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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 250A2C433E0 for ; Tue, 26 May 2020 19:22:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F2EC820776 for ; Tue, 26 May 2020 19:22:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590520948; bh=GU2D2mRPFvVsOoMBcRg66MyY3nXhu9te59IzEmrUMN8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=YMS4n6mktywR4BRltLsUs6uSXSONUNEl2LKNkXoWLBszyLWsmNO2LWx5BS42tPaLC 2hker7s91Hke0TlRhP+hwX9MOk4WxxP3j3a7L930IN3lk5vf8lglqOmtNwjXmfJenn qJrXzlq+hhX7f3WkQakYe9zQHRD66oQVflZbjIEE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391944AbgEZTW0 (ORCPT ); Tue, 26 May 2020 15:22:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:39354 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390048AbgEZTKM (ORCPT ); Tue, 26 May 2020 15:10:12 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.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 BCAAF208B3; Tue, 26 May 2020 19:10:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590520212; bh=GU2D2mRPFvVsOoMBcRg66MyY3nXhu9te59IzEmrUMN8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dLMc7xtUFONavf120fZnPFi6Q6PiRiEV3RceEHLrKnVeZnQ7WIljHYnBTSYzIbIv9 6hRgS0d//LZSKN6DIRvBT1euNy7i2bTt1/30po6G8KdokZOgr4mNyh+cSspEuw8vxU YFGBYKlWSws1x1SkYAFUTBHHA/EYtLuesgvX+a4U= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tetsuo Handa , Josh Poimboeuf , "Peter Zijlstra (Intel)" Subject: [PATCH 5.4 101/111] x86/unwind/orc: Fix unwind_get_return_address_ptr() for inactive tasks Date: Tue, 26 May 2020 20:53:59 +0200 Message-Id: <20200526183942.478236620@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200526183932.245016380@linuxfoundation.org> References: <20200526183932.245016380@linuxfoundation.org> User-Agent: quilt/0.66 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 From: Josh Poimboeuf commit 187b96db5ca79423618dfa29a05c438c34f9e1f0 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/unwind_orc.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/arch/x86/kernel/unwind_orc.c +++ b/arch/x86/kernel/unwind_orc.c @@ -311,12 +311,19 @@ EXPORT_SYMBOL_GPL(unwind_get_return_addr 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;