1. 默认目标__build
2. 初始化obj-y、obj-m等变量
3. -include include/config/auto.conf
内含CONFIG_RING_BUFFER=y等变量列表
4. include scripts/Kbuild.include
内含各辅助函数、变量的定义
如变量build := -f $(if $(KBUILD_SRC),$(srctree)/)scripts/Makefile.build obj
5. include $(kbuild-file)
变量obj传进来目录内的Makefile(或Kbuild优先)
6. include scripts/Makefile.lib
内含c_flags、a_flags各编译标志变量
处理obj-y、obj-m等变量
7. 若有$(hostprogs-y)或$(hostprogs-m)需要编译主机程序，则include scripts/Makefile.host
8. builtin-target、lib-target、modorder-target
9. __build: $(if $(KBUILD_BUILTIN),$(builtin-target) $(lib-target) $(extra-y)) \
$(if $(KBUILD_MODULES),$(obj-m) $(modorder-target)) \
$(subdir-ym) $(always)
10. .c、.S等文件的编译规则
11. 递归进入子目录的规则
$(subdir-ym):
$(Q)$(MAKE) $(build)=$@
通常内核各个文件都是由-f参数使用scripts/Makefile.build文件来作为Makefile进行目标的编译
对目标的编译主要使用如下格式：
$(Q)$(MAKE) $(build)=目录 [目标]
build变量在scripts/Kbuild.include中定义
展开即：
make -f scripts/Makefile.build obj=目录 [目标]
