From: "mark at klomp dot org" <sourceware-bugzilla@sourceware.org>
To: elfutils-devel@sourceware.org
Subject: [Bug libdw/22452] Failed to obtain CFI data for a OP_call_frame_CFA when looking for func entrypoc in an s390 kernel module
Date: Mon, 20 Nov 2017 09:28:00 -0000 [thread overview]
Message-ID: <bug-22452-10460-bpvGvRipTs@http.sourceware.org/bugzilla/> (raw)
In-Reply-To: <bug-22452-10460@http.sourceware.org/bugzilla/>
https://sourceware.org/bugzilla/show_bug.cgi?id=22452
--- Comment #12 from Mark Wielaard <mark at klomp dot org> ---
(In reply to H. Brueckner from comment #10)
> (In reply to Mark Wielaard from comment #9)
> > But the output does confirm what I feared. The R_390_PC32 .rela.eh_frame
> > relocations are not "simple". They are load based.
>
> So now it comes to that point I have feared, as it looks like the libdw just
> performs "simple" relocations. Your comment and the ebl_reloc_simple_type()
> call in libdwfl/relocate.c proofs that. Anyhow, do you plan to extend the
> relocation code to support more complex relocations tool?
>
> > It might not be too hard to add support for those.
>
> What needs to be done / is necessary for that?
We would need to extend ebl_reloc_simple_type, or add a new ebl backend hook,
that signals a relocation uses the load address. Then in libdwfl/relocate.c use
that to adjust the value to include the load address that libdwfl assigns to
the section (given by struct dwfl_relocation start). This is similar to what
arch/s390/kernel/module.c in the kernel does, but slightly more complicated
because we want it to work "offline" cross architecture.
This would be helpful in general for any ET_REL file for which we want to
inspect the .eh_frame section CFI data. But since this is just for the kernel
modules at the moment I would wait with implementing it till you have
experimented with adjusting the kernel build like suggested in comment #11.
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next prev parent reply other threads:[~2017-11-20 9:28 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-17 14:29 [Bug libdw/22452] New: " brueckner at linux dot vnet.ibm.com
2017-11-17 15:27 ` [Bug libdw/22452] " mark at klomp dot org
2017-11-17 15:38 ` brueckner at linux dot vnet.ibm.com
2017-11-17 15:44 ` brueckner at linux dot vnet.ibm.com
2017-11-17 15:53 ` mark at klomp dot org
2017-11-17 15:56 ` mark at klomp dot org
2017-11-17 16:02 ` brueckner at linux dot vnet.ibm.com
2017-11-17 16:03 ` brueckner at linux dot vnet.ibm.com
2017-11-17 16:04 ` brueckner at linux dot vnet.ibm.com
2017-11-17 16:46 ` mark at klomp dot org
2017-11-20 8:09 ` brueckner at linux dot vnet.ibm.com
2017-11-20 8:11 ` krebbel at linux dot vnet.ibm.com
2017-11-20 9:28 ` mark at klomp dot org [this message]
2017-11-20 10:08 ` krebbel at linux dot vnet.ibm.com
2017-11-20 14:00 ` brueckner at linux dot vnet.ibm.com
2017-12-10 15:45 ` [Bug libdw/22452] Extend ebl_reloc_ hooks with relocations against load address for use in libdwfl/relocate.c mark at klomp dot org
2018-03-05 12:52 ` mark at klomp dot org
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