>  
> -#define ISTACK_SIZE NBPG
> +#define ISTACK_SIZE (NBPG * 2)
>  vaddr_t istack;
>  /* 
>   * This code uses bitfield operators for most page table entries.  
> 
> This seems to fix the problem for me. So unless there are hidden
> assumptions in the code that ISTACK_SIZE is just NBPG, I would propose
> this change to go into -current and pulled up to the 1.6 branch.
> 
> The larger size could possibly be made dependent on IPSEC, but since the
> interrupt stack is allocated only once anyway, this seems a bit
> over-frugal to me.
> 
Yes, thanks for finding this. Even though I donīt like that people write
in-kernel code that eats up the stack (and especially not on interrupt
level, there may be nested interrupts) it would be OK to do in this case.
There are no dependencies on the interrupt stack size elsewhere, just 
enlarge it.

-- Ragge