Builds an ARM kernel intended to allow QEMU emulation of Raspberry Pi OS images (typically Raspbian). rpiq-kernel is based off the beloved qemu-rpi-kernel, but at this point has wildly diverged.
The rpiq-kernel is intended for use with QEMU virt devices, and so includes the necessary kernel configs. This allows you to spin up VMs that more closely resemble Raspberry Pi hardware in its specs as compared to what qemu-rpi-kernel allows. It tracks the rpi-4.19.y branch, and uses the vexpress board config. In addition to the virt device configs, rpiq-kernel also enables some features I selfishly need, such as Docker capability and XFS. I am open to piling more dishes into the kitchen sink.
The Raspberry Pi published Linux kernel is in a git submodule, so you'll need to make sure that you've pulled it in addition to this repo. See regular git submodule documentation.
You'll need an ARM cross compiler. On Debian/Ubuntu systems, you
install the gcc-arm-linux-gnueabihf package.
You'll also need QEMU, natch, which should be installable easily by any reasonable Linux distribution, or Homebrew if you've chosen the cushy life of an OS X user.
Building is easy:
$ ./build-rpiq-kernel
... wait for it to compile (~8m on my 2016-ish laptop)
$ ls output/
rpiq-kernel-4.19.97-r2 vexpress-v2p-ca9.dtb
The rpiq-kernel- file is your kernel. The .dtb file is used if
you're emulating a VExpress board, but if you use virt emulation you
don't need it.
If you have a Raspbian image, you can run it like so:
$ qemu-system-arm -M virt -m 1024 -drive file=2019-09-26-raspbian-buster-lite.img,if=none,format=raw,id=disk -device virtio-blk-device,drive=disk -netdev user,id=network -device virtio-net-device,netdev=network -device virtio-rng-pci -kernel output/rpiq-kernel-4.19.97-r2 -append 'console=ttyAMA0,115200 root=/dev/vda2' -nographic
Or, using the convenience script:
$ ./run-qemu output/rpiq-kernel-4.19.97-r2 2019-09-26-raspbian-buster-lite.img
This starts QEMU up and boots via the text-only serial console. It does not appear to be possible to get QEMU to set up a display in ARM mode, so you're stuck with the serial console.
If you want to start up QEMU as a VExpress board rather than virt, then:
$ qemu-system-arm -M vexpress-a9 -cpu cortex-a9 -dtb output/vexpress-v2p-ca9.dtb -m 1024 -drive file=2019-09-26-raspbian-buster-lite.img,if=sd,format=raw,id=disk -net user -kernel output/rpiq-kernel-4.19.97-r2 -append 'console=ttyAMA0,115200 root=/dev/mmcblk0p2' -nographic
But honestly I don't know why you'd want to do that cause it's slower.
You can add extra kernel configs to a custom_config file. For
example:
$ echo "CONFIG_BTRFS_FS=y" > custom_config
Just in case you don't have a Linux machine, you can run the build in
a Vagrant VM with the supplied Vagrantfile.
First, make sure that you've set up git submodules on your host machine and have the Linux source. Git performance in Vagrant VMs can be really bad.
$ vagrant up
$ vagrant ssh
... logs into the VM
$ cd /vagrant
$ ./build-rpiq-kernel
... ctrl-d to log out
$ vagrant destroy
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Raspberry Pi Foundation Linux kernel: https://github.com/raspberrypi/linux
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Info about virt and ARM builds: https://wiki.qemu.org/Documentation/Platforms/ARM
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Fantastic reference on how QEMU devices work and the inspiration for virt: https://www.qemu.org/2018/02/09/understanding-qemu-devices/
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rpiq-kernel has only been tested with Raspbian and private RPi compatible Linuxes. Notably, NOOBS is untested.
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Tested with QEMU that ships with Ubuntu Bionic (version 2.11+), and hand built QEMU version 4+.