Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755177AbYLWFs0 (ORCPT ); Tue, 23 Dec 2008 00:48:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751204AbYLWFsR (ORCPT ); Tue, 23 Dec 2008 00:48:17 -0500 Received: from TYO201.gate.nec.co.jp ([202.32.8.193]:33677 "EHLO tyo201.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751182AbYLWFsR (ORCPT ); Tue, 23 Dec 2008 00:48:17 -0500 Message-ID: <49507B88.1030407@ct.jp.nec.com> Date: Mon, 22 Dec 2008 21:47:52 -0800 From: Hiroshi Shimamoto User-Agent: Thunderbird 2.0.0.18 (Windows/20081105) MIME-Version: 1.0 To: Brian Gerst CC: Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , linux-kernel@vger.kernel.org Subject: Re: [RFC -tip 2/4] x86: uaccess: introduce __{get|put}_user exception handling framework References: <49507534.5080401@ct.jp.nec.com> <495075B0.9020104@ct.jp.nec.com> <73c1f2160812222138g3968afb5v20662338ea0cf5d5@mail.gmail.com> In-Reply-To: <73c1f2160812222138g3968afb5v20662338ea0cf5d5@mail.gmail.com> 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 Content-Length: 1230 Lines: 31 Brian Gerst wrote: > On Tue, Dec 23, 2008 at 12:22 AM, Hiroshi Shimamoto > wrote: >> From: Hiroshi Shimamoto >> >> Impact: introduce new framework >> >> Introduce exception handling framework. >> __{get|put}_user_ex_try() begins exception block and >> __{get|put}_user_ex_catch() ends block and if an exception occurred in this >> block using __{get|put}_user_ex, direct jump to __{get|put}_user_ex_catch() >> and err is set to specified value. > > You shouldn't do this. According to the gcc manual[1], "Speaking of > labels, jumps from one asm to another are not supported. The > compiler's optimizers do not know about these jumps, and therefore > they cannot take account of them when deciding how to optimize." > > [1] http://gcc.gnu.org/onlinedocs/gcc-4.3.2/gcc/Extended-Asm.html > thanks so much for this information! I didn't know about this and it's what I want to know, thinking about this series. Thanks, Hiroshi -- 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/