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sysrq.c

/* -*- 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/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

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_DATA(0)->node_zonelists[ZONE_NORMAL],
                  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",
};

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 */
      NULL,                   /* l */
      &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 */
      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);

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