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Index > Windows > Push offset in a DLL

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DustWolf



Joined: 26 Jan 2006
Posts: 373
Location: Ljubljana, Slovenia
DustWolf
Hello,

I'm evidently having a problem expressing myself properly in this code:
Code:
proc WriteEntry         uses esi edi ebx,fileName,entryText

locals
lineBreak    db      13,10,0
fileHandle   dd      ?
textLen      dd      0
lenGot       dd      ?
endl

     invoke     CreateFile,[fileName],GENERIC_WRITE,0,0,OPEN_ALWAYS,FILE_ATTRIBUTE_TEMPORARY,0
     mov        [fileHandle],eax

     ;code to calculate textLen here

     invoke     WriteFile,[fileHandle],entryText,[textLen],lenGot,0

     invoke     CloseHandle,[fileHandle]
     ret

endp    


The code is supposed to open a file, write something to it and close it.

The assembler says it has a problem in pushing the local "entryText" and "lenGot"'s offsets to the stack. How to fix this?

Am I getting at this problem the wrong way?
Post 23 Nov 2006, 17:17
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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia
vid
local labels are defined as:

Code:
label lenGot dword at [ebp-8]
    


that means, if you try to just "push lenGot", it is as if you would write "push dword [ebp-8]". and this is not possible.

you can do it this way:
Code:
lea eax, [lenGot]  ;lea eax, [ebp-8]
invoke Proc, 1, 2, eax, 3
    
.

or, FASM high-level call macros have feature that does this for you. it's pseudo-operator "addr". used like this:

Code:
invoke     WriteFile,[fileHandle],addr entryText,[textLen],addr lenGot,0
    
Post 23 Nov 2006, 18:06
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asmfan



Joined: 11 Aug 2006
Posts: 392
Location: Russian
asmfan
i would suggest avoiding of using addr over other ways cuz it spoils edx and
Code:
invoke   SomeProc, [param1], edx, addr local1    

will compile correctly but behave WRONG.

_________________
Any offers?
Post 23 Nov 2006, 20:09
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DustWolf



Joined: 26 Jan 2006
Posts: 373
Location: Ljubljana, Slovenia
DustWolf
vid wrote:
Code:
invoke     WriteFile,[fileHandle],addr entryText,[textLen],addr lenGot,0
    


This still generates the same error. The long version is fine tho.
Post 23 Nov 2006, 20:22
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asmfan



Joined: 11 Aug 2006
Posts: 392
Location: Russian
asmfan
By the way, include extended inc files - *x.inc or *xp.inc instead of win32*.inc to have support of "addr"
Post 23 Nov 2006, 20:27
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DustWolf



Joined: 26 Jan 2006
Posts: 373
Location: Ljubljana, Slovenia
DustWolf
I am having some further trouble here...

For example:
Code:
proc Plop         uses esi edi ebx,mesage
        mov     eax,[mesage]
        invoke  MessageBox,0,eax,0,MB_OK
        ret
endp
    


With imports defined and all, when used like this:
Code:
                invoke   Plop,entryText
                invoke  ExitProcess,0

entryText       db      'Works!',0    


Crashes. Why?
Post 23 Nov 2006, 23:25
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LocoDelAssembly
Your code has a bug


Joined: 06 May 2005
Posts: 4633
Location: Argentina
LocoDelAssembly
because you are issuing a "call dword ptr [Plop]" due to the use of invoke instead of stdcall
Post 24 Nov 2006, 00:26
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