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=-14.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL 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 BDF30C433ED for ; Thu, 1 Apr 2021 18:55:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8805161007 for ; Thu, 1 Apr 2021 18:55:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235302AbhDASzi (ORCPT ); Thu, 1 Apr 2021 14:55:38 -0400 Received: from linux.microsoft.com ([13.77.154.182]:42664 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237955AbhDASxP (ORCPT ); Thu, 1 Apr 2021 14:53:15 -0400 Received: from [192.168.254.32] (unknown [47.187.194.202]) by linux.microsoft.com (Postfix) with ESMTPSA id 527A620ABC27; Thu, 1 Apr 2021 11:53:13 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 527A620ABC27 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1617303193; bh=u325FlALmyhfVu2h9i2pftAUehF46sneQVwUlnNlb1s=; h=Subject:From:To:Cc:References:Date:In-Reply-To:From; b=W3lEpvprUanbv8tw2BwtQbbTSrqEoQnyqfD4f2rLBQ4ImnKlyKze626f8At7UqqDX XnJkTN64B9OzIjMST/j2qgnyLNo0nBa4VklH0RxsvySAzDZLr0bGWquTNqCflDnMYM miec66nAfloXZn8cdFA5Cv+j9TSi2gTyYiJ8Gmok= Subject: Re: [RFC PATCH v1 3/4] arm64: Detect FTRACE cases that make the stack trace unreliable From: "Madhavan T. Venkataraman" To: Mark Brown Cc: mark.rutland@arm.com, jpoimboe@redhat.com, jthierry@redhat.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org References: <77bd5edeea72d44533c769b1e8c0fea7a9d7eb3a> <20210330190955.13707-1-madvenka@linux.microsoft.com> <20210330190955.13707-4-madvenka@linux.microsoft.com> <20210401142759.GJ4758@sirena.org.uk> <0bece48b-5fee-2bd1-752e-66d2b89cc5ad@linux.microsoft.com> <20210401182810.GO4758@sirena.org.uk> <2a56fe4b-9929-0d8b-aa49-c2b1c1b82b79@linux.microsoft.com> Message-ID: Date: Thu, 1 Apr 2021 13:53:12 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <2a56fe4b-9929-0d8b-aa49-c2b1c1b82b79@linux.microsoft.com> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/1/21 1:40 PM, Madhavan T. Venkataraman wrote: >>> So, it is only defined if CONFIG_FUNCTION_GRAPH_TRACER is defined. I can address >>> this as well as your comment by defining another label whose name is more meaningful >>> to our use: >>> +SYM_INNER_LABEL(ftrace_trampoline, SYM_L_GLOBAL) // checked by the unwinder >>> #ifdef CONFIG_FUNCTION_GRAPH_TRACER >>> SYM_INNER_LABEL(ftrace_graph_call, SYM_L_GLOBAL) // ftrace_graph_caller(); >>> nop // If enabled, this will be replaced >>> // "b ftrace_graph_caller" >>> #endif >> I'm not sure we need to bother with that, you'd still need the & I think. > I think we need to bother with that. If CONFIG_FUNCTION_GRAPH_TRACER is not on but > CONFIG_DYNAMIC_FTRACE_WITH_REGS is, then ftrace_graph_call() will not occur in the stack > trace taken from a tracer function. The unwinder still needs to recognize an ftrace frame. > I don't want to assume ftrace_common_return which is the label that currently follows > the above code. So, we need a different label outside the above ifdef. Alternatively, I could just move the SYM_INNER_LABEL(ftrace_graph_call..) to outside the ifdef. Madhavan