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flat assembler > Windows > [solved]Why DLL not working without WINAPI?

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CrawlUp



Joined: 23 May 2017
Posts: 8
Location: the USSR
I'm a newbie. I create a DLL library and if my function does not have a call WINAPI, the library does not want to load into my program.


This is a working DLL--
Code:
format PE GUI 4.0 DLL entry DllEntryPoint include 'win32a.inc' ;__________________________________________________________ section '.code' code readable executable proc DllEntryPoint hinstDLL,fdwReason,lpvReserved mov eax,TRUE ret endp proc myFunction invoke MessageBox,0,str_dll,head_dll,MB_OK ret endp ;_________________________________________________________ section '.data' data readable writeable str_dll db 'DLL is working',0 head_dll db 'My dll',0 ;__________________________________________________________ section '.idata' import data readable writeable library user,'USER32.DLL' import user, MessageBox,'MessageBoxA' ;_________________________________________________________ section '.edata' export data readable export 'new.DLL', myFunction,'myFunction' ;_________________________________________________________ section '.reloc' fixups data readable discardable


This is not working code--
Code:
format PE GUI 4.0 DLL entry DllEntryPoint include 'win32a.inc' ;__________________________________________________________ section '.code' code readable executable proc DllEntryPoint hinstDLL,fdwReason,lpvReserved mov eax,TRUE ret endp proc myFunction mov eax, edx ;Any code without WINAPI calls ;..... ret endp ;_________________________________________________________ section '.edata' export data readable export 'new.DLL', myFunction,'myFunction' ;_________________________________________________________ section '.reloc' fixups data readable discardable


My program use DLL library-
Code:
format PE GUI 4.0 entry start include 'win32a.inc' section '.text' code readable executable start: invoke myFunction invoke ExitProcess,0 ;______________________________________________________________________ section '.idata' import data readable writeable library kernel,'KERNEL32.DLL',\ newdll,'new.DLL' import kernel, ExitProcess,'ExitProcess' import newdll, myFunction,'myFunction'

Translate: new.dll either not designed to run under Windows or contains an error......bla..bla...bla..


Description:
Filesize: 28.91 KB
Viewed: 1390 Time(s)

ошибочный образ.png




Last edited by CrawlUp on 23 May 2017, 15:59; edited 2 times in total
Post 23 May 2017, 05:57
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Grom PE



Joined: 13 Mar 2008
Posts: 113
Location: i@grompe.org.ru
The problem is actually the declared but empty relocation section.

If you forcre it to generate at least one relocation, by adding
Code:
dummy: mov eax, dummy

anywhere in code section, it will work.
Post 23 May 2017, 07:56
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 15871
Location: 162173 Ryugu
If you don't want to pollute your code with dummy instructions you can populate the relocation data with this:
Code:
data fixups dd 0,8 end data
You can put that anywhere in your code, you don't need an extra section for it. And you will have to remove the 'fixups' flag from any existing section because you can't have two fixuos locations.
Post 23 May 2017, 09:32
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Tomasz Grysztar
Assembly Artist


Joined: 16 Jun 2003
Posts: 6873
Location: Kraków, Poland
There is also a different way to avoid creation of an empty section when the relocation directory is empty - you can put the fixups inside a section that already contains some other data:
Code:
section '.rdata' data readable data export export 'new.DLL', myFunction,'myFunction' end data data fixups end data
This works well in modern Windows, but it had not been working in Windows 9x line. But I'd guess that's not a serious problem nowadays.
Post 23 May 2017, 10:57
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CrawlUp



Joined: 23 May 2017
Posts: 8
Location: the USSR
Quote:
data fixups
dd 0,8
end data


It works well

Code:
format PE GUI 4.0 DLL entry DllEntryPoint include 'win32a.inc' ;__________________________________________________________ section '.code' code readable executable proc DllEntryPoint hinstDLL,fdwReason,lpvReserved mov eax,TRUE ret endp proc myFunction ret endp ;_________________________________________________________ section '.edata' export data readable export 'new.DLL', myFunction,'myFunction' ;_________________________________________________________ section '.reloc' fixups data readable discardable dd 0,8 ;But it's completely unclear why this is needed

dd 0,8 ; But it's completely unclear why this is needed


Quote:
dummy: mov eax, dummy

This does not work in more than one place code
Post 23 May 2017, 10:58
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CrawlUp



Joined: 23 May 2017
Posts: 8
Location: the USSR
Thank you all for your help. I will read the link.
Post 23 May 2017, 11:11
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