edk2/MdeModulePkg/Core/Dxe/Event/Tpl.c

/** @file
  Task priority (TPL) functions.

Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include "DxeMain.h"
#include "Event.h"

//
// Maximum interrupt nesting depth allowed by the UEFI/PI specifications.
// Comprised of 3 software TPL levels (TPL_APPLICATION, TPL_CALLBACK,
// TPL_NOTIFY) plus 16 hardware interrupt priority levels (TPL 16..31).
//
#define MAX_INTERRUPT_ENABLE_NEST_DEPTH  (3 + 16)

//
// Counter for tracking interrupt enable recursion depth.
// Incremented on entry to CoreSetInterruptState(TRUE) and decremented on exit.
// Prevents stack overflow from infinite interrupt recursion loops.
// Must not exceed MAX_INTERRUPT_ENABLE_NEST_DEPTH per UEFI/PI specs.
//
static volatile UINTN  mInterruptEnableNestDepth = 0;

/**
  Set Interrupt State.

  @param  Enable  The state of enable or disable interrupt

**/
VOID
CoreSetInterruptState (
  IN BOOLEAN  Enable
  )
{
  EFI_STATUS  Status;
  BOOLEAN     InSmm;

  if (gCpu == NULL) {
    return;
  }

  if (!Enable) {
    gCpu->DisableInterrupt (gCpu);
    return;
  }

  if (gSmmBase2 != NULL) {
    Status = gSmmBase2->InSmm (gSmmBase2, &InSmm);
    if (EFI_ERROR (Status) || InSmm) {
      return;
    }
  }

  mInterruptEnableNestDepth++;
  ASSERT (mInterruptEnableNestDepth < MAX_INTERRUPT_ENABLE_NEST_DEPTH);

  gCpu->EnableInterrupt (gCpu);

  mInterruptEnableNestDepth--;
}

/**
  Raise the task priority level to the new level.
  High level is implemented by disabling processor interrupts.

  @param  NewTpl  New task priority level

  @return The previous task priority level

**/
EFI_TPL
EFIAPI
CoreRaiseTpl (
  IN EFI_TPL  NewTpl
  )
{
  EFI_TPL  OldTpl;

  OldTpl = gEfiCurrentTpl;
  if (OldTpl > NewTpl) {
    DEBUG ((DEBUG_ERROR, "FATAL ERROR - RaiseTpl with OldTpl(0x%x) > NewTpl(0x%x)\n", OldTpl, NewTpl));
    ASSERT (FALSE);
  }

  ASSERT (VALID_TPL (NewTpl));

  //
  // If raising to high level, disable interrupts
  //
  if ((NewTpl >= TPL_HIGH_LEVEL) &&  (OldTpl < TPL_HIGH_LEVEL)) {
    CoreSetInterruptState (FALSE);
  }

  //
  // Set the new value
  //
  gEfiCurrentTpl = NewTpl;

  return OldTpl;
}

/**
  Lowers the task priority to the previous value.   If the new
  priority unmasks events at a higher priority, they are dispatched.

  @param  NewTpl  New, lower, task priority

**/
VOID
EFIAPI
CoreRestoreTpl (
  IN EFI_TPL  NewTpl
  )
{
  EFI_TPL  OldTpl;
  EFI_TPL  PendingTpl;

  OldTpl = gEfiCurrentTpl;
  if (NewTpl > OldTpl) {
    DEBUG ((DEBUG_ERROR, "FATAL ERROR - RestoreTpl with NewTpl(0x%x) > OldTpl(0x%x)\n", NewTpl, OldTpl));
    ASSERT (FALSE);
  }

  ASSERT (VALID_TPL (NewTpl));

  //
  // If lowering below HIGH_LEVEL, make sure
  // interrupts are enabled
  //

  if ((OldTpl >= TPL_HIGH_LEVEL) &&  (NewTpl < TPL_HIGH_LEVEL)) {
    gEfiCurrentTpl = TPL_HIGH_LEVEL;
  }

  //
  // Dispatch any pending events
  //
  while (gEventPending != 0) {
    PendingTpl = (UINTN)HighBitSet64 (gEventPending);
    if (PendingTpl <= NewTpl) {
      break;
    }

    gEfiCurrentTpl = PendingTpl;
    if (gEfiCurrentTpl < TPL_HIGH_LEVEL) {
      CoreSetInterruptState (TRUE);
    }

    CoreDispatchEventNotifies (gEfiCurrentTpl);
  }

  //
  // Set the new value
  //

  gEfiCurrentTpl = NewTpl;

  //
  // If lowering below HIGH_LEVEL, make sure
  // interrupts are enabled
  //
  if (gEfiCurrentTpl < TPL_HIGH_LEVEL) {
    CoreSetInterruptState (TRUE);
  }
}