/* -*- 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/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/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/hrtimer.h>
#include <linux/oom.h>
#include <linux/slab.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       = "loglevel(0-9)",
        .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 */

static void sysrq_handle_crash(int key, struct tty_struct *tty)
{
        char *killer = NULL;

        panic_on_oops = 1;      /* force panic */
        wmb();
        *killer = 1;
}
static struct sysrq_key_op sysrq_crash_op = {
        .handler        = sysrq_handle_crash,
        .help_msg       = "Crash",
        .action_msg     = "Trigger a crash",
        .enable_mask    = SYSRQ_ENABLE_DUMP,
};

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 clockevent devices & pending hrtimers (no others)",
};

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)
{
        /*
         * Fall back to the workqueue based printing if the
         * backtrace printing did not succeed or the
         * architecture has no support for it:
         */
        if (!trigger_all_cpu_backtrace()) {
                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       = "show-backtrace-all-active-cpus(L)",
        .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);
        perf_event_print_debug();
}
static struct sysrq_key_op sysrq_showregs_op = {
        .handler        = sysrq_handle_showregs,
        .help_msg       = "show-registers(P)",
        .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       = "show-task-states(T)",
        .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(W)",
        .action_msg     = "Show Blocked State",
        .enable_mask    = SYSRQ_ENABLE_DUMP,
};

#ifdef CONFIG_TRACING
#include <linux/ftrace.h>

static void sysrq_ftrace_dump(int key, struct tty_struct *tty)
{
        ftrace_dump();
}
static struct sysrq_key_op sysrq_ftrace_dump_op = {
        .handler        = sysrq_ftrace_dump,
        .help_msg       = "dump-ftrace-buffer(Z)",
        .action_msg     = "Dump ftrace buffer",
        .enable_mask    = SYSRQ_ENABLE_DUMP,
};
#else
#define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)0)
#endif

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       = "show-memory-usage(M)",
        .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       = "terminate-all-tasks(E)",
        .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, NULL);
}

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       = "memory-full-oom-kill(F)",
        .action_msg     = "Manual OOM execution",
        .enable_mask    = SYSRQ_ENABLE_SIGNAL,
};

#ifdef CONFIG_BLOCK
static void sysrq_handle_thaw(int key, struct tty_struct *tty)
{
        emergency_thaw_all();
}
static struct sysrq_key_op sysrq_thaw_op = {
        .handler        = sysrq_handle_thaw,
        .help_msg       = "thaw-filesystems(J)",
        .action_msg     = "Emergency Thaw of all frozen filesystems",
        .enable_mask    = SYSRQ_ENABLE_SIGNAL,
};
#endif

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-all-tasks(I)",
        .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-all-RT-tasks(N)",
        .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_crash_op,                /* c & ibm_emac driver debug */
        &sysrq_showlocks_op,            /* d */
        &sysrq_term_op,                 /* e */
        &sysrq_moom_op,                 /* f */
        /* g: May be registered for the kernel debugger */
        NULL,                           /* g */
        NULL,                           /* h - reserved for help */
        &sysrq_kill_op,                 /* i */
#ifdef CONFIG_BLOCK
        &sysrq_thaw_op,                 /* j */
#else
        NULL,                           /* j */
#endif
        &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 for frame buffer console restore */
        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 */
        &sysrq_ftrace_dump_op,          /* 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);
        /*
         * Raise the apparent loglevel to maximum so that the sysrq header
         * is shown to provide the user with positive feedback.  We do not
         * simply emit this at KERN_EMERG as that would change message
         * routing in the consumers of /proc/kmsg.
         */
        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