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=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 A53E4C33CB1 for ; Fri, 17 Jan 2020 11:49:59 +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 6B3D32082F for ; Fri, 17 Jan 2020 11:49:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="BWGLjaYa" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6B3D32082F 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-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=QL9c9ARNOWOgmqWIEy9brJ/b9S1ss4JEUeQ0nfH+Igw=; b=BWGLjaYa9DdUmN VrwoJJyIj8O4SI3qPTO/16MBKLm8cW+3rj9KVoSyB11db9xOwT+aJy0aIGb+BYAroczYelwLIdvTB rs+744OHMOI4j7/k3zb2Z3wjRbQ1IjcbqI/YuRJLau9JQ35WjjL9eVMdw7dP7gDFrHwGkt2le8FGC Rr4s6E4VSkPMKeXXuebw1e3dxPQn//PLziE1l0/xeemjGfd2LIO71WsFmHsz4K9rUmNNidt3hBxUO Keovt4ns+6ofv9pc7l9gRY1qyeSQHMgDWaRf+DIa8rjLCav1RkOGwwEztFDoJ7gyhDHxINrMiNXTv uXZMhIsGlpnh5XDfAfJQ==; 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 1isQ8U-0008D0-IP; Fri, 17 Jan 2020 11:49:58 +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 1isQ8M-0008CQ-7Y for linux-arm-kernel@lists.infradead.org; Fri, 17 Jan 2020 11:49:56 +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 7480C11D4; Fri, 17 Jan 2020 03:49:46 -0800 (PST) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.197.42]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AFE053F6C4; Fri, 17 Jan 2020 03:49:44 -0800 (PST) Date: Fri, 17 Jan 2020 11:49:42 +0000 From: Catalin Marinas To: Amit Daniel Kachhap Subject: Re: [PATCH v3 15/16] arm64: compile the kernel with ptrauth return address signing Message-ID: <20200117114942.GG26090@arrakis.emea.arm.com> References: <1576486038-9899-1-git-send-email-amit.kachhap@arm.com> <1576486038-9899-16-git-send-email-amit.kachhap@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1576486038-9899-16-git-send-email-amit.kachhap@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200117_034950_359213_2AB5F20A X-CRM114-Status: GOOD ( 23.47 ) 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 , Suzuki K Poulose , Ard Biesheuvel , Richard Henderson , Kristina Martsenko , James Morse , Ramana Radhakrishnan , Mark Brown , Vincenzo Frascino , Will Deacon , Dave Martin , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Dec 16, 2019 at 02:17:17PM +0530, Amit Daniel Kachhap wrote: > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 06b5025..f0798b7 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -1466,6 +1466,7 @@ config ARM64_PTR_AUTH > bool "Enable support for pointer authentication" > default y > depends on !KVM || ARM64_VHE > + depends on GCC_VERSION >= 70000 || CLANG_VERSION >= 80000 Please don't add checks on compiler versions. Use cc-option when you need a certain option rather than guessing which compiler version supports it. People may do backports of different features, so the version is not relevant. > help > Pointer authentication (part of the ARMv8.3 Extensions) provides > instructions for signing and authenticating pointers against secret > @@ -1473,11 +1474,17 @@ config ARM64_PTR_AUTH > and other attacks. > > This option enables these instructions at EL0 (i.e. for userspace). > - > Choosing this option will cause the kernel to initialise secret keys > for each process at exec() time, with these keys being > context-switched along with the process. > > + If the compiler supports the -mbranch-protection or > + -msign-return-address flag (e.g. GCC 7 or later), then this option > + will also cause the kernel itself to be compiled with return address > + protection. In this case, and if the target hardware is known to > + support pointer authentication, then CONFIG_STACKPROTECTOR can be > + disabled with minimal loss of protection. > + > The feature is detected at runtime. If the feature is not present in > hardware it will not be advertised to userspace/KVM guest nor will it > be enabled. However, KVM guest also require VHE mode and hence > @@ -1488,6 +1495,18 @@ config ARM64_PTR_AUTH > have address auth and the late CPU has then system panic will occur. > On such a system, this option should not be selected. > > +config CC_HAS_BRANCH_PROT_PAC_RET > + # GCC 9 or later, clang 8 or later > + def_bool $(cc-option,-mbranch-protection=pac-ret+leaf) > + > +config CC_HAS_SIGN_RETURN_ADDRESS > + # GCC 7, 8 > + def_bool $(cc-option,-msign-return-address=all) > + > +config AS_HAS_PAC > + def_bool $(as-option,-Wa,-march=armv8.3-a) > + depends on CC_IS_CLANG First, as I commented on the previous patch, clang seems to ignore -Wa, so you can write whatever you want after it and it seems to be always true. Second, if you need the assembler to support certain features, it needs to be checked irrespective of whether the compiler is gcc or clang. Binutils is a separate package. > + > endmenu > > config ARM64_SVE > diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile > index 1fbe24d..6a1da59 100644 > --- a/arch/arm64/Makefile > +++ b/arch/arm64/Makefile > @@ -72,6 +72,17 @@ stack_protector_prepare: prepare0 > include/generated/asm-offsets.h)) > endif > > +ifeq ($(CONFIG_ARM64_PTR_AUTH),y) > +branch-prot-flags-$(CONFIG_CC_HAS_SIGN_RETURN_ADDRESS) := -msign-return-address=all > +branch-prot-flags-$(CONFIG_CC_HAS_BRANCH_PROT_PAC_RET) := -mbranch-protection=pac-ret+leaf > +# -march=armv8.3-a enables the non-nops instructions for PAC, to avoid the compiler > +# to generate them and consequently to break the single image contract we pass it > +# only to the assembler when clang is selected as a compiler. For the GNU toolchain > +# this option is not used. > +branch-prot-flags-$(CONFIG_AS_HAS_PAC) += -Wa,-march=armv8.3-a > +KBUILD_CFLAGS += $(branch-prot-flags-y) > +endif So, does this actually work with clang? Please check the clang issue in case I'm mistaken. Otherwise, you could use as-instr as in this patch: https://lore.kernel.org/linux-arm-kernel/20200115113008.3334-3-catalin.marinas@arm.com/ Also Will had a preference for warning during build if the user requested a feature in .config (i.e. PAC) but the compiler/assembler does not support it (that was for the LSE patch above). You could attempt something similar with this patch. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel