[TUHS] 211bsd: kernel panic after a 'here document' in tcsh

Walter F.J. Mueller w.f.j.mueller at retro11.de
Thu Jun 8 06:14:07 AEST 2017


Hi,

a few remarks on the feedback on the kernel panic after a 'here document' in tcsh.

To Michael Kjörling question:
 > I'm curious whether the same thing happens if you try that in some
 > other shell? (Not sure how widely here documents were supported back
 > then, but I'm asking anyway.)
And Johnny Billquist remark
 > Not sure if any of the other shells have this.

'here documents' are available and work fine in sh and csh.
And are in fact used, examples

   /usr/adm/daily     (a /bin/sh script)
     su uucp << EOF
           /etc/uucp/clean.daily
     EOF

   /usr/crash/why     (a /bin/csh script)
     adb -k {unix,core}.$1 << 'EOF'
     version/sn"Backtrace:"n
     $c
     'EOF'

To Michael Kjörling remark
 > The PC value in the panic report ("pc 161324") strikes me as high
and Johnny Billquist remark
 > This is in kernel mode, and that is in the I/O page.

211bsd uses split I/D space and uses all 64 kB I space for code.
The top 8 kB are in fact  the overlay area, and the crash happened
in overlay 4 (as indicated by ov 4). With a simple

   nm /unix | sort | grep " 4"

one gets

   161254 t ~psignal 4
   162302 t ~issignal 4

so the crash is just 050 bytes after the entry point of psignal. So the
PC address is fine and not the problem. For psignal look at

   http://www.retro11.de/ouxr/211bsd/usr/src/sys/sys/kern_sig.c.html#s:_psignal

the crash must be one of the first lines. psignal is an internal kernel
function, called from

   http://www.retro11.de/ouxr/211bsd/usr/src/sys/sys/kern_sig.c.html#xref:s:_psignal

and has nothing to do with the libc function psignal

   http://www.retro11.de/ouxr/211bsd/usr/man/cat3/psignal.0.html
   http://www.retro11.de/ouxr/211bsd/usr/src/lib/libc/gen/psignal.c.html

To Johnny Billquist remark
 > Could you (Walter) try the latest version of 2.11BSD and see if you
 > still get that crash?

very interesting that you see a core dump of tcsh rather a kernel panic.

Whatever tcsh does, it should not lead to a kernel panic, and if it does,
it is primarily a bug of the kernel. It looks like there are two issues,
one in tcsh, and one in the kernel. I've a hunch were this might come from,
but that will take a weekend or two to check on.


		With best regards,  Walter


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