u-boot 编译流程 (一)

最新推荐文章于 2025-07-06 17:32:09 发布

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最新推荐文章于 2025-07-06 17:32:09 发布 · 575 阅读

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本文详细解析了U-Boot的.config文件生成过程，并指导如何添加自定义配置。从make命令执行开始，逐步介绍了scripts_basic、outputmakefile的生成及fixdep的作用。最后，通过实例演示了如何为特定目录添加编译选项。

1 `.config`文件产生

研究.config文件的产生流程，添加自己的配置
U-Boot 2017.11
Source Insight
Ubuntu 18.04
arm-linux-gnueabi-xxx

1.1 find %config

当我们执行sudo make smdk5250_defconfig命令行后，make会进入顶层Makefile文件,执行下面的语句. 而%config依赖scripts_basic 和 ouputmakefile, 所以我问首先去看scripts_basic

%config: scripts_basic outputmakefile FORCE	
	@echo "eric_debug.........start:$@"
	$(Q)$(MAKE) $(build)=scripts/kconfig $@
	@echo "eric_debug.........end $@"

1.2 find scripts_basic

在顶层Makefile中会发现如下代码段

scripts_basic:
	$(Q)$(MAKE) $(build)=scripts/basic
	$(Q)rm -f .tmp_quiet_recordmcount

make 直接执行命令行$(Q)$(MAKE) $(build)=scripts/basic，展开后得到下面的片段，默认目标是all

$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.build obj=scripts/basic

1.2.1 进入Makefile.build 执行

包含scripts/basic/Makefile
包含scripts/Makefile.host

将obj=scripts/basic通过下面的语句, 展开后得到 include ./scripts/basic/Makefile .

PHONY := __build
__build:
src := scripts/basic
include scripts/Kbuild.include

# For backward compatibility check that these variables do not change
save-cflags := $(CFLAGS)

#kbuild-dir := ./scripts/basic
kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
#kbuild-file := ./scripts/basic/Makefile
kbuild-file := $(if $(wildcard $(kbuild-dir)/Kbuild),$(kbuild-dir)/Kbuild,$(kbuild-dir)/Makefile)
#include ./scripts/basic/Makefile
include $(kbuild-file)

ifneq ($(hostprogs-y)$(hostprogs-m),)
include scripts/Makefile.host
endif

__build: $(if $(KBUILD_BUILTIN),$(builtin-target) $(lib-target) $(extra-y)) \
	 $(