Re: LPC BoF - Linux Kernel Debugging & Drgn
Stephen Brennan <[email protected]>
| Newsgroups | org.kernel.vger.linux-debuggers |
|---|---|
| Message-ID | <[email protected]> |
Hi everyone,
Thank you for joining the BoF, by all indication it was quite
successful, despite my apparent attempts at sabotage by changing the
room last minute. I took notes as we went (though couldn't cover
everything), which I've included below.
Thanks,
Stephen
---
* Drgn within IPython notebooks! Useful to help people follow & understand debugging sessions. -Shung-Hsi Yu
* What is the criteria for "contrib/" vs "helpers/"? - Sweet Tea Dorminy.
-> Unit test cases!
-> Converting contrib/ to helpers/ is a valid and good on-ramp to drgn development.
-> Though, not all contrib scripts are expected to make it in.
-> There is also a "tools/" directory which is actually tested & supported.
* Is there a "rosetta stone" comparison between operations in drgn and crash?
-> Not currently!
-> I (Stephen) have some which I could move out of an internal wiki into Drgn's wiki.
* Drgn "commands" vs Crash commands. Drgn does not yet have a command structure, it's been discussed.
* What is the status of drgn without debuginfo? https://github.com/osandov/drgn/issues/176
-> Symbol tables implemented, kallsyms in review.
-> Minimal BTF implementation, has some issues.
-> CTF is used in production at Oracle.
* What is the "backend" of drgn? How could you glue kgdb into Drgn?
-> The memory reader interface is the main way.
-> In addition to implementing memory readers, you'd need a way to communicate the "vmcoreinfo" to drgn. This provides info such as kernel version and kaslr offset.
-> We have a way to provide vmcoreinfo manually.
-> we're discussing gdbstub options: https://github.com/osandov/drgn/wiki/gdbstub-protocol-proposal:-linux.vmcoreinfo-query-packet
* What's the minimum I need to do with root in drgn?
-> just opening /proc/kcore
* Writing to kernel memory! New feature as of yesterday!
-> See https://blog.osandov.com/2024/09/17/calling-linux-kernel-functions-from-userspace.html
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