|
> From: owens@netptc.net > To: motamedi24@hotmail.com; debian-user@lists.debian.org > Subject: RE: Decompiler? > Date: Mon, 22 Feb 2010 16:26:31 -0800 > > > > > > > > >---- Original Message ---- > >From: motamedi24@hotmail.com > >To: debian-user@lists.debian.org > >Subject: RE: Decompiler? > >Date: Mon, 22 Feb 2010 05:11:07 +0000 > > > >> > >> > >> > >> > >>> Date: Sun, 21 Feb 2010 07:28:01 -0500 > >>> From: zlinuxman@wowway.com > >>> To: debian-user@lists.debian.org > >>> Subject: Re: Decompiler? > >>> > >>> 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. > >>> > >>> > >>> > >>> -- > >>> To UNSUBSCRIBE, email to debian-user-REQUEST@lists.debian.org > >>> with a subject of "unsubscribe". Trouble? Contact > >listmaster@lists.debian.org > >>> Archive: > >http://lists.debian.org/1425884921.13942331266755281555.JavaMail.root > >@md01.wow.synacor.com > >>> > >> > >> > >> > >>Thank you for your reply . Actually my Debian server is running an > >application program that sends commands toward an attached network > >element . The commands deal with 'profile read' , 'profile modify' , > >and 'profile delete' issues . On the application gui , there is an > >option to try for 'profile replace' that I cannot find the related > >command . As there is a need to try for this 'profile replace' in > >batch file , so I need to find the exact command syntax for this > >purpose . I tried to capture it through tracing with 'tcpdump' but it > >was un-successful . So I dis-assembled the code and I was lucky to > >find the related subroutine . It is short in length but I cannot > >decode it to find the logic in behind . So I need to find a > >de-compiler to de-compile it to some sor t of higher level languages > >to see if I can understand the login behind . Please give me a hint > >on how to accomplish this . > >> > >> > I think you already got your answer although you may not like it. If > the program was written in assembler than a dis-assembler will give > you the source code; however even if you have that you still do not > have the whole picture (e.g. the symbol tables). If the program was > written in a HLL such as C I know of no way to go from the machine > code back to the source code. In fact looking at the machine code > won't even tell you what HLL the source was written in or what > compiler was used. I think you are proceeding down the wrong path. > Larry > >> > >> > >>_________________________________________________________________ > >>Hotmail: Trusted email with Microsoft’s powerful SPAM prot ection. > >>https://signup.live.com/signup.aspx?id=60969 > > Thank you for your reply . It seems that this case is closed . Hotmail: Trusted email with powerful SPAM protection. Sign up now. |