Fatal trap 12: page fault while in kernel mode
cpuid = 1; apic id = 00
fault virtual address   = 0x10
fault code              = supervisor write, page not present
instruction pointer     = 0x20:0xc0a462b1
stack pointer           = 0x28:0xe78e3a70
frame pointer           = 0x28:0xe78e3a90
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         = 2009 (qemu)
trap number             = 12
panic: page fault
cpuid = 1
Uptime: 9m55s
Physical memory: 1011 MB
Dumping 58 MB: 43 27 11

#0  doadump () at pcpu.h:195
195             __asm __volatile("movl %%fs:0,%0" : "=r" (td));
(kgdb) bt
#0  doadump () at pcpu.h:195
#1  0xc0754457 in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:409
#2  0xc0754719 in panic (fmt=Variable "fmt" is not available.
) at /usr/src/sys/kern/kern_shutdown.c:563
#3  0xc0a4905c in trap_fatal (frame=0xe78e3a30, eva=16) at /usr/src/sys/i386/i386/trap.c:899
#4  0xc0a492e0 in trap_pfault (frame=0xe78e3a30, usermode=0, eva=16) at /usr/src/sys/i386/i386/trap.c:812
#5  0xc0a49c8c in trap (frame=0xe78e3a30) at /usr/src/sys/i386/i386/trap.c:490
#6  0xc0a2fc0b in calltrap () at /usr/src/sys/i386/i386/exception.s:139
#7  0xc0a462b1 in pmap_extract (pmap=0x0, va=3885268992) at atomic.h:149
#8  0xc457e725 in ?? ()
#9  0x00000000 in ?? ()
#10 0xe7948000 in ?? ()
#11 0xc465c000 in ?? ()
#12 0x000003c0 in ?? ()
#13 0xc457c877 in ?? ()
#14 0xe78e3ac4 in ?? ()
#15 0xc0bfb680 in enumerators ()
#16 0xe78e3ad0 in ?? ()
#17 0xc0a37e75 in lapic_handle_timer (frame=0xc4623000) at /usr/src/sys/i386/i386/local_apic.c:697
Previous frame inner to this frame (corrupt stack?)
(kgdb) list *0xc0a462b1
0xc0a462b1 is in pmap_extract (atomic.h:149).
144     static __inline int
145     atomic_cmpset_int(volatile u_int *dst, u_int exp, u_int src)
146     {
147             u_char res;
148
149             __asm __volatile(
150             "       " MPLOCKED "            "
151             "       cmpxchgl %2,%1 ;        "
152             "       sete    %0 ;            "
153             "1:                             "
(kgdb) up
#1  0xc0754457 in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:409
409                     doadump();
(kgdb)