Re: [Question] arch-independent way to differentiate between user and kernel

[Ingo Molnar]

* Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:

> Hi all,
> 
> I'm dealing with a problem where I want to know from __do_IRQ in 
> kernel/irq/handle.c if the interrupt occurred while the process was in 
> user space or kernel space.  But the trick here is that it must work 
> on all architectures.
> 
> Does anyone know of some way that that function can tell if it had 
> interrupted the kernel or user space?  I know of serveral 
> arch-dependent ways, but that's not acceptable right now.

i dont think there's any. user_mode(regs) gets the closest - it might 
make sense to generalize it over all arches.

update_process_times() gets an arch-independent 'was the tick user-space 
or kernel-space' flag, so the best starting point would be to look at 
the output of:

 for N in `find . -name '*.c' | xargs grep update_process_times |
  grep arch`; do echo $N; done | grep update_process_times |
   sort | uniq -c

which gives:

      2 update_process_times()
      1 update_process_times(CHOOSE_MODE(user_context(UPT_SP(regs)),
      6 update_process_times(user);
      1 update_process_times(user_mode(fp));
     33 update_process_times(user_mode(regs));
      2 update_process_times(user_mode_vm(regs));

so ~33 calls use user_mode(regs), and the rest needs to be reviewed and 
possibly changed. Looks doable.

	Ingo
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