EIP-4399 implementation of nim-vm

what's new:
- `RANDOM` OPCODE
- `random` field of BlockHeader(previously `mixDigest`)
- `PostMerge` temporary name

nimbus/forks.nim

@@ -18,3 +18,6 @@ type
     FkIstanbul       = "Istanbul"
     FkBerlin         = "Berlin"
     FkLondon         = "London"
+    # TODO: PostMerge is a temporary name
+    # until we have an official name
+    FkPostMerge      = "PostMerge"

nimbus/p2p/executor/calculate_reward.nim

@@ -24,6 +24,7 @@ const
   eth5 = 5.eth
   eth3 = 3.eth
   eth2 = 2.eth
+  eth0 = 0.u256
 
   # Note than the `blockRewards` were previously exported but nowhere
   # used otherwise.
@@ -37,7 +38,8 @@ const
     eth2, # FkPetersburg
     eth2, # FkIstanbul
     eth2, # FkBerlin
-    eth2  # FkLondon
+    eth2, # FkLondon
+    eth0  # FkPostMerge
   ]
 
 {.push raises: [Defect].}

nimbus/transaction/host_services.nim

@@ -61,17 +61,24 @@ proc setupTxContext(host: TransactionHost) =
   # vmState.gasLimit now unused
   host.txContext.block_gas_limit  = vmState.gasLimit
   # vmState.difficulty now unused
-  host.txContext.block_difficulty = vmState.difficulty.toEvmc
   host.txContext.chain_id         = vmState.chaindb.config.chainId.uint.u256.toEvmc
   host.txContext.block_base_fee   = vmState.baseFee.toEvmc
 
   # Most host functions do `flip256` in `evmc_host_glue`, but due to this
   # result being cached, it's better to do `flip256` when filling the cache.
   host.txContext.tx_gas_price     = flip256(host.txContext.tx_gas_price)
-  host.txContext.block_difficulty = flip256(host.txContext.block_difficulty)
   host.txContext.chain_id         = flip256(host.txContext.chain_id)
   host.txContext.block_base_fee   = flip256(host.txContext.block_base_fee)
 
+  # EIP-4399
+  # Transfer block randomness to difficulty OPCODE
+  let difficulty = vmState.difficulty.toEvmc
+  if difficulty.isZero:
+    # no flipping, because hash is a 32 bytes array
+    host.txContext.block_difficulty = vmState.random.toEvmc
+  else:
+    host.txContext.block_difficulty = flip256(difficulty)
+
   host.cachedTxContext = true
 
 const use_evmc_glue = defined(evmc_enabled)

nimbus/transaction/host_types.nim

@@ -94,6 +94,9 @@ template isCreate*(kind: EvmcCallKind): bool =
 template isStatic*(msg: EvmcMessage): bool =
   EVMC_STATIC in msg.flags
 
+template isZero*(n: evmc_bytes32): bool =
+  n == default(evmc_bytes32)
+
 # Nim quirks: Exporting `evmc_status_code` (etc) are needed to access the enum
 # values, even though alias `EnumStatusCode` is already exported.  Exporting
 # `evmc_flags` won't export the flags, `evmc_flag_bit_shifts` must be used.

nimbus/utils/tx_pool/tx_chain.nim

@@ -78,7 +78,11 @@ proc resetTxEnv(dh: TxChainRef; parent: BlockHeader; fee: Option[UInt256])
     parent    = parent,
     timestamp = getTime().utc.toTime,
     gasLimit  = (if dh.maxMode: dh.limits.maxLimit else: dh.limits.trgLimit),
-    fee       = fee,
+    fee       = fee,    
+    # EIP-4399 extra complexity
+    # TODO: make sure from where or what value
+    # this `random` param should be
+    random    = Hash256(), 
     miner     = dh.miner,
     chainDB   = dh.db)
 

nimbus/vm/computation.nim

@@ -51,6 +51,15 @@ template getDifficulty*(c: Computation): DifficultyInt =
   else:
     c.vmState.difficulty
 
+template getRandom*(c: Computation): Hash256 =
+  when evmc_enabled:
+    # EIP-4399
+    # no flipping because `block_difficulty` in this context
+    # is a 32 bytes array
+    Hash256.fromEvmc c.host.getTxContext().block_difficulty
+  else:
+    c.vmState.random
+
 template getGasLimit*(c: Computation): GasInt =
   when evmc_enabled:
     c.host.getTxContext().block_gas_limit.GasInt

nimbus/vm/evmc_host.nim

@@ -16,7 +16,15 @@ proc hostGetTxContextImpl(ctx: Computation): nimbus_tx_context {.cdecl.} =
   result.block_number = vmstate.blockNumber.truncate(int64)
   result.block_timestamp = vmstate.timestamp.toUnix()
   result.block_gas_limit = int64(vmstate.gasLimit)
-  result.block_difficulty = toEvmc(vmstate.difficulty)
+
+  # EIP-4399
+  # Transfer block randomness to difficulty OPCODE
+  let difficulty = toEvmc(vmstate.difficulty)
+  if difficulty == default(evmc_bytes32): # or difficulty.isZero
+    result.block_difficulty = vmState.random.toEvmc
+  else:
+    result.block_difficulty = difficulty
+
   result.chain_id = toEvmc(vmstate.chaindb.config.chainId.uint.u256)
   result.block_base_fee = toEvmc(vmstate.baseFee)
 

nimbus/vm/interpreter/gas_costs.nim

@@ -761,7 +761,8 @@ const
     FkPetersburg: SpuriousGasFees,
     FkIstanbul: IstanbulGasFees,
     FkBerlin: BerlinGasFees,
-    FkLondon: LondonGasFees
+    FkLondon: LondonGasFees,
+    FkPostMerge: LondonGasFees
   ]
 
 
@@ -773,6 +774,7 @@ gasCosts(FkConstantinople, constantinople, ConstantinopleGasCosts)
 gasCosts(FkIstanbul, istanbul, IstanbulGasCosts)
 gasCosts(FkBerlin, berlin, BerlinGasCosts)
 gasCosts(FkLondon, london, LondonGasCosts)
+gasCosts(FkPostMerge, postMerge, PostMergeGasCosts)
 
 proc forkToSchedule*(fork: Fork): GasCosts =
   if fork < FkHomestead:
@@ -789,8 +791,10 @@ proc forkToSchedule*(fork: Fork): GasCosts =
     IstanbulGasCosts
   elif fork < FkLondon:
     BerlinGasCosts
-  else:
+  elif fork < FkPostMerge:
     LondonGasCosts
+  else:
+    PostMergeGasCosts
 
 const
   ## Precompile costs

nimbus/vm/interpreter/opcode_values.nim

@@ -188,3 +188,7 @@ fill_enum_holes:
       Revert =         0xfd, # Halt execution reverting state changes but returning data and remaining gas.
       Invalid =        0xfe, # Designated invalid instruction.
       SelfDestruct =   0xff  # Halt execution and register account for later deletion.
+
+const
+  # EIP-4399 new opcode
+  Random* = Difficulty

nimbus/vm/interpreter/opcodes_impl.nim

@@ -412,6 +412,11 @@ op difficulty, inline = true:
   ## 0x44, Get the block's difficulty
   push: c.getDifficulty()
 
+op randomEIP4399, inline = true:
+  ## since EIP-4399 0x44 renamed from `DIFFICULTY` to `RANDOM`
+  ## 0x44, Get the block's randomness
+  push: c.getRandom()
+
 op gasLimit, inline = true:
   ## 0x45, Get the block's gas limit
   push: c.getGasLimit()

nimbus/vm/interpreter_dispatch.nim

@@ -249,11 +249,18 @@ let BerlinOpDispatch {.compileTime.}: array[Op, NimNode] = genBerlinJumpTable(Is
 
 proc genLondonJumpTable(ops: array[Op, NimNode]): array[Op, NimNode] {.compileTime.} =
   result = ops
-  # incoming EIP-3198 and EIP-3529
+  # EIP-3198 and EIP-3529
   result[BaseFee] = newIdentNode "baseFee"
 
 let LondonOpDispatch {.compileTime.}: array[Op, NimNode] = genLondonJumpTable(BerlinOpDispatch)
 
+proc genPostMergeJumpTable(ops: array[Op, NimNode]): array[Op, NimNode] {.compileTime.} =
+  result = ops
+  # EIP-4399
+  result[Random] = newIdentNode "randomEIP4399"
+
+let PostMergeOpDispatch {.compileTime.}: array[Op, NimNode] = genPostMergeJumpTable(LondonOpDispatch)
+
 proc opTableToCaseStmt(opTable: array[Op, NimNode], c: NimNode): NimNode =
 
   let instr = quote do: `c`.instr
@@ -345,6 +352,9 @@ macro genBerlinDispatch(c: Computation): untyped =
 macro genLondonDispatch(c: Computation): untyped =
   result = opTableToCaseStmt(LondonOpDispatch, c)
 
+macro genPostMergeDispatch(c: Computation): untyped =
+  result = opTableToCaseStmt(PostMergeOpDispatch, c)
+
 proc frontierVM(c: Computation) =
   genFrontierDispatch(c)
 
@@ -375,6 +385,9 @@ proc berlinVM(c: Computation) {.gcsafe.} =
 proc londonVM(c: Computation) {.gcsafe.} =
   genLondonDispatch(c)
 
+proc postMergeVM(c: Computation) {.gcsafe.} =
+  genPostMergeDispatch(c)
+
 proc selectVM(c: Computation, fork: Fork) {.gcsafe.} =
   # TODO: Optimise getting fork and updating opCodeExec only when necessary
   case fork
@@ -396,8 +409,10 @@ proc selectVM(c: Computation, fork: Fork) {.gcsafe.} =
     c.istanbulVM()
   of FkBerlin:
     c.berlinVM()
-  else:
+  of FkLondon:
     c.londonVM()
+  else:
+    c.postMergeVM()
 
 proc executeOpcodes(c: Computation) =
   let fork = c.fork

nimbus/vm/state.nim

@@ -59,6 +59,7 @@ proc init(
       timestamp:   EthTime;
       gasLimit:    GasInt;
       fee:         Option[Uint256];
+      random:      Hash256;
       miner:       EthAddress;
       chainDB:     BaseChainDB;
       tracer:      TransactionTracer)
@@ -70,6 +71,7 @@ proc init(
   self.timestamp = timestamp
   self.gasLimit = gasLimit
   self.fee = fee
+  self.random = random
   self.chaindb = chainDB
   self.tracer = tracer
   self.logEntries = @[]
@@ -84,6 +86,7 @@ proc init(
       timestamp:   EthTime;
       gasLimit:    GasInt;
       fee:         Option[Uint256];
+      random:      Hash256;
       miner:       EthAddress;
       chainDB:     BaseChainDB;
       tracerFlags: set[TracerFlags])
@@ -96,6 +99,7 @@ proc init(
     timestamp = timestamp,
     gasLimit  = gasLimit,
     fee       = fee,
+    random    = random,
     miner     = miner,
     chainDB   = chainDB,
     tracer    = tracer)
@@ -117,6 +121,7 @@ proc new*(
       timestamp:   EthTime;         ## tx env: time stamp
       gasLimit:    GasInt;          ## tx env: gas limit
       fee:         Option[Uint256]; ## tx env: optional base fee
+      random:      Hash256;          ## tx env: POS block randomness
       miner:       EthAddress;      ## tx env: coinbase(PoW) or signer(PoA)
       chainDB:     BaseChainDB;     ## block chain database
       tracerFlags: set[TracerFlags] = {};
@@ -136,6 +141,7 @@ proc new*(
     timestamp   = timestamp,
     gasLimit    = gasLimit,
     fee         = fee,
+    random      = random,
     miner       = miner,
     chainDB     = chainDB,
     tracerFlags = tracerFlags)
@@ -145,6 +151,7 @@ proc reinit*(self:      BaseVMState;     ## Object descriptor
              timestamp: EthTime;         ## tx env: time stamp
              gasLimit:  GasInt;          ## tx env: gas limit
              fee:       Option[Uint256]; ## tx env: optional base fee
+             random:    Hash256;         ## tx env: POS block randomness
              miner:     EthAddress;      ## tx env: coinbase(PoW) or signer(PoA)
              pruneTrie: bool = true): bool
     {.gcsafe, raises: [Defect,CatchableError].} =
@@ -169,6 +176,7 @@ proc reinit*(self:      BaseVMState;     ## Object descriptor
       timestamp   = timestamp,
       gasLimit    = gasLimit,
       fee         = fee,
+      random      = random,
       miner       = miner,
       chainDB     = db,
       tracer      = tracer)
@@ -191,6 +199,7 @@ proc reinit*(self:      BaseVMState; ## Object descriptor
     timestamp = header.timestamp,
     gasLimit  = header.gasLimit,
     fee       = header.fee,
+    random    = header.random,
     miner     = self.chainDB.getMinerAddress(header),
     pruneTrie = pruneTrie)
 
@@ -227,6 +236,7 @@ proc init*(
             header.timestamp,
             header.gasLimit,
             header.fee,
+            header.random,
             chainDB.getMinerAddress(header),
             chainDB,
             tracerFlags)

nimbus/vm/types.nim

@@ -38,6 +38,7 @@ type
     timestamp*     : EthTime
     gasLimit*      : GasInt
     fee*           : Option[Uint256]
+    random*        : Hash256
     name*          : string
     flags*         : set[VMFlag]
     tracer*        : TransactionTracer