I spoke too soon with regards to NetBSD 4 not panicing:

db> tr
panic: Segv in kernel mode: pc %x addr %x
Stack traceback :
0x89d75c64: trap+0x619(0x89d75d28)
0x89d75d28: trap type=0xc code=0x867cb60f pc=0x801acc04 psl=0xc00000
0x89d75cf4: pmap_page_protect_long+0x244(0x80422df0,0x1)
0x89d75d78: uvm_loan+0x377(0x83b892ac,0x1ad000,0x3000,0x86fae7e0,0x2)
0x89d75de8: pipe_write+0x394(0x86605744,0x86605770,0x89d75e9c,0x86712c1c,0x1)
0x89d75e58: 
dofilewrite+0x77(0x80cb28cc,0x1,0x86605744,0x1ad000,0x2430,0x8660577
0,0x1,0x89d75f74)
0x89d75ed0: sys_write+0x4b(0x80cb28cc,0x89d75f54,0x89d75f74)
0x89d75f24: syscall_plain+0xa7(0x89d75fb4)

John
-- 
Today is the day that my destiny calls me!
   Meowth