n132 / KZone

A Play Ground for learning Kernel.

KZone

A Play Ground for Learning Kernel. The infrastructure to play with the Linux kernel.

You can write and compile your kernel module to debug some features you are interested at with this repository.

I steal the scripts from RetSpill and KHeap

How to use this repo

Create an Image

cd scripts && ./create-image.sh && popd

Compile the Linux Kernel

cd kernel && ./build.sh v5.4.268
cp ./kernel-v5.4.268/arch/x86/boot/bzImage ../zone
popd

Run the kernel in a VM

cd zone
./kz

Compile your kernel modules

cd zone/module/
make
popd

Play with your modules

cd zone
./kz cp ./module/ko_n132.ko

Create an Image

Use the script to create an image.

./create-image.sh --distribution bookworm

You can mount and umount to modify the image:

sudo mount ./bookworm.img /mnt/
# Modify the content of the image
sudo umount  /mnt/

Compile Linux Kernel

Use this script to compile the kernel.

Example, ./build.sh v5.4.268.

Sometimes (v5.4.268 is fine) you need to patch the default config for some new versions or compile the modules: You may need to compile the modules and copy them to the disk imge, which may also require you to expand your disk image to store these compiled modules: aka modify the script and recreate the disk. Kindly attach the commands you may need if you really want to use the oldconfig:

make CC=clang -j$(nproc) modules_install INSTALL_MOD_PATH=$where_you_mount_the_disk_img

Script kz

kz support 3 sub-command:

• kz
  • Same as kz run
• kz run
  • Start a VM
  • Using the fist disk image at $(pwd)/img/*.img
  • Using the first Kernel Image at $(pwd)/bzImage
• kz cp <host_file>
  • Copy the file on host to the VM
• kz sh
  • SSH connect to the VM

Tips for Kernel Debugging

vmlinux

• Using gdb vmlinux to debug the kernel makes life easier
• If you compile the kernel with keeping debug symbols, you'll find vmlinux at the root of source directory

extract-vmlinux

• extract-vmlinux is a tool that extract vmlinux from bzImage.
• Usgae: extract-vmlinux ./bzImage > vmlinux.raw

vmlinux-to-elf

• A tool to recover symbols from kallsyms
• Installation: pip3 install --upgrade git+https://github.com/marin-m/vmlinux-to-elf
• Usage: vmlinux-to-elf ./vmlinux.raw vmlinux

Template of x.sh

Format: .img

#!/bin/sh
gcc ./fs/exp.c -masm=intel -o ./fs/exp -lx -lpthread --static -w &&\
echo "[+] Compile - Done" &&\
cd /home/n132/tap/KZone/scripts
sudo mount buster.img fs
sleep .5
cp /home/n132/tap/KZone/zone/fs/exp /home/n132/tap/KZone/scripts/fs
sudo umount fs
cd /home/n132/tap/KZone/zone/
echo "[+] repacking - Done" &&\
echo "[+] Filesystem - Done" &&\
echo "[...] run.sh" &&\
sudo ./kz run

TODO

• support lower versions of kernel