Linux Kernel - Let's contribute

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Let's contribute! Levente Kurusa Presented by Fedora Project Hungary Licensed under CC-BY-SA Linux Kernel

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Topics 1. Quick introduction 2. Random configurations 3. Kernel testing a. Stable kernels b. RC kernels 4. Checkpatch patches

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Quick introduction

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Linux powers the world! Servers! The cloud! Desktop? Maybe this year? Open source contribution is always a big plus when it comes to job search! Linux is cool! Why not? Why?

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86% say Linux advanced their career 93% of HR will recruit a Linux pro next year 75% already received a call this year! Interesting projects! Greater pay check! (+10% this year) Some statistics

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First steps Fetch the Linux kernel source code For random configurations: linux-next http://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git For stable testing: linux-stable http://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git For Rcs, simply clone down Linus' tree http://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

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Eudyptula Challenge http://eudyptula-challenge.org/ Series of programming tasks Hard, but fun!

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Linux-next The current state of the kernel Merged together by Stephen Rothwell An excellent opportunity to start Default configurations are tested

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Linux-stable Collection of important patches to old kernel release Backports needed! Maintained by Greg KH and others Documentation/stable_kernel_rules.txt

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Random configurations

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Randomized configurations of the kernel Often have a lot of problems GCC warnings GCC errors kconfig errors/warnings They sometimes don't even boot Extremely useful! What are randconfigs?

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$ make randconfig Completely nonsense config! Try to build it: $ make -j`nproc` Your first randconfig

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Possible errors Undeclared functions Kconfig circular dependencies Boot failure Test in emulator!

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Kernel testing

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Run the latest kernel Quite easy! $ make defconfig $ make localmodconfig $ make -j`nproc` # make headers_install # make install # reboot

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Actual testing If you test linux-stable ... and things break: Report it! ... if nothing breaks: Break it! (repeat) If you test linux-next ... it's risky to try on your computer

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Actual testing I use my own tiny project. LATTE – Linux Automatic Testing Tool for Expert (https://github.com/levex/latte) Emulators are great. Benchmarks are also fun. perf

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perf # perf list # perf record # perf report # perf stat -e

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Sending your first patch ● Also known as: Checkpatch patches

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Checkpatch? scripts/checkpatch.pl Checks for common errors in the patch ... and files with the --file switch Not just coding style, but bugs as well!

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Getting maintainers scripts/get_maintainer.pl Gives you a list of maintainers for that particular patch or file ... or you can manually browse through the MAINTAINERS file

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Creating the patch $ git reset --hard HEAD [work...] $ git diff [review work...] $ git commit -as $ git format-patch -1 … and then the hardest part

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Sending it 9 out of 10 will fail this step git send-email Thunderbird and such can do it as well, but it's hard to configure them properly.