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To: freebsd-stable@freebsd.org
Subject: Re: Trap 12/supervisor read, page not present 
In-reply-to: Your message of "Sat, 15 Jun 1996 05:34:17 PDT."
             <199606151234.FAA19027@Root.COM> 
Date: Sun, 16 Jun 1996 12:51:52 BST
From: David Malone <dwmalone@maths.tcd.ie>
Message-ID:  <9606161251.aa07235@salmon.maths.tcd.ie>
Sender: owner-stable@freebsd.org
X-Loop: FreeBSD.org
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> >Fatal trap 12: page fault while in kernel mode
> >fault virtual address	= 0x0
> >fault code		= supervisor read, page not present
> >instruction pointer	= 0x8:0xf019ab26
> >code segment		= base 0x0, limit 0xfffff, type 0x1b
> >			= DPL 0, pres 1, def32 1, gran 1
> >processor eflags	= interrupt enabled, resume, IOPL = 0
> >current process		= 22777 (sh)
> >interrupt mask		= net tty bio 
> >p\M^?\^Cge fault
> >
> >And here's the surrounding bits from the kernel:
> >f019a818 T _pmap_is_referenced
> >f019a9ac T _pmap_is_modified
> >f019ab74 T _pmap_clear_modify
> 
>    This appears to be a "known" bug. I didn't notice in your original message;
> was this with 2.1R or a recent SUP of -stable? If it was -stable, when did you
> SUP it? I just committed some fixes to CVS that might solve this problem. Can
> you update your kernel sources and see if the problem persists? Be sure you
> have rev 1.22.4.3 of vm_map.c - this was the last set of changes I made. The
> changes should be SUPable in about 3 hours from the date of this message.

I supped the -stable stuff a few hours after I got this message ( the file
you mention was at version 1.22.4.4 ) and it didn't stay up for more that
about 2 minutes, I have a vmcore if its of any use, the message was

Fatal trap 12: page fault while in kernel mode
fault virtual address   = 0xf0f6d318
fault code              = supervisor read, page not present
instruction pointer     = 0x8:0xf010ee04
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, def32 1, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 356 (reboot)
interrupt mask          =

( I'd just installed and rebooted, and wanted to reboot again, loged
in as root, typed reboot and then if fell over before shutting down ).
I'm not sure if I've done this quite right - but this is what
"gdb -k kernel.0 vmcore.0" gave me for a back trace :

#0  0xf01938bb in boot ()
#1  0xf01160c5 in panic ()
#2  0xf0101275 in db_panic ()
#3  0xf010115e in db_command ()
#4  0xf01012dd in db_command_loop ()
#5  0xf0103c78 in db_trap ()
#6  0xf019082a in kdb_trap ()
#7  0xf0198703 in trap_fatal ()
#8  0xf0198280 in trap_pfault ()
#9  0xf0197ed3 in trap ()
#10 0xf0191091 in calltrap ()
#11 0xf1297cba in end ()
#12 0xf012cfbf in vclean ()
#13 0xf012d0f4 in vgone ()
#14 0xf1297267 in end ()
#15 0xf012dea8 in dounmount ()
#16 0xf012c169 in vfs_unmountall ()
#17 0xf019384f in boot ()
#18 0xf01145c1 in reboot ()
#19 0xf01989ef in syscall ()
#20 0xf01910db in Xsyscall ()
#21 0x10d3 in ?? ()

	David.