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[英]Unable to receive customized message sent from kernel module to user application using NETLINK_ROUTE channel
[英]Unable to print the message sent from user space C application to linux kernel module
我開發了一個簡單的 linux kernel 模塊:
#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
ssize_t exer_open(struct inode *pinode, struct file *pfile) {
return 0;
}
ssize_t exer_read(struct file *pfile, char __user *buffer, size_t length, loff_t *offset) {
return 0;
}
ssize_t exer_write(struct file *pfile, const char __user *buffer, size_t length, loff_t *offset) {
return length;
}
ssize_t exer_close(struct inode *pinode, struct file *pfile) {
return 0;
}
struct file_operations exer_file_operations = {
.owner = THIS_MODULE,
.open = exer_open,
.read = exer_read,
.write = exer_write,
.release = exer_close,
};
int exer_simple_module_init(void) {
printk(KERN_ALERT "Inside the %s function\n", __FUNCTION__);
register_chrdev(240, "Simple Char Drv", &exer_file_operations);
return 0;
}
void exer_simple_module_exit(void) {
unregister_chrdev(240, "Simple Char Drv");
}
module_init(exer_simple_module_init);
module_exit(exer_simple_module_exit);
我使用insmod
命令將此模塊插入 kernel 沒有任何問題。
我想使用這個模塊來打印由我開發的用戶空間程序發送給它的消息:
#include<stdio.h>
#include<stdlib.h>
#include<errno.h>
#include<fcntl.h>
#include<string.h>
#include<unistd.h>
int main()
{
int ret, fd;
char stringToSend[] = "Hello World !";
fd = open("/dev/char_device", O_RDWR); // Open the device with read/write access
if (fd < 0)
{
perror("Failed to open the device...");
return errno;
}
ret = write(fd, stringToSend, strlen(stringToSend)); // Send the string to the LKM
if (ret < 0)
{
perror("Failed to write the message to the device.");
return errno;
}
return 0;
}
當我使用tail -f /var/log/messages
命令執行程序並檢查 kernel 日志時,我可以看到: user.alert kernel: Inside the exer_read function
看到消息“Hello World!”
我不知道我在這里缺少什么,尤其是我仍然是開發模塊和使用它的初學者。 請幫幫我!
對於仍然找不到解決方案的人,我有一個答案。
這是模塊:
#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/uaccess.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Gaston");
MODULE_DESCRIPTION("A simple Linux char driver");
MODULE_VERSION("0.1");
#define MAX 256
static char message[MAX] =""; ///< Memory for the string that is passed from userspace
ssize_t exer_open(struct inode *pinode, struct file *pfile) {
printk(KERN_INFO "Device has been opened\n");
return 0;
}
ssize_t exer_read(struct file *pfile, char __user *buffer, size_t length, loff_t *offset) {
return 0;
}
ssize_t exer_write(struct file *pfile, const char __user *buffer, size_t length, loff_t *offset) {
if (length > MAX)
return -EINVAL;
if (copy_from_user(message, buffer, length) != 0)
return -EFAULT;
printk(KERN_INFO "Received %s characters from the user\n", message);
return 0;
}
ssize_t exer_close(struct inode *pinode, struct file *pfile) {
printk(KERN_INFO "Device successfully closed\n");
return 0;
}
struct file_operations exer_file_operations = {
.owner = THIS_MODULE,
.open = exer_open,
.read = exer_read,
.write = exer_write,
.release = exer_close,
};
int exer_simple_module_init(void) {
printk(KERN_INFO "Initializing the LKM\n");
register_chrdev(240, "Simple Char Drv", &exer_file_operations);
return 0;
}
void exer_simple_module_exit(void) {
unregister_chrdev(240, "Simple Char Drv");
}
module_init(exer_simple_module_init);
module_exit(exer_simple_module_exit);
Ans 這是應用程序:
#include<stdio.h>
#include<stdlib.h>
#include<errno.h>
#include<fcntl.h>
#include<string.h>
#include<unistd.h>
#define BUFFER_LENGTH 256
int main()
{
int ret, fd;
char stringToSend[BUFFER_LENGTH];
fd = open("/dev/char_device", O_RDWR); // Open the device with read/write access
if (fd < 0)
{
perror("Failed to open the device...");
return errno;
}
printf("Type in a short string to send to the kernel module:\n");
scanf("%s", stringToSend); // Read in a string (with spaces)
printf("Writing message to the device [%s].\n", stringToSend);
ret = write(fd, stringToSend, strlen(stringToSend)); // Send the string to the LKM
if (ret < 0)
{
perror("Failed to write the message to the device.");
return errno;
}
return 0;
}
你會看到這會正常工作。
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