From patchwork Mon Aug 17 13:27:27 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrzej Pietrasiewicz X-Patchwork-Id: 11718255 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 7305713A4 for ; Mon, 17 Aug 2020 13:27:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 640DC2078D for ; Mon, 17 Aug 2020 13:27:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728605AbgHQN1j (ORCPT ); Mon, 17 Aug 2020 09:27:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43088 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728465AbgHQN1h (ORCPT ); Mon, 17 Aug 2020 09:27:37 -0400 Received: from bhuna.collabora.co.uk (bhuna.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e3e3]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 85C85C061389; Mon, 17 Aug 2020 06:27:36 -0700 (PDT) Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: andrzej.p) with ESMTPSA id B0C12297BA4 From: Andrzej Pietrasiewicz To: linux-kernel@vger.kernel.org Cc: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , Greg Kroah-Hartman , Jiri Slaby , Dmitry Torokhov , Andrzej Pietrasiewicz , linux-input@vger.kernel.org, dri-devel@lists.freedesktop.org, kernel@collabora.com Subject: [PATCH v2 2/2] tty/sysrq: Add configurable handler to execute a compound action Date: Mon, 17 Aug 2020 15:27:27 +0200 Message-Id: <20200817132727.14564-3-andrzej.p@collabora.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200817132727.14564-1-andrzej.p@collabora.com> References: <20200817132727.14564-1-andrzej.p@collabora.com> Sender: linux-input-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-input@vger.kernel.org Userland might want to execute e.g. 'w' (show blocked tasks), followed by 's' (sync), followed by 1000 ms delay and then followed by 'c' (crash) upon a single magic SysRq. Or one might want to execute the famous "Raising Elephants Is So Utterly Boring" action. This patch adds a configurable handler, triggered with 'C', for this exact purpose. The user specifies the composition of the compound action using syntax similar to getopt, where each letter corresponds to an individual action and a colon followed by a number corresponds to a delay of that many milliseconds, e.g.: ws:1000c or r:100eis:1000ub Signed-off-by: Andrzej Pietrasiewicz --- Documentation/admin-guide/sysrq.rst | 9 ++++ drivers/tty/sysrq.c | 82 ++++++++++++++++++++++++++++- include/linux/sysrq.h | 1 + 3 files changed, 91 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/sysrq.rst b/Documentation/admin-guide/sysrq.rst index 67dfa4c29093..80bdd8bf9636 100644 --- a/Documentation/admin-guide/sysrq.rst +++ b/Documentation/admin-guide/sysrq.rst @@ -32,6 +32,7 @@ to 1. Here is the list of possible values in /proc/sys/kernel/sysrq: 64 = 0x40 - enable signalling of processes (term, kill, oom-kill) 128 = 0x80 - allow reboot/poweroff 256 = 0x100 - allow nicing of all RT tasks + 512 = 0x200 - allow compound action You can set the value in the file by the following command:: @@ -148,6 +149,14 @@ Command Function ``z`` Dump the ftrace buffer +``C`` Execute a predefined, compound action. The action is defined with + sysrq.sysrq_compound_action module parameter, whose value contains known + command keys (except ``C`` to prevent recursion). The command keys can + be optionally followed by a colon and a number of milliseconds to wait + after executing the last action. For example: + + sysrq.sysrq_compound_action=r:100eis:1000ub + ``0``-``9`` Sets the console log level, controlling which kernel messages will be printed to your console. (``0``, for example would make it so that only emergency messages like PANICs or OOPSes would diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index 959f9e121cc6..fec770de325b 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -20,6 +20,7 @@ #include #include #include +#include #include #include #include @@ -438,6 +439,15 @@ static const struct sysrq_key_op sysrq_unrt_op = { .enable_mask = SYSRQ_ENABLE_RTNICE, }; +static void sysrq_action_compound(int key); + +static struct sysrq_key_op sysrq_action_compound_op = { + .handler = sysrq_action_compound, + .help_msg = "execute-compound-action(C)", + .action_msg = "Execute compound action", + .enable_mask = SYSRQ_ENABLE_COMPOUND, +}; + /* Key Operations table and lock */ static DEFINE_SPINLOCK(sysrq_key_table_lock); @@ -500,7 +510,7 @@ static const struct sysrq_key_op *sysrq_key_table[62] = { &sysrq_ftrace_dump_op, /* z */ NULL, /* A */ NULL, /* B */ - NULL, /* C */ + &sysrq_action_compound_op, /* C */ NULL, /* D */ NULL, /* E */ NULL, /* F */ @@ -633,6 +643,7 @@ EXPORT_SYMBOL(handle_sysrq); #ifdef CONFIG_INPUT static int sysrq_reset_downtime_ms; +static char *sysrq_compound_action; /* Simple translation table for the SysRq keys */ static const unsigned char sysrq_xlate[KEY_CNT] = @@ -786,6 +797,62 @@ static void sysrq_of_get_keyreset_config(void) { } #endif +#define SYSRQ_COMPOUND_ACTION_VALIDATE 0 +#define SYSRQ_COMPOUND_ACTION_RUN 1 + +static int sysrq_process_compound_action(int pass) +{ + const char *action = sysrq_compound_action; + const struct sysrq_key_op *op_p; + int ret; + unsigned int delay; + + while (*action) { + op_p = __sysrq_get_key_op(*action); + if (!op_p) + return -EINVAL; + + /* Don't allow calling ourselves recursively */ + if (op_p == &sysrq_action_compound_op) + return -EINVAL; + + if (pass == SYSRQ_COMPOUND_ACTION_RUN) + __handle_sysrq(*action, false); + + if (*++action == ':') { + ret = sscanf(action++, ":%u", &delay); + if (ret < 1) /* we want at least ":[0-9]" => 1 item */ + return -EINVAL; + + while (*action >= '0' && *action <= '9') + ++action; + if (pass == SYSRQ_COMPOUND_ACTION_RUN) + mdelay(delay); + } + } + + return 0; +} + +static void sysrq_action_compound(int key) +{ + if (!sysrq_compound_action) { + pr_err("Unconfigured compound action for %s\n", + sysrq_action_compound_op.help_msg); + + return; + } + + if (sysrq_process_compound_action(SYSRQ_COMPOUND_ACTION_VALIDATE)) { + pr_err("Incorrect compound action %s for %s\n", + sysrq_compound_action, + sysrq_action_compound_op.help_msg); + + return; + } + + sysrq_process_compound_action(SYSRQ_COMPOUND_ACTION_RUN); +} static void sysrq_reinject_alt_sysrq(struct work_struct *work) { @@ -1077,8 +1144,21 @@ module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); +module_param(sysrq_compound_action, charp, 0644); +MODULE_PARM_DESC(sysrq_compound_action, + "\tCompound sysrq action to be executed on Alt-Shift-SysRq-C\n" + "\tThe compound action definition consists of known SysRq action letters except 'C',\n" + "\teach letter can be optionally followed by a colon and a number of milliseconds to wait\n" + "\tafter executing the last action.\n" + "\tExample:\n" + "\tTo unRaw, wait 100ms, tErminate, kIll, Sync, wait 1000ms, Unmount, Boot\n" + "\tsysrq.sysrq_compound_action=r:100eis:1000ub"); #else +{ +} + +static void sysrq_action_compound(int key) static inline void sysrq_register_handler(void) { } diff --git a/include/linux/sysrq.h b/include/linux/sysrq.h index 3a582ec7a2f1..6df4442f12a9 100644 --- a/include/linux/sysrq.h +++ b/include/linux/sysrq.h @@ -28,6 +28,7 @@ #define SYSRQ_ENABLE_SIGNAL 0x0040 #define SYSRQ_ENABLE_BOOT 0x0080 #define SYSRQ_ENABLE_RTNICE 0x0100 +#define SYSRQ_ENABLE_COMPOUND 0x0200 struct sysrq_key_op { void (* const handler)(int);