From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sog-mx-1.v43.ch3.sourceforge.com ([172.29.43.191] helo=mx.sourceforge.net) by sfs-ml-1.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1QvMfy-0008Qp-6q for user-mode-linux-devel@lists.sourceforge.net; Mon, 22 Aug 2011 05:03:54 +0000 Received: from terminus.zytor.com ([198.137.202.10] helo=mail.zytor.com) by sog-mx-1.v43.ch3.sourceforge.com with esmtps (TLSv1:AES256-SHA:256) (Exim 4.76) id 1QvMfx-0001uQ-DM for user-mode-linux-devel@lists.sourceforge.net; Mon, 22 Aug 2011 05:03:54 +0000 Message-ID: <4E51E325.2050502@zytor.com> Date: Sun, 21 Aug 2011 22:03:33 -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> <20110822040759.GQ2203@ZenIV.linux.org.uk> <4E51D70A.1060001@zytor.com> <20110822042605.GR2203@ZenIV.linux.org.uk> In-Reply-To: <20110822042605.GR2203@ZenIV.linux.org.uk> 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: Al Viro Cc: Andrew Lutomirski , user-mode-linux-devel@lists.sourceforge.net, Richard Weinberger , linux-kernel@vger.kernel.org, mingo@redhat.com, Linus Torvalds On 08/21/2011 09:26 PM, Al Viro wrote: > On Sun, Aug 21, 2011 at 09:11:54PM -0700, H. Peter Anvin wrote: >>> lack of point - the *only* CPU where it would matter would be K6-2, IIRC, >>> and (again, IIRC) it had some differences in SYSCALL semantics compared to >>> K7 (which supports SYSENTER as well). Bugger if I remember what those >>> differences might've been... Some flag not cleared? >> >> The most likely reason for a binary to execute a stray SYSCALL is >> because they read it out of the vdso. Totally daft, but we certainly >> see a lot of stupid things as evidenced by the JIT thread earlier this >> month. > > Um... What, blindly, no matter what surrounds it in there? What will > happen to the same eager JIT when it steps on SYSENTER? The JIT will have had to manage SYSENTER already. It's not a change, whereas SYSCALL would be. We could just try it, and see if anything breaks, of course. -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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752470Ab1HVFEM (ORCPT ); Mon, 22 Aug 2011 01:04:12 -0400 Received: from terminus.zytor.com ([198.137.202.10]:53440 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751077Ab1HVFEH (ORCPT ); Mon, 22 Aug 2011 01:04:07 -0400 Message-ID: <4E51E325.2050502@zytor.com> Date: Sun, 21 Aug 2011 22:03:33 -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: Al Viro CC: Linus Torvalds , Andrew Lutomirski , 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> <20110822040759.GQ2203@ZenIV.linux.org.uk> <4E51D70A.1060001@zytor.com> <20110822042605.GR2203@ZenIV.linux.org.uk> In-Reply-To: <20110822042605.GR2203@ZenIV.linux.org.uk> 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 On 08/21/2011 09:26 PM, Al Viro wrote: > On Sun, Aug 21, 2011 at 09:11:54PM -0700, H. Peter Anvin wrote: >>> lack of point - the *only* CPU where it would matter would be K6-2, IIRC, >>> and (again, IIRC) it had some differences in SYSCALL semantics compared to >>> K7 (which supports SYSENTER as well). Bugger if I remember what those >>> differences might've been... Some flag not cleared? >> >> The most likely reason for a binary to execute a stray SYSCALL is >> because they read it out of the vdso. Totally daft, but we certainly >> see a lot of stupid things as evidenced by the JIT thread earlier this >> month. > > Um... What, blindly, no matter what surrounds it in there? What will > happen to the same eager JIT when it steps on SYSENTER? The JIT will have had to manage SYSENTER already. It's not a change, whereas SYSCALL would be. We could just try it, and see if anything breaks, of course. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.