u-boot-2020.01 编译流程分析-makefile_u-boot 2020.01-优快云博客

本文链接：https://blog.youkuaiyun.com/weixin_39035140/article/details/117070093

标题

1、编译u-boot镜像执行的命令

   make DEVICE_TREE=stm32mp157a-fsmp1a  all

2、从编译命令入手可以查看all这个目标

在看源码之前用一张图将依赖关系展示出来：
在这里插入图片描述

2.1 从顶层Makefile找到all目标，定义如下：

960 all:        $(ALL-y)                                                                      
961	eq ($(CONFIG_DEPRECATED),y)
962	 $(warning "You have deprecated configuration options enabled in your .config!

2.2 发现all目标又依赖于ALL-y目标，ALL-y目标定义如下：

846 ALL-y += u-boot.srec u-boot.bin u-boot.sym System.map binary_size_check

2.3、u-boot.srec、u-boot.sym、System.map目标都依赖u-boot

1169 u-boot.hex u-boot.srec: u-boot FORCE
1170     $(call if_changed,objcopy)
1683 u-boot.sym: u-boot FORCE                                                        
1684     $(call if_changed,sym)
1875 System.map: u-boot                                                              
1876         @$(call SYSTEM_MAP,$<) > $@

而binary_size_check依赖u-boot-nodtb.bin FORCE

binary_size_check: u-boot-nodtb.bin FORCE

其中打开设备树以后u-boot.binu-boot-dtb.bin—>u-boot-nodtb.bin dts/dt.dtb
所以u-boot.bin、binary_size_check目标依赖u-boot-nodtb.bin：

1140 u-boot.bin: u-boot-nodtb.bin FORCE
1141     $(call if_changed,copy)

而u-boot-nodtb.bin、dts/dt.dtb都依赖u-boot

1235 u-boot-nodtb.bin: u-boot FORCE                                                  
1236     $(call if_changed,objcopy)
1237     $(call DO_STATIC_RELA,$<,$@,$(CONFIG_SYS_TEXT_BASE))
1238     $(BOARD_SIZE_CHECK)
1086 dts/dt.dtb: u-boot
1087     $(Q)$(MAKE) $(build)=dts dtbs

2.4 得出的结果：ALL-y的依赖u-boot.srec u-boot.bin u-boot.sym System.map binary_size_check又全部依赖u-boot
2.5 u-boot目标

1670 u-boot: $(u-boot-init) $(u-boot-main) u-boot.lds FORCE                          
1671     +$(call if_changed,u-boot__)
1672 ifeq ($(CONFIG_KALLSYMS),y)
1673     $(call cmd,smap)
1674     $(call cmd,u-boot__) common/system_map.o
1675 endif
1676 
1677 ifeq ($(CONFIG_RISCV),y)
1678     @tools/prelink-riscv $@ 0
1679 endif

2.6、u-boot-init、u-boot-main目标

781 u-boot-init := $(head-y)                                                        
782 u-boot-main := $(libs-y)

2.7、libs-y目标
其被定义为各层驱动目录下build-in.o的集合
2.8、heda-y

95 head-y := arch/arm/cpu/$(CPU)/start.o

1656 quiet_cmd_u-boot__ ?= LD      $@
1657       cmd_u-boot__ ?= $(LD) $(LDFLAGS) $(LDFLAGS_u-boot) -o $@ \
1658       -T u-boot.lds $(u-boot-init)                             \
1659       --start-group $(u-boot-main) --end-group                 \
1660       $(PLATFORM_LIBS) -Map u-boot.map;                        \
1661       $(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)

总结：u-boot 依赖 $(u - b o o t - i n i t) ，$ (u-boot-main) 和 u-boot.lds ，而$(u-boot-init) $(u-boot-main) 依赖 $(u-boot-dirs), $KaTeX parse error: Expected group after '_' at position 59: \dots命令行执行cmd_u-boot_̲_将$ (u-boot-int)到$(u-boot-main)通过u-boot.lds链接起来.