[HOWTO][KERNEL][G800F][exynos] Custom kernel tutorial topic

This is a short tutorial on how to compile and flash a (customized) Linux kernel on your G800F.
Note that this tutorial is only for the G800F as G800H/M/Y/... have a totally different architecture (SoC,...).

Toolchain
First of all get a decent toolchain (gcc,...). There are some prebuilt ones at android.googlesource.com.
If you have git installed fetch the arm-eabi-4.6 toolchain with:

Code:

---

git clone https://android.googlesource.com/platform/prebuilts/gcc/linux-x86/arm/arm-eabi-4.6

---

Other toolchains might work but I had no luck with a Linaro toolchain optimized for the Cortex-A7 (ARM-architecture of the Exynos 3470) - the kernel did not boot at all.
Also the arm-eabi-4.8 toolchain from android.googlesource.com aborted with a compile error, so use the 4.6 version.

Fetch the Linux Kernel sources
Now you have to fetch the kernel sources. At the moment there are only the official sources from Samsung's open source server.
http://opensource.samsung.com/recept...Value=SM-G800F

Select a source package:
The source packages at this server contain the kernel sources (Kernel.tar.gz), some part of the Android system (Platform.tar.gz) and some build instructions (README_*). There are multiple versions of the source packages. You can find an explanation of the versioning scheme here: samsung-firmware-version-number.html

For example the version part of a source package G800FXXU1ANG1 is NG1 which stands for N=2014, G=July, 1=1st release.
G800FXXU1ANJ2 is N=2014, J=October, 2nd release.

In addition Samsung adds country code post-fixes like "_MEA" which might contain regional adaptions. See http://forum.xda-developers.com/show...25&postcount=5 for an explanation and list of country codes. For example MEA probably stands for "MIDDLE EAST ASIA".

So the newest source packages are G800FXXU1ANG1 and G800FXXU1ANG4 (MEA). I compared the kernel sources of both packages and found no difference. Seems as if only the Android part was changed. Both are from July so not very up-to-date. At least they are based on a 3.4.39 kernel which matches the kernel version of G800FXXU1ANL1.

Mirror:
Note that downloading a source package from Samsung's Open Source server takes a lot of time as the download speed is very poor. It took 12-24 hours for me.
You can also download the sources from my github repository:
https://github.com/tobigun/samsung-kernel-smg800f

At the moment the master contains the G800FXXU1ANG1 kernel sources but might be updated as soon as a newer kernel source is released.

Compile the Kernel
Prepare the build by applying the S5 Mini kernel config:

Code:

---

ARCH=arm CROSS_COMPILE=<PATH_TO_TOOLCHAIN>/bin/arm-eabi- make kminilte_00_defconfig

---

If you want to change the config now, you can do this with:

Code:

---

ARCH=arm CROSS_COMPILE=<PATH_TO_TOOLCHAIN>/bin/arm-eabi- make menuconfig

---

After you have done some changes to the kernel sources you can build it with:

Code:

---

ARCH=arm CROSS_COMPILE=<PATH_TO_TOOLCHAIN>/bin/arm-eabi- make -j4

---

If you do not want to build with multiple CPUs you can remove the "-j4" from the command line (which also is handy if an error occurred).
In either case the resulting kernel image will be in "arch/arm/boot/zImage".

Note that kernel module support is disabled in the S5 mini config so everything you need (all drivers, ...) is in the zImage. There is no need to copy additional kernel modules to the filesystem.

Flashing the Kernel
Almost done. It is not possible to flash the kernel image directly. Instead you have to put the kernel image and a ramdisk together into a flasable boot.img. The easiest way to get such a boot.img is to use an existing boot.img and replace just the kernel image.

1. Get a decent boot.img
There are at least two ways:

a) Download the current firmware image from SamMobile (http://www.sammobile.com/firmwares/database/SM-G800F/) and extract the boot.img. With 7-zip there will be an error message if you extract the .tar.md5 inside the zip - just ignore the message and extract the boot.img file.

b) Extract the current boot.img from the device's flash with (root required):

• Connect to the device (with "adb shell" or ssh).


• Then copy the contents of the boot-partition to a file:
  
  
  

  Code:

  
  

  ---

  dd if=/dev/block/mmcblk0p9 of=boot.img

  ---

  
  

2. Replace kernel image
For this step AIK (Android Image Kitchen) is required.

• Download it at http://forum.xda-developers.com/show....php?t=2073775. Probably you want AIK-Linux-v1.7-ALL.tar.gz (or newer).


• Extract the files.

Now unpack the boot image, replace the kernel image and repack it (with the original ramdisk) to a new boot.img:

Code:

---

./unpackimg.sh boot.img
cp <KERNEL_BUILD_DIR>/arch/arm/boot/zImage split_img/boot.img-zImage  (Note: the zImage name inside split_img might differ)
./repackimg.sh --original

---

The new boot.img is "image-new.img". Rename it to boot.img and flash it.

3. Flash new boot.img
Important notice:
- You flash this image at your own responsibility. I am not responsible for any damage that might be caused by flashing this image (bricked device, lost data, ...)
- Flashing this kernel image will trigger the KNOX counter, so your warranty will be void.
- The image is only for S5 Mini SM-G800F (Exynos)
- The kernel is not tested well. It might be instable, crash your device, drain your battery, or even might damage your smartphone (e.g. if an OTG device drains too much power)
- Backup your data before flashing
- Make sure you have the current firmware of your device (e.g. from SamMobile) so you can flash it back in case something goes wrong.

There are multiple ways to flash the boot.img to your device:
a) From recovery with an update.zip
b) Using Odin
c) Directly with dd

a) From recovery with an update.zip
TODO

b) Using Odin
At least some versions of Odin3 (e.g. v3.07) need a tar.md5 instead of a "simple" tar file. Although a simple tar-file can be selected in Odin, the image will not be flashed correctly.
To create a tar.md5 file download CF-Auto-Root)[*]Reboot your device into Odin mode: turn off your device, then press Volume-Down + Home + Power button at the same time and release them. Confirm the following message with the Volume-Up button.[*]Connect your device to your PC via USB[*]Make sure the device driver's are installed on your PC[*]Start Odin

• Select PDA and select the kernel image (boot.tar.md5)


• Check that only "Auto Reboot" and "F. Reset Time" is set


• Click on "Start": the kernel image should be flashed now and the device should reboot afterwards

[/LIST]
c) Directly with dd

• Connect to the device (with "adb shell" or ssh).


• Then copy the contents of the boot.img file to the boot-partition:
  
  
  

  Code:

  
  

  ---

  dd if=boot.img of=/dev/block/mmcblk0p9

  ---

  
  


• Reboot

Done
You can now check in "Settings - Device Info - Kernel-Version" if your kernel is used.

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