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=-7.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 3B16BC04EBF for ; Tue, 4 Dec 2018 11:30:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EC86720851 for ; Tue, 4 Dec 2018 11:30:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="y6rBE6IT" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EC86720851 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 S1726792AbeLDLaL (ORCPT ); Tue, 4 Dec 2018 06:30:11 -0500 Received: from mail.kernel.org ([198.145.29.99]:41374 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726737AbeLDK51 (ORCPT ); Tue, 4 Dec 2018 05:57:27 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7A2C1214DE; Tue, 4 Dec 2018 10:57:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1543921047; bh=YNBnpgMt8ovF4tGQpHsT8DYxI7egCexXJPRPnk+jtsU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=y6rBE6ITVgu9pkQC2p7caRF2GaNl9JzCgBh9d1ErdmavmwUEPIHbth2eO/N7Cck76 8fPrSwqh7B1/F6JDrRCVykfeVQNFt0h0t7cIA62izpHKv9b3296/OhqFa4yrMtJ5AE 1H93BJKPhmt7DjSB0rbrv6uYeW1Y6u7lQtketlcY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Peter Zijlstra , Andy Lutomirski , Linus Torvalds , Jiri Kosina , Tom Lendacky , Josh Poimboeuf , Andrea Arcangeli , David Woodhouse , Tim Chen , Andi Kleen , Dave Hansen , Casey Schaufler , Asit Mallick , Arjan van de Ven , Jon Masters , Waiman Long , Dave Stewart , Kees Cook Subject: [PATCH 4.19 059/139] x86/speculation: Enable prctl mode for spectre_v2_user Date: Tue, 4 Dec 2018 11:49:00 +0100 Message-Id: <20181204103652.415521380@linuxfoundation.org> X-Mailer: git-send-email 2.19.2 In-Reply-To: <20181204103649.950154335@linuxfoundation.org> References: <20181204103649.950154335@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Archived-At: List-Archive: List-Post: 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Gleixner tglx@linutronix.de commit 7cc765a67d8e04ef7d772425ca5a2a1e2b894c15 upstream Now that all prerequisites are in place: - Add the prctl command line option - Default the 'auto' mode to 'prctl' - When SMT state changes, update the static key which controls the conditional STIBP evaluation on context switch. - At init update the static key which controls the conditional IBPB evaluation on context switch. Signed-off-by: Thomas Gleixner Reviewed-by: Ingo Molnar Cc: Peter Zijlstra Cc: Andy Lutomirski Cc: Linus Torvalds Cc: Jiri Kosina Cc: Tom Lendacky Cc: Josh Poimboeuf Cc: Andrea Arcangeli Cc: David Woodhouse Cc: Tim Chen Cc: Andi Kleen Cc: Dave Hansen Cc: Casey Schaufler Cc: Asit Mallick Cc: Arjan van de Ven Cc: Jon Masters Cc: Waiman Long Cc: Greg KH Cc: Dave Stewart Cc: Kees Cook Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20181125185005.958421388@linutronix.de Signed-off-by: Greg Kroah-Hartman --- Documentation/admin-guide/kernel-parameters.txt | 7 +++- arch/x86/kernel/cpu/bugs.c | 41 ++++++++++++++++++------ 2 files changed, 38 insertions(+), 10 deletions(-) --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4211,9 +4211,14 @@ off - Unconditionally disable mitigations. Is enforced by spectre_v2=off + prctl - Indirect branch speculation is enabled, + but mitigation can be enabled via prctl + per thread. The mitigation control state + is inherited on fork. + auto - Kernel selects the mitigation depending on the available CPU features and vulnerability. - Default is off. + Default is prctl. Not specifying this option is equivalent to spectre_v2_user=auto. --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -255,11 +255,13 @@ enum spectre_v2_user_cmd { SPECTRE_V2_USER_CMD_NONE, SPECTRE_V2_USER_CMD_AUTO, SPECTRE_V2_USER_CMD_FORCE, + SPECTRE_V2_USER_CMD_PRCTL, }; static const char * const spectre_v2_user_strings[] = { [SPECTRE_V2_USER_NONE] = "User space: Vulnerable", [SPECTRE_V2_USER_STRICT] = "User space: Mitigation: STIBP protection", + [SPECTRE_V2_USER_PRCTL] = "User space: Mitigation: STIBP via prctl", }; static const struct { @@ -270,6 +272,7 @@ static const struct { { "auto", SPECTRE_V2_USER_CMD_AUTO, false }, { "off", SPECTRE_V2_USER_CMD_NONE, false }, { "on", SPECTRE_V2_USER_CMD_FORCE, true }, + { "prctl", SPECTRE_V2_USER_CMD_PRCTL, false }, }; static void __init spec_v2_user_print_cond(const char *reason, bool secure) @@ -324,12 +327,15 @@ spectre_v2_user_select_mitigation(enum s smt_possible = false; switch (spectre_v2_parse_user_cmdline(v2_cmd)) { - case SPECTRE_V2_USER_CMD_AUTO: case SPECTRE_V2_USER_CMD_NONE: goto set_mode; case SPECTRE_V2_USER_CMD_FORCE: mode = SPECTRE_V2_USER_STRICT; break; + case SPECTRE_V2_USER_CMD_AUTO: + case SPECTRE_V2_USER_CMD_PRCTL: + mode = SPECTRE_V2_USER_PRCTL; + break; } /* Initialize Indirect Branch Prediction Barrier */ @@ -340,6 +346,9 @@ spectre_v2_user_select_mitigation(enum s case SPECTRE_V2_USER_STRICT: static_branch_enable(&switch_mm_always_ibpb); break; + case SPECTRE_V2_USER_PRCTL: + static_branch_enable(&switch_mm_cond_ibpb); + break; default: break; } @@ -352,6 +361,12 @@ spectre_v2_user_select_mitigation(enum s if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED) return; + /* + * If SMT is not possible or STIBP is not available clear the STIPB + * mode. + */ + if (!smt_possible || !boot_cpu_has(X86_FEATURE_STIBP)) + mode = SPECTRE_V2_USER_NONE; set_mode: spectre_v2_user = mode; /* Only print the STIBP mode when SMT possible */ @@ -550,6 +565,15 @@ static void update_stibp_strict(void) on_each_cpu(update_stibp_msr, NULL, 1); } +/* Update the static key controlling the evaluation of TIF_SPEC_IB */ +static void update_indir_branch_cond(void) +{ + if (sched_smt_active()) + static_branch_enable(&switch_to_cond_stibp); + else + static_branch_disable(&switch_to_cond_stibp); +} + void arch_smt_update(void) { /* Enhanced IBRS implies STIBP. No update required. */ @@ -565,6 +589,7 @@ void arch_smt_update(void) update_stibp_strict(); break; case SPECTRE_V2_USER_PRCTL: + update_indir_branch_cond(); break; } @@ -1036,7 +1061,8 @@ static char *stibp_state(void) case SPECTRE_V2_USER_STRICT: return ", STIBP: forced"; case SPECTRE_V2_USER_PRCTL: - return ""; + if (static_key_enabled(&switch_to_cond_stibp)) + return ", STIBP: conditional"; } return ""; } @@ -1044,14 +1070,11 @@ static char *stibp_state(void) static char *ibpb_state(void) { if (boot_cpu_has(X86_FEATURE_IBPB)) { - switch (spectre_v2_user) { - case SPECTRE_V2_USER_NONE: - return ", IBPB: disabled"; - case SPECTRE_V2_USER_STRICT: + if (static_key_enabled(&switch_mm_always_ibpb)) return ", IBPB: always-on"; - case SPECTRE_V2_USER_PRCTL: - return ""; - } + if (static_key_enabled(&switch_mm_cond_ibpb)) + return ", IBPB: conditional"; + return ", IBPB: disabled"; } return ""; }