android7.1 rk3288 编译流程

make调用build/core/main.mk产生各种目标文件：droid_targets: droidcore dist_files

# Build files and then package it into the rom formats

.PHONY: droidcore

droidcore: files \

systemimage \
$(INSTALLED_BOOTIMAGE_TARGET) \
$(INSTALLED_RECOVERYIMAGE_TARGET) \
$(INSTALLED_USERDATAIMAGE_TARGET) \
$(INSTALLED_CACHEIMAGE_TARGET) \
$(INSTALLED_VENDORIMAGE_TARGET) \
$(INSTALLED_SYSTEMOTHERIMAGE_TARGET) \
$(INSTALLED_FILES_FILE) \
$(INSTALLED_FILES_FILE_VENDOR) \
$(INSTALLED_FILES_FILE_SYSTEMOTHER)

最终使用make_ext4fs产生镜像文件：

make_ext4fs -s -T -1 -S out/target/product/rk3288/root/file_contexts.bin -L system -l 2147483648 -a system out/target/product/rk3288/obj/PACKAGING/systemimage_intermediates/system.img out/target/product/rk3288/system out/target/product/rk3288/system

boot.img在一般情况下包括了ramdisk、kernel,  KERNEL_CMDLINE, FLASH_PAGE_SIZE四个部分.

ramdisk.img来自out/target/product/rk3288/root，此目录主要是由system/core/rootdir目录拷贝得到的。

还有从其他位置如device等copy过来的文件。