drivers/watchdog/xen_wdt.c

   1 /*
   2  *      Xen Watchdog Driver
   3  *
   4  *      (c) Copyright 2010 Novell, Inc.
   5  *
   6  *      This program is free software; you can redistribute it and/or
   7  *      modify it under the terms of the GNU General Public License
   8  *      as published by the Free Software Foundation; either version
   9  *      2 of the License, or (at your option) any later version.
  10  */
  11
  12 #define DRV_NAME        "wdt"
  13 #define DRV_VERSION     "0.01"
  14 #define PFX             DRV_NAME ": "
  15
  16 #include <linux/bug.h>
  17 #include <linux/errno.h>
  18 #include <linux/fs.h>
  19 #include <linux/hrtimer.h>
  20 #include <linux/kernel.h>
  21 #include <linux/ktime.h>
  22 #include <linux/init.h>
  23 #include <linux/miscdevice.h>
  24 #include <linux/module.h>
  25 #include <linux/moduleparam.h>
  26 #include <linux/platform_device.h>
  27 #include <linux/spinlock.h>
  28 #include <linux/uaccess.h>
  29 #include <linux/watchdog.h>
  30 #include <xen/xen.h>
  31 #include <asm/xen/hypercall.h>
  32 #include <xen/interface/sched.h>
  33
  34 static struct platform_device *platform_device;
  35 static DEFINE_SPINLOCK(wdt_lock);
  36 static struct sched_watchdog wdt;
  37 static __kernel_time_t wdt_expires;
  38 static bool is_active, expect_release;
  39
  40 #define WATCHDOG_TIMEOUT 60 /* in seconds */
  41 static unsigned int timeout = WATCHDOG_TIMEOUT;
  42 module_param(timeout, uint, S_IRUGO);
  43 MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds "
  44         "(default=" __MODULE_STRING(WATCHDOG_TIMEOUT) ")");
  45
  46 static bool nowayout = WATCHDOG_NOWAYOUT;
  47 module_param(nowayout, bool, S_IRUGO);
  48 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
  49         "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  50
  51 static inline __kernel_time_t set_timeout(void)
  52 {
  53         wdt.timeout = timeout;
  54         return ktime_to_timespec(ktime_get()).tv_sec + timeout;
  55 }
  56
  57 static int xen_wdt_start(void)
  58 {
  59         __kernel_time_t expires;
  60         int err;
  61
  62         spin_lock(&wdt_lock);
  63
  64         expires = set_timeout();
  65         if (!wdt.id)
  66                 err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
  67         else
  68                 err = -EBUSY;
  69         if (err > 0) {
  70                 wdt.id = err;
  71                 wdt_expires = expires;
  72                 err = 0;
  73         } else
  74                 BUG_ON(!err);
  75
  76         spin_unlock(&wdt_lock);
  77
  78         return err;
  79 }
  80
  81 static int xen_wdt_stop(void)
  82 {
  83         int err = 0;
  84
  85         spin_lock(&wdt_lock);
  86
  87         wdt.timeout = 0;
  88         if (wdt.id)
  89                 err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
  90         if (!err)
  91                 wdt.id = 0;
  92
  93         spin_unlock(&wdt_lock);
  94
  95         return err;
  96 }
  97
  98 static int xen_wdt_kick(void)
  99 {
 100         __kernel_time_t expires;
 101         int err;
 102
 103         spin_lock(&wdt_lock);
 104
 105         expires = set_timeout();
 106         if (wdt.id)
 107                 err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
 108         else
 109                 err = -ENXIO;
 110         if (!err)
 111                 wdt_expires = expires;
 112
 113         spin_unlock(&wdt_lock);
 114
 115         return err;
 116 }
 117
 118 static int xen_wdt_open(struct inode *inode, struct file *file)
 119 {
 120         int err;
 121
 122         /* /dev/watchdog can only be opened once */
 123         if (xchg(&is_active, true))
 124                 return -EBUSY;
 125
 126         err = xen_wdt_start();
 127         if (err == -EBUSY)
 128                 err = xen_wdt_kick();
 129         return err ?: nonseekable_open(inode, file);
 130 }
 131
 132 static int xen_wdt_release(struct inode *inode, struct file *file)
 133 {
 134         if (expect_release)
 135                 xen_wdt_stop();
 136         else {
 137                 printk(KERN_CRIT PFX
 138                        "unexpected close, not stopping watchdog!\n");
 139                 xen_wdt_kick();
 140         }
 141         is_active = false;
 142         expect_release = false;
 143         return 0;
 144 }
 145
 146 static ssize_t xen_wdt_write(struct file *file, const char __user *data,
 147                              size_t len, loff_t *ppos)
 148 {
 149         /* See if we got the magic character 'V' and reload the timer */
 150         if (len) {
 151                 if (!nowayout) {
 152                         size_t i;
 153
 154                         /* in case it was set long ago */
 155                         expect_release = false;
 156
 157                         /* scan to see whether or not we got the magic
 158                            character */
 159                         for (i = 0; i != len; i++) {
 160                                 char c;
 161                                 if (get_user(c, data + i))
 162                                         return -EFAULT;
 163                                 if (c == 'V')
 164                                         expect_release = true;
 165                         }
 166                 }
 167
 168                 /* someone wrote to us, we should reload the timer */
 169                 xen_wdt_kick();
 170         }
 171         return len;
 172 }
 173
 174 static long xen_wdt_ioctl(struct file *file, unsigned int cmd,
 175                           unsigned long arg)
 176 {
 177         int new_options, retval = -EINVAL;
 178         int new_timeout;
 179         int __user *argp = (void __user *)arg;
 180         static const struct watchdog_info ident = {
 181                 .options =              WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
 182                 .firmware_version =     0,
 183                 .identity =             DRV_NAME,
 184         };
 185
 186         switch (cmd) {
 187         case WDIOC_GETSUPPORT:
 188                 return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
 189
 190         case WDIOC_GETSTATUS:
 191         case WDIOC_GETBOOTSTATUS:
 192                 return put_user(0, argp);
 193
 194         case WDIOC_SETOPTIONS:
 195                 if (get_user(new_options, argp))
 196                         return -EFAULT;
 197
 198                 if (new_options & WDIOS_DISABLECARD)
 199                         retval = xen_wdt_stop();
 200                 if (new_options & WDIOS_ENABLECARD) {
 201                         retval = xen_wdt_start();
 202                         if (retval == -EBUSY)
 203                                 retval = xen_wdt_kick();
 204                 }
 205                 return retval;
 206
 207         case WDIOC_KEEPALIVE:
 208                 xen_wdt_kick();
 209                 return 0;
 210
 211         case WDIOC_SETTIMEOUT:
 212                 if (get_user(new_timeout, argp))
 213                         return -EFAULT;
 214                 if (!new_timeout)
 215                         return -EINVAL;
 216                 timeout = new_timeout;
 217                 xen_wdt_kick();
 218                 /* fall through */
 219         case WDIOC_GETTIMEOUT:
 220                 return put_user(timeout, argp);
 221
 222         case WDIOC_GETTIMELEFT:
 223                 retval = wdt_expires - ktime_to_timespec(ktime_get()).tv_sec;
 224                 return put_user(retval, argp);
 225         }
 226
 227         return -ENOTTY;
 228 }
 229
 230 static const struct file_operations xen_wdt_fops = {
 231         .owner =                THIS_MODULE,
 232         .llseek =               no_llseek,
 233         .write =                xen_wdt_write,
 234         .unlocked_ioctl =       xen_wdt_ioctl,
 235         .open =                 xen_wdt_open,
 236         .release =              xen_wdt_release,
 237 };
 238
 239 static struct miscdevice xen_wdt_miscdev = {
 240         .minor =        WATCHDOG_MINOR,
 241         .name =         "watchdog",
 242         .fops =         &xen_wdt_fops,
 243 };
 244
 245 static int __devinit xen_wdt_probe(struct platform_device *dev)
 246 {
 247         struct sched_watchdog wd = { .id = ~0 };
 248         int ret = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wd);
 249
 250         switch (ret) {
 251         case -EINVAL:
 252                 if (!timeout) {
 253                         timeout = WATCHDOG_TIMEOUT;
 254                         printk(KERN_INFO PFX
 255                                "timeout value invalid, using %d\n", timeout);
 256                 }
 257
 258                 ret = misc_register(&xen_wdt_miscdev);
 259                 if (ret) {
 260                         printk(KERN_ERR PFX
 261                                "cannot register miscdev on minor=%d (%d)\n",
 262                                WATCHDOG_MINOR, ret);
 263                         break;
 264                 }
 265
 266                 printk(KERN_INFO PFX
 267                        "initialized (timeout=%ds, nowayout=%d)\n",
 268                        timeout, nowayout);
 269                 break;
 270
 271         case -ENOSYS:
 272                 printk(KERN_INFO PFX "not supported\n");
 273                 ret = -ENODEV;
 274                 break;
 275
 276         default:
 277                 printk(KERN_INFO PFX "bogus return value %d\n", ret);
 278                 break;
 279         }
 280
 281         return ret;
 282 }
 283
 284 static int __devexit xen_wdt_remove(struct platform_device *dev)
 285 {
 286         /* Stop the timer before we leave */
 287         if (!nowayout)
 288                 xen_wdt_stop();
 289
 290         misc_deregister(&xen_wdt_miscdev);
 291
 292         return 0;
 293 }
 294
 295 static void xen_wdt_shutdown(struct platform_device *dev)
 296 {
 297         xen_wdt_stop();
 298 }
 299
 300 static int xen_wdt_suspend(struct platform_device *dev, pm_message_t state)
 301 {
 302         return xen_wdt_stop();
 303 }
 304
 305 static int xen_wdt_resume(struct platform_device *dev)
 306 {
 307         return xen_wdt_start();
 308 }
 309
 310 static struct platform_driver xen_wdt_driver = {
 311         .probe          = xen_wdt_probe,
 312         .remove         = __devexit_p(xen_wdt_remove),
 313         .shutdown       = xen_wdt_shutdown,
 314         .suspend        = xen_wdt_suspend,
 315         .resume         = xen_wdt_resume,
 316         .driver         = {
 317                 .owner  = THIS_MODULE,
 318                 .name   = DRV_NAME,
 319         },
 320 };
 321
 322 static int __init xen_wdt_init_module(void)
 323 {
 324         int err;
 325
 326         if (!xen_domain())
 327                 return -ENODEV;
 328
 329         printk(KERN_INFO PFX "Xen WatchDog Timer Driver v%s\n", DRV_VERSION);
 330
 331         err = platform_driver_register(&xen_wdt_driver);
 332         if (err)
 333                 return err;
 334
 335         platform_device = platform_device_register_simple(DRV_NAME,
 336                                                                   -1, NULL, 0);
 337         if (IS_ERR(platform_device)) {
 338                 err = PTR_ERR(platform_device);
 339                 platform_driver_unregister(&xen_wdt_driver);
 340         }
 341
 342         return err;
 343 }
 344
 345 static void __exit xen_wdt_cleanup_module(void)
 346 {
 347         platform_device_unregister(platform_device);
 348         platform_driver_unregister(&xen_wdt_driver);
 349         printk(KERN_INFO PFX "module unloaded\n");
 350 }
 351
 352 module_init(xen_wdt_init_module);
 353 module_exit(xen_wdt_cleanup_module);
 354
 355 MODULE_AUTHOR("Jan Beulich <jbeulich@novell.com>");
 356 MODULE_DESCRIPTION("Xen WatchDog Timer Driver");
 357 MODULE_VERSION(DRV_VERSION);
 358 MODULE_LICENSE("GPL");
 359 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);