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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8C025C00140 for ; Mon, 8 Aug 2022 09:42:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242346AbiHHJmI (ORCPT ); Mon, 8 Aug 2022 05:42:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45136 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242414AbiHHJmG (ORCPT ); Mon, 8 Aug 2022 05:42:06 -0400 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [IPv6:2001:4d48:ad52:32c8:5054:ff:fe00:142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6FAFBD43 for ; Mon, 8 Aug 2022 02:42:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=jabxQNmKugX49duLCRQ1WxMQ73IJlWHxcJdvAYi/ZBE=; b=i59R3fYUn+GkU9gh8J01B+Jci2 8u6oRdOJM59SLJ9LoeHMpXvk6LWZcrP48cIqymCTEFH3Q4/xWKwd8iPqqJABo20JHYDnP576C/AUD MqxdUvz9EkoN8qAUskgdRpw7cOrrs33snGkeSqBpfghmx6lh24pJMs5lKsFK/2W1WAmH/hYUUA36q CR5fwThXeAq8bX0xWv5jYu9PMpF1yiKgMdVpcOhQWVx3dkjyW156fq1GczQxEmFFinsoHPIFecsDE OYRieMMqGBnXUrtI+zuhi1q/+Yj09hNaJJ0ZXCkQiXv4d+oZfpPFRX3Ns/Vq35oXEIJd9eAd91GMr xO1LBn8A==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:33716) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1oKzGm-0007tv-Ay; Mon, 08 Aug 2022 10:41:56 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.94.2) (envelope-from ) id 1oKzGj-0005Kl-N4; Mon, 08 Aug 2022 10:41:54 +0100 Date: Mon, 8 Aug 2022 10:41:53 +0100 From: "Russell King (Oracle)" To: Zhen Lei Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, patches@armlinux.org.uk Subject: Re: [PATCH] ARM: Remove the special printing format of pc and lr in __show_regs() Message-ID: References: <20220801032016.1524-1-thunder.leizhen@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220801032016.1524-1-thunder.leizhen@huawei.com> Sender: Russell King (Oracle) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 01, 2022 at 11:20:16AM +0800, Zhen Lei wrote: > Currently, instruction pointers are printed in [<%08lx>] format to make > them more visible. However, it is not necessary in __show_regs() because > they have the prefix 'pc :' or 'lr :', and it is also inconsistent with > that of other registers, which causes misalignment. The formatting is not "to make them more visible" - it was to mark the addresses that we wanted the ksymoops utility to translate to kernel symbols before we had kallsyms in the kernel. If one disables kallsyms, then we still need a way to translate kernel addresses to symbols. I notice there is a script which helps with this that is part of the kernel source - scripts/decode_stacktrace.sh. I haven't tried this on arm32 since I always use kallsyms - and I suspect that is rather universally true as it avoids needing System.map files etc to decode the oops. That said, if you're building a kernel for small systems, you probably don't want the overhead of kallsyms. So, there's an argument for keeping it - it's an API in that it provides hints to scripting to identify which values need to be converted to symbols. There's also the argument for getting rid of it, which is that hardly anyone does that anymore. The question is, which is the more important argument, and I don't think there's a definite answer. So I'm inclined to leave this as-is. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!