From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750972Ab1HVEG0 (ORCPT ); Mon, 22 Aug 2011 00:06:26 -0400 Received: from terminus.zytor.com ([198.137.202.10]:50875 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750733Ab1HVEGZ (ORCPT ); Mon, 22 Aug 2011 00:06:25 -0400 Message-ID: <4E51D597.3060800@zytor.com> Date: Sun, 21 Aug 2011 21:05:43 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:5.0) Gecko/20110707 Thunderbird/5.0 MIME-Version: 1.0 To: Andrew Lutomirski , Borislav Petkov CC: Al Viro , Linus Torvalds , mingo@redhat.com, Richard Weinberger , user-mode-linux-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: SYSCALL, ptrace and syscall restart breakages (Re: [RFC] weird crap with vdso on uml/i386) References: <20110821063443.GH2203@ZenIV.linux.org.uk> <20110821084230.GI2203@ZenIV.linux.org.uk> <20110821144352.GJ2203@ZenIV.linux.org.uk> <20110821164124.GL2203@ZenIV.linux.org.uk> <20110822011645.GM2203@ZenIV.linux.org.uk> <4E51B56F.3080301@zytor.com> <20110822020737.GP2203@ZenIV.linux.org.uk> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Borislav, We're tracking down an issue with the way system call arguments are handled on 32 bits. We have a solution for SYSENTER but not SYSCALL; fixing SYSCALL "properly" appears to be very difficult at best. So the question is: how much overhead would it be to simply fall back to int $0x80 or some other legacy-style domain crossing instruction for 32-bit system calls on AMD64 processors? We don't ever use SYSCALL in legacy mode, so native i386 kernels are unaffected. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sog-mx-3.v43.ch3.sourceforge.com ([172.29.43.193] helo=mx.sourceforge.net) by sfs-ml-2.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1QvLmD-00039L-Iw for user-mode-linux-devel@lists.sourceforge.net; Mon, 22 Aug 2011 04:06:17 +0000 Received: from terminus.zytor.com ([198.137.202.10] helo=mail.zytor.com) by sog-mx-3.v43.ch3.sourceforge.com with esmtps (TLSv1:AES256-SHA:256) (Exim 4.76) id 1QvLmC-0003Rt-RY for user-mode-linux-devel@lists.sourceforge.net; Mon, 22 Aug 2011 04:06:17 +0000 Message-ID: <4E51D597.3060800@zytor.com> Date: Sun, 21 Aug 2011 21:05:43 -0700 From: "H. Peter Anvin" MIME-Version: 1.0 References: <20110821063443.GH2203@ZenIV.linux.org.uk> <20110821084230.GI2203@ZenIV.linux.org.uk> <20110821144352.GJ2203@ZenIV.linux.org.uk> <20110821164124.GL2203@ZenIV.linux.org.uk> <20110822011645.GM2203@ZenIV.linux.org.uk> <4E51B56F.3080301@zytor.com> <20110822020737.GP2203@ZenIV.linux.org.uk> In-Reply-To: List-Id: The user-mode Linux development list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: user-mode-linux-devel-bounces@lists.sourceforge.net Subject: Re: [uml-devel] SYSCALL, ptrace and syscall restart breakages (Re: [RFC] weird crap with vdso on uml/i386) To: Andrew Lutomirski , Borislav Petkov Cc: user-mode-linux-devel@lists.sourceforge.net, Richard Weinberger , linux-kernel@vger.kernel.org, mingo@redhat.com, Al Viro , Linus Torvalds Borislav, We're tracking down an issue with the way system call arguments are handled on 32 bits. We have a solution for SYSENTER but not SYSCALL; fixing SYSCALL "properly" appears to be very difficult at best. So the question is: how much overhead would it be to simply fall back to int $0x80 or some other legacy-style domain crossing instruction for 32-bit system calls on AMD64 processors? We don't ever use SYSCALL in legacy mode, so native i386 kernels are unaffected. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. ------------------------------------------------------------------------------ uberSVN's rich system and user administration capabilities and model configuration take the hassle out of deploying and managing Subversion and the tools developers use with it. Learn more about uberSVN and get a free download at: http://p.sf.net/sfu/wandisco-dev2dev _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel