From 7e66630c1b2a4889542f04060ade3967e0aa631d Mon Sep 17 00:00:00 2001
From: Aiken Harris <harraiken91@gmail.com>
Date: Thu, 6 Aug 2026 16:03:56 +0200
Subject: [PATCH] Add guarded region support

---
 xtoskrnl/includes/ke/kthread.hh |  4 ++
 xtoskrnl/ke/kthread.cc          | 87 +++++++++++++++++++++++++++++++++
 2 files changed, 91 insertions(+)

diff --git a/xtoskrnl/includes/ke/kthread.hh b/xtoskrnl/includes/ke/kthread.hh
index 2774a3ebb..2e291ab49 100644
--- a/xtoskrnl/includes/ke/kthread.hh
+++ b/xtoskrnl/includes/ke/kthread.hh
@@ -24,6 +24,8 @@ namespace KE
             STATIC XTAPI VOID AttachThread(IN PKTHREAD Thread);
             STATIC XTFASTCALL VOID EnterCriticalRegion();
             STATIC XTFASTCALL VOID EnterCriticalRegion(IN PKTHREAD Thread);
+            STATIC XTFASTCALL VOID EnterGuardedRegion();
+            STATIC XTFASTCALL VOID EnterGuardedRegion(IN PKTHREAD Thread);
             STATIC XTAPI PETHREAD GetInitialThread(VOID);
             STATIC XTAPI XTSTATUS InitializeIdleThread(IN PKPROCESS IdleProcess,
                                                        IN OUT PKTHREAD IdleThread,
@@ -40,6 +42,8 @@ namespace KE
                                                    IN BOOLEAN AttachToProcess);
             STATIC XTFASTCALL VOID LeaveCriticalRegion();
             STATIC XTFASTCALL VOID LeaveCriticalRegion(IN PKTHREAD Thread);
+            STATIC XTFASTCALL VOID LeaveGuardedRegion();
+            STATIC XTFASTCALL VOID LeaveGuardedRegion(IN PKTHREAD Thread);
 
         private:
             STATIC XTAPI VOID HandleSystemThreadExit(VOID);
diff --git a/xtoskrnl/ke/kthread.cc b/xtoskrnl/ke/kthread.cc
index d8e4d824c..f9de62e13 100644
--- a/xtoskrnl/ke/kthread.cc
+++ b/xtoskrnl/ke/kthread.cc
@@ -111,6 +111,42 @@ KE::KThread::EnterCriticalRegion(IN PKTHREAD Thread)
     AR::CpuFunctions::ReadWriteBarrier();
 }
 
+/**
+ * Disables the delivery of special APCs for the current thread.
+ *
+ * @return This routine does not return any value.
+ *
+ * @since XT 1.0
+ */
+XTFASTCALL
+VOID
+KE::KThread::EnterGuardedRegion()
+{
+    /* Prevent the thread from being preempted by an APC */
+    EnterGuardedRegion(KE::Processor::GetCurrentThread());
+}
+
+/**
+ * Disables the delivery of special APCs for the specified thread.
+ *
+ * @param Thread
+ *        Supplies a pointer to the thread object whose APC delivery is to be disabled.
+ *
+ * @return This routine does not return any value.
+ *
+ * @since XT 1.0
+ */
+XTFASTCALL
+VOID
+KE::KThread::EnterGuardedRegion(IN PKTHREAD Thread)
+{
+    /* Disable Special APCs */
+    Thread->SpecialApcDisable--;
+
+    /* Prevent the compiler from reordering code */
+    AR::CpuFunctions::ReadWriteBarrier();
+}
+
 /**
  * Retrieves a pointer to the system's initial executive thread object.
  *
@@ -437,6 +473,57 @@ KE::KThread::LeaveCriticalRegion(IN PKTHREAD Thread)
     }
 }
 
+/**
+ * Re-enables the delivery of special APCs for the current thread.
+ *
+ * @return This routine does not return any value.
+ *
+ * @since XT 1.0
+ */
+XTFASTCALL
+VOID
+KE::KThread::LeaveGuardedRegion()
+{
+    /* Allow APCs to preempt the thread */
+    LeaveGuardedRegion(KE::Processor::GetCurrentThread());
+}
+
+
+/**
+ * Re-enables the delivery of special APCs for the specified thread.
+ *
+ * @param Thread
+ *        Supplies a pointer to the thread object whose APC delivery is to be re-enabled.
+ *
+ * @return This routine does not return any value.
+ *
+ * @since XT 1.0
+ */
+XTFASTCALL
+VOID
+KE::KThread::LeaveGuardedRegion(IN PKTHREAD Thread)
+{
+    /* Ensure the compiler does not reorder code */
+    AR::CpuFunctions::ReadWriteBarrier();
+
+    /* Re-enable APC delivery */
+    Thread->SpecialApcDisable++;
+
+    /* Check if APC delivery is enabled */
+    if(!Thread->SpecialApcDisable)
+    {
+        /* Memory barrier */
+        AR::CpuFunctions::MemoryBarrier();
+
+        /* Check for any pending kernel APCs */
+        if(!RTL::LinkedList::ListEmpty(&Thread->ApcState.ApcListHead[KernelMode]))
+        {
+            /* Initiate delivery of the pending APCs */
+            KE::Apc::CheckApcDelivery();
+        }
+    }
+}
+
 /**
  * Suspend APC-built thread NOP routine. It takes no actions.
  *