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Precedence: bulk X-Mailing-List: linux-debuggers@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: EeajtucEeUsYaWvYonTnf3F-7rk7ugp5mb14RiiSFCU_1765987871 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Hi Stephen, Hi Omar, On Fri, 05 Dec 2025 10:38:05 -0800 Stephen Brennan wrote: > Philipp Rudo writes: > > 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... > > Thanks for taking a deeper look! No worries on timing, it's not urgent. > If you think the most likely fix will be to backport commit > b9f174c811e3a ("x86/unwind/orc: Add ELF section with ORC version > identifier"), then I believe the drgn workaround I proposed in the > Github issue [1] should work fine: once the .orc_header section is > found, drgn will detect it and use the correct hash. The only difference > being that the "true" first broken version was 5.14.0-517.el9, which > might be worth encoding in the code in case somebody ever runs drgn > against a weird unreleased version from that development period. > > [1]: https://github.com/osandov/drgn/issues/578#issuecomment-3614826789 I had a look today. Unfortunately backporting b9f174c811e3 ("x86/unwind/orc: Add ELF section with ORC version identifier") isn't as straight forward as I hoped. The problem is that the RHEL9 kernel is missing commit 321648455061 ("kbuild: use obj-y instead extra-y for objects placed at the head"). Without that commit Omar's fix won't work as intended and in fact causes problems... I found an internal discussion about backporting 321648455061 ("kbuild: use obj-y instead extra-y for objects placed at the head"). But back then (~2 years ago) it was deemed to be too invasive to backport for RHEL9. I don't think this will change now even later in the RHEL9 life cycle. All in all I'm afraid we are stuck with Stephen's work around. Thanks Philipp > > > 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, that helps a lot! > Stephen > > > Thanks > > Philipp > > > > > > On Thu, 04 Dec 2025 12:06:54 -0800 > > Stephen Brennan 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 > >> >