vmwatchdog.c

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/*
 * Watchdog implementation based on z/VM Watchdog Timer API
 *
 * Copyright IBM Corp. 2004, 2009
 *
 * The user space watchdog daemon can use this driver as
 * /dev/vmwatchdog to have z/VM execute the specified CP
 * command when the timeout expires. The default command is
 * "IPL", which which cause an immediate reboot.
 */
#define KMSG_COMPONENT "vmwatchdog"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

#include <linux/init.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/slab.h>
#include <linux/suspend.h>
#include <linux/watchdog.h>

#include <asm/ebcdic.h>
#include <asm/io.h>
#include <asm/uaccess.h>

#define MAX_CMDLEN 240
#define MIN_INTERVAL 15
static char vmwdt_cmd[MAX_CMDLEN] = "IPL";
static bool vmwdt_conceal;

static bool vmwdt_nowayout = WATCHDOG_NOWAYOUT;

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Arnd Bergmann <[email protected]>");
MODULE_DESCRIPTION("z/VM Watchdog Timer");
module_param_string(cmd, vmwdt_cmd, MAX_CMDLEN, 0644);
MODULE_PARM_DESC(cmd, "CP command that is run when the watchdog triggers");
module_param_named(conceal, vmwdt_conceal, bool, 0644);
MODULE_PARM_DESC(conceal, "Enable the CONCEAL CP option while the watchdog "
        " is active");
module_param_named(nowayout, vmwdt_nowayout, bool, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started"
        " (default=CONFIG_WATCHDOG_NOWAYOUT)");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);

static unsigned int vmwdt_interval = 60;
static unsigned long vmwdt_is_open;
static int vmwdt_expect_close;

static DEFINE_MUTEX(vmwdt_mutex);

#define VMWDT_OPEN  0   /* devnode is open or suspend in progress */
#define VMWDT_RUNNING   1   /* The watchdog is armed */

enum vmwdt_func {
    /* function codes */
    wdt_init   = 0,
    wdt_change = 1,
    wdt_cancel = 2,
    /* flags */
    wdt_conceal = 0x80000000,
};

static int __diag288(enum vmwdt_func func, unsigned int timeout,
                char *cmd, size_t len)
{
    register unsigned long __func asm("2") = func;
    register unsigned long __timeout asm("3") = timeout;
    register unsigned long __cmdp asm("4") = virt_to_phys(cmd);
    register unsigned long __cmdl asm("5") = len;
    int err;

    err = -EINVAL;
    asm volatile(
        "   diag    %1,%3,0x288\n"
        "0: la  %0,0\n"
        "1:\n"
        EX_TABLE(0b,1b)
        : "+d" (err) : "d"(__func), "d"(__timeout),
          "d"(__cmdp), "d"(__cmdl) : "1", "cc");
    return err;
}

static int vmwdt_keepalive(void)
{
    /* we allocate new memory every time to avoid having
     * to track the state. static allocation is not an
     * option since that might not be contiguous in real
     * storage in case of a modular build */
    static char *ebc_cmd;
    size_t len;
    int ret;
    unsigned int func;

    ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
    if (!ebc_cmd)
        return -ENOMEM;

    len = strlcpy(ebc_cmd, vmwdt_cmd, MAX_CMDLEN);
    ASCEBC(ebc_cmd, MAX_CMDLEN);
    EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);

    func = vmwdt_conceal ? (wdt_init | wdt_conceal) : wdt_init;
    set_bit(VMWDT_RUNNING, &vmwdt_is_open);
    ret = __diag288(func, vmwdt_interval, ebc_cmd, len);
    WARN_ON(ret != 0);
    kfree(ebc_cmd);
    return ret;
}

static int vmwdt_disable(void)
{
    int ret = __diag288(wdt_cancel, 0, "", 0);
    WARN_ON(ret != 0);
    clear_bit(VMWDT_RUNNING, &vmwdt_is_open);
    return ret;
}

static int __init vmwdt_probe(void)
{
    /* there is no real way to see if the watchdog is supported,
     * so we try initializing it with a NOP command ("BEGIN")
     * that won't cause any harm even if the following disable
     * fails for some reason */
    static char __initdata ebc_begin[] = {
        194, 197, 199, 201, 213
    };
    if (__diag288(wdt_init, 15, ebc_begin, sizeof(ebc_begin)) != 0)
        return -EINVAL;
    return vmwdt_disable();
}

static int vmwdt_open(struct inode *i, struct file *f)
{
    int ret;
    if (test_and_set_bit(VMWDT_OPEN, &vmwdt_is_open))
        return -EBUSY;
    ret = vmwdt_keepalive();
    if (ret)
        clear_bit(VMWDT_OPEN, &vmwdt_is_open);
    return ret ? ret : nonseekable_open(i, f);
}

static int vmwdt_close(struct inode *i, struct file *f)
{
    if (vmwdt_expect_close == 42)
        vmwdt_disable();
    vmwdt_expect_close = 0;
    clear_bit(VMWDT_OPEN, &vmwdt_is_open);
    return 0;
}

static struct watchdog_info vmwdt_info = {
    .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
    .firmware_version = 0,
    .identity = "z/VM Watchdog Timer",
};

static int __vmwdt_ioctl(unsigned int cmd, unsigned long arg)
{
    switch (cmd) {
    case WDIOC_GETSUPPORT:
        if (copy_to_user((void __user *)arg, &vmwdt_info,
                    sizeof(vmwdt_info)))
            return -EFAULT;
        return 0;
    case WDIOC_GETSTATUS:
    case WDIOC_GETBOOTSTATUS:
        return put_user(0, (int __user *)arg);
    case WDIOC_GETTEMP:
        return -EINVAL;
    case WDIOC_SETOPTIONS:
        {
            int options, ret;
            if (get_user(options, (int __user *)arg))
                return -EFAULT;
            ret = -EINVAL;
            if (options & WDIOS_DISABLECARD) {
                ret = vmwdt_disable();
                if (ret)
                    return ret;
            }
            if (options & WDIOS_ENABLECARD) {
                ret = vmwdt_keepalive();
            }
            return ret;
        }
    case WDIOC_GETTIMEOUT:
        return put_user(vmwdt_interval, (int __user *)arg);
    case WDIOC_SETTIMEOUT:
        {
            int interval;
            if (get_user(interval, (int __user *)arg))
                return -EFAULT;
            if (interval < MIN_INTERVAL)
                return -EINVAL;
            vmwdt_interval = interval;
        }
        return vmwdt_keepalive();
    case WDIOC_KEEPALIVE:
        return vmwdt_keepalive();
    }
    return -EINVAL;
}

static long vmwdt_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
{
    int rc;

    mutex_lock(&vmwdt_mutex);
    rc = __vmwdt_ioctl(cmd, arg);
    mutex_unlock(&vmwdt_mutex);
    return (long) rc;
}

static ssize_t vmwdt_write(struct file *f, const char __user *buf,
                size_t count, loff_t *ppos)
{
    if(count) {
        if (!vmwdt_nowayout) {
            size_t i;

            /* note: just in case someone wrote the magic character
             * five months ago... */
            vmwdt_expect_close = 0;

            for (i = 0; i != count; i++) {
                char c;
                if (get_user(c, buf+i))
                    return -EFAULT;
                if (c == 'V')
                    vmwdt_expect_close = 42;
            }
        }
        /* someone wrote to us, we should restart timer */
        vmwdt_keepalive();
    }
    return count;
}

static int vmwdt_resume(void)
{
    clear_bit(VMWDT_OPEN, &vmwdt_is_open);
    return NOTIFY_DONE;
}

/*
 * It makes no sense to go into suspend while the watchdog is running.
 * Depending on the memory size, the watchdog might trigger, while we
 * are still saving the memory.
 * We reuse the open flag to ensure that suspend and watchdog open are
 * exclusive operations
 */
static int vmwdt_suspend(void)
{
    if (test_and_set_bit(VMWDT_OPEN, &vmwdt_is_open)) {
        pr_err("The system cannot be suspended while the watchdog"
            " is in use\n");
        return notifier_from_errno(-EBUSY);
    }
    if (test_bit(VMWDT_RUNNING, &vmwdt_is_open)) {
        clear_bit(VMWDT_OPEN, &vmwdt_is_open);
        pr_err("The system cannot be suspended while the watchdog"
            " is running\n");
        return notifier_from_errno(-EBUSY);
    }
    return NOTIFY_DONE;
}

/*
 * This function is called for suspend and resume.
 */
static int vmwdt_power_event(struct notifier_block *this, unsigned long event,
                 void *ptr)
{
    switch (event) {
    case PM_POST_HIBERNATION:
    case PM_POST_SUSPEND:
        return vmwdt_resume();
    case PM_HIBERNATION_PREPARE:
    case PM_SUSPEND_PREPARE:
        return vmwdt_suspend();
    default:
        return NOTIFY_DONE;
    }
}

static struct notifier_block vmwdt_power_notifier = {
    .notifier_call = vmwdt_power_event,
};

static const struct file_operations vmwdt_fops = {
    .open    = &vmwdt_open,
    .release = &vmwdt_close,
    .unlocked_ioctl = &vmwdt_ioctl,
    .write   = &vmwdt_write,
    .owner   = THIS_MODULE,
    .llseek  = noop_llseek,
};

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

static int __init vmwdt_init(void)
{
    int ret;

    ret = vmwdt_probe();
    if (ret)
        return ret;
    ret = register_pm_notifier(&vmwdt_power_notifier);
    if (ret)
        return ret;
    /*
     * misc_register() has to be the last action in module_init(), because
     * file operations will be available right after this.
     */
    ret = misc_register(&vmwdt_dev);
    if (ret) {
        unregister_pm_notifier(&vmwdt_power_notifier);
        return ret;
    }
    return 0;
}
module_init(vmwdt_init);

static void __exit vmwdt_exit(void)
{
    unregister_pm_notifier(&vmwdt_power_notifier);
    misc_deregister(&vmwdt_dev);
}
module_exit(vmwdt_exit);