dsutils.c

linux-2.6.15.6

/*******************************************************************************
 *
 * Module Name: dsutils - Dispatcher utilities
 *
 ******************************************************************************/

/*
 * Copyright (C) 2000 - 2005, R. Byron Moore
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions, and the following disclaimer,
 *    without modification.
 * 2. Redistributions in binary form must reproduce at minimum a disclaimer
 *    substantially similar to the "NO WARRANTY" disclaimer below
 *    ("Disclaimer") and any redistribution must be conditioned upon
 *    including a substantially similar Disclaimer requirement for further
 *    binary redistribution.
 * 3. Neither the names of the above-listed copyright holders nor the names
 *    of any contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * Alternatively, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") version 2 as published by the Free
 * Software Foundation.
 *
 * NO WARRANTY
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGES.
 */

#include <acpi/acpi.h>
#include <acpi/acparser.h>
#include <acpi/amlcode.h>
#include <acpi/acdispat.h>
#include <acpi/acinterp.h>
#include <acpi/acnamesp.h>
#include <acpi/acdebug.h>

#define _COMPONENT          ACPI_DISPATCHER
ACPI_MODULE_NAME("dsutils")

/*******************************************************************************
 *
 * FUNCTION:    acpi_ds_clear_implicit_return
 *
 * PARAMETERS:  walk_state          - Current State
 *
 * RETURN:      None.
 *
 * DESCRIPTION: Clear and remove a reference on an implicit return value.  Used
 *              to delete "stale" return values (if enabled, the return value
 *              from every operator is saved at least momentarily, in case the
 *              parent method exits.)
 *
 ******************************************************************************/
void acpi_ds_clear_implicit_return(struct acpi_walk_state *walk_state)
{
	ACPI_FUNCTION_NAME("ds_clear_implicit_return");

	/*
	 * Slack must be enabled for this feature
	 */
	if (!acpi_gbl_enable_interpreter_slack) {
		return;
	}

	if (walk_state->implicit_return_obj) {
		/*
		 * Delete any "stale" implicit return. However, in
		 * complex statements, the implicit return value can be
		 * bubbled up several levels.
		 */
		ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
				  "Removing reference on stale implicit return obj %p\n",
				  walk_state->implicit_return_obj));

		acpi_ut_remove_reference(walk_state->implicit_return_obj);
		walk_state->implicit_return_obj = NULL;
	}
}

#ifndef ACPI_NO_METHOD_EXECUTION
/*******************************************************************************
 *
 * FUNCTION:    acpi_ds_do_implicit_return
 *
 * PARAMETERS:  return_desc         - The return value
 *              walk_state          - Current State
 *              add_reference       - True if a reference should be added to the
 *                                    return object
 *
 * RETURN:      TRUE if implicit return enabled, FALSE otherwise
 *
 * DESCRIPTION: Implements the optional "implicit return".  We save the result
 *              of every ASL operator and control method invocation in case the
 *              parent method exit.  Before storing a new return value, we
 *              delete the previous return value.
 *
 ******************************************************************************/

u8
acpi_ds_do_implicit_return(union acpi_operand_object *return_desc,
			   struct acpi_walk_state *walk_state, u8 add_reference)
{
	ACPI_FUNCTION_NAME("ds_do_implicit_return");

	/*
	 * Slack must be enabled for this feature, and we must
	 * have a valid return object
	 */
	if ((!acpi_gbl_enable_interpreter_slack) || (!return_desc)) {
		return (FALSE);
	}

	ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
			  "Result %p will be implicitly returned; Prev=%p\n",
			  return_desc, walk_state->implicit_return_obj));

	/*
	 * Delete any "stale" implicit return value first. However, in
	 * complex statements, the implicit return value can be
	 * bubbled up several levels, so we don't clear the value if it
	 * is the same as the return_desc.
	 */
	if (walk_state->implicit_return_obj) {
		if (walk_state->implicit_return_obj == return_desc) {
			return (TRUE);
		}
		acpi_ds_clear_implicit_return(walk_state);
	}

	/* Save the implicit return value, add a reference if requested */

	walk_state->implicit_return_obj = return_desc;
	if (add_reference) {
		acpi_ut_add_reference(return_desc);
	}

	return (TRUE);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ds_is_result_used
 *
 * PARAMETERS:  Op                  - Current Op
 *              walk_state          - Current State
 *
 * RETURN:      TRUE if result is used, FALSE otherwise
 *
 * DESCRIPTION: Check if a result object will be used by the parent
 *
 ******************************************************************************/

u8
acpi_ds_is_result_used(union acpi_parse_object * op,
		       struct acpi_walk_state * walk_state)
{
	const struct acpi_opcode_info *parent_info;

	ACPI_FUNCTION_TRACE_PTR("ds_is_result_used", op);

	/* Must have both an Op and a Result Object */

	if (!op) {
		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Null Op\n"));
		return_VALUE(TRUE);
	}

	/*
	 * We know that this operator is not a
	 * Return() operator (would not come here.) The following code is the
	 * optional support for a so-called "implicit return". Some AML code
	 * assumes that the last value of the method is "implicitly" returned
	 * to the caller. Just save the last result as the return value.
	 * NOTE: this is optional because the ASL language does not actually
	 * support this behavior.
	 */
	(void)acpi_ds_do_implicit_return(walk_state->result_obj, walk_state,
					 TRUE);

	/*
	 * Now determine if the parent will use the result
	 *
	 * If there is no parent, or the parent is a scope_op, we are executing
	 * at the method level. An executing method typically has no parent,
	 * since each method is parsed separately.  A method invoked externally
	 * via execute_control_method has a scope_op as the parent.
	 */
	if ((!op->common.parent) ||
	    (op->common.parent->common.aml_opcode == AML_SCOPE_OP)) {
		/* No parent, the return value cannot possibly be used */

		ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
				  "At Method level, result of [%s] not used\n",
				  acpi_ps_get_opcode_name(op->common.
							  aml_opcode)));
		return_VALUE(FALSE);
	}

	/* Get info on the parent. The root_op is AML_SCOPE */

	parent_info =
	    acpi_ps_get_opcode_info(op->common.parent->common.aml_opcode);
	if (parent_info->class == AML_CLASS_UNKNOWN) {
		ACPI_DEBUG_PRINT((ACPI_DB_ERROR,
				  "Unknown parent opcode. Op=%p\n", op));
		return_VALUE(FALSE);
	}

	/*
	 * Decide what to do with the result based on the parent.  If
	 * the parent opcode will not use the result, delete the object.
	 * Otherwise leave it as is, it will be deleted when it is used
	 * as an operand later.
	 */
	switch (parent_info->class) {
	case AML_CLASS_CONTROL:

		switch (op->common.parent->common.aml_opcode) {
		case AML_RETURN_OP:

			/* Never delete the return value associated with a return opcode */

			goto result_used;

		case AML_IF_OP:
		case AML_WHILE_OP:

			/*
			 * If we are executing the predicate AND this is the predicate op,
			 * we will use the return value
			 */
			if ((walk_state->control_state->common.state ==
			     ACPI_CONTROL_PREDICATE_EXECUTING)
			    && (walk_state->control_state->control.
				predicate_op == op)) {
				goto result_used;
			}
			break;

		default:
			/* Ignore other control opcodes */
			break;
		}

		/* The general control opcode returns no result */

		goto result_not_used;

	case AML_CLASS_CREATE:

		/*
		 * These opcodes allow term_arg(s) as operands and therefore
		 * the operands can be method calls.  The result is used.
		 */
		goto result_used;

	case AML_CLASS_NAMED_OBJECT:

		if ((op->common.parent->common.aml_opcode == AML_REGION_OP) ||
		    (op->common.parent->common.aml_opcode == AML_DATA_REGION_OP)
		    || (op->common.parent->common.aml_opcode == AML_PACKAGE_OP)
		    || (op->common.parent->common.aml_opcode ==
			AML_VAR_PACKAGE_OP)
		    || (op->common.parent->common.aml_opcode == AML_BUFFER_OP)
		    || (op->common.parent->common.aml_opcode ==
			AML_INT_EVAL_SUBTREE_OP)) {
			/*
			 * These opcodes allow term_arg(s) as operands and therefore
			 * the operands can be method calls.  The result is used.
			 */
			goto result_used;
		}

		goto result_not_used;

	default:

		/*
		 * In all other cases. the parent will actually use the return
		 * object, so keep it.
		 */
		goto result_used;
	}

      result_used:
	ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
			  "Result of [%s] used by Parent [%s] Op=%p\n",
			  acpi_ps_get_opcode_name(op->common.aml_opcode),
			  acpi_ps_get_opcode_name(op->common.parent->common.
						  aml_opcode), op));

	return_VALUE(TRUE);

      result_not_used:
	ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
			  "Result of [%s] not used by Parent [%s] Op=%p\n",
			  acpi_ps_get_opcode_name(op->common.aml_opcode),
			  acpi_ps_get_opcode_name(op->common.parent->common.
						  aml_opcode), op));

	return_VALUE(FALSE);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ds_delete_result_if_not_used
 *
 * PARAMETERS:  Op              - Current parse Op
 *              result_obj      - Result of the operation
 *              walk_state      - Current state
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Used after interpretation of an opcode.  If there is an internal
 *              result descriptor, check if the parent opcode will actually use
 *              this result.  If not, delete the result now so that it will
 *              not become orphaned.
 *
 ******************************************************************************/

void
acpi_ds_delete_result_if_not_used(union acpi_parse_object *op,
				  union acpi_operand_object *result_obj,
				  struct acpi_walk_state *walk_state)
{
	union acpi_operand_object *obj_desc;
	acpi_status status;

	ACPI_FUNCTION_TRACE_PTR("ds_delete_result_if_not_used", result_obj);

	if (!op) {
		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Null Op\n"));
		return_VOID;
	}

	if (!result_obj) {
		return_VOID;
	}

	if (!acpi_ds_is_result_used(op, walk_state)) {
		/* Must pop the result stack (obj_desc should be equal to result_obj) */

		status = acpi_ds_result_pop(&obj_desc, walk_state);
		if (ACPI_SUCCESS(status)) {
			acpi_ut_remove_reference(result_obj);
		}
	}

	return_VOID;
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ds_resolve_operands