Adding system calls to the kernel

yakul · 11-19-2005, 04:42 AM

Hello

I have linux red hat8 installed.
I want to add a system call to the kernel and recompile the kernel.
What I did is I added My.c inside linux-2.4.18-14custom/kernel
The code for My.c is:

Code:

#include <linux/kernel.h>
#include <linux/sched.h>
#include <errno.h>
//#include <current.h>

int sys_getpath (int pid, int * array, int size)
{
 task_struct * pTask;

 printk ("This is get path V0P02\n");
 //  pTask = current;
 printk ("%d", pTask->pid);
 while (pTask->pid!=1)
   {
     pTask = pTask->p_pptr; 
     printk ("%d", pTask->pid);
   }

 return 0;
}

The problem I have as when I add #include <linux/sched.h> I get all sort of errors on sched.h when compiling with gcc -c My.c or gcc My.c -c

I also tried to compile user.c in the kernel, because it also has an include to sched.h, and I got about the same errors on sched.h

So how am I suppose to create My.o from My.c?
Is there something I am missing?

Thanks in advance.

btmiller · 11-19-2005, 09:38 PM

You really need to modify the Makefile to add your source file and let it compile the kernel. Remember, the object code generated from your source file must be linked with the rest of the kernel code to make a working image. In addition, the Makefiles also set up various environment things (defining macros, optimization levels, etc.) to make sure that kernel code is generated directly. So you really should add your new source file to the appropriate Makefile in the kernel source tree.

Also, your syscall will not be accessible if you modify the entry.S file for your architecture and add it to the system call table. Otherwise the syscall interrupt handler will have no idea about what it is.