android编译系统分析（三）make

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android编译系统分析（三）make
http://blog.csdn.net/u011913612/article/details/52434411

这篇博客的目标是摸清楚默认编译整个Android系统时代码的流程。

当我们执行make的时候，会查找当前的Makefie文件或者makefile文件并且执行，在android顶级源码目录下面，确实有个Makefile,它之后一行内容：
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### DO NOT EDIT THIS FILE ###
include build/core/main.mk
### DO NOT EDIT THIS FILE ###
因此，正真执行的是build/core/main.mk
一.依赖浅析

当我们执行make命令的时候，如果没有传入一个目标，那么就会执行默认的目标。注意，我们在编译android系统的时候，只需要执行make就可以了，那么很显然它会执行默认的目标了，那么默认的目标是什么呢？

在build/core/main.mk中：
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# This is the default target.  It must be the first declared target.
.PHONY: droid
DEFAULT_GOAL := droid
$(DEFAULT_GOAL):
在main.mk开始不久，就出现了一个伪目标，即便你看不懂Makefile也没有关系，注释上说的很清楚了，他就是默认的目标了。而且这个默认的目标是一个伪目标。make工具遇到伪目标以后，会检查解析伪目标的依赖，如果伪目标存在依赖，就会检查这些依赖，如果这些依赖是伪目标，继续检查这个伪目标的依赖，如果不是伪目标，就会生成这个目标。

阅读一个Makefile,理清目标的依赖关系很重，下图列出了部分重要的以来关系：

在对依赖关系有个了解之后，我们开始顺着make的加载流程，看看它到底做了什么。

首先，我觉得很重要的就是加载特定产品的配置信息。

二.配置产品信息

首先，大致的流程如下图所示：

在product_config.mk中：
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ifneq ($(strip $(TARGET_BUILD_APPS)),)
# An unbundled app build needs only the core product makefiles.
all_product_configs := $(call get-product-makefiles,
    $(SRC_TARGET_DIR)/product/AndroidProducts.mk)
else
# Read in all of the product definitions specified by the AndroidProducts.mk
# files in the tree.
all_product_configs := $(get-all-product-makefiles)
endif
1.AndoridProducts.mk
使用get-all-product-makefiles获取所有的AndoridProducts.mk文件：
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define get-all-product-makefiles
$(call get-product-makefiles,$(_find-android-products-files))
endef
调用_find-android-products-files获取所有的AndroidProducts.mk，然后交由get-product-makefiles函数处理。
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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
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define get-product-makefiles
$(sort
  $(foreach f,$(1),
    $(eval PRODUCT_MAKEFILES :=)
    $(eval LOCAL_DIR := $(patsubst %/,%,$(dir $(f))))
    $(eval include $(f))
    $(PRODUCT_MAKEFILES)
   )
  $(eval PRODUCT_MAKEFILES :=)
  $(eval LOCAL_DIR :=)
)
endef
可以看到最终处理的结果是加载了AndroidProducts.mk，返回了一个排好顺序的PRODUCT_MAKEFILES。
这里把所有的AndroidProducts.mk都加载进来了，但是我们只需要我们产品的配置信息呀，所以接着做一个查找，找到属于我们产品的AndroidProducts.mk:
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# Find the product config makefile for the current product.
# all_product_configs consists items like:
# <product_name>:<path_to_the_product_makefile>
# or just <path_to_the_product_makefile> in case the product name is the
# same as the base filename of the product config makefile.
current_product_makefile :=
all_product_makefiles :=
$(foreach f, $(all_product_configs),
    $(eval _cpm_words := $(subst :,$(space),$(f)))
    $(eval _cpm_word1 := $(word 1,$(_cpm_words)))
    $(eval _cpm_word2 := $(word 2,$(_cpm_words)))
    $(if $(_cpm_word2),
        $(eval all_product_makefiles += $(_cpm_word2))
        $(if $(filter $(TARGET_PRODUCT),$(_cpm_word1)),
            $(eval current_product_makefile += $(_cpm_word2)),),
        $(eval all_product_makefiles += $(f))
        $(if $(filter $(TARGET_PRODUCT),$(basename $(notdir $(f)))),
            $(eval current_product_makefile += $(f)),)))
_cpm_words :=
_cpm_word1 :=
_cpm_word2 :=
current_product_makefile := $(strip $(current_product_makefile))
all_product_makefiles := $(strip $(all_product_makefiles))
2.current_product_makefile
最终找到的结果存储在current_product_makefile中。关于它的值，这里举例说明：
加入我们在lunch的时候选择了 5：
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1. aosp_arm-eng
2. aosp_arm64-eng
3. aosp_mips-eng
4. aosp_mips64-eng
5. aosp_x86-eng
6. aosp_x86_64-eng
那么经过以上查找current_product_makefile就等于device/generic/x86/mini_x86.mk
3.加载产品配置文件
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ifneq (,$(filter product-graph dump-products, $(MAKECMDGOALS)))
# Import all product makefiles.
$(call import-products, $(all_product_makefiles))
else
# Import just the current product.
ifndef current_product_makefile
$(error Can not locate config makefile for product "$(TARGET_PRODUCT)")
endif
ifneq (1,$(words $(current_product_makefile)))
$(error Product "$(TARGET_PRODUCT)" ambiguous: matches $(current_product_makefile))
endif
$(call import-products, $(current_product_makefile))
endif  # Import all or just the current product makefile

# Sanity check
$(check-all-products)
在import-products中导入产品的配置信息，这里就是device/generic/x86/mini_x86.mk。

4然后获取TARGET_DEVICE的值：
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# Find the device that this product maps to.
TARGET_DEVICE := $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_DEVICE)
此时，TARGET_DEVICE = mini_x86.mk；
5获取要拷贝的文件
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# A list of words like <source path>:<destination path>[:<owner>].
# The file at the source path should be copied to the destination path
# when building  this product.  <destination path> is relative to
# $(PRODUCT_OUT), so it should look like, e.g., "system/etc/file.xml".
# The rules for these copy steps are defined in build/core/Makefile.
# The optional :<owner> is used to indicate the owner of a vendor file.
PRODUCT_COPY_FILES :=
    $(strip $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_COPY_FILES))
这个变量也很重要，它存储了需要拷贝的文件。格式为 <source path>:<destination path>，在build/core/Makefile一开始就会先拷贝这个变量指定的文件。
6.加载BoardConfig.mk

又回到envsetup.mk中：
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# Boards may be defined under $(SRC_TARGET_DIR)/board/$(TARGET_DEVICE)
# or under vendor/*/$(TARGET_DEVICE).  Search in both places, but
# make sure only one exists.
# Real boards should always be associated with an OEM vendor.
board_config_mk :=
    $(strip $(wildcard
        $(SRC_TARGET_DIR)/board/$(TARGET_DEVICE)/BoardConfig.mk
        $(shell test -d device && find device -maxdepth 4 -path '*/$(TARGET_DEVICE)/BoardConfig.mk')
        $(shell test -d vendor && find vendor -maxdepth 4 -path '*/$(TARGET_DEVICE)/BoardConfig.mk')
    ))
ifeq ($(board_config_mk),)
  $(error No config file found for TARGET_DEVICE $(TARGET_DEVICE))
endif
ifneq ($(words $(board_config_mk)),1)
  $(error Multiple board config files for TARGET_DEVICE $(TARGET_DEVICE): $(board_config_mk))
endif
include $(board_config_mk)
ifeq ($(TARGET_ARCH),)
  $(error TARGET_ARCH not defined by board config: $(board_config_mk))
endif
BoardConfig.mk中配置了重要的板级信息，比如cpu架构等。
至此，配置一个产品所需的AndroidProducts.mk,具体产品的配置文件，比如这里的mini_x86.mk以及BoardConfig.mk都加载进来了。

三.加载所有模块

加载完单板信息，make又回到main.mk中，不就就发现了ONE_SHOT_MAKEFILE变量的判断：

1ONE_SHOT_MAKEFILE
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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-PATH
GET-INSTALL-PATH:
    @$(foreach m, $(ALL_MODULES), $(if $(ALL_MODULES.$(m).INSTALLED),
        echo 'INSTALL-PATH: $(m) $(ALL_MODULES.$(m).INSTALLED)';))

else # ONE_SHOT_MAKEFILE

ifneq ($(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_bother

endif # ONE_SHOT_MAKEFILE
如果这个变量定义了，那么，就是编译一个模块，在上一篇博客中已将分析过了，如果没有定义，就说明是编译整个系统。
```
MAKECMDGOALS是make的一个环境变量，当我们执行make的时候并没有设置它，因此它为空。所以dont_bother不等于true,因此，就会加载所有的Android.mk.这里使用
```
```
一个python脚本查找系统中所有的Android.mk，然后Include进来。
```
```
四 收集所有要安装的模块
```
```
在main.mk中继续往下看：
```
3.1FULL_BUILD
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ifdef FULL_BUILD
  # The base list of modules to build for this product is specified
  # by the appropriate product definition file, which was included
  # by product_config.mk.
  product_MODULES := $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_PACKAGES)
  # Filter out the overridden packages before doing expansion
  product_MODULES := $(filter-out $(foreach p, $(product_MODULES),
      $(PACKAGES.$(p).OVERRIDES)), $(product_MODULES))

  # Resolve the :32 :64 module name
  modules_32 := $(patsubst %:32,%,$(filter %:32, $(product_MODULES)))
  modules_64 := $(patsubst %:64,%,$(filter %:64, $(product_MODULES)))
  modules_rest := $(filter-out %:32 %:64,$(product_MODULES))
  # Note for 32-bit product, $(modules_32) and $(modules_64) will be
  # added as their original module names.
  product_MODULES := $(call get-32-bit-modules-if-we-can, $(modules_32))
  product_MODULES += $(modules_64)
  # For the rest we add both
  product_MODULES += $(call get-32-bit-modules, $(modules_rest))
  product_MODULES += $(modules_rest)

  $(call expand-required-modules,product_MODULES,$(product_MODULES))

  product_FILES := $(call module-installed-files, $(product_MODULES))
  ifeq (0,1)
    $(info product_FILES for $(TARGET_DEVICE) ($(INTERNAL_PRODUCT)):)
    $(foreach p,$(product_FILES),$(info :   $(p)))
    $(error done)
  endif
else
  # We're not doing a full build, and are probably only including
  # a subset of the module makefiles.  Don't try to build any modules
  # requested by the product, because we probably won't have rules
  # to build them.
  product_FILES :=
endif
在执行make的时候，FULL_BUILD：=true
```
product_MODULES是所有产品配置文件中添加的要打包进系统镜像中的模块，它只是一个名字，比如上篇博客分析过的screencap。
```
```
product_FILES获取对应模块的.INSTALLED的值。
```
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define module-installed-files
$(foreach module,$(1),$(ALL_MODULES.$(module).INSTALLED))
endef
在加载单个模块的时候，会给每一个模块生成另外两个值：
```
$(ALL_MODULES.$(target)).BUILT
$(ALL_MODULES.$(target)).INSTALLED
```
```
它们在base_rule.mk中生成：
```
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ALL_MODULES.$(my_register_name).BUILT :=
    $(ALL_MODULES.$(my_register_name).BUILT) $(LOCAL_BUILT_MODULE)
ifneq (true,$(LOCAL_UNINSTALLABLE_MODULE))
ALL_MODULES.$(my_register_name).INSTALLED :=
    $(strip $(ALL_MODULES.$(my_register_name).INSTALLED) $(LOCAL_INSTALLED_MODULE))
ALL_MODULES.$(my_register_name).BUILT_INSTALLED :=
    $(strip $(ALL_MODULES.$(my_register_name).BUILT_INSTALLED) $(LOCAL_BUILT_MODULE):$(LOCAL_INSTALLED_MODULE))
endif
```
$(ALL_MODULES.$(target)).BUILT代表的一般是out/target/product/xxx/obj下编译生成的模块。
```
```
$(ALL_MODULES.$(target)).INSTALLED代表的是out/target/product/xxx/system下生成的模块。
```
3.2 全部安装模块
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modules_to_install := $(sort
    $(ALL_DEFAULT_INSTALLED_MODULES)
    $(product_FILES)
    $(foreach tag,$(tags_to_install),$($(tag)_MODULES))
    $(CUSTOM_MODULES)
  )
```
ALL_DEFAULT_INSTALLED_MODULES是系统默认要安装的模块，product_FILES是特定产品附加的要安装的模块，foreach找到的是特定
```
```
TAG的模块，以及加上CUSTOM_MODULES,这样modules_to_install就是全部的要安装的模块了。
```
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ALL_DEFAULT_INSTALLED_MODULES := $(modules_to_install)
include $(BUILD_SYSTEM)/Makefile
然后把modules_to_install的值全部赋给ALL_DEFAULT_INSTALLED_MODULES,接着加载build/core/Makefile。这个Makefile会使用
```
ALL_DEFAULT_INSTALLED_MODULES变量最终生成所有的镜像文件。生成镜像文件的过程放在下一节讨论。
```
四.编译所有模块

依赖关系我们在一开始就做了简单的梳理，现在开始分析编译所有模块的依赖关系。

从droid目标定义的地方来看，没有看到它的依赖，但我们向下搜索，就会发现：
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.PHONY: apps_only
apps_only: $(unbundled_build_modules)

droid: apps_only
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# Building a full system-- the default is to build droidcore
droid: droidcore dist_files
我们会发现它有出现了两个依赖，那它到底依赖哪一个呢？

droid依赖哪一个取决于ifneq ($(TARGET_BUILD_APPS),)是否成立,也就是有没有给TARGET_BUILD_APPS赋值过，源码如下：
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ifneq ($(TARGET_BUILD_APPS),)
  # If this build is just for apps, only build apps and not the full system by default.

  unbundled_build_modules :=
  ifneq ($(filter all,$(TARGET_BUILD_APPS)),)
    # If they used the magic goal "all" then build all apps in the source tree.
    unbundled_build_modules := $(foreach m,$(sort $(ALL_MODULES)),$(if $(filter APPS,$(ALL_MODULES.$(m).CLASS)),$(m)))
  else
    unbundled_build_modules := $(TARGET_BUILD_APPS)
  endif

...

.PHONY: apps_only
apps_only: $(unbundled_build_modules)

droid: apps_only

else # TARGET_BUILD_APPS
  $(call dist-for-goals, droidcore,
    $(INTERNAL_UPDATE_PACKAGE_TARGET)
    $(INTERNAL_OTA_PACKAGE_TARGET)
    $(BUILT_OTATOOLS_PACKAGE)
    $(SYMBOLS_ZIP)
    $(INSTALLED_FILES_FILE)
    $(INSTALLED_BUILD_PROP_TARGET)
    $(BUILT_TARGET_FILES_PACKAGE)
    $(INSTALLED_ANDROID_INFO_TXT_TARGET)
    $(INSTALLED_RAMDISK_TARGET)
   )
# Building a full system-- the default is to build droidcore
droid: droidcore dist_files

endif # TARGET_BUILD_APPS
我们期望的是整个系统的编译，所以，droid依赖的是droidcore 和 dist_files
4.1droidcore的定义：
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# 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_FILES_FILE)
可以droidcore又是一个伪目标，它又依赖于files 等一系列目标，从名字来看，这些目标应该是systemimage,userdataimage,recoryimage等，也就是说，droidcore的最终目的就是生成system.img,userdata.img等系统镜像文件。

看到变量的定义就明白了：

1.boot.img:

INSTALLED_BOOTIMAGE_TARGET := $(PRODUCT_OUT)/boot.img

2.recovery.img:

INSTALLED_RECOVERYIMAGE_TARGET := $(PRODUCT_OUT)/recovery.img

3.userdata.img:

INSTALLED_USERDATAIMAGE_TARGET := $(BUILT_USERDATAIMAGE_TARGET)

--->BUILT_USERDATAIMAGE_TARGET := $(PRODUCT_OUT)/userdata.img

4.cache.img

INSTALLED_CACHEIMAGE_TARGET := $(BUILT_CACHEIMAGE_TARGET)

--->BUILT_CACHEIMAGE_TARGET := $(PRODUCT_OUT)/cache.img

5.vendor.img

INSTALLED_VENDORIMAGE_TARGET := $(BUILT_VENDORIMAGE_TARGET)

BUILT_VENDORIMAGE_TARGET := $(PRODUCT_OUT)/vendor.img

因此，droidcore的最终目的就是生成这些.Img文件。

dist_files的定义：
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# dist_files only for putting your library into the dist directory with a full build.
.PHONY: dist_files
从定义来看，dist_files也是个伪目标，并且它没有任何依赖，作用是完整编译系统的时候拷贝库文件。

4.2.files

它的第一个目标是files:
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# All the droid stuff, in directories
.PHONY: files
files: prebuilt
        $(modules_to_install)
        $(INSTALLED_ANDROID_INFO_TXT_TARGET)、
1.1files又依赖了三个目标，第一个是prebuilt:
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# -------------------------------------------------------------------
# This is used to to get the ordering right, you can also use these,
# but they're considered undocumented, so don't complain if their
# behavior changes.
.PHONY: prebuilt
prebuilt: $(ALL_PREBUILT）
prebuilt又是一个伪目标，它又依赖于ALL_PREBUILT变量指向的目标，ALL_PREBUILT是一些预编译模块：
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Android.mk (makefileframeworksasecmdsmgr):ALL_PREBUILT += $(TARGET_OUT)/bin/bmgr
Android.mk (makefileframeworksasecmdsime):ALL_PREBUILT += $(TARGET_OUT)/bin/ime
Android.mk (makefileframeworksasecmdsinput):ALL_PREBUILT += $(TARGET_OUT)/bin/input
Android.mk (makefileframeworksasecmdspm):ALL_PREBUILT += $(TARGET_OUT)/bin/pm
Android.mk (makefileframeworksasecmdssvc):ALL_PREBUILT += $(TARGET_OUT)/bin/svc
4.3modules_to_install

modules_to_install := $(sort
$(ALL_DEFAULT_INSTALLED_MODULES)
$(product_FILES)
$(foreach tag,$(tags_to_install),$($(tag)_MODULES))
$(CUSTOM_MODULES)
)

这个变量之前已经分析过，它包含所有的要安装的模块，make会为这个目标生成依赖关系链，也就是会给其中的每一个模块生成依赖关系链，然后编译每一个模块，这个过程在上一节中已经说过了。
至此，所有应该编译的模块都已经被编译，剩下的就是打包镜像文件了。这将在下一节讨论。
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原文地址：https://www.cnblogs.com/ztguang/p/12645309.html

android编译系统分析（三）make

一.依赖浅析

二.配置产品信息

1.AndoridProducts.mk

2.current_product_makefile

3.加载产品配置文件

4然后获取TARGET_DEVICE的值：

5获取要拷贝的文件

6.加载BoardConfig.mk

三.加载所有模块

1ONE_SHOT_MAKEFILE

3.1FULL_BUILD

3.2 全部安装模块

四.编译所有模块

4.1droidcore的定义：

4.2.files

4.3modules_to_install