gevm

An Ethereum Virtual Machine (EVM) implementation from scratch, written in Go.

Warning

This implementation is for educational purposes and not for production use.

This project is an isolated EVM implementation, meaning it has no state for accounts. However, memory, storage, and event logs are tracked, although everything resets after each EVM execution.

Prerequisites

The Go programming language should be installed: https://go.dev/dl/
Ethereum Virtual Machine: https://ethereum.org/en/developers/docs/evm/
EVM opcodes: https://www.evm.codes/

Running the EVM

To run the EVM:

Navigate to the command directory:
```
cd cmd/gevm
```
Execute the main program:
```
go run main.go
```
Some simple example bytecodes are provided. There is also an example from an actual compiled contract, which is commented out. Uncomment it to run it.

Dynamic Gas Calculation

Dynamic gas calculation is supported (memory expansion cost and storage operations). Functions for this are located in gevm/common.go, and the dgMap[Opcode]uint64 in gevm/evm.go holds records of each opcode that has dynamic gas. The dynamic gas is calculated at runtime for any opcode that has dynamic gas during execution, and the dgMap is updated to store this gas cost.

EVM Structure

The main EVM files are located in /gevm. Here are some key structures:

ExecutionRuntime represents the execution runtime during EVM execution.

type ExecutionRuntime struct {
    PC         uint64
    Code       []byte
    Gas        uint64
    Refund     uint64
    StopFlag   bool
    RevertFlag bool
    ReturnData []byte
    LogRecord  *LogRecord
    Block      *Block
}

ExecutionEnvironment encapsulates the EVM execution data environment, including the stack, memory, storage, and transient storage.

type ExecutionEnvironment struct {
    Stack     *Stack
    Memory    *Memory
    Storage   *Storage
    Transient *TransientStorage
}

TransactionContext holds transaction-specific information during EVM execution.

type TransactionContext struct {
    Sender   common.Address
    Value    uint64
    Calldata []byte
}

ChainConfig stores network configuration parameters.

type ChainConfig struct {
    ChainID  uint64
    GasLimit uint64
}

Block represents a block.

type Block struct {
    Coinbase  common.Address
    GasPrice  uint64
    Number    uint64
    Timestamp time.Time
    BaseFee   uint64
}

All these are initialized with the NewEVM function found in gevm/evm.go.

Tests

To run unit tests:

go test -v

For a better understanding of the project, explore the files in /gevm.

Supported Opcodes

The implementation supports 131 out of the 143 EVM opcodes.

Unsupported Opcodes

The following opcodes are not supported:

CREATE
CALL
CALLCODE
DELEGATECALL
CREATE2
EXTCODEHASH
DIFFICULTY
STATICCALL
SELFBALANCE
SELFDESTRUCT
EIP-4844 opcodes: BLOBHASH, BLOBBASEFEE

These opcodes typically require state management. All other opcodes are supported, including EIP-1153 transient storage opcodes TLOAD and TSTORE.

Resources

EVM opcodes (highly recommended, has accurate gas costs for opcodes): https://www.evm.codes/
EVM from scratch book: https://evm-from-scratch.xyz/

Contributing

Contributions are welcome! Please feel free to create an issue or submit a pull request.

parsaaba / EVM-from-scratch