Linux内核模块(Module)的单独编译

1. 模块文件

   /*
   * file name: hello.c
   */
   
   #include
   
   
   #include                                                          
   
   
   #include
   
   
   MODULE_AUTHOR("Kevin Taylor");
   MODULE_LICENSE("GPL");
   
   static int nbr = 10; 
   module_param(nbr, int, S_IRUGO);
   
   static int __init hello_init(void)
   {
      int i;
   
      printk(KERN_ALERT"Init hello mudule...\n");
   
      for(i=0;i"Hello, how are you? %d\n", i); 
      }   
   
      return 0;
   }
   
   static void __exit hello_exit(void)
   {
      printk(KERN_ALERT"Exit hello mudule...\n");
      printk(KERN_ALERT"I come from hello's module, I have been unload.\n");
   }
   
   module_init(hello_init);
   module_exit(hello_exit);
   
   MODULE_DESCRIPTION("A Simple Hello World");
   MODULE_ALIAS("A simplest module");

2. Makefile

   
   #makefile for the hello.c                                                       
   
   
   obj-m := hello.o
   CURRENT_PATH := $(shell pwd)
   LINUX_KERNEL := $(shell uname -r)
   LINUX_KERNEL_PATH := /usr/src/linux-headers-$(LINUX_KERNEL)
   all:
      $(MAKE) -C $(LINUX_KERNEL_PATH) M=$(CURRENT_PATH) modules
   clean:
      rm *.ko
      rm *.o

3. 编译模块

   make

   编译成功会输出如下信息：

   make -C /usr/src/linux-headers-4.15.0-29-generic M=/home/yumo/Learn/driver/modules modules
   make[1]: Entering directory '/usr/src/linux-headers-4.15.0-29-generic'
    CC [M]  /home/yumo/Learn/driver/modules/hello.o
    Building modules, stage 2.
    MODPOST 1 modules
    CC      /home/yumo/Learn/driver/modules/hello.mod.o
    LD [M]  /home/yumo/Learn/driver/modules/hello.ko
   make[1]: Leaving directory '/usr/src/linux-headers-4.15.0-29-generic'

4. 加载模块到内核中

   sudo insmod ./hello.ko

5. 验证模块是否加载成功

   lsmod # 查看所有已加载的模块

6. 加载模块时传递参数

   sudo insmod hello.ko nbr=4

   查看最近的8条日志信息：dmesg | tail -8

   [16331.599330] Hello, how are you? 9
   [18297.411389] Exit hello mudule...
   [18297.411394] I come from hello's module, I have been unload.
   [18330.125440] Init hello mudule...
   [18330.125450] Hello, how are you? 0
   [18330.125453] Hello, how are you? 1
   [18330.125456] Hello, how are you? 2
   [18330.125459] Hello, how are you? 3

   在加载模块时动态设置了模块文件中的变量nbr(在模块文件中默认值为10)，从打印的日志信息可以看出，初始化函数中循环只执行了4次，说明加载模块时传递的参数已成功。

7. 查看模块信息

   sudo modinfo hello.ko

   输出的模块信息

   filename:       /home/yumo/Learn/driver/modules/hello.ko
   alias:          A simplest module
   description:    A Simple Hello World
   license:        GPL
   author:         Kevin Taylor
   srcversion:     A9C1413760EC5E7C4FD9DF6
   depends:        
   retpoline:      Y
   name:           hello
   vermagic:       4.15.0-29-generic SMP mod_unload 
   parm:           nbr:int

8. 查看内核的日志信息

   dmesg # 查看当前所有的内核日志信息
   dmesg | tail -12  # 查看内核最近输出的12条日志信息

   最近的12条内核日志信息

   [15645.089201] I come from hello's module, I have been unload.
   [16331.599309] Init hello mudule...
   [16331.599316] Hello, how are you? 0
   [16331.599318] Hello, how are you? 1
   [16331.599320] Hello, how are you? 2
   [16331.599321] Hello, how are you? 3
   [16331.599323] Hello, how are you? 4
   [16331.599324] Hello, how are you? 5
   [16331.599326] Hello, how are you? 6
   [16331.599327] Hello, how are you? 7
   [16331.599329] Hello, how are you? 8
   [16331.599330] Hello, how are you? 9

   dmesg小结

   1. 执行dmesg命令用于查询内核的日志信息，方括号中的内容为time stamp，该时间戳默认是系统从开机到输出该条日志信息时的运行时间，以秒为单位。

   2. 以当前时间的为时间戳显示时间信息 ：dmesg -T

      [Wed Aug  1 10:17:34 2018] Init hello mudule...
      [Wed Aug  1 10:17:34 2018] Hello, how are you? 0
      [Wed Aug  1 10:17:34 2018] Hello, how are you? 1

   3. 显示系统运行时间以及打印两条日志信息的时间间隔

      [16331.599309 <  686.510108>] Init hello mudule...
      [16331.599316 <    0.000007>] Hello, how are you? 0
      [16331.599318 <    0.000002>] Hello, how are you? 1
      [16331.599320 <    0.000002>] Hello, how are you? 2

   4. 显示最近输出的n条日志信息：dmesg | tail -n

   5. 以上参数可以混合使用，如：

      [Wed Aug  1 10:06:19 2018 < 5352.292092>] I come from hello's module, I have been unload.
      [Wed Aug  1 10:17:45 2018 <  686.510108>] Init hello mudule...
      [Wed Aug  1 10:17:45 2018 <    0.000007>] Hello, how are you? 0
      [Wed Aug  1 10:17:45 2018 <    0.000002>] Hello, how are you? 1
      [Wed Aug  1 10:17:45 2018 <    0.000002>] Hello, how are you? 2
      [Wed Aug  1 10:17:45 2018 <    0.000001>] Hello, how are you? 3
      [Wed Aug  1 10:17:45 2018 <    0.000002>] Hello, how are you? 4
      [Wed Aug  1 10:17:45 2018 <    0.000001>] Hello, how are you? 5
      [Wed Aug  1 10:17:45 2018 <    0.000002>] Hello, how are you? 6
      [Wed Aug  1 10:17:45 2018 <    0.000001>] Hello, how are you? 7
      [Wed Aug  1 10:17:45 2018 <    0.000002>] Hello, how are you? 8
      [Wed Aug  1 10:17:45 2018 <    0.000001>] Hello, how are you? 9

      即打印最近的12条日志信息，同时输出打印日志信息的当前时间以及相邻两条日志信息的时间间隔。

9. 从内核中移除模块

   sudo rmmod hello.ko