- char *data, *data2, *data3;
- int i, pagesize;
- int fd;
-
- pagesize = getpagesize();
-
- /*
- * First, make a file with some known garbage in it.
- */
- data = malloc(pagesize);
- if (!data)
- exit(1);
- for (i = 0; i < pagesize; ++i)
- *(data + i) = rand();
- umask(0);
- fd = creat("conftestmmap", 0600);
- if (fd < 0)
- exit(1);
- if (write(fd, data, pagesize) != pagesize)
- exit(1);
- close(fd);
-
- /*
- * Next, try to mmap the file at a fixed address which
- * already has something else allocated at it. If we can,
- * also make sure that we see the same garbage.
- */
- fd = open("conftestmmap", O_RDWR);
- if (fd < 0)
- exit(1);
- data2 = malloc(2 * pagesize);
- if (!data2)
- exit(1);
- data2 += (pagesize - ((int) data2 & (pagesize - 1))) & (pagesize - 1);
- if (data2 != mmap(data2, pagesize, PROT_READ | PROT_WRITE,
- MAP_PRIVATE | MAP_FIXED, fd, 0L))
- exit(1);
- for (i = 0; i < pagesize; ++i)
- if (*(data + i) != *(data2 + i))
- exit(1);
-
- /*
- * Finally, make sure that changes to the mapped area
- * do not percolate back to the file as seen by read().
- * (This is a bug on some variants of i386 svr4.0.)
- */
- for (i = 0; i < pagesize; ++i)
- *(data2 + i) = *(data2 + i) + 1;
- data3 = malloc(pagesize);
- if (!data3)
- exit(1);
- if (read(fd, data3, pagesize) != pagesize)
- exit(1);
- for (i = 0; i < pagesize; ++i)
- if (*(data + i) != *(data3 + i))
- exit(1);
- close(fd);
- unlink("conftestmmap");
- exit(0);
-}