#include <string.h>
#include <unistd.h>
#include <sys/mman.h>
int
main(void)
{
const size_t page_len = sysconf(_SC_PAGESIZE);
const size_t tail_len = 257;
if (tail_len >= page_len)
return 77;
void *p = mmap(NULL, page_len * 2, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (p == MAP_FAILED || mprotect(p + page_len, page_len, PROT_NONE))
return 77;
memset(p, 0, page_len);
char *addr = p + page_len - tail_len;
memset(addr, '/', tail_len - 1);
if (chdir(addr))
return 77;
return 0;
}