linux内核demo

1，hello:
最基本的hello world内核模块
make
sudo insmod hello.ko
dmesg |tail
sudo rmmod hello

/*************** hello.c ***************/
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("djwow");
static int hello_init(void)
{
printk(KERN_ALERT "Hello, world!n");
return 0;
}
static void hello_exit(void)
{
printk(KERN_ALERT "Goodbye, My Dear World!n");
}
module_init(hello_init);
module_exit(hello_exit);

makefile:

obj-m = hello.o
KVERSION = $(shell uname -r)
all:
make -C /lib/modules/$(KVERSION)/build M=$(PWD) modules
clean:
make -C /lib/modules/$(KVERSION)/build M=$(PWD) clean

2，hello-1,hello-2:
hello-2导出了一个hello_data的全局变量，供hello-1中的模块使用。
先编译hello-2。并将目录下的Module.symvers拷贝到hello-1中。然后再编译hello-1。
然后先安装hello-2中的模块，再运行hello-1中的模块。
或者将hello-1中的KBUILD_EXTRA_SYMBOLS = /mnt/hgfs/MallocFreeIBM/Linux/10ten-hellokernel/demo/hello-2/Module.symvers中的/mnt/hgfs/MallocFreeIBM/Linux/10ten-hellokernel/demo/hello-2修改为你自己对应的hello-2的路径。


hello-1.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
MODULE_LICENSE("GPL");
extern int hello_data;
static int hello_init(void)
{
printk(KERN_ERR "hello,kernel!,this is hello modulen");
printk(KERN_ERR "hello_data:%dn",++hello_data);
return 0;
}
static void hello_exit(void)
{
printk(KERN_ERR "hello_data:%dn",--hello_data);
printk(KERN_ERR "Leave hello module!n");
}
module_init(hello_init);
module_exit(hello_exit);
MODULE_AUTHOR("djwow");
MODULE_DESCRIPTION("This is hello module");
MODULE_ALIAS("A simple example");

hello_2.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
MODULE_LICENSE("GPL");
unsigned int hello_data=100;
EXPORT_SYMBOL(hello_data);
static int hello_h_init(void)
{
hello_data+=5;
printk(KERN_ERR "hello_data:%dnhello kernel,this is hello_h modulen",hello_data);
return 0;
}
static void hello_h_exit(void)
{
hello_data-=5;
printk(KERN_ERR "hello_data:%dnleave hello_h modulen",hello_data);
}
module_init(hello_h_init);
module_exit(hello_h_exit);
MODULE_AUTHOR("djwow.com");

makefile

obj-m=hello_2.o
KVERSION = $(shell uname -r)
all:
make -C /lib/modules/$(KVERSION)/build M=$(PWD) modules
clean:
make -C /lib/modules/$(KVERSION)/build M=$(PWD) clean

3，hello-param用于向模块动态传递参数
编译之后运行方法：
insmod hello who="world" times=5 

#include <linux/init.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
MODULE_LICENSE("Dual BSD/GPL");
static char *who= "world";
static int times = 1;
module_param(times,int,S_IRUSR);
module_param(who,charp,S_IRUSR);
static int hello_init(void)
{
int i;
for(i=0;i<times;i++)
printk(KERN_ALERT "(%d) hello, %s!n",i,who);
return 0;
}
static void hello_exit(void)
{
printk(KERN_ALERT"Goodbye, %s!n",who);
}
module_init(hello_init);
module_exit(hello_exit);

makefile:

obj-m = hello.o
KVERSION = $(shell uname -r)
all:
make -C /lib/modules/$(KVERSION)/build M=$(PWD) modules
clean:
make -C /lib/modules/$(KVERSION)/build M=$(PWD) clean

4，kernel-client 通信demop 顺便演示了timer使用
先分别运行make编译好client和kernel程序。
然后，加载驱动:sudo insmod timer-kernel.ko 
然后，
cat /proc/devices,查看second对应的主功能号，如251
sudo mknod /dev/second c 251 0
然后运行client:
./timer-client


client:

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
int main(void)
{
int fd, i;
int data;
fd = open("/dev/second",O_RDONLY);
if (fd < 0)
{
printf("open /dev/second errorn");
}
for(i = 0; ; i++)
{
read(fd, &data, sizeof(data));
printf("read /dev/second is %dn",data);
sleep(1);
}
close(fd);
}

makefile:

timer-client:timer-client.o
gcc -o timer-client timer-client.o
timer-client.o:timer-client.c
gcc -c timer-client.c -o timer-client.o
clean:
rm -f *.o timer-client

kernel:

#include <linux/module.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/cdev.h>
#include <asm/io.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <linux/timer.h>
#include <asm/atomic.h>
#define SECOND_MAJOR 0
static int second_major = SECOND_MAJOR;
struct second_dev
{
struct cdev cdev;
atomic_t counter;
struct timer_list s_timer;
};
struct second_dev *second_devp;
static void second_timer_handle(unsigned long arg)
{
mod_timer(&second_devp->s_timer, jiffies + HZ);
atomic_inc(&second_devp->counter);
printk(KERN_INFO "current jiffies is %ldn",jiffies);
}
int second_open(struct inode *inode, struct file *filp)
{
init_timer(&second_devp->s_timer);
second_devp->s_timer.function = &second_timer_handle;
second_devp->s_timer.expires = jiffies + HZ;
add_timer(&second_devp->s_timer);
atomic_set(&second_devp->counter, 0);
return 0;
}
int second_release(struct inode *inode, struct file *filp)
{
del_timer(&second_devp->s_timer);
return 0;
}
static ssize_t second_read(struct file *filp, char __user *buf, size_t count,
loff_t *ppos)
{
int counter;
counter = atomic_read(&second_devp->counter);
if (put_user(counter, (int *)buf))
{
return -EFAULT;
}else
{
return sizeof(unsigned int);
}
}
static const struct file_operations second_fops =
{
.owner = THIS_MODULE,
.open = second_open,
.release = second_release,
.read = second_read,
};
static void second_setup_cdev(struct second_dev *dev, int index)
{
int err, devno = MKDEV(second_major, index);
cdev_init(&dev->cdev, &second_fops);
dev->cdev.owner = THIS_MODULE;
dev->cdev.ops = &second_fops;
err = cdev_add(&dev->cdev, devno, 1);
if (err)
{
printk(KERN_NOTICE "Error %d add second%d", err, index);
}
}
int second_init(void)
{
int ret;
dev_t devno = MKDEV(second_major, 0);
if (second_major)
{
ret = register_chrdev_region(devno, 1, "second");
}else
{
ret = alloc_chrdev_region(&devno, 0, 1, "second");
second_major = MAJOR(devno);
}
if (ret < 0)
{
return ret;
}
second_devp = kmalloc(sizeof(struct second_dev), GFP_KERNEL);
if (!second_devp)
{
ret = -ENOMEM;
goto fail_malloc;
}
memset(second_devp, 0, sizeof(struct second_dev));
second_setup_cdev(second_devp, 0);
return 0;
fail_malloc:
unregister_chrdev_region(devno, 1);
return ret;
}
void second_exit(void)
{
cdev_del(&second_devp->cdev);
kfree(second_devp);
unregister_chrdev_region(MKDEV(second_major, 0), 1);
}
MODULE_AUTHOR("djwow");
MODULE_LICENSE("Dual BSD/GPL");
module_param(second_major, int, S_IRUGO);
module_init(second_init);
module_exit(second_exit);

5,char_drv 通信demo 

另外一个例子可以看我了另一篇文件

http://blog.csdn.net/zhuhuibeishadiao/article/details/51456791

先运行make编译好kernel程序。
然后，加载驱动:sudo insmod char_drv.ko
然后，
cat /proc/devices,查看mem_dev对应的主功能号，如251
sudo mknod /dev/memdev0 c 251 0
然后运行client:
gcc -o test_char_drv test_char_drv.c 
./test_char_drv


R3:

#include <stdio.h>
#include <string.h>
int main()
{
FILE *fp0 = NULL;
char Buf[4096];
/*初始化Buf*/
strcpy(Buf,"Mem is char dev!");
printf("BUF: %sn",Buf);
/*打开设备文件*/
fp0 = fopen("/dev/memdev0","r+");
if (fp0 == NULL)
{
printf("Open Memdev0 Error!n");
return -1;
}
/*写入设备*/
fwrite(Buf, sizeof(Buf), 1, fp0);
/*重新定位文件位置（思考没有该指令，会有何后果)*/
fseek(fp0,0,SEEK_SET);
/*清除Buf*/
strcpy(Buf,"Buf is NULL!");
printf("BUF: %sn",Buf);
/*读出设备*/
fread(Buf, sizeof(Buf), 1, fp0);
/*检测结果*/
printf("BUF: %sn",Buf);
return 0;
}

R0:

char_drv.h
#ifndef _MEMDEV_H_
#define _MEMDEV_H_
#ifndef MEMDEV_MAJOR
#define MEMDEV_MAJOR 251
/*预设的mem的主设备号*/
#endif
#ifndef MEMDEV_NR_DEVS
#define MEMDEV_NR_DEVS 2
/*设备数*/
#endif
#ifndef MEMDEV_SIZE
#define MEMDEV_SIZE 4096
#endif
/*mem设备描述结构体*/
struct mem_dev
{
char *data;
unsigned long size;
};
#endif /* _MEMDEV_H_ */

char_drv.c

#include "char_drv.h"
#include <linux/module.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/cdev.h>
#include <asm/io.h>
#include <asm/system.h>
#include <asm/uaccess.h>
static int mem_major = MEMDEV_MAJOR;
module_param(mem_major, int, S_IRUGO);
struct mem_dev *mem_devp; /*设备结构体指针*/
struct cdev cdev;
/*文件打开函数*/
int mem_open(struct inode *inode, struct file *filp)
{
struct mem_dev *dev;
/*获取次设备号*/
int num = MINOR(inode->i_rdev);
if (num >= MEMDEV_NR_DEVS)
return -ENODEV;
dev = &mem_devp[num];
/*将设备描述结构指针赋值给文件私有数据指针*/
filp->private_data = dev;
return 0;
}
/*文件释放函数*/
int mem_release(struct inode *inode, struct file *filp)
{
return 0;
}
/*读函数*/
static ssize_t mem_read(struct file *filp, char __user *buf, size_t size, loff_t *ppos)
{
unsigned long p =
*ppos;
/*记录文件指针偏移位置*/
unsigned int count = size;
/*记录需要读取的字节数*/
int ret = 0;
/*返回值*/
struct mem_dev *dev = filp->private_data; /*获得设备结构体指针*/
/*判断读位置是否有效*/
if (p >= MEMDEV_SIZE)
/*要读取的偏移大于设备的内存空间*/
return 0;
if (count > MEMDEV_SIZE - p)
/*要读取的字节大于设备的内存空间*/
count = MEMDEV_SIZE - p;
/*读数据到用户空间:内核空间->用户空间交换数据*/
if (copy_to_user(buf, (void*)(dev->data + p), count))
{
ret =
- EFAULT;
}
else
{
*ppos += count;
ret = count;
printk(KERN_INFO "read %d bytes(s) from %ldn", count, p);
}
return ret;
}
/*写函数*/
static ssize_t mem_write(struct file *filp, const char __user *buf, size_t size, loff_t *ppos)
{
unsigned long p =
*ppos;
unsigned int count = size;
int ret = 0;
struct mem_dev *dev = filp->private_data; /*获得设备结构体指针*/
/*分析和获取有效的写长度*/
if (p >= MEMDEV_SIZE)
return 0;
if (count > MEMDEV_SIZE - p)
/*要写入的字节大于设备的内存空间*/
count = MEMDEV_SIZE - p;
/*从用户空间写入数据*/
if (copy_from_user(dev->data + p, buf, count))
ret =
- EFAULT;
else
{
*ppos += count;
/*增加偏移位置*/
ret = count;
/*返回实际的写入字节数*/
printk(KERN_INFO "written %d bytes(s) from %ldn", count, p);
}
return ret;
}
/* seek文件定位函数 */
static loff_t mem_llseek(struct file *filp, loff_t offset, int whence)
{
loff_t newpos;
switch(whence) {
case 0: /* SEEK_SET */
/*相对文件开始位置偏移*/
newpos = offset;
/*更新文件指针位置*/
break;
case 1: /* SEEK_CUR */
newpos = filp->f_pos + offset;
break;
case 2: /* SEEK_END */
newpos = MEMDEV_SIZE -1 + offset;
break;
default: /* can't happen */
return -EINVAL;
}
if ((newpos<0) || (newpos>MEMDEV_SIZE))
return -EINVAL;
filp->f_pos = newpos;
return newpos;
}
/*文件操作结构体*/
static const struct file_operations mem_fops =
{
.owner = THIS_MODULE,
.llseek = mem_llseek,
.read = mem_read,
.write = mem_write,
.open = mem_open,
.release = mem_release,
};
/*设备驱动模块加载函数*/
static int memdev_init(void)
{
int result;
int i;
dev_t devno = MKDEV(mem_major, 0);
/* 申请设备号，当xxx_major不为0时，表示静态指定；当为0时，表示动态申请*/
/* 静态申请设备号*/
if (mem_major)
result = register_chrdev_region(devno, 2, "mem_dev");
else
/* 动态分配设备号 */
{
result = alloc_chrdev_region(&devno, 0, 2, "mem_dev");
mem_major = MAJOR(devno);
/*获得申请的主设备号*/
}
if (result < 0)
return result;
/*初始化cdev结构，并传递file_operations结构指针*/
cdev_init(&cdev, &mem_fops);
cdev.owner = THIS_MODULE;
/*指定所属模块*/
cdev.ops = &mem_fops;
/* 注册字符设备 */
cdev_add(&cdev, MKDEV(mem_major, 0), MEMDEV_NR_DEVS);
/* 为设备描述结构分配内存*/
mem_devp = kmalloc(MEMDEV_NR_DEVS * sizeof(struct mem_dev), GFP_KERNEL);
if (!mem_devp)
/*申请失败*/
{
result =
- ENOMEM;
goto fail_malloc;
}
memset(mem_devp, 0, sizeof(struct mem_dev));
/*为设备分配内存*/
for (i=0; i < MEMDEV_NR_DEVS; i++)
{
mem_devp[i].size = MEMDEV_SIZE;
mem_devp[i].data = kmalloc(MEMDEV_SIZE, GFP_KERNEL);
memset(mem_devp[i].data, 0, MEMDEV_SIZE);
}
return 0;
fail_malloc:
unregister_chrdev_region(devno, 1);
return result;
}
/*模块卸载函数*/
static void memdev_exit(void)
{
cdev_del(&cdev);
/*注销设备*/
kfree(mem_devp);
/*释放设备结构体内存*/
unregister_chrdev_region(MKDEV(mem_major, 0), 2); /*释放设备号*/
}
MODULE_AUTHOR("djwow");
MODULE_LICENSE("GPL");
module_init(memdev_init);
module_exit(memdev_exit);

最后

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