Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756688Ab0DFOvu (ORCPT ); Tue, 6 Apr 2010 10:51:50 -0400 Received: from mail-pz0-f193.google.com ([209.85.222.193]:50599 "EHLO mail-pz0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754745Ab0DFOvp convert rfc822-to-8bit (ORCPT ); Tue, 6 Apr 2010 10:51:45 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=kbyiFrSMzKK1B3pLvtBnfadBL6bISy+eHJgHlX8m8EaIP3FQca+ij4G40oQqiV7Bon dGVjOFR3OSY9F5dZfcaNeHbcboqxntEZo/SfIr7qXJJ+xytW2RBYjcACyV9qeWkJmxJh RfS2gevAJpErTIBhPr1ZwOv9UVzHJaarG+Gzo= MIME-Version: 1.0 In-Reply-To: <1270277000.2686.20.camel@sbs-t61> References: <1270277000.2686.20.camel@sbs-t61> Date: Tue, 6 Apr 2010 10:51:44 -0400 Message-ID: Subject: Re: [PATCH 1/4] [tip:x86/mm] Correcting improper large page preservation From: Siarhei Liakh To: Suresh Siddha Cc: "linux-kernel@vger.kernel.org" , "linux-security-module@vger.kernel.org" , "linux-next@vger.kernel.org" , Arjan van de Ven , James Morris , Andrew Morton , Andi Kleen , Thomas Gleixner , "H. Peter Anvin" , Ingo Molnar , Rusty Russell , Stephen Rothwell , Dave Jones 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: 1454 Lines: 33 On Sat, Apr 3, 2010 at 2:43 AM, Suresh Siddha wrote: > On Wed, 2010-03-31 at 18:59 -0700, Siarhei Liakh wrote: >> + ? ? /* >> + ? ? ?* .data and .bss should always be writable. >> + ? ? ?*/ >> + ? ? if ((within(pfn, __pa((unsigned long)_sdata) >> PAGE_SHIFT, >> + ? ? ? ? ? ? ? ?__pa((unsigned long)_edata) >> PAGE_SHIFT)) || >> + ? ? ? ? (within(pfn, __pa((unsigned long)__bss_start) >> PAGE_SHIFT, >> + ? ? ? ? ? ? ? ?__pa((unsigned long)__bss_stop) >> PAGE_SHIFT))) { >> + ? ? ? ? ? ? pgprot_val(required) |= _PAGE_RW; >> + ? ? } > > I have reviewed this patch and the only comment I have is: > > On 64bit kernels, kernel text/data mapping and kernel identity mappings > are different virtual addresses mapping to same pfn ranges. For the > data/bss pages, does it help (in identifying certain data corruptions > more easily) in making the kernel identity mapping to be set to > read-only and enforce the need of RW only for the kernel data mappings. > > Or is there some obscure code that uses something like > __va(__pa(data_symbol)) and writes to it? > > If not, we can remove the __pa() constructs above and use the addr for > comparisons. Done. Patch V2 have been posted. -- 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/