0 Indicates success.
-1 Indicates an error; errno is set to one of the
following values:
o EACCESS - The prot argument specifies a
protection that conflicts with the access
permission set for the underlying file.
o EINVAL - The prot argument is invalid, or
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.