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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
35static struct platform_device *platform_device;
36static DEFINE_SPINLOCK(wdt_lock);
37static struct sched_watchdog wdt;
38static __kernel_time_t wdt_expires;
39static bool is_active, expect_release;
40
41#define WATCHDOG_TIMEOUT 60
42static unsigned int timeout = WATCHDOG_TIMEOUT;
43module_param(timeout, uint, S_IRUGO);
44MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds "
45 "(default=" __MODULE_STRING(WATCHDOG_TIMEOUT) ")");
46
47static bool nowayout = WATCHDOG_NOWAYOUT;
48module_param(nowayout, bool, S_IRUGO);
49MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
50 "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
51
52static inline __kernel_time_t set_timeout(void)
53{
54 wdt.timeout = timeout;
55 return ktime_to_timespec(ktime_get()).tv_sec + timeout;
56}
57
58static 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
82static 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
99static 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
119static int xen_wdt_open(struct inode *inode, struct file *file)
120{
121 int err;
122
123
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
133static 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
148static ssize_t xen_wdt_write(struct file *file, const char __user *data,
149 size_t len, loff_t *ppos)
150{
151
152 if (len) {
153 if (!nowayout) {
154 size_t i;
155
156
157 expect_release = false;
158
159
160
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
171 xen_wdt_kick();
172 }
173 return len;
174}
175
176static 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
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
232static 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
241static struct miscdevice xen_wdt_miscdev = {
242 .minor = WATCHDOG_MINOR,
243 .name = "watchdog",
244 .fops = &xen_wdt_fops,
245};
246
247static 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
283static int xen_wdt_remove(struct platform_device *dev)
284{
285
286 if (!nowayout)
287 xen_wdt_stop();
288
289 misc_deregister(&xen_wdt_miscdev);
290
291 return 0;
292}
293
294static void xen_wdt_shutdown(struct platform_device *dev)
295{
296 xen_wdt_stop();
297}
298
299static 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
308static 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
316static 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
328static 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
351static 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
358module_init(xen_wdt_init_module);
359module_exit(xen_wdt_cleanup_module);
360
361MODULE_AUTHOR("Jan Beulich <jbeulich@novell.com>");
362MODULE_DESCRIPTION("Xen WatchDog Timer Driver");
363MODULE_VERSION(DRV_VERSION);
364MODULE_LICENSE("GPL");
365
