Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756486Ab1D1NaZ (ORCPT ); Thu, 28 Apr 2011 09:30:25 -0400 Received: from vpn.id2.novell.com ([195.33.99.129]:54823 "EHLO vpn.id2.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754197Ab1D1NaU convert rfc822-to-8bit (ORCPT ); Thu, 28 Apr 2011 09:30:20 -0400 Message-Id: <4DB98854020000780003EA4D@vpn.id2.novell.com> X-Mailer: Novell GroupWise Internet Agent 8.0.1 Date: Thu, 28 Apr 2011 14:31:32 +0100 From: "Jan Beulich" To: "Heiko Carstens" Cc: , , "Geert Uytterhoeven" , , , , Subject: Re: [PATCH] allow placing exception table in .rodata (and do so on x86) References: <4DB85404020000780003E6D7@vpn.id2.novell.com> <20110428104306.GC2431@osiris.boeblingen.de.ibm.com> <4DB96E6A020000780003E9EB@vpn.id2.novell.com> <4DB9748B020000780003EA01@vpn.id2.novell.com> <20110428125302.GD2431@osiris.boeblingen.de.ibm.com> In-Reply-To: <20110428125302.GD2431@osiris.boeblingen.de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2091 Lines: 42 >>> On 28.04.11 at 14:53, Heiko Carstens wrote: > On Thu, Apr 28, 2011 at 01:07:07PM +0100, Jan Beulich wrote: >> >>> On 28.04.11 at 13:47, Geert Uytterhoeven wrote: >> > On Thu, Apr 28, 2011 at 13:40, Jan Beulich wrote: >> >>>>> On 28.04.11 at 12:43, Heiko Carstens wrote: >> >>> On Wed, Apr 27, 2011 at 04:36:04PM +0100, Jan Beulich wrote: >> >>> That's odd. The kernel actually writes to it (sort_main_extable()), so >> >>> it shouldn't be in the ro data section, but the data section. >> >> >> >> This area does get written, but only at boot time, before read-only >> >> data gets set to r/o (on x86 at least). With this in mind, it's better >> >> to place it in .rodata, as that way run-time protection will be in place >> >> (and I think you agree that it was misplaced in .text in any case). >> > >> > Which means it may be in ROM (which is really read-only) on some embedded >> > devices, so it cannot be sorted? >> >> Perhaps - but since sorting is a requirement, people building such >> systems must have found a way... Anyway, I don't see where both > > Yes, we found a way on s390: we put the exception table in the data section. > >> your and Heiko's comment are heading, since the situation is even >> worse without the patch afaics (since .text gets marked read-only >> as much as .rodata does, and could equally be placed in ROM). > > My point is that your default is wrong. If it makes sense to put the extable > into the rodata section then an architecture could do so. However making the > default to put data into the rodata section that is actually written to is > the wrong approach. > It just asks for breakage. The patch doesn't make this the default - it just makes it possible for an architecture to do so. Jan -- 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/