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Date: Mon, 23 Feb 1998 22:56:20 +0100 (MET)
From: Andreas Schulz <ats@freebsd.first.gmd.de>
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Subject: kern/5827: Kernel panics in current (3.0)
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>Number:         5827
>Category:       kern
>Synopsis:       kernel panics in current (3.0)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:
>Keywords:
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Feb 23 14:10:07 PST 1998
>Last-Modified:
>Originator:     Andreas Schulz
>Organization:
GMD-FIRST
>Release:        FreeBSD 3.0-971022-SNAP i386
>Environment:

Kernel sources as of last weekend.

>Description:

kernel panics with a "Fatal trap 9: general protection fault while
in kernel mode"  at address 0x8:0xf0196f9f which translates to the
"stosl" in "generic_bzero". 

>How-To-Repeat:

Boot a current kernel on an AMD K6 :-). The panics happen after the
"npx0: INT 16 interface" line.

>Fix:
	
I have fixed it for the moment on my box with a save of %es, move from
%ds to %es before the "stosl" and a restore afterwards. 
It looks like %es segment gets somewhere overwritten in the kernel.
It is not sufficient to explicitly set it in locore.s, also tried
after snooping around in the bootblock code and locore.s. 
I suspect you will only see this problem with the AMD K6 or a Cyrix
chip. The Pentium and 486 use another bzero routine in the kernel.

>Audit-Trail:
>Unformatted:

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