copy_to_user() returns an error

["John Que" <qwejohn@xxxxxxxxx>]

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

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