MS COFF and help converting NASM to fasm

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Manos

Joined: 24 Aug 2003
Posts: 35
Location: Greece

Manos

Hi.

How can I use the command line tool, (FASM.EXE), to build MS COFF files instead of executables, by using the format MS COFF directive with high level istructions, like invoke ?
The following example does not work:

format MS COFF

include 'C:\Fasm\INCLUDE\win32ax.inc'

.code

start:
invoke MessageBox,HWND_DESKTOP,"Hi! I'm the example program!",0,MB_OK
invoke ExitProcess,0

.end start

Manos.

20 Nov 2016, 11:41

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 18068
Location: In your JS exploiting you and your system

revolution

There is an MSCOFF.ASM example file in the download:

Code:

; example of making Win32 COFF object file

format MS COFF

extrn '__imp__MessageBoxA@16' as MessageBox:dword

section '.text' code readable executable

 public _demo

 _demo:
        push    0
        push    _caption
        push    _message
        push    0
        call    [MessageBox]
        ret

section '.data' data readable writeable

 _caption db 'Win32 assembly',0
 _message db 'Coffee time!',0

20 Nov 2016, 12:26

Manos

Joined: 24 Aug 2003
Posts: 35
Location: Greece

Manos

I know the above example.

But instead of: extrn '__imp__MessageBoxA@16' as MessageBox:dword
I want to use: include 'C:\Fasm\INCLUDE\win32ax.inc'
and instead of pushing the parameters on the stack and calling the function,
I want to use: invoke MessageBox, etc,
just like MASM projects.

Manos.

20 Nov 2016, 12:53

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 18068
Location: In your JS exploiting you and your system

revolution

You don't need to include the entire win32 set. Just this might be all you need:

Code:

include 'macro/proc32.inc'

20 Nov 2016, 13:00

Manos

Joined: 24 Aug 2003
Posts: 35
Location: Greece

Manos

revolution wrote:

You don't need to include the entire win32 set. Just this might be all you need:
Code:
include 'macro/proc32.inc'    

It is not enough.

Try to assemble the following code:

format MS COFF

include 'C:\Fasm\INCLUDE\win32ax.inc'

.code

start:
invoke MessageBox,HWND_DESKTOP,"Hi! I'm the example program!",0,MB_OK
invoke ExitProcess,0

.end start

Manos.

20 Nov 2016, 13:33

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 18068
Location: In your JS exploiting you and your system

revolution

You don't need ".end" with COFF. The linker will set the entry address. And don't use win32ax, try the include I posted above.

Code:

format MS COFF

include 'macro/proc32.inc'

extrn '__imp__MessageBoxA@16' as MessageBox:dword

section '.text' code readable executable

public MyCode

MyCode:
        invoke MessageBox,0,caption,message,0
        ret

section '.data' data readable writeable

caption db 'Win32 assembly',0
message db 'Coffee time!',0

20 Nov 2016, 13:38

Manos

Joined: 24 Aug 2003
Posts: 35
Location: Greece

Manos

Hi revolution.

I know your above example.

But because I am building an IDE for plain C, MASM and FASM,
I would like to avoid the: extrn '__imp__MessageBoxA@16' as MessageBox:dword.

I want to use: 'C:\Fasm\INCLUDE\win32ax.inc',
like I do in MASM.

Manos.

20 Nov 2016, 13:58

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 18068
Location: In your JS exploiting you and your system

revolution

win32ax won't work for you. You will need to write some type of macro or include file to create all the import names. You will need the extrn's to be included somewhere in the source that fasm sees. Currently there is no file that will do that for you in the fasm download.

20 Nov 2016, 14:10

Manos

Joined: 24 Aug 2003
Posts: 35
Location: Greece

Manos

Yes, you are right.

I have to implement my own include files.

Thank you for your replies,

Manos.

20 Nov 2016, 15:44

Manos

Joined: 24 Aug 2003
Posts: 35
Location: Greece

Manos

In NASM there is the expression: times ($$-$) & 3 nop

How can I phrase the above in FASM ?

Thanks,
Manos.

21 Nov 2016, 21:38

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 18068
Location: In your JS exploiting you and your system

revolution

Replace & with and

22 Nov 2016, 03:08

Manos

Joined: 24 Aug 2003
Posts: 35
Location: Greece

Manos

revolution wrote:

Replace & with

Thang you, it is correct, but I have also to replace the: $$-$ with: $-$$
The correct is: times ($-$$) and 3 nop

Manos.

22 Nov 2016, 11:53

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 18068
Location: In your JS exploiting you and your system

revolution

Manos wrote:

The correct is: times ($-$$) and 3 nop

Okay, I'm not 100% with NASM syntax. In that case you could also write:

Code:

align 4

Last edited by revolution on 22 Nov 2016, 13:38; edited 1 time in total

22 Nov 2016, 13:05

Manos

Joined: 24 Aug 2003
Posts: 35
Location: Greece

Manos

revolution wrote:

Manos wrote:
The correct is: times ($-$$) and 3 nop
Okay, I'm not 100% with NASM syntax. In that case you could also write:
Code:
align 4    

I thought to use: align 4, but I prefer to avoid macros, because my C compiler can emit plain FASM code.
My C compiler, (wcc32), accepts also inline assembly.
Because my IDE use wcc32, I wish my IDE to mix C and assembly modules.
I have implemented, also a linker, named wlink32 and
a RC compiler, but I have upload only wlink32 for now.
Have a look there: http://www.manoscoder.gr/w32cc/viewtopic.php?f=12&t=24

Thank you,
Manos.

22 Nov 2016, 13:37

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 18068
Location: In your JS exploiting you and your system

revolution

Align is not a macro in fasm.

22 Nov 2016, 13:38

Manos

Joined: 24 Aug 2003
Posts: 35
Location: Greece

Manos

OK.

I 'll test this later.

Manos.

22 Nov 2016, 13:40

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 18068
Location: In your JS exploiting you and your system

revolution

Oh wait. $-$$ gives you the offset. I think that $$-$ is what you wanted, the negative offset.

22 Nov 2016, 13:40

Manos

Joined: 24 Aug 2003
Posts: 35
Location: Greece

Manos

revolution wrote:

Oh wait. $-$$ gives you the offset. I think that $$-$ is what you wanted, the negative offset.

The first worked fine.

I 'll test for the $$-$

Manos.

22 Nov 2016, 13:50

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 18068
Location: In your JS exploiting you and your system

revolution

Manos wrote:

revolution wrote:
Oh wait. $-$$ gives you the offset. I think that $$-$ is what you wanted, the negative offset.

The first worked fine.

If the positive offset is 1 mod 4 then you get only one byte of padding. If the positive offset is 3 mod 4 then you get three bytes of padding.

22 Nov 2016, 14:05

Manos

Joined: 24 Aug 2003
Posts: 35
Location: Greece

Manos

revolution wrote:

Manos wrote:

revolution wrote:
Oh wait. $-$$ gives you the offset. I think that $$-$ is what you wanted, the negative offset.

The first worked fine.
If the positive offset is 1 mod 4 then you get only one byte of padding. If the positive offset is 3 mod 4 then you get three bytes of padding.

Yes, you are right.
I tested the: $$-$ and it works OK also.
Finally, I 'll use the: $$-$

Thank you again.

P.S.
Did you download my wlink32 ?

Manos.

22 Nov 2016, 14:13

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