Accessing a Matrix field in a Global
Not sure why you're referencing "entry" in your code, I'd think the code should be:

{% for block in footer.links %}
  {% if block.navigationLinks | length %}
    &lt;h3&gt;{{ block.navigationHeadline }}&lt;/h3&gt;
    {# Show the navigationHeadline if it has links #}
    &lt;ul&gt;
      {% for row in block.navigationLinks %}
        &lt;li&gt;{{ row.linkLabel }} - {{ row.linkUrl }}&lt;/li&gt;
      {% endfor %}
    &lt;/ul&gt;
  {% endif %}
{% endfor %}


So, "links" is the matrix on your "footer" global, which you can access from anywhere. You loop over that, get a block for each matrix block, and access "navigationHeadline" and "navigationLinks" through that.