Date: Thu, 24 Oct 2002 17:18:59 +0200 From: Alexander Leidinger <Alexander@Leidinger.net> To: Terry Lambert <tlambert2@mindspring.com> Cc: current@freebsd.org Subject: Re: page fault while in vm86 mode Message-ID: <20021024171859.3b05571b.Alexander@Leidinger.net> In-Reply-To: <3DB076F2.FB650CD7@mindspring.com> References: <20021018121229.1bff0d43.Alexander@Leidinger.net> <3DB076F2.FB650CD7@mindspring.com>
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On Fri, 18 Oct 2002 14:02:42 -0700
Terry Lambert <tlambert2@mindspring.com> wrote:
> Alexander Leidinger wrote:
> > Fatal trap 12: page fault while in vm86 mode
> ^
> |
> a page fault
>
> > #4 0xc0265055 in trap_pfault (frame=0xc0545fa8, usermode=0, eva=803202)
> ^ ^ ^
> | | |
> | | On a user address
> | In kernel mode
> A trap from kernel code
Ok, now with a Aug 22 kernel instead of an Aug 8 kernel:
---snip--
Fatal trap 12: page fault while in vm86 mode
fault virtual address = 0xc4182
fault code = user read, page not present
instruction pointer = 0xc000:0x4182
stack pointer = 0x0:0xfc0
frame pointer = 0x0:0x0
code segment = base 0x0, limit 0x0, type 0x0
= DPL 0, pres 0, def32 0, gran 0
processor eflags = interrupt enabled, resume, vm86, IOPL = 0
current process = 27349 (XFree86)
trap number = 12
panic: page fault
Uptime: 14h31m0s
pfs_vncache_unload(): 1 entries remaining
Dumping 639 MB
(kgdb) bt
#0 doadump () at ../../../kern/kern_shutdown.c:225
#1 0xc01a1712 in boot (howto=260) at ../../../kern/kern_shutdown.c:356
#2 0xc01a1b2d in panic (fmt=0xc02b8bc0 "%s")
at ../../../kern/kern_shutdown.c:509
#3 0xc02704b7 in trap_fatal (frame=0xc0540fa8, eva=803202)
at ../../../i386/i386/trap.c:847
#4 0xc027026d in trap_pfault (frame=0xc0540fa8, usermode=0, eva=803202)
at ../../../i386/i386/trap.c:761
#5 0xc026fe9b in trap (frame=
{tf_fs = 0, tf_es = 0, tf_ds = 0, tf_edi = 19158, tf_esi = 19182, tf_ebp = 0, tf_isp = -1068232748, tf_ebx = 13, tf_edx = 980, tf_ecx = 12, tf_eax = 13, tf_trapno = 12, tf_err = 4, tf_eip = 16770, tf_cs = 49152, tf_eflags = 721410, tf_esp = 4032, tf_ss = 0}) at ../../../i386/i386/trap.c:447
(kgdb) up 4
#4 0xc027026d in trap_pfault (frame=0xc0540fa8, usermode=0, eva=803202)
at ../../../i386/i386/trap.c:761
761 trap_fatal(frame, eva);
(kgdb) list
756 PCPU_GET(curpcb) != NULL &&
757 PCPU_GET(curpcb)->pcb_onfault != NULL) {
758 frame->tf_eip = (int)PCPU_GET(curpcb)->pcb_onfault;
759 return (0);
760 }
761 trap_fatal(frame, eva);
762 return (-1);
763 }
764
765 /* kludge to pass faulting virtual address to sendsig */
(kgdb)
---snip---
> > This doesn't look much to me. I'm used to see more frames here. What can I do
> > do debug this further?
>
> You can load up gdb, and decode all the variables in the trap_pfault()
> function, so that we can tell which code path resulted in the problem.
>
> Specifically, we need to know whether:
>
> o Which map vm->vm_map refers to?
(kgdb) print vm
$1 = (struct vmspace *) 0x104
(kgdb) print vm->vm_map
---Can't read userspace from dump, or kernel process---
(kgdb) print *vm
---Can't read userspace from dump, or kernel process
> o Whether vm_fault failed?
(kgdb) print rv
$4 = 1
> o The value of 'map' and the value of 'kmem_map' and 'kernel_map'?
(kgdb) print map
$5 = (struct vm_map *) 0x1
(kgdb) print kmem_map
$6 = 0xc0834078
(kgdb) print kernel_map
$7 = 0xc0834000
> o The value of p->p_lock
(kgdb) print p
$8 = (struct proc *) 0xc55ef8c0
(kgdb) print p->p_lock
$9 = 0 '\0'
> o The value of td->td_intr_nesting_level == 0
(kgdb) print td
No symbol "td" in current context.
> o If PCPU_GET(curpcb) is non-NULL
How do I do this with gdb?
> o If so, if PCPU_GET(curpcb)->pcb_onfault is non-NULL
Bye,
Alexander.
--
The three Rs of Microsoft support: Retry, Reboot, Reinstall.
http://www.Leidinger.net Alexander @ Leidinger.net
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