well i havent used ida linux much but try using objdump

for example
this could fetch all the rel calls and thier opcodes

 objdump -d /bin/ls  -j .text -M intel | grep 'call' | grep 'e8' | more
 80499ac:       e8 3f fd ff ff          call   0x80496f0
 80499b8:       e8 00 00 00 00          call   0x80499bd
 8049a40:       e8 bb 65 fb f7          call   0x0
 8049a92:       e8 39 fb ff ff          call   0x80495d0
 8049ab0:       e8 db fd ff ff          call   0x8049890
 8049ad2:       e8 f9 fa ff ff          call   0x80495d0
 8049b00:       e8 0b fa ff ff          call   0x8049510
 8049b71:       e8 4a f9 ff ff          call   0x80494c0
 8049b8f:       e8 9c fb ff ff          call   0x8049730
 8049c04:       e8 e7 b7 00 00          call   0x80553f0
 8049cb8:       e8 03 aa 00 00          call   0x80546c0
 8049cdc:       e8 2f 7e 00 00          call   0x8051b10
 8049d03:       e8 68 fb ff ff          call   0x8049870
 8049d17:       e8 44 a9 00 00          call   0x8054660
 8049d45:       e8 26 fb ff ff          call   0x8049870