From patchwork Wed May 3 12:23:27 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jiri Slaby X-Patchwork-Id: 9709707 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id CD30A60351 for ; Wed, 3 May 2017 12:24:04 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B7F1F28636 for ; Wed, 3 May 2017 12:24:04 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id AA6202862B; Wed, 3 May 2017 12:24:04 +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=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C3F0F28631 for ; Wed, 3 May 2017 12:24:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752135AbdECMYA (ORCPT ); Wed, 3 May 2017 08:24:00 -0400 Received: from mx2.suse.de ([195.135.220.15]:38615 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751005AbdECMXt (ORCPT ); Wed, 3 May 2017 08:23:49 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id E42E3AEC2; Wed, 3 May 2017 12:23:41 +0000 (UTC) From: Jiri Slaby To: stable@vger.kernel.org Cc: Josh Poimboeuf , "Rafael J . Wysocki" , linux-acpi@vger.kernel.org, Borislav Petkov , Len Brown , Thomas Gleixner , Jiri Slaby Subject: [patch added to 3.12-stable] ftrace/x86: Fix triple fault with graph tracing and suspend-to-ram Date: Wed, 3 May 2017 14:23:27 +0200 Message-Id: <20170503122327.12095-49-jslaby@suse.cz> X-Mailer: git-send-email 2.12.2 In-Reply-To: <20170503122327.12095-1-jslaby@suse.cz> References: <20170503122327.12095-1-jslaby@suse.cz> Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Josh Poimboeuf This patch has been added to the 3.12 stable tree. If you have any objections, please let us know. =============== commit 34a477e5297cbaa6ecc6e17c042a866e1cbe80d6 upstream. On x86-32, with CONFIG_FIRMWARE and multiple CPUs, if you enable function graph tracing and then suspend to RAM, it will triple fault and reboot when it resumes. The first fault happens when booting a secondary CPU: startup_32_smp() load_ucode_ap() prepare_ftrace_return() ftrace_graph_is_dead() (accesses 'kill_ftrace_graph') The early head_32.S code calls into load_ucode_ap(), which has an an ftrace hook, so it calls prepare_ftrace_return(), which calls ftrace_graph_is_dead(), which tries to access the global 'kill_ftrace_graph' variable with a virtual address, causing a fault because the CPU is still in real mode. The fix is to add a check in prepare_ftrace_return() to make sure it's running in protected mode before continuing. The check makes sure the stack pointer is a virtual kernel address. It's a bit of a hack, but it's not very intrusive and it works well enough. For reference, here are a few other (more difficult) ways this could have potentially been fixed: - Move startup_32_smp()'s call to load_ucode_ap() down to *after* paging is enabled. (No idea what that would break.) - Track down load_ucode_ap()'s entire callee tree and mark all the functions 'notrace'. (Probably not realistic.) - Pause graph tracing in ftrace_suspend_notifier_call() or bringup_cpu() or __cpu_up(), and ensure that the pause facility can be queried from real mode. Reported-by: Paul Menzel Signed-off-by: Josh Poimboeuf Tested-by: Paul Menzel Reviewed-by: Steven Rostedt (VMware) Cc: "Rafael J . Wysocki" Cc: linux-acpi@vger.kernel.org Cc: Borislav Petkov Cc: Len Brown Link: http://lkml.kernel.org/r/5c1272269a580660703ed2eccf44308e790c7a98.1492123841.git.jpoimboe@redhat.com Signed-off-by: Thomas Gleixner Signed-off-by: Jiri Slaby --- arch/x86/kernel/ftrace.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index f8ab203fb676..b8162154e615 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -735,6 +735,18 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, unsigned long return_hooker = (unsigned long) &return_to_handler; + /* + * When resuming from suspend-to-ram, this function can be indirectly + * called from early CPU startup code while the CPU is in real mode, + * which would fail miserably. Make sure the stack pointer is a + * virtual address. + * + * This check isn't as accurate as virt_addr_valid(), but it should be + * good enough for this purpose, and it's fast. + */ + if (unlikely((long)__builtin_frame_address(0) >= 0)) + return; + if (unlikely(atomic_read(¤t->tracing_graph_pause))) return;