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=-9.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT 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 7A01AC2BA83 for ; Thu, 13 Feb 2020 09:52:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4F2B72073C for ; Thu, 13 Feb 2020 09:52:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729874AbgBMJwA (ORCPT ); Thu, 13 Feb 2020 04:52:00 -0500 Received: from mx2.suse.de ([195.135.220.15]:41202 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729632AbgBMJv6 (ORCPT ); Thu, 13 Feb 2020 04:51:58 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id D016FB1F2; Thu, 13 Feb 2020 09:51:54 +0000 (UTC) From: Petr Mladek To: Sergey Senozhatsky , Steven Rostedt , Benjamin Herrenschmidt Cc: Peter Zijlstra , John Ogness , linux-kernel@vger.kernel.org Subject: [PATCH v4 2/3] printk: Fix preferred console selection with multiple matches Date: Thu, 13 Feb 2020 10:51:32 +0100 Message-Id: <20200213095133.23176-3-pmladek@suse.com> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20200213095133.23176-1-pmladek@suse.com> References: <20200213095133.23176-1-pmladek@suse.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Benjamin Herrenschmidt In the following circumstances, the rule of selecting the console corresponding to the last "console=" entry on the command line as the preferred console (CON_CONSDEV, ie, /dev/console) fails. This is a specific example, but it could happen with different consoles that have a similar name aliasing mechanism. - The kernel command line has both console=tty0 and console=ttyS0 in that order (the latter with speed etc... arguments). This is common with some cloud setups such as Amazon Linux. - add_preferred_console is called early to register "uart0". In our case that happens from acpi_parse_spcr() on arm64 since the "enable_console" argument is true on that architecture. This causes "uart0" to become entry 0 of the console_cmdline array. Now, because of the above, what happens is: - add_preferred_console is called by the cmdline parsing for tty0 and ttyS0 respectively, thus occupying entries 1 and 2 of the console_cmdline array (since this happens after ACPI SPCR parsing). At that point preferred_console is set to 2 as expected. - When the tty layer kicks in, it will call register_console for tty0. This will match entry 1 in console_cmdline array. It isn't our preferred console but because it's our only console at this point, it will end up "first" in the consoles list. - When 8250 probes the actual serial port later on, it calls register_console for ttyS0. At that point the loop in register_console tries to match it with the entries in the console_cmdline array. Ideally this should match ttyS0 in entry 2, which is preferred, causing it to be inserted first and to replace tty0 as CONSDEV. However, 8250 provides a "match" hook in its struct console, and that hook will match "uart" as an alias to "ttyS". So we match uart0 at entry 0 in the array which is not the preferred console and will not match entry 2 which is since we break out of the loop on the first match. As a result, we don't set CONSDEV and don't insert it first, but second in the console list. As a result, we end up with tty0 remaining first in the array, and thus /dev/console going there instead of the last user specified one which is ttyS0. This tentative fix register_console() to scan first for consoles specified on the command line, and only if none is found, to then scan for consoles specified by the architecture. Signed-off-by: Benjamin Herrenschmidt Reviewed-by: Petr Mladek --- kernel/printk/console_cmdline.h | 1 + kernel/printk/printk.c | 29 ++++++++++++++++++----------- 2 files changed, 19 insertions(+), 11 deletions(-) diff --git a/kernel/printk/console_cmdline.h b/kernel/printk/console_cmdline.h index 11f19c466af5..3ca74ad391d6 100644 --- a/kernel/printk/console_cmdline.h +++ b/kernel/printk/console_cmdline.h @@ -6,6 +6,7 @@ struct console_cmdline { char name[16]; /* Name of the driver */ int index; /* Minor dev. to use */ + bool user_specified; /* Specified by command line vs. platform */ char *options; /* Options for the driver */ #ifdef CONFIG_A11Y_BRAILLE_CONSOLE char *brl_options; /* Options for braille driver */ diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 0ebcdf53e75d..f76ef3f0efca 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2116,7 +2116,7 @@ asmlinkage __visible void early_printk(const char *fmt, ...) #endif static int __add_preferred_console(char *name, int idx, char *options, - char *brl_options) + char *brl_options, bool user_specified) { struct console_cmdline *c; int i; @@ -2131,6 +2131,8 @@ static int __add_preferred_console(char *name, int idx, char *options, if (strcmp(c->name, name) == 0 && c->index == idx) { if (!brl_options) preferred_console = i; + if (user_specified) + c->user_specified = true; return 0; } } @@ -2140,6 +2142,7 @@ static int __add_preferred_console(char *name, int idx, char *options, preferred_console = i; strlcpy(c->name, name, sizeof(c->name)); c->options = options; + c->user_specified = user_specified; braille_set_options(c, brl_options); c->index = idx; @@ -2194,7 +2197,7 @@ static int __init console_setup(char *str) idx = simple_strtoul(s, NULL, 10); *s = 0; - __add_preferred_console(buf, idx, options, brl_options); + __add_preferred_console(buf, idx, options, brl_options, true); console_set_on_cmdline = 1; return 1; } @@ -2215,7 +2218,7 @@ __setup("console=", console_setup); */ int add_preferred_console(char *name, int idx, char *options) { - return __add_preferred_console(name, idx, options, NULL); + return __add_preferred_console(name, idx, options, NULL, false); } bool console_suspend_enabled = true; @@ -2636,7 +2639,7 @@ early_param("keep_bootcon", keep_bootcon_setup); * Care need to be taken with consoles that are statically * enabled such as netconsole */ -static int try_enable_new_console(struct console *newcon) +static int try_enable_new_console(struct console *newcon, bool user_specified) { struct console_cmdline *c; int i; @@ -2644,6 +2647,8 @@ static int try_enable_new_console(struct console *newcon) for (i = 0, c = console_cmdline; i < MAX_CMDLINECONSOLES && c->name[0]; i++, c++) { + if (c->user_specified != user_specified) + continue; if (!newcon->match || newcon->match(newcon, c->name, c->index, c->options) != 0) { /* default matching */ @@ -2673,9 +2678,10 @@ static int try_enable_new_console(struct console *newcon) /* * Some consoles, such as pstore and netconsole, can be enabled even - * without matching. + * without matching. Accept the pre-enabled consoles only when match() + * and setup() had a change to be called. */ - if (newcon->flags & CON_ENABLED) + if (newcon->flags & CON_ENABLED && c->user_specified == user_specified) return 0; return -ENOENT; @@ -2752,11 +2758,12 @@ void register_console(struct console *newcon) } } - /* - * See if this console matches one we selected on - * the command line or if it was statically enabled - */ - err = try_enable_new_console(newcon); + /* See if this console matches one we selected on the command line */ + err = try_enable_new_console(newcon, true); + + /* If not, try to match against the platform default(s) */ + if (err == -ENOENT) + err = try_enable_new_console(newcon, false); /* printk() messages are not printed to the Braille console. */ if (err || newcon->flags & CON_BRL) -- 2.16.4