[PATCH] ppc32: handle Book E debug exceptions on kernel stack
Josh Boyer
jwboyer at jdub.homelinux.org
Thu Feb 23 21:54:02 EST 2006
On Wed, 2006-02-22 at 22:19 -0600, Kumar Gala wrote:
> On Tue, 14 Feb 2006, Dale Farnsworth wrote:
>
> > From: Dale Farnsworth <dale at farnsworth.org>
> >
> > On PPC Book E processsors, we currently handle debug
> > exceptions on the critical exception stack (debug stack
> > for E200). This causes problems with the kgdb single
> > step handler, which calls smp_processor_id() and spin_lock(),
> > which reference current_thread_info(), which only works when
> > we are on the kernel stack.
> >
> > We address this by switching to the kernel stack early while
> > handling debug exceptions. Note that the entry values of r10
> > and r11 are still saved on the critical exception (or debug) stack.
> >
> > Signed-off-by: Dale Farnsworth <dale at farnsworth.org>
> >
>
> Paul,
>
> We were wondering if you or David remember why a specific critical
> exception stack was added in the 40x port from 2.4 to 2.6?
I think Matt did that. And if I remember correctly, it was to avoid
corruption if you were in the middle of handling a normal interrupt and
a critical interrupt came in.
josh
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