Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754549AbbHMVq5 (ORCPT ); Thu, 13 Aug 2015 17:46:57 -0400 Received: from mail-io0-f181.google.com ([209.85.223.181]:32923 "EHLO mail-io0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751682AbbHMVqz (ORCPT ); Thu, 13 Aug 2015 17:46:55 -0400 MIME-Version: 1.0 In-Reply-To: <55CD0F29.4070604@gmail.com> References: <55CA90B4.2010205@list.ru> <55CCD921.4040301@list.ru> <20150813200823.GS2059@uranus> <55CD0F29.4070604@gmail.com> Date: Thu, 13 Aug 2015 14:46:54 -0700 X-Google-Sender-Auth: hUPllGXFvEO8V8n_Mt31elfmq4E Message-ID: Subject: Re: [regression] x86/signal/64: Fix SS handling for signals delivered to 64-bit programs breaks dosemu From: Linus Torvalds To: Raymond Jennings Cc: Cyrill Gorcunov , Andy Lutomirski , Pavel Emelyanov , Stas Sergeev , Linux kernel Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 846 Lines: 22 On Thu, Aug 13, 2015 at 2:42 PM, Raymond Jennings wrote: > > I am curious about what's supposed to happen normally on signal delivery. > > Is SS a register that's supposed to be preserved like EIP/RIP and CS when a > signal is delivered? What exactly does "supposed" mean? On x86-64, we traditionally haven't touched SS, because it doesn't really matter in 64-bit long mode. And apparently dosemu depended on that behavior. So clearly, we're not "supposed" to save/restore it. Because reality matters a hell of a lot more than any theoretical arguments. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/