From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 101121 invoked by alias); 20 Nov 2017 10:08:26 -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 98537 invoked by uid 48); 20 Nov 2017 10:08:23 -0000 From: "krebbel at linux dot vnet.ibm.com" 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 10:08:00 -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: krebbel at linux dot vnet.ibm.com X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Resolution: X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: unassigned at sourceware dot org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: 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: 2017-q4/txt/msg00063.txt.bz2 https://sourceware.org/bugzilla/show_bug.cgi?id=3D22452 --- Comment #13 from Andreas Krebbel --- The .eh_frame section in an .o file uses PC-relative relocations in order to get its offset to the code determined during final link step. It probably d= oes this to avoid runtime relocations which would be necessary for an absolute relocation. .eh_frame is read-only in the mapping, so runtime relocs are not supposed to occur after final link step. Since in the kernel module scenario libdw has to deal with the .eh_frame section from the .o file it encounters these PC-relative relocs which it ca= nnot handle. I agree with Mark that libdw does not really need to support these relocs since they only occur in that weird scenario which can be avoided us= ing .debug_frame instead. .debug_frame does not have a location in the address space so a PC-relative relocation would be pointless. Instead it is supposed to be read by tools w= here applying absolute relocs is no problem. --=20 You are receiving this mail because: You are on the CC list for the bug.