Writing a file in /proc continuouly floods the dmesg - c

Question

I am trying to read/Write a variable in the linux kernel module using /proc file entry facility.
Kernel module compiles successfully but when tried writing it via
echo 1 > My_file
This operation didn't finish.
Also, dmesg console is continuously flooded with some random value.
[ 1171.481231] proc_write_flag New_Flag 1124646486
[ 1171.481245] proc_write_flag New_Flag 1124646486
[ 1171.481259] proc_write_flag New_Flag 1124646486
[ 1171.481271] proc_write_flag New_Flag 1124646486
[ 1171.481473] ^C
I am new to linux device drivers and trying to use /proc facility provided by the linux kernel. I tried removing the this kernel module, but again, the operation didn't finish.
what is causing this behaviour and how can i rectify it?
Here is the code:
int my_flag;
static struct proc_dir_entry *pdir = NULL;
MODULE_LICENSE("GPL");
MODULE_AUTHOR("GPL");
static ssize_t proc_read_flag(struct file* page,char __user * data, size_t count, loff_t *offset);
static ssize_t proc_write_flag(struct file *file, const char __user* ubuf, size_t count, loff_t* offset);
static struct file_operations myops =
{
.owner = THIS_MODULE,
.read = proc_read_flag,
.write= proc_write_flag,
};
//ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
//Updated Read function after the reply.
static ssize_t proc_read_flag(struct file* page,char __user * data, size_t count,loff_t *offset)
{
int ret;
if( count >my_flag) //my_flag holds the count of chars received by write function.
count = my_flag;
ret = copy_to_user(data, my_buf, my_flag );
printk("%s: ret = %d ,my_flag %d\n",__FUNCTION__, ret, my_flag);
return ( my_flag - ret );
}
//ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
//Updated Write function After the reply.
static ssize_t proc_write_flag(struct file *file, const char __user* ubuf, size_t count, loff_t* offset)
{
if( copy_from_user(my_buf,ubuf,count) ){ //Returns No. of bytes could not copy
return -EFAULT;
}
my_flag = count;
printk("%s New_Flag %d Data: %s\n",__FUNCTION__,my_flag,my_buf);
return count;
}
int init_module(void)
{
struct proc_dir_entry *pfile = NULL;
pdir = proc_mkdir("My_dir",NULL);
if(!pdir){
return -ENOMEM;
}
pfile = proc_create("My_file", 0666, pdir, &myops);
if(!pfile)
return -ENOMEM;
printk("Proc_entry Created Successfully, Module initialized\n");
return 0;
}
void cleanup_function(void)
{
remove_proc_entry("My_file", pdir);
remove_proc_entry("My_dir", NULL);
printk("Removing Proc_entry!!!");
}

Answer 1

The write function should return the number of bytes you processed.
In your case, 'proc_write_flag' function is returning 'ret' which is 0.
which means it will be invoked repeatedly until you process 'count' number of bytes from 'ubuf'
Similarly, 'proc_read_flag' should return the number of bytes you wrote into 'data'. In your case it is returning 0 (len)
There are other problems in 'proc_write_flag' function.
'buf' array isn't initialize and casting 'buf'(address) to int will not give you the expected answer.
Start with this http://tuxthink.blogspot.com/2013/12/creating-directory-under-proc-in-kernel.html
Then look into kstrtol() function.