From f00223b5cc99a8f3f1b6a15658d8c854c177932a Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Fri, 4 Sep 2026 20:25:14 +0200
Subject: x86_64/cpu: handle #DF inside the arch code

A double fault is a very x86-64 specific type of exception and not
recoverable in a generalized way. Thus we should handle it internally,
with handling currently being triggering a panic, and not forward it to
the architecture-independent kernel layer.
---
 arch/x86_64/arch/cpu/interrupts.cpp | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

(limited to 'arch')

diff --git a/arch/x86_64/arch/cpu/interrupts.cpp b/arch/x86_64/arch/cpu/interrupts.cpp
index cf225a90..94806621 100644
--- a/arch/x86_64/arch/cpu/interrupts.cpp
+++ b/arch/x86_64/arch/cpu/interrupts.cpp
@@ -6,6 +6,7 @@
 #include <kapi/cpu.hpp>
 #include <kapi/interrupts.hpp>
 #include <kapi/memory.hpp>
+#include <kapi/system.hpp>
 
 #include <kstd/print.hpp>
 
@@ -124,6 +125,12 @@ namespace arch::cpu
       }
       pic_master_control_port::write(pic_end_of_interrupt);
     }
+
+    auto handle_double_fault(interrupt_frame * frame) -> void
+    {
+      kapi::system::panic("[ARCH:CPU] Double fault! Possible kernel stack corruption! rsp was {}",
+                          frame->cpu_saved.rsp);
+    }
   }  // namespace
 
   extern "C"
@@ -134,7 +141,11 @@ namespace arch::cpu
     {
       auto [number, code] = frame->interrupt;
 
-      if (number < number_of_exception_vectors)
+      if (number == static_cast<std::uint64_t>(exception::double_fault))
+      {
+        handle_double_fault(frame);
+      }
+      else if (number < number_of_exception_vectors)
       {
         if (!dispatch_exception(frame))
         {
-- 
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