What do panic messages mean?

[Brandon S. Allbery]

As quoted from <170 at pigs.UUCP> by haugj at pigs.UUCP (The Beach Bum):
+---------------
| In article <446 at sysco>, chapman at sco.COM (brian chapman) writes:
| ] In article <2375 at rpp386.UUCP> jfh at rpp386.UUCP (The Beach Bum) writes:
| ] [ now, what i want to know is what is a DNA trap?  does this mean the
| ] [ machine has been genetically mutated?
| ] 
| ] DNA is Device Not Availible (floating point device, that is)
| ] Meaning the kernel is executing *87 instructions.  Or trying to.
| 
| its True Meaning(tm), how come i don't see it when i am executing
| 80387 instructions?  i mean, i use floating point code, but never
+---------------

Here's how it works on the 386 boxes I've used:

The user-mode trap table is set up so that if an 80387 instruction is seen
and the 80387 is not installed, the instruction traps to an emulator.
However, there is no such arrangement in the kernel -- so if the kernel
tries to run an 80387 instruction and there's no 80387 chip the system panics.
This presumably is because the emulator can't easily be made to work in
kernel mode; also, the kernel shouldn't need to do floating point unless
some kind of special device driver is used -- in which case you probably
want the 80387 anyway, for speed.  (The system'd get pretty slow if the
kernel were spending large amounts of its time in the emulator called from
kernel mode.)
-- 
Brandon S. Allbery			  | "Given its constituency, the only
uunet!marque,sun!mandrill}!ncoast!allbery | thing I expect to be "open" about
Delphi: ALLBERY	       MCI Mail: BALLBERY | [the Open Software Foundation] is
comp.sources.misc: ncoast!sources-misc    | its mouth."  --John Gilmore