misc/74171: Fatal trap 12: page fault while in kernel mode

[Robert Watson]

The following reply was made to PR kern/74171; it has been noted by GNATS.

From: Robert Watson <rwatson at FreeBSD.org>
To: freebsd-gnats-submit at FreeBSD.org
Cc:  
Subject: Re: misc/74171: Fatal trap 12: page fault while in kernel mode
Date: Mon, 3 Jan 2005 12:17:35 +0000 (GMT)

 On Sat, 20 Nov 2004, Normal User wrote:
 
 > Fatal trap 12: page fault while in kernel mode
 > fault virtual address  = 0x138
 > fault code             = supervisor read, page not present
 > instruction pointer    = 0x8:0xc183300d
 > stack pointer          = 0x10:0xcc721c80
 > frame pointer          = 0x10:0xcc721c90
 > code segment           = base 0x0, limit 0xfffff, type 0x1b
 >                        = DPL0, pres1, def32 1, gran 1
 > procesor eflags        = resume, IOPL = 0
 > current process        = 35 (swi5: tty:ltmdm++)
 > trap number            = 12
 > panic: page fault
 > Uptime: 3h9m23s
 
 This is a NULL pointer dereference in the kernel or a loaded kernel
 module.  Given that it's in the swi for ltmdm, it's likely a bug in the
 ltmdm driver, perhaps due to changes in the kernel that the driver has not
 been updated for.  For debugging purposes, it would be useful to have a
 DDB stack trace in the PR.  Could you compile your kernel with "options
 DDB", reproduce the panic, and use the "trace" command to generate a stack
 trace?  If performed with a serial console, you won't need to do a manual
 copy-and-paste.  Alternatively, you could build a kernel with debugging
 symbols and use gdb on a core dump, but the DDB trace is usually usefully
 concise.
 
 Thanks!
 
 Robert N M Watson
 
 
 > 
 > dmesg reports
 > 
 > ltmdm0: <Lucent Winmodem> port 0xe800-0xe8ff,0xec00-0xec07 mem 0xdfffff00-0xdfffffff irq 19 at device 8.0 on pci0
 > ltmdm0: [GIANT-LOCKED]
 > ltmdm0: type Virtual 16550A
 > 
 > 
 > >How-To-Repeat:
 >       just dial my phone number...
 > >Fix:
 > 
 > >Release-Note:
 > >Audit-Trail:
 > >Unformatted:
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