プログラムのソース

#define handle_error(msg) \
do { perror(msg); exit(EXIT_FAILURE); } while (0)

char *buffer;

static void
handler(int sig, siginfo_t *si, void *unused)
{
printf("Got SIGSEGV at address: 0x%lx\n",
(long) si->si_addr);
exit(EXIT_FAILURE);
}

int
main(void)
{
char *p;
int pagesize;
struct sigaction sa;

sa.sa_flags = SA_SIGINFO;
sigemptyset(&sa.sa_mask);
sa.sa_sigaction = handler;
if (sigaction(SIGSEGV, &sa, NULL) == -1)
handle_error("sigaction");

pagesize = sysconf(_SC_PAGE_SIZE);
if (pagesize == -1)
handle_error("sysconf");

/* Allocate a buffer aligned on a page boundary;
initial protection is PROT_READ | PROT_WRITE */

buffer = memalign(pagesize, 4 * pagesize);
if (buffer == NULL)
handle_error("memalign");

printf("Start of region: 0x%lx\n", (long) buffer);

if (mprotect(buffer + pagesize * 2, pagesize,
PROT_READ) == -1)
handle_error("mprotect");

for (p = buffer ; ; )
*(p++) = 'a';

printf("Loop completed\n"); /* Should never happen */
exit(EXIT_SUCCESS);
}