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cc23-renode/talk.md
Sean Cross bd13845287 initial commit 
Signed-off-by: Sean Cross <sean@xobs.io>
2023-08-15 12:19:20 +02:00

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Emulating the Badge under Renode (Eventually)

Talk Outline

  • What is Renode?
  • How is it extensible?
  • What is the state of the badge?

About Me

What is Renode?

Target Platforms

  • Windows
  • Mac
  • Linux
  • CI

Whole-system Emulator

  • Emulates CPU cores
  • Emulates peripherals
  • Emulates interconnects

CPU Cores

  • x86
  • arm
  • arm64
  • ppc
  • riscv
  • sparc
  • xtensa

Peripherals

[Image of a CPU chart]

Peripherals Are Just Memory Addresses That Are Special

  • In a MMIO system, writing to a memory address does a thing
  • Reading from an address gets a result
  • Interrupts are just GPIOs

10% of the Functionality Gets You 90% of the Way There

  • E.g. in a serial device, baudrate, timers, and parity/stop can be ignored
  • Just "Tx", "Rx", and interrupt setup
  • Most software works just fine if you return zeroes for invalid addresses

SVD files are your friend

  • Your chip probably comes with a SVD file
  • This gives a map of RAM and peripherals
  • Renode can parse this and use it for logging / defaults

Existing Peripherals in Renode

Creating Peripherals

  • Renode is written in C#
  • Like Java, C# has an eval() function
  • Peripherals can be written and loaded at runtime

Networks in Renode

  • Built-in support for CAN, Ethernet, and Wireless
  • Also possible to add networks at runtime
  • No latency, just packets of data
    • Different devices run at different speeds

Other Goodies

  • LCD monitor with touchscreen support
  • Python interpreter for quick hacks
  • Attach GDB to any CPU core
  • Attach a serial port to a network connection
  • Scriptable with Robot framework
  • Log function calls

Shortcomings

  • Unable to unload modules
    • Need to restart Renode when you change a file
  • No real audio support
    • Support for verifying I2S, but can't play it
  • Only x64 hosts
    • Runs under Rosetta on Mac
  • Documentation needs work
    • Use the source!

Extending Renode

First, Betrusted

  • FPGA with VexRiscv
  • 2nd FPGA with smaller VexRiscv
  • 16-bit COM bus between them
  • AES extensions
  • x25519 "ENGINE" accelerator
  • SHA accelerator
  • Battery charger and manager
  • Custom lcd, timers, and USB

Emulating it under Renode

  • Good enough to catch bugs!

ENGINE bug

  1. Added test vectors to the OS
  2. Ran test vectors on physical device
  3. Got test vectors passing in Renode
  • Yay!
  1. Someone (without a device!) decided to add more vectors
  2. Tested in Renode
  3. Passed
  4. Failed on hardware
  5. Bug in detecting overflow condition for normalization in hardware
  6. 817e284a3d

Getting Started with Renode

  1. Renode Platform Definition (.repl)
  2. Renode Script (.resc)

Example project repl

Example project resc

Running it

How to Extend Renode

  1. Find a peripheral that does what you want
  • You might even find a compatible peripheral!
  1. Copy it to your project
  2. Change the constructor
  3. Change the register set
  4. Import the .cs file into Renode
  5. Add it to your platform file

Demonstration!

Running Badge Software in Renode

It Doesn't

Xtensa is a New Architecture

  • Added support for ESP32 family
  • Merged quickly
  • Few others use Xtensa

Extensive use of Boot ROM

  • Pulled ROM off device with esptool
  • Load into RAM
  • Set entrypoint

Add a serial port

  • Immediately get output
  • Breaks immediately

Load SVD file

Add Peripherals

Slowly Advance

What's Left

  • SPI Controller
  • Interrupt Controller

Getting involved!

  • Try Renode for your projects!
  • Add CI tests for your firmware!
  • Explore binaries for unknown targets!

Thank you!