From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753722AbeBKSvo (ORCPT ); Sun, 11 Feb 2018 13:51:44 -0500 Received: from smtp.gentoo.org ([140.211.166.183]:58414 "EHLO smtp.gentoo.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753602AbeBKSvm (ORCPT ); Sun, 11 Feb 2018 13:51:42 -0500 Date: Sun, 11 Feb 2018 18:51:34 +0000 From: Sergei Trofimovich To: "Luck, Tony" Cc: Fenghua Yu , linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org, stanton_arch@mail.com Subject: Re: [PATCH] ia64: fix ptrace(PTRACE_GETREGS) (unbreaks strace, gdb) Message-ID: <20180211185134.76ccfd45@sf> In-Reply-To: <20180202230220.13b74e8c@sf> References: <20180202221224.16597-1-slyfox@gentoo.org> <20180202222231.23favlxecnxcencr@agluck-desk> <20180202230220.13b74e8c@sf> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2 Feb 2018 23:02:20 +0000 Sergei Trofimovich wrote: > On Fri, 2 Feb 2018 14:22:32 -0800 > "Luck, Tony" wrote: > > > On Fri, Feb 02, 2018 at 10:12:24PM +0000, Sergei Trofimovich wrote: > > > The strace breakage looks like that: > > > ./strace: get_regs: get_regs_error: Input/output error > > > > > > It happens because ia64 needs to load unwind tables > > > to read certain registers. Unwind tables fail to load > > > due to GCC quirk on the following code: > > > > > > extern char __end_unwind[]; > > > const struct unw_table_entry *end = (struct unw_table_entry *)table_end; > > > table->end = segment_base + end[-1].end_offset; > > > > > > GCC does not generate correct code for this single memory > > > reference after constant propagation (see https://gcc.gnu.org/PR84184). > > > > I'm not seeing this ... probably because I build with > > a pre-historic 4.3.4 version of gcc. > > > > Do you know which version(s) are affected? I'm not looking > > for an exhaustive list, just the one on which you found this > > would be good. > > > > -Tony > > Original bug https://bugs.gentoo.org/518130 claims regression appeared > around gcc-4.5. Locally am seeing the problem with gcc-6.4.0, gcc-7.2.0 and > gcc-8 (HEAD). Another report on the positive patch effect: rx2600 boots successfully with this patch (did not without, my guess is due to early access fault at bad address): https://bugs.gentoo.org/579278#c13 Tested-by: stanton_arch@mail.com -- Sergei