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=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 5B40DC433DF for ; Tue, 26 May 2020 19:02:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3712C20873 for ; Tue, 26 May 2020 19:02:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590519746; bh=6CTDi3al0Q/3yK2SyadCrdfzsLUV+RIHWoudrYcmdTk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=iihZiqadCcZa2nK9LqT3dxulToq4lJ+3MGxzRysVW2bH6G8q4Qkym5sEwUeadxVE6 L9Bj9YcQhRbGZ9jpkTyeEUF+kWUKPgcrjhCt44dwDzVlRYwkoQUy8TR9VJQxOY0Taz 9X7ekdlq0c3hJynX7Y/SWa2BUkw6/IFx/H5GD+JI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390393AbgEZTCZ (ORCPT ); Tue, 26 May 2020 15:02:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:57126 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391068AbgEZTCW (ORCPT ); Tue, 26 May 2020 15:02:22 -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 AF550208A7; Tue, 26 May 2020 19:02:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590519742; bh=6CTDi3al0Q/3yK2SyadCrdfzsLUV+RIHWoudrYcmdTk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WbihwtIGY/cUEAMBcrN7KzQdvr0ncmBYwnv+shR4iGE5IbczbgNpQ2XiafVAg9/s9 PrTXjxRj84fbqNADEBK1P1K/Ola0j0fjYRrY9SAxsz7ZEdUD0bxzf5LKMNtPLGsLNy doEG42unkrKFUoh4Of2TfPP+6ZIULI95Hrr4mZbE= 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 4.14 57/59] x86/unwind/orc: Fix unwind_get_return_address_ptr() for inactive tasks Date: Tue, 26 May 2020 20:53:42 +0200 Message-Id: <20200526183924.293521788@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200526183907.123822792@linuxfoundation.org> References: <20200526183907.123822792@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 @@ -255,12 +255,19 @@ 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;