Help Convert DLL Export Function Syntax

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Ultraplayer

Joined: 12 Aug 2021
Posts: 3

Ultraplayer 12 Aug 2021, 11:02

I am trying to convert the pascal code for a .DLL library.

Pascal version:

Code:

function luaopen_random(L: lua_State): Integer; cdecl;
begin
  // ... skipped...
  Result := 1;
end;

Disassembler C++ version:

Code:

signed int __cdecl luaopen_random(int a1)
{
  signed int v1; // eax
  return 1;
}

I found this topic about ccall directive, but FASM say - Extra character on line.
My INCORRECT ver:

Code:

proc ccall luaopen_random L: DWORD
  mov eax, 1
endp ; <<-- [Error] Extra character on line

How to make it properly?

12 Aug 2021, 11:02

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20450
Location: In your JS exploiting you and your system

revolution 12 Aug 2021, 11:18

Something like this maybe?

Code:

include 'win32ax.inc'
proc luaopen_random ccall, L
  mov ecx, [L]
  mov eax, 1
  ret
endp

12 Aug 2021, 11:18

Ultraplayer

Joined: 12 Aug 2021
Posts: 3

Ultraplayer 12 Aug 2021, 16:50

revolution wrote:

Something like this maybe?

Code:

include 'win32ax.inc'
proc luaopen_random ccall, L
  mov ecx, [L]
  mov eax, 1
  ret
endp

Thanks, it finally compiled! But, after "ccall" directive I can't make any calls!

Code:

proc luaopen_luadlgs ccall, L
  invoke  MessageBoxA,NULL,_e1,NULL,MB_ICONINFORMATION+MB_OK ; -- Illegal instruction
  cinvoke  MessageBoxA,NULL,_e1,NULL,MB_ICONINFORMATION+MB_OK ; -- Illegal instruction
  call  MessageBoxA ; -- Illegal instruction
  stdcall MessageBoxA ; -- Illegal instruction
end;

12 Aug 2021, 16:50

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20450
Location: In your JS exploiting you and your system

revolution 12 Aug 2021, 20:27

There is a mistake. Change ccall to c

Code:

include 'win32ax.inc'
proc luaopen_random c, L
  mov ecx, [L]
  mov eax, 1
  ret
endp
ccall luaopen_random

12 Aug 2021, 20:27

Ultraplayer

Joined: 12 Aug 2021
Posts: 3

Ultraplayer 12 Aug 2021, 20:37

revolution wrote:

There is a mistake. Change ccall to c

It works! Thank you!

12 Aug 2021, 20:37

Roman

Joined: 21 Apr 2012
Posts: 1847

Roman 15 Aug 2021, 14:43

revolution wrote:

proc luaopen_random c, L
mov ecx, [L]
mov eax, 1
ret
endp
ccall luaopen_random

And how in this case proc get params c and L ?

15 Aug 2021, 14:43

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20450
Location: In your JS exploiting you and your system

revolution 15 Aug 2021, 15:25

c isn't a parameter, it is a modifier to make it a ccall function.

To read L: mov ecx, [L]

Call it with: ccall luaopen_random, my_L_value

15 Aug 2021, 15:25

Roman

Joined: 21 Apr 2012
Posts: 1847

Roman 16 Aug 2021, 03:33

Ccall luaopen_random, param.
This is work only for 32 bit?

16 Aug 2021, 03:33

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20450
Location: In your JS exploiting you and your system

revolution 16 Aug 2021, 04:01

For DLLs in Windows 64-bit you need to use fastcall to make it standard.

If you want to use ccall in Windows then you can, but you need to make your own macros and things to support it.

16 Aug 2021, 04:01

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