Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752529AbdHNSmw (ORCPT ); Mon, 14 Aug 2017 14:42:52 -0400 Received: from mail-qt0-f174.google.com ([209.85.216.174]:34669 "EHLO mail-qt0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750989AbdHNSmv (ORCPT ); Mon, 14 Aug 2017 14:42:51 -0400 Subject: Re: [kernel-hardening] [PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled To: Tycho Andersen , Mark Rutland Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-hardening@lists.openwall.com, Marco Benatto , Juerg Haefliger References: <20170809200755.11234-1-tycho@docker.com> <20170809200755.11234-7-tycho@docker.com> <20170811211302.limmjv4rmq23b25b@smitten> <20170812111733.GA16374@remoulade> <20170814162219.h2lcmli677bx2lwh@smitten> From: Laura Abbott Message-ID: <86105819-3ec6-e220-5ba3-787bbeecb6ba@redhat.com> Date: Mon, 14 Aug 2017 11:42:45 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170814162219.h2lcmli677bx2lwh@smitten> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1587 Lines: 49 On 08/14/2017 09:22 AM, Tycho Andersen wrote: > On Sat, Aug 12, 2017 at 12:17:34PM +0100, Mark Rutland wrote: >> Hi, >> >> On Fri, Aug 11, 2017 at 03:13:02PM -0600, Tycho Andersen wrote: >>> On Fri, Aug 11, 2017 at 10:25:14AM -0700, Laura Abbott wrote: >>>> On 08/09/2017 01:07 PM, Tycho Andersen wrote: >>>>> @@ -190,7 +202,7 @@ static void init_pmd(pud_t *pud, unsigned long addr, unsigned long end, >>>>> next = pmd_addr_end(addr, end); >>>>> >>>>> /* try section mapping first */ >>>>> - if (((addr | next | phys) & ~SECTION_MASK) == 0 && >>>>> + if (use_section_mapping(addr, next, phys) && >>>>> (flags & NO_BLOCK_MAPPINGS) == 0) { >>>>> pmd_set_huge(pmd, phys, prot); >>>>> >>>>> >>>> >>>> There is already similar logic to disable section mappings for >>>> debug_pagealloc at the start of map_mem, can you take advantage >>>> of that? >>> >>> You're suggesting something like this instead? Seems to work fine. >>> >>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >>> index 38026b3ccb46..3b2c17bbbf12 100644 >>> --- a/arch/arm64/mm/mmu.c >>> +++ b/arch/arm64/mm/mmu.c >>> @@ -434,6 +434,8 @@ static void __init map_mem(pgd_t *pgd) >>> >>> if (debug_pagealloc_enabled()) >>> flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; >>> + if (IS_ENABLED(CONFIG_XPFO)) >>> + flags |= NO_BLOCK_MAPPINGS; >>> >> >> IIUC, XPFO carves out individual pages just like DEBUG_PAGEALLOC, so you'll >> also need NO_CONT_MAPPINGS. > > Yes, thanks! > > Tycho > Setting NO_CONT_MAPPINGS fixes the TLB conflict aborts I was seeing on my machine. Thanks, Laura