Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753198Ab0KPPcd (ORCPT ); Tue, 16 Nov 2010 10:32:33 -0500 Received: from mail-pw0-f46.google.com ([209.85.160.46]:35614 "EHLO mail-pw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752670Ab0KPPcc convert rfc822-to-8bit (ORCPT ); Tue, 16 Nov 2010 10:32:32 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=gMDViC3yfx5oRVPndggUv1vAWa9AhVB7UWwTWfbIvthhVYn5gs9Ygof4sDXWMg0XfZ tXh7pnZ9MQmwW8OTnFkF4/QLg5EDFJ6HZpKN83jaLcMK2gh51Vsr0dfxOEZcvxnDQT2X cLEywcxaHOE7noQh0s/12AKXIWNR+Ot55Mn9o= MIME-Version: 1.0 In-Reply-To: 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> Date: Tue, 16 Nov 2010 15:32:30 +0000 X-Google-Sender-Auth: n1W8nhvi64hO90bqJiG0ARwy2Cg Message-ID: Subject: Re: [PATCH v2 05/20] ARM: LPAE: Introduce L_PTE_NOEXEC and L_PTE_NOWRITE From: Catalin Marinas To: Russell King - ARM Linux Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2335 Lines: 54 On 16 November 2010 15:18, Catalin Marinas wrote: > On 15 November 2010 18:30, Russell King - ARM Linux > wrote: >> On Fri, Nov 12, 2010 at 06:00:25PM +0000, Catalin Marinas wrote: >>> The LPAE page table format needs to explicitly disable execution or >>> write permissions on a page by setting the corresponding bits (similar >>> to the classic page table format with Access Flag enabled). This patch >>> introduces null definitions for the 2-level format and the actual noexec >>> and nowrite bits for the LPAE format. It also changes several PTE >>> maintenance macros and masks. >>> >>> Signed-off-by: Catalin Marinas >>> --- >>> ?arch/arm/include/asm/pgtable-2level.h | ? ?2 + >>> ?arch/arm/include/asm/pgtable.h ? ? ? ?| ? 44 +++++++++++++++++++++------------ >>> ?arch/arm/mm/mmu.c ? ? ? ? ? ? ? ? ? ? | ? ?6 ++-- >>> ?3 files changed, 33 insertions(+), 19 deletions(-) >>> >>> diff --git a/arch/arm/include/asm/pgtable-2level.h b/arch/arm/include/asm/pgtable-2level.h >>> index 36bdef7..4e21166 100644 >>> --- a/arch/arm/include/asm/pgtable-2level.h >>> +++ b/arch/arm/include/asm/pgtable-2level.h >>> @@ -128,6 +128,8 @@ >>> ?#define L_PTE_USER ? ? ? ? ? (1 << 8) >>> ?#define L_PTE_EXEC ? ? ? ? ? (1 << 9) >>> ?#define L_PTE_SHARED ? ? ? ? (1 << 10) ? ? ? /* shared(v6), coherent(xsc3) */ >>> +#define L_PTE_NOEXEC ? ? ? ? (0) >>> +#define L_PTE_NOWRITE ? ? ? ? ? ? ? ?(0) >> >> 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: > > ? ? ? ?tst ? ? r1, #L_PTE_NOWRITE > ? ? ? ?orrne ? r3, r3, #PTE_EXT_APX > ? ? ? ?tsteq ? r1, #L_PTE_DIRTY > ? ? ? ?orreq ? r3, r3, #PTE_EXT_APX I think that would work with 3 instructions: eor r1, r1, L_PTE_DIRTY tst r1, #L_PTE_NOWRITE | L_PTE_DIRTY orrne r3, r3, #PTE_EXT_APX -- Catalin -- 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/