Officially Become a Kernel Hacker! by m.crivellari

Description

My studies as well my spare time are dedicated to the Linux Kernel. Currently I'm focusing on interrupts on x86_64, but my interests are not restricted to one specific topic, for now.

I also "played" a little bit with kernel modules (ie lantern, a toy packet analyzer) and I've added a new syscall in order read from a task A, the memory of a task B.

Maybe this will be a good chance to...

Goals

• create my first kernel patch

Resources

• https://www.kernel.org/doc/html/latest/process/submitting-patches.html
• https://git-send-email.io/ (mentioned also in the kernel doc)
• https://javiercarrascocruz.github.io/kernel-contributor-1

Achivements

• found while working on a bug, this is the 1st patch: cifs: avoid deadlocks while updating iface

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early stage kdump support by mbrugger

Project Description

When we experience a early boot crash, we are not able to analyze the kernel dump, as user-space wasn't able to load the crash system. The idea is to make the crash system compiled into the host kernel (think of initramfs) so that we can create a kernel dump really early in the boot process.

Goal for the Hackweeks

1. Investigate if this is possible and the implications it would have (done in HW21)
2. Hack up a PoC (done in HW22 and HW23)
3. Prepare RFC series (giving it's only one week, we are entering wishful thinking territory here).

update HW23

• I was able to include the crash kernel into the kernel Image.
• I'll need to find a way to load that from init/main.c:start_kernel() probably after kcsan_init()
• I workaround for a smoke test was to hack kexec_file_load() systemcall which has two problems:
  1. My initramfs in the porduction kernel does not have a new enough kexec version, that's not a blocker but where the week ended
  2. As the crash kernel is part of init.data it will be already stale once I can call kexec_file_load() from user-space.

The solution is probably to rewrite the POC so that the invocation can be done from init.text (that's my theory) but I'm not sure if I can reuse the kexec infrastructure in the kernel from there, which I rely on heavily.

update HW24

• Day1
  • rebased on v6.12 with no problems others then me breaking the config
  • setting up a new compilation and qemu/virtme env
  • getting desperate as nothing works that used to work
• Day 2
  • getting to call the invocation of loading the early kernel from __init after kcsan_init()

• Day 3

  • fix problem of memdup not being able to alloc so much memory... use 64K page sizes for now
  • code refactoring
  • I'm now able to load the crash kernel
  • When using virtme I can boot into the crash kernel, also it doesn't boot completely (major milestone!), crash in elfcorehdr_read_notes()

• Day 4

  • ... more to come (hopefully)

• Day 5

  • ...

Resources

• Kdump talk oSC 2018

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Hacking on sched_ext by flonnegren

Description

Sched_ext upstream has some interesting issues open for grabs:

• core event counters
• topology: Use cpumasks

Goals

Send patches to sched_ext upstream

Also set up perfetto to trace some of the example schedulers.

Resources

https://github.com/sched-ext/scx

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Improve various phones kernel mainline support (Qualcomm, Exynos, MediaTek) by pvorel

Similar to previous hackweeks ( https://hackweek.opensuse.org/projects/improve-qualcomm-soc-msm8994-slash-msm8992-kernel-mainline-support, https://hackweek.opensuse.org/projects/test-mainline-kernel-on-an-older-qualcomm-soc-msm89xx-explore-mainline-kernel-qualcomm-mainlining) try to improve kernel mainline support of various phones.

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Kill DMA and DMA32 memory zones by ptesarik

Description

Provide a better allocator for DMA-capable buffers, making the DMA and DMA32 zones obsolete.

Goals

Make a PoC kernel which can boot a x86 VM and a Raspberry Pi (because early RPi4 boards have some of the weirdest DMA constraints).

Resources

• LPC2024 talk:
• video:

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SMB3 Server written entirely in Rust by dmulder

Description

Given the number of bugs frequently discovered in the Samba code caused by memory issues, it makes sense to re-write the smbd service purely in Rust code. Meanwhile, it would be wise to abandon backwards compatibility here with insecure protocol versions, and simply implement the SMB3 spec.

Goals

Get a simple server up and running and get it merged into upstream Samba (which now has Rust build support).

Resources

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