drivers/char/sysrq.c - kernel/msm-4.19 - Gitiles

 /* -*- linux-c -*-
  *
  *	$Id: sysrq.c,v 1.15 1998/08/23 14:56:41 mj Exp $
  *
  *	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
  */

 #include <linux/sched.h>
 #include <linux/interrupt.h>
 #include <linux/mm.h>
 #include <linux/fs.h>
 #include <linux/tty.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/quotaops.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/suspend.h>
 #include <linux/writeback.h>
 #include <linux/buffer_head.h>		/* for fsync_bdev() */
 #include <linux/swap.h>
 #include <linux/spinlock.h>
 #include <linux/vt_kern.h>
 #include <linux/workqueue.h>
 #include <linux/kexec.h>
 #include <linux/irq.h>
 #include <linux/hrtimer.h>
 #include <linux/oom.h>

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

 /* Whether we react on sysrq keys or just ignore them */
 int __read_mostly __sysrq_enabled = 1;

 static int __read_mostly sysrq_always_enabled;

 int sysrq_on(void)
 {
 	return __sysrq_enabled || sysrq_always_enabled;
 }

 /*
  * A value of 1 means 'all', other nonzero values are an op mask:
  */
 static inline int 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 = 1;
 	printk(KERN_INFO "debug: sysrq always enabled.\n");

 	return 1;
 }

 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);


 static void sysrq_handle_loglevel(int key, struct tty_struct *tty)
 {
 	int i;
 	i = key - '0';
 	console_loglevel = 7;
 	printk("Loglevel set to %d\n", i);
 	console_loglevel = i;
 }
 static struct sysrq_key_op sysrq_loglevel_op = {
 	.handler	= sysrq_handle_loglevel,
 	.help_msg	= "loglevel0-8",
 	.action_msg	= "Changing Loglevel",
 	.enable_mask	= SYSRQ_ENABLE_LOG,
 };

 #ifdef CONFIG_VT
 static void sysrq_handle_SAK(int key, struct tty_struct *tty)
 {
 	struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
 	schedule_work(SAK_work);
 }
 static struct sysrq_key_op sysrq_SAK_op = {
 	.handler	= sysrq_handle_SAK,
 	.help_msg	= "saK",
 	.action_msg	= "SAK",
 	.enable_mask	= SYSRQ_ENABLE_KEYBOARD,
 };
 #else
 #define sysrq_SAK_op (*(struct sysrq_key_op *)0)
 #endif

 #ifdef CONFIG_VT
 static void sysrq_handle_unraw(int key, struct tty_struct *tty)
 {
 	struct kbd_struct *kbd = &kbd_table[fg_console];

 	if (kbd)
 		kbd->kbdmode = default_utf8 ? VC_UNICODE : VC_XLATE;
 }
 static struct sysrq_key_op sysrq_unraw_op = {
 	.handler	= sysrq_handle_unraw,
 	.help_msg	= "unRaw",
 	.action_msg	= "Keyboard mode set to system default",
 	.enable_mask	= SYSRQ_ENABLE_KEYBOARD,
 };
 #else
 #define sysrq_unraw_op (*(struct sysrq_key_op *)0)
 #endif /* CONFIG_VT */

 #ifdef CONFIG_KEXEC
 static void sysrq_handle_crashdump(int key, struct tty_struct *tty)
 {
 	crash_kexec(get_irq_regs());
 }
 static struct sysrq_key_op sysrq_crashdump_op = {
 	.handler	= sysrq_handle_crashdump,
 	.help_msg	= "Crashdump",
 	.action_msg	= "Trigger a crashdump",
 	.enable_mask	= SYSRQ_ENABLE_DUMP,
 };
 #else
 #define sysrq_crashdump_op (*(struct sysrq_key_op *)0)
 #endif

 static void sysrq_handle_reboot(int key, struct tty_struct *tty)
 {
 	lockdep_off();
 	local_irq_enable();
 	emergency_restart();
 }
 static struct sysrq_key_op sysrq_reboot_op = {
 	.handler	= sysrq_handle_reboot,
 	.help_msg	= "reBoot",
 	.action_msg	= "Resetting",
 	.enable_mask	= SYSRQ_ENABLE_BOOT,
 };

 static void sysrq_handle_sync(int key, struct tty_struct *tty)
 {
 	emergency_sync();
 }
 static struct sysrq_key_op sysrq_sync_op = {
 	.handler	= sysrq_handle_sync,
 	.help_msg	= "Sync",
 	.action_msg	= "Emergency Sync",
 	.enable_mask	= SYSRQ_ENABLE_SYNC,
 };

 static void sysrq_handle_show_timers(int key, struct tty_struct *tty)
 {
 	sysrq_timer_list_show();
 }

 static struct sysrq_key_op sysrq_show_timers_op = {
 	.handler	= sysrq_handle_show_timers,
 	.help_msg	= "show-all-timers(Q)",
 	.action_msg	= "Show Pending Timers",
 };

 static void sysrq_handle_mountro(int key, struct tty_struct *tty)
 {
 	emergency_remount();
 }
 static struct sysrq_key_op sysrq_mountro_op = {
 	.handler	= sysrq_handle_mountro,
 	.help_msg	= "Unmount",
 	.action_msg	= "Emergency Remount R/O",
 	.enable_mask	= SYSRQ_ENABLE_REMOUNT,
 };

 #ifdef CONFIG_LOCKDEP
 static void sysrq_handle_showlocks(int key, struct tty_struct *tty)
 {
 	debug_show_all_locks();
 }

 static struct sysrq_key_op sysrq_showlocks_op = {
 	.handler	= sysrq_handle_showlocks,
 	.help_msg	= "show-all-locks(D)",
 	.action_msg	= "Show Locks Held",
 };
 #else
 #define sysrq_showlocks_op (*(struct sysrq_key_op *)0)
 #endif

 #ifdef CONFIG_SMP
 static DEFINE_SPINLOCK(show_lock);

 static void showacpu(void *dummy)
 {
 	unsigned long flags;

 	/* Idle CPUs have no interesting backtrace. */
 	if (idle_cpu(smp_processor_id()))
 		return;

 	spin_lock_irqsave(&show_lock, flags);
 	printk(KERN_INFO "CPU%d:\n", smp_processor_id());
 	show_stack(NULL, NULL);
 	spin_unlock_irqrestore(&show_lock, flags);
 }

 static void sysrq_showregs_othercpus(struct work_struct *dummy)
 {
 	smp_call_function(showacpu, NULL, 0);
 }

 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);

 static void sysrq_handle_showallcpus(int key, struct tty_struct *tty)
 {
 	struct pt_regs *regs = get_irq_regs();
 	if (regs) {
 		printk(KERN_INFO "CPU%d:\n", smp_processor_id());
 		show_regs(regs);
 	}
 	schedule_work(&sysrq_showallcpus);
 }

 static struct sysrq_key_op sysrq_showallcpus_op = {
 	.handler	= sysrq_handle_showallcpus,
 	.help_msg	= "aLlcpus",
 	.action_msg	= "Show backtrace of all active CPUs",
 	.enable_mask	= SYSRQ_ENABLE_DUMP,
 };
 #endif

 static void sysrq_handle_showregs(int key, struct tty_struct *tty)
 {
 	struct pt_regs *regs = get_irq_regs();
 	if (regs)
 		show_regs(regs);
 }
 static struct sysrq_key_op sysrq_showregs_op = {
 	.handler	= sysrq_handle_showregs,
 	.help_msg	= "showPc",
 	.action_msg	= "Show Regs",
 	.enable_mask	= SYSRQ_ENABLE_DUMP,
 };

 static void sysrq_handle_showstate(int key, struct tty_struct *tty)
 {
 	show_state();
 }
 static struct sysrq_key_op sysrq_showstate_op = {
 	.handler	= sysrq_handle_showstate,
 	.help_msg	= "showTasks",
 	.action_msg	= "Show State",
 	.enable_mask	= SYSRQ_ENABLE_DUMP,
 };

 static void sysrq_handle_showstate_blocked(int key, struct tty_struct *tty)
 {
 	show_state_filter(TASK_UNINTERRUPTIBLE);
 }
 static struct sysrq_key_op sysrq_showstate_blocked_op = {
 	.handler	= sysrq_handle_showstate_blocked,
 	.help_msg	= "shoW-blocked-tasks",
 	.action_msg	= "Show Blocked State",
 	.enable_mask	= SYSRQ_ENABLE_DUMP,
 };


 static void sysrq_handle_showmem(int key, struct tty_struct *tty)
 {
 	show_mem();
 }
 static struct sysrq_key_op sysrq_showmem_op = {
 	.handler	= sysrq_handle_showmem,
 	.help_msg	= "showMem",
 	.action_msg	= "Show Memory",
 	.enable_mask	= SYSRQ_ENABLE_DUMP,
 };

 /*
  * Signal sysrq helper function.  Sends a signal to all user processes.
  */
 static void send_sig_all(int sig)
 {
 	struct task_struct *p;

 	for_each_process(p) {
 		if (p->mm && !is_global_init(p))
 			/* Not swapper, init nor kernel thread */
 			force_sig(sig, p);
 	}
 }

 static void sysrq_handle_term(int key, struct tty_struct *tty)
 {
 	send_sig_all(SIGTERM);
 	console_loglevel = 8;
 }
 static struct sysrq_key_op sysrq_term_op = {
 	.handler	= sysrq_handle_term,
 	.help_msg	= "tErm",
 	.action_msg	= "Terminate All Tasks",
 	.enable_mask	= SYSRQ_ENABLE_SIGNAL,
 };

 static void moom_callback(struct work_struct *ignored)
 {
 	out_of_memory(node_zonelist(0, GFP_KERNEL), GFP_KERNEL, 0);
 }

 static DECLARE_WORK(moom_work, moom_callback);

 static void sysrq_handle_moom(int key, struct tty_struct *tty)
 {
 	schedule_work(&moom_work);
 }
 static struct sysrq_key_op sysrq_moom_op = {
 	.handler	= sysrq_handle_moom,
 	.help_msg	= "Full",
 	.action_msg	= "Manual OOM execution",
 	.enable_mask	= SYSRQ_ENABLE_SIGNAL,
 };

 static void sysrq_handle_kill(int key, struct tty_struct *tty)
 {
 	send_sig_all(SIGKILL);
 	console_loglevel = 8;
 }
 static struct sysrq_key_op sysrq_kill_op = {
 	.handler	= sysrq_handle_kill,
 	.help_msg	= "kIll",
 	.action_msg	= "Kill All Tasks",
 	.enable_mask	= SYSRQ_ENABLE_SIGNAL,
 };

 static void sysrq_handle_unrt(int key, struct tty_struct *tty)
 {
 	normalize_rt_tasks();
 }
 static struct sysrq_key_op sysrq_unrt_op = {
 	.handler	= sysrq_handle_unrt,
 	.help_msg	= "Nice",
 	.action_msg	= "Nice All RT Tasks",
 	.enable_mask	= SYSRQ_ENABLE_RTNICE,
 };

 /* Key Operations table and lock */
 static DEFINE_SPINLOCK(sysrq_key_table_lock);

 static struct sysrq_key_op *sysrq_key_table[36] = {
 	&sysrq_loglevel_op,		/* 0 */
 	&sysrq_loglevel_op,		/* 1 */
 	&sysrq_loglevel_op,		/* 2 */
 	&sysrq_loglevel_op,		/* 3 */
 	&sysrq_loglevel_op,		/* 4 */
 	&sysrq_loglevel_op,		/* 5 */
 	&sysrq_loglevel_op,		/* 6 */
 	&sysrq_loglevel_op,		/* 7 */
 	&sysrq_loglevel_op,		/* 8 */
 	&sysrq_loglevel_op,		/* 9 */

 	/*
 	 * a: Don't use for system provided sysrqs, it is handled specially on
 	 * sparc and will never arrive.
 	 */
 	NULL,				/* a */
 	&sysrq_reboot_op,		/* b */
 	&sysrq_crashdump_op,		/* c & ibm_emac driver debug */
 	&sysrq_showlocks_op,		/* d */
 	&sysrq_term_op,			/* e */
 	&sysrq_moom_op,			/* f */
 	/* g: May be registered by ppc for kgdb */
 	NULL,				/* g */
 	NULL,				/* h */
 	&sysrq_kill_op,			/* i */
 	NULL,				/* j */
 	&sysrq_SAK_op,			/* k */
 #ifdef CONFIG_SMP
 	&sysrq_showallcpus_op,		/* l */
 #else
 	NULL,				/* l */
 #endif
 	&sysrq_showmem_op,		/* m */
 	&sysrq_unrt_op,			/* n */
 	/* o: This will often be registered as 'Off' at init time */
 	NULL,				/* o */
 	&sysrq_showregs_op,		/* p */
 	&sysrq_show_timers_op,		/* q */
 	&sysrq_unraw_op,		/* r */
 	&sysrq_sync_op,			/* s */
 	&sysrq_showstate_op,		/* t */
 	&sysrq_mountro_op,		/* u */
 	/* v: May be registered at init time by SMP VOYAGER */
 	NULL,				/* v */
 	&sysrq_showstate_blocked_op,	/* w */
 	/* x: May be registered on ppc/powerpc for xmon */
 	NULL,				/* x */
 	/* y: May be registered on sparc64 for global register dump */
 	NULL,				/* y */
 	NULL				/* z */
 };

 /* key2index calculation, -1 on invalid index */
 static int sysrq_key_table_key2index(int key)
 {
 	int retval;

 	if ((key >= '0') && (key <= '9'))
 		retval = key - '0';
 	else if ((key >= 'a') && (key <= 'z'))
 		retval = key + 10 - 'a';
 	else
 		retval = -1;
 	return retval;
 }

 /*
  * get and put functions for the table, exposed to modules.
  */
 struct sysrq_key_op *__sysrq_get_key_op(int key)
 {
         struct sysrq_key_op *op_p = NULL;
         int i;

 	i = sysrq_key_table_key2index(key);
 	if (i != -1)
 	        op_p = sysrq_key_table[i];
         return op_p;
 }

 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
 {
         int i = sysrq_key_table_key2index(key);

         if (i != -1)
                 sysrq_key_table[i] = op_p;
 }

 /*
  * This is the non-locking version of handle_sysrq.  It must/can only be called
  * by sysrq key handlers, as they are inside of the lock
  */
 void __handle_sysrq(int key, struct tty_struct *tty, int check_mask)
 {
 	struct sysrq_key_op *op_p;
 	int orig_log_level;
 	int i;
 	unsigned long flags;

 	spin_lock_irqsave(&sysrq_key_table_lock, flags);
 	orig_log_level = console_loglevel;
 	console_loglevel = 7;
 	printk(KERN_INFO "SysRq : ");

         op_p = __sysrq_get_key_op(key);
         if (op_p) {
 		/*
 		 * Should we check for enabled operations (/proc/sysrq-trigger
 		 * should not) and is the invoked operation enabled?
 		 */
 		if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 			printk("%s\n", op_p->action_msg);
 			console_loglevel = orig_log_level;
 			op_p->handler(key, tty);
 		} else {
 			printk("This sysrq operation is disabled.\n");
 		}
 	} else {
 		printk("HELP : ");
 		/* Only print the help msg once per handler */
 		for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 			if (sysrq_key_table[i]) {
 				int j;

 				for (j = 0; sysrq_key_table[i] !=
 						sysrq_key_table[j]; j++)
 					;
 				if (j != i)
 					continue;
 				printk("%s ", sysrq_key_table[i]->help_msg);
 			}
 		}
 		printk("\n");
 		console_loglevel = orig_log_level;
 	}
 	spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
 }

 /*
  * This function is called by the keyboard handler when SysRq is pressed
  * and any other keycode arrives.
  */
 void handle_sysrq(int key, struct tty_struct *tty)
 {
 	if (sysrq_on())
 		__handle_sysrq(key, tty, 1);
 }
 EXPORT_SYMBOL(handle_sysrq);

 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
                                 struct sysrq_key_op *remove_op_p)
 {

 	int retval;
 	unsigned long flags;

 	spin_lock_irqsave(&sysrq_key_table_lock, flags);
 	if (__sysrq_get_key_op(key) == remove_op_p) {
 		__sysrq_put_key_op(key, insert_op_p);
 		retval = 0;
 	} else {
 		retval = -1;
 	}
 	spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
 	return retval;
 }

 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
 {
 	return __sysrq_swap_key_ops(key, op_p, NULL);
 }
 EXPORT_SYMBOL(register_sysrq_key);

 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
 {
 	return __sysrq_swap_key_ops(key, NULL, op_p);
 }
 EXPORT_SYMBOL(unregister_sysrq_key);

 #ifdef CONFIG_PROC_FS
 /*
  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
  */
 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
 				   size_t count, loff_t *ppos)
 {
 	if (count) {
 		char c;

 		if (get_user(c, buf))
 			return -EFAULT;
 		__handle_sysrq(c, NULL, 0);
 	}
 	return count;
 }

 static const struct file_operations proc_sysrq_trigger_operations = {
 	.write		= write_sysrq_trigger,
 };

 static int __init sysrq_init(void)
 {
 	proc_create("sysrq-trigger", S_IWUSR, NULL, &proc_sysrq_trigger_operations);
 	return 0;
 }
 module_init(sysrq_init);
 #endif
	/* -- linux-c --
	*
	* $Id: sysrq.c,v 1.15 1998/08/23 14:56:41 mj Exp $
	*
	* 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
	*/

	#include <linux/sched.h>
	#include <linux/interrupt.h>
	#include <linux/mm.h>
	#include <linux/fs.h>
	#include <linux/tty.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/quotaops.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/suspend.h>
	#include <linux/writeback.h>
	#include <linux/buffer_head.h> /* for fsync_bdev() */
	#include <linux/swap.h>
	#include <linux/spinlock.h>
	#include <linux/vt_kern.h>
	#include <linux/workqueue.h>
	#include <linux/kexec.h>
	#include <linux/irq.h>
	#include <linux/hrtimer.h>
	#include <linux/oom.h>

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

	/* Whether we react on sysrq keys or just ignore them */
	int __read_mostly __sysrq_enabled = 1;

	static int __read_mostly sysrq_always_enabled;

	int sysrq_on(void)
	{
	return __sysrq_enabled \|\| sysrq_always_enabled;
	}

	/*
	* A value of 1 means 'all', other nonzero values are an op mask:
	*/
	static inline int 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 = 1;
	printk(KERN_INFO "debug: sysrq always enabled.\n");

	return 1;
	}

	__setup("sysrq_always_enabled", sysrq_always_enabled_setup);


	static void sysrq_handle_loglevel(int key, struct tty_struct *tty)
	{
	int i;
	i = key - '0';
	console_loglevel = 7;
	printk("Loglevel set to %d\n", i);
	console_loglevel = i;
	}
	static struct sysrq_key_op sysrq_loglevel_op = {
	.handler = sysrq_handle_loglevel,
	.help_msg = "loglevel0-8",
	.action_msg = "Changing Loglevel",
	.enable_mask = SYSRQ_ENABLE_LOG,
	};

	#ifdef CONFIG_VT
	static void sysrq_handle_SAK(int key, struct tty_struct *tty)
	{
	struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
	schedule_work(SAK_work);
	}
	static struct sysrq_key_op sysrq_SAK_op = {
	.handler = sysrq_handle_SAK,
	.help_msg = "saK",
	.action_msg = "SAK",
	.enable_mask = SYSRQ_ENABLE_KEYBOARD,
	};
	#else
	#define sysrq_SAK_op ((struct sysrq_key_op )0)
	#endif

	#ifdef CONFIG_VT
	static void sysrq_handle_unraw(int key, struct tty_struct *tty)
	{
	struct kbd_struct *kbd = &kbd_table[fg_console];

	if (kbd)
	kbd->kbdmode = default_utf8 ? VC_UNICODE : VC_XLATE;
	}
	static struct sysrq_key_op sysrq_unraw_op = {
	.handler = sysrq_handle_unraw,
	.help_msg = "unRaw",
	.action_msg = "Keyboard mode set to system default",
	.enable_mask = SYSRQ_ENABLE_KEYBOARD,
	};
	#else
	#define sysrq_unraw_op ((struct sysrq_key_op )0)
	#endif /* CONFIG_VT */

	#ifdef CONFIG_KEXEC
	static void sysrq_handle_crashdump(int key, struct tty_struct *tty)
	{
	crash_kexec(get_irq_regs());
	}
	static struct sysrq_key_op sysrq_crashdump_op = {
	.handler = sysrq_handle_crashdump,
	.help_msg = "Crashdump",
	.action_msg = "Trigger a crashdump",
	.enable_mask = SYSRQ_ENABLE_DUMP,
	};
	#else
	#define sysrq_crashdump_op ((struct sysrq_key_op )0)
	#endif

	static void sysrq_handle_reboot(int key, struct tty_struct *tty)
	{
	lockdep_off();
	local_irq_enable();
	emergency_restart();
	}
	static struct sysrq_key_op sysrq_reboot_op = {
	.handler = sysrq_handle_reboot,
	.help_msg = "reBoot",
	.action_msg = "Resetting",
	.enable_mask = SYSRQ_ENABLE_BOOT,
	};

	static void sysrq_handle_sync(int key, struct tty_struct *tty)
	{
	emergency_sync();
	}
	static struct sysrq_key_op sysrq_sync_op = {
	.handler = sysrq_handle_sync,
	.help_msg = "Sync",
	.action_msg = "Emergency Sync",
	.enable_mask = SYSRQ_ENABLE_SYNC,
	};

	static void sysrq_handle_show_timers(int key, struct tty_struct *tty)
	{
	sysrq_timer_list_show();
	}

	static struct sysrq_key_op sysrq_show_timers_op = {
	.handler = sysrq_handle_show_timers,
	.help_msg = "show-all-timers(Q)",
	.action_msg = "Show Pending Timers",
	};

	static void sysrq_handle_mountro(int key, struct tty_struct *tty)
	{
	emergency_remount();
	}
	static struct sysrq_key_op sysrq_mountro_op = {
	.handler = sysrq_handle_mountro,
	.help_msg = "Unmount",
	.action_msg = "Emergency Remount R/O",
	.enable_mask = SYSRQ_ENABLE_REMOUNT,
	};

	#ifdef CONFIG_LOCKDEP
	static void sysrq_handle_showlocks(int key, struct tty_struct *tty)
	{
	debug_show_all_locks();
	}

	static struct sysrq_key_op sysrq_showlocks_op = {
	.handler = sysrq_handle_showlocks,
	.help_msg = "show-all-locks(D)",
	.action_msg = "Show Locks Held",
	};
	#else
	#define sysrq_showlocks_op ((struct sysrq_key_op )0)
	#endif

	#ifdef CONFIG_SMP
	static DEFINE_SPINLOCK(show_lock);

	static void showacpu(void *dummy)
	{
	unsigned long flags;

	/* Idle CPUs have no interesting backtrace. */
	if (idle_cpu(smp_processor_id()))
	return;

	spin_lock_irqsave(&show_lock, flags);
	printk(KERN_INFO "CPU%d:\n", smp_processor_id());
	show_stack(NULL, NULL);
	spin_unlock_irqrestore(&show_lock, flags);
	}

	static void sysrq_showregs_othercpus(struct work_struct *dummy)
	{
	smp_call_function(showacpu, NULL, 0);
	}

	static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);

	static void sysrq_handle_showallcpus(int key, struct tty_struct *tty)
	{
	struct pt_regs *regs = get_irq_regs();
	if (regs) {
	printk(KERN_INFO "CPU%d:\n", smp_processor_id());
	show_regs(regs);
	}
	schedule_work(&sysrq_showallcpus);
	}

	static struct sysrq_key_op sysrq_showallcpus_op = {
	.handler = sysrq_handle_showallcpus,
	.help_msg = "aLlcpus",
	.action_msg = "Show backtrace of all active CPUs",
	.enable_mask = SYSRQ_ENABLE_DUMP,
	};
	#endif

	static void sysrq_handle_showregs(int key, struct tty_struct *tty)
	{
	struct pt_regs *regs = get_irq_regs();
	if (regs)
	show_regs(regs);
	}
	static struct sysrq_key_op sysrq_showregs_op = {
	.handler = sysrq_handle_showregs,
	.help_msg = "showPc",
	.action_msg = "Show Regs",
	.enable_mask = SYSRQ_ENABLE_DUMP,
	};

	static void sysrq_handle_showstate(int key, struct tty_struct *tty)
	{
	show_state();
	}
	static struct sysrq_key_op sysrq_showstate_op = {
	.handler = sysrq_handle_showstate,
	.help_msg = "showTasks",
	.action_msg = "Show State",
	.enable_mask = SYSRQ_ENABLE_DUMP,
	};

	static void sysrq_handle_showstate_blocked(int key, struct tty_struct *tty)
	{
	show_state_filter(TASK_UNINTERRUPTIBLE);
	}
	static struct sysrq_key_op sysrq_showstate_blocked_op = {
	.handler = sysrq_handle_showstate_blocked,
	.help_msg = "shoW-blocked-tasks",
	.action_msg = "Show Blocked State",
	.enable_mask = SYSRQ_ENABLE_DUMP,
	};


	static void sysrq_handle_showmem(int key, struct tty_struct *tty)
	{
	show_mem();
	}
	static struct sysrq_key_op sysrq_showmem_op = {
	.handler = sysrq_handle_showmem,
	.help_msg = "showMem",
	.action_msg = "Show Memory",
	.enable_mask = SYSRQ_ENABLE_DUMP,
	};

	/*
	* Signal sysrq helper function. Sends a signal to all user processes.
	*/
	static void send_sig_all(int sig)
	{
	struct task_struct *p;

	for_each_process(p) {
	if (p->mm && !is_global_init(p))
	/* Not swapper, init nor kernel thread */
	force_sig(sig, p);
	}
	}

	static void sysrq_handle_term(int key, struct tty_struct *tty)
	{
	send_sig_all(SIGTERM);
	console_loglevel = 8;
	}
	static struct sysrq_key_op sysrq_term_op = {
	.handler = sysrq_handle_term,
	.help_msg = "tErm",
	.action_msg = "Terminate All Tasks",
	.enable_mask = SYSRQ_ENABLE_SIGNAL,
	};

	static void moom_callback(struct work_struct *ignored)
	{
	out_of_memory(node_zonelist(0, GFP_KERNEL), GFP_KERNEL, 0);
	}

	static DECLARE_WORK(moom_work, moom_callback);

	static void sysrq_handle_moom(int key, struct tty_struct *tty)
	{
	schedule_work(&moom_work);
	}
	static struct sysrq_key_op sysrq_moom_op = {
	.handler = sysrq_handle_moom,
	.help_msg = "Full",
	.action_msg = "Manual OOM execution",
	.enable_mask = SYSRQ_ENABLE_SIGNAL,
	};

	static void sysrq_handle_kill(int key, struct tty_struct *tty)
	{
	send_sig_all(SIGKILL);
	console_loglevel = 8;
	}
	static struct sysrq_key_op sysrq_kill_op = {
	.handler = sysrq_handle_kill,
	.help_msg = "kIll",
	.action_msg = "Kill All Tasks",
	.enable_mask = SYSRQ_ENABLE_SIGNAL,
	};

	static void sysrq_handle_unrt(int key, struct tty_struct *tty)
	{
	normalize_rt_tasks();
	}
	static struct sysrq_key_op sysrq_unrt_op = {
	.handler = sysrq_handle_unrt,
	.help_msg = "Nice",
	.action_msg = "Nice All RT Tasks",
	.enable_mask = SYSRQ_ENABLE_RTNICE,
	};

	/* Key Operations table and lock */
	static DEFINE_SPINLOCK(sysrq_key_table_lock);

	static struct sysrq_key_op *sysrq_key_table[36] = {
	&sysrq_loglevel_op, /* 0 */
	&sysrq_loglevel_op, /* 1 */
	&sysrq_loglevel_op, /* 2 */
	&sysrq_loglevel_op, /* 3 */
	&sysrq_loglevel_op, /* 4 */
	&sysrq_loglevel_op, /* 5 */
	&sysrq_loglevel_op, /* 6 */
	&sysrq_loglevel_op, /* 7 */
	&sysrq_loglevel_op, /* 8 */
	&sysrq_loglevel_op, /* 9 */

	/*
	* a: Don't use for system provided sysrqs, it is handled specially on
	* sparc and will never arrive.
	*/
	NULL, /* a */
	&sysrq_reboot_op, /* b */
	&sysrq_crashdump_op, /* c & ibm_emac driver debug */
	&sysrq_showlocks_op, /* d */
	&sysrq_term_op, /* e */
	&sysrq_moom_op, /* f */
	/* g: May be registered by ppc for kgdb */
	NULL, /* g */
	NULL, /* h */
	&sysrq_kill_op, /* i */
	NULL, /* j */
	&sysrq_SAK_op, /* k */
	#ifdef CONFIG_SMP
	&sysrq_showallcpus_op, /* l */
	#else
	NULL, /* l */
	#endif
	&sysrq_showmem_op, /* m */
	&sysrq_unrt_op, /* n */
	/* o: This will often be registered as 'Off' at init time */
	NULL, /* o */
	&sysrq_showregs_op, /* p */
	&sysrq_show_timers_op, /* q */
	&sysrq_unraw_op, /* r */
	&sysrq_sync_op, /* s */
	&sysrq_showstate_op, /* t */
	&sysrq_mountro_op, /* u */
	/* v: May be registered at init time by SMP VOYAGER */
	NULL, /* v */
	&sysrq_showstate_blocked_op, /* w */
	/* x: May be registered on ppc/powerpc for xmon */
	NULL, /* x */
	/* y: May be registered on sparc64 for global register dump */
	NULL, /* y */
	NULL /* z */
	};

	/* key2index calculation, -1 on invalid index */
	static int sysrq_key_table_key2index(int key)
	{
	int retval;

	if ((key >= '0') && (key <= '9'))
	retval = key - '0';
	else if ((key >= 'a') && (key <= 'z'))
	retval = key + 10 - 'a';
	else
	retval = -1;
	return retval;
	}

	/*
	* get and put functions for the table, exposed to modules.
	*/
	struct sysrq_key_op *__sysrq_get_key_op(int key)
	{
	struct sysrq_key_op *op_p = NULL;
	int i;

	i = sysrq_key_table_key2index(key);
	if (i != -1)
	op_p = sysrq_key_table[i];
	return op_p;
	}

	static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
	{
	int i = sysrq_key_table_key2index(key);

	if (i != -1)
	sysrq_key_table[i] = op_p;
	}

	/*
	* This is the non-locking version of handle_sysrq. It must/can only be called
	* by sysrq key handlers, as they are inside of the lock
	*/
	void __handle_sysrq(int key, struct tty_struct *tty, int check_mask)
	{
	struct sysrq_key_op *op_p;
	int orig_log_level;
	int i;
	unsigned long flags;

	spin_lock_irqsave(&sysrq_key_table_lock, flags);
	orig_log_level = console_loglevel;
	console_loglevel = 7;
	printk(KERN_INFO "SysRq : ");

	op_p = __sysrq_get_key_op(key);
	if (op_p) {
	/*
	* Should we check for enabled operations (/proc/sysrq-trigger
	* should not) and is the invoked operation enabled?
	*/
	if (!check_mask \|\| sysrq_on_mask(op_p->enable_mask)) {
	printk("%s\n", op_p->action_msg);
	console_loglevel = orig_log_level;
	op_p->handler(key, tty);
	} else {
	printk("This sysrq operation is disabled.\n");
	}
	} else {
	printk("HELP : ");
	/* Only print the help msg once per handler */
	for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
	if (sysrq_key_table[i]) {
	int j;

	for (j = 0; sysrq_key_table[i] !=
	sysrq_key_table[j]; j++)
	;
	if (j != i)
	continue;
	printk("%s ", sysrq_key_table[i]->help_msg);
	}
	}
	printk("\n");
	console_loglevel = orig_log_level;
	}
	spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
	}

	/*
	* This function is called by the keyboard handler when SysRq is pressed
	* and any other keycode arrives.
	*/
	void handle_sysrq(int key, struct tty_struct *tty)
	{
	if (sysrq_on())
	__handle_sysrq(key, tty, 1);
	}
	EXPORT_SYMBOL(handle_sysrq);

	static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
	struct sysrq_key_op *remove_op_p)
	{

	int retval;
	unsigned long flags;

	spin_lock_irqsave(&sysrq_key_table_lock, flags);
	if (__sysrq_get_key_op(key) == remove_op_p) {
	__sysrq_put_key_op(key, insert_op_p);
	retval = 0;
	} else {
	retval = -1;
	}
	spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
	return retval;
	}

	int register_sysrq_key(int key, struct sysrq_key_op *op_p)
	{
	return __sysrq_swap_key_ops(key, op_p, NULL);
	}
	EXPORT_SYMBOL(register_sysrq_key);

	int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
	{
	return __sysrq_swap_key_ops(key, NULL, op_p);
	}
	EXPORT_SYMBOL(unregister_sysrq_key);

	#ifdef CONFIG_PROC_FS
	/*
	* writing 'C' to /proc/sysrq-trigger is like sysrq-C
	*/
	static ssize_t write_sysrq_trigger(struct file file, const char __user buf,
	size_t count, loff_t *ppos)
	{
	if (count) {
	char c;

	if (get_user(c, buf))
	return -EFAULT;
	__handle_sysrq(c, NULL, 0);
	}
	return count;
	}

	static const struct file_operations proc_sysrq_trigger_operations = {
	.write = write_sysrq_trigger,
	};

	static int __init sysrq_init(void)
	{
	proc_create("sysrq-trigger", S_IWUSR, NULL, &proc_sysrq_trigger_operations);
	return 0;
	}
	module_init(sysrq_init);
	#endif