From fddded8d204374febcba210b8e2e325973f973b2 Mon Sep 17 00:00:00 2001
From: kalaposfos13 <153381648+kalaposfos13@users.noreply.github.com>
Date: Wed, 16 Jul 2025 17:06:58 +0200
Subject: [PATCH] Add an unreachable on hitting ud2 instead of getting stuck in
 an infinite loop (#3257)

* Add an unreachable on hitting ud2 instead of getting stuck in an infinite loop

* Add [[unlikely]] to get ahead of the inevitable PR review comment
---
 src/core/cpu_patches.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/core/cpu_patches.cpp b/src/core/cpu_patches.cpp
index e4f65cd31..8c0897a48 100644
--- a/src/core/cpu_patches.cpp
+++ b/src/core/cpu_patches.cpp
@@ -753,6 +753,10 @@ static bool PatchesIllegalInstructionHandler(void* context) {
             ZydisDecodedOperand operands[ZYDIS_MAX_OPERAND_COUNT];
             const auto status =
                 Common::Decoder::Instance()->decodeInstruction(instruction, operands, code_address);
+            if (ZYAN_SUCCESS(status) && instruction.mnemonic == ZydisMnemonic::ZYDIS_MNEMONIC_UD2)
+                [[unlikely]] {
+                UNREACHABLE_MSG("ud2 at code address {:#x}", (u64)code_address);
+            }
             LOG_ERROR(Core, "Failed to patch address {:x} -- mnemonic: {}", (u64)code_address,
                       ZYAN_SUCCESS(status) ? ZydisMnemonicGetString(instruction.mnemonic)
                                            : "Failed to decode");