params: core, core/vm, miner: 64bit gas instructions

Reworked the EVM gas instructions to use 64bit integers rather than
arbitrary size big ints. All gas operations, be it additions,
multiplications or divisions, are checked and guarded against 64 bit
integer overflows.

In additon, most of the protocol paramaters in the params package have
been converted to uint64 and are now constants rather than variables.

* common/math: added overflow check ops
* core: vmenv, env renamed to evm
* eth, internal/ethapi, les: unmetered eth_call and cancel methods
* core/vm: implemented big.Int pool for evm instructions
* core/vm: unexported intPool methods & verification methods
* core/vm: added memoryGasCost overflow check and test

1 files changed, 11 insertions, 67 deletions

diff --git a/core/vm/common.go b/core/vm/common.go
index 2878b92d2..b7b9a6a9c 100644
--- a/core/vm/common.go
+++ b/core/vm/common.go
@@ -21,28 +21,11 @@ import (
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/params"
-)
-
-// Type is the VM type accepted by **NewVm**
-type Type byte
-
-const (
-	StdVmTy Type = iota // Default standard VM
-	JitVmTy             // LLVM JIT VM
-	MaxVmTy
 )
 
 var (
-	Pow256 = common.BigPow(2, 256) // Pow256 is 2**256
-
 	U256 = common.U256 // Shortcut to common.U256
 	S256 = common.S256 // Shortcut to common.S256
-
-	Zero = common.Big0 // Shortcut to common.Big0
-	One  = common.Big1 // Shortcut to common.Big1
-
-	max = big.NewInt(math.MaxInt64) // Maximum 64 bit integer
 )
 
 // calculates the memory size required for a step
@@ -54,48 +37,6 @@ func calcMemSize(off, l *big.Int) *big.Int {
 	return new(big.Int).Add(off, l)
 }
 
-// calculates the quadratic gas
-func quadMemGas(mem *Memory, newMemSize, gas *big.Int) {
-	if newMemSize.Cmp(common.Big0) > 0 {
-		newMemSizeWords := toWordSize(newMemSize)
-		newMemSize.Mul(newMemSizeWords, u256(32))
-
-		if newMemSize.Cmp(u256(int64(mem.Len()))) > 0 {
-			// be careful reusing variables here when changing.
-			// The order has been optimised to reduce allocation
-			oldSize := toWordSize(big.NewInt(int64(mem.Len())))
-			pow := new(big.Int).Exp(oldSize, common.Big2, Zero)
-			linCoef := oldSize.Mul(oldSize, params.MemoryGas)
-			quadCoef := new(big.Int).Div(pow, params.QuadCoeffDiv)
-			oldTotalFee := new(big.Int).Add(linCoef, quadCoef)
-
-			pow.Exp(newMemSizeWords, common.Big2, Zero)
-			linCoef = linCoef.Mul(newMemSizeWords, params.MemoryGas)
-			quadCoef = quadCoef.Div(pow, params.QuadCoeffDiv)
-			newTotalFee := linCoef.Add(linCoef, quadCoef)
-
-			fee := newTotalFee.Sub(newTotalFee, oldTotalFee)
-			gas.Add(gas, fee)
-		}
-	}
-}
-
-// Simple helper
-func u256(n int64) *big.Int {
-	return big.NewInt(n)
-}
-
-// Mainly used for print variables and passing to Print*
-func toValue(val *big.Int) interface{} {
-	// Let's assume a string on right padded zero's
-	b := val.Bytes()
-	if b[0] != 0 && b[len(b)-1] == 0x0 && b[len(b)-2] == 0x0 {
-		return string(b)
-	}
-
-	return val
-}
-
 // getData returns a slice from the data based on the start and size and pads
 // up to size with zero's. This function is overflow safe.
 func getData(data []byte, start, size *big.Int) []byte {
@@ -106,14 +47,17 @@ func getData(data []byte, start, size *big.Int) []byte {
 	return common.RightPadBytes(data[s.Uint64():e.Uint64()], int(size.Uint64()))
 }
 
-// useGas attempts to subtract the amount of gas and returns whether it was
-// successful
-func useGas(gas, amount *big.Int) bool {
-	if gas.Cmp(amount) < 0 {
-		return false
+// bigUint64 returns the integer casted to a uint64 and returns whether it
+// overflowed in the process.
+func bigUint64(v *big.Int) (uint64, bool) {
+	return v.Uint64(), v.BitLen() > 64
+}
+
+// toWordSize returns the ceiled word size required for memory expansion.
+func toWordSize(size uint64) uint64 {
+	if size > math.MaxUint64-31 {
+		return math.MaxUint64/32 + 1
 	}
 
-	// Sub the amount of gas from the remaining
-	gas.Sub(gas, amount)
-	return true
+	return (size + 31) / 32
 }