How to Extract a Device Tree File from Android Firmware Files

Up to now, all our cheap Android devices were based on older Linux kernel (3.0.x, 3.4.x) that still used board files (arch/arm/board, but we’ve recently seen companies like Amlogic and Rockchip release source code with Linux kernel 3.10.x. One of the key differences between these version are the move from board files to flattened device tree and multi-platform support. If it is fully implemented, a single kernel image should be able to boot multiple hardware platforms, and all low level configuration handled by the device tree file. Since I’ve connected the serial port of Tronsmart Vega S89 for debugging, and it’s a slow news day, I thought I might try to boot the Linux kernel I compiled myself, but one of the challenge was to get the device tree file. I’ll show how to extract it from the firmware. It should also be possible to get it directly from the flash, but “cat /proc/mtd” does not show a complete list of partition as in previous versions.

I’ve performed the steps below in Ubuntu 14.04. The first thing is to install some tools: the device tree compiler that we’ll use to decompile the dtb (binary) file into a dtd (text) file, and split_bootimg.pl a standard PERL script to extract files from boot.img:


I’ll use M8 / TM8 firmware (Amlogic S802) as an example. The exact procedure will vary between firmware files, but if you can boot.img, the procedure should be platform independent and work for any ARM SoC. After having downloaded and extracted the firmware file (TM8 ap6330_03102014A_0410_ROOT.rar), let’s create a working directory, and unzip the “OTA” file.


We now get a bunch of files, including boot.img. Great! Time to run split_bootimg.pl script to extract its content:


So we’ve got the kernel, a ramdisk, and a “second file” that happens to be the dtb file. We can now decompile it with dtc (device tree compiler) as follows:


That’s it. Here’s M8 device tree file.

I’ve done the same for Tronsmart Vega S89 (Elite). S89 firmware is usually distributed as an IMG file to be used with AML Flash Burning tool, but I haven’t found a way to extract such file yet. however, I’ve found an “OTA” firmware, to be updated via SD Card, on freaktab, and could extract the device tree file for Tronsmart Vega S89 Elite & Vega S89. Both M8 and S89 Elite DTD files are very similar, but the maximum CPU frequency seems to be higher in M8, and there are other apparently minor differences. Vega S89 DTD file appears to be much different however.

Support CNX Software - Donate via PayPal, become a Patron on Patreon, or buy review samples
Subscribe
Notify of
guest
57 Comments
oldest
newest most voted
m][sko
6 years ago

Did you finally boot up fully working kernel now?

Alain Theriault
Alain Theriault
6 years ago

This looks like fun… let me know how I can help.

gizmomelb
gizmomelb
6 years ago

hey cnxsoft, don’t know if it’s of any use – but I extracted the partitions with boot.img etc. on my Beelink 16GB (Tronsmart Standard S89 hardware-a-like) if those files are of any use to putter around in?

I’m mostly a windows guy, I need to set up a *nix box for playing around on (mm.. maybe I could use my raspberry pi for that).

Dante
6 years ago

M8 is better then S89 Elite?
Antutu benchmark? I Can’t find anything good about m8 (S802).

Thanks

gizmomelb
gizmomelb
6 years ago

hey cnxsoft – I extracted the boot.img from the NAND using adb shell and some help from Finless Bob on freaktab.

http://www.freaktab.com/showthread.php?12472-factory-default-firmware-images&highlight=

I have the extracted files from the 100k4 NAND, I’ve since updated to 101k4 but haven’t extracted the files again (is there any point if we can unpack the firmware update?).

I’m happy to help out in any way I can. I have two Beelink M8 round boxes, one for testing – my USB -> serial cable/adapter arrived today as I need to update my Gotek floppy emulator (another project).

gizmomelb
gizmomelb
6 years ago

@Dante

Hi Dante! The square S802 boxes are going by the M8 brand, however Beelink have a round (Tronsmart S89 clone essentially – same motherboard, different firmware but you can flash with the S89 firmware) S802 device which is named M8 (and another one named S82). Confusing!

gizmomelb
gizmomelb
6 years ago

Hi cnxsoft – yeah I’ll go virtualbox or if I look around I can probably find an old VMDK VMware ubuntu image I was using to play around with thin client firmware from quite a few years back.

m][sko
6 years ago


I don’t have any problem with debian 7.0 armhf rootfs with kernel 3.0 over NFS
But it is maybe that you use initrd https://www.ibm.com/developerworks/library/l-initrd/
As I build most amlogic modules as static as I don’t need any hotplug 🙂

I didn’t use linaro(Ubuntu).

m][sko
6 years ago

@m][sko
my uboot paramters for AML8726-MX,
http://pastebin.com/V6bhWYqh

John
John
5 years ago

I have a problem: When run the command “split_bootimg.pl boot.img” i’m getting just kernel and ramdisk. I don’t have the second.gz file. What can i do?

John
John
5 years ago


Yes, my kernel version is less then 3.7. I have 3.4.5. In this what can i do to make my device tree?

Joel
Joel
5 years ago

I am in the same situation….no boot.img-second.gz file. LG Optimus Fx3Q, Android 4.1.2, kernel version unknown (I am running a custom one, but probably less than 3.7).

So all it takes is recompiling the kernel against a newer source? Are there any roadblocks/considerations/gremlins associated with such a task?

Joel
Joel
5 years ago

Would merging the kernel source with say, the Optimus F6 (a similar device, which I think has a 3.7+ kernel out there) be any easier? Or is that what you had in mind with my original question?

I’ve compiled Linux Kernels before (the Debian way), so merging the kernel sources, although daunting, seems less of a chore than writing a device tree by hand (especially when I don’t know where to start). Sadly, although similar, the F6 tree does not work for this device (ROM won’t compile).

Thanks for your opinion.

Jon Smirl
5 years ago

Check and see if the device tree is exposed in /proc. Exposing it is a kernel option. Also the dtc compiler is part of the Linux kernel tree. You don’t have to build it separately. It is possible to append the DTB onto the end of the kernel image, in that case it is not a separate file. It is still there, just harder to get to. Just because these chips are on Linux 3.10 does not force them onto device tree. I have several systems here still using board files on 3.10. I really, really wish these vendors could… Read more »

Li
Li
5 years ago

I got the blog has incorrect magic number error.

dtc -I dtb boot.img-second.gz -O dts -o meson8.dtd
DTC: dtb->dts on file “boot.img-second.gz”
FATAL ERROR: Blob has incorrect magic number

mdel
mdel
4 years ago

cnxsoft : I’ve done the same for Tronsmart Vega S89 (Elite). S89 firmware is usually distributed as an IMG file to be used with AML Flash Burning tool, but I haven’t found a way to extract such file yet A quick follow up on that, it’s only for Amlogic but i found a way to get your dtb out of an .img update (not ota zip) blob. I’m using Amlogic Customization Tool (apparently official tool sourced from some russian forums). It’s purpose is to edit an existing img data file and basically have access to any part of the data,… Read more »

ugh
ugh
4 years ago

I try to copy text from the examples, and a bar appears over what I’m trying to copy. I select from below, copy, and it copies a bunch of line numbers. I triple-click to select a line, and the whole thing fades into a different style and discards my selection, so I have to make it again. I try to select another box, the bar appears and moves what I just tried to select down. Dude, they’re boxes of text. Stop trying to be more clever than you are with this nonsense. It’s bad enough that you have a wall… Read more »

Jeff
Jeff
4 years ago

cnxsoft,

I will like to know, I have three different boxes, two uses the same S802 and one S812 and have Openelec.zip for all and the original .img and .zip. The architecture I reckon are all different ie: Ethernet chip etc.

I was able to pull the DTD for the M8 from your instructions above from the original K200-ota file fine, and I am sure can do the same for OpenELEC.zip. my question is.

If I have the LibreELEC.zip how can I put this DTD into it to boot? As I am having bootings issues with LE on the M8.

Jeff
Jeff
4 years ago

cnxsoft,

What I will like you to help me with is how to put this DTD I pulled into the a source code. You showed us how to pull the DTD of any Amlogic FW; now, can you show us how we can put this information into any source code.

Kutlay
Kutlay
4 years ago

i have a mtk device and i cant build kernel and our provider doesnt send an ota update how can i do? Can i try fake ota update? Thanks..

Annonymous
Annonymous
3 years ago

I didn’t get this command
” Writing boot.img-second.gz … complete. ”

I got the kernel and ramdisk file. so no dtb file extracted.
Well. I need these all foe compiling CM13

Vincent
Vincent
3 years ago

I didn’t get this command
” Writing boot.img-second.gz … complete. ”

I got the kernel and ramdisk file. so no dtb file extracted.

Help!

Vincent
Vincent
3 years ago


Hi,

Thanks for the quick reply. The device is Xiaomi Mi 5, Kernel version 3.18.20

So what should be done in my case?

Thanks!

Shams Sayied
Shams Sayied
3 years ago

Hi, My entire mobile firmware file link is here ==>

https://drive.google.com/file/d/0B1dRSby1cq8jU3FiOG1fZjFsVEk/view?usp=sharing

Would you please give me device and vendor tree??

Shams Sayied
Shams Sayied
3 years ago


Bro there is no kernel for my device.

MBD
MBD
3 years ago

Why my Second size: 0 (0x00000000)?

Page size: 2048 (0x00000800)
Kernel size: 4759152 (0x00489e70)
Ramdisk size: 1690049 (0x0019c9c1)
Second size: 0 (0x00000000)
Board name:
Command line:
Writing boot.img-kernel … complete.
Writing boot.img-ramdisk.gz … complete.

—-
I used boot.img size 8M from Samsung S3 device

eugene28
eugene28
2 years ago

dtb.img file extracted from boot.img this way, not compatible with latest Libreelec, Ubuntu images. Do you know why?

Tony
Tony
2 years ago

What is the use of this .dts file?
How to use it to compile kernel without source using a similar device’s kernel source ?

orinoco77
orinoco77
2 years ago

I’ve been searching high and low for a way to make an 800×480 LCD with HDMI input work with my h96 pro TV stick, and I’ve got an idea that the reason might be that the resolution the LCD needs isn’t defined in the DTS/DTB. Does that sound likely? I suspect the stick has been built just to deal with modern resolutions for TVs, of 720p and above (up to 4K with this one), and it has no information about how to output to a display that reports such a low resolution. I’ve gone through all the other things I… Read more »

Advertisements