Subject: Re: random signals kill my processes with -current
To: Jason Thorpe <thorpej@nas.NASA.GOV>
From: Chris G. Demetriou <cgd@CS.cmu.edu>
Date: 01/27/1997 17:13:31
> On Mon, 27 Jan 1997 16:49:21 -0500
> "Perry E. Metzger" <firstname.lastname@example.org> 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
(2) it could still clobber the user area with impunity.