drivers/char/sysrq.c - kernel/msm-4.9 - 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/config.h>
 #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/quotaops.h>
 #include <linux/smp_lock.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 <asm/ptrace.h>

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

 /* Loglevel sysrq handler */
 static void sysrq_handle_loglevel(int key, struct pt_regs *pt_regs,
 				  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,
 };


 /* SAK sysrq handler */
 #ifdef CONFIG_VT
 static void sysrq_handle_SAK(int key, struct pt_regs *pt_regs,
 			     struct tty_struct *tty)
 {
 	if (tty)
 		do_SAK(tty);
 	reset_vc(vc_cons[fg_console].d);
 }
 static struct sysrq_key_op sysrq_SAK_op = {
 	.handler	= sysrq_handle_SAK,
 	.help_msg	= "saK",
 	.action_msg	= "SAK",
 	.enable_mask	= SYSRQ_ENABLE_KEYBOARD,
 };
 #endif

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

 	if (kbd)
 		kbd->kbdmode = VC_XLATE;
 }
 static struct sysrq_key_op sysrq_unraw_op = {
 	.handler	= sysrq_handle_unraw,
 	.help_msg	= "unRaw",
 	.action_msg	= "Keyboard mode set to XLATE",
 	.enable_mask	= SYSRQ_ENABLE_KEYBOARD,
 };
 #endif /* CONFIG_VT */

 #ifdef CONFIG_KEXEC
 /* crashdump sysrq handler */
 static void sysrq_handle_crashdump(int key, struct pt_regs *pt_regs,
 				struct tty_struct *tty)
 {
 	crash_kexec(pt_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,
 };
 #endif

 /* reboot sysrq handler */
 static void sysrq_handle_reboot(int key, struct pt_regs *pt_regs,
 				struct tty_struct *tty)
 {
 	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 pt_regs *pt_regs,
 			      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_mountro(int key, struct pt_regs *pt_regs,
 				 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,
 };

 /* END SYNC SYSRQ HANDLERS BLOCK */

 #ifdef CONFIG_DEBUG_MUTEXES

 static void
 sysrq_handle_showlocks(int key, struct pt_regs *pt_regs, struct tty_struct *tty)
 {
 	mutex_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",
 };

 #endif

 /* SHOW SYSRQ HANDLERS BLOCK */

 static void sysrq_handle_showregs(int key, struct pt_regs *pt_regs,
 				  struct tty_struct *tty)
 {
 	if (pt_regs)
 		show_regs(pt_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 pt_regs *pt_regs,
 				   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_showmem(int key, struct pt_regs *pt_regs,
 				 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,
 };

 /* SHOW SYSRQ HANDLERS BLOCK */


 /* SIGNAL SYSRQ HANDLERS BLOCK */

 /* 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 && p->pid != 1)
 			/* Not swapper, init nor kernel thread */
 			force_sig(sig, p);
 	}
 }

 static void sysrq_handle_term(int key, struct pt_regs *pt_regs,
 			      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(void *ignored)
 {
 	out_of_memory(GFP_KERNEL, 0);
 }

 static DECLARE_WORK(moom_work, moom_callback, NULL);

 static void sysrq_handle_moom(int key, struct pt_regs *pt_regs,
 			      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",
 };

 static void sysrq_handle_kill(int key, struct pt_regs *pt_regs,
 			      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,
 };

 /* END SIGNAL SYSRQ HANDLERS BLOCK */

 static void sysrq_handle_unrt(int key, struct pt_regs *pt_regs,
 				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);
 #define SYSRQ_KEY_TABLE_LENGTH 36
 static struct sysrq_key_op *sysrq_key_table[SYSRQ_KEY_TABLE_LENGTH] = {
 /* 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 */	&sysrq_loglevel_op,
 /* a */	NULL, /* Don't use for system provided sysrqs,
 		 it is handled specially on the sparc
 		 and will never arrive */
 /* b */	&sysrq_reboot_op,
 #ifdef CONFIG_KEXEC
 /* c */ &sysrq_crashdump_op,
 #else
 /* c */	NULL,
 #endif
 #ifdef CONFIG_DEBUG_MUTEXES
 /* d */ &sysrq_showlocks_op,
 #else
 /* d */ NULL,
 #endif
 /* e */	&sysrq_term_op,
 /* f */	&sysrq_moom_op,
 /* g */	NULL,
 /* h */	NULL,
 /* i */	&sysrq_kill_op,
 /* j */	NULL,
 #ifdef CONFIG_VT
 /* k */	&sysrq_SAK_op,
 #else
 /* k */	NULL,
 #endif
 /* l */	NULL,
 /* m */	&sysrq_showmem_op,
 /* n */	&sysrq_unrt_op,
 /* o */	NULL, /* This will often be registered
 		 as 'Off' at init time */
 /* p */	&sysrq_showregs_op,
 /* q */	NULL,
 #ifdef CONFIG_VT
 /* r */	&sysrq_unraw_op,
 #else
 /* r */ NULL,
 #endif
 /* s */	&sysrq_sync_op,
 /* t */	&sysrq_showstate_op,
 /* u */	&sysrq_mountro_op,
 /* v */	NULL, /* May be assigned at init time by SMP VOYAGER */
 /* w */	NULL,
 /* x */	NULL,
 /* y */	NULL,
 /* z */	NULL
 };

 /* 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;
         int i;

 	i = sysrq_key_table_key2index(key);
         op_p = (i == -1) ? NULL : sysrq_key_table[i];
         return op_p;
 }

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

 	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 pt_regs *pt_regs, struct tty_struct *tty, int check_mask)
 {
 	struct sysrq_key_op *op_p;
 	int orig_log_level;
 	int i, j;
 	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_enabled == 1 ||
 		    (sysrq_enabled & op_p->enable_mask)) {
 			printk ("%s\n", op_p->action_msg);
 			console_loglevel = orig_log_level;
 			op_p->handler(key, pt_regs, tty);
 		}
 		else
 			printk("This sysrq operation is disabled.\n");
 	} else {
 		printk("HELP : ");
 		/* Only print the help msg once per handler */
 		for (i=0; i<SYSRQ_KEY_TABLE_LENGTH; i++)
 		if (sysrq_key_table[i]) {
 			for (j=0; sysrq_key_table[i] != sysrq_key_table[j]; j++);
 			if (j == i)
 				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 pt_regs *pt_regs, struct tty_struct *tty)
 {
 	if (!sysrq_enabled)
 		return;
 	__handle_sysrq(key, pt_regs, tty, 1);
 }

 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);
 }

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

 EXPORT_SYMBOL(handle_sysrq);
 EXPORT_SYMBOL(register_sysrq_key);
 EXPORT_SYMBOL(unregister_sysrq_key);
	/* -- 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/config.h>
	#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/quotaops.h>
	#include <linux/smp_lock.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 <asm/ptrace.h>

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

	/* Loglevel sysrq handler */
	static void sysrq_handle_loglevel(int key, struct pt_regs *pt_regs,
	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,
	};


	/* SAK sysrq handler */
	#ifdef CONFIG_VT
	static void sysrq_handle_SAK(int key, struct pt_regs *pt_regs,
	struct tty_struct *tty)
	{
	if (tty)
	do_SAK(tty);
	reset_vc(vc_cons[fg_console].d);
	}
	static struct sysrq_key_op sysrq_SAK_op = {
	.handler = sysrq_handle_SAK,
	.help_msg = "saK",
	.action_msg = "SAK",
	.enable_mask = SYSRQ_ENABLE_KEYBOARD,
	};
	#endif

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

	if (kbd)
	kbd->kbdmode = VC_XLATE;
	}
	static struct sysrq_key_op sysrq_unraw_op = {
	.handler = sysrq_handle_unraw,
	.help_msg = "unRaw",
	.action_msg = "Keyboard mode set to XLATE",
	.enable_mask = SYSRQ_ENABLE_KEYBOARD,
	};
	#endif /* CONFIG_VT */

	#ifdef CONFIG_KEXEC
	/* crashdump sysrq handler */
	static void sysrq_handle_crashdump(int key, struct pt_regs *pt_regs,
	struct tty_struct *tty)
	{
	crash_kexec(pt_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,
	};
	#endif

	/* reboot sysrq handler */
	static void sysrq_handle_reboot(int key, struct pt_regs *pt_regs,
	struct tty_struct *tty)
	{
	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 pt_regs *pt_regs,
	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_mountro(int key, struct pt_regs *pt_regs,
	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,
	};

	/* END SYNC SYSRQ HANDLERS BLOCK */

	#ifdef CONFIG_DEBUG_MUTEXES

	static void
	sysrq_handle_showlocks(int key, struct pt_regs pt_regs, struct tty_struct tty)
	{
	mutex_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",
	};

	#endif

	/* SHOW SYSRQ HANDLERS BLOCK */

	static void sysrq_handle_showregs(int key, struct pt_regs *pt_regs,
	struct tty_struct *tty)
	{
	if (pt_regs)
	show_regs(pt_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 pt_regs *pt_regs,
	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_showmem(int key, struct pt_regs *pt_regs,
	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,
	};

	/* SHOW SYSRQ HANDLERS BLOCK */


	/* SIGNAL SYSRQ HANDLERS BLOCK */

	/* 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 && p->pid != 1)
	/* Not swapper, init nor kernel thread */
	force_sig(sig, p);
	}
	}

	static void sysrq_handle_term(int key, struct pt_regs *pt_regs,
	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(void *ignored)
	{
	out_of_memory(GFP_KERNEL, 0);
	}

	static DECLARE_WORK(moom_work, moom_callback, NULL);

	static void sysrq_handle_moom(int key, struct pt_regs *pt_regs,
	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",
	};

	static void sysrq_handle_kill(int key, struct pt_regs *pt_regs,
	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,
	};

	/* END SIGNAL SYSRQ HANDLERS BLOCK */

	static void sysrq_handle_unrt(int key, struct pt_regs *pt_regs,
	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);
	#define SYSRQ_KEY_TABLE_LENGTH 36
	static struct sysrq_key_op *sysrq_key_table[SYSRQ_KEY_TABLE_LENGTH] = {
	/* 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 */ &sysrq_loglevel_op,
	/* a / NULL, / Don't use for system provided sysrqs,
	it is handled specially on the sparc
	and will never arrive */
	/* b */ &sysrq_reboot_op,
	#ifdef CONFIG_KEXEC
	/* c */ &sysrq_crashdump_op,
	#else
	/* c */ NULL,
	#endif
	#ifdef CONFIG_DEBUG_MUTEXES
	/* d */ &sysrq_showlocks_op,
	#else
	/* d */ NULL,
	#endif
	/* e */ &sysrq_term_op,
	/* f */ &sysrq_moom_op,
	/* g */ NULL,
	/* h */ NULL,
	/* i */ &sysrq_kill_op,
	/* j */ NULL,
	#ifdef CONFIG_VT
	/* k */ &sysrq_SAK_op,
	#else
	/* k */ NULL,
	#endif
	/* l */ NULL,
	/* m */ &sysrq_showmem_op,
	/* n */ &sysrq_unrt_op,
	/* o / NULL, / This will often be registered
	as 'Off' at init time */
	/* p */ &sysrq_showregs_op,
	/* q */ NULL,
	#ifdef CONFIG_VT
	/* r */ &sysrq_unraw_op,
	#else
	/* r */ NULL,
	#endif
	/* s */ &sysrq_sync_op,
	/* t */ &sysrq_showstate_op,
	/* u */ &sysrq_mountro_op,
	/* v / NULL, / May be assigned at init time by SMP VOYAGER */
	/* w */ NULL,
	/* x */ NULL,
	/* y */ NULL,
	/* z */ NULL
	};

	/* 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;
	int i;

	i = sysrq_key_table_key2index(key);
	op_p = (i == -1) ? NULL : sysrq_key_table[i];
	return op_p;
	}

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

	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 pt_regs pt_regs, struct tty_struct tty, int check_mask)
	{
	struct sysrq_key_op *op_p;
	int orig_log_level;
	int i, j;
	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_enabled == 1 \|\|
	(sysrq_enabled & op_p->enable_mask)) {
	printk ("%s\n", op_p->action_msg);
	console_loglevel = orig_log_level;
	op_p->handler(key, pt_regs, tty);
	}
	else
	printk("This sysrq operation is disabled.\n");
	} else {
	printk("HELP : ");
	/* Only print the help msg once per handler */
	for (i=0; i<SYSRQ_KEY_TABLE_LENGTH; i++)
	if (sysrq_key_table[i]) {
	for (j=0; sysrq_key_table[i] != sysrq_key_table[j]; j++);
	if (j == i)
	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 pt_regs pt_regs, struct tty_struct tty)
	{
	if (!sysrq_enabled)
	return;
	__handle_sysrq(key, pt_regs, tty, 1);
	}

	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);
	}

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

	EXPORT_SYMBOL(handle_sysrq);
	EXPORT_SYMBOL(register_sysrq_key);
	EXPORT_SYMBOL(unregister_sysrq_key);