#include <linux/init.h>
#include <linux/module.h>
#include <linux/printk.h>

#include <linux/proc_fs.h>

// #define NAME "keylogger"
#define NAME "_test_module"

ssize_t proc_read(struct file *file, char __user *user, size_t size, loff_t *off);
ssize_t proc_write(struct file *file, const char __user *user, size_t size, loff_t *off);

static struct proc_dir_entry *proc = NULL;
static const struct proc_ops proc_fops = {
    .proc_read  = proc_read,
    .proc_write = proc_write,
};

static char *msg_buf = NULL;

#define COPY_TO_USER(_msg, _len)                       \
    if(copy_to_user(user, _msg, _len)) return -EFAULT; \
    *off += _len;                                      \
    user += _len;

ssize_t proc_read(struct file *file, char __user *user, size_t size, loff_t *off)
{
    printk("FILE READ KEK\n");

    if (*off > 0) return 0; // we have already written

    if(msg_buf == NULL) {
        COPY_TO_USER("You have no previous messages\n", 30);
        return 30;
    }

    size_t len = strlen(msg_buf);
    if(size < (len + 24)) return 0;

    COPY_TO_USER("Your last message was: ", 23);
    COPY_TO_USER(msg_buf, len);
    COPY_TO_USER("\n", 1);

    return len + 24;
}

ssize_t proc_write(struct file *file, const char __user *user, size_t size, loff_t *off)
{
    printk("FIEL WRITE KEK\n");

    kfree(msg_buf);
    if((msg_buf = kmalloc(size + 1, GFP_KERNEL)) == NULL) {
       return -ENOMEM;
    }

    if(copy_from_user(msg_buf, user, size)) {
        return -EFAULT;
    }

    msg_buf[size] = '\0';
    if(msg_buf[size-1] == '\n') msg_buf[size-1] = '\0';

    return size;
}

static int __init init_keylogger(void)
{
    printk("Init Kek\n");

    if((proc = proc_create(NAME, 0666, NULL, &proc_fops)) == NULL)
        return -ENOMEM;
    return 0;
}

static void __exit exit_keylogger(void)
{
    printk("Exit Kek\n");

    proc_remove(proc);
    kfree(msg_buf);
}

module_init(init_keylogger);
module_exit(exit_keylogger);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Kartofen");
MODULE_DESCRIPTION("A simple keylogger kernel module");


// Key logging example code

// #include <linux/module.h>
// #include <linux/init.h>
// #include <linux/keyboard.h>

// static struct notifier_block nb;

// static int keylogger_notify(struct notifier_block *nblock,
//                             unsigned long code, void *_param)
// {
//     struct keyboard_notifier_param *param = _param;

//     if (code == KBD_KEYCODE && param->value == 1) {
//         printk(KERN_INFO "Key pressed: %d\n", param->value);
//     }

//     return NOTIFY_OK;
// }

// static int __init keylogger_init(void)
// {
//     nb.notifier_call = keylogger_notify;
//     register_keyboard_notifier(&nb);
//     return 0;
// }

// static void __exit keylogger_exit(void)
// {
//     unregister_keyboard_notifier(&nb);
// }

// module_init(keylogger_init);
// module_exit(keylogger_exit);
// MODULE_LICENSE("GPL");