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From: ramanujan@dec-verdi.UUCP
Newsgroups: net.arch
Subject: Re: red and green (?) stack violations
Message-ID: <2506@decwrl.DEC.COM>
Date: Tue, 22-Apr-86 12:50:03 EST
Article-I.D.: decwrl.2506
Posted: Tue Apr 22 12:50:03 1986
Date-Received: Thu, 24-Apr-86 04:52:56 EST
Sender: daemon@decwrl.DEC.COM
Organization: Digital Equipment Corporation
Lines: 23


>What is a "red and green" stack violation?  I've heard references to this
>over the years, but no one has given me a satisfying explanation.
>Does it exist only on obscure members of the PDP-11 family, or is it
a >common, universal condition to which DEC has assigned a cute name?
 
>(I may have the colors wrong.  I'm colorblind anyway.  :-)

The colors I have heard of in reference to stack violations in the PDP-11
world are 'red' and 'yellow' . These are meant to protect the kernel mode
stack . The following is my understanding of what these traps are :

- If the virtual address of a kernel stack reference is less than 400 (octal)
  , a 'yellow' stack trap occurs at the end of the instruction making the
  reference.
- If an abort of any kind occurs during a push to kernel stack due to an
  interrupt,trap or another abort sequence a 'red' stack trap will occur.

Raj_Ramanujan

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General Disclaimer : The opinions expressed above are mine alone ....