From 6e31eb17fef4a033de4291e3f70644be3311491c Mon Sep 17 00:00:00 2001
From: dbanks12 <david@aztecprotocol.com>
Date: Wed, 27 Nov 2024 20:28:40 +0000
Subject: [PATCH] feat_exceptional halts_ in AVM (like div/0) consume all
 remaining allocated gas

---
 .../simulator/src/avm/avm_simulator.test.ts   | 20 +++++++++++++++++--
 .../simulator/src/avm/avm_simulator.ts        |  6 ++++--
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/yarn-project/simulator/src/avm/avm_simulator.test.ts b/yarn-project/simulator/src/avm/avm_simulator.test.ts
index 06811af15577..b1dd154c035e 100644
--- a/yarn-project/simulator/src/avm/avm_simulator.test.ts
+++ b/yarn-project/simulator/src/avm/avm_simulator.test.ts
@@ -58,6 +58,7 @@ import {
   SStore,
   SendL2ToL1Message,
   Set,
+  Div,
 } from './opcodes/index.js';
 import { encodeToBytecode } from './serialization/bytecode_serialization.js';
 import { Opcode } from './serialization/instruction_serialization.js';
@@ -111,8 +112,23 @@ describe('AVM simulator: injected bytecode', () => {
     expect(results.reverted).toBe(true);
     expect(results.output).toEqual([]);
     expect(results.revertReason?.message).toEqual('Not enough L2GAS gas left');
-    expect(context.machineState.l2GasLeft).toEqual(0);
-    expect(context.machineState.daGasLeft).toEqual(0);
+    expect(results.gasLeft.l2Gas).toEqual(0);
+    expect(results.gasLeft.daGas).toEqual(0);
+  });
+
+  it('An exceptional halt should consume all allocated gas', async () => {
+    const context = initContext();
+
+    // should halt with tag mismatch
+    const badBytecode = encodeToBytecode([
+      new Div(/*indirect=*/ 0, /*aOffset=*/ 0, /*bOffset=*/ 0, /*dstOffset=*/ 0).as(Opcode.DIV_8, Div.wireFormat8),
+    ]);
+    const results = await new AvmSimulator(context).executeBytecode(markBytecodeAsAvm(badBytecode));
+    expect(results.reverted).toBe(true);
+    expect(results.output).toEqual([]);
+    expect(results.revertReason?.message).toMatch(/Tag mismatch/);
+    expect(results.gasLeft.l2Gas).toEqual(0);
+    expect(results.gasLeft.daGas).toEqual(0);
   });
 });
 
diff --git a/yarn-project/simulator/src/avm/avm_simulator.ts b/yarn-project/simulator/src/avm/avm_simulator.ts
index 643fae72da0c..b392602e7e54 100644
--- a/yarn-project/simulator/src/avm/avm_simulator.ts
+++ b/yarn-project/simulator/src/avm/avm_simulator.ts
@@ -109,7 +109,7 @@ export class AvmSimulator {
       return new AvmContractCallResult(
         /*reverted=*/ true,
         /*output=*/ [],
-        /*gasLeft=*/ { l2Gas: 0, daGas: 0 },
+        /*gasLeft=*/ { l2Gas: 0, daGas: 0 }, // consumes all allocated gas
         revertReason,
       );
     }
@@ -190,8 +190,10 @@ export class AvmSimulator {
       }
 
       const revertReason = revertReasonFromExceptionalHalt(err, this.context);
+      // Exceptional halts consume all allocated gas
+      const noGasLeft = { l2Gas: 0, daGas: 0, };
       // Note: "exceptional halts" cannot return data, hence [].
-      const results = new AvmContractCallResult(/*reverted=*/ true, /*output=*/ [], machineState.gasLeft, revertReason);
+      const results = new AvmContractCallResult(/*reverted=*/ true, /*output=*/ [], noGasLeft, revertReason);
       this.log.debug(`Context execution results: ${results.toString()}`);
 
       this.tallyPrintFunction();