From a0e707d35f49f34cef18316b795ff95e95e97dfb Mon Sep 17 00:00:00 2001
From: Aiken Harris <harraiken91@gmail.com>
Date: Sat, 4 Jul 2026 14:08:05 +0200
Subject: [PATCH] Implement buffer return logic for general lookaside lists

---
 xtoskrnl/ex/laslist.cc          | 70 ++++++++++++++++++++++++++++++++-
 xtoskrnl/includes/ex/laslist.hh |  4 ++
 2 files changed, 73 insertions(+), 1 deletion(-)

diff --git a/xtoskrnl/ex/laslist.cc b/xtoskrnl/ex/laslist.cc
index 22ab895..fe793eb 100644
--- a/xtoskrnl/ex/laslist.cc
+++ b/xtoskrnl/ex/laslist.cc
@@ -79,7 +79,6 @@ EX::LookasideList::AllocateFromLookasideList(IN PPAGED_LOOKASIDE_LIST LookasideL
     return Buffer;
 }
 
-
 /**
  * Allocates a memory block from the specified per-processor lookaside list.
  *
@@ -138,6 +137,75 @@ EX::LookasideList::AllocateFromPerProcessorList(IN NONPAGED_LOOKASIDE_NUMBER Num
     return Entry;
 }
 
+/**
+ * Returns a previously allocated memory block to the specified non-paged lookaside list.
+ *
+ * @param LookasideList
+ *        Supplies a pointer to the non-paged lookaside list.
+ *
+ * @param Entry
+ *        Supplies a pointer to the memory block being freed.
+ *
+ * @return This routine does not return any value.
+ *
+ * @since XT 1.0
+ */
+XTAPI
+VOID
+EX::LookasideList::FreeToLookasideList(IN PNONPAGED_LOOKASIDE_LIST LookasideList,
+                                       IN PVOID Entry)
+{
+    /* Increment the tracking metric */
+    LookasideList->Global.TotalFrees++;
+
+    /* Verify if the lookaside list has reached its maximum capacity threshold */
+    if(RTL::SinglyList::QueryListDepth(&LookasideList->Global.ListHead) >= LookasideList->Global.Depth)
+    {
+        /* The list is full, record a capacity miss */
+        LookasideList->Global.FreeMisses++;
+        (LookasideList->Global.Free)(Entry);
+    }
+    else
+    {
+        /* Push the block onto the lookaside list */
+        RTL::Atomic::PushEntrySingleList(&LookasideList->Global.ListHead, (PSINGLE_LIST_ENTRY)Entry);
+    }
+}
+
+/**
+ * Returns a previously allocated memory block to the specified paged lookaside list.
+ *
+ * @param LookasideList
+ *        Supplies a pointer to the paged lookaside list.
+ *
+ * @param Entry
+ *        Supplies a pointer to the memory block being freed.
+ *
+ * @return This routine does not return any value.
+ *
+ * @since XT 1.0
+ */
+XTAPI
+VOID
+EX::LookasideList::FreeToLookasideList(IN PPAGED_LOOKASIDE_LIST LookasideList,
+                                       IN PVOID Entry)
+{
+    /* Increment the tracking metric */
+    LookasideList->Global.TotalFrees++;
+
+    /* Verify if the lookaside list has reached its maximum capacity threshold */
+    if(RTL::SinglyList::QueryListDepth(&LookasideList->Global.ListHead) >= LookasideList->Global.Depth)
+    {
+        /* The list is full, record a capacity miss */
+        LookasideList->Global.FreeMisses++;
+        (LookasideList->Global.Free)(Entry);
+    }
+    else
+    {
+        /* Push the block onto the lookaside list */
+        RTL::Atomic::PushEntrySingleList(&LookasideList->Global.ListHead, (PSINGLE_LIST_ENTRY)Entry);
+    }
+}
 
 /**
  * Frees a memory block back to the specified per-processor lookaside list.
diff --git a/xtoskrnl/includes/ex/laslist.hh b/xtoskrnl/includes/ex/laslist.hh
index 6f424c6..98688e3 100644
--- a/xtoskrnl/includes/ex/laslist.hh
+++ b/xtoskrnl/includes/ex/laslist.hh
@@ -31,6 +31,10 @@ namespace EX
             STATIC XTAPI PVOID AllocateFromLookasideList(IN PNONPAGED_LOOKASIDE_LIST LookasideList);
             STATIC XTAPI PVOID AllocateFromLookasideList(IN PPAGED_LOOKASIDE_LIST LookasideList);
             STATIC XTAPI PVOID AllocateFromPerProcessorList(IN NONPAGED_LOOKASIDE_NUMBER Number);
+            STATIC XTAPI VOID FreeToLookasideList(IN PNONPAGED_LOOKASIDE_LIST LookasideList,
+                                                  IN PVOID Entry);
+            STATIC XTAPI VOID FreeToLookasideList(IN PPAGED_LOOKASIDE_LIST LookasideList,
+                                                  IN PVOID Entry);
             STATIC XTAPI VOID FreeToPerProcessorList(IN NONPAGED_LOOKASIDE_NUMBER Number,
                                                      IN PVOID Entry);
             STATIC XTAPI VOID InitializeLookasideList(IN OUT PGENERAL_LOOKASIDE LookasideList,