2006/8/20, 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 ??)
may be, but had this been the problem then you would have failed while in module_init. After allocation you had myTable NULL. kmalloc takes care of that.
...
...
...
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));
Are you sure that 'data' has been malloc'ed in user space before doing ioctl ?
that is one problem that comes to my mind ? CMIIW.
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
thanks
-Manoj
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