test, cmd/evm, core, core/vm: illegal code hash implementation

This implements a generic approach to enabling soft forks by allowing
anyone to put in hashes of contracts that should not be interacted from.
This will help "The DAO" in their endevour to stop any whithdrawals from
any DAO contract by convincing the mining community to accept their code
hash.

cmd/utils/flags.go

@@ -163,6 +163,10 @@ var (
 	}
 	// Miner settings
 	// TODO: refactor CPU vs GPU mining flags
+	IllegalCodeHashesFlag = cli.StringFlag{
+		Name:  "illegal-code-hashes",
+		Usage: "Comma separated list of code-hashes to ignore any interaction from",
+	}
 	MiningEnabledFlag = cli.BoolFlag{
 		Name:  "mine",
 		Usage: "Enable mining",
@@ -640,6 +644,16 @@ func MakePasswordList(ctx *cli.Context) []string {
 	return lines
 }
 
+// ParseIllegalCodeHashes parses a comma separated list of hashes.
+func ParseIllegalCodeHashes(ctx *cli.Context) map[common.Hash]struct{} {
+	splittedHexHashes := strings.Split(ctx.GlobalString(IllegalCodeHashesFlag.Name), ",")
+	illegalCodeHashes := make(map[common.Hash]struct{})
+	for _, hexHash := range splittedHexHashes {
+		illegalCodeHashes[common.HexToHash(strings.TrimSpace(hexHash))] = struct{}{}
+	}
+	return illegalCodeHashes
+}
+
 // MakeSystemNode sets up a local node, configures the services to launch and
 // assembles the P2P protocol stack.
 func MakeSystemNode(name, version string, relconf release.Config, extra []byte, ctx *cli.Context) *node.Node {
@@ -676,6 +690,8 @@ func MakeSystemNode(name, version string, relconf release.Config, extra []byte,
 	}
 	// Configure the Ethereum service
 	accman := MakeAccountManager(ctx)
+	// parse the illegal code hashes and set them to the core package.
+	core.IllegalCodeHashes = ParseIllegalCodeHashes(ctx)
 
 	// initialise new random number generator
 	rand := rand.New(rand.NewSource(time.Now().UnixNano()))