objdump shows a weird view of ELF files: use readelf whenever possible:
- http://stackoverflow.com/questions/22160621/objdump-not-showing-all-sections
- http://stackoverflow.com/questions/8979664/readelf-vs-objdump-why-are-both-needed
Things which it can do that readelf cannot:
- disassemble
Most useful command objdump command:
objdump -Sr a.o
See assembler instructions of object file or executable:
objdump -d a.o
Only disassembles sections which should contain assembly code like .text.
Sample output on a x86_64 Linux hello world:
hello_world.o: file format elf64-x86-64
Disassembly of section .text:
0000000000000000 <_start>:
0: b8 01 00 00 00 mov $0x1,%eax
5: bf 01 00 00 00 mov $0x1,%edi
a: 48 be 00 00 00 00 00 movabs $0x0,%rsi
11: 00 00 00
14: ba 0d 00 00 00 mov $0xd,%edx
19: 0f 05 syscall
1b: b8 3c 00 00 00 mov $0x3c,%eax
20: bf 00 00 00 00 mov $0x0,%edi
25: 0f 05 syscall
For executable files, it still writes Disassembly of section .text:, but it means segment .text, it is purely wrong.
Similar to -d, but also intermingle original C code with disassembly if there is debug information available for that:
gcc -ggdb3 -o a.o a.c
objdump -S a.o
Select which section to act on.
Seems impossible, use GDB instead.
http://stackoverflow.com/questions/22769246/disassemble-one-function-using-objdump
Disassemble with Intel syntax:
objdump -M intel -d main.o