Customized Android firmware¶
There are two ways to customize Android firmware:
Change the source code and compile the firmware.
Tailoring the existing firmware.
In the former method, Android can be customized from all levels, with great freedom, but high requirements for the compilation environment and technology, which can be referred to Compile Android firmware. Now introduce the latter method, which is divided into three phases: unpacking, customization and packaging. The host operating system is Linux, and the tools used are open source software.
release_update.img contains the boot loader
loader.img and the actual firmware data -
release_update.img |- loader.img `- update.img
update.img is a composite file containing multiple files described by package-file. A typical package-file is:
# NAME Relative path # #HWDEF HWDEF package-file package-file bootloader RK3288Loader_uboot_Apr212014_134842.bin parameter rk3288-3.10-uboot-data1G.parameter.txt uboot Image/uboot.img misc Image/misc.img resource Image/resource.img kernel Image/kernel.img boot Image/boot.img recovery Image/recovery.img system Image/system.img backup RESERVED update-script update-script recover-script recover-script
Packing instruction file for the update.img, a package-file is also contained in the update.img.
Boot loader(i.e. bootloader).
Parameter file, which can be used to set the kernel startup parameters, and there are important partition information in it.
Image of the partition, which is used to control whether the Android starts normally or enters the emergency mode(Recovery Mode).
Resource image, which contains the boot image and the device tree blob information of the kernel.
The memory boot disk (initrd) of the Android kernel, which is the root file system that is loaded first after the kernel startup and contains important initialization actions, in general, the change is not required.
Image in the emergency mode for Android, which contains the root file system of the kernel and emergency modes.
Corresponding to the /system partition of Android, and it is the following custom object.
Unpacking, is to extract the
release_update.img, then the extracted with
package-file statement by multiple files.
Packaging is an inverse process to synthesize the multiple files listed in the package-file to
update.img, add to the
loader.img, and finally generate the
git clone https://github.com/TeeFirefly/rk2918_tools.git cd rk2918_tools make sudo cp afptool img_unpack img_maker mkkrnlimg /usr/local/bin
$ cd /path/to/your/firmware/dir $ img_unpack Firefly-RK3288_Android4.4_20140818.img img rom version: 4.4.2 build time: 2014-08-18 14:25:57 chip: 80 checking md5sum....OK
$ cd img $ afptool -unpack update.img update Check file...OK ------- UNPACK ------- package-file 0x00000800 0x00000285 RK3288Loader_uboot_Apr212014_134842.bin 0x00001000 0x0004694E rk3288-3.10-uboot-data1G.parameter.txt 0x00048000 0x000005A1 Image/misc.img 0x00048800 0x0000C000 Image/kernel.img 0x00055000 0x00578E3C Image/resource.img 0x005CE000 0x0001C400 Image/boot.img 0x005EA800 0x0011F6CF Image/recovery.img 0x0070A000 0x0040F6AE Image/system.img 0x00B19800 0x180EF000 RESERVED 0x00000000 0x00000000 update-script 0x18C09000 0x000003A5 recover-script 0x18C09800 0x0000010A UnPack OK!
View the file tree under the update directory
$ cd update/ $ tree . ├── Image │ ├── boot.img │ ├── kernel.img │ ├── misc.img │ ├── recovery.img │ ├── resource.img │ ├── uboot.img │ └── system.img ├── package-file ├── recover-script ├── RESERVED ├── rk3288-3.10-uboot-data1G.parameter.txt ├── RK3288Loader_uboot_Apr212014_134842.bin └── update-script
Now that the firmware has been unpacked successfully, let’s start customizing it.
Customize the system.img¶
System.img is an ext4 file format image file that can be mounted directly to the system for modification:
sudo mkdir -p /mnt/system sudo mount -o loop Image/system.img /mnt/system cd /mnt/system # Notice how much space is left when modify inside,and don't add too much APK. # After modification, uninstall. cd / sudo umount /mnt/system
Note: The remaining space of the
system.img is basically 0. If the file is not deleted, the capacity of
system.img needs to be expanded, and the partition Settings in the parameter file are adjusted accordingly according to the final file size. The following is an example of how to extend the space. Before extending, run mount to see how the system is mounted and ensure that system.img has been unmounted:
# Increase the space by 128M dd if=/dev/zero bs=1M count=128 >> Image/system.img # Extend file system information e2fsck -f Image/system.img resize2fs Image/system.img
First, check the size of
system.img and make necessary size adjustments against the partition of the
parameter file.(Refer to the documentation The file format parameter.
For example, the system partition size in
parameter.txt file, you can find the
CMDLINE line and then find the
Before @ is the size of the partition, the unit is 512 bytes, so the size of the system partition is:
$ echo $(( 0x00200000 * 512 / 1024 / 1024))M 1024M
As long as the size of
system.img does not exceed 768M, the parameter file does not need to be changed.
If the partition does not change, you can use the upgrade tool to upgrade the new
system.img directly to the
system partition on the development board for testing. Otherwise, you need to make new firmware and burn it before testing.
Here are the steps required to package it into a unified firmware
# The current directory is still update/, which contains the package-file, and the files listed by the package-file exist # Copy the parameter file to the paramter, by default, the afptool is used to $ cp rk3288-3.10-uboot-data1G.parameter.txt parameter $ afptool -pack . ../update_new.img ------ PACKAGE ------ Add file: ./package-file Add file: ./RK3288Loader_uboot_Apr212014_134842.bin Add file: ./rk3288-3.10-uboot-data1G.parameter.txt Add file: ./Image/uboot.img Add file: ./Image/misc.img Add file: ./Image/kernel.img Add file: ./Image/resource.img Add file: ./Image/boot.img Add file: ./Image/recovery.img Add file: ./Image/system.img Add file: ./RESERVED Add file: ./update-script Add file: ./recover-script Add CRC... ------ OK ------ Pack OK!
Compose release_update.img ：
$ img_maker -rk32 loader.img update_new.img release_update_new.img generate image... append md5sum... success!
release_update_new.img is a unified firmware file that can be upgraded for the final generation
Q1 : Where’s the firmware version Settings?
A1 : In the parameter file, you can find the downward direction and modify it. Note that the version number is a number, and the middle two dots cannot be omitted.