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=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 B9B30C2BA19 for ; Tue, 14 Apr 2020 10:49:52 +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 83101206D5 for ; Tue, 14 Apr 2020 10:49:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="lTTUQUna" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 83101206D5 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-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.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=fSqT6MAQ6vo7TKpsS+dGHm3Nb2OYpd0o2toll717bXM=; b=lTTUQUnaxoe0RSZ+4G5f2kLoZ PkZTauFQ8V0/wc+pCewrjD809laZYZHw3O/QdCyJvPk3an7OHScjasCRIlhNle/UhbIkMgb5hI4r+ S5BvDT7J+CvF0Ne8BIP+57Bje/WsC1V+cqP6AugIP4NLwIQ+Sc3lsaB9+Zd1iohLTk40Y7b+CLHIU en8Vz7LJ1YpkN5zowwZLWms9F8XEvbNgBkaB3n+34jo9yiH18Y3aTVMDsK/icxfvSA1P9E+8HmCeI 10mCoRUQH72dPwwRnaOUIoScdIPXWhpwCR5DU3CXEWjPpSiQNr5Uoab3iCt7YUKcCZ+hT/yFtToSB i7pltH16g==; 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 1jOJ8X-00062A-KP; Tue, 14 Apr 2020 10:49:49 +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 1jOJ8U-00061a-7I for linux-arm-kernel@lists.infradead.org; Tue, 14 Apr 2020 10:49:47 +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 8154F1FB; Tue, 14 Apr 2020 03:49:45 -0700 (PDT) Received: from [10.57.26.12] (unknown [10.57.26.12]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A4F883F6C4; Tue, 14 Apr 2020 03:49:42 -0700 (PDT) Subject: Re: [PATCH] arm64: Optimize ptrauth by enabling it for non-leaf functions To: Will Deacon References: <1586856741-26839-1-git-send-email-amit.kachhap@arm.com> <20200414100033.GA26395@willie-the-truck> From: Amit Kachhap Message-ID: <075bd3bb-e3d8-bf51-ddad-a27f726c5806@arm.com> Date: Tue, 14 Apr 2020 16:19:28 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20200414100033.GA26395@willie-the-truck> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200414_034946_310377_07A24726 X-CRM114-Status: GOOD ( 13.27 ) 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: Mark Rutland , Catalin Marinas , Mark Brown , James Morse , Vincenzo Frascino , linux-arm-kernel@lists.infradead.org, Daniel Kiss Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, On 4/14/20 3:30 PM, Will Deacon wrote: > On Tue, Apr 14, 2020 at 03:02:21PM +0530, Amit Daniel Kachhap wrote: >> Compilers are optimized to not store the stack frame record for the leaf >> function in the stack so applying pointer authentication in the leaf >> function is not useful from security point of view. > > I'm missing the reasoning here -- why don't we care about leaf functions? > > Sounds like there's a performance/security trade-off that needs spelling > out and justifying with some numbers, or is it clear-cut and I'm missing > something? Since lr is not stored on the stack so this function cannot be used for ROP gadget attack. Sure this also provides performance benefit. I will provide the percentage of code size reduction. Cheers, Amit > > Will > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel