[ETCM-921] Implement EXTCODECOPY

src/main/scala/io/iohk/ethereum/vm/OpCode.scala

@@ -199,6 +199,8 @@ abstract class OpCode(val code: Byte, val delta: Int, val alpha: Int, val constG
 
   protected def availableInContext[W <: WorldStateProxy[W, S], S <: Storage[S]]: ProgramState[W, S] => Boolean = _ =>
     true
+
+  protected def isEip2929Enabled(etcFork: EtcFork): Boolean = etcFork >= EtcForks.Magneto
 }
 
 sealed trait ConstGas { self: OpCode =>
@@ -478,23 +480,36 @@ case object EXTCODESIZE extends OpCode(0x3b, 1, 1, _.G_zero) {
       state.config.feeSchedule.G_extcode
   }
 
-  private def isEip2929Enabled(etcFork: EtcFork): Boolean = etcFork >= EtcForks.Magneto
-
 }
 
-case object EXTCODECOPY extends OpCode(0x3c, 4, 0, _.G_extcode) {
+case object EXTCODECOPY extends OpCode(0x3c, 4, 0, _.G_zero) {
   protected def exec[W <: WorldStateProxy[W, S], S <: Storage[S]](state: ProgramState[W, S]): ProgramState[W, S] = {
     val (Seq(address, memOffset, codeOffset, size), stack1) = state.stack.pop(4)
-    val codeCopy = OpCode.sliceBytes(state.world.getCode(Address(address)), codeOffset, size)
+    val addr = Address(address)
+    val codeCopy = OpCode.sliceBytes(state.world.getCode(addr), codeOffset, size)
     val mem1 = state.memory.store(memOffset, codeCopy)
-    state.withStack(stack1).withMemory(mem1).step()
+    state.withStack(stack1).withMemory(mem1).addAccessedAddress(addr).step()
   }
 
   protected def varGas[W <: WorldStateProxy[W, S], S <: Storage[S]](state: ProgramState[W, S]): BigInt = {
     val (Seq(_, memOffset, _, size), _) = state.stack.pop(4)
     val memCost = state.config.calcMemCost(state.memory.size, memOffset, size)
     val copyCost = state.config.feeSchedule.G_copy * wordsForBytes(size)
-    memCost + copyCost
+
+    val currentBlockNumber = state.env.blockHeader.number
+    val etcFork = state.config.blockchainConfig.etcForkForBlockNumber(currentBlockNumber)
+    val eip2929Enabled = isEip2929Enabled(etcFork)
+
+    val accessCost = if (eip2929Enabled) {
+      val (addr, _) = state.stack.pop
+      if (state.accessedAddresses.contains(Address(addr))) {
+        state.config.feeSchedule.G_warm_storage_read
+      } else {
+        state.config.feeSchedule.G_cold_account_access
+      }
+    } else
+      state.config.feeSchedule.G_extcode
+    memCost + copyCost + accessCost
   }
 }
 

src/test/scala/io/iohk/ethereum/vm/OpCodeGasSpecPostEip2929.scala

@@ -5,6 +5,8 @@ import org.scalatest.matchers.should.Matchers
 import org.scalatestplus.scalacheck.ScalaCheckPropertyChecks
 
 import io.iohk.ethereum.domain.Address
+import io.iohk.ethereum.domain.UInt256
+import io.iohk.ethereum.domain.UInt256._
 import io.iohk.ethereum.vm.Generators._
 
 import Fixtures.blockchainConfig
@@ -47,4 +49,64 @@ class OpCodeGasSpecPostEip2929 extends AnyFunSuite with OpCodeTesting with Match
       stateOut.accessedAddresses should contain(addr)
     }
   }
+
+  test(EXTCODECOPY) { op =>
+    val table = Table[UInt256, Boolean, BigInt](
+      ("size", "accessed", "expectedGas"),
+      (0, false, G_cold_account_access),
+      (0, true, G_warm_storage_read),
+      (1, false, G_cold_account_access + G_copy * 1),
+      (1, true, G_warm_storage_read + G_copy * 1),
+      (32, false, G_cold_account_access + G_copy * 1),
+      (32, true, G_warm_storage_read + G_copy * 1),
+      (33, false, G_cold_account_access + G_copy * 2),
+      (33, true, G_warm_storage_read + G_copy * 2),
+      (Two ** 16, false, G_cold_account_access + G_copy * 2048),
+      (Two ** 16, true, G_warm_storage_read + G_copy * 2048),
+      (Two ** 16 + 1, false, G_cold_account_access + G_copy * 2049),
+      (Two ** 16 + 1, true, G_warm_storage_read + G_copy * 2049)
+    )
+
+    forAll(table) { (size, accessed, expectedGas) =>
+      val initState = getProgramStateGen(
+        evmConfig = config,
+        blockNumberGen = getUInt256Gen(Fixtures.MagnetoBlockNumber)
+      ).sample.get
+      // Pick an address (small, so it fits into memory) that is not on the precompiles list
+      val addr = getUInt256Gen(max = 1000).map(Address(_)).retryUntil(!initState.accessedAddresses.contains(_)).sample.get
+      val stackIn = Stack.empty().push(Seq(size, Zero, Zero, addr.toUInt256))
+      val memIn = Memory.empty.store(addr.toUInt256, Array.fill[Byte](size.toInt)(-1))
+      val stateIn = initState.withStack(stackIn).withMemory(memIn).copy(gas = expectedGas)
+
+      val stateOut = if (accessed) op.execute(stateIn.addAccessedAddress(addr)) else op.execute(stateIn)
+
+      verifyGas(expectedGas, stateIn, stateOut, allowOOG = false)
+      stateOut.accessedAddresses should contain(addr)
+    }
+
+    val maxGas = 2 * (G_cold_account_access + G_copy * 8)
+    val stateGen = getProgramStateGen(
+      evmConfig = config,
+      blockNumberGen = getUInt256Gen(Fixtures.MagnetoBlockNumber),
+      stackGen = getStackGen(elems = 4, maxUInt = UInt256(256)),
+      gasGen = getBigIntGen(max = maxGas),
+      memGen = getMemoryGen(256)
+    )
+
+    forAll(stateGen) { stateIn =>
+      val stateOut = op.execute(stateIn)
+
+      val (Seq(address, offset, _, size), _) = stateIn.stack.pop(4)
+      val addr = Address(address)
+      val memCost = config.calcMemCost(stateIn.memory.size, offset, size)
+      val copyCost = G_copy * wordsForBytes(size)
+      val expectedGas =
+        if (stateIn.accessedAddresses.contains(addr))
+          G_warm_storage_read + memCost + copyCost
+        else G_cold_account_access + memCost + copyCost
+
+      verifyGas(expectedGas, stateIn, stateOut)
+    }
+  }
+
 }