[uml-devel] adding a system call in uml

[uml-devel] adding a system call in uml

[Mohammad Jawwad]

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Hello,

 

How does one add a system call to user mode linux?

I followed the instructions here:=

http://user-mode-linux.sourceforge.net/lksct/

 

Instead of using his stub(which dosent work) I used this one:

 

#include <stdio.h>

#include <sys/syscall.h>

#include <linux/unistd.h>

 

int main()

{

    syscall(253);   // I assigned number 253 to my system call in unistd.h

    return 0;

}

 

The program compiles but dosent print out the the output from the printk()
statement.

Has anybody successfully installed a system call in uml?

 

Thank you


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Re: [uml-devel] adding a system call in uml

[Blaisorblade]

On Saturday 03 February 2007 06:36, Mohammad Jawwad wrote:
> Hello,
>
>
>
> How does one add a system call to user mode linux?
>
> I followed the instructions here:=
>
> http://user-mode-linux.sourceforge.net/lksct/

It's from 2002, (I've seen this in the homepage), it's outdated. No 
information about kernel development lasts for so long.

Those instructions could be meaningful for 2.4, and _maybe_ early 2.6 UML 
kernels (I didn't look at the details).
Which UML version did you use?

These days, to add a syscall to a 32bit UML you must patch x86 sources, and 
for a 64bit UML, the x86-64 sources. There will be more info on doing that in 
various websites.So look for info on doing that.

Files to modify are, at least:
For x86:
include/asm-i386/unistd.h
arch/i386/kernel/syscall_table.S

For x86_64:
include/asm-x86_64/unistd.h

Those files are included/reused by UML - this was done to make it easier to 
keep syscall tables in sync.

Also, syscall 253 is already assigned these days.

> The program compiles but dosent print out the the output from the printk()
> statement.
>
> Has anybody successfully installed a system call in uml?

-- 
Inform me of my mistakes, so I can add them to my list!
Paolo Giarrusso, aka Blaisorblade
http://www.user-mode-linux.org/~blaisorblade
Chiacchiera con i tuoi amici in tempo reale! 
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