Ethereum Virtual Machine (EVM) Runtime Operations

Table of Contents

Introduction
Module Contents
- Functions
Module Details
- get_valid_jump_destinations

Introduction

Runtime related operations used while executing EVM code.

Module Contents

Functions

get_valid_jump_destinations

Analyze the evm code to obtain the set of valid jump destinations.

Module Details

get_valid_jump_destinations

get_valid_jump_destinations(code: bytes) → Set[ethereum.base_types.Uint]

Analyze the evm code to obtain the set of valid jump destinations.

Valid jump destinations are defined as follows:

The jump destination is less than the length of the code.
The jump destination should have the JUMPDEST opcode (0x5B).
The jump destination shouldn’t be part of the data corresponding to PUSH-N opcodes.

Note - Jump destinations are 0-indexed.

Parameters: code – The EVM code which is to be executed.
Returns: valid_jump_destinations – The set of valid jump destinations in the code.
Return type: Set[Uint]

def get_valid_jump_destinations(code: bytes) -> Set[Uint]:
    valid_jump_destinations = set()
    pc = Uint(0)

    while pc < len(code):
        try:
            current_opcode = Ops(code[pc])
        except ValueError:
            # Skip invalid opcodes, as they don't affect the jumpdest
            # analysis. Nevertheless, such invalid opcodes would be caught
            # and raised when the interpreter runs.
            pc += 1
            continue

        if current_opcode == Ops.JUMPDEST:
            valid_jump_destinations.add(pc)
        elif Ops.PUSH1.value <= current_opcode.value <= Ops.PUSH32.value:
            # If PUSH-N opcodes are encountered, skip the current opcode along
            # with the trailing data segment corresponding to the PUSH-N
            # opcodes.
            push_data_size = current_opcode.value - Ops.PUSH1.value + 1
            pc += push_data_size

        pc += 1

    return valid_jump_destinations