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/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
  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
  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
 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
 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
 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
 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
 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
 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
 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
 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  */
 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  */
 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
 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
 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);