Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757493AbYGNSeT (ORCPT ); Mon, 14 Jul 2008 14:34:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753803AbYGNSeJ (ORCPT ); Mon, 14 Jul 2008 14:34:09 -0400 Received: from smtp-out04.alice-dsl.net ([88.44.63.6]:4114 "EHLO smtp-out04.alice-dsl.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752189AbYGNSeI (ORCPT ); Mon, 14 Jul 2008 14:34:08 -0400 To: Linus Torvalds Cc: Ingo Molnar , Linux Kernel Mailing List , Andrew Morton , Avi Kivity Subject: Re: [git pull] core, x86: make LIST_POISON less deadly From: Andi Kleen References: <20080714144828.GA22666@elte.hu> <20080714151247.GA27145@elte.hu> Date: Mon, 14 Jul 2008 20:33:23 +0200 In-Reply-To: (Linus Torvalds's message of "Mon, 14 Jul 2008 08:59:44 -0700 (PDT)") Message-ID: <8763r8z570.fsf@basil.nowhere.org> User-Agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/21.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-OriginalArrivalTime: 14 Jul 2008 18:33:22.0809 (UTC) FILETIME=[1897B690:01C8E5E0] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1327 Lines: 34 Linus Torvalds writes: > >> We dont do any instruction decoding in #GP handlers to figure out what >> happened, while in the pagefault case we know which address faulted, >> etc. > > Why would we care? It would be very obvious from the instruction > disassembly plus the register contents. No need to decode instructions. The issue is that the kernel cannot detect it (short of running the KVM x86 emulator on #GP, but surely you're not suggesting that), so it cannot print something out. You would always need someone skilled in x86 assembler code [a lot of kernel developers actually aren't] to look at the oops and say: ok it was a bad list poison. Currently it is very obvious because the fault address is printed even if you don't know any x86 assembler. I would consider that a regression. That is why I suggested using a canonical address. Also BTW if a CPU ever supports more than 40 bits virtual there will be so many kernel changes needed (5 level page tables) that changing the poison too is the smallest of your worries. -Andi -- 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/