Android系统篇(二)——Android编译核心Build系统
《深入解析Android5.0系统》 一书笔记
Android的Build系统非常的庞大,他是基于GUN Make以及shell来构建的,我们主要的面对方向是Android.mk文件,这也是Android为我们处理好的,不用直接跟shell打交道,Build不光可以处理系统的编译打包,还能生成img镜像等,十分的强大。
从大的方面来说,Build系统分为三大块,第一块处于build/core目录下的文件,这是Build的基础框架和核心部分,第二块处于device目录下的文件,存放的是项目的一些配置信息,第三块就是各大模块的Android.mk了。
我们本篇文章依葫芦画瓢的来侃侃Build,我也是跟着书上来的,我也不是很会C/C++
在说Build前,我简单带过一下,我们之前有教过通过SecureCRT远程连接Linux,我们现在用Xshell去连接
其实Xshell连接是非常简单的,我们只需要在ubuntu的终端输入ifconfig,来查看你的ip:比如我的ip是:192.111.11.11(假设)
那么我的Xshell只需要新建一个端口
但是如果连接失败,那你就要检查一下ssh了,在ubuntu的终端输入:
ps -e |grep ssh
如果没有反应,说明你的ssh没有安装
sudo apt install openssh-server
最后就可成功连接了
一.Build系统核心
我们进入build/core目录下,这个目录里有很多的mk文件以及shell脚本,perl脚本,我们跟踪一下源码的编译
source build/envsetup.shlunchmake
我们顺着这三条命令来查看源码
1.envsetup.sh
这个脚本我们先来看看他的内容是什么,我们打开build/envsetup.sh,可以看到里面的脚本中,中间部分插入了lunch选择的参数列表,在结尾处,find了device和vendor目录下的vendorsetuo.sh文件,然后运行他们,我们找一下,看下是否有vendorsetuo.sh,在 device/lge/hammerhead/目录下可以看到有一个vendorsetuo.sh脚本
我们打开它你可以发现,它里面就一行代码
add_lunch_combo aosp_hammerhead-userdebug
它依旧调用add_lunch_combo函数,这样看来,envsetup.sh除了建立shell命令外,就是执行这一句命令了,我们来看下add_lunch_combo的定义:
add_lunch_combo命令的功能,是将调用这个命令所传递的参数放在一个全局的数组变量LUNCH_MENU_CHOICES中,执行lunch就是打印出这个数组的内容了,也就是我们上篇末尾所展示的样子,还记得吗?我选了5
envsetup.sh中还定义了一些实用的shell脚本
- lunch:指定编译产品
- tapas:以交互方式
- croot:快速切换到源码的根目录
- m:编译整个源码,可以不用切换到根目录
- mm:编译当前目录下的源码,不包含他们的依赖模块
- mmm:编译指定目录下的所有模块,不包含他们的依赖模块
- mma:编译当前目录下的源码,包含他们的依赖模块
- mmmma:编译指定目录下的所有模块,包含他们的依赖模块
- cgrep:对系统下所有的C/C++执行grep命令
- ggrep:对系统本地所有的Gradle执行grep命令
- jgrep:对系统下所有的Java执行grep命令
- resgrep:对系统下所有的res目录下的xml执行grep命令
- sgrep:对系统下所有的源文件执行grep命令
- godir:根据godir后的参数文件名在整个目录下查找,并且切换目录
2.lunch命令的功能
我们来看第二行代码lunch,这里我们分析下这个函数
function lunch(){ local answer # 如果lunch后面没有参数,那么打印菜单,并将选择值放入answer # 如果有参数,直接赋值 if [ "$1" ] ; then answer=$1 else print_lunch_menu echo -n "Which would you like? [aosp_arm-eng] " read answer fi local selection= # 如果answer为空,则selection=aosp_arm-eng # 如果answer为数字并且小于或等于菜单数目,则把相应的菜单栏的数字赋值给他 # 如果answer包含了一个-,则将answer赋值给selection,否则报错 if [ -z "$answer" ] then selection=aosp_arm-eng elif (echo -n $answer | grep -q -e "^[0-9][0-9]*$") then if [ $answer -le ${#LUNCH_MENU_CHOICES[@]} ] then selection=${LUNCH_MENU_CHOICES[$(($answer-1))]} fi elif (echo -n $answer | grep -q -e "^[^\-][^\-]*-[^\-][^\-]*$") then selection=$answer fi if [ -z "$selection" ] then echo echo "Invalid lunch combo: $answer" return 1 fi export TARGET_BUILD_APPS= # 将selection中的-分割前半部分给product # 并调用函数check_product去检查是否存在这个配置文件 local product=$(echo -n $selection | sed -e "s/-.*$//") check_product $product if [ $? -ne 0 ] then echo echo "** Don't have a product spec for: '$product'" echo "** Do you have the right repo manifest?" product= fi # 将selection中的-分割前半部分给variant # 并调用函数check_variant来检查这个值是否是:eng,user,debuguser local variant=$(echo -n $selection | sed -e "s/^[^\-]*-//") check_variant $variant if [ $? -ne 0 ] then echo echo "** Invalid variant: '$variant'" echo "** Must be one of ${VARIANT_CHOICES[@]}" variant= fi if [ -z "$product" -o -z "$variant" ] then echo return 1 fi # 将变量product赋值给TARGET_PRODUCT # 将变量variant赋值给TARGET_BUILD_VARIANT # 将TARGET_BUILD_TYP的环境变量设置为release export TARGET_PRODUCT=$product export TARGET_BUILD_VARIANT=$variant export TARGET_BUILD_TYPE=release echo # 设置更多的环境变量 set_stuff_for_environment printconfig}
lunch命令如果没有带参数,直接菜单选择,他的格式如下:
lunch<product_name>-<build_variant>
product_name必须是你定义好的产品配置,build_variant必须是eng,user,debuguser其中一个
lunch命令主要还是根据你输入的产品配置并且设置环境变量,环境变量和产品编译相关的主要是下面这些:
- TARGET_PRODUCT 对应 product_name
- TARGET_BUILD_VARIAN 对应 build_variant
- TARGET_BUILD_TYPE 一般是release
最后他调用set_stuff_for_environment还会设置一些
3.Build相关的环境变量
我们注意看,执行完我们可以看到打印了很多的配置信息
这些配置将影响到我们的编译过程,我们来分析下
- PLATFORM_VERSION_CODENAME
- 表示平台版本的名称
- PLATFORM_VERSION
- Android平台的版本号
- TARGET_PRODUCT
- 所编译的产品名称
- TARGET_BUILD_VARIANT
- 所编译产品的类型
- TARGET_BUILD_TYPE
- 编译的类型,debug和release
- TARGET_BUILD_APPS
- 编译Android系统时,这个值为null,编译单模块时,这个值为所编译模块的路径
- TARGET_ARCH
- 表示编译目标的CPU架构
- TARGET_ARCH_VARIANT
- 表示编译目标的CPU架构版本
- TARGET_CPU_VARIANT
- 表示编译目标的CPU代号
- TARGET_2ND_ARCH
- 表示编译目标的第二CPU架构
- TARGET_2ND_ARCH_VARIANT
- 表示编译目标的第二CPU架构版本
- TARGET_2ND_CPU_VARIANT
- 表示编译目标的第二CPU代号
- HOST_ARCH
- 表示编译平台的架构
- HOST_OS
- 表示编译平台的操作系统
- HOST_OS_EXTRA
- 编译系统之外的额外信息
- BUILD_ID
- BUILD_ID会出现在版本信息中,可以利用
- OUT_DIR
- 编译结果输出的路径
这些变量中第二CPU是Android5.0才加入的,因为当运行64位环境的时候还要考虑32
对于环境变量的修改,可以放到产品的定义中,也可以临时的修改,比如:
make BUILD_ID="liuguilin"
4.Build系统的层次关系
我们lunch后,就是make了,make 后面可以接参数,也是编译过程的开始,make最终生成的也是zip以及各种img,Build会收集编译模块编译,然后复制二进制文件,产品配置文件等最后打包。
一套Android的源码能编译出多个不同的产品配置,我们反过来看,实际上我们也可以猜想到,源码的各个模块都是分开的,当我们选定了一个产品配置之后,Build会把他们拼接起来,我们来看下具体的工作流程:
在执行make后,实际上执行的是根目录/Makefile文件
include build/core/main.mk
可以看到,他里面就一行代码,执行了main.mk,我们查看main.mk就可以发现,他实际上是通过include将所有的mk都包含进来,最终在内存中形成一个编译脚本的集合,这才是最终形态的Makefile
Makefile是很庞大的,但是他主要由三种内容构成:变量定义,函数定义和目标,我们如果有必要,还是要看一下他们的亲戚关系:
这些mk文件的主要作用,我们来看下:
- main.mk
- Build的主控文件,主要作用是包含其他mk,以及定义几个最重要的编译目标,同时检查编译工具的版本,90如gcc等
- help.mk
- Build的帮助文件,输入make help会打印出相关的信息
- config.mk
- Build的配置文件,主要是区分各个产品的配置,并将这些编译器参数引入产品配置BoardConfig.mk,同时也配置了一些编译器的路径等
- pathmap.mk
- 给一些头文件所在的路径定义别名,将framework下的源码目录按类别引用
- buildspec.mk
- 产品定义的参数,不常用
- envsetup.mk
- 包含进product_config.mk文件并且根据其内容设置编译产品所需要的环境变量,并检查合法性,指定输出路径等
- version_defaults.mk
- 定义系统版本相关的配置
- build_id.mk
- 定义环境变量 BUILD_ID
- product_config.mk
- 包含系统所有的AndroidProdut.mk文件,并根据当前的产品配置来设置相关的环境变量
- product.mk
- 定义product_config.mk文件中使用的各种函数
- combo/select.mk
- 根据环境变量的设置,指定对应的系统和架构总所使用的工具和路径
- clang/config.mk
- 定义了LLVM编译器clang在不同架构下的路径和参数
- dumpvar.mk
- 打印输出本次编译的配置结果
- cleanbuild.mk
- 包含了源码中所有的CleanSoec.mk,定义编译目标dataclean和installclean
- definitions.mk
- 定义了大量Build中使用的函数,如果熟悉这些函数,编写产品配置会清晰很多
- dex_preopt.mk
- 定义了dex优化相关的路径和参数
- pdk_config.mk
- 编译pdk的配置文件
- post_clean.mk
- 比较当前系统的overlay目录和上一次build发生的变化
- legacy_prebuilts.mk
- 定义系统orebuild模块列表
- Makefile
- 系统最终编译完成所需要的各种目标和规则
总结:Build系统中定义了大量的编译变量,每一个都是很值得我们去了解熟悉的,虽然Google并没有给出太多的介绍。
5.分析main.mk文件
由于太多了,我们分段来分析
- 1.检查gun make 的版本号是否大于等于3.81,否则报错停止编译
# Check for broken versions of make.# (Allow any version under Cygwin since we don't actually build the platform there.)ifeq (,$(findstring CYGWIN,$(shell uname -sm)))ifneq (1,$(strip $(shell expr $(MAKE_VERSION) \>= 3.81)))$(warning ********************************************************************************)$(warning * You are using version $(MAKE_VERSION) of make.)$(warning * Android can only be built by versions 3.81 and higher.)$(warning * see https://source.android.com/source/download.html)$(warning ********************************************************************************)$(error stopping)endifendif
- 2.定义缺省的编译目标为“droid”,因此,命令make 相当于 “make droid”
# This is the default target. It must be the first declared target..PHONY: droidDEFAULT_GOAL := droid$(DEFAULT_GOAL):
- 3.引入几个mk文件,注意 include和-include的区别,后者包含的文件如果不存在不会报错,前者会停止编译
# Targets that provide quick help on the build system.include $(BUILD_SYSTEM)/help.mk# Set up various standard variables based on configuration# and host information.include $(BUILD_SYSTEM)/config.mk# This allows us to force a clean build - included after the config.mk# environment setup is done, but before we generate any dependencies. This# file does the rm -rf inline so the deps which are all done below will# be generated correctlyinclude $(BUILD_SYSTEM)/cleanbuild.mk# Include the google-specific config-include vendor/google/build/config.mkVERSION_CHECK_SEQUENCE_NUMBER := 5-include $(OUT_DIR)/versions_checked.mk
- 4.检查JAVA的版本是否是1.7或者1.6,不然则会报错推出,如果使用的版本是1.7,还要求必须是openJDK1.7版本
# Check for the correct version of java, should be 1.7 by# default, and 1.6 if LEGACY_USE_JAVA6 is set.ifeq ($(LEGACY_USE_JAVA6),)required_version := "1.7.x"required_javac_version := "1.7"java_version := $(shell echo '$(java_version_str)' | grep '^java .*[ "]1\.7[\. "$$]')javac_version := $(shell echo '$(javac_version_str)' | grep '[ "]1\.7[\. "$$]')else # if LEGACY_USE_JAVA6required_version := "1.6.x"required_javac_version := "1.6"java_version := $(shell echo '$(java_version_str)' | grep '^java .*[ "]1\.6[\. "$$]')javac_version := $(shell echo '$(javac_version_str)' | grep '[ "]1\.6[\. "$$]')endif # if LEGACY_USE_JAVA6ifeq ($(strip $(java_version)),)$(info ************************************************************)$(info You are attempting to build with the incorrect version)$(info of java.)$(info $(space))$(info Your version is: $(java_version_str).)$(info The required version is: $(required_version))$(info $(space))$(info Please follow the machine setup instructions at)$(info $(space)$(space)$(space)$(space)https://source.android.com/source/initializing.html)$(info ************************************************************)$(error stop)endif# Check for the current JDK.## For Java 1.7, we require OpenJDK on linux and Oracle JDK on Mac OS.# For Java 1.6, we require Oracle for all host OSes.requires_openjdk := falseifeq ($(LEGACY_USE_JAVA6),)ifeq ($(HOST_OS), linux)requires_openjdk := trueendifendif# Check for the current jdkifeq ($(requires_openjdk), true)# The user asked for java7 openjdk, so check that the host# java version is really openjdkifeq ($(shell echo '$(java_version_str)' | grep -i openjdk),)$(info ************************************************************)$(info You asked for an OpenJDK 7 build but your version is)$(info $(java_version_str).)$(info ************************************************************)$(error stop)endif # java version is not OpenJdkelse # if requires_openjdkifneq ($(shell echo '$(java_version_str)' | grep -i openjdk),)$(info ************************************************************)$(info You are attempting to build with an unsupported JDK.)$(info $(space))$(info You use OpenJDK but only Sun/Oracle JDK is supported.)$(info Please follow the machine setup instructions at)$(info $(space)$(space)$(space)$(space)https://source.android.com/source/download.html)$(info ************************************************************)$(error stop)endif # java version is not Sun Oracle JDKendif # if requires_openjdk# Check for the correct version of javacifeq ($(strip $(javac_version)),)$(info ************************************************************)$(info You are attempting to build with the incorrect version)$(info of javac.)$(info $(space))$(info Your version is: $(javac_version_str).)$(info The required version is: $(required_javac_version))$(info $(space))$(info Please follow the machine setup instructions at)$(info $(space)$(space)$(space)$(space)https://source.android.com/source/download.html)$(info ************************************************************)$(error stop)endif
- 5.将变量VERSIONS_CHECKED 和 BUILD_EMULATOR写入out/versions_checked.mk,下次build时会重新包含这些文件
$(shell echo 'VERSIONS_CHECKED := $(VERSION_CHECK_SEQUENCE_NUMBER)' \ > $(OUT_DIR)/versions_checked.mk)$(shell echo 'BUILD_EMULATOR ?= $(BUILD_EMULATOR)' \ >> $(OUT_DIR)/versions_checked.mk)
- 6.再包含3个mk
# Bring in standard build system definitions.include $(BUILD_SYSTEM)/definitions.mk# Bring in dex_preopt.mkinclude $(BUILD_SYSTEM)/dex_preopt.mkifneq ($(filter user userdebug eng,$(MAKECMDGOALS)),)$(info ***************************************************************)$(info ***************************************************************)$(info Do not pass '$(filter user userdebug eng,$(MAKECMDGOALS))' on \ the make command line.)$(info Set TARGET_BUILD_VARIANT in buildspec.mk, or use lunch or)$(info choosecombo.)$(info ***************************************************************)$(info ***************************************************************)$(error stopping)endififneq ($(filter-out $(INTERNAL_VALID_VARIANTS),$(TARGET_BUILD_VARIANT)),)$(info ***************************************************************)$(info ***************************************************************)$(info Invalid variant: $(TARGET_BUILD_VARIANT)$(info Valid values are: $(INTERNAL_VALID_VARIANTS)$(info ***************************************************************)$(info ***************************************************************)$(error stopping)endif# -----------------------------------------------------------------# Variable to check java support level inside PDK build.# Not necessary if the components is not in PDK.# not defined : not supported# "sdk" : sdk API only# "platform" : platform API supprotedTARGET_BUILD_JAVA_SUPPORT_LEVEL := platform# -----------------------------------------------------------------# The pdk (Platform Development Kit) buildinclude build/core/pdk_config.mk
- 7.如果变量ONE_SHOT_MAKEFLTE的值不为空,那么将他定义的文件包含进来,当编译一个单独的模块时,ONE_SHOT_MAKEFLTE的值会设为一个模块的make文件路径,如果值ONE_SHOT_MAKEFLTE为空,说明正在编译整个系统,因此,调用findleayes.py脚本搜索系统里所有的Android.mk文件并将它们包含进来
ifneq ($(ONE_SHOT_MAKEFILE),)# We've probably been invoked by the "mm" shell function# with a subdirectory's makefile.include $(ONE_SHOT_MAKEFILE)# Change CUSTOM_MODULES to include only modules that were# defined by this makefile; this will install all of those# modules as a side-effect. Do this after including ONE_SHOT_MAKEFILE# so that the modules will be installed in the same place they# would have been with a normal make.CUSTOM_MODULES := $(sort $(call get-tagged-modules,$(ALL_MODULE_TAGS)))FULL_BUILD :=# Stub out the notice targets, which probably aren't defined# when using ONE_SHOT_MAKEFILE.NOTICE-HOST-%: ;NOTICE-TARGET-%: ;# A helper goal printing out install paths.PHONY: GET-INSTALL-PATHGET-INSTALL-PATH: @$(foreach m, $(ALL_MODULES), $(if $(ALL_MODULES.$(m).INSTALLED), \ echo 'INSTALL-PATH: $(m) $(ALL_MODULES.$(m).INSTALLED)';))else # ONE_SHOT_MAKEFILEifneq ($(dont_bother),true)## Include all of the makefiles in the system## Can't use first-makefiles-under here because# --mindepth=2 makes the prunes not work.subdir_makefiles := \ $(shell build/tools/findleaves.py --prune=$(OUT_DIR) --prune=.repo --prune=.git $(subdirs) Android.mk)$(foreach mk, $(subdir_makefiles), $(info including $(mk) ...)$(eval include $(mk)))endif # dont_botherendif # ONE_SHOT_MAKEFILE
- 8.根据编译类型来设置ro.secure的属性
## user/userdebug ##user_variant := $(filter user userdebug,$(TARGET_BUILD_VARIANT))enable_target_debugging := truetags_to_install :=ifneq (,$(user_variant)) # Target is secure in user builds. ADDITIONAL_DEFAULT_PROPERTIES += ro.secure=1 ifeq ($(user_variant),userdebug) # Pick up some extra useful tools tags_to_install += debug # Enable Dalvik lock contention logging for userdebug builds. ADDITIONAL_BUILD_PROPERTIES += dalvik.vm.lockprof.threshold=500 else # Disable debugging in plain user builds. enable_target_debugging := endif # Turn on Dalvik preoptimization for libdvm.so user builds, but only if not # explicitly disabled and the build is running on Linux (since host # Dalvik isn't built for non-Linux hosts). ifeq (,$(WITH_DEXPREOPT)) ifeq ($(DALVIK_VM_LIB),libdvm.so) ifeq ($(user_variant),user) ifeq ($(HOST_OS),linux) WITH_DEXPREOPT := true endif endif endif endif # Disallow mock locations by default for user builds ADDITIONAL_DEFAULT_PROPERTIES += ro.allow.mock.location=0else # !user_variant # Turn on checkjni for non-user builds. ADDITIONAL_BUILD_PROPERTIES += ro.kernel.android.checkjni=1 # Set device insecure for non-user builds. ADDITIONAL_DEFAULT_PROPERTIES += ro.secure=0 # Allow mock locations by default for non user builds ADDITIONAL_DEFAULT_PROPERTIES += ro.allow.mock.location=1endif # !user_variantifeq (true,$(strip $(enable_target_debugging))) # Target is more debuggable and adbd is on by default ADDITIONAL_DEFAULT_PROPERTIES += ro.debuggable=1 # Include the debugging/testing OTA keys in this build. INCLUDE_TEST_OTA_KEYS := trueelse # !enable_target_debugging # Target is less debuggable and adbd is off by default ADDITIONAL_DEFAULT_PROPERTIES += ro.debuggable=0endif # !enable_target_debugging## eng ##ifeq ($(TARGET_BUILD_VARIANT),eng)tags_to_install := debug engifneq ($(filter ro.setupwizard.mode=ENABLED, $(call collapse-pairs, $(ADDITIONAL_BUILD_PROPERTIES))),) # Don't require the setup wizard on eng builds ADDITIONAL_BUILD_PROPERTIES := $(filter-out ro.setupwizard.mode=%,\ $(call collapse-pairs, $(ADDITIONAL_BUILD_PROPERTIES))) \ ro.setupwizard.mode=OPTIONALendififndef is_sdk_build # Don't even verify the image on eng builds to speed startup ADDITIONAL_BUILD_PROPERTIES += dalvik.vm.image-dex2oat-filter=verify-none # Don't compile apps on eng builds to speed startup ADDITIONAL_BUILD_PROPERTIES += dalvik.vm.dex2oat-filter=interpret-onlyendifendif
- 9.包含进post_clean.mk和legacypre_buildts.mk脚本,根据legacypre_buildts.mk中定义的变量GRANDFATHERED_ALL_PREBUILT检查是否有不在这个列表的prebuilt模块,如果有则报错推出
# Now with all Android.mks loaded we can do post cleaning steps.include $(BUILD_SYSTEM)/post_clean.mkifeq ($(stash_product_vars),true) $(call assert-product-vars, __STASHED)endifinclude $(BUILD_SYSTEM)/legacy_prebuilts.mkifneq ($(filter-out $(GRANDFATHERED_ALL_PREBUILT),$(strip $(notdir $(ALL_PREBUILT)))),) $(warning *** Some files have been added to ALL_PREBUILT.) $(warning *) $(warning * ALL_PREBUILT is a deprecated mechanism that) $(warning * should not be used for new files.) $(warning * As an alternative, use PRODUCT_COPY_FILES in) $(warning * the appropriate product definition.) $(warning * build/target/product/core.mk is the product) $(warning * definition used in all products.) $(warning *) $(foreach bad_prebuilt,$(filter-out $(GRANDFATHERED_ALL_PREBUILT),$(strip $(notdir $(ALL_PREBUILT)))),$(warning * unexpected $(bad_prebuilt) in ALL_PREBUILT)) $(warning *) $(error ALL_PREBUILT contains unexpected files)endif
- 10.xxx
未完待续
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