This can be seen as a subproject of ethtool netlink interface but from the technical view it's independent.
Every new piece of software is going to be buggy and with frequent changes and rewrites, new regressions are introduced. Automated selftests can help a lot but as ethtool deals with hardware devices, we do not want these tests to depend on a specific hardware. The netdevsim driver was created as a virtual device which (unlike e.g. dummy) cannot be used for actual network traffic but implements various configuration interfaces so that it can be used for their (automated) testing.
Currently (February 2020, before Hackweek 19), netdevsim driver does not provide ethtool_ops
callbacks so that it cannot be used with ethtool.
The goal is to implement at least basic ethtool_ops
callbacks so that netdevsim can be used for automated testing of both kernel ethtool code and userspace ethtool utility. Ideally, use could set internal values used for replies so that various corner cases can be also tested.
Looking for hackers with the skills:
This project is part of:
Hack Week 18 Hack Week 19
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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()