Android Booting Scenarios
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The document outlines an Android internals course that will teach students how to develop embedded systems using Google Android. The course objectives are to customize and install Android for target platforms. Prerequisites include experience with C/C++, basic Java, Linux command line, and optionally embedded systems development. The course will cover topics like the Android source code, compiling and booting Android kernels, supporting new boards, and using ADB for development and debugging. Labs will provide hands-on experience with these topics.
![Fastboot Command
Usage: fastboot [ <option> ] <command>
Command Description
update <filename> Reflash device from filename
flashall Flash boot + recovery + system
flash <partition> [ <filename> ] Write a file to a flash Partion
erase <partition> Erase a flash partition
getvar <variable> Display a bootloader variable
boot <kernel> [ <ramdisk> ] Download and boot kernel
flash:raw boot <kernel> [ <ramdisk> ] Create bootimage and flash it
devices List all connected devices
continue Continue with autoboot
reboot Reboot device normally
reboot-bootloader Reboot device into bootloader
Android Internals @ SAS 15 08/23/12](https://image.slidesharecdn.com/androidbootingscenarios-120823132116-phpapp01/85/Android-Booting-Scenarios-15-320.jpg)
Android Booting Scenarios
- 2. Course Objectives Develop embedded systems with Google Android Customize and install Google Android for your target platform Android Internals @ SAS 2 08/23/12
- 3. Course Prerequisites C/C++ Basic Java Basic Unix/Linux command line interface experience An extra 1 day training may be needed. Embedded systems development is a plus. Android Internals @ SAS 3 08/23/12
- 4. Course Notes Ask any time. Set your cell to silent. Course assumes Linux is already ported to your hardware. An extra 5 days training may be needed. Android Internals @ SAS 4 08/23/12
- 5. Outline Lectures Labs Introduction to Android Android Source Code Android Source Code & Compilation 1st Compilation Linux Kernel Introduction Compile and Boot an Android Kernel Changes Introduced in the Android Kernel Android Booting Scenarios Supporting a New Board Developing and Debugging with ADB Use ADB Android Filesystem Layout Android Build System System Customization Android Native Layer Building a Library Adding a Native Application to the Build Android Internals @ SAS 5 08/23/12
- 6. How does Embedded Linux System Boot? We will talk about bootloader and Init process only. Android Internals @ SAS 6 08/23/12
- 7. What does a Bootloader do? Basic HW initialization Loading of an application binary, usually an operating system kernel Decompression of the application binary Execution of the application Most bootloaders provide a shell with various commands implementing different operations. Loading data Memory inspection HW diagnostics Testing ... Android Internals @ SAS 7 08/23/12
- 8. PC Boatloaders BIOS executes from on board ROM. Basic HW initialization + 1st BIOS bootloader loading 1st stage bootloader loads a full 1st stage bootloader boatloader. Full bootloader with full functionality and features. Full boatloader It can load a kernel from a filesystem. Kernel Examples: GRUB Syslinux Android Internals @ SAS 8 08/23/12
- 9. Booting on Embedded CPUs – NOR Flash CPU starts executing code at a fixed address when powered up. HW design ensures that a NOR flash is at this address. It can hold the 1st stage bootloader or even a full bootloader. NOR flashes are very expensive and limited in size. Not very common nowdays Android Internals @ SAS 9 08/23/12
- 10. Booting on Embedded CPUs – !NOR Flash ROM code is stored in an internal ROM in the CPU. ROM code ROM code loads bootstrap bootloader from non-volatile Bootstrap bootloader storage into SRAM. Full boatloader Bootstrap loads full bootloader into DRAM which in return loads the kernel in the DRAM. Kernel Android Internals @ SAS 10 08/23/12
- 11. Examples of Embedded Bootloaders U-Boot http://www.denx.de/wiki/U-Boot Barebox http://www.barebox.org Redboot Yaboot PMON ... Android Internals @ SAS 11 08/23/12
- 12. Android Bootloader The bootloader is outside the realm of Android itself. The first-stage bootloader will provide support for: Loading recovery images to the system flash Putting the device into a mode where the developer can perform development tasks AKA fastboot mode These features should be disabled in production. In addition, it supports normal booting sequence. Android Internals @ SAS 12 08/23/12
- 13. What is Fastboot? A protocol to communicate bootloaders over USB. It is synchronous and driven by the host. Accessible with the fastboot command. Allows to: Transmit data Flash the various partitions of the device Get variables from the bootloader Control the boot sequence Android Internals @ SAS 13 08/23/12
- 14. Fastboot Usage 1. Make sure that ADB or SDK installed on host. 2. Install fastboot for your host. 3. Turn off the device. 4. Boot device into bootloader. 5. Make sure the device is in FASTBOOT and not HBOOT. 6. Connect the device to the computer via USB. 7. On your computer, open terminal and run fastboot command. Android Internals @ SAS 14 08/23/12
- 15. Fastboot Command Usage: fastboot [ <option> ] <command> Command Description update <filename> Reflash device from filename flashall Flash boot + recovery + system flash <partition> [ <filename> ] Write a file to a flash Partion erase <partition> Erase a flash partition getvar <variable> Display a bootloader variable boot <kernel> [ <ramdisk> ] Download and boot kernel flash:raw boot <kernel> [ <ramdisk> ] Create bootimage and flash it devices List all connected devices continue Continue with autoboot reboot Reboot device normally reboot-bootloader Reboot device into bootloader Android Internals @ SAS 15 08/23/12
- 16. Fastboot Command cont’d Option Description -w Erase userdata and cache -s <serial number> Specify device serial number -p <product> Specify product name -c <cmdline> Override kernel commandline -i <vendor id> Specify a custom USB vendor id -b <base_addr> Specify a custom kernel base address -n <page size> Specify the nand page size. default:2048 Android Internals @ SAS 16 08/23/12
- 17. Fastboot Session Example Android Internals @ SAS 17 08/23/12
- 18. Init Starts Daemons Including usbd adbd debuggerd rild ... Daemon Daemon Daemon Init Android Internals @ SAS 18 08/23/12
- 19. Init Starts Zygote Process A Zygote process: Initializes a Dalvik VM instance Loads classes Listens for requests to spawn VMs Forks on requests VMs using copy-on-write to minimize footprint Daemon Daemon Zygote Daemon Init Android Internals @ SAS 19 08/23/12
- 20. Init Starts Runtime Process A runtime process: Initializes a service manager and registers it as a default context manager for Binder services Service Manager Daemon Daemon Runtime Zygote Daemon Init Android Internals @ SAS 20 08/23/12
- 21. Runtime Requests to Start the System Server Process Requested from Zygote Zygote forks a new VM for the system server process and starts the server. System Server Service Dalvik Manager VM Daemon Daemon Runtime Zygote Daemon Init Android Internals @ SAS 21 08/23/12
- 22. System Server Starts the Native System Servers Including: Surface flinger Audio flinger ... Daemon Daemon Flingers System Native system servers register Server with service manager as IPC Service Dalvik service targets. Manager VM Daemon Daemon Runtime Zygote Daemons Init Android Internals @ SAS 22 08/23/12
- 23. System Server Starts the Android Managed Services Including Content manager Window manager Telephony service Daemon Daemon Daemon Daemon Flingers Managers Activity manager … System Server Service Dalvik Manager VM Daemon Daemon Runtime Zygote Daemon Init Android Internals @ SAS 23 08/23/12
- 24. Android Managed Services Register with the Service Manager Daemon Daemon Daemon Daemon Flingers Managers System Server Service Dalvik Manager VM Daemon Daemon Runtime Zygote Daemon Init Android Internals @ SAS 24 08/23/12
- 25. Android Startup Overview System Startup Android Internals @ SAS 25 08/23/12
- 26. Android Startup Overview – Home Window libc Android Internals @ SAS 26 08/23/12
- 27. Android Startup Overview – Any Application libc Android Internals @ SAS 27 08/23/12
- 28. How do Layers Interact? There are 3 main scenarios for the app to talk to the native libraries. Directly Through a service Through a daemon Depends on: Applications Application Native library implementation Application Framework Android version Libraries Linux Kernel Android Internals @ SAS 28 08/23/12
- 29. Direct Layers Interaction Applications Application Binder IPC Application Framework Runtime Service JNI Native Service Binding Libraries Dynamic Loading HAL Library Linux Kernel Device Driver Android Internals @ SAS 29 08/23/12
- 30. Direct Layers Interaction – Location ManagerApplications Application Binder IPC Application Framework Location Manager Service GPS Location Provider JNI GPS Location Provider Binder Libraries Dynamic Loading libgps.so Linux Kernel GPS Device Driver Android Internals @ SAS 30 08/23/12
- 31. Through a Service Layers Interaction Applications Application Binder IPC Application Framework Runtime Service JNI Binder IPC Native Service Binding Native Service Libraries Dynamic Loading HAL Library Linux Kernel Device Driver Android Internals @ SAS 31 08/23/12
- 32. Through a Service Layers Interaction – Media Player Applications Application Binder IPC Application Framework Media Player JNI Binder IPC Media Player Binder Audio Flinger Libraries Dynamic Loading Media Framework libaudio.so Linux Kernel ALSA Speakers Device Driver Android Internals @ SAS 32 08/23/12
- 33. Through a Daemon Layers Interaction Applications Application Binder IPC Application Framework Runtime Service JNI Sockets Native Service Binding Native Daemon Libraries Dynamic Loading HAL Library Linux Kernel Device Driver Android Internals @ SAS 33 08/23/12
- 34. Android Internals @ SAS 34 08/23/12
Editor's Notes
- #19: Init starts Linux daemons, including: • USB Daemon (usbd) to manage USB connections • Android Debug Bridge (adbd) to manage ADB connections • Debugger Daemon (debuggerd) to manage debug processes requests (dump memory, etc.) • Radio Interface Layer Daemon (rild) to manage communication with the radio
- #22: System server is the java framework corresponding to the native service manager.
- #23: A flinger is like a user space driver that combines different inputs from different applications and send them to the HW device.