unsupported 16-bit application

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deama

Joined: 10 Feb 2016
Posts: 6

deama 10 Feb 2016, 22:41

I'm trying to run this code

Code:

org 100h
use16

display_text = 9

mov ah,display_text
mov dx,hello
int 21h

int 20h

hello db "Hello World!",24h

but it just comes up with some error saying:

The program or feature "/??/C:/Users/deama/Desktop/New/folder/Hello.COM" cannot start or run due to incompatibility with 64-bit versions of Windows. Please contact the software vendor to ask if a 64-bit Windows compatible version is available

Any ideas?

10 Feb 2016, 22:41

l_inc

Joined: 23 Oct 2009
Posts: 881

l_inc 10 Feb 2016, 23:41

deama
The ideas are pretty much what the message says: you cannot run 16-bit applications in 64-bit Windows. It doesn't support those. But you can run them in an emulator such as DOSBox.

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10 Feb 2016, 23:41

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20759
Location: In your JS exploiting you and your system

revolution 11 Feb 2016, 01:42

Yes. The 64-bit "long" mode in the CPU does not have to capability to run 16-bit code. It is not just Windows that has this problem, but all OSes that use 64-bit mode on x86 CPUs.

If you run Windows in 32-bit mode then you can still use 16-bit code with v8086 mode, which is supported natively by the CPU.

11 Feb 2016, 01:42

l_inc

Joined: 23 Oct 2009
Posts: 881

l_inc 11 Feb 2016, 12:57

revolution

Quote:

The 64-bit "long" mode in the CPU does not have to capability to run 16-bit code. It is not just Windows that has this problem, but all OSes that use 64-bit mode on x86 CPUs.

This is not quite true. While the long mode (IA-32e in the Intel's terminology) does not support virtual 8086 it still can run in the compatibility submode, which in turn supports 16-bit segments where 16-bit code can run natively. In this case it's really about 64-bit Windows not supporting 16-bit segments. Ntvdm was indeed virtual 8086 and that's why it doesn't exist in 64-bit Windows, but (undocumented) support for 16-bit segments was terminated for non-technical reasons.

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11 Feb 2016, 12:57

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20759
Location: In your JS exploiting you and your system

revolution 11 Feb 2016, 15:25

Unless I misunderstand something, the availability of 16-bit segments is quite different from the availability of v8086 mode. v8086 mode is more than just having 16-bit segments enabled. Using v8086 mode to run 16-bit DOS *.com and *.exe files is quite important if one doesn't want to, or can't, emulate.

Anyhow, thanks for the comment. Perhaps someone out there is writing a 64-bit OS and wants such a thing.

11 Feb 2016, 15:25

l_inc

Joined: 23 Oct 2009
Posts: 881

l_inc 11 Feb 2016, 15:36

revolution

Quote:

the availability of 16-bit segments is quite different from the availability of v8086 mode. v8086 mode is more than just having 16-bit segments enabled

You are totally right. I just wanted to point out that it's a bit too broad-brushy to say that 16-bit code in long mode is not natively supported by the CPU.

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11 Feb 2016, 15:36

deama

Joined: 10 Feb 2016
Posts: 6

deama 12 Feb 2016, 19:17

So, how do I make that run in 64-bit?

12 Feb 2016, 19:17

AsmGuru62

Joined: 28 Jan 2004
Posts: 1738
Location: Toronto, Canada

AsmGuru62 13 Feb 2016, 14:52

Your 64 bit OS runs DOSBox.
Inside DOSBox you run your 16-bit application.
You have to download DOSBox - it is very simple emulator.

13 Feb 2016, 14:52

deama

Joined: 10 Feb 2016
Posts: 6

deama 13 Feb 2016, 17:00

But how do I change the code to make it run on a 64-bit OS?

13 Feb 2016, 17:00

AsmGuru62

Joined: 28 Jan 2004
Posts: 1738
Location: Toronto, Canada

AsmGuru62 13 Feb 2016, 18:03

Oh, I see... you need to re-write your 16-bit application to be a 32-bit or 64-bit Windows application.
I suppose, it is not an easy task, especially, if you have a large 16-bit legacy program.

13 Feb 2016, 18:03

l_inc

Joined: 23 Oct 2009
Posts: 881

l_inc 13 Feb 2016, 19:46

AsmGuru62
The correct answer is actually DOSBox. But I already gave it, so it's a bit demotivating to comment any more.

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Faith is a superposition of knowledge and fallacy

13 Feb 2016, 19:46

deama

Joined: 10 Feb 2016
Posts: 6

deama 14 Feb 2016, 23:05

I don't wanna run it in DOSBox, I wanna run it on my 64-bit machine.

I see, guess I'll try some other stuff out. Any idea how I can just write the simplest "hello world" message output on a cmd?

14 Feb 2016, 23:05

Trinitek

Joined: 06 Nov 2011
Posts: 257

Trinitek 15 Feb 2016, 09:20

Interestingly, there doesn't seem to be any console examples packaged with FASM. Confused

You can link msvcrt.dll and invoke printf.

15 Feb 2016, 09:20

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8466
Location: Kraków, Poland

Tomasz Grysztar 15 Feb 2016, 09:41

Trinitek wrote:

Interestingly, there doesn't seem to be any console examples packaged with FASM.

EXAMPLES\WIN64\DLL contains a console example for 64-bit Windows.

15 Feb 2016, 09:41

deama

Joined: 10 Feb 2016
Posts: 6

deama 15 Feb 2016, 20:27

Right...
How would you load that? Is it ".include 'something.dll' " or?

15 Feb 2016, 20:27

Trinitek

Joined: 06 Nov 2011
Posts: 257

Trinitek 15 Feb 2016, 22:31

This is how it's done.

Code:

format PE64 console
entry start

include 'include/win64a.inc'

section '.text' code readable executable

    start:
        invoke printf, message
        invoke ExitProcess, 0

section '.data' data readable

    message db "Hello world!", 0
    
section '.idata' import data readable writeable

    library kernel32, 'KERNEL32.DLL',\
            msvcrt, 'MSVCRT.DLL'

    include 'include/api/kernel32.inc'

    import  msvcrt,\
            printf, 'printf'

The idea is that you first "link" the DLLs that you need, and then you "import" the functions you want to use from those DLLs. The import statement for the ExitProcess function is in api/kernel32.inc, so I didn't have to explicitly write that.

Quote:

EXAMPLES\WIN64\DLL contains a console example for 64-bit Windows.

Ah, thanks.

15 Feb 2016, 22:31

Mikl___

Joined: 30 Dec 2014
Posts: 143
Location: Russian Federation, Irkutsk

Mikl___ 16 Feb 2016, 03:20

Trinitek wrote:

Interestingly, there doesn't seem to be any console examples packaged with FASM.

Examples for Win64 Iczelion tutorial contains console examples for 64-bit Windows

16 Feb 2016, 03:20

deama

Joined: 10 Feb 2016
Posts: 6

deama 16 Feb 2016, 21:27

It keeps giving me a "File not found" error on those "include" statements, in the above code and in Iczelion's examples...

EDIT: ah, wait, fixed it; apparentely removing the "include/" works.

16 Feb 2016, 21:27

Trinitek

Joined: 06 Nov 2011
Posts: 257

Trinitek 16 Feb 2016, 21:32

My PATH is a little screwy, so I had to drag the include folder into my working directory.

16 Feb 2016, 21:32

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