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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 40D28C433FE for ; Thu, 6 Oct 2022 15:50:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=nnNeiaW6/NDIqBVlMWGmtHPVW29VF/ydRYaOwJbXXiQ=; b=ffMXsLK2ZSYeC6 miAsYZkowY2aQN00gyls6lNAJyH5gGq8l7IdmmPcudclsEbmSV1p/6jt6EgiDTYMItRBKtJloLPpp NFWu2Vr04MDD4aGbWLbXfD0DCuxd+hFeWdAXRzXERgDbRvqCNYeGGAYFUqhx8yKr+KjD40G1aoFUO I2bPEsKyheyeIthZ4/V8sGFoSyOjJ5VNIV0wO89sWR4NjNpi74Skl/MD+zMXa9cmfauFlqn1EwFqB wCb72K1NB8tLTPXxFVap/aKtKmJEk5ZC5NmW90AvTyEuZQIWP2Zy5Y2PGO7Ez9dS3w4a9yJJCuBVm 8r0GtpdnIuBoF62f6zAA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1ogT7e-003YVS-Kk; Thu, 06 Oct 2022 15:49:18 +0000 Received: from pandora.armlinux.org.uk ([2001:4d48:ad52:32c8:5054:ff:fe00:142]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1ogT7b-003YPk-IF for linux-arm-kernel@lists.infradead.org; Thu, 06 Oct 2022 15:49:17 +0000 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=QuZz8k2+JN5p6IBaNBoYZDigG3l7QUcuLSFQDGVYW/E=; b=WmchLnWUuGFKLIX9KHEuJpAXw0 oZXMNCSC33npvBaMgldYfdQ+ktWQRQET3pH18I3e23DQ6BmgsfIy1iQlosdAUM0d0ghS6paEZWVM0 Pddqad8n55d8F2/NtouF5UjNlNvphVfJle/PdizkeEJutYXMZoxhE3n2bTrnwwHm8Tq4vfR/zsUTy XpDTOBGbqRcxYoM+zM+vMtQV5KB/UuEzYK9DurZZtl8NHSenRN+agNeYDNfJC+OXqKexTT4DGysVa b3VYKr34M0SWrKQm36qHR07H8MqBKms96I8ODtQiZB+rWhb8q/BxBIxECHVkyoBwctTFazmkkgqB3 NAQH1E3Q==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:34608) 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 1ogT7U-0001jw-Vw; Thu, 06 Oct 2022 16:49:09 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.94.2) (envelope-from ) id 1ogT7T-0006QF-U5; Thu, 06 Oct 2022 16:49:07 +0100 Date: Thu, 6 Oct 2022 16:49:07 +0100 From: "Russell King (Oracle)" To: Luis Machado Cc: linux-arm-kernel@lists.infradead.org Subject: Re: RFC: FPA support removal from gdb and its impact on kgdb Message-ID: References: <5b0d81f2-00ed-cf3c-8869-420326595e0a@arm.com> <0bb128e7-14a3-4dc7-62b1-f3424155ee09@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <0bb128e7-14a3-4dc7-62b1-f3424155ee09@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221006_084915_624719_5E0DC9D3 X-CRM114-Status: GOOD ( 21.04 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Oct 06, 2022 at 02:42:09PM +0100, Luis Machado wrote: > Hi Russel, > > On 10/5/22 17:54, Russell King (Oracle) wrote: > > Given this, and this is a fundamental interface between two different > > pieces of software, I fail to see how you can even consider removing > > support for this - if you remove support from gdb, then later gdb > > will be unable to debug existing kernels. > > It is being considered because not even the Linux kernel uses these > registers anymore. The kgdb implementation was based on what GDB exposed > long ago. The kernel has never used the FPA not even an emulation of the FPA. The kernel has provided a number of FPA emulation options over the years for userspace to use, but never for its own use. So kgdb's inclusion if these is merely to make kgdb's stub work with gdb and nothing else. > > In kernel-land, we have a rule: don't break userspace. I think there > > should also be a rule for userspace: don't break the kernel! > > That's fair, and I'm not seeking to proactively break the kernel. That's > why I listed some possible solutions. > > The best one is to update kgdb to send back XML data and drop the fp > registers. On GDB's side, we can carry compatibility code that will > guarantee things will work until it makes sense to remove the > compatibility layer altogether. > > Does that sound like a good compromise? Yes, thanks. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last! _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel