Date: Sat, 19 Apr 1997 00:30:01 -0700 (PDT) From: David Greenman <dg@root.com> To: freebsd-bugs Subject: Re: kern/3329: Panic when using tcpdump on fxp device Message-ID: <199704190730.AAA00313@freefall.freebsd.org>
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The following reply was made to PR kern/3329; it has been noted by GNATS.
From: David Greenman <dg@root.com>
To: tege@nada.kth.se
Cc: FreeBSD-gnats-submit@freebsd.org
Subject: Re: kern/3329: Panic when using tcpdump on fxp device
Date: Sat, 19 Apr 1997 00:23:38 -0700
>A `cp foo bar' command issued at the NFS client where both foo and bar lives
>at the same NFS server triggers an immediate panic in the NFS server when a
>tcpdump of the fxp device is running on the server.
>
>The NFS server panics with:
>
> Fatal trap 12: page fault while in kernel mode
> fault virtual address = 0x37353a40
> fault code = supervisor read, page not present
> instruction pointer = 0x8:0xf013e3dd
> stack pointer = 0x10:0xf01e7ec4
> frame pointer = 0x10:0xf01e7ecc
> 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 = Idle
> interrupt mask = not tty
> panic: page fault
>
>Running gdb on the kernel reveals that the crash happens in bpf_filter.c:
>
> 0xf013e3dd <m_xhalf+49>: movw (%ebx),%ax
>
>Both machines were rebooted immediately prior to this crash. (BPF was
>enabled in order to track down a hang in the client when using the fxp
>devices for the NFS traffic. The problem described in this report inhibited
>my investigation of the hang--I will resume it if the BPF problem is
>resolved. I might also try doing the tcpdump on the client and see if it
>panics like the server or if it merely hangs.)
I'm not able to reproduce either the hang or panic problems here. I just
did a code review of the fxp driver's handling of the bpf_tap call and there's
nothing wrong with it. In short, I'm at a complete loss to explain the problem
you're having. A complete traceback with function arguments might be useful.
-DG
David Greenman
Core-team/Principal Architect, The FreeBSD Project
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