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 2E502C43332 for ; Thu, 18 Mar 2021 20:30:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B702B64F30 for ; Thu, 18 Mar 2021 20:30:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233113AbhCRU3i (ORCPT ); Thu, 18 Mar 2021 16:29:38 -0400 Received: from linux.microsoft.com ([13.77.154.182]:46606 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231137AbhCRU3U (ORCPT ); Thu, 18 Mar 2021 16:29:20 -0400 Received: from [192.168.254.32] (unknown [47.187.194.202]) by linux.microsoft.com (Postfix) with ESMTPSA id D6CA420B39C5; Thu, 18 Mar 2021 13:29:19 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com D6CA420B39C5 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1616099360; bh=NYashDADQj5U4guXBYGYNqz58yYoc5xd3wmlNGCFhJ4=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=WvyUdTts2mfk1Bx6gUPgrA0HI+h5qR0lj4zP6ln5NPlgKiOTvJ0IDP/b4qceWrr30 mnVWKgo6OAeSIZ5XaFS7CO5iNxLoZrbGY0l+N7k/A1CwAGZTFFaB6/KHrePgTSP2Ol WIGUdney3aQu7Sy585CzEDMgc/7tqk1W3eUuLlUQ= Subject: Re: [RFC PATCH v2 3/8] arm64: Terminate the stack trace at TASK_FRAME and EL0_FRAME 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: <5997dfe8d261a3a543667b83c902883c1e4bd270> <20210315165800.5948-1-madvenka@linux.microsoft.com> <20210315165800.5948-4-madvenka@linux.microsoft.com> <20210318182607.GO5469@sirena.org.uk> From: "Madhavan T. Venkataraman" Message-ID: Date: Thu, 18 Mar 2021 15:29:19 -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: <20210318182607.GO5469@sirena.org.uk> 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 3/18/21 1:26 PM, Mark Brown wrote: > On Mon, Mar 15, 2021 at 11:57:55AM -0500, madvenka@linux.microsoft.com wrote: > >> + /* Terminal record, nothing to unwind */ >> + if (fp == (unsigned long) regs->stackframe) { >> + if (regs->frame_type == TASK_FRAME || >> + regs->frame_type == EL0_FRAME) >> + return -ENOENT; >> return -EINVAL; >> + } > > This is conflating the reliable stacktrace checks (which your series > will later flag up with frame->reliable) with verifying that we found > the bottom of the stack by looking for this terminal stack frame record. > For the purposes of determining if the unwinder got to the bottom of the > stack we don't care what stack type we're looking at, we just care if it > managed to walk to this defined final record. > > At the minute nothing except reliable stack trace has any intention of > checking the specific return code but it's clearer to be consistent. > So, you are saying that the type check is redundant. OK. I will remove it and just return -ENOENT on reaching the final record. Madhavan