Re: Unknown ORC entry type 5 on RHEL 9 kernel

[Philipp Rudo <prudo@redhat.com>]

Hi Stephen,

thanks for letting me know. And yes that is something we need to fix in
the kernel rather than drgn.

I took a quick look and found that the change was included when
backporting fb799447ae29 ("x86,objtool: Split UNWIND_HINT_EMPTY in two")
for 9.6. Thing is that I'll be heading to LPC tomorrow and won't have
time to work on it properly before that...

One more hint. When you want to get the history of RHEL, it's better to
check the centos-stream repo then the changelog. There you have the
full git history (modulo some embargoed CVE fixes).

https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9

Thanks
Philipp


On Thu, 04 Dec 2025 12:06:54 -0800
Stephen Brennan <stephen.s.brennan@oracle.com> wrote:

> Hi Philipp,
> 
> I wanted to let you know about an issue with drgn's stack unwinding on
> the RHEL 9 kernel. It looks like that kernel backports some ORC changes,
> without including a change Omar made (including an .orc_header section)
> to help identify the ORC format version. I've included more details on
> this drgn issue:
> 
> https://github.com/osandov/drgn/issues/578
> 
> The result is that drgn can't unwind stacks on the RHEL 9 kernel. I
> think the best path forward would be to include the .orc_header patch:
> b9f174c811e3a ("x86/unwind/orc: Add ELF section with ORC version identifier")
> 
> As it is, the RHEL 9 drgn can't unwind stacks on the RHEL 9 kernel,
> which seems less than ideal.
> 
> Thanks,
> Stephen
>