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General => The Campus => Topic started by: sunshine33 on April 13, 2018, 07:12:50 AM

Title: Some questions about parts of code i cant understand .
Post by: sunshine33 on April 13, 2018, 07:12:50 AM
This is for learning purposes only and  for having a deeper understanding .

In this section of the code

Code Select
SUB_L00401000:
  push ebx
  sub esp,00000038h
  mov eax,[L00482600]
  test eax,eax
  jz L00401029
  mov dword ptr [esp+08h],00000000h
  mov dword ptr [esp+04h],00000002h
  mov dword ptr [esp],00000000h
  call eax
  sub esp,0000000Ch

Code Select
L00401110:
  push ebx
  sub esp,00000028h
  mov eax,[esp+30h]
  mov eax,[eax]
  mov eax,[eax]
  cmp eax,C0000091h
  ja L00401160
  cmp eax,C000008Dh
  jc L00401177

What does these mean ?

QuoteSUB_L00401000:
QuoteL00401110:




Title: Re: Some questions about parts of code i cant understand .
Post by: Lonewolff on April 13, 2018, 07:17:22 AM
They are labels.

For example jz L00401029 will jump to the routine labelled L00401029:

Saves you having to know exact memory locations etc..
Title: Re: Some questions about parts of code i cant understand .
Post by: sunshine33 on April 13, 2018, 07:20:24 AM
Are they also called subroutines or functions ?
Title: Re: Some questions about parts of code i cant understand .
Post by: Lonewolff on April 13, 2018, 07:30:12 AM
Someone correct me if I am wrong (still learning), but I believe they are subroutines in this case.
Title: Re: Some questions about parts of code i cant understand .
Post by: zedd151 on April 13, 2018, 07:47:16 AM
Quote from: Lonewolff on April 13, 2018, 07:30:12 AM
Someone correct me if I am wrong (still learning), but I believe they are subroutines in this case.

I guess it depends on the software authors intent I believe.
Title: Re: Some questions about parts of code i cant understand .
Post by: RuiLoureiro on April 13, 2018, 08:03:27 AM
Quote from: Lonewolff on April 13, 2018, 07:30:12 AM
Someone correct me if I am wrong (still learning), but I believe they are subroutines in this case.
What do you call a subroutine ?
             If it is to be called by "call ..." it should end with "ret". If not it is a piece of code  :t
Title: Re: Some questions about parts of code i cant understand .
Post by: Lonewolff on April 13, 2018, 08:05:42 AM
I stand corrected  :t
Title: Re: Some questions about parts of code i cant understand .
Post by: LordAdef on April 13, 2018, 08:38:56 PM
you took this code out of a disassembler, right?
Title: Re: Some questions about parts of code i cant understand .
Post by: sunshine33 on April 14, 2018, 12:21:15 AM
Yes ,
And i don't know how to code complicated things like that right now .
Title: Re: Some questions about parts of code i cant understand .
Post by: LordAdef on April 14, 2018, 12:26:54 AM
Quote from: sunshine33 on April 14, 2018, 12:21:15 AM
Yes ,
And i don't know how to code complicated things like that right now .


Yep. Look, we don't really know what you are after, but looks like reverse engeneering. You are not going to learn Assembly this way. You need to learn the foundation first without messing with someone else's code.


This place is full of invaluable resources, if you really want to learn
Title: Re: Some questions about parts of code i cant understand .
Post by: sunshine33 on April 14, 2018, 12:36:50 AM
Thanks for the reply
But somebody gave this little application called simplecppreverseme.exe when we were talking about some reverse engineering basics .
I still have that application with me .If anybody wants i can share that .

I disassembled it and there were more than 1500 lines of subroutines in it .
I got stuck again .

Then i was thinking about starting from scratch once again
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