kimconcepcion / kernelhacking

Repo for Linux kernel hacking...

KernelHacking

Repo for Linux kernel hacking on Beaglebone Black...

1. Get cross compiler (I use gcc with support for hard floating points from Linaro, works on Centos 8 & Fedora 40.7)

$ wget https://releases.linaro.org/components/toolchain/binaries/7.5-2019.12/arm-linux-gnueabihf/gcc-linaro-7.5.0-2019.12-x86_64_arm-linux-gnueabihf.tar.xz

2. Clone Beagleboard kernel

$ git clone https://github.com/beagleboard/linux.git

3. Checkout kernel version on your Beagle e.g. 4.19

$ git checkout 4.19

4. Get defconfig file from linux-headers and copy into .config in Beagleboard kernel

Get defconfig from target & transfer to build machine with e.g. scp

$ zcat /proc/config.gz > beagle_config

$ cp beagle_config .config

5. Build kernel image (use -j with 2x cpu cores to speed up build)

$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- LOADADDR=0x80008000 uImage -j<2xcores>

6. Build device tree (use -j with 2x cpu cores to speed up build)

$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- uImage dtb.am335x-boneblack -j<2xcores>

7. Build kernel modules (use -j with 2x cpu cores to speed up build)

$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- INSTALL_MOD_PATH= modules_install -j<2xcores>

8. Root file system

Download already built RFS here: https://www.dropbox.com/s/k93doprl261hwn2/rootfs.tar.xz?dl=0

$ tar -xf rootfs.tar.xz

$ sudo cp -r rootfs <path-to-sd_card>

$ cd <path-to-sd_card>/rootfs

$ sudo mv ./* ../

$ cd ..

$ sudo rmdir rootfs

9. Prepare sd_card (card capacity should atleast be greater than 2gb!)

First step is to delete umount all partitions on the card & then delete all partitions. Remember to take backups of the content on the card if necessary.

Second step is to create atleast two partitions for boot files and for the root file system. Boot partition is called BOOT & root file system can be called RFS.

I personally use gparted to configure my sd card. Partition setup with 60mb for BOOT and 14gb for RFS: