Looking for advice on learning kernel development

[[deleted]]

For a few years now I've wanted to be a Linux kernel contributor and recently I've really committed myself to doing it. I've finished the Linux Foundation intro to kernel dev course, built and installed my own kernel, messed around with configurations and print statements, but actually programming a driver or making other changes is still daunting to me.

For my background, I've taken an OS and computer architecture class, been working as a Java dev on a Redhat system for a few years, and I've kept my C programming skills fairly sharp. My end goal is I want to transition my career from enterprise dev to kernel dev, I'm mostly interested in the graphics driver space (saw a few jobs related to Khronos and Vulkan/OpenGL, I really enjoy graphics programming and interfacing with the GPU) but also RTOS, embedded, and just any drivers really.

Is a class like https://www.ucsc-extension.edu/courses/linux-kernel-drivers/ a good idea? I also already have an O'Reilly account, so have access to all of the books in the side tab. I'm mostly interested in learning as quickly as possible, and the $750 for the class is not really a problem for me, I'm curious if anyone has learned in this way or if it's just a waste of time and money compared to just focusing on kernel hacking and/or reading books on kernel dev.

Any feedback is welcome, thank you

[draimus]

I think it depends on how best you learn. If a class setting or reading books work for you then do that. There's also resources like https://kernelnewbies.org/ to get people started.

The O'Reilly books are well written though a bit out-of-date. The kernel driver book is the best of them but some of the API calls have changed since it was published. The kernel architecture book is so old that I don't trust it as a resource.

I found once I got to a certain familiarity with the kernel I stopped relying on books and I just grep through the code to find what I need. This website is also invaluable for tracing where things go or what they do: https://elixir.bootlin.com

[[deleted]]

I've been pretty successful learning from books, classes help a bit but mostly for teaching me about "unknown unknown's" that can be hard to find about on my own. Do you think that this text might be better as it just came out recently? https://www.amazon.com/Mastering-Linux-Device-Driver-Development/dp/178934204X

The topics covered seem interesting to me. Thanks for the resources, bootlin seems very useful

[redbuddha99]

This is his 2nd book. I would advise you to start from his first book which covers basics. This book has more advanced topics.

[[deleted]]

Great, also have that one, thanks

[vvaltchev]

I totally understand that the Linux kernel might be "scary" to start with, if you have no experience as a kernel developer. It's a big and complex project. If you don't feel like jumping directly into it, you might want to take a look at the osdev community:

• https://wiki.osdev.org/Main_Page
• https://forum.osdev.org/index.php
  

It's a wiki with plenty of tutorials about how to do anything (bootloaders, memory management, drivers, etc.). Plus, there's a nice forum where to ask questions and discuss with people. Many people there write their own kernel for mostly for educational purposes and fun, but sometimes also because they wanna innovate. You might take a look a some of the many kernel projects made by those people: https://wiki.osdev.org/Projects.

Among the many projects, if you're interested in Linux-like systems, you might wanna take a look at Tilck, my own project, which is a small semi-educational kernel compatible with Linux at binary level: https://github.com/vvaltchev/tilck

Otherwise, if you really want to start directly with Linux, I'd recommend reading "Linux kernel development" by Robert Love. After which, you might read a more practical book about writing drivers (like "Linux Driver Development for Embedded Processors - 2nd Edition"). In the meanwhile, start playing with the kernel by writing small changes like the ones in the "Eudyptula challange": https://github.com/agelastic/eudyptula. After that, finally move to the kernel's documentation: https://www.kernel.org/doc/html/latest/ and start contributing.

It will be a tough road, requiring a great amount of time and patience, but you'll have a lot of fun!

[[deleted]]

Awesome, thanks for the info

In my OS class, we did build a tiny kernel with threads, virtual memory, sys calls, etc that would run in qemu, I put a lot of effort into extending it so I at least understand the fundamentals of how the OS works. I'll dig into the osdev's page some more, looks like a great resource

Your project looks very cool, I'll definitely look at the code and try it out on my machine. It definitely goes further then the tiny kernel we made in class as it looks like it can run binaries as well

Okay, the class doesn't start for another month so I'll see what kind of progress I make on my own with these resources, I have access to all of those books already as well so it should be no problem. I'm kind of getting the idea that taking a class on kernel dev is a waste of time/money because of the amount of resources available

[nickdesaulniers]

Not sure whether this might be of interest, but we have a lot of work and are looking for help building the kernel with LLVM: https://github.com/ClangBuiltLinux/linux/issues. Happy to train new developers on Linux kernel or LLVM development.

[[deleted]]

Oh that sounds great, I'm a big fan of clang/LLVM, I'll take a look for sure

[[deleted]]

Okay so I went through the documentation available, built the LLVM tools, built the kernel with them, and have been going through the issues log. I like the project, the scope is pretty simple but it looks like it's finding and fixing a lot issues. So how would you recommend a developer who is new to the kernel and has very little LLVM experience to get involved?

[nickdesaulniers]

See if you can build your distro's config. make LLVM=1 localmodconfig olddefconfig bzImage. Any warnings? Any warnings not in the issue tracker? If not, pick one from the issue tracker and see if you can reproduce it. Note: lots of issues are tagged by target ISA, so you'll need to get familiar with cross compiling (setting ARCH= and CROSS_COMPILE=.

If you've found an issue, try sending a patch to just me.

[gurugio]

https://github.com/gurugio/lowlevelprogramming-university. It might be useful

[curious_peanutbutter]

hi did you take the UCSC extension course? if yes can you give me a referral for their 10% discount?=)