assign value of register to an constant

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marcinzabrze12

Joined: 07 Aug 2011
Posts: 61

marcinzabrze12 14 Mar 2012, 18:46

Is possible to assign a value of register (value at now) to an constant ?
While i try something like:

Code:

macro  const  ConstName, reg
{
    ConstName   equ reg 
}

Then ConstName is changed every time when "reg" is changed.
Compiller dont let me do:

Code:

macro const  ConstName, reg 
{
       ConstName  =   reg
}

; now when i use in code:

      const      x, eax;   error:  "invalid value"

Someone can tell me what is wrong ? Sorry for my english.

14 Mar 2012, 18:46

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20533
Location: In your JS exploiting you and your system

revolution 14 Mar 2012, 19:25

No macro is required.

Code:

x equ eax

14 Mar 2012, 19:25

marcinzabrze12

Joined: 07 Aug 2011
Posts: 61

marcinzabrze12 14 Mar 2012, 20:11

It isn't work corectly because if you change EAX then X will be change too.
I want to have a constant value of register at current time.

Code:


;====================================================
macro   ShowV  arg   {
           push   eax ebx ecx edx esi edi
           local buffer
           jmp   @f
                   buffer         db  20 dup (0)
@@: cinvoke      wsprintf, buffer, '%d', arg
    invoke       MessageBox, 0, buffer, 'ShowValue', 0
    pop          edi esi edx ecx ebx eax}  
;====================================================
start:

        mov        eax, 100 ; load value for test it
        x          equ  eax
        ShowV      x        ;  its display 100 - everything ok now

        inc        eax      ; we change the EAX 
        ShowV      x        ; its display  101 because eax is changed. i nedd to 
                            ; have  x = 100 at this line.

14 Mar 2012, 20:11

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20533
Location: In your JS exploiting you and your system

revolution 14 Mar 2012, 20:22

The CPU does not have a register named x (which is what you want to do here) so what you really want is to define a memory variable to save the value of eax so you can retrieve it later.

Code:

x dd ?
;...
mov eax,100
mov [x],eax
ShowV [x]
inc eax
ShowV [x]

14 Mar 2012, 20:22

marcinzabrze12

Joined: 07 Aug 2011
Posts: 61

marcinzabrze12 14 Mar 2012, 21:01

Yea. Sorry for a problem. Now i understand why it is impossible ...please forgot about it.
Thanx for help.

14 Mar 2012, 21:01

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