Slow program?

Index > Main > Slow program?

Author

Thread

Mino

Joined: 14 Jan 2018
Posts: 163

Mino 14 Jun 2018, 20:17

Hello,
my compiler generates code, rather "respectable" for the moment (to you to judge), however, I have the impression that programs following the following code model are slow, at least at closing time :

Code:

format PE
entry main

section '.idata' data readable import ; idata
include 'INCLUDE\win32a.inc'
library msvcrt, 'msvcrt.dll', \
        kernel32, 'kernel32.dll'
import kernel32, ExitProcess, 'ExitProcess'
import msvcrt, printf, 'printf'

section '.data' data readable writeable ; data
GVUN0 db "Hello, world!"

section '.code' code executable ; code
main:
        push ebp
        mov ebp, esp
        mov DWORD [ebp-4], edi
        mov DWORD [ebp-16], esi
        invoke printf, GVUN0
        mov esp, ebp
        pop ebp
        call _StopProgram
        ret

_StopProgram:
        call ExitProcess
        ret

Indeed, I have time to launch the program with a double click so that the console remains active a few seconds. Ditto online from order.
What could give this unwanted effect?
Thank you Smile

_________________
The best way to predict the future is to invent it.

14 Jun 2018, 20:17

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20445
Location: In your JS exploiting you and your system

revolution 14 Jun 2018, 20:38

You haven't terminated the GVUN0 string. Maybe printf is busy processing some bad data.

ExitProcess takes one parameter as the exit code, but you don't have any value there so the exit value will be some random value.

But the most serious problem is that you didn't restore the stack after calling printf. All of MSVCRT API calls are ccall, so you can use cinvoke.

14 Jun 2018, 20:38

Mino

Joined: 14 Jan 2018
Posts: 163

Mino 14 Jun 2018, 21:00

Thank you for your answer,
so I changed the code as you advised, but it still has the same effect:

Code:

format PE
entry main

section '.idata' data readable import ; idata
include 'INCLUDE\win32a.inc'
library msvcrt, 'msvcrt.dll', \
        kernel32, 'kernel32.dll'
import kernel32, ExitProcess, 'ExitProcess'
import msvcrt, printf, 'printf'

section '.data' data readable writeable ; data
GVUN0 db "Hello, world!", 10, 0

section '.code' code executable ; code
main:
        push ebp
        mov ebp, esp
        mov DWORD [ebp-4], edi
        mov DWORD [ebp-16], esi
        cinvoke printf, GVUN0
        mov esp, ebp
        pop ebp
        call _StopProgram
        ret

_StopProgram:
        cinvoke ExitProcess, 0
        ret

14 Jun 2018, 21:00

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20445
Location: In your JS exploiting you and your system

revolution 15 Jun 2018, 04:34

Well ExitProcess is not part of MSVCRT, it is stdcall so it should use invoke. But that won't matter here since it never returns.

But anyhow, you can do things like log the time stamp counter before and after each API call and print those value just before exiting to see where the main time usage is happening. Or try using a debugger.

15 Jun 2018, 04:34

< Last Thread | Next Thread >

Forum Rules:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum