ethereum.forks.istanbul.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

61
STACK_DEPTH_LIMIT = Uint(1024)

MAX_CODE_SIZE

62
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.
65
@final
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
    <snip>
105
    tx_state = message.tx_env.state
106
    refund_counter = U256(0)
107
    if message.target == Bytes0(b""):
108
        if account_deployable(tx_state, message.current_target):
109
            evm = process_create_message(message)
110
        else:
111
            return MessageCallOutput(
112
                gas_left=Uint(0),
113
                refund_counter=U256(0),
114
                logs=tuple(),
115
                accounts_to_delete=set(),
116
                touched_accounts=set(),
117
                error=AddressCollision(),
118
            )
119
    else:
120
        evm = process_message(message)
121
        if account_exists_and_is_empty(tx_state, Address(message.target)):
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.istanbul.vm.Evm Items containing execution specific objects.

def process_create_message(message: Message) -> Evm:
150
    <snip>
164
    tx_state = message.tx_env.state
165
    # take snapshot of state before processing the message
166
    snapshot = copy_tx_state(tx_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 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(tx_state, message.current_target)
176
177
    # In the previously mentioned edge case the preexisting storage is ignored
178
    # for gas refund purposes. In order to do this we must track created
179
    # accounts.
180
    mark_account_created(tx_state, message.current_target)
181
182
    increment_nonce(tx_state, message.current_target)
183
    evm = process_message(message)
184
    if not evm.error:
185
        contract_code = evm.output
186
        contract_code_gas = (
187
            ulen(contract_code) * GasCosts.CODE_DEPOSIT_PER_BYTE
188
        )
189
        try:
190
            charge_gas(evm, contract_code_gas)
191
            if len(contract_code) > MAX_CODE_SIZE:
192
                raise OutOfGasError
193
        except ExceptionalHalt as error:
194
            restore_tx_state(tx_state, snapshot)
195
            evm.gas_left = Uint(0)
196
            evm.output = b""
197
            evm.error = error
198
        else:
199
            set_code(tx_state, message.current_target, contract_code)
200
    else:
201
        restore_tx_state(tx_state, snapshot)
202
    return evm

process_message

Move ether and execute the relevant code.

Parameters

message : Transaction specific items.

Returns

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

def process_message(message: Message) -> Evm:
206
    <snip>
220
    tx_state = message.tx_env.state
221
    if message.depth > STACK_DEPTH_LIMIT:
222
        raise StackDepthLimitError("Stack depth limit reached")
223
224
    code = message.code
225
    valid_jump_destinations = get_valid_jump_destinations(code)
226
    evm = Evm(
227
        pc=Uint(0),
228
        stack=[],
229
        memory=bytearray(),
230
        code=code,
231
        gas_left=message.gas,
232
        valid_jump_destinations=valid_jump_destinations,
233
        logs=(),
234
        refund_counter=0,
235
        running=True,
236
        message=message,
237
        output=b"",
238
        accounts_to_delete=set(),
239
        touched_accounts=set(),
240
        return_data=b"",
241
        error=None,
242
    )
243
244
    # take snapshot of state before processing the message
245
    snapshot = copy_tx_state(tx_state)
246
247
    touch_account(tx_state, message.current_target)
248
249
    if message.should_transfer_value and message.value != 0:
250
        move_ether(
251
            tx_state,
252
            message.caller,
253
            message.current_target,
254
            message.value,
255
        )
256
257
    try:
258
        if evm.message.code_address in PRE_COMPILED_CONTRACTS:
259
            evm_trace(evm, PrecompileStart(evm.message.code_address))
260
            PRE_COMPILED_CONTRACTS[evm.message.code_address](evm)
261
            evm_trace(evm, PrecompileEnd())
262
        else:
263
            while evm.running and evm.pc < ulen(evm.code):
264
                try:
265
                    op = Ops(evm.code[evm.pc])
266
                except ValueError as e:
267
                    raise InvalidOpcode(evm.code[evm.pc]) from e
268
269
                evm_trace(evm, OpStart(op))
270
                op_implementation[op](evm)
271
                evm_trace(evm, OpEnd())
272
273
            evm_trace(evm, EvmStop(Ops.STOP))
274
275
    except ExceptionalHalt as error:
276
        evm_trace(evm, OpException(error))
277
        evm.gas_left = Uint(0)
278
        evm.output = b""
279
        evm.error = error
280
    except Revert as error:
281
        evm_trace(evm, OpException(error))
282
        evm.error = error
283
284
    if evm.error:
285
        restore_tx_state(tx_state, snapshot)
286
    return evm