hiiii every body i am just a beginner in kernel module programming.
i want help regarding it .
i have written a simple module and trying to complie it but it is giving the error that linux/module.h file is not there though i have seprately specified the pat of file but then dependencies are missing please help me out......
thanx in advance.

Perhaps you should begin by studying a small existing module.

No, seriously...

hiii....
i have written a simple module which is as follows
#include <linux/module.h>

int init_module(void)
{
printk("<1>Hello, world\n");
return 0;
}
void cleanup_module(void)
{
printk("<1>Goodbye cruel world\n");
}
first the error was that linux/module.h
file not found ..............
then i gave the path where file is but it is giving dependencies error .........
can u suggest me any tutorial or sol of this prob ..........
thanx in advance......

Well, you haven’t told us how you are building this module. Since the error is occurring during building, it would seem this is an important detail…

In any case, the recommended method of compilation is to use the kernel’s own build system. E.g., for a simple, one-file module try something like this:
(where $filename is the name of your C sourcefile).

You can read more about the 2.6 kernel build system in just about any kernel programming guide or tutorial.

i m buliding this module by following set of command
first im creating object file by
#gcc -c -i hello.c
during compilation its is giving error

and the command u have suggested i have tried
it is giving this >
now what i have to supply ????????/
plz reply..........
thanx in advance

Well, that’s your problem then…
I suggest you carefully look at the command suggested, and make sure you copy-and-paste it correctly. For example, if my file is called hello.c, this is what I do:
In any case, I would read (yes, as in ) any linux 2.6 kernel programming guide (or even the official document), for generic build instructions.

By all means, look at the literally-hundreds of existing modules that are available in your Linux distro! (You might have to install "source" packages to see them.)

The most common way to approach any kernel-module is to find something that's "almost" what you want, then practice installing it, and then use it as a starting-point. "If you are starting from scratch, on anything, you are doing something wrong."

thank you sir ,
sir i have tried wat you told me to do ...........
again i am getting error that is given below...........
make -C "/lib/modules/$(uname -r)/build" M=$PWD obj-m="$(basename $hello .c).o"
make: Entering directory `/usr/src/kernels/linux-2.6.23'
LD /root/device/built-in.o
make[1]: *** No rule to make target `/root/device/.c.c', needed by `/root/device/.c.o'. Stop.
make: *** [_module_/root/device] Error 2
make: Leaving directory `/usr/src/kernels/linux-2.6.23'

please read it and reply.......
i have also compiled a new kernle 2.6.23
and have includede all the kernel headers .......
though my prob is not solved...........
please help me out ...........

Hmmm… What could be the problem?
It doesn’t look like you’ve looked at any of the seven links I had in my last post. In fact, you barely managed to read my post (you seem to have missed an entire line).

sir i have read the pdf you have provided and followed the things given dere .........
but prob is not solved the prob i m getting is below.............
make -C "/lib/modules/$(uname -r)/build" M=$PWD obj-m="$(basename $hello .c).o"
make: Entering directory `/usr/src/kernels/2.6.21-1.3194.fc7-i686'
make[1]: *** No rule to make target `/root/device/.c.c', needed by `/root/device/.c.o'. Stop.
make: *** [_module_/root/device] Error 2
make: Leaving directory `/usr/src/kernels/2.6.21-1.3194.fc7-i686'
please sir tell y dis error is occuring ..........
thanx for the material provided ...........

First, did you not see the highlighted string from my previous post?
Had you read any of those articles, you would have found that the obj-m should hold a list of object files which shall be linked to be loadable kernel object files. The dependency resolution shall assume (this assumption may be overridden) that the sole source file corresponding to said object file has the same basename (without extension) and has extension “.c”.

So if you want a kernel object file named “foo.ko”, you would set “obj-m=foo.o”, and the kernel build system would compile such an object from the file “foo.c”. Conversely, if you have a source file named “bar.c” and wanted to compile it, you would set “obj-m=bar.o”, and the end-result would be a file named “bar.ko”.

Now, suppose you have a file named “hello.c”. How do you go about compiling it? You could do this:
Or this:
Or even this:

sir,
i have tread all those links and was successful in loading and
umloading the module. the problem is solved.now when i have written a module and loaded it tell me the next step to follow for learning the programming.
thank you for the co operation.

hello ,
coincidentally i was trying the same thing on 2.6.23 kernel
i did exactly
make -C "/lib/modules/$(uname -r)/build" M=$PWD obj-m="helloworld.o"

my file name was helloworld.c
and $PWD was /root

file helloworld.c is :
#include<linux/init.h>
#include<linux/module.h>

MODULE_LICENSE("Dual BSD/GPL");

static int hello_init(void)
{
printk(KERN_ALERT "Hello, World\n");
return 0;
}

static void hello_exit(void)
{
printk(KERN_ALERT "Goodbye, cruel world\n");
}

module_init(hello_init);
module_exit(hello_exit);

as taken from a e-book on module and device drivers programming for the 2.6.* kernels.

but i was getting errors :
make: Entering directory `/usr/src/linux-2.6.23.1'
scripts/Makefile.build:33: /root/Makefile: No such file or directory
make[1]: *** No rule to make target `/root/Makefile'. Stop.
make: *** [_module_/root] Error 2
make: Leaving directory `/usr/src/linux-2.6.23.1'

please can any one help me out ...

i tried out this thing :
i made a makefile :
obj-m := helloworld.o

then i did this :
make -C /usr/src/linux SUBDIRS=$PWD modules

it also gave errors

but when i did cp makefile Makefile
it compiled succesfully.

why did it not happen wid
make -C "/lib/modules/$(uname -r)/build" M=$PWD obj-m="helloworld.o"

plz someone explain this to me, cos i feel its understanding is crucial for further study in this field.

#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..........