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=-11.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 89140C433E0 for ; Fri, 22 May 2020 18:04:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6F8B220663 for ; Fri, 22 May 2020 18:04:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730923AbgEVSEK (ORCPT ); Fri, 22 May 2020 14:04:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59224 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730674AbgEVSEK (ORCPT ); Fri, 22 May 2020 14:04:10 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1EF2BC061A0E; Fri, 22 May 2020 11:04:10 -0700 (PDT) Received: from [5.158.153.53] (helo=tip-bot2.lab.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jcC1c-0002Ke-4Y; Fri, 22 May 2020 20:04:04 +0200 Received: from [127.0.1.1] (localhost [IPv6:::1]) by tip-bot2.lab.linutronix.de (Postfix) with ESMTP id AF4F61C0095; Fri, 22 May 2020 20:04:03 +0200 (CEST) Date: Fri, 22 May 2020 18:04:03 -0000 From: "tip-bot2 for Josh Poimboeuf" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/urgent] x86/unwind/orc: Fix unwind_get_return_address_ptr() for inactive tasks Cc: Tetsuo Handa , Josh Poimboeuf , "Peter Zijlstra (Intel)" , x86 , LKML In-Reply-To: <20200522135435.vbxs7umku5pyrdbk@treble> References: <20200522135435.vbxs7umku5pyrdbk@treble> MIME-Version: 1.0 Message-ID: <159017064350.17951.16969339378626322681.tip-bot2@tip-bot2> X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit 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 The following commit has been merged into the x86/urgent branch of tip: Commit-ID: 187b96db5ca79423618dfa29a05c438c34f9e1f0 Gitweb: https://git.kernel.org/tip/187b96db5ca79423618dfa29a05c438c34f9e1f0 Author: Josh Poimboeuf AuthorDate: Fri, 22 May 2020 08:54:35 -05:00 Committer: Peter Zijlstra CommitterDate: Fri, 22 May 2020 19:55:17 +02:00 x86/unwind/orc: Fix unwind_get_return_address_ptr() for inactive tasks Normally, show_trace_log_lvl() scans the stack, looking for text addresses to print. In parallel, it unwinds the stack with unwind_next_frame(). If the stack address matches the pointer returned by unwind_get_return_address_ptr() for the current frame, the text address is printed normally without a question mark. Otherwise it's considered a breadcrumb (potentially from a previous call path) and it's printed with a question mark to indicate that the address is unreliable and typically can be ignored. Since the following commit: f1d9a2abff66 ("x86/unwind/orc: Don't skip the first frame for inactive tasks") ... for inactive tasks, show_trace_log_lvl() prints *only* unreliable addresses (prepended with '?'). That happens because, for the first frame of an inactive task, unwind_get_return_address_ptr() returns the wrong return address pointer: one word *below* the task stack pointer. show_trace_log_lvl() starts scanning at the stack pointer itself, so it never finds the first 'reliable' address, causing only guesses to being printed. The first frame of an inactive task isn't a normal stack frame. It's actually just an instance of 'struct inactive_task_frame' which is left behind by __switch_to_asm(). Now that this inactive frame is actually exposed to callers, fix unwind_get_return_address_ptr() to interpret it properly. Fixes: f1d9a2abff66 ("x86/unwind/orc: Don't skip the first frame for inactive tasks") Reported-by: Tetsuo Handa Signed-off-by: Josh Poimboeuf Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200522135435.vbxs7umku5pyrdbk@treble --- arch/x86/kernel/unwind_orc.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c index fa79e42..7f969b2 100644 --- a/arch/x86/kernel/unwind_orc.c +++ b/arch/x86/kernel/unwind_orc.c @@ -320,12 +320,19 @@ EXPORT_SYMBOL_GPL(unwind_get_return_address); unsigned long *unwind_get_return_address_ptr(struct unwind_state *state) { + struct task_struct *task = state->task; + if (unwind_done(state)) return NULL; if (state->regs) return &state->regs->ip; + if (task != current && state->sp == task->thread.sp) { + struct inactive_task_frame *frame = (void *)task->thread.sp; + return &frame->ret_addr; + } + if (state->sp) return (unsigned long *)state->sp - 1;