From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 20374 invoked by alias); 5 Mar 2018 12:52:55 -0000 Mailing-List: contact elfutils-devel-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Post: List-Help: List-Subscribe: Sender: elfutils-devel-owner@sourceware.org Received: (qmail 20328 invoked by uid 48); 5 Mar 2018 12:52:51 -0000 From: "mark at klomp dot org" To: elfutils-devel@sourceware.org Subject: [Bug libdw/22452] Extend ebl_reloc_ hooks with relocations against load address for use in libdwfl/relocate.c Date: Mon, 05 Mar 2018 12:52:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: elfutils X-Bugzilla-Component: libdw X-Bugzilla-Version: unspecified X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: mark at klomp dot org X-Bugzilla-Status: RESOLVED X-Bugzilla-Resolution: FIXED X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: unassigned at sourceware dot org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_status resolution Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: http://sourceware.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-SW-Source: 2018-q1/txt/msg00063.txt.bz2 https://sourceware.org/bugzilla/show_bug.cgi?id=3D22452 Mark Wielaard changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution|--- |FIXED --- Comment #16 from Mark Wielaard --- (In reply to Mark Wielaard from comment #15) > Did you manage to get a kernel build change upstream? > It would be nice to point people at it in this bug in case they hit the s= ame > issue. So they know how to rebuild their kernel. commit bc3703f21cec8a2ac6a64f6fb3686fbcb1ba1513 Author: Hendrik Brueckner Date: Mon Nov 20 11:41:07 2017 +0100 s390/kernel: emit CFI data in .debug_frame and discard .eh_frame sectio= ns Using perf probe and libdw on kernel modules failed to find CFI data for symbols. The CFI data is stored in the .eh_frame section. The elfutils libdw is not able to extract the CFI data correctly, because the .eh_frame section requires "non-simple" relocations for kernel modules. The suggestion is to avoid these "non-simple" relocations by emitting the CFI data in the .debug_frame section. Let gcc emit respective directives by specifying the -fno-asynchronous-unwind-tables option. Using the .debug_frame section for CFI data, the .eh_frame section becomes unused and, thus, discard it for kernel and modules builds The vDSO requires the .eh_frame section and, hence, emit the CFI data in both, the .eh_frame and .debug_frame sections. See also discussion on elfutils/libdw bugzilla: https://sourceware.org/bugzilla/show_bug.cgi?id=3D22452 Suggested-by: Mark Wielaard Signed-off-by: Hendrik Brueckner Reviewed-by: Heiko Carstens Signed-off-by: Martin Schwidefsky > I have retitled this bug and will keep it open in case someone has > time for implementing the ebl hooks for relative load address relocations. I think the above kernel fix is a better. And there really is not much bene= fit to have relative load address relocations for .eh_frame except for these ET= _REL .ko files. Also, nobody seems to have time. So lets close this for now. --=20 You are receiving this mail because: You are on the CC list for the bug.