How Can I use the C runtime library with FASM like memcpy?

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mikawawa

Joined: 22 May 2012
Posts: 5

mikawawa

I love FASM, but unfortunately I'm newb. So here is my first question:
How Can I use the C runtime library with FASM like memcpy and strlen etc?

I need help, Please

02 May 2014, 03:15

Walter

Joined: 26 Jan 2013
Posts: 143

Walter

Here is one way:

Code:

;***************
;*mikawawa.asm *
;***************

format pe console
entry start

include 'win32ax.inc'

section '.data' data readable writeable

strName1 db 'mikawawa',0
strName2 rb 32

section '.code' code readable executable

start:

    cinvoke memcpy,strName2,strName1,3
    cinvoke memcpy,strName2+3,strName1+3,6
    cinvoke printf,'%s%c%c',strName2,0x0d,0x0a

    cinvoke strlen,strName2
    cinvoke printf,'Length of string is: %d',eax

    invoke  ExitProcess,0
         
section '.idata' import data readable

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

    import msvcrt,\
           memcpy,'memcpy',\
           strlen,'strlen',\
           printf,'printf'

02 May 2014, 04:29

mikawawa

Joined: 22 May 2012
Posts: 5

mikawawa

Walter wrote:

Here is one way:

Code:

;***************
;*mikawawa.asm *
;***************

format pe console
entry start

include 'win32ax.inc'

section '.data' data readable writeable

strName1 db 'mikawawa',0
strName2 rb 32

section '.code' code readable executable

start:

    cinvoke memcpy,strName2,strName1,3
    cinvoke memcpy,strName2+3,strName1+3,6
    cinvoke printf,'%s%c%c',strName2,0x0d,0x0a

    cinvoke strlen,strName2
    cinvoke printf,'Length of string is: %d',eax

    invoke  ExitProcess,0
         
section '.idata' import data readable

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

    import msvcrt,\
           memcpy,'memcpy',\
           strlen,'strlen',\
           printf,'printf'

thank you very much, bro. I checked the FASM api directory and I didnt find the msvcrt.inc, so I thought I couldnt import the CRT functions directly. thanks again

02 May 2014, 05:06

mikawawa

Joined: 22 May 2012
Posts: 5

mikawawa

BTW, in msdn there is a function called CopyMemory, but it is not imported from any library, if I want to use it with FASM, what should I do?

02 May 2014, 05:18

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 17663
Location: In your JS exploiting you and your system

revolution

mikawawa wrote:

BTW, in msdn there is a function called CopyMemory, but it is not imported from any library, if I want to use it with FASM, what should I do?

Code:

rep movsb ;<--- copy memory

02 May 2014, 06:03

mikawawa

Joined: 22 May 2012
Posts: 5

mikawawa

revolution wrote:

mikawawa wrote:
BTW, in msdn there is a function called CopyMemory, but it is not imported from any library, if I want to use it with FASM, what should I do?
Code:
rep movsb ;<--- copy memory    

OK, I knew that. thanks all the same.

02 May 2014, 06:36

JohnFound

Joined: 16 Jun 2003
Posts: 3502
Location: Bulgaria

JohnFound

mikawawa wrote:

OK, I knew that. thanks all the same.

Using external functions is of course important, for example for interfacing with the OS, but it should not be overused. Try to make the simple tasks in assembly way. It will be simpler, smaller and more readable. As always, the balance is important.

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02 May 2014, 07:13

AsmGuru62

Joined: 28 Jan 2004
Posts: 1419
Location: Toronto, Canada

AsmGuru62

I think CopyMemory is a macro... I may be wrong, however.

02 May 2014, 14:20

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 17663
Location: In your JS exploiting you and your system

revolution

AsmGuru62 wrote:

I think CopyMemory is a macro... I may be wrong, however.

This link suggests that it is implemented in Kernel32.dll

http://msdn.microsoft.com/en-us/library/windows/desktop/aa366535%28v=vs.85%29.aspx

02 May 2014, 14:25

mikawawa

Joined: 22 May 2012
Posts: 5

mikawawa

revolution wrote:

AsmGuru62 wrote:
I think CopyMemory is a macro... I may be wrong, however.
This link suggests that it is implemented in Kernel32.dll

http://msdn.microsoft.com/en-us/library/windows/desktop/aa366535%28v=vs.85%29.aspx

Oh, damn it! I didn't check it online, because I have a local msdn, although it is a little older, but I thought it might not be much more different. Well, seems I was totally wrong, thank you, bro. I really appreciate it!

03 May 2014, 01:07

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 17663
Location: In your JS exploiting you and your system

revolution

mikawawa wrote:

... bro ...

Or sis. Hehe Razz

03 May 2014, 01:26

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