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=-2.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 565B6C43331 for ; Mon, 30 Mar 2020 13:42:30 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 18CB420716 for ; Mon, 30 Mar 2020 13:42:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="KiPBH/Kq"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="y+WW+flN" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 18CB420716 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject: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=7zlXyqiuSiafJNbYgfpQ2MUeqVLeQZw8QhQG5b7sXO0=; b=KiPBH/Kq1Bf1gc POvXr0etldWuSdALLD/u1wNQdz+Fu6NgHzvYvOlFeeanxgOx6qvrJYp1rwcDNfK/SpYvrwB8I/S4y bcAHkIdUvdAPoR1iH1DQl1srQynozrQIR7Z3dQJcNxRbIeBiFLQqR+LXQ3fpyLVVtDN6gSALo+ZRw 7RZqhxIYyxaiMfSgv/j6z4XZ/4ihOLov2/DQ7+1O8U7DwGDWUmzxM1k3XwR4sx4sE9r1h3IY2jVGj 0dA2+Xi32PiGKVgiYSbAt0YYf7IRntlhqRRfvq9KWnaaStFw2w7q5oQ3ZiRy3CnAj78Xtc3rk8r4r 8MT4yvbqWRWSuzV2vD7w==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jIugM-0007zj-P4; Mon, 30 Mar 2020 13:42:26 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jIugJ-0007yx-7s for linux-arm-kernel@lists.infradead.org; Mon, 30 Mar 2020 13:42:24 +0000 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id CE23F20716; Mon, 30 Mar 2020 13:42:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585575742; bh=K1ockVl39gLdCpYbJ/oumXMVl7UViARe6VaNnMLxqQE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=y+WW+flNgwBuY4vM8P2peunT13HsbPj9+bVg64Dt3LiH5tYdg0HURnKiVRM2WEUip f0QlWIfFPWVK5vDpokgaphtYQchufagDj5lljP672VWezTcGBAVZHHRp5HGnsTkRbL iPJDJaaWrbYP5EfzjYyIS3hdjUDuVhrkQ/ftk3EY= Date: Mon, 30 Mar 2020 14:42:18 +0100 From: Will Deacon To: Mark Rutland Subject: Re: [PATCH] arm64: hw_breakpoint: don't clear debug registers in halt mode Message-ID: <20200330134218.GB10633@willie-the-truck> References: <20200328083209.21793-1-tingwei@codeaurora.org> <20200330123946.GH1309@C02TD0UTHF1T.local> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200330123946.GH1309@C02TD0UTHF1T.local> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200330_064223_298103_5DC414E3 X-CRM114-Status: GOOD ( 14.35 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Catalin Marinas , linux-arm-kernel@lists.infradead.org, Tingwei Zhang , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Mar 30, 2020 at 01:39:46PM +0100, Mark Rutland wrote: > On Sat, Mar 28, 2020 at 04:32:09PM +0800, Tingwei Zhang wrote: > > If external debugger sets a breakpoint for one Kernel function > > when device is in bootloader mode and loads Kernel, this breakpoint > > will be wiped out in hw_breakpoint_reset(). To fix this, check > > MDSCR_EL1.HDE in hw_breakpoint_reset(). When MDSCR_EL1.HDE is > > 0b1, halting debug is enabled. Don't reset debug registers in this case. > > I don't think this is sufficient, because the kernel can still > subsequently mess with breakpoints, and the HW debugger might not be > attached at this point in time anyhow. > > I reckon this should hang off the existing "nodebumon" command line > option, and we shouldn't use HW breakpoints at all when that is passed. > Then you can pass that to prevent the kernel stomping on the external > debugger. > > Will, thoughts? I was going to suggest the same thing, although we will also need to take care to reset the registers if "nodebugmon" is toggled at runtime via the "debug_enabled" file in debugfs. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel