in your kernel module try to print current->pid
is it same as the user space process id ?
i think when in kernel module you are not in the same process context whihc you want to refer ...
Nidhi
On Wed, Apr 28, 2010 at 10:38 AM, Yang Fangkai <wolfgang.yang@xxxxxxxxx> wrote:
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 does output bff91914
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!!
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Thanks & Regards
Nidhi Mittal Hada
Scientific officer D
Computer Division
Bhabha Atomic Research Center
Mumbai
