On Sun, 21 Feb 2010 05:06:21 -0500 (EST), Hadi Motamedi wrote:
>
> Dear All
>
> I have disassembled the object file on my Debian server , by the following :
>
> #objdump wmain
>
> In the output , I have recognized the intended subroutine that I need to
> find the exact command syntax that it sends out. To this end, I asked
> you guys on how to capture it through 'tcpdump' but didn't success. I
> read this segment assembly language code but it is somewhat difficult to
> decode. Can you please let me know what Debian decompiler is suitable for
> this case? I tried with 'decompyle' but it didn't get through.
First, let me make sure I understand what you are asking. You have some
binary object code and you want to transform it back into the C source
code that it came from. Is that right? Or did I misunderstand you?
If that is what you want, then I doubt that it is possible. I've never
heard of a decompiler. I have heard of a disassembler, but even they
have their limitations. I myself have done extensive work as a programmer
on a disassembler for the s390 platform. It happens to be the disassembler
resident in the TRACK for z/VM freeware program. So I am speaking from
experience here. Even a disassembler is a guess. Here are some things that
you lose, even in a disassembler:
1. All comments.
2. The names of all variables
3. The distinction between code and data
For example, if I encounter the hex string '41101004' that could be a
LA 1,4(,1)
instruction. But it might not be an instruction. It might be data. It
might be
DC F'1091571716'
Or maybe it's a floating point number in traditional s390 hexadecimal
floating point format. Or maybe it's part of an escape sequence of codes
to be sent to a printer. You can never be sure. All these uncertainties
are present in a disassembler. In assembly language, there is pretty much
a one-to-one correspondence between assembler instructions and machine
instructions. But in a high-level language, that is not so. A single
statement in source code may generate a long sequence of machine instructions.
How do you know where one statement ends and another begins?
In short, I doubt if it is possible. Even if you do find something that
purports to be a decompiler, its output will almost certainly not match
the original input. Compilation is a one-way process.
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