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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 5100BC04EB8 for ; Thu, 6 Dec 2018 23:44:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1569A2146D for ; Thu, 6 Dec 2018 23:44:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1569A2146D 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-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726412AbeLFXoc (ORCPT ); Thu, 6 Dec 2018 18:44:32 -0500 Received: from foss.arm.com ([217.140.101.70]:35906 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726249AbeLFXob (ORCPT ); Thu, 6 Dec 2018 18:44:31 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 1255915AD; Thu, 6 Dec 2018 15:44:31 -0800 (PST) Received: from beelzebub.austin.arm.com (beelzebub.austin.arm.com [10.118.12.119]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 851EA3F5AF; Thu, 6 Dec 2018 15:44:30 -0800 (PST) From: Jeremy Linton To: linux-arm-kernel@lists.infradead.org Cc: catalin.marinas@arm.com, will.deacon@arm.com, marc.zyngier@arm.com, suzuki.poulose@arm.com, dave.martin@arm.com, shankerd@codeaurora.org, mark.rutland@arm.com, linux-kernel@vger.kernel.org, ykaukab@suse.de, Jeremy Linton Subject: [PATCH 2/6] arm64: add sysfs vulnerability show for meltdown Date: Thu, 6 Dec 2018 17:44:04 -0600 Message-Id: <20181206234408.1287689-3-jeremy.linton@arm.com> X-Mailer: git-send-email 2.17.2 In-Reply-To: <20181206234408.1287689-1-jeremy.linton@arm.com> References: <20181206234408.1287689-1-jeremy.linton@arm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add a simple state machine which will track whether all the online cores in a machine are vulnerable. Once that is done we have a fairly authoritative view of the machine vulnerability, which allows us to make a judgment about machine safety if it hasn't been mitigated. Signed-off-by: Jeremy Linton --- arch/arm64/kernel/cpufeature.c | 31 ++++++++++++++++++++++++++----- 1 file changed, 26 insertions(+), 5 deletions(-) diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 242898395f68..bea9adfef7fa 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -905,6 +905,8 @@ has_useable_cnp(const struct arm64_cpu_capabilities *entry, int scope) return has_cpuid_feature(entry, scope); } +static enum { A64_MELT_UNSET, A64_MELT_SAFE, A64_MELT_UNKN } __meltdown_safe = A64_MELT_UNSET; + #ifdef CONFIG_UNMAP_KERNEL_AT_EL0 static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */ @@ -928,6 +930,15 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, { char const *str = "command line option"; + bool meltdown_safe = is_cpu_meltdown_safe() || + has_cpuid_feature(entry, scope); + + /* Only safe if all booted cores are known safe */ + if (meltdown_safe && __meltdown_safe == A64_MELT_UNSET) + __meltdown_safe = A64_MELT_SAFE; + else if (!meltdown_safe) + __meltdown_safe = A64_MELT_UNKN; + /* * For reasons that aren't entirely clear, enabling KPTI on Cavium * ThunderX leads to apparent I-cache corruption of kernel text, which @@ -949,11 +960,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) return true; - if (is_cpu_meltdown_safe()) - return false; - - /* Defer to CPU feature registers */ - return !has_cpuid_feature(entry, scope); + return !meltdown_safe; } static void @@ -1920,3 +1927,17 @@ static int __init enable_mrs_emulation(void) } core_initcall(enable_mrs_emulation); + +#ifdef CONFIG_GENERIC_CPU_VULNERABILITIES +ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, + char *buf) +{ + if (arm64_kernel_unmapped_at_el0()) + return sprintf(buf, "Mitigation: KPTI\n"); + + if (__meltdown_safe == A64_MELT_SAFE) + return sprintf(buf, "Not affected\n"); + + return sprintf(buf, "Unknown\n"); +} +#endif -- 2.17.2