How to get disassemble command line?

Question

I'm currently learning ASM programming, and I would like to disassembly a file .c. However after execute the command line

set disassembly-flavor test.c

I use the command:

disassembly test.c

and my terminal displayed

disassemble: command not found

Does anyone know can I get the command "disassemble" on my computer ?

Thanks

score 7 · Answer 1 · answered Mar 06 '16 at 11:58

First, a file with a .c extension most likely is a C source file. No use in disassembling it. To verify that a file actually is a program, use the file command:

$ file test.c
test.c: ASCII text
$ file /bin/bash
/bin/bash: ELF 64-bit LSB  executable, x86-64, version 1 (SYSV), dynamically linked
(uses shared libs), for GNU/Linux 2.6.24,
BuildID[sha1]=54967822da027467f21e65a1eac7576dec7dd821, stripped

As for disassembling, use objdump instead. From the manpage:

NAME
       objdump - display information from object files.

SYNOPSIS
       objdump [...]
               [-d|--disassemble]

So to disassemble, let's say, a file called a.out, use

$ objdump -d a.out 

a.out:     file format elf64-x86-64


Disassembly of section .init:

00000000004003a8 <_init>:
  4003a8:   48 83 ec 08             sub    $0x8,%rsp
  4003ac:   48 8b 05 45 0c 20 00    mov    0x200c45(%rip),%rax        # 600ff8 <_DYNAMIC+0x1d0>
  4003b3:   48 85 c0                test   %rax,%rax
  4003b6:   74 05                   je     4003bd <_init+0x15>
  4003b8:   e8 33 00 00 00          callq  4003f0 <__gmon_start__@plt>
  4003bd:   48 83 c4 08             add    $0x8,%rsp
  4003c1:   c3                      retq   
[...] and so on...

j0h · Answer 2 · 2016-03-06T18:09:32.723

I think what you want is a function of gdb, the gnu debugger, which has a disassemble command. First, you would compile test.c with debugging flags on, like this: gcc -Wall -g -o test test.c

or something along those lines. Then, you would run the application with gdb as an argument:

gdb test

once you are in gdb, you can use the disassemble command like this:

(gdb) break main
(gdb) disassemble main

Take this trivial program named test.cpp:

#include <iostream>
using namespace std;
int main ()
{
    int a=0;
    for (int b = 0; b < 11; b++){
        a=b+2;
        cout << a << "\n\t";
    }
cout << "Hello World \n";     
return 0;
}

now I will compile it, with debug flags:

g++ -Wall -g test.cpp -o test

Then you say, but j0h, this is a C question... to which I say, gdb doesn't care what language you use. you can debug and disassemble c, c++, assembly, fortran, and a variety of other things, just compile with the -g option, thats what is important.

once we load the program into gdb, and break main, we cam run disassemble:

Breakpoint 1 at 0x4007da
(gdb) disassemble main
Dump of assembler code for function main:
   0x00000000004007d6 <+0>: push   %rbp
   0x00000000004007d7 <+1>: mov    %rsp,%rbp
   0x00000000004007da <+4>: sub    $0x10,%rsp
   0x00000000004007de <+8>: movl   $0x0,-0x4(%rbp)
   0x00000000004007e5 <+15>:    movl   $0x0,-0x8(%rbp)
   0x00000000004007ec <+22>:    jmp    0x400817 <main+65>
   0x00000000004007ee <+24>:    mov    -0x8(%rbp),%eax
   0x00000000004007f1 <+27>:    add    $0x2,%eax
   0x00000000004007f4 <+30>:    mov    %eax,-0x4(%rbp)
   0x00000000004007f7 <+33>:    mov    -0x4(%rbp),%eax
   0x00000000004007fa <+36>:    mov    %eax,%esi
   0x00000000004007fc <+38>:    mov    $0x601080,%edi
   0x0000000000400801 <+43>:    callq  0x400670 <_ZNSolsEi@plt>
   0x0000000000400806 <+48>:    mov    $0x400914,%esi
   0x000000000040080b <+53>:    mov    %rax,%rdi
---Type <return> to continue, or q <return> to quit---

Here is a tutorial: http://www.unknownroad.com/rtfm/gdbtut/gdbadvanced.html

objdump can list the contents, but I don’t think you’ll be able to interact with your code the same way as if you use the debugger.

How to get disassemble command line?

2 Answers2