EXTMOD))/).tmp_versions

# Files to ignore in find ... statements

RCS_FIND_IGNORE := /( -name SCCS -o -name BitKeeper -o -name.svn -o -name CVS -o -name .pc -o -name .hg -o -name .git /) -prune-o

export RCS_TAR_IGNORE := --exclude SCCS --exclude BitKeeper--exclude .svn --exclude CVS --exclude .pc --exclude .hg --exclude.git

#===========================================================================

# Rules shared between *config targets and build targets

# Basic helpers built in scripts这里生成基本的scripts配置工具fixdepdocproc两个/

PHONY += scripts_basic #定义一个伪目标

scripts_basic: #该伪目标要执行的操作

$(Q)$(MAKE) $(build)=scripts/basic

#build := -f $(if $(KBUILD_SRC),$(srctree)/)scripts/Makefile.buildobj 定义在Kbuild.include中我们在前面

#包含了该文件

#src := $(obj)因为我们Makefile.build中需要带入参数obj用于赋给src

#这里会执行.../scripts/Makefile.build文件===========================

#Makefile.build中包含了scripts/basic/Makefile

# To avoid any implicit rule to kick in, define an emptycommand.

scripts/basic/%: scripts_basic ;

PHONY += outputmakefile

# outputmakefile generates a Makefile in the output directory, ifusing a

# separate output directory. This allows convenient use of make inthe

# output directory.

outputmakefile:

ifneq ($(KBUILD_SRC),) #$(CONFIG_SHELL)即被设置为/bin/sh或者其它shell

$(Q)$(CONFIG_SHELL) $(srctree)/scripts/mkmakefile/#这里的用shell执行mkmakefile

$(srctree) $(objtree) $(VERSION) $(PATCHLEVEL) #并在输出目录中输出

#这个规则的命令运行一个shell脚本scripts/mkmakefile，

#并传递四个参数。这个脚本主要是在$(objtree)参数指定的目录中

#生成一个Makefile文件。由于这里KBUILD_SRC为空，

#所以这个脚本并不会被执行

endif

# To make sure we do not include .config for any of the *configtargets

# catch them early, and hand them over toscripts/kconfig/Makefile

# It is allowed to specify more targets when calling make,including

# mixing *config targets and build targets.

# For example 'make oldconfig all'.

# Detect when mixed targets is specified, and make a secondinvocation

# of make so .config is not included in this case either (for*config).

#GNU configure 中的build/target和host的区别

#build就是现在使用的机器,即编译平台

#host就是我们的目标机,编译好的程序运行的平台

#target一般在构建编译本身的时候(gcc),采用target

no-dot-config-targets := clean mrproper distclean /

cscope TAGStags help %docs check% /

include/linux/version.h headers_% /

kernelrelease kernelversion

#这里是默认值,

config-targets := 0#如果有config %config则为1

mixed-targets := 0#当有config %config还有其它目标时为1

dot-config := 1 #当有config %config时肯定为1

#根据输出参数修改

#make后面的目标包括三类:

#(1)和.config无关的目标即(no_dot_config-targets)比如:clean,mrproper,distclean,

# headers_install,kernelrelease,kernelversion等等；

#(2)和.config相关的目标dot_config

# a:配置目标(config targets)主要是产生.config文件

# b:构建目标(buildtargets)主要是使用.config像all,vmlinux,modules,zImage,等等

#(3)single targets

# 上面没有列出的,如:dir/,dir/file，dir/file.ko

ifneq ($(filter $(no-dot-config-targets),$(MAKECMDGOALS)),)#如果我们命令行目标CMDGOALS

#有任何clean之类的命令

ifeq ($(filter-out $(no-dot-config-targets),$(MAKECMDGOALS)),)#且除了clean之类目标外为空

#那么标识应该删除.config文件

dot-config := 0

endif

endif

ifeq ($(KBUILD_EXTMOD),)

ifneq ($(filter config %config,$(MAKECMDGOALS)),)#这里就是匹配我们命令行

#中是否有menuconfig/xconfig等有则表示

#这是一条配置命令,因而config-targets置1

#标识应该生成.config文件

config-targets := 1

ifneq ($(filter-out config%config,$(MAKECMDGOALS)),)#如果不仅有config目标

#还有别的目标,表示为混合目标模式

mixed-targets := 1

endif

endif

endif

# ============混合模式则则执行以下规则===========

ifeq ($(mixed-targets),1) #如果是混合模式则则执行以下规则

# We're called with mixed targets (*config and buildtargets).

# Handle them one by one.

#%代表make 后带任何目标都执行该命令

#那就是

%:: FORCE

$(Q)$(MAKE) -C $(srctree) KBUILD_SRC= $@

#从代码中可以看出，这里使用了一个双冒号的模式匹配规则。

#百分号代表任何目标都使用这个规则，其中

#$(srctree) 为内核代码树所在目 录 ， KBUILD_SRC 定义为空 。

#所以如果 make 命令为 ： make s3c2410_defconfig all

#那么构建系统就会分别执行下面两条命令：

#make -C $(srctree) KBUILD_SRC= s3c2410_defconfig

#make -C $(srctree) KBUILD_SRC= all

#这其实和简单的用手动的输入两条连续命令

#(make s3c2410_defconfig 和 make all) 是一样效果的。

# ============%configtarge配置时执行以下规则===========

#这里是%config target时执行的规则!!!!!!!!!!!!!!!!!!!!!!!!!!

else

ifeq ($(config-targets),1)

#===========================================================================

# *config targets only - make sure prerequisites are updated, anddescend

# in scripts/kconfig to make the *config target

# Read arch specific Makefile to set KBUILD_DEFCONFIG asneeded.

# KBUILD_DEFCONFIG may point out an alternative defaultconfiguration

# used for 'make defconfig'

include$(srctree)/arch/$(SRCARCH)/Makefile #直接包含平台架构下

#的makefile

export KBUILD_DEFCONFIG

###############执行makemenuconfig的入口点#####################

#生配置工具,根据我们的kconfig

config %config: scripts_basicoutputmakefile FORCE

$(Q)mkdir -p include/linux include/config

$(Q)$(MAKE) $(build)=scripts/kconfig $@

#在顶层目录执行”make
menuconfig”会执行顶层Makefile 第415行的规则

#config %config: scripts_basic outputmakefile FORCE

#$(Q)mkdir -p include/linux include/config

#$(Q)$(MAKE) $(build)=scripts/kconfig $@

#这里"menuconfig"与模式"%config”匹配。所以其执行的规则如下：

#menuconfig: scripts_basic outputmakefile FORCE

#$(Q)mkdir -p include/linux include/config

#$(Q)$(MAKE) $(build)=scripts/kconfig menuconfig

#$@代表规则中目标变量，在多目标的模式规则中，它代表的是哪个触发规则被执行的目标文件名，如上句解释，这里是menuconfig出发的规则

#build := -f $(if$(KBUILD_SRC),$(srctree)/)scripts/Makefile.build obj

#之所以我们引用$(build)=...每次都要是build带一个等于号的

#的原因就是因为$(build)变量后面带了一个obj,从而得到 ... /Makefile.build obj= xxx用于指定

#我们的obj目录是哪里!!!!!!!!!!!!

#这个规则有三个依赖：scripts_basic、outputmakefile、FORCE

#PHONY +=scripts_basic #定义一个伪目标

#scripts_basic: #该伪目标要执行的操作

# $(Q)$(MAKE) $(build)=scripts/basic

#build := -f $(if $(KBUILD_SRC),$(srctree)/)scripts/Makefile.buildobj

#等价于

#@ make -f scripts/Makefile.buildobj=scripts/basic

#这个命令依然是执行scripts/Makefile.build这个makefile文件。

#并执行它里面$@表示menuconfig的规则。

#@ make -f scripts/Makefile.build obj=scripts/kconfig
menuconfig

根据上面的分析，

#在Makefile.build会包含scripts/kconfig/Makefile文件!!!!!!!!!!!!!。

#然后执行以menuconfig为目标的规则，

#在scripts/kconfig/Makefile的13行定义

#menuconfig: $(obj)/mconf

# $< arch/$(ARCH)/Kconfig

#即$<表示依赖集$(obj)/mconf这个是一个解析Kconfig的程序

#arch/$(ARCH)/Kconfig 是被解析的文件

# ===============编译模块或者目标时目标=========================

# Build targets only - this includes vmlinux, arch specifictargets, clean

# targets and others. In general all targets except *configtargets.

else

ifeq ($(KBUILD_EXTMOD),) #

# Additional helpers built in scripts/

# Carefully list dependencies so we do not try to build scriptstwice

# in parallel

PHONY += scripts

scripts: scripts_basic include/config/auto.conf

$(Q)$(MAKE) $(build)=$(@)

#这里生成scripts_basic include/config/auto.conf

# Objects we will link into vmlinux / subdirs we need tovisit

init-y := init/

drivers-y := drivers/ sound/

net-y := net/

libs-y := lib/

core-y := usr/

endif # KBUILD_EXTMOD

ifeq($(dot-config),1) #若.config已经被配置,则可包含产生的auto.conf文件

#
Read in config

-includeinclude/config/auto.conf

ifeq ($(KBUILD_EXTMOD),)

# Read in dependencies to all Kconfig* files, make sure torun

# oldconfig if changes are detected.

-include include/config/auto.conf.cmd

# To avoid any implicit rule to kick in, define an emptycommand

$(KCONFIG_CONFIG) include/config/auto.conf.cmd: ;

# If .config is newer than include/config/auto.conf, someonetinkered

# with it and forgot to run make oldconfig.

# if auto.conf.cmd is missing then we are probably in a cleanedtree so

# we execute the config step to be sure to catch updated Kconfigfiles

#这里是生成我们的需要的三个文件

include/config/auto.conf: $(KCONFIG_CONFIG)include/config/auto.conf.cmd

$(Q)$(MAKE) -f $(srctree)/Makefilesilentoldconfig

else

# external modules needs include/linux/autoconf.h andinclude/config/auto.conf

# but do not care if they are up-to-date. Use auto.conf to triggerthe test

PHONY += include/config/auto.conf

include/config/auto.conf:

$(Q)test -e include/linux/autoconf.h -a -e $@ ||( /

echo; /

echo " ERROR: Kernelconfiguration isinvalid."; /

echo" include/linux/autoconf.h or $@ aremissing."; /

echo" Run 'make oldconfig && makeprepare' on kernel src to fix it."; /

echo; /

/bin/false)

endif # KBUILD_EXTMOD

else

# Dummy target needed, because used as prerequisite

include/config/auto.conf: ;

endif # $(dot-config)

#==============the read targetsstarts======================

#==============vmlinux all modules and other targets============

# The all: target is the default when no target is given onthe

# command line.

# This allow a user to issue only 'make' to build a kernelincluding modules

# Defaults vmlinux but it is usually overridden in the archmakefile

all: vmlinux #这个是默认的目标

ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE

KBUILD_CFLAGS += -Os

else

KBUILD_CFLAGS += -O2

endif

ifneq (CONFIG_FRAME_WARN,0)

KBUILD_CFLAGS += $(callcc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})

endif

# Force gcc to behave correct even for buggy distributions

# Arch Makefiles may override this setting

KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)

include $(srctree)/arch/$(SRCARCH)/Makefile

ifdef CONFIG_FRAME_POINTER

KBUILD_CFLAGS += -fno-omit-frame-pointer-fno-optimize-sibling-calls

else

KBUILD_CFLAGS += -fomit-frame-pointer

endif

ifdef CONFIG_DEBUG_INFO

KBUILD_CFLAGS += -g

KBUILD_AFLAGS += -gdwarf-2

endif

# We trigger additional mismatches with less inlining

ifdef CONFIG_DEBUG_SECTION_MISMATCH

KBUILD_CFLAGS += $(call cc-option,-fno-inline-functions-called-once)

endif

# arch Makefile may override CC so keep this after arch Makefileis included

NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC)-print-file-name=include)

CHECKFLAGS += $(NOSTDINC_FLAGS)

# warn about C99 declaration after statement

KBUILD_CFLAGS += $(callcc-option,-Wdeclaration-after-statement,)

# disable pointer signed / unsigned warnings in gcc 4.0

KBUILD_CFLAGS += $(call cc-option,-Wno-pointer-sign,)

# Add user supplied CPPFLAGS, AFLAGS and CFLAGS as the lastassignments

# But warn user when we do so

warn-assign = /

$(warning "WARNING: Appending $$K$(1) ($(K$(1))) from $(originK$(1)) to kernel $$$(1)")

ifneq ($(KCPPFLAGS),)

$(call warn-assign,CPPFLAGS)

KBUILD_CPPFLAGS += $(KCPPFLAGS)

endif

ifneq ($(KAFLAGS),)

$(call warn-assign,AFLAGS)

KBUILD_AFLAGS += $(KAFLAGS)

endif

ifneq ($(KCFLAGS),)

$(call warn-assign,CFLAGS)

KBUILD_CFLAGS += $(KCFLAGS)

endif

# Use --build-id when available.

LDFLAGS_BUILD_ID = $(patsubst -Wl$(comma)%,%,/

$(call ld-option, -Wl$(comma)--build-id,))

LDFLAGS_MODULE += $(LDFLAGS_BUILD_ID)

LDFLAGS_vmlinux += $(LDFLAGS_BUILD_ID)

# Default kernel image to build when no specific target isgiven.

# KBUILD_IMAGE may be overruled on the command line or

# set in the environment

# Also any assignments in arch/$(ARCH)/Makefile take precedenceover

# this default value

export KBUILD_IMAGE ?=vmlinux

#

# INSTALL_PATH specifies where to place the updated kernel andsystem map

# images. Default is /boot, but you can set it to othervalues

export INSTALL_PATH ?= /boot

#默认的安装目录

#

# INSTALL_MOD_PATH specifies a prefix to MODLIB for moduledirectory

# relocations required by build roots. This isnot defined in the

# makefile but the argument can be passed to make if needed.

#

MODLIB =$(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE)

export MODLIB

#

# INSTALL_MOD_STRIP, if defined, will causemodules to be

# stripped after they areinstalled. If INSTALL_MOD_STRIP is '1',then

# the default option --strip-debug will beused. Otherwise,

# INSTALL_MOD_STRIP will used as the options tothe strip command.

ifdef INSTALL_MOD_STRIP

ifeq ($(INSTALL_MOD_STRIP),1)

mod_strip_cmd = $(STRIP) --strip-debug

else

mod_strip_cmd = $(STRIP) $(INSTALL_MOD_STRIP)

endif # INSTALL_MOD_STRIP=1

else

mod_strip_cmd = true

endif # INSTALL_MOD_STRIP

export mod_strip_cmd

#这里是编译的主体!!!!!!!!!!!!!!!!!!!!!!!

ifeq ($(KBUILD_EXTMOD),)#如果外部模块为空,即编译内核

core-y += kernel/ mm/ fs/ ipc/security/ crypto/ block/

#此时我们的core-y目标需要添加各个模块

#vmlinux-dirs即我们编译内核需要添加的各个模块

#所在的内核目录

vmlinux-dirs := $(patsubst %/,%,$(filter %/,$(init-y) $(init-m) /

$(core-y) $(core-m) $(drivers-y) $(drivers-m) /

$(net-y) $(net-m) $(libs-y) $(libs-m)))

#这里的vmlinux即取目录名称

vmlinux-alldirs := $(sort $(vmlinux-dirs)$(patsubst %/,%,$(filter %/, /#sort is a sequence!

$(init-n) $(init-) /

$(core-n) $(core-) $(drivers-n) $(drivers-) /

$(net-n) $(net-) $(libs-n) $(libs-))))

#################重点###############################

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

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

init-y := $(patsubst %/,%/built-in.o, $(init-y))#这里所有的init/都被

#init/built-in.o所替代

core-y := $(patsubst %/,%/built-in.o, $(core-y))#同上

#vmlinux-main即由各个目录下的build-in.o链接而成

drivers-y := $(patsubst %/, %/built-in.o,$(drivers-y))

net-y := $(patsubst %/,%/built-in.o, $(net-y))

libs-y1 := $(patsubst %/,%/lib.a, $(libs-y))

libs-y2 := $(patsubst %/,%/built-in.o, $(libs-y))

libs-y := $(libs-y1)$(libs-y2)

# Build vmlinux

#---------------------------------------------------------------------------

# vmlinux is built from the objects selected by $(vmlinux-init)and

# $(vmlinux-main). Most are built-in.o files from top-leveldirectories

# in the kernel tree, others are specified inarch/$(ARCH)/Makefile.

# Ordering when linking is important, and $(vmlinux-init) must befirst.

#

# vmlinux

# ^

# |

# +-<$(vmlinux-init)

# | +--<init/version.o + more

# |

# +--<$(vmlinux-main)

# | +--< driver/built-in.o mm/built-in.o + more

# |

# +-< kallsyms.o(see description in CONFIG_KALLSYMS section)

#

# vmlinux version (uname -v) cannot be updated during normal

# descending-into-subdirs phase since we do not yet know if we needto

# update vmlinux.

# Therefore this step is delayed until just before final link ofvmlinux -

# except in the kallsyms case where it is done just before addingthe

# symbols to the kernel.

#

# System.map is generated to document addresses of all kernelsymbols

vmlinux-init := $(head-y)$(init-y)#head-y定义在/arch/xx/Makefile

#head-y :=arch/x86/kernel/head_$(BITS).o

#head-y +=arch/x86/kernel/head$(BITS).o

#head-y +=arch/x86/kernel/init_task.o

vmlinux-main := $(core-y) $(libs-y) $(drivers-y) $(net-y)#the mainbody of linux kernel;

vmlinux-all := $(vmlinux-init)$(vmlinux-main)

vmlinux-lds :=arch/$(SRCARCH)/kernel/vmlinux.lds

#使用与架构相关的

#链接文件lds

export KBUILD_VMLINUX_OBJS := $(vmlinux-all)

# Rule to link vmlinux - also used during CONFIG_KALLSYMS

# May be overridden by arch/$(ARCH)/Makefile

quiet_cmd_vmlinux__ ?=LD $@ #?=means the defualts if without otheroperation

cmd_vmlinux__ ?= $(LD) $(LDFLAGS) $(LDFLAGS_vmlinux) -o $@ /

-T $(vmlinux-lds)$(vmlinux-init) /

--start-group $(vmlinux-main)--end-group /

$(filter-out $(vmlinux-lds) $(vmlinux-init) $(vmlinux-main)vmlinux.o FORCE ,$^)

# Generate new vmlinux version

quiet_cmd_vmlinux_version =GEN .version

cmd_vmlinux_version = set-e; /

if [ ! -r .version ];then /

rm -f.version; /

echo 1>.version; /

else /

mv .version.old_version; /

expr 0$$(cat .old_version) + 1>.version; /

fi; /

$(MAKE) $(build)=init

# Generate System.map

quiet_cmd_sysmap = SYSMAP

cmd_sysmap = $(CONFIG_SHELL) $(srctree)/scripts/mksysmap

# Link of vmlinux

# If CONFIG_KALLSYMS is set .version is already updated

# Generate System.map and verify that the content isconsistent

# Use + in front of the vmlinux_version rule to silent warning withmake -j2

# First command is ':' to allow us to use + in front of therule

#以下是一个命令包,即一组命令可能在多个规则中使用

#相同的一组命令,通过define来定义这组命令作为一个命令,以后

#在需要的规则中通过变量名直接引用!!!!!!!

definerule_vmlinux__

#这里是执行vmlinux的规则

:

$(if $(CONFIG_KALLSYMS),,+$(callcmd,vmlinux_version))

$(call cmd,vmlinux__)

#cmd = @$(echo-cmd) $(cmd_$(1))

#即被展开为cmd_vmlinux__!!!!!!!!!!!!!!!=======

#而此命令为一个连接命令,如下!!!!!!!!========即我们连接命令

#cmd_vmlinux__ ?= $(LD) $(LDFLAGS) $(LDFLAGS_vmlinux) -o $@ /

# -T $(vmlinux-lds)$(vmlinux-init) /

# --start-group $(vmlinux-main)--end-group /

# $(filter-out $(vmlinux-lds) $(vmlinux-init) $(vmlinux-main)vmlinux.o FORCE ,$^)

$(Q)echo 'cmd_$@ := $(cmd_vmlinux__)'> $(@D)/.$(@F).cmd

$(Q)$(if$($(quiet)cmd_sysmap), #生成System.map /

echo ' $($(quiet)cmd_sysmap) System.map'&&) /

$(cmd_sysmap) $@System.map; /

if [ $$? -ne 0 ];then /

rm -f$@; /

/bin/false; /

fi;

$(verify_kallsyms)

endef

#至此我们的vmlinux就链接完成了,接下来就是我们的bzImage了!!!

ifdef CONFIG_KALLSYMS

# Generate section listing all symbols and add it into vmlinux$(kallsyms.o)

# It's a three stage process:

# o .tmp_vmlinux1 has all symbols and sections, but __kallsymsis

# empty

# Running kallsyms on thatgives us .tmp_kallsyms1.o with

# the right size - vmlinuxversion (uname -v) is updated during this step

# o .tmp_vmlinux2 now has a __kallsyms section of the rightsize,

# but due to the added section,some addresses have shifted.

# From here, we generate acorrect .tmp_kallsyms2.o

# o The correct .tmp_kallsyms2.o is linked into the finalvmlinux.

# o Verify that the System.map from vmlinux matches the mapfrom

# .tmp_vmlinux2, just in casewe did not generate kallsyms correctly.

# o If CONFIG_KALLSYMS_EXTRA_PASS is set, do an extra passusing

# .tmp_vmlinux3 and.tmp_kallsyms3.o. This is only meant as a

# temporary bypass to allow thekernel to be built while the

# maintainers work out whatwent wrong with kallsyms.

ifdef CONFIG_KALLSYMS_EXTRA_PASS

last_kallsyms := 3

else

last_kallsyms := 2

endif

kallsyms.o := .tmp_kallsyms$(last_kallsyms).o

#以下是一个命令包,即一组命令可能在多个规则中使用

#相同的一组命令,通过define来定义这组命令作为一个命令,以后

#在需要的规则中通过变量名直接引用!!!!!!!

define verify_kallsyms #这里是命令包名称

$(Q)$(if$($(quiet)cmd_sysmap), /

echo ' $($(quiet)cmd_sysmap) .tmp_System.map'&&) /

$(cmd_sysmap).tmp_vmlinux$(last_kallsyms) .tmp_System.map

$(Q)cmp -s System.map .tmp_System.map|| /

(echo Inconsistent kallsymsdata; /

echo Try settingCONFIG_KALLSYMS_EXTRA_PASS; /

rm .tmp_kallsyms* ; /bin/false)

endef

# Update vmlinux version before link

# Use + in front of this rule to silent warning about make-j1

# First command is ':' to allow us to use + in front of thisrule

cmd_ksym_ld = $(cmd_vmlinux__)

define rule_ksym_ld

:

+$(call cmd,vmlinux_version)

$(call cmd,vmlinux__)

$(Q)echo 'cmd_$@ := $(cmd_vmlinux__)'> $(@D)/.$(@F).cmd

endef

# Generate .S file with all kernel symbols

quiet_cmd_kallsyms =KSYM $@

cmd_kallsyms = $(NM) -n $< | $(KALLSYMS) /

$(if $(CONFIG_KALLSYMS_ALL),--all-symbols) > $@

.tmp_kallsyms1.o .tmp_kallsyms2.o .tmp_kallsyms3.o: %.o: %.Sscripts FORCE

$(call if_changed_dep,as_o_S)

.tmp_kallsyms%.S: .tmp_vmlinux% $(KALLSYMS)

$(call cmd,kallsyms)

# .tmp_vmlinux1 must be complete except kallsyms, so updatevmlinux version

.tmp_vmlinux1: $(vmlinux-lds) $(vmlinux-all) FORCE

$(call if_changed_rule,ksym_ld)

.tmp_vmlinux2: $(vmlinux-lds) $(vmlinux-all) .tmp_kallsyms1.oFORCE

$(call if_changed,vmlinux__)

.tmp_vmlinux3: $(vmlinux-lds) $(vmlinux-all) .tmp_kallsyms2.oFORCE

$(call if_changed,vmlinux__)

# Needs to visit scripts/ before $(KALLSYMS) can be used.

$(KALLSYMS): scripts ;

# Generate some data for debugging strange kallsymsproblems

debug_kallsyms: .tmp_map$(last_kallsyms)

.tmp_map%: .tmp_vmlinux% FORCE

($(OBJDUMP) -h $< | $(AWK) '/^+[0-9]/{print $$4 " 0 " $$2}'; $(NM) $<) | sort> $@

.tmp_map3: .tmp_map2

.tmp_map2: .tmp_map1

endif # ifdef CONFIG_KALLSYMS

# Do modpost on a prelinked vmlinux. The finally linked vmlinuxhas

# relevant sections renamed as per the linker script.

quiet_cmd_vmlinux-modpost =LD $@

cmd_vmlinux-modpost = $(LD) $(LDFLAGS) -r -o$@ /

$(vmlinux-init) --start-group $(vmlinux-main)--end-group /

$(filter-out $(vmlinux-init) $(vmlinux-main)FORCE ,$^)

define rule_vmlinux-modpost: #定义命令包

+$(call cmd,vmlinux-modpost)

$(Q)$(MAKE) -f$(srctree)/scripts/Makefile.modpost $@

$(Q)echo 'cmd_$@ := $(cmd_vmlinux-modpost)'> $(dot-target).cmd

endef

#==================================================

#==================================================

#vmlinux的依赖目标集,开始真正的做主目录下的映像文件

# vmlinux image - including updated kernel symbols

vmlinux: $(vmlinux-lds) $(vmlinux-init) $(vmlinux-main) vmlinux.o$(kallsyms.o) FORCE

ifdef CONFIG_HEADERS_CHECK #这里主要是头检验

$(Q)$(MAKE) -f $(srctree)/Makefileheaders_check

#PHONY += headers_check 当make -f $(srctree)/Makefileheaders_check执行以下命令

#headers_check: headers_install

# $(Q)$(MAKE) -f$(srctree)/scripts/Makefile.headersinst ARCH=$(SRCARCH) obj=includeHDRCHECK=1

endif

ifdef CONFIG_SAMPLES

#配置样本即调用Makefile.build 到Samples目录下make生成样本

$(Q)$(MAKE) $(build)=samples

endif

$(callvmlinux-modpost)#vmlinux-modpost没有被定义,是一条多余的没有被定义的变量

$(call if_changed_rule,vmlinux__)

#在我们所以依赖目标都生成后我们开始链接!!!!!!!!!!===========

#if_changed_rule = $(if $(strip $(any-prereq) $(arg-check)), /

# @set-e; /

# $(rule_$(1)))即执行rule_vmlinux__ 924line

$(Q)rm -f .old_version

# build vmlinux.o first to catch section mismatch errorsearly

ifdef CONFIG_KALLSYMS

.tmp_vmlinux1: vmlinux.o

endif

#modpost-init表示除了init/下的built-in.o

modpost-init := $(filter-out init/built-in.o,$(vmlinux-init))

vmlinux.o: $(modpost-init) $(vmlinux-main) FORCE

$(callif_changed_rule,vmlinux-modpost)#这里是没有存在的,无效

# The actual objects are generated when descending,

# make sure no implicit rule kicks in

$(sort $(vmlinux-init) $(vmlinux-main)) $(vmlinux-lds):$(vmlinux-dirs) ;

# Handle descending into subdirectories listed in$(vmlinux-dirs)

# Preset locale variables to speed up the build process. Limitlocale

# tweaks to this spot to avoid wrong language settings whenrunning

# make menuconfig etc.

# Error messages still appears in the original language

###############真正执行动作!!!!!!####################

PHONY += $(vmlinux-dirs) #伪目标

$(vmlinux-dirs): prepare scripts

$(Q)$(MAKE) $(build)=$@

#(1)build=-f scripts/Makefile.buildobj=<dir> 进行实际的编

#等价于make -f scripts/Makefile.buildobj=$@

#在Makefile.build中第一个真正的依赖规则是__build 大概在93行进入这里我们

#__build又依赖于各个目录下的build-in.o或者lib.a等

#$@表示vmlinux-dirs变量中的各个目标用于传给obj

#vmlinux-dirs := $(patsubst %/,%,$(filter %/,$(init-y) $(init-m) /

# $(core-y) $(core-m) $(drivers-y) $(drivers-m) /

# $(net-y) $(net-m) $(libs-y) $(libs-m)))

#(2)这里的依赖目标有两个prepare:和scripts

# L1180 prepare: prepare0

# L646 PHONY += scripts

# scripts: scripts_basic include/config/auto.conf

# Build the kernel release string

#

# The KERNELRELEASE value built here is stored in the file

# include/config/kernel.release, and is used when executingseveral

# make targets, such as "make install" or "makemodules_install."

#

# The eventual kernel release string consists of the followingfields,

# shown in a hierarchical format to show how smaller parts areconcatenated

# to form the larger and final value, with values coming fromplaces like

# the Makefile, kernel config options, make command line optionsand/or

# SCM tag information.

#

# $(KERNELVERSION)

# $(VERSION) eg,2

# $(PATCHLEVEL) eg,6

# $(SUBLEVEL) eg,18

# $(EXTRAVERSION) eg, -rc6

# $(localver-full)

# $(localver)

# localversion* (files withoutbackups, containing '~')

# $(CONFIG_LOCALVERSION) (from kernel configsetting)

# $(localver-auto) (only ifCONFIG_LOCALVERSION_AUTO is set)

# ./scripts/setlocalversion (SCM tag, if oneexists)

# $(LOCALVERSION) (from makecommand line if provided)

#

# Note how the final $(localver-auto) string isincluded *only* if the

# kernel config option CONFIG_LOCALVERSION_AUTO isselected. Also, at the

# moment, only git is supported but other SCMs can edit thescript

# scripts/setlocalversion and add the appropriate checks asneeded.

pattern = ".*/localversion[^~]*"

string = $(shell cat /dev/null /

`find$(objtree) $(srctree) -maxdepth 1 -regex $(pattern) | sort -u`)

localver = $(subst $(space),, $(string) /

$(patsubst "%",%,$(CONFIG_LOCALVERSION)))

# If CONFIG_LOCALVERSION_AUTO is set scripts/setlocalversion iscalled

# and if the SCM is know a tag from the SCM is appended.

# The appended tag is determined by the SCM used.

#

# Currently, only git is supported.

# Other SCMs can edit scripts/setlocalversion and add theappropriate

# checks as needed.

ifdef CONFIG_LOCALVERSION_AUTO

_localver-auto = $(shell $(CONFIG_SHELL) /

$(srctree)/scripts/setlocalversion $(srctree))

localver-auto =$(LOCALVERSION)$(_localver-auto)

endif

localver-full = $(localver)$(localver-auto)

# Store (new) KERNELRELASE string ininclude/config/kernel.release

kernelrelease = $(KERNELVERSION)$(localver-full)

include/config/kernel.release: include/config/auto.conf FORCE

$(Q)rm -f $@

$(Q)echo $(kernelrelease) > $@

# Things we need to do before we recursively start building thekernel

# or the modules are listed in "prepare".

# A multi level approach is used. prepareN is processed beforeprepareN-1.

# archprepare is used in arch Makefiles and when processed asmsymlink,

# version.h and scripts_basic is processed / created.

# Listed in dependency order

PHONY += prepare archprepare prepare0 prepare1 prepare2prepare3

#定义多个伪目标

# prepare3 is used to check if we are building in a separate outputdirectory,

#第三步主要检查我们是否为自定义了输出目录

# and if so do:

# 1) Check that make has not been executed in the kernel src$(srctree)

# 2) Create the include2 directory, used for the second asmsymlink

prepare3: include/config/kernel.release

ifneq ($(KBUILD_SRC),)

@echo ' Using $(srctree) assource for kernel'

$(Q)if [ -f $(srctree)/.config -o -d$(srctree)/include/config ]; then /

echo " $(srctree) is not clean, please run 'make mrproper'";/

echo " in the'$(srctree)' directory.";/

/bin/false; /

fi;

$(Q)if [ ! -d include2 ]; then mkdir -p include2;fi;

$(Q)ln -fsn $(srctree)/include/asm-$(SRCARCH)include2/asm

endif

# prepare2 creates a makefile if using a separate outputdirectory

prepare2: prepare3 outputmakefile

prepare1: prepare2 include/linux/version.hinclude/linux/utsrelease.h /

include/asm include/config/auto.conf

$(cmd_crmodverdir)

archprepare: prepare1 scripts_basic

prepare0: archprepare FORCE

$(Q)$(MAKE) $(build)=.

$(Q)$(MAKE) $(build)=. missing-syscalls

# All the preparing..

prepare: prepare0

# Leave this as default for preprocessing vmlinux.lds.S, which isnow

# done in arch/$(ARCH)/kernel/Makefile

export CPPFLAGS_vmlinux.lds += -P -C -U$(ARCH)

# The asm symlink changes when $(ARCH) changes.

# Detect this and ask user to run make mrproper

#set -e 是设置一种shell状态即如果它执行的任何一条命令的退出码非零

#都立刻终止

include/asm: FORCE

$(Q)set -e; asmlink=`readlink include/asm | cut-d '-' -f 2`; /

if [ -L include/asm ];then /

if [ "$$asmlink" !="$(SRCARCH)" ];then /

echo "ERROR:the symlink $@ points to asm-$$asmlink but asm-$(SRCARCH) wasexpected"; /

echo" set ARCH or save .config and run 'make mrproper' to fixit"; /

exit1; /

fi; /

else /

echo ' SYMLINK $@ ->include/asm-$(SRCARCH)'; /

if [ ! -d include ];then /

mkdir -pinclude; /

fi; /

ln -fsn asm-$(SRCARCH)$@; /

fi

# Generate some files

#---------------------------------------------------------------------------

# KERNELRELEASE can change from a few different places, meaningversion.h

# needs to be updated, so this check is forced on all builds

uts_len := 64

define filechk_utsrelease.h

if [ `echo -n "$(KERNELRELEASE)" | wc -c ` -gt$(uts_len) ]; then /

echo '"$(KERNELRELEASE)"exceeds $(uts_len) characters'>&2; /

exit1; /

fi; /

(echo /#define UTS_RELEASE/"$(KERNELRELEASE)/";)

endef

define filechk_version.h

(echo /#define LINUX_VERSION_CODE$(shell /

expr $(VERSION) Kbuild)))

PHONY += headers_install_all

headers_install_all: include/linux/version.h scripts_basicFORCE

$(Q)$(MAKE) $(build)=scriptsscripts/unifdef

$(Q)for arch in $(HDRARCHES); do /

$(MAKE) ARCH=$$arch -f$(srctree)/scripts/Makefile.headersinst obj=includeBIASMDIR=-bi-$$arch ;/

done

PHONY += headers_install

headers_install: include/linux/version.h scripts_basic FORCE

@if [ ! -r$(srctree)/include/asm-$(SRCARCH)/Kbuild ]; then /

echo '*** Error: Headers notexportable for this architecture ($(SRCARCH))'; /

exit 1 ; fi

$(Q)$(MAKE) $(build)=scriptsscripts/unifdef

$(Q)$(MAKE) -f$(srctree)/scripts/Makefile.headersinst ARCH=$(SRCARCH)obj=include

PHONY += headers_check_all

headers_check_all: headers_install_all

$(Q)for arch in $(HDRARCHES); do /

$(MAKE) ARCH=$$arch -f$(srctree)/scripts/Makefile.headersinst obj=includeBIASMDIR=-bi-$$arch HDRCHECK=1 ;/

done

PHONY += headers_check

headers_check: headers_install

$(Q)$(MAKE) -f$(srctree)/scripts/Makefile.headersinst ARCH=$(SRCARCH) obj=includeHDRCHECK=1

#---------------------------------------------------------------------------

# Modules

ifdef CONFIG_MODULES

# By default, build modules as well

all: modules

# Build modules

#

# A module can be listed more than once in obj-mresulting in

# duplicate lines in modules.orderfiles. Those are removed

# using awk while concatenating to the finalfile.

PHONY += modules

modules: $(vmlinux-dirs) $(if $(KBUILD_BUILTIN),vmlinux)

$(Q)$(AWK) '!x[$$0]++'$(vmlinux-dirs:%=$(objtree)/%/modules.order) >$(objtree)/modules.order

@echo ' Building modules, stage2.';

$(Q)$(MAKE) -f$(srctree)/scripts/Makefile.modpost

# Target to prepare building external modules

PHONY += modules_prepare

modules_prepare: prepare scripts

# Target to install modules

PHONY += modules_install

modules_install: _modinst_ _modinst_post

PHONY += _modinst_

_modinst_:

@if [ -z "`$(DEPMOD) -V2>/dev/null | grep module-init-tools`" ]; then/

echo "Warning: you may need toinstall module-init-tools"; /

echo "See http://www.codemonkey.org.uk/docs/post-halloween-2.6.txt";/
sleep 1; /

fi

@rm -rf $(MODLIB)/kernel

@rm -f $(MODLIB)/source

@mkdir -p $(MODLIB)/kernel

@ln -s $(srctree) $(MODLIB)/source

@if [ ! $(objtree) -ef $(MODLIB)/build ]; then /

rm -f $(MODLIB)/build ; /

ln -s $(objtree)$(MODLIB)/build ; /

fi

@cp -f $(objtree)/modules.order $(MODLIB)/

$(Q)$(MAKE) -f$(srctree)/scripts/Makefile.modinst

# This depmod is only for convenience to give the initial

# boot a modules.dep even before / is mountedread-write. However the

# boot script depmod is the master version.

PHONY += _modinst_post

_modinst_post: _modinst_

$(call cmd,depmod)

else # CONFIG_MODULES

# Modules not configured

#---------------------------------------------------------------------------

modules modules_install: FORCE

@echo

@echo "The present kernel configuration hasmodules disabled."

@echo "Type 'make config' and enable loadablemodule support."

@echo "Then build a kernel with module supportenabled."

@echo

@exit 1

endif # CONFIG_MODULES

###

# Cleaning is done on three levels.

# makeclean Delete most generated files

# Leave enough to build external modules

# make mrproper Delete the current configuration,and all generated files

# make distclean Remove editor backup files, patch leftover filesand the like

# Directories & files removed with 'makeclean'