Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!rice!sun-spots-request
From: sanzgiri@flamingo.metaphor.com
Newsgroups: comp.sys.sun
Subject: Context switching on SPARC
Keywords: Miscellaneous
Message-ID: <10201@brazos.Rice.edu>
Date: 24 Jul 90 18:43:28 GMT
Sender: root@rice.edu
Organization: Sun-Spots
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Approved: Sun-Spots@rice.edu
X-Sun-Spots-Digest: Volume 9, Issue 277, message 16
Originator: spots@titan.rice.edu

I'd appreciate help on either or both of the following 2 related
questions: (both about context switching - within a process - on the
SPARC)

1) I'd like to write a piece of code that "fakes" a setjmp call from a
   previously non-existent context. I want to do this so that the
   corresponding longjmp call will branch to a given function pointer and use
   a given pointer as its stack pointer. Doing the "obvious thing" leads to
   segmentation violations, bus errors etc.

2) How does one write a piece of assembly code that will restore an
   arbitrary register state? Again, doing the "obvious thing" leads to
   illegal instruction errors or similar junk.

I am pretty sure the above problems are related to the "windowing"
architecture of the processor - wherein you must not only restore the
given window but its predecessors as well while remaining compatible with
the overflow-underflow processing - in order to switch contexts. But I am
unable to get any meaningful help from either of the SPARC architecture
manual or the Sun-4 assembly language reference manual. Enquiries with Sun
haven't turned anything up yet.

E-mail would be great. (I'll summarise). Posted replies OK too.