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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";
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 access its root FS
* In case of failure, we exit so that the watchdog device
* notices it and can reboot.
*/
static inline void try_stat() {
void *heap;
heap = (void*)sbrk(NULL);
if (brk(heap + sizeof (struct stat)))
exit(1);
memset(heap, 0, sizeof (struct stat));
if (stat(root_str, heap) == -1)
exit(1);
if (brk(heap))
exit(1);
}
int main (void) {
int dev;
if (fork() > 0)
return 0;
for (dev = 2; dev >= 0; dev--)
close(dev);
chdir(root_str);
setsid();
/* 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) && (write(dev, dev_wd_str, 1) != 1)) {
/* write error, we'll restart */
close(dev);
dev = -1;
}
try_malloc();
try_fork();
try_stat();
/* avoid a fast loop */
sleep(1);
}
/* we never get there theorically... */
return 0;
}
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