Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756605Ab0KPST3 (ORCPT ); Tue, 16 Nov 2010 13:19:29 -0500 Received: from caramon.arm.linux.org.uk ([78.32.30.218]:49626 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756444Ab0KPST2 (ORCPT ); Tue, 16 Nov 2010 13:19:28 -0500 Date: Tue, 16 Nov 2010 18:19:06 +0000 From: Russell King - ARM Linux To: Catalin Marinas Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 05/20] ARM: LPAE: Introduce L_PTE_NOEXEC and L_PTE_NOWRITE Message-ID: <20101116181906.GA21926@n2100.arm.linux.org.uk> References: <1289584840-18097-1-git-send-email-catalin.marinas@arm.com> <1289584840-18097-6-git-send-email-catalin.marinas@arm.com> <20101115183014.GD31421@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1320 Lines: 33 On Tue, Nov 16, 2010 at 03:18:03PM +0000, Catalin Marinas wrote: > On 15 November 2010 18:30, Russell King - ARM Linux > wrote: > > Let's not make this more complicated than it has to be. ?If we need the > > inverse of WRITE and EXEC, then that's what we should change everyone to, > > not invent a new system to work along side the old system. > > This adds an additional instruction in set_pte_ext, unless you can > write the bit checking in a better way: It actually results in the same number of instructions. From memory: ARMv3-ARMv5: - eor r3, r1, #L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_WRITE | L_PTE_DIRTY - tst r3, #L_PTE_WRITE | L_PTE_DIRTY @ write and dirty? - orreq r2, r2, #PTE_SMALL_AP_UNO_SRW + eor r3, r1, #L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY + tst r3, #L_PTE_RDONLY | L_PTE_DIRTY @ write and dirty? + orreq r2, r2, #PTE_SMALL_AP_UNO_SRW and for ARMv6+: - tst r1, #L_PTE_WRITE - tstne r1, #L_PTE_DIRTY - orreq r3, r3, #PTE_EXT_APX + eor r1, r1, #L_PTE_DIRTY + tst r1, #L_PTE_RDONLY | L_PTE_DIRTY + orrne r3, r3, #PTE_EXT_APX -- 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/