What is Renode?

Renode is an Emulator

• Windows
• Mac
• Linux
• CI
• Github Actions

Whole-system Emulator

• CPU cores
• Peripherals
• Interconnections

Whole-system Emulator

CPU Cores

• x86
• arm
• arm64
• ppc
• riscv
• spark
• xtensa

Peripherals

Memory is Just a Peripheral

• When you write to memory, it remembers the data
• When you read from memory, you get the value
• Your program is just initialised memory

Peripherals Are Just Special Memory

• Writing to a memory address does a thing
• Reading from an address gets a result
• Interrupts are just GPIOs

Peripherals Are Just Special Memory

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

• Built-in peripherals for a number of devices
• STM32
• NRF52
• IMXRT
• LiteX
• See https://github.com/renode/renode-infrastructure/tree/master/src/Emulator/Peripherals/Peripherals for more

Creating New 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 develop the OS!
• 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
4. • Yay!
5. Someone (without a device!) decided to add more vectors
6. Tested in Renode
7. Passed
8. Failed on hardware
9. Bug in detecting overflow condition for normalization in hardware
10. https://github.com/betrusted-io/gateware/commit/817e284a3d92037b8cb0686735578d2bb60853e9

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
2. • You might even find a compatible peripheral!
3. Copy it to your project
4. Change the constructor
5. Change the register set
6. Import the `.cs` file into Renode
7. Add it to your platform file

Demonstration!

Running Badge Software in Renode

It Doesn't

Xtensa is an Uncommon Architecture

• Audio DSPs
• Possibly Intel?
• NXP

Extensive use of Boot ROM

Extensive use of Boot ROM

$ esptool.py dump_mem \    
	0x3ff90000 \       
	65536 \
	irom.bin

Add a serial port

namespace Antmicro.Renode.Peripherals.UART {
  public class ESP32_UART : UARTBase, IDoubleWordPeripheral,
							IKnownSize {
    private readonly DoubleWordRegisterCollection registers;
    public ESP32_UART(Machine machine) : base(machine) {
      registers = new DoubleWordRegisterCollection(this,
	  			new Dictionary<long, DoubleWordRegister> {
        {0x00, new DoubleWordRegister(this).WithValueField(0,8,
				writeCallback: (_, v) => TransmitCharacter((byte)v))}
      });
    }
				

Add a serial port

{0x00, new DoubleWordRegister(this)
		.WithValueField(0, 8,
			writeCallback: (_, v) => TransmitCharacter((byte)v))}
				

Load SVD file

sysbus:
	init:
		ApplySVD @esp32s3.svd

Load SVD file

extmem: Unhandled read from offset 0x64.
extmem: Unhandled write to offset 0x64, value 0x3.
sysbus: Read from an unimplemented register SYSTEM:SYSCLK_CONF
	(0x600C0060), returning a value from SVD: 0x1. (3)
sysbus: Read from an unimplemented register SYSTEM:PERIP_CLK_EN0
	(0x600C0018), returning a value from SVD: 0xF9C1E06F.
sysbus: Write of value 0xF9C1E06F to an unimplemented register
	SYSTEM:PERIP_CLK_EN0 (0x600C0018) generated from SVD.
sysbus: Read from an unimplemented register SYSTEM:PERIP_RST_EN0
	(0x600C0020), returning a value from SVD: 0x0.
sysbus: Write of value 0x0 to an unimplemented register SYSTEM:PERIP_RST_EN0 
	0x600C0020) generated from SVD.
sysbus: Read from an unimplemented register SYSTEM:PERIP_RST_EN0
	(0x600C0020), returning a value from SVD: 0x0.
sysbus: Write of value 0x4 to an unimplemented register SYSTEM:PERIP_RST_EN0 (0x600C0020) generated from SVD.						
					

Add Peripherals

Slowly Advance

GDB with ELF

What's Left?

• SPI Controller
• Interrupt Controller