dumb question: How to create your own log files in a kernel module?

dumb question: How to create your own log files in a kernel module?

[Xin Zhao]

Can anyone give me a hand? or point me to somewhere I can find related
information?

Thanks in advance!

Xin

Re: dumb question: How to create your own log files in a kernel module?

[Richard B. Johnson]

On Thu, 28 Apr 2005, Xin Zhao wrote:

> Can anyone give me a hand? or point me to somewhere I can find related
> information?
>
> Thanks in advance!
>
> Xin


printk(KERN_XXX"whatever") was designed for this.

#define	KERN_EMERG	"<0>"	/* system is unusable			*/
#define	KERN_ALERT	"<1>"	/* action must be taken immediately	*/
#define	KERN_CRIT	"<2>"	/* critical conditions			*/
#define	KERN_ERR	"<3>"	/* error conditions			*/
#define	KERN_WARNING	"<4>"	/* warning conditions			*/
#define	KERN_NOTICE	"<5>"	/* normal but significant condition	*/
#define	KERN_INFO	"<6>"	/* informational			*/
#define	KERN_DEBUG	"<7>"	/* debug-level messages			*/
 	printk(KERN_DEBUG fmt,##arg)
 	printk(KERN_INFO fmt,##arg)

You could define your own, KERN_PRIVATE "<8>" and have the syslog
facility filter on that.

Other ways are to write stuff to a buffer or linked-list and
read it out using an ioctl() or read() in your module. If you
do this, make sure that your module code doesn't wait forever
if the buffer gets full.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.11 on an i686 machine (5537.79 BogoMips).
  Notice : All mail here is now cached for review by Dictator Bush.
                  98.36% of all statistics are fiction.

Re: dumb question: How to create your own log files in a kernel module?

[Xin Zhao]

Thanks for kind help. 

I know printk can do this job. But what I really want is to print logs
to a file specified by me instead of /var/log/messages. And, the
messages irrelevant to my module should not be written into that file.
 Now my log mixed with other logs in /var/log/message, which bother me
much. :(

I guess the KERN_PRIVATE might work for this. Can you give me more details?

Thanks again!

Xin

On 4/28/05, Richard B. Johnson <linux-os@analogic.com> wrote:
> On Thu, 28 Apr 2005, Xin Zhao wrote:
> 
> > Can anyone give me a hand? or point me to somewhere I can find related
> > information?
> >
> > Thanks in advance!
> >
> > Xin
> 
> printk(KERN_XXX"whatever") was designed for this.
> 
> #define KERN_EMERG      "<0>"   /* system is unusable                   */
> #define KERN_ALERT      "<1>"   /* action must be taken immediately     */
> #define KERN_CRIT       "<2>"   /* critical conditions                  */
> #define KERN_ERR        "<3>"   /* error conditions                     */
> #define KERN_WARNING    "<4>"   /* warning conditions                   */
> #define KERN_NOTICE     "<5>"   /* normal but significant condition     */
> #define KERN_INFO       "<6>"   /* informational                        */
> #define KERN_DEBUG      "<7>"   /* debug-level messages                 */
>         printk(KERN_DEBUG fmt,##arg)
>         printk(KERN_INFO fmt,##arg)
> 
> You could define your own, KERN_PRIVATE "<8>" and have the syslog
> facility filter on that.
> 
> Other ways are to write stuff to a buffer or linked-list and
> read it out using an ioctl() or read() in your module. If you
> do this, make sure that your module code doesn't wait forever
> if the buffer gets full.
> 
> Cheers,
> Dick Johnson
> Penguin : Linux version 2.6.11 on an i686 machine (5537.79 BogoMips).
>   Notice : All mail here is now cached for review by Dictator Bush.
>                   98.36% of all statistics are fiction.
>

Re: dumb question: How to create your own log files in a kernel module?

[Michael Opdenacker]

Hi Xin,

>I know printk can do this job. But what I really want is to print logs
>to a file specified by me instead of /var/log/messages. And, the
>messages irrelevant to my module should not be written into that file.
> Now my log mixed with other logs in /var/log/message, which bother me
>much. :(
>
You seem to make a confusion here...

Don't forget that files are only an abstraction for userspace. They are 
only meant to be read and written from userspace. Kernel code can never 
read or write files. In the case of /var/log/messages, this file is 
created by the syslogd program from the kernel buffer, not by the kernel 
itself.

You could just echo something specific to your driver in your printk 
strings, and grep this specific thing in /var/log/messages. You have 
your file!

    Cheers,

    Michael.

-- 
Michael Opdenacker
http://free-electrons.com
+33 621 604 642

Re: dumb question: How to create your own log files in a kernel module?

[Chris Wedgwood]

On Thu, Apr 28, 2005 at 02:10:39PM -0400, Xin Zhao wrote:

> Can anyone give me a hand? or point me to somewhere I can find
> related information?

man syslogd

Re: dumb question: How to create your own log files in a kernel module?

[Bodo Eggert <harvested.in.lkml@posting.7eggert.dyndns.org>]

Xin Zhao <uszhaoxin@gmail.com> wrote:

> Thanks for kind help.
> 
> I know printk can do this job. But what I really want is to print logs
> to a file specified by me instead of /var/log/messages.

RTFM.

man 5 syslogd.conf
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