我开发了一个简单的 linux 内核模块:
#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
将此模块插入内核命令没有任何问题。我想使用这个模块来打印我开发的用户空间程序发送给它的消息:
#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;
}
当我使用
tail -f /var/log/messages
执行程序并检查内核日志时我可以看到的命令:user.alert kernel: Inside the exer_read function
但我看不到消息“Hello World!”我不知道我在这里缺少什么,尤其是我仍然是开发模块和使用它的初学者。请帮帮我!
最佳答案
对于仍然找不到解决方案的人,我有一个答案。
这是模块:
#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 这是应用程序:
#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;
}
你会看到这会正常工作。
关于linux-kernel - 无法打印从用户空间 C 应用程序发送到 linux 内核模块的消息,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/58665952/