hi,
intel processors got 4 privilage mode,0-3,
when processor is in kernel mode the segmentation
hardware loaded the segment descriptor with kernel
code and kernel data segment and set their flag to
highest privilage level,you are in user code and user
data segment and trying to access something which you
never reach,if you need to access any kernel data
structure then data segment must set to kernel data
segment,but still yr code segment remains set tp user
code segment this is again checked by processor,so u
never access kernel data struture from
user mode,
thus kernel modules are used for these things which
are dynamically linked kernel code extensions,
yes you directly get pid from task structure,
but genrally,usual way is to use the functions
exported by kernel to get yr work done ,you will get
this from /proc/ksyms
lots of info. is on web about module programming and
yes the bible for newbies linux device driver by
rubini is always there
Prasanna
--- Vincenzo Mallozzi <vinjunior@yahoo.it> wrote:
> Hi all,
> I'm trying to develop a C program that access to
> process descriptor information but I have had some
> problem with libraries.
> In particular, I've developed a program like this:
>
> #include <linux/sched.h>
>
> int main(void){
> pid_t pid;
> ....
> task_struct process = find_task_by_pid(pid);
> ...
> }
>
> but the compiler can't find get_task_by_pid
> function,
> while this is a function declared in
> include/linux/sched.h.
> What's wrong?
> Are there other methods to access process descriptor
> pointer?
> Thanks.
> Vincenzo Mallozzi.
>
>
>
>
>
>
>
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