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") = func;
  58         register unsigned long __timeout asm("3") = timeout;
  59         register unsigned long __cmdp asm("4") = virt_to_phys(cmd);
  60         register unsigned long __cmdl asm("5") = len;
  61         int err;
  62
  63         err = -EINVAL;
  64         asm volatile(
  65                 "       diag    %1,%3,0x288\n"
  66                 "0:     la      %0,0\n"
  67                 "1:\n"
  68                 EX_TABLE(0b,1b)
  69                 : "+d" (err) : "d"(__func), "d"(__timeout),
  70                   "d"(__cmdp), "d"(__cmdl) : "1", "cc");
  71         return err;
  72 }
  73
  74 static int vmwdt_keepalive(void)
  75 {
  76         /* we allocate new memory every time to avoid having
  77          * to track the state. static allocation is not an
  78          * option since that might not be contiguous in real
  79          * storage in case of a modular build */
  80         static char *ebc_cmd;
  81         size_t len;
  82         int ret;
  83         unsigned int func;
  84
  85         ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
  86         if (!ebc_cmd)
  87                 return -ENOMEM;
  88
  89         len = strlcpy(ebc_cmd, vmwdt_cmd, MAX_CMDLEN);
  90         ASCEBC(ebc_cmd, MAX_CMDLEN);
  91         EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
  92
  93         func = vmwdt_conceal ? (wdt_init | wdt_conceal) : wdt_init;
  94         ret = __diag288(func, vmwdt_interval, ebc_cmd, len);
  95         WARN_ON(ret != 0);
  96         kfree(ebc_cmd);
  97         return ret;
  98 }
  99
 100 static int vmwdt_disable(void)
 101 {
 102         int ret = __diag288(wdt_cancel, 0, "", 0);
 103         WARN_ON(ret != 0);
 104         return ret;
 105 }
 106
 107 static int __init vmwdt_probe(void)
 108 {
 109         /* there is no real way to see if the watchdog is supported,
 110          * so we try initializing it with a NOP command ("BEGIN")
 111          * that won't cause any harm even if the following disable
 112          * fails for some reason */
 113         static char __initdata ebc_begin[] = {
 114                 194, 197, 199, 201, 213
 115         };
 116         if (__diag288(wdt_init, 15, ebc_begin, sizeof(ebc_begin)) != 0)
 117                 return -EINVAL;
 118         return vmwdt_disable();
 119 }
 120
 121 static int vmwdt_open(struct inode *i, struct file *f)
 122 {
 123         int ret;
 124         if (test_and_set_bit(0, &vmwdt_is_open))
 125                 return -EBUSY;
 126         ret = vmwdt_keepalive();
 127         if (ret)
 128                 clear_bit(0, &vmwdt_is_open);
 129         return ret ? ret : nonseekable_open(i, f);
 130 }
 131
 132 static int vmwdt_close(struct inode *i, struct file *f)
 133 {
 134         if (vmwdt_expect_close == 42)
 135                 vmwdt_disable();
 136         vmwdt_expect_close = 0;
 137         clear_bit(0, &vmwdt_is_open);
 138         return 0;
 139 }
 140
 141 static struct watchdog_info vmwdt_info = {
 142         .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
 143         .firmware_version = 0,
 144         .identity = "z/VM Watchdog Timer",
 145 };
 146
 147 static int vmwdt_ioctl(struct inode *i, struct file *f,
 148                           unsigned int cmd, unsigned long arg)
 149 {
 150         switch (cmd) {
 151         case WDIOC_GETSUPPORT:
 152                 if (copy_to_user((void __user *)arg, &vmwdt_info,
 153                                         sizeof(vmwdt_info)))
 154                         return -EFAULT;
 155                 return 0;
 156         case WDIOC_GETSTATUS:
 157         case WDIOC_GETBOOTSTATUS:
 158                 return put_user(0, (int __user *)arg);
 159         case WDIOC_GETTEMP:
 160                 return -EINVAL;
 161         case WDIOC_SETOPTIONS:
 162                 {
 163                         int options, ret;
 164                         if (get_user(options, (int __user *)arg))
 165                                 return -EFAULT;
 166                         ret = -EINVAL;
 167                         if (options & WDIOS_DISABLECARD) {
 168                                 ret = vmwdt_disable();
 169                                 if (ret)
 170                                         return ret;
 171                         }
 172                         if (options & WDIOS_ENABLECARD) {
 173                                 ret = vmwdt_keepalive();
 174                         }
 175                         return ret;
 176                 }
 177         case WDIOC_GETTIMEOUT:
 178                 return put_user(vmwdt_interval, (int __user *)arg);
 179         case WDIOC_SETTIMEOUT:
 180                 {
 181                         int interval;
 182                         if (get_user(interval, (int __user *)arg))
 183                                 return -EFAULT;
 184                         if (interval < MIN_INTERVAL)
 185                                 return -EINVAL;
 186                         vmwdt_interval = interval;
 187                 }
 188                 return vmwdt_keepalive();
 189         case WDIOC_KEEPALIVE:
 190                 return vmwdt_keepalive();
 191         }
 192
 193         return -EINVAL;
 194 }
 195
 196 static ssize_t vmwdt_write(struct file *f, const char __user *buf,
 197                                 size_t count, loff_t *ppos)
 198 {
 199         if(count) {
 200                 if (!vmwdt_nowayout) {
 201                         size_t i;
 202
 203                         /* note: just in case someone wrote the magic character
 204                          * five months ago... */
 205                         vmwdt_expect_close = 0;
 206
 207                         for (i = 0; i != count; i++) {
 208                                 char c;
 209                                 if (get_user(c, buf+i))
 210                                         return -EFAULT;
 211                                 if (c == 'V')
 212                                         vmwdt_expect_close = 42;
 213                         }
 214                 }
 215                 /* someone wrote to us, we should restart timer */
 216                 vmwdt_keepalive();
 217         }
 218         return count;
 219 }
 220
 221 static const struct file_operations vmwdt_fops = {
 222         .open    = &vmwdt_open,
 223         .release = &vmwdt_close,
 224         .ioctl   = &vmwdt_ioctl,
 225         .write   = &vmwdt_write,
 226         .owner   = THIS_MODULE,
 227 };
 228
 229 static struct miscdevice vmwdt_dev = {
 230         .minor      = WATCHDOG_MINOR,
 231         .name       = "watchdog",
 232         .fops       = &vmwdt_fops,
 233 };
 234
 235 static int __init vmwdt_init(void)
 236 {
 237         int ret;
 238
 239         ret = vmwdt_probe();
 240         if (ret)
 241                 return ret;
 242         return misc_register(&vmwdt_dev);
 243 }
 244 module_init(vmwdt_init);
 245
 246 static void __exit vmwdt_exit(void)
 247 {
 248         WARN_ON(misc_deregister(&vmwdt_dev) != 0);
 249 }
 250 module_exit(vmwdt_exit);