@ethereumjs/vm

Execution Context for the Ethereum EVM Implementation.

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

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

INSTALL

npm install @ethereumjs/vm

USAGE

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

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

const tx = Transaction.fromTxData({
  gasLimit: BigInt(21000),
  value: BigInt(1),
  to: Address.zero(),
  v: BigInt(37),
  r: BigInt('62886504200765677832366398998081608852310526822767264927793100349258111544447'),
  s: BigInt('21948396863567062449199529794141973192314514851405455194940751428901681436138'),
})
await vm.runTx({ tx, skipBalance: true })

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.

API

Docs

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

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

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

Execution Environment (EEI) and State

This package provides a concrete implementation of the @ethereumjs/evm EEI interface to instantiate a VM/EVM combination with an Ethereum mainnet compatible execution context.

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:

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

const common = new Common({ chain: Chain.Goerli })
const hardforkByBlockNumber = true
const vm = new VM({ common, hardforkByBlockNumber })

const serialized = Buffer.from('f901f7a06bfee7294bf4457...', 'hex')
const block = Block.fromRLPSerializedBlock(serialized, { hardforkByBlockNumber })
const result = await vm.runBlock(block)

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:

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

const common = new Common({ chain: Chain.Mainnet, hardfork: Hardfork.Berlin })
const vm = new VM({ common })

Custom genesis state support

Genesis state code logic has been reworked substantially along the v6 breaking releases and a lot of the genesis state code moved from both the @ethereumjs/common and @ethereumjs/block libraries to the @ethereumjs/blockchain library, see PR #1916 for an overview on the broad set of changes.

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

If you want to create a new instance of the VM and add your own genesis state, you can do it by passing a Blockchain instance with custom genesis state set with the genesisState constructor option and passing the flag activateGenesisState in VMOpts.

import { Common } from '@ethereumjs/common'
import { VM } from '@ethereumjs/vm'
import myCustomChain1 from '[PATH_TO_MY_CHAINS]/myCustomChain1.json'
import chain1GenesisState from '[PATH_TO_GENESIS_STATES]/chain1GenesisState.json'

const common = new Common({
  // TODO: complete example
})
const blockchain = await Blockchain.create({
  // TODO: complete example
})
const vm = await VM.create({ common, activateGenesisState: true })

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

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.:

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 })

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

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 withing 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 withing 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=[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=vm:tx ts-node test.ts

Run all loggers currently available:

DEBUG=vm:*,vm:*:* ts-node test.ts

Run only the gas loggers:

DEBUG=vm:*:gas ts-node test.ts

Excluding the state logger:

DEBUG=vm:*,vm:*:*,-vm:state ts-node test.ts

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

DEBUG=vm:tx,vm:evm,vm:ops:sstore,vm:*:gas ts-node 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 do improvements on the libraries have a look at our contribution guidelines.