Function map_msg_buf_in_both_spaces 

fn map_msg_buf_in_both_spaces(
    msg_buf_phys: u64,
    sender_as: &AddressSpace,
    receiver_as: &AddressSpace,
) -> Result<(), &'static str>

Map a message buffer’s physical page into both address spaces at N3_SHARED_MSG_BUF_VA.