From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/11115 Path: news.gmane.org!.POSTED!not-for-mail From: Szabolcs Nagy Newsgroups: gmane.linux.lib.musl.general Subject: Re: musl segfaulting when compiled with -O2 Date: Wed, 8 Mar 2017 02:18:43 +0100 Message-ID: <20170308011842.GI2082@port70.net> References: <20170307203234.GC18936@gmail.com> <20170307203905.GT1520@brightrain.aerifal.cx> <20170307205529.GD18936@gmail.com> <20170307214540.GU1520@brightrain.aerifal.cx> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: blaine.gmane.org 1488935939 11715 195.159.176.226 (8 Mar 2017 01:18:59 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 8 Mar 2017 01:18:59 +0000 (UTC) User-Agent: Mutt/1.6.0 (2016-04-01) To: musl@lists.openwall.com Original-X-From: musl-return-11130-gllmg-musl=m.gmane.org@lists.openwall.com Wed Mar 08 02:18:55 2017 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by blaine.gmane.org with smtp (Exim 4.84_2) (envelope-from ) id 1clQFf-0002B9-0c for gllmg-musl@m.gmane.org; Wed, 08 Mar 2017 02:18:51 +0100 Original-Received: (qmail 14076 invoked by uid 550); 8 Mar 2017 01:18:55 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Original-Received: (qmail 14055 invoked from network); 8 Mar 2017 01:18:54 -0000 Mail-Followup-To: musl@lists.openwall.com Content-Disposition: inline In-Reply-To: <20170307214540.GU1520@brightrain.aerifal.cx> Xref: news.gmane.org gmane.linux.lib.musl.general:11115 Archived-At: * Rich Felker [2017-03-07 16:45:40 -0500]: > On Tue, Mar 07, 2017 at 05:55:29PM -0300, Breno Leitao wrote: > > $ wget http://cdn-fastly.deb.debian.org/debian/pool/main/m/musl/musl_1.1.16-2_ppc64el.deb > > > > $ dpkg-deb -x musl_1.1.16-2_ppc64el.deb . > > > > $ lib/powerpc64le-linux-musl/libc.so > > [2] 25672 segmentation fault (core dumped) lib/powerpc64le-linux-musl/libc.so > > Can you do a register dump and a dissassembly dump and around the > point that crashes? The Debian package is fully stripped (lacks debug > symbols) so it's hard to follow what it's doing, but I didn't see > anything obviously wrong. > > Rich i used qemu-ppc64le -singlestep -d in_asm,cpu to debug this the relevant code is the end of _dlstart_c: ... 8c574: 09 00 00 48 bl 8c57c 8c578: 28 98 fa ff fsub f31,f26,f19 8c57c: a6 02 48 7d mflr r10 8c580: 00 00 2a 81 lwz r9,0(r10) 8c584: 14 52 29 7d add r9,r9,r10 8c588: a6 03 29 7d mtctr r9 8c58c: 18 00 41 f8 std r2,24(r1) 8c590: 78 3b e4 7c mr r4,r7 8c594: 78 4b 2c 7d mr r12,r9 8c598: 21 04 80 4e bctrl it's a pc relative address load and jump (to call __dls2): bl 1f data // data == 0xfffa9828 1: mflr r10 // r10 = &data == 0x8c57c lwz r9,0(r10) // r9 = *r10 (== data) add r9,r9,r10 // r9 += r10 (== 0xfffa9828+0x8c57c = 0x100035da0) mtctr r9 // ctr = r9 (== 0x100035da0) std r2,24(r1) mr r4,r7 mr r12,r9 bctrl // ctr(r12,r4) it seems __dls2 is at 0x35da0 so the pc relative data should have been signextended.