Re: question about get_user
I believe that you are having pid and passing that to your character driver.
How about using find_task_by_id(pid) function in your virtual driver. it
returns pointer to task_struct for particular pid.
e.g.
pid_t pid;
struct task_struct *my;
my = find_task_by_id(pid)
printf("%s",my->comm); //print or do whatever you want to do with it
Regards,
_-_Mayank Rana_-_
--- On Wed, 4/28/10, Manish Katiyar wrote:
From: Manish Katiyar
Subject: Re: question about get_user
To: "Yang Fangkai"
Cc: "nidhi mittal hada" , "Kernelnewbies"
Date: Wednesday, April 28, 2010, 12:49 PM
On Wed, Apr 28, 2010 at 12:24 PM, Yang Fangkai wrote:
> Hi, Nidhi,
>
> Thanks! Now I know what is the problem.
>
> But in my project, I am developing a virtual char device driver
> such that user can read any process's memory contents by specifying
> its pid and virtual address. Therefore, a device /dev/gh is
> registered, and the user try to do something like:
>
> echo -n targetpid>/dev/gh & echo -n addr>/dev/gh
>
> Therefore, the target process can't be modified. The device driver
> will retrieve the value by pid and virtual address and return it to
> user at terminal.
Isn't it something similar to ptrace with PTRACE_PEEKTEXT, PTRACE_PEEKDATA
Thanks -
Manish
> I don't know how to solve this problem with get_user
> under my scenario. Thank you!
>
> Fangkai
>
> On Wed, Apr 28, 2010 at 1:42 AM, nidhi mittal hada
> wrote:
>> 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,,addrees you want to send)
>>
>>
>> Now in kernel module
>>
>> get_user(kernel data variable, );
>>
>> Nidhi
>>
>>
>>
>>
>>
>>
>>
>> On Wed, Apr 28, 2010 at 11:55 AM, Yang Fangkai
>> 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
>>> 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
>>> > 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
>>
>>
>>
>
> --
> 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 -
Manish
==
[$\*.^ -- I miss being one of them
==
--
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
Re: question about get_user
Nidhi,
I have thought about this possibility but that seems to be
incredibly complicated. I need to go through all the paging mechanism
or even deal with page fault manually! That is a bit too far than I
plan to do.
Thanks!
Fangkai
On Wed, Apr 28, 2010 at 2:55 AM, nidhi mittal hada
wrote:
>
> that clearly shows that
> the process you will call module from is not the one whose address you
> want to get value of ...
>
>
> i think with using pid you will search list of processes maintained by
> kernel
> and then you need to traverse mm_struct of reqd process
> then virtual memory address space of the process vm_areas
>
> and then you will find what is the value present at a particular address
> for a particular process
>
>
> Nidhi
>
> On Wed, Apr 28, 2010 at 12:24 PM, Yang Fangkai
> wrote:
>>
>> Hi, Nidhi,
>>
>> Thanks! Now I know what is the problem.
>>
>> But in my project, I am developing a virtual char device driver
>> such that user can read any process's memory contents by specifying
>> its pid and virtual address. Therefore, a device /dev/gh is
>> registered, and the user try to do something like:
>>
>> echo -n targetpid>/dev/gh & echo -n addr>/dev/gh
>>
>> Therefore, the target process can't be modified. The device driver
>> will retrieve the value by pid and virtual address and return it to
>> user at terminal. I don't know how to solve this problem with get_user
>> under my scenario. Thank you!
>>
>> Fangkai
>>
>> On Wed, Apr 28, 2010 at 1:42 AM, nidhi mittal hada
>> wrote:
>> > 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,,addrees you want to send)
>> >
>> >
>> > Now in kernel module
>> >
>> > get_user(kernel data variable, );
>> >
>> > Nidhi
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> > On Wed, Apr 28, 2010 at 11:55 AM, Yang Fangkai
>> > 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
>> >> 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
>> >> >
>> >> > 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
>> >
>> >
>> >
>
>
>
> --
> Thanks & Regards
> Nidhi Mittal Hada
> Scientific officer D
> Computer Division
> Bhabha Atomic Research Center
> Mumbai
>
>
>
--
To unsubscribe from this list: send an email with
"unsubscribe kernelnewbies" to ecar..
Re: question about get_user
that clearly shows that
the process you will call module from is not the one whose address you
want to get value of ...
i think with using pid you will search list of processes maintained by
kernel
and then you need to traverse mm_struct of reqd process
then virtual memory address space of the process vm_areas
and then you will find what is the value present at a particular address
for a particular process
Nidhi
On Wed, Apr 28, 2010 at 12:24 PM, Yang Fangkai wrote:
> Hi, Nidhi,
>
> Thanks! Now I know what is the problem.
>
> But in my project, I am developing a virtual char device driver
> such that user can read any process's memory contents by specifying
> its pid and virtual address. Therefore, a device /dev/gh is
> registered, and the user try to do something like:
>
> echo -n targetpid>/dev/gh & echo -n addr>/dev/gh
>
> Therefore, the target process can't be modified. The device driver
> will retrieve the value by pid and virtual address and return it to
> user at terminal. I don't know how to solve this problem with get_user
> under my scenario. Thank you!
>
> Fangkai
>
> On Wed, Apr 28, 2010 at 1:42 AM, nidhi mittal hada
> wrote:
> > 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,,addrees you want to send)
> >
> >
> > Now in kernel module
> >
> > get_user(kernel data variable, );
> >
> > Nidhi
> >
> >
> >
> >
> >
> >
> >
> > On Wed, Apr 28, 2010 at 11:55 AM, Yang Fangkai
> > 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
> >> 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
> >
> >
> >
>
--
Thanks & Regards
Nidhi Mittal Hada
Scientific officer D
Computer Division
Bhabha Atomic Research Center
Mumbai
Re: question about get_user
Oh, yes, something like that... Maybe I should have used ptrace to
solve this problem instead of by get_user..
Thanks!
Fangkai
On Wed, Apr 28, 2010 at 2:19 AM, Manish Katiyar wrote:
> On Wed, Apr 28, 2010 at 12:24 PM, Yang Fangkai
> wrote:
>> Hi, Nidhi,
>>
>> Thanks! Now I know what is the problem.
>>
>> But in my project, I am developing a virtual char device driver
>> such that user can read any process's memory contents by specifying
>> its pid and virtual address. Therefore, a device /dev/gh is
>> registered, and the user try to do something like:
>>
>> echo -n targetpid>/dev/gh & echo -n addr>/dev/gh
>>
>> Therefore, the target process can't be modified. The device driver
>> will retrieve the value by pid and virtual address and return it to
>> user at terminal.
>
> Isn't it something similar to ptrace with PTRACE_PEEKTEXT, PTRACE_PEEKDATA
>
> Thanks -
> Manish
>> I don't know how to solve this problem with get_user
>> under my scenario. Thank you!
>>
>> Fangkai
>>
>> On Wed, Apr 28, 2010 at 1:42 AM, nidhi mittal hada
>> wrote:
>>> 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,,addrees you want to send)
>>>
>>>
>>> Now in kernel module
>>>
>>> get_user(kernel data variable, );
>>>
>>> Nidhi
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> On Wed, Apr 28, 2010 at 11:55 AM, Yang Fangkai
>>> 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
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
> 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
>>>
>>>
>>>
>>
>> --
>> 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 -
> Manish
> ==
> [$\*.^ -- I miss being one of them
> ==
>
--
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
Re: question about get_user
On Wed, Apr 28, 2010 at 12:24 PM, Yang Fangkai wrote:
> Hi, Nidhi,
>
> Thanks! Now I know what is the problem.
>
> But in my project, I am developing a virtual char device driver
> such that user can read any process's memory contents by specifying
> its pid and virtual address. Therefore, a device /dev/gh is
> registered, and the user try to do something like:
>
> echo -n targetpid>/dev/gh & echo -n addr>/dev/gh
>
> Therefore, the target process can't be modified. The device driver
> will retrieve the value by pid and virtual address and return it to
> user at terminal.
Isn't it something similar to ptrace with PTRACE_PEEKTEXT, PTRACE_PEEKDATA
Thanks -
Manish
> I don't know how to solve this problem with get_user
> under my scenario. Thank you!
>
> Fangkai
>
> On Wed, Apr 28, 2010 at 1:42 AM, nidhi mittal hada
> wrote:
>> 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,,addrees you want to send)
>>
>>
>> Now in kernel module
>>
>> get_user(kernel data variable, );
>>
>> Nidhi
>>
>>
>>
>>
>>
>>
>>
>> On Wed, Apr 28, 2010 at 11:55 AM, Yang Fangkai
>> 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
>>> 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
>>> > 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
>>
>>
>>
>
> --
> 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 -
Manish
==
[$\*.^ -- I miss being one of them
==
--
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
Re: question about get_user
Hi, Nidhi,
Thanks! Now I know what is the problem.
But in my project, I am developing a virtual char device driver
such that user can read any process's memory contents by specifying
its pid and virtual address. Therefore, a device /dev/gh is
registered, and the user try to do something like:
echo -n targetpid>/dev/gh & echo -n addr>/dev/gh
Therefore, the target process can't be modified. The device driver
will retrieve the value by pid and virtual address and return it to
user at terminal. I don't know how to solve this problem with get_user
under my scenario. Thank you!
Fangkai
On Wed, Apr 28, 2010 at 1:42 AM, nidhi mittal hada
wrote:
> 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,,addrees you want to send)
>
>
> Now in kernel module
>
> get_user(kernel data variable, );
>
> Nidhi
>
>
>
>
>
>
>
> On Wed, Apr 28, 2010 at 11:55 AM, Yang Fangkai
> 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
>> 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
>> > 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
>
>
>
--
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
Re: question about get_user
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,,addrees you want to send)
Now in kernel module
get_user(kernel data variable, );
Nidhi
On Wed, Apr 28, 2010 at 11:55 AM, Yang Fangkai 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
> 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
> > 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
Re: question about get_user
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
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
> 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
>
>
>
--
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
Re: question about get_user
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 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
question about get_user
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
