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core/vm: Hide read only flag from Interpreter interface (ethereum#17461
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…) (#6)

Makes Interface interface a bit more stateless and abstract.

Obviously this change is dictated by EVMC design. The EVMC tries to keep the responsibility for EVM features totally inside the VMs, if feasible. This makes VM "stateless" because VM does not need to pass any information between executions, all information is included in parameters of the execute function.
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5chdn authored Sep 8, 2018
1 parent 8b9b149 commit e256eb5
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Showing 3 changed files with 17 additions and 31 deletions.
21 changes: 7 additions & 14 deletions core/vm/evm.go
Original file line number Diff line number Diff line change
Expand Up @@ -41,7 +41,7 @@ type (
)

// run runs the given contract and takes care of running precompiles with a fallback to the byte code interpreter.
func run(evm *EVM, contract *Contract, input []byte) ([]byte, error) {
func run(evm *EVM, contract *Contract, input []byte, readOnly bool) ([]byte, error) {
if contract.CodeAddr != nil {
precompiles := PrecompiledContractsHomestead
if evm.ChainConfig().IsByzantium(evm.BlockNumber) {
Expand All @@ -61,7 +61,7 @@ func run(evm *EVM, contract *Contract, input []byte) ([]byte, error) {
}(evm.interpreter)
evm.interpreter = interpreter
}
return interpreter.Run(contract, input)
return interpreter.Run(contract, input, readOnly)
}
}
return nil, ErrNoCompatibleInterpreter
Expand Down Expand Up @@ -210,7 +210,7 @@ func (evm *EVM) Call(caller ContractRef, addr common.Address, input []byte, gas
evm.vmConfig.Tracer.CaptureEnd(ret, gas-contract.Gas, time.Since(start), err)
}()
}
ret, err = run(evm, contract, input)
ret, err = run(evm, contract, input, false)

// When an error was returned by the EVM or when setting the creation code
// above we revert to the snapshot and consume any gas remaining. Additionally
Expand Down Expand Up @@ -255,7 +255,7 @@ func (evm *EVM) CallCode(caller ContractRef, addr common.Address, input []byte,
contract := NewContract(caller, to, value, gas)
contract.SetCallCode(&addr, evm.StateDB.GetCodeHash(addr), evm.StateDB.GetCode(addr))

ret, err = run(evm, contract, input)
ret, err = run(evm, contract, input, false)
if err != nil {
evm.StateDB.RevertToSnapshot(snapshot)
if err != errExecutionReverted {
Expand Down Expand Up @@ -288,7 +288,7 @@ func (evm *EVM) DelegateCall(caller ContractRef, addr common.Address, input []by
contract := NewContract(caller, to, nil, gas).AsDelegate()
contract.SetCallCode(&addr, evm.StateDB.GetCodeHash(addr), evm.StateDB.GetCode(addr))

ret, err = run(evm, contract, input)
ret, err = run(evm, contract, input, false)
if err != nil {
evm.StateDB.RevertToSnapshot(snapshot)
if err != errExecutionReverted {
Expand All @@ -310,13 +310,6 @@ func (evm *EVM) StaticCall(caller ContractRef, addr common.Address, input []byte
if evm.depth > int(params.CallCreateDepth) {
return nil, gas, ErrDepth
}
// Make sure the readonly is only set if we aren't in readonly yet
// this makes also sure that the readonly flag isn't removed for
// child calls.
if !evm.interpreter.IsReadOnly() {
evm.interpreter.SetReadOnly(true)
defer func() { evm.interpreter.SetReadOnly(false) }()
}

var (
to = AccountRef(addr)
Expand All @@ -331,7 +324,7 @@ func (evm *EVM) StaticCall(caller ContractRef, addr common.Address, input []byte
// When an error was returned by the EVM or when setting the creation code
// above we revert to the snapshot and consume any gas remaining. Additionally
// when we're in Homestead this also counts for code storage gas errors.
ret, err = run(evm, contract, input)
ret, err = run(evm, contract, input, true)
if err != nil {
evm.StateDB.RevertToSnapshot(snapshot)
if err != errExecutionReverted {
Expand Down Expand Up @@ -382,7 +375,7 @@ func (evm *EVM) create(caller ContractRef, code []byte, gas uint64, value *big.I
}
start := time.Now()

ret, err := run(evm, contract, nil)
ret, err := run(evm, contract, nil, false)

// check whether the max code size has been exceeded
maxCodeSizeExceeded := evm.ChainConfig().IsEIP158(evm.BlockNumber) && len(ret) > params.MaxCodeSize
Expand Down
25 changes: 9 additions & 16 deletions core/vm/interpreter.go
Original file line number Diff line number Diff line change
Expand Up @@ -48,7 +48,7 @@ type Config struct {
type Interpreter interface {
// Run loops and evaluates the contract's code with the given input data and returns
// the return byte-slice and an error if one occurred.
Run(contract *Contract, input []byte) ([]byte, error)
Run(contract *Contract, input []byte, static bool) ([]byte, error)
// CanRun tells if the contract, passed as an argument, can be
// run by the current interpreter. This is meant so that the
// caller can do something like:
Expand All @@ -61,10 +61,6 @@ type Interpreter interface {
// }
// ```
CanRun([]byte) bool
// IsReadOnly reports if the interpreter is in read only mode.
IsReadOnly() bool
// SetReadOnly sets (or unsets) read only mode in the interpreter.
SetReadOnly(bool)
}

// EVMInterpreter represents an EVM interpreter
Expand Down Expand Up @@ -125,7 +121,7 @@ func (in *EVMInterpreter) enforceRestrictions(op OpCode, operation operation, st
// It's important to note that any errors returned by the interpreter should be
// considered a revert-and-consume-all-gas operation except for
// errExecutionReverted which means revert-and-keep-gas-left.
func (in *EVMInterpreter) Run(contract *Contract, input []byte) (ret []byte, err error) {
func (in *EVMInterpreter) Run(contract *Contract, input []byte, readOnly bool) (ret []byte, err error) {
if in.intPool == nil {
in.intPool = poolOfIntPools.get()
defer func() {
Expand All @@ -138,6 +134,13 @@ func (in *EVMInterpreter) Run(contract *Contract, input []byte) (ret []byte, err
in.evm.depth++
defer func() { in.evm.depth-- }()

// Make sure the readOnly is only set if we aren't in readOnly yet.
// This makes also sure that the readOnly flag isn't removed for child calls.
if readOnly && !in.readOnly {
in.readOnly = true
defer func() { in.readOnly = false }()
}

// Reset the previous call's return data. It's unimportant to preserve the old buffer
// as every returning call will return new data anyway.
in.returnData = nil
Expand Down Expand Up @@ -263,13 +266,3 @@ func (in *EVMInterpreter) Run(contract *Contract, input []byte) (ret []byte, err
func (in *EVMInterpreter) CanRun(code []byte) bool {
return true
}

// IsReadOnly reports if the interpreter is in read only mode.
func (in *EVMInterpreter) IsReadOnly() bool {
return in.readOnly
}

// SetReadOnly sets (or unsets) read only mode in the interpreter.
func (in *EVMInterpreter) SetReadOnly(ro bool) {
in.readOnly = ro
}
2 changes: 1 addition & 1 deletion eth/tracers/tracer_test.go
Original file line number Diff line number Diff line change
Expand Up @@ -49,7 +49,7 @@ func runTrace(tracer *Tracer) (json.RawMessage, error) {
contract := vm.NewContract(account{}, account{}, big.NewInt(0), 10000)
contract.Code = []byte{byte(vm.PUSH1), 0x1, byte(vm.PUSH1), 0x1, 0x0}

_, err := env.Interpreter().Run(contract, []byte{})
_, err := env.Interpreter().Run(contract, []byte{}, false)
if err != nil {
return nil, err
}
Expand Down

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