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Linux/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         int err = 0;
136 
137         if (expect_release)
138                 err = xen_wdt_stop();
139         else {
140                 pr_crit("unexpected close, not stopping watchdog!\n");
141                 xen_wdt_kick();
142         }
143         is_active = err;
144         expect_release = false;
145         return err;
146 }
147 
148 static ssize_t xen_wdt_write(struct file *file, const char __user *data,
149                              size_t len, loff_t *ppos)
150 {
151         /* See if we got the magic character 'V' and reload the timer */
152         if (len) {
153                 if (!nowayout) {
154                         size_t i;
155 
156                         /* in case it was set long ago */
157                         expect_release = false;
158 
159                         /* scan to see whether or not we got the magic
160                            character */
161                         for (i = 0; i != len; i++) {
162                                 char c;
163                                 if (get_user(c, data + i))
164                                         return -EFAULT;
165                                 if (c == 'V')
166                                         expect_release = true;
167                         }
168                 }
169 
170                 /* someone wrote to us, we should reload the timer */
171                 xen_wdt_kick();
172         }
173         return len;
174 }
175 
176 static long xen_wdt_ioctl(struct file *file, unsigned int cmd,
177                           unsigned long arg)
178 {
179         int new_options, retval = -EINVAL;
180         int new_timeout;
181         int __user *argp = (void __user *)arg;
182         static const struct watchdog_info ident = {
183                 .options =              WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
184                 .firmware_version =     0,
185                 .identity =             DRV_NAME,
186         };
187 
188         switch (cmd) {
189         case WDIOC_GETSUPPORT:
190                 return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
191 
192         case WDIOC_GETSTATUS:
193         case WDIOC_GETBOOTSTATUS:
194                 return put_user(0, argp);
195 
196         case WDIOC_SETOPTIONS:
197                 if (get_user(new_options, argp))
198                         return -EFAULT;
199 
200                 if (new_options & WDIOS_DISABLECARD)
201                         retval = xen_wdt_stop();
202                 if (new_options & WDIOS_ENABLECARD) {
203                         retval = xen_wdt_start();
204                         if (retval == -EBUSY)
205                                 retval = xen_wdt_kick();
206                 }
207                 return retval;
208 
209         case WDIOC_KEEPALIVE:
210                 xen_wdt_kick();
211                 return 0;
212 
213         case WDIOC_SETTIMEOUT:
214                 if (get_user(new_timeout, argp))
215                         return -EFAULT;
216                 if (!new_timeout)
217                         return -EINVAL;
218                 timeout = new_timeout;
219                 xen_wdt_kick();
220                 /* fall through */
221         case WDIOC_GETTIMEOUT:
222                 return put_user(timeout, argp);
223 
224         case WDIOC_GETTIMELEFT:
225                 retval = wdt_expires - ktime_to_timespec(ktime_get()).tv_sec;
226                 return put_user(retval, argp);
227         }
228 
229         return -ENOTTY;
230 }
231 
232 static const struct file_operations xen_wdt_fops = {
233         .owner =                THIS_MODULE,
234         .llseek =               no_llseek,
235         .write =                xen_wdt_write,
236         .unlocked_ioctl =       xen_wdt_ioctl,
237         .open =                 xen_wdt_open,
238         .release =              xen_wdt_release,
239 };
240 
241 static struct miscdevice xen_wdt_miscdev = {
242         .minor =        WATCHDOG_MINOR,
243         .name =         "watchdog",
244         .fops =         &xen_wdt_fops,
245 };
246 
247 static int xen_wdt_probe(struct platform_device *dev)
248 {
249         struct sched_watchdog wd = { .id = ~0 };
250         int ret = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wd);
251 
252         switch (ret) {
253         case -EINVAL:
254                 if (!timeout) {
255                         timeout = WATCHDOG_TIMEOUT;
256                         pr_info("timeout value invalid, using %d\n", timeout);
257                 }
258 
259                 ret = misc_register(&xen_wdt_miscdev);
260                 if (ret) {
261                         pr_err("cannot register miscdev on minor=%d (%d)\n",
262                                WATCHDOG_MINOR, ret);
263                         break;
264                 }
265 
266                 pr_info("initialized (timeout=%ds, nowayout=%d)\n",
267                         timeout, nowayout);
268                 break;
269 
270         case -ENOSYS:
271                 pr_info("not supported\n");
272                 ret = -ENODEV;
273                 break;
274 
275         default:
276                 pr_info("bogus return value %d\n", ret);
277                 break;
278         }
279 
280         return ret;
281 }
282 
283 static int xen_wdt_remove(struct platform_device *dev)
284 {
285         /* Stop the timer before we leave */
286         if (!nowayout)
287                 xen_wdt_stop();
288 
289         misc_deregister(&xen_wdt_miscdev);
290 
291         return 0;
292 }
293 
294 static void xen_wdt_shutdown(struct platform_device *dev)
295 {
296         xen_wdt_stop();
297 }
298 
299 static int xen_wdt_suspend(struct platform_device *dev, pm_message_t state)
300 {
301         typeof(wdt.id) id = wdt.id;
302         int rc = xen_wdt_stop();
303 
304         wdt.id = id;
305         return rc;
306 }
307 
308 static int xen_wdt_resume(struct platform_device *dev)
309 {
310         if (!wdt.id)
311                 return 0;
312         wdt.id = 0;
313         return xen_wdt_start();
314 }
315 
316 static struct platform_driver xen_wdt_driver = {
317         .probe          = xen_wdt_probe,
318         .remove         = xen_wdt_remove,
319         .shutdown       = xen_wdt_shutdown,
320         .suspend        = xen_wdt_suspend,
321         .resume         = xen_wdt_resume,
322         .driver         = {
323                 .owner  = THIS_MODULE,
324                 .name   = DRV_NAME,
325         },
326 };
327 
328 static int __init xen_wdt_init_module(void)
329 {
330         int err;
331 
332         if (!xen_domain())
333                 return -ENODEV;
334 
335         pr_info("Xen WatchDog Timer Driver v%s\n", DRV_VERSION);
336 
337         err = platform_driver_register(&xen_wdt_driver);
338         if (err)
339                 return err;
340 
341         platform_device = platform_device_register_simple(DRV_NAME,
342                                                                   -1, NULL, 0);
343         if (IS_ERR(platform_device)) {
344                 err = PTR_ERR(platform_device);
345                 platform_driver_unregister(&xen_wdt_driver);
346         }
347 
348         return err;
349 }
350 
351 static void __exit xen_wdt_cleanup_module(void)
352 {
353         platform_device_unregister(platform_device);
354         platform_driver_unregister(&xen_wdt_driver);
355         pr_info("module unloaded\n");
356 }
357 
358 module_init(xen_wdt_init_module);
359 module_exit(xen_wdt_cleanup_module);
360 
361 MODULE_AUTHOR("Jan Beulich <jbeulich@novell.com>");
362 MODULE_DESCRIPTION("Xen WatchDog Timer Driver");
363 MODULE_VERSION(DRV_VERSION);
364 MODULE_LICENSE("GPL");
365 

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