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.yang@xxxxxxxxx> 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
<nidhimittal19@xxxxxxxxx> 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.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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>> 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
