《Android系统学习》第四章：分析Android系统编译过程
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以下是加载命令和选择平台编译选项，也就是设置编译环境变量。
一、/build/envsetup.sh之初始化......
add_lunch_combo full-eng
add_lunch_combo full_x86-eng
add_lunch_combo vbox_x86-eng
#模拟器
......
# Execute the contents of any vendorsetup.sh files we can find.
for f in `/bin/ls vendor/*/vendorsetup.sh vendor/*/*/vendorsetup.sh device/*/*/vendorsetup.sh 2> /dev/null`
do
echo "including $f"
. $f
done
unset f
#遍历/vendor/*/vendorsetup.sh、/vendor/*/*/vendorsetup.sh和/device/*/*/vendorsetup.sh文件；
#eg：/device/tank/tanka3/vendorsetup.sh
add_lunch_combo full_tanka3-userdebug
二、/build/envsetup.sh之add_lunch_combo命令
function add_lunch_combo(){
local new_combo=$1
local c
for c in ${LUNCH_MENU_CHOICES[@]} ; do
if [ "$new_combo" = "$c" ] ; then
return
fi
done
LUNCH_MENU_CHOICES=(${LUNCH_MENU_CHOICES[@]} $new_combo)
}三、/build/envsetup.sh之lunch命令
function lunch(){
......
check_product $product
#从上处剥离$product == full_tanka3
......
}
function check_product(){
......
CALLED_FROM_SETUP=true BUILD_SYSTEM=build/core \
TARGET_PRODUCT=$1 \
TARGET_BUILD_VARIANT= \
TARGET_BUILD_TYPE= \
TARGET_BUILD_APPS= \
get_build_var TARGET_DEVICE > /dev/null
......
}
function get_build_var(){
......
CALLED_FROM_SETUP=true BUILD_SYSTEM=build/core \
make --no-print-directory -C "$T" -f build/core/config.mk dumpvar-$1
}
四、/build/core/config.mk
......
include $(BUILD_SYSTEM)/envsetup.mk
......
board_config_mk := \
$(strip $(wildcard \
$(SRC_TARGET_DIR)/board/$(TARGET_DEVICE)/BoardConfig.mk \
device/*/$(TARGET_DEVICE)/BoardConfig.mk \
vendor/*/$(TARGET_DEVICE)/BoardConfig.mk \
))
#查找/device/tank/tanka3/BoardConfig.mk
#模拟器查找/build/target/board/emulator/BoardConfig.mk
......
五、/build/core/envsetup.mk
...... include $(BUILD_SYSTEM)/product_config.mk ...... ifeq ($(TARGET_ARCH),) TARGET_ARCH := arm endif ......
六、/build/core/product_config.mk
...... include $(BUILD_SYSTEM)/product.mk ......
七、/build/core/product.mk
...... define _find-android-products-files $(shell test -d device && find device -maxdepth 6 -name AndroidProducts.mk) \ $(shell test -d vendor && find vendor -maxdepth 6 -name AndroidProducts.mk) \ $(SRC_TARGET_DIR)/product/AndroidProducts.mk endef ...... #查找/device/tank/tanka3/AndroidProducts.mk #模拟器查找/build/target/product/AndroidProducts.mk
以上执行完后，后设置如下环境变量：
PLATFORM_VERSION_CODENAME=REL PLATFORM_VERSION=4.0.3 TARGET_PRODUCT=full_tanka3 TARGET_BUILD_VARIANT=userdebug TARGET_BUILD_TYPE=release TARGET_BUILD_APPS= TARGET_ARCH=arm TARGET_ARCH_VARIANT=armv7-a-neon HOST_ARCH=x86 HOST_OS=linux HOST_BUILD_TYPE=release BUILD_ID=IML74K====================================================================================================================================
以下是真正开始编译：
一、/Makefile
include build/core/main.mk
二、/build/core/main.mk
...... include $(BUILD_SYSTEM)/config.mk ......
三、/build/core/config.mk
后边与上面《四-七》一一对应。==============================================================================================================================
定制自己厂商目录：
一、mkdir /device/tank
二、mkdir /device/tank/tanka3
三、cd /device/tank/tanka3
touch vendorsetup.sh touch BoardConfig.mk touch AndroidProducts.mk //包含full_tanka3.mk touch full_tanka3.mk //包含device.mk touch device.mk
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补充：
在BoardConfig.mk文件中可以设置对象CPU架构、类型以及交叉编译工具链路径，如：
TARGET_ARCH=mips #架构，若不设置、由/build/core/envsetup.mk默认设置arm TARGET_ARCH_VARIANT := mips32r2-fp #核类型，若不设置、由/build/core/combo/TARGET_linux-arm.mk默认设置armv5te TARGET_ARCH_VERSION=mips32 TARGET_TOOLS_PREFIX := #交叉编译工具链，若不设置、由build/core/combo/TARGET_linux-arm.mk默认设置 #TARGET_TOOLS_PREFIX := prebuilt/$(HOST_PREBUILT_TAG)/toolchain/arm-eabi-4.4.3/bin/arm-
其他主要文件或目录：
build/core/combo/TARGET_linux-arm.mk
//决定arm架构的具体类型（如果TARGET_ARCH_VARIANT未定义）以及交叉编译工具链路径
...... ifeq ($(strip $(TARGET_ARCH_VARIANT)),) TARGET_ARCH_VARIANT := armv5te endif ...... ifeq ($(strip $(TARGET_TOOLS_PREFIX)),) TARGET_TOOLS_PREFIX := prebuilt/$(HOST_PREBUILT_TAG)/toolchain/arm-eabi-4.4.3/bin/arm-eabi- endif ......
build/core/combo/arch/arm/
bionic/libc/arch-arm/
bionic/libm/Android.mk
bionic/linker/Android.mk
arm架构交叉编译工具链路径：
prebuilt/ndk/android-ndk-r4/platforms/android-8/arch-arm/