Verkle EXTCODECOPY implementation (#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.
+// IsCode checks if the position is in a code segment.
-func (bits *bitvec) codeSegment(pos uint64) bool {
+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)) {
+	if contract != nil && startOffset+size > uint64(len(code)) {
-		endOffset = uint64(len(contract.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