Dependency.c

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#include "PeiMain.h"
#include "Dependency.h"
 
BOOLEAN
IsPpiInstalled (
  IN EFI_PEI_SERVICES  **PeiServices,
  IN EVAL_STACK_ENTRY  *Stack
  )
{
  VOID        *PeiInstance;
  EFI_STATUS  Status;
  EFI_GUID    PpiGuid;
 
  //
  // If there is no GUID to evaluate, just return current result on stack.
  //
  if (Stack->Operator == NULL) {
    return Stack->Result;
  }
 
  //
  // Copy the GUID into a local variable so that there are no
  // possibilities of alignment faults for cross-compilation
  // environments such as Intel?Itanium(TM).
  //
  CopyMem (&PpiGuid, Stack->Operator, sizeof (EFI_GUID));
 
  //
  // Check if the PPI is installed.
  //
  Status = PeiServicesLocatePpi (
             &PpiGuid,        // GUID
             0,               // INSTANCE
             NULL,            // EFI_PEI_PPI_DESCRIPTOR
             &PeiInstance     // PPI
             );
 
  if (EFI_ERROR (Status)) {
    return FALSE;
  }
 
  return TRUE;
}
 
BOOLEAN
PeimDispatchReadiness (
  IN EFI_PEI_SERVICES  **PeiServices,
  IN VOID              *DependencyExpression
  )
{
  DEPENDENCY_EXPRESSION_OPERAND  *Iterator;
  EVAL_STACK_ENTRY               *StackPtr;
  EVAL_STACK_ENTRY               EvalStack[MAX_GRAMMAR_SIZE];
 
  Iterator = DependencyExpression;
 
  StackPtr = EvalStack;
 
  while (TRUE) {
    switch (*(Iterator++)) {
      //
      // For performance reason we put the frequently used items in front of
      // the rarely used  items
      //
 
      case (EFI_DEP_PUSH):
        //
        // Check to make sure the dependency grammar doesn't overflow the
        // EvalStack on the push
        //
        if (StackPtr > &EvalStack[MAX_GRAMMAR_SIZE-1]) {
          DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Underflow Error)\n"));
          return FALSE;
        }
 
        //
        // Push the pointer to the PUSH opcode operator (pointer to PPI GUID)
        // We will evaluate if the PPI is installed on the POP operation.
        //
        StackPtr->Operator = (VOID *)Iterator;
        Iterator           = Iterator + sizeof (EFI_GUID);
        DEBUG ((DEBUG_DISPATCH, "  PUSH GUID(%g) = %a\n", StackPtr->Operator, IsPpiInstalled (PeiServices, StackPtr) ? "TRUE" : "FALSE"));
        StackPtr++;
        break;
 
      case (EFI_DEP_AND):
      case (EFI_DEP_OR):
        if (*(Iterator - 1) == EFI_DEP_AND) {
          DEBUG ((DEBUG_DISPATCH, "  AND\n"));
        } else {
          DEBUG ((DEBUG_DISPATCH, "  OR\n"));
        }
 
        //
        // Check to make sure the dependency grammar doesn't underflow the
        // EvalStack on the two POPs for the AND operation.  Don't need to
        // check for the overflow on PUSHing the result since we already
        // did two POPs.
        //
        if (StackPtr < &EvalStack[2]) {
          DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Underflow Error)\n"));
          return FALSE;
        }
 
        //
        // Evaluate the first POPed operator only. If the operand is
        // EFI_DEP_AND and the POPed operator evaluates to FALSE, or the
        // operand is EFI_DEP_OR and the POPed operator evaluates to TRUE,
        // we don't need to check the second operator, and the result will be
        // evaluation of the POPed operator. Otherwise, don't POP the second
        // operator since it will now evaluate to the final result on the
        // next operand that causes a POP.
        //
        StackPtr--;
        //
        // Iterator has increased by 1 after we retrieve the operand, so here we
        // should get the value pointed by (Iterator - 1), in order to obtain the
        // same operand.
        //
        if (*(Iterator - 1) == EFI_DEP_AND) {
          if (!(IsPpiInstalled (PeiServices, StackPtr))) {
            (StackPtr-1)->Result   = FALSE;
            (StackPtr-1)->Operator = NULL;
          }
        } else {
          if (IsPpiInstalled (PeiServices, StackPtr)) {
            (StackPtr-1)->Result   = TRUE;
            (StackPtr-1)->Operator = NULL;
          }
        }
 
        break;
 
      case (EFI_DEP_END):
        DEBUG ((DEBUG_DISPATCH, "  END\n"));
        StackPtr--;
        //
        // Check to make sure EvalStack is balanced.  If not, then there is
        // an error in the dependency grammar, so return EFI_INVALID_PARAMETER.
        //
        if (StackPtr != &EvalStack[0]) {
          DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Underflow Error)\n"));
          return FALSE;
        }
 
        DEBUG ((DEBUG_DISPATCH, "  RESULT = %a\n", IsPpiInstalled (PeiServices, StackPtr) ? "TRUE" : "FALSE"));
        return IsPpiInstalled (PeiServices, StackPtr);
 
      case (EFI_DEP_NOT):
        DEBUG ((DEBUG_DISPATCH, "  NOT\n"));
        //
        // Check to make sure the dependency grammar doesn't underflow the
        // EvalStack on the POP for the NOT operation.  Don't need to
        // check for the overflow on PUSHing the result since we already
        // did a POP.
        //
        if (StackPtr < &EvalStack[1]) {
          DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Underflow Error)\n"));
          return FALSE;
        }
 
        (StackPtr-1)->Result   = (BOOLEAN) !IsPpiInstalled (PeiServices, (StackPtr-1));
        (StackPtr-1)->Operator = NULL;
        break;
 
      case (EFI_DEP_TRUE):
      case (EFI_DEP_FALSE):
        if (*(Iterator - 1) == EFI_DEP_TRUE) {
          DEBUG ((DEBUG_DISPATCH, "  TRUE\n"));
        } else {
          DEBUG ((DEBUG_DISPATCH, "  FALSE\n"));
        }
 
        //
        // Check to make sure the dependency grammar doesn't overflow the
        // EvalStack on the push
        //
        if (StackPtr > &EvalStack[MAX_GRAMMAR_SIZE-1]) {
          DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Underflow Error)\n"));
          return FALSE;
        }
 
        //
        // Iterator has increased by 1 after we retrieve the operand, so here we
        // should get the value pointed by (Iterator - 1), in order to obtain the
        // same operand.
        //
        if (*(Iterator - 1) == EFI_DEP_TRUE) {
          StackPtr->Result = TRUE;
        } else {
          StackPtr->Result = FALSE;
        }
 
        StackPtr->Operator = NULL;
        StackPtr++;
        break;
 
      default:
        DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Invalid opcode)\n"));
        //
        // The grammar should never arrive here
        //
        return FALSE;
    }
  }
}