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166 | @pytest.mark.parametrize(
"pattern",
[
# Periodic tiles: the branch predictor learns the period, so these
# measure analysis with the predictor warm.
Op.STOP,
Op.JUMPDEST,
Op.PUSH1[bytes(Op.JUMPDEST)],
Op.PUSH2[bytes(Op.JUMPDEST + Op.JUMPDEST)],
Op.PUSH1[bytes(Op.JUMPDEST)] + Op.JUMPDEST,
Op.PUSH2[bytes(Op.JUMPDEST + Op.JUMPDEST)] + Op.JUMPDEST,
Op.SWAPN[bytes(Op.JUMPDEST)],
Op.DUPN[bytes(Op.JUMPDEST)],
Op.EXCHANGE[bytes(Op.JUMPDEST)],
# Non-repeating random initcode defeats the predictor. The alphabets
# straddle the thresholds analysis loops branch on (0x5b JUMPDEST,
# 0x60 PUSH1); the weighted variant makes PUSH1 half of all bytes, so
# the PUSH1 threshold is a 50/50 branch.
pytest.param(
RandomInitcode((Op.STOP, Op.JUMPDEST, Op.PUSH1)),
id="random_stop_jumpdest_push1",
),
pytest.param(
RandomInitcode((Op.STOP, Op.JUMPDEST)),
id="random_stop_jumpdest",
),
pytest.param(
RandomInitcode((Op.JUMPDEST, Op.PUSH1)),
id="random_jumpdest_push1",
),
pytest.param(
RandomInitcode(
(Op.STOP, Op.JUMPDEST, Op.PUSH1), weights=(1, 1, 2)
),
id="random_stop_jumpdest_2push1",
),
],
ids=lambda x: x.hex(),
)
def test_jumpdest_analysis(
benchmark_test: BenchmarkTestFiller,
pre: Alloc,
fork: Fork,
pattern: Bytecode | RandomInitcode,
gas_benchmark_value: int,
tx_gas_limit: int,
) -> None:
"""
Benchmark jumpdest analysis of CREATE initcode.
Each CREATE runs a max-size initcode that jumps straight to its last byte,
so its cost is almost all analysis. Tiled patterns repeat with a period the
branch predictor learns; ``RandomInitcode`` does not repeat.
"""
initcode_size = fork.max_initcode_size()
if isinstance(pattern, RandomInitcode):
# Deploy the random bytes as two max-size contracts and EXTCODECOPY
# them in; no calldata, whose floor would exceed small gas budgets.
chunk = fork.max_code_size()
assert initcode_size % chunk == 0
full = pattern.code(initcode_size)
code_prepare_initcode = Bytecode()
for offset in range(0, initcode_size, chunk):
source = pre.deploy_contract(code=full[offset : offset + chunk])
code_prepare_initcode += Op.EXTCODECOPY(
address=source, dest_offset=offset, size=chunk
)
tx_data = b""
else:
# Tile a small calldata window to fill the initcode: cheap, but the
# period is learnable.
tx_data_len = 1024
tx_data = bytes(pattern) * (tx_data_len // len(pattern))
tx_data += (tx_data_len - len(tx_data)) * bytes(Op.JUMPDEST)
assert initcode_size % len(tx_data) == 0
code_prepare_initcode = sum(
(
Op.CALLDATACOPY(
dest_offset=i * len(tx_data),
offset=0,
size=Op.CALLDATASIZE,
)
for i in range(initcode_size // len(tx_data))
),
Bytecode(),
)
# Jump to the last byte, forcing a full analysis, and make it a JUMPDEST.
initcode_prefix = Op.JUMP(initcode_size - 1)
code_prepare_initcode += Op.MSTORE(
0, Op.PUSH32[bytes(initcode_prefix).ljust(32, bytes(Op.JUMPDEST))]
)
code_prepare_initcode += Op.MSTORE(
initcode_size - 32, Op.PUSH32[bytes(Op.JUMPDEST) * 32]
)
# Mix the returned address into the initcode so each analysis is unique.
attack_block = (
Op.PUSH1[len(initcode_prefix)]
+ Op.MSTORE
+ Op.CREATE(value=Op.PUSH0, offset=Op.PUSH0, size=Op.MSIZE)
)
setup = code_prepare_initcode + Op.CREATE(
value=Op.PUSH0, offset=Op.PUSH0, size=Op.MSIZE
)
overhead = len(setup) + len(Op.JUMPDEST) + len(Op.JUMP(len(setup)))
iterations = (fork.max_code_size() - overhead) // len(attack_block)
loop_contract = pre.deploy_contract(
code=setup
+ Op.JUMPDEST
+ attack_block * iterations
+ Op.JUMP(len(setup))
)
create = Op.CREATE.with_metadata(init_code_size=initcode_size)
if create.state_cost(fork) > 0:
# Pre-fund the CREATE targets so creation skips NEW_ACCOUNT. Each
# transaction runs out of gas and reverts, so every transaction reuses
# the same targets and one transaction's gas bounds how many there are.
create_cost = create.execution_cost(fork)
tx_budget = min(gas_benchmark_value, tx_gas_limit)
for nonce in range(1, tx_budget // create_cost + 2):
pre.fund_address(
compute_create_address(address=loop_contract, nonce=nonce), 1
)
benchmark_test(
tx=Transaction(
to=loop_contract,
data=tx_data,
gas_limit=gas_benchmark_value,
sender=pre.fund_eoa(),
)
)
|