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=-3.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_NONE,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by archive.lwn.net (Postfix) with ESMTPS id 5A1727D910 for ; Wed, 11 Mar 2020 16:31:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject: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=gOkyqeHcckYIe1NG1l0dSH8XTOoaC1bDAUgZTcjt+YM=; b=T/qX+sfugsp60U TEanQoQrciBoZ8N/MqDlhq/GEogsGUSSRzI57wNk8MhRNSCdqO0JbeBnYDyqSkuiM+E2D/MzOXlOT Bj70KAkBi/Hwl8FyYcqXK7skvOckon5ecSkYNKw+niDFkue+bvPyOgeBp9SZNKJBzoX74DG1arNf+ jGi6ZRFkHQmT5EGzi/0C6y7QlCDpno8ViJQzK7qeenXge+mUAG4S1KT1H/DQYqbyjQqQcYRNFWpZ4 HV/BaWC2lfWvk1VS9xDRDUWGN7mWZsA2r33yjcaO57Gl0mf60LjYDkTqVVBoUEOUB++NJ5qmHO1bv /DspVSvlE4/9H1kJHaFQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jC4GH-0002aD-8C; Wed, 11 Mar 2020 16:31:13 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jC4GD-0002Xm-Jz for linux-arm-kernel@lists.infradead.org; Wed, 11 Mar 2020 16:31:10 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E968E31B; Wed, 11 Mar 2020 09:31:08 -0700 (PDT) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.196.71]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D8A643F6CF; Wed, 11 Mar 2020 09:31:05 -0700 (PDT) Date: Wed, 11 Mar 2020 16:31:03 +0000 From: Catalin Marinas To: Mark Brown Subject: Re: [PATCH v8 03/11] arm64: Basic Branch Target Identification support Message-ID: <20200311163103.GL3216816@arrakis.emea.arm.com> References: <20200227174417.23722-1-broonie@kernel.org> <20200227174417.23722-4-broonie@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200227174417.23722-4-broonie@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200311_093109_698558_6A190971 X-CRM114-Status: GOOD ( 15.40 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paul Elliott , Peter Zijlstra , Andrew Jones , Amit Kachhap , Vincenzo Frascino , Will Deacon , linux-arch@vger.kernel.org, Marc Zyngier , Eugene Syromiatnikov , Szabolcs Nagy , Dave Martin , "H . J . Lu " , Yu-cheng Yu , Kees Cook , Arnd Bergmann , Jann Horn , Richard Henderson , Kristina =?utf-8?Q?Mart=C5=A1enko?= , Alexander Viro , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, Florian Weimer , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Sudakshina Das Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+lwn-linux-arm-kernel=archive.lwn.net@lists.infradead.org Archived-At: List-Archive: On Thu, Feb 27, 2020 at 05:44:09PM +0000, Mark Brown wrote: > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 0b30e884e088..e37f4f07b990 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -1519,6 +1519,28 @@ endmenu > > menu "ARMv8.5 architectural features" > > +config ARM64_BTI > + bool "Branch Target Identification support" > + default y > + help > + Branch Target Identification (part of the ARMv8.5 Extensions) > + provides a mechanism to limit the set of locations to which computed > + branch instructions such as BR or BLR can jump. > + > + To make use of BTI on CPUs that support it, say Y. > + > + BTI is intended to provide complementary protection to other control > + flow integrity protection mechanisms, such as the Pointer > + authentication mechanism provided as part of the ARMv8.3 Extensions. > + For this reason, it does not make sense to enable this option without > + also enabling support for pointer authentication. Thus, when > + enabling this option you should also select ARM64_PTR_AUTH=y. > + > + Userspace binaries must also be specifically compiled to make use of > + this mechanism. If you say N here or the hardware does not support > + BTI, such binaries can still run, but you get no additional > + enforcement of branch destinations. To keep the series bisectable, I'd move the Kconfig into a separate patch towards the end. It looks like the feature is only partially supported after patch 3, so let's not advertise it here. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel