Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!uw-beaver!rice!sun-spots-request
From: agesen@daimi.dk (Ole Agesen)
Newsgroups: comp.sys.sun
Subject: Help needed: clearing the 68020 cache.
Keywords: Software
Message-ID: <83@brazos.Rice.edu>
Date: 6 Jul 89 09:26:13 GMT
Sender: root@rice.edu
Organization: Sun-Spots
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X-Sun-Spots-Digest: Volume 8, Issue 68, message 8 of 22

Help needed....

The MC68020 incorporates an on-chip cache memory. The cache is used to
store the instruction stream prefetch accesses from the main memory.  I'm
currently implementing a kind of incremental linking implying the need to
write self-modifying code. Therefore, I have to clear the cache upon a
modification of the code. According to the MC68020 User's Manual the cache
is cleared by issuing a MOVEC instruction (move control register).
However, this is a privileged instruction (requiring supervisor state).

Can anyone tell me how to clear the cache?
  Can I get supervisor privileges for a user process?
  Is there a kernel operation clearing the cache?
  Can I easily create a modified kernel with the desired operation?
  Other (more) realistic possibilities?

(We are using Unix 4.0 on sun 3/50).


Thanks in advance!

Ole Agesen