Is there any way to get information about current session from gv$session in oracle?

Try this:

SELECT SID, SERIAL#
FROM V$SESSION
WHERE AUDSID = Sys_Context('USERENV', 'SESSIONID');

Since you're interested in current session, the current session must be on the local instance (by definition), so use V$SESSION instead of GV$SESSION. Also, all you need is AUDSID to uniquely identify your session.

If you've got some reason you really need to use GV$SESSION (can't imagine why that would be), you could do this instead:

SELECT SID, SERIAL#
    FROM GV$SESSION
    WHERE AUDSID = Sys_Context('USERENV', 'SESSIONID')
      AND INST_ID = USERENV('Instance');

Also, an alternate way to get the SID of the current session is:

select sid from v$mystat where rownum=1;

Hope that helps.