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The Linux Kernel Module Programming Guide
- synergy20 2y agoqemu is a good way to experience with kernel hacking Hopefully someone can update the LDD(linux device driver) and Linux kernel books. In fact Linux Foundation should sponsor such efforts since technical book like this is hard to make any profit.
- deivid 2y agoI've written a little bit about writing a driver & using QEMU to create a custom device for it at [0] & [1] [0]: https://blog.davidv.dev/posts/learning-pcie/ https://blog.davidv.dev/posts/learning-pcie/ [1]: https://blog.davidv.dev/posts/pcie-driver-dma/ https://blog.davidv.dev/posts/pcie-driver-dma/
- j33zusjuice 2y agoAre you the David V from Meta, who had bytelab.codes? I recently discovered that blog, and was very excited by the content, only to find he last updated in 2022. Either way, I’m excited to see your site, too! I love finding well-written kernel-level stuff.
- troop 2y agoDid some digging (embarrassingly) and I don't think they are the same person. Regardless it's quite an interesting blog post!
- commandersaki 2y agoThe wireguard test suite that’s now in the kernel is an excellent way to experiment with using qemu to develop kernel modules and also do automated tests. I’d link but cumbersome to find on phone.
- synergy20 2y agodo you mean this one: https://git.zx2c4.com/wireguard-linux/tree/tools/testing/selftests/wireguard https://git.zx2c4.com/wireguard-linux/tree/tools/testing/sel... there are only 3 files under drivers/net/wireguard/selftest and no qemu there in linux kernel git allowedips.c counter.c ratelimiter.c
- commandersaki 2y agoYes, but it's hard to find in the kernel: https://github.com/torvalds/linux/tree/5437f30d3458ad36e83ab96088d490ebfee844d8/tools/testing/selftests/wireguard https://github.com/torvalds/linux/tree/5437f30d3458ad36e83ab...
- donaldihunter 2y agovirtme-ng https://github.com/arighi/virtme-ng https://github.com/arighi/virtme-ng makes it really easy to launch development kernels in qemu.
- znpy 2y agoGreg KH said pretty explicitly there won’t be a 4th edition LDD
- j33zusjuice 2y agoDid he give any context for why? ROI for him, or?
- sthuck 2y agoI'm purely guessing here, but also considering I read him and Linus both say "we have enough kernel developers", I think it's likely they don't want to encourage low quality contributions from new developers.
- saagarjha 2y agoI wonder what a good way to help developers improve the quality of their contributions would be
- mardifoufs 2y agoWouldn't it be helpful then to put out more information on how to be a good contributor? I'm not sure how a technical book about the kernel would lead to worse contributions, you'd think a lack of readily available information and educational material would do that.
- heavyset_go 2y agoSeems short-sighted. People retire, get new jobs, and move on from projects all the time.
- iam-TJ 2y agoI use qemu extensively especially for early-stage kernel debugging when no console is available; one such was just this week with v6.8 where, on arm64, any kernel command-line parameter >= 146 characters hangs the kernel instantly and silently. Here's how I used qemu + gdb (on Debian 12 Bookworm amd64 host) to emulate and execute the arm64 kernel build to single-step the problematic code to identify the cause. 1. In a prepared kernel build system (i.e; all build dependencies and cross-compile tools installed) build the kernel image. I do this in an unprivileged systemd-nspawn amd64 container to avoid messy -dev package installs on the host. Nspawn bind-mounts the host's source-code tree which includes a separate build directory: cd "${SRC_DIR}" # copy/install/configure a suitable ${BUILD_DIR}/.config; review/edit with: make V=1 ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- O=${BUILD_DIR} -j 4 menuconfig # build the kernel export KBUILD_BUILD_USER=linux; export KBUILD_BUILD_HOST=iam.tj; time make V=1 LOCALVERSION="" ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- O=${BUILD_DIR} -j 12 Image # build gdb helper (Python) scripts export KBUILD_BUILD_USER=linux; export KBUILD_BUILD_HOST=iam.tj; time make V=1 LOCALVERSION="" ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- O=${BUILD_DIR} scripts_gdb This will create the debug symbols needed by gdb in ${BUILD_DIR}/vmlinux and the executable kernel in ${BUILD_DIR}/arch/arm64/boot/Image 2. Install "gdb" (and if doing foreign architecture debugging "gdb-multiarch") on the host as well as "qemu-system-arm" 3. Execute the kernel but -S[uspend] it and have QEMU listen for a connection from gdb: qemu-system-aarch64 -machine virt,gic-version=3 -cpu max,pauth-impdef=on -smp 2 -m 4096 -nographic -kernel ${BUILD_DIR}/arch/arm64/boot/Image -append "debug $( for l in {144..157}; do echo -n param$l=$(pwgen $((l-9)) 1)' '; done )" -initrd rootfs/boot/initrd.img-6.8.12-arm64-debug -S -gdb tcp::1234 The -append and -initrd shown here are optional; in my case no -initrd is actually needed since the (silent) panic occurs in the first few instructions the kernel executes. If debugging loadable modules however they would be in the initrd and loaded in the usual way. If the problem being diagnosed occurs after the root file-system and userspace proper are active then one would need to add the appropriate qemu options for the emulated storage device where the root file-system lives. 4. In another terminal shell (I use "tmux" and create a new tmux window) start the debugger: cd ${BUILD_DIR} # this cd is important - gdb needs to be in the base of the BUILD directory gdb-multiarch ./vmlinux 5. In the gdb shell: target remote :1234 break __parse_cmdline continue At this point the usual gdb functionality is available to examine memory, variables, single-step, view the stack and so on. For more details on debugging kernel using gdb and the gdb scripts lx-* see https://www.kernel.org/doc/html/latest/dev-tools/gdb-kernel-debugging.html https://www.kernel.org/doc/html/latest/dev-tools/gdb-kernel-... Edit: Forgot to note that for gdb to be able to use the lx-* Python scripts it usually needs the path authorising: echo "add-auto-load-safe-path ${SRC_DIR}/scripts/gdb/vmlinux-gdb.py" > ~/.gdbinit
- asicsp 2y agoSee also: https://0xax.gitbooks.io/linux-insides/content/index.html https://0xax.gitbooks.io/linux-insides/content/index.html
- simonz05 2y agoSee also The Linux Memory Manager: https://linuxmemory.org/chapters https://linuxmemory.org/chapters Last update the author sent out was in early July noting that the book is now in editing: > I am happy to report that I have completed the first draft of the book [...] > I am now in an editing phase, which may well take some time. Sadly I can't give a reasonable estimate as this will be done in concert with my publisher.
- ototot 2y agohttps://news.ycombinator.com/item?id=35782630 https://news.ycombinator.com/item?id=35782630 https://news.ycombinator.com/item?id=28283030 https://news.ycombinator.com/item?id=28283030
- Anne165Hernadez 2y ago[flagged]
- donpdonp 2y agoA detailed, hands-on, build a kernel module right away kind of tutorial. Bravo.
- anta40 2y agoWhat about Linux kernel programming in general, e.g hacking the filesystem or memory management parts? Many years ago there was "Linux Kernel Development" by Robert Love, probably not updated anymore.
- zeehio 2y ago> 1.7 Before delving into code... Did the authors use an LLM to write or improve the text? I have no problem with that but I feel I'd like to know how much work is LLM based before reading.
- ashconnor 2y agoPerfectly valid synonym for 'dive' in this context.
- ugh123 2y agoI wouldn't think it matters as long as the [human] authors review it for accuracy.
- BossingAround 2y agoWhy would "Before delving into code..." be a red flag that marks the text as LLM-generated?
- SPascareli13 2y agoSomeone said that the word "delve" is a favourite of AI and a sign that something was AI written.
- cloudwalk9 2y agoI don't usually suspect AI unless I see in a closing paragraph "However, it is important to note..."
- BossingAround 2y agoReally... It's also one of non-native speakers' favorite words.
- stevenhuang 2y agoThe proclivity to suggest something is LLM generated when it isn't is such a fun one. Almost like a Rorschach test for literary exposure. The answer in this context is no (you've might not been exposed to enough fiction).
- philipreis 2y agoI've read it first time about 22 years ago :)
- tdiff 2y agoSome examples seem hard to play with, unfortunately. For instance, "Detecting button presses" assumes one is able to build modules for RPi, which probably is not trivial by itself (e.g., requires cross-compilation).
- yjftsjthsd-h 2y agoI'll grant that it's a bit of friction, but you can just run a compiler on the pi?
- kkjkj 2y ago[dead]