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 79EBEC432C0 for ; Tue, 26 Nov 2019 07:00:31 +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 3E0D2206BF for ; Tue, 26 Nov 2019 07:00:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="mfkz319S" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3E0D2206BF 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=p8YY/qAK9dqf0CeO7e6fKtkcJcX/utS86aDSPvzeP28=; b=mfkz319SpUTi1eRYwR23N//iE iI2ahZHe7NFFQcKqlkfXnC1IrvWOiFDlsvXmcXFkK6ZH3N5E6A+yvaaKSBXCawgaW2g+IFtisSAMV q0UgUKHjbjYvQc8gKJivZiG9P6iqVq+3yrGAJjRUGUa4BESjP/LHR3TjjeWrCgZMitBXCEJ3ZS0gc vCqy49P3gXI3xvuSgXwSdfk8WpMY1UL8foJpwIS3kf/W7gQ/OHbbI1LjCjfYs7ocXPyt5NS8M4iHY QdDDSRGr/H8u2qXx+WJXVhOflGyuyYw2c95Y3kTE47/xpZQDEAZmzuAsdtTXuGd1PGSCtgx7L4ZIq 2HM/X3kzQ==; 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 1iZUpq-0002Lj-Fm; Tue, 26 Nov 2019 07:00:30 +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 1iZUpn-0002LC-Tu for linux-arm-kernel@lists.infradead.org; Tue, 26 Nov 2019 07:00:29 +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 32FB530E; Mon, 25 Nov 2019 23:00:25 -0800 (PST) Received: from [10.163.1.198] (unknown [10.163.1.198]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 92C173F6C4; Mon, 25 Nov 2019 23:03:23 -0800 (PST) Subject: Re: [PATCH v2 13/14] arm64: compile the kernel with ptrauth return address signing To: Mark Brown References: <1574166746-27197-1-git-send-email-amit.kachhap@arm.com> <1574166746-27197-14-git-send-email-amit.kachhap@arm.com> <20191121150605.GC4071@sirena.org.uk> From: Amit Kachhap Message-ID: <7cdad21e-d50e-86d4-5ea8-4b85e52f4673@arm.com> Date: Tue, 26 Nov 2019 12:30:13 +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: <20191121150605.GC4071@sirena.org.uk> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191125_230028_007017_A3B65A32 X-CRM114-Status: GOOD ( 19.95 ) 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 , Kees Cook , Ard Biesheuvel , Catalin Marinas , Suzuki K Poulose , Will Deacon , Kristina Martsenko , James Morse , Ramana Radhakrishnan , Vincenzo Frascino , Dave Martin , linux-arm-kernel@lists.infradead.org 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 Mark, On 11/21/19 8:36 PM, Mark Brown wrote: > On Tue, Nov 19, 2019 at 06:02:25PM +0530, Amit Daniel Kachhap wrote: > >> +config CC_HAS_BRANCH_PROT_PAC_RET >> + # GCC 9 or later >> + def_bool $(cc-option,-mbranch-protection=pac-ret+leaf) > > clang also supports this option, as of clang-8 I think. ok. I will test and update the comment here. > >> +ifeq ($(CONFIG_ARM64_PTR_AUTH),y) >> +pac-flags-$(CONFIG_CC_HAS_SIGN_RETURN_ADDRESS) := -msign-return-address=all >> +pac-flags-$(CONFIG_CC_HAS_BRANCH_PROT_PAC_RET) := -mbranch-protection=pac-ret+leaf >> +KBUILD_CFLAGS += $(pac-flags-y) >> +endif > > This is going to be a bit annoying with BTI as we need to set > -mbranch-protection=bti too. This means we end up with type > bti+pac-ret+leaf which is annoying to arrange. There is the convenient > branch protection type standard which does enable both in one option but > that only enables non-leaf pac-ret so you need to explicitly spell out > pac-ret so you can turn on leaf as well. I'm not sure I can think of > anything much better than adding another case for BTI at the top so we > end up with something along the lines of: Yes. The reason for keeping pac-ret+leaf is to cover all functions in the earlier offline discussions. As you pointed out I can add CC_HAS_BRANCH_PROT_PAC_RET_LEAF config name to make it more meaningful > > ifeq ($(CONFIG_ARM64_BTI_KERNEL),y) > branch-prot-flags-$(CONFIG_CC_HAS_BRANCH_PROT_BTI) := -mbranch-protection=bti+pac-ret+leaf > else ifeq ($(CONFIG_ARM64_PTR_AUTH),y) > branch-prot-flags-$(CONFIG_CC_HAS_BRANCH_PROT_PAC_RET) := -mbranch-protection=pac-ret+leaf > endif > KBUILD_CFLAGS += $(branch-prot-flags-y) > > with a separate section for the signed return address bit. It would be > helpful to avoid the immediate refactoring when adding BTI by splitting > things up with a more generic name. I agree with your concern for separate section when BTI support is added. I will do it in my next iteration. //Amit > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel