From patchwork Mon Feb 17 09:27:47 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Amit Daniel Kachhap X-Patchwork-Id: 11385915 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 018381580 for ; Mon, 17 Feb 2020 09:32:33 +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 D3C8220679 for ; Mon, 17 Feb 2020 09:32:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="CWJp7gQN" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D3C8220679 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+patchwork-linux-arm=patchwork.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=SCo7CVpHbL6ZiumIvlxhlbeKclQjrgWkS8nDZv4iKVA=; b=CWJp7gQNs92xgGbjYQdocV05MA URmvPSuWE6xM3EDZb10WC6qoAbm+iBv9JilQqgquYWqSuKAId7z/xbDs4DP1VLl3ZL73Q/ezuh+K0 JglQ7MrW3XY1+UNLk5ovWvxHUQMPnYpfNtWsLjkdD0Wjr1NwdGRcGXoH5jVnLhkghxOh2nZqXJZQL hYrNAAcWdqekifXwLVoeSqBB3IWdQQ1eXavzk+Jb90zWCNYSAwx9D0DDLizFoXv7PyIlLznYrwqTM CpgRTsMSx3n0Ib8txeHlxfV5ZrPh8F3D4OrKneOXcDeRua4mp20Dgne/Ax31nSqLC5eGYdOfBBplu /O0ptBoQ==; 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 1j3clN-0002eO-P3; Mon, 17 Feb 2020 09:32:25 +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 1j3ciI-0006b6-H0 for linux-arm-kernel@lists.infradead.org; Mon, 17 Feb 2020 09:29:17 +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 000A1328; Mon, 17 Feb 2020 01:29:13 -0800 (PST) Received: from a075553-lin.blr.arm.com (a075553-lin.blr.arm.com [10.162.17.32]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id BD5DF3F6CF; Mon, 17 Feb 2020 01:29:09 -0800 (PST) From: Amit Daniel Kachhap To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 16/17] arm64: compile the kernel with ptrauth return address signing Date: Mon, 17 Feb 2020 14:57:47 +0530 Message-Id: <1581931668-11559-17-git-send-email-amit.kachhap@arm.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1581931668-11559-1-git-send-email-amit.kachhap@arm.com> References: <1581931668-11559-1-git-send-email-amit.kachhap@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200217_012914_679883_2FBA640B X-CRM114-Status: GOOD ( 18.94 ) X-Spam-Score: -2.3 (--) X-Spam-Report: SpamAssassin version 3.4.3 on bombadil.infradead.org summary: Content analysis details: (-2.3 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at https://www.dnswl.org/, medium trust [217.140.110.172 listed in list.dnswl.org] 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record 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 , Kristina Martsenko , Dave Martin , Masahiro Yamada , Mark Brown , James Morse , Ramana Radhakrishnan , Amit Daniel Kachhap , Vincenzo Frascino , Will Deacon , Ard Biesheuvel MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.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. Clang uses an external assembler hence this patch makes sure that the correct parameters (-march=armv8.3-a) are passed down to help it recognize the ptrauth instructions. This option is not used for GNU toolchain. Cc: Catalin Marinas Cc: Will Deacon Cc: Masahiro Yamada Reviewed-by: Kees Cook Co-developed-by: Vincenzo Frascino Signed-off-by: Vincenzo Frascino Signed-off-by: Kristina Martsenko [Amit: Cover leaf function, comments] Signed-off-by: Amit Daniel Kachhap --- arch/arm64/Kconfig | 20 +++++++++++++++++++- arch/arm64/Makefile | 11 +++++++++++ 2 files changed, 30 insertions(+), 1 deletion(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 115ceea..0f3ea01 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1499,6 +1499,7 @@ config ARM64_PTR_AUTH bool "Enable support for pointer authentication" default y depends on !KVM || ARM64_VHE + depends on (CC_HAS_SIGN_RETURN_ADDRESS || CC_HAS_BRANCH_PROT_PAC_RET) && AS_HAS_PAC help Pointer authentication (part of the ARMv8.3 Extensions) provides instructions for signing and authenticating pointers against secret @@ -1506,11 +1507,17 @@ 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 @@ -1522,6 +1529,17 @@ config ARM64_PTR_AUTH but with the feature disabled. 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 $(as-option,-Wa$(comma)-march=armv8.3-a) + endmenu menu "ARMv8.5 architectural features" diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index dca1a97..ce5bdeb 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -65,6 +65,17 @@ 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 += $(branch-prot-flags-y) +endif + ifeq ($(CONFIG_CPU_BIG_ENDIAN), y) KBUILD_CPPFLAGS += -mbig-endian CHECKFLAGS += -D__AARCH64EB__