From 51e5582ed8eced3255541905cf0a320c5f6e982a Mon Sep 17 00:00:00 2001
From: Jochem Brouwer <jochembrouwer96@gmail.com>
Date: Fri, 27 May 2022 16:15:47 +0200
Subject: [PATCH] vm/evm: ensure exp dynamic gas calculated in gas.ts not
 functions.ts

---
 packages/vm/src/evm/evm.ts               |  2 +-
 packages/vm/src/evm/opcodes/codes.ts     |  2 +-
 packages/vm/src/evm/opcodes/functions.ts | 12 +-----------
 packages/vm/src/evm/opcodes/gas.ts       | 20 ++++++++++++++++++++
 4 files changed, 23 insertions(+), 13 deletions(-)

diff --git a/packages/vm/src/evm/evm.ts b/packages/vm/src/evm/evm.ts
index c8b0b2f7b6..c0362e44a4 100644
--- a/packages/vm/src/evm/evm.ts
+++ b/packages/vm/src/evm/evm.ts
@@ -165,7 +165,7 @@ export interface ExecResult {
   /**
    * Amount of gas the code used to run
    */
-  gasUsed: bigint
+  gasUsed: bigint //TODO misleading; does not cover upfront cost (does it cover callvalue?)
   /**
    * Return value from the contract
    */
diff --git a/packages/vm/src/evm/opcodes/codes.ts b/packages/vm/src/evm/opcodes/codes.ts
index 01d1c1c498..d1274d244c 100644
--- a/packages/vm/src/evm/opcodes/codes.ts
+++ b/packages/vm/src/evm/opcodes/codes.ts
@@ -57,7 +57,7 @@ const opcodes: OpcodeEntry = {
   0x07: { name: 'SMOD', isAsync: false, dynamicGas: false },
   0x08: { name: 'ADDMOD', isAsync: false, dynamicGas: false },
   0x09: { name: 'MULMOD', isAsync: false, dynamicGas: false },
-  0x0a: { name: 'EXP', isAsync: false, dynamicGas: false },
+  0x0a: { name: 'EXP', isAsync: false, dynamicGas: true },
   0x0b: { name: 'SIGNEXTEND', isAsync: false, dynamicGas: false },
 
   // 0x10 range - bit ops
diff --git a/packages/vm/src/evm/opcodes/functions.ts b/packages/vm/src/evm/opcodes/functions.ts
index 22b775a0ba..1287940834 100644
--- a/packages/vm/src/evm/opcodes/functions.ts
+++ b/packages/vm/src/evm/opcodes/functions.ts
@@ -164,22 +164,12 @@ export const handlers: Map<number, OpHandler> = new Map([
   // 0x0a: EXP
   [
     0x0a,
-    function (runState, common) {
+    function (runState) {
       const [base, exponent] = runState.stack.popN(2)
       if (exponent === BigInt(0)) {
         runState.stack.push(BigInt(1))
         return
       }
-      let byteLength = exponent.toString(2).length / 8
-      if (byteLength > Math.trunc(byteLength)) {
-        byteLength = Math.trunc(byteLength) + 1
-      }
-      if (byteLength < 1 || byteLength > 32) {
-        trap(ERROR.OUT_OF_RANGE)
-      }
-      const gasPrice = common.param('gasPrices', 'expByte')
-      const amount = BigInt(byteLength) * gasPrice
-      runState.interpreter.useGas(amount, 'EXP opcode') // TODO Why is this not in gas.ts??
 
       if (base === BigInt(0)) {
         runState.stack.push(base)
diff --git a/packages/vm/src/evm/opcodes/gas.ts b/packages/vm/src/evm/opcodes/gas.ts
index 0c6c5ea263..5fdb5120e1 100644
--- a/packages/vm/src/evm/opcodes/gas.ts
+++ b/packages/vm/src/evm/opcodes/gas.ts
@@ -34,6 +34,26 @@ export interface SyncDynamicGasHandler {
 
 export const dynamicGasHandlers: Map<number, AsyncDynamicGasHandler | SyncDynamicGasHandler> =
   new Map<number, AsyncDynamicGasHandler>([
+    [
+      /* EXP */
+      0x0a,
+      async function (runState, gas, common): Promise<bigint> {
+        const [_base, exponent] = runState.stack.peek(2)
+        if (exponent === BigInt(0)) {
+          return gas
+        }
+        let byteLength = exponent.toString(2).length / 8
+        if (byteLength > Math.trunc(byteLength)) {
+          byteLength = Math.trunc(byteLength) + 1
+        }
+        if (byteLength < 1 || byteLength > 32) {
+          trap(ERROR.OUT_OF_RANGE)
+        }
+        const expPricePerByte = common.param('gasPrices', 'expByte')
+        gas += BigInt(byteLength) * expPricePerByte
+        return gas
+      },
+    ],
     [
       /* SHA3 */
       0x20,