ethereum.homestead.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
56 | STACK_DEPTH_LIMIT = Uint(1024) |
---|
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. `error`: The error from the execution if any.
59 | @dataclass |
---|
class MessageCallOutput:
gas_left
73 | gas_left: Uint |
---|
refund_counter
74 | refund_counter: U256 |
---|
logs
75 | logs: Tuple[Log, ...] |
---|
accounts_to_delete
76 | accounts_to_delete: Set[Address] |
---|
error
77 | error: Optional[Exception] |
---|
process_message_call
If message.current
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.
env : External items required for EVM execution.
Returns
output : MessageCallOutput
Output of the message call
def process_message_call(message: Message, env: Environment) -> MessageCallOutput:
83 | """ |
---|---|
84 | If `message.current` is empty then it creates a smart contract |
85 | else it executes a call from the `message.caller` to the `message.target`. |
86 |
|
87 | Parameters |
88 | ---------- |
89 | message : |
90 | Transaction specific items. |
91 |
|
92 | env : |
93 | External items required for EVM execution. |
94 |
|
95 | Returns |
96 | ------- |
97 | output : `MessageCallOutput` |
98 | Output of the message call |
99 | """ |
100 | if message.target == Bytes0(b""): |
101 | is_collision = account_has_code_or_nonce( |
102 | env.state, message.current_target |
103 | ) |
104 | if is_collision: |
105 | return MessageCallOutput( |
106 | Uint(0), U256(0), tuple(), set(), AddressCollision() |
107 | ) |
108 | else: |
109 | evm = process_create_message(message, env) |
110 | else: |
111 | evm = process_message(message, env) |
112 | |
113 | if evm.error: |
114 | logs: Tuple[Log, ...] = () |
115 | accounts_to_delete = set() |
116 | refund_counter = U256(0) |
117 | else: |
118 | logs = evm.logs |
119 | accounts_to_delete = evm.accounts_to_delete |
120 | refund_counter = U256(evm.refund_counter) |
121 | |
122 | tx_end = TransactionEnd( |
123 | int(message.gas) - int(evm.gas_left), evm.output, evm.error |
124 | ) |
125 | evm_trace(evm, tx_end) |
126 | |
127 | return MessageCallOutput( |
128 | gas_left=evm.gas_left, |
129 | refund_counter=refund_counter, |
130 | logs=logs, |
131 | accounts_to_delete=accounts_to_delete, |
132 | error=evm.error, |
133 | ) |
process_create_message
Executes a call to create a smart contract.
Parameters
message : Transaction specific items. env : External items required for EVM execution.
Returns
evm: :py:class:~ethereum.homestead.vm.Evm
Items containing execution specific objects.
def process_create_message(message: Message, env: Environment) -> Evm:
137 | """ |
---|---|
138 | Executes a call to create a smart contract. |
139 |
|
140 | Parameters |
141 | ---------- |
142 | message : |
143 | Transaction specific items. |
144 | env : |
145 | External items required for EVM execution. |
146 |
|
147 | Returns |
148 | ------- |
149 | evm: :py:class:`~ethereum.homestead.vm.Evm` |
150 | Items containing execution specific objects. |
151 | """ |
152 | # take snapshot of state before processing the message |
153 | begin_transaction(env.state) |
154 | |
155 | # If the address where the account is being created has storage, it is |
156 | # destroyed. This can only happen in the following highly unlikely |
157 | # circumstances: |
158 | # * The address created by two `CREATE` calls collide. |
159 | # * The first `CREATE` left empty code. |
160 | destroy_storage(env.state, message.current_target) |
161 | |
162 | evm = process_message(message, env) |
163 | if not evm.error: |
164 | contract_code = evm.output |
165 | contract_code_gas = Uint(len(contract_code)) * GAS_CODE_DEPOSIT |
166 | try: |
167 | charge_gas(evm, contract_code_gas) |
168 | except ExceptionalHalt as error: |
169 | rollback_transaction(env.state) |
170 | evm.gas_left = Uint(0) |
171 | evm.error = error |
172 | else: |
173 | set_code(env.state, message.current_target, contract_code) |
174 | commit_transaction(env.state) |
175 | else: |
176 | rollback_transaction(env.state) |
177 | return evm |
process_message
Executes a call to create a smart contract.
Parameters
message : Transaction specific items. env : External items required for EVM execution.
Returns
evm: :py:class:~ethereum.homestead.vm.Evm
Items containing execution specific objects
def process_message(message: Message, env: Environment) -> Evm:
181 | """ |
---|---|
182 | Executes a call to create a smart contract. |
183 |
|
184 | Parameters |
185 | ---------- |
186 | message : |
187 | Transaction specific items. |
188 | env : |
189 | External items required for EVM execution. |
190 |
|
191 | Returns |
192 | ------- |
193 | evm: :py:class:`~ethereum.homestead.vm.Evm` |
194 | Items containing execution specific objects |
195 | """ |
196 | if message.depth > STACK_DEPTH_LIMIT: |
197 | raise StackDepthLimitError("Stack depth limit reached") |
198 | |
199 | # take snapshot of state before processing the message |
200 | begin_transaction(env.state) |
201 | |
202 | touch_account(env.state, message.current_target) |
203 | |
204 | if message.should_transfer_value and message.value != 0: |
205 | move_ether( |
206 | env.state, message.caller, message.current_target, message.value |
207 | ) |
208 | |
209 | evm = execute_code(message, env) |
210 | if evm.error: |
211 | # revert state to the last saved checkpoint |
212 | # since the message call resulted in an error |
213 | rollback_transaction(env.state) |
214 | else: |
215 | commit_transaction(env.state) |
216 | return evm |
execute_code
Executes bytecode present in the message
.
Parameters
message : Transaction specific items. env : External items required for EVM execution.
Returns
evm: ethereum.vm.EVM
Items containing execution specific objects
def execute_code(message: Message, env: Environment) -> Evm:
220 | """ |
---|---|
221 | Executes bytecode present in the `message`. |
222 |
|
223 | Parameters |
224 | ---------- |
225 | message : |
226 | Transaction specific items. |
227 | env : |
228 | External items required for EVM execution. |
229 |
|
230 | Returns |
231 | ------- |
232 | evm: `ethereum.vm.EVM` |
233 | Items containing execution specific objects |
234 | """ |
235 | code = message.code |
236 | valid_jump_destinations = get_valid_jump_destinations(code) |
237 | |
238 | evm = Evm( |
239 | pc=Uint(0), |
240 | stack=[], |
241 | memory=bytearray(), |
242 | code=code, |
243 | gas_left=message.gas, |
244 | env=env, |
245 | valid_jump_destinations=valid_jump_destinations, |
246 | logs=(), |
247 | refund_counter=0, |
248 | running=True, |
249 | message=message, |
250 | output=b"", |
251 | accounts_to_delete=set(), |
252 | error=None, |
253 | ) |
254 | try: |
255 | if evm.message.code_address in PRE_COMPILED_CONTRACTS: |
256 | evm_trace(evm, PrecompileStart(evm.message.code_address)) |
257 | PRE_COMPILED_CONTRACTS[evm.message.code_address](evm) |
258 | evm_trace(evm, PrecompileEnd()) |
259 | return evm |
260 |
|
261 | while evm.running and evm.pc < ulen(evm.code): |
262 | try: |
263 | op = Ops(evm.code[evm.pc]) |
264 | except ValueError: |
265 | raise InvalidOpcode(evm.code[evm.pc]) |
266 |
|
267 | evm_trace(evm, OpStart(op)) |
268 | op_implementation[op](evm) |
269 | evm_trace(evm, OpEnd()) |
270 |
|
271 | evm_trace(evm, EvmStop(Ops.STOP)) |
272 |
|
273 | except ExceptionalHalt as error: |
274 | evm_trace(evm, OpException(error)) |
275 | evm.gas_left = Uint(0) |
276 | evm.error = error |
277 | return evm |