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/*
* wdd - simple watchdog daemon - 2003-2004 - willy tarreau
*/
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
const char dev_wd_str[] = "/dev/watchdog"; /* standard entry */
const char dev_misc_str[] = "/dev/misc/watchdog"; /* devfs entry */
const char root_str[] = "/";
/*
* This function checks if the system can allocate memory
* In case of failure, we exit so that the watchdog device
* notices it and can reboot.
*/
static inline void try_malloc() {
void *heap;
heap = (void*)sbrk(NULL);
if (brk(heap + 4096))
exit(1);
memset(heap, 0, 4096);
if (brk(heap))
exit(1);
}
/*
* This function checks if the system can fork
* In case of failure, we exit so that the watchdog device
* notices it and can reboot.
*/
static inline void try_fork() {
int pid;
pid = fork();
if (pid < 0) /* exit on error */
exit(1);
else if (pid == 0) /* child returns cleanly */
exit(0);
if (waitpid(pid, NULL, 0) != pid) /* father checks child */
exit(1);
}
/*
* This function checks if the system can stat a given directory entry on the
* VFS. In case of failure, we either report the problem, or exit so that the
* watchdog device notices it and can reboot.
*/
static inline int try_stat(const char *file, int do_exit) {
void *heap;
int ret;
heap = (void*)sbrk(NULL);
if (brk(heap + sizeof (struct stat)))
exit(1);
memset(heap, 0, sizeof (struct stat));
ret = stat(file, heap);
if (brk(heap))
exit(1);
if (ret == -1) {
if (do_exit)
exit(1);
else
return 0;
}
return 1;
}
int main (int argc, char **argv) {
int dev;
int curr_file;
if (argc > 1) {
/* we'll do a quick check on all the arguments to
* ensure that they are valid at load time, and avoid
* an accidental start of the watchdog which could be
* a disaster in case of a file name error.
*/
for (curr_file = 1; curr_file < argc; ) {
if (try_stat(argv[curr_file], 0))
curr_file++;
else {
/* remove this file from the list, and make it noticeable from 'ps' */
*argv[curr_file] = '!';
argv[curr_file] = argv[--argc];
}
}
}
if (fork() > 0)
return 0;
for (dev = 2; dev >= 0; dev--)
close(dev);
chdir(root_str);
setsid();
curr_file = 1; /* start with first file in the list */
/* let's try indefinitely to open the watchdog device */
/* note that dev is -1 now ;-) */
while (1) {
if (dev == -1)
dev = open(dev_wd_str, O_RDWR);
if (dev == -1)
dev = open(dev_misc_str, O_RDWR);
if ((dev != -1) && (write(dev, dev_wd_str, 1) != 1)) {
/* write error, we'll restart */
close(dev);
dev = -1;
}
try_malloc();
try_fork();
if (argc > 1) {
try_stat(argv[curr_file], 1);
curr_file++;
if (curr_file >= argc)
curr_file = 1;
} else {
try_stat(root_str, 1);
}
/* avoid a fast loop */
sleep(1);
}
/* we never get there theorically... */
return 0;
}
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