我正在尝试构建一个简单的内核模块。以下是其中涉及的文件的内容:
模块.c:
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/kernel.h>
#include "header.h"
static int device_open(struct inode *inode, struct file *file)
{
printk("\n Open \n");
return 0;
}
static int device_ioctl(struct inode *inode, struct file *filp, unsigned int cmd, unsigned long args)
{
switch(cmd)
{
case IOCTL_CMD:
printk(KERN_ALERT "\n %s \n", (char *)args);
break;
}
return 0;
}
static int device_release(struct inode *inode, struct file *file)
{
printk("\n Release \n");
return 0;
}
static struct class *my_class;
static struct file_operations fops={
.open = device_open,
.release = device_release,
.compat_ioctl = device_ioctl
};
static int hello_init(void)
{
major_no = register_chrdev(0, DEVICE_NAME, &fops);
printk("\n Major_no : %d", major_no);
my_class = class_create(THIS_MODULE, DEVICE_NAME);
device_create(my_class, NULL, MKDEV(major_no,0), NULL, DEVICE_NAME);
printk("\n Device Initialized in kernel ....!!!");
return 0;
}
static void hello_exit(void)
{
printk("\n Device is Released or closed \n");
device_destroy(my_class,MKDEV(major_no,0));
class_unregister(my_class);
class_destroy(my_class);
unregister_chrdev(major_no, DEVICE_NAME);
printk("\n===============================================================\n");
}
module_init(hello_init);
module_exit(hello_exit);
MODULE_LICENSE("GPL");
应用程序
#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include "header.h"
int main()
{
int fd;
char * msg = "yahoooo";
fd = open(DEVICE_PATH, O_RDWR);
ioctl(fd, IOCTL_CMD, msg);
printf("ioctl executed\n");
close(fd);
return 0;
}
标头.h:
#include <linux/ioctl.h>
#include <linux/kdev_t.h> /* for MKDEV */
#define DEVICE_NAME "my_dev"
#define DEVICE_PATH "/dev/my_dev"
#define WRITE 0
static int major_no;
#define MAGIC_NO '4'
/*
* Set the message of the device driver
*/
#define IOCTL_CMD _IOR(MAGIC_NO, 0, char *)
我的模块加载完美(我可以在 hello_init() 函数中看到消息)。但是当我运行 appln.c 程序时,即使它进行了 ioctl() 调用,我也看不到它的结果。有人能告诉我为什么模块忽略了我的 ioctl 调用吗?
谢谢,
答案1
一些东西:
- 您想使用“unlocked_ioctl”而不是“compat_ioctl”。
“device_ioctl”的函数接口是错误的(参见
include/linux/fs.h
),应该是:long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
- appln.c 不检查错误代码(打开,读写控制)。
修复该问题后,代码就可以正常工作了。
答案2
最小可运行示例
在完全可重现的 QEMU + Buildroot 环境中进行了测试,因此可能有助于其他人完成他们的ioctl
工作。GitHub 上游:
内核模块|
共享标头|
用户空间。
最令人恼火的是了解到一些低 ID 被劫持:https://stackoverflow.com/questions/10071296/ioctl-is-not-called-if-cmd-2,您必须使用_IOx
宏。
内核模块:
#include <asm/uaccess.h> /* copy_from_user, copy_to_user */
#include <linux/debugfs.h>
#include <linux/module.h>
#include <linux/printk.h> /* printk */
#include "ioctl.h"
MODULE_LICENSE("GPL");
static struct dentry *dir;
static long unlocked_ioctl(struct file *filp, unsigned int cmd, unsigned long argp)
{
void __user *arg_user;
union {
int i;
lkmc_ioctl_struct s;
} arg_kernel;
arg_user = (void __user *)argp;
pr_info("cmd = %x\n", cmd);
switch (cmd) {
case LKMC_IOCTL_INC:
if (copy_from_user(&arg_kernel.i, arg_user, sizeof(arg_kernel.i))) {
return -EFAULT;
}
pr_info("0 arg = %d\n", arg_kernel.i);
arg_kernel.i += 1;
if (copy_to_user(arg_user, &arg_kernel.i, sizeof(arg_kernel.i))) {
return -EFAULT;
}
break;
case LKMC_IOCTL_INC_DEC:
if (copy_from_user(&arg_kernel.s, arg_user, sizeof(arg_kernel.s))) {
return -EFAULT;
}
pr_info("1 arg = %d %d\n", arg_kernel.s.i, arg_kernel.s.j);
arg_kernel.s.i += 1;
arg_kernel.s.j -= 1;
if (copy_to_user(arg_user, &arg_kernel.s, sizeof(arg_kernel.s))) {
return -EFAULT;
}
break;
default:
return -EINVAL;
break;
}
return 0;
}
static const struct file_operations fops = {
.owner = THIS_MODULE,
.unlocked_ioctl = unlocked_ioctl
};
static int myinit(void)
{
dir = debugfs_create_dir("lkmc_ioctl", 0);
/* ioctl permissions are not automatically restricted by rwx as for read / write,
* but we could of course implement that ourselves:
* https://stackoverflow.com/questions/29891803/user-permission-check-on-ioctl-command */
debugfs_create_file("f", 0, dir, NULL, &fops);
return 0;
}
static void myexit(void)
{
debugfs_remove_recursive(dir);
}
module_init(myinit)
module_exit(myexit)
共享标头:
#ifndef IOCTL_H
#define IOCTL_H
#include <linux/ioctl.h>
typedef struct {
int i;
int j;
} lkmc_ioctl_struct;
#define LKMC_IOCTL_MAGIC 0x33
#define LKMC_IOCTL_INC _IOWR(LKMC_IOCTL_MAGIC, 0, int)
#define LKMC_IOCTL_INC_DEC _IOWR(LKMC_IOCTL_MAGIC, 1, lkmc_ioctl_struct)
#endif
用户空间:
#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include "../ioctl.h"
int main(int argc, char **argv)
{
int fd, arg_int, ret;
lkmc_ioctl_struct arg_struct;
if (argc < 2) {
puts("Usage: ./prog <ioctl-file>");
return EXIT_FAILURE;
}
fd = open(argv[1], O_RDONLY);
if (fd == -1) {
perror("open");
return EXIT_FAILURE;
}
/* 0 */
{
arg_int = 1;
ret = ioctl(fd, LKMC_IOCTL_INC, &arg_int);
if (ret == -1) {
perror("ioctl");
return EXIT_FAILURE;
}
printf("arg = %d\n", arg_int);
printf("ret = %d\n", ret);
printf("errno = %d\n", errno);
}
puts("");
/* 1 */
{
arg_struct.i = 1;
arg_struct.j = 1;
ret = ioctl(fd, LKMC_IOCTL_INC_DEC, &arg_struct);
if (ret == -1) {
perror("ioctl");
return EXIT_FAILURE;
}
printf("arg = %d %d\n", arg_struct.i, arg_struct.j);
printf("ret = %d\n", ret);
printf("errno = %d\n", errno);
}
close(fd);
return EXIT_SUCCESS;
}