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Date:      Sat, 20 Dec 1997 16:06:47 +0100 (CET)
From:      Pierre Beyssac <pb@fasterix.freenix.org>
To:        FreeBSD-gnats-submit@FreeBSD.ORG
Subject:   kern/5350: simple csh script panics kernel
Message-ID:  <199712201506.QAA01418@fasterix.frmug.org>
Resent-Message-ID: <199712201520.HAA22031@hub.freebsd.org>

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>Number:         5350
>Category:       kern
>Synopsis:       simple csh script panics kernel
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Dec 20 07:20:01 PST 1997
>Last-Modified:
>Originator:     Pierre Beyssac
>Organization:
individual
>Release:        FreeBSD 3.0-CURRENT i386
>Environment:

December 19 -current, K6 64Mb RAM.

>Description:

The following csh script causes a kernel panic:

#!/bin/csh -f
nonexistentfile1
rm nonexistentfile2

The panic is a "supervisor read, page not present". I haven't been
able to obtain a crash dump, the fault address is generally 0, the
instruction pointer is sometimes 0 too. I haven't been able to
obtain a stack dump either even with a DDB-compiled kernel (DDB
gets a page fault in the "trace" command).

At least once, the instruction pointer was pointing to somewhere
near kernel function sigreturn (sigreturn+262 in my kernel, compiled
with -O), this happens to be the "d" in string "BIOS basemem (%ldK)".

>How-To-Repeat:

Run the script (it's a simplified version of a script taken from
Bochs which only seems to panic the machine once in every two
tries).

It even works in single-user mode, with just / mounted read only:
this should be quite easy to reproduce as it only seems to be an
interaction between csh and the kernel.

>Fix:

>Audit-Trail:
>Unformatted:



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