I got it to happen.  However, I have omited most of the parameter info,
since I am re typing this in.

Here is what happens:

Checking for core dump...
panic: getblk: block invarient failed
Stopped in savecore at  cpu_Debugger +0x4:     leave
db> trace
cpu_Debugger(c18ec788,0,0,c5434d9c,c0159ea0) at cpu_Debugger+0x4
panic(<omited>) at panic+0x64
getblk(<omited>) at getblk+0xe4
bread(<omited>) at bread+0x2d
spec_read(<omited>) at spec_read+0x25c
ufsspec_read(<omited>) at ufsspec_read+0x2d
vn_read(<omited>) at vn_read+0xba
dofileread(<omited>) at dofileread+0x93
sys_pread(<omited>) at sys_pread+0xec
syscall() at syscall+0x1d8
------- syscall (number 198) -------------
 0x805f823