StandaloneMmPkg/Drivers/MmCommunicationNotifyDxe/MmCommunicationNotifyDxe.c

/** @file
  MmCommunicationNotifyDxe driver creates the notifications of
  some protocols and event.

  Copyright (c) 2025, Intel Corporation. All rights reserved.<BR>
  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include "MmCommunicationNotifyDxe.h"

//
// PI 1.7 MM Communication Protocol 2 instance
//
EFI_MM_COMMUNICATION2_PROTOCOL  *mMmCommunication2;
MM_COMM_BUFFER                  mMmCommonBuffer;
EFI_SMM_ACCESS2_PROTOCOL        *mSmmAccess;
BOOLEAN                         mSmmLocked = FALSE;
BOOLEAN                         mEndOfDxe  = FALSE;

//
// Table of Protocol notification and GUIDed Event notifications that the Standalone Mm requires
//
MM_EVENT_NOTIFICATION  mMmEvents[] = {
  //
  // Declare protocol notification on DxeMmReadyToLock protocols.  When this notification is established,
  // the associated event is immediately signalled, so the notification function will be executed and the
  // DXE Mm Ready To Lock Protocol will be found if it is already in the handle database.
  //
  { ProtocolNotify, TRUE,  &gEfiDxeMmReadyToLockProtocolGuid, MmReadyToLockEventNotify, &gEfiDxeMmReadyToLockProtocolGuid, NULL },
  //
  // Declare event notification on Ready To Boot Event Group.  This is an extra event notification that is
  // used to make sure SMRAM is locked before any boot options are processed.
  //
  { EventNotify,    TRUE,  &gEfiEventReadyToBootGuid,         MmReadyToLockEventNotify, &gEfiEventReadyToBootGuid,         NULL },
  //
  // Declare event notification on Ready To Boot Event Group.  This is used to inform the MM Core
  // to notify MM driver that system enter ready to boot.
  //
  { EventNotify,    FALSE, &gEfiEventReadyToBootGuid,         MmGuidedEventNotify,      &gEfiEventReadyToBootGuid,         NULL },
  //
  // Declare event notification on EndOfDxe event.  When this notification is established,
  // the associated event is immediately signalled, so the notification function will be executed and the
  // End Of Dxe Protocol will be found if it is already in the handle database.
  //
  { EventNotify,    TRUE,  &gEfiEndOfDxeEventGroupGuid,       MmGuidedEventNotify,      &gEfiEndOfDxeEventGroupGuid,       NULL },
  //
  // Declare event notification on EndOfDxe event.  This is used to set EndOfDxe event signaled flag.
  //
  { EventNotify,    TRUE,  &gEfiEndOfDxeEventGroupGuid,       MmEndOfDxeEventNotify,    &gEfiEndOfDxeEventGroupGuid,       NULL },
  //
  // Declare event notification on Exit Boot Services Event Group.  This is used to inform the MM Core
  // to notify MM driver that system enter exit boot services.
  //
  { EventNotify,    FALSE, &gEfiEventExitBootServicesGuid,    MmGuidedEventNotify,      &gEfiEventExitBootServicesGuid,    NULL },
  //
  // Terminate the table of event notifications
  //
  { EndNotify,      FALSE, NULL,                              NULL,                     NULL,                              NULL }
};

/**
  Event notification that is fired when GUIDed Event Group is signaled.

  @param  Event                 The Event that is being processed, not used.
  @param  Context               Event Context, not used.

**/
VOID
EFIAPI
MmGuidedEventNotify (
  IN EFI_EVENT  Event,
  IN VOID       *Context
  )
{
  UINTN                      Size;
  EFI_MM_COMMUNICATE_HEADER  *CommunicateHeader;

  CommunicateHeader = (EFI_MM_COMMUNICATE_HEADER *)(UINTN)mMmCommonBuffer.PhysicalStart;

  //
  // Use Guid to initialize EFI_MM_COMMUNICATE_HEADER structure
  //
  CopyGuid (&CommunicateHeader->HeaderGuid, (EFI_GUID *)Context);
  CommunicateHeader->MessageLength = 1;
  CommunicateHeader->Data[0]       = 0;

  //
  // Generate the Software SMI and return the result
  //
  Size = sizeof (EFI_MM_COMMUNICATE_HEADER);
  mMmCommunication2->Communicate (mMmCommunication2, CommunicateHeader, CommunicateHeader, &Size);
}

/**
  Event notification that is fired every time a DxeSmmReadyToLock protocol is added
  or if gEfiEventReadyToBootGuid is signaled.

  @param  Event                 The Event that is being processed, not used.
  @param  Context               Event Context, not used.

**/
VOID
EFIAPI
MmReadyToLockEventNotify (
  IN EFI_EVENT  Event,
  IN VOID       *Context
  )
{
  EFI_STATUS  Status;
  VOID        *Interface;
  UINTN       Index;

  //
  // See if we are already locked
  //
  if (mSmmLocked) {
    return;
  }

  //
  // Make sure this notification is for this handler
  //
  if (CompareGuid ((EFI_GUID *)Context, &gEfiDxeMmReadyToLockProtocolGuid)) {
    Status = gBS->LocateProtocol (&gEfiDxeMmReadyToLockProtocolGuid, NULL, &Interface);
    if (EFI_ERROR (Status)) {
      return;
    }
  } else {
    //
    // If MM is not locked yet and we got here from gEfiEventReadyToBootGuid being
    // signaled, then gEfiDxeMmReadyToLockProtocolGuid was not installed as expected.
    // Print a warning on debug builds.
    //
    DEBUG ((DEBUG_WARN, "DXE Mm Ready To Lock Protocol not installed before Ready To Boot signal\n"));
  }

  if (!mEndOfDxe) {
    DEBUG ((DEBUG_ERROR, "EndOfDxe Event must be signaled before DxeSmmReadyToLock Protocol installation!\n"));
    REPORT_STATUS_CODE (
      EFI_ERROR_CODE | EFI_ERROR_UNRECOVERED,
      (EFI_SOFTWARE_SMM_DRIVER | EFI_SW_EC_ILLEGAL_SOFTWARE_STATE)
      );
    ASSERT (FALSE);
  }

  //
  // Lock the SMRAM (Note: Locking SMRAM may not be supported on all platforms)
  //
  mSmmAccess->Lock (mSmmAccess);

  //
  // Close protocol and event notification events that do not apply after the
  // DXE MM Ready To Lock Protocol has been installed or the Ready To Boot
  // event has been signalled.
  //
  for (Index = 0; mMmEvents[Index].NotifyFunction != NULL; Index++) {
    if (mMmEvents[Index].CloseOnLock) {
      gBS->CloseEvent (mMmEvents[Index].Event);
    }
  }

  //
  // Inform MM Core that the DxeSmmReadyToLock protocol was installed
  //
  MmGuidedEventNotify (Event, (VOID *)&gEfiDxeMmReadyToLockProtocolGuid);

  //
  // Print debug message that the SMRAM window is now locked.
  //
  DEBUG ((DEBUG_INFO, "MmCommunicationNotifyDxe locked SMRAM window\n"));

  //
  // Set flag so this operation will not be performed again
  //
  mSmmLocked = TRUE;
}

/**
  Event notification that is fired when EndOfDxe Event Group is signaled.

  @param  Event                 The Event that is being processed, not used.
  @param  Context               Event Context, not used.

**/
VOID
EFIAPI
MmEndOfDxeEventNotify (
  IN EFI_EVENT  Event,
  IN VOID       *Context
  )
{
  mEndOfDxe = TRUE;
}

/**
  The Entry Point for MmCommunicateNotifyDxe driver.

  @param  ImageHandle    The firmware allocated handle for the EFI image.
  @param  SystemTable    A pointer to the EFI System Table.

  @retval EFI_SUCCESS    The entry point is executed successfully.
  @retval Other          Some error occurred when executing this entry point.

**/
EFI_STATUS
EFIAPI
MmCommunicationNotifyEntryPoint (
  IN EFI_HANDLE        ImageHandle,
  IN EFI_SYSTEM_TABLE  *SystemTable
  )
{
  EFI_STATUS         Status;
  EFI_HOB_GUID_TYPE  *GuidHob;
  MM_COMM_BUFFER     *MmCommonBuffer;
  UINTN              Index;
  VOID               *Registration;

  //
  // Locate gMmCommBufferHobGuid and cache the content
  //
  GuidHob = GetFirstGuidHob (&gMmCommBufferHobGuid);
  ASSERT (GuidHob != NULL);
  MmCommonBuffer = GET_GUID_HOB_DATA (GuidHob);
  CopyMem (&mMmCommonBuffer, MmCommonBuffer, sizeof (MM_COMM_BUFFER));

  //
  // Get SMM Access Protocol
  //
  Status = gBS->LocateProtocol (&gEfiSmmAccess2ProtocolGuid, NULL, (VOID **)&mSmmAccess);
  ASSERT_EFI_ERROR (Status);

  //
  // Get MM Communication Protocol 2 instance
  //
  Status = gBS->LocateProtocol (&gEfiMmCommunication2ProtocolGuid, NULL, (VOID **)&mMmCommunication2);
  ASSERT_EFI_ERROR (Status);

  //
  // Create the set of protocol and event notifications that the Standalone Mm requires
  //
  for (Index = 0; mMmEvents[Index].NotificationType != EndNotify; Index++) {
    if (mMmEvents[Index].NotificationType == ProtocolNotify) {
      mMmEvents[Index].Event = EfiCreateProtocolNotifyEvent (
                                 mMmEvents[Index].Guid,
                                 TPL_CALLBACK,
                                 mMmEvents[Index].NotifyFunction,
                                 mMmEvents[Index].NotifyContext,
                                 &Registration
                                 );
    } else {
      Status = gBS->CreateEventEx (
                      EVT_NOTIFY_SIGNAL,
                      TPL_CALLBACK,
                      mMmEvents[Index].NotifyFunction,
                      mMmEvents[Index].NotifyContext,
                      mMmEvents[Index].Guid,
                      &mMmEvents[Index].Event
                      );
      ASSERT_EFI_ERROR (Status);
    }
  }

  return EFI_SUCCESS;
}