/*
* Watchdog implementation based on z/VM Watchdog Timer API
*
* The user space watchdog daemon can use this driver as
* /dev/vmwatchdog to have z/VM execute the specified CP
* command when the timeout expires. The default command is
* "IPL", which which cause an immediate reboot.
*/
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/watchdog.h>
#include <linux/smp_lock.h>
#include <asm/ebcdic.h>
#include <asm/io.h>
#include <asm/uaccess.h>
#define MAX_CMDLEN 240
#define MIN_INTERVAL 15
static char vmwdt_cmd[MAX_CMDLEN] = "IPL";
static int vmwdt_conceal;
static int vmwdt_nowayout = WATCHDOG_NOWAYOUT;
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Arnd Bergmann <arndb@de.ibm.com>");
MODULE_DESCRIPTION("z/VM Watchdog Timer");
module_param_string(cmd, vmwdt_cmd, MAX_CMDLEN, 0644);
MODULE_PARM_DESC(cmd, "CP command that is run when the watchdog triggers");
module_param_named(conceal, vmwdt_conceal, bool, 0644);
MODULE_PARM_DESC(conceal, "Enable the CONCEAL CP option while the watchdog "
" is active");
module_param_named(nowayout, vmwdt_nowayout, bool, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started"
" (default=CONFIG_WATCHDOG_NOWAYOUT)");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
static unsigned int vmwdt_interval = 60;
static unsigned long vmwdt_is_open;
static int vmwdt_expect_close;
enum vmwdt_func {
/* function codes */
wdt_init = 0,
wdt_change = 1,
wdt_cancel = 2,
/* flags */
wdt_conceal = 0x80000000,
};
static int __diag288(enum vmwdt_func func, unsigned int timeout,
char *cmd, size_t len)
{
register unsigned long __func asm("2") = func;
register unsigned long __timeout asm("3") = timeout;
register unsigned long __cmdp asm("4") = virt_to_phys(cmd);
register unsigned long __cmdl asm("5") = len;
int err;
err = -EINVAL;
asm volatile(
" diag %1,%3,0x288\n"
"0: la %0,0\n"
"1:\n"
EX_TABLE(0b,1b)
: "+d" (err) : "d"(__func), "d"(__timeout),
"d"(__cmdp), "d"(__cmdl) : "1", "cc");
return err;
}
static int vmwdt_keepalive(void)
{
/* we allocate new memory every time to avoid having
* to track the state. static allocation is not an
* option since that might not be contiguous in real
* storage in case of a modular build */
static char *ebc_cmd;
size_t len;
int ret;
unsigned int func;
ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
if (!ebc_cmd)
return -ENOMEM;
len = strlcpy(ebc_cmd, vmwdt_cmd, MAX_CMDLEN);
ASCEBC(ebc_cmd, MAX_CMDLEN);
EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
func = vmwdt_conceal ? (wdt_init | wdt_conceal) : wdt_init;
ret = __diag288(func, vmwdt_interval, ebc_cmd, len);
WARN_ON(ret != 0);
kfree(ebc_cmd);
return ret;
}
static int vmwdt_disable(void)
{
int ret = __diag288(wdt_cancel, 0, "", 0);
WARN_ON(ret != 0);
return ret;
}
static int __init vmwdt_probe(void)
{
/* there is no real way to see if the watchdog is supported,
* so we try initializing it with a NOP command ("BEGIN")
* that won't cause any harm even if the following disable
* fails for some reason */
static char __initdata ebc_begin[] = {
194, 197, 199, 201, 213
};
if (__diag288(wdt_init, 15, ebc_begin, sizeof(ebc_begin)) != 0)
return -EINVAL;
return vmwdt_disable();
}
static int vmwdt_open(struct inode *i, struct file *f)
{
int ret;
lock_kernel();
if (test_and_set_bit(0, &vmwdt_is_open)) {
unlock_kernel();
return -EBUSY;
}
ret = vmwdt_keepalive();
if (ret)
clear_bit(0, &vmwdt_is_open);
unlock_kernel();
return ret ? ret : nonseekable_open(i, f);
}
static int vmwdt_close(struct inode *i, struct file *f)
{
if (vmwdt_expect_close == 42)
vmwdt_disable();
vmwdt_expect_close = 0;
clear_bit(0, &vmwdt_is_open);
return 0;
}
static struct watchdog_info vmwdt_info = {
.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
.firmware_version = 0,
.identity = "z/VM Watchdog Timer",
};
static int vmwdt_ioctl(struct inode *i, struct file *f,
unsigned int cmd, unsigned long arg)
{
switch (cmd) {
case WDIOC_GETSUPPORT:
if (copy_to_user((void __user *)arg, &vmwdt_info,
sizeof(vmwdt_info)))
return -EFAULT;
return 0;
case WDIOC_GETSTATUS:
case WDIOC_GETBOOTSTATUS:
return put_user(0, (int __user *)arg);
case WDIOC_GETTEMP:
return -EINVAL;
case WDIOC_SETOPTIONS:
{
int options, ret;
if (get_user(options, (int __user *)arg))
return -EFAULT;
ret = -EINVAL;
if (options & WDIOS_DISABLECARD) {
ret = vmwdt_disable();
if (ret)
return ret;
}
if (options & WDIOS_ENABLECARD) {
ret = vmwdt_keepalive();
}
return ret;
}
case WDIOC_GETTIMEOUT:
return put_user(vmwdt_interval, (int __user *)arg);
case WDIOC_SETTIMEOUT:
{
int interval;
if (get_user(interval, (int __user *)arg))
return -EFAULT;
if (interval < MIN_INTERVAL)
return -EINVAL;
vmwdt_interval = interval;
}
return vmwdt_keepalive();
case WDIOC_KEEPALIVE:
return vmwdt_keepalive();
}
return -EINVAL;
}
static ssize_t vmwdt_write(struct file *f, const char __user *buf,
size_t count, loff_t *ppos)
{
if(count) {
if (!vmwdt_nowayout) {
size_t i;
/* note: just in case someone wrote the magic character
* five months ago... */
vmwdt_expect_close = 0;
for (i = 0; i != count; i++) {
char c;
if (get_user(c, buf+i))
return -EFAULT;
if (c == 'V')
vmwdt_expect_close = 42;
}
}
/* someone wrote to us, we should restart timer */
vmwdt_keepalive();
}
return count;
}
static const struct file_operations vmwdt_fops = {
.open = &vmwdt_open,
.release = &vmwdt_close,
.ioctl = &vmwdt_ioctl,
.write = &vmwdt_write,
.owner = THIS_MODULE,
};
static struct miscdevice vmwdt_dev = {
.minor = WATCHDOG_MINOR,
.name = "watchdog",
.fops = &vmwdt_fops,
};
static int __init vmwdt_init(void)
{
int ret;
ret = vmwdt_probe();
if (ret)
return ret;
return misc_register(&vmwdt_dev);
}
module_init(vmwdt_init);
static void __exit vmwdt_exit(void)
{
WARN_ON(misc_deregister(&vmwdt_dev) != 0);
}
module_exit(vmwdt_exit);
