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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 29FC5FA372D for ; Thu, 17 Oct 2019 08:18:11 +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 E733B20820 for ; Thu, 17 Oct 2019 08:18:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="brLA1cMW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E733B20820 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:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:References: In-Reply-To:Message-Id:Date:Subject:To:From:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=HFnUfm04yYhpWcSZX8CKU6gsyqv/VdQgOdSQGuDdH2w=; b=brLA1cMW46WcjKKSFrWlak2lG1 5crXw6JqYWuwGpYdAh0+oFbVHF2zBnL8prMk4Z5gquaIgOAMQH8ifMSx4i+a+3/wK41tj95MysEq0 FXv45WbQHU4bU08/5S/NASo66om3urxX/MOpZq51YIbL9+v2Eym24D4xkAjE0TBtXXGmQew4JgEEN /mMia5uAkDPUJ3SIgKYZRm0PC40EDHFTf60jstvrS9vhu4MCPbTxKWqeulKF0Utf2tufn95gZMgnz 4LMsRnKM8wiCICHtglRFTc+shYV2PCC1Pe8Dy1LzfYQcSjo+/gHGp+bKhA2RZr1FVCkOtNM3rFCzc 1+QN8izA==; 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 1iL0z3-0004xm-FW; Thu, 17 Oct 2019 08:18:09 +0000 Received: from [217.140.110.172] (helo=foss.arm.com) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iL0wS-000256-65 for linux-arm-kernel@lists.infradead.org; Thu, 17 Oct 2019 08:15:32 +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 B771428; Thu, 17 Oct 2019 01:15:25 -0700 (PDT) Received: from a075553-lin.blr.arm.com (a075553-lin.blr.arm.com [10.162.0.144]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 1D0E63F6C4; Thu, 17 Oct 2019 01:15:21 -0700 (PDT) From: Amit Daniel Kachhap To: linux-arm-kernel@lists.infradead.org Subject: [PATCH 11/11] arm64: compile the kernel with ptrauth return address signing Date: Thu, 17 Oct 2019 13:44:25 +0530 Message-Id: <1571300065-10236-12-git-send-email-amit.kachhap@arm.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1571300065-10236-1-git-send-email-amit.kachhap@arm.com> References: <1571300065-10236-1-git-send-email-amit.kachhap@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191017_011528_461741_832A4972 X-CRM114-Status: GOOD ( 16.97 ) 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 , Catalin Marinas , Ard Biesheuvel , Will Deacon , Kristina Martsenko , James Morse , Ramana Radhakrishnan , Amit Daniel Kachhap , Vincenzo Frascino , Dave Martin MIME-Version: 1.0 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 From: Kristina Martsenko Compile all functions with two ptrauth instructions: PACIASP in the prologue to sign the return address, and AUTIASP in the epilogue to authenticate the return address (from the stack). If authentication fails, the return will cause an instruction abort to be taken, followed by an oops and killing the task. This should help protect the kernel against attacks using return-oriented programming. As ptrauth protects the return address, it can also serve as a replacement for CONFIG_STACKPROTECTOR, although note that it does not protect other parts of the stack. The new instructions are in the HINT encoding space, so on a system without ptrauth they execute as NOPs. CONFIG_ARM64_PTR_AUTH now not only enables ptrauth for userspace and KVM guests, but also automatically builds the kernel with ptrauth instructions if the compiler supports it. If there is no compiler support, we do not warn that the kernel was built without ptrauth instructions. GCC 7 and 8 support the -msign-return-address option, while GCC 9 deprecates that option and replaces it with -mbranch-protection. Support both options. Reviewed-by: Kees Cook Signed-off-by: Kristina Martsenko Signed-off-by: Amit Daniel Kachhap --- Changes since RFC v2: - Removed function attribute definition [Suzuki] - Added comments about GCC versions to Kconfig symbols [Kees] - Added a note in Kconfig (and the commit message) about STACKPROTECTOR - Changed GCC option to protect all functions with ptrauth and just non-leaf. arch/arm64/Kconfig | 16 +++++++++++++++- arch/arm64/Makefile | 6 ++++++ 2 files changed, 21 insertions(+), 1 deletion(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 8e86f6a..f83db93 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1399,11 +1399,17 @@ 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 @@ -1413,6 +1419,14 @@ config ARM64_PTR_AUTH then the secondary CPU will be offlined. On such a system, this option should not be selected. +config CC_HAS_BRANCH_PROT_PAC_RET + # GCC 9 or later + def_bool $(cc-option,-mbranch-protection=pac-ret+leaf) + +config CC_HAS_SIGN_RETURN_ADDRESS + # GCC 7, 8 + def_bool $(cc-option,-msign-return-address=all) + endmenu config ARM64_SVE diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 84a3d50..4dbe86a 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -88,6 +88,12 @@ stack_protector_prepare: prepare0 include/generated/asm-offsets.h)) endif +ifeq ($(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 += $(pac-flags-y) +endif + ifeq ($(CONFIG_CPU_BIG_ENDIAN), y) KBUILD_CPPFLAGS += -mbig-endian CHECKFLAGS += -D__AARCH64EB__ -- 2.7.4 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel