forked from cerc-io/laconicd-deprecated
evm: refactor state transition (#41)
* evm: keeper statedb refactor * keeper: implement stateDB account, balance, nonce and suicide functions * keeper: implement stateDB code and iterator functions * keeper: implement stateDB log and preimage functions * update code to use CommitStateDB * tests updates * journal changes (wip) * cache fields * journal and logs * minor cleanup * evm: state transition refactor * evm: unpack revert errors * evm: update state transition (wip) * evm: remove journal related changes * evm: delete empty account code and storage state * update gas limit * evm: header hash to/from context * evm: minor params and state transition changes * ante: state transition changes * ante: refactor default sig gas consumer * ante: ignore gas costs from ops other than intrinsic gas * ante: CanTransferDecorator * evm: refund gas * update comments * state transition comments * ante: CanTransfer and AccessList decorator tests * evm: cleanup state transition * ignore nonce increment during ante handler on contract creation * fix ante tests * more test fixes
This commit is contained in:
Federico Kunze
@@ -0,0 +1,264 @@
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package keeper
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import (
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"errors"
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"fmt"
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"math/big"
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"os"
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"time"
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"github.com/cosmos/cosmos-sdk/telemetry"
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sdk "github.com/cosmos/cosmos-sdk/types"
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sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
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authtypes "github.com/cosmos/cosmos-sdk/x/auth/types"
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"github.com/cosmos/ethermint/x/evm/types"
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"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/core"
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"github.com/ethereum/go-ethereum/core/vm"
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"github.com/ethereum/go-ethereum/params"
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)
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// NewEVM generates an ethereum VM from the provided Message fields and the ChainConfig.
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func (k *Keeper) NewEVM(msg core.Message, config *params.ChainConfig) *vm.EVM {
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blockCtx := vm.BlockContext{
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CanTransfer: core.CanTransfer,
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Transfer: core.Transfer,
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GetHash: k.GetHashFn(),
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Coinbase: common.Address{}, // there's no beneficiary since we're not mining
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GasLimit: k.ctx.BlockGasMeter().Limit(),
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BlockNumber: big.NewInt(k.ctx.BlockHeight()),
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Time: big.NewInt(k.ctx.BlockHeader().Time.Unix()),
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Difficulty: big.NewInt(0), // unused. Only required in PoW context
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}
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txCtx := core.NewEVMTxContext(msg)
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vmConfig := k.VMConfig()
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return vm.NewEVM(blockCtx, txCtx, k, config, vmConfig)
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}
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// VMConfig creates an EVM configuration from the module parameters and the debug setting.
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// The config generated uses the default JumpTable from the EVM.
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func (k Keeper) VMConfig() vm.Config {
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params := k.GetParams(k.ctx)
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return vm.Config{
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Debug: k.debug,
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Tracer: vm.NewJSONLogger(&vm.LogConfig{Debug: k.debug}, os.Stderr), // TODO: consider using the Struct Logger too
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NoRecursion: false, // TODO: consider disabling recursion though params
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ExtraEips: params.EIPs(),
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}
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}
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// GetHashFn implements vm.GetHashFunc for Ethermint. It handles 3 cases:
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// 1. The requested height matches the current height from context (and thus same epoch number)
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// 2. The requested height is from an previous height from the same chain epoch
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// 3. The requested height is from a height greater than the latest one
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func (k Keeper) GetHashFn() vm.GetHashFunc {
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return func(height uint64) common.Hash {
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switch {
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case k.ctx.BlockHeight() == int64(height):
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// Case 1: The requested height matches the one from the context so we can retrieve the header
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// hash directly from the context.
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// TODO: deprecate field from the keeper on next SDK release
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return k.headerHash
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case k.ctx.BlockHeight() > int64(height):
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// Case 2: if the chain is not the current height we need to retrieve the hash from the store for the
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// current chain epoch. This only applies if the current height is greater than the requested height.
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return k.GetHeightHash(k.ctx, height)
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default:
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// Case 3: heights greater than the current one returns an empty hash.
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return common.Hash{}
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}
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}
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}
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// TransitionDb runs and attempts to perform a state transition with the given transaction (i.e Message), that will
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// only be persisted to the underlying KVStore if the transaction does not error.
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//
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// Gas tracking
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//
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// Ethereum consumes gas according to the EVM opcodes instead of general reads and writes to store. Because of this, the
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// state transition needs to ignore the SDK gas consumption mechanism defined by the GasKVStore and instead consume the
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// amount of gas used by the VM execution. The amount of gas used is tracked by the EVM and returned in the execution
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// result.
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//
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// Prior to the execution, the starting tx gas meter is saved and replaced with an infinite gas meter in a new context
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// in order to ignore the SDK gas consumption config values (read, write, has, delete).
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// After the execution, the gas used from the message execution will be added to the starting gas consumed, taking into
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// consideration the amount of gas returned. Finally, the context is updated with the EVM gas consumed value prior to
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// returning.
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//
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// For relevant discussion see: https://github.com/cosmos/cosmos-sdk/discussions/9072
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func (k *Keeper) TransitionDb(msg core.Message) (*types.ExecutionResult, error) {
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defer telemetry.ModuleMeasureSince(types.ModuleName, time.Now(), types.MetricKeyTransitionDB)
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cfg, found := k.GetChainConfig(k.ctx)
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if !found {
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return nil, types.ErrChainConfigNotFound
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}
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evm := k.NewEVM(msg, cfg.EthereumConfig(k.eip155ChainID))
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// create an ethereum StateTransition instance and run TransitionDb
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result, err := k.ApplyMessage(evm, msg)
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if err != nil {
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return nil, err
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}
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return result, nil
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}
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// Gas consumption notes (write doc from this)
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// gas = remaining gas = limit - consumed
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// Gas consumption in ethereum:
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// 0. Buy gas -> deduct gasLimit * gasPrice from user account
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// 0.1 leftover gas = gas limit
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// 1. consume intrinsic gas
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// 1.1 leftover gas = leftover gas - intrinsic gas
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// 2. Exec vm functions by passing the gas (i.e remaining gas)
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// 2.1 final leftover gas returned after spending gas from the opcodes jump tables
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// 3. Refund amount = max(gasConsumed / 2, gas refund), where gas refund is a local variable
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// TODO: (@fedekunze) currently we consume the entire gas limit in the ante handler, so if a transaction fails
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// the amount spent will be grater than the gas spent in an Ethereum tx (i.e here the leftover gas won't be refunded).
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func (k *Keeper) ApplyMessage(evm *vm.EVM, msg core.Message) (*types.ExecutionResult, error) {
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var (
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ret []byte // return bytes from evm execution
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contract common.Address
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contractAddr string
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vmErr, err error // vm errors do not effect consensus and are therefore not assigned to err
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)
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sender := vm.AccountRef(msg.From())
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contractCreation := msg.To() == nil
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// transaction gas meter (tracks limit and usage)
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gasConsumed := k.ctx.GasMeter().GasConsumed()
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leftoverGas := k.ctx.GasMeter().Limit() - k.ctx.GasMeter().GasConsumedToLimit()
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// NOTE: Since CRUD operations on the SDK store consume gasm we need to set up an infinite gas meter so that we only consume
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// the gas used by the Ethereum message execution.
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// Not setting the infinite gas meter here would mean that we are incurring in additional gas costs
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k.WithContext(k.ctx.WithGasMeter(sdk.NewInfiniteGasMeter()))
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// NOTE: gas limit is the GasLimit defied in the message minus the Intrinsic Gas that has already been
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// consumed on the AnteHandler.
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// ensure gas is consistent during CheckTx
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if k.ctx.IsCheckTx() {
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if err := k.checkGasConsumption(msg, gasConsumed, contractCreation); err != nil {
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return nil, err
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}
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}
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if contractCreation {
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ret, contract, leftoverGas, vmErr = evm.Create(sender, msg.Data(), leftoverGas, msg.Value())
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contractAddr = contract.Hex()
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} else {
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ret, leftoverGas, vmErr = evm.Call(sender, *msg.To(), msg.Data(), leftoverGas, msg.Value())
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}
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// refund gas prior to handling the vm error in order to set the updated gas meter
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gasConsumed, leftoverGas, err = k.refundGas(msg, leftoverGas)
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if err != nil {
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return nil, err
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}
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if vmErr != nil {
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if errors.Is(vmErr, vm.ErrExecutionReverted) {
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// unpack the return data bytes from the err if the execution has been reverted on the VM
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return nil, types.NewExecErrorWithReson(ret)
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}
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// wrap the VM error
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return nil, sdkerrors.Wrap(types.ErrVMExecution, vmErr.Error())
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}
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return &types.ExecutionResult{
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Response: &types.MsgEthereumTxResponse{
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ContractAddress: contractAddr,
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Ret: ret,
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},
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GasInfo: types.GasInfo{
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GasLimit: k.ctx.GasMeter().Limit(),
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GasConsumed: gasConsumed,
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GasRefunded: leftoverGas,
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},
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}, nil
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}
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// checkGasConsumption verifies that the amount of gas consumed so far matches the intrinsic gas value.
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func (k *Keeper) checkGasConsumption(msg core.Message, gasConsumed uint64, isContractCreation bool) error {
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cfg, _ := k.GetChainConfig(k.ctx)
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ethCfg := cfg.EthereumConfig(k.eip155ChainID)
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height := big.NewInt(k.ctx.BlockHeight())
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homestead := ethCfg.IsHomestead(height)
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istanbul := ethCfg.IsIstanbul(height)
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intrinsicGas, err := core.IntrinsicGas(msg.Data(), msg.AccessList(), isContractCreation, homestead, istanbul)
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if err != nil {
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// should have already been checked on Ante Handler
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return err
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}
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if intrinsicGas != gasConsumed {
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return fmt.Errorf("inconsistent gas. Expected gas consumption to be %d (intrinsic gas only), got %d", intrinsicGas, gasConsumed)
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}
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return nil
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}
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// refundGas transfers the leftover gas to the sender of the message, caped to half of the total gas
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// consumed in the transaction. Additionally, the function sets the total gas consumed to the value
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// returned by the EVM execution, thus ignoring the previous intrinsic gas inconsumed during in the
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// AnteHandler.
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func (k *Keeper) refundGas(msg core.Message, leftoverGas uint64) (consumed, leftover uint64, err error) {
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gasConsumed := msg.Gas() - leftoverGas
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// Apply refund counter, capped to half of the used gas.
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refund := gasConsumed / 2
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if refund > k.GetRefund() {
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refund = k.GetRefund()
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}
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leftoverGas += refund
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gasConsumed = msg.Gas() - leftoverGas
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// Return EVM tokens for remaining gas, exchanged at the original rate.
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remaining := new(big.Int).Mul(new(big.Int).SetUint64(leftoverGas), msg.GasPrice())
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switch remaining.Sign() {
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case -1:
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// negative refund errors
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return 0, 0, fmt.Errorf("refunded amount value cannot be negative %d", remaining.Int64())
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case 1:
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// positive amount refund
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params := k.GetParams(k.ctx)
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refundedCoins := sdk.Coins{sdk.NewCoin(params.EvmDenom, sdk.NewIntFromBigInt(remaining))}
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// refund to sender from the fee collector module account, which is the escrow account in charge of collecting tx fees
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if err := k.bankKeeper.SendCoinsFromModuleToAccount(k.ctx, authtypes.FeeCollectorName, msg.From().Bytes(), refundedCoins); err != nil {
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return 0, 0, sdkerrors.Wrapf(sdkerrors.ErrInsufficientFunds, "fee collector account failed to refund fees: %s", err.Error())
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}
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default:
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// no refund, consume gas and update the tx gas meter
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}
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// set the gas consumed into the context with the new gas meter. This gas meter will have the
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// original gas limit defined in the msg and will consume the gas now that the amount has been
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// refunded
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gasMeter := sdk.NewGasMeter(msg.Gas())
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gasMeter.ConsumeGas(gasConsumed, "update gas consumption after refund")
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k.WithContext(k.ctx.WithGasMeter(gasMeter))
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return gasConsumed, leftoverGas, nil
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}
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