mmap.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <sys/types.h>
#include <sys/mman.h>

int
main(int argc, char *argv[])
{
	void *addr;

	addr = mmap(NULL, getpagesize(),
	    PROT_MAX(PROT_READ|PROT_WRITE|PROT_EXEC) | PROT_READ |
	    PROT_WRITE, MAP_ANONYMOUS | MAP_SHARED, -1, 0);

	printf("addr: 0x%016lx\n", (unsigned long)addr);

	if (mprotect(addr, getpagesize(), PROT_READ|PROT_EXEC))
		perror("mprotect");

	while (printf("%d\n", getpid()))
		sleep(5);


	return (0);
}