Problem with a return value and StdOut

[xassiz]

Hello.

I was coding a tool that returns the offset address of a function of a specific library.

The problem is when I use GetProcAddress.

I save the return value:

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mov resultado, eax

But when I show it:

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invoke MessageBox, NULL, addr resultado, addr title, 0

The output are strange characters. I think I have to show it as hex. But how?

Other problem I have, is my StdOut doesn't run.

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invoke StdOut, addr resultado

It doesn't throw errors, but it doesn't do nothing u.u


Thanks!

[dedndave]

uhex$ macro will convert it to hex for you
refer to masm32\help\hlhelp.chm

StdOut is a console function
presumably, this is s GUI app

[Neil]

The message box is expecting Ascii characters & you have missed out the window handle (First parameter)

[xassiz]

StdOut is a console function
presumably, this is s GUI app

You say is a GUI app because the MessageBox? I want to replace the MessageBoxes by StdOuts :toothy

The message box is expecting Ascii characters

If StdOut works, I'll can show you how is the output (I can't copy it from the MessageBox) :dazzled:

[Neil]

The message box will work with a console application. Why not use print ustr$ (eax)

[xassiz]

The message box will work with a console application. Why not use print ustr$ (eax)

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C:\Users\Pablo\Desktop\BuscaOffsets.asm(33) : error A2008: syntax error : ustr$
_
Assembly Error

I do:

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print ustr$(eax)
or

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print ustr$(addr resultado)

[Neil]

Have you got these includes at the start of your program?

    include \masm32\include\masm32rt.inc
    include \masm32\macros\macros.asm

[dedndave]

ok
first - if you want to make a console app, use the correct batch file or link command line switch
the batch file to use is buildc.bat - build.bat is for GUI apps

second - it is important to note that the print macro will destroy the EAX contents
so, if you want to use the value later on...

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        push    eax
        print   uhex$(eax),13,10          ;use uhex$ for hex output - ustr will show decimal - addresses make more sense in hex
        pop     eax

also, Neil is right - you have to include the right stuff - masm32rt.inc is the easy way
i am fairly certain that it already takes care of macros.asm, though   :bg
have a look inside that file to see what it does for you

give me a few minutes and i'll post an example...

[dedndave]

here you go....

[Neil]

Yes Dave you're right, masm32rt.inc does include macros.asm. I was trying to get some response as to what exactly had been coded.

[xassiz]

Well.. See my code:

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.386
.model flat, stdcall
option casemap :none

include \masm32\include\windows.inc
include \masm32\include\kernel32.inc
include \masm32\include\user32.inc
include \masm32\include\masm32.inc
include \masm32\include\masm32rt.inc
includelib \masm32\lib\kernel32.lib
includelib \masm32\lib\user32.lib
includelib \masm32\lib\masm32.lib

Main PROTO

.data
    libreria db "msvcrt.dll",0
    funcion db "system",0
    error db "No se encontro el proceso.",0

.code
codigo:
    invoke Main

Main PROC
    LOCAL resultado:DWORD
   
    invoke LoadLibrary, addr libreria
    invoke GetProcAddress, eax, addr funcion
    mov resultado, eax
    cmp resultado, NULL
    je Error
    invoke MessageBox, NULL, addr resultado, addr funcion, 0
    print ustr$(addr resultado) ;nothing :S
    invoke ExitProcess, 0

Error:
    invoke MessageBox, NULL, addr error, addr libreria, 0
    invoke ExitProcess, 0
Main ENDP


end codigo
Also I tried uhex$ and it isn't the output I want.

Thanks!

[Neil]

invoke GetProcAddress, eax, addr funcion, eax should contain the handle of the module, I cannot see where you get that in your code.

[dedndave]

the way you structured the program, you are asking for a memory leak
that is because Main creates a local variable which is not released
you want to RET from Main, back to where you invoked it
also, i am still not convinced that you do not want hex output - lol

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include \masm32\include\masm32rt.inc

Main PROTO

.data
    libreria db "msvcrt.dll",0
    funcion db "system",0
    error db "No se encontro el proceso.",0

.code
codigo:
    invoke Main
    invoke ExitProcess, 0

Main PROC
    LOCAL resultado:DWORD
   
    invoke LoadLibrary, addr libreria
    invoke GetProcAddress, eax, addr funcion
    mov resultado, eax
    cmp eax, NULL
    je Error
    invoke MessageBox, NULL, uhex$(addr resultado), addr funcion, 0
    print ustr$(addr resultado) ;nothing :S
    jmp short Exit_Main

Error:
    invoke MessageBox, NULL, addr error, addr libreria, 0

Exit_Main:
    ret
Main ENDP

end codigo

[qWord]

also show us your linker call - sounds like you are building an GUI app instead of an console application.

EDIT: BTW: as long as using masm32rt.inc (or msvcrt.inc/lib),  you can directly call all CRT functions by adding the prefix 'crt_' to the function name:

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invoke crt_system,...

[xassiz]

I downloaded MASM32, so I'm using qeditor. I save and click Build All in Project menu.

EDIT
Sorry, I've just seen Console Build All", StdOut works now too.

Output:

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C:\Users\Pablo\Desktop>BuscaOffsets
o▒3uö ↑

That characters?