I think I have seen this twice already with 17 June kernel.  Otherwise the
kernel seems to be more stable (no vm specific panics) but I cannot be sure
as holidays just started so load dropped considerably.

kernel and crash dump are

ftp://ftp.clinet.fi/pub/FreeBSD/crashdumps/*.89.gz

hsu#news.clinet.fi Sat 3: gdb -k kernel.89 vmcore.89
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GDB 4.13 (i386-unknown-freebsd), 
Copyright 1994 Free Software Foundation, Inc...
IdlePTD 26a000
current pcb at 221684
panic: page fault
#0  boot (howto=256) at ../../i386/i386/machdep.c:940
940                                     dumppcb.pcb_cr3 = rcr3();
(kgdb) bt
#0  boot (howto=256) at ../../i386/i386/machdep.c:940
#1  0xf0117546 in panic (fmt=0xf01cbe6c "page fault")
    at ../../kern/subr_prf.c:127
#2  0xf01cc9da in trap_fatal (frame=0xefbffef0) at ../../i386/i386/trap.c:745
#3  0xf01cc4cc in trap_pfault (frame=0xefbffef0, usermode=0)
    at ../../i386/i386/trap.c:656
#4  0xf01cc19b in trap (frame={tf_es = 16, tf_ds = 16, tf_edi = 0, 
      tf_esi = -215522560, tf_ebp = -272629960, tf_isp = -272629992, 
      tf_ebx = -215686656, tf_edx = 14751796, tf_ecx = -215522560, tf_eax = 0, 
      tf_trapno = 12, tf_err = 2, tf_eip = -267337695, tf_cs = 8, 
      tf_eflags = 66118, tf_esp = -266342168, tf_ss = -215522560})
    at ../../i386/i386/trap.c:319
#5  0xf01c4271 in calltrap ()
#6  0xf010bde4 in exit (p=0xf3276300, uap=0xefbfff94, retval=0xefbfff84)
    at ../../kern/kern_exit.c:96
#7  0xf01ccc85 in syscall (frame={tf_es = 39, tf_ds = 39, tf_edi = 0, 
      tf_esi = -1, tf_ebp = -272640756, tf_isp = -272629788, 
      tf_ebx = 134758496, tf_edx = 0, tf_ecx = 1, tf_eax = 1, tf_trapno = 12, 
      tf_err = 7, tf_eip = 134711469, tf_cs = 31, tf_eflags = 658, 
      tf_esp = -272640776, tf_ss = 39}) at ../../i386/i386/trap.c:895
#8  0xf01c42c5 in Xsyscall ()
Cannot access memory at address 0xefbfd50c.
(kgdb) up
#1  0xf0117546 in panic (fmt=0xf01cbe6c "page fault")
    at ../../kern/subr_prf.c:127
127             boot(bootopt);
(kgdb) list
122
123     #if defined(DDB)
124             if (debugger_on_panic)
125                     Debugger ("panic");
126     #endif
127             boot(bootopt);
128     }
129
130     /*
131      * Warn that a system table is full.
(kgdb) up
#2  0xf01cc9da in trap_fatal (frame=0xefbffef0) at ../../i386/i386/trap.c:745
745                     panic(trap_msg[type]);
(kgdb) up
#3  0xf01cc4cc in trap_pfault (frame=0xefbffef0, usermode=0)
    at ../../i386/i386/trap.c:656
656                     trap_fatal(frame);
(kgdb) up
#4  0xf01cc19b in trap (frame={tf_es = 16, tf_ds = 16, tf_edi = 0, 
      tf_esi = -215522560, tf_ebp = -272629960, tf_isp = -272629992, 
      tf_ebx = -215686656, tf_edx = 14751796, tf_ecx = -215522560, tf_eax = 0, 
      tf_trapno = 12, tf_err = 2, tf_eip = -267337695, tf_cs = 8, 
      tf_eflags = 66118, tf_esp = -266342168, tf_ss = -215522560})
    at ../../i386/i386/trap.c:319
319                             (void) trap_pfault(&frame, FALSE);
(kgdb) up
#5  0xf01c4271 in calltrap ()
(kgdb) up
#6  0xf010bde4 in exit (p=0xf3276300, uap=0xefbfff94, retval=0xefbfff84)
    at ../../kern/kern_exit.c:96
96              exit1(p, W_EXITCODE(uap->rval, 0));
(kgdb) list
91                      int     rval;
92              } */ *uap;
93              int *retval;
94      {
95
96              exit1(p, W_EXITCODE(uap->rval, 0));
97              /* NOTREACHED */
98      }
99
100     /*
(kgdb) print uap
$1 = (struct rexit_args *) 0x0
(kgdb) print p
$2 = (struct proc *) 0xf3276300
(kgdb) print *p
$3 = {p_forw = 0xf024b84c, p_back = 0x0, p_list = {le_next = 0x0, 
    le_prev = 0xf02454d8}, p_cred = 0xf31a93c0, p_fd = 0xf3074400, 
  p_stats = 0xf7196258, p_limit = 0xf020c52c, p_vmspace = 0xf324e200, 
  p_sigacts = 0xf7196128, p_flag = 24582, p_stat = 5 '\005', 
  p_pad1 = "\001\001", p_pid = 14861, p_pglist = {le_next = 0x0, 
    le_prev = 0xf32e4e34}, p_pptr = 0xf32e4e00, p_sibling = {le_next = 0x0, 
    le_prev = 0xf32e4e48}, p_children = {lh_first = 0x0}, p_oppid = 0, 
  p_dupfd = 0, p_estcpu = 2245, p_cpticks = 1990, p_pctcpu = 4, p_wchan = 0x0, 
  p_wmesg = 0xf012c775 "biowait", p_swtime = 1, p_slptime = 0, p_realtimer = {
    it_interval = {tv_sec = 0, tv_usec = 0}, it_value = {tv_sec = 0, 
      tv_usec = 0}}, p_rtime = {tv_sec = 0, tv_usec = 34136}, p_uticks = 2, 
  p_sticks = 1980, p_iticks = 12, p_traceflag = 0, p_tracep = 0x0, 
  p_siglist = 0, p_textvp = 0xf30ab500, p_lock = 0 '\000', 
  p_pad2 = "\000\000", p_locks = 0, p_simple_locks = 0, p_hash = {
    le_next = 0x0, le_prev = 0xe11834}, p_sigmask = 0, 
  p_sigignore = 4294967295, p_sigcatch = 20483, p_priority = 16 '\020', 
  p_usrpri = 127 '\177', p_nice = 0 '\000', 
  p_comm = "cc\000e\000\000r\000\000\000\000\000\000\000\000\000", 
  p_pgrp = 0xf31a9380, p_sysent = 0xf01ff8c0, p_rtprio = {type = 1, prio = 0}, 
  p_addr = 0xf7196000, p_md = {md_flags = 0, md_regs = 0xefbfffbc}, 
  p_xstat = 0, p_acflag = 0, p_ru = 0xf3467700}
(kgdb) up  
#7  0xf01ccc85 in syscall (frame={tf_es = 39, tf_ds = 39, tf_edi = 0, 
      tf_esi = -1, tf_ebp = -272640756, tf_isp = -272629788, 
      tf_ebx = 134758496, tf_edx = 0, tf_ecx = 1, tf_eax = 1, tf_trapno = 12, 
      tf_err = 7, tf_eip = 134711469, tf_cs = 31, tf_eflags = 658, 
      tf_esp = -272640776, tf_ss = 39}) at ../../i386/i386/trap.c:895
895             error = (*callp->sy_call)(p, args, rval);
(kgdb) print p
$4 = (struct proc *) 0xf3276300
(kgdb) print args
$5 = {0, 1, 134328416, 134344720, 134344716, -272629828, 2, 0}
(kgdb) print rval
$6 = {0, 0}
(kgdb) down
#6  0xf010bde4 in exit (p=0xf3276300, uap=0xefbfff94, retval=0xefbfff84)
    at ../../kern/kern_exit.c:96
96              exit1(p, W_EXITCODE(uap->rval, 0));
(kgdb) list
91                      int     rval;
92              } */ *uap;
93              int *retval;
94      {
95
96              exit1(p, W_EXITCODE(uap->rval, 0));
97              /* NOTREACHED */
98      }
99
100     /*
(kgdb) print uap
$7 = (struct rexit_args *) 0x0
(kgdb)

This might be a compiler optimization ghost.  I'm compiling with -O.

Fix: 

I do not know.
How-To-Repeat: 
I do not know