how to call dll written in foxpro from oracle stored procedure?

Question

i installed oracle11g in OEL5.9. i need to call a DLL written in FOXPRO from one of my stored procedures. i tried this code:

create or replace function test (x pls_integer,     
                                 y  pls_integer    
                                 )

Return pls_integer  

IS EXTERNAL  

Name "t_dll"    

LIBRARY newtest 

LANGUAGE C     


PARAMETERS (x long,   

            y long, 

            return long);

but it raised this error:

ora-06522 invalid elf header

i understood that LINUX uses SO files instead of DLL. now i want to know how can i convert DLL to SO? does external procedures work just for c and java? if yes,so how can i call FOXPRO procedures in oracle? any one can help me? thanks in advace