you should somehow call the kernel module from user space program ...
may be using ioctl ..
so that you are in same process context --- as the one you are sending
address from .
write char dev driver with ioctl method defined
then call ioctl from user space
ioctl(fd,<IOCTL_CMD>,addrees you want to send)
Now in kernel module
get_user(kernel data variable, <user space address>);
Nidhi
On Wed, Apr 28, 2010 at 11:55 AM, Yang Fangkai <wolfgang.y...@gmail.com>wrote:
> Hi, Nidhi,
>
> Thanks for your reply! Yes, you are right. I pass the address
> to the module from bash command echo, therefore when the address is
> referred, the current pid is bash's pid, instead of the simple program
> I wrote.
>
> But how can I fix this problem?
>
> Thank you!
>
> Fangkai
>
> On Wed, Apr 28, 2010 at 1:01 AM, nidhi mittal hada
> <nidhimitta...@gmail.com> wrote:
> >
> > 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.y...@gmail.com>
> > 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!!
> >>
> >> --
> >> To unsubscribe from this list: send an email with
> >> "unsubscribe kernelnewbies" to ecar...@nl.linux.org
> >> Please read the FAQ at http://kernelnewbies.org/FAQ
> >>
> >
> >
> >
> > --
> > Thanks & Regards
> > Nidhi Mittal Hada
> > Scientific officer D
> > Computer Division
> > Bhabha Atomic Research Center
> > Mumbai
> >
> >
> >
>
--
Thanks & Regards
Nidhi Mittal Hada
Scientific officer D
Computer Division
Bhabha Atomic Research Center
Mumbai
