• 【BSP开发之kernel】Linux启动流程以及编译流程分析

    文章目录

    linux 顶层Makefile分析

    MAKEFLAGS += -rR

# 静默输出 make V=1 静默输出
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

# 设置编译结果输出目录 make O=path
ifeq ("$(origin O)", "command line")
  KBUILD_OUTPUT := $(O)
endif

# 默认编译目标
PHONY := _all
_all:

# 代码检查 make C=1 使能带代码检查
# make C=2 检查所有的源码文件
ifeq ("$(origin C)", "command line")
  KBUILD_CHECKSRC = $(C)
endif
ifndef KBUILD_CHECKSRC
  KBUILD_CHECKSRC = 0
endif

ifdef SUBDIRS
  KBUILD_EXTMOD ?= $(SUBDIRS)
endif

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

PHONY += all
ifeq ($(KBUILD_EXTMOD),)
_all: all
else
_all: modules
endif

ifeq ($(KBUILD_SRC),)
        # building in the source tree
        srctree := .
else
        ifeq ($(KBUILD_SRC)/,$(dir $(CURDIR)))
                # building in a subdirectory of the source tree
                srctree := ..
        else
                srctree := $(KBUILD_SRC)
        endif
endif
objtree		:= .
src		:= $(srctree)
obj		:= $(objtree)

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

export srctree objtree VPATH

# 设置架构以及交叉编译器
ARCH		= arm
CROSS_COMPILE	=arm-linux-gnueabi-


KCONFIG_CONFIG	?= .config
export KCONFIG_CONFIG

# SHELL used by kbuild
# CONFIG_SHELL := $(shell if [ -x "$$BASH" ]; then echo $$BASH; \
# 	  else if [ -x /bin/bash ]; then echo /bin/bash; \
# 	  else echo sh; fi ; fi)
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
INSTALLKERNEL  := installkernel
DEPMOD		= /sbin/depmod
PERL		= perl
PYTHON		= python
CHECK		= sparse

CHECKFLAGS     := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ \
		  -Wbitwise -Wno-return-void $(CF)
CFLAGS_MODULE   =
AFLAGS_MODULE   =
LDFLAGS_MODULE  =
CFLAGS_KERNEL	=
AFLAGS_KERNEL	=
CFLAGS_GCOV	= -fprofile-arcs -ftest-coverage


# 添加头文件目录
USERINCLUDE    := \
		-I$(srctree)/arch/$(hdr-arch)/include/uapi \
		-Iarch/$(hdr-arch)/include/generated/uapi \
		-I$(srctree)/include/uapi \
		-Iinclude/generated/uapi \
                -include $(srctree)/include/linux/kconfig.h
LINUXINCLUDE    := \
		-I$(srctree)/arch/$(hdr-arch)/include \
		-Iarch/$(hdr-arch)/include/generated/uapi \
		-Iarch/$(hdr-arch)/include/generated \
		$(if $(KBUILD_SRC), -I$(srctree)/include) \
		-Iinclude \
		$(USERINCLUDE)

# make xxx_deconfig 配置过程
config-targets := 0
mixed-targets  := 0
dot-config     := 1
ifneq ($(filter $(no-dot-config-targets), $(MAKECMDGOALS)),)
	ifeq ($(filter-out $(no-dot-config-targets), $(MAKECMDGOALS)),)
		dot-config := 0
	endif
endif
ifeq ($(KBUILD_EXTMOD),)
        ifneq ($(filter config %config,$(MAKECMDGOALS)),)
                config-targets := 1
                ifneq ($(words $(MAKECMDGOALS)),1)
                        mixed-targets := 1
                endif
        endif
endif

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
ifeq ($(config-targets),1)

include $(srctree)/arch/$(SRCARCH)/Makefile
export KBUILD_DEFCONFIG KBUILD_KCONFIG

config: scripts_basic outputmakefile FORCE
	$(Q)$(MAKE) $(build)=scripts/kconfig $@

%config: scripts_basic outputmakefile FORCE
	$(Q)$(MAKE) $(build)=scripts/kconfig $@
else
ifeq ($(KBUILD_EXTMOD),)
PHONY += scripts
scripts: scripts_basic include/config/auto.conf include/config/tristate.conf \
	 asm-generic
	$(Q)$(MAKE) $(build)=$(@)
init-y		:= init/
drivers-y	:= drivers/ sound/ firmware/
net-y		:= net/
libs-y		:= lib/
core-y		:= usr/
endif # KBUILD_EXTMOD

ifeq ($(dot-config),1)
ifeq ($(KBUILD_EXTMOD),)
-include include/config/auto.conf.cmd

$(KCONFIG_CONFIG) include/config/auto.conf.cmd: ;
include/config/%.conf: $(KCONFIG_CONFIG) include/config/auto.conf.cmd
	$(Q)$(MAKE) -f $(srctree)/Makefile silentoldconfig
else
PHONY += include/config/auto.conf
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 # KBUILD_EXTMOD

else
include/config/auto.conf: ;
endif # $(dot-config)
all: vmlinux

    • 1
    • 2
    • 3
    • 4
    • 5
    • 6
    • 7
    • 8
    • 9
    • 10
    • 11
    • 12
    • 13
    • 14
    • 15
    • 16
    • 17
    • 18
    • 19
    • 20
    • 21
    • 22
    • 23
    • 24
    • 25
    • 26
    • 27
    • 28
    • 29
    • 30
    • 31
    • 32
    • 33
    • 34
    • 35
    • 36
    • 37
    • 38
    • 39
    • 40
    • 41
    • 42
    • 43
    • 44
    • 45
    • 46
    • 47
    • 48
    • 49
    • 50
    • 51
    • 52
    • 53
    • 54
    • 55
    • 56
    • 57
    • 58
    • 59
    • 60
    • 61
    • 62
    • 63
    • 64
    • 65
    • 66
    • 67
    • 68
    • 69
    • 70
    • 71
    • 72
    • 73
    • 74
    • 75
    • 76
    • 77
    • 78
    • 79
    • 80
    • 81
    • 82
    • 83
    • 84
    • 85
    • 86
    • 87
    • 88
    • 89
    • 90
    • 91
    • 92
    • 93
    • 94
    • 95
    • 96
    • 97
    • 98
    • 99
    • 100
    • 101
    • 102
    • 103
    • 104
    • 105
    • 106
    • 107
    • 108
    • 109
    • 110
    • 111
    • 112
    • 113
    • 114
    • 115
    • 116
    • 117
    • 118
    • 119
    • 120
    • 121
    • 122
    • 123
    • 124
    • 125
    • 126
    • 127
    • 128
    • 129
    • 130
    • 131
    • 132
    • 133
    • 134
    • 135
    • 136
    • 137
    • 138
    • 139
    • 140
    • 141
    • 142
    • 143
    • 144
    • 145
    • 146
    • 147
    • 148
    • 149
    • 150
    • 151
    • 152
    • 153
    • 154
    • 155
    • 156
    • 157
    • 158
    • 159
    • 160
    • 161
    • 162
    • 163
    • 164
    • 165
    • 166
    • 167
    • 168
    • 169
    • 170
    • 171
    • 172
    • 173
    • 174
    • 175
    • 176
    • 177
    • 178
    • 179
    • 180
    • 181
    • 182
    • 183
    • 184
    • 185
    • 186
    • 187
    • 188
    • 189
    • 190
    • 191
    • 192
    • 193
    • 194
    • 195
    • 196
    • 197
    • 198

    make 过程分析

    _all-->all-->vmlinux-->scripts/link-vmlinux.sh 
                       head-y  arch/arm/kernel/head.o
                       init -y init/built-in.o
                       libs-y  libs-y = arch/arm/lib/lib.a lib/lib.a arch/arm/lib/built-in.o lib/built-in.o
                       drivers-y = drivers/built-in.o sound/built-in.o firmware/built-in.o
                       net-y   snet/built-in.o
                       core-y   usr kernel fs ipc security crypto block
                            usr/built-in.o arch/arm/vfp/built-in.o \
                            arch/arm/vdso/built-in.o arch/arm/kernel/built-in.o \
                            arch/arm/mm/built-in.o arch/arm/common/built-in.o \
                            arch/arm/probes/built-in.o arch/arm/net/built-in.o \
                            arch/arm/crypto/built-in.o arch/arm/firmware/built-in.o \
                            arch/arm/mach-imx/built-in.o kernel/built-in.o\
                            mm/built-in.o fs/built-in.o \
                            ipc/built-in.o security/built-in.o \
                            crypto/built-in.o block/built-in.o

    • 1
    • 2
    • 3
    • 4
    • 5
    • 6
    • 7
    • 8
    • 9
    • 10
    • 11
    • 12
    • 13
    • 14
    • 15
    • 16

    arch/arm/kernel/vmlinux.lds 就是整个 Linux 的链接脚本。

    最终 vmlinux 依赖于以下文件：

    vmlinux-deps = arch/arm/kernel/vmlinux.lds arch/arm/kernel/head.o \
init/built-in.o usr/built-in.o \
arch/arm/vfp/built-in.o arch/arm/vdso/built-in.o \
arch/arm/kernel/built-in.o arch/arm/mm/built-in.o \
arch/arm/common/built-in.o arch/arm/probes/built-in.o \
arch/arm/net/built-in.o arch/arm/crypto/built-in.o \
arch/arm/firmware/built-in.o arch/arm/mach-imx/built-in.o \
kernel/built-in.o mm/built-in.o \
fs/built-in.o ipc/built-in.o \
security/built-in.o crypto/built-in.o\
block/built-in.o arch/arm/lib/lib.a\
lib/lib.a arch/arm/lib/built-in.o\
lib/built-in.o drivers/built-in.o \
sound/built-in.o firmware/built-in.o \
net/built-in.o

    • 1
    • 2
    • 3
    • 4
    • 5
    • 6
    • 7
    • 8
    • 9
    • 10
    • 11
    • 12
    • 13
    • 14
    • 15

    子文件夹编译

    vmlinux-dirs = init usr arch/arm/vfp \
arch/arm/vdso arch/arm/kernel arch/arm/mm \
arch/arm/common arch/arm/probes arch/arm/net \
arch/arm/crypto arch/arm/firmware arch/arm/mach-imx\
kernel mm fs \
ipc security crypto \
block drivers sound \
firmware net arch/arm/lib \
lib
$(vmlinux-dirs): prepare scripts
    $(Q)$(MAKE) $(build)=$@

    • 1
    • 2
    • 3
    • 4
    • 5
    • 6
    • 7
    • 8
    • 9
    • 10
    • 11

    展开就是 @ make -f ./scripts/Makefile.build obj=$@
    以 init 为例子目录编译脚本为:
    @ make -f ./scripts/Makefile.build obj=init

    Makefile.build 编译出子文件 build-in.o 过程分析

    _build–>: $(builtin-target)
    $(lib-target)
    $(extra-y)
    $(subdir-ym)
    $(always)

    $(builtin-target): $(obj-y) FORCE
    $(call if_changed,link_o_target) -->= $(obj)/built-in.o

    vmlinux、Image，zImage、uImage 的区别

    vmlinux 是编译出来的最原始的内核文件，是未压缩的
Image 是 Linux 内核镜像文件，但是 Image 仅包含可执行的二进制数据。Image 就是使

    • 1
    • 2

    用 objcopy 取消掉 vmlinux 中的一些其他信息
    zImage 是经过 gzip 压缩后的 Image
    uImage 是老版本 uboot 专用的镜像文件，uImag 是在 zImage 前面加了一个长度为 64
    字节的“头”，这个头信息描述了该镜像文件的类型、加载位置、生成时间、大小等信息

    内核启动流程分析

  • 相关阅读:
    rocky9.1 深度学习环境配置
    自己动手写编译器:词法解析的系统化研究
    java培训技术数据绑定流程原理
    【Python 自动化办公】docx module 的坑
    深度讲解TS：这样学TS，迟早进大厂【08】：对象的类型—接口
    【Centos7.9通过systemctl启动zookeeper和kafka失败】
    【docker】修改Docker默认存储位置修改配置文件方式
    centos离线安装包(https部署下需要mod_ssl)
    LeetCode 2483. 商店的最少代价【字符串,前后缀分解】1494
    springBoot实现发布订阅
  • 原文地址：https://blog.csdn.net/yy197696/article/details/126187026