core/vm: use 64-bit memory calculations

ethereum · Mar 7, 2019 · e17df3e · e17df3e
1 parent 6a4bf5d
commit e17df3e
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Showing 4 changed files with 106 additions and 57 deletions.
diff --git a/core/vm/common.go b/core/vm/common.go
@@ -23,13 +23,47 @@ import (
 	"github.com/ethereum/go-ethereum/common/math"
 )
 
-// calculates the memory size required for a step
-func calcMemSize(off, l *big.Int) *big.Int {
+// calcMemSize64 calculates the required memory size, and returns
+// the size and whether the result overflowed uint64
+func calcMemSize64(off, l *big.Int) (uint64, bool) {
+	// if length is zero, memsize is always zero, regardless of offset
 	if l.Sign() == 0 {
-		return common.Big0
+		return 0, true
 	}
+	// Check that neither offset nor length overflows
+	if off.BitLen() > 64 || l.BitLen() > 64 {
+		return 0, true
+	}
+
+	offset64 := off.Uint64()
+	length64 := l.Uint64()
+	val := offset64 + length64
+	// Check that the total doesn't overflow
+	if val < offset64 {
+		return 0, true
+	}
+	return val, false
+}
 
-	return new(big.Int).Add(off, l)
+// calcMemSize64WithUint calculates the required memory size, and returns
+// the size and whether the result overflowed uint64
+// Identical to calcMemSize64, but length is a uint64
+func calcMemSize64WithUint(off *big.Int, length64 uint64) (uint64, bool) {
+	// if length is zero, memsize is always zero, regardless of offset
+	if length64 == 0 {
+		return 0, true
+	}
+	// Check that offset doesn't overflow
+	if off.BitLen() > 64 {
+		return 0, true
+	}
+	offset64 := off.Uint64()
+	val := offset64 + length64
+	// Check that the total doesn't overflow
+	if val < offset64 {
+		return 0, true
+	}
+	return val, false
 }
 
 // getData returns a slice from the data based on the start and size and pads

diff --git a/core/vm/interpreter.go b/core/vm/interpreter.go
@@ -229,7 +229,7 @@ func (in *EVMInterpreter) Run(contract *Contract, input []byte, readOnly bool) (
 		// calculate the new memory size and expand the memory to fit
 		// the operation
 		if operation.memorySize != nil {
-			memSize, overflow := bigUint64(operation.memorySize(stack))
+			memSize, overflow := operation.memorySize(stack)
 			if overflow {
 				return nil, errGasUintOverflow
 			}

diff --git a/core/vm/jump_table.go b/core/vm/jump_table.go
@@ -18,16 +18,15 @@ package vm
 
 import (
 	"errors"
-	"math/big"
 
 	"github.com/ethereum/go-ethereum/params"
 )
 
 type (
 	executionFunc func(pc *uint64, interpreter *EVMInterpreter, contract *Contract, memory *Memory, stack *Stack) ([]byte, error)
 	gasFunc       func(params.GasTable, *EVM, *Contract, *Stack, *Memory, uint64) (uint64, error) // last parameter is the requested memory size as a uint64
-	//stackValidationFunc func(*Stack) error
-	memorySizeFunc func(*Stack) *big.Int
+	// memorySizeFunc returns the required size, and whether the operation overflowed a uint64
+	memorySizeFunc func(*Stack) (size uint64, overflow bool)
 )
 
 var errGasUintOverflow = errors.New("gas uint64 overflow")

diff --git a/core/vm/memory_table.go b/core/vm/memory_table.go
@@ -16,82 +16,98 @@
 
 package vm
 
-import (
-	"math/big"
-
-	"github.com/ethereum/go-ethereum/common/math"
-)
-
-func memorySha3(stack *Stack) *big.Int {
-	return calcMemSize(stack.Back(0), stack.Back(1))
+func memorySha3(stack *Stack) (uint64, bool) {
+	return calcMemSize64(stack.Back(0), stack.Back(1))
 }
 
-func memoryCallDataCopy(stack *Stack) *big.Int {
-	return calcMemSize(stack.Back(0), stack.Back(2))
+func memoryCallDataCopy(stack *Stack) (uint64, bool) {
+	return calcMemSize64(stack.Back(0), stack.Back(2))
 }
 
-func memoryReturnDataCopy(stack *Stack) *big.Int {
-	return calcMemSize(stack.Back(0), stack.Back(2))
+func memoryReturnDataCopy(stack *Stack) (uint64, bool) {
+	return calcMemSize64(stack.Back(0), stack.Back(2))
 }
 
-func memoryCodeCopy(stack *Stack) *big.Int {
-	return calcMemSize(stack.Back(0), stack.Back(2))
+func memoryCodeCopy(stack *Stack) (uint64, bool) {
+	return calcMemSize64(stack.Back(0), stack.Back(2))
 }
 
-func memoryExtCodeCopy(stack *Stack) *big.Int {
-	return calcMemSize(stack.Back(1), stack.Back(3))
+func memoryExtCodeCopy(stack *Stack) (uint64, bool) {
+	return calcMemSize64(stack.Back(1), stack.Back(3))
 }
 
-func memoryMLoad(stack *Stack) *big.Int {
-	return calcMemSize(stack.Back(0), big.NewInt(32))
+func memoryMLoad(stack *Stack) (uint64, bool) {
+	return calcMemSize64WithUint(stack.Back(0), 32)
 }
 
-func memoryMStore8(stack *Stack) *big.Int {
-	return calcMemSize(stack.Back(0), big.NewInt(1))
+func memoryMStore8(stack *Stack) (uint64, bool) {
+	return calcMemSize64WithUint(stack.Back(0), 1)
 }
 
-func memoryMStore(stack *Stack) *big.Int {
-	return calcMemSize(stack.Back(0), big.NewInt(32))
+func memoryMStore(stack *Stack) (uint64, bool) {
+	return calcMemSize64WithUint(stack.Back(0), 32)
 }
 
-func memoryCreate(stack *Stack) *big.Int {
-	return calcMemSize(stack.Back(1), stack.Back(2))
+func memoryCreate(stack *Stack) (uint64, bool) {
+	return calcMemSize64(stack.Back(1), stack.Back(2))
 }
 
-func memoryCreate2(stack *Stack) *big.Int {
-	return calcMemSize(stack.Back(1), stack.Back(2))
+func memoryCreate2(stack *Stack) (uint64, bool) {
+	return calcMemSize64(stack.Back(1), stack.Back(2))
 }
 
-func memoryCall(stack *Stack) *big.Int {
-	x := calcMemSize(stack.Back(5), stack.Back(6))
-	y := calcMemSize(stack.Back(3), stack.Back(4))
-
-	return math.BigMax(x, y)
+func memoryCall(stack *Stack) (uint64, bool) {
+	x, overflow := calcMemSize64(stack.Back(5), stack.Back(6))
+	if overflow {
+		return 0, true
+	}
+	y, overflow := calcMemSize64(stack.Back(3), stack.Back(4))
+	if overflow {
+		return 0, true
+	}
+	if x > y {
+		return x, false
+	}
+	return y, false
 }
-
-func memoryDelegateCall(stack *Stack) *big.Int {
-	x := calcMemSize(stack.Back(4), stack.Back(5))
-	y := calcMemSize(stack.Back(2), stack.Back(3))
-
-	return math.BigMax(x, y)
+func memoryDelegateCall(stack *Stack) (uint64, bool) {
+	x, overflow := calcMemSize64(stack.Back(4), stack.Back(5))
+	if overflow {
+		return 0, true
+	}
+	y, overflow := calcMemSize64(stack.Back(2), stack.Back(3))
+	if overflow {
+		return 0, true
+	}
+	if x > y {
+		return x, false
+	}
+	return y, false
 }
 
-func memoryStaticCall(stack *Stack) *big.Int {
-	x := calcMemSize(stack.Back(4), stack.Back(5))
-	y := calcMemSize(stack.Back(2), stack.Back(3))
-
-	return math.BigMax(x, y)
+func memoryStaticCall(stack *Stack) (uint64, bool) {
+	x, overflow := calcMemSize64(stack.Back(4), stack.Back(5))
+	if overflow {
+		return 0, true
+	}
+	y, overflow := calcMemSize64(stack.Back(2), stack.Back(3))
+	if overflow {
+		return 0, true
+	}
+	if x > y {
+		return x, false
+	}
+	return y, false
 }
 
-func memoryReturn(stack *Stack) *big.Int {
-	return calcMemSize(stack.Back(0), stack.Back(1))
+func memoryReturn(stack *Stack) (uint64, bool) {
+	return calcMemSize64(stack.Back(0), stack.Back(1))
 }
 
-func memoryRevert(stack *Stack) *big.Int {
-	return calcMemSize(stack.Back(0), stack.Back(1))
+func memoryRevert(stack *Stack) (uint64, bool) {
+	return calcMemSize64(stack.Back(0), stack.Back(1))
 }
 
-func memoryLog(stack *Stack) *big.Int {
-	mSize, mStart := stack.Back(1), stack.Back(0)
-	return calcMemSize(mStart, mSize)
+func memoryLog(stack *Stack) (uint64, bool) {
+	return calcMemSize64(stack.Back(0), stack.Back(1))
 }