drivers/s390/char/vmwatchdog.c

   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/suspend.h>
  21 #include <linux/watchdog.h>
  22 #include <linux/smp_lock.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 int vmwdt_conceal;
  32
  33 static int 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 #define VMWDT_OPEN      0       /* devnode is open or suspend in progress */
  53 #define VMWDT_RUNNING   1       /* The watchdog is armed */
  54
  55 enum vmwdt_func {
  56         /* function codes */
  57         wdt_init   = 0,
  58         wdt_change = 1,
  59         wdt_cancel = 2,
  60         /* flags */
  61         wdt_conceal = 0x80000000,
  62 };
  63
  64 static int __diag288(enum vmwdt_func func, unsigned int timeout,
  65                             char *cmd, size_t len)
  66 {
  67         register unsigned long __func asm("2") = func;
  68         register unsigned long __timeout asm("3") = timeout;
  69         register unsigned long __cmdp asm("4") = virt_to_phys(cmd);
  70         register unsigned long __cmdl asm("5") = len;
  71         int err;
  72
  73         err = -EINVAL;
  74         asm volatile(
  75                 "       diag    %1,%3,0x288\n"
  76                 "0:     la      %0,0\n"
  77                 "1:\n"
  78                 EX_TABLE(0b,1b)
  79                 : "+d" (err) : "d"(__func), "d"(__timeout),
  80                   "d"(__cmdp), "d"(__cmdl) : "1", "cc");
  81         return err;
  82 }
  83
  84 static int vmwdt_keepalive(void)
  85 {
  86         /* we allocate new memory every time to avoid having
  87          * to track the state. static allocation is not an
  88          * option since that might not be contiguous in real
  89          * storage in case of a modular build */
  90         static char *ebc_cmd;
  91         size_t len;
  92         int ret;
  93         unsigned int func;
  94
  95         ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
  96         if (!ebc_cmd)
  97                 return -ENOMEM;
  98
  99         len = strlcpy(ebc_cmd, vmwdt_cmd, MAX_CMDLEN);
 100         ASCEBC(ebc_cmd, MAX_CMDLEN);
 101         EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
 102
 103         func = vmwdt_conceal ? (wdt_init | wdt_conceal) : wdt_init;
 104         set_bit(VMWDT_RUNNING, &vmwdt_is_open);
 105         ret = __diag288(func, vmwdt_interval, ebc_cmd, len);
 106         WARN_ON(ret != 0);
 107         kfree(ebc_cmd);
 108         return ret;
 109 }
 110
 111 static int vmwdt_disable(void)
 112 {
 113         int ret = __diag288(wdt_cancel, 0, "", 0);
 114         WARN_ON(ret != 0);
 115         clear_bit(VMWDT_RUNNING, &vmwdt_is_open);
 116         return ret;
 117 }
 118
 119 static int __init vmwdt_probe(void)
 120 {
 121         /* there is no real way to see if the watchdog is supported,
 122          * so we try initializing it with a NOP command ("BEGIN")
 123          * that won't cause any harm even if the following disable
 124          * fails for some reason */
 125         static char __initdata ebc_begin[] = {
 126                 194, 197, 199, 201, 213
 127         };
 128         if (__diag288(wdt_init, 15, ebc_begin, sizeof(ebc_begin)) != 0)
 129                 return -EINVAL;
 130         return vmwdt_disable();
 131 }
 132
 133 static int vmwdt_open(struct inode *i, struct file *f)
 134 {
 135         int ret;
 136         lock_kernel();
 137         if (test_and_set_bit(VMWDT_OPEN, &vmwdt_is_open)) {
 138                 unlock_kernel();
 139                 return -EBUSY;
 140         }
 141         ret = vmwdt_keepalive();
 142         if (ret)
 143                 clear_bit(VMWDT_OPEN, &vmwdt_is_open);
 144         unlock_kernel();
 145         return ret ? ret : nonseekable_open(i, f);
 146 }
 147
 148 static int vmwdt_close(struct inode *i, struct file *f)
 149 {
 150         if (vmwdt_expect_close == 42)
 151                 vmwdt_disable();
 152         vmwdt_expect_close = 0;
 153         clear_bit(VMWDT_OPEN, &vmwdt_is_open);
 154         return 0;
 155 }
 156
 157 static struct watchdog_info vmwdt_info = {
 158         .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
 159         .firmware_version = 0,
 160         .identity = "z/VM Watchdog Timer",
 161 };
 162
 163 static int vmwdt_ioctl(struct inode *i, struct file *f,
 164                           unsigned int cmd, unsigned long arg)
 165 {
 166         switch (cmd) {
 167         case WDIOC_GETSUPPORT:
 168                 if (copy_to_user((void __user *)arg, &vmwdt_info,
 169                                         sizeof(vmwdt_info)))
 170                         return -EFAULT;
 171                 return 0;
 172         case WDIOC_GETSTATUS:
 173         case WDIOC_GETBOOTSTATUS:
 174                 return put_user(0, (int __user *)arg);
 175         case WDIOC_GETTEMP:
 176                 return -EINVAL;
 177         case WDIOC_SETOPTIONS:
 178                 {
 179                         int options, ret;
 180                         if (get_user(options, (int __user *)arg))
 181                                 return -EFAULT;
 182                         ret = -EINVAL;
 183                         if (options & WDIOS_DISABLECARD) {
 184                                 ret = vmwdt_disable();
 185                                 if (ret)
 186                                         return ret;
 187                         }
 188                         if (options & WDIOS_ENABLECARD) {
 189                                 ret = vmwdt_keepalive();
 190                         }
 191                         return ret;
 192                 }
 193         case WDIOC_GETTIMEOUT:
 194                 return put_user(vmwdt_interval, (int __user *)arg);
 195         case WDIOC_SETTIMEOUT:
 196                 {
 197                         int interval;
 198                         if (get_user(interval, (int __user *)arg))
 199                                 return -EFAULT;
 200                         if (interval < MIN_INTERVAL)
 201                                 return -EINVAL;
 202                         vmwdt_interval = interval;
 203                 }
 204                 return vmwdt_keepalive();
 205         case WDIOC_KEEPALIVE:
 206                 return vmwdt_keepalive();
 207         }
 208
 209         return -EINVAL;
 210 }
 211
 212 static ssize_t vmwdt_write(struct file *f, const char __user *buf,
 213                                 size_t count, loff_t *ppos)
 214 {
 215         if(count) {
 216                 if (!vmwdt_nowayout) {
 217                         size_t i;
 218
 219                         /* note: just in case someone wrote the magic character
 220                          * five months ago... */
 221                         vmwdt_expect_close = 0;
 222
 223                         for (i = 0; i != count; i++) {
 224                                 char c;
 225                                 if (get_user(c, buf+i))
 226                                         return -EFAULT;
 227                                 if (c == 'V')
 228                                         vmwdt_expect_close = 42;
 229                         }
 230                 }
 231                 /* someone wrote to us, we should restart timer */
 232                 vmwdt_keepalive();
 233         }
 234         return count;
 235 }
 236
 237 static int vmwdt_resume(void)
 238 {
 239         clear_bit(VMWDT_OPEN, &vmwdt_is_open);
 240         return NOTIFY_DONE;
 241 }
 242
 243 /*
 244  * It makes no sense to go into suspend while the watchdog is running.
 245  * Depending on the memory size, the watchdog might trigger, while we
 246  * are still saving the memory.
 247  * We reuse the open flag to ensure that suspend and watchdog open are
 248  * exclusive operations
 249  */
 250 static int vmwdt_suspend(void)
 251 {
 252         if (test_and_set_bit(VMWDT_OPEN, &vmwdt_is_open)) {
 253                 pr_err("The watchdog is in use. "
 254                         "This prevents hibernation or suspend.\n");
 255                 return NOTIFY_BAD;
 256         }
 257         if (test_bit(VMWDT_RUNNING, &vmwdt_is_open)) {
 258                 clear_bit(VMWDT_OPEN, &vmwdt_is_open);
 259                 pr_err("The watchdog is running. "
 260                         "This prevents hibernation or suspend.\n");
 261                 return NOTIFY_BAD;
 262         }
 263         return NOTIFY_DONE;
 264 }
 265
 266 /*
 267  * This function is called for suspend and resume.
 268  */
 269 static int vmwdt_power_event(struct notifier_block *this, unsigned long event,
 270                              void *ptr)
 271 {
 272         switch (event) {
 273         case PM_POST_HIBERNATION:
 274         case PM_POST_SUSPEND:
 275                 return vmwdt_resume();
 276         case PM_HIBERNATION_PREPARE:
 277         case PM_SUSPEND_PREPARE:
 278                 return vmwdt_suspend();
 279         default:
 280                 return NOTIFY_DONE;
 281         }
 282 }
 283
 284 static struct notifier_block vmwdt_power_notifier = {
 285         .notifier_call = vmwdt_power_event,
 286 };
 287
 288 static const struct file_operations vmwdt_fops = {
 289         .open    = &vmwdt_open,
 290         .release = &vmwdt_close,
 291         .ioctl   = &vmwdt_ioctl,
 292         .write   = &vmwdt_write,
 293         .owner   = THIS_MODULE,
 294 };
 295
 296 static struct miscdevice vmwdt_dev = {
 297         .minor      = WATCHDOG_MINOR,
 298         .name       = "watchdog",
 299         .fops       = &vmwdt_fops,
 300 };
 301
 302 static int __init vmwdt_init(void)
 303 {
 304         int ret;
 305
 306         ret = vmwdt_probe();
 307         if (ret)
 308                 return ret;
 309         ret = register_pm_notifier(&vmwdt_power_notifier);
 310         if (ret)
 311                 return ret;
 312         ret = misc_register(&vmwdt_dev);
 313         if (ret) {
 314                 unregister_pm_notifier(&vmwdt_power_notifier);
 315                 return ret;
 316         }
 317         return 0;
 318 }
 319 module_init(vmwdt_init);
 320
 321 static void __exit vmwdt_exit(void)
 322 {
 323         unregister_pm_notifier(&vmwdt_power_notifier);
 324         misc_deregister(&vmwdt_dev);
 325 }
 326 module_exit(vmwdt_exit);