makefile-5.3.12

78 阅读 0 评论 52 点赞

我是靠谱客的博主悦耳可乐，最近开发中收集的这篇文章主要介绍makefile-5.3.12，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

构建顺序

代码分析

版本号等的定义，并将默认目标定义好，即_all，最后通过_all的依赖项决定到编译哪个目标。

VERSION = 5
PATCHLEVEL = 3
SUBLEVEL = 12
EXTRAVERSION =
NAME = Bobtail Squid
PHONY := _all
_all:

linux的编译可以指定输出路径的，如果自行指定输出路径，则会在对应路径再次运行make。所以会分为两步进行。同样的，即使不指定输出路径，也会进行两步。分别为make和sub-make。make是用户自行调用的，sub-make是由make调用的在输出路径下的make。

路径确定

# sub_make_done表示当前是否正在进行sub-make
# need-sub-make表示当前make是否需要进行sub-make
ifneq ($(sub_make_done),1)
# 不让make使用隐式规则，这样避免一些难以确定的问题。
MAKEFLAGS += -rR
# 字符集定义
unexport LC_ALL
LC_COLLATE=C
LC_NUMERIC=C
export LC_COLLATE LC_NUMERIC
# 避免环境变量的影响
unexport GREP_OPTIONS
# 通过一些小手段来控制输出的详细程度
ifeq ("$(origin V)", "command line")
KBUILD_VERBOSE = $(V)
endif
ifndef KBUILD_VERBOSE
KBUILD_VERBOSE = 0
endif
ifeq ($(KBUILD_VERBOSE),1)
quiet =
Q =
else
quiet=quiet_
Q = @
endif
ifneq ($(findstring s,$(filter-out --%,$(MAKEFLAGS))),)
quiet=silent_
endif
export quiet Q KBUILD_VERBOSE
# 指定的输出目录，通过make O=...传入
ifeq ("$(origin O)", "command line")
KBUILD_OUTPUT := $(O)
endif
ifneq ($(KBUILD_OUTPUT),)
# 保证输出目录存在
abs_objtree := $(shell mkdir -p $(KBUILD_OUTPUT) && cd $(KBUILD_OUTPUT) && pwd)
$(if $(abs_objtree),, 
$(error failed to create output directory "$(KBUILD_OUTPUT)"))
abs_objtree := $(realpath $(abs_objtree))
else
abs_objtree := $(CURDIR)
endif # ifneq ($(KBUILD_OUTPUT),)
ifeq ($(abs_objtree),$(CURDIR))
MAKEFLAGS += --no-print-directory
else
need-sub-make := 1
endif
# 通过Makefile的路径来确定源码目录，并保证目录没有":"和空格
abs_srctree := $(realpath $(dir $(lastword $(MAKEFILE_LIST))))
ifneq ($(words $(subst :, ,$(abs_srctree))), 1)
$(error source directory cannot contain spaces or colons)
endif
# 如果源码目录跟输出目录不同，则需要sub-make
ifneq ($(abs_srctree),$(abs_objtree))
MAKEFLAGS += --include-dir=$(abs_srctree)
need-sub-make := 1
endif
# make 3.x的'MAKEFLAGS += -rR'并不是立马生效 ，所以需要sub-make来屏蔽隐式规则，同时屏蔽当前makefile的隐式规则
ifneq ($(filter 3.%,$(MAKE_VERSION)),)
need-sub-make := 1
$(lastword $(MAKEFILE_LIST)): ;
endif
取消回显没有别的export abs_srctree abs_objtree
export sub_make_done := 1
ifeq ($(need-sub-make),1)
PHONY += $(MAKECMDGOALS) sub-make
$(filter-out _all sub-make $(lastword $(MAKEFILE_LIST)), $(MAKECMDGOALS)) _all: sub-make
@:
# 在输出目录下调用make
sub-make:
$(Q)$(MAKE) -C $(abs_objtree) -f $(abs_srctree)/Makefile $(MAKECMDGOALS)
endif # need-sub-make
endif # sub_make_done

正式编译

如果不需要sub-make，则当前的make调用需要进行真正的编译操作。

ifeq ($(need-sub-make),)
...
endif
# need-sub-make

MAKEFLAGS += --no-print-directory
# C=1只检查需要重新编译的文件
# C=2 检查所有的文件
ifeq ("$(origin C)", "command line")
KBUILD_CHECKSRC = $(C)
endif
ifndef KBUILD_CHECKSRC
KBUILD_CHECKSRC = 0
endif

确定M的值，确定需要编译的外部模块

ifeq ("$(origin M)", "command line")
KBUILD_EXTMOD := $(M)
endif
export KBUILD_CHECKSRC KBUILD_EXTMOD

确定源码路径

ifeq ($(abs_srctree),$(abs_objtree))
# building in the source tree
srctree := .
building_out_of_srctree :=
else
ifeq ($(abs_srctree)/,$(dir $(abs_objtree)))
# building in a subdirectory of the source tree
srctree := ..
else
srctree := $(abs_srctree)
endif
building_out_of_srctree := 1
endif
ifneq ($(KBUILD_ABS_SRCTREE),)
srctree := $(abs_srctree)
endif
objtree
:= .
VPATH
:= $(srctree)
export building_out_of_srctree srctree objtree VPATH

version_h := include/generated/uapi/linux/version.h
old_version_h := include/linux/version.h
# 清理用的target
clean-targets := %clean mrproper cleandocs
# 不需要依赖.config的target
no-dot-config-targets := $(clean-targets) 
cscope gtags TAGS tags help% %docs check% coccicheck 
$(version_h) headers headers_% archheaders archscripts 
%asm-generic kernelversion %src-pkg
# 不需要同步config的target
no-sync-config-targets := $(no-dot-config-targets) install %install 
kernelrelease
config-targets
:= 0
mixed-targets
:= 0
dot-config
:= 1
may-sync-config := 1
# 确定是否需要依赖.config
ifneq ($(filter $(no-dot-config-targets), $(MAKECMDGOALS)),)
ifeq ($(filter-out $(no-dot-config-targets), $(MAKECMDGOALS)),)
dot-config := 0
endif
endif
# 确定是否需要同步config
ifneq ($(filter $(no-sync-config-targets), $(MAKECMDGOALS)),)
ifeq ($(filter-out $(no-sync-config-targets), $(MAKECMDGOALS)),)
may-sync-config := 0
endif
endif
# 如果是构建外部模块，则不需要同步config
ifneq ($(KBUILD_EXTMOD),)
may-sync-config := 0
endif
# 确定是不是config 与build的混合目标
ifeq ($(KBUILD_EXTMOD),)
ifneq ($(filter config %config,$(MAKECMDGOALS)),)
config-targets := 1
ifneq ($(words $(MAKECMDGOALS)),1)
mixed-targets := 1
endif
endif
endif
# 如 "make -j clean all", "make -j mrproper defconfig all"等，清理target与非清理target也是混合目标
ifneq ($(filter $(clean-targets),$(MAKECMDGOALS)),)
ifneq ($(filter-out $(clean-targets),$(MAKECMDGOALS)),)
mixed-targets := 1
endif
endif
# install和modules_install也需要按顺序进行
ifneq ($(filter install,$(MAKECMDGOALS)),)
ifneq ($(filter modules_install,$(MAKECMDGOALS)),)
mixed-targets := 1
endif
endif

如果是混合目标，则需要一个一个处理

ifeq ($(mixed-targets),1)
PHONY += $(MAKECMDGOALS) __build_one_by_one
$(filter-out __build_one_by_one, $(MAKECMDGOALS)): __build_one_by_one
@:
__build_one_by_one:
$(Q)set -e; 
for i in $(MAKECMDGOALS); do 
$(MAKE) -f $(srctree)/Makefile $$i; 
done
else

# 引入kbuild工具包
include scripts/Kbuild.include
#获取版本信息，通常是在config的过程中生成的kernel.release文件。
KERNELRELEASE = $(shell cat include/config/kernel.release 2> /dev/null)
KERNELVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)
export VERSION PATCHLEVEL SUBLEVEL KERNELRELEASE KERNELVERSION
# 引入架构解析相关的工具包
include scripts/subarch.include
# 确定目标架构
ARCH
?= $(SUBARCH)
# 使用对应架构的源码
UTS_MACHINE
:= $(ARCH)
SRCARCH
:= $(ARCH)
ifeq ($(ARCH),i386)
SRCARCH := x86
endif
ifeq ($(ARCH),x86_64)
SRCARCH := x86
endif
ifeq ($(ARCH),sparc32)
SRCARCH := sparc
endif
ifeq ($(ARCH),sparc64)
SRCARCH := sparc
endif
ifeq ($(ARCH),sh64)
SRCARCH := sh
endif
# 内核编译使用的配置文件
KCONFIG_CONFIG	?= .config
export KCONFIG_CONFIG
# 内核编译使用的shell
CONFIG_SHELL := $(shell if [ -x "$$BASH" ]; then echo $$BASH; 
else if [ -x /bin/bash ]; then echo /bin/bash; 
else echo sh; fi ; fi)
HOST_LFS_CFLAGS := $(shell getconf LFS_CFLAGS 2>/dev/null)
HOST_LFS_LDFLAGS := $(shell getconf LFS_LDFLAGS 2>/dev/null)
HOST_LFS_LIBS := $(shell getconf LFS_LIBS 2>/dev/null)
# 本机使用的编译器及其参数
HOSTCC
= gcc
HOSTCXX
= g++
KBUILD_HOSTCFLAGS
:= -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 
-fomit-frame-pointer -std=gnu89 $(HOST_LFS_CFLAGS) 
$(HOSTCFLAGS)
KBUILD_HOSTCXXFLAGS := -O2 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS)
KBUILD_HOSTLDFLAGS
:= $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
KBUILD_HOSTLDLIBS
:= $(HOST_LFS_LIBS) $(HOSTLDLIBS)
# 交叉编译使用的工具链
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
OBJSIZE
= $(CROSS_COMPILE)size
PAHOLE
= pahole
LEX
= flex
YACC
= bison
AWK
= awk
INSTALLKERNEL
:= installkernel
DEPMOD
= /sbin/depmod
PERL
= perl
PYTHON
= python
PYTHON2
= python2
PYTHON3
= python3
CHECK
= sparse
CHECKFLAGS
:= -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ 
-Wbitwise -Wno-return-void -Wno-unknown-attribute $(CF)
NOSTDINC_FLAGS :=
CFLAGS_MODULE
=
AFLAGS_MODULE
=
LDFLAGS_MODULE
=
CFLAGS_KERNEL	=
AFLAGS_KERNEL	=
LDFLAGS_vmlinux =
# 用户空间API路径
USERINCLUDE
:= 
-I$(srctree)/arch/$(SRCARCH)/include/uapi 
-I$(objtree)/arch/$(SRCARCH)/include/generated/uapi 
-I$(srctree)/include/uapi 
-I$(objtree)/include/generated/uapi 
-include $(srctree)/include/linux/kconfig.h
# 系统空间头文件路径
LINUXINCLUDE
:= 
-I$(srctree)/arch/$(SRCARCH)/include 
-I$(objtree)/arch/$(SRCARCH)/include/generated 
$(if $(building_out_of_srctree),-I$(srctree)/include) 
-I$(objtree)/include 
$(USERINCLUDE)
KBUILD_AFLAGS
:= -D__ASSEMBLY__ -fno-PIE
KBUILD_CFLAGS
:= -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs 
-fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE 
-Werror=implicit-function-declaration -Werror=implicit-int 
-Wno-format-security 
-std=gnu89
KBUILD_CPPFLAGS := -D__KERNEL__
KBUILD_AFLAGS_KERNEL :=
KBUILD_CFLAGS_KERNEL :=
KBUILD_AFLAGS_MODULE
:= -DMODULE
KBUILD_CFLAGS_MODULE
:= -DMODULE
KBUILD_LDFLAGS_MODULE := -T $(srctree)/scripts/module-common.lds
KBUILD_LDFLAGS :=
GCC_PLUGINS_CFLAGS :=
CLANG_FLAGS :=
export ARCH SRCARCH CONFIG_SHELL HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE AS LD CC
export CPP AR NM STRIP OBJCOPY OBJDUMP OBJSIZE PAHOLE LEX YACC AWK INSTALLKERNEL
export PERL PYTHON PYTHON2 PYTHON3 CHECK CHECKFLAGS MAKE UTS_MACHINE HOSTCXX
export KBUILD_HOSTCXXFLAGS KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS LDFLAGS_MODULE
export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS KBUILD_LDFLAGS
export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE
export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE CFLAGS_UBSAN
export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE
export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_LDFLAGS_MODULE
export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL
export KBUILD_ARFLAGS
# find 命令需要忽略的文件名
export 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

config目标与build目标的共用规则

# 引入基本的脚本工具包
PHONY += scripts_basic
scripts_basic:
$(Q)$(MAKE) $(build)=scripts/basic
$(Q)rm -f .tmp_quiet_recordmcount
# 如果build路径下有.gitignore，则将该目录直接加入忽略列表。
PHONY += outputmakefile
outputmakefile:
ifdef building_out_of_srctree
$(Q)ln -fsn $(srctree) source
$(Q)$(CONFIG_SHELL) $(srctree)/scripts/mkmakefile $(srctree)
$(Q)test -e .gitignore || 
{ echo "# this is build directory, ignore it"; echo "*"; } > .gitignore
endif
ifneq ($(shell $(CC) --version 2>&1 | head -n 1 | grep clang),)
ifneq ($(CROSS_COMPILE),)
CLANG_FLAGS	+= --target=$(notdir $(CROSS_COMPILE:%-=%))
GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
CLANG_FLAGS	+= --prefix=$(GCC_TOOLCHAIN_DIR)
GCC_TOOLCHAIN	:= $(realpath $(GCC_TOOLCHAIN_DIR)/..)
endif
ifneq ($(GCC_TOOLCHAIN),)
CLANG_FLAGS	+= --gcc-toolchain=$(GCC_TOOLCHAIN)
endif
ifeq ($(shell $(AS) --version 2>&1 | head -n 1 | grep clang),)
CLANG_FLAGS	+= -no-integrated-as
endif
CLANG_FLAGS	+= -Werror=unknown-warning-option
KBUILD_CFLAGS	+= $(CLANG_FLAGS)
KBUILD_AFLAGS	+= $(CLANG_FLAGS)
export CLANG_FLAGS
endif
CC_VERSION_TEXT = $(shell $(CC) --version 2>/dev/null | head -n 1)

config目标

ifeq ($(config-targets),1)
# 直接使用Kconfig来进行配置
include arch/$(SRCARCH)/Makefile
export KBUILD_DEFCONFIG KBUILD_KCONFIG CC_VERSION_TEXT
config: scripts_basic outputmakefile FORCE
$(Q)$(MAKE) $(build)=scripts/kconfig $@
%config: scripts_basic outputmakefile FORCE
$(Q)$(MAKE) $(build)=scripts/kconfig $@
else

build目标

5.x版本的编译过程，每次make调用都只处理一个target，极大减小make目标之间的耦合度。

# 指定默认的target
PHONY += all
ifeq ($(KBUILD_EXTMOD),)
_all: all
else
_all: modules
endif

判断是否编译内部模块，是否编译外部模块。通常情况下只编译内部模块

KBUILD_MODULES :=
KBUILD_BUILTIN := 1
# 如果在编译modules时，指定了MODVERSIONS，那就需要考虑内部对象，所以需要重构内部模块，保证校验和是相等的
# 这是官方注释，不太明白，等遇到对应案例时再说。
ifeq ($(MAKECMDGOALS),modules)
KBUILD_BUILTIN := $(if $(CONFIG_MODVERSIONS),1)
endif
ifneq ($(filter all _all modules,$(MAKECMDGOALS)),)
KBUILD_MODULES := 1
endif
ifeq ($(MAKECMDGOALS),)
KBUILD_MODULES := 1
endif
export KBUILD_MODULES KBUILD_BUILTIN
ifeq ($(dot-config),1)
include include/config/auto.conf
endif

需要编译的文件夹，旧版本应该是叫子目录

ifeq ($(KBUILD_EXTMOD),)
init-y
:= init/
# 初始化
drivers-y	:= drivers/ sound/
# 驱动和声音
drivers-$(CONFIG_SAMPLES) += samples/
drivers-$(CONFIG_KERNEL_HEADER_TEST) += include/	# 头文件
net-y
:= net/
# 网络
libs-y
:= lib/
# 基础库
core-y
:= usr/
virt-y
:= virt/
# 虚拟化
endif # KBUILD_EXTMOD

all: vmlinux
CFLAGS_GCOV	:= -fprofile-arcs -ftest-coverage 
$(call cc-option,-fno-tree-loop-im) 
$(call cc-disable-warning,maybe-uninitialized,)
export CFLAGS_GCOV
# The arch Makefiles can override CC_FLAGS_FTRACE. We may also append it later.
ifdef CONFIG_FUNCTION_TRACER
CC_FLAGS_FTRACE := -pg
endif
RETPOLINE_CFLAGS_GCC := -mindirect-branch=thunk-extern -mindirect-branch-register
RETPOLINE_VDSO_CFLAGS_GCC := -mindirect-branch=thunk-inline -mindirect-branch-register
RETPOLINE_CFLAGS_CLANG := -mretpoline-external-thunk
RETPOLINE_VDSO_CFLAGS_CLANG := -mretpoline
RETPOLINE_CFLAGS := $(call cc-option,$(RETPOLINE_CFLAGS_GCC),$(call cc-option,$(RETPOLINE_CFLAGS_CLANG)))
RETPOLINE_VDSO_CFLAGS := $(call cc-option,$(RETPOLINE_VDSO_CFLAGS_GCC),$(call cc-option,$(RETPOLINE_VDSO_CFLAGS_CLANG)))
export RETPOLINE_CFLAGS
export RETPOLINE_VDSO_CFLAGS
# 由不同架构的Makefile自行决定以下编译参数
ARCH_CPPFLAGS :=
ARCH_AFLAGS :=
ARCH_CFLAGS :=
include arch/$(SRCARCH)/Makefile

对配置文件的检查，这里涉及到一个规则，那就是include时，会检查文件是否存在，而这个目标同样是由Makefile中的目标处理的。也就是说这个过程是make执行时处理的，即，解析时，会告知用户这个文件不存在，而后在运行时，调用对应的目标来处理。

ifeq ($(dot-config),1)
ifeq ($(may-sync-config),1)
#如果需要同步配置，则需要这个文件
include include/config/auto.conf.cmd
$(KCONFIG_CONFIG):
@echo >&2 '***'
@echo >&2 '*** Configuration file "$@" not found!'
@echo >&2 '***'
@echo >&2 '*** Please run some configurator (e.g. "make oldconfig" or'
@echo >&2 '*** "make menuconfig" or "make xconfig").'
@echo >&2 '***'
@/bin/false
# 如果$(KCONFIG_CONFIG)比这几个文件要新，则syncconfig.
%/auto.conf %/auto.conf.cmd %/tristate.conf: $(KCONFIG_CONFIG)
$(Q)$(MAKE) -f $(srctree)/Makefile syncconfig
else
# External modules and some install targets need include/generated/autoconf.h
# and include/config/auto.conf but do not care if they are up-to-date.
# Use auto.conf to trigger the test
PHONY += include/config/auto.conf
# 有些目标并不关心 auto.conf文件是否是最新，就不需要同步配置文件，则只需要这几个文件存在就行。
include/config/auto.conf:
$(Q)test -e include/generated/autoconf.h -a -e $@ || (

echo >&2;

echo >&2 "
ERROR: Kernel configuration is invalid.";

echo >&2 "
include/generated/autoconf.h or $@ are missing.";
echo >&2 "
Run 'make oldconfig && make prepare' on kernel src to fix it.";	
echo >&2 ;

/bin/false)
endif # may-sync-config
endif # $(dot-config)

很多编译选项跟优化选项，要不要一条条看呢。。。(待）

#
KBUILD_CFLAGS	+= $(call cc-option,-fno-delete-null-pointer-checks,)
KBUILD_CFLAGS	+= $(call cc-disable-warning,frame-address,)
KBUILD_CFLAGS	+= $(call cc-disable-warning, format-truncation)
KBUILD_CFLAGS	+= $(call cc-disable-warning, format-overflow)
KBUILD_CFLAGS	+= $(call cc-disable-warning, address-of-packed-member)
ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
KBUILD_CFLAGS	+= -Os
else
KBUILD_CFLAGS
+= -O2
endif
ifdef CONFIG_CC_DISABLE_WARN_MAYBE_UNINITIALIZED
KBUILD_CFLAGS
+= -Wno-maybe-uninitialized
endif
# Tell gcc to never replace conditional load with a non-conditional one
KBUILD_CFLAGS	+= $(call cc-option,--param=allow-store-data-races=0)
include scripts/Makefile.kcov
include scripts/Makefile.gcc-plugins
ifdef CONFIG_READABLE_ASM
# Disable optimizations that make assembler listings hard to read.
# reorder blocks reorders the control in the function
# ipa clone creates specialized cloned functions
# partial inlining inlines only parts of functions
KBUILD_CFLAGS += $(call cc-option,-fno-reorder-blocks,) 
$(call cc-option,-fno-ipa-cp-clone,) 
$(call cc-option,-fno-partial-inlining)
endif
ifneq ($(CONFIG_FRAME_WARN),0)
KBUILD_CFLAGS += $(call cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})
endif
stackp-flags-$(CONFIG_CC_HAS_STACKPROTECTOR_NONE) := -fno-stack-protector
stackp-flags-$(CONFIG_STACKPROTECTOR)
:= -fstack-protector
stackp-flags-$(CONFIG_STACKPROTECTOR_STRONG)
:= -fstack-protector-strong
KBUILD_CFLAGS += $(stackp-flags-y)
ifdef CONFIG_CC_IS_CLANG
KBUILD_CPPFLAGS += -Qunused-arguments
KBUILD_CFLAGS += -Wno-format-invalid-specifier
KBUILD_CFLAGS += -Wno-gnu
# Quiet clang warning: comparison of unsigned expression < 0 is always false
KBUILD_CFLAGS += -Wno-tautological-compare
# CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the
# source of a reference will be _MergedGlobals and not on of the whitelisted names.
# See modpost pattern 2
KBUILD_CFLAGS += -mno-global-merge
else
# These warnings generated too much noise in a regular build.
# Use make W=1 to enable them (see scripts/Makefile.extrawarn)
KBUILD_CFLAGS += -Wno-unused-but-set-variable
# Warn about unmarked fall-throughs in switch statement.
# Disabled for clang while comment to attribute conversion happens and
# https://github.com/ClangBuiltLinux/linux/issues/636 is discussed.
KBUILD_CFLAGS += $(call cc-option,-Wimplicit-fallthrough,)
endif
KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
ifdef CONFIG_FRAME_POINTER
KBUILD_CFLAGS	+= -fno-omit-frame-pointer -fno-optimize-sibling-calls
else
# Some targets (ARM with Thumb2, for example), can't be built with frame
# pointers.
For those, we don't have FUNCTION_TRACER automatically
# select FRAME_POINTER.
However, FUNCTION_TRACER adds -pg, and this is
# incompatible with -fomit-frame-pointer with current GCC, so we don't use
# -fomit-frame-pointer with FUNCTION_TRACER.
ifndef CONFIG_FUNCTION_TRACER
KBUILD_CFLAGS	+= -fomit-frame-pointer
endif
endif
# Initialize all stack variables with a pattern, if desired.
ifdef CONFIG_INIT_STACK_ALL
KBUILD_CFLAGS	+= -ftrivial-auto-var-init=pattern
endif
DEBUG_CFLAGS	:= $(call cc-option, -fno-var-tracking-assignments)
ifdef CONFIG_DEBUG_INFO
ifdef CONFIG_DEBUG_INFO_SPLIT
DEBUG_CFLAGS	+= -gsplit-dwarf
else
DEBUG_CFLAGS	+= -g
endif
KBUILD_AFLAGS	+= -Wa,-gdwarf-2
endif
ifdef CONFIG_DEBUG_INFO_DWARF4
DEBUG_CFLAGS	+= -gdwarf-4
endif
ifdef CONFIG_DEBUG_INFO_REDUCED
DEBUG_CFLAGS	+= $(call cc-option, -femit-struct-debug-baseonly) 
$(call cc-option,-fno-var-tracking)
endif
KBUILD_CFLAGS += $(DEBUG_CFLAGS)
export DEBUG_CFLAGS
ifdef CONFIG_FUNCTION_TRACER
ifdef CONFIG_FTRACE_MCOUNT_RECORD
# gcc 5 supports generating the mcount tables directly
ifeq ($(call cc-option-yn,-mrecord-mcount),y)
CC_FLAGS_FTRACE	+= -mrecord-mcount
export CC_USING_RECORD_MCOUNT := 1
endif
ifdef CONFIG_HAVE_NOP_MCOUNT
ifeq ($(call cc-option-yn, -mnop-mcount),y)
CC_FLAGS_FTRACE	+= -mnop-mcount
CC_FLAGS_USING	+= -DCC_USING_NOP_MCOUNT
endif
endif
endif
ifdef CONFIG_HAVE_FENTRY
ifeq ($(call cc-option-yn, -mfentry),y)
CC_FLAGS_FTRACE	+= -mfentry
CC_FLAGS_USING	+= -DCC_USING_FENTRY
endif
endif
export CC_FLAGS_FTRACE
KBUILD_CFLAGS	+= $(CC_FLAGS_FTRACE) $(CC_FLAGS_USING)
KBUILD_AFLAGS	+= $(CC_FLAGS_USING)
ifdef CONFIG_DYNAMIC_FTRACE
ifdef CONFIG_HAVE_C_RECORDMCOUNT
BUILD_C_RECORDMCOUNT := y
export BUILD_C_RECORDMCOUNT
endif
endif
endif
# We trigger additional mismatches with less inlining
ifdef CONFIG_DEBUG_SECTION_MISMATCH
KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)
endif
ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections
LDFLAGS_vmlinux += --gc-sections
endif
ifdef CONFIG_LIVEPATCH
KBUILD_CFLAGS += $(call cc-option, -flive-patching=inline-clone)
endif
# arch Makefile may override CC so keep this after arch Makefile is included
NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
# warn about C99 declaration after statement
KBUILD_CFLAGS += -Wdeclaration-after-statement
# Variable Length Arrays (VLAs) should not be used anywhere in the kernel
KBUILD_CFLAGS += -Wvla
# disable pointer signed / unsigned warnings in gcc 4.0
KBUILD_CFLAGS += -Wno-pointer-sign
# disable stringop warnings in gcc 8+
KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation)
# disable invalid "can't wrap" optimizations for signed / pointers
KBUILD_CFLAGS	+= $(call cc-option,-fno-strict-overflow)
# clang sets -fmerge-all-constants by default as optimization, but this
# is non-conforming behavior for C and in fact breaks the kernel, so we
# need to disable it here generally.
KBUILD_CFLAGS	+= $(call cc-option,-fno-merge-all-constants)
# for gcc -fno-merge-all-constants disables everything, but it is fine
# to have actual conforming behavior enabled.
KBUILD_CFLAGS	+= $(call cc-option,-fmerge-constants)
# Make sure -fstack-check isn't enabled (like gentoo apparently did)
KBUILD_CFLAGS
+= $(call cc-option,-fno-stack-check,)
# conserve stack if available
KBUILD_CFLAGS
+= $(call cc-option,-fconserve-stack)
# Prohibit date/time macros, which would make the build non-deterministic
KBUILD_CFLAGS
+= $(call cc-option,-Werror=date-time)
# enforce correct pointer usage
KBUILD_CFLAGS
+= $(call cc-option,-Werror=incompatible-pointer-types)
# Require designated initializers for all marked structures
KBUILD_CFLAGS
+= $(call cc-option,-Werror=designated-init)
# change __FILE__ to the relative path from the srctree
KBUILD_CFLAGS	+= $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
# ensure -fcf-protection is disabled when using retpoline as it is
# incompatible with -mindirect-branch=thunk-extern
ifdef CONFIG_RETPOLINE
KBUILD_CFLAGS += $(call cc-option,-fcf-protection=none)
endif
# use the deterministic mode of AR if available
KBUILD_ARFLAGS := $(call ar-option,D)
include scripts/Makefile.kasan
include scripts/Makefile.extrawarn
include scripts/Makefile.ubsan
# Add any arch overrides and user supplied CPPFLAGS, AFLAGS and CFLAGS as the
# last assignments
KBUILD_CPPFLAGS += $(ARCH_CPPFLAGS) $(KCPPFLAGS)
KBUILD_AFLAGS
+= $(ARCH_AFLAGS)
$(KAFLAGS)
KBUILD_CFLAGS
+= $(ARCH_CFLAGS)
$(KCFLAGS)
KBUILD_LDFLAGS_MODULE += --build-id
LDFLAGS_vmlinux += --build-id
ifeq ($(CONFIG_STRIP_ASM_SYMS),y)
LDFLAGS_vmlinux	+= $(call ld-option, -X,)
endif
# insure the checker run with the right endianness
CHECKFLAGS += $(if $(CONFIG_CPU_BIG_ENDIAN),-mbig-endian,-mlittle-endian)
# the checker needs the correct machine size
CHECKFLAGS += $(if $(CONFIG_64BIT),-m64,-m32)

（待）

export KBUILD_IMAGE ?= vmlinux
export	INSTALL_PATH ?= /boot
# device tree binary, device tree script，设备树相关的安装地址
export INSTALL_DTBS_PATH ?= $(INSTALL_PATH)/dtbs/$(KERNELRELEASE)
MODLIB	= $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE)
export MODLIB
# 在安装模块之后对其进行strip
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
# 安装模块之后进行压缩
mod_compress_cmd = true
ifdef CONFIG_MODULE_COMPRESS
ifdef CONFIG_MODULE_COMPRESS_GZIP
mod_compress_cmd = gzip -n -f
endif # CONFIG_MODULE_COMPRESS_GZIP
ifdef CONFIG_MODULE_COMPRESS_XZ
mod_compress_cmd = xz -f
endif # CONFIG_MODULE_COMPRESS_XZ
endif # CONFIG_MODULE_COMPRESS
export mod_compress_cmd
ifdef CONFIG_MODULE_SIG_ALL
$(eval $(call config_filename,MODULE_SIG_KEY))
mod_sign_cmd = scripts/sign-file $(CONFIG_MODULE_SIG_HASH) $(MODULE_SIG_KEY_SRCPREFIX)$(CONFIG_MODULE_SIG_KEY) certs/signing_key.x509
else
mod_sign_cmd = true
endif
export mod_sign_cmd
HOST_LIBELF_LIBS = $(shell pkg-config libelf --libs 2>/dev/null || echo -lelf)
ifdef CONFIG_STACK_VALIDATION
has_libelf := $(call try-run,
echo "int main() {}" | $(HOSTCC) -xc -o /dev/null $(HOST_LIBELF_LIBS) -,1,0)
ifeq ($(has_libelf),1)
objtool_target := tools/objtool FORCE
else
SKIP_STACK_VALIDATION := 1
export SKIP_STACK_VALIDATION
endif
endif

PHONY += prepare0
export MODORDER := $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/)modules.order

接下来是内核编译部分

ifeq ($(KBUILD_EXTMOD),)

根据配置决定处理文件夹路径

# linux内核对应文件夹
core-y
+= kernel/ certs/ mm/ fs/ ipc/ security/ crypto/ block/
# vmlinux构建所需的文件夹
vmlinux-dirs	:= $(patsubst %/,%,$(filter %/, $(init-y) $(init-m) 
$(core-y) $(core-m) $(drivers-y) $(drivers-m) 
$(net-y) $(net-m) $(libs-y) $(libs-m) $(virt-y)))
vmlinux-alldirs	:= $(sort $(vmlinux-dirs) Documentation 
$(patsubst %/,%,$(filter %/, $(init-) $(core-) 
$(drivers-) $(net-) $(libs-) $(virt-))))
init-y
:= $(patsubst %/, %/built-in.a, $(init-y))
core-y
:= $(patsubst %/, %/built-in.a, $(core-y))
drivers-y	:= $(patsubst %/, %/built-in.a, $(drivers-y))
net-y
:= $(patsubst %/, %/built-in.a, $(net-y))
libs-y1
:= $(patsubst %/, %/lib.a, $(libs-y))
libs-y2
:= $(patsubst %/, %/built-in.a, $(filter-out %.a, $(libs-y)))
virt-y
:= $(patsubst %/, %/built-in.a, $(virt-y))

链接vmlinux所需的依赖项

# Externally visible symbols (used by link-vmlinux.sh)
export KBUILD_VMLINUX_OBJS := $(head-y) $(init-y) $(core-y) $(libs-y2) 
$(drivers-y) $(net-y) $(virt-y)
export KBUILD_VMLINUX_LIBS := $(libs-y1)
export KBUILD_LDS
:= arch/$(SRCARCH)/kernel/vmlinux.lds
export LDFLAGS_vmlinux
# used by scripts/package/Makefile
export KBUILD_ALLDIRS := $(sort $(filter-out arch/%,$(vmlinux-alldirs)) LICENSES arch include scripts tools)
vmlinux-deps := $(KBUILD_LDS) $(KBUILD_VMLINUX_OBJS) $(KBUILD_VMLINUX_LIBS)

这部分估计是去除不需要export的符号（待）

# Recurse until adjust_autoksyms.sh is satisfied
PHONY += autoksyms_recursive
ifdef CONFIG_TRIM_UNUSED_KSYMS
autoksyms_recursive: $(vmlinux-deps) modules.order
$(Q)$(CONFIG_SHELL) $(srctree)/scripts/adjust_autoksyms.sh 
"$(MAKE) -f $(srctree)/Makefile vmlinux"
endif
# For the kernel to actually contain only the needed exported symbols,
# we have to build modules as well to determine what those symbols are.
# (this can be evaluated only once include/config/auto.conf has been included)
ifdef CONFIG_TRIM_UNUSED_KSYMS
KBUILD_MODULES := 1
endif
autoksyms_h := $(if $(CONFIG_TRIM_UNUSED_KSYMS), include/generated/autoksyms.h)
$(autoksyms_h):
$(Q)mkdir -p $(dir $@)
$(Q)touch $@

link vmlinux时的target及相关命令

ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)
# vmlinux链接命令
cmd_link-vmlinux =

$(CONFIG_SHELL) $< $(LD) $(KBUILD_LDFLAGS) $(LDFLAGS_vmlinux) ;

$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)
vmlinux: scripts/link-vmlinux.sh autoksyms_recursive $(vmlinux-deps) FORCE
+$(call if_changed,link-vmlinux)
targets := vmlinux
# The actual objects are generated when descending,
# make sure no implicit rule kicks in
$(sort $(vmlinux-deps)): $(vmlinux-dirs) ;
# Handle descending into subdirectories listed in $(vmlinux-dirs)
# Preset locale variables to speed up the build process. Limit locale
# tweaks to this spot to avoid wrong language settings when running
# make menuconfig etc.
# Error messages still appears in the original language
PHONY += $(vmlinux-dirs)
$(vmlinux-dirs): prepare
$(Q)$(MAKE) $(build)=$@ need-builtin=1 need-modorder=1
filechk_kernel.release = 
echo "$(KERNELVERSION)$$($(CONFIG_SHELL) $(srctree)/scripts/setlocalversion $(srctree))"
# Store (new) KERNELRELEASE string in include/config/kernel.release
include/config/kernel.release: FORCE
$(call filechk,kernel.release)
# Additional helpers built in scripts/
# Carefully list dependencies so we do not try to build scripts twice
# in parallel
PHONY += scripts
scripts: scripts_basic scripts_dtc
$(Q)$(MAKE) $(build)=$(@)
# Things we need to do before we recursively start building the kernel
# or the modules are listed in "prepare".
# A multi level approach is used. prepareN is processed before prepareN-1.
# archprepare is used in arch Makefiles and when processed asm symlink,
# version.h and scripts_basic is processed / created.
PHONY += prepare archprepare prepare3
# prepare3 is used to check if we are building in a separate output directory,
# and if so do:
# 1) Check that make has not been executed in the kernel src $(srctree)
prepare3: include/config/kernel.release
ifdef building_out_of_srctree
@$(kecho) '
Using $(srctree) as source for kernel'
$(Q)if [ -f $(srctree)/.config -o 
-d $(srctree)/include/config -o 
-d $(srctree)/arch/$(SRCARCH)/include/generated ]; then 
echo >&2 "
$(srctree) is not clean, please run 'make ARCH=$(ARCH) mrproper'"; 
echo >&2 "
in the '$(srctree)' directory.";
/bin/false; 
fi;
endif
archprepare: archheaders archscripts scripts prepare3 outputmakefile 
asm-generic $(version_h) $(autoksyms_h) include/generated/utsrelease.h
prepare0: archprepare
$(Q)$(MAKE) $(build)=scripts/mod
$(Q)$(MAKE) $(build)=.
# All the preparing..
prepare: prepare0 prepare-objtool
# Support for using generic headers in asm-generic
asm-generic := -f $(srctree)/scripts/Makefile.asm-generic obj
PHONY += asm-generic uapi-asm-generic
asm-generic: uapi-asm-generic
$(Q)$(MAKE) $(asm-generic)=arch/$(SRCARCH)/include/generated/asm 
generic=include/asm-generic
uapi-asm-generic:
$(Q)$(MAKE) $(asm-generic)=arch/$(SRCARCH)/include/generated/uapi/asm 
generic=include/uapi/asm-generic
PHONY += prepare-objtool
prepare-objtool: $(objtool_target)
ifeq ($(SKIP_STACK_VALIDATION),1)
ifdef CONFIG_UNWINDER_ORC
@echo "error: Cannot generate ORC metadata for CONFIG_UNWINDER_ORC=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2
@false
else
@echo "warning: Cannot use CONFIG_STACK_VALIDATION=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2
endif
endif
# Generate some files
# ---------------------------------------------------------------------------
# KERNELRELEASE can change from a few different places, meaning version.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;

exit 1;

fi;

echo #define UTS_RELEASE "$(KERNELRELEASE)"
endef
define filechk_version.h
echo #define LINUX_VERSION_CODE $(shell

expr $(VERSION) * 65536 + 0$(PATCHLEVEL) * 256 + 0$(SUBLEVEL)); 
echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))'
endef
$(version_h): FORCE
$(call filechk,version.h)
$(Q)rm -f $(old_version_h)
include/generated/utsrelease.h: include/config/kernel.release FORCE
$(call filechk,utsrelease.h)
PHONY += headerdep
headerdep:
$(Q)find $(srctree)/include/ -name '*.h' | xargs --max-args 1 
$(srctree)/scripts/headerdep.pl -I$(srctree)/include
# ---------------------------------------------------------------------------
# Kernel headers
#Default location for installed headers
export INSTALL_HDR_PATH = $(objtree)/usr
quiet_cmd_headers_install = INSTALL $(INSTALL_HDR_PATH)/include
cmd_headers_install = 
mkdir -p $(INSTALL_HDR_PATH); 
rsync -mrl --include='*/' --include='*.h' --exclude='*' 
usr/include $(INSTALL_HDR_PATH)
PHONY += headers_install
headers_install: headers
$(call cmd,headers_install)
PHONY += archheaders archscripts
hdr-inst := -f $(srctree)/scripts/Makefile.headersinst obj
PHONY += headers
headers: $(version_h) scripts_unifdef uapi-asm-generic archheaders archscripts
$(if $(wildcard $(srctree)/arch/$(SRCARCH)/include/uapi/asm/Kbuild),, 
$(error Headers not exportable for the $(SRCARCH) architecture))
$(Q)$(MAKE) $(hdr-inst)=include/uapi
$(Q)$(MAKE) $(hdr-inst)=arch/$(SRCARCH)/include/uapi
PHONY += headers_check
headers_check: headers
$(Q)$(MAKE) $(hdr-inst)=include/uapi HDRCHECK=1
$(Q)$(MAKE) $(hdr-inst)=arch/$(SRCARCH)/include/uapi HDRCHECK=1
ifdef CONFIG_HEADERS_INSTALL
prepare: headers
endif
ifdef CONFIG_HEADERS_CHECK
all: headers_check
endif
PHONY += scripts_unifdef
scripts_unifdef: scripts_basic
$(Q)$(MAKE) $(build)=scripts scripts/unifdef
# ---------------------------------------------------------------------------
# Kernel selftest
PHONY += kselftest
kselftest:
$(Q)$(MAKE) -C $(srctree)/tools/testing/selftests run_tests
PHONY += kselftest-clean
kselftest-clean:
$(Q)$(MAKE) -C $(srctree)/tools/testing/selftests clean
PHONY += kselftest-merge
kselftest-merge:
$(if $(wildcard $(objtree)/.config),, $(error No .config exists, config your kernel first!))
$(Q)find $(srctree)/tools/testing/selftests -name config | 
xargs $(srctree)/scripts/kconfig/merge_config.sh -m $(objtree)/.config
+$(Q)$(MAKE) -f $(srctree)/Makefile olddefconfig
# ---------------------------------------------------------------------------
# Devicetree files
ifneq ($(wildcard $(srctree)/arch/$(SRCARCH)/boot/dts/),)
dtstree := arch/$(SRCARCH)/boot/dts
endif
ifneq ($(dtstree),)
%.dtb: prepare3 scripts_dtc
$(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@
PHONY += dtbs dtbs_install dt_binding_check
dtbs dtbs_check: prepare3 scripts_dtc
$(Q)$(MAKE) $(build)=$(dtstree)
dtbs_check: export CHECK_DTBS=1
dtbs_check: dt_binding_check
dtbs_install:
$(Q)$(MAKE) $(dtbinst)=$(dtstree)
ifdef CONFIG_OF_EARLY_FLATTREE
all: dtbs
endif
endif
PHONY += scripts_dtc
scripts_dtc: scripts_basic
$(Q)$(MAKE) $(build)=scripts/dtc
dt_binding_check: scripts_dtc
$(Q)$(MAKE) $(build)=Documentation/devicetree/bindings
# ---------------------------------------------------------------------------
# Modules
ifdef CONFIG_MODULES
# By default, build modules as well
all: modules
# Build modules
#
# A module can be listed more than once in obj-m resulting in
# duplicate lines in modules.order files.
Those are removed
# using awk while concatenating to the final file.
PHONY += modules
modules: $(if $(KBUILD_BUILTIN),vmlinux) modules.order modules.builtin
@$(kecho) '
Building modules, stage 2.';
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
$(Q)$(CONFIG_SHELL) $(srctree)/scripts/modules-check.sh
modules.order: $(vmlinux-dirs)
$(Q)$(AWK) '!x[$$0]++' $(addsuffix /$@, $(vmlinux-dirs)) > $@
modbuiltin-dirs := $(addprefix _modbuiltin_, $(vmlinux-dirs))
modules.builtin: $(modbuiltin-dirs)
$(Q)$(AWK) '!x[$$0]++' $(addsuffix /$@, $(vmlinux-dirs)) > $@
PHONY += $(modbuiltin-dirs)
# tristate.conf is not included from this Makefile. Add it as a prerequisite
# here to make it self-healing in case somebody accidentally removes it.
$(modbuiltin-dirs): include/config/tristate.conf
$(Q)$(MAKE) $(modbuiltin)=$(patsubst _modbuiltin_%,%,$@)
# Target to prepare building external modules
PHONY += modules_prepare
modules_prepare: prepare
# Target to install modules
PHONY += modules_install
modules_install: _modinst_ _modinst_post
PHONY += _modinst_
_modinst_:
@rm -rf $(MODLIB)/kernel
@rm -f $(MODLIB)/source
@mkdir -p $(MODLIB)/kernel
@ln -s $(abspath $(srctree)) $(MODLIB)/source
@if [ ! $(objtree) -ef
$(MODLIB)/build ]; then 
rm -f $(MODLIB)/build ; 
ln -s $(CURDIR) $(MODLIB)/build ; 
fi
@sed 's:^:kernel/:' modules.order > $(MODLIB)/modules.order
@sed 's:^:kernel/:' modules.builtin > $(MODLIB)/modules.builtin
@cp -f $(objtree)/modules.builtin.modinfo $(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 mounted read-write.
However the
# boot script depmod is the master version.
PHONY += _modinst_post
_modinst_post: _modinst_
$(call cmd,depmod)
ifeq ($(CONFIG_MODULE_SIG), y)
PHONY += modules_sign
modules_sign:
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modsign
endif
else # CONFIG_MODULES
# Modules not configured
# ---------------------------------------------------------------------------
PHONY += modules modules_install
modules modules_install:
@echo >&2
@echo >&2 "The present kernel configuration has modules disabled."
@echo >&2 "Type 'make config' and enable loadable module support."
@echo >&2 "Then build a kernel with module support enabled."
@echo >&2
@exit 1
endif # CONFIG_MODULES
###
# Cleaning is done on three levels.
# make clean
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 files and the like
# Directories & files removed with 'make clean'
CLEAN_DIRS
+= include/ksym
CLEAN_FILES += modules.builtin.modinfo
# Directories & files removed with 'make mrproper'
MRPROPER_DIRS
+= include/config include/generated

arch/$(SRCARCH)/include/generated .tmp_objdiff
MRPROPER_FILES += .config .config.old .version 
Module.symvers 
signing_key.pem signing_key.priv signing_key.x509	
x509.genkey extra_certificates signing_key.x509.keyid	
signing_key.x509.signer vmlinux-gdb.py
# Directories & files removed with 'make distclean'
DISTCLEAN_DIRS
+=
DISTCLEAN_FILES += tags TAGS cscope* GPATH GTAGS GRTAGS GSYMS
# clean - Delete most, but leave enough to build external modules
#
clean: rm-dirs
:= $(CLEAN_DIRS)
clean: rm-files := $(CLEAN_FILES)
clean-dirs
:= $(addprefix _clean_, . $(vmlinux-alldirs))
PHONY += $(clean-dirs) clean archclean vmlinuxclean
$(clean-dirs):
$(Q)$(MAKE) $(clean)=$(patsubst _clean_%,%,$@)
vmlinuxclean:
$(Q)$(CONFIG_SHELL) $(srctree)/scripts/link-vmlinux.sh clean
$(Q)$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) clean)
clean: archclean vmlinuxclean
# mrproper - Delete all generated files, including .config
#
mrproper: rm-dirs
:= $(wildcard $(MRPROPER_DIRS))
mrproper: rm-files := $(wildcard $(MRPROPER_FILES))
mrproper-dirs
:= $(addprefix _mrproper_,scripts)
PHONY += $(mrproper-dirs) mrproper
$(mrproper-dirs):
$(Q)$(MAKE) $(clean)=$(patsubst _mrproper_%,%,$@)
mrproper: clean $(mrproper-dirs)
$(call cmd,rmdirs)
$(call cmd,rmfiles)
# distclean
#
distclean: rm-dirs
:= $(wildcard $(DISTCLEAN_DIRS))
distclean: rm-files := $(wildcard $(DISTCLEAN_FILES))
PHONY += distclean
distclean: mrproper
$(call cmd,rmdirs)
$(call cmd,rmfiles)
@find $(srctree) $(RCS_FIND_IGNORE) 
( -name '*.orig' -o -name '*.rej' -o -name '*~' 
-o -name '*.bak' -o -name '#*#' -o -name '*%' 
-o -name 'core' ) 
-type f -print | xargs rm -f
# Packaging of the kernel to various formats
# ---------------------------------------------------------------------------
package-dir	:= scripts/package
%src-pkg: FORCE
$(Q)$(MAKE) $(build)=$(package-dir) $@
%pkg: include/config/kernel.release FORCE
$(Q)$(MAKE) $(build)=$(package-dir) $@
# Brief documentation of the typical targets used
# ---------------------------------------------------------------------------
boards := $(wildcard $(srctree)/arch/$(SRCARCH)/configs/*_defconfig)
boards := $(sort $(notdir $(boards)))
board-dirs := $(dir $(wildcard $(srctree)/arch/$(SRCARCH)/configs/*/*_defconfig))
board-dirs := $(sort $(notdir $(board-dirs:/=)))
PHONY += help
help:
@echo
'Cleaning targets:'
@echo
'
clean
- Remove most generated files but keep the config and'
@echo
'
enough build support to build external modules'
@echo
'
mrproper
- Remove all generated files + config + various backup files'
@echo
'
distclean
- mrproper + remove editor backup and patch files'
@echo
''
@echo
'Configuration targets:'
@$(MAKE) -f $(srctree)/scripts/kconfig/Makefile help
@echo
''
@echo
'Other generic targets:'
@echo
'
all
- Build all targets marked with [*]'
@echo
'* vmlinux
- Build the bare kernel'
@echo
'* modules
- Build all modules'
@echo
'
modules_install - Install all modules to INSTALL_MOD_PATH (default: /)'
@echo
'
dir/
- Build all files in dir and below'
@echo
'
dir/file.[ois]
- Build specified target only'
@echo
'
dir/file.ll
- Build the LLVM assembly file'
@echo
'
(requires compiler support for LLVM assembly generation)'
@echo
'
dir/file.lst
- Build specified mixed source/assembly target only'
@echo
'
(requires a recent binutils and recent build (System.map))'
@echo
'
dir/file.ko
- Build module including final link'
@echo
'
modules_prepare - Set up for building external modules'
@echo
'
tags/TAGS
- Generate tags file for editors'
@echo
'
cscope
- Generate cscope index'
@echo
'
gtags
- Generate GNU GLOBAL index'
@echo
'
kernelrelease
- Output the release version string (use with make -s)'
@echo
'
kernelversion
- Output the version stored in Makefile (use with make -s)'
@echo
'
image_name
- Output the image name (use with make -s)'
@echo
'
headers_install - Install sanitised kernel headers to INSTALL_HDR_PATH'; 
echo
'
(default: $(INSTALL_HDR_PATH))'; 
echo
''
@echo
'Static analysers:'
@echo
'
checkstack
- Generate a list of stack hogs'
@echo
'
namespacecheck
- Name space analysis on compiled kernel'
@echo
'
versioncheck
- Sanity check on version.h usage'
@echo
'
includecheck
- Check for duplicate included header files'
@echo
'
export_report
- List the usages of all exported symbols'
@echo
'
headers_check
- Sanity check on exported headers'
@echo
'
headerdep
- Detect inclusion cycles in headers'
@echo
'
coccicheck
- Check with Coccinelle'
@echo
''
@echo
'Kernel selftest:'
@echo
'
kselftest
- Build and run kernel selftest (run as root)'
@echo
'
Build, install, and boot kernel before'
@echo
'
running kselftest on it'
@echo
'
kselftest-clean - Remove all generated kselftest files'
@echo
'
kselftest-merge - Merge all the config dependencies of kselftest to existing'
@echo
'
.config.'
@echo
''
@$(if $(dtstree), 
echo 'Devicetree:'; 
echo '* dtbs
- Build device tree blobs for enabled boards'; 
echo '
dtbs_install
- Install dtbs to $(INSTALL_DTBS_PATH)'; 
echo '')
@echo 'Userspace tools targets:'
@echo '
use "make tools/help"'
@echo '
or
"cd tools; make help"'
@echo
''
@echo
'Kernel packaging:'
@$(MAKE) $(build)=$(package-dir) help
@echo
''
@echo
'Documentation targets:'
@$(MAKE) -f $(srctree)/Documentation/Makefile dochelp
@echo
''
@echo
'Architecture specific targets ($(SRCARCH)):'
@$(if $(archhelp),$(archhelp),
echo '
No architecture specific help defined for $(SRCARCH)')
@echo
''
@$(if $(boards), 
$(foreach b, $(boards), 
printf "
%-24s - Build for %s\n" $(b) $(subst _defconfig,,$(b));) 
echo '')
@$(if $(board-dirs), 
$(foreach b, $(board-dirs), 
printf "
%-16s - Show %s-specific targets\n" help-$(b) $(b);) 
printf "
%-16s - Show all of the above\n" help-boards; 
echo '')
@echo
'
make V=0|1 [targets] 0 => quiet build (default), 1 => verbose build'
@echo
'
make V=2
[targets] 2 => give reason for rebuild of target'
@echo
'
make O=dir [targets] Locate all output files in "dir", including .config'
@echo
'
make C=1
[targets] Check re-compiled c source with $$CHECK (sparse by default)'
@echo
'
make C=2
[targets] Force check of all c source with $$CHECK'
@echo
'
make RECORDMCOUNT_WARN=1 [targets] Warn about ignored mcount sections'
@echo
'
make W=n
[targets] Enable extra gcc checks, n=1,2,3 where'
@echo
'
1: warnings which may be relevant and do not occur too often'
@echo
'
2: warnings which occur quite often but may still be relevant'
@echo
'
3: more obscure warnings, can most likely be ignored'
@echo
'
Multiple levels can be combined with W=12 or W=123'
@echo
''
@echo
'Execute "make" or "make all" to build all targets marked with [*] '
@echo
'For further info see the ./README file'
help-board-dirs := $(addprefix help-,$(board-dirs))
help-boards: $(help-board-dirs)
boards-per-dir = $(sort $(notdir $(wildcard $(srctree)/arch/$(SRCARCH)/configs/$*/*_defconfig)))
$(help-board-dirs): help-%:
@echo
'Architecture specific targets ($(SRCARCH) $*):'
@$(if $(boards-per-dir), 
$(foreach b, $(boards-per-dir), 
printf "
%-24s - Build for %s\n" $*/$(b) $(subst _defconfig,,$(b));) 
echo '')
# Documentation targets
# ---------------------------------------------------------------------------
DOC_TARGETS := xmldocs latexdocs pdfdocs htmldocs epubdocs cleandocs 
linkcheckdocs dochelp refcheckdocs
PHONY += $(DOC_TARGETS)
$(DOC_TARGETS): scripts_basic FORCE
$(Q)$(MAKE) $(build)=Documentation $@
# Misc
# ---------------------------------------------------------------------------
PHONY += scripts_gdb
scripts_gdb: prepare0
$(Q)$(MAKE) $(build)=scripts/gdb
$(Q)ln -fsn $(abspath $(srctree)/scripts/gdb/vmlinux-gdb.py)
ifdef CONFIG_GDB_SCRIPTS
all: scripts_gdb
endif

内核编译部分结束

else # KBUILD_EXTMOD

模块编译部分开始

###
# External module support.
# When building external modules the kernel used as basis is considered
# read-only, and no consistency checks are made and the make
# system is not used on the basis kernel. If updates are required
# in the basis kernel ordinary make commands (without M=...) must
# be used.
#
# The following are the only valid targets when building external
# modules.
# make M=dir clean
Delete all automatically generated files
# make M=dir modules
Make all modules in specified dir
# make M=dir
Same as 'make M=dir modules'
# make M=dir modules_install
#
Install the modules built in the module directory
#
Assumes install directory is already created
# We are always building modules
KBUILD_MODULES := 1
PHONY += $(objtree)/Module.symvers
$(objtree)/Module.symvers:
@test -e $(objtree)/Module.symvers || ( 
echo; 
echo "
WARNING: Symbol version dump $(objtree)/Module.symvers"; 
echo "
is missing; modules will have no dependencies and modversions."; 
echo )
module-dirs := $(addprefix _module_,$(KBUILD_EXTMOD))
PHONY += $(module-dirs) modules
$(module-dirs): prepare $(objtree)/Module.symvers
$(Q)$(MAKE) $(build)=$(patsubst _module_%,%,$@) need-modorder=1
modules: $(module-dirs)
@$(kecho) '
Building modules, stage 2.';
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
PHONY += modules_install
modules_install: _emodinst_ _emodinst_post
install-dir := $(if $(INSTALL_MOD_DIR),$(INSTALL_MOD_DIR),extra)
PHONY += _emodinst_
_emodinst_:
$(Q)mkdir -p $(MODLIB)/$(install-dir)
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modinst
PHONY += _emodinst_post
_emodinst_post: _emodinst_
$(call cmd,depmod)
clean-dirs := $(addprefix _clean_,$(KBUILD_EXTMOD))
PHONY += $(clean-dirs) clean
$(clean-dirs):
$(Q)$(MAKE) $(clean)=$(patsubst _clean_%,%,$@)
clean: rm-files := $(KBUILD_EXTMOD)/Module.symvers
PHONY += help
help:
@echo
'
Building external modules.'
@echo
'
Syntax: make -C path/to/kernel/src M=$$PWD target'
@echo
''
@echo
'
modules
- default target, build the module(s)'
@echo
'
modules_install - install the module'
@echo
'
clean
- remove generated files in module directory only'
@echo
''
PHONY += prepare
endif # KBUILD_EXTMOD
clean: $(clean-dirs)
$(call cmd,rmdirs)
$(call cmd,rmfiles)
@find $(if $(KBUILD_EXTMOD), $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE) 
( -name '*.[aios]' -o -name '*.ko' -o -name '.*.cmd' 
-o -name '*.ko.*' 
-o -name '*.dtb' -o -name '*.dtb.S' -o -name '*.dt.yaml' 
-o -name '*.dwo' -o -name '*.lst' 
-o -name '*.su' -o -name '*.mod' 
-o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' 
-o -name '*.lex.c' -o -name '*.tab.[ch]' 
-o -name '*.asn1.[ch]' 
-o -name '*.symtypes' -o -name 'modules.order' 
-o -name modules.builtin -o -name '.tmp_*.o.*' 
-o -name '*.c.[012]*.*' 
-o -name '*.ll' 
-o -name '*.gcno' ) -type f -print | xargs rm -f
# Generate tags for editors
# ---------------------------------------------------------------------------
quiet_cmd_tags = GEN
$@
cmd_tags = $(CONFIG_SHELL) $(srctree)/scripts/tags.sh $@
tags TAGS cscope gtags: FORCE
$(call cmd,tags)
# Scripts to check various things for consistency
# ---------------------------------------------------------------------------
PHONY += includecheck versioncheck coccicheck namespacecheck export_report
includecheck:
find $(srctree)/* $(RCS_FIND_IGNORE) 
-name '*.[hcS]' -type f -print | sort 
| xargs $(PERL) -w $(srctree)/scripts/checkincludes.pl
versioncheck:
find $(srctree)/* $(RCS_FIND_IGNORE) 
-name '*.[hcS]' -type f -print | sort 
| xargs $(PERL) -w $(srctree)/scripts/checkversion.pl
coccicheck:
$(Q)$(CONFIG_SHELL) $(srctree)/scripts/$@
namespacecheck:
$(PERL) $(srctree)/scripts/namespace.pl
export_report:
$(PERL) $(srctree)/scripts/export_report.pl
PHONY += checkstack kernelrelease kernelversion image_name
# UML needs a little special treatment here.
It wants to use the host
# toolchain, so needs $(SUBARCH) passed to checkstack.pl.
Everyone
# else wants $(ARCH), including people doing cross-builds, which means
# that $(SUBARCH) doesn't work here.
ifeq ($(ARCH), um)
CHECKSTACK_ARCH := $(SUBARCH)
else
CHECKSTACK_ARCH := $(ARCH)
endif
checkstack:
$(OBJDUMP) -d vmlinux $$(find . -name '*.ko') | 
$(PERL) $(srctree)/scripts/checkstack.pl $(CHECKSTACK_ARCH)
kernelrelease:
@echo "$(KERNELVERSION)$$($(CONFIG_SHELL) $(srctree)/scripts/setlocalversion $(srctree))"
kernelversion:
@echo $(KERNELVERSION)
image_name:
@echo $(KBUILD_IMAGE)
# Clear a bunch of variables before executing the submake
ifeq ($(quiet),silent_)
tools_silent=s
endif
tools/: FORCE
$(Q)mkdir -p $(objtree)/tools
$(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(abspath $(objtree)) subdir=tools -C $(srctree)/tools/
tools/%: FORCE
$(Q)mkdir -p $(objtree)/tools
$(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(abspath $(objtree)) subdir=tools -C $(srctree)/tools/ $*
# Single targets
# ---------------------------------------------------------------------------
# Single targets are compatible with:
# - build with mixed source and output
# - build with separate output dir 'make O=...'
# - external modules
#
#
target-dir => where to store outputfile
#
build-dir
=> directory in kernel source tree to use
build-target = $(if $(KBUILD_EXTMOD), $(KBUILD_EXTMOD)/)$@
build-dir = $(patsubst %/,%,$(dir $(build-target)))
%.i: prepare FORCE
$(Q)$(MAKE) $(build)=$(build-dir) $(build-target)
%.ll: prepare FORCE
$(Q)$(MAKE) $(build)=$(build-dir) $(build-target)
%.lst: prepare FORCE
$(Q)$(MAKE) $(build)=$(build-dir) $(build-target)
%.o: prepare FORCE
$(Q)$(MAKE) $(build)=$(build-dir) $(build-target)
%.s: prepare FORCE
$(Q)$(MAKE) $(build)=$(build-dir) $(build-target)
%.symtypes: prepare FORCE
$(Q)$(MAKE) $(build)=$(build-dir) $(build-target)
ifeq ($(KBUILD_EXTMOD),)
# For the single build of an in-tree module, use a temporary file to avoid
# the situation of modules_install installing an invalid modules.order.
%.ko: MODORDER := .modules.tmp
endif
%.ko: prepare FORCE
$(Q)$(MAKE) $(build)=$(build-dir) $(build-target:.ko=.mod)
$(Q)echo $(build-target) > $(MODORDER)
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
# Modules
PHONY += /
/: ./
%/: prepare FORCE
$(Q)$(MAKE) KBUILD_MODULES=1 $(build)=$(build-dir) need-modorder=1
# FIXME Should go into a make.lib or something
# ===========================================================================
quiet_cmd_rmdirs = $(if $(wildcard $(rm-dirs)),CLEAN
$(wildcard $(rm-dirs)))
cmd_rmdirs = rm -rf $(rm-dirs)
quiet_cmd_rmfiles = $(if $(wildcard $(rm-files)),CLEAN
$(wildcard $(rm-files)))
cmd_rmfiles = rm -f $(rm-files)
# Run depmod only if we have System.map and depmod is executable
quiet_cmd_depmod = DEPMOD
$(KERNELRELEASE)
cmd_depmod = $(CONFIG_SHELL) $(srctree)/scripts/depmod.sh $(DEPMOD) 
$(KERNELRELEASE)
# read saved command lines for existing targets
existing-targets := $(wildcard $(sort $(targets)))
-include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
endif
# ifeq ($(config-targets),1)
endif
# ifeq ($(mixed-targets),1)