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evm

README.md

@ethereumjs/evm

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TypeScript implementation of the Ethereum EVM.

Installation

To obtain the latest version, simply require the project using npm:

npm install @ethereumjs/evm

This package provides the core Ethereum Virtual Machine (EVM) implementation which is capable of executing EVM-compatible bytecode. The package has been extracted from the @ethereumjs/vm package along the VM v6 release.

Note that this package atm cannot be run in a standalone mode but needs to be executed via the VM package which provides an outer Ethereum mainnet compatible execution context. Standalone functionality will be added along a future non-breaking release.

Note: If you want to work with EIP-4844 related functionality, you will have additional manual installation steps for the KZG setup, see related section below.

Usage

import { Blockchain } from '@ethereumjs/blockchain'
import { Chain, Common, Hardfork } from '@ethereumjs/common'
import { EEI } from '@ethereumjs/vm'
import { EVM } from '@ethereumjs/evm'
import { DefaultStateManager } from '@ethereumjs/statemanager'

// Note: in a future release there will be an EEI default implementation
// which will ease standalone initialization
const main = async () => {
  const common = new Common({ chain: Chain.Mainnet, hardfork: Hardfork.London })
  const stateManager = new DefaultStateManager()
  const blockchain = await Blockchain.create()
  const eei = new EEI(stateManager, common, blockchain)

  const evm = new EVM({
    common,
    eei,
  })

  const STOP = '00'
  const ADD = '01'
  const PUSH1 = '60'

  // Note that numbers added are hex values, so '20' would be '32' as decimal e.g.
  const code = [PUSH1, '03', PUSH1, '05', ADD, STOP]

  evm.events.on('step', function (data) {
    // Note that data.stack is not immutable, i.e. it is a reference to the vm's internal stack object
    console.log(`Opcode: ${data.opcode.name}\tStack: ${data.stack}`)
  })

  evm
    .runCode({
      code: Buffer.from(code.join(''), 'hex'),
      gasLimit: BigInt(0xffff),
    })
    .then((results) => {
      console.log(`Returned: ${results.returnValue.toString('hex')}`)
      console.log(`gasUsed: ${results.executionGasUsed.toString()}`)
    })
    .catch(console.error)
}

void main()

Example

This projects contain the following examples:

  1. ./examples/decode-opcodes: Decodes a binary EVM program into its opcodes.
  2. ./examples/runCode: Show how to use this library in a browser.

All of the examples have their own README.md explaining how to run them.

API

Docs

For documentation on EVM instantiation, exposed API and emitted events see generated API docs.

BigInt Support

Starting with v1 the usage of BN.js for big numbers has been removed from the library and replaced with the usage of the native JS BigInt data type (introduced in ES2020).

Please note that number-related API signatures have changed along with this version update and the minimal build target has been updated to ES2020.

Architecture

VM/EVM Relation

This package contains the inner Ethereum Virtual Machine core functionality which was included in the @ethereumjs/vm package up till v5 and has been extracted along the v6 release.

This will make it easier to customize the inner EVM, which can now be passed as an optional argument to the outer VM instance.

At the moment the EVM package can not be run standalone and it is therefore recommended for most use cases to rather use the VM package and access EVM functionality through the vm.evm property.

Execution Environment (EEI) and State

For the EVM to properly work it needs access to a respective execution environment (to e.g. request on information like block hashes) as well as the connection to an outer account and contract state.

To ensure a unified interface the EVM provides a TypeScript EEI interface providing which includes the necessary function signatures for access to environmental parameters as well as the VM state.

The @ethereumjs/vm provides a concrete implementation of this interface which can be used to instantiate the EVM within an Ethereum mainnet compatible execution context.

Browser

To build the EVM for standalone use in the browser, see: Running the EVM in a browser.

Setup

Hardfork Support

The EthereumJS EVM implements all hardforks from Frontier (chainstart) up to the latest active mainnet hardfork.

Currently the following hardfork rules are supported:

  • chainstart (a.k.a. Frontier)
  • homestead
  • tangerineWhistle
  • spuriousDragon
  • byzantium
  • constantinople
  • petersburg
  • istanbul
  • muirGlacier (only mainnet and ropsten)
  • berlin (v5.2.0+)
  • london (v5.4.0+)
  • arrowGlacier (only mainnet) (v5.6.0+)
  • merge (only goerli, ropsten and soon mainnet)

Default: merge (taken from Common.DEFAULT_HARDFORK)

A specific hardfork EVM ruleset can be activated by passing in the hardfork along the Common instance to the outer @ethereumjs/vm instance.

EIP Support

It is possible to individually activate EIP support in the EVM by instantiate the Common instance passed to the outer VM with the respective EIPs, e.g.:

import { Chain, Common } from '@ethereumjs/common'
import { VM } from '@ethereumjs/vm'

const common = new Common({ chain: Chain.Mainnet, eips: [2537] })
const vm = new VM({ common })

Currently supported EIPs:

  • EIP-1153 - Transient Storage Opcodes (experimental)
  • EIP-1559 - Fee Market (london EIP)
  • EIP-2315 - Simple subroutines (experimental)
  • EIP-2537 - BLS precompiles (experimental)
  • EIP-2565 - ModExp gas cost (berlin EIP)
  • EIP-2718 - Typed transactions (berlin EIP)
  • EIP-2929 - Gas cost increases for state access opcodes (berlin EIP)
  • EIP-2930 - Optional Access Lists Typed Transactions (berlin EIP)
  • EIP-3198 - BASEFEE opcode (london EIP)
  • EIP-3529 - Reduction in refunds (london EIP)
  • EIP-3540 - EVM Object Format (EOF) v1 (experimental)
  • EIP-3541 - Reject new contracts starting with the 0xEF byte (london EIP)
  • EIP-3670 - EOF - Code Validation (experimental)
  • EIP-3855 - PUSH0 instruction
  • EIP-3860 - Limit and meter initcode
  • EIP-4399 - Supplant DIFFICULTY opcode with PREVRANDAO (Merge)
  • EIP-4844 - Shard Blob Transactions (experimental)
  • EIP-4895 - Beacon chain push withdrawals as operations
  • EIP-5133 - Delaying Difficulty Bomb to mid-September 2022

EIP-4844 Shard Blob Transactions Support (experimental)

This library supports an experimental version of the blob transaction type introduced with EIP-4844 as being specified in the 01d3209 EIP version from February 8, 2023 and deployed along eip4844-devnet-4 (January 2023) starting with v1.3.0.

Initialization

To run EVM related EIP-4844 functionality you have to active the EIP in the associated @ethereumjs/common library:

import { Common, Chain, Hardfork } from '@ethereumjs/common'

const common = new Common({ chain: Chain.Mainnet, hardfork: Hardfork.Shanghai, eips: [4844] })

EIP-4844 comes with a new opcode DATAHASH and adds a new point evaluation precompile at address 0x14.

Note: Usage of the point evaluation precompile needs a manual KZG library installation and global initialization, see KZG Setup for instructions.

Tracing Events

Our TypeScript EVM is implemented as an AsyncEventEmitter and events are submitted along major execution steps which you can listen to.

You can subscribe to the following events:

  • beforeMessage: Emits a Message right after running it.
  • afterMessage: Emits an EVMResult right after running a message.
  • step: Emits an InterpreterStep right before running an EVM step.
  • newContract: Emits a NewContractEvent right before creating a contract. This event contains the deployment code, not the deployed code, as the creation message may not return such a code.

An example for the step event can be found in the initial usage example in this README.

Asynchronous event handlers

You can perform asynchronous operations from within an event handler and prevent the EVM to keep running until they finish.

In order to do that, your event handler has to accept two arguments. The first one will be the event object, and the second one a function. The EVM won't continue until you call this function.

If an exception is passed to that function, or thrown from within the handler or a function called by it, the exception will bubble into the EVM and interrupt it, possibly corrupting its state. It's strongly recommended not to do that.

Synchronous event handlers

If you want to perform synchronous operations, you don't need to receive a function as the handler's second argument, nor call it.

Note that if your event handler receives multiple arguments, the second one will be the continuation function, and it must be called.

If an exception is thrown from within the handler or a function called by it, the exception will bubble into the EVM and interrupt it, possibly corrupting its state. It's strongly recommended not to throw from within event handlers.

Understanding the EVM

If you want to understand your EVM runs we have added a hierarchically structured list of debug loggers for your convenience which can be activated in arbitrary combinations. We also use these loggers internally for development and testing. These loggers use the debug library and can be activated on the CL with DEBUG=ethjs,[Logger Selection] node [Your Script to Run].js and produce output like the following:

EthereumJS EVM Debug Logger

The following loggers are currently available:

Logger Description
evm  EVM control flow, CALL or CREATE message execution
evm:gas  EVM gas logger
evm:eei:gas  EEI gas logger
evm:ops  Opcode traces
evm:ops:[Lower-case opcode name] Traces on a specific opcode

Here are some examples for useful logger combinations.

Run one specific logger:

DEBUG=ethjs,evm ts-node test.ts

Run all loggers currently available:

DEBUG=ethjs,evm:*,evm:*:* ts-node test.ts

Run only the gas loggers:

DEBUG=ethjs,evm:*:gas ts-node test.ts

Excluding the ops logger:

DEBUG=ethjs,evm:*,evm:*:*,-evm:ops ts-node test.ts

Run some specific loggers including a logger specifically logging the SSTORE executions from the EVM (this is from the screenshot above):

DEBUG=ethjs,evm,evm:ops:sstore,evm:*:gas ts-node test.ts

Internal Structure

The EVM processes state changes at many levels.

  • runCall
    • checkpoint state
    • transfer value
    • load code
    • runCode
    • materialize created contracts
    • revert or commit checkpoint
  • runCode
    • iterate over code
    • run op codes
    • track gas usage
  • OpFns
    • run individual op code
    • modify stack
    • modify memory
    • calculate fee

The opFns for CREATE, CALL, and CALLCODE call back up to runCall.

TODO: this section likely needs an update.

Development

See @ethereumjs/vm README.

EthereumJS

See our organizational documentation for an introduction to EthereumJS as well as information on current standards and best practices. If you want to join for work or carry out improvements on the libraries, please review our contribution guidelines first.

License

MPL-2.0