baidu.xml, /usr/share/firefox/searchplugins
<SearchPlugin xmlns="http://www.mozilla.org/2007/browser/search/">
<ShortName>Baidu</ShortName>
<Description>Baidu Web page search</Description>
<InputEncoding>gb2312</InputEncoding>
<Image width="16" height="16">data:image/x-icon;base64,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</Image>
<Url type="text/html" method="GET" template="http://www.baidu.com/s">
<Param name="wd" value="{searchTerms}"/>
<Param name="cl" value="3"/>
</Url>
<SearchForm>http://www.baidu.com</SearchForm>
</SearchPlugin>
本来自己做的，图标做的不好，直接把别人的搬过来了.
重启firefox即可