Return_Values

   0                  Indicates success.
   -1                 Indicates an error; errno is set to one of the
                      following values:

                      o  EIO - An I/O error occurred while reading
                         from or writing to the file system.

                      o  ENOMEM - The range specified by
                         [addr, addr + len] is invalid for a
                         process's address space, or the range
                         specifies one or more unmapped pages.

                      o  EINVAL - The addr argument is not a
                         multiple of the page size as returned by
                         sysconf(_SC_PAGE_SIZE).

                      o  EFAULT - The range [addr, addr + len]
                         includes an invalid address.