#include <signal.h>
#include <sys/mman.h>
#include <string.h>
+#include <unistd.h>
+unsigned long page_size;
void *guard;
void handler(int signo, siginfo_t *info, void *uctx) {
- mprotect(guard, 4096, PROT_READ | PROT_WRITE);
+ mprotect(guard, page_size, PROT_READ | PROT_WRITE);
}
int main() {
+ page_size = sysconf(_SC_PAGESIZE);
struct sigaction a, old;
memset(&a, 0, sizeof(a));
memset(&old, 0, sizeof(old));
a.sa_sigaction = handler;
a.sa_flags = SA_SIGINFO;
sigaction(SIGSEGV, &a, &old);
- guard = (char *)mmap(0, 3 * 4096, PROT_NONE, MAP_ANON | MAP_PRIVATE, -1, 0) +
- 4096;
+ guard = mmap(0, 3 * page_size, PROT_NONE, MAP_ANON | MAP_PRIVATE, -1, 0);
+ guard = (char*)guard + page_size; // work around a kernel bug
for (int i = 0; i < 1000000; i++) {
- mprotect(guard, 4096, PROT_NONE);
+ mprotect(guard, page_size, PROT_NONE);
*(int*)guard = 1;
}
sigaction(SIGSEGV, &old, 0);