drivers/watchdog/xen_wdt.c

   1 /*
   2  *      Xen Watchdog Driver
   3  *
   4  *      (c) Copyright 2010,2011 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 pr_fmt(fmt)     KBUILD_MODNAME ": " fmt
  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 #ifdef CONFIG_PARAVIRT_XEN
  31 #include <xen/xen.h>
  32 #include <asm/xen/hypercall.h>
  33 #endif
  34 #include <xen/interface/sched.h>
  35
  36 static struct platform_device *platform_device;
  37 static DEFINE_SPINLOCK(wdt_lock);
  38 static struct sched_watchdog wdt;
  39 static __kernel_time_t wdt_expires;
  40 static bool is_active, expect_release;
  41
  42 #define WATCHDOG_TIMEOUT 60 /* in seconds */
  43 static unsigned int timeout = WATCHDOG_TIMEOUT;
  44 module_param(timeout, uint, S_IRUGO);
  45 MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds "
  46         "(default=" __MODULE_STRING(WATCHDOG_TIMEOUT) ")");
  47
  48 static bool nowayout = WATCHDOG_NOWAYOUT;
  49 module_param(nowayout, bool, S_IRUGO);
  50 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
  51         "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  52
  53 static inline __kernel_time_t set_timeout(void)
  54 {
  55         wdt.timeout = timeout;
  56         return ktime_to_timespec(ktime_get()).tv_sec + timeout;
  57 }
  58
  59 static int xen_wdt_start(void)
  60 {
  61         __kernel_time_t expires;
  62         int err;
  63
  64         spin_lock(&wdt_lock);
  65
  66         expires = set_timeout();
  67         if (!wdt.id)
  68                 err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
  69         else
  70                 err = -EBUSY;
  71         if (err > 0) {
  72                 wdt.id = err;
  73                 wdt_expires = expires;
  74                 err = 0;
  75         } else
  76                 BUG_ON(!err);
  77
  78         spin_unlock(&wdt_lock);
  79
  80         return err;
  81 }
  82
  83 static int xen_wdt_stop(void)
  84 {
  85         int err = 0;
  86
  87         spin_lock(&wdt_lock);
  88
  89         wdt.timeout = 0;
  90         if (wdt.id)
  91                 err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
  92         if (!err)
  93                 wdt.id = 0;
  94
  95         spin_unlock(&wdt_lock);
  96
  97         return err;
  98 }
  99
 100 static int xen_wdt_kick(void)
 101 {
 102         __kernel_time_t expires;
 103         int err;
 104
 105         spin_lock(&wdt_lock);
 106
 107         expires = set_timeout();
 108         if (wdt.id)
 109                 err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
 110         else
 111                 err = -ENXIO;
 112         if (!err)
 113                 wdt_expires = expires;
 114
 115         spin_unlock(&wdt_lock);
 116
 117         return err;
 118 }
 119
 120 static int xen_wdt_open(struct inode *inode, struct file *file)
 121 {
 122         int err;
 123
 124         /* /dev/watchdog can only be opened once */
 125         if (xchg(&is_active, true))
 126                 return -EBUSY;
 127
 128         err = xen_wdt_start();
 129         if (err == -EBUSY)
 130                 err = xen_wdt_kick();
 131         return err ?: nonseekable_open(inode, file);
 132 }
 133
 134 static int xen_wdt_release(struct inode *inode, struct file *file)
 135 {
 136         if (expect_release)
 137                 xen_wdt_stop();
 138         else {
 139                 pr_crit("unexpected close, not stopping watchdog!\n");
 140                 xen_wdt_kick();
 141         }
 142         is_active = false;
 143         expect_release = false;
 144         return 0;
 145 }
 146
 147 static ssize_t xen_wdt_write(struct file *file, const char __user *data,
 148                              size_t len, loff_t *ppos)
 149 {
 150         /* See if we got the magic character 'V' and reload the timer */
 151         if (len) {
 152                 if (!nowayout) {
 153                         size_t i;
 154
 155                         /* in case it was set long ago */
 156                         expect_release = false;
 157
 158                         /* scan to see whether or not we got the magic
 159                            character */
 160                         for (i = 0; i != len; i++) {
 161                                 char c;
 162                                 if (get_user(c, data + i))
 163                                         return -EFAULT;
 164                                 if (c == 'V')
 165                                         expect_release = true;
 166                         }
 167                 }
 168
 169                 /* someone wrote to us, we should reload the timer */
 170                 xen_wdt_kick();
 171         }
 172         return len;
 173 }
 174
 175 static long xen_wdt_ioctl(struct file *file, unsigned int cmd,
 176                           unsigned long arg)
 177 {
 178         int new_options, retval = -EINVAL;
 179         int new_timeout;
 180         int __user *argp = (void __user *)arg;
 181         static const struct watchdog_info ident = {
 182                 .options =              WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
 183                 .firmware_version =     0,
 184                 .identity =             DRV_NAME,
 185         };
 186
 187         switch (cmd) {
 188         case WDIOC_GETSUPPORT:
 189                 return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
 190
 191         case WDIOC_GETSTATUS:
 192         case WDIOC_GETBOOTSTATUS:
 193                 return put_user(0, argp);
 194
 195         case WDIOC_SETOPTIONS:
 196                 if (get_user(new_options, argp))
 197                         return -EFAULT;
 198
 199                 if (new_options & WDIOS_DISABLECARD)
 200                         retval = xen_wdt_stop();
 201                 if (new_options & WDIOS_ENABLECARD) {
 202                         retval = xen_wdt_start();
 203                         if (retval == -EBUSY)
 204                                 retval = xen_wdt_kick();
 205                 }
 206                 return retval;
 207
 208         case WDIOC_KEEPALIVE:
 209                 xen_wdt_kick();
 210                 return 0;
 211
 212         case WDIOC_SETTIMEOUT:
 213                 if (get_user(new_timeout, argp))
 214                         return -EFAULT;
 215                 if (!new_timeout)
 216                         return -EINVAL;
 217                 timeout = new_timeout;
 218                 xen_wdt_kick();
 219                 /* fall through */
 220         case WDIOC_GETTIMEOUT:
 221                 return put_user(timeout, argp);
 222
 223         case WDIOC_GETTIMELEFT:
 224                 retval = wdt_expires - ktime_to_timespec(ktime_get()).tv_sec;
 225                 return put_user(retval, argp);
 226         }
 227
 228         return -ENOTTY;
 229 }
 230
 231 static const struct file_operations xen_wdt_fops = {
 232         .owner =                THIS_MODULE,
 233         .llseek =               no_llseek,
 234         .write =                xen_wdt_write,
 235         .unlocked_ioctl =       xen_wdt_ioctl,
 236         .open =                 xen_wdt_open,
 237         .release =              xen_wdt_release,
 238 };
 239
 240 static struct miscdevice xen_wdt_miscdev = {
 241         .minor =        WATCHDOG_MINOR,
 242         .name =         "watchdog",
 243         .fops =         &xen_wdt_fops,
 244 };
 245
 246 static int __devinit xen_wdt_probe(struct platform_device *dev)
 247 {
 248         struct sched_watchdog wd = { .id = ~0 };
 249         int ret = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wd);
 250
 251         switch (ret) {
 252         case -EINVAL:
 253                 if (!timeout) {
 254                         timeout = WATCHDOG_TIMEOUT;
 255                         pr_info("timeout value invalid, using %d\n", timeout);
 256                 }
 257
 258                 ret = misc_register(&xen_wdt_miscdev);
 259                 if (ret) {
 260                         pr_err("cannot register miscdev on minor=%d (%d)\n",
 261                                WATCHDOG_MINOR, ret);
 262                         break;
 263                 }
 264
 265                 pr_info("initialized (timeout=%ds, nowayout=%d)\n",
 266                         timeout, nowayout);
 267                 break;
 268
 269         case -ENOSYS:
 270                 pr_info("not supported\n");
 271                 ret = -ENODEV;
 272                 break;
 273
 274         default:
 275                 pr_info("bogus return value %d\n", ret);
 276                 break;
 277         }
 278
 279         return ret;
 280 }
 281
 282 static int __devexit xen_wdt_remove(struct platform_device *dev)
 283 {
 284         /* Stop the timer before we leave */
 285         if (!nowayout)
 286                 xen_wdt_stop();
 287
 288         misc_deregister(&xen_wdt_miscdev);
 289
 290         return 0;
 291 }
 292
 293 static void xen_wdt_shutdown(struct platform_device *dev)
 294 {
 295         xen_wdt_stop();
 296 }
 297
 298 static int xen_wdt_suspend(struct platform_device *dev, pm_message_t state)
 299 {
 300         return xen_wdt_stop();
 301 }
 302
 303 static int xen_wdt_resume(struct platform_device *dev)
 304 {
 305         return xen_wdt_start();
 306 }
 307
 308 static struct platform_driver xen_wdt_driver = {
 309         .probe          = xen_wdt_probe,
 310         .remove         = __devexit_p(xen_wdt_remove),
 311         .shutdown       = xen_wdt_shutdown,
 312         .suspend        = xen_wdt_suspend,
 313         .resume         = xen_wdt_resume,
 314         .driver         = {
 315                 .owner  = THIS_MODULE,
 316                 .name   = DRV_NAME,
 317         },
 318 };
 319
 320 static int __init xen_wdt_init_module(void)
 321 {
 322         int err;
 323
 324 #ifdef CONFIG_PARAVIRT_XEN
 325         if (!xen_domain())
 326                 return -ENODEV;
 327 #endif
 328
 329         printk(KERN_INFO "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         pr_info("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);