#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

#define PAGE_SIZE 4096

int main(int argc, char **argv)
{
	int fd, err;
	int towrite = PAGE_SIZE;
	char *p;
	volatile char *map1, *map2;
	unsigned char b[4];

	fd = open (argc>2?argv[1]:"/tmp/testfile", O_CREAT|O_TRUNC|O_RDWR, 0644);
	if (!fd<0) {
		perror("open");
		close(fd);
		return 1;
	}
	
	p = malloc(PAGE_SIZE);
	if (!p) {
		fprintf(stderr, "malloc failed\n");
		return 2;
	}
	memset(p, 0, PAGE_SIZE);

	while(towrite) {
		err = write(fd, p, PAGE_SIZE);

		if (err < 0) {
			perror("write");
			close(fd);
			return 3;
		}
		towrite -= err;
	}

	map1 = mmap(0, PAGE_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
	if (!map1) {
		perror("mmap 1");
		close(fd);
		return 4;
	}
	/* Make sure the second mapping is _immediately_ after the first */
	map2 = mmap((void *)map1+PAGE_SIZE, PAGE_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_FIXED, fd, 0);
	if (!map2) {
		perror("mmap 2");
		munmap((void *)map1, PAGE_SIZE);
		close(fd);
		return 5;
	}
	
	printf("Mapped page twice, at 0x%08lx and 0x%08lx\n", 
	       (unsigned long)map1, (unsigned long) map2);

	/* Some arches (ARM) allocate cache lines only on read */
	(void)map1[0];
	(void)map2[0];

	map1[0] = 0x55;
	map2[1] = 0xaa;
	map1[2] = 0xa5;
	map2[3] = 0x5a;

	b[0] = map2[0];
	b[1] = map1[1];
	b[2] = map2[2];
	b[3] = map1[3];

	if (b[0] != 0x55 || b[1] != 0xaa || b[2] != 0xa5 || b[3] != 0x5a) {
		printf("Your cache is broken\n");
		return 6;
	} else {
		printf("Your cache appears to be OK\n");
	}

	munmap((void *)map1, PAGE_SIZE);
	munmap((void *)map2, PAGE_SIZE);
	close(fd);	
}