Get_user running at kernel mode returns error
- by Fangkai Yang
Hi, all,
I have a problem with get_user() macro. What I did is as follows:
I run the following program
int main()
{
int a = 20;
printf("address of a: %p", &a);
sleep(200);
return 0;
}
When the program runs, it outputs the address of a, say, 0xbff91914.
Then I pass this address to a module running in Kernel Mode that retrieves the contents at this address (at the time when I did this, I also made sure the process didn't terminate, because I put it to sleep for 200 seconds... ):
The address is firstly sent as a string, and I cast them into pointer type.
int * ptr = (int*)simple_strtol(buffer, NULL,16);
printk("address: %p",ptr); // I use this line to make sure the cast is correct. When running, it outputs bff91914, as expected.
int val = 0;
int res;
res= get_user(val, (int*) ptr);
However, res is always not 0, meaning that get_user returns error. I am wondering what is the problem....
Thank you!!
-- Fangkai
