Re: copy_to_user() returns an error

[denz aberilla <denzzzhome@xxxxxxxxx>]

Hello, I'm not sure why you're seeing the errors but my question is did you tag your module_init() with "__init" ??? ...because this will destroy that function after it's called during insmod and I think it takes all it's variables with it to the grave.

 

  Dennis E. A.

----- Original Message ----
From: John Que <qwejohn@xxxxxxxxx>
To: kernelnewbies@xxxxxxxxxxxx
Sent: Sunday, August 20, 2006 7:44:55 PM
Subject: copy_to_user() returns an error

Hello,
I am trying to copy a table (an array of structs) from
kernel to user space in a kernel module ioctl method.

I do it thus;
...
...
struct myStruct
    {
    char* name;
    int value1;
    int value2;
    struct myStruct *next;
    };
    
static struct myStruct* myTable = NULL;     
there is allocation of memOry for myTable in the module init() thus:
myTable = kmalloc( MAXELEM* sizeof(struct MYStruct), GFP_KERNEL);
and it is filled with values.

(MAXENTIRES is 1000 - maybe it is too big ??)
...
...
...
static int my_ioctl(struct inode* inode,
                                      struct file* file,
                                        unsigned int cmd,
                                        unsigned long data)
  {
    switch (cmd)
        {
        case MYIOCTL:
            {
            int res;    

            res = copy_to_user((void __user*)data,
                                        relayTable,
                                        numberOfPorts* sizeof(struct relayStruct));
                                        
                                        
            printk("res is %d\n",res);
            }
        ...
        ...
        }
        
copy_to_user() should return 0 in case of success;
I keep getting positive number after calling copy_to_user();
(it is 240 or 160 or 80, depends on which trial I made)

I also tried to copy only one element (numberOfPorts=1) , and
I had also tried : copy_to_user((struct relayStruct*)data,
and also copy_to_user() returned error.

When I try to use this IOCTL from user space I get garbage
for the table entries.

Any ideas what is wrong here?

Regards,
John

--
Kernelnewbies: Help each other learn about the Linux kernel.
Archive:       http://mail.nl.linux.org/kernelnewbies/
FAQ:           http://kernelnewbies.org/faq/