Re: [PATCH] x86/dumpstack/64: Add guard pages to stack_info

[Peter Zijlstra]

On Thu, Sep 16, 2021 at 10:00:15AM +0200, Peter Zijlstra wrote:
> On Thu, Sep 16, 2021 at 11:47:49AM +0800, 王贇 wrote:
> 
> > I did some debug and found the issue, we are missing:
> > 
> > @@ -122,7 +137,10 @@ static __always_inline bool in_exception_stack(unsigned long *stack, struct stac
> >         info->type      = ep->type;
> >         info->begin     = (unsigned long *)begin;
> >         info->end       = (unsigned long *)end;
> > -       info->next_sp   = (unsigned long *)regs->sp;
> > +
> > +       if (!(ep->type & STACK_TYPE_GUARD))
> > +               info->next_sp   = (unsigned long *)regs->sp;
> > +
> >         return true;
> >  }
> > 
> > as the guard page are not working as real stack I guess?
> 
> Correct, but I thought I put if (type & GUARD) terminators in all paths
> that ended up caring about ->next_sp. Clearly I seem to have missed one
> :/
> 
> Let me try and figure out where that happens.

Oh, I'm an idiot... yes it tries to read regs the stack, but clearly
that won't work for the guard page.