What is "objdump"

objdump (part of the GNU Binutils) is a program for displaying various information about object files. For instance, it can be used as a disassembler to view an executable in assembly form. It is part of the GNU Binutils for fine-grained control over executables and other binary data.

For example,

$ objdump -D -M intel file.bin | grep main.: -A20

This performs disassembly on the file «file.bin», with the assembly code shown in Intel syntax. We then redirect it to grep, which searches the main function and displays 20 lines of its code.

Example output:

4004ed: 55 push rbp 4004ee: 48 89 e5 mov rbp,rsp 4004f1: c7 45 ec 00 00 00 00 mov DWORD PTR [rbp-0x14],0x0 4004f8: c7 45 f0 01 00 00 00 mov DWORD PTR [rbp-0x10],0x1 4004ff: c7 45 f4 02 00 00 00 mov DWORD PTR [rbp-0xc],0x2 400506: c7 45 f8 03 00 00 00 mov DWORD PTR [rbp-0x8],0x3 40050d: c7 45 fc 04 00 00 00 mov DWORD PTR [rbp-0x4],0x4 400514: c7 45 ec 00 00 00 00 mov DWORD PTR [rbp-0x14],0x0 40051b: eb 13 jmp 400530 <main+0x43> 40051d: 8b 05 15 0b 20 00 mov eax,DWORD PTR [rip+0x200b15] # 601038 <globalA> 400523: 83 e8 01 sub eax,0x1 400526: 89 05 0c 0b 20 00 mov DWORD PTR [rip+0x200b0c],eax # 601038 <globalA> 40052c: 83 45 ec 01 add DWORD PTR [rbp-0x14],0x1 400530: 8b 05 02 0b 20 00 mov eax,DWORD PTR [rip+0x200b02] # 601038 <globalA> 400536: 39 45 ec cmp DWORD PTR [rbp-0x14],eax 400539: 7c e2 jl 40051d <main+0x30> 40053b: 5d pop rbp 40053c: c3 ret 40053d: 0f 1f 00 nop DWORD PTR [rax]

objdump uses the BFD library to read the contents of object files.

Similar utilities are Borland TDUMP, Microsoft DUMPBIN, and (also included in the binutils package), readelf that can only read ELF files and it does not use the BFD library.