linux内核模块加载

首先需要安装库文件 yum install kernel-devel kernel，支持内核编程。
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然后编写内核模块程序
#include
#include
#include
#include
#include
#include

MODULE_AUTHOR("Me");
MODULE_LICENSE("GPL");

#define MYCDEV_MAJOR 231 /*给定的主设备号*/
#define MYCDEV_SIZE 100

static int mycdev_open(struct inode *inode, struct file *fp)
{
    return 0;
}

static int mycdev_release(struct inode *inode, struct file *fp)
{
    return 0;
}

static ssize_t mycdev_read(struct file *fp, char __user *buf, size_t size, loff_t *pos)
{
    unsigned long p = *pos;
    unsigned int count = size;
    //char kernel_buf[MYCDEV_SIZE]="This is mycdev!";
    char kernel_buf[MYCDEV_SIZE];
    int i;

    memset(kernel_buf,0,MYCDEV_SIZE);
    memcpy(kernel_buf, "This is mycdev!", MYCDEV_SIZE);

    if(p >= MYCDEV_SIZE)
        return -1;
    if(count > MYCDEV_SIZE)
        count = MYCDEV_SIZE - p;

    if (copy_to_user(buf, kernel_buf, count) != 0) {
        printk("read error!\n");
        return -1;
    }

    /*
    for (i = 0; i < count; i++) {
        __put_user(i, buf);//write 'i' from kernel space to user space's buf;
        buf++;
    }
    */

    printk("reader: %d bytes was read...\n", count);
    return count;
}

static ssize_t mycdev_write(struct file *fp, const char __user *buf, size_t size, loff_t *pos)
{
    return size;
}

/* 填充 mycdev的 file operation 结构*/
static const struct file_operations mycdev_fops =
{
    .owner = THIS_MODULE,
    .read = mycdev_read,
    .write = mycdev_write,
    .open = mycdev_open,
    .release = mycdev_release,
};

/*模块初始化函数*/
static int __init mycdev_init(void)
{
    int ret;
    printk("mycdev module is staring..\n");
    ret=register_chrdev(MYCDEV_MAJOR,"my_cdev",&mycdev_fops); /*注册驱动程序*/
    if(ret<0){
        printk("register failed..\n");
        return 0;
    }else{
        printk("register success..\n");
    }
    return 0;
}

/*模块卸载函数*/
static void __exit mycdev_exit(void)
{
    printk("mycdev module is leaving..\n");
    unregister_chrdev(MYCDEV_MAJOR,"my_cdev"); /*注销驱动程序*/
}

module_init(mycdev_init);
module_exit(mycdev_exit);

以上保存为mydev.c
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编写测试程序
#include
#include
#include
#include
#include

int main()
{
    int testdev;
    int i, ret;
    char buf[15];

    testdev = open("/dev/mycdev", O_RDWR);

    if (-1 == testdev) {
        printf("cannot open file.\n");
        exit(1);
    }

    if (ret = read(testdev, buf, 15) <15) {
        printf("read error!\n");
        exit(1);
    }

    printf("%s\n", buf);

    close(testdev);

    return 0;
}


以上保存为mydev_test.c

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编写Makefile文件

obj-m:=mydev.o          
PWD:=$(shell pwd)     
CUR_PATH:=$(shell uname -r)   
KERNEL_PATH:=/usr/src/kernels/$(CUR_PATH)  

all:
    make -C $(KERNEL_PATH) M=$(PWD) modules
   
clean:
    make -C $(KERNEL_PATH) M=$(PWD) clean

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命令 #make
结果 :
make -C /usr/src/kernels/2.6.32-279.9.1.el6.i686        M=/root/桌面/homework       modules
make[1]: Entering directory `/usr/src/kernels/2.6.32-279.9.1.el6.i686'
  CC [M]  /root/桌面/homework/mydev.o
/root/桌面/homework/mydev.c: In function ‘mycdev_read’:
/root/桌面/homework/mydev.c:30: warning: unused variable ‘i’
  Building modules, stage 2.
  MODPOST 1 modules
  CC      /root/桌面/homework/mydev.mod.o
  LD [M]  /root/桌面/homework/mydev.ko.unsigned
  NO SIGN [M] /root/桌面/homework/mydev.ko
make[1]: Leaving directory `/usr/src/kernels/2.6.32-279.9.1.el6.i686'




[root@bogon 桌面]# insmod mydev.ko
[root@bogon 桌面]# cat /proc/devices
[root@bogon 桌面]# mknod /dev/mydev c 231 0
[root@bogon 桌面]# chmod 777 /dev/mydev
[root@bogon 桌面]# gcc mycdev_test.c -o mydev_test
[root@bogon 桌面]# ./mydev_test
[root@bogon 桌面]# dmesg