path: root/drivers/tty/sysrq.c

// SPDX-License-Identifier: GPL-2.0
/*
 *	Linux Magic System Request Key Hacks
 *
 *	(c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
 *	based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz>
 *
 *	(c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com>
 *	overhauled to use key registration
 *	based upon discusions in irc://irc.openprojects.net/#kernelnewbies
 *
 *	Copyright (c) 2010 Dmitry Torokhov
 *	Input handler conversion
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/sched/signal.h>
#include <linux/sched/rt.h>
#include <linux/sched/debug.h>
#include <linux/sched/task.h>
#include <linux/ctype.h>
#include <linux/interrupt.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/kdev_t.h>
#include <linux/major.h>
#include <linux/reboot.h>
#include <linux/sysrq.h>
#include <linux/kbd_kern.h>
#include <linux/proc_fs.h>
#include <linux/nmi.h>
#include <linux/quotaops.h>
#include <linux/perf_event.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/suspend.h>
#include <linux/writeback.h>
#include <linux/swap.h>
#include <linux/spinlock.h>
#include <linux/vt_kern.h>
#include <linux/workqueue.h>
#include <linux/hrtimer.h>
#include <linux/oom.h>
#include <linux/slab.h>
#include <linux/input.h>
#include <linux/uaccess.h>
#include <linux/moduleparam.h>
#include <linux/jiffies.h>
#include <linux/syscalls.h>
#include <linux/of.h>
#include <linux/rcupdate.h>

#include <asm/ptrace.h>
#include <asm/irq_regs.h>

/* Whether we react on sysrq keys or just ignore them */
static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
static bool __read_mostly sysrq_always_enabled;

static bool sysrq_on(void)
{
	return sysrq_enabled || sysrq_always_enabled;
}

/**
 * sysrq_mask - Getter for sysrq_enabled mask.
 *
 * Return: 1 if sysrq is always enabled, enabled sysrq_key_op mask otherwise.
 */
int sysrq_mask(void)
{
	if (sysrq_always_enabled)
		return 1;
	return sysrq_enabled;
}
EXPORT_SYMBOL_GPL(sysrq_mask);

/*
 * A value of 1 means 'all', other nonzero values are an op mask:
 */
static bool sysrq_on_mask(int mask)
{
	return sysrq_always_enabled ||
	       sysrq_enabled == 1 ||
	       (sysrq_enabled & mask);
}

static int __init sysrq_always_enabled_setup(char *str)
{
	sysrq_always_enabled = true;
	pr_info("sysrq always enabled.\n");

	return 1;
}

__setup("sysrq_always_enabled", sysrq_always_enabled_setup);


static void sysrq_handle_loglevel(u8 key)
{
	u8 loglevel = key - '0';

	console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
	pr_info("Loglevel set to %u\n", loglevel);
	console_loglevel = loglevel;
}
static const struct sysrq_key_op sysrq_loglevel_op = {
	.handler	= sysrq_handle_loglevel,
	.help_msg	= "loglevel(0-9)",
	.action_msg	= "Changing Loglevel",
	.enable_mask	= SYSRQ_ENABLE_LOG,
};

#ifdef CONFIG_VT
static void sysrq_handle_SAK(u8 key)
{
	struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;

	schedule_work(SAK_work);
}
static const struct sysrq_key_op sysrq_SAK_op = {
	.handler	= sysrq_handle_SAK,
	.help_msg	= "sak(k)",
	.action_msg	= "SAK",
	.enable_mask	= SYSRQ_ENABLE_KEYBOARD,
};
#else
#define sysrq_SAK_op (*(const struct sysrq_key_op *)NULL)
#endif

#ifdef CONFIG_VT
static void sysrq_handle_unraw(u8 key)
{
	vt_reset_unicode(fg_console);
}

static const struct sysrq_key_op sysrq_unraw_op = {
	.handler	= sysrq_handle_unraw,
	.help_msg	= "unraw(r)",
	.action_msg	= "Keyboard mode set to system default",
	.enable_mask	= SYSRQ_ENABLE_KEYBOARD,
};
#else
#define sysrq_unraw_op (*(const struct sysrq_key_op *)NULL)
#endif /* CONFIG_VT */

static void sysrq_handle_crash(u8 key)
{
	/* release the RCU read lock before crashing */
	rcu_read_unlock();

	panic("sysrq triggered crash\n");
}
static const struct sysrq_key_op sysrq_crash_op = {
	.handler	= sysrq_handle_crash,
	.help_msg	= "crash(c)",
	.action_msg	= "Trigger a crash",
	.enable_mask	= SYSRQ_ENABLE_DUMP,
};

static void sysrq_handle_reboot(u8 key)
{
	lockdep_off();
	local_irq_enable();
	emergency_restart();
}
static const struct sysrq_key_op sysrq_reboot_op = {