Also, the list maninpulation logics are duplicated in MmiManage () and Unregister(). can you try to avoid it?

From: Liu, Zhiguang <zhiguang.liu@intel.com>
Sent: Monday, March 18, 2024 10:19
To: devel@edk2.groups.io <devel@edk2.groups.io>
Cc: Liu, Zhiguang <zhiguang.liu@intel.com>; Liming Gao <gaoliming@byosoft.com.cn>; Wu, Jiaxin <jiaxin.wu@intel.com>; Ni, Ray <ray.ni@intel.com>; Laszlo Ersek <lersek@redhat.com>; Ard Biesheuvel <ardb+tianocore@kernel.org>; Sami Mujawar <sami.mujawar@arm.com>
Subject: [PATCH 6/6] StandaloneMmPkg: Support to unregister MMI handler in MMI handlers

Unregistering MMI handler will free the MMI_HANDLER. However, the
MmiManage() may be using the link node from MMI_HANDLER for loop if
the unregistering happens in MMI handlers.
To avoid that, the idea is to inform MmiHandlerUnRegister() whether
it's running or not running on the stack of MmiManage(), and to
postpone MMI_HANDLER deletion until after the loop finishes.

Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Jiaxin Wu <jiaxin.wu@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Signed-off-by: Zhiguang Liu <zhiguang.liu@intel.com>
---
 StandaloneMmPkg/Core/Mmi.c | 102 +++++++++++++++++++++++++++++++++++--
 1 file changed, 98 insertions(+), 4 deletions(-)

diff --git a/StandaloneMmPkg/Core/Mmi.c b/StandaloneMmPkg/Core/Mmi.c
index 0de6fd17fc..d9cdd1f1a7 100644
--- a/StandaloneMmPkg/Core/Mmi.c
+++ b/StandaloneMmPkg/Core/Mmi.c
@@ -34,8 +34,14 @@ typedef struct {
   LIST_ENTRY                    Link;        // Link on MMI_ENTRY.MmiHandlers
   EFI_MM_HANDLER_ENTRY_POINT    Handler;     // The mm handler's entry point
   MMI_ENTRY                     *MmiEntry;
+  BOOLEAN                       NeedDeleted; // To delete this MMI_HANDLER later
 } MMI_HANDLER;
 
+//
+// mMmiManageCallingDepth is used to track the depth of recursive calls of MmiManage.
+//
+UINTN  mMmiManageCallingDepth = 0;
+
 LIST_ENTRY  mRootMmiHandlerList = INITIALIZE_LIST_HEAD_VARIABLE (mRootMmiHandlerList);
 LIST_ENTRY  mMmiEntryList       = INITIALIZE_LIST_HEAD_VARIABLE (mMmiEntryList);
 
@@ -126,11 +132,14 @@ MmiManage (
 {
   LIST_ENTRY   *Link;
   LIST_ENTRY   *Head;
+  LIST_ENTRY   *EntryLink;
   MMI_ENTRY    *MmiEntry;
   MMI_HANDLER  *MmiHandler;
   BOOLEAN      SuccessReturn;
+  BOOLEAN      CanReturn;
   EFI_STATUS   Status;
 
+  mMmiManageCallingDepth++;
   Status        = EFI_NOT_FOUND;
   SuccessReturn = FALSE;
   if (HandlerType == NULL) {
@@ -171,7 +180,12 @@ MmiManage (
         // no additional handlers will be processed and EFI_INTERRUPT_PENDING will be returned.
         //
         if (HandlerType != NULL) {
-          return EFI_INTERRUPT_PENDING;
+          //
+          // Won't go to next Handler, and will return with EFI_INTERRUPT_PENDING later
+          //
+          SuccessReturn = FALSE;
+          Status        = EFI_INTERRUPT_PENDING;
+          CanReturn     = TRUE;
         }
 
         break;
@@ -183,7 +197,10 @@ MmiManage (
         // additional handlers will be processed.
         //
         if (HandlerType != NULL) {
-          return EFI_SUCCESS;
+          //
+          // Won't go to next Handler, and return with EFI_SUCCESS
+          //
+          CanReturn = TRUE;
         }
 
         SuccessReturn = TRUE;
@@ -211,12 +228,78 @@ MmiManage (
         ASSERT_EFI_ERROR (Status);
         break;
     }
+
+    if (CanReturn) {
+      break;
+    }
   }
 
   if (SuccessReturn) {
     Status = EFI_SUCCESS;
   }
 
+  ASSERT (mMmiManageCallingDepth > 0);
+  mMmiManageCallingDepth--;
+
+  //
+  // The MmiHandlerUnRegister won't take effect inside MmiManage.
+  // Before returned from MmiManage, delete the MmiHandler which is
+  // marked as NeedDeleted.
+  // Note that MmiManage can be called recursively.
+  //
+  if (mMmiManageCallingDepth == 0) {
+    //
+    // Go through all MmiHandler in root Mmi handlers
+    //
+    for ( Link = GetFirstNode (&mRootMmiHandlerList)
+          ; !IsNull (&mRootMmiHandlerList, Link);
+          )
+    {
+      MmiHandler = CR (Link, MMI_HANDLER, Link, MMI_HANDLER_SIGNATURE);
+      Link       = GetNextNode (&mRootMmiHandlerList, Link);
+      if (MmiHandler->NeedDeleted) {
+        //
+        // Remove MmiHandler if the NeedDeleted is set.
+        //
+        RemoveEntryList (&MmiHandler->Link);
+        FreePool (MmiHandler);
+      }
+    }
+
+    //
+    // Go through all MmiHandler in non-root MMI handlers
+    //
+    for ( EntryLink = GetFirstNode (&mMmiEntryList)
+          ; !IsNull (&mMmiEntryList, EntryLink);
+          )
+    {
+      MmiEntry  = CR (EntryLink, MMI_ENTRY, AllEntries, MMI_ENTRY_SIGNATURE);
+      EntryLink = GetNextNode (&mMmiEntryList, EntryLink);
+      for ( Link = GetFirstNode (&MmiEntry->MmiHandlers)
+            ; !IsNull (&MmiEntry->MmiHandlers, Link);
+            )
+      {
+        MmiHandler = CR (Link, MMI_HANDLER, Link, MMI_HANDLER_SIGNATURE);
+        Link       = GetNextNode (&MmiEntry->MmiHandlers, Link);
+        if (MmiHandler->NeedDeleted) {
+          //
+          // Remove MmiHandler if the NeedDeleted is set.
+          //
+          RemoveEntryList (&MmiHandler->Link);
+          FreePool (MmiHandler);
+        }
+      }
+
+      if (IsListEmpty (&MmiEntry->MmiHandlers)) {
+        //
+        // No handler registered for this MmiEntry now, remove the MMI_ENTRY
+        //
+        RemoveEntryList (&MmiEntry->AllEntries);
+        FreePool (MmiEntry);
+      }
+    }
+  }
+
   return Status;
 }
 
@@ -252,8 +335,9 @@ MmiHandlerRegister (
     return EFI_OUT_OF_RESOURCES;
   }
 
-  MmiHandler->Signature = MMI_HANDLER_SIGNATURE;
-  MmiHandler->Handler   = Handler;
+  MmiHandler->Signature   = MMI_HANDLER_SIGNATURE;
+  MmiHandler->Handler     = Handler;
+  MmiHandler->NeedDeleted = FALSE;
 
   if (HandlerType == NULL) {
     //
@@ -311,6 +395,16 @@ MmiHandlerUnRegister (
 
   MmiEntry = MmiHandler->MmiEntry;
 
+  if (mMmiManageCallingDepth > 0) {
+    //
+    // This function is called from MmiManage()
+    // Do not delete or remove MmiHandler or MmiEntry now.
+    // Set the NeedDeleted field in MmiHandler so that MmiManage will delete it later
+    //
+    MmiHandler->NeedDeleted = TRUE;
+    return EFI_SUCCESS;
+  }
+
   RemoveEntryList (&MmiHandler->Link);
   FreePool (MmiHandler);
 
--
2.31.1.windows.1

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