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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 085CFC433DB for ; Tue, 23 Mar 2021 10:37:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CE5CE619BB for ; Tue, 23 Mar 2021 10:37:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230289AbhCWKhY (ORCPT ); Tue, 23 Mar 2021 06:37:24 -0400 Received: from foss.arm.com ([217.140.110.172]:43670 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230334AbhCWKgu (ORCPT ); Tue, 23 Mar 2021 06:36:50 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E25D81042; Tue, 23 Mar 2021 03:36:49 -0700 (PDT) Received: from C02TD0UTHF1T.local (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B8EE63F719; Tue, 23 Mar 2021 03:36:47 -0700 (PDT) Date: Tue, 23 Mar 2021 10:36:44 +0000 From: Mark Rutland To: "Madhavan T. Venkataraman" Cc: Mark Brown , 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 Subject: Re: [RFC PATCH v2 3/8] arm64: Terminate the stack trace at TASK_FRAME and EL0_FRAME Message-ID: <20210323103644.GC95840@C02TD0UTHF1T.local> References: <5997dfe8d261a3a543667b83c902883c1e4bd270> <20210315165800.5948-1-madvenka@linux.microsoft.com> <20210315165800.5948-4-madvenka@linux.microsoft.com> <20210318182607.GO5469@sirena.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On Thu, Mar 18, 2021 at 03:29:19PM -0500, Madhavan T. Venkataraman wrote: > > > 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. Yes please; and please fold that into the same patch that adds the final records. Thanks, Mark.