From patchwork Tue Nov 14 09:35:25 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tomas Mudrunka X-Patchwork-Id: 744408 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8FFD4C4332F for ; Tue, 14 Nov 2023 09:35:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230271AbjKNJfv (ORCPT ); Tue, 14 Nov 2023 04:35:51 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41008 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232533AbjKNJft (ORCPT ); Tue, 14 Nov 2023 04:35:49 -0500 Received: from harvie.cz (harvie.cz [77.87.242.242]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 087971AD for ; Tue, 14 Nov 2023 01:35:45 -0800 (PST) Received: from anemophobia.amit.cz (unknown [31.30.84.130]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by harvie.cz (Postfix) with ESMTPSA id 5124E180251; Tue, 14 Nov 2023 10:35:34 +0100 (CET) From: Tomas Mudrunka To: gregkh@linuxfoundation.org Cc: jirislaby@kernel.org, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, tomas.mudrunka@gmail.com, corbet@lwn.net, linux-doc@vger.kernel.org Subject: [PATCH v2] /proc/sysrq-trigger: accept multiple keys at once Date: Tue, 14 Nov 2023 10:35:25 +0100 Message-ID: <20231114093525.71871-1-tomas.mudrunka@gmail.com> X-Mailer: git-send-email 2.42.1 In-Reply-To: <2023111330-headstone-pyromania-c57e@gregkh> References: <2023111330-headstone-pyromania-c57e@gregkh> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org Just for convenience. This way we can do: `echo _reisub > /proc/sysrq-trigger` Instead of: `for i in r e i s u b; do echo "$i" > /proc/sysrq-trigger; done;` This can be very useful when trying to execute sysrq combo remotely or from userspace. When sending keys in multiple separate writes, userspace can be killed before whole combo is completed. Therefore putting all keys in single write is more robust approach. Signed-off-by: Tomas Mudrunka --- Documentation/admin-guide/sysrq.rst | 4 ++++ drivers/tty/sysrq.c | 17 ++++++++++++++--- 2 files changed, 18 insertions(+), 3 deletions(-) diff --git a/Documentation/admin-guide/sysrq.rst b/Documentation/admin-guide/sysrq.rst index 51906e473..9d46a33e5 100644 --- a/Documentation/admin-guide/sysrq.rst +++ b/Documentation/admin-guide/sysrq.rst @@ -79,6 +79,10 @@ On all echo t > /proc/sysrq-trigger + Alternatively write key combo prepended by underscore. e.g.:: + + echo _reisub > /proc/sysrq-trigger + The :kbd:`` is case sensitive. What are the 'command' keys? diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index 6b4a28bcf..3455e6dd3 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -1150,16 +1150,27 @@ EXPORT_SYMBOL(unregister_sysrq_key); #ifdef CONFIG_PROC_FS /* * writing 'C' to /proc/sysrq-trigger is like sysrq-C + * If first character in write is underscore, all characters are interpreted. */ static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { - if (count) { + char bulk = false; + size_t i; + + for (i = 0; i < count; i++) { char c; - if (get_user(c, buf)) + if (get_user(c, buf+i)) return -EFAULT; - __handle_sysrq(c, false); + + if (c == '_') + bulk = true; + else + __handle_sysrq(c, false); + + if (!bulk) + break; } return count;