Esempio n. 1
0
/**
  Initialize debug agent.

  This function is used to set up debug enviroment for source level debug
  in SMM code.

  If InitFlag is DEBUG_AGENT_INIT_SMM, it will overirde IDT table entries
  and initialize debug port. It will get debug agent Mailbox from GUIDed HOB,
  it it exists, debug agent wiil copied it into the local Mailbox in SMM space.
  it will overirde IDT table entries and initialize debug port. Context will be
  NULL.
  If InitFlag is DEBUG_AGENT_INIT_ENTER_SMI, debug agent will save Debug
  Registers and get local Mailbox in SMM space. Context will be NULL.
  If InitFlag is DEBUG_AGENT_INIT_EXIT_SMI, debug agent will restore Debug
  Registers. Context will be NULL.

  @param[in] InitFlag     Init flag is used to decide initialize process.
  @param[in] Context      Context needed according to InitFlag.
  @param[in] Function     Continue function called by debug agent library; it was
                          optional.

**/
VOID
EFIAPI
InitializeDebugAgent (
  IN UINT32                InitFlag,
  IN VOID                  *Context, OPTIONAL
  IN DEBUG_AGENT_CONTINUE  Function  OPTIONAL
  )
{
  EFI_STATUS                    Status;
  UINT64                        DebugPortHandle;
  IA32_IDT_GATE_DESCRIPTOR      IdtEntry[33];
  IA32_DESCRIPTOR               IdtDescriptor;
  IA32_DESCRIPTOR               *Ia32Idtr;
  IA32_IDT_ENTRY                *Ia32IdtEntry;
  IA32_DESCRIPTOR               Idtr;
  UINT16                        IdtEntryCount;
  DEBUG_AGENT_MAILBOX           *Mailbox;
  UINT64                        *MailboxLocation;
  UINT32                        DebugTimerFrequency;
  BOOLEAN                       PeriodicMode;
  UINTN                         TimerCycle;

  switch (InitFlag) {
  case DEBUG_AGENT_INIT_SMM:
    //
    // Install configuration table for persisted vector handoff info
    //
    Status = gSmst->SmmInstallConfigurationTable (
                      gSmst,
                      &gEfiVectorHandoffTableGuid,
                      (VOID *) &mVectorHandoffInfoDebugAgent[0],
                      sizeof (EFI_VECTOR_HANDOFF_INFO) * mVectorHandoffInfoCount
                      );
    if (EFI_ERROR (Status)) {
      DEBUG ((EFI_D_ERROR, "DebugAgent: Cannot install configuration table for persisted vector handoff info!\n"));
      CpuDeadLoop ();
    }
    //
    // Check if Debug Agent initialized in DXE phase
    //
    Status = EfiGetSystemConfigurationTable (&gEfiDebugAgentGuid, (VOID **) &Mailbox);
    if (Status == EFI_SUCCESS && Mailbox != NULL) {
      VerifyMailboxChecksum (Mailbox);
      mMailboxPointer = Mailbox;
      break;
    }
    //
    // Check if Debug Agent initialized in SEC/PEI phase
    //
    Mailbox = GetMailboxFromHob (); 
    if (Mailbox != NULL) {
      mMailboxPointer = Mailbox;
      break;
    }
    //
    // Debug Agent was not initialized before, use the local mailbox.
    //
    ZeroMem (&mLocalMailbox, sizeof (DEBUG_AGENT_MAILBOX));
    Mailbox = &mLocalMailbox;
    //
    // Save original IDT entries
    //
    AsmReadIdtr (&IdtDescriptor);      
    CopyMem (&IdtEntry, (VOID *)IdtDescriptor.Base, 33 * sizeof(IA32_IDT_GATE_DESCRIPTOR));
    //
    // Initialized Debug Agent
    //
    InitializeDebugIdt ();
    //
    // Initialize Debug Timer hardware and save its frequency
    //
    InitializeDebugTimer (&DebugTimerFrequency, TRUE);
    UpdateMailboxContent (Mailbox, DEBUG_MAILBOX_DEBUG_TIMER_FREQUENCY, DebugTimerFrequency);

    DebugPortHandle = (UINT64) (UINTN)DebugPortInitialize ((DEBUG_PORT_HANDLE) (UINTN)Mailbox->DebugPortHandle, NULL);
    UpdateMailboxContent (Mailbox, DEBUG_MAILBOX_DEBUG_PORT_HANDLE_INDEX, DebugPortHandle);
    mMailboxPointer = Mailbox;
    //
    // Trigger one software interrupt to inform HOST
    //
    TriggerSoftInterrupt (SYSTEM_RESET_SIGNATURE);

    SetDebugFlag (DEBUG_AGENT_FLAG_MEMORY_READY, 1);
    //
    // Memory has been ready
    //
    if (IsHostAttached ()) {
      //
      // Trigger one software interrupt to inform HOST
      //
      TriggerSoftInterrupt (MEMORY_READY_SIGNATURE);
    }
    //
    // Find and report PE/COFF image info to HOST
    //  
    FindAndReportModuleImageInfo (SIZE_4KB);
    //
    // Restore saved IDT entries
    //     
    CopyMem ((VOID *)IdtDescriptor.Base, &IdtEntry, 33 * sizeof(IA32_IDT_GATE_DESCRIPTOR));

    break;

  case DEBUG_AGENT_INIT_ENTER_SMI:
    SaveDebugRegister ();
    if (!mSmmDebugIdtInitFlag) {
      //
      // We only need to initialize Debug IDT table at first SMI entry
      // after SMM relocation.
      //
      InitializeDebugIdt ();
      mSmmDebugIdtInitFlag = TRUE;
    }
    //
    // Check if CPU APIC Timer is working, otherwise initialize it.
    //
    InitializeLocalApicSoftwareEnable (TRUE);
    GetApicTimerState (NULL, &PeriodicMode, NULL);
    TimerCycle = GetApicTimerInitCount ();
    if (!PeriodicMode || TimerCycle == 0) {
      InitializeDebugTimer (NULL, FALSE);
    }
    Mailbox = GetMailboxPointer ();
    if (GetDebugFlag (DEBUG_AGENT_FLAG_AGENT_IN_PROGRESS) == 1) {
      //
      // If Debug Agent has been communicaton state with HOST, we need skip
      // any break points set in SMM, set Skip Breakpoint flag
      //
      mSkipBreakpoint = TRUE;
    }
    if (GetDebugFlag (DEBUG_AGENT_FLAG_BREAK_ON_NEXT_SMI) == 1) {
      if (mSkipBreakpoint) {
        //
        // Print warning message if ignore smm entry break
        //
        DebugPortWriteBuffer ((DEBUG_PORT_HANDLE) (UINTN)Mailbox->DebugPortHandle,
                               (UINT8 *)mWarningMsgIgnoreSmmEntryBreak,
                               AsciiStrLen (mWarningMsgIgnoreSmmEntryBreak)
                               );
      } else {
        //
        // If SMM entry break is set, SMM code will be break at here.
        //
        CpuBreakpoint ();
      }
    }
    break;

  case DEBUG_AGENT_INIT_EXIT_SMI:
    Mailbox = GetMailboxPointer ();
    //
    // Clear Skip Breakpoint flag
    //
    mSkipBreakpoint = FALSE;
    RestoreDebugRegister ();
    break;

  case DEBUG_AGENT_INIT_THUNK_PEI_IA32TOX64:
    if (Context == NULL) {
      DEBUG ((EFI_D_ERROR, "DebugAgent: Input parameter Context cannot be NULL!\n"));
      CpuDeadLoop ();
    } else {
      Ia32Idtr =  (IA32_DESCRIPTOR *) Context;
      Ia32IdtEntry = (IA32_IDT_ENTRY *)(Ia32Idtr->Base);
      MailboxLocation = (UINT64 *) (UINTN) (Ia32IdtEntry[DEBUG_MAILBOX_VECTOR].Bits.OffsetLow + 
                                  (UINT32) (Ia32IdtEntry[DEBUG_MAILBOX_VECTOR].Bits.OffsetHigh << 16));
      mMailboxPointer = (DEBUG_AGENT_MAILBOX *)(UINTN)(*MailboxLocation);
      VerifyMailboxChecksum (mMailboxPointer);
      //
      // Get original IDT address and size.
      //
      AsmReadIdtr ((IA32_DESCRIPTOR *) &Idtr);
      IdtEntryCount = (UINT16) ((Idtr.Limit + 1) / sizeof (IA32_IDT_GATE_DESCRIPTOR));
      if (IdtEntryCount < 33) {
        Idtr.Limit = (UINT16) (sizeof (IA32_IDT_GATE_DESCRIPTOR) * 33 - 1);
        Idtr.Base  = (UINTN) &mIdtEntryTable;
        ZeroMem (&mIdtEntryTable, Idtr.Limit + 1);
        AsmWriteIdtr ((IA32_DESCRIPTOR *) &Idtr);
      }

      InitializeDebugIdt ();
      //
      // Initialize Debug Timer hardware and save its frequency
      //
      InitializeDebugTimer (&DebugTimerFrequency, TRUE);
      UpdateMailboxContent (mMailboxPointer, DEBUG_MAILBOX_DEBUG_TIMER_FREQUENCY, DebugTimerFrequency);
      //
      // Enable Debug Timer interrupt and CPU interrupt
      //
      SaveAndSetDebugTimerInterrupt (TRUE);
      EnableInterrupts ();

      FindAndReportModuleImageInfo (SIZE_4KB);
    }
    break;

  default:
    //
    // Only DEBUG_AGENT_INIT_PREMEM_SEC and DEBUG_AGENT_INIT_POSTMEM_SEC are allowed for this 
    // Debug Agent library instance.
    //
    DEBUG ((EFI_D_ERROR, "Debug Agent: The InitFlag value is not allowed!\n"));
    CpuDeadLoop ();
    break;    
  }
}
Esempio n. 2
0
/**
  Initialize debug agent.

  This function is used to set up debug environment for SEC and PEI phase.

  If InitFlag is DEBUG_AGENT_INIT_PREMEM_SEC, it will overirde IDT table entries
  and initialize debug port. It will enable interrupt to support break-in feature.
  It will set up debug agent Mailbox in cache-as-ramfrom. It will be called before
  physical memory is ready.
  If InitFlag is DEBUG_AGENT_INIT_POSTMEM_SEC, debug agent will build one GUIDed
  HOB to copy debug agent Mailbox. It will be called after physical memory is ready.

  This function is used to set up debug environment to support source level debugging.
  If certain Debug Agent Library instance has to save some private data in the stack,
  this function must work on the mode that doesn't return to the caller, then
  the caller needs to wrap up all rest of logic after InitializeDebugAgent() into one
  function and pass it into InitializeDebugAgent(). InitializeDebugAgent() is
  responsible to invoke the passing-in function at the end of InitializeDebugAgent().

  If the parameter Function is not NULL, Debug Agent Library instance will invoke it by
  passing in the Context to be its parameter.

  If Function() is NULL, Debug Agent Library instance will return after setup debug
  environment.

  @param[in] InitFlag     Init flag is used to decide the initialize process.
  @param[in] Context      Context needed according to InitFlag; it was optional.
  @param[in] Function     Continue function called by debug agent library; it was
                          optional.

**/
VOID
EFIAPI
InitializeDebugAgent (
  IN UINT32                InitFlag,
  IN VOID                  *Context, OPTIONAL
  IN DEBUG_AGENT_CONTINUE  Function  OPTIONAL
  )
{
  DEBUG_AGENT_MAILBOX              *Mailbox;
  DEBUG_AGENT_MAILBOX              *NewMailbox;
  DEBUG_AGENT_MAILBOX              MailboxInStack;
  DEBUG_AGENT_PHASE2_CONTEXT       Phase2Context;
  DEBUG_AGENT_CONTEXT_POSTMEM_SEC  *DebugAgentContext;
  EFI_STATUS                       Status;
  IA32_DESCRIPTOR                  *Ia32Idtr;
  IA32_IDT_ENTRY                   *Ia32IdtEntry;
  UINT64                           DebugPortHandle;
  UINT64                           MailboxLocation;
  UINT64                           *MailboxLocationPointer;
  EFI_PHYSICAL_ADDRESS             Address;
  UINT32                           DebugTimerFrequency;
  BOOLEAN                          CpuInterruptState;

  //
  // Disable interrupts and save current interrupt state
  //
  CpuInterruptState = SaveAndDisableInterrupts();

  switch (InitFlag) {

  case DEBUG_AGENT_INIT_PREMEM_SEC:

    InitializeDebugIdt ();

    MailboxLocation = (UINT64)(UINTN)&MailboxInStack;
    Mailbox = &MailboxInStack;
    ZeroMem ((VOID *) Mailbox, sizeof (DEBUG_AGENT_MAILBOX));
    //
    // Get and save debug port handle and set the length of memory block.
    //
    SetLocationSavedMailboxPointerInIdtEntry (&MailboxLocation);
    //
    // Force error message could be printed during the first shakehand between Target/HOST.
    //
    SetDebugFlag (DEBUG_AGENT_FLAG_PRINT_ERROR_LEVEL, DEBUG_AGENT_ERROR);
    //
    // Save init arch type when debug agent initialized
    //
    SetDebugFlag (DEBUG_AGENT_FLAG_INIT_ARCH, DEBUG_ARCH_SYMBOL);
    //
    // Initialize Debug Timer hardware and save its frequency
    //
    InitializeDebugTimer (&DebugTimerFrequency, TRUE);
    UpdateMailboxContent (Mailbox, DEBUG_MAILBOX_DEBUG_TIMER_FREQUENCY, DebugTimerFrequency);

    Phase2Context.InitFlag = InitFlag;
    Phase2Context.Context  = Context;
    Phase2Context.Function = Function;
    DebugPortInitialize ((VOID *) &Phase2Context, InitializeDebugAgentPhase2);
    //
    // If reaches here, it means Debug Port initialization failed.
    //
    DEBUG ((EFI_D_ERROR, "Debug Agent: Debug port initialization failed.\n"));

    break;

  case DEBUG_AGENT_INIT_POSTMEM_SEC:
    Mailbox = GetMailboxPointer ();
    //
    // Memory has been ready
    //
    SetDebugFlag (DEBUG_AGENT_FLAG_MEMORY_READY, 1);
    if (IsHostAttached ()) {
      //
      // Trigger one software interrupt to inform HOST
      //
      TriggerSoftInterrupt (MEMORY_READY_SIGNATURE);
    }
    //
    // Install Vector Handoff Info PPI to persist vectors used by Debug Agent
    //
    Status = PeiServicesInstallPpi (&mVectorHandoffInfoPpiList[0]);
    if (EFI_ERROR (Status)) {
      DEBUG ((EFI_D_ERROR, "DebugAgent: Failed to install Vector Handoff Info PPI!\n"));
      CpuDeadLoop ();
    }
    //
    // Fix up Debug Port handle address and mailbox address
    //
    DebugAgentContext = (DEBUG_AGENT_CONTEXT_POSTMEM_SEC *) Context;
    if (DebugAgentContext != NULL) {
      DebugPortHandle = (UINT64)(UINT32)(Mailbox->DebugPortHandle + DebugAgentContext->StackMigrateOffset);
      UpdateMailboxContent (Mailbox, DEBUG_MAILBOX_DEBUG_PORT_HANDLE_INDEX, DebugPortHandle);
      Mailbox = (DEBUG_AGENT_MAILBOX *) ((UINTN) Mailbox + DebugAgentContext->StackMigrateOffset);
      MailboxLocation = (UINT64)(UINTN)Mailbox;
      //
      // Build mailbox location in HOB and fix-up its address
      //
      MailboxLocationPointer = BuildGuidDataHob (
                                 &gEfiDebugAgentGuid,
                                 &MailboxLocation,
                                 sizeof (UINT64)
                                 );
      MailboxLocationPointer = (UINT64 *) ((UINTN) MailboxLocationPointer + DebugAgentContext->HeapMigrateOffset);
    } else {
      //
      // DebugAgentContext is NULL. Then, Mailbox can directly be copied into memory.
      // Allocate ACPI NVS memory for new Mailbox and Debug Port Handle buffer
      //
      Status = PeiServicesAllocatePages (
                 EfiACPIMemoryNVS,
                 EFI_SIZE_TO_PAGES (sizeof(DEBUG_AGENT_MAILBOX) + PcdGet16(PcdDebugPortHandleBufferSize)),
                 &Address
                 );
      if (EFI_ERROR (Status)) {
        DEBUG ((EFI_D_ERROR, "DebugAgent: Failed to allocate pages!\n"));
        CpuDeadLoop ();
      }
      NewMailbox = (DEBUG_AGENT_MAILBOX *) (UINTN) Address;
      //
      // Copy Mailbox and Debug Port Handle buffer to new location in ACPI NVS memory, because original Mailbox
      // and Debug Port Handle buffer in the allocated pool that may be marked as free by DXE Core after DXE Core
      // reallocates the HOB.
      //
      CopyMem (NewMailbox, Mailbox, sizeof (DEBUG_AGENT_MAILBOX));
      CopyMem (NewMailbox + 1, (VOID *)(UINTN)Mailbox->DebugPortHandle, PcdGet16(PcdDebugPortHandleBufferSize));
      UpdateMailboxContent (NewMailbox, DEBUG_MAILBOX_DEBUG_PORT_HANDLE_INDEX, (UINT64)(UINTN)(NewMailbox + 1));
      MailboxLocation = (UINT64)(UINTN)NewMailbox;
      //
      // Build mailbox location in HOB
      //
      MailboxLocationPointer = BuildGuidDataHob (
                                 &gEfiDebugAgentGuid,
                                 &MailboxLocation,
                                 sizeof (UINT64)
                                 );
    }
    //
    // Update IDT entry to save the location saved mailbox pointer
    //
    SetLocationSavedMailboxPointerInIdtEntry (MailboxLocationPointer);
    break;

  case DEBUG_AGENT_INIT_PEI:
    if (Context == NULL) {
      DEBUG ((EFI_D_ERROR, "DebugAgent: Input parameter Context cannot be NULL!\n"));
      CpuDeadLoop ();
    }
    //
    // Check if Debug Agent has initialized before
    //
    if (IsDebugAgentInitialzed()) {
      DEBUG ((EFI_D_WARN, "Debug Agent: It has already initialized in SEC Core!\n"));
      break;
    }
    //
    // Install Vector Handoff Info PPI to persist vectors used by Debug Agent
    //
    Status = PeiServicesInstallPpi (&mVectorHandoffInfoPpiList[0]);
    if (EFI_ERROR (Status)) {
      DEBUG ((EFI_D_ERROR, "DebugAgent: Failed to install Vector Handoff Info PPI!\n"));
      CpuDeadLoop ();
    }
    //
    // Set up IDT entries
    //
    InitializeDebugIdt ();
    //
    // Build mailbox in HOB and setup Mailbox Set In Pei flag
    //
    Mailbox = AllocateZeroPool (sizeof (DEBUG_AGENT_MAILBOX));
    if (Mailbox == NULL) {
      DEBUG ((EFI_D_ERROR, "DebugAgent: Failed to allocate memory!\n"));
      CpuDeadLoop ();
    } else {
      MailboxLocation = (UINT64)(UINTN)Mailbox;
      MailboxLocationPointer = BuildGuidDataHob (
                                 &gEfiDebugAgentGuid,
                                 &MailboxLocation,
                                 sizeof (UINT64)
                                 );
      //
      // Initialize Debug Timer hardware and save its frequency
      //
      InitializeDebugTimer (&DebugTimerFrequency, TRUE);
      UpdateMailboxContent (Mailbox, DEBUG_MAILBOX_DEBUG_TIMER_FREQUENCY, DebugTimerFrequency);
      //
      // Update IDT entry to save the location pointer saved mailbox pointer
      //
      SetLocationSavedMailboxPointerInIdtEntry (MailboxLocationPointer);
    }
    //
    // Save init arch type when debug agent initialized
    //
    SetDebugFlag (DEBUG_AGENT_FLAG_INIT_ARCH, DEBUG_ARCH_SYMBOL);
    //
    // Register for a callback once memory has been initialized.
    // If memery has been ready, the callback funtion will be invoked immediately
    //
    Status = PeiServicesNotifyPpi (&mMemoryDiscoveredNotifyList[0]);
    if (EFI_ERROR (Status)) {
      DEBUG ((EFI_D_ERROR, "DebugAgent: Failed to register memory discovered callback function!\n"));
      CpuDeadLoop ();
    }
    //
    // Set HOB check flag if memory has not been ready yet
    //
    if (GetDebugFlag (DEBUG_AGENT_FLAG_MEMORY_READY) == 0) {
      SetDebugFlag (DEBUG_AGENT_FLAG_CHECK_MAILBOX_IN_HOB, 1);
    }

    Phase2Context.InitFlag = InitFlag;
    Phase2Context.Context  = Context;
    Phase2Context.Function = Function;
    DebugPortInitialize ((VOID *) &Phase2Context, InitializeDebugAgentPhase2);

    FindAndReportModuleImageInfo (4);

    break;

  case DEBUG_AGENT_INIT_THUNK_PEI_IA32TOX64:
    if (Context == NULL) {
      DEBUG ((EFI_D_ERROR, "DebugAgent: Input parameter Context cannot be NULL!\n"));
      CpuDeadLoop ();
    } else {
      Ia32Idtr =  (IA32_DESCRIPTOR *) Context;
      Ia32IdtEntry = (IA32_IDT_ENTRY *)(Ia32Idtr->Base);
      MailboxLocationPointer = (UINT64 *) (UINTN) (Ia32IdtEntry[DEBUG_MAILBOX_VECTOR].Bits.OffsetLow +
                                         (UINT32) (Ia32IdtEntry[DEBUG_MAILBOX_VECTOR].Bits.OffsetHigh << 16));
      Mailbox = (DEBUG_AGENT_MAILBOX *) (UINTN)(*MailboxLocationPointer);
      //
      // Mailbox should valid and setup before executing thunk code
      //
      VerifyMailboxChecksum (Mailbox);

      DebugPortHandle = (UINT64) (UINTN)DebugPortInitialize ((VOID *)(UINTN)Mailbox->DebugPortHandle, NULL);
      UpdateMailboxContent (Mailbox, DEBUG_MAILBOX_DEBUG_PORT_HANDLE_INDEX, DebugPortHandle);
      //
      // Set up IDT entries
      //
      InitializeDebugIdt ();
      //
      // Update IDT entry to save location pointer saved the mailbox pointer
      //
      SetLocationSavedMailboxPointerInIdtEntry (MailboxLocationPointer);

      FindAndReportModuleImageInfo (4);
    }
    break;

  default:
    //
    // Only DEBUG_AGENT_INIT_PREMEM_SEC and DEBUG_AGENT_INIT_POSTMEM_SEC are allowed for this
    // Debug Agent library instance.
    //
    DEBUG ((EFI_D_ERROR, "Debug Agent: The InitFlag value is not allowed!\n"));
    CpuDeadLoop ();
    break;
  }

  if (InitFlag == DEBUG_AGENT_INIT_POSTMEM_SEC) {
    //
    // Restore CPU Interrupt state and keep debug timer interrupt state as is
    // in DEBUG_AGENT_INIT_POSTMEM_SEC case
    //
    SetInterruptState (CpuInterruptState);
  } else {
    //
    // Enable Debug Timer interrupt
    //
    SaveAndSetDebugTimerInterrupt (TRUE);
    //
    // Enable CPU interrupts so debug timer interrupts can be delivered
    //
    EnableInterrupts ();
  }
  //
  // If Function is not NULL, invoke it always whatever debug agent was initialized sucesssfully or not.
  //
  if (Function != NULL) {
    Function (Context);
  }
  //
  // Set return status for DEBUG_AGENT_INIT_PEI
  //
  if (InitFlag == DEBUG_AGENT_INIT_PEI && Context != NULL) {
    *(EFI_STATUS *)Context = EFI_SUCCESS;
  }
}
Esempio n. 3
0
/**
  Initialize debug agent.

  This function is used to set up debug enviroment for DXE phase.

  If this function is called by DXE Core, Context must be the pointer
  to HOB list which will be used to get GUIDed HOB. It will enable
  interrupt to support break-in feature.
  If this function is called by DXE module, Context must be NULL. It
  will enable interrupt to support break-in feature.

  @param[in] InitFlag     Init flag is used to decide initialize process.
  @param[in] Context      Context needed according to InitFlag.
  @param[in] Function     Continue function called by debug agent library; it was
                          optional.

**/
VOID
EFIAPI
InitializeDebugAgent (
  IN UINT32                InitFlag,
  IN VOID                  *Context, OPTIONAL
  IN DEBUG_AGENT_CONTINUE  Function  OPTIONAL
  )
{
  UINT64                       *MailboxLocation;
  DEBUG_AGENT_MAILBOX          *Mailbox;
  BOOLEAN                      InterruptStatus;
  VOID                         *HobList;
  IA32_DESCRIPTOR              IdtDescriptor;
  IA32_DESCRIPTOR              *Ia32Idtr;
  IA32_IDT_ENTRY               *Ia32IdtEntry;

  if (InitFlag == DEBUG_AGENT_INIT_DXE_AP) {
    //
    // Invoked by AP, enable interrupt to let AP could receive IPI from other processors
    //
    EnableInterrupts ();
    return ;
  }

  //
  // Disable Debug Timer interrupt
  //
  SaveAndSetDebugTimerInterrupt (FALSE);
  //
  // Save and disable original interrupt status
  //
  InterruptStatus = SaveAndDisableInterrupts ();

  //
  // Try to get mailbox firstly
  //
  HobList         = NULL;
  Mailbox         = NULL;
  MailboxLocation = NULL;

  switch (InitFlag) {

  case DEBUG_AGENT_INIT_DXE_LOAD:
    //
    // Check if Debug Agent has been initialized before
    //
    if (IsDebugAgentInitialzed ()) {
      DEBUG ((EFI_D_INFO, "Debug Agent: The former agent will be overwritten by the new one!\n"));
    }

    mMultiProcessorDebugSupport = TRUE;
    //
    // Save original IDT table
    //
    AsmReadIdtr (&IdtDescriptor);
    mSaveIdtTableSize = IdtDescriptor.Limit + 1;
    mSavedIdtTable    = AllocateCopyPool (mSaveIdtTableSize, (VOID *) IdtDescriptor.Base);
    //
    // Initialize Debug Timer hardware and save its initial count
    //
    mDebugMpContext.DebugTimerInitCount = InitializeDebugTimer ();
    //
    // Check if Debug Agent initialized in DXE phase
    //
    Mailbox = GetMailboxFromConfigurationTable ();
    if (Mailbox == NULL) {
      //
      // Try to get mailbox from GUIDed HOB build in PEI
      //
      HobList = GetHobList ();
      Mailbox = GetMailboxFromHob (HobList);
    }
    //
    // Set up IDT table and prepare for IDT entries
    //
    SetupDebugAgentEnviroment (Mailbox);
    //
    // For DEBUG_AGENT_INIT_S3, needn't to install configuration table and EFI Serial IO protocol
    // For DEBUG_AGENT_INIT_DXE_CORE, InternalConstructorWorker() will invoked in Constructor()
    //
    InternalConstructorWorker ();
    //
    // Enable interrupt to receive Debug Timer interrupt
    //
    EnableInterrupts ();

    mDebugAgentInitialized = TRUE;
    FindAndReportModuleImageInfo (SIZE_4KB);

    *(EFI_STATUS *)Context = EFI_SUCCESS;

    if (gST->ConOut != NULL) {
      Print (L"Debug Agent: Initialized successfully!\r\n");
      Print (L"If the Debug Port is serial port, please make sure this serial port isn't connected by ISA Serial driver\r\n");
      Print (L"You could do the following steps to disconnect the serial port:\r\n");
      Print (L"1: Shell> drivers\r\n");
      Print (L"   ...\r\n");
      Print (L"   V  VERSION  E G G #D #C DRIVER NAME                         IMAGE NAME\r\n");
      Print (L"   == ======== = = = == == =================================== ===================\r\n");
      Print (L"   8F 0000000A B - -  1 14 PCI Bus Driver                      PciBusDxe\r\n");
      Print (L"   91 00000010 ? - -  -  - ATA Bus Driver                      AtaBusDxe\r\n");
      Print (L"   ...\r\n");
      Print (L"   A7 0000000A B - -  1  1 ISA Serial Driver                   IsaSerialDxe\r\n");
      Print (L"   ...\r\n");
      Print (L"2: Shell> dh -d A7\r\n");
      Print (L"   A7: Image(IsaSerialDxe) ImageDevPath (..9FB3-11D4-9A3A-0090273FC14D))DriverBinding ComponentName ComponentName2\r\n");
      Print (L"        Driver Name    : ISA Serial Driver\r\n");
      Print (L"        Image Name     : FvFile(93B80003-9FB3-11D4-9A3A-0090273FC14D)\r\n");
      Print (L"        Driver Version : 0000000A\r\n");
      Print (L"        Driver Type    : BUS\r\n");
      Print (L"        Configuration  : NO\r\n");
      Print (L"        Diagnostics    : NO\r\n");
      Print (L"        Managing       :\r\n");
      Print (L"          Ctrl[EA] : PciRoot(0x0)/Pci(0x1F,0x0)/Serial(0x0)\r\n");
      Print (L"            Child[EB] : PciRoot(0x0)/Pci(0x1F,0x0)/Serial(0x0)/Uart(115200,8,N,1)\r\n");
      Print (L"3: Shell> disconnect EA\r\n");
      Print (L"4: Shell> load -nc DebugAgentDxe.efi\r\n\r\n");
    }
    break;

  case DEBUG_AGENT_INIT_DXE_UNLOAD:
    if (mDebugAgentInitialized) {
      if (IsHostAttached ()) {
        Print (L"Debug Agent: Host is still connected, please de-attach TARGET firstly!\r\n");
        *(EFI_STATUS *)Context = EFI_ACCESS_DENIED;
        //
        // Enable Debug Timer interrupt again
        //
        SaveAndSetDebugTimerInterrupt (TRUE);
      } else {
        //
        // Restore original IDT table
        //
        AsmReadIdtr (&IdtDescriptor);
        IdtDescriptor.Limit = (UINT16) (mSaveIdtTableSize - 1);
        CopyMem ((VOID *) IdtDescriptor.Base, mSavedIdtTable, mSaveIdtTableSize);
        AsmWriteIdtr (&IdtDescriptor);
        FreePool (mSavedIdtTable);
        mDebugAgentInitialized = FALSE;
        *(EFI_STATUS *)Context = EFI_SUCCESS;
      }
    } else {
      Print (L"Debug Agent: It hasn't been initialized, cannot unload it!\r\n");
      *(EFI_STATUS *)Context = EFI_NOT_STARTED;
    }

    //
    // Restore interrupt state.
    //
    SetInterruptState (InterruptStatus);
    break;

  case DEBUG_AGENT_INIT_DXE_CORE:
    mDxeCoreFlag                = TRUE;
    mMultiProcessorDebugSupport = TRUE;
    //
    // Initialize Debug Timer hardware and its initial count
    //
    mDebugMpContext.DebugTimerInitCount = InitializeDebugTimer ();
    //
    // Try to get mailbox from GUIDed HOB build in PEI
    //
    HobList = Context;
    Mailbox = GetMailboxFromHob (HobList);
    //
    // Set up IDT table and prepare for IDT entries
    //
    SetupDebugAgentEnviroment (Mailbox);
    //
    // Enable interrupt to receive Debug Timer interrupt
    //
    EnableInterrupts ();

    break;

  case DEBUG_AGENT_INIT_S3:

    if (Context != NULL) {
      Ia32Idtr =  (IA32_DESCRIPTOR *) Context;
      Ia32IdtEntry = (IA32_IDT_ENTRY *)(Ia32Idtr->Base);
      MailboxLocation = (UINT64 *) (UINTN) (Ia32IdtEntry[DEBUG_MAILBOX_VECTOR].Bits.OffsetLow +
                                           (Ia32IdtEntry[DEBUG_MAILBOX_VECTOR].Bits.OffsetHigh << 16));
      Mailbox = (DEBUG_AGENT_MAILBOX *)(UINTN)(*MailboxLocation);
      VerifyMailboxChecksum (Mailbox);
    }
    //
    // Save Mailbox pointer in global variable
    //
    mMailboxPointer = Mailbox;
    //
    // Set up IDT table and prepare for IDT entries
    //
    SetupDebugAgentEnviroment (Mailbox);
    //
    // Disable interrupt
    //
    DisableInterrupts ();
    FindAndReportModuleImageInfo (SIZE_4KB);
    if (GetDebugFlag (DEBUG_AGENT_FLAG_BREAK_BOOT_SCRIPT) == 1) {
      //
      // If Boot Script entry break is set, code will be break at here.
      //
      CpuBreakpoint ();
    }
    break;

  default:
    //
    // Only DEBUG_AGENT_INIT_PREMEM_SEC and DEBUG_AGENT_INIT_POSTMEM_SEC are allowed for this
    // Debug Agent library instance.
    //
    DEBUG ((EFI_D_ERROR, "Debug Agent: The InitFlag value is not allowed!\n"));
    CpuDeadLoop ();
    break;
  }
}