[Question] How get instruction pointer of user space ???

[liyu@WAN]

Hi everyone:

   I am implemnting one ioctl() in one character device.

   That need know instruction pointer of user space. I am on i386 
platform.
I can sure I am in process context. and enter kernel by system call way.

   As I known, in default case, each task have one kernel stack, its length
is THREAD_SIZE(2 pages),  and current_thread_info() is at its top. the
struct pt_regs is at bottom of this stack.

   so I write the code like here:

   pt_regs = ((struct pt_regs *)(THREAD_SIZE + current_thread_info()))+1;
   return pt_regs->eip;

   but it do not work! even, I get segment fault and kernel Oops at 
sometime.
  
   Also, I am sure current_thread_info() return right value of current 
user task.

   Any idea on here?

   thanks


                                                                  sailor.






  




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