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To: Antony <antony@turtle.ee.ncku.edu.tw>
cc: hackers@freefall.freebsd.org
Subject: Re: What is Fatal trap 12 ?? 
In-reply-to: Your message of "Mon, 30 Dec 1996 16:47:15 +0800."
             <199612300847.QAA15779@turtle.ee.ncku.edu.tw> 
From: David Greenman <dg@root.com>
Reply-To: dg@root.com
Date: Mon, 30 Dec 1996 01:02:16 -0800
Sender: owner-hackers@FreeBSD.ORG
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>
>	I enabled KTRACE, DDB, DIAGNOSTIC , and modified some source
>	file of /sys/netinent/ip_input.c, and in some place, it shows
>
>Dec 30 16:01:34 hawk /kernel: Fatal trap 12: page fault while in kernel mode
>Dec 30 16:01:34 hawk /kernel: fault virtual address     = 0xf0a1a004
>Dec 30 16:01:34 hawk /kernel: fault code                = supervisor read, page
>not present
>Dec 30 16:01:34 hawk /kernel: instruction pointer       = 0x8:0xf0a106b4
>Dec 30 16:01:34 hawk /kernel: code segment              = base 0x0, limit 0xfff
>f, type 0x1b
>Dec 30 16:01:34 hawk /kernel:                   = DPL 0, pres 1, def32 1, gran
>Dec 30 16:01:34 hawk /kernel: processor eflags  = interrupt enabled, resume, IO
>L = 0
>Dec 30 16:01:34 hawk /kernel: current process           = Idle
>Dec 30 16:01:34 hawk /kernel: interrupt mask            =
>Dec 30 16:01:34 hawk /kernel:
>Dec 30 16:01:35 hawk /kernel:      
>
>	Any idea about what the hell it is ? 

   It means that you are referencing an unmapped section of memory in the
kernel, causing a page fault (trap 12).

-DG

David Greenman
Core-team/Principal Architect, The FreeBSD Project