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This chapter provides an overview of Fault Proof Program development on top of the custom FPVM targets supported by Kona. At a high level, a Fault Proof Program is not much different from a regular no_std Rust program. A custom entrypoint is provided, and the program is compiled down to a custom target, which is then executed on the FPVM. Fault Proof Programs are structured with 3 stages:
  1. Prologue: The bootstrapping stage, where the program is loaded into memory and the initial state is set up. During this phase, the program’s initial state is written to the FPVM’s memory, and the program’s entrypoint is set.
  2. Execution: The main execution stage, where the program is executed on the FPVM. During this phase, the program’s entrypoint is called, and the program is executed until it exits.
  3. Epilogue: The finalization stage, where the program’s final state is read from the FPVM’s memory. During this phase, the program’s final state is inspected and properties of the state transition are verified.
The following sections will provide a more in-depth overview of each of these stages, as well as the tools and abstractions provided by Kona for developing your own Fault Proof Programs.