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-1.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1QvJvm-0002zU-Ms for user-mode-linux-devel@lists.sourceforge.net; Mon, 22 Aug 2011 02:08:02 +0000 Received: from zeniv.linux.org.uk ([195.92.253.2]) by sog-mx-3.v43.ch3.sourceforge.com with esmtps (TLSv1:AES256-SHA:256) (Exim 4.76) id 1QvJvm-0007ih-2B for user-mode-linux-devel@lists.sourceforge.net; Mon, 22 Aug 2011 02:08:02 +0000 Date: Mon, 22 Aug 2011 03:07:38 +0100 From: Al Viro Message-ID: <20110822020737.GP2203@ZenIV.linux.org.uk> 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> MIME-Version: 1.0 Content-Disposition: inline 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 Cc: user-mode-linux-devel@lists.sourceforge.net, Richard Weinberger , linux-kernel@vger.kernel.org, mingo@redhat.com, "H. Peter Anvin" , Linus Torvalds On Sun, Aug 21, 2011 at 10:01:40PM -0400, Andrew Lutomirski wrote: > 3. We're worried that pt_regs-using compat syscalls might want the > regs to appear to match the actual arguments (why?) run strace and you'll see why. > 4. ptrace expects the "registers" when SYSCALL happens to match the > int 0x80 convention. (This is, IMO, sick.) That's what ptrace is *for*. It's there to let debuggers play with the program being debugged, including taking a look at the syscall arguments and modifying them. In a predictable way, please. ------------------------------------------------------------------------------ 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 S1756662Ab1HVCIF (ORCPT ); Sun, 21 Aug 2011 22:08:05 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:49510 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756550Ab1HVCID (ORCPT ); Sun, 21 Aug 2011 22:08:03 -0400 Date: Mon, 22 Aug 2011 03:07:38 +0100 From: Al Viro To: Andrew Lutomirski Cc: "H. Peter Anvin" , 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) Message-ID: <20110822020737.GP2203@ZenIV.linux.org.uk> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Aug 21, 2011 at 10:01:40PM -0400, Andrew Lutomirski wrote: > 3. We're worried that pt_regs-using compat syscalls might want the > regs to appear to match the actual arguments (why?) run strace and you'll see why. > 4. ptrace expects the "registers" when SYSCALL happens to match the > int 0x80 convention. (This is, IMO, sick.) That's what ptrace is *for*. It's there to let debuggers play with the program being debugged, including taking a look at the syscall arguments and modifying them. In a predictable way, please.