Newsgroups: comp.arch
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: Why my stack grew up and this was wrong
Message-ID: <1990Dec9.021210.15950@zoo.toronto.edu>
Organization: U of Toronto Zoology
References: <7298@uklirb.informatik.uni-kl.de> <11336@pt.cs.cmu.edu>
Date: Sun, 9 Dec 90 02:12:10 GMT

In article <11336@pt.cs.cmu.edu> lindsay@gandalf.cs.cmu.edu (Donald Lindsay) writes:
>Further, we used to use software overflow checks. The correct answer
>now is to have the OS put invalid pages at appropriate places. This
>is a genuine improvement: it has perfect coverage (unlike some of the
>old software schemes), and it should have no runtime overhead.

Actually, no, it doesn't have perfect coverage:  if you happen to grow the
stack by a really large amount, you can leap over the invalid page and
end up in another region of memory without detecting it until you try to
access some of that big lump.  Still generally a reasonable approach,
mind you, since that sort of thing isn't common.
-- 
"The average pointer, statistically,    |Henry Spencer at U of Toronto Zoology
points somewhere in X." -Hugh Redelmeier| henry@zoo.toronto.edu   utzoo!henry