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=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 DB60BECDFBD for ; Fri, 20 Jul 2018 12:32:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9EFA920854 for ; Fri, 20 Jul 2018 12:32:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9EFA920854 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388529AbeGTNUQ (ORCPT ); Fri, 20 Jul 2018 09:20:16 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:39860 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388160AbeGTNUQ (ORCPT ); Fri, 20 Jul 2018 09:20:16 -0400 Received: from localhost (LFbn-1-12238-233.w90-92.abo.wanadoo.fr [90.92.53.233]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id ECCC6C50; Fri, 20 Jul 2018 12:31:08 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , Will Deacon , Marc Zyngier , Catalin Marinas Subject: [PATCH 4.9 61/66] arm64: ssbd: Add prctl interface for per-thread mitigation Date: Fri, 20 Jul 2018 14:14:18 +0200 Message-Id: <20180720121412.220311864@linuxfoundation.org> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180720121407.228772286@linuxfoundation.org> References: <20180720121407.228772286@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Marc Zyngier commit 9cdc0108baa8ef87c76ed834619886a46bd70cbe upstream. If running on a system that performs dynamic SSBD mitigation, allow userspace to request the mitigation for itself. This is implemented as a prctl call, allowing the mitigation to be enabled or disabled at will for this particular thread. Acked-by: Will Deacon Signed-off-by: Marc Zyngier Signed-off-by: Catalin Marinas Signed-off-by: Marc Zyngier Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kernel/Makefile | 1 arch/arm64/kernel/ssbd.c | 108 +++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 109 insertions(+) create mode 100644 arch/arm64/kernel/ssbd.c --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -50,6 +50,7 @@ arm64-obj-$(CONFIG_RANDOMIZE_BASE) += ka arm64-obj-$(CONFIG_HIBERNATION) += hibernate.o hibernate-asm.o arm64-obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o \ cpu-reset.o +arm64-obj-$(CONFIG_ARM64_SSBD) += ssbd.o ifeq ($(CONFIG_KVM),y) arm64-obj-$(CONFIG_HARDEN_BRANCH_PREDICTOR) += bpi.o --- /dev/null +++ b/arch/arm64/kernel/ssbd.c @@ -0,0 +1,108 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2018 ARM Ltd, All Rights Reserved. + */ + +#include +#include +#include +#include + +#include + +/* + * prctl interface for SSBD + */ +static int ssbd_prctl_set(struct task_struct *task, unsigned long ctrl) +{ + int state = arm64_get_ssbd_state(); + + /* Unsupported */ + if (state == ARM64_SSBD_UNKNOWN) + return -EINVAL; + + /* Treat the unaffected/mitigated state separately */ + if (state == ARM64_SSBD_MITIGATED) { + switch (ctrl) { + case PR_SPEC_ENABLE: + return -EPERM; + case PR_SPEC_DISABLE: + case PR_SPEC_FORCE_DISABLE: + return 0; + } + } + + /* + * Things are a bit backward here: the arm64 internal API + * *enables the mitigation* when the userspace API *disables + * speculation*. So much fun. + */ + switch (ctrl) { + case PR_SPEC_ENABLE: + /* If speculation is force disabled, enable is not allowed */ + if (state == ARM64_SSBD_FORCE_ENABLE || + task_spec_ssb_force_disable(task)) + return -EPERM; + task_clear_spec_ssb_disable(task); + clear_tsk_thread_flag(task, TIF_SSBD); + break; + case PR_SPEC_DISABLE: + if (state == ARM64_SSBD_FORCE_DISABLE) + return -EPERM; + task_set_spec_ssb_disable(task); + set_tsk_thread_flag(task, TIF_SSBD); + break; + case PR_SPEC_FORCE_DISABLE: + if (state == ARM64_SSBD_FORCE_DISABLE) + return -EPERM; + task_set_spec_ssb_disable(task); + task_set_spec_ssb_force_disable(task); + set_tsk_thread_flag(task, TIF_SSBD); + break; + default: + return -ERANGE; + } + + return 0; +} + +int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which, + unsigned long ctrl) +{ + switch (which) { + case PR_SPEC_STORE_BYPASS: + return ssbd_prctl_set(task, ctrl); + default: + return -ENODEV; + } +} + +static int ssbd_prctl_get(struct task_struct *task) +{ + switch (arm64_get_ssbd_state()) { + case ARM64_SSBD_UNKNOWN: + return -EINVAL; + case ARM64_SSBD_FORCE_ENABLE: + return PR_SPEC_DISABLE; + case ARM64_SSBD_KERNEL: + if (task_spec_ssb_force_disable(task)) + return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE; + if (task_spec_ssb_disable(task)) + return PR_SPEC_PRCTL | PR_SPEC_DISABLE; + return PR_SPEC_PRCTL | PR_SPEC_ENABLE; + case ARM64_SSBD_FORCE_DISABLE: + return PR_SPEC_ENABLE; + default: + return PR_SPEC_NOT_AFFECTED; + } +} + +int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which) +{ + switch (which) { + case PR_SPEC_STORE_BYPASS: + return ssbd_prctl_get(task); + default: + return -ENODEV; + } +}