Printk defined loglevels not found

[Elleroth]

Hi all,

I've been trying to simply use printk for a while now as I'm doing a little kernel
modding, however, things aren't going as smoothly as I would've wished.

Here's the very simple code:

#include <linux/kernel.h>

int main()
   {
   printk(KERN_DEBUG "This is a test\n");

   return 0;
   }

For whatever reason, it can't find the definition for "KERN_DEBUG" (or any
defined log level for that matter) even though I can clearly see them DEFINE-d
in /usr/src/kernel/linux-2.26.8-57/include/linux/kernel.h .

I'm at a loss as to what is causing this.
Any ideas would be most appreciated.

Thank you,
-Elleroth

(Oh and this was my first post ever on the Linux Forums! Yay me)

[gerard4143]

I believe printk can only be used in kernel modules not user processes..

This guide should start in the right direction...

The Linux Kernel Module Programming Guide

[Elleroth]

Excellent.

Looks like it compiled okay after embedding it into kernel/sched.c so I'm going to assume that you're correct.

Thanks,
-Elleroth

[Elleroth]

Well it seems to be in the kernel, but it doesn't want to print.

The message is nowhere within /var/log/ and I can't get it to print to any log or the
terminal. (I even tried fiddling with /proc/sys/kernel/printk but that didn't seem to
help.)

Everything compiled beautifully; What could have gone wrong?

-Elleroth

[gerard4143]

You'll have to post some code for any reasonable answers...

[Elleroth]

Sorry... I assumed that since it compiled properly, it wouldn't be necessary.

Here's the code (modified sched_rt.c; lines 1767 - 1789):

/* 
 * Function: getTimesliceRatio
 * 
  * Returns the number of processes that are siblings of the 
 *  process defined by the task_struct passed-in.
 */
int getTimeSliceRatio(struct task_struct *ts)
	{
	//Get the sibling list head
	int timeslice_ratio = 1;
	struct list_head head_struct = ts->sibling;
	struct list_head *head = head_struct.next;
	while(head != NULL)
		{
		if(head->next != NULL)	//...and if next node is NOT NULL
			{
			head = head->next;
			timeslice_ratio++;
			}
		else			//...Otherwise the list is exhausted
			{ }
		}

	printk(KERN_DEBUG "Number of siblings for process %d is: %d\n",
				ts->pid, timeslice_ratio);
	
	//Return the number of siblings that this process has
	return timeslice_ratio;
	}

Seems like it should work, but I'm getting no messages sent anywhere.

Thanks for all your speedy replies,
-John

[Elleroth]

I've just been informed that I cannot use these forums for aid on school assignments. Please close this thread (everything is working now anyway).