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,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 B8046C282D8 for ; Fri, 1 Feb 2019 20:54:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 89EA6218AF for ; Fri, 1 Feb 2019 20:54:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728919AbfBAUym (ORCPT ); Fri, 1 Feb 2019 15:54:42 -0500 Received: from mga18.intel.com ([134.134.136.126]:59549 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726506AbfBAUyj (ORCPT ); Fri, 1 Feb 2019 15:54:39 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 01 Feb 2019 12:54:39 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,549,1539673200"; d="scan'208";a="140866329" Received: from chang-linux-2.sc.intel.com ([10.3.52.165]) by fmsmga004.fm.intel.com with ESMTP; 01 Feb 2019 12:54:38 -0800 From: "Chang S. Bae" To: Andy Lutomirski , Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , Andi Kleen Cc: Markus T Metzger , Ravi Shankar , "Chang S . Bae" , LKML Subject: [PATCH v5 02/13] x86/fsgsbase/64: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE Date: Fri, 1 Feb 2019 12:53:07 -0800 Message-Id: <20190201205319.15995-3-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20190201205319.15995-1-chang.seok.bae@intel.com> References: <20190201205319.15995-1-chang.seok.bae@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andy Lutomirski This is temporary. It will allow the next few patches to be tested incrementally. Setting unsafe_fsgsbase is a root hole. Don't do it. [ chang: Minor fix. Add the TAINT_INSECURE flag. ] Signed-off-by: Andy Lutomirski Signed-off-by: Chang S. Bae Reviewed-by: Andi Kleen Reviewed-by: Andy Lutomirski Cc: Thomas Gleixner Cc: Ingo Molnar Cc: H. Peter Anvin --- .../admin-guide/kernel-parameters.txt | 3 +++ arch/x86/kernel/cpu/common.c | 27 +++++++++++++++++++ 2 files changed, 30 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index d59dff450614..871260e3e832 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2760,6 +2760,9 @@ no5lvl [X86-64] Disable 5-level paging mode. Forces kernel to use 4-level paging instead. + unsafe_fsgsbase [X86] Allow FSGSBASE instructions. This will be + replaced with a nofsgsbase flag. + no_console_suspend [HW] Never suspend the console Disable suspending of consoles during suspend and diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index cb28e98a0659..6e2cba21328f 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -365,6 +365,25 @@ static __always_inline void setup_umip(struct cpuinfo_x86 *c) cr4_clear_bits(X86_CR4_UMIP); } +/* + * Temporary hack: FSGSBASE is unsafe until a few kernel code paths are + * updated. This allows us to get the kernel ready incrementally. Setting + * unsafe_fsgsbase and TAINT_INSECURE flags will allow the series to be + * bisected if necessary. + * + * Once all the pieces are in place, these will go away and be replaced with + * a nofsgsbase chicken flag. + */ +static bool unsafe_fsgsbase; + +static __init int setup_unsafe_fsgsbase(char *arg) +{ + unsafe_fsgsbase = true; + add_taint(TAINT_INSECURE, LOCKDEP_STILL_OK); + return 1; +} +__setup("unsafe_fsgsbase", setup_unsafe_fsgsbase); + /* * Protection Keys are not available in 32-bit mode. */ @@ -1352,6 +1371,14 @@ static void identify_cpu(struct cpuinfo_x86 *c) setup_smap(c); setup_umip(c); + /* Enable FSGSBASE instructions if available. */ + if (cpu_has(c, X86_FEATURE_FSGSBASE)) { + if (unsafe_fsgsbase) + cr4_set_bits(X86_CR4_FSGSBASE); + else + clear_cpu_cap(c, X86_FEATURE_FSGSBASE); + } + /* * The vendor-specific functions might have changed features. * Now we do "generic changes." -- 2.19.1