轉載：http://home.lupaworld.com/home-space-uid-131820-do-blog-id-149451.html
Android 的核心 Makefile 爲 build/core/main.mk (有關該Makefile的分析請見
http://heaven.branda.to/~thinker/GinGin_CGI.py/show_id_doc/393 )，其中編譯的內核的target爲 INSTALLED_BOOTIMAGE_TARGET 即 out/target/product/dream-open/boot.img
boot.img的生成在下面的Makefile中
build/core/Makefile: 293
$(INSTALLED_BOOTIMAGE_TARGET): $(MKEXT2IMG) $(INTERNAL_BOOTIMAGE_FILES)
$(call pretty,"Target boot image: $@")
$(hide) $(MKEXT2BOOTIMG) $(INTERNAL_BOOTIMAGE_ARGS) --output $@
上面的語句翻譯下來爲：
out/target/product/dream-open/boot.img: out/host/linux-x86/bin/genext2fs out/target/product/dream-open/kernel out/target/product/dream-open/ramdisk.img
$(call pretty,"Target boot image: out/target/product/dream-open/boot.img")
$(hide) external/genext2fs/mkbootimg_ext2.sh --kernel out/target/product/dream-open/kernel --ramdisk out/target/product/dream-open/ramdisk.img --cmdline "no_console_suspend=1 console=null" --output out/target/product/dream-open/boot.img
可見boot.img 是由 kernel 和 ramdisk.img 通過腳本mkbootimg_ext2.sh生成的。
那個out/target/product/dream-open/kernel 從哪裏來的呢？請看下面的Makefile
vendor/htc/dream-open/AndroidBoard.mk:3
ifeq ($(TARGET_PREBUILT_KERNEL),)
TARGET_PREBUILT_KERNEL := $(LOCAL_PATH)/kernel
endif
file := $(INSTALLED_KERNEL_TARGET)
ALL_PREBUILT += $(file)
$(file): $(TARGET_PREBUILT_KERNEL) | $(ACP)
$(transform-prebuilt-to-target)
可見內核在 vendor/htc/dream-open/kernel，該文件是預編譯好的，從android的版本庫上直接下載下來的。