Verkle EXTCODECOPY implementation (ethereum#55)

* core/vm: verkle extcodecopy naive way (do jumpdest analysis on target contract every EXTCODECOPY)

* no double-charge

* address edge-case in touchEachChunksAndChargeGas

* simplify line

Co-authored-by: Guillaume Ballet <3272758+gballet@users.noreply.github.com>

core/vm/analysis.go

@@ -61,8 +61,8 @@ func (bits bitvec) set16(pos uint64) {
  bits[pos/8+2] = ^a
 }
 
-// codeSegment checks if the position is in a code segment.
-func (bits *bitvec) codeSegment(pos uint64) bool {
+// IsCode checks if the position is in a code segment.
+func (bits *bitvec) IsCode(pos uint64) bool {
  return ((*bits)[pos/8] & (0x80 >> (pos % 8))) == 0
 }
 

core/vm/contract.go

@@ -28,6 +28,13 @@ type ContractRef interface {
  Address() common.Address
 }
 
+// AnalyzedContract is an interface for a piece of contract
+// code that has undegone jumpdest analysis, and whose bytecode
+// can be queried to determine if it is "contract code"
+type AnalyzedContract interface {
+ IsCode(dest uint64) bool
+}
+
 // AccountRef implements ContractRef.
 //
 // Account references are used during EVM initialisation and
@@ -104,7 +111,7 @@ func (c *Contract) validJumpdest(dest *uint256.Int) bool {
 func (c *Contract) IsCode(udest uint64) bool {
  // Do we already have an analysis laying around?
  if c.analysis != nil {
- return c.analysis.codeSegment(udest)
+ return c.analysis.IsCode(udest)
  }
  // Do we have a contract hash already?
  // If we do have a hash, that means it's a 'regular' contract. For regular
@@ -120,7 +127,7 @@ func (c *Contract) IsCode(udest uint64) bool {
  }
  // Also stash it in current contract for faster access
  c.analysis = analysis
- return analysis.codeSegment(udest)
+ return analysis.IsCode(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
@@ -129,7 +136,7 @@ func (c *Contract) IsCode(udest uint64) bool {
  if c.analysis == nil {
  c.analysis = codeBitmap(c.Code)
  }
- return c.analysis.codeSegment(udest)
+ return c.analysis.IsCode(udest)
 }
 
 // AsDelegate sets the contract to be a delegate call and returns the current

core/vm/gas_table.go

@@ -121,7 +121,7 @@ func gasCodeCopy(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memory
  uint64Length = 0xffffffffffffffff
  }
  _, offset, nonPaddedSize := getDataAndAdjustedBounds(contract.Code, uint64CodeOffset, uint64Length)
- statelessGas = touchEachChunksAndChargeGas(offset, nonPaddedSize, contract.Address().Bytes()[:], nil, evm.Accesses)
+ statelessGas = touchEachChunksAndChargeGas(offset, nonPaddedSize, contract.Address().Bytes()[:], nil, nil, evm.Accesses)
  }
  usedGas, err := gasCodeCopyStateful(evm, contract, stack, mem, memorySize)
  return usedGas + statelessGas, err
@@ -133,6 +133,7 @@ func gasExtCodeCopy(evm *EVM, contract *Contract, stack *Stack, mem *Memory, mem
  var (
  codeOffset = stack.Back(2)
  length = stack.Back(3)
+ targetAddr = stack.Back(0).Bytes20()
  )
  uint64CodeOffset, overflow := codeOffset.Uint64WithOverflow()
  if overflow {
@@ -148,7 +149,7 @@ func gasExtCodeCopy(evm *EVM, contract *Contract, stack *Stack, mem *Memory, mem
  // behavior from CODECOPY which only charges witness access costs for the part of the range
  // which overlaps in the account code. TODO: clarify this is desired behavior and amend the
  // spec.
- statelessGas = touchEachChunksAndChargeGas(uint64CodeOffset, uint64Length, nil, nil, evm.Accesses)
+ statelessGas = touchEachChunksAndChargeGas(uint64CodeOffset, uint64Length, targetAddr[:], nil, nil, evm.Accesses)
  }
  usedGas, err := gasExtCodeCopyStateful(evm, contract, stack, mem, memorySize)
  return usedGas + statelessGas, err

core/vm/instructions.go

@@ -19,7 +19,6 @@ package vm
 import (
  "github.com/ethereum/go-ethereum/common"
  "github.com/ethereum/go-ethereum/core/types"
- "github.com/ethereum/go-ethereum/log"
  "github.com/ethereum/go-ethereum/params"
  trieUtils "github.com/ethereum/go-ethereum/trie/utils"
  "github.com/holiman/uint256"
@@ -373,21 +372,21 @@ func opCodeCopy(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([
 
  paddedCodeCopy, copyOffset, nonPaddedCopyLength := getDataAndAdjustedBounds(scope.Contract.Code, uint64CodeOffset, length.Uint64())
  if interpreter.evm.Accesses != nil {
- touchEachChunksAndChargeGas(copyOffset, nonPaddedCopyLength, scope.Contract.Address().Bytes()[:], scope.Contract, interpreter.evm.Accesses)
+ touchEachChunksAndChargeGas(copyOffset, nonPaddedCopyLength, scope.Contract.Address().Bytes()[:], scope.Contract.Code, scope.Contract, interpreter.evm.Accesses)
  }
  scope.Memory.Set(memOffset.Uint64(), uint64(len(paddedCodeCopy)), paddedCodeCopy)
  return nil, nil
 }
 
 // touchEachChunksAndChargeGas is a helper function to touch every chunk in a code range and charge witness gas costs
-func touchEachChunksAndChargeGas(offset, size uint64, address []byte, contract *Contract, accesses *types.AccessWitness) uint64 {
+func touchEachChunksAndChargeGas(offset, size uint64, address []byte, code []byte, contract AnalyzedContract, accesses *types.AccessWitness) uint64 {
  // note that in the case where the copied code is outside the range of the
  // contract code but touches the last leaf with contract code in it,
  // we don't include the last leaf of code in the AccessWitness. The
  // reason that we do not need the last leaf is the account's code size
  // is already in the AccessWitness so a stateless verifier can see that
  // the code from the last leaf is not needed.
- if contract != nil && (size == 0 || offset > uint64(len(contract.Code))) {
+ if contract != nil && (size == 0 || offset > uint64(len(code))) {
  return 0
  }
  var (
@@ -397,17 +396,13 @@ func touchEachChunksAndChargeGas(offset, size uint64, address []byte, contract *
  startOffset uint64
  endOffset uint64
  numLeaves uint64
- code []byte
  index [32]byte
  )
- if contract != nil {
- code = contract.Code[:]
- }
  // startLeafOffset, endLeafOffset is the evm code offset of the first byte in the first leaf touched
  // and the evm code offset of the last byte in the last leaf touched
  startOffset = offset - (offset % 31)
- if contract != nil && startOffset+size > uint64(len(contract.Code)) {
- endOffset = uint64(len(contract.Code))
+ if contract != nil && startOffset+size > uint64(len(code)) {
+ endOffset = uint64(len(code))
  } else {
  endOffset = startOffset + size
  }
@@ -431,11 +426,11 @@ func touchEachChunksAndChargeGas(offset, size uint64, address []byte, contract *
  index[31] = subIndex
 
  var value []byte
- if contract != nil {
+ if len(code) > 0 {
  // the offset into the leaf that the first PUSH occurs
  var firstPushOffset uint64 = 0
  // Look for the first code byte (i.e. no pushdata)
- for ; firstPushOffset < 31 && firstPushOffset+uint64(i)*31 < uint64(len(contract.Code)) && !contract.IsCode(uint64(i)*31+firstPushOffset); firstPushOffset++ {
+ for ; firstPushOffset < 31 && firstPushOffset+uint64(i)*31 < uint64(len(code)) && !contract.IsCode(uint64(i)*31+firstPushOffset); firstPushOffset++ {
  }
  curEnd := (uint64(i) + 1) * 31
  if curEnd > endOffset {
@@ -472,7 +467,11 @@ func opExtCodeCopy(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext)
  }
  addr := common.Address(a.Bytes20())
  if interpreter.evm.Accesses != nil {
- log.Warn("setting witness values for extcodecopy is not currently implemented")
+ code := interpreter.evm.StateDB.GetCode(addr)
+ paddedCodeCopy, copyOffset, nonPaddedCopyLength := getDataAndAdjustedBounds(code, uint64CodeOffset, length.Uint64())
+ cb := codeBitmap(code)
+ touchEachChunksAndChargeGas(copyOffset, nonPaddedCopyLength, addr[:], code, &cb, interpreter.evm.Accesses)
+ scope.Memory.Set(memOffset.Uint64(), length.Uint64(), paddedCodeCopy)
  } else {
  codeCopy := getData(interpreter.evm.StateDB.GetCode(addr), uint64CodeOffset, length.Uint64())
  scope.Memory.Set(memOffset.Uint64(), length.Uint64(), codeCopy)
@@ -977,7 +976,7 @@ func makePush(size uint64, pushByteSize int) executionFunc {
  }
 
  if interpreter.evm.Accesses != nil {
- statelessGas := touchEachChunksAndChargeGas(uint64(startMin), uint64(pushByteSize), scope.Contract.Address().Bytes()[:], scope.Contract, interpreter.evm.Accesses)
+ statelessGas := touchEachChunksAndChargeGas(uint64(startMin), uint64(pushByteSize), scope.Contract.Address().Bytes()[:], scope.Contract.Code, scope.Contract, interpreter.evm.Accesses)
  scope.Contract.UseGas(statelessGas)
  }
 

core/vm/interpreter.go

@@ -194,7 +194,7 @@ func (in *EVMInterpreter) Run(contract *Contract, input []byte, readOnly bool) (
  if in.evm.TxContext.Accesses != nil && !contract.IsDeployment {
  // if the PC ends up in a new "page" of verkleized code, charge the
  // associated witness costs.
- contract.Gas -= touchEachChunksAndChargeGas(pc, 1, contract.Address().Bytes()[:], contract, in.evm.TxContext.Accesses)
+ contract.Gas -= touchEachChunksAndChargeGas(pc, 1, contract.Address().Bytes()[:], contract.Code, contract, in.evm.TxContext.Accesses)
  }
 
  // TODO how can we tell if we are in stateless mode here and need to get the op from the witness