> On Mon, 27 Jan 1997 16:49:21 -0500 
>  "Perry E. Metzger" <perry@piermont.com> wrote:
> 
>  > The 4.4 book claimed that most 4.4. ports already had a guard page at
>  > the end of the kernel stack -- I was unaware that this was not the
>  > case any longer.
> 
> So, the hp300 port had this long ago... it was a bit easier to do
> in 4.4BSD because of the double-mapping of the kernel stack.  I.e.
> the "guard page" address never changed, because the kernel stack
> for all processes was mapped to the same address (kstack) upon
> context switch.

Uh, as noted previously, i don't believe this.  Are you saying that it
had a guard page between the kernel stack and 'struct user'?

If not, then:

	(1) it didn't have a guard page at the end of the kernel
	    stack, and

	(2) it could still clobber the user area with impunity.


cgd