Re: [PATCH 3/5] stack overflow safe kdump (2.6.16-rc1-i386) - fault

[Andrew Morton <akpm@osdl.org>]

Andi Kleen <ak@suse.de> wrote:
>
> On Wednesday 25 January 2006 08:15, Andrew Morton wrote:
> > Fernando Luis Vazquez Cao <fernando@intellilink.co.jp> wrote:
> > > When we have a bloated stack it is likely that it ends up making an
> > > invalid memory access that in turn causes a page fault. Take this case
> > > into account in the page fault code.
> > >
> > > +	if (!virt_addr_valid(tsk)) {
> >
> > Is virt_addr_valid() a sufficiently strong test here?  One could probe the
> > address to see if it generates a fault, like the __get_user() in
> > kmem_cache_create().
> 
> Recursive page faults are always risky because if things go bad they
> can lead to unbounded recursion.   I think the scheduler knows anyways
> which process currently executes on a CPU so it might be better to get
> the information from there.
> 

It might be nmi-in-interrupt.

But then, the interrupt code knows what CPU it's running on too.