Return_Values

   x                  The address where the mapping is placed.
   MAP_FAILED         Indicates an error; errno is set to one of the
                      following values:

                      o  EACCES - The file referred to by filedes
                         is not open for read access, or the file
                         is not open for write access and PROT_WRITE
                         was set for a MAP_SHARED mapping operation.

                      o  EBADF - The filedes argument is not a valid
                         file descriptor.

                      o  EINVAL -The flags or prot argument is
                         invalid, or the addr argument or off
                         argument is not a multiple of the page
                         size returned by sysconf(_SC_PAGE_SIZE).

                      o  ENODEV - The file descriptor filedes refers
                         to an object that cannot be mapped, such as
                         a terminal.

                      o  ENOMEM - There is not enough address space
                         to map len bytes.

                      o  ENXIO - The addresses specified by the
                         range [off, off + len] are invalid for
                         filedes.

                      o  EFAULT - The addr argument is an invalid
                         address.