ethereum.forks.byzantium.vm.interpreterethereum.forks.constantinople.vm.interpreter

Ethereum Virtual Machine (EVM) Interpreter.

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

Introduction

A straightforward interpreter that executes EVM code.

STACK_DEPTH_LIMIT

62
STACK_DEPTH_LIMIT = Uint(1024)

MAX_CODE_SIZE

63
MAX_CODE_SIZE = 0x6000

MessageCallOutput

Output of a particular message call.

Contains the following:

  1. `gas_left`: remaining gas after execution.
  2. `refund_counter`: gas to refund after execution.
  3. `logs`: list of `Log` generated during execution.
  4. `accounts_to_delete`: Contracts which have self-destructed.
  5. `touched_accounts`: Accounts that have been touched.
  6. `error`: The error from the execution if any.
66
@dataclass
class MessageCallOutput:

gas_left

81
    gas_left: Uint

refund_counter

82
    refund_counter: U256

logs

83
    logs: Tuple[Log, ...]

accounts_to_delete

84
    accounts_to_delete: Set[Address]

touched_accounts

85
    touched_accounts: Set[Address]

error

86
    error: Optional[EthereumException]

process_message_call

If message.target is empty then it creates a smart contract else it executes a call from the message.caller to the message.target.

Parameters

message : Transaction specific items.

Returns

output : MessageCallOutput Output of the message call

def process_message_call(message: Message) -> MessageCallOutput:
90
    """
91
    If `message.target` is empty then it creates a smart contract
92
    else it executes a call from the `message.caller` to the `message.target`.
93
94
    Parameters
95
    ----------
96
    message :
97
        Transaction specific items.
98
99
    Returns
100
    -------
101
    output : `MessageCallOutput`
102
        Output of the message call
103
104
    """
105
    block_env = message.block_env
106
    refund_counter = U256(0)
107
    if message.target == Bytes0(b""):
108
        is_collision = account_has_code_or_nonce(
109
            block_env.state, message.current_target
110
        ) or account_has_storage(block_env.state, message.current_target)
111
        if is_collision:
112
            return MessageCallOutput(
113
                Uint(0), U256(0), tuple(), set(), set(), AddressCollision()
114
            )
115
        else:
116
            evm = process_create_message(message)
117
    else:
118
        evm = process_message(message)
119
        if account_exists_and_is_empty(
120
            block_env.state, Address(message.target)
121
        ):
122
            evm.touched_accounts.add(Address(message.target))
123
124
    if evm.error:
125
        logs: Tuple[Log, ...] = ()
126
        accounts_to_delete = set()
127
        touched_accounts = set()
128
    else:
129
        logs = evm.logs
130
        accounts_to_delete = evm.accounts_to_delete
131
        touched_accounts = evm.touched_accounts
132
        refund_counter += U256(evm.refund_counter)
133
134
    tx_end = TransactionEnd(
135
        int(message.gas) - int(evm.gas_left), evm.output, evm.error
136
    )
137
    evm_trace(evm, tx_end)
138
139
    return MessageCallOutput(
140
        gas_left=evm.gas_left,
141
        refund_counter=refund_counter,
142
        logs=logs,
143
        accounts_to_delete=accounts_to_delete,
144
        touched_accounts=touched_accounts,
145
        error=evm.error,
146
    )

process_create_message

Executes a call to create a smart contract.

Parameters

message : Transaction specific items.

Returns

evm: :py:class:~ethereum.forks.byzantium.vm.Evm~ethereum.forks.constantinople.vm.Evm Items containing execution specific objects.

def process_create_message(message: Message) -> Evm:
150
    """
151
    Executes a call to create a smart contract.
152
153
    Parameters
154
    ----------
155
    message :
156
        Transaction specific items.
157
158
    Returns
159
    -------
160
    evm: :py:class:`~ethereum.forks.byzantium.vm.Evm`
160
    evm: :py:class:`~ethereum.forks.constantinople.vm.Evm`
161
        Items containing execution specific objects.
162
163
    """
164
    state = message.block_env.state
165
    # take snapshot of state before processing the message
166
    begin_transaction(state)
167
168
    # If the address where the account is being created has storage, it is
169
    # destroyed. This can only happen in the following highly unlikely
170
    # circumstances:
171
    # * The address created by two `CREATE` calls collide.
171
    # * The address created by a `CREATE` call collides with a subsequent
172
    #   `CREATE` or `CREATE2` call.
173
    # * The first `CREATE` happened before Spurious Dragon and left empty
174
    #   code.
175
    destroy_storage(state, message.current_target)
176
177
    increment_nonce(state, message.current_target)
178
    evm = process_message(message)
179
    if not evm.error:
180
        contract_code = evm.output
181
        contract_code_gas = (
182
            Uint(len(contract_code)) * GAS_CODE_DEPOSIT_PER_BYTE
183
        )
184
        try:
185
            charge_gas(evm, contract_code_gas)
186
            if len(contract_code) > MAX_CODE_SIZE:
187
                raise OutOfGasError
188
        except ExceptionalHalt as error:
189
            rollback_transaction(state)
190
            evm.gas_left = Uint(0)
191
            evm.output = b""
192
            evm.error = error
193
        else:
194
            set_code(state, message.current_target, contract_code)
195
            commit_transaction(state)
196
    else:
197
        rollback_transaction(state)
198
    return evm

process_message

Move ether and execute the relevant code.

Parameters

message : Transaction specific items.

Returns

evm: :py:class:~ethereum.forks.byzantium.vm.Evm~ethereum.forks.constantinople.vm.Evm Items containing execution specific objects

def process_message(message: Message) -> Evm:
202
    """
203
    Move ether and execute the relevant code.
204
205
    Parameters
206
    ----------
207
    message :
208
        Transaction specific items.
209
210
    Returns
211
    -------
211
    evm: :py:class:`~ethereum.forks.byzantium.vm.Evm`
212
    evm: :py:class:`~ethereum.forks.constantinople.vm.Evm`
213
        Items containing execution specific objects
214
215
    """
216
    state = message.block_env.state
217
    if message.depth > STACK_DEPTH_LIMIT:
218
        raise StackDepthLimitError("Stack depth limit reached")
219
220
    code = message.code
221
    valid_jump_destinations = get_valid_jump_destinations(code)
222
    evm = Evm(
223
        pc=Uint(0),
224
        stack=[],
225
        memory=bytearray(),
226
        code=code,
227
        gas_left=message.gas,
228
        valid_jump_destinations=valid_jump_destinations,
229
        logs=(),
230
        refund_counter=0,
231
        running=True,
232
        message=message,
233
        output=b"",
234
        accounts_to_delete=set(),
235
        touched_accounts=set(),
236
        return_data=b"",
237
        error=None,
238
    )
239
240
    # take snapshot of state before processing the message
241
    begin_transaction(state)
242
243
    touch_account(state, message.current_target)
244
245
    if message.should_transfer_value and message.value != 0:
246
        move_ether(
247
            state, message.caller, message.current_target, message.value
248
        )
249
250
    try:
251
        if evm.message.code_address in PRE_COMPILED_CONTRACTS:
252
            evm_trace(evm, PrecompileStart(evm.message.code_address))
253
            PRE_COMPILED_CONTRACTS[evm.message.code_address](evm)
254
            evm_trace(evm, PrecompileEnd())
255
        else:
256
            while evm.running and evm.pc < ulen(evm.code):
257
                try:
258
                    op = Ops(evm.code[evm.pc])
259
                except ValueError as e:
260
                    raise InvalidOpcode(evm.code[evm.pc]) from e
261
262
                evm_trace(evm, OpStart(op))
263
                op_implementation[op](evm)
264
                evm_trace(evm, OpEnd())
265
266
            evm_trace(evm, EvmStop(Ops.STOP))
267
268
    except ExceptionalHalt as error:
269
        evm_trace(evm, OpException(error))
270
        evm.gas_left = Uint(0)
271
        evm.output = b""
272
        evm.error = error
273
    except Revert as error:
274
        evm_trace(evm, OpException(error))
275
        evm.error = error
276
277
    if evm.error:
278
        # revert state to the last saved checkpoint
279
        # since the message call resulted in an error
280
        rollback_transaction(state)
281
    else:
282
        commit_transaction(state)
283
    return evm