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 pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  13
  14 #define DRV_NAME        "wdt"
  15 #define DRV_VERSION     "0.01"
  16
  17 #include <linux/bug.h>
  18 #include <linux/errno.h>
  19 #include <linux/fs.h>
  20 #include <linux/hrtimer.h>
  21 #include <linux/kernel.h>
  22 #include <linux/ktime.h>
  23 #include <linux/init.h>
  24 #include <linux/miscdevice.h>
  25 #include <linux/module.h>
  26 #include <linux/moduleparam.h>
  27 #include <linux/platform_device.h>
  28 #include <linux/spinlock.h>
  29 #include <linux/uaccess.h>
  30 #include <linux/watchdog.h>
  31 #include <xen/xen.h>
  32 #include <asm/xen/hypercall.h>
  33 #include <xen/interface/sched.h>
  34
  35 static struct platform_device *platform_device;
  36 static DEFINE_SPINLOCK(wdt_lock);
  37 static struct sched_watchdog wdt;
  38 static __kernel_time_t wdt_expires;
  39 static bool is_active, expect_release;
  40
  41 #define WATCHDOG_TIMEOUT 60 /* in seconds */
  42 static unsigned int timeout = WATCHDOG_TIMEOUT;
  43 module_param(timeout, uint, S_IRUGO);
  44 MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds "
  45         "(default=" __MODULE_STRING(WATCHDOG_TIMEOUT) ")");
  46
  47 static bool nowayout = WATCHDOG_NOWAYOUT;
  48 module_param(nowayout, bool, S_IRUGO);
  49 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
  50         "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  51
  52 static inline __kernel_time_t set_timeout(void)
  53 {
  54         wdt.timeout = timeout;
  55         return ktime_to_timespec(ktime_get()).tv_sec + timeout;
  56 }
  57
  58 static int xen_wdt_start(void)
  59 {
  60         __kernel_time_t expires;
  61         int err;
  62
  63         spin_lock(&wdt_lock);
  64
  65         expires = set_timeout();
  66         if (!wdt.id)
  67                 err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
  68         else
  69                 err = -EBUSY;
  70         if (err > 0) {
  71                 wdt.id = err;
  72                 wdt_expires = expires;
  73                 err = 0;
  74         } else
  75                 BUG_ON(!err);
  76
  77         spin_unlock(&wdt_lock);
  78
  79         return err;
  80 }
  81
  82 static int xen_wdt_stop(void)
  83 {
  84         int err = 0;
  85
  86         spin_lock(&wdt_lock);
  87
  88         wdt.timeout = 0;
  89         if (wdt.id)
  90                 err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
  91         if (!err)
  92                 wdt.id = 0;
  93
  94         spin_unlock(&wdt_lock);
  95
  96         return err;
  97 }
  98
  99 static int xen_wdt_kick(void)
 100 {
 101         __kernel_time_t expires;
 102         int err;
 103
 104         spin_lock(&wdt_lock);
 105
 106         expires = set_timeout();
 107         if (wdt.id)
 108                 err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
 109         else
 110                 err = -ENXIO;
 111         if (!err)
 112                 wdt_expires = expires;
 113
 114         spin_unlock(&wdt_lock);
 115
 116         return err;
 117 }
 118
 119 static int xen_wdt_open(struct inode *inode, struct file *file)
 120 {
 121         int err;
 122
 123         /* /dev/watchdog can only be opened once */
 124         if (xchg(&is_active, true))
 125                 return -EBUSY;
 126
 127         err = xen_wdt_start();
 128         if (err == -EBUSY)
 129                 err = xen_wdt_kick();
 130         return err ?: nonseekable_open(inode, file);
 131 }
 132
 133 static int xen_wdt_release(struct inode *inode, struct file *file)
 134 {
 135         if (expect_release)
 136                 xen_wdt_stop();
 137         else {
 138                 pr_crit("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                         pr_info("timeout value invalid, using %d\n", timeout);
 255                 }
 256
 257                 ret = misc_register(&xen_wdt_miscdev);
 258                 if (ret) {
 259                         pr_err("cannot register miscdev on minor=%d (%d)\n",
 260                                WATCHDOG_MINOR, ret);
 261                         break;
 262                 }
 263
 264                 pr_info("initialized (timeout=%ds, nowayout=%d)\n",
 265                         timeout, nowayout);
 266                 break;
 267
 268         case -ENOSYS:
 269                 pr_info("not supported\n");
 270                 ret = -ENODEV;
 271                 break;
 272
 273         default:
 274                 pr_info("bogus return value %d\n", ret);
 275                 break;
 276         }
 277
 278         return ret;
 279 }
 280
 281 static int __devexit xen_wdt_remove(struct platform_device *dev)
 282 {
 283         /* Stop the timer before we leave */
 284         if (!nowayout)
 285                 xen_wdt_stop();
 286
 287         misc_deregister(&xen_wdt_miscdev);
 288
 289         return 0;
 290 }
 291
 292 static void xen_wdt_shutdown(struct platform_device *dev)
 293 {
 294         xen_wdt_stop();
 295 }
 296
 297 static int xen_wdt_suspend(struct platform_device *dev, pm_message_t state)
 298 {
 299         return xen_wdt_stop();
 300 }
 301
 302 static int xen_wdt_resume(struct platform_device *dev)
 303 {
 304         return xen_wdt_start();
 305 }
 306
 307 static struct platform_driver xen_wdt_driver = {
 308         .probe          = xen_wdt_probe,
 309         .remove         = __devexit_p(xen_wdt_remove),
 310         .shutdown       = xen_wdt_shutdown,
 311         .suspend        = xen_wdt_suspend,
 312         .resume         = xen_wdt_resume,
 313         .driver         = {
 314                 .owner  = THIS_MODULE,
 315                 .name   = DRV_NAME,
 316         },
 317 };
 318
 319 static int __init xen_wdt_init_module(void)
 320 {
 321         int err;
 322
 323         if (!xen_domain())
 324                 return -ENODEV;
 325
 326         pr_info("Xen WatchDog Timer Driver v%s\n", DRV_VERSION);
 327
 328         err = platform_driver_register(&xen_wdt_driver);
 329         if (err)
 330                 return err;
 331
 332         platform_device = platform_device_register_simple(DRV_NAME,
 333                                                                   -1, NULL, 0);
 334         if (IS_ERR(platform_device)) {
 335                 err = PTR_ERR(platform_device);
 336                 platform_driver_unregister(&xen_wdt_driver);
 337         }
 338
 339         return err;
 340 }
 341
 342 static void __exit xen_wdt_cleanup_module(void)
 343 {
 344         platform_device_unregister(platform_device);
 345         platform_driver_unregister(&xen_wdt_driver);
 346         pr_info("module unloaded\n");
 347 }
 348
 349 module_init(xen_wdt_init_module);
 350 module_exit(xen_wdt_cleanup_module);
 351
 352 MODULE_AUTHOR("Jan Beulich <jbeulich@novell.com>");
 353 MODULE_DESCRIPTION("Xen WatchDog Timer Driver");
 354 MODULE_VERSION(DRV_VERSION);
 355 MODULE_LICENSE("GPL");
 356 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);