Locking it down: pass old data too

• pass the kernel both the expected old data and the new data

  • compare each word against both old and new

    • already new? do nothing

    • matches old? update to new

    • match neither? sigexit(SIGILL)

• sounds nice, but the kernel isn't really checking the data for validity

• there's a corner case where an entry can legitimately change the value it should resolve to

  • will remove