Mastering Ethereum

Chapter 13. The Ethereum Virtual Machine

At the heart of the Ethereum protocol and operation is the Ethereum Virtual Machine, or EVM for short. As you might guess from the name, it is a computation engine, not hugely dissimilar to the virtual machines of Microsoft’s .NET Framework, or interpreters of other bytecode-compiled programming languages such as Java. In this chapter we take a detailed look at the EVM, including its instruction set, structure, and operation, within the context of Ethereum state updates.

What Is the EVM?

The EVM is the part of Ethereum that handles smart contract deployment and execution. Simple value transfer transactions from one EOA to another don’t need to involve it, practically speaking, but everything else will involve a state update computed by the EVM. At a high level, the EVM running on the Ethereum blockchain can be thought of as a global decentralized computer containing millions of executable objects, each with its own permanent data store.

The EVM is a quasi–Turing-complete state machine; “quasi” because all execution processes are limited to a finite number of computational steps by the amount of gas available for any given smart contract execution. As such, the halting problem is “solved” (all program executions will halt) and the situation where execution might (accidentally or maliciously) run forever, thus bringing the Ethereum platform to halt in its entirety, is avoided.

The EVM has a stack-based architecture, storing all in-memory ...