From patchwork Thu Dec 6 23:44:04 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeremy Linton X-Patchwork-Id: 10717255 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C4DFF13BB for ; Thu, 6 Dec 2018 23:45:02 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B0FD02D799 for ; Thu, 6 Dec 2018 23:45:02 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 9F5132EC24; Thu, 6 Dec 2018 23:45:02 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 29C402D799 for ; Thu, 6 Dec 2018 23:44:58 +0000 (UTC) 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=hOrTUISbDkkst7OWFo98mPKiR4areBh+n0mptjrE4Ms=; b=EZEVkMDNzdvMo8Qhj408UHUxK2 Q857ytKGe1bnN5ycMgM3vg4DY52tDb0tGpuYKvgUX3nt2u9vy5Ttl0Mr56lT0vW1zdD9SHVnE+NJq +x/0nB5y46YC2au0qPaodk7hvxZ8kyCb/4XbTmIFOV8UvWdT81HM4ZfztnJcluLoWN+tbptzTtdjY sOPFGEPa9qPnJqCfb1/sCoraLmbA65kN79BFsKUKCuJd8vCmq0WuzHga1Wjwt166TUP7mekHEi5qi JjI7xAKRPAw/A558I/XRn/EnCAOzr4WyuJIAcDGmcMSCeLz2fCsSHvhvPIfjtJFrKwga8V7azHAeA Es+Y771g==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gV3K7-00026J-W6; Thu, 06 Dec 2018 23:44:52 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gV3Jq-0001q2-AB for linux-arm-kernel@lists.infradead.org; Thu, 06 Dec 2018 23:44:37 +0000 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 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> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20181206_154434_492271_BCEB96F6 X-CRM114-Status: GOOD ( 13.36 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, suzuki.poulose@arm.com, marc.zyngier@arm.com, catalin.marinas@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, Jeremy Linton , ykaukab@suse.de, dave.martin@arm.com, shankerd@codeaurora.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP 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