初步Linux内核模块编程

àì夳堔傛蜴生んèń 2022-04-10 04:24 293阅读 0赞

## 基本命令 ##

lsmod                    // 查看当前已加载的模块
    insmod testmodule.ko     // 加载testmodule模块
    rmmod testmodule         // 卸载testmodule模块
    dmesg                    // dmesg用来显示内核环缓冲区内容，内核将各种消息存放在这里

## 简单实例 ##

模块源代码testmodule1.c如下

// 源码来自《操作系统概念-第九版》
    // 《operating system concepts, 9th edition》
    #include <linux/init.h>
    #include <linux/kernel.h>
    #include <linux/module.h>
    /* This function is called when the module is loaded. */
    int simple init(void)
    { 
    	printk(KERN INFO "Loading Module\n");
    	return 0;
    }
    /* This function is called when the module is removed. */
    void simple exit(void)
    { 
    	printk(KERN INFO "Removing Module\n");
    }
    /* Macros for registering module entry and exit points. */
    module init(simple init);
    module exit(simple exit);
    MODULE LICENSE("GPL");
    MODULE DESCRIPTION("Simple Module");
    MODULE AUTHOR("SGG");

testmodule1.c的Makefile如下

ifneq ($(KERNELRELEASE),)
    	obj-m:=testmodule1.o
    else
    	PWD:=$(shell pwd)
    	KDIR:=/lib/modules/$(shell uname -r)/build
    all:
    	make -C $(KDIR) M=$(PWD) modules
    endif

Linux内核链表操作  
《operating system concepts，9th edition》p96习题。  
源代码testmodule2.c如下:

#include <linux/init.h>
    #include <linux/module.h>
    #include <linux/kernel.h>
    #include <linux/list.h>
    #include <linux/types.h>
    #include <linux/slab.h>
    
    /* This function is called when the module is loaded. */
    int simple_init(void)
    { 
        printk(KERN_INFO "Loading Module\n");
    	// declare a list_head object by using LIST_HEAD macro
        static LIST_HEAD(birthday_list);         
        struct birthday
        { 
            int day;
            int month;
            int year;
            struct list_head list;
        };
        struct birthday *ptr, *next;
        struct birthday *Bob;
        struct birthday *Alice;
        struct birthday *youngseaz;
    
        Bob = kmalloc(sizeof(*Bob), GFP_KERNEL);
        Bob -> day = 1;
        Bob -> month = 1;
        Bob -> year = 1990;
    	// initializes the list member in struct birthday
        INIT_LIST_HEAD(&Bob -> list);
    
        Alice = kmalloc(sizeof(*Alice), GFP_KERNEL);
        Alice -> day = 2;
        Alice -> month = 2;
        Alice -> year = 1991;
        INIT_LIST_HEAD(&Alice -> list);
        
        youngseaz = kmalloc(sizeof(*youngseaz), GFP_KERNEL);
        youngseaz -> day = 1;
        youngseaz -> month = 1;
        youngseaz -> year = 2000;
        INIT_LIST_HEAD(&youngseaz -> list);
    
    	//add this instance to the end of the linked list using the list add tail() macro
        list_add_tail(&Bob -> list, &birthday_list);
        list_add_tail(&Alice -> list, &birthday_list);
        list_add_tail(&youngseaz -> list, &birthday_list);
    
        list_for_each_entry(ptr, &birthday_list, list)
        { 
    
            printk(KERN_INFO "%d/%d/%d \n", ptr -> month, ptr -> day,  ptr -> year);
        }
        
        //removing all elements from a linked list is 
        list_for_each_entry_safe(ptr, next, &birthday_list, list)
        { 
    	/* Removing elements from the list involves using the list_del() macro, which is passed a pointer to struct list head */
            list_del(&ptr->list);
            kfree(ptr);
        }
    
           return 0;
    }
    
    /* This function is called when the module is removed. */
    void simple_exit(void) 
    { 
        printk(KERN_INFO "Removing Module\n");
    }
    
    /* Macros for registering module entry and exit points. */
    module_init( simple_init );
    module_exit( simple_exit );
    MODULE_LICENSE("GPL");
    MODULE_DESCRIPTION("Simple Module");
    MODULE_AUTHOR("SGG");

testmodule2.c的Makefile如下

ifneq ($(KERNELRELEASE),)
    	obj-m:=testmodule2.o
    else
    	PWD:=$(shell pwd)
    	KDIR:=/lib/modules/$(shell uname -r)/build
    all:
    	make -C $(KDIR) M=$(PWD) modules
    endif