Linux 内核入门(内核传递参数，内核符号symbol)

女爷i 2023-05-22 12:29 72阅读 0赞

1，我们现在用最简单的hello\_word.c来引出内核：

hello.c和Makefile实现：

#include <linux/init.h>             
    #include <linux/module.h>          
    #include <linux/kernel.h>   
    
    //指定license版本
    MODULE_LICENSE("GPL");              
    
    //设置初始化入口函数
    static int __init hello_world_init(void)
    {
        printk("<0>" "hello world!!!\n");
        return 0;
    }
    
    //设置出口函数
    static void __exit hello_world_exit(void)
    {
        printk(KERN_DEBUG "goodbye world!!!\n");
    }
    
    //将上述定义的init()和exit()函数定义为模块入口/出口函数
    module_init(hello_world_init);
    module_exit(hello_world_exit);

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

编译和怎么实现模块安装和模块卸载和查看模块

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwMDA4MzI1_size_16_color_FFFFFF_t_70][]

我们加入打印printk时，我们需要怎么看打印（在ubuntu系统中，其他的printk等级打印在以后的日记中补充），查看kern.log

cat /sys/log/kern.log

![20200417203345918.PNG][]

2，内核参数初始化举例：

内核中传递参数和main函数传递参数(int main(int argc char\*\* argv),有两个传入参数argc和argv)

内核函数实现param.c

#include<linux/init.h>
    #include<linux/module.h>
    
    MODULE_LICENSE("Dual BSD/GPL");
    
    static short m_short = 1;
    static int m_int = 100;
    static long m_long = 100000;
    static char* m_char = "hello";
    static int m_array[2]= {1,3};
    
    //模块参数描述
    module_param(m_short,short,S_IRWXU);
    MODULE_PARM_DESC(m_port,"one short integer");
    
    module_param(m_int,int,S_IRWXU);
    MODULE_PARM_DESC(m_int,"one int integer");
    
    module_param(m_long,long,S_IRWXU);
    MODULE_PARM_DESC(m_long,"one long integer");
    
    //字符串
    module_param(m_char,charp,0);
    MODULE_PARM_DESC(m_char,"one char string");
    
    //数组参数描述
    module_param_array(m_array,int.NULL,0);
    MODULE_PARM_DESC(m_array,"one integer array");
    
    static int __init param_init(void)
    {
    	printk(KERNEL_EMERG "enter param_init\n");
    	
    	printk(KERNEL_EMERG "m_short = %d\n",m_short);
    	printk(KERNEL_EMERG "m_int = %d\n",m_int);
    	printk(KERNEL_EMERG "m_long = %ld\n",m_long);
    	
    	printk(KERNEL_EMERG "m_char = %s\n",m_char);
    	
    	printk(KERNEL_EMERG "m_array[0] = %d\n",m_array[0]);
    	printk(KERNEL_EMERG "m_array[1] = %d\n",m_array[1]);
    	
    	return 0;
    }
    
    static void __exit param_exit(void)
    {
    	printk(KERNEL_EMERG "enter param_exit\n");
    }
    
    module_init(param_init);
    module_exit(param_exit);
    
    MODULE_AUTHOR("taotao");
    MODULE_VERSION("0.0.1");

makefile:

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

1,编译和安装模块实现：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwMDA4MzI1_size_16_color_FFFFFF_t_70 1][]

我们还可以改变输入参数，实现如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwMDA4MzI1_size_16_color_FFFFFF_t_70 2][]

3，在内核中我们要想用函数模块怎么整，下面就引入symbol内核导出符号：

首先，我们实现1\_call\_symbol.c(被调用)和1\_module\_symbol.c（调用）

//call_symbol.c
    #include<linux/init.h>
    #include<linux/module.h>
    
    MODULE_LICENSE("Dual BSD/GPL");
    
    int esdexp_mult(int x,int y)
    {
    	printk(KERNEL_EMERG"module_paramm.c:esdexp_mult:enter\n");
    	return (x*y);
    }
    
    int esdexp_devid(int x,int y)
    {
    	printk(KERNEL_EMERG"module_paramm.c:esdexp_devid:enter\n");
    	return (x/y);
    }
    
    
    EXPORT_SYMBOL(esdexp_mult);
    EXPORT_SYMBOL(esdexp_devid);
    
    
    MODULE_AUTHOR("taotao");
    MODULE_VERSION("0.0.1");

//module_symbol.c
    #include<linux/init.h>
    #include<linux/module.h>
    
    MODULE_LICENSE("Dual BSD/GPL");
    
    
    //导入符号函数
    extern int esdexp_mult(int x,int y);
    extern int esdexp_devid(int x,int y);
    
    static int _init esdexp_init(void)    //此处必须用static
    {
    	int mult_answer;
    	printk(KERNEL_EMERG "esdexp_init enter\n");
    	mult_answer = esdexp_mult(3,4);
    	printk(KERNEL_EMERG " mult_answer = %d\n",mult_answer);
    	return 0;
    }
    
    static void _init esdexp_exit(void)    //此处必须用static
    {
    	int devid_answer;
    	printk(KERNEL_EMERG "esdexp_exit enter\n");
    	devid_answer = esdexp_devid(4,4);
    	printk(KERNEL_EMERG " devid_answer = %d\n",devid_answer);
    }
    
    
    module_init(esdexp_init);
    module_exit(esdexp_exit);
    
    MODULE_AUTHOR("taotao");
    MODULE_VERSION("0.0.1");

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

编译结果如下：

/proc/kallsyms 查看内核符号调用的符号表

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwMDA4MzI1_size_16_color_FFFFFF_t_70 3][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwMDA4MzI1_size_16_color_FFFFFF_t_70 4][]

运行结果如下：

![20200417210630359.PNG][]

最后我们可以看看驱动文件的信息：用modinfo:

![20200419143449421.PNG][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwMDA4MzI1_size_16_color_FFFFFF_t_70]: /images/20230521/52e8bc680fee4e0686e16676b2995909.png
[20200417203345918.PNG]: /images/20230521/59d025c9fa7c40e6acf8d40b71640cb7.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwMDA4MzI1_size_16_color_FFFFFF_t_70 1]: /images/20230521/10814ff1013e481c85faffa887a5e672.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwMDA4MzI1_size_16_color_FFFFFF_t_70 2]: /images/20230521/231dd6a59f8641e4951ce11502cc61c3.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwMDA4MzI1_size_16_color_FFFFFF_t_70 3]: /images/20230521/31772f8b76ca47858cdfaeca13cb506d.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwMDA4MzI1_size_16_color_FFFFFF_t_70 4]: /images/20230521/ebafc68791c44fdea4dbcaecb4e70431.png
[20200417210630359.PNG]: /images/20230521/ce674b75c2164e45b824483019ed8b2d.png
[20200419143449421.PNG]: /images/20230521/8f8c48d53c49446898dee33712f4fe41.png