Location of windows function return

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Ariiio

Joined: 03 Feb 2024
Posts: 5
Location: Germany

Ariiio 03 Feb 2024, 18:45

I'm trying to get the cursor position with the windows function "GetCursorPos". As far as I know it takes in a POINT, puts the coordinates in that point and returns 1 if successful. I put 0 into ecx as that is supposed to be the POINT, and since POINT is just a x and y coordinate it should work.

Problem 1:
The function doesnt seem to return 1 into eax, so either it doesnt work for some reason or I did something wrong with passing the arguments

Problem 2:
Since the function is supposed to put the coordinates into the POINT (ecx) it should do just that. ecx does change, but it doesnt look anythingl like ax and y coordinates. When I put my mouse into the upper left corner of my screen (0x0) ecx isnt 0 which doesnt make sense?

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03 Feb 2024, 18:45

Furs

Joined: 04 Mar 2016
Posts: 2493

Furs 03 Feb 2024, 19:00

The argument is a pointer (i.e. the address) of the POINT structure. Also, it needs to be pushed on the stack since you're using 32-bit?

03 Feb 2024, 19:00

macomics

Joined: 26 Jan 2021
Posts: 926
Location: Russia

macomics 03 Feb 2024, 19:55

Code:

format PE
entry start

include 'win32a.inc'

section '.text' code readable writeable
start:
    sub esp, 8 ; 0x4
    ; mov ecx, 0x0
    ; xor eax, eax
    push esp
    call [GetCursorPos]
    pop eax ; x
    pop edx ; y

    push 0
    call [ExitProcess]

section '.idata' import data readable writeable
    library kernel, 'KERNEL32.DLL',\
        user, 'USER32.DLL'

    import kernel,\
        ExitProcess, 'ExitProcess'
        
    import user,\
        GetCursorPos, 'GetCursorPos'

03 Feb 2024, 19:55

Ariiio

Joined: 03 Feb 2024
Posts: 5
Location: Germany

Ariiio 03 Feb 2024, 20:09

Furs wrote:

The argument is a pointer (i.e. the address) of the POINT structure. Also, it needs to be pushed on the stack since you're using 32-bit?

You are right, completely forgot it took in a pointer. Thanks for mentioning the arguments having to get pushed on the stack in x86, probably got it confused with x64

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03 Feb 2024, 20:09

Ariiio

Joined: 03 Feb 2024
Posts: 5
Location: Germany

Ariiio 03 Feb 2024, 20:10

macomics wrote:

Code:

format PE
entry start

include 'win32a.inc'

section '.text' code readable writeable
start:
    sub esp, 8 ; 0x4
    ; mov ecx, 0x0
    ; xor eax, eax
    push esp
    call [GetCursorPos]
    pop eax ; x
    pop edx ; y

    push 0
    call [ExitProcess]

section '.idata' import data readable writeable
    library kernel, 'KERNEL32.DLL',\
        user, 'USER32.DLL'

    import kernel,\
        ExitProcess, 'ExitProcess'
        
    import user,\
        GetCursorPos, 'GetCursorPos'

thanks, works perfectly

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03 Feb 2024, 20:10

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