Android的启动
1.Linux内核启动
Android本质上就是一个基于Linux内核的操作系统,一个完整的Linux系统首先会将一个Linux内核装载到内存,也就是编译Linux内核源代码生成的bzImage文件,当Linux内核加载完后,要做的第一件事就是调用init程序。
2.init进程(init.c)
init是kernel启动的第一个进程,相应的代码在./system/core/init/下,可以从该目录下的init.c,init.c这个文件做了下面几件事:
1. 初始化属性
2. 处理配置文件的命令(主要是init.rc文件),包括处理各种Action。
3. 性能分析(使用bootchart工具)。
4. 无限循环执行command(作为父进程启动其他的子进程)。
2 .1 2.1初始化语言(init.rc,AIL)
分析init.rc就先要了解AIL,详见AIL.doc
AM335x下有:
Init.rc(入口)
init.usb.rc
Init.trace.rc
init.am335xevm.rc
init.am335xevm.usb.rc
分析init.rc脚步前需要了解什么是AIL,http://dengzhangtao.iteye.com/blog/1984286
# Copyright (C) 2012 The Android Open Source Project
#
# IMPORTANT: Do not create world writable files or directories.
# This is a common source of Android security bugs.
#
import /init.${ro.hardware}.rc
import /init.usb.rc
import /init.trace.rc
on early-init
# Set init and its forked children's oom_adj.进程的oom_adj值也就代表了它的优先级。oom_adj值越高代表该进程优先级越低
write /proc/1/oom_adj -16
#启动ueventd服务
start ueventd
# create mountpoints
mkdir /mnt 0775 root system
on init
#设置系统时钟基准
sysclktz 0
loglevel 3
# setup the global environment
export PATH /sbin:/vendor/bin:/system/sbin:/system/bin:/system/xbin
export LD_LIBRARY_PATH /vendor/lib:/system/lib
export ANDROID_BOOTLOGO 1
export ANDROID_ROOT /system
export ANDROID_ASSETS /system/app
export ANDROID_DATA /data
export ASEC_MOUNTPOINT /mnt/asec
export LOOP_MOUNTPOINT /mnt/obb
export BOOTCLASSPATH /system/framework/core.jar:/system/framework/core-junit.jar:/system/framework/bouncycastle.jar:/system/framework/ext.jar:/system/framework/framework.jar:/system/framework/android.policy.jar:/system/framework/services.jar:/system/framework/apache-xml.jar
# Backward compatibility
symlink /system/etc /etc
symlink /sys/kernel/debug /d
# Right now vendor lives on the same filesystem as system,
# but someday that may change.
symlink /system/vendor /vendor
# Create cgroup mount point for cpu accounting 目录, 权限 ,所有者 ,用户组
mkdir /acct
mount cgroup none /acct cpuacct
mkdir /acct/uid
mkdir /system
mkdir /data 0771 system system
mkdir /cache 0770 system cache
mkdir /config 0500 root root
# Directory for putting things only root should see.
mkdir /mnt/secure 0700 root root
# Directory for staging bindmounts
mkdir /mnt/secure/staging 0700 root root
# Directory-target for where the secure container
# imagefile directory will be bind-mounted
mkdir /mnt/secure/asec 0700 root root
# Secure container public mount points.
mkdir /mnt/asec 0700 root system
mount tmpfs tmpfs /mnt/asec mode=0755,gid=1000
# Filesystem image public mount points.
mkdir /mnt/obb 0700 root system
mount tmpfs tmpfs /mnt/obb mode=0755,gid=1000
write /proc/sys/kernel/panic_on_oops 1
write /proc/sys/kernel/hung_task_timeout_secs 0
write /proc/cpu/alignment 4
write /proc/sys/kernel/sched_latency_ns 10000000
write /proc/sys/kernel/sched_wakeup_granularity_ns 2000000
write /proc/sys/kernel/sched_compat_yield 1
write /proc/sys/kernel/sched_child_runs_first 0
write /proc/sys/kernel/randomize_va_space 2
write /proc/sys/kernel/kptr_restrict 2
write /proc/sys/kernel/dmesg_restrict 1
write /proc/sys/vm/mmap_min_addr 32768
write /proc/sys/kernel/sched_rt_runtime_us 950000
write /proc/sys/kernel/sched_rt_period_us 1000000
# Create cgroup mount points for process groups
mkdir /dev/cpuctl
mount cgroup none /dev/cpuctl cpu
chown system system /dev/cpuctl
chown system system /dev/cpuctl/tasks
chmod 0660 /dev/cpuctl/tasks
write /dev/cpuctl/cpu.shares 1024
write /dev/cpuctl/cpu.rt_runtime_us 950000
write /dev/cpuctl/cpu.rt_period_us 1000000
mkdir /dev/cpuctl/apps
chown system system /dev/cpuctl/apps/tasks
chmod 0666 /dev/cpuctl/apps/tasks
write /dev/cpuctl/apps/cpu.shares 1024
write /dev/cpuctl/apps/cpu.rt_runtime_us 800000
write /dev/cpuctl/apps/cpu.rt_period_us 1000000
mkdir /dev/cpuctl/apps/bg_non_interactive
chown system system /dev/cpuctl/apps/bg_non_interactive/tasks
chmod 0666 /dev/cpuctl/apps/bg_non_interactive/tasks
# 5.0 %
write /dev/cpuctl/apps/bg_non_interactive/cpu.shares 52
write /dev/cpuctl/apps/bg_non_interactive/cpu.rt_runtime_us 700000
write /dev/cpuctl/apps/bg_non_interactive/cpu.rt_period_us 1000000
# Allow everybody to read the xt_qtaguid resource tracking misc dev.
# This is needed by any process that uses socket tagging.
chmod 0644 /dev/xt_qtaguid
#on fs
# mount mtd partitions
# Mount /system rw first to give the filesystem a chance to save a checkpoint
# mount yaffs2 mtd@system /system
# mount yaffs2 mtd@system /system ro remount
# mount yaffs2 mtd@userdata /data nosuid nodev
# mount yaffs2 mtd@cache /cache nosuid nodev
on post-fs
# once everything is setup, no need to modify /
# mount rootfs rootfs / ro remount
# We chown/chmod /cache again so because mount is run as root + defaults
chown system cache /cache
chmod 0770 /cache
# This may have been created by the recovery system with odd permissions
chown system cache /cache/recovery
chmod 0770 /cache/recovery
#change permissions on vmallocinfo so we can grab it from bugreports
chown root log /proc/vmallocinfo
chmod 0440 /proc/vmallocinfo
#change permissions on kmsg & sysrq-trigger so bugreports can grab kthread stacks
chown root system /proc/kmsg
chmod 0440 /proc/kmsg
chown root system /proc/sysrq-trigger
chmod 0220 /proc/sysrq-trigger
# create the lost+found directories, so as to enforce our permissions
mkdir /cache/lost+found 0770 root root
on post-fs-data
# We chown/chmod /data again so because mount is run as root + defaults
chown system system /data
chmod 0771 /data
# Create dump dir and collect dumps.
# Do this before we mount cache so eventually we can use cache for
# storing dumps on platforms which do not have a dedicated dump partition.
mkdir /data/dontpanic 0750 root log
# Collect apanic data, free resources and re-arm trigger
copy /proc/apanic_console /data/dontpanic/apanic_console
chown root log /data/dontpanic/apanic_console
chmod 0640 /data/dontpanic/apanic_console
copy /proc/apanic_threads /data/dontpanic/apanic_threads
chown root log /data/dontpanic/apanic_threads
chmod 0640 /data/dontpanic/apanic_threads
write /proc/apanic_console 1
# create basic filesystem structure
mkdir /data/misc 01771 system misc
mkdir /data/misc/bluetoothd 0770 bluetooth bluetooth
mkdir /data/misc/bluetooth 0770 system system
mkdir /data/misc/keystore 0700 keystore keystore
mkdir /data/misc/keychain 0771 system system
mkdir /data/misc/vpn 0770 system vpn
mkdir /data/misc/systemkeys 0700 system system
# give system access to wpa_supplicant.conf for backup and restore
mkdir /data/misc/wifi 0770 wifi wifi
chmod 0660 /data/misc/wifi/wpa_supplicant.conf
mkdir /data/local 0751 root root
# For security reasons, /data/local/tmp should always be empty.
# Do not place files or directories in /data/local/tmp
mkdir /data/local/tmp 0771 shell shell
mkdir /data/data 0771 system system
mkdir /data/app-private 0771 system system
mkdir /data/app-asec 0700 root root
mkdir /data/app 0771 system system
mkdir /data/property 0700 root root
mkdir /data/ssh 0750 root shell
mkdir /data/ssh/empty 0700 root root
# create dalvik-cache, so as to enforce our permissions
mkdir /data/dalvik-cache 0771 system system
# create resource-cache and double-check the perms
mkdir /data/resource-cache 0771 system system
chown system system /data/resource-cache
chmod 0771 /data/resource-cache
# create the lost+found directories, so as to enforce our permissions
mkdir /data/lost+found 0770 root root
# create directory for DRM plug-ins - give drm the read/write access to
# the following directory.
mkdir /data/drm 0770 drm drm
# If there is no fs-post-data action in the init.<device>.rc file, you
# must uncomment this line, otherwise encrypted filesystems
# won't work.
# Set indication (checked by vold) that we have finished this action
#setprop vold.post_fs_data_done 1
on boot
# basic network init
ifup lo
hostname localhost
domainname localdomain
# set RLIMIT_NICE to allow priorities from 19 to -20
setrlimit 13 40 40
# Memory management. Basic kernel parameters, and allow the high
# level system server to be able to adjust the kernel OOM driver
# parameters to match how it is managing things.
write /proc/sys/vm/overcommit_memory 1
write /proc/sys/vm/min_free_order_shift 4
chown root system /sys/module/lowmemorykiller/parameters/adj
chmod 0664 /sys/module/lowmemorykiller/parameters/adj
chown root system /sys/module/lowmemorykiller/parameters/minfree
chmod 0664 /sys/module/lowmemorykiller/parameters/minfree
# Tweak background writeout
write /proc/sys/vm/dirty_expire_centisecs 200
write /proc/sys/vm/dirty_background_ratio 5
# Permissions for System Server and daemons.
chown radio system /sys/android_power/state
chown radio system /sys/android_power/request_state
chown radio system /sys/android_power/acquire_full_wake_lock
chown radio system /sys/android_power/acquire_partial_wake_lock
chown radio system /sys/android_power/release_wake_lock
chown system system /sys/power/state
chown system system /sys/power/wakeup_count
chown radio system /sys/power/wake_lock
chown radio system /sys/power/wake_unlock
chmod 0660 /sys/power/state
chmod 0660 /sys/power/wake_lock
chmod 0660 /sys/power/wake_unlock
chown system system /sys/devices/system/cpu/cpufreq/interactive/timer_rate
chmod 0660 /sys/devices/system/cpu/cpufreq/interactive/timer_rate
chown system system /sys/devices/system/cpu/cpufreq/interactive/min_sample_time
chmod 0660 /sys/devices/system/cpu/cpufreq/interactive/min_sample_time
chown system system /sys/devices/system/cpu/cpufreq/interactive/hispeed_freq
chmod 0660 /sys/devices/system/cpu/cpufreq/interactive/hispeed_freq
chown system system /sys/devices/system/cpu/cpufreq/interactive/go_hispeed_load
chmod 0660 /sys/devices/system/cpu/cpufreq/interactive/go_hispeed_load
chown system system /sys/devices/system/cpu/cpufreq/interactive/above_hispeed_delay
chmod 0660 /sys/devices/system/cpu/cpufreq/interactive/above_hispeed_delay
chown system system /sys/devices/system/cpu/cpufreq/interactive/boost
chmod 0660 /sys/devices/system/cpu/cpufreq/interactive/boost
chown system system /sys/devices/system/cpu/cpufreq/interactive/boostpulse
chown system system /sys/devices/system/cpu/cpufreq/interactive/input_boost
chmod 0660 /sys/devices/system/cpu/cpufreq/interactive/input_boost
# Assume SMP uses shared cpufreq policy for all CPUs
chown system system /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
chmod 0660 /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
chown system system /sys/class/timed_output/vibrator/enable
chown system system /sys/class/leds/keyboard-backlight/brightness
chown system system /sys/class/leds/lcd-backlight/brightness
chown system system /sys/class/leds/button-backlight/brightness
chown system system /sys/class/leds/jogball-backlight/brightness
chown system system /sys/class/leds/red/brightness
chown system system /sys/class/leds/green/brightness
chown system system /sys/class/leds/blue/brightness
chown system system /sys/class/leds/red/device/grpfreq
chown system system /sys/class/leds/red/device/grppwm
chown system system /sys/class/leds/red/device/blink
chown system system /sys/class/leds/red/brightness
chown system system /sys/class/leds/green/brightness
chown system system /sys/class/leds/blue/brightness
chown system system /sys/class/leds/red/device/grpfreq
chown system system /sys/class/leds/red/device/grppwm
chown system system /sys/class/leds/red/device/blink
chown system system /sys/class/timed_output/vibrator/enable
chown system system /sys/module/sco/parameters/disable_esco
chown system system /sys/kernel/ipv4/tcp_wmem_min
chown system system /sys/kernel/ipv4/tcp_wmem_def
chown system system /sys/kernel/ipv4/tcp_wmem_max
chown system system /sys/kernel/ipv4/tcp_rmem_min
chown system system /sys/kernel/ipv4/tcp_rmem_def
chown system system /sys/kernel/ipv4/tcp_rmem_max
chown root radio /proc/cmdline
# Define TCP buffer sizes for various networks
# ReadMin, ReadInitial, ReadMax, WriteMin, WriteInitial, WriteMax,
setprop net.tcp.buffersize.default 4096,87380,110208,4096,16384,110208
setprop net.tcp.buffersize.wifi 524288,1048576,2097152,262144,524288,1048576
setprop net.tcp.buffersize.lte 524288,1048576,2097152,262144,524288,1048576
setprop net.tcp.buffersize.umts 4094,87380,110208,4096,16384,110208
setprop net.tcp.buffersize.hspa 4094,87380,262144,4096,16384,262144
setprop net.tcp.buffersize.edge 4093,26280,35040,4096,16384,35040
setprop net.tcp.buffersize.gprs 4092,8760,11680,4096,8760,11680
# Set this property so surfaceflinger is not started by system_init
setprop system_init.startsurfaceflinger 0
class_start core
class_start main
on nonencrypted
class_start late_start
on charger
class_start charger
on property:vold.decrypt=trigger_reset_main
class_reset main
on property:vold.decrypt=trigger_load_persist_props
load_persist_props
on property:vold.decrypt=trigger_post_fs_data
trigger post-fs-data
on property:vold.decrypt=trigger_restart_min_framework
class_start main
on property:vold.decrypt=trigger_restart_framework
class_start main
class_start late_start
on property:vold.decrypt=trigger_shutdown_framework
class_reset late_start
class_reset main
## Daemon processes to be run by init.
#ueventd服务会读取 /ueventd.rc 和 /ueventd.$hadrware.rc 文件,解析跟 init.rc 解析类似,
#主要是对文件系统的权限和用户进行设置:(代码:system/core/init/ueventd.c)
service ueventd /sbin/ueventd
class core
critical
#控制台中可以执行root权限的话 user shell 改为 user root
service console /system/bin/sh
class core
console
disabled
# user shell
group log
on property:ro.debuggable=1
start console
# adbd is controlled via property triggers in init.<platform>.usb.rc
# adb 命令
service adbd /sbin/adbd
class core
disabled
# adbd on at boot in emulator
on property:ro.kernel.qemu=1
start adbd
#服务管理 是应用程序与服务沟通的桥梁。
service servicemanager /system/bin/servicemanager
class core
user system
group system
critical
#onrestart 当服务重启,执行一个命令
onrestart restart zygote
onrestart restart media
onrestart restart surfaceflinger
onrestart restart drm
#当有这外存储设备插入时,就需要监视这种变化,并加载相应的驱动程序,然后报告给系统和应用程序有新存储设备可以使用。
# /system/vold/main.cpp
service vold /system/bin/vold
class core
socket vold stream 0660 root mount
ioprio be 2
#netd功能:
# (1)Linux Kernel 用于检测 network 相关的所有 event 事件。
# (2)Netd 作为 Kernel 与 Framework 之间通信的桥梁。
# (3)Framework 层操作 Netd,向 Netd 发送操作命令。
# (4)UI 与 Framework 交互,用于用户进行网络的操控。
service netd /system/bin/netd
class main
socket netd stream 0660 root system
socket dnsproxyd stream 0660 root inet
socket mdns stream 0660 root system
#debug服务,Log的使用
service debuggerd /system/bin/debuggerd
class main
# modify by dengzt 2013,8,28
#电话服务
#service ril-daemon /system/bin/rild
# class main
# socket rild stream 660 root radio
# socket rild-debug stream 660 radio system
# user root
# group radio cache inet misc audio sdcard_r sdcard_rw log
#管理设备的帧缓冲区
service surfaceflinger /system/bin/surfaceflinger
class main
user system
group graphics
onrestart restart zygote
#根据用户的命令创建应用程序
service zygote /system/bin/app_process -Xzygote /system/bin --zygote --start-system-server
class main
socket zygote stream 660 root system
onrestart write /sys/android_power/request_state wake
onrestart write /sys/power/state on
onrestart restart media
onrestart restart netd
#DRM,英文全称为Digital Rights Management,译为数字版权管理
service drm /system/bin/drmserver
class main
user drm
group drm system inet drmrpc sdcard_r
#多媒体服务,照相,音频
service media /system/bin/mediaserver
class main
user media
group audio camera inet net_bt net_bt_admin net_bw_acct drmrpc
ioprio rt 4
#开机动画服务
service bootanim /system/bin/bootanimation
class main
user graphics
group graphics
disabled
oneshot
#跨进程的数据交互是通过dbus来的,这里默认是蓝牙才能访问
service dbus /system/bin/dbus-daemon --system --nofork
class main
socket dbus stream 660 bluetooth bluetooth
user bluetooth
group bluetooth net_bt_admin
#service bluetoothd /system/bin/bluetoothd -n
# class main
# socket bluetooth stream 660 bluetooth bluetooth
# socket dbus_bluetooth stream 660 bluetooth bluetooth
# init.rc does not yet support applying capabilities, so run as root and
# let bluetoothd drop uid to bluetooth with the right linux capabilities
# group bluetooth net_bt_admin misc
# disabled
#apk安装服务,源码frameworks/base/cmds/installd/
service installd /system/bin/installd
class main
socket installd stream 600 system system
service flash_recovery /system/etc/install-recovery.sh
class main
oneshot
#VPN服务
service racoon /system/bin/racoon
class main
socket racoon stream 600 system system
# IKE uses UDP port 500. Racoon will setuid to vpn after binding the port.
group vpn net_admin inet
disabled
oneshot
#Media Transfer Protocol多媒体传输协议服务
service mtpd /system/bin/mtpd
class main
socket mtpd stream 600 system system
user vpn
group vpn net_admin inet net_raw
disabled
oneshot
#应用签名服务
service keystore /system/bin/keystore /data/misc/keystore
class main
user keystore
group keystore drmrpc
socket keystore stream 666
#性能测试工具
service dumpstate /system/bin/dumpstate -s
class main
socket dumpstate stream 0660 shell log
disabled
oneshot
#SSH为一项创建在应用层和传输层基础上的安全协议,为计算机上的Shell(壳层)提供安全的传输和使用环境。
service sshd /system/bin/start-ssh
class main
disabled
#Bonjour技术在android平台上的定制为mdnsd 使用Bonjour的设备在网络中自动组播它们自己的服务信息并监听其它设备的服务信息。设备之间就像在打招呼
service mdnsd /system/bin/mdnsd
class main
user mdnsr
group inet net_raw
socket mdnsd stream 0660 mdnsr inet
disabled
oneshot
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13. **Material Design**:Google推出的Material Design设计语言在Android开发中广泛使用,源代码可能会展示如何遵循这一设计指南创建界面。 14. **第三方库集成**:许多Android开发者会使用如Butter Knife(注解...
而`android 项目开发详解代码`很可能是一个包含所有上述组件的源代码目录,你可以通过阅读和运行这些代码来加深对Android开发的理解。 此外,学习Android开发还需要掌握一些基本的工具,如Android Studio IDE,它...
总之,《Android系统源代码情景分析 第3版》是一本全面而深入的Android开发指南,无论你是初学者还是有经验的开发者,都能从中受益匪浅,提升你的Android开发技能。配合书中的实际代码示例和解析,你将能够更好地...
《Android Framework 开发揭秘》这本书深入剖析了Android系统的内部运作机制,是Android开发者提升技术深度...通过学习本书,读者将能够更深入地掌握Android开发,从而在Android平台上创造出更高效、更稳定的应用程序。
1. **Android Studio简介**:作为Android开发的主要集成开发环境(IDE),Android Studio提供了丰富的工具和功能,如项目模板、调试器、代码补全等,使得开发过程更加高效。初学者需要熟悉其界面布局和基本操作,如...
《Android系统源代码情景分析》随书光盘内容(源代码) 目录如下: 第1篇 初识Android系统 第1章 准备知识 1.1 Linux内核参考书籍 1.2 Android应用程序参考书籍 1.3 下载、编译和运行Android源代码 1.3.1 下载...
书中的每个章节都配有相应的源代码,旨在帮助读者通过实践来掌握Android开发技能。以下是对这些章节代码的详细解读: 1. **EX_04_12**:这个章节可能涉及的是Android的布局管理器(如LinearLayout, RelativeLayout...