Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752012AbdHLLRn (ORCPT ); Sat, 12 Aug 2017 07:17:43 -0400 Received: from foss.arm.com ([217.140.101.70]:52328 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750872AbdHLLRm (ORCPT ); Sat, 12 Aug 2017 07:17:42 -0400 Date: Sat, 12 Aug 2017 12:17:34 +0100 From: Mark Rutland To: Tycho Andersen Cc: Laura Abbott , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-hardening@lists.openwall.com, Marco Benatto , Juerg Haefliger Subject: Re: [kernel-hardening] [PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled Message-ID: <20170812111733.GA16374@remoulade> References: <20170809200755.11234-1-tycho@docker.com> <20170809200755.11234-7-tycho@docker.com> <20170811211302.limmjv4rmq23b25b@smitten> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170811211302.limmjv4rmq23b25b@smitten> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1313 Lines: 39 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. Thanks Mark.