/** @file
  MM Driver Dispatcher Dependency Evaluator

  This routine evaluates a dependency expression (DEPENDENCY_EXPRESSION) to determine
  if a driver can be scheduled for execution.  The criteria for
  scheduling is that the dependency expression is satisfied.

  Copyright (c) 2009 - 2010, Intel Corporation. All rights reserved.<BR>
  Copyright (c) 2016 - 2021, Arm Limited. All rights reserved.<BR>
  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include "StandaloneMmCore.h"

///
/// Define the initial size of the dependency expression evaluation stack
///
#define DEPEX_STACK_SIZE_INCREMENT  0x1000

//
// Global stack used to evaluate dependency expressions
//
BOOLEAN  *mDepexEvaluationStack        = NULL;
BOOLEAN  *mDepexEvaluationStackEnd     = NULL;
BOOLEAN  *mDepexEvaluationStackPointer = NULL;

/**
  Grow size of the Depex stack

  @retval EFI_SUCCESS           Stack successfully growed.
  @retval EFI_OUT_OF_RESOURCES  There is not enough system memory to grow the stack.

**/
EFI_STATUS
GrowDepexStack (
  VOID
  )
{
  BOOLEAN  *NewStack;
  UINTN    Size;

  Size = DEPEX_STACK_SIZE_INCREMENT;
  if (mDepexEvaluationStack != NULL) {
    Size = Size + (mDepexEvaluationStackEnd - mDepexEvaluationStack);
  }

  NewStack = AllocatePool (Size * sizeof (BOOLEAN));
  if (NewStack == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }

  if (mDepexEvaluationStack != NULL) {
    //
    // Copy to Old Stack to the New Stack
    //
    CopyMem (
      NewStack,
      mDepexEvaluationStack,
      (mDepexEvaluationStackEnd - mDepexEvaluationStack) * sizeof (BOOLEAN)
      );

    //
    // Free The Old Stack
    //
    FreePool (mDepexEvaluationStack);
  }

  //
  // Make the Stack pointer point to the old data in the new stack
  //
  mDepexEvaluationStackPointer = NewStack + (mDepexEvaluationStackPointer - mDepexEvaluationStack);
  mDepexEvaluationStack        = NewStack;
  mDepexEvaluationStackEnd     = NewStack + Size;

  return EFI_SUCCESS;
}

/**
  Push an element onto the Boolean Stack.

  @param  Value                 BOOLEAN to push.

  @retval EFI_SUCCESS           The value was pushed onto the stack.
  @retval EFI_OUT_OF_RESOURCES  There is not enough system memory to grow the stack.

**/
EFI_STATUS
PushBool (
  IN BOOLEAN  Value
  )
{
  EFI_STATUS  Status;

  //
  // Check for a stack overflow condition
  //
  if (mDepexEvaluationStackPointer == mDepexEvaluationStackEnd) {
    //
    // Grow the stack
    //
    Status = GrowDepexStack ();
    if (EFI_ERROR (Status)) {
      return Status;
    }
  }

  //
  // Push the item onto the stack
  //
  *mDepexEvaluationStackPointer = Value;
  mDepexEvaluationStackPointer++;

  return EFI_SUCCESS;
}

/**
  Pop an element from the Boolean stack.

  @param  Value                 BOOLEAN to pop.

  @retval EFI_SUCCESS           The value was popped onto the stack.
  @retval EFI_ACCESS_DENIED     The pop operation underflowed the stack.

**/
EFI_STATUS
PopBool (
  OUT BOOLEAN  *Value
  )
{
  //
  // Check for a stack underflow condition
  //
  if (mDepexEvaluationStackPointer == mDepexEvaluationStack) {
    return EFI_ACCESS_DENIED;
  }

  //
  // Pop the item off the stack
  //
  mDepexEvaluationStackPointer--;
  *Value = *mDepexEvaluationStackPointer;
  return EFI_SUCCESS;
}

/**
  This is the POSTFIX version of the dependency evaluator.  This code does
  not need to handle Before or After, as it is not valid to call this
  routine in this case. POSTFIX means all the math is done on top of the stack.

  @param  DriverEntry           DriverEntry element to update.

  @retval TRUE                  If driver is ready to run.
  @retval FALSE                 If driver is not ready to run or some fatal error
                                was found.

**/
BOOLEAN
MmIsSchedulable (
  IN  EFI_MM_DRIVER_ENTRY  *DriverEntry
  )
{
  EFI_STATUS   Status;
  CONST UINT8  *Iterator;
  BOOLEAN      Operator;
  BOOLEAN      Operator2;
  EFI_GUID     DriverGuid;
  VOID         *Interface;

  Operator  = FALSE;
  Operator2 = FALSE;

  if (DriverEntry->After || DriverEntry->Before) {
    //
    // If Before or After Depex skip as MmInsertOnScheduledQueueWhileProcessingBeforeAndAfter ()
    // processes them.
    //
    return FALSE;
  }

  DEBUG ((DEBUG_DISPATCH, "Evaluate MM DEPEX for FFS(%g)\n", &DriverEntry->FileName));

  if (DriverEntry->Depex == NULL) {
    //
    // A NULL Depex means that the MM driver is not built correctly.
    // All MM drivers must have a valid depex expression.
    //
    DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Depex is empty)\n"));
    ASSERT (FALSE);
    return FALSE;
  }

  //
  // Clean out memory leaks in Depex Boolean stack. Leaks are only caused by
  // incorrectly formed DEPEX expressions
  //
  mDepexEvaluationStackPointer = mDepexEvaluationStack;

  Iterator = DriverEntry->Depex;

  while (TRUE) {
    //
    // Check to see if we are attempting to fetch dependency expression instructions
    // past the end of the dependency expression.
    //
    if (((UINTN)Iterator - (UINTN)DriverEntry->Depex) >= DriverEntry->DepexSize) {
      DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Attempt to fetch past end of depex)\n"));
      return FALSE;
    }

    //
    // Look at the opcode of the dependency expression instruction.
    //
    switch (*Iterator) {
      case EFI_DEP_BEFORE:
      case EFI_DEP_AFTER:
        //
        // For a well-formed Dependency Expression, the code should never get here.
        // The BEFORE and AFTER are processed prior to this routine's invocation.
        // If the code flow arrives at this point, there was a BEFORE or AFTER
        // that were not the first opcodes.
        //
        DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Unexpected BEFORE or AFTER opcode)\n"));
        ASSERT (FALSE);

      case EFI_DEP_PUSH:
        //
        // Push operator is followed by a GUID. Test to see if the GUID protocol
        // is installed and push the boolean result on the stack.
        //
        CopyMem (&DriverGuid, Iterator + 1, sizeof (EFI_GUID));

        Status = MmLocateProtocol (&DriverGuid, NULL, &Interface);
        if (EFI_ERROR (Status)) {
          DEBUG ((DEBUG_DISPATCH, "  PUSH GUID(%g) = FALSE\n", &DriverGuid));
          Status = PushBool (FALSE);
        } else {
          DEBUG ((DEBUG_DISPATCH, "  PUSH GUID(%g) = TRUE\n", &DriverGuid));
          Status = PushBool (TRUE);
        }

        if (EFI_ERROR (Status)) {
          DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Unexpected error)\n"));
          return FALSE;
        }

        Iterator += sizeof (EFI_GUID);
        break;

      case EFI_DEP_AND:
        DEBUG ((DEBUG_DISPATCH, "  AND\n"));
        Status = PopBool (&Operator);
        if (EFI_ERROR (Status)) {
          DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Unexpected error)\n"));
          return FALSE;
        }

        Status = PopBool (&Operator2);
        if (EFI_ERROR (Status)) {
          DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Unexpected error)\n"));
          return FALSE;
        }

        Status = PushBool ((BOOLEAN)(Operator && Operator2));
        if (EFI_ERROR (Status)) {
          DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Unexpected error)\n"));
          return FALSE;
        }

        break;

      case EFI_DEP_OR:
        DEBUG ((DEBUG_DISPATCH, "  OR\n"));
        Status = PopBool (&Operator);
        if (EFI_ERROR (Status)) {
          DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Unexpected error)\n"));
          return FALSE;
        }

        Status = PopBool (&Operator2);
        if (EFI_ERROR (Status)) {
          DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Unexpected error)\n"));
          return FALSE;
        }

        Status = PushBool ((BOOLEAN)(Operator || Operator2));
        if (EFI_ERROR (Status)) {
          DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Unexpected error)\n"));
          return FALSE;
        }

        break;

      case EFI_DEP_NOT:
        DEBUG ((DEBUG_DISPATCH, "  NOT\n"));
        Status = PopBool (&Operator);
        if (EFI_ERROR (Status)) {
          DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Unexpected error)\n"));
          return FALSE;
        }

        Status = PushBool ((BOOLEAN)(!Operator));
        if (EFI_ERROR (Status)) {
          DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Unexpected error)\n"));
          return FALSE;
        }

        break;

      case EFI_DEP_TRUE:
        DEBUG ((DEBUG_DISPATCH, "  TRUE\n"));
        Status = PushBool (TRUE);
        if (EFI_ERROR (Status)) {
          DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Unexpected error)\n"));
          return FALSE;
        }

        break;

      case EFI_DEP_FALSE:
        DEBUG ((DEBUG_DISPATCH, "  FALSE\n"));
        Status = PushBool (FALSE);
        if (EFI_ERROR (Status)) {
          DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Unexpected error)\n"));
          return FALSE;
        }

        break;

      case EFI_DEP_END:
        DEBUG ((DEBUG_DISPATCH, "  END\n"));
        Status = PopBool (&Operator);
        if (EFI_ERROR (Status)) {
          DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Unexpected error)\n"));
          return FALSE;
        }

        DEBUG ((DEBUG_DISPATCH, "  RESULT = %a\n", Operator ? "TRUE" : "FALSE"));
        return Operator;

      default:
        DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Unknown opcode)\n"));
        goto Done;
    }

    //
    // Skip over the Dependency Op Code we just processed in the switch.
    // The math is done out of order, but it should not matter. That is
    // we may add in the sizeof (EFI_GUID) before we account for the OP Code.
    // This is not an issue, since we just need the correct end result. You
    // need to be careful using Iterator in the loop as its intermediate value
    // may be strange.
    //
    Iterator++;
  }

Done:
  return FALSE;
}