From bdd36cdc1a1fb411bc8edc5f8ec81115be99ab48 Mon Sep 17 00:00:00 2001
From: Kun Qin <kuqin@microsoft.com>
Date: Thu, 23 Jul 2026 17:12:02 -0700
Subject: [PATCH] SecurityPkg: Tcg2StandaloneMmArm: Align PP buffer with
 ARM_FFA_ARGS

The misc MM communicate buffer now stores the FF-A direct message
registers in an ARM_FFA_ARGS layout that preserves the native register
indices. The TCG physical presence callback must therefore locate the
TCG_NVS payload at the correct register offset instead of the start of
the communication buffer.

Point LocalTcgNvs at CommBuffer + OFFSET_OF (ARM_FFA_ARGS, Arg4) and
validate the buffer size against sizeof (ARM_FFA_ARGS). Add a
STATIC_ASSERT to guarantee TCG_NVS fits within the register space
available for the direct message payload, and include ArmFfaLib.h for
the ARM_FFA_ARGS definition.

Signed-off-by: Kun Qin <kun.qin@microsoft.com>
---
 SecurityPkg/Tcg/Tcg2StandaloneMmArm/Tcg2StandaloneMmArm.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/SecurityPkg/Tcg/Tcg2StandaloneMmArm/Tcg2StandaloneMmArm.c b/SecurityPkg/Tcg/Tcg2StandaloneMmArm/Tcg2StandaloneMmArm.c
index aed3f6a7eb..7651edb70b 100644
--- a/SecurityPkg/Tcg/Tcg2StandaloneMmArm/Tcg2StandaloneMmArm.c
+++ b/SecurityPkg/Tcg/Tcg2StandaloneMmArm/Tcg2StandaloneMmArm.c
@@ -18,12 +18,15 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
 #include <PiMm.h>
 #include <IndustryStandard/TcgPhysicalPresence.h>
 #include <Guid/TpmNvsMm.h>
+#include <Library/ArmFfaLib.h>
 #include <Library/DebugLib.h>
 #include <Library/BaseMemoryLib.h>
 #include <Library/MmServicesTableLib.h>
 #include <Library/StandaloneMmMemLib.h>
 #include <Library/Tcg2PhysicalPresenceLib.h>
 
+STATIC_ASSERT (sizeof (TCG_NVS) <= (sizeof (ARM_FFA_ARGS) - OFFSET_OF (ARM_FFA_ARGS, Arg4)), "TCG_NVS size is larger than direct message buffer size");
+
 /**
   This function checks if the required instance is a supported TPM 2.0 instance.
   It currently supports two instances: dTPM and FFA.
@@ -97,7 +100,7 @@ PhysicalPresenceCallback (
     return EFI_INVALID_PARAMETER;
   }
 
-  if (*CommBufferSize < sizeof (TCG_NVS)) {
+  if (*CommBufferSize < sizeof (ARM_FFA_ARGS)) {
     return EFI_INVALID_PARAMETER;
   }
 
@@ -107,7 +110,7 @@ PhysicalPresenceCallback (
   }
 
   // Enough complaints, now get to work...
-  LocalTcgNvs = (TCG_NVS *)CommBuffer;
+  LocalTcgNvs = (TCG_NVS *)((UINT8 *)CommBuffer + OFFSET_OF (ARM_FFA_ARGS, Arg4));
 
   if (LocalTcgNvs->PhysicalPresence.Parameter == TCG_ACPI_FUNCTION_RETURN_REQUEST_RESPONSE_TO_OS) {
     LocalTcgNvs->PhysicalPresence.ReturnCode = Tcg2PhysicalPresenceLibReturnOperationResponseToOsFunction (