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 #include <linux/smp_lock.h>
  17
  18 #include <asm/ebcdic.h>
  19 #include <asm/io.h>
  20 #include <asm/uaccess.h>
  21
  22 #define MAX_CMDLEN 240
  23 #define MIN_INTERVAL 15
  24 static char vmwdt_cmd[MAX_CMDLEN] = "IPL";
  25 static int vmwdt_conceal;
  26
  27 static int vmwdt_nowayout = WATCHDOG_NOWAYOUT;
  28
  29 MODULE_LICENSE("GPL");
  30 MODULE_AUTHOR("Arnd Bergmann <arndb@de.ibm.com>");
  31 MODULE_DESCRIPTION("z/VM Watchdog Timer");
  32 module_param_string(cmd, vmwdt_cmd, MAX_CMDLEN, 0644);
  33 MODULE_PARM_DESC(cmd, "CP command that is run when the watchdog triggers");
  34 module_param_named(conceal, vmwdt_conceal, bool, 0644);
  35 MODULE_PARM_DESC(conceal, "Enable the CONCEAL CP option while the watchdog "
  36                 " is active");
  37 module_param_named(nowayout, vmwdt_nowayout, bool, 0);
  38 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started"
  39                 " (default=CONFIG_WATCHDOG_NOWAYOUT)");
  40 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
  41
  42 static unsigned int vmwdt_interval = 60;
  43 static unsigned long vmwdt_is_open;
  44 static int vmwdt_expect_close;
  45
  46 enum vmwdt_func {
  47         /* function codes */
  48         wdt_init   = 0,
  49         wdt_change = 1,
  50         wdt_cancel = 2,
  51         /* flags */
  52         wdt_conceal = 0x80000000,
  53 };
  54
  55 static int __diag288(enum vmwdt_func func, unsigned int timeout,
  56                             char *cmd, size_t len)
  57 {
  58         register unsigned long __func asm("2") = func;
  59         register unsigned long __timeout asm("3") = timeout;
  60         register unsigned long __cmdp asm("4") = virt_to_phys(cmd);
  61         register unsigned long __cmdl asm("5") = len;
  62         int err;
  63
  64         err = -EINVAL;
  65         asm volatile(
  66                 "       diag    %1,%3,0x288\n"
  67                 "0:     la      %0,0\n"
  68                 "1:\n"
  69                 EX_TABLE(0b,1b)
  70                 : "+d" (err) : "d"(__func), "d"(__timeout),
  71                   "d"(__cmdp), "d"(__cmdl) : "1", "cc");
  72         return err;
  73 }
  74
  75 static int vmwdt_keepalive(void)
  76 {
  77         /* we allocate new memory every time to avoid having
  78          * to track the state. static allocation is not an
  79          * option since that might not be contiguous in real
  80          * storage in case of a modular build */
  81         static char *ebc_cmd;
  82         size_t len;
  83         int ret;
  84         unsigned int func;
  85
  86         ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
  87         if (!ebc_cmd)
  88                 return -ENOMEM;
  89
  90         len = strlcpy(ebc_cmd, vmwdt_cmd, MAX_CMDLEN);
  91         ASCEBC(ebc_cmd, MAX_CMDLEN);
  92         EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
  93
  94         func = vmwdt_conceal ? (wdt_init | wdt_conceal) : wdt_init;
  95         ret = __diag288(func, vmwdt_interval, ebc_cmd, len);
  96         WARN_ON(ret != 0);
  97         kfree(ebc_cmd);
  98         return ret;
  99 }
 100
 101 static int vmwdt_disable(void)
 102 {
 103         int ret = __diag288(wdt_cancel, 0, "", 0);
 104         WARN_ON(ret != 0);
 105         return ret;
 106 }
 107
 108 static int __init vmwdt_probe(void)
 109 {
 110         /* there is no real way to see if the watchdog is supported,
 111          * so we try initializing it with a NOP command ("BEGIN")
 112          * that won't cause any harm even if the following disable
 113          * fails for some reason */
 114         static char __initdata ebc_begin[] = {
 115                 194, 197, 199, 201, 213
 116         };
 117         if (__diag288(wdt_init, 15, ebc_begin, sizeof(ebc_begin)) != 0)
 118                 return -EINVAL;
 119         return vmwdt_disable();
 120 }
 121
 122 static int vmwdt_open(struct inode *i, struct file *f)
 123 {
 124         int ret;
 125         lock_kernel();
 126         if (test_and_set_bit(0, &vmwdt_is_open)) {
 127                 unlock_kernel();
 128                 return -EBUSY;
 129         }
 130         ret = vmwdt_keepalive();
 131         if (ret)
 132                 clear_bit(0, &vmwdt_is_open);
 133         unlock_kernel();
 134         return ret ? ret : nonseekable_open(i, f);
 135 }
 136
 137 static int vmwdt_close(struct inode *i, struct file *f)
 138 {
 139         if (vmwdt_expect_close == 42)
 140                 vmwdt_disable();
 141         vmwdt_expect_close = 0;
 142         clear_bit(0, &vmwdt_is_open);
 143         return 0;
 144 }
 145
 146 static struct watchdog_info vmwdt_info = {
 147         .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
 148         .firmware_version = 0,
 149         .identity = "z/VM Watchdog Timer",
 150 };
 151
 152 static int vmwdt_ioctl(struct inode *i, struct file *f,
 153                           unsigned int cmd, unsigned long arg)
 154 {
 155         switch (cmd) {
 156         case WDIOC_GETSUPPORT:
 157                 if (copy_to_user((void __user *)arg, &vmwdt_info,
 158                                         sizeof(vmwdt_info)))
 159                         return -EFAULT;
 160                 return 0;
 161         case WDIOC_GETSTATUS:
 162         case WDIOC_GETBOOTSTATUS:
 163                 return put_user(0, (int __user *)arg);
 164         case WDIOC_GETTEMP:
 165                 return -EINVAL;
 166         case WDIOC_SETOPTIONS:
 167                 {
 168                         int options, ret;
 169                         if (get_user(options, (int __user *)arg))
 170                                 return -EFAULT;
 171                         ret = -EINVAL;
 172                         if (options & WDIOS_DISABLECARD) {
 173                                 ret = vmwdt_disable();
 174                                 if (ret)
 175                                         return ret;
 176                         }
 177                         if (options & WDIOS_ENABLECARD) {
 178                                 ret = vmwdt_keepalive();
 179                         }
 180                         return ret;
 181                 }
 182         case WDIOC_GETTIMEOUT:
 183                 return put_user(vmwdt_interval, (int __user *)arg);
 184         case WDIOC_SETTIMEOUT:
 185                 {
 186                         int interval;
 187                         if (get_user(interval, (int __user *)arg))
 188                                 return -EFAULT;
 189                         if (interval < MIN_INTERVAL)
 190                                 return -EINVAL;
 191                         vmwdt_interval = interval;
 192                 }
 193                 return vmwdt_keepalive();
 194         case WDIOC_KEEPALIVE:
 195                 return vmwdt_keepalive();
 196         }
 197
 198         return -EINVAL;
 199 }
 200
 201 static ssize_t vmwdt_write(struct file *f, const char __user *buf,
 202                                 size_t count, loff_t *ppos)
 203 {
 204         if(count) {
 205                 if (!vmwdt_nowayout) {
 206                         size_t i;
 207
 208                         /* note: just in case someone wrote the magic character
 209                          * five months ago... */
 210                         vmwdt_expect_close = 0;
 211
 212                         for (i = 0; i != count; i++) {
 213                                 char c;
 214                                 if (get_user(c, buf+i))
 215                                         return -EFAULT;
 216                                 if (c == 'V')
 217                                         vmwdt_expect_close = 42;
 218                         }
 219                 }
 220                 /* someone wrote to us, we should restart timer */
 221                 vmwdt_keepalive();
 222         }
 223         return count;
 224 }
 225
 226 static const struct file_operations vmwdt_fops = {
 227         .open    = &vmwdt_open,
 228         .release = &vmwdt_close,
 229         .ioctl   = &vmwdt_ioctl,
 230         .write   = &vmwdt_write,
 231         .owner   = THIS_MODULE,
 232 };
 233
 234 static struct miscdevice vmwdt_dev = {
 235         .minor      = WATCHDOG_MINOR,
 236         .name       = "watchdog",
 237         .fops       = &vmwdt_fops,
 238 };
 239
 240 static int __init vmwdt_init(void)
 241 {
 242         int ret;
 243
 244         ret = vmwdt_probe();
 245         if (ret)
 246                 return ret;
 247         return misc_register(&vmwdt_dev);
 248 }
 249 module_init(vmwdt_init);
 250
 251 static void __exit vmwdt_exit(void)
 252 {
 253         WARN_ON(misc_deregister(&vmwdt_dev) != 0);
 254 }
 255 module_exit(vmwdt_exit);