[root@localhost /home/ahao.mah/main]

#cat  hello.c

// Defining __KERNEL__ and MODULE allows us to access kernel-level code not usually available to userspace programs.

#undef __KERNEL__

#define __KERNEL__

#undef MODULE

#define MODULE

// Linux Kernel/LKM headers: module.h is needed by all modules and kernel.h is needed for KERN_INFO.

#include <linux/module.h>    // included for all kernel modules

#include <linux/kernel.h>    // included for KERN_INFO

#include <linux/init.h>        // included for __init and __exit macros

static int __init hello_init(void)

{

    printk(KERN_INFO "Hello world!\n");

    return 0;    // Non-zero return means that the module couldn't be loaded.

}

static void __exit hello_cleanup(void)

{

    printk(KERN_INFO "Cleaning up module.\n");

}

module_init(hello_init);

module_exit(hello_cleanup);

[root@localhost /home/ahao.mah/main]

#cat Makefile

obj-m := hello.o

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

PWD := $(shell pwd)

all:

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

clean:

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

[root@localhost /home/ahao.mah/main]

#ll Makefile hello.c

-rw-r--r-- 1 root root 785 Dec 21 15:48 hello.c

-rwxr-xr-x 1 root root 170 Dec 21 15:51 Makefile

[root@localhost /home/ahao.mah/main]

#make

make -C /lib/modules/3.10.0-327.ali2000.alios7.x86_64/build M=/home/ahao.mah/main modules

make[1]: Entering directory `/usr/src/kernels/3.10.0-327.ali2000.alios7.x86_64'

  CC [M]  /home/ahao.mah/main/hello.o

  Building modules, stage 2.

  MODPOST 1 modules

  CC      /home/ahao.mah/main/hello.mod.o

  LD [M]  /home/ahao.mah/main/hello.ko

make[1]: Leaving directory `/usr/src/kernels/3.10.0-327.ali2000.alios7.x86_64'

[root@localhost /home/ahao.mah/main]

#ls

hello.c  hello.ko  hello.mod.c  hello.mod.o  hello.o  Makefile  modules.order  Module.symvers

[root@localhost /home/ahao.mah/main]

#lsmod  | grep hello

[root@localhost /home/ahao.mah/main]

#insmod hello.ko

[root@localhost /home/ahao.mah/main]

#lsmod  | grep hello

hello                  12428  0

[root@localhost /home/ahao.mah/main]

#tail /var/log/messages

Dec 21 15:52:43 rt2m09617 kernel: hello: module license 'unspecified' taints kernel.

Dec 21 15:52:43 rt2m09617 kernel: Disabling lock debugging due to kernel taint

Dec 21 15:52:43 rt2m09617 kernel: hello: module verification failed: signature and/or required key missing - tainting kernel

Dec 21 15:52:43 rt2m09617 kernel: Hello world!