Android init介绍(下) _Android

得意犹堪夸世俗，诏黄新湿字如鸦。这篇文章主要讲述Android init介绍(下)相关的知识，希望能为你提供帮助。
上一篇: < Android init介绍(上)>
5. AIL在init启动过程中，系统服务等均是通过解析rc文件来启动，而rc文件则是由android初始化语言(Android Init Language)的脚本写成
5.1 格式介绍
AIL以Section为区分，由如下import、action和service三类Section
5.1.1 import section主要用于导入其他rc文件

import < path>

上面的命令将导入path指定的文件然后被解析为action和service
5.1.2 action sectionaction section由trigger和一些command组成
以on开头，trigger是判断条件，command是具体执行一些操作；当满足trigger条件时，执行这些command
格式如下

on < trigger> [& & < trigger> ]* < command> < command> < command>

trigger的内容包含如下

/* * 事件触发器 * -- 表示当trigger early或QueueEventTrigger("early")调用时触发 */ on early/* * 属性触发器 * -- 表示当sys.boot_from_charger_mode的值通过property_set设置为1时触发 */ on property:sys.boot_from_charger_mode=1/* * 多个条件用& & 连接 * -- 表示当zygote-start触发并且ro.crypto.state属性值为unencrypted时触发 on zygote-start & & property:ro.crypto.state=unencrypted

command就是一些具体的操作，由BuiltinFunctionMap::Map(builtin_functions)定义来执行特定的操作

// 终止charger服务 class_stop charger // 开启watchdogd服务 start watchdogd // 触发late-init trigger late-init

5.1.3 service sectionservice section由service加上一些option组成
以service开头，name是为服务名称，pathname为服务的执行文件路径，argument表示执行文件带的参数，option表示这个服务的一些配置，option由OptionParserMap::Map(option_parsers)定义

service < name> < pathname> [ < argument> ]* < option> < option> ...

5.2 文件解析

/* * 初始化Subcontext */ InitializeSubcontexts() SelinuxHasVendorInit() Subcontext::Subcontext() Subcontext::Fork() fork() execv("/init", {"/init", "subcontext", "u:r:vendor_init:s0", fd, nullptr})// 创建ActionManager实例 ActionManager::GetInstance() // 创建ServiceList实例 ServiceList::GetInstance()LoadBootScripts() CreateParser(ActionManager, ServiceList) Parser::ParseConfig("/init.rc") Parser::ParseConfig("/system/etc/init") Parser::ParseConfig("/vendor/etc/init") Parser::ParseConfigFile() Parser::ParseData()

【Android init介绍(下)】可以看出rc文件文件主要位于[/]、[/system/etc/init/]、[/vendor/etc/init/]

# tree / . +--- init.environ.rc +--- init.rc +--- init.recovery.hardware.rc +--- init.usb.configfs.rc +--- init.usb.rc +--- init.zygote32.rc +--- init.zygote64_32.rc

# tree /system/etc/init/ . +--- android.hidl.allocator@1.0-service.rc +--- atrace.rc +--- atrace_userdebug.rc +--- audioserver.rc +--- blank_screen.rc +--- bootanim.rc +--- bootstat-debug.rc +--- bootstat.rc +--- cameraserver.rc +--- com.android.car.powertestservice.rc +--- com.android.car.procfsinspector.rc +--- drmserver.rc +--- dumpstate.rc +--- gatekeeperd.rc +--- gsi |+--- init.vndk-27.rc +--- hwservicemanager.rc +--- incidentd.rc +--- init-debug.rc +--- init.gsi.rc +--- installd.rc +--- keystore.rc +--- lmkd.rc +--- logcatd.rc +--- logd.rc +--- logtagd.rc +--- mdnsd.rc +--- mediadrmserver.rc +--- mediaextractor.rc +--- mediametrics.rc +--- mediaserver.rc +--- mtpd.rc +--- netd.rc +--- perfetto.rc +--- perfprofd.rc +--- racoon.rc +--- recovery-persist.rc +--- recovery-refresh.rc +--- servicemanager.rc +--- statsd.rc +--- storaged.rc +--- surfaceflinger.rc +--- thermalservice.rc +--- tombstoned.rc +--- uncrypt.rc +--- update_engine.rc +--- update_verifier.rc +--- usbd.rc +--- vdc.rc +--- vold.rc +--- vr_hwc.rc +--- wait_for_keymaster.rc +--- wifi-events.rc +--- wificond.rc

# tree /vendor/etc/init/ . +--- android.automotive.evs.manager@1.0.rc +--- android.hardware.audio@2.0-service.rc +--- android.hardware.boot@1.0-service.rc +--- android.hardware.broadcastradio@intel-service.rc +--- android.hardware.camera.provider@2.4-external-service.rc +--- android.hardware.camera.provider@2.4-service.rc +--- android.hardware.cas@1.0-service.rc +--- android.hardware.configstore@1.1-service.rc +--- android.hardware.drm@1.0-service.rc +--- android.hardware.drm@1.1-service.clearkey.rc +--- android.hardware.dumpstate@1.0-service.rc +--- android.hardware.gatekeeper@1.0-service.rc +--- android.hardware.graphics.allocator@2.0-service.rc +--- android.hardware.graphics.composer@2.1-service.rc +--- android.hardware.health@2.0-service.`hardware`.rc +--- android.hardware.keymaster@3.0-service.rc +--- android.hardware.light@2.0-service.rc +--- android.hardware.media.omx@1.0-service.rc +--- android.hardware.memtrack@1.0-service.rc +--- android.hardware.power@1.2-service.rc +--- android.hardware.sensors@1.0-service.rc +--- android.hardware.thermal@1.1-service.`hardware`.rc +--- android.hardware.usb@1.0-service.rc +--- android.hardware.wifi@1.0-service.rc +--- daemon_cl.rc +--- hostapd.android.rc +--- host_server.rc +--- hw |+--- init.coredump.rc |+--- init.crashlogd.rc |+--- init.dvc_desc.rc |+--- init.`hardware`.rc |+--- init.kernel.rc |+--- init.logs.rc |+--- init.npk.rc +--- name_server.rc +--- rild.rc +--- SampleDriverAll.rc +--- vndservicemanager.rc

5.3 事件触发

/* * am为ActionManager::GetInstance() * QueueEventTrigger构造了一个EventTrigger对象, 放到事件队列中 * !!!注意此处并没有触发 */ am.QueueEventTrigger("early-init"); am.QueueEventTrigger("init"); am.QueueEventTrigger("late-init"); /* * QueueBuiltinAction构造了一个Action对象, 放到事件队列和动作队列中 * !!!注意此处并没有触发 */ am.QueueBuiltinAction(wait_for_coldboot_done_action,"wait_for_coldboot_done"); am.QueueBuiltinAction(MixHwrngIntoLinuxRngAction,"MixHwrngIntoLinuxRng"); am.QueueBuiltinAction(SetMmapRndBitsAction,"SetMmapRndBits"); am.QueueBuiltinAction(SetKptrRestrictAction,"SetKptrRestrict"); am.QueueBuiltinAction(keychord_init_action,"keychord_init"); am.QueueBuiltinAction(console_init_action,"console_init"); am.QueueBuiltinAction(MixHwrngIntoLinuxRngAction,"MixHwrngIntoLinuxRng"); am.QueueBuiltinAction(queue_property_triggers_action, "queue_property_triggers"); while (true) { ... if (!(waiting_for_prop || Service::is_exec_service_running())) { // 依次触发early-init、init、late-init的命令 am.ExecuteOneCommand(); } ... }

5.4 详细过程
Android启动过程中重要的trigger事件如下

- early-init +--- start ueventd - init - charger/* 当ro.bootmode为charger执行 */ - late-init +--- early-fs +--- fs/* 挂载系统分区 */ +--- mount_all /vendor/etc/fstab.${ro.hardware} +--- post-fs/* 执行依赖文件系统的命令 */ +--- load_system_props +--- load_properties_from_file("/system/build.prop", NULL); +--- load_properties_from_file("/odm/build.prop", NULL); +--- load_properties_from_file("/vendor/build.prop", NULL); +--- load_properties_from_file("/factory/factory.prop", "ro.*"); +--- load_recovery_id_prop(); +--- start logd +--- start servicemanager +--- start hwservicemanager +--- start vndservicemanager +--- late-fs +--- class_start early_hal +--- post-fs-data/* data分区初始化 */ +--- start vold +--- installkey /data +--- bootchart start +--- init_user0 +--- zygote-start +--- exec_start update_verifier_nonencrypted +--- start netd +--- start zygote +--- start zygote_secondary +--- load_persist_props_action +--- load_persist_props +--- LoadPersistentProperties() +--- start logd +--- start logd-reinit +--- firmware_mounts_complete +--- rm /dev/.booting +--- early-boot +--- boot+--- property:sys.boot_completed=1 +--- bootchart stop

参考:
< Android系统启动流程>
< Android 9.0 init进程分析>
< Android 8.1 启动篇(一) -- 深入研究 init>