// Copyright 2015 The go-ethereum Authors // This file is part of the go-ethereum library. // // The go-ethereum library is free software: you can redistribute it and/or modify // it under the terms of the GNU Lesser General Public License as published by // the Free Software Foundation, either version 3 of the License, or // (at your option) any later version. // // The go-ethereum library is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU Lesser General Public License for more details. // // You should have received a copy of the GNU Lesser General Public License // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>. package vm import ( "math/big" "github.com/ethereum/go-ethereum/common" "github.com/holiman/uint256" ) // ContractRef is a reference to the contract's backing object type ContractRef interface { Address() common.Address } // AccountRef implements ContractRef. // // Account references are used during EVM initialisation and // it's primary use is to fetch addresses. Removing this object // proves difficult because of the cached jump destinations which // are fetched from the parent contract (i.e. the caller), which // is a ContractRef. type AccountRef common.Address // Address casts AccountRef to a Address func (ar AccountRef) Address() common.Address { return (common.Address)(ar) } // Contract represents an ethereum contract in the state database. It contains // the contract code, calling arguments. Contract implements ContractRef type Contract struct { // CallerAddress is the result of the caller which initialised this // contract. However when the "call method" is delegated this value // needs to be initialised to that of the caller's caller. CallerAddress common.Address caller ContractRef self ContractRef jumpdests map[common.Hash]bitvec // Aggregated result of JUMPDEST analysis. analysis bitvec // Locally cached result of JUMPDEST analysis Code []byte CodeHash common.Hash CodeAddr *common.Address Input []byte Gas uint64 value *big.Int } // NewContract returns a new contract environment for the execution of EVM. func NewContract(caller ContractRef, object ContractRef, value *big.Int, gas uint64) *Contract { c := &Contract{CallerAddress: caller.Address(), caller: caller, self: object} if parent, ok := caller.(*Contract); ok { // Reuse JUMPDEST analysis from parent context if available. c.jumpdests = parent.jumpdests } else { c.jumpdests = make(map[common.Hash]bitvec) } // Gas should be a pointer so it can safely be reduced through the run // This pointer will be off the state transition c.Gas = gas // ensures a value is set c.value = value return c } func (c *Contract) validJumpdest(dest *uint256.Int) bool { udest, overflow := dest.Uint64WithOverflow() // PC cannot go beyond len(code) and certainly can't be bigger than 63bits. // Don't bother checking for JUMPDEST in that case. if overflow || udest >= uint64(len(c.Code)) { return false } // Only JUMPDESTs allowed for destinations if OpCode(c.Code[udest]) != JUMPDEST { return false } return c.isCode(udest) } func (c *Contract) validJumpSubdest(udest uint64) bool { // PC cannot go beyond len(code) and certainly can't be bigger than 63 bits. // Don't bother checking for BEGINSUB in that case. if int64(udest) < 0 || udest >= uint64(len(c.Code)) { return false } // Only BEGINSUBs allowed for destinations if OpCode(c.Code[udest]) != BEGINSUB { return false } return c.isCode(udest) } // isCode returns true if the provided PC location is an actual opcode, as // opposed to a data-segment following a PUSHN operation. func (c *Contract) isCode(udest uint64) bool { // Do we already have an analysis laying around? if c.analysis != nil { return c.analysis.codeSegment(udest) } // Do we have a contract hash already? // If we do have a hash, that means it's a 'regular' contract. For regular // contracts ( not temporary initcode), we store the analysis in a map if c.CodeHash != (common.Hash{}) { // Does parent context have the analysis? analysis, exist := c.jumpdests[c.CodeHash] if !exist { // Do the analysis and save in parent context // We do not need to store it in c.analysis analysis = codeBitmap(c.Code) c.jumpdests[c.CodeHash] = analysis } // Also stash it in current contract for faster access c.analysis = analysis return analysis.codeSegment(udest) } // We don't have the code hash, most likely a piece of initcode not already // in state trie. In that case, we do an analysis, and save it locally, so // we don't have to recalculate it for every JUMP instruction in the execution // However, we don't save it within the parent context if c.analysis == nil { c.analysis = codeBitmap(c.Code) } return c.analysis.codeSegment(udest) } // AsDelegate sets the contract to be a delegate call and returns the current // contract (for chaining calls) func (c *Contract) AsDelegate() *Contract { // NOTE: caller must, at all times be a contract. It should never happen // that caller is something other than a Contract. parent := c.caller.(*Contract) c.CallerAddress = parent.CallerAddress c.value = parent.value return c } // GetOp returns the n'th element in the contract's byte array func (c *Contract) GetOp(n uint64) OpCode { return OpCode(c.GetByte(n)) } // GetByte returns the n'th byte in the contract's byte array func (c *Contract) GetByte(n uint64) byte { if n < uint64(len(c.Code)) { return c.Code[n] } return 0 } // Caller returns the caller of the contract. // // Caller will recursively call caller when the contract is a delegate // call, including that of caller's caller. func (c *Contract) Caller() common.Address { return c.CallerAddress } // UseGas attempts the use gas and subtracts it and returns true on success func (c *Contract) UseGas(gas uint64) (ok bool) { if c.Gas < gas { return false } c.Gas -= gas return true } // Address returns the contracts address func (c *Contract) Address() common.Address { return c.self.Address() } // Value returns the contract's value (sent to it from it's caller) func (c *Contract) Value() *big.Int { return c.value } // SetCallCode sets the code of the contract and address of the backing data // object func (c *Contract) SetCallCode(addr *common.Address, hash common.Hash, code []byte) { c.Code = code c.CodeHash = hash c.CodeAddr = addr } // SetCodeOptionalHash can be used to provide code, but it's optional to provide hash. // In case hash is not provided, the jumpdest analysis will not be saved to the parent context func (c *Contract) SetCodeOptionalHash(addr *common.Address, codeAndHash *codeAndHash) { c.Code = codeAndHash.code c.CodeHash = codeAndHash.hash c.CodeAddr = addr }