FTrace on MPC8xx

[Joakim Tjernlund]

Stefan Roese <ml at stefan-roese.de> wrote on 2011/04/13 17:21:33:
>
> Hi Joakim,
>
> On Wednesday 13 April 2011 16:58:21 Joakim Tjernlund wrote:
> > > This is on a 2.6.38 kernel (2.6.32 fails too). Debugging shows that
> > > __copy_tofrom_user() fails with return code 4 (called via
> > > ftrace_modify_code()).
> > >
> > > Before digging deeper: Has anybody tried/tested ftrace on MPC8xx? Any
> > > ideas what going wrong here?
> >
> > Just an idea, remove the usage of dcbX insn, these has been problematic
> > before.
>
> I originally tested with 2.6.32. Same problem there. And your 8xx patches with
> the dcbX changes are not included in 2.6.32 yet.

OK

>
> > How big was the size to copy_tofrom_user()? Did it mange to copy
> > any bytes?
>
> The size in __copy_tofrom_user is 4. And its the first call in
> ftrace_modify_code() that fails directly. This works just fine on a PPC440EPx
> board.

Since the size is only 4 it would not use dcbX anyway(I think).
Then is is probably called with the wrong addresses?

 Jocke