Description
Improve UML handling of segmentation faults in kernel mode. Although such page faults are generally caused by a kernel bug, it is annoying if they cause an infinite loop, or panic the kernel. More importantly, a robust implementation allows to write KUnit tests for various guard pages, preventing potential kernel self-protection regressions.
Goals
Convert the UML page fault handler to use oops_* helpers, go through a few review rounds and finally get my patch series merged in 6.14.
Resources
Wrong initial attempt: https://lore.kernel.org/lkml/20231215121431.680-1-petrtesarik@huaweicloud.com/T/
Looking for hackers with the skills:
This project is part of:
Hack Week 24
Comments
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Modernize ocfs2 by goldwynr
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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
- Investigate if this is possible and the implications it would have (done in HW21)
- Hack up a PoC (done in HW22 and HW23)
- 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 afterkcsan_init()
- I workaround for a smoke test was to hack
kexec_file_load()
systemcall which has two problems:- My initramfs in the porduction kernel does not have a new enough kexec version, that's not a blocker but where the week ended
- 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
afterkcsan_init()
- getting to call the invocation of loading the early kernel from
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
- crash systems crashes (no pun intended) in
copy_old_mempage()
link; will need to understand elfcorehdr... - call path
vmcore_init() -> parse_crash_elf_headers() -> elfcorehdr_read() -> read_from_oldmem() -> copy_oldmem_page() -> copy_to_iter()
- crash systems crashes (no pun intended) in
Day 5
- hacking
arch/arm64/kernel/crash_dump.c:copy_old_mempage()
to see if crash system really starts. It does. - fun fact: retested with more reserved memory and with UEFI FW, host kernel crashes in init but directly starts the crash kernel, so it works (somehow) \o/
- hacking
TODOs
- fix elfcorehdr so that we actually can make use of all this...
- test where in the boot
__init()
chain we can/should callkexec_early_dump()
Kill DMA and DMA32 memory zones by ptesarik
Description
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Goals
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Description
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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
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Modularization and Modernization of cifs.ko for Enhanced SMB Protocol Support by hcarvalho
Creator:
Enzo Matsumiya ematsumiya@suse.de @ SUSE Samba team
Members:
Henrique Carvalho henrique.carvalho@suse.com @ SUSE Samba team
Description
Split cifs.ko in 2 separate modules; one for SMB 1.0 and 2.0.x, and another for SMB 2.1, 3.0, and 3.1.1.
Goals
Primary
Start phasing out/deprecation of older SMB versions
Secondary
- Clean up of the code (with focus on the newer versions)
- Update cifs-utils
- Update documentation
- Improve backport workflow (see below)
Technical details
Ideas for the implementation.
- fs/smb/client/{old,new}.c to generate the respective modules
- Maybe don't create separate folders? (re-evaluate as things progresses!)
- Remove server->{ops,vals} if possible
- Clean up fs_context.* -- merge duplicate options into one, handle them in userspace utils
- Reduce code in smb2pdu.c -- tons of functions with very similar init/setup -> send/recv -> handle/free flow
- Restructure multichannel
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- Extra channel just point to "channel 0" as the primary server, no need to allocate an extra TCPServerInfo for each one
- Authentication mechanisms
- Modernize algorithms (references: himmelblau, IAKERB/Local KDC, SCRAM, oauth2 (Azure), etc.