From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E8528C433E0 for ; Fri, 5 Mar 2021 20:39:40 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 5135864FEA for ; Fri, 5 Mar 2021 20:39:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5135864FEA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=desiato.20200630; h=Sender:Content-Transfer-Encoding :Content-Type:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=FPXMwIzfpu6dswtRYMJkNfeEn4mobzRGF7Pw88Zl+0c=; b=ItVA7LRqQiMZG/L+8KHnrBUQ0 dRl/l5DpaL2KvwzPuvQI1/vQOYlRzBv7idUaf7/jwCe560qnULeHfvwHKPHbgwVdQIfV8OuX8zqVH tK/DvMebRaT7IGlP9KbcYZS55khOZi7TS1LDtvEQL1z2ZLIBDzidVe6sJDbGynJwBo4t+X4foOhsp yXz5yDNZNBGVkZjrMSMVR+X6sCIDu8uDMVnYj7deUr5F/lMSnWtecF41zUxH6wg4wNAMDs7XHsfQv 9aTop6bGzCDDxQUyMLsMksmv/+GASVFAbzhN4fThl4JzIwXw2BX/0Nmd2yakKyEIgPtFJg2ShmCFV y2Mn2bQSA==; Received: from localhost ([::1] helo=desiato.infradead.org) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lIHCe-00GP5A-Pm; Fri, 05 Mar 2021 20:37:41 +0000 Received: from mail.kernel.org ([198.145.29.99]) by desiato.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lIHCX-00GP3J-8O for linux-arm-kernel@lists.infradead.org; Fri, 05 Mar 2021 20:37:36 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 2476964F69; Fri, 5 Mar 2021 20:37:29 +0000 (UTC) Date: Fri, 5 Mar 2021 20:37:27 +0000 From: Catalin Marinas To: Ard Biesheuvel Cc: Linux ARM , Marc Zyngier , Will Deacon , Mark Rutland , Anshuman Khandual , Quentin Perret , Android Kernel Team Subject: Re: [PATCH 2/2] arm64: mm: use XN table mapping attributes for the linear region Message-ID: <20210305203727.GA5710@arm.com> References: <20210304171145.12281-1-ardb@kernel.org> <20210304171145.12281-3-ardb@kernel.org> <20210305190600.GK23855@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210305_203733_932588_32E35137 X-CRM114-Status: GOOD ( 20.12 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Mar 05, 2021 at 08:17:07PM +0100, Ard Biesheuvel wrote: > On Fri, 5 Mar 2021 at 20:06, Catalin Marinas wrote: > > On Thu, Mar 04, 2021 at 06:11:45PM +0100, Ard Biesheuvel wrote: > > > The way the arm64 kernel virtual address space is constructed guarantees > > > that swapper PGD entries are never shared between the linear region on > > > the one hand, and the vmalloc region on the other, which is where all > > > kernel text, module text and BPF text mappings reside. > > > > > > This means that mappings in the linear region (which never require > > > executable permissions) never share any table entries at any level with > > > mappings that do require executable permissions, and so we can set the > > > table-level PXN/UXN attributes for all table entries that are created > > > while setting up mappings in the linear region. Since swapper's PGD > > > level page table is mapped r/o itself, this adds another layer of > > > robustness to the way the kernel manages its own page tables. > > > > In ARMv8.1 the architecture added the possibility of disabling the > > hierarchical page table permissions (FEAT_HPDS) so that we can use these > > bits for software. > > Sure, but I don't think there is a shortage of software bits in table > descriptors, right? And we don't enable the feature in the first > place. We are short of software bits but in the *pte*, so disabling the hierarchical permissions doesn't anyway help. So, ignore me, the patches are fine ;). -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel