Change output data (modify MZ stub of PE from source code)

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Leo_yz

Joined: 05 Feb 2010
Posts: 2
Location: Russia

Leo_yz 09 May 2010, 14:11

How can I change the output data at compile stage?
I need to write addr of label to MZ-header.(STUB or somewhere)
For example:

Code:

format PE GUI 4.0
entry start
section '' code readable writeable
somedata db 'data',0

start:
ret

I need to write addr of label to "somedata" after MZ-signature - at offset 0x2 of EXE file. How can it be done?
Help me please Embarassed

EDIT by DOS386 : enhanced subject

09 May 2010, 14:11

edemko

Joined: 18 Jul 2009
Posts: 549

edemko 09 May 2010, 14:56

store dword 'leo:' at $xxxxxxxx

edit: weird i cannot store to $400'000

09 May 2010, 14:56

Leo_yz

Joined: 05 Feb 2010
Posts: 2
Location: Russia

Leo_yz 09 May 2010, 15:50

Quote:

Both load and store directives are limited to operate on places in current addressing space. The $$ symbol is always equal to the base address of current addressing space, and the $ symbol is the address of current position in that addressing space, therefore these two values define limits of the area, where load and store can operate.

09 May 2010, 15:50

edemko

Joined: 18 Jul 2009
Posts: 549

edemko 09 May 2010, 19:32

edit
Hope Tomasz will ever fix that.
Number display macros you can use to see addresses etc:
http://board.flatassembler.net/topic.php?t=11516

Last edited by edemko on 17 May 2010, 12:29; edited 1 time in total

09 May 2010, 19:32

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 09 May 2010, 19:57

You can't do that*. Also, are you sure you want it at that offset?? Note those are not unused bytes: http://www.delorie.com/djgpp/doc/exe/

*Well you could by using "format binary as 'exe'" and then defining all the MZ and PE structures yourself instead of letting fasm do that for you. Some people posted examples in this forum but I can't find them now... Also, you could use the debugging information and an external tool that search for your label in the .fas file and then patches the executable with the address the file says the label is located at.

09 May 2010, 19:57

edemko

Joined: 18 Jul 2009
Posts: 549

edemko 09 May 2010, 20:07

...or you are just approaching masm Sad

fasm must go forward Smile

he might wants some file stamping or
needS to write addr of label to MZ-header.(STUB or somewhere)

masm: no provocation - facts

09 May 2010, 20:07

DOS386

Joined: 08 Dec 2006
Posts: 1900

DOS386 10 May 2010, 08:09

Quote:

I need to write addr of label to "somedata" after MZ-signature - at offset 0x2 of EXE file. How can it be done? Help me please

Bad idea.

Quote:

Some people posted examples in this forum but I can't find them now

Can't find the forest anymore because of all the trees Laughing

http://board.flatassembler.net/topic.php?t=10874

Code:

; *** MZ-Header, stub (0,$60) ***

ccstacktop = $1040 ; MZ header $20 ; Program $0040 ; Heap 0 ; Stack $1000

  db "MZ"          ; Mark's Sigi
  dw $60           ; Bytes in last block (0 is full, includes header size)
  dw 1             ; Blocks per 512 Bytes (includes header size)
  db 0,0           ; No relocs
  db 2,0           ; Header size
  dw $1000         ; Min (Heap + Stack) 4 KiB
  dw $1000         ; Max (Heap + Stack) 4 KiB
  dw 0             ; Stack segment: SS=CS !!!
  dw ccstacktop    ; Stack size (almost 4 KiB) / pointer in bytes !!!
  db 0,0,0,0,0,0   ; CHK, IP, CS
  dw $1C           ; Useless reloc offset
  db 0,0           ; Useless "overlay"
  db 0,0,0,0       ; Padding / empty reloc

; org = $20 , should be 0 but irrelevant 

  db $0E,$1F         ; PUSH CS   | POPE DS
  db $B4,9,$BA,$20,0 ; MOV AH, 9 | MOV DX, $0020
  db $CD,$21         ; INT $21
  db $B8,1,$4C       ; MOV AX, $4C01
  db $CD,$21         ; INT $21
  db 0,0             ; Wasting 2 bytes

; org = $30

  db 0,0,0,0,0,0,0,0,0,0,0,0   ; Wasting 12 bytes
  db $60,0,0,0                 ; PE begins here

; org = $40, should be $20

  db "Need HX-DOS Extender to run !",$0D,$0A,$24 ; 29 chars + 3 special

; org = $60, content moved by +$20 bytes

; *** PE-Header ($60,$1 ***

db "PE", 0, 0 ; Signature

Put it somewhere where I wrote "padding" or "wasting" Wink

Quote:

edit: weird i cannot store to $400'000

better: $0040'0000 AKA 4 MiB

10 May 2010, 08:09

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