DTrace panic while probing syscall::open (and possibly many others)

OK, so I first posted a thread on the forums about this in 7.2-RELEASE:
http://forums.freebsd.org/showthread.php?t=3834
Then filed a PR, kern/134408:
http://www.freebsd.org/cgi/query-pr.cgi?pr=134408

The very same bug remains in 8-CURRENT/amd64 as of May 13, ~10(am)
GMT+2.

Steps to reproduce:
1) Build DTrace capable kernel (I followed the wiki DTrace instructions)
2) Reboot; kldload dtraceall
3) dtrace -n 'syscall::open:entry { self->path = arg0; }  
syscall::open:return { printf("%s\n", copyinstr(self->path)); }'
4) Crash.

Backtrace:
[root_at_vmware /usr/obj/usr/src/sys/DTRACE]# kgdb kernel.debug /var/ 
crash/vmcore.3
GNU gdb 6.1.1 [FreeBSD]
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and  
you are
welcome to change it and/or distribute copies of it under certain  
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for  
details.
This GDB was configured as "amd64-marcel-freebsd"...

Unread portion of the kernel message buffer:
panic: from debugger
cpuid = 0
Uptime: 3m10s
Physical memory: 368 MB
Dumping 81 MB: 66 50 34 18 2

Reading symbols from /boot/kernel/dtraceall.ko...Reading symbols from / 
boot/kernel/dtraceall.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/dtraceall.ko
Reading symbols from /boot/kernel/profile.ko...Reading symbols from / 
boot/kernel/profile.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/profile.ko
Reading symbols from /boot/kernel/opensolaris.ko...Reading symbols  
from /boot/kernel/opensolaris.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/opensolaris.ko
Reading symbols from /boot/kernel/cyclic.ko...Reading symbols from / 
boot/kernel/cyclic.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/cyclic.ko
Reading symbols from /boot/kernel/dtrace.ko...Reading symbols from / 
boot/kernel/dtrace.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/dtrace.ko
Reading symbols from /boot/kernel/systrace.ko...Reading symbols from / 
boot/kernel/systrace.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/systrace.ko
Reading symbols from /boot/kernel/sdt.ko...Reading symbols from /boot/ 
kernel/sdt.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/sdt.ko
Reading symbols from /boot/kernel/fbt.ko...Reading symbols from /boot/ 
kernel/fbt.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/fbt.ko
Reading symbols from /boot/kernel/dtnfsclient.ko...Reading symbols  
from /boot/kernel/dtnfsclient.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/dtnfsclient.ko
Reading symbols from /boot/kernel/dtmalloc.ko...Reading symbols from / 
boot/kernel/dtmalloc.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/dtmalloc.ko
#0  doadump () at pcpu.h:223
223		__asm __volatile("movq %%gs:0,%0" : "=r" (td));
(kgdb) bt
#0  doadump () at pcpu.h:223
#1  0xffffffff80566b23 in boot (howto=260) at /usr/src/sys/kern/ 
kern_shutdown.c:420
#2  0xffffffff80566fac in panic (fmt=Variable "fmt" is not available.
) at /usr/src/sys/kern/kern_shutdown.c:576
#3  0xffffffff801d3ef7 in db_panic (addr=Variable "addr" is not  
available.
) at /usr/src/sys/ddb/db_command.c:478
#4  0xffffffff801d43a1 in db_command (last_cmdp=0xffffffff80bd3620,  
cmd_table=Variable "cmd_table" is not available.
) at /usr/src/sys/ddb/db_command.c:445
#5  0xffffffff801d45f0 in db_command_loop () at /usr/src/sys/ddb/ 
db_command.c:498
#6  0xffffffff801d6599 in db_trap (type=Variable "type" is not  
available.
) at /usr/src/sys/ddb/db_main.c:229
#7  0xffffffff80597135 in kdb_trap (type=10, code=0,  
tf=0xfffffffe4e64e450) at /usr/src/sys/kern/subr_kdb.c:534
#8  0xffffffff80843f81 in trap (frame=0xfffffffe4e64e450) at /usr/src/ 
sys/amd64/amd64/trap.c:606
#9  0xffffffff8081edc7 in calltrap () at /usr/src/sys/amd64/amd64/ 
exception.S:223
#10 0xffffffff8123c128 in dtrace_panic (format=Variable "format" is  
not available.
)
     at /usr/src/sys/modules/dtrace/dtrace/../../../cddl/contrib/ 
opensolaris/uts/common/dtrace/dtrace.c:601
#11 0xffffffff8123c200 in dtrace_copycheck  
(uaddr=18446744071581326184, kaddr=Variable "kaddr" is not available.
) at dtrace_isa.c:527
#12 0xffffffff8123c2bc in dtrace_copyinstr (uaddr=34365395808,  
kaddr=18446744066201920856, size=256,
     flags=0xffffffff8122f120) at dtrace_isa.c:558
#13 0xffffffff81249e84 in dtrace_dif_emulate (difo=0xffffff00026a2d80,  
mstate=0xfffffffe4e64ea00,
     vstate=0xffffff0002548838, state=0xffffff0002548800)
     at /usr/src/sys/modules/dtrace/dtrace/../../../cddl/contrib/ 
opensolaris/uts/common/dtrace/dtrace.c:3446
#14 0xffffffff8124b20a in dtrace_probe (id=Variable "id" is not  
available.
)
     at /usr/src/sys/modules/dtrace/dtrace/../../../cddl/contrib/ 
opensolaris/uts/common/dtrace/dtrace.c:6220
#15 0xffffffff8137b155 in systrace_probe () from /boot/kernel/ 
systrace.ko
#16 0xffffffff80843c4d in syscall (frame=0xfffffffe4e64ec90) at /usr/ 
src/sys/amd64/amd64/trap.c:990
#17 0xffffffff8081f050 in Xfast_syscall () at /usr/src/sys/amd64/amd64/ 
exception.S:364
#18 0x00000008005411fc in ?? ()
Previous frame inner to this frame (corrupt stack?)

Hope this helps to fix this bug - I assume syscall::open isn't the  
only probe
affected as it's simply the very first one I tried.

Same panic on two computers (a "real" one, A64 3200+, nForce4, 2GB RAM;
and a Macbook Pro C2D running VMware Fusion). Same panic in 7.2 and 8.0.

Regards,
Thomas