￭ Pack/Repack RK30 recovery.img－Lexra Pixnet

Build Mkbootimg / Unmkbootimg

https://github.com/pbatard/bootimg-tools/tree/master/mkbootimg

# gcc mkbootimg.c -o mkbootimg
# gcc unmkbootimg.c -o unmkbootimg
# cp ./mkbootimg /usr/local/bin/
# cp ./unmkbootimg /usr/local/bin/

Structure of Recovery.img

+-----------------+ 
| boot header     | 1 page
+-----------------+
| kernel          | n pages  
+-----------------+
| ramdisk         | m pages  
+-----------------+
| second stage    | o pages
+-----------------+

n = (kernel_size + page_size - 1) / page_size
m = (ramdisk_size + page_size - 1) / page_size
o = (second_size + page_size - 1) / page_size

0. all entities are page_size aligned in flash
1. kernel and ramdisk are required (size != 0)
2. second is optional (second_size == 0 -> no second)

# cat /proc/mtd

Unmkbootimg

# mkdir -p unpacked-recovery && rm -rf unpacked-recovery/* && cd unpacked-recovery

# unmkbootimg -i ../recovery.img 
kernel written to 'kernel' (4528360 bytes)
ramdisk written to 'ramdisk.cpio.gz' (4202750 bytes)

To rebuild this boot image, you can use the command:
  mkbootimg --base 0 --pagesize 16384 --kernel_offset 0x60408000 --ramdisk_offset 0x62000000 --second_offset 0x60f00000 --tags_offset 0x60088000 --kernel kernel --ramdisk ramdisk.cpio.gz -o ../recovery.img

The "unmkbootimg" command will split the image file into kernel and ramdisk parts.

# ls -l
total 8532
-rw-r--r-- 1 root root 4528360 12月 14 14:22 kernel
-rw-r--r-- 1 root root 4202750 12月 14 14:22 ramdisk.cpio.gz

Decode Ramdisk

# mkdir -p ramdisk && rm -rf ramdisk/*
# cd ramdisk
# gunzip -c ../ramdisk.cpio.gz | cpio -i
12039 blocks

# ls
charger                           property_contexts
default.prop                      res
etc                               rk30xxnand_ko.ko.3.10.0
file_contexts                     sbin
fstab.rk30board.bootmode.emmc     seapp_contexts
fstab.rk30board.bootmode.unknown  sepolicy
init                              tmp
init.bootmode.emmc.rc             ueventd.rc
init.bootmode.unknown.rc          ueventd.rk30board.rc
init.rc

For now you can hack the ramdisk (initramfs) in the recovery.img .

Compress the Files Back into Ramdisk

# find . | cpio -o -H newc | gzip > ../ramdisk.cpio.gz
12039 blocks
# rm -rf ramdisk

Mkbootimg

# cd unpacked-recovery
# mkbootimg --base 0 --pagesize 16384 --kernel_offset 0x60408000 --ramdisk_offset 0x62000000 --second_offset 0x60f00000 --tags_offset 0x60088000 --kernel kernel --ramdisk ramdisk.cpio.gz -o ../recovery.img

Flash Recovery.img

adb shell chmod 777 /mnt/asec/
adb push recovery.img /mnt/asec/recovery.img
adb shell dd if=/mnt/asec/recovery.img of=/dev/block/rknand_recovery
adb shell rm -rf /mnt/asec/recovery.img
adb reboot

參考資料:
http://www.imajeenyus.com/computer/20130301_android_tablet/android/unpack_repack_recovery_image.html

Email: jasonc@mail2000.com.tw