On Tue, Sep 25, 2001 at 10:01:03AM +0200, Peter Wullinger wrote:
> On Tue, Sep 25, 2001 at 09:56:07AM +0200, Bernd Walter wrote:
> > On Mon, Sep 24, 2001 at 06:14:34PM -0700, Bakul Shah wrote:
> > > FWIW, in a Unix port we did I remember putting the user
> > > struct *above* the kernel stack. The stack grew down so you
> > > hit the red zone (the guard pages) without clobbering the
> > > user struct. Since struct user _ended_ on a page boundary,
> > > its size was needed at locore.s assembly time but that was a
> > > small price to pay for the added safety.
> >
> > I don't think a guard page can help here, because the page fault
> > handler needs a working stack.
> >
> Depends on what is does ... if it just panics and syncs and does
> not care overwriting the user struct of the current process (which
> is lost anyway), is this much of a problem?
Please correct me if I'm missing something.
If it is overwriting there is no page fault thus no guard page and
no panic.
If you would have a page fault there is no space where the CPU can
write the state information to for entering the handler.
--
B.Walter COSMO-Project http://www.cosmo-project.de
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