// SPDX-License-Identifier: GPL-2.0+
/*
 * ipmi_watchdog.c
 *
 * A watchdog timer based upon the IPMI interface.
 *
 * Author: MontaVista Software, Inc.
 *         Corey Minyard <minyard@mvista.com>
 *         source@mvista.com
 *
 * Copyright 2002 MontaVista Software Inc.
 */

#define pr_fmt(fmt) "IPMI Watchdog: " fmt

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/ipmi.h>
#include <linux/ipmi_smi.h>
#include <linux/mutex.h>
#include <linux/watchdog.h>
#include <linux/miscdevice.h>
#include <linux/init.h>
#include <linux/completion.h>
#include <linux/kdebug.h>
#include <linux/rwsem.h>
#include <linux/errno.h>
#include <linux/uaccess.h>
#include <linux/notifier.h>
#include <linux/nmi.h>
#include <linux/reboot.h>
#include <linux/wait.h>
#include <linux/poll.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/delay.h>
#include <linux/atomic.h>
#include <linux/sched/signal.h>

#ifdef CONFIG_X86
/*
 * This is ugly, but I've determined that x86 is the only architecture
 * that can reasonably support the IPMI NMI watchdog timeout at this
 * time.  If another architecture adds this capability somehow, it
 * will have to be a somewhat different mechanism and I have no idea
 * how it will work.  So in the unlikely event that another
 * architecture supports this, we can figure out a good generic
 * mechanism for it at that time.
 */
#include <asm/kdebug.h>
#include <asm/nmi.h>
#define HAVE_DIE_NMI
#endif

/*
 * The IPMI command/response information for the watchdog timer.
 */

/* values for byte 1 of the set command, byte 2 of the get response. */
#define WDOG_DONT_LOG           (1 << 7)
#define WDOG_DONT_STOP_ON_SET   (1 << 6)
#define WDOG_SET_TIMER_USE(byte, use) \
        byte = ((byte) & 0xf8) | ((use) & 0x7)
#define WDOG_GET_TIMER_USE(byte) ((byte) & 0x7)
#define WDOG_TIMER_USE_BIOS_FRB2        1
#define WDOG_TIMER_USE_BIOS_POST        2
#define WDOG_TIMER_USE_OS_LOAD          3
#define WDOG_TIMER_USE_SMS_OS           4
#define WDOG_TIMER_USE_OEM              5

/* values for byte 2 of the set command, byte 3 of the get response. */
#define WDOG_SET_PRETIMEOUT_ACT(byte, use) \
        byte = ((byte) & 0x8f) | (((use) & 0x7) << 4)
#define WDOG_GET_PRETIMEOUT_ACT(byte) (((byte) >> 4) & 0x7)
#define WDOG_PRETIMEOUT_NONE            0
#define WDOG_PRETIMEOUT_SMI             1
#define WDOG_PRETIMEOUT_NMI             2
#define WDOG_PRETIMEOUT_MSG_INT         3

/* Operations that can be performed on a pretimout. */
#define WDOG_PREOP_NONE         0
#define WDOG_PREOP_PANIC        1
/* Cause data to be available to read.  Doesn't work in NMI mode. */
#define WDOG_PREOP_GIVE_DATA    2

/* Actions to perform on a full timeout. */
#define WDOG_SET_TIMEOUT_ACT(byte, use) \
        byte = ((byte) & 0xf8) | ((use) & 0x7)
#define WDOG_GET_TIMEOUT_ACT(byte) ((byte) & 0x7)
#define WDOG_TIMEOUT_NONE               0
#define WDOG_TIMEOUT_RESET              1
#define WDOG_TIMEOUT_POWER_DOWN         2
#define WDOG_TIMEOUT_POWER_CYCLE        3

/*
 * Byte 3 of the get command, byte 4 of the get response is the
 * pre-timeout in seconds.
 */

/* Bits for setting byte 4 of the set command, byte 5 of the get response. */
#define WDOG_EXPIRE_CLEAR_BIOS_FRB2     (1 << 1)
#define WDOG_EXPIRE_CLEAR_BIOS_POST     (1 << 2)
#define WDOG_EXPIRE_CLEAR_OS_LOAD       (1 << 3)
#define WDOG_EXPIRE_CLEAR_SMS_OS        (1 << 4)
#define WDOG_EXPIRE_CLEAR_OEM           (1 << 5)

/*
 * Setting/getting the watchdog timer value.  This is for bytes 5 and
 * 6 (the timeout time) of the set command, and bytes 6 and 7 (the
 * timeout time) and 8 and 9 (the current countdown value) of the
 * response.  The timeout value is given in seconds (in the command it
 * is 100ms intervals).
 */
#define WDOG_SET_TIMEOUT(byte1, byte2, val) \
        (byte1) = (((val) * 10) & 0xff), (byte2) = (((val) * 10) >> 8)
#define WDOG_GET_TIMEOUT(byte1, byte2) \
        (((byte1) | ((byte2) << 8)) / 10)

#define IPMI_WDOG_RESET_TIMER           0x22
#define IPMI_WDOG_SET_TIMER             0x24
#define IPMI_WDOG_GET_TIMER             0x25

#define IPMI_WDOG_TIMER_NOT_INIT_RESP   0x80

static DEFINE_MUTEX(ipmi_watchdog_mutex);
static bool nowayout = WATCHDOG_NOWAYOUT;

static struct ipmi_user *watchdog_user;
static int watchdog_ifnum;

/* Default the timeout to 10 seconds. */
static int timeout = 10;

/* The pre-timeout is disabled by default. */
static int pretimeout;

/* Default timeout to set on panic */
static int panic_wdt_timeout = 255;

/* Default action is to reset the board on a timeout. */
static unsigned char action_val = WDOG_TIMEOUT_RESET;

static char action[16] = "reset";

static unsigned char preaction_val = WDOG_PRETIMEOUT_NONE;

static char preaction[16] = "pre_none";

static unsigned char preop_val = WDOG_PREOP_NONE;

static char preop[16] = "preop_none";
static DEFINE_SPINLOCK(ipmi_read_lock);
static char data_to_read;
static DECLARE_WAIT_QUEUE_HEAD(read_q);
static struct fasync_struct *fasync_q;
static atomic_t pretimeout_since_last_heartbeat;
static char expect_close;

static int ifnum_to_use = -1;

/* Parameters to ipmi_set_timeout */
#define IPMI_SET_TIMEOUT_NO_HB                  0
#define IPMI_SET_TIMEOUT_HB_IF_NECESSARY        1
#define IPMI_SET_TIMEOUT_FORCE_HB               2

static int ipmi_set_timeout(int do_heartbeat);
static void ipmi_register_watchdog(int ipmi_intf);
static void ipmi_unregister_watchdog(int ipmi_intf);

/*
 * If true, the driver will start running as soon as it is configured
 * and ready.
 */
static int start_now;

static int set_param_timeout(const char *val, const struct kernel_param *kp)
{
        char *endp;
        int  l;
        int  rv = 0;

        if (!val)
                return -EINVAL;
        l = simple_strtoul(val, &endp, 0);
        if (endp == val)
                return -EINVAL;

        *((int *)kp->arg) = l;
        if (watchdog_user)
                rv = ipmi_set_timeout(IPMI_SET_TIMEOUT_HB_IF_NECESSARY);

        return rv;
}

static const struct kernel_param_ops param_ops_timeout = {
        .set = set_param_timeout,
        .get = param_get_int,
};
#define param_check_timeout param_check_int

typedef int (*action_fn)(const char *intval, char *outval);

static int action_op(const char *inval, char *outval);
static int preaction_op(const char *inval, char *outval);
static int preop_op(const char *inval, char *outval);
static void check_parms(void);

static int set_param_str(const char *val, const struct kernel_param *kp)
{
        action_fn  fn = (action_fn) kp->arg;
        int        rv = 0;
        char       valcp[16];
        char       *s;

        strncpy(valcp, val, 15);
        valcp[15] = '\0';

        s = strstrip(valcp);

        rv = fn(s, NULL);
        if (rv)
                goto out;

        check_parms();
        if (watchdog_user)
                rv = ipmi_set_timeout(IPMI_SET_TIMEOUT_HB_IF_NECESSARY);

 out:
        return rv;
}

static int get_param_str(char *buffer, const struct kernel_param *kp)
{
        action_fn fn = (action_fn) kp->arg;
        int       rv;

        rv = fn(NULL, buffer);
        if (rv)
                return rv;
        return strlen(buffer);
}


static int set_param_wdog_ifnum(const char *val, const struct kernel_param *kp)
{
        int rv = param_set_int(val, kp);
        if (rv)
                return rv;
        if ((ifnum_to_use < 0) || (ifnum_to_use == watchdog_ifnum))
                return 0;

        ipmi_unregister_watchdog(watchdog_ifnum);
        ipmi_register_watchdog(ifnum_to_use);
        return 0;
}

static const struct kernel_param_ops param_ops_wdog_ifnum = {
        .set = set_param_wdog_ifnum,
        .get = param_get_int,
};

#define param_check_wdog_ifnum param_check_int

static const struct kernel_param_ops param_ops_str = {
        .set = set_param_str,
        .get = get_param_str,
};

module_param(ifnum_to_use, wdog_ifnum, 0644);
MODULE_PARM_DESC(ifnum_to_use, "The interface number to use for the watchdog "
                 "timer.  Setting to -1 defaults to the first registered "
                 "interface");

module_param(timeout, timeout, 0644);
MODULE_PARM_DESC(timeout, "Timeout value in seconds.");

module_param(pretimeout, timeout, 0644);
MODULE_PARM_DESC(pretimeout, "Pretimeout value in seconds.");

module_param(panic_wdt_timeout, timeout, 0644);
MODULE_PARM_DESC(panic_wdt_timeout, "Timeout value on kernel panic in seconds.");

module_param_cb(action, &param_ops_str, action_op, 0644);
MODULE_PARM_DESC(action, "Timeout action. One of: "
                 "reset, none, power_cycle, power_off.");

module_param_cb(preaction, &param_ops_str, preaction_op, 0644);
MODULE_PARM_DESC(preaction, "Pretimeout action.  One of: "
                 "pre_none, pre_smi, pre_nmi, pre_int.");

module_param_cb(preop, &param_ops_str, preop_op, 0644);
MODULE_PARM_DESC(preop, "Pretimeout driver operation.  One of: "
                 "preop_none, preop_panic, preop_give_data.");

module_param(start_now, int, 0444);
MODULE_PARM_DESC(start_now, "Set to 1 to start the watchdog as"
                 "soon as the driver is loaded.");

module_param(nowayout, bool, 0644);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
                 "(default=CONFIG_WATCHDOG_NOWAYOUT)");

/* Default state of the timer. */
static unsigned char ipmi_watchdog_state = WDOG_TIMEOUT_NONE;

/* Is someone using the watchdog?  Only one user is allowed. */
static unsigned long ipmi_wdog_open;

/*
 * If set to 1, the heartbeat command will set the state to reset and
 * start the timer.  The timer doesn't normally run when the driver is
 * first opened until the heartbeat is set the first time, this
 * variable is used to accomplish this.
 */
static int ipmi_start_timer_on_heartbeat;

/* IPMI version of the BMC. */
static unsigned char ipmi_version_major;
static unsigned char ipmi_version_minor;

/* If a pretimeout occurs, this is used to allow only one panic to happen. */
static atomic_t preop_panic_excl = ATOMIC_INIT(-1);

#ifdef HAVE_DIE_NMI
static int testing_nmi;
static int nmi_handler_registered;
#endif

static int __ipmi_heartbeat(void);

/*
 * We use a mutex to make sure that only one thing can send a set a
 * message at one time.  The mutex is claimed when a message is sent
 * and freed when both the send and receive messages are free.
 */
static atomic_t msg_tofree = ATOMIC_INIT(0);
static DECLARE_COMPLETION(msg_wait);
static void msg_free_smi(struct ipmi_smi_msg *msg)
{
        if (atomic_dec_and_test(&msg_tofree))
                complete(&msg_wait);
}
static void msg_free_recv(struct ipmi_recv_msg *msg)
{
        if (atomic_dec_and_test(&msg_tofree))
                complete(&msg_wait);
}
static struct ipmi_smi_msg smi_msg = {
        .done = msg_free_smi
};
static struct ipmi_recv_msg recv_msg = {
        .done = msg_free_recv
};

static int __ipmi_set_timeout(struct ipmi_smi_msg  *smi_msg,
                              struct ipmi_recv_msg *recv_msg,
                              int                  *send_heartbeat_now)
{
        struct kernel_ipmi_msg            msg;
        unsigned char                     data[6];
        int                               rv;
        struct ipmi_system_interface_addr addr;
        int                               hbnow = 0;


        data[0] = 0;
        WDOG_SET_TIMER_USE(data[0], WDOG_TIMER_USE_SMS_OS);

        if ((ipmi_version_major > 1)
            || ((ipmi_version_major == 1) && (ipmi_version_minor >= 5))) {
                /* This is an IPMI 1.5-only feature. */
                data[0] |= WDOG_DONT_STOP_ON_SET;
        } else if (ipmi_watchdog_state != WDOG_TIMEOUT_NONE) {
                /*
                 * In ipmi 1.0, setting the timer stops the watchdog, we
                 * need to start it back up again.
                 */
                hbnow = 1;
        }

        data[1] = 0;
        WDOG_SET_TIMEOUT_ACT(data[1], ipmi_watchdog_state);
        if ((pretimeout > 0) && (ipmi_watchdog_state != WDOG_TIMEOUT_NONE)) {
            WDOG_SET_PRETIMEOUT_ACT(data[1], preaction_val);
            data[2] = pretimeout;
        } else {
            WDOG_SET_PRETIMEOUT_ACT(data[1], WDOG_PRETIMEOUT_NONE);
            data[2] = 0; /* No pretimeout. */
        }
        data[3] = 0;
        WDOG_SET_TIMEOUT(data[4], data[5], timeout);

        addr.addr_type = IPMI_SYSTEM_INTERFACE_ADDR_TYPE;
        addr.channel = IPMI_BMC_CHANNEL;
        addr.lun = 0;

        msg.netfn = 0x06;
        msg.cmd = IPMI_WDOG_SET_TIMER;
        msg.data = data;
        msg.data_len = sizeof(data);
        rv = ipmi_request_supply_msgs(watchdog_user,
                                      (struct ipmi_addr *) &addr,
                                      0,
                                      &msg,
                                      NULL,
                                      smi_msg,
                                      recv_msg,
                                      1);
        if (rv)
                pr_warn("set timeout error: %d\n", rv);
        else if (send_heartbeat_now)
                *send_heartbeat_now = hbnow;

        return rv;
}

static int _ipmi_set_timeout(int do_heartbeat)
{
        int send_heartbeat_now;
        int rv;

        if (!watchdog_user)
                return -ENODEV;

        atomic_set(&msg_tofree, 2);

        rv = __ipmi_set_timeout(&smi_msg,
                                &recv_msg,
                                &send_heartbeat_now);
        if (rv)
                return rv;

        wait_for_completion(&msg_wait);

        if ((do_heartbeat == IPMI_SET_TIMEOUT_FORCE_HB)
                || ((send_heartbeat_now)
                    && (do_heartbeat == IPMI_SET_TIMEOUT_HB_IF_NECESSARY)))
                rv = __ipmi_heartbeat();

        return rv;
}

static int ipmi_set_timeout(int do_heartbeat)
{
        int rv;

        mutex_lock(&ipmi_watchdog_mutex);
        rv = _ipmi_set_timeout(do_heartbeat);
        mutex_unlock(&ipmi_watchdog_mutex);

        return rv;
}

static atomic_t panic_done_count = ATOMIC_INIT(0);

static void panic_smi_free(struct ipmi_smi_msg *msg)
{
        atomic_dec(&panic_done_count);
}
static void panic_recv_free(struct ipmi_recv_msg *msg)
{
        atomic_dec(&panic_done_count);
}

static struct ipmi_smi_msg panic_halt_heartbeat_smi_msg = {
        .done = panic_smi_free
};
static struct ipmi_recv_msg panic_halt_heartbeat_recv_msg = {
        .done = panic_recv_free
};

static void panic_halt_ipmi_heartbeat(void)
{
        struct kernel_ipmi_msg             msg;
        struct ipmi_system_interface_addr addr;
        int rv;

        /*
         * Don't reset the timer if we have the timer turned off, that
         * re-enables the watchdog.
         */
        if (ipmi_watchdog_state == WDOG_TIMEOUT_NONE)
                return;

        addr.addr_type = IPMI_SYSTEM_INTERFACE_ADDR_TYPE;
        addr.channel = IPMI_BMC_CHANNEL;
        addr.lun = 0;

        msg.netfn = 0x06;
        msg.cmd = IPMI_WDOG_RESET_TIMER;
        msg.data = NULL;
        msg.data_len = 0;
        atomic_add(1, &panic_done_count);
        rv = ipmi_request_supply_msgs(watchdog_user,
                                      (struct ipmi_addr *) &addr,
                                      0,
                                      &msg,
                                      NULL,
                                      &panic_halt_heartbeat_smi_msg,
                                      &panic_halt_heartbeat_recv_msg,
                                      1);
        if (rv)
                atomic_sub(1, &panic_done_count);
}

static struct ipmi_smi_msg panic_halt_smi_msg = {
        .done = panic_smi_free
};
static struct ipmi_recv_msg panic_halt_recv_msg = {
        .done = panic_recv_free
};

/*
 * Special call, doesn't claim any locks.  This is only to be called
 * at panic or halt time, in run-to-completion mode, when the caller
 * is the only CPU and the only thing that will be going is these IPMI
 * calls.
 */
static void panic_halt_ipmi_set_timeout(void)
{
        int send_heartbeat_now;
        int rv;

        /* Wait for the messages to be free. */
        while (atomic_read(&panic_done_count) != 0)
                ipmi_poll_interface(watchdog_user);
        atomic_add(1, &panic_done_count);
        rv = __ipmi_set_timeout(&panic_halt_smi_msg,
                                &panic_halt_recv_msg,
                                &send_heartbeat_now);
        if (rv) {
                atomic_sub(1, &panic_done_count);
                pr_warn("Unable to extend the watchdog timeout\n");
        } else {
                if (send_heartbeat_now)
                        panic_halt_ipmi_heartbeat();
        }
        while (atomic_read(&panic_done_count) != 0)
                ipmi_poll_interface(watchdog_user);
}

static int __ipmi_heartbeat(void)
{
        struct kernel_ipmi_msg msg;
        int rv;
        struct ipmi_system_interface_addr addr;
        int timeout_retries = 0;

restart:
        /*
         * Don't reset the timer if we have the timer turned off, that
         * re-enables the watchdog.
         */
        if (ipmi_watchdog_state == WDOG_TIMEOUT_NONE)
                return 0;

        atomic_set(&msg_tofree, 2);

        addr.addr_type = IPMI_SYSTEM_INTERFACE_ADDR_TYPE;
        addr.channel = IPMI_BMC_CHANNEL;
        addr.lun = 0;

        msg.netfn = 0x06;
        msg.cmd = IPMI_WDOG_RESET_TIMER;
        msg.data = NULL;
        msg.data_len = 0;
        rv = ipmi_request_supply_msgs(watchdog_user,
                                      (struct ipmi_addr *) &addr,
                                      0,
                                      &msg,
                                      NULL,
                                      &smi_msg,
                                      &recv_msg,
                                      1);
        if (rv) {
                pr_warn("heartbeat send failure: %d\n", rv);
                return rv;
        }

        /* Wait for the heartbeat to be sent. */
        wait_for_completion(&msg_wait);

        if (recv_msg.msg.data[0] == IPMI_WDOG_TIMER_NOT_INIT_RESP)  {
                timeout_retries++;
                if (timeout_retries > 3) {
                        pr_err("Unable to restore the IPMI watchdog's settings, giving up\n");
                        rv = -EIO;
                        goto out;
                }

                /*
                 * The timer was not initialized, that means the BMC was
                 * probably reset and lost the watchdog information.  Attempt
                 * to restore the timer's info.  Note that we still hold
                 * the heartbeat lock, to keep a heartbeat from happening
                 * in this process, so must say no heartbeat to avoid a
                 * deadlock on this mutex
                 */
                rv = _ipmi_set_timeout(IPMI_SET_TIMEOUT_NO_HB);
                if (rv) {
                        pr_err("Unable to send the command to set the watchdog's settings, giving up\n");
                        goto out;
                }

                /* Might need a heartbeat send, go ahead and do it. */
                goto restart;
        } else if (recv_msg.msg.data[0] != 0) {
                /*
                 * Got an error in the heartbeat response.  It was already
                 * reported in ipmi_wdog_msg_handler, but we should return
                 * an error here.
                 */
                rv = -EINVAL;
        }

out:
        return rv;
}

static int _ipmi_heartbeat(void)
{
        int rv;

        if (!watchdog_user)
                return -ENODEV;

        if (ipmi_start_timer_on_heartbeat) {
                ipmi_start_timer_on_heartbeat = 0;
                ipmi_watchdog_state = action_val;
                rv = _ipmi_set_timeout(IPMI_SET_TIMEOUT_FORCE_HB);
        } else if (atomic_cmpxchg(&pretimeout_since_last_heartbeat, 1, 0)) {
                /*
                 * A pretimeout occurred, make sure we set the timeout.
                 * We don't want to set the action, though, we want to
                 * leave that alone (thus it can't be combined with the
                 * above operation.
                 */
                rv = _ipmi_set_timeout(IPMI_SET_TIMEOUT_HB_IF_NECESSARY);
        } else {
                rv = __ipmi_heartbeat();
        }

        return rv;
}

static int ipmi_heartbeat(void)
{
        int rv;

        mutex_lock(&ipmi_watchdog_mutex);
        rv = _ipmi_heartbeat();
        mutex_unlock(&ipmi_watchdog_mutex);

        return rv;
}

static struct watchdog_info ident = {
        .options        = 0,    /* WDIOF_SETTIMEOUT, */
        .firmware_version = 1,
        .identity       = "IPMI"
};

static int ipmi_ioctl(struct file *file,
                      unsigned int cmd, unsigned long arg)
{
        void __user *argp = (void __user *)arg;
        int i;
        int val;

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                i = copy_to_user(argp, &ident, sizeof(ident));
                return i ? -EFAULT : 0;

        case WDIOC_SETTIMEOUT:
                i = copy_from_user(&val, argp, sizeof(int));
                if (i)
                        return -EFAULT;
                timeout = val;
                return _ipmi_set_timeout(IPMI_SET_TIMEOUT_HB_IF_NECESSARY);

        case WDIOC_GETTIMEOUT:
                i = copy_to_user(argp, &timeout, sizeof(timeout));
                if (i)
                        return -EFAULT;
                return 0;

        case WDIOC_SETPRETIMEOUT:
                i = copy_from_user(&val, argp, sizeof(int));
                if (i)
                        return -EFAULT;
                pretimeout = val;
                return _ipmi_set_timeout(IPMI_SET_TIMEOUT_HB_IF_NECESSARY);

        case WDIOC_GETPRETIMEOUT:
                i = copy_to_user(argp, &pretimeout, sizeof(pretimeout));
                if (i)
                        return -EFAULT;
                return 0;

        case WDIOC_KEEPALIVE:
                return _ipmi_heartbeat();

        case WDIOC_SETOPTIONS:
                i = copy_from_user(&val, argp, sizeof(int));
                if (i)
                        return -EFAULT;
                if (val & WDIOS_DISABLECARD) {
                        ipmi_watchdog_state = WDOG_TIMEOUT_NONE;
                        _ipmi_set_timeout(IPMI_SET_TIMEOUT_NO_HB);
                        ipmi_start_timer_on_heartbeat = 0;
                }

                if (val & WDIOS_ENABLECARD) {
                        ipmi_watchdog_state = action_val;
                        _ipmi_set_timeout(IPMI_SET_TIMEOUT_FORCE_HB);
                }
                return 0;

        case WDIOC_GETSTATUS:
                val = 0;
                i = copy_to_user(argp, &val, sizeof(val));
                if (i)
                        return -EFAULT;
                return 0;

        default:
                return -ENOIOCTLCMD;
        }
}

static long ipmi_unlocked_ioctl(struct file *file,
                                unsigned int cmd,
                                unsigned long arg)
{
        int ret;

        mutex_lock(&ipmi_watchdog_mutex);
        ret = ipmi_ioctl(file, cmd, arg);
        mutex_unlock(&ipmi_watchdog_mutex);

        return ret;
}

static ssize_t ipmi_write(struct file *file,
                          const char  __user *buf,
                          size_t      len,
                          loff_t      *ppos)
{
        int rv;

        if (len) {
                if (!nowayout) {
                        size_t i;

                        /* In case it was set long ago */
                        expect_close = 0;

                        for (i = 0; i != len; i++) {
                                char c;

                                if (get_user(c, buf + i))
                                        return -EFAULT;
                                if (c == 'V')
                                        expect_close = 42;
                        }
                }
                rv = ipmi_heartbeat();
                if (rv)
                        return rv;
        }
        return len;
}

static ssize_t ipmi_read(struct file *file,
                         char        __user *buf,
                         size_t      count,
                         loff_t      *ppos)
{
        int          rv = 0;
        wait_queue_entry_t wait;

        if (count <= 0)
                return 0;

        /*
         * Reading returns if the pretimeout has gone off, and it only does
         * it once per pretimeout.
         */
        spin_lock_irq(&ipmi_read_lock);
        if (!data_to_read) {
                if (file->f_flags & O_NONBLOCK) {
                        rv = -EAGAIN;
                        goto out;
                }

                init_waitqueue_entry(&wait, current);
                add_wait_queue(&read_q, &wait);
                while (!data_to_read) {
                        set_current_state(TASK_INTERRUPTIBLE);
                        spin_unlock_irq(&ipmi_read_lock);
                        schedule();
                        spin_lock_irq(&ipmi_read_lock);
                }
                remove_wait_queue(&read_q, &wait);

                if (signal_pending(current)) {
                        rv = -ERESTARTSYS;
                        goto out;
                }
        }
        data_to_read = 0;

 out:
        spin_unlock_irq(&ipmi_read_lock);

        if (rv == 0) {
                if (copy_to_user(buf, &data_to_read, 1))
                        rv = -EFAULT;
                else
                        rv = 1;
        }

        return rv;
}

static int ipmi_open(struct inode *ino, struct file *filep)
{
        switch (iminor(ino)) {
        case WATCHDOG_MINOR:
                if (test_and_set_bit(0, &ipmi_wdog_open))
                        return -EBUSY;


                /*
                 * Don't start the timer now, let it start on the
                 * first heartbeat.
                 */
                ipmi_start_timer_on_heartbeat = 1;
                return stream_open(ino, filep);

        default:
                return (-ENODEV);
        }
}

static __poll_t ipmi_poll(struct file *file, poll_table *wait)
{
        __poll_t mask = 0;

        poll_wait(file, &read_q, wait);

        spin_lock_irq(&ipmi_read_lock);
        if (data_to_read)
                mask |= (EPOLLIN | EPOLLRDNORM);
        spin_unlock_irq(&ipmi_read_lock);

        return mask;
}

static int ipmi_fasync(int fd, struct file *file, int on)
{
        int result;

        result = fasync_helper(fd, file, on, &fasync_q);

        return (result);
}

static int ipmi_close(struct inode *ino, struct file *filep)
{
        if (iminor(ino) == WATCHDOG_MINOR) {
                if (expect_close == 42) {
                        mutex_lock(&ipmi_watchdog_mutex);
                        ipmi_watchdog_state = WDOG_TIMEOUT_NONE;
                        _ipmi_set_timeout(IPMI_SET_TIMEOUT_NO_HB);
                        mutex_unlock(&ipmi_watchdog_mutex);
                } else {
                        pr_crit("Unexpected close, not stopping watchdog!\n");
                        ipmi_heartbeat();
                }
                clear_bit(0, &ipmi_wdog_open);
        }

        expect_close = 0;

        return 0;
}

static const struct file_operations ipmi_wdog_fops = {
        .owner   = THIS_MODULE,
        .read    = ipmi_read,
        .poll    = ipmi_poll,
        .write   = ipmi_write,
        .unlocked_ioctl = ipmi_unlocked_ioctl,
        .open    = ipmi_open,
        .release = ipmi_close,
        .fasync  = ipmi_fasync,
        .llseek  = no_llseek,
};

static struct miscdevice ipmi_wdog_miscdev = {
        .minor          = WATCHDOG_MINOR,
        .name           = "watchdog",
        .fops           = &ipmi_wdog_fops
};

static void ipmi_wdog_msg_handler(struct ipmi_recv_msg *msg,
                                  void                 *handler_data)
{
        if (msg->msg.cmd == IPMI_WDOG_RESET_TIMER &&
                        msg->msg.data[0] == IPMI_WDOG_TIMER_NOT_INIT_RESP)
                pr_info("response: The IPMI controller appears to have been reset, will attempt to reinitialize the watchdog timer\n");
        else if (msg->msg.data[0] != 0)
                pr_err("response: Error %x on cmd %x\n",
                       msg->msg.data[0],
                       msg->msg.cmd);

        ipmi_free_recv_msg(msg);
}

static void ipmi_wdog_pretimeout_handler(void *handler_data)
{
        if (preaction_val != WDOG_PRETIMEOUT_NONE) {
                if (preop_val == WDOG_PREOP_PANIC) {
                        if (atomic_inc_and_test(&preop_panic_excl))
                                panic("Watchdog pre-timeout");
                } else if (preop_val == WDOG_PREOP_GIVE_DATA) {
                        unsigned long flags;

                        spin_lock_irqsave(&ipmi_read_lock, flags);
                        data_to_read = 1;
                        wake_up_interruptible(&read_q);
                        kill_fasync(&fasync_q, SIGIO, POLL_IN);
                        spin_unlock_irqrestore(&ipmi_read_lock, flags);
                }
        }

        /*
         * On some machines, the heartbeat will give an error and not
         * work unless we re-enable the timer.  So do so.
         */
        atomic_set(&pretimeout_since_last_heartbeat, 1);
}

static void ipmi_wdog_panic_handler(void *user_data)
{
        static int panic_event_handled;

        /*
         * On a panic, if we have a panic timeout, make sure to extend
         * the watchdog timer to a reasonable value to complete the
         * panic, if the watchdog timer is running.  Plus the
         * pretimeout is meaningless at panic time.
         */
        if (watchdog_user && !panic_event_handled &&
            ipmi_watchdog_state != WDOG_TIMEOUT_NONE) {
                /* Make sure we do this only once. */
                panic_event_handled = 1;

                timeout = panic_wdt_timeout;
                pretimeout = 0;
                panic_halt_ipmi_set_timeout();
        }
}

static const struct ipmi_user_hndl ipmi_hndlrs = {
        .ipmi_recv_hndl           = ipmi_wdog_msg_handler,
        .ipmi_watchdog_pretimeout = ipmi_wdog_pretimeout_handler,
        .ipmi_panic_handler       = ipmi_wdog_panic_handler
};

static void ipmi_register_watchdog(int ipmi_intf)
{
        int rv = -EBUSY;

        if (watchdog_user)
                goto out;

        if ((ifnum_to_use >= 0) && (ifnum_to_use != ipmi_intf))
                goto out;

        watchdog_ifnum = ipmi_intf;

        rv = ipmi_create_user(ipmi_intf, &ipmi_hndlrs, NULL, &watchdog_user);
        if (rv < 0) {
                pr_crit("Unable to register with ipmi\n");
                goto out;
        }

        rv = ipmi_get_version(watchdog_user,
                              &ipmi_version_major,
                              &ipmi_version_minor);
        if (rv) {
                pr_warn("Unable to get IPMI version, assuming 1.0\n");
                ipmi_version_major = 1;
                ipmi_version_minor = 0;
        }

        rv = misc_register(&ipmi_wdog_miscdev);

        if (rv < 0) {
                ipmi_destroy_user(watchdog_user);
                watchdog_user = NULL;
                pr_crit("Unable to register misc device\n");
        }

#ifdef HAVE_DIE_NMI
        if (nmi_handler_registered) {
                int old_pretimeout = pretimeout;
                int old_timeout = timeout;
                int old_preop_val = preop_val;

                /*
                 * Set the pretimeout to go off in a second and give
                 * ourselves plenty of time to stop the timer.
                 */
                ipmi_watchdog_state = WDOG_TIMEOUT_RESET;
                preop_val = WDOG_PREOP_NONE; /* Make sure nothing happens */
                pretimeout = 99;
                timeout = 100;

                testing_nmi = 1;

                rv = ipmi_set_timeout(IPMI_SET_TIMEOUT_FORCE_HB);
                if (rv) {
                        pr_warn("Error starting timer to test NMI: 0x%x.  The NMI pretimeout will likely not work\n",
                                rv);
                        rv = 0;
                        goto out_restore;
                }

                msleep(1500);

                if (testing_nmi != 2) {
                        pr_warn("IPMI NMI didn't seem to occur.  The NMI pretimeout will likely not work\n");
                }
 out_restore:
                testing_nmi = 0;
                preop_val = old_preop_val;
                pretimeout = old_pretimeout;
                timeout = old_timeout;
        }
#endif

 out:
        if ((start_now) && (rv == 0)) {
                /* Run from startup, so start the timer now. */
                start_now = 0; /* Disable this function after first startup. */
                ipmi_watchdog_state = action_val;
                ipmi_set_timeout(IPMI_SET_TIMEOUT_FORCE_HB);
                pr_info("Starting now!\n");
        } else {
                /* Stop the timer now. */
                ipmi_watchdog_state = WDOG_TIMEOUT_NONE;
                ipmi_set_timeout(IPMI_SET_TIMEOUT_NO_HB);
        }
}

static void ipmi_unregister_watchdog(int ipmi_intf)
{
        int rv;
        struct ipmi_user *loc_user = watchdog_user;

        if (!loc_user)
                return;

        if (watchdog_ifnum != ipmi_intf)
                return;

        /* Make sure no one can call us any more. */
        misc_deregister(&ipmi_wdog_miscdev);

        watchdog_user = NULL;

        /*
         * Wait to make sure the message makes it out.  The lower layer has
         * pointers to our buffers, we want to make sure they are done before
         * we release our memory.
         */
        while (atomic_read(&msg_tofree))
                msg_free_smi(NULL);

        mutex_lock(&ipmi_watchdog_mutex);

        /* Disconnect from IPMI. */
        rv = ipmi_destroy_user(loc_user);
        if (rv)
                pr_warn("error unlinking from IPMI: %d\n",  rv);

        /* If it comes back, restart it properly. */
        ipmi_start_timer_on_heartbeat = 1;

        mutex_unlock(&ipmi_watchdog_mutex);
}

#ifdef HAVE_DIE_NMI
static int
ipmi_nmi(unsigned int val, struct pt_regs *regs)
{
        /*
         * If we get here, it's an NMI that's not a memory or I/O
         * error.  We can't truly tell if it's from IPMI or not
         * without sending a message, and sending a message is almost
         * impossible because of locking.
         */

        if (testing_nmi) {
                testing_nmi = 2;
                return NMI_HANDLED;
        }

        /* If we are not expecting a timeout, ignore it. */
        if (ipmi_watchdog_state == WDOG_TIMEOUT_NONE)
                return NMI_DONE;

        if (preaction_val != WDOG_PRETIMEOUT_NMI)
                return NMI_DONE;

        /*
         * If no one else handled the NMI, we assume it was the IPMI
         * watchdog.
         */
        if (preop_val == WDOG_PREOP_PANIC) {
                /* On some machines, the heartbeat will give
                   an error and not work unless we re-enable
                   the timer.   So do so. */
                atomic_set(&pretimeout_since_last_heartbeat, 1);
                if (atomic_inc_and_test(&preop_panic_excl))
                        nmi_panic(regs, "pre-timeout");
        }

        return NMI_HANDLED;
}
#endif

static int wdog_reboot_handler(struct notifier_block *this,
                               unsigned long         code,
                               void                  *unused)
{
        static int reboot_event_handled;

        if ((watchdog_user) && (!reboot_event_handled)) {
                /* Make sure we only do this once. */
                reboot_event_handled = 1;

                if (code == SYS_POWER_OFF || code == SYS_HALT) {
                        /* Disable the WDT if we are shutting down. */
                        ipmi_watchdog_state = WDOG_TIMEOUT_NONE;
                        ipmi_set_timeout(IPMI_SET_TIMEOUT_NO_HB);
                } else if (ipmi_watchdog_state != WDOG_TIMEOUT_NONE) {
                        /* Set a long timer to let the reboot happen or
                           reset if it hangs, but only if the watchdog
                           timer was already running. */
                        if (timeout < 120)
                                timeout = 120;
                        pretimeout = 0;
                        ipmi_watchdog_state = WDOG_TIMEOUT_RESET;
                        ipmi_set_timeout(IPMI_SET_TIMEOUT_NO_HB);
                }
        }
        return NOTIFY_OK;
}

static struct notifier_block wdog_reboot_notifier = {
        .notifier_call  = wdog_reboot_handler,
        .next           = NULL,
        .priority       = 0
};

static void ipmi_new_smi(int if_num, struct device *device)
{
        ipmi_register_watchdog(if_num);
}

static void ipmi_smi_gone(int if_num)
{
        ipmi_unregister_watchdog(if_num);
}

static struct ipmi_smi_watcher smi_watcher = {
        .owner    = THIS_MODULE,
        .new_smi  = ipmi_new_smi,
        .smi_gone = ipmi_smi_gone
};

static int action_op(const char *inval, char *outval)
{
        if (outval)
                strcpy(outval, action);

        if (!inval)
                return 0;

        if (strcmp(inval, "reset") == 0)
                action_val = WDOG_TIMEOUT_RESET;
        else if (strcmp(inval, "none") == 0)
                action_val = WDOG_TIMEOUT_NONE;
        else if (strcmp(inval, "power_cycle") == 0)
                action_val = WDOG_TIMEOUT_POWER_CYCLE;
        else if (strcmp(inval, "power_off") == 0)
                action_val = WDOG_TIMEOUT_POWER_DOWN;
        else
                return -EINVAL;
        strcpy(action, inval);
        return 0;
}

static int preaction_op(const char *inval, char *outval)
{
        if (outval)
                strcpy(outval, preaction);

        if (!inval)
                return 0;

        if (strcmp(inval, "pre_none") == 0)
                preaction_val = WDOG_PRETIMEOUT_NONE;
        else if (strcmp(inval, "pre_smi") == 0)
                preaction_val = WDOG_PRETIMEOUT_SMI;
#ifdef HAVE_DIE_NMI
        else if (strcmp(inval, "pre_nmi") == 0)
                preaction_val = WDOG_PRETIMEOUT_NMI;
#endif
        else if (strcmp(inval, "pre_int") == 0)
                preaction_val = WDOG_PRETIMEOUT_MSG_INT;
        else
                return -EINVAL;
        strcpy(preaction, inval);
        return 0;
}

static int preop_op(const char *inval, char *outval)
{
        if (outval)
                strcpy(outval, preop);

        if (!inval)
                return 0;

        if (strcmp(inval, "preop_none") == 0)
                preop_val = WDOG_PREOP_NONE;
        else if (strcmp(inval, "preop_panic") == 0)
                preop_val = WDOG_PREOP_PANIC;
        else if (strcmp(inval, "preop_give_data") == 0)
                preop_val = WDOG_PREOP_GIVE_DATA;
        else
                return -EINVAL;
        strcpy(preop, inval);
        return 0;
}

static void check_parms(void)
{
#ifdef HAVE_DIE_NMI
        int do_nmi = 0;
        int rv;

        if (preaction_val == WDOG_PRETIMEOUT_NMI) {
                do_nmi = 1;
                if (preop_val == WDOG_PREOP_GIVE_DATA) {
                        pr_warn("Pretimeout op is to give data but NMI pretimeout is enabled, setting pretimeout op to none\n");
                        preop_op("preop_none", NULL);
                        do_nmi = 0;
                }
        }
        if (do_nmi && !nmi_handler_registered) {
                rv = register_nmi_handler(NMI_UNKNOWN, ipmi_nmi, 0,
                                                "ipmi");
                if (rv) {
                        pr_warn("Can't register nmi handler\n");
                        return;
                } else
                        nmi_handler_registered = 1;
        } else if (!do_nmi && nmi_handler_registered) {
                unregister_nmi_handler(NMI_UNKNOWN, "ipmi");
                nmi_handler_registered = 0;
        }
#endif
}

static int __init ipmi_wdog_init(void)
{
        int rv;

        if (action_op(action, NULL)) {
                action_op("reset", NULL);
                pr_info("Unknown action '%s', defaulting to reset\n", action);
        }

        if (preaction_op(preaction, NULL)) {
                preaction_op("pre_none", NULL);
                pr_info("Unknown preaction '%s', defaulting to none\n",
                        preaction);
        }

        if (preop_op(preop, NULL)) {
                preop_op("preop_none", NULL);
                pr_info("Unknown preop '%s', defaulting to none\n", preop);
        }

        check_parms();

        register_reboot_notifier(&wdog_reboot_notifier);

        rv = ipmi_smi_watcher_register(&smi_watcher);
        if (rv) {
#ifdef HAVE_DIE_NMI
                if (nmi_handler_registered)
                        unregister_nmi_handler(NMI_UNKNOWN, "ipmi");
#endif
                unregister_reboot_notifier(&wdog_reboot_notifier);
                pr_warn("can't register smi watcher\n");
                return rv;
        }

        pr_info("driver initialized\n");

        return 0;
}

static void __exit ipmi_wdog_exit(void)
{
        ipmi_smi_watcher_unregister(&smi_watcher);
        ipmi_unregister_watchdog(watchdog_ifnum);

#ifdef HAVE_DIE_NMI
        if (nmi_handler_registered)
                unregister_nmi_handler(NMI_UNKNOWN, "ipmi");
#endif

        unregister_reboot_notifier(&wdog_reboot_notifier);
}
module_exit(ipmi_wdog_exit);
module_init(ipmi_wdog_init);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Corey Minyard <minyard@mvista.com>");
MODULE_DESCRIPTION("watchdog timer based upon the IPMI interface.");