ethereum.homestead.vm.runtime

Ethereum Virtual Machine (EVM) Runtime Operations ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. contents:: Table of Contents :backlinks: none :local:

Introduction

Runtime related operations used while executing EVM code.

get_valid_jump_destinations

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: Set[Uint] The set of valid jump destinations in the code.

def get_valid_jump_destinations(​code: bytes​) -> Set[Uint]:
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    """
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    Analyze the evm code to obtain the set of valid jump destinations.
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    Valid jump destinations are defined as follows:
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        * The jump destination is less than the length of the code.
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        * The jump destination should have the `JUMPDEST` opcode (0x5B).
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        * The jump destination shouldn't be part of the data corresponding to
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          `PUSH-N` opcodes.
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    Note - Jump destinations are 0-indexed.
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    Parameters
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    ----------
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    code :
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        The EVM code which is to be executed.
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    Returns
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    -------
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    valid_jump_destinations: `Set[Uint]`
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        The set of valid jump destinations in the code.
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    """
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    valid_jump_destinations = set()
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    pc = Uint(0)
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    while pc < ulen(code):
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        try:
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            current_opcode = Ops(code[pc])
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        except ValueError:
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            # Skip invalid opcodes, as they don't affect the jumpdest
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            # analysis. Nevertheless, such invalid opcodes would be caught
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            # and raised when the interpreter runs.
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            pc += Uint(1)
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            continue
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        if current_opcode == Ops.JUMPDEST:
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            valid_jump_destinations.add(pc)
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        elif Ops.PUSH1.value <= current_opcode.value <= Ops.PUSH32.value:
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            # If PUSH-N opcodes are encountered, skip the current opcode along
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            # with the trailing data segment corresponding to the PUSH-N
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            # opcodes.
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            push_data_size = current_opcode.value - Ops.PUSH1.value + 1
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            pc += Uint(push_data_size)
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        pc += Uint(1)
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    return valid_jump_destinations