UBOOT编译--- include/config.h、 include/autoconf.mk、include/autoconf.mk.dep、u-boot.cfg(三)

1. 前言

　UBOOT版本：uboot2018.03，开发板myimx8mmek240。

2. 概述

本节主要接上一节解析 ：include/config.h、 include/autoconf.mk、include/autoconf.mk.dep、spl/include/autoconf.mk、u-boot.cfg、spl/u-boot.cfg。

3 语句 $ (Q) $(MAKE) -f $(srctree)/scripts/Makefile.autoconf

由于未指定目标，采用默认目标__all

#note：scripts/Makefile.autoconf
__all: include/autoconf.mk include/autoconf.mk.dep

ifeq ($(shell grep -q '^CONFIG_SPL=y' include/config/auto.conf 2>/dev/null && echo y),y) //本人单板该条件成立
__all: spl/include/autoconf.mk

endif


include/autoconf.mk.dep: include/config.h FORCE
	$(call cmd,autoconf_dep)
	
spl/include/autoconf.mk: spl/u-boot.cfg
	$(Q)mkdir -p $(dir $@)
	$(call cmd,autoconf)
	
	
u-boot.cfg: include/config.h FORCE
	$(call cmd,u_boot_cfg)

spl/u-boot.cfg: include/config.h FORCE
	$(Q)mkdir -p $(dir $@)
	$(call cmd,u_boot_cfg,-DCONFIG_SPL_BUILD)
	
	
include/config.h: scripts/Makefile.autoconf create_symlink FORCE
	$(call filechk,config_h)

3.1 依赖include/autoconf.mk

include/autoconf.mk: u-boot.cfg
	$(call cmd,autoconf)
u-boot.cfg: include/config.h FORCE
	$(call cmd,u_boot_cfg)

3.1.1 include/config.h的规则

include/config.h: scripts/Makefile.autoconf create_symlink FORCE
	$(call filechk,config_h)

3.1.1.1 FORCE

参见UBOOT编译--- make xxx_deconfig过程详解(一)4.3小节。

3.1.1.2 create_symlink

为mach相关的头文件在arch/arm/include/asm/arch创建软连接。

#note：scripts/Makefile.autoconf
# symbolic links
# If arch/$(ARCH)/mach-$(SOC)/include/mach exists,
# make a symbolic link to that directory.
# Otherwise, create a symbolic link to arch/$(ARCH)/include/asm/arch-$(SOC).
PHONY += create_symlink
create_symlink:
ifdef CONFIG_CREATE_ARCH_SYMLINK
ifneq ($(KBUILD_SRC),)
	$(Q)mkdir -p include/asm
	$(Q)if [ -d $(KBUILD_SRC)/arch/$(ARCH)/mach-$(SOC)/include/mach ]; then	\
		dest=arch/$(ARCH)/mach-$(SOC)/include/mach;			\
	else									\
		dest=arch/$(ARCH)/include/asm/arch-$(if $(SOC),$(SOC),$(CPU));	\
	fi;									\
	ln -fsn $(KBUILD_SRC)/$$dest include/asm/arch
else
	$(Q)if [ -d arch/$(ARCH)/mach-$(SOC)/include/mach ]; then	\
		dest=../../mach-$(SOC)/include/mach;			\
	else								\
		dest=arch-$(if $(SOC),$(SOC),$(CPU));			\
	fi;								\
	ln -fsn $$dest arch/$(ARCH)/include/asm/arch
endif
endif

如果采用直接在源目录编译的方式时KBUILD_SRC为空，走else分支。对于我调试的单板ARCH=arm，SOC=imx8m，因此执行else语句展开为：

if [ -d arch/arm/mach-imx8m/include/mach ]; then        \
        dest=../../mach-imx8m/include/mach;                     \
else                                                            \
        dest=arch-imx8m;                        \
fi;                                                             \
ln -fsn $dest arch/arm/include/asm/arch

由于我使用的单板设备商提供的源码中没有arch/arm/mach-imx8m/include/mach 和arch-imx8m目录(而是直接在arch/arm/include/asm/arch目录下提供必要的头文件，当然一般不建议这么做)。执行该句相当于未执行。

3.1.1.3 scripts/Makefile.autoconf

指定的依赖文件。

3.1.1.4 规则 $(call filechk,config_h)

#note：scripts/Kbuild.include
###
# filechk is used to check if the content of a generated file is updated.
# Sample usage:
# define filechk_sample
#	echo $KERNELRELEASE
# endef
# version.h : Makefile
#	$(call filechk,sample)
# The rule defined shall write to stdout the content of the new file.
# The existing file will be compared with the new one.
# - If no file exist it is created
# - If the content differ the new file is used
# - If they are equal no change, and no timestamp update
# - stdin is piped in from the first prerequisite ($<) so one has
#   to specify a valid file as first prerequisite (often the kbuild file)
define filechk
	$(Q)set -e;				\
	$(kecho) '  CHK     $@';		\
	mkdir -p $(dir $@);			\
	$(filechk_$(1)) < $< > $@.tmp;		\
	if [ -r $@ ] && cmp -s $@ $@.tmp; then	\
		rm -f $@.tmp;			\
	else					\
		$(kecho) '  UPD     $@';	\
		mv -f $@.tmp $@;		\
	fi
endef

上述代码中$@为3.2.1小节的目标：‘include/config.h’，‘ $ (1)’为第一个参数config_h，‘$<’ 为第一个依赖scripts/Makefile.autoconf展开为：

	$(Q)set -e;				\
	$(kecho) '  CHK     include/config.h';		\
	mkdir -p $(dir $@);			\
	$(filechk_config_h) < scripts/Makefile.autoconf > include/config.h.tmp;		\
	if [ -r include/config.h ] && cmp -s include/config.h include/config.h.tmp; then	\
		rm -f include/config.h.tmp;			\
	else					\
		$(kecho) '  UPD     include/config.h';	\
		mv -f include/config.h.tmp include/config.h;		\
	fi

filechk_config_h定义在scripts/Makefile.autoconf中

#note：scripts/Makefile.autoconf
# Prior to Kconfig, it was generated by mkconfig. Now it is created here.
define filechk_config_h
	(echo "/* Automatically generated - do not edit */";		\
	for i in $$(echo $(CONFIG_SYS_EXTRA_OPTIONS) | sed 's/,/ /g'); do \
		echo \#define CONFIG_$$i				\
		| sed '/=/ {s/=/	/;q; } ; { s/$$/	1/; }'; \
	done;								\
	echo \#define CONFIG_BOARDDIR board/$(if $(VENDOR),$(VENDOR)/)$(BOARD);\
	echo \#include \<config_defaults.h\>;				\
	echo \#include \<config_uncmd_spl.h\>;				\
	echo \#include \<configs/$(CONFIG_SYS_CONFIG_NAME).h\>;		\
	echo \#include \<asm/config.h\>;				\
	echo \#include \<linux/kconfig.h\>;				\
	echo \#include \<config_fallbacks.h\>;)
endef

其中CONFIG_SYS_EXTRA_OPTIONS为xxx_deconfig中定义：CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=arch/arm/mach-imx/spl_sd.cfg,SPL_TEXT_BASE=0x7E1000"。具体编译命令如下：

set -e; : '  CHK     include/config.h'; mkdir -p include/;      (echo "/* Automatically generated - do not edit */"; for i in $(echo "IMX_CONFIG=arch/arm/mach-imx/spl_sd.cfg,SPL_TEXT_BASE=0x7E1000" | sed 's/,/ /g'); do echo \#define CONFIG_$i | sed '/=/ {s/=/   /;q; } ; { s/$/ 1/; }'; done; echo \#define CONFIG_BOARDDIR board/myzr/myimx8mm; echo \#include \<config_defaults.h\>; echo \#include \<config_uncmd_spl.h\>; echo \#include \<configs/"myimx8mmek240".h\>; echo \#include \<asm/config.h\>; echo \#include \<linux/kconfig.h\>; echo \#include \<config_fallbacks.h\>;) < scripts/Makefile.autoconf > include/config.h.tmp; if [ -r include/config.h ] && cmp -s include/config.h include/config.h.tmp; then rm -f include/config.h.tmp; else : '  UPD     include/config.h'; mv -f include/config.h.tmp include/config.h; fi

include/config.h内容如下：

3.1.2 u-boot.cfg的规则 $(call cmd,u_boot_cfg)

#note：scripts/Makefile.autoconf
# echo command.
# Short version is used, if $(quiet) equals `quiet_', otherwise full one.
echo-cmd = $(if $($(quiet)cmd_$(1)),\
	echo '  $(call escsq,$($(quiet)cmd_$(1)))$(echo-why)';)

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

quiet定义在顶层Makefile，默认值(空)，escsq的作用是转义在回显语句中使用的单引号。为了方便理解，这里把静默编译功能关掉，即quiet=quiet_。

quiet_cmd_u_boot_cfg = CFG     $@     //编译时经常看的就是这句打印
      cmd_u_boot_cfg = \
	$(CPP) $(c_flags) $2 -DDO_DEPS_ONLY -dM $(srctree)/include/common.h > $@.tmp && { \
		grep 'define CONFIG_' $@.tmp > $@;			\
		rm $@.tmp;						\
	} || {								\
		rm $@.tmp; false;					\
	}

上诉命展开如下：

  /home/h/my-work/03_toolchain/gcc-linaro-7.3.1-2018.05-x86_64_aarch64-linux-gnu/bin/aarch64-linux-gnu-gcc -E -Wall -Wstrict-prototypes -Wno-format-security -fno-builtin -ffreestanding -fshort-wchar -O2 -fno-stack-protector -fno-delete-null-pointer-checks -g -fstack-usage -Wno-format-nonliteral -Werror=date-time  -D__KERNEL__ -D__UBOOT__   -D__ARM__           -fno-pic  -mstrict-align  -ffunction-sections -fdata-sections -fno-common -ffixed-r9    -fno-common -ffixed-x18 -pipe -Iinclude  -I./arch/arm/include -include ./include/linux/kconfig.h  -nostdinc -isystem /home/h/my-work/03_toolchain/gcc-linaro-7.3.1-2018.05-x86_64_aarch64-linux-gnu/bin/../lib/gcc/aarch64-linux-gnu/7.3.1/include  -DDO_DEPS_ONLY -dM ./include/common.h > u-boot.cfg.tmp && { grep 'define CONFIG_' u-boot.cfg.tmp > u-boot.cfg; rm u-boot.cfg.tmp; } || { rm u-boot.cfg.tmp; false; }

$2为空，编译选项“-dM”的作用是输出include/common.h中定义的所有宏。根据上面的规则，编译器提取include/common.h中(include/common.h文件包含了include/config.h文件，而include/config.h文件又包含了其它头文件，这里面的内容都会得到解析。 )定义的宏，然后输出给u-boot.cfg.tmp，然后查找和处理以“CONFIG_”开头的宏定义的功能并输出给u-boot.cfg。

3.1.3 include/autoconf.mk的规则 $(call cmd,autoconf)

# We are migrating from board headers to Kconfig little by little.
# In the interim, we use both of
#  - include/config/auto.conf (generated by Kconfig)
#  - include/autoconf.mk      (used in the U-Boot conventional configuration)
# The following rule creates autoconf.mk
# include/config/auto.conf is grepped in order to avoid duplication of the
# same CONFIG macros
quiet_cmd_autoconf = GEN     $@     //编译时经常看的就是这句打印
      cmd_autoconf = \
		sed -n -f $(srctree)/tools/scripts/define2mk.sed $< |			\
		while read line; do							\
			if [ -n "${KCONFIG_IGNORE_DUPLICATES}" ] ||			\
			   ! grep -q "$${line%=*}=" include/config/auto.conf; then	\
				echo "$$line";						\
			fi								\
		done > $@

上诉命展开如下：

sed -n -f ./tools/scripts/define2mk.sed u-boot.cfg | while read line; do if [ -n "" ] || ! grep -q "${line%=*}=" include/config/auto.conf; then echo "$line"; fi done > include/autoconf.mk

上面语句就是寻找u-boot.cfg 中有但是include/config/auto.conf没有的行，并把摘到的内容输出到include/autoconf.mk中 。

3.2 include/autoconf.mk.dep

include/autoconf.mk.dep: include/config.h FORCE
	$(call cmd,autoconf_dep)

#note：scripts/Makefile.autoconf
# echo command.
# Short version is used, if $(quiet) equals `quiet_', otherwise full one.
echo-cmd = $(if $($(quiet)cmd_$(1)),\
	echo '  $(call escsq,$($(quiet)cmd_$(1)))$(echo-why)';)

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

quiet定义在顶层Makefile，默认值(空)，escsq的作用是转义在回显语句中使用的单引号。为了方便理解，这里把静默编译功能关掉，即quiet=quiet_。

quiet_cmd_autoconf_dep = GEN     $@
      cmd_autoconf_dep = $(CC) -x c -DDO_DEPS_ONLY -M -MP $(c_flags) \
	-MQ include/config/auto.conf $(srctree)/include/common.h > $@ || {	\
		rm $@; false;							\
	}

上诉命展开如下：

   /home/h/my-work/03_toolchain/gcc-linaro-7.3.1-2018.05-x86_64_aarch64-linux-gnu/bin/aarch64-linux-gnu-gcc -x c -DDO_DEPS_ONLY -M -MP -Wall -Wstrict-prototypes -Wno-format-security -fno-builtin -ffreestanding -fshort-wchar -O2 -fno-stack-protector -fno-delete-null-pointer-checks -g -fstack-usage -Wno-format-nonliteral -Werror=date-time  -D__KERNEL__ -D__UBOOT__   -D__ARM__           -fno-pic  -mstrict-align  -ffunction-sections -fdata-sections -fno-common -ffixed-r9    -fno-common -ffixed-x18 -pipe -Iinclude  -I./arch/arm/include -include ./include/linux/kconfig.h  -nostdinc -isystem /home/h/my-work/03_toolchain/gcc-linaro-7.3.1-2018.05-x86_64_aarch64-linux-gnu/bin/../lib/gcc/aarch64-linux-gnu/7.3.1/include -MQ include/config/auto.conf ./include/common.h > include/autoconf.mk.dep || { rm include/autoconf.mk.dep; false; }

分析：include/autoconf.mk.dep依赖 include/config.h，其中include/config.h为动态创建。
（1）-M 生成目标依赖关系，其中目标的格式为源文件去路径文件名+.o后缀。生成文件的依赖关系，同时也把一些标准库的头文件包含了进来。本质是告诉预处理器输出一个适合 make 的规则，用于描述各目标文件的依赖关系。对于每个源文件，预处理器输出 一个 make 规则，该规则的目标项 (target) 是源文件对应的目标文件名，依赖项 (dependency) 是源文件中 “#include” 引用的所有文件，生成的规则可以是单行，但如果太长，就用’'换行符续成多行。规则显示在标准输出，不产生预处理过的 C 程序。
-M 处理后的格式如下：

（2）-MP生成的依赖文件里面，依赖规则中的所有 .h 依赖项都会在该文件中生成一个伪目标，其不依赖任何其他依赖项。该伪规则将避免删除了对应的头文件而没有更新 “Makefile” 去匹配新的依赖关系而导致 make 出错的情况出现。
-MP 处理后的格式如下：

（3）-MQ相当于-MT，覆盖默认的源文件去路径文件名+.o后缀的目标生成格式，采用指定的字符串，这里对应include/config/auto.conf；
-MQ 处理后的格式如下：

（4）$@为自动变量，代表依赖关系中的目标，这里对应include/autoconf.mk.dep；
（5）-x c，指定源文件使用C语言语法；

总体来说：该依赖关系用来生成include/autoconf.mk.dep，生成的方法是生成 include/common.h的依赖关系。

3.3 spl/u-boot.cfg

spl/u-boot.cfg: include/config.h FORCE
	$(Q)mkdir -p $(dir $@)
	$(call cmd,u_boot_cfg,-DCONFIG_SPL_BUILD)

cmd的定义在本篇前面已经讲过，这里略过，直接展开$(call cmd,u_boot_cfg,-DCONFIG_SPL_BUILD)：

```c
quiet_cmd_u_boot_cfg = CFG     $@     //编译时经常看的就是这句打印
      cmd_u_boot_cfg = \
	$(CPP) $(c_flags) $2 -DDO_DEPS_ONLY -dM $(srctree)/include/common.h > $@.tmp && { \
		grep 'define CONFIG_' $@.tmp > $@;			\
		rm $@.tmp;						\
	} || {								\
		rm $@.tmp; false;					\
	}

上诉命展开如下：

 /home/h/my-work/03_toolchain/gcc-linaro-7.3.1-2018.05-x86_64_aarch64-linux-gnu/bin/aarch64-linux-gnu-gcc -E -Wall -Wstrict-prototypes -Wno-format-security -fno-builtin -ffreestanding -fshort-wchar -O2 -fno-stack-protector -fno-delete-null-pointer-checks -g -fstack-usage -Wno-format-nonliteral -Werror=date-time  -D__KERNEL__ -D__UBOOT__   -D__ARM__           -fno-pic  -mstrict-align  -ffunction-sections -fdata-sections -fno-common -ffixed-r9    -fno-common -ffixed-x18 -pipe -Iinclude  -I./arch/arm/include -include ./include/linux/kconfig.h  -nostdinc -isystem /home/h/my-work/03_toolchain/gcc-linaro-7.3.1-2018.05-x86_64_aarch64-linux-gnu/bin/../lib/gcc/aarch64-linux-gnu/7.3.1/include -DCONFIG_SPL_BUILD -DDO_DEPS_ONLY -dM ./include/common.h > spl/u-boot.cfg.tmp && { grep 'define CONFIG_' spl/u-boot.cfg.tmp > spl/u-boot.cfg; rm spl/u-boot.cfg.tmp; } || { rm spl/u-boot.cfg.tmp; false; }

$2为-DCONFIG_SPL_BUILD(新增宏定义CONFIG_SPL_BUILD )，编译选项“-dM”的作用是输出include/common.h中定义的所有宏。根据上面的规则，编译器提取include/common.h中(include/common.h文件包含了include/config.h文件，而include/config.h文件又包含了其它头文件，这里面的内容都会得到解析。 )定义的宏，然后输出给spl/u-boot.cfg.tmp，然后查找和处理以“CONFIG_”开头的宏定义的功能并输出给spl/u-boot.cfg。

spl/u-boot.cfg和u-boot.cfg的区别主要是根据是否定义CONFIG_SPL_BUILD宏，代码会有不同的分支。

3.4 spl/include/autoconf.mk

spl/include/autoconf.mk: spl/u-boot.cfg
	$(Q)mkdir -p $(dir $@)
	$(call cmd,autoconf)

# We are migrating from board headers to Kconfig little by little.
# In the interim, we use both of
#  - include/config/auto.conf (generated by Kconfig)
#  - include/autoconf.mk      (used in the U-Boot conventional configuration)
# The following rule creates autoconf.mk
# include/config/auto.conf is grepped in order to avoid duplication of the
# same CONFIG macros
quiet_cmd_autoconf = GEN     $@     //编译时经常看的就是这句打印
      cmd_autoconf = \
		sed -n -f $(srctree)/tools/scripts/define2mk.sed $< |			\
		while read line; do							\
			if [ -n "${KCONFIG_IGNORE_DUPLICATES}" ] ||			\
			   ! grep -q "$${line%=*}=" include/config/auto.conf; then	\
				echo "$$line";						\
			fi								\
		done > $@

上诉命展开如下：

sed -n -f ./tools/scripts/define2mk.sed spl/u-boot.cfg | while read line; do if [ -n "" ] || ! grep -q "${line%=*}=" include/config/auto.conf; then echo "$line"; fi done > spl/include/autoconf.mk

上面语句就是寻找spl/u-boot.cfg中有但是include/config/auto.conf没有的行，并把摘到的内容输出到spl/include/autoconf.mk中 。

4. 总结（包含上一篇文章）

#顶层Makefile
|--- include/config/%.conf: $(KCONFIG_CONFIG) include/config/auto.conf.cmd //KCONFIG_CONFIG = .config
    |
    |--- $(Q)$(MAKE) -f $(srctree)/Makefile silentoldconfig
    |    |--- #顶层Makefile
    |    |--- %config: scripts_basic outputmakefile FORCE
    |         |--- $(Q)$(MAKE) $(build)=scripts/kconfig $@
    |         |    |--- #scripts/kconfig/Makefile
    |         |    |--- silentoldconfig: $(obj)/conf
    |                  |--- $(Q)mkdir -p include/config include/generated
    |                  |--- $(Q)test -e include/generated/autoksyms.h || touch   include/generated/autoksyms.h
    |                  |--- $< $(silent) --$@ $(Kconfig) //等价于 scripts/kconfig/conf -s --myimx8mmek240-8mm-2g_defconfig .config
    |
    |--- $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.autoconf //未指定目标，采用默认目标__all
    |    |--- #scripts/Makefile.autoconf
    |    |--- __all: include/autoconf.mk include/autoconf.mk.dep
    |    |    |--- include/autoconf.mk: u-boot.cfg
    |    |    |    |--- $(call cmd,autoconf_dep)//通过编译选项"-M"、"-MP"、"-MQ"生成 include/common.h的依赖关系
    |    |
    |    |---__all: spl/include/autoconf.mk
    |         |--- spl/include/autoconf.mk: spl/u-boot.cfg 
    |    |    |    |--- $(Q)mkdir -p $(dir $@)
    |    |    |    |--- $(call cmd,autoconf)//寻找spl/u-boot.cfg中有但是include/config/auto.conf没有的行,并把摘到的内容输出到spl/include/autoconf.mk中 

include/config.h: scripts/Makefile.autoconf create_symlink FORCE
    $(call filechk,config_h) //生成include/config.h文件

u-boot.cfg: include/config.h FORCE
    $(call cmd,u_boot_cfg) //通过编译选项"-dM"输出include/common.h中定义的所有宏

spl/u-boot.cfg: include/config.h FORCE
    $(Q)mkdir -p $(dir $@)
    $(call cmd,u_boot_cfg,-DCONFIG_SPL_BUILD)//通过宏 CONFIG_SPL_BUILD 和编译选项"-dM"输出include/common.h中定义的所有宏_SPL_BUILD)//通过宏 CONFIG_SPL_BUILD 和编译选项"-dM"输出include/common.h中定义的所有宏                                    

5. 参考

（1）Linux Makefile 生成 *.d 依赖文件以及 gcc -M -MF -MP 等相关选项说明
（2）gcc -M -MM -MQ -MF -MT -MD(示例代码)
（3）gcc 选项 -M -MQ