GNU bug report logs - #42227
BPF in linux-libre

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From: John Soo <jsoo1 <at> asu.edu>
To: Mathieu Othacehe <othacehe <at> gnu.org>
Cc: 42227 <at> debbugs.gnu.org
Subject: [bug#42227] BPF in linux-libre
Date: Thu, 30 Jul 2020 19:20:27 -0700

Hi Mathieu!


> Thanks for your patience!

No problem. I'm quite busy too.

>> I also added debugfs as a requirement for a bpf system.  To use it
>> %bpf-file-systems can be used in place of %base-file-systems in the
>> operating system definition.
>
> Actually, I wonder if we could mount debugfs by default, by adding it to
> %base-file-systems. Any objections?

That seems ok. I did find a few questions about debugfs on old irc logs
and mailing lists.  My only concern again is that I would prefer to opt
in to such a thing.  debugfs is much simpler than the bpf kernel flags
though, so maybe it will be ok to remove in the future.

> In the meantime I pushed the bcc patch with a few edits. Regarding
> bpftrace, I'd like to avoid the "-DHAVE_BFD_DISASM=OFF" patching, I
> found this ticket which seems related:
> https://github.com/iovisor/bpftrace/issues/1106, but didn't make any
> significant progress yet.

I have tried every which way I can to make HAVE_BFD_DISASM work.  A kind
persn from the bpftrace irc directed me to this PR:
https://github.com/iovisor/bpftrace/pull/1095

But I cannot see anything guix does differently that would cause it to
fail. My only feeling is perhaps our configure flags for binutils might
be causing the issue.

As is, however, bpftrace does work even with out HAVE_BFD_DISASM and I
even used it to debug a few processes recently.

Thanks again!

- John

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