For this post, we assume that you already have a working root filesystem as we did in “Building kernel and filesystem using Yocto for Raspberry Pi / Creating Embedded Linux for RPi using Yocto” since we just want to showcase how to manually compile kernel for RPi.
Download Linux kernel source code from raspberry pi git
$ mkdir -p /home/myuser/rpi $ cd /home/myuser/rpi $ git clone git://github.com/raspberrypi/linux.git --depth=1 This will download the default HEAD branch from the remote repository.
$ cd linux $ git branch
* rpi-4.9.ydownloading toolchain
$ cd /home/myuser/rpi $ git clone https://github.com/raspberrypi/tools --depth 1 $ cd tools$ git branch
* masterexport toolchain path
$ export PATH=$PATH:/home/myuser/rpi/tools/arm-bcm2708/arm-bcm2708-linux-gnueabi/bin Configuring Linux Kernel
$ cd linux default configuration file for RPi3 is arch/arm/configs/bcm2709_defconfig
$ make ARCH=arm CROSS_COMPILE=arm-bcm2708-linux-gnueabi- bcm2709_defconfig Above command will do the default configuration of kernel for compilation for RPi
Now, we will compile the kernel to create kernel binary using below command,
$ make ARCH=arm CROSS_COMPILE=arm-bcm2708-linux-gnueabi- zImage modules dtbs This command will create, kernel zImage at arch/arm/boot/zImage
$ file arch/arm/boot/zImage
arch/arm/boot/zImage: Linux kernel ARM boot executable zImage (little-endian)Now, we have to copy this image into first partition of the SD card by using standard name as “kernel7.img” as,
$ sudo cp -r arch/arm/boot/zImage /media/myuser/raspberrypi/kernel7.img Assuming that first partition of sdcard is mounted at /media/myuser/raspberrypi/ ( you can check same using df -h command )
Now, put unmount this SD card and put to RPi and power ON RPi,
You can check now the booted kernel is what we manually compiled as,
root@raspberrypi3:~# cat /proc/version
Linux version 4.9.45-v7+ (myuser@myhost) (gcc version 4.7.1 20120402 (prerelease) (crosstool-NG 1.15.2) )
#1 SMP Mon Aug 28 19:52:58 IST 2017
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