From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yw1-f201.google.com (mail-yw1-f201.google.com [209.85.128.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E90471E874 for ; Thu, 22 Feb 2024 19:23:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708629827; cv=none; b=EJ3TJ5GkHv63Qxy/vQCEFX2+d9AYvAIWOb0is5OTNriv158u/zRfTJtXhwhsRVTiDY4cOeTrqrCYlfT7/0JdC3mtPeGt59FGky6pdSd84tksZuwmnZ7evLuXXKFaKWIgX9OAkfbe69DymOguxc/QoapiUBMnrZAJd8d2fCMfW4k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708629827; c=relaxed/simple; bh=gKo/P0bQL66mpMQ285UxKp7suX6+SFfQgZr5WjHyN6A=; h=Date:Message-Id:Mime-Version:Subject:From:To:Cc:Content-Type; b=r6L1BDb/q5879J7ASrmO1jAJWam9UNNhLSTcGWFXnBELXOGfsJuz2LumHXvpgE1t3igw4plGT6VczKpPftTCn5lbuzYrbdgnQKYntptlngsyhCnX17a0aR+jenvEAGkOrytKoa/iLfun9tHK4DG8ZpI7S8yXaXvRH6g8tpLl3Ek= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--pcc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=m/Jss5I8; arc=none smtp.client-ip=209.85.128.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--pcc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="m/Jss5I8" Received: by mail-yw1-f201.google.com with SMTP id 00721157ae682-6089b90acddso1462577b3.3 for ; Thu, 22 Feb 2024 11:23:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1708629825; x=1709234625; darn=vger.kernel.org; h=cc:to:from:subject:mime-version:message-id:date:from:to:cc:subject :date:message-id:reply-to; bh=Rcd3xiyDExY5/l4KiLEuLxdganpWypINeNzRdzc4lE8=; b=m/Jss5I8tdKFsnqT4oR2aaXw48zt3OEtg9w+TZuc9gkUSa5NPh6qdpfxmm/FgonM4C uMqoAPQ9Nq6lZ3ix/z7X0dHNhvecmuKqci/aeQlr8YGcz7GR1a2E38dkZZAyeo+/7ooL tHAaqOdljmow4OuHap5yJs6uh9OooONEVRlDOUWm+aK/DnIGXBWO7lmQAVzUuarr7IFH 8mNikNNNhcxjFihEWZF8N9NMiSBRCrlIjfDpOvUho3kfbHjaZuJGc5RLU1CP+PI/jM9d DDiZrUoZ+XEAZqXZMl1EocbHO+uNuSCFRpMQO1gTlsxDqadpXfl5d28/RTuyUtok3mb9 51oQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1708629825; x=1709234625; h=cc:to:from:subject:mime-version:message-id:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=Rcd3xiyDExY5/l4KiLEuLxdganpWypINeNzRdzc4lE8=; b=C51zpjZmplFY0maAbZJ25WP3AYI7J1mPacnMDx3svMpMh0r//kmyq4oP2Syfyezoiu qVEvLvyQAoPanIKfLIRVRDupuJu/SmuiLm9nnSs3uXYr1JyAQZZGLiU0fnX08Q0sBNwh RszVoWXnMZbdN5WN9oYOLpBevZHoJ3TQuSJ/7rrLrKrfx3T5Xh0tV4jteNcMHk2/hLPN Ti2KUQ+KZmZEhE1p9v9TtAaIljo6T9AKFxJG8M3NJvKGanrAJAM/dnB3dLtyekEl0DkS qqgNrcgXSNuiNq3noFlY14+QIB9BXu1emDn4P3piSPGKsb1YbesLAj0wWgVeXYy1YXl0 J7kw== X-Forwarded-Encrypted: i=1; AJvYcCWTOGNDPxvmsunw/MbBtgn8oQ37kf4jbkJYzn6WgE31Dl5+hEw1xVHS81kAaiNC6rRhY4bLF9X3qCCgbfKcOO9mRnZWA40tAbN88pB8 X-Gm-Message-State: AOJu0Yz7O+PRjkzfbW7807eAdfUobwjrX+Bpp0BwiBNWA8jkFla0XTmb ZDLMfXwcYgizpSGlEUxfMYb99Qqwaq1fudQFz4XLigGPXSWxNEr5mXCFTTFnFLfeKQ== X-Google-Smtp-Source: AGHT+IHzo0vV16bgCE5M3R2Na6hfj983quOy6yIVGG4Q5IoKGE0CF3K5gfQ3L9X52uStrwORe3dfl2c= X-Received: from pcc-desktop.svl.corp.google.com ([2620:15c:2d3:205:26c7:da00:ce0c:dbd5]) (user=pcc job=sendgmr) by 2002:a81:4ecd:0:b0:607:c633:2997 with SMTP id c196-20020a814ecd000000b00607c6332997mr24485ywb.5.1708629824985; Thu, 22 Feb 2024 11:23:44 -0800 (PST) Date: Thu, 22 Feb 2024 11:23:28 -0800 Message-Id: <20240222192329.1047386-1-pcc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.44.0.rc1.240.g4c46232300-goog Subject: [PATCH] serial: Lock console when calling into driver before registration From: Peter Collingbourne To: Greg Kroah-Hartman , Jiri Slaby , Petr Mladek , Steven Rostedt , John Ogness , Sergey Senozhatsky Cc: Peter Collingbourne , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, stable@vger.kernel.org Content-Type: text/plain; charset="UTF-8" During the handoff from earlycon to the real console driver, we have two separate drivers operating on the same device concurrently. In the case of the 8250 driver these concurrent accesses cause problems due to the driver's use of banked registers, controlled by LCR.DLAB. It is possible for the setup(), config_port(), pm() and set_mctrl() callbacks to set DLAB, which can cause the earlycon code that intends to access TX to instead access DLL, leading to missed output and corruption on the serial line due to unintended modifications to the baud rate. In particular, for setup() we have: univ8250_console_setup() -> serial8250_console_setup() -> uart_set_options() -> serial8250_set_termios() -> serial8250_do_set_termios() -> serial8250_do_set_divisor() For config_port() we have: serial8250_config_port() -> autoconfig() For pm() we have: serial8250_pm() -> serial8250_do_pm() -> serial8250_set_sleep() For set_mctrl() we have (for some devices): serial8250_set_mctrl() -> omap8250_set_mctrl() -> __omap8250_set_mctrl() To avoid such problems, let's make it so that the console is locked during pre-registration calls to these callbacks, which will prevent the earlycon driver from running concurrently. Remove the partial solution to this problem in the 8250 driver that locked the console only during autoconfig_irq(), as this would result in a deadlock with the new approach. The console continues to be locked during autoconfig_irq() because it can only be called through uart_configure_port(). Although this patch introduces more locking than strictly necessary (and in particular it also locks during the call to rs485_config() which is not affected by this issue as far as I can tell), it follows the principle that it is the responsibility of the generic console code to manage the earlycon handoff by ensuring that earlycon and real console driver code cannot run concurrently, and not the individual drivers. Signed-off-by: Peter Collingbourne Link: https://linux-review.googlesource.com/id/I7cf8124dcebf8618e6b2ee543fa5b25532de55d8 Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org --- drivers/tty/serial/8250/8250_port.c | 6 ------ drivers/tty/serial/serial_core.c | 10 ++++++++++ kernel/printk/printk.c | 20 +++++++++++++++++--- 3 files changed, 27 insertions(+), 9 deletions(-) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 8ca061d3bbb9..1d65055dde27 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -1329,9 +1329,6 @@ static void autoconfig_irq(struct uart_8250_port *up) inb_p(ICP); } - if (uart_console(port)) - console_lock(); - /* forget possible initially masked and pending IRQ */ probe_irq_off(probe_irq_on()); save_mcr = serial8250_in_MCR(up); @@ -1371,9 +1368,6 @@ static void autoconfig_irq(struct uart_8250_port *up) if (port->flags & UPF_FOURPORT) outb_p(save_ICP, ICP); - if (uart_console(port)) - console_unlock(); - port->irq = (irq > 0) ? irq : 0; } diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index d6a58a9e072a..128aa0e0ae24 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -2608,7 +2608,11 @@ uart_configure_port(struct uart_driver *drv, struct uart_state *state, port->type = PORT_UNKNOWN; flags |= UART_CONFIG_TYPE; } + if (uart_console(port)) + console_lock(); port->ops->config_port(port, flags); + if (uart_console(port)) + console_unlock(); } if (port->type != PORT_UNKNOWN) { @@ -2616,6 +2620,9 @@ uart_configure_port(struct uart_driver *drv, struct uart_state *state, uart_report_port(drv, port); + if (uart_console(port)) + console_lock(); + /* Power up port for set_mctrl() */ uart_change_pm(state, UART_PM_STATE_ON); @@ -2632,6 +2639,9 @@ uart_configure_port(struct uart_driver *drv, struct uart_state *state, uart_rs485_config(port); + if (uart_console(port)) + console_unlock(); + /* * If this driver supports console, and it hasn't been * successfully registered yet, try to re-register it. diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index f2444b581e16..db69545e6250 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3263,6 +3263,20 @@ static int __init keep_bootcon_setup(char *str) early_param("keep_bootcon", keep_bootcon_setup); +static int console_call_setup(struct console *newcon, char *options) +{ + int err; + + if (!newcon->setup) + return 0; + + console_lock(); + err = newcon->setup(newcon, options); + console_unlock(); + + return err; +} + /* * This is called by register_console() to try to match * the newly registered console with any of the ones selected @@ -3298,8 +3312,8 @@ static int try_enable_preferred_console(struct console *newcon, if (_braille_register_console(newcon, c)) return 0; - if (newcon->setup && - (err = newcon->setup(newcon, c->options)) != 0) + err = console_call_setup(newcon, c->options); + if (err != 0) return err; } newcon->flags |= CON_ENABLED; @@ -3325,7 +3339,7 @@ static void try_enable_default_console(struct console *newcon) if (newcon->index < 0) newcon->index = 0; - if (newcon->setup && newcon->setup(newcon, NULL) != 0) + if (console_call_setup(newcon, NULL) != 0) return; newcon->flags |= CON_ENABLED; -- 2.44.0.rc1.240.g4c46232300-goog