Merge head 'for-linus' of master.kernel.org:/pub/scm/linux/kernel/git/shaggy/jfs-2.6
[linux-2.6] / drivers / s390 / char / vmwatchdog.c
1 /*
2  * Watchdog implementation based on z/VM Watchdog Timer API
3  *
4  * The user space watchdog daemon can use this driver as
5  * /dev/vmwatchdog to have z/VM execute the specified CP
6  * command when the timeout expires. The default command is
7  * "IPL", which which cause an immediate reboot.
8  */
9 #include <linux/init.h>
10 #include <linux/fs.h>
11 #include <linux/kernel.h>
12 #include <linux/miscdevice.h>
13 #include <linux/module.h>
14 #include <linux/moduleparam.h>
15 #include <linux/watchdog.h>
16
17 #include <asm/ebcdic.h>
18 #include <asm/io.h>
19 #include <asm/uaccess.h>
20
21 #define MAX_CMDLEN 240
22 #define MIN_INTERVAL 15
23 static char vmwdt_cmd[MAX_CMDLEN] = "IPL";
24 static int vmwdt_conceal;
25
26 static int vmwdt_nowayout = WATCHDOG_NOWAYOUT;
27
28 MODULE_LICENSE("GPL");
29 MODULE_AUTHOR("Arnd Bergmann <arndb@de.ibm.com>");
30 MODULE_DESCRIPTION("z/VM Watchdog Timer");
31 module_param_string(cmd, vmwdt_cmd, MAX_CMDLEN, 0644);
32 MODULE_PARM_DESC(cmd, "CP command that is run when the watchdog triggers");
33 module_param_named(conceal, vmwdt_conceal, bool, 0644);
34 MODULE_PARM_DESC(conceal, "Enable the CONCEAL CP option while the watchdog "
35                 " is active");
36 module_param_named(nowayout, vmwdt_nowayout, bool, 0);
37 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started"
38                 " (default=CONFIG_WATCHDOG_NOWAYOUT)");
39 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
40
41 static unsigned int vmwdt_interval = 60;
42 static unsigned long vmwdt_is_open;
43 static int vmwdt_expect_close;
44
45 enum vmwdt_func {
46         /* function codes */
47         wdt_init   = 0,
48         wdt_change = 1,
49         wdt_cancel = 2,
50         /* flags */
51         wdt_conceal = 0x80000000,
52 };
53
54 static int __diag288(enum vmwdt_func func, unsigned int timeout,
55                             char *cmd, size_t len)
56 {
57         register unsigned long __func asm("2");
58         register unsigned long __timeout asm("3");
59         register unsigned long __cmdp asm("4");
60         register unsigned long __cmdl asm("5");
61         int err;
62
63         __func = func;
64         __timeout = timeout;
65         __cmdp = virt_to_phys(cmd);
66         __cmdl = len;
67         err = 0;
68         asm volatile (
69 #ifdef __s390x__
70                        "diag %2,%4,0x288\n"
71                 "1:     \n"
72                 ".section .fixup,\"ax\"\n"
73                 "2:     lghi %0,%1\n"
74                 "       jg 1b\n"
75                 ".previous\n"
76                 ".section __ex_table,\"a\"\n"
77                 "       .align 8\n"
78                 "       .quad 1b,2b\n"
79                 ".previous\n"
80 #else
81                        "diag %2,%4,0x288\n"
82                 "1:     \n"
83                 ".section .fixup,\"ax\"\n"
84                 "2:     lhi %0,%1\n"
85                 "       bras 1,3f\n"
86                 "       .long 1b\n"
87                 "3:     l 1,0(1)\n"
88                 "       br 1\n"
89                 ".previous\n"
90                 ".section __ex_table,\"a\"\n"
91                 "       .align 4\n"
92                 "       .long 1b,2b\n"
93                 ".previous\n"
94 #endif
95                 : "+&d"(err)
96                 : "i"(-EINVAL), "d"(__func), "d"(__timeout),
97                   "d"(__cmdp), "d"(__cmdl)
98                 : "1", "cc");
99         return err;
100 }
101
102 static int vmwdt_keepalive(void)
103 {
104         /* we allocate new memory every time to avoid having
105          * to track the state. static allocation is not an
106          * option since that might not be contiguous in real
107          * storage in case of a modular build */
108         static char *ebc_cmd;
109         size_t len;
110         int ret;
111         unsigned int func;
112
113         ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
114         if (!ebc_cmd)
115                 return -ENOMEM;
116
117         len = strlcpy(ebc_cmd, vmwdt_cmd, MAX_CMDLEN);
118         ASCEBC(ebc_cmd, MAX_CMDLEN);
119         EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
120
121         func = vmwdt_conceal ? (wdt_init | wdt_conceal) : wdt_init;
122         ret = __diag288(func, vmwdt_interval, ebc_cmd, len);
123         kfree(ebc_cmd);
124
125         if (ret) {
126                 printk(KERN_WARNING "%s: problem setting interval %d, "
127                         "cmd %s\n", __FUNCTION__, vmwdt_interval,
128                         vmwdt_cmd);
129         }
130         return ret;
131 }
132
133 static int vmwdt_disable(void)
134 {
135         int ret = __diag288(wdt_cancel, 0, "", 0);
136         if (ret) {
137                 printk(KERN_WARNING "%s: problem disabling watchdog\n",
138                         __FUNCTION__);
139         }
140         return ret;
141 }
142
143 static int __init vmwdt_probe(void)
144 {
145         /* there is no real way to see if the watchdog is supported,
146          * so we try initializing it with a NOP command ("BEGIN")
147          * that won't cause any harm even if the following disable
148          * fails for some reason */
149         static char __initdata ebc_begin[] = {
150                 194, 197, 199, 201, 213
151         };
152         if (__diag288(wdt_init, 15, ebc_begin, sizeof(ebc_begin)) != 0) {
153                 printk(KERN_INFO "z/VM watchdog not available\n");
154                 return -EINVAL;
155         }
156         return vmwdt_disable();
157 }
158
159 static int vmwdt_open(struct inode *i, struct file *f)
160 {
161         int ret;
162         if (test_and_set_bit(0, &vmwdt_is_open))
163                 return -EBUSY;
164         ret = vmwdt_keepalive();
165         if (ret)
166                 clear_bit(0, &vmwdt_is_open);
167         return ret ? ret : nonseekable_open(i, f);
168 }
169
170 static int vmwdt_close(struct inode *i, struct file *f)
171 {
172         if (vmwdt_expect_close == 42)
173                 vmwdt_disable();
174         vmwdt_expect_close = 0;
175         clear_bit(0, &vmwdt_is_open);
176         return 0;
177 }
178
179 static struct watchdog_info vmwdt_info = {
180         .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
181         .firmware_version = 0,
182         .identity = "z/VM Watchdog Timer",
183 };
184
185 static int vmwdt_ioctl(struct inode *i, struct file *f,
186                           unsigned int cmd, unsigned long arg)
187 {
188         switch (cmd) {
189         case WDIOC_GETSUPPORT:
190                 if (copy_to_user((void __user *)arg, &vmwdt_info,
191                                         sizeof(vmwdt_info)))
192                         return -EFAULT;
193                 return 0;
194         case WDIOC_GETSTATUS:
195         case WDIOC_GETBOOTSTATUS:
196                 return put_user(0, (int *)arg);
197         case WDIOC_GETTEMP:
198                 return -EINVAL;
199         case WDIOC_SETOPTIONS:
200                 {
201                         int options, ret;
202                         if (get_user(options, (int __user *)arg))
203                                 return -EFAULT;
204                         ret = -EINVAL;
205                         if (options & WDIOS_DISABLECARD) {
206                                 ret = vmwdt_disable();
207                                 if (ret)
208                                         return ret;
209                         }
210                         if (options & WDIOS_ENABLECARD) {
211                                 ret = vmwdt_keepalive();
212                         }
213                         return ret;
214                 }
215         case WDIOC_GETTIMEOUT:
216                 return put_user(vmwdt_interval, (int __user *)arg);
217         case WDIOC_SETTIMEOUT:
218                 {
219                         int interval;
220                         if (get_user(interval, (int __user *)arg))
221                                 return -EFAULT;
222                         if (interval < MIN_INTERVAL)
223                                 return -EINVAL;
224                         vmwdt_interval = interval;
225                 }
226                 return vmwdt_keepalive();
227         case WDIOC_KEEPALIVE:
228                 return vmwdt_keepalive();
229         }
230
231         return -EINVAL;
232 }
233
234 static ssize_t vmwdt_write(struct file *f, const char __user *buf,
235                                 size_t count, loff_t *ppos)
236 {
237         if(count) {
238                 if (!vmwdt_nowayout) {
239                         size_t i;
240
241                         /* note: just in case someone wrote the magic character
242                          * five months ago... */
243                         vmwdt_expect_close = 0;
244
245                         for (i = 0; i != count; i++) {
246                                 char c;
247                                 if (get_user(c, buf+i))
248                                         return -EFAULT;
249                                 if (c == 'V')
250                                         vmwdt_expect_close = 42;
251                         }
252                 }
253                 /* someone wrote to us, we should restart timer */
254                 vmwdt_keepalive();
255         }
256         return count;
257 }
258
259 static struct file_operations vmwdt_fops = {
260         .open    = &vmwdt_open,
261         .release = &vmwdt_close,
262         .ioctl   = &vmwdt_ioctl,
263         .write   = &vmwdt_write,
264         .owner   = THIS_MODULE,
265 };
266
267 static struct miscdevice vmwdt_dev = {
268         .minor      = WATCHDOG_MINOR,
269         .name       = "watchdog",
270         .fops       = &vmwdt_fops,
271 };
272
273 static int __init vmwdt_init(void)
274 {
275         int ret;
276
277         ret = vmwdt_probe();
278         if (ret)
279                 return ret;
280         return misc_register(&vmwdt_dev);
281 }
282 module_init(vmwdt_init);
283
284 static void __exit vmwdt_exit(void)
285 {
286         WARN_ON(misc_deregister(&vmwdt_dev) != 0);
287 }
288 module_exit(vmwdt_exit);