Get value from dd

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Roman

Joined: 21 Apr 2012
Posts: 1839

Roman 10 Feb 2020, 15:23

Code:

Zval dd 10,55
Mov eax, [Zval] ;it's ok

But how get value to eax, 10?

I know abaut EQU.
But some times not handful EQU.

Code:

Mov eax, magic Zval;= Mov eax, 10

10 Feb 2020, 15:23

sts-q

Joined: 29 Nov 2018
Posts: 57

sts-q 10 Feb 2020, 15:33

zval = 1055h
zval_location dd zval

mov eax, zval ; eax = 1055h
mov ax, [zval_location] ; ax = 1055h

Rolling Eyes

Last edited by sts-q on 10 Feb 2020, 15:35; edited 1 time in total

10 Feb 2020, 15:33

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20430
Location: In your JS exploiting you and your system

revolution 10 Feb 2020, 15:35

If you mean the address of Zval then:

Code:

org 0x100
Zval dd 1,2,3,4
mov eax, Zval ;<--- the address, 0x100
mov ebx, [Zval} ;<--- the first value, 1
mov ecx, [eax] ;<--- also the first value, 1

10 Feb 2020, 15:35

Roman

Joined: 21 Apr 2012
Posts: 1839

Roman 10 Feb 2020, 16:00

Not I mean get value from Zval,
But not Mov eax, [Zval]
Its read from memory slow
I want get to eax 10 from Zval!

Unusual method. And for this need unusual macros!

10 Feb 2020, 16:00

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8357
Location: Kraków, Poland

Tomasz Grysztar 10 Feb 2020, 16:06

You probably mean this then:

Code:

Zval dd 10,55

load tmp dword from Zval
Mov eax, tmp

If you switch sections, then you also need addressing space label:

Code:

__DATA::
Zval dd 10,55

; ...in another section:
load tmp dword from __DATA:Zval
Mov eax, tmp

Note that in fasm 1 you can only LOAD from previously generated data. Forward-referencing LOAD is possible only with fasmg.

10 Feb 2020, 16:06

Roman

Joined: 21 Apr 2012
Posts: 1839

Roman 10 Feb 2020, 16:09

Thanks this is I want.

10 Feb 2020, 16:09

Roman

Joined: 21 Apr 2012
Posts: 1839

Roman 10 Feb 2020, 16:34

What about load tmp peace of code from?

Code:

Lb: Inc ebx
Load tmp lb 
Tmp ; in this place we get Inc ebx

10 Feb 2020, 16:34

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8357
Location: Kraków, Poland

Tomasz Grysztar 10 Feb 2020, 16:47

Roman wrote:

What about load tmp peace of code from?
Code:
Lb: Inc ebx
Load tmp lb 
Tmp ; in this place we get Inc ebx
    

You need to know the size of what you're copying:

Code:

Lb: Inc ebx
Load tmp byte from Lb
db tmp

In general:

Code:

Lb: Inc ebx
.size = $ - Lb

repeat Lb.size
        Load tmp byte from Lb+%-1
        db tmp
end repeat

10 Feb 2020, 16:47

Roman

Joined: 21 Apr 2012
Posts: 1839

Roman 10 Feb 2020, 17:22

Amazing and cool!
Thanks.

10 Feb 2020, 17:22

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