kdev

Welcome to the kdev readme!

Introduction

Kdev is a python based Linux kernel build script. You can use this script to build kernel and rootfs image for a supported target platform. It also has support for creating kernel image in both efi and bootimage format.

Enviroment setup

Get kdev repo

git clone --recursive https://github.com/knsathya/kdev.git
cd kdev
ln -s [path to your kernel] kernel

Library requirements

python > 2.7
sudo apt-get install virtualenv
mkdir ~/pyenv
virtualenv --python=python2.7 ~/pyenv
source ~/pyenv/bin/activate
pip install -r scripts/requirements.txt

How to build

First set your environment by sourcing scripts/setenv.sh

source ~/pyenv/bin/activate; source scripts/setenv.sh

You can build kdev image(rootfs + bzImage) by executing the build.py. Before you run this script you should make sure you have valid "kernel" project checked out out in the current directory.

python build.py

Once you run this script, it will parse the target-recipes folder and will display the list of valid build targets and request user to select the build target. You can also skip this selection by setting the following environment variable.

export SELECTED_TARGET_DIR=target-recipes/<soc>/<board>/

To get more info on various options of build.py,

python build.py -h

usage: build.py [-h] [-k KERNEL_DIR] [-r ROOTFS_DIR] [-o OUT_DIR]
                [-t RECIPE_DIR] [--build-efi] [--skip-build-rootfs] [--log]
                [-v]

kdev build app

optional arguments:
  -h, --help            show this help message and exit
  -k KERNEL_DIR, --kernel-dir KERNEL_DIR
                        kernel source directory
  -r ROOTFS_DIR, --rootfs-dir ROOTFS_DIR
                        rootfs directory
  -o OUT_DIR, --out-dir OUT_DIR
                        out directory
  -t RECIPE_DIR, --target-recipe RECIPE_DIR
                        target recipe directory
  --build-efi           Build efi image
  --skip-build-rootfs   skip building rootfs
  --log                 logs to file
  -v, --version         show program's version number and exit

After successfully running this script, it will generate the kdev images in the "out" folder. For example, for bxt_joule_pr0, you can find images under,

out/bxt_joule_pr0/images

Following are the list of out dir content.

• images/bzImage.efi - kernel image with EFI stub.
• kernel-obj - obj directory for kernel.
• rootfs - copy of rootfs.
• images/rootfs.img - cpio.gz format of rootfs image.
• images/rootfs.img.ext2 - rootfs image in ext2 format.

How to add a new target recipe

To create a new target recipe, create a separate target folder under "target-recipes" in the following format.

mkdir target-recipes/<soc>/<board>

Each target recipe should contain following files. If one of this file is missing, then it will not be considered as a valid target.

board.cfg - config file to specify board params
cmdline - kernel command line parameters
kernel.config - Target kernel config

Following is the board.cfg format.

[board_options]
arch = x86_64
soc = bxt 
board = joule
version = pr0 
target_name = ${soc}_${board}_${version}

[build_options]
build_efi = true
build_bootimg = true
build_yocto = true
kernel_config = ./kernel.config
kernel_diffconfig =
cmdline = ./cmdline

[rootfs_options]
use_initramfs = false
rootfs_name = busybox
gen_cpioimage = true
gen_hdimage = true

[bootimg_options]
base = 0x10000000
kernel_offset = 0x00008000
ramdisk_offset = 0x01000000
second_offset =
os_version = "v1.0"
os_patch_level = "1" 
tags_offset =
pagesize = 4096
use_id = false

Testing kernel+rootfs on target device

To test the kernel on target device create a USB drive with two partitions one for bzImage.efi (boot) and another to host the rootfs (linux filesystem) using the fdisk utility

1. Connect USB drive to Linux host machine

2. Check mount node name (ex . /dev/sde )

   dmesg | tail -20

3. Create partitions

   fdisk /dev/sde

4. Choose option n to create new partition of a desired size

5. Choose option n again to create another partition

6. Save changes and exit fdisk utility

7. Format the first partition with vfat type

   sudo mkfs.vfat -I -n BOOT /dev/sdx1 (here x to be changed with your device node number)

8. Format the second partion using ext4

   sudo mkfs.ext4 -v -L ROOTFS /dev/sdx2

9. Copy bzImage to first partition

   sudo mount /dev/sdx1 boot sudo cp bzImage boot

10. Write Rootfs contents to second partition

    dd if=rootfs.img.ext2 of=/dev/sdx2 bs=4096 conv=noerror

11. Unmount and eject the drive. Your drive is ready to be used as a EFI bootable disk . To boot from USB from EFI shell, execute a startup.nsh with the boot command. A sample startup.nsh script content is shown below

    @echo -off
    mode 80 25
    ;clean the screen
    
    cls
    fs0:
    echo "Loading the kernel............"
    bzImage.efi root=/dev/sda2 rw console=ttyS2,115200n8 rootwait init=/sbin/init
    echo "........Done "
    echo "Kernel loading Completed"
    :END
    

12. To test USB device you can make use of tools in https://gitlab.com/felipebalbi/usb-tools. Ensure that libcomposite and Zero gadget modules are loaded prior to running the tests and the OTG mode is set to "device".

    insmod /lib/modules/4.20.0-rc4-quilt-2e5dc0ac-00064-g1ceae536e4c5/kernel/drivers/usb/gadget/libcomposite.ko

    insmod /lib/modules/4.20.0-rc4-quilt-2e5dc0ac-00064-g1ceae536e4c5/kernel/drivers/usb/gadget/legacy/g_zero.ko

    echo device > /sys/class/usb_role/intel_xhci_usb_sw-role-switch/role