Today, I found out about using objdump in Linux to find the disassembled code of programs in At&t syntax. While using objdump, the disassembled code looked fine but lacked the 'l' ending after the mnemonic (It should be "movl" not "mov"). Is there any way I can configure objdump to fix this issue?
The current disassembled program generated:
stuff: file format elf32-i386
Disassembly of section .text:
08049000 <_start>:
8049000: eb 00 jmp 8049002 <print_stuff>
08049002 <print_stuff>:
8049002: b8 04 00 00 00 mov $0x4,%eax
8049007: bb 01 00 00 00 mov $0x1,%ebx
804900c: b9 05 00 00 00 mov $0x5,%ecx
8049011: ba 0b 00 00 00 mov $0xb,%edx
8049016: cd 80 int $0x80
8049018: eb 00 jmp 804901a <end_program>
0804901a <end_program>:
804901a: b8 01 00 00 00 mov $0x1,%eax
804901f: bb 05 00 00 00 mov $0x5,%ebx
8049024: cd 80 int $0x80
What I want it to look like:
stuff: file format elf32-i386
Disassembly of section .text:
08049000 <_start>:
8049000: eb 00 jmp 8049002 <print_stuff>
08049002 <print_stuff>:
8049002: b8 04 00 00 00 movl $0x4,%eax
8049007: bb 01 00 00 00 movl $0x1,%ebx
804900c: b9 05 00 00 00 movl $0x5,%ecx
8049011: ba 0b 00 00 00 movl $0xb,%edx
8049016: cd 80 int $0x80
8049018: eb 00 jmp 804901a <end_program>
0804901a <end_program>:
804901a: b8 01 00 00 00 movl $0x1,%eax
804901f: bb 05 00 00 00 movl $0x5,%ebx
8049024: cd 80 int $0x80
To clutter your output with redundant suffixes even when it's implied by a register operand, use
objdump -d -M suffix foo
From the objdump(1) man page:
"
suffix"
When in AT&T mode and also for a limited set of instructions when in Intel mode, instructs the disassembler to print a mnemonic suffix even when the suffix could be inferred by the operands or, for certain instructions, the execution mode's defaults.
BTW, the "limited subset of Intel syntax" includes instructions like relative jmp rel32, e.g.
$ objdump -d -M intel /bin/ls
...
436e: e9 12 fe ff ff jmp 4185 <__cxa_atexit@plt+0x155>
$ objdump -d -M intel,suffix /bin/ls
...
436e: e9 12 fe ff ff jmpq 4185 <__cxa_atexit@plt+0x155>
(Related: What is callq instruction? - objdump -Mintel prints callq / retq even without the suffix option.)
The intel-syntax effect doesn't include instructions like add or mov or even movzx. With a memory operand, they'd explicitly indicate size as qword ptr [rdi] for example, and objdump does always include that even when it's implied by the other operand.