Faulttolerant Typed Assembly Language

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Fault-tolerant Typed Assembly Language
Frances Perry, Lester Mackey, George A. Reis, Jay
Ligatti, David I. August, and David
Walker Princeton University
TALFT An Idealized Fault-tolerant System

• Goal Detect all faults that change a programs
  observable behavior and prove that well-typed
  programs always detect a single fault.
• General Strategy Two redundant and independent
  copies of each computation (labeled green and
  blue) that are compared before stores and control
  flow transfers.

The TALFT Machine

• A machine state consists of a code memory C, a
  value memory M, a register file R, a current
  instruction ir, and a store queue Q.

• A value is observed when it is stored to memory.
• Q buffers a store from the green computation
  until the corresponding blue store is performed.
• Special hardware is used by memory and control
  flow instructions to detect mismatches between
  the computations and trigger the special fault
  state.

Frances Perry. CRA-W/CDC Programming Languages
Summer School. May 9-11, 2007.