panic in amap_wipeout() (was: ipnat ftp proxy suddenly stopped working)

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

So the machine where ipnat's ftp proxy misbehaved just paniced:

uvm_fault(0xffffffff8076d460, 0x0, 1) -> e
fatal page fault in supervisor mode
trap type 6 code 0 rip ffffffff8045102e cs 8 rflags 10212 cr2  8 cpl 0 rsp fffffe812a095a90
kernel: page fault trap, code=0
Stopped in pid 27044.1 (perl) at	netbsd:amap_wipeout+0x81:	movq	8
(%rax),%rdx
db{0}> bt
amap_wipeout() at netbsd:amap_wipeout+0x81
uvm_unmap_detach() at netbsd:uvm_unmap_detach+0x43
uvmspace_free() at netbsd:uvmspace_free+0xe7
exit1() at netbsd:exit1+0x175
sys_exit() at netbsd:sys_exit+0x3e
syscall() at netbsd:syscall+0xc4
db{0}> show reg
ds	92d8
es	0
fs	2c80
gs	4b73
rdi	ffffffff8075e100	amep_list_lock
rsi	0
rbp	fffffe812a095ab0
rbx	fffffe8294b648e8
rdx	2
rcx	fffffe841338a140
rax	0
r8	fffffe83f3c192d8
r9	2
r10	0
r11	1
r12	2
r13	fffffe825f43cb88
r14	0
r15	fffffe811d870520
rip	ffffffff8045102e	amap_wipeout+0x81
cs	8
rflags	10212
rsp	fffffe812a095a90
ss	10
netbsd:amap_wipeout+0x81:	movq	8(%rax),%rdx
db{0}>

Since it's a development server, I let it sit in DDB in case someone wants me 
to examine something.