#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/proc_fs.h>
#include <asm/uaccess.h>

#define USER_ROOT_DIR   "shallnet"
#define USER_ENTRY      "file"

struct sln_kbuff {
    char    buf[1024];
};

struct proc_dir_entry   *root_dir, *entry;
struct sln_kbuff        *kbuff;

static int proc_write(struct file *filep,
                    const char __user *buffer,
                    unsigned long len,
                    void *data)
{
    if (copy_from_user(kbuff->buf, buffer, len)) {
        return -1;
    }

    kbuff->buf[len] = '\0';
    return len;
}

static int proc_read(char *page,
                    char **start,
                    off_t off,
                    int count,
                    int *eof,
                    void *data)
{
    int     len;

    len = sprintf(page, "You get msg from kernel is: %s", kbuff->buf);

    return len;
}

static int __init proc_init(void)
{
    printk("Hello, %s\n", __func__);

    kbuff = kmalloc(sizeof(struct sln_kbuff), GFP_KERNEL);
    if (NULL == kbuff) {
        printk("kmalloc() failed!");
        return -1;
    }

    root_dir = proc_mkdir(USER_ROOT_DIR, NULL);
    if (NULL == root_dir) {
        printk("proc_mkdir create dir %s failed!\n", USER_ROOT_DIR);
        return -1;
    }

    entry = create_proc_entry(USER_ENTRY, 0666, root_dir);
    if (NULL == entry) {
        printk("create_proc_entry create entry %s failed\n", USER_ENTRY);
        goto err;
    }

    entry->read_proc = proc_read;
    entry->write_proc = proc_write;
    return 0;

err:
    remove_proc_entry(USER_ROOT_DIR, NULL);
    return -1;
}

static void __exit proc_exit(void)
{
    printk("Bye, %s\n", __func__);

    remove_proc_entry(USER_ENTRY, root_dir);
    remove_proc_entry(USER_ROOT_DIR, NULL);
}

module_init(proc_init);
module_exit(proc_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("shallnet");
MODULE_DESCRIPTION("blog.csdn.net/shallnet");
 

# echo "Proc" > /proc/shallnet/file
# cat /proc/shallnet/file
You get msg from kernel is: Proc
#