A little help with illegal instruction

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mangoe

Joined: 31 Mar 2022
Posts: 8

mangoe

hi guys, i am new to asembly language and when i try to run this code it gives me illegal instruction in line 22 " user, 'user32.dll' ",what can i do?

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31 Mar 2022, 14:35

ProMiNick

Joined: 24 Mar 2012
Posts: 656
Location: Russian Federation, Sochi

ProMiNick

Code:

  library kernel,'KERNEL32.DLL',
          user,'USER32.DLL'

missed symbol "\" that concatenates line with next line

Code:

  library kernel,'KERNEL32.DLL',\
          user,'USER32.DLL'

31 Mar 2022, 14:54

Ali.Z

Joined: 08 Jan 2018
Posts: 510

Ali.Z

also ExitProcess requires an argument to be passed, refer to https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-exitprocess

edit:
or clear EAX and use RET instruction.

_________________
Asm For Wise Humans

31 Mar 2022, 18:30

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 18466
Location: In your JS exploiting you and your system

revolution

Ali.Z wrote:

also ExitProcess requires an argument to be passed, refer to https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-exitprocess

This isn't so important. All that happens is the result from the previous call is used for the exit status. In some cases this is exactly what you might want.

Ali.Z wrote:

... use RET instruction.

No, please don't do this. There is no documentation guaranteeing this works. It might work now only by happy accident.

31 Mar 2022, 20:01

macomics

Joined: 26 Jan 2021
Posts: 479
Location: Russia

macomics

Ali.Z wrote:

also ExitProcess requires an argument to be passed, refer to https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-exitprocess

edit:
or clear EAX and use RET instruction.

MessageBox has 4 arguments, and 5 values are pushed into the stack before calling it, i.e. the argument for ExitProcess is pushed into the stack before calling MessageBox. Wink

31 Mar 2022, 23:05

mangoe

Joined: 31 Mar 2022
Posts: 8

mangoe

ProMiNick wrote:

Code:

  library kernel,'KERNEL32.DLL',
          user,'USER32.DLL'

missed symbol "\" that concatenates line with next line

Code:

  library kernel,'KERNEL32.DLL',\
          user,'USER32.DLL'

i try and it gave me "Error: write failed" warning, so confusing. Does it case sensitive?

01 Apr 2022, 01:13

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 18466
Location: In your JS exploiting you and your system

revolution

You get "Error: write failed" if the target exe is open. Windows locks the file.

So you need to either save as a new name. Or close the app before re-assembling.

01 Apr 2022, 01:17

mangoe

Joined: 31 Mar 2022
Posts: 8

mangoe

Ali.Z wrote:

also ExitProcess requires an argument to be passed, refer to https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-exitprocess

edit:
or clear EAX and use RET instruction.

i think that you assumed me to have some experience with programing. To be honest i am also new with programing too, in fact i am cosidering a carres change, that why i am learning C and asembly at the moment. Can you make it more detail what i need to do? Question

01 Apr 2022, 01:24

mangoe

Joined: 31 Mar 2022
Posts: 8

mangoe

revolution wrote:

You get "Error: write failed" if the target exe is open. Windows locks the file.

So you need to either save as a new name. Or close the app before re-assembling.

I save it with a same name but into different folder and it works. Thank you very much. However i still don't know how it work, can you explain to me? I have no background on programing though.

01 Apr 2022, 02:55

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 18466
Location: In your JS exploiting you and your system

revolution

If you have "firefox.exe" open then Windows will lock the file so you can't write to it. This is the same for your app. If you have it open, Windows prevents you from writing to it. So fasm can't update app.exe while it is running. Close it before updating.

01 Apr 2022, 03:03

macomics

Joined: 26 Jan 2021
Posts: 479
Location: Russia

macomics

revolution wrote:

If you have "firefox.exe" open then Windows will lock the file so you can't write to it. This is the same for your app. If you have it open, Windows prevents you from writing to it. So fasm can't update app.exe while it is running. Close it before updating.

Look into the processes and search by name. It is possible that one of the previously launched programs remained stuck in memory and terminate all such hung programs. After that, try to assemble again. Or close all currently open MessageBox that are still hanging visible. In the case of console programs, sometimes it is necessary to restart the opened console.

01 Apr 2022, 05:41

mangoe

Joined: 31 Mar 2022
Posts: 8

mangoe

Ah i see it now, so i need to clear my previous run out of memory before starting a new one. Thank for all the help.

01 Apr 2022, 09:40

Ali.Z

Joined: 08 Jan 2018
Posts: 510

Ali.Z

mangoe wrote:

Can you make it more detail what i need to do?

Sorry, I did not open my eyes wide open; you can safely ignore my useless post.

_________________
Asm For Wise Humans

01 Apr 2022, 16:41

macomics

Joined: 26 Jan 2021
Posts: 479
Location: Russia

macomics

I haven't looked into the IDE for Windows before, but there is a suggestion. Add a setting that allows you to specify the path and name of the debugger program and the menu item that runs the program in the debugger.

Otherwise, newcomers will have similar incidents. Processes will hang in memory if they did not terminate on their own.

01 Apr 2022, 17:12

ProMiNick

Joined: 24 Mar 2012
Posts: 656
Location: Russian Federation, Sochi

ProMiNick

If newcomer can`t detect hang of compilled program or can`t destroy such app via Taskmgr he is not skilled enought to start programming from windows environment at all, even more he is not skilled enought to be user of such OS.

01 Apr 2022, 19:23

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 18466
Location: In your JS exploiting you and your system

revolution

ProMiNick wrote:

If newcomer can`t detect hang of compilled program or can`t destroy such app via Taskmgr he is not skilled enought to start programming from windows environment at all, even more he is not skilled enought to be user of such OS.

We all have to start somewhere. Give people a chance.

01 Apr 2022, 20:10

macomics

Joined: 26 Jan 2021
Posts: 479
Location: Russia

macomics

ProMiNick wrote:

If newcomer can`t detect hang of compilled program or can`t destroy such app via Taskmgr he is not skilled enought to start programming from windows environment at all, even more he is not skilled enought to be user of such OS.

I'm talking about improvement and creation, and they're about their own shortcomings and pessimism.

01 Apr 2022, 21:22

ProMiNick

Joined: 24 Mar 2012
Posts: 656
Location: Russian Federation, Sochi

ProMiNick

there is no sense in talking about improvement and creation.
Willing to improve? - do it.
The main problem is what? failed compilation if output is locked by exe execution.
So in moment where output name of compilation is resolved (somewhere before write from fasm.inc called) there could be forced try of taskkill of process that could exist & lock output.
but if fasm will start to kill processes it will be classified as attacking software. And this feature could be exploited in abnormal way.

01 Apr 2022, 22:10

mangoe

Joined: 31 Mar 2022
Posts: 8

mangoe

ProMiNick wrote:

If newcomer can`t detect hang of compilled program or can`t destroy such app via Taskmgr he is not skilled enought to start programming from windows environment at all, even more he is not skilled enought to be user of such OS.

Well as i said i have no background in Computer science at all and i want a career change that why i want to learn about programing. But you are right i am not skilled enought to be user and to start programing in Window enviroment, that's why i am learning because i'm always curious about how computer and programing work. Be patient man or you can just ignore my post from now on cause i gonna ask millions more stupid questions about flat and asembly.

02 Apr 2022, 03:31

mangoe

Joined: 31 Mar 2022
Posts: 8

mangoe

Ali.Z wrote:

mangoe wrote:
Can you make it more detail what i need to do?

Sorry, I did not open my eyes wide open; you can safely ignore my useless post.

That's my fault. Thank you for your time answering my post.

02 Apr 2022, 03:35

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