VM: Add option to add custom opcodes

packages/vm/examples/decode-opcodes.ts

@@ -6,7 +6,7 @@ import Common, { Chain, Hardfork } from '@ethereumjs/common'
 import { getOpcodesForHF } from '../src/evm/opcodes'
 
 const common = new Common({ chain: Chain.Mainnet, hardfork: Hardfork.Istanbul })
-const opcodes = getOpcodesForHF(common)
+const opcodes = getOpcodesForHF(common).opcodes
 
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packages/vm/src/evm/interpreter.ts

@@ -5,9 +5,8 @@ import { ERROR, VmError } from '../exceptions'
 import Memory from './memory'
 import Stack from './stack'
 import EEI from './eei'
-import { Opcode, handlers as opHandlers, OpHandler, AsyncOpHandler } from './opcodes'
+import { Opcode, OpHandler, AsyncOpHandler } from './opcodes'
 import * as eof from './opcodes/eof'
-import { dynamicGasHandlers } from './opcodes/gas'
 
 export interface InterpreterOpts {
   pc?: number
@@ -179,7 +178,7 @@ export default class Interpreter {
     const gasLimitClone = this._eei.getGasLeft()
 
     if (opInfo.dynamicGas) {
-      const dynamicGasHandler = dynamicGasHandlers.get(this._runState.opCode)!
+      const dynamicGasHandler = this._vm._dynamicGasHandlers.get(this._runState.opCode)!
       // This function updates the gas BN in-place using `i*` methods
       // It needs the base fee, for correct gas limit calculation for the CALL opcodes
       await dynamicGasHandler(this._runState, gas, this._vm._common)
@@ -214,7 +213,7 @@ export default class Interpreter {
    * Get the handler function for an opcode.
    */
   getOpHandler(opInfo: Opcode): OpHandler {
-    return opHandlers.get(opInfo.code)!
+    return this._vm._handlers.get(opInfo.code)!
   }
 
   /**

packages/vm/src/evm/opcodes/codes.ts

@@ -1,5 +1,8 @@
 import Common from '@ethereumjs/common'
+import { CustomOpcode } from '../types'
 import { getFullname } from './util'
+import { AsyncDynamicGasHandler, dynamicGasHandlers, SyncDynamicGasHandler } from './gas'
+import { handlers, OpHandler } from './functions'
 
 export class Opcode {
   readonly code: number
@@ -293,15 +296,25 @@ function createOpcodes(opcodes: OpcodeEntryFee): OpcodeList {
   return result
 }
 
+type OpcodeContext = {
+  dynamicGasHandlers: Map<number, AsyncDynamicGasHandler | SyncDynamicGasHandler>
+  handlers: Map<number, OpHandler>
+  opcodes: OpcodeList
+}
+
 /**
  * Get suitable opcodes for the required hardfork.
  *
  * @param common {Common} Ethereumjs Common metadata object.
+ * @param customOpcodes List with custom opcodes (see VM `customOpcodes` option description).
  * @returns {OpcodeList} Opcodes dictionary object.
  */
-export function getOpcodesForHF(common: Common): OpcodeList {
+export function getOpcodesForHF(common: Common, customOpcodes?: CustomOpcode[]): OpcodeContext {
   let opcodeBuilder: any = { ...opcodes }
 
+  const handlersCopy = new Map(handlers)
+  const dynamicGasHandlersCopy = new Map(dynamicGasHandlers)
+
   for (let fork = 0; fork < hardforkOpcodes.length; fork++) {
     if (common.gteHardfork(hardforkOpcodes[fork].hardforkName)) {
       opcodeBuilder = { ...opcodeBuilder, ...hardforkOpcodes[fork].opcodes }
@@ -322,5 +335,40 @@ export function getOpcodesForHF(common: Common): OpcodeList {
     opcodeBuilder[key].fee = common.param('gasPrices', opcodeBuilder[key].name.toLowerCase())
   }
 
-  return createOpcodes(opcodeBuilder)
+  if (customOpcodes) {
+    for (const _code of customOpcodes) {
+      const code = <any>_code
+      if (code.logicFunction === undefined) {
+        delete opcodeBuilder[code.opcode]
+        continue
+      }
+
+      // Sanity checks
+      if (code.opcodeName === undefined || code.baseFee === undefined) {
+        throw new Error(
+          `Custom opcode ${code.opcode} does not have the required values: opcodeName and baseFee are required`
+        )
+      }
+      const entry = {
+        [code.opcode]: {
+          name: code.opcodeName,
+          isAsync: true,
+          dynamicGas: code.gasFunction !== undefined,
+          fee: code.baseFee,
+        },
+      }
+      opcodeBuilder = { ...opcodeBuilder, ...entry }
+      if (code.gasFunction) {
+        dynamicGasHandlersCopy.set(code.opcode, code.gasFunction)
+      }
+      // logicFunction is never undefined
+      handlersCopy.set(code.opcode, code.logicFunction)
+    }
+  }
+
+  return {
+    dynamicGasHandlers: dynamicGasHandlersCopy,
+    handlers: handlersCopy,
+    opcodes: createOpcodes(opcodeBuilder),
+  }
 }