an idea by sleep_walker
Current status
Sometimes customer report an error which occurs with kernel package provided by L3 team (which we call PTF). To do the analysis we usually need to prepare kernel source code. That usually means to go back to maintenance update tag in git repository and apply all the patches provided in the used PTF.
Idea
We could use clones of kernel.git and kernel-source.git repositories on l3slave to store used tree and make it quickly available.
It can be implemented as ptfbuild hook for kernel packages or as script calling ptfbuild.
When build of PTF is requested, project diff would be generated (usually consists of series.conf entry, added patch to tarballs, changelog entry, ...), new branch in kernel-source.git generated, patch applied and commited. For kernel.git would be generated equivalent branch with patch as well.
Expected result
With this we could provide to R&D used kernel source easily for error analysis, backporting or we could base PTFs on PTFs more quickly.
No Hackers yet
This project is part of:
Hack Week 11
Activity
Comments
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over 10 years ago by sleep_walker | Reply
I discussed this with Michal Marek and redesigned whole idea. I re-formulated the idea and send proposal to L3 team.
Similar Projects
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()