Android

Android Build System(1)

2024年 6月 17日 /

本文说明Android编译系统的整体架构，编译过程

编译系统综述

发展历史

  • Android 7 之前，Android 使用GNU Make和Shell编译

  • Android 7 Google引入ninja用来替代make，并且提供了kati工具，将Android.mk转换为ninja的构建规则文件

  • Android 8 Google引入了Soong，soong是整个Android构建系统的核心，他调用kati、Make、Ninja构建系统，完成整个构建

  • 下一代构建分布式编译系统bazel，到Android 14 尚未正式发布，将大幅提高编译速度

Android版本 编译系统
7.0 之前 Make 、Shell
7.0 引入ninjia、kati
8.0 引入soong和blueprint，Android.mk逐渐作废
NA Google正在开发全新的bazel分布式编译系统

编译系统架构

soong

整个系统的核心，soong调用kati/ckati、ninja、make等，完成对整个Android的编译。源码目录：build/soong

kati/ckati

将Android.mk转换为ninja的构建规则文件，kati使用go语言开发，后续为了提高性能使用c++重写，即ckati

blueprint

bluprint是go语言开发的生成ninja manifest的库，官方解释参考blueprint reference:

Blueprint is a meta-build system that reads in Blueprints files that describe modules that need to be built, and produces a Ninja manifest describing the commands that need to be run and their dependencies. Where most build systems use built-in rules or a domain-specific language to describe the logic for converting module descriptions to build rules, Blueprint delegates this to per-project build logic written in Go. For large, heterogenous projects this allows the inherent complexity of the build logic to be maintained in a high-level language, while still allowing simple changes to individual modules by modifying easy to understand Blueprints files.

Blueprint是一个元编译系统，Blueprint读入描述需要编译的模块的 Blueprints files ，输出ninja manifest文件，manifest文件中包含模块的依赖和编译模块所需要的命令。

大部分编译系统使用内置的规则或特定领域的语言，来描述如何将模块定义转换为编译规则的逻辑，Blueprint的目的就是代理实现这种逻辑。

source 执行流程

soource执行的build/ensetup.sh，首先会执行最下面的三行语句

validate_current_shell
source_vendorsetup
addcompletions

主要是source_vendorsetup函数，此函数的作用是 查找device vendor product下的vendorsetup.sh并执行，查找的最大深度是4。例如输出如下：

including device/qcom/common/cuttlestone/vendorsetup.sh
including vendor/long/common/vendorsetup.sh
including vendor/qcom/opensource/core-utils/vendorsetup.sh
including vendor/qcom/proprietary/common/vendorsetup.sh
including vendor/qcom/proprietary/prebuilt_HY11/vendorsetup.sh

所以：vendor可以通过vendorsetup.sh来做一些编译前的准备工作，比如创建软连接之类的。

luncher 执行流程

在luncher函数的实现中，是调用print_lunch_menu函数输出找到的产品选项

print_lunch_menu的实现如下：

function print_lunch_menu()
{
    local uname=$(uname)
    local choices
    choices=$(TARGET_BUILD_APPS= TARGET_PRODUCT= TARGET_BUILD_VARIANT= get_build_var COMMON_LUNCH_CHOICES 2>/dev/null)
    local ret=$?

    local i=1
    local choice
    for choice in $(echo $choices)
    do
        echo "     $i. $choice"
        i=$(($i+1))
    done
}

核心逻辑是通过get_build_var COMMON_LUNCH_CHOICES 2 获取所有的编译选项。

get_build_var实现如下：

# Get the exact value of a build variable.
function get_build_var()
{
    if [ "$BUILD_VAR_CACHE_READY" = "true" ]
    then
        eval "echo \"\${var_cache_$1}\""
        return 0
    fi

    local T=$(gettop)
    if [ ! "$T" ]; then
        echo "Couldn't locate the top of the tree.  Try setting TOP." >&2
        return 1
    fi
    (\cd $T; build/soong/soong_ui.bash --dumpvar-mode $1)
}

get_build_var主要是调用build/soong/soong_ui.bash –dumpvar-mode COMMON_LUNCH_CHOICES 来获取值。

build/soong/soong_ui.bash

soong_ui.bash 核心逻辑如下：

# Save the current PWD for use in soong_ui
export ORIGINAL_PWD=${PWD}
export TOP=$(gettop)
source ${TOP}/build/soong/scripts/microfactory.bash

soong_build_go soong_ui android/soong/cmd/soong_ui
soong_build_go mk2rbc android/soong/mk2rbc/cmd
soong_build_go rbcrun rbcrun/cmd

cd ${TOP}
exec "$(getoutdir)/soong_ui" "$@"
@startmindmap
* soong_ui.bash
** build/soong/scripts/microfactory.bash
*** setup GOROOT
*** 定义soong_build_go
*** build/blueprint/microfactory/microfactory.bash
**** 定义build_go
** soong_build_go soong_ui android/soong/cmd/soong_ui\nsoong_build_go mk2rbc android/soong/mk2rbc/cmd\nsoong_build_go rbcrun rbcrun/cmd 
*** 编译soong_ui等可执行程序
** exec "$(getoutdir)/soong_ui" "$@"
*** 通过soong_ui执行命令
@endmindmap

product_config.mk的处理

android_products_makefiles保存的是所有的AndroidProducts.mk文件列表：

# Products are defined in AndroidProducts.mk files:
android_products_makefiles := $(file <$(OUT_DIR)/.module_paths/AndroidProducts.mk.list) \
  $(SRC_TARGET_DIR)/product/AndroidProducts.mk

下面这段代码用于根据第一个参数是否包含冒号来设置 _product-spec 变量的值。如果参数中包含冒号，则变量值将设置为参数本身。否则，变量值将设置为文件名和参数的组合，中间用冒号分隔。

# Products are defined in AndroidProducts.mk files:

_product-spec=$(strip \
    $(if $(findstring :,$(1)), \
        $(1), \
        $(basename $(notdir $(1))):$(1) \
    ) \
)

对每个AndroidProducts.mk文件，执行下面的操作：

# Build cumulative lists of all product specs/lunch choices/Starlark-based products.
product_paths :=
common_lunch_choices :=
products_using_starlark_config :=
$(foreach f,$(android_products_makefiles), \
    $(call _read-ap-file,$(f)) \
    $(eval product_paths += $(ap_product_paths)) \
    $(eval common_lunch_choices += $(ap_common_lunch_choices)) \
    $(eval products_using_starlark_config += $(ap_products_using_starlark_config)) \
)

_read-ap-file的定义如下，主要是读取AndroidProducts.mk，并进行初步的校验，校验失败则报错。$(f) 代表一个AndroidProducts.mk文件

# Reads given AndroidProduct.mk file and sets the following variables:
#  ap_product_paths -- the list of <product>:<path> pairs
#  ap_common_lunch_choices -- the list of <product>-<build variant> items
#  ap_products_using_starlark_config -- the list of products using starlark config
# In addition, validates COMMON_LUNCH_CHOICES and STARLARK_OPT_IN_PRODUCTS values
define _read-ap-file
  $(eval PRODUCT_MAKEFILES :=) \
  $(eval COMMON_LUNCH_CHOICES :=) \
  $(eval STARLARK_OPT_IN_PRODUCTS := ) \
  $(eval ap_product_paths :=) \
  # 清空上面几个变量的值
  $(eval LOCAL_DIR := $(patsubst %/,%,$(dir $(f)))) \
  # 设置LOCAL_DIR的值
  $(eval include $(f)) \
  # include f代表的makefile
  $(foreach p, $(PRODUCT_MAKEFILES),$(eval ap_product_paths += $(call _product-spec,$(p)))) \
  # $(PRODUCT_MAKEFILES)是某个AndroidProduct.mk中定义的变量，所以遍历$(PRODUCT_MAKEFILES) 中的每个item，然后获取到_product-spec，即每一个都代表一个规格
  $(eval ap_common_lunch_choices  := $(COMMON_LUNCH_CHOICES)) \
  # AndroidMakefile中定义的COMMON_LUNCH_CHOICES变量
  $(eval ap_products_using_starlark_config := $(STARLARK_OPT_IN_PRODUCTS)) \
  $(eval _products := $(call _first,$(ap_product_paths),:)) \
  # 当前AndroidProduct.mk中定义的所有产品
  $(eval _bad := $(filter-out $(_products),$(call _first,$(ap_common_lunch_choices),-))) \
  # 校验1：根据-拆分COMMON_LUNCH_CHOICES中的所有字符串，从_products中过滤掉，如果过滤结果还有值，说明有配置存在错误
  $(if $(_bad),$(error COMMON_LUNCH_CHOICES contains products(s) not defined in this file: $(_bad))) \
  $(eval _bad := $(filter-out %-eng %-userdebug %-user,$(ap_common_lunch_choices))) \
  # 校验2：校验variant是否正常
  $(if $(_bad),$(error invalid variant in COMMON_LUNCH_CHOICES: $(_bad)))
  $(eval _bad := $(filter-out $(_products),$(ap_products_using_starlark_config))) \
  $(if $(_bad),$(error STARLARK_OPT_IN_PRODUCTS contains product(s) not defined in this file: $(_bad)))
endef
@startmindmap
* product_config.mk
** $(BUILD_SYSTEM)/node_fns.mk
   *** 定义了一组var相关的操作函数
** $(BUILD_SYSTEM)/product.mk
   *** 定义产品Product相关Makefile变量
       **** 这些变量都以 PRODUCT_ 开头
       **** _product_single_value_vars(只能保存一个值)
       **** _product_list_vars(可以保存多个值)
   *** 定义Product 相关Makefile函数
       **** inherit-product
       **** inherit-product-if-exists
** $(BUILD_SYSTEM)/device.mk
   *** 定义device 相关Makefile变量 \nDEVICE_NAME\nDEVICE_BOARD\nDEVICE_REGION
   *** 定义Product 相关Makefile函数 \ninherit-device\ndump-device\nimport-devices
@endmindmap

BoardConfig.mk

BoardConfig.mk是必须的，因为如果device或者vendor/$(PRODUCT_DEVICE)/BoardConfig.mk找不到，则lunch命令会报错，不报错如下：

In file included from build/make/core/config.mk:356:
In file included from build/make/core/envsetup.mk:371:
build/make/core/board_config.mk:228: error: No config file found for TARGET_DEVICE orange_x86_64.
16:50:34 dumpvars failed with: exit status 1

build/make/core/board_config.mk 228行的代码如下：

# Boards may be defined under $(SRC_TARGET_DIR)/board/$(TARGET_DEVICE)
# or under vendor/*/$(TARGET_DEVICE).  Search in both places, but
# make sure only one exists.
# Real boards should always be associated with an OEM vendor.
ifdef TARGET_DEVICE_DIR
  ifneq ($(origin TARGET_DEVICE_DIR),command line)
    $(error TARGET_DEVICE_DIR may not be set manually)
  endif
  board_config_mk := $(TARGET_DEVICE_DIR)/BoardConfig.mk
else
  board_config_mk := \
    $(strip $(sort $(wildcard \
      $(SRC_TARGET_DIR)/board/$(TARGET_DEVICE)/BoardConfig.mk \
      $(shell test -d device && find -L device -maxdepth 4 -path '*/$(TARGET_DEVICE)/BoardConfig.mk') \
      $(shell test -d vendor && find -L vendor -maxdepth 4 -path '*/$(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
  TARGET_DEVICE_DIR := $(patsubst %/,%,$(dir $(board_config_mk)))
  .KATI_READONLY := TARGET_DEVICE_DIR
endif

其中TARGET_DEVICE_DIR是在make/core/product_config.mk中赋值的，相关代码如下：

# Quick check and assign default values
TARGET_DEVICE := $(PRODUCT_DEVICE)

Reference

https://blog.csdn.net/daoshuti/article/details/108513754

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