1 files changed, 42 insertions, 0 deletions
diff --git a/UefiCpuPkg/Library/SmmRelocationLib/Ia32/Semaphore.c b/UefiCpuPkg/Library/SmmRelocationLib/Ia32/Semaphore.c
new file mode 100644
index 0000000000..ba329d6ba2
--- /dev/null
+++ b/UefiCpuPkg/Library/SmmRelocationLib/Ia32/Semaphore.c
@@ -0,0 +1,42 @@
+/** @file
+  Semaphore mechanism to indicate to the BSP that an AP has exited SMM
+  after SMBASE relocation.
+
+  Copyright (c) 2024, Intel Corporation. All rights reserved.<BR>
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include "InternalSmmRelocationLib.h"
+
+UINTN             mSmmRelocationOriginalAddress;
+volatile BOOLEAN  *mRebasedFlag;
+
+/**
+  Hook return address of SMM Save State so that semaphore code
+  can be executed immediately after AP exits SMM to indicate to
+  the BSP that an AP has exited SMM after SMBASE relocation.
+
+  @param[in] CpuIndex     The processor index.
+  @param[in] RebasedFlag  A pointer to a flag that is set to TRUE
+                          immediately after AP exits SMM.
+
+**/
+VOID
+SemaphoreHook (
+  IN UINTN             CpuIndex,
+  IN volatile BOOLEAN  *RebasedFlag
+  )
+{
+  SMRAM_SAVE_STATE_MAP  *CpuState;
+
+  mRebasedFlag = RebasedFlag;
+
+  CpuState                      = (SMRAM_SAVE_STATE_MAP *)(UINTN)(SMM_DEFAULT_SMBASE + SMRAM_SAVE_STATE_MAP_OFFSET);
+  mSmmRelocationOriginalAddress = (UINTN)HookReturnFromSmm (
+                                           CpuIndex,
+                                           CpuState,
+                                           (UINT64)(UINTN)&SmmRelocationSemaphoreComplete,
+                                           (UINT64)(UINTN)&SmmRelocationSemaphoreComplete
+                                           );
+}