From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753073AbeBBWWm (ORCPT ); Fri, 2 Feb 2018 17:22:42 -0500 Received: from mga06.intel.com ([134.134.136.31]:25343 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752215AbeBBWWd (ORCPT ); Fri, 2 Feb 2018 17:22:33 -0500 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.46,451,1511856000"; d="scan'208";a="24494127" Date: Fri, 2 Feb 2018 14:22:32 -0800 From: "Luck, Tony" To: Sergei Trofimovich Cc: Fenghua Yu , linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] ia64: fix ptrace(PTRACE_GETREGS) (unbreaks strace, gdb) Message-ID: <20180202222231.23favlxecnxcencr@agluck-desk> References: <20180202221224.16597-1-slyfox@gentoo.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180202221224.16597-1-slyfox@gentoo.org> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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