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