1 /*
2 * Watchdog implementation based on z/VM Watchdog Timer API
3 *
4 * Copyright IBM Corp. 2004,2009
5 *
6 * The user space watchdog daemon can use this driver as
7 * /dev/vmwatchdog to have z/VM execute the specified CP
8 * command when the timeout expires. The default command is
9 * "IPL", which which cause an immediate reboot.
10 */
11 #define KMSG_COMPONENT "vmwatchdog"
12 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
13
14 #include <linux/init.h>
15 #include <linux/fs.h>
16 #include <linux/kernel.h>
17 #include <linux/miscdevice.h>
18 #include <linux/module.h>
19 #include <linux/moduleparam.h>
20 #include <linux/slab.h>
21 #include <linux/suspend.h>
22 #include <linux/watchdog.h>
23
24 #include <asm/ebcdic.h>
25 #include <asm/io.h>
26 #include <asm/uaccess.h>
27
28 #define MAX_CMDLEN 240
29 #define MIN_INTERVAL 15
30 static char vmwdt_cmd[MAX_CMDLEN] = "IPL";
31 static bool vmwdt_conceal;
32
33 static bool vmwdt_nowayout = WATCHDOG_NOWAYOUT;
34
35 MODULE_LICENSE("GPL");
36 MODULE_AUTHOR("Arnd Bergmann <arndb@de.ibm.com>");
37 MODULE_DESCRIPTION("z/VM Watchdog Timer");
38 module_param_string(cmd, vmwdt_cmd, MAX_CMDLEN, 0644);
39 MODULE_PARM_DESC(cmd, "CP command that is run when the watchdog triggers");
40 module_param_named(conceal, vmwdt_conceal, bool, 0644);
41 MODULE_PARM_DESC(conceal, "Enable the CONCEAL CP option while the watchdog "
42 " is active");
43 module_param_named(nowayout, vmwdt_nowayout, bool, 0);
44 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started"
45 " (default=CONFIG_WATCHDOG_NOWAYOUT)");
46 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
47
48 static unsigned int vmwdt_interval = 60;
49 static unsigned long vmwdt_is_open;
50 static int vmwdt_expect_close;
51
52 static DEFINE_MUTEX(vmwdt_mutex);
53
54 #define VMWDT_OPEN 0 /* devnode is open or suspend in progress */
55 #define VMWDT_RUNNING 1 /* The watchdog is armed */
56
57 enum vmwdt_func {
58 /* function codes */
59 wdt_init = 0,
60 wdt_change = 1,
61 wdt_cancel = 2,
62 /* flags */
63 wdt_conceal = 0x80000000,
64 };
65
__diag288(enum vmwdt_func func,unsigned int timeout,char * cmd,size_t len)66 static int __diag288(enum vmwdt_func func, unsigned int timeout,
67 char *cmd, size_t len)
68 {
69 register unsigned long __func asm("2") = func;
70 register unsigned long __timeout asm("3") = timeout;
71 register unsigned long __cmdp asm("4") = virt_to_phys(cmd);
72 register unsigned long __cmdl asm("5") = len;
73 int err;
74
75 err = -EINVAL;
76 asm volatile(
77 " diag %1,%3,0x288\n"
78 "0: la %0,0\n"
79 "1:\n"
80 EX_TABLE(0b,1b)
81 : "+d" (err) : "d"(__func), "d"(__timeout),
82 "d"(__cmdp), "d"(__cmdl) : "1", "cc");
83 return err;
84 }
85
vmwdt_keepalive(void)86 static int vmwdt_keepalive(void)
87 {
88 /* we allocate new memory every time to avoid having
89 * to track the state. static allocation is not an
90 * option since that might not be contiguous in real
91 * storage in case of a modular build */
92 static char *ebc_cmd;
93 size_t len;
94 int ret;
95 unsigned int func;
96
97 ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
98 if (!ebc_cmd)
99 return -ENOMEM;
100
101 len = strlcpy(ebc_cmd, vmwdt_cmd, MAX_CMDLEN);
102 ASCEBC(ebc_cmd, MAX_CMDLEN);
103 EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
104
105 func = vmwdt_conceal ? (wdt_init | wdt_conceal) : wdt_init;
106 set_bit(VMWDT_RUNNING, &vmwdt_is_open);
107 ret = __diag288(func, vmwdt_interval, ebc_cmd, len);
108 WARN_ON(ret != 0);
109 kfree(ebc_cmd);
110 return ret;
111 }
112
vmwdt_disable(void)113 static int vmwdt_disable(void)
114 {
115 int ret = __diag288(wdt_cancel, 0, "", 0);
116 WARN_ON(ret != 0);
117 clear_bit(VMWDT_RUNNING, &vmwdt_is_open);
118 return ret;
119 }
120
vmwdt_probe(void)121 static int __init vmwdt_probe(void)
122 {
123 /* there is no real way to see if the watchdog is supported,
124 * so we try initializing it with a NOP command ("BEGIN")
125 * that won't cause any harm even if the following disable
126 * fails for some reason */
127 static char __initdata ebc_begin[] = {
128 194, 197, 199, 201, 213
129 };
130 if (__diag288(wdt_init, 15, ebc_begin, sizeof(ebc_begin)) != 0)
131 return -EINVAL;
132 return vmwdt_disable();
133 }
134
vmwdt_open(struct inode * i,struct file * f)135 static int vmwdt_open(struct inode *i, struct file *f)
136 {
137 int ret;
138 if (test_and_set_bit(VMWDT_OPEN, &vmwdt_is_open))
139 return -EBUSY;
140 ret = vmwdt_keepalive();
141 if (ret)
142 clear_bit(VMWDT_OPEN, &vmwdt_is_open);
143 return ret ? ret : nonseekable_open(i, f);
144 }
145
vmwdt_close(struct inode * i,struct file * f)146 static int vmwdt_close(struct inode *i, struct file *f)
147 {
148 if (vmwdt_expect_close == 42)
149 vmwdt_disable();
150 vmwdt_expect_close = 0;
151 clear_bit(VMWDT_OPEN, &vmwdt_is_open);
152 return 0;
153 }
154
155 static struct watchdog_info vmwdt_info = {
156 .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
157 .firmware_version = 0,
158 .identity = "z/VM Watchdog Timer",
159 };
160
__vmwdt_ioctl(unsigned int cmd,unsigned long arg)161 static int __vmwdt_ioctl(unsigned int cmd, unsigned long arg)
162 {
163 switch (cmd) {
164 case WDIOC_GETSUPPORT:
165 if (copy_to_user((void __user *)arg, &vmwdt_info,
166 sizeof(vmwdt_info)))
167 return -EFAULT;
168 return 0;
169 case WDIOC_GETSTATUS:
170 case WDIOC_GETBOOTSTATUS:
171 return put_user(0, (int __user *)arg);
172 case WDIOC_GETTEMP:
173 return -EINVAL;
174 case WDIOC_SETOPTIONS:
175 {
176 int options, ret;
177 if (get_user(options, (int __user *)arg))
178 return -EFAULT;
179 ret = -EINVAL;
180 if (options & WDIOS_DISABLECARD) {
181 ret = vmwdt_disable();
182 if (ret)
183 return ret;
184 }
185 if (options & WDIOS_ENABLECARD) {
186 ret = vmwdt_keepalive();
187 }
188 return ret;
189 }
190 case WDIOC_GETTIMEOUT:
191 return put_user(vmwdt_interval, (int __user *)arg);
192 case WDIOC_SETTIMEOUT:
193 {
194 int interval;
195 if (get_user(interval, (int __user *)arg))
196 return -EFAULT;
197 if (interval < MIN_INTERVAL)
198 return -EINVAL;
199 vmwdt_interval = interval;
200 }
201 return vmwdt_keepalive();
202 case WDIOC_KEEPALIVE:
203 return vmwdt_keepalive();
204 }
205 return -EINVAL;
206 }
207
vmwdt_ioctl(struct file * f,unsigned int cmd,unsigned long arg)208 static long vmwdt_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
209 {
210 int rc;
211
212 mutex_lock(&vmwdt_mutex);
213 rc = __vmwdt_ioctl(cmd, arg);
214 mutex_unlock(&vmwdt_mutex);
215 return (long) rc;
216 }
217
vmwdt_write(struct file * f,const char __user * buf,size_t count,loff_t * ppos)218 static ssize_t vmwdt_write(struct file *f, const char __user *buf,
219 size_t count, loff_t *ppos)
220 {
221 if(count) {
222 if (!vmwdt_nowayout) {
223 size_t i;
224
225 /* note: just in case someone wrote the magic character
226 * five months ago... */
227 vmwdt_expect_close = 0;
228
229 for (i = 0; i != count; i++) {
230 char c;
231 if (get_user(c, buf+i))
232 return -EFAULT;
233 if (c == 'V')
234 vmwdt_expect_close = 42;
235 }
236 }
237 /* someone wrote to us, we should restart timer */
238 vmwdt_keepalive();
239 }
240 return count;
241 }
242
vmwdt_resume(void)243 static int vmwdt_resume(void)
244 {
245 clear_bit(VMWDT_OPEN, &vmwdt_is_open);
246 return NOTIFY_DONE;
247 }
248
249 /*
250 * It makes no sense to go into suspend while the watchdog is running.
251 * Depending on the memory size, the watchdog might trigger, while we
252 * are still saving the memory.
253 * We reuse the open flag to ensure that suspend and watchdog open are
254 * exclusive operations
255 */
vmwdt_suspend(void)256 static int vmwdt_suspend(void)
257 {
258 if (test_and_set_bit(VMWDT_OPEN, &vmwdt_is_open)) {
259 pr_err("The system cannot be suspended while the watchdog"
260 " is in use\n");
261 return notifier_from_errno(-EBUSY);
262 }
263 if (test_bit(VMWDT_RUNNING, &vmwdt_is_open)) {
264 clear_bit(VMWDT_OPEN, &vmwdt_is_open);
265 pr_err("The system cannot be suspended while the watchdog"
266 " is running\n");
267 return notifier_from_errno(-EBUSY);
268 }
269 return NOTIFY_DONE;
270 }
271
272 /*
273 * This function is called for suspend and resume.
274 */
vmwdt_power_event(struct notifier_block * this,unsigned long event,void * ptr)275 static int vmwdt_power_event(struct notifier_block *this, unsigned long event,
276 void *ptr)
277 {
278 switch (event) {
279 case PM_POST_HIBERNATION:
280 case PM_POST_SUSPEND:
281 return vmwdt_resume();
282 case PM_HIBERNATION_PREPARE:
283 case PM_SUSPEND_PREPARE:
284 return vmwdt_suspend();
285 default:
286 return NOTIFY_DONE;
287 }
288 }
289
290 static struct notifier_block vmwdt_power_notifier = {
291 .notifier_call = vmwdt_power_event,
292 };
293
294 static const struct file_operations vmwdt_fops = {
295 .open = &vmwdt_open,
296 .release = &vmwdt_close,
297 .unlocked_ioctl = &vmwdt_ioctl,
298 .write = &vmwdt_write,
299 .owner = THIS_MODULE,
300 .llseek = noop_llseek,
301 };
302
303 static struct miscdevice vmwdt_dev = {
304 .minor = WATCHDOG_MINOR,
305 .name = "watchdog",
306 .fops = &vmwdt_fops,
307 };
308
vmwdt_init(void)309 static int __init vmwdt_init(void)
310 {
311 int ret;
312
313 ret = vmwdt_probe();
314 if (ret)
315 return ret;
316 ret = register_pm_notifier(&vmwdt_power_notifier);
317 if (ret)
318 return ret;
319 /*
320 * misc_register() has to be the last action in module_init(), because
321 * file operations will be available right after this.
322 */
323 ret = misc_register(&vmwdt_dev);
324 if (ret) {
325 unregister_pm_notifier(&vmwdt_power_notifier);
326 return ret;
327 }
328 return 0;
329 }
330 module_init(vmwdt_init);
331
vmwdt_exit(void)332 static void __exit vmwdt_exit(void)
333 {
334 unregister_pm_notifier(&vmwdt_power_notifier);
335 misc_deregister(&vmwdt_dev);
336 }
337 module_exit(vmwdt_exit);
338