Linux核心模組驅動載入與dmesg除錯
阿新 • • 發佈：2021-03-16
因為近期用到了Linux核心的相關知識，下面隨筆將給出核心模組的編寫記錄，供大家參考。
1、執行環境
Ubuntu 版本：20.04
Linux核心版本：5.4.0-42-generic
gcc版本：gcc version 9.3.0
驅動和一般應用程式的執行方式很大不同
2、核心模組模型說明
（1）驅動和一般應用程式的執行方式很大不同
一般應用由main函式開始執行，流程基本由程式自身控制
驅動程式沒有main函式，由回撥方式驅動執行
（2）回撥方式：
先向核心註冊函式，然後應用程式觸發這些函式的執行
例如：驅動程式在初始化時，向核心註冊處理某個裝置寫操作的函式
當應用程式使用write系統呼叫寫該裝置時，核心就會呼叫註冊的上述函式
3、核心模型常見的回撥函式舉例
（1）DriverInitialize
驅動初始化函式，通過巨集靜態註冊；
$ insmod PrintModule.ko，安裝驅動並觸發該函式，通常會建立裝置物件；
（2）DriverUninitialize
驅動銷燬函式，通過巨集靜態註冊；
$ rmmod PrintModule，解除安裝驅動並觸發該函式；
（3）DriverOpen
開啟裝置函式，動態註冊；
應用呼叫open函式開啟裝置物件時，會觸發該函式；
（4）DriverRead
讀裝置函式，動態註冊；
應用呼叫read函式讀裝置時，會觸發該函式；
（5）DriverWrite
寫裝置函式，動態註冊；
應用呼叫write函式寫裝置時，會觸發該函式；
（7）DriverIOControl
裝置控制函式，動態註冊；
應用呼叫ioctl函式操作裝置時，會觸發該函式；
（8）DriverMMap
裝置記憶體對映函式，動態註冊；
應用呼叫mmap函式時，會觸發該函式；
下面給出驅動模組編寫函式：
4、DriverMain.c
1 #include "DriverMain.h"
2
3 #include "DriverFileOperations.h"
4
5 #include "ToolFunctions.h"
6
7
8
9 MODULE_LICENSE("Dual BSD/GPL");
10
11
12
13 struct SLDriverParameters gslDriverParameters = {0};
14
15
16
17 struct file_operations gslNvmDriverFileOperations =
18
19 {
20
21 .owner = THIS_MODULE,
22
23 .open = DriverOpen,
24
25 .release = DriverClose,
26
27 .read = DriverRead,
28
29 .write = DriverWrite,
30
31 .unlocked_ioctl = DriverIOControl,
32
33 .mmap = DriverMMap,
34
35 };
36
37
38
39 int InitalizeCharDevice(void)
40
41 {
42
43 int result;
44
45 struct device *pdevice;
46
47
48
49 result = alloc_chrdev_region(&(gslDriverParameters.uiDeviceNumber), 0, 1, DEVICE_NAME);
50
51 if(result < 0)
52
53 {
54
55 printk(KERN_ALERT DEVICE_NAME " alloc_chrdev_region error\n");
56
57 return result;
58
59 }
60
61
62
63 gslDriverParameters.pslDriverClass = class_create(THIS_MODULE, DEVICE_NAME);
64
65 if(IS_ERR(gslDriverParameters.pslDriverClass))
66
67 {
68
69 printk(KERN_ALERT DEVICE_NAME " class_create error\n");
70
71
72
73 result = PTR_ERR(gslDriverParameters.pslDriverClass);
74
75 goto CLASS_CREATE_ERROR;
76
77 }
78
79
80
81 cdev_init(&(gslDriverParameters.slCharDevice), &gslNvmDriverFileOperations);
82
83 gslDriverParameters.slCharDevice.owner = THIS_MODULE;
84
85
86
87 result = cdev_add(&(gslDriverParameters.slCharDevice), gslDriverParameters.uiDeviceNumber, 1);
88
89 if(result < 0)
90
91 {
92
93 printk(KERN_ALERT DEVICE_NAME " cdev_add error\n");
94
95 goto CDEV_ADD_ERROR;
96
97 }
98
99
100
101 pdevice = device_create(gslDriverParameters.pslDriverClass, NULL, gslDriverParameters.uiDeviceNumber, NULL, DEVICE_NAME);
102
103 if(IS_ERR(pdevice))
104
105 {
106
107 printk(KERN_ALERT DEVICE_NAME " device_create error\n");
108
109
110
111 result = PTR_ERR(pdevice);
112
113 goto DEVICE_CREATE_ERROR;
114
115 }
116
117
118
119 return 0;
120
121
122
123 DEVICE_CREATE_ERROR:
124
125 cdev_del(&(gslDriverParameters.slCharDevice));
126
127
128
129 CDEV_ADD_ERROR:
130
131 class_destroy(gslDriverParameters.pslDriverClass);
132
133
134
135 CLASS_CREATE_ERROR:
136
137 unregister_chrdev_region(gslDriverParameters.uiDeviceNumber, 1);
138
139
140
141 return result;
142
143 }
144
145
146
147 void UninitialCharDevice(void)
148
149 {
150
151 device_destroy(gslDriverParameters.pslDriverClass, gslDriverParameters.uiDeviceNumber);
152
153
154
155 cdev_del(&(gslDriverParameters.slCharDevice));
156
157
158
159 class_destroy(gslDriverParameters.pslDriverClass);
160
161
162
163 unregister_chrdev_region(gslDriverParameters.uiDeviceNumber, 1);
164
165 }
166
167
168
169 static int DriverInitialize(void)
170
171 {
172
173 DEBUG_PRINT(DEVICE_NAME " Initialize\n");
174
175
176
177 return InitalizeCharDevice();
178
179 }
180
181
182
183 static void DriverUninitialize(void)
184
185 {
186
187 DEBUG_PRINT(DEVICE_NAME " Uninitialize\n");
188
189
190
191 UninitialCharDevice();
192
193 }
194
195
196
197 module_init(DriverInitialize);
198
199 module_exit(DriverUninitialize);5、DriverMain.h
1 #ifndef DriverMain_H
2
3 #define DriverMain_H
4
5
6
7 #include <linux/init.h>
8
9 #include <linux/module.h>
10
11 #include <asm/mtrr.h>
12
13 #include <linux/device.h>
14
15 #include <linux/mm.h>
16
17 #include <linux/cdev.h>
18
19 #include <linux/slab.h>
20
21
22
23 #define DEVICE_NAME "msg_printer"
24
25
26
27 struct SLDriverParameters
28
29 {
30
31 struct class *pslDriverClass;
32
33 dev_t uiDeviceNumber;
34
35 struct cdev slCharDevice;
36
37 };
38
39
40
41 extern struct SLDriverParameters gslDriverParameters;
42
43
44
45 #endif
6、DriverFileOperations.c
1 #include "DriverMain.h"
2
3 #include "DriverFileOperations.h"
4
5 #include "ToolFunctions.h"
6
7
8
9 MODULE_LICENSE("Dual BSD/GPL");
10
11
12
13 struct SLDriverParameters gslDriverParameters = {0};
14
15
16
17 struct file_operations gslNvmDriverFileOperations =
18
19 {
20
21 .owner = THIS_MODULE,
22
23 .open = DriverOpen,
24
25 .release = DriverClose,
26
27 .read = DriverRead,
28
29 .write = DriverWrite,
30
31 .unlocked_ioctl = DriverIOControl,
32
33 .mmap = DriverMMap,
34
35 };
36
37
38
39 int InitalizeCharDevice(void)
40
41 {
42
43 int result;
44
45 struct device *pdevice;
46
47
48
49 result = alloc_chrdev_region(&(gslDriverParameters.uiDeviceNumber), 0, 1, DEVICE_NAME);
50
51 if(result < 0)
52
53 {
54
55 printk(KERN_ALERT DEVICE_NAME " alloc_chrdev_region error\n");
56
57 return result;
58
59 }
60
61
62
63 gslDriverParameters.pslDriverClass = class_create(THIS_MODULE, DEVICE_NAME);
64
65 if(IS_ERR(gslDriverParameters.pslDriverClass))
66
67 {
68
69 printk(KERN_ALERT DEVICE_NAME " class_create error\n");
70
71
72
73 result = PTR_ERR(gslDriverParameters.pslDriverClass);
74
75 goto CLASS_CREATE_ERROR;
76
77 }
78
79
80
81 cdev_init(&(gslDriverParameters.slCharDevice), &gslNvmDriverFileOperations);
82
83 gslDriverParameters.slCharDevice.owner = THIS_MODULE;
84
85
86
87 result = cdev_add(&(gslDriverParameters.slCharDevice), gslDriverParameters.uiDeviceNumber, 1);
88
89 if(result < 0)
90
91 {
92
93 printk(KERN_ALERT DEVICE_NAME " cdev_add error\n");
94
95 goto CDEV_ADD_ERROR;
96
97 }
98
99
100
101 pdevice = device_create(gslDriverParameters.pslDriverClass, NULL, gslDriverParameters.uiDeviceNumber, NULL, DEVICE_NAME);
102
103 if(IS_ERR(pdevice))
104
105 {
106
107 printk(KERN_ALERT DEVICE_NAME " device_create error\n");
108
109
110
111 result = PTR_ERR(pdevice);
112
113 goto DEVICE_CREATE_ERROR;
114
115 }
116
117
118
119 return 0;
120
121
122
123 DEVICE_CREATE_ERROR:
124
125 cdev_del(&(gslDriverParameters.slCharDevice));
126
127
128
129 CDEV_ADD_ERROR:
130
131 class_destroy(gslDriverParameters.pslDriverClass);
132
133
134
135 CLASS_CREATE_ERROR:
136
137 unregister_chrdev_region(gslDriverParameters.uiDeviceNumber, 1);
138
139
140
141 return result;
142
143 }
144
145
146
147 void UninitialCharDevice(void)
148
149 {
150
151 device_destroy(gslDriverParameters.pslDriverClass, gslDriverParameters.uiDeviceNumber);
152
153
154
155 cdev_del(&(gslDriverParameters.slCharDevice));
156
157
158
159 class_destroy(gslDriverParameters.pslDriverClass);
160
161
162
163 unregister_chrdev_region(gslDriverParameters.uiDeviceNumber, 1);
164
165 }
166
167
168
169 static int DriverInitialize(void)
170
171 {
172
173 DEBUG_PRINT(DEVICE_NAME " Initialize\n");
174
175
176
177 return InitalizeCharDevice();
178
179 }
180
181
182
183 static void DriverUninitialize(void)
184
185 {
186
187 DEBUG_PRINT(DEVICE_NAME " Uninitialize\n");
188
189
190
191 UninitialCharDevice();
192
193 }
194
195
196
197 module_init(DriverInitialize);
198
199 module_exit(DriverUninitialize);
7、DriverFileOperations.h
1 #ifndef DriverFileOperations_H 2 3 #define DriverFileOperations_H 4 5 int DriverOpen(struct inode *pslINode, struct file *pslFileStruct) 6 7 int DriverClose(struct inode *pslINode, struct file *pslFileStruct); 8 9 ssize_t DriverRead(struct file *pslFileStruct, char __user *pBuffer, size_t nCount, loff_t *pOffset); 10 11 ssize_t DriverWrite(struct file *pslFileStruct, const char __user *pBuffer, size_t nCount, loff_t *pOffset); 12 13 long DriverIOControl(struct file *pslFileStruct, unsigned int uiCmd, unsigned long ulArg); 14 15 int DriverMMap(struct file *pslFileStruct, struct vm_area_struct *pslVirtualMemoryArea); 16 17 #endif
8、編譯核心模組的MakeFile檔案：
1 ifneq ($(KERNELRELEASE),) 2 3 obj-m := PrintModule.o 4 5 PrintModule-objs := DriverMain.o DriverFileOperations.o 6 7 EXTRA_CFLAGS := -DTEST_DEBUG -ggdb -O0 8 9 else 10 11 KERNELDIR ?= /lib/modules/$(shell uname -r)/build 12 13 PWD := $(shell pwd) 14 15 default: 16 17 $(MAKE) -C $(KERNELDIR) M=$(PWD) modules 18 19 rm *.order *.symvers *.mod.c *.o .*.o.cmd .*.cmd .tmp_versions -rf 20 21 endif
9、執行測試
首先執行MakeFile檔案，通過終端輸入make命令即可，生成PrintModule.ko和PrintModule.mod：
之後載入核心驅動，通過輸入$ sudo insmod PrintModule.ko命令，之後檢視dmesg檢視驅動資訊（也可通過輸出除錯資訊的函式printk來進行除錯），具體如下：
隨之通過輸入$ sudo rmmod PrintModule命令來解除安裝驅動，也是通過dmesg來檢視核心驅動資訊（也可通過輸出除錯資訊的函式printk來進行除錯）：
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