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=-3.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 A39BBC47254 for ; Tue, 5 May 2020 14:14:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8BBC9206FA for ; Tue, 5 May 2020 14:14:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729650AbgEEOOo (ORCPT ); Tue, 5 May 2020 10:14:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48730 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1729628AbgEEOOl (ORCPT ); Tue, 5 May 2020 10:14:41 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 971D8C061A0F for ; Tue, 5 May 2020 07:14:40 -0700 (PDT) Received: from p5de0bf0b.dip0.t-ipconnect.de ([93.224.191.11] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jVyKv-0000xa-8y; Tue, 05 May 2020 16:14:17 +0200 Received: from nanos.tec.linutronix.de (localhost [IPv6:::1]) by nanos.tec.linutronix.de (Postfix) with ESMTP id 864EEFFC8D; Tue, 5 May 2020 16:14:16 +0200 (CEST) Message-Id: <20200505134340.429059405@linutronix.de> User-Agent: quilt/0.65 Date: Tue, 05 May 2020 15:41:15 +0200 From: Thomas Gleixner To: LKML Cc: x86@kernel.org, "Paul E. McKenney" , Andy Lutomirski , Alexandre Chartre , Frederic Weisbecker , Paolo Bonzini , Sean Christopherson , Masami Hiramatsu , Petr Mladek , Steven Rostedt , Joel Fernandes , Boris Ostrovsky , Juergen Gross , Brian Gerst , Mathieu Desnoyers , Josh Poimboeuf , Will Deacon Subject: [patch V4 part 2 03/18] x86/entry: Mark enter_from_user_mode() noinstr References: <20200505134112.272268764@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-transfer-encoding: 8-bit X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Both the callers in the low level ASM code and __context_tracking_exit() which is invoked from enter_from_user_mode() via user_exit_irqoff() are marked NOKPROBE. Allowing enter_from_user_mode() to be probed is inconsistent at best. Aside of that while function tracing per se is safe the function trace entry/exit points can be used via BPF as well which is not safe to use before context tracking has reached CONTEXT_KERNEL and adjusted RCU. Mark it noinstr which moves it into the instrumentation protected text section and includes notrace. Note, this needs further fixups in context tracking to ensure that the full call chain is protected. Will be addressed in follow up changes. Signed-off-by: Thomas Gleixner --- arch/x86/entry/common.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -41,7 +41,7 @@ #ifdef CONFIG_CONTEXT_TRACKING /* Called on entry from user mode with IRQs off. */ -__visible inline void enter_from_user_mode(void) +__visible inline noinstr void enter_from_user_mode(void) { CT_WARN_ON(ct_state() != CONTEXT_USER); user_exit_irqoff();