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=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 A9C4EC4332B for ; Mon, 23 Mar 2020 10:50:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7B3C72076A for ; Mon, 23 Mar 2020 10:50:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="G6nGo2oO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728077AbgCWKuL (ORCPT ); Mon, 23 Mar 2020 06:50:11 -0400 Received: from mail-lf1-f65.google.com ([209.85.167.65]:32867 "EHLO mail-lf1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727874AbgCWKuL (ORCPT ); Mon, 23 Mar 2020 06:50:11 -0400 Received: by mail-lf1-f65.google.com with SMTP id c20so9844318lfb.0 for ; Mon, 23 Mar 2020 03:50:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=siKVSOSU2AuaxCnLGzXMnO9hKgx66VndyuGaKMeNzAk=; b=G6nGo2oOHsvAJv17GKLVj/we/ZtSZ5nznKfQGFsZUvB0VOn3+E48g1tAniEG6MbQJZ rrvKvQOjOvESLanVYURjrhMorX//raN51ngN7gFqvLotu/J3Bpfm3tWa1GLzg9eUdTwr 3vyjfUUPciutYkb1atk8VnFy6OP2Kn+bEkh+dDu6hLeFTR4M1G60Sh5YEp0svmCNjikN GZht+smbCmDEgUh2xS22ASBe1nev4M1nKPx9THcQYg1YCsc/fjWgZVlbCmkdc5k9W5bq BYA+XbwtiTxIzHn25uyyIQnUUDdZwF9QbB3JqIaCCZOj8AmOxsWHHCy9kCLRBJtBGKf8 LAIg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=siKVSOSU2AuaxCnLGzXMnO9hKgx66VndyuGaKMeNzAk=; b=JaUfEEjj6qo7b6vn0bbzITpzI4hM2hAzwRaTPpOc8x71K5CFHKfQykhbHQeXbdXpF5 e+QLB4zJTEJFQxpNJzFrg0VcKY14Owm44fLwISlcAswh6zd2BDsFDZBq+MeYu6IE6l1o G0u6aa4RANL7dACIu7Jt4/1DJ68GF6xH3sVdrTk6Tag5y4gVd/P4jFuGdYf5cJVXsBaO bNQC9/JkFo5Gz2PqDSP7YYMEejb/mQzl+XkiKoFP9go+bXVqx84LevCx8Si26EHeqvAo nsqDVUB43vYaGhRGPFQGzHUW2mbthXerppOiKPE7HAdCBpLVzRo/wyffDiwae7ZxZAnH 7Pow== X-Gm-Message-State: ANhLgQ24iT+hfgHD+ISbtE/bLNOOww7vVvW8BOQvKG23tvEd62etrTZ2 J/MRuMYJcArpQSWmM4nWuIW5DQrMxY8= X-Google-Smtp-Source: ADFU+vuqCztGnSgEvaBbLfIgKv+NmYx+f8L26fTeb1SeELM4AjCd4cDOrJ1+xvWKNWCkk/mTRWYUDw== X-Received: by 2002:a19:4f0c:: with SMTP id d12mr4078302lfb.117.1584960608526; Mon, 23 Mar 2020 03:50:08 -0700 (PDT) Received: from [192.168.0.74] ([178.233.178.9]) by smtp.gmail.com with ESMTPSA id t136sm4144179lff.48.2020.03.23.03.50.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 Mar 2020 03:50:07 -0700 (PDT) Subject: [RFC PATCH 2/3] vt: Set as preferred console when a non-dummy backend, is bound To: Greg Kroah-Hartman , Jiri Slaby , Petr Mladek , Sergey Senozhatsky Cc: Steven Rostedt , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <44156595-0eee-58da-4376-fd25b634d21b@gmail.com> From: Alper Nebi Yasak Message-ID: <611f42ec-194c-a121-bba1-5f0ac8e2109b@gmail.com> Date: Mon, 23 Mar 2020 13:50:03 +0300 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <44156595-0eee-58da-4376-fd25b634d21b@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When a machine's device-tree has a "chosen" node with a "stdout-path" property that specified console is added as the preferred console by of_console_check via an add_preferred_console call. The property is quite common in kernel device-tree definitions. As far as I can tell, it is set to provide a reasonable default value for earlycon, and the (usually serial) console is set as preferred to avoid output going to VT's dummy backend instead of a working console. However, a chosen stdout-path property is included even in device-trees of systems that are designed to be used with a built-in display, e.g. several ARM Chromebooks. In these cases where CONFIG_VT_CONSOLE is enabled and no console argument is given on the kernel commandline, tty0 is still registered (presumably based on the order of of_console_check and vt's register_console calls) but ends up not being the preferred console. As a result, it is possible for early userspace prompts (encryption passphrase requests, emergency shells) to end up in a console that the user doesn't expect or even have access to. This patch tries to set tty0 as the /dev/console whenever a non-dummy backend tries to register as its default, unless the preferred console was set from the kernel commandline arguments. On a Samsung Chromebook Plus (Google Kevin, rk3399-gru-kevin.dts), boot messages are still visible on the framebuffer without this patch, but it isn't the preferred console due to the device-tree having a stdout-path property (from rk3399-gru.dtsi): $ sudo dmesg | grep -i "console\|printk" [ 0.000000] printk: bootconsole [uart0] enabled [ 0.010232] Console: colour dummy device 80x25 [ 0.015107] printk: console [tty0] enabled [ 0.019601] printk: bootconsole [uart0] disabled [ 7.145478] printk: console [ttyS2] enabled [ 9.316094] Console: switching to colour frame buffer device 300x100 $ cat /proc/consoles ttyS2 -W- (EC p a) 4:66 tty0 -WU (E ) 4:7 And on the same machine, with this patch: $ sudo dmesg | grep -i "console\|printk" [ 0.000000] printk: bootconsole [uart0] enabled [ 0.010257] Console: colour dummy device 80x25 [ 0.015132] printk: console [tty0] enabled [ 0.019626] printk: bootconsole [uart0] disabled [ 4.741120] printk: console [ttyS2] enabled [ 6.779994] Console: switching to colour frame buffer device 300x100 [ 6.836117] printk: switching to console [tty0] $ cat /proc/consoles tty0 -WU (EC ) 4:7 ttyS2 -W- (E p a) 4:66 Signed-off-by: Alper Nebi Yasak --- drivers/tty/vt/vt.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index bbc26d73209..0fc462ae8b2 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -3566,6 +3566,13 @@ static int do_bind_con_driver(const struct consw *csw, int first, int last, pr_cont("to %s\n", desc); } +#ifdef CONFIG_VT_CONSOLE + if (!console_set_on_cmdline && deflt && conswitchp != &dummy_con) { + add_preferred_console("tty", 0, NULL); + update_console_to_preferred(); + } +#endif + retval = 0; err: module_put(owner); -- 2.26.0.rc2