Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756805Ab1CRS4T (ORCPT ); Fri, 18 Mar 2011 14:56:19 -0400 Received: from e4.ny.us.ibm.com ([32.97.182.144]:33682 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756345Ab1CRS4O (ORCPT ); Fri, 18 Mar 2011 14:56:14 -0400 Date: Sat, 19 Mar 2011 00:19:22 +0530 From: Srikar Dronamraju To: Roland McGrath Cc: Thomas Gleixner , Peter Zijlstra , Ingo Molnar , Steven Rostedt , Linux-mm , Arnaldo Carvalho de Melo , Linus Torvalds , Andi Kleen , Christoph Hellwig , Masami Hiramatsu , Oleg Nesterov , Andrew Morton , SystemTap , Jim Keniston , Ananth N Mavinakayanahalli , LKML , "Paul E. McKenney" Subject: Re: [PATCH v2 2.6.38-rc8-tip 6/20] 6: x86: analyze instruction and determine fixups. Message-ID: <20110318184922.GA31152@linux.vnet.ibm.com> Reply-To: Srikar Dronamraju References: <20110314133403.27435.7901.sendpatchset@localhost6.localdomain6> <20110314133507.27435.71382.sendpatchset@localhost6.localdomain6> <20110318182457.GA24048@linux.vnet.ibm.com> <20110318183629.2AB052C286@topped-with-meat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20110318183629.2AB052C286@topped-with-meat.com> User-Agent: Mutt/1.5.20 (2009-06-14) X-Content-Scanned: Fidelis XPS MAILER Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1210 Lines: 32 * Roland McGrath [2011-03-18 11:36:29]: > > handle_riprel_insn() returns 0 if the instruction is not rip-relative > > returns 1 if its rip-relative but can use XOL slots. > > returns -1 if its rip-relative but cannot use XOL. > > > > We dont see any instructions that are rip-relative and cannot use XOL. > > so the check and return are redundant and I will remove that in the next > > patch. > > How is that? You can only adjust a rip-relative instruction correctly if > the instruction copy is within 2GB of the original target address, which > cannot be presumed to always be the case in user address space layout > (unlike the kernel). > So we rewrite the copy of instruction (stored in XOL) such that it accesses its memory operand indirectly thro a scratch register. The contents of the scratch register are stored before singlestep and restored later. Can you please tell us if this doesnt work? -- Thanks and Regards Srikar -- 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/