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A fault-injection framework using Chisel and FIRRTL


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Chained Hierarchical Injection for Fault Resiliency Evaluation (Chiffre)

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This provides a framework for automatically instrumenting a hardware design with run-time configurable fault injectors. This relies on three major components:

  • A Chisel library that emits annotations marking specific circuit components as fault injectable
  • New FIRRTL passes that instrument the circuit components with run-time configurable fault injectors
  • A utility for configuring fault injectors at run time

More information can be found in a CARRV 2018 workshop paper, Chiffre: A Configurable Hardware Fault Injection Framework for RISC-V Systems:

  author = {Eldridge, Schuyler and Buyuktosunoglu, Alper and Bose, Pradip},
  title = {Chiffre: A Configurable Hardware Fault Injection Framework for RISC-V Systems},
  booktitle = {2nd Workshop on Computer Architecture Research with RISC-V (CARRV '18)},
  year = {2018},


There are currently two major usage classes: standalone injection and Rocket Chip-assisted injection.

In Standalone Injection you define and implement a fault injection controller, MyController, that manages a specific scan chain. You then annotate specific circuit components with the isFaulty method indicating which scan chain they belong to and what type of fault injector to use. An overall example of this is shown below.

import chisel3._
import chiffre._

/* A controller for injectors on the "main" scan chain */
class MyController extends Module with ChiffreController {
  val io = IO(new Bundle{})
  lazy val scanId = "main"
  // MyController body with scan chain logic not shown

/* A module with faulty components */
class MyModule extends Module with ChiffreInjectee {
  val io = IO(new Bundle{})
  val x = Reg(UInt(1.W))
  val y = Reg(UInt(4.W))
  val z = Reg(UInt(8.W))
  isFaulty(x, "main", classOf[inject.LfsrInjector32])
  isFaulty(y, "main", classOf[inject.StuckAt])
  isFaulty(z, "main", classOf[inject.CycleInjector32])

In Rocket-Chip Assisted Injection, the fault controller is a provided Rocket Custom Coprocessor (RoCC) called LeChiffre. This can then be used to orchestrate fault injection experiments in external components or inside Rocket itself. We provide an example patch that makes certain control and status registers (CSRs) in rocket fault injectable and a bare metal test program that makes sure this fault injection is working. You can build an emulator with the correct configuration using the following (note: this will clone the chiffre repository inside of your Rocket Chip clone directory):

git clone chiffre
git apply le-chiffre/patches/rocket-chip-fault-cycle.patch
cd emulator
make CONFIG=LeChiffreConfig ROCKETCHIP_ADDONS="chiffre/le-chiffre chiffre"

You can then run the test provided by chiffre/tests (instructions provided in that directory).