LinuxQuestions.org - Compile a kernel module

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Compile a kernel module

I'm having problems to compile a simple Hello World module. I'm using the kernel 2.6 with a SUSE 10.0 distribution and gcc 4.0.2.
The problem is that the Makefile doesn't compile the module, it doesnt create .o or .ko objects. Can anyone help?

*** Here is the code:

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>

MODULE_LICENSE("GPL");

static int hello_init(void)
{
printk(KERN_ALERT "Hello World\n");
return 0;
}
static void hello_cleanup(void) {
printk(KERN_ALERT "Bye!\n");
}
module_init(hello_init);
module_exit(hello_cleanup);

*** The Makefile:

obj-m := hello.o
KDIR := /lib/modules/$(shell uname -r)/build
PWD := $(shell pwd)
default:
$(MAKE) -C $(KDIR) SUBDIRS=$(PWD) modules

*** The Output:

unit1:/home/rui/module # make
make -C /lib/modules/2.6.13-15-smp/build SUBDIRS=/home/rui/module modules
make[1]: Entering directory `/usr/src/linux-2.6.13-15-obj/i386/smp'
make -C ../../../linux-2.6.13-15 O=../linux-2.6.13-15-obj/i386/smp modules
Building modules, stage 2.
MODPOST
make[1]: Leaving directory `/usr/src/linux-2.6.13-15-obj/i386/smp'

You need a tab character before $(MAKE) in the default rule. Not spaces... a tab.

Actually there is a TAB before $(MAKE) in my Makefile. Without the tab the message is diferent. It says that there is nothing to be done for default.
The question continues...

Sorry, looks like no whitespace at all in the original post.

I have to rebuild a kernel network module with each new Fedora kernel release if I want IPv6 to work. Here's how I do it. Maybe it'll help...

Code:

[root@osprey net]# pwd

/usr/src/redhat/BUILD/kernel-2.6.15/linux-2.6.15/drivers/net

[root@osprey net]# ls -l via-velocity*

-rw-r--r--  2 root root 88117 Mar  2 18:28 via-velocity.c

-rw-r--r--  2 root root 50028 Jan  2 21:21 via-velocity.h

[root@osprey net]# cat Makefile

obj-m := via-velocity.o



KDIR  := /lib/modules/$(shell uname -r)/build

PWD  := $(shell pwd)



default:

        $(MAKE) -C $(KDIR) M=$(PWD) modules



[root@osprey net]# make

make -C /lib/modules/2.6.15-1.1833_FC4/build M=/usr/src/redhat/BUILD/kernel-2.6.15/linux-2.6.15/drivers/net modules

make[1]: Entering directory `/usr/src/kernels/2.6.15-1.1833_FC4-x86_64'

  CC [M]  /usr/src/redhat/BUILD/kernel-2.6.15/linux-2.6.15/drivers/net/via-velocity.o

  Building modules, stage 2.

  MODPOST

  CC      /usr/src/redhat/BUILD/kernel-2.6.15/linux-2.6.15/drivers/net/via-velocity.mod.o

  LD [M]  /usr/src/redhat/BUILD/kernel-2.6.15/linux-2.6.15/drivers/net/via-velocity.ko

make[1]: Leaving directory `/usr/src/kernels/2.6.15-1.1833_FC4-x86_64'

[root@osprey net]# ls -l via-velocity*

-rw-r--r--  2 root root  88117 Mar  2 18:28 via-velocity.c

-rw-r--r--  2 root root  50028 Jan  2 21:21 via-velocity.h

-rw-r--r--  1 root root 426144 Mar 11 07:58 via-velocity.ko

-rw-r--r--  1 root root  2957 Mar 11 07:58 via-velocity.mod.c

-rw-r--r--  1 root root  44960 Mar 11 07:58 via-velocity.mod.o

-rw-r--r--  1 root root 382592 Mar 11 07:58 via-velocity.o

[root@osprey net]#

That's exactly what I wanted. But didn't get it...
I'm wondering about the file vermagic.o. That file should be in /init and doesn't appear in my directory. I read that all the modules must pass through a linking step with this file. Does it appear for you? Do you know how can I create it? Maybe I forgot something in the kernel's configuration.

I have no vermagic.o anywhere on my system.

I did notice one difference between your Makefile and mine; you have "SUBDIRS=" where I have "M=". I don't really know if it's important or not.