1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/ktestmodule/ktest.c	Wed May 10 13:11:31 2017 +0300
     1.3 @@ -0,0 +1,91 @@
     1.4 +#include <asm/uaccess.h>
     1.5 +#include <linux/fs.h>
     1.6 +#include <linux/kernel.h>
     1.7 +#include <linux/module.h>
     1.8 +#include <linux/slab.h>
     1.9 +
    1.10 +#define DEV_NAME "ktest"
    1.11 +
    1.12 +static int ktest_init(void);
    1.13 +static void ktest_fini(void);
    1.14 +
    1.15 +static int ktest_open(struct inode *inode, struct file *file);
    1.16 +static int ktest_release(struct inode *inode, struct file *file);
    1.17 +static ssize_t ktest_read(struct file *file, char *buf, size_t buf_size,
    1.18 +		loff_t *offset);
    1.19 +
    1.20 +static int dev_num;
    1.21 +static struct file_operations ops = {
    1.22 +	.open = ktest_open,
    1.23 +	.release = ktest_release,
    1.24 +	.read = ktest_read
    1.25 +};
    1.26 +static int hello_counter;
    1.27 +
    1.28 +/* macros */
    1.29 +
    1.30 +MODULE_LICENSE("GPL");
    1.31 +MODULE_AUTHOR("hikiko");
    1.32 +MODULE_DESCRIPTION("my kernel helloworld");
    1.33 +
    1.34 +module_init(ktest_init);
    1.35 +module_exit(ktest_fini);
    1.36 +
    1.37 +static int ktest_init(void)
    1.38 +{
    1.39 +	hello_counter = 0;
    1.40 +
    1.41 +	/* register character device */
    1.42 +	if((dev_num = register_chrdev(0, DEV_NAME, &ops)) < 0) {
    1.43 +		printk(KERN_ALERT "Failed to register character device.\n");
    1.44 +		return -1;
    1.45 +	}
    1.46 +	printk(KERN_INFO "Registered character device. Name: %s number: %d.\n", DEV_NAME, dev_num);
    1.47 +	return 0;
    1.48 +}
    1.49 +
    1.50 +static void ktest_fini(void)
    1.51 +{
    1.52 +	unregister_chrdev(dev_num, DEV_NAME);
    1.53 +	printk(KERN_INFO "Unregistered character device. Name: %s number: %d.\n", DEV_NAME, dev_num);
    1.54 +}
    1.55 +
    1.56 +static int ktest_open(struct inode *inode, struct file *file)
    1.57 +{
    1.58 +	/* 1 device file only => we ignore the params ^ */
    1.59 +	try_module_get(THIS_MODULE);
    1.60 +	return 0;
    1.61 +}
    1.62 +
    1.63 +static int ktest_release(struct inode *inode, struct file *file)
    1.64 +{
    1.65 +	module_put(THIS_MODULE);
    1.66 +	return 0;
    1.67 +}
    1.68 +
    1.69 +static ssize_t ktest_read(struct file *file, char *buf, size_t buf_size,
    1.70 +		loff_t *offset)
    1.71 +{
    1.72 +	/* buf = userspace buffer,
    1.73 +	 * kbuf = kernel buffer */
    1.74 +
    1.75 +	char *kbuf;
    1.76 +	int bytes;
    1.77 +
    1.78 +	if(!(kbuf = kmalloc(buf_size, GFP_KERNEL))) {
    1.79 +		printk(KERN_ALERT "Failed to allocate memory.\n");
    1.80 +		return -ENOMEM;
    1.81 +	}
    1.82 +
    1.83 +	/* fill kbuf and copy to userspace buf */
    1.84 +	bytes = snprintf(kbuf, buf_size, "Hello world, num: %d.\n", ++hello_counter);
    1.85 +
    1.86 +	if(copy_to_user(buf, kbuf, bytes))
    1.87 +	{
    1.88 +		kfree(kbuf);
    1.89 +		return -EFAULT;
    1.90 +	}
    1.91 +
    1.92 +	kfree(kbuf);
    1.93 +	return bytes;
    1.94 +}