On Mon, Jul 05, 2010 at 02:35:33PM +0100, Ralf Baechle wrote:
> On Mon, Jul 05, 2010 at 02:09:31PM +0100, Matt Fleming wrote:
>
> > > Which often isn't so helpful. The alarm gets triggered on the last stack
> > > pointer decrement but according to murphy the overflow has happened 10
> > > levels up in the callchain.
> >
> > Last decrement? The alarm should be triggered the next time the
> > function in which the overflow occurs makes a function call. I don't
> > see how you could go down a level of the callchain and not trigger the
> > alarm if the overflow has happened?
>
> guilt()
> {
> char array[6000];
>
> blurb(&array);
> }
>
> blurb(void *p)
> {
> frob(p);
> }
>
> With the deep nesting of the current kernel there is a good chance a
> check in mcount will not be triggered in blurb() but possibly in frob
> or even further down the callchain.
Ah, I think I see what you mean. You're saying that you may not find
the culprit function using the massive amount of stack spac, which
eventually leads to the overflow? Yeah, that's a fair point. I think
if the mcount technique was used in conjunction with
CONFIG_DEBUG_STACK_USAGE it might be more helpful in that situation.
