@ethereumjs/vm

Execution Context for the Ethereum EVM Implementation.

This package provides an Ethereum mainnet compatible execution context for the @ethereumjs/evm EVM implementation.

So beyond bytecode processing this package allows to run or build new Ethereum blocks or single transactions and update a blockchain state accordingly.

Note that up till v5 this package also was the bundled package for the EVM implementation itself.

Installation

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

npm install @ethereumjs/vm

Note: Starting with the Dencun hardfork EIP-4844 related functionality will become an integrated part of the EVM functionality with the activation of the point evaluation precompile. It is therefore strongly recommended to always run the EVM with a KZG library installed and initialized, see KZG Setup for instructions.

Usage

Running a Transaction

// ./examples/runTx.ts

import { Address } from '@ethereumjs/util'
import { Chain, Common, Hardfork } from '@ethereumjs/common'
import { LegacyTransaction } from '@ethereumjs/tx'
import { VM } from '@ethereumjs/vm'

const main = async () => {
  const common = new Common({ chain: Chain.Mainnet, hardfork: Hardfork.Shanghai })
  const vm = await VM.create({ common })

  const tx = LegacyTransaction.fromTxData({
    gasLimit: BigInt(21000),
    gasPrice: BigInt(1000000000),
    value: BigInt(1),
    to: Address.zero(),
    v: BigInt(37),
    r: BigInt('62886504200765677832366398998081608852310526822767264927793100349258111544447'),
    s: BigInt('21948396863567062449199529794141973192314514851405455194940751428901681436138'),
  })
  const res = await vm.runTx({ tx, skipBalance: true })
  console.log(res.totalGasSpent) // 21000n - gas cost for simple ETH transfer
}

main()

Additionally to the VM.runTx() method there is an API method VM.runBlock() which allows to run the whole block and execute all included transactions along.

Note: with the switch from v7 to v8 the old direct new VM() constructor usage has been fully deprecated and a VM can now solely be instantiated with the async static VM.create() constructor. This also goes for the underlying EVM if you use a custom EVM.

Building a Block

The VM package can also be used to construct a new valid block by executing and then integrating txs one-by-one.

The following non-complete example gives some illustration on how to use the Block Builder API:

// ./examples/buildBlock.ts

import { Block } from '@ethereumjs/block'
import { Chain, Common, Hardfork } from '@ethereumjs/common'
import { LegacyTransaction } from '@ethereumjs/tx'
import { Account, Address, bytesToHex, hexToBytes, randomBytes } from '@ethereumjs/util'
import { VM } from '@ethereumjs/vm'

const main = async () => {
  const common = new Common({ chain: Chain.Mainnet })
  const vm = await VM.create({ common })

  const parentBlock = Block.fromBlockData(
    { header: { number: 1n } },
    { skipConsensusFormatValidation: true }
  )
  const headerData = {
    number: 2n,
  }
  const blockBuilder = await vm.buildBlock({
    parentBlock, // the parent @ethereumjs/block Block
    headerData, // header values for the new block
    blockOpts: {
      calcDifficultyFromHeader: parentBlock.header,
      freeze: false,
      skipConsensusFormatValidation: true,
      putBlockIntoBlockchain: false,
    },
  })

  const pk = hexToBytes('0x26f81cbcffd3d23eace0bb4eac5274bb2f576d310ee85318b5428bf9a71fc89a')
  const address = Address.fromPrivateKey(pk)
  const account = new Account(0n, 0xfffffffffn)
  await vm.stateManager.putAccount(address, account) // create a sending account and give it a big balance
  const tx = LegacyTransaction.fromTxData({ gasLimit: 0xffffff, gasPrice: 75n }).sign(pk)
  await blockBuilder.addTransaction(tx)

  // Add more transactions

  const block = await blockBuilder.build()
  console.log(`Built a block with hash ${bytesToHex(block.hash())}`)
}

main()

WASM Crypto Support

This library by default uses JavaScript implementations for the basic standard crypto primitives like hashing or signature verification (for included txs). See @ethereumjs/common README for instructions on how to replace with e.g. a more performant WASM implementation by using a shared common instance.

Example

This projects contain the following examples:

./examples/run-blockchain: Loads tests data, including accounts and blocks, and runs all of them in the VM.
./examples/run-solidity-contract: Compiles a Solidity contract, and calls constant and non-constant functions.

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

Browser

With the breaking release round in Summer 2023 we have added hybrid ESM/CJS builds for all our libraries (see section below) and have eliminated many of the caveats which had previously prevented a frictionless browser usage.

It is now easily possible to run a browser build of one of the EthereumJS libraries within a modern browser using the provided ESM build. For a setup example see ./examples/browser.html.

API

Docs

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

Hybrid CJS/ESM Builds

With the breaking releases from Summer 2023 we have started to ship our libraries with both CommonJS (cjs folder) and ESM builds (esm folder), see package.json for the detailed setup.

If you use an ES6-style import in your code files from the ESM build will be used:

import { EthereumJSClass } from '@ethereumjs/[PACKAGE_NAME]'

If you use Node.js specific require, the CJS build will be used:

const { EthereumJSClass } = require('@ethereumjs/[PACKAGE_NAME]')

Using ESM will give you additional advantages over CJS beyond browser usage like static code analysis / Tree Shaking which CJS can not provide.

Buffer -> Uint8Array

With the breaking releases from Summer 2023 we have removed all Node.js specific Buffer usages from our libraries and replace these with Uint8Array representations, which are available both in Node.js and the browser (Buffer is a subclass of Uint8Array).

We have converted existing Buffer conversion methods to Uint8Array conversion methods in the @ethereumjs/util bytes module, see the respective README section for guidance.

BigInt Support

Starting with v6 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

Starting with the VM v6 version the inner Ethereum Virtual Machine core previously included in this library has been extracted to an own package @ethereumjs/evm.

It is still possible to access all EVM functionality through the evm property of the initialized vm object, e.g.:

vm.evm.runCode()
vm.evm.events.on('step', function (data) {
  console.log(`Opcode: ${data.opcode.name}\tStack: ${data.stack}`)
})

Note that it's now also possible to pass in an own or customized EVM instance by using the optional evm constructor option.

State and Blockchain Information

With VM v7 a previously needed EEI interface for EVM/VM communication is not needed any more and the API has been simplified, also see the respective EVM README section. Most of the EEI related logic is now either handled internally or more generic functionality being taken over by the @ethereumjs/statemanager package, with the EVM now taking in both an (optional) stateManager and blockchain argument for the constructor (which the VM passes over by default).

With VM v6 the previously included StateManager has been extracted to its own package @ethereumjs/statemanager. The StateManager package provides a unified state interface and it is now also possible to provide a modified or custom StateManager to the VM via the optional stateManager constructor option.

Setup

Chain Support

Starting with v5.1.0 the VM supports running both Ethash/PoW and Clique/PoA blocks and transactions. Clique support has been added along the work on PR #1032 and follow-up PRs and (block) validation checks and the switch of the execution context now happens correctly.

Ethash/PoW Chains

@ethereumjs/blockchain validates the PoW algorithm with @ethereumjs/ethash and validates blocks' difficulty to match their canonical difficulty.

Clique/PoA Chains

The following is a simple example for a block run on Goerli:

// ./examples/runGoerliBlock.ts

import { Block } from '@ethereumjs/block'
import { Chain, Common } from '@ethereumjs/common'
import { bytesToHex, hexToBytes } from '@ethereumjs/util'
import { VM } from '../src/vm.js'
import goerliBlock2 from './testData/goerliBlock2.json'

const main = async () => {
  const common = new Common({ chain: Chain.Goerli, hardfork: 'london' })
  const vm = await VM.create({ common, setHardfork: true })

  const block = Block.fromRPC(goerliBlock2, undefined, { common })
  const result = await vm.runBlock({ block, generate: true, skipHeaderValidation: true }) // we skip header validaiton since we are running a block without the full Ethereum history available
  console.log(`The state root for Goerli block 2 is ${bytesToHex(result.stateRoot)}`)
}

main()

Hardfork Support

For hardfork support see the Hardfork Support section from the underlying @ethereumjs/evm instance.

An explicit HF in the VM - which is then passed on to the inner EVM - can be set with:

// ./examples/runTx.ts#L1-L8

import { Address } from '@ethereumjs/util'
import { Chain, Common, Hardfork } from '@ethereumjs/common'
import { LegacyTransaction } from '@ethereumjs/tx'
import { VM } from '@ethereumjs/vm'

const main = async () => {
  const common = new Common({ chain: Chain.Mainnet, hardfork: Hardfork.Shanghai })
  const vm = await VM.create({ common })

Custom genesis state support

Genesis in v7 (removed genesis dependency)

Genesis state was huge and had previously been bundled with the Blockchain package with the burden going over to the VM, since Blockchain is a dependency.

Starting with the v7 release genesis state has been removed from blockchain and moved into its own auxiliary package @ethereumjs/genesis, from which it can be included if needed (for most - especially VM - use cases it is not necessary), see PR #2844.

For initializing a custom genesis state you can use the genesisState constructor option in the Blockchain and VM library in a similar way this had been done in the Common library before.

// ./examples/vmWithGenesisState.ts

import { Blockchain } from '@ethereumjs/blockchain'
import { Chain } from '@ethereumjs/common'
import { getGenesis } from '@ethereumjs/genesis'
import { Address } from '@ethereumjs/util'
import { VM } from '@ethereumjs/vm'

const main = async () => {
  const genesisState = getGenesis(Chain.Mainnet)

  const blockchain = await Blockchain.create({ genesisState })
  const vm = await VM.create({ blockchain, genesisState })
  const account = await vm.stateManager.getAccount(
    Address.fromString('0x000d836201318ec6899a67540690382780743280')
  )
  console.log(
    `This balance for account 0x000d836201318ec6899a67540690382780743280 in this chain's genesis state is ${Number(
      account?.balance
    )}`
  )
}
main()

Genesis state can be configured to contain both EOAs as well as (system) contracts with initial storage values set.

Genesis in v6

For the v6 release responsibility for setting up a custom genesis state moved from the Common library to the Blockchain package, see PR #1924 for some work context.

A genesis state can be set along Blockchain creation by passing in a custom genesisBlock and genesisState. For mainnet and the official test networks like sepolia or goerli genesis is already provided with the block data coming from @ethereumjs/common. The genesis state is being integrated in the Blockchain library (see genesisStates folder).

EIP Support

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

// ./examples/vmWithEIPs.ts

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

const main = async () => {
  const common = new Common({ chain: Chain.Mainnet, eips: [3074] })
  const vm = await VM.create({ common })
  console.log(`EIP 3074 is active in the VM - ${vm.common.isActivatedEIP(3074)}`)
}
main()

For a list with supported EIPs see the @ethereumjs/evm documentation.

EIP-4844 Shard Blob Transactions Support

This library supports the blob transaction type introduced with EIP-4844.

Initialization

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

// ./examples/vmWith4844.ts

import { Common, Chain, Hardfork } from '@ethereumjs/common'
import { VM } from '../src/vm.js'

const main = async () => {
  const common = new Common({ chain: Chain.Mainnet, hardfork: Hardfork.Shanghai, eips: [4844] })
  const vm = await VM.create({ common })
  console.log(`4844 is active in the VM - ${vm.common.isActivatedEIP(4844)}`)
}

main()

EIP-4844 comes with a new opcode BLOBHASH and adds a new point evaluation precompile at address 0x14 in the underlying @ethereumjs/evm package.

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 VM 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:

beforeBlock: Emits a Block right before running it.
afterBlock: Emits AfterBlockEvent right after running a block.
beforeTx: Emits a Transaction right before running it.
afterTx: Emits a AfterTxEvent right after running a transaction.

Please note that there are additional EVM-specific events in the @ethereumjs/evm package.

Asynchronous event handlers

You can perform asynchronous operations from within an event handler and prevent the VM 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 VM 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 VM 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 VM and interrupt it, possibly corrupting its state. It's strongly recommended not to throw from within event handlers.

Understanding the VM

If you want to understand your VM 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 VM Debug Logger

The following loggers are currently available:

Logger	Description
`vm:block`	Block operations (run txs, generating receipts, block rewards,...)
`vm:tx`	Transaction operations (account updates, checkpointing,...)
`vm:tx:gas`	Transaction gas logger
`vm:state`	StateManager logger

Note that there are additional EVM-specific loggers in the @ethereumjs/evm package.

Here are some examples for useful logger combinations.

Run one specific logger:

DEBUG=ethjs,vm:tx tsx test.ts

Run all loggers currently available:

DEBUG=ethjs,vm:*,vm:*:* tsx test.ts

Run only the gas loggers:

DEBUG=ethjs,vm:*:gas tsx test.ts

Excluding the state logger:

DEBUG=ethjs,vm:*,vm:*:*,-vm:state tsx test.ts

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

DEBUG=ethjs,vm:tx,vm:evm,vm:ops:sstore,vm:*:gas tsx test.ts

Internal Structure

The VM processes state changes at many levels.

runBlockchain
- for every block, runBlock
runBlock
- for every tx, runTx
- pay miner and uncles
runTx
- check sender balance
- check sender nonce
- runCall
- transfer gas charges

TODO: this section likely needs an update.

Development

Developer documentation - currently mainly with information on testing and debugging - can be found here.

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.