““Learning AOSP”Learning AOSP”Android Booting ProcessAndroid Booting Process

Nanik TolaramNanik Tolaram@nanikjava@nanikjava

ozandroid.infoozandroid.info

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ArchitectureArchitecture

Questions !Questions ! What happened when I press power on button in my Android What happened when I press power on button in my Android

device ?device ?

What is Android boot sequence ?What is Android boot sequence ?

What is bootloader ?What is bootloader ?

What is Zygote ?What is Zygote ?

What is init.rc ?What is init.rc ?

What is System Server ?What is System Server ?

Boot Execution PathBoot Execution PathBoot ROM

Boot Loader

Kernel

Init

Zygote

System Servers

hardware

boot.img, C & ASM, rootfs

system.img,Android framework & apps

u-boot or different fork

Boot ROM & Boot LoaderBoot ROM & Boot LoaderPower ON

On chip ROM (during CPU production)

Primary Boot Loader

Secondary Boot Loader

Hardware Init Modem Image Execution

Kernel Image Download & Execution

1st loaded from flash (normally)/fastboot

KernelKernel Nothing Special ! Nothing Special !

Standard Linux Kernel ExecutionStandard Linux Kernel Execution

Hardware & Android Device DriversHardware & Android Device Drivers

Needed in recovery and system partitionNeeded in recovery and system partition

InitInit Main entry point to AndroidMain entry point to Android init.rc and other .rc configinit.rc and other .rc config Initialisation and preparationInitialisation and preparation

Android framework initialisationAndroid framework initialisation Environment properties setupEnvironment properties setup Security setupSecurity setup

Mounting of different media partitionsMounting of different media partitions System servers initialisationSystem servers initialisation

ZygoteZygote Initialise during Initialise during Init Init processprocess

service zygote /system/bin/app_process -Xzygote /system/bin --zygote --start-system-service zygote /system/bin/app_process -Xzygote /system/bin --zygote --start-system-serverserver

Registers server socketRegisters server socket Preload Java classes from “preloaded-Preload Java classes from “preloaded-

classes” fileclasses” file Preload native themes and layoutsPreload native themes and layouts

System ServersSystem Servers System Servers written both as Native & System Servers written both as Native &

JavaJava startSystemServer() methodstartSystemServer() method Power Manager, Zygote, Activity Power Manager, Zygote, Activity

Manager, Telephony Registry, Battery Manager, Telephony Registry, Battery Service and many moreService and many more

Boot CompleteBoot Complete ACTION_BOOT_COMPLETED ACTION_BOOT_COMPLETED

broadcast Intent will firebroadcast Intent will fire

Boot Sequence DecisionBoot Sequence DecisionBootloader Microcode

Boot Partition

System Partition Recovery Partition

Recovery

Y

N

Execute Recovery AppRun Android Stack

Bootloader (1st, 2nd, nth)

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