问未能使用不使用调试器的copy_to_user获取内核数据

EN

#include <linux/module.h>
#include <linux/debugfs.h>
#include <linux/fs.h>
#include <linux/uaccess.h>

#define LEN 512 

static struct dentry *test_dir;
static struct dentry *test_file;

static char ker_buf[LEN] ;
/* read file operation */
static ssize_t test_read(struct file *fp, char __user *user_buffer, size_t count, loff_t *position){
    printk(KERN_NOTICE "debugfs_read called, count %d\n", count);
    return copy_to_user(user_buffer, ker_buf, LEN);

}

static ssize_t test_write(struct file *fp, const char __user *user_buffer, size_t count, loff_t *position){
    printk(KERN_NOTICE "debugfs_write called, count %d\n",count);
    if(count > LEN )
        return -EINVAL;

    copy_from_user(ker_buf, user_buffer, count);
    printk(KERN_NOTICE "write buffer complete: %s\n",ker_buf);
    return count;
}

static struct file_operations fops_debug = {
    .read = test_read,
    .write = test_write,
};

static int __init init_debug(void)
{
    test_dir = debugfs_create_dir("debugexercise", NULL);
    if(NULL == test_dir){
        printk(KERN_ERR "debugfs_create_dir() Failed\n");
        return -1;
    }
    else
        printk(KERN_NOTICE "debugexercise created\n");

    test_file = debugfs_create_file("text", 0644, test_dir, NULL, &fops_debug);
    if(NULL == test_file){
        printk(KERN_ERR "debugfs_create_file() Failed\n");
        debugfs_remove(test_dir);
        return -1;
    }
    else
        printk(KERN_NOTICE "text under debugexercise created\n");

    return 0;
}

static void __exit exit_debug(void)
{
    printk(KERN_NOTICE "removing module\n");
    debugfs_remove(test_file);
    debugfs_remove(test_dir);
}
module_init(init_debug)
module_exit(exit_debug)
MODULE_LICENSE("GPL");