Examples for: Learning KVM - implement your own Linux kernel
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hypervisor Check IO permission in hypervisor.c Oct 23, 2018
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README.md

KVM-Kernel Example

The source code are examples on my blog: Learning KVM - implement your own Linux kernel.

I've described how to implement a KVM-based hypervisor and key points to implement Linux kernel on my blog. You can leave comments in the blog or file issues here if you have questions or find any bugs.

Dir

Hypervisor

The KVM-based hypervisor, its role is like qemu-system.

Kernel

A extremely simple Linux kernel, supports few syscalls.

User

Simple ELF(s) for testing our kernel. Pre-built user program was provided, and you can re-generate by the following commands:

$ pip2 install pwntools
$ cd user
$ ./gen.py

NOTE: You have to install Python 2.x in advance.

Setup

Check KVM support

Check if your CPU supports virtualization:

$ egrep '(vmx|svm)' /proc/cpuinfo

NOTE: CPUs in VM might not support virtualization (i.e. no nested virtualization). For example, EC2 on AWS doesn't support using KVM.

Install KVM device

Check if KVM device exists:

$ ls -la /dev/kvm

If /dev/kvm is not found, you can enable it (on Ubuntu) with:

$ sudo apt install qemu-kvm

If you are not root, you need to add yourself into the kvm group to have permission for accessing /dev/kvm.

$ sudo usermod -a -G kvm `whoami`

Remember to logout and login to have the group changing effective.

How to run

$ git clone https://github.com/david942j/kvm-kernel-example
$ cd kvm-kernel-example && make
$ hypervisor/hypervisor.elf kernel/kernel.bin user/orw.elf /etc/os-release
# NAME="Ubuntu"
# VERSION="18.04.1 LTS (Bionic Beaver)"
# ID=ubuntu
# ID_LIKE=debian
# PRETTY_NAME="Ubuntu 18.04.1 LTS"
# VERSION_ID="18.04"
# HOME_URL="https://www.ubuntu.com/"
# SUPPORT_URL="https://help.ubuntu.com/"
# BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
# PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
# VERSION_CODENAME=bionic
# UBUNTU_CODENAME=bionic
# +++ exited with 0 +++

Environment

I only tested the code on Ubuntu 18.04, but I expected it works on all KVM-supported x86 Linux distributions. File an issue if you find it's not true.