/*
 * A test program to reveal a system has virtual cache aliasing problem.
 *
 * It does mmap() a file and write some stuff to the file
 * Immediately it will read the file through read() and try to verify
 * the written data.
 *
 * Normally it should succeed.  But on a badly implemented system
 * (such as MIPS as of 2003/10/14), it shows up on quite a few boards.
 */

#include <unistd.h>
#include <sys/mman.h>
#include <assert.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#define	TEST_FNAME 	"test.data"
#define TEST_SIZE	1000000

#if 0
#define WRITE_START	0xcf375		/* 848757 */
#define WRITE_SIZE	4536
#endif

#define	PATTERN		"shittystuff"
#define PATTERN_SIZE	(sizeof(PATTERN) -1 )

void create_file()
{
	int ret;
	int fd = open(TEST_FNAME, O_RDWR | O_CREAT, S_IRWXU);
	// printf("fd = %d\n",fd );
	assert(fd > 0);
	lseek(fd, TEST_SIZE-1, SEEK_SET);
	ret=write(fd, "c", 1);
	assert(ret == 1);
	close(fd);
}

char buf[102400];
void check_write(int WRITE_START, int WRITE_SIZE)
{
	int fd, ret;
	int size;
	char * dst;

	fd = open(TEST_FNAME, O_RDONLY);
	assert(fd > 0);
	lseek(fd, WRITE_START, SEEK_SET);
	ret = read(fd, buf, WRITE_SIZE);
	assert(ret == WRITE_SIZE);

	for(size=0, dst = buf; size < WRITE_SIZE; ) {
		int s = PATTERN_SIZE;
		if (size + s > WRITE_SIZE)
			s = WRITE_SIZE - size;
		if (strncmp(dst, PATTERN, s) != 0) {
			printf("differ!\n");
		}
		size += s;
		dst += s;
	}

	close(fd);
}

void do_mmap_write(int WRITE_START, int WRITE_SIZE)
{
	int fd;
	char * addr;
	char *dst;
	int size;
	int ret;

	fd = open(TEST_FNAME, O_RDWR);
	// printf("fd = %d\n", fd);
	assert(fd > 0);

	addr = mmap(NULL, TEST_SIZE, PROT_WRITE|PROT_READ, MAP_SHARED, fd, 0);
	// printf("file mapped at %p\n", addr);

	for (size=0, dst = addr + WRITE_START; size < WRITE_SIZE; ) {
		int s = PATTERN_SIZE;
		if (size + s > WRITE_SIZE)
			s = WRITE_SIZE - size;
		memcpy(dst, PATTERN, s);
		size += s;
		dst += s;
	}

	// check
	// msync(addr, TEST_SIZE, MS_SYNC);
	check_write(WRITE_START, WRITE_SIZE);

	// clean up
	ret = munmap(addr, TEST_SIZE);
	close(fd);
	assert(ret == 0);
}


void gen_params(int *start, int *size)
{
	/* size is between 4096 and 8192 */
	*size = random() % 4096 + 4096;
	*start = random() % (TEST_SIZE - *size - 1);
	// printf("start = %d, size = %d\n", *start, *size);

	assert(*size >= 4096);
	assert(*size <= 8192);
	assert(*start > 0);
	assert(*start + *size < TEST_SIZE);

}
main()
{
	create_file();
	for(;;) {
		int write_start, write_size;
		gen_params(&write_start, &write_size);
		do_mmap_write(write_start, write_size);
		// check_write(write_start, write_size);
	}
}