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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 7FCDCC282DD for ; Fri, 10 Jan 2020 16:51:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5C961206ED for ; Fri, 10 Jan 2020 16:51:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728929AbgAJQu7 (ORCPT ); Fri, 10 Jan 2020 11:50:59 -0500 Received: from smtprelay0078.hostedemail.com ([216.40.44.78]:54765 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728543AbgAJQu7 (ORCPT ); Fri, 10 Jan 2020 11:50:59 -0500 Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay02.hostedemail.com (Postfix) with ESMTP id 9F9C34DA5; Fri, 10 Jan 2020 16:50:57 +0000 (UTC) X-Session-Marker: 6A6F6540706572636865732E636F6D X-HE-Tag: doll74_8316ba625761 X-Filterd-Recvd-Size: 3602 Received: from XPS-9350.home (unknown [47.151.135.224]) (Authenticated sender: joe@perches.com) by omf05.hostedemail.com (Postfix) with ESMTPA; Fri, 10 Jan 2020 16:50:56 +0000 (UTC) Message-ID: <5293a7cb1ccb16275ddb36c7f26fb9e83f4fac9b.camel@perches.com> Subject: Re: [PATCH-next 3/3] serial/sysrq: Add MAGIC_SYSRQ_SERIAL_SEQUENCE From: Joe Perches To: Dmitry Safonov , linux-kernel@vger.kernel.org Cc: Dmitry Safonov <0x7f454c46@gmail.com>, Greg Kroah-Hartman , Jiri Slaby , Vasiliy Khoruzhick , linux-serial@vger.kernel.org Date: Fri, 10 Jan 2020 08:50:03 -0800 In-Reply-To: <20200109215444.95995-4-dima@arista.com> References: <20200109215444.95995-1-dima@arista.com> <20200109215444.95995-4-dima@arista.com> Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.34.1-2 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2020-01-09 at 21:54 +0000, Dmitry Safonov wrote: > Many embedded boards have a disconnected TTL level serial which can > generate some garbage that can lead to spurious false sysrq detects. trivia: > diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c [] > @@ -3081,6 +3081,38 @@ void uart_insert_char(struct uart_port *port, unsigned int status, [] > +const char sysrq_toggle_seq[] = CONFIG_MAGIC_SYSRQ_SERIAL_SEQUENCE; static const? > +static int uart_try_toggle_sysrq(struct uart_port *port, unsigned int ch) This function return might read better as bool not int > +{ > + if (sysrq_toggle_seq[0] == '\0') > + return 0; > + > + BUILD_BUG_ON(ARRAY_SIZE(sysrq_toggle_seq) >= sizeof(port->sysrq_seq)*U8_MAX); > + if (sysrq_toggle_seq[port->sysrq_seq] != ch) { > + port->sysrq_seq = 0; > + return 0; > + } > + > + /* Without the last \0 */ > + if (++port->sysrq_seq < (ARRAY_SIZE(sysrq_toggle_seq) - 1)) { > + port->sysrq = jiffies + HZ*5; > + return 1; > + } > + > + schedule_work(&sysrq_enable_work); > + > + port->sysrq = 0; > + return 1; > +} [] > diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h > index 255e86a474e9..1f4443db5474 100644 > --- a/include/linux/serial_core.h > +++ b/include/linux/serial_core.h > @@ -243,10 +243,10 @@ struct uart_port { > unsigned long sysrq; /* sysrq timeout */ > unsigned int sysrq_ch; /* char for sysrq */ > unsigned char has_sysrq; > + unsigned char sysrq_seq; /* index in sysrq_toggle_seq */ unsigned int? Or maybe set a maximum length of MAGIC_SYSRQ_SERIAL_SEQUENCE. > > unsigned char hub6; /* this should be in the 8250 driver */ > unsigned char suspended; > - unsigned char unused; > const char *name; /* port name */ > struct attribute_group *attr_group; /* port specific attributes */ > const struct attribute_group **tty_groups; /* all attributes (serial core use only) */ > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 330909c600b1..f6f3e82fee25 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -431,6 +431,14 @@ config MAGIC_SYSRQ_SERIAL > This option allows you to decide whether you want to enable the > magic SysRq key. > > +config MAGIC_SYSRQ_SERIAL_SEQUENCE > + string "Char sequence that enables magic SysRq over serial" > + depends on MAGIC_SYSRQ_SERIAL > + default "" > + help > + Specifies a sequence of characters that can follow BREAK to enable > + SysRq on a serial console. > + > config DEBUG_FS > bool "Debug Filesystem" > help