[PATCH] ARM: add warning for invalid kernel page faults

[linux@arm.linux.org.uk (Russell King - ARM Linux)]

On Mon, Sep 28, 2009 at 02:33:27PM +0300, Imre Deak wrote:
> On Mon, Sep 28, 2009 at 01:26:24PM +0200, ext Russell King - ARM Linux wrote:
> > On Mon, Sep 28, 2009 at 02:01:58PM +0300, Imre Deak wrote:
> > > On Mon, Sep 28, 2009 at 12:27:10PM +0200, ext Russell King - ARM Linux wrote:
> > > > [...]
> > > >
> > > > Now you're talking about different code - the bit I quoted was what was
> > > > in your submitted patch, without deletion of intervening lines.  There
> > > > was no else clause in your patch.
> > > > 
> > > > Please, go back and look at your original patch.
> > > 
> > > Ah, sorry. Missed that line when rebasing. I'll send an updated one.
> > 
> > Now I see what you're getting at.  Yes, we can make this a debugging
> > option, but I believe it should exhibit the right behaviour.
> > 
> > In other words (and as I already covered) it should invoke the standard
> > no_context thing if there isn't a fixup handler in place rather than
> > continuing blindly on to try to handle the fault.  So, it should be:
> > 
> > 	if (!down_read_trylock(&mm->mmap_sem)) {
> > 		if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc))
> > 			goto no_context;
> > 		down_read(&mm->mmap_sem);
> > 	} else {
> > +#ifdef CONFIG_DEBUG_VM
> > +		if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc))
> > +			goto no_context;
> > +#endif
> 
> Ok, agreed. Do you need an updated patch?

Yes, I would like a patch, and preferably tested please.  We've had a
number of not-tested patches hitting the kernel recently and I'd like
to cut down on those.