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=-6.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 20F65C07E96 for ; Thu, 15 Jul 2021 16:13:43 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 E16C9613D3 for ; Thu, 15 Jul 2021 16:13:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E16C9613D3 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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=bombadil.20210309; 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=EqhYEOn3wG3VckZajdA8b7wAOG8b8WnXtBJdFL8G630=; b=EQnf6qv+2JZknb bB5J5CAHL0h5+doTbnYl9XM48+QlHWiWMy5LSqc5GRk8nhzgUsHzUdt98Xl9aFAeVn9OYNNu6TUi0 Jt9T02jM4lzYfWB2suqmXsO5xFlksMy29vdew/R1VJl/BEfLbCCltDUiPbxCLiteIdnhuMqJYQqpU jZb7k6ockLdIUHLpGp8gpvtni0sqFeqgwBNSp8VeQQCQpTqxc++gW336q5NkuqtHTfwY0R2VsZuOQ NcrMJbtO6oN7+mdr9/PaE1W0XdpHggezmS1SQxHJM3b/bBTPWEgKI0JVVNxJtfSwgzPjsZuV4TEyI MeMYxnHlvKZPmvSETsIA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1m43xV-001JpA-0V; Thu, 15 Jul 2021 16:11:33 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1m43xR-001JoW-6n for linux-arm-kernel@lists.infradead.org; Thu, 15 Jul 2021 16:11:30 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id E833F613D3; Thu, 15 Jul 2021 16:11:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1626365488; bh=BqPWp6clZ7F0TElgG64DFBiNqF9htAnOC4b/fvl7mq8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=euOq/nPtjh0bKq82+JtLC6s8JCEVuSevkb1pnXVMbZoOpzDZP8gsb0vdyFDtYxnBy yCFXcAzliWtFxLxC9KyxKynqmtk9tBuqftA6U/n47ZikKCTMNAfXJGtHTMz51Io+4L W42C7UooFM47wZ2iPHT3cIG7grffz+r5T2jmjFI2VKddwSdTEnxkY7E8ymhM3N33GB pTmut0PBcgKxdA89ZwkazMgVK4aHPuOCvxyGd5FYN7/HjT2XKBwIO2W+zP1xE9oWoS ov4dzXC3m4BTIoMr/Ck7P3uUDxuNV1Urqons5UL/woOQIF4/sXjMOH2eAoz0/W6J4O fe0VdFfU7lEBQ== Date: Thu, 15 Jul 2021 17:11:24 +0100 From: Will Deacon To: Robin Murphy Cc: Yuan Li , catalin.marinas@arm.com, linux-arm-kernel@lists.infradead.org, twd2.me@gmail.com Subject: Re: [PATCH] ARM64: Provide the ARM64_TBI option Message-ID: <20210715161124.GA1330@willie-the-truck> References: <20210714180640.22229-1-lydorazoe@gmail.com> <854a541f-0156-2465-b640-47c0d065f87f@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <854a541f-0156-2465-b640-47c0d065f87f@arm.com> 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-20210715_091129_302266_C38FD794 X-CRM114-Status: GOOD ( 14.50 ) 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 Wed, Jul 14, 2021 at 07:43:03PM +0100, Robin Murphy wrote: > On 2021-07-14 19:06, Yuan Li wrote: > > The ARM64 provides the Top Byte Ignore (TBI) early on, so the kernel turns TBI > > on by default, but, it does not provide any option to turn the feature off. > > > > In ARMv8.3, the Pointer Authentication (PA) was introduced, and if TBI is > > turned off, the PA will be able to use the top byte, resulting longer pointer > > authentication codes, which is more secure. > > > > This patch changes the default support for the TBI to an option that can be > > turned off. > > This would have to be something that processes explicitly opt in to. See > Documentation/arm64/tagged-pointers.rst - silently disabling TBI0 *will* > break existing userspace software. Maybe the patch from Peter: https://lore.kernel.org/r/20210622051204.3682580-1-pcc@google.com is a better starting point? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel