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         char cmd[] = {'\0'};
 116         int ret = __diag288(wdt_cancel, 0, cmd, 0);
 117         WARN_ON(ret != 0);
 118         clear_bit(VMWDT_RUNNING, &vmwdt_is_open);
 119         return ret;
 120 }
 121
 122 static int __init vmwdt_probe(void)
 123 {
 124         /* there is no real way to see if the watchdog is supported,
 125          * so we try initializing it with a NOP command ("BEGIN")
 126          * that won't cause any harm even if the following disable
 127          * fails for some reason */
 128         char ebc_begin[] = {
 129                 194, 197, 199, 201, 213
 130         };
 131         if (__diag288(wdt_init, 15, ebc_begin, sizeof(ebc_begin)) != 0)
 132                 return -EINVAL;
 133         return vmwdt_disable();
 134 }
 135
 136 static int vmwdt_open(struct inode *i, struct file *f)
 137 {
 138         int ret;
 139         if (test_and_set_bit(VMWDT_OPEN, &vmwdt_is_open))
 140                 return -EBUSY;
 141         ret = vmwdt_keepalive();
 142         if (ret)
 143                 clear_bit(VMWDT_OPEN, &vmwdt_is_open);
 144         return ret ? ret : nonseekable_open(i, f);
 145 }
 146
 147 static int vmwdt_close(struct inode *i, struct file *f)
 148 {
 149         if (vmwdt_expect_close == 42)
 150                 vmwdt_disable();
 151         vmwdt_expect_close = 0;
 152         clear_bit(VMWDT_OPEN, &vmwdt_is_open);
 153         return 0;
 154 }
 155
 156 static struct watchdog_info vmwdt_info = {
 157         .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
 158         .firmware_version = 0,
 159         .identity = "z/VM Watchdog Timer",
 160 };
 161
 162 static int __vmwdt_ioctl(unsigned int cmd, unsigned long arg)
 163 {
 164         switch (cmd) {
 165         case WDIOC_GETSUPPORT:
 166                 if (copy_to_user((void __user *)arg, &vmwdt_info,
 167                                         sizeof(vmwdt_info)))
 168                         return -EFAULT;
 169                 return 0;
 170         case WDIOC_GETSTATUS:
 171         case WDIOC_GETBOOTSTATUS:
 172                 return put_user(0, (int __user *)arg);
 173         case WDIOC_GETTEMP:
 174                 return -EINVAL;
 175         case WDIOC_SETOPTIONS:
 176                 {
 177                         int options, ret;
 178                         if (get_user(options, (int __user *)arg))
 179                                 return -EFAULT;
 180                         ret = -EINVAL;
 181                         if (options & WDIOS_DISABLECARD) {
 182                                 ret = vmwdt_disable();
 183                                 if (ret)
 184                                         return ret;
 185                         }
 186                         if (options & WDIOS_ENABLECARD) {
 187                                 ret = vmwdt_keepalive();
 188                         }
 189                         return ret;
 190                 }
 191         case WDIOC_GETTIMEOUT:
 192                 return put_user(vmwdt_interval, (int __user *)arg);
 193         case WDIOC_SETTIMEOUT:
 194                 {
 195                         int interval;
 196                         if (get_user(interval, (int __user *)arg))
 197                                 return -EFAULT;
 198                         if (interval < MIN_INTERVAL)
 199                                 return -EINVAL;
 200                         vmwdt_interval = interval;
 201                 }
 202                 return vmwdt_keepalive();
 203         case WDIOC_KEEPALIVE:
 204                 return vmwdt_keepalive();
 205         }
 206         return -EINVAL;
 207 }
 208
 209 static long vmwdt_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
 210 {
 211         int rc;
 212
 213         mutex_lock(&vmwdt_mutex);
 214         rc = __vmwdt_ioctl(cmd, arg);
 215         mutex_unlock(&vmwdt_mutex);
 216         return (long) rc;
 217 }
 218
 219 static ssize_t vmwdt_write(struct file *f, const char __user *buf,
 220                                 size_t count, loff_t *ppos)
 221 {
 222         if(count) {
 223                 if (!vmwdt_nowayout) {
 224                         size_t i;
 225
 226                         /* note: just in case someone wrote the magic character
 227                          * five months ago... */
 228                         vmwdt_expect_close = 0;
 229
 230                         for (i = 0; i != count; i++) {
 231                                 char c;
 232                                 if (get_user(c, buf+i))
 233                                         return -EFAULT;
 234                                 if (c == 'V')
 235                                         vmwdt_expect_close = 42;
 236                         }
 237                 }
 238                 /* someone wrote to us, we should restart timer */
 239                 vmwdt_keepalive();
 240         }
 241         return count;
 242 }
 243
 244 static int vmwdt_resume(void)
 245 {
 246         clear_bit(VMWDT_OPEN, &vmwdt_is_open);
 247         return NOTIFY_DONE;
 248 }
 249
 250 /*
 251  * It makes no sense to go into suspend while the watchdog is running.
 252  * Depending on the memory size, the watchdog might trigger, while we
 253  * are still saving the memory.
 254  * We reuse the open flag to ensure that suspend and watchdog open are
 255  * exclusive operations
 256  */
 257 static int vmwdt_suspend(void)
 258 {
 259         if (test_and_set_bit(VMWDT_OPEN, &vmwdt_is_open)) {
 260                 pr_err("The system cannot be suspended while the watchdog"
 261                         " is in use\n");
 262                 return notifier_from_errno(-EBUSY);
 263         }
 264         if (test_bit(VMWDT_RUNNING, &vmwdt_is_open)) {
 265                 clear_bit(VMWDT_OPEN, &vmwdt_is_open);
 266                 pr_err("The system cannot be suspended while the watchdog"
 267                         " is running\n");
 268                 return notifier_from_errno(-EBUSY);
 269         }
 270         return NOTIFY_DONE;
 271 }
 272
 273 /*
 274  * This function is called for suspend and resume.
 275  */
 276 static int vmwdt_power_event(struct notifier_block *this, unsigned long event,
 277                              void *ptr)
 278 {
 279         switch (event) {
 280         case PM_POST_HIBERNATION:
 281         case PM_POST_SUSPEND:
 282                 return vmwdt_resume();
 283         case PM_HIBERNATION_PREPARE:
 284         case PM_SUSPEND_PREPARE:
 285                 return vmwdt_suspend();
 286         default:
 287                 return NOTIFY_DONE;
 288         }
 289 }
 290
 291 static struct notifier_block vmwdt_power_notifier = {
 292         .notifier_call = vmwdt_power_event,
 293 };
 294
 295 static const struct file_operations vmwdt_fops = {
 296         .open    = &vmwdt_open,
 297         .release = &vmwdt_close,
 298         .unlocked_ioctl = &vmwdt_ioctl,
 299         .write   = &vmwdt_write,
 300         .owner   = THIS_MODULE,
 301         .llseek  = noop_llseek,
 302 };
 303
 304 static struct miscdevice vmwdt_dev = {
 305         .minor      = WATCHDOG_MINOR,
 306         .name       = "watchdog",
 307         .fops       = &vmwdt_fops,
 308 };
 309
 310 static int __init vmwdt_init(void)
 311 {
 312         int ret;
 313
 314         ret = vmwdt_probe();
 315         if (ret)
 316                 return ret;
 317         ret = register_pm_notifier(&vmwdt_power_notifier);
 318         if (ret)
 319                 return ret;
 320         /*
 321          * misc_register() has to be the last action in module_init(), because
 322          * file operations will be available right after this.
 323          */
 324         ret = misc_register(&vmwdt_dev);
 325         if (ret) {
 326                 unregister_pm_notifier(&vmwdt_power_notifier);
 327                 return ret;
 328         }
 329         return 0;
 330 }
 331 module_init(vmwdt_init);
 332
 333 static void __exit vmwdt_exit(void)
 334 {
 335         unregister_pm_notifier(&vmwdt_power_notifier);
 336         misc_deregister(&vmwdt_dev);
 337 }
 338 module_exit(vmwdt_exit);