panic:munhash message from 4.2bsd

[der Mouse]

In article <424 at usfvax2.UUCP>, hall at usfvax2.UUCP (Dr. Larry Hall) writes:
> We have encountered the following system problem and wonder if any
> one out there knows about it.  We are running 4.2bsd on a VAX 11/750.

> When we get in dbx and read in the symbolic information and
> executable code and then type run the operating system crashes with
> the message  "panic:munhash".

> This does not occur when we try to run the program outside of dbx.
> Does anyone know what the error  panic:munhash  means?

Our 4.2 system would crash reliably with panic: munhash whenever anyone
attempted to set a breakpoint with any debugger.  Poking around, it
turned out that it crashed whenever anyone attempted to use ptrace() to
write to the child's text segment (which setting a breakpoint does).
There were two casts in the kernel which, though perfectly correct,
produced incorrect code because there was something wrong with the
compiler.  You could comment out the casts in the source, or even just
adb the kernel and change two instructions (extv to extzv, I think).  I
forget further details, but someone posted the fix to net.unix-wizards
at the time (this was some time ago, it was still called
net.unix-wizards).

If nobody comes forward with this, I can go to the backup tapes and
resurrect our 4.2 kernel source long enough to dig out these changes
(we aren't running 4.2 any more).

					der Mouse

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