kernel module programming

osor · 11-03-2007, 02:41 PM

Quote:

Originally Posted by sniffer_raghav

problem is that
printk is not giving message on the terminal

You are not in userspace.

printf() — print formatted strings to stdout (i.e., “the terminal”).

printk() — print formatted strings of a specific priority on the (circular) kernel log buffer.

It is up to you how to access the kernel log buffer. Some examples include using the dmesg utility, opening a userspace connection to /proc/kmsg, and using the userspace functions klogctl()/syslog().

osor · 11-03-2007, 03:16 PM

Quote:

Originally Posted by dale_chip

but when i did cp makefile Makefile
it compiled succesfully.

When dealing with external module building, a makefile is usually the best way to go. If for some reason all built-ins in the kernel tree are not built, it may not assume KBUILD_EXTMOD and will instead try to build the module by descending into your directory and using your makefile (this method is used on page 24 of this book). Whenever this is done by the kernel build system, all makefiles should be named “Makefile” (other names include “Kbuild”).

If, for some reason, you want to continue using the one-liner, try appending the target “modules” to the command.

itz2000 · 11-03-2007, 03:27 PM

Quote:

Originally Posted by sniffer_raghav

#include<linux/module.h>
#include<linux/kernel.h>
#include<linux/init.h>
static int hello3_data __initdata = 3;
static int __init hello_3_init(void)
{
printk(KERN_INFO "Hello, world %d\n", hello3_data);
return 0;
}
static void __exit hello_3_exit(void)
{
printk(KERN_INFO "Goodbye, world 3\n");
}
module_init(hello_3_init);
module_exit(hello_3_exit);

sir i have successfully compiled the above code but problem is that
printk is not giving message on the terminal ......
y is it so sir explain ...........
thank you..........

After you do insmod check out the dmesg

Code:

insmod MODULE-NAME
dmesg

it should be appear on last line the (module_init function)
and if you do

Code:

rmmod MODULE-NAME
dmesg

you'll receive on the last line the other message which is the module_exit function.

I hope it will help.

knockout_artist · 11-11-2007, 03:43 PM

.

Already answered

sixerjman · 11-15-2007, 06:09 AM

http://tldp.org/LDP/lkmpg/2.6/html/index.html

madluther · 11-15-2007, 07:44 PM

A very good resource for Kernel Programming is http://kernelnewbies.org/

Mad.

ravi_chobey · 11-26-2007, 12:39 AM

pls use this command you will be getting the dsired output:

dmesg -c
dmesg

Ravi

Ashok_mittal · 12-12-2007, 04:12 AM

Quote:

Originally Posted by sniffer_raghav

#include<linux/module.h>
#include<linux/kernel.h>
#include<linux/init.h>
static int hello3_data __initdata = 3;
static int __init hello_3_init(void)
{
printk(KERN_INFO "Hello, world %d\n", hello3_data);
return 0;
}
static void __exit hello_3_exit(void)
{
printk(KERN_INFO "Goodbye, world 3\n");
}
module_init(hello_3_init);
module_exit(hello_3_exit);

sir i have successfully compiled the above code but problem is that
printk is not giving message on the terminal ......
y is it so sir explain ...........
thank you..........

You can this in /var/tmp/message.for print message on terminal include linux/tty.h and then instead of printk write console_print(....).