Digging Into Android Startup

Walkthrough of the boot process of an Android device, and the major components involved in launching application processes.

Transcript

1. Digging Into Android Startup Dave Smith NewCircle, Inc. @devunwired 1
2. Device Startup 2 Bootloader(s) Linux Kernel Init/ Zygote(s) SystemServer Home App
3. Early Stages 3 Bootloader(s) Li2leKernel, U-Boot, UEFI Linux Kernel initramfs
4. ramdisk.img RootFS 4 default.prop dev/ file_contexts fstab.goldfish init init.environ.rc init.goldfish.rc init.rc init.trace.rc init.usb.rc init.zygote32.rc proc/ property_contexts sbin/ seapp_contexts selinux_version sepolicy service_contexts sys/ ueventd.goldfish.rc ueventd.rc
5. 5 system_server zygote Init ZygoteInit SystemServer LocationManagerService Launcher installd logd lmkd ueventd … PowerManagerService ActivityManagerService LauncherActivity
6. 6 system_server zygote Init ZygoteInit SystemServer LocationManagerService Launcher installd logd lmkd ueventd … PowerManagerService ActivityManagerService LauncherActivity
7. init.*.rc 7 on init mkdir /system mkdir /data 0771 system system mkdir /cache 0770 system cache mkdir /config 0500 root root # See storage config details at http://source.android.com/tech/storage/ mkdir /mnt/shell 0700 shell shell mkdir /mnt/media_rw 0700 media_rw media_rw mkdir /storage 0751 root sdcard_r ... on fs mount_all /fstab.goldfish ... on property:selinux.reload_policy=1 restart ueventd restart installd ... on property:sys.usb.config=adb write /sys/class/android_usb/android0/enable 0 write /sys/class/android_usb/android0/idVendor 18d1 write /sys/class/android_usb/android0/idProduct 4EE7 write /sys/class/android_usb/android0/functions ${sys.usb.config} write /sys/class/android_usb/android0/enable 1 start adbd setprop sys.usb.state ${sys.usb.config}
8. Mounted Partitions 8 # Android fstab file. #<src> <mnt_point> <type> <mnt_flags and options> <fs_mgr_flags> # The filesystem that contains the filesystem checker binary (typically / system) cannot # specify MF_CHECK, and must come before any filesystems that do specify MF_CHECK /dev/block/mtdblock0 /system ext4 ro,barrier=1 wait /dev/block/mtdblock1 /data ext4 noatime,nosuid,nodev,barrier=1,nomblk_io_submit wait,check /dev/block/mtdblock2 /cache ext4 noatime,nosuid,nodev wait,check /devices/platform/goldfish_mmc.0 auto vfat defaults voldmanaged=sdcard:auto /fstab.goldfish
9. init.*.rc 9 class_start core class_start main service logd /system/bin/logd class core socket logd stream 0666 logd logd socket logdr seqpacket 0666 logd logd socket logdw dgram 0222 logd logd seclabel u:r:logd:s0 ... service installd /system/bin/installd class main socket installd stream 600 system system ... service servicemanager /system/bin/servicemanager class core user system group system critical onrestart restart healthd onrestart restart zygote onrestart restart media onrestart restart surfaceflinger onrestart restart drm ...
10. 10 system_server zygote Init ZygoteInit SystemServer LocationManagerService Launcher installd logd lmkd ueventd … PowerManagerService ActivityManagerService LauncherActivity
11. Zygote 11 zygote Preloaded Java Classes Preloaded Framework Resources VM/Runtime Preloaded Shared Libraries 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
12. Look Familiar? 12 java.lang.NullPointerException: Attempt to invoke virtual method 'xxx' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360) at android.app.ActivityThread.access$800(ActivityThread.java:144) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5221) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
13. 13 system_server zygote Init ZygoteInit SystemServer LocationManagerService Launcher installd logd lmkd ueventd … PowerManagerService ActivityManagerService LauncherActivity
14. ActivityManagerService 14 Broadcast: action.PRE_BOOT_COMPLETED Launch Home Activity
15. Default Launcher Application 15 <intent-filter>
 <action android:name="android.intent.action.MAIN" />
 <category android:name="android.intent.category.HOME" />
 </intent-filter>
16. ActivityManagerService 16 Broadcast: action.PRE_BOOT_COMPLETED Broadcast: action.BOOT_COMPLETED Launch Home Activity
17. App Launch 17 system_server ActivityManagerService Current App MainActivity Next App ActivityThread zygote ZygoteInit android.os.Process ActivityManagerNative NewActivity ActivityManagerNative start() fork() scheduleLaunchActivity() attachApplication()
18. 64-bit Support 18 Zygote32 Zygote64 Zygote service zygote /system/bin/app_process64 -Xzygote /system/bin --zygote --start-system-server --socket-name=zygote 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 service zygote_secondary /system/bin/app_process32 -Xzygote /system/bin --zygote --socket-name=zygote_secondary class main socket zygote_secondary stream 660 root system onrestart restart zygote
19. 64-bit Support • Zygote ABI Selection – adb install --abi – ApplicationInfo.primaryCpuAbi • Inferred from native ABIs in the APK – getprop ro.product.cpu.abilist • Nexus 9 • [arm64-v8a,armeabi-v7a,armeabi] • Defaults to first item • Precompiled cache is now split by arch – arm/arm64 – x86/x86_64 19
20. Let's Connect! • Dave Smith • Twitter: @devunwired • Google+ – http://plus.google.com/+DaveSmithDev • Blog – http://wiresareobsolete.com • Training – http://newcircle.com 20