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248 lines
8.2 KiB
C
248 lines
8.2 KiB
C
/** @file
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PEI Dispatcher Dependency Evaluator
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This routine evaluates a dependency expression (DEPENDENCY_EXPRESSION) to determine
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if a driver can be scheduled for execution. The criteria for
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schedulability is that the dependency expression is satisfied.
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Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
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SPDX-License-Identifier: BSD-2-Clause-Patent
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**/
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#include "PeiMain.h"
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#include "Dependency.h"
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/**
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This routine determines if a PPI has been installed.
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The truth value of a GUID is determined by if the PPI has
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been published and can be queried from the PPI database.
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@param PeiServices An indirect pointer to the EFI_PEI_SERVICES table published by the PEI Foundation
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@param Stack Reference to EVAL_STACK_ENTRY that contains PPI GUID to check
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@retval TRUE if the PPI is already installed.
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@retval FALSE if the PPI has yet to be installed.
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**/
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BOOLEAN
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IsPpiInstalled (
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IN EFI_PEI_SERVICES **PeiServices,
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IN EVAL_STACK_ENTRY *Stack
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)
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{
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VOID *PeiInstance;
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EFI_STATUS Status;
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EFI_GUID PpiGuid;
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//
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// If there is no GUID to evaluate, just return current result on stack.
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//
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if (Stack->Operator == NULL) {
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return Stack->Result;
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}
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//
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// Copy the Guid into a locale variable so that there are no
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// possibilities of alignment faults for cross-compilation
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// environments such as Intel?Itanium(TM).
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//
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CopyMem(&PpiGuid, Stack->Operator, sizeof(EFI_GUID));
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//
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// Check if the PPI is installed.
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//
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Status = PeiServicesLocatePpi(
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&PpiGuid, // GUID
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0, // INSTANCE
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NULL, // EFI_PEI_PPI_DESCRIPTOR
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&PeiInstance // PPI
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);
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if (EFI_ERROR(Status)) {
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return FALSE;
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}
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return TRUE;
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}
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/**
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This is the POSTFIX version of the dependency evaluator. When a
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PUSH [PPI GUID] is encountered, a pointer to the GUID is stored on
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the evaluation stack. When that entry is poped from the evaluation
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stack, the PPI is checked if it is installed. This method allows
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some time savings as not all PPIs must be checked for certain
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operation types (AND, OR).
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@param PeiServices An indirect pointer to the EFI_PEI_SERVICES table published by the PEI Foundation
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@param DependencyExpression Pointer to a dependency expression. The Grammar adheres to
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the BNF described above and is stored in postfix notation.
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@retval TRUE if it is a well-formed Grammar
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@retval FALSE if the dependency expression overflows the evaluation stack
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if the dependency expression underflows the evaluation stack
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if the dependency expression is not a well-formed Grammar.
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**/
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BOOLEAN
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PeimDispatchReadiness (
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IN EFI_PEI_SERVICES **PeiServices,
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IN VOID *DependencyExpression
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)
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{
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DEPENDENCY_EXPRESSION_OPERAND *Iterator;
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EVAL_STACK_ENTRY *StackPtr;
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EVAL_STACK_ENTRY EvalStack[MAX_GRAMMAR_SIZE];
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Iterator = DependencyExpression;
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StackPtr = EvalStack;
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while (TRUE) {
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switch (*(Iterator++)) {
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//
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// For performance reason we put the frequently used items in front of
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// the rarely used items
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//
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case (EFI_DEP_PUSH):
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//
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// Check to make sure the dependency grammar doesn't overflow the
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// EvalStack on the push
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//
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if (StackPtr > &EvalStack[MAX_GRAMMAR_SIZE-1]) {
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DEBUG ((DEBUG_DISPATCH, " RESULT = FALSE (Underflow Error)\n"));
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return FALSE;
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}
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//
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// Push the pointer to the PUSH opcode operator (pointer to PPI GUID)
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// We will evaluate if the PPI is insalled on the POP operation.
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//
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StackPtr->Operator = (VOID *) Iterator;
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Iterator = Iterator + sizeof (EFI_GUID);
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DEBUG ((DEBUG_DISPATCH, " PUSH GUID(%g) = %a\n", StackPtr->Operator, IsPpiInstalled (PeiServices, StackPtr) ? "TRUE" : "FALSE"));
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StackPtr++;
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break;
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case (EFI_DEP_AND):
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case (EFI_DEP_OR):
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if (*(Iterator - 1) == EFI_DEP_AND) {
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DEBUG ((DEBUG_DISPATCH, " AND\n"));
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} else {
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DEBUG ((DEBUG_DISPATCH, " OR\n"));
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}
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//
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// Check to make sure the dependency grammar doesn't underflow the
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// EvalStack on the two POPs for the AND operation. Don't need to
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// check for the overflow on PUSHing the result since we already
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// did two POPs.
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//
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if (StackPtr < &EvalStack[2]) {
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DEBUG ((DEBUG_DISPATCH, " RESULT = FALSE (Underflow Error)\n"));
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return FALSE;
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}
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//
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// Evaluate the first POPed operator only. If the operand is
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// EFI_DEP_AND and the POPed operator evaluates to FALSE, or the
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// operand is EFI_DEP_OR and the POPed operator evaluates to TRUE,
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// we don't need to check the second operator, and the result will be
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// evaluation of the POPed operator. Otherwise, don't POP the second
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// operator since it will now evaluate to the final result on the
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// next operand that causes a POP.
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//
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StackPtr--;
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//
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// Iterator has increased by 1 after we retrieve the operand, so here we
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// should get the value pointed by (Iterator - 1), in order to obtain the
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// same operand.
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//
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if (*(Iterator - 1) == EFI_DEP_AND) {
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if (!(IsPpiInstalled (PeiServices, StackPtr))) {
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(StackPtr-1)->Result = FALSE;
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(StackPtr-1)->Operator = NULL;
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}
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} else {
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if (IsPpiInstalled (PeiServices, StackPtr)) {
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(StackPtr-1)->Result = TRUE;
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(StackPtr-1)->Operator = NULL;
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}
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}
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break;
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case (EFI_DEP_END):
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DEBUG ((DEBUG_DISPATCH, " END\n"));
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StackPtr--;
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//
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// Check to make sure EvalStack is balanced. If not, then there is
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// an error in the dependency grammar, so return EFI_INVALID_PARAMETER.
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//
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if (StackPtr != &EvalStack[0]) {
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DEBUG ((DEBUG_DISPATCH, " RESULT = FALSE (Underflow Error)\n"));
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return FALSE;
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}
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DEBUG ((DEBUG_DISPATCH, " RESULT = %a\n", IsPpiInstalled (PeiServices, StackPtr) ? "TRUE" : "FALSE"));
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return IsPpiInstalled (PeiServices, StackPtr);
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case (EFI_DEP_NOT):
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DEBUG ((DEBUG_DISPATCH, " NOT\n"));
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//
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// Check to make sure the dependency grammar doesn't underflow the
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// EvalStack on the POP for the NOT operation. Don't need to
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// check for the overflow on PUSHing the result since we already
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// did a POP.
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//
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if (StackPtr < &EvalStack[1]) {
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DEBUG ((DEBUG_DISPATCH, " RESULT = FALSE (Underflow Error)\n"));
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return FALSE;
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}
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(StackPtr-1)->Result = (BOOLEAN) !IsPpiInstalled (PeiServices, (StackPtr-1));
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(StackPtr-1)->Operator = NULL;
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break;
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case (EFI_DEP_TRUE):
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case (EFI_DEP_FALSE):
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if (*(Iterator - 1) == EFI_DEP_TRUE) {
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DEBUG ((DEBUG_DISPATCH, " TRUE\n"));
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} else {
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DEBUG ((DEBUG_DISPATCH, " FALSE\n"));
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}
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//
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// Check to make sure the dependency grammar doesn't overflow the
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// EvalStack on the push
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//
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if (StackPtr > &EvalStack[MAX_GRAMMAR_SIZE-1]) {
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DEBUG ((DEBUG_DISPATCH, " RESULT = FALSE (Underflow Error)\n"));
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return FALSE;
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}
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//
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// Iterator has increased by 1 after we retrieve the operand, so here we
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// should get the value pointed by (Iterator - 1), in order to obtain the
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// same operand.
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//
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if (*(Iterator - 1) == EFI_DEP_TRUE) {
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StackPtr->Result = TRUE;
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} else {
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StackPtr->Result = FALSE;
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}
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StackPtr->Operator = NULL;
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StackPtr++;
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break;
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default:
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DEBUG ((DEBUG_DISPATCH, " RESULT = FALSE (Invalid opcode)\n"));
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//
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// The grammar should never arrive here
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//
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return FALSE;
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}
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}
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}
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