ACPICA: Several fixes for internal method result stack

fixes STACK_OVERFLOW exception on nested method calls. internal
bugzilla 262 and 275.

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Alexey Starikovskiy <astarikovskiy@suse.de>
Signed-off-by: Len Brown <len.brown@intel.com>

4 files changed, 158 insertions, 459 deletions

diff --git a/drivers/acpi/dispatcher/dsopcode.c b/drivers/acpi/dispatcher/dsopcode.c
index f501e083aac7..0c4630dc09f3 100644
--- a/drivers/acpi/dispatcher/dsopcode.c
+++ b/drivers/acpi/dispatcher/dsopcode.c
@@ -808,6 +808,12 @@ acpi_ds_eval_data_object_operands(struct acpi_walk_state *walk_state,
 
         /* The first operand (for all of these data objects) is the length */
 
+        /*
+         * Set proper index into operand stack for acpi_ds_obj_stack_push
+         * invoked inside acpi_ds_create_operand.
+         */
+        walk_state->operand_index = walk_state->num_operands;
+
         status = acpi_ds_create_operand(walk_state, op->common.value.arg, 1);
         if (ACPI_FAILURE(status)) {
                 return_ACPI_STATUS(status);
@@ -1070,8 +1076,7 @@ acpi_ds_exec_end_control_op(struct acpi_walk_state * walk_state,
                          * is set to anything other than zero!
                          */
                         walk_state->return_desc = walk_state->operands[0];
-                } else if ((walk_state->results) &&
-                           (walk_state->results->results.num_results > 0)) {
+                } else if (walk_state->result_count) {
 
                         /* Since we have a real Return(), delete any implicit return */
 
diff --git a/drivers/acpi/dispatcher/dsutils.c b/drivers/acpi/dispatcher/dsutils.c
index 71503c036f7c..d2a8cfdaec22 100644
--- a/drivers/acpi/dispatcher/dsutils.c
+++ b/drivers/acpi/dispatcher/dsutils.c
@@ -630,9 +630,7 @@ acpi_ds_create_operand(struct acpi_walk_state *walk_state,
                          * Use value that was already previously returned
                          * by the evaluation of this argument
                          */
-                        status =
-                            acpi_ds_result_pop_from_bottom(&obj_desc,
-                                                           walk_state);
+                        status = acpi_ds_result_pop(&obj_desc, walk_state);
                         if (ACPI_FAILURE(status)) {
                                 /*
                                  * Only error is underflow, and this indicates
@@ -698,27 +696,54 @@ acpi_ds_create_operands(struct acpi_walk_state *walk_state,
 {
         acpi_status status = AE_OK;
         union acpi_parse_object *arg;
-        u32 arg_count = 0;
+        union acpi_parse_object *arguments[ACPI_OBJ_NUM_OPERANDS];
+        u8 arg_count = 0;
+        u8 count = 0;
+        u8 index = walk_state->num_operands;
+        u8 i;
 
         ACPI_FUNCTION_TRACE_PTR(ds_create_operands, first_arg);
 
-        /* For all arguments in the list... */
+        /* Get all arguments in the list */
 
         arg = first_arg;
         while (arg) {
-                status = acpi_ds_create_operand(walk_state, arg, arg_count);
-                if (ACPI_FAILURE(status)) {
-                        goto cleanup;
+                if (index >= ACPI_OBJ_NUM_OPERANDS) {
+                        return_ACPI_STATUS(AE_BAD_DATA);
                 }
 
-                ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
-                                  "Arg #%d (%p) done, Arg1=%p\n", arg_count,
-                                  arg, first_arg));
+                arguments[index] = arg;
+                walk_state->operands[index] = NULL;
 
                 /* Move on to next argument, if any */
 
                 arg = arg->common.next;
                 arg_count++;
+                index++;
+        }
+
+        index--;
+
+        /* It is the appropriate order to get objects from the Result stack */
+
+        for (i = 0; i < arg_count; i++) {
+                arg = arguments[index];
+
+                /* Force the filling of the operand stack in inverse order */
+
+                walk_state->operand_index = index;
+
+                status = acpi_ds_create_operand(walk_state, arg, index);
+                if (ACPI_FAILURE(status)) {
+                        goto cleanup;
+                }
+
+                count++;
+                index--;
+
+                ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
+                                  "Arg #%d (%p) done, Arg1=%p\n", index, arg,
+                                  first_arg));
         }
 
         return_ACPI_STATUS(status);
@@ -729,9 +754,8 @@ acpi_ds_create_operands(struct acpi_walk_state *walk_state,
          * pop everything off of the operand stack and delete those
          * objects
          */
-        (void)acpi_ds_obj_stack_pop_and_delete(arg_count, walk_state);
+        acpi_ds_obj_stack_pop_and_delete(arg_count, walk_state);
 
-        ACPI_EXCEPTION((AE_INFO, status, "While creating Arg %d",
-                        (arg_count + 1)));
+        ACPI_EXCEPTION((AE_INFO, status, "While creating Arg %d", index));
         return_ACPI_STATUS(status);
 }
diff --git a/drivers/acpi/dispatcher/dswexec.c b/drivers/acpi/dispatcher/dswexec.c
index 69693fa07224..12b148587e3d 100644
--- a/drivers/acpi/dispatcher/dswexec.c
+++ b/drivers/acpi/dispatcher/dswexec.c
@@ -285,11 +285,6 @@ acpi_ds_exec_begin_op(struct acpi_walk_state *walk_state,
         switch (opcode_class) {
         case AML_CLASS_CONTROL:
 
-                status = acpi_ds_result_stack_push(walk_state);
-                if (ACPI_FAILURE(status)) {
-                        goto error_exit;
-                }
-
                 status = acpi_ds_exec_begin_control_op(walk_state, op);
                 break;
 
@@ -305,20 +300,11 @@ acpi_ds_exec_begin_op(struct acpi_walk_state *walk_state,
                         status = acpi_ds_load2_begin_op(walk_state, NULL);
                 }
 
-                if (op->common.aml_opcode == AML_REGION_OP) {
-                        status = acpi_ds_result_stack_push(walk_state);
-                }
                 break;
 
         case AML_CLASS_EXECUTE:
         case AML_CLASS_CREATE:
-                /*
-                 * Most operators with arguments (except create_xxx_field operators)
-                 * Start a new result/operand state
-                 */
-                if (walk_state->op_info->object_type != ACPI_TYPE_BUFFER_FIELD) {
-                        status = acpi_ds_result_stack_push(walk_state);
-                }
+
                 break;
 
         default:
@@ -374,6 +360,7 @@ acpi_status acpi_ds_exec_end_op(struct acpi_walk_state *walk_state)
         /* Init the walk state */
 
         walk_state->num_operands = 0;
+        walk_state->operand_index = 0;
         walk_state->return_desc = NULL;
         walk_state->result_obj = NULL;
 
@@ -400,13 +387,6 @@ acpi_status acpi_ds_exec_end_op(struct acpi_walk_state *walk_state)
                         goto cleanup;
                 }
 
-                /* Done with this result state (Now that operand stack is built) */
-
-                status = acpi_ds_result_stack_pop(walk_state);
-                if (ACPI_FAILURE(status)) {
-                        goto cleanup;
-                }
-
                 /*
                  * All opcodes require operand resolution, with the only exceptions
                  * being the object_type and size_of operators.
@@ -487,16 +467,6 @@ acpi_status acpi_ds_exec_end_op(struct acpi_walk_state *walk_state)
 
                         status = acpi_ds_exec_end_control_op(walk_state, op);
 
-                        /* Make sure to properly pop the result stack */
-
-                        if (ACPI_SUCCESS(status)) {
-                                status = acpi_ds_result_stack_pop(walk_state);
-                        } else if (status == AE_CTRL_PENDING) {
-                                status = acpi_ds_result_stack_pop(walk_state);
-                                if (ACPI_SUCCESS(status)) {
-                                        status = AE_CTRL_PENDING;
-                                }
-                        }
                         break;
 
                 case AML_TYPE_METHOD_CALL:
@@ -632,13 +602,6 @@ acpi_status acpi_ds_exec_end_op(struct acpi_walk_state *walk_state)
                                 break;
                         }
 
-                        /* Done with result state (Now that operand stack is built) */
-
-                        status = acpi_ds_result_stack_pop(walk_state);
-                        if (ACPI_FAILURE(status)) {
-                                goto cleanup;
-                        }
-
                         /*
                          * If a result object was returned from above, push it on the
                          * current result stack
@@ -671,8 +634,6 @@ acpi_status acpi_ds_exec_end_op(struct acpi_walk_state *walk_state)
                                 if (ACPI_FAILURE(status)) {
                                         break;
                                 }
-
-                                status = acpi_ds_result_stack_pop(walk_state);
                         }
                         break;
 
diff --git a/drivers/acpi/dispatcher/dswstate.c b/drivers/acpi/dispatcher/dswstate.c
index 5afcdd9c7449..698d2e1c219e 100644
--- a/drivers/acpi/dispatcher/dswstate.c
+++ b/drivers/acpi/dispatcher/dswstate.c
@@ -49,85 +49,9 @@
 #define _COMPONENT          ACPI_DISPATCHER
 ACPI_MODULE_NAME("dswstate")
 
-/* Local prototypes */
-#ifdef ACPI_OBSOLETE_FUNCTIONS
-acpi_status
-acpi_ds_result_insert(void *object,
-                      u32 index, struct acpi_walk_state *walk_state);
-
-acpi_status acpi_ds_obj_stack_delete_all(struct acpi_walk_state *walk_state);
-
-acpi_status
-acpi_ds_obj_stack_pop_object(union acpi_operand_object **object,
-                             struct acpi_walk_state *walk_state);
-
-void *acpi_ds_obj_stack_get_value(u32 index,
-                                  struct acpi_walk_state *walk_state);
-#endif
-
-#ifdef ACPI_FUTURE_USAGE
-/*******************************************************************************
- *
- * FUNCTION:    acpi_ds_result_remove
- *
- * PARAMETERS:  Object              - Where to return the popped object
- *              Index               - Where to extract the object
- *              walk_state          - Current Walk state
- *
- * RETURN:      Status
- *
- * DESCRIPTION: Pop an object off the bottom of this walk's result stack.  In
- *              other words, this is a FIFO.
- *
- ******************************************************************************/
-
-acpi_status
-acpi_ds_result_remove(union acpi_operand_object **object,
-                      u32 index, struct acpi_walk_state *walk_state)
-{
-        union acpi_generic_state *state;
-
-        ACPI_FUNCTION_NAME(ds_result_remove);
-
-        state = walk_state->results;
-        if (!state) {
-                ACPI_ERROR((AE_INFO, "No result object pushed! State=%p",
-                            walk_state));
-                return (AE_NOT_EXIST);
-        }
-
-        if (index >= ACPI_OBJ_MAX_OPERAND) {
-                ACPI_ERROR((AE_INFO,
-                            "Index out of range: %X State=%p Num=%X",
-                            index, walk_state, state->results.num_results));
-        }
-
-        /* Check for a valid result object */
-
-        if (!state->results.obj_desc[index]) {
-                ACPI_ERROR((AE_INFO,
-                            "Null operand! State=%p #Ops=%X, Index=%X",
-                            walk_state, state->results.num_results, index));
-                return (AE_AML_NO_RETURN_VALUE);
-        }
-
-        /* Remove the object */
-
-        state->results.num_results--;
-
-        *object = state->results.obj_desc[index];
-        state->results.obj_desc[index] = NULL;
-
-        ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
-                          "Obj=%p [%s] Index=%X State=%p Num=%X\n",
-                          *object,
-                          (*object) ? acpi_ut_get_object_type_name(*object) :
-                          "NULL", index, walk_state,
-                          state->results.num_results));
-
-        return (AE_OK);
-}
-#endif                          /*  ACPI_FUTURE_USAGE  */
+  /* Local prototypes */
+static acpi_status acpi_ds_result_stack_push(struct acpi_walk_state *ws);
+static acpi_status acpi_ds_result_stack_pop(struct acpi_walk_state *ws);
 
 /*******************************************************************************
  *
@@ -138,122 +62,67 @@ acpi_ds_result_remove(union acpi_operand_object **object,
  *
  * RETURN:      Status
  *
- * DESCRIPTION: Pop an object off the bottom of this walk's result stack.  In
- *              other words, this is a FIFO.
+ * DESCRIPTION: Pop an object off the top of this walk's result stack
  *
  ******************************************************************************/
 
 acpi_status
-acpi_ds_result_pop(union acpi_operand_object ** object,
-                   struct acpi_walk_state * walk_state)
+acpi_ds_result_pop(union acpi_operand_object **object,
+                   struct acpi_walk_state *walk_state)
 {
         acpi_native_uint index;
         union acpi_generic_state *state;
+        acpi_status status;
 
         ACPI_FUNCTION_NAME(ds_result_pop);
 
         state = walk_state->results;
-        if (!state) {
-                return (AE_OK);
-        }
-
-        if (!state->results.num_results) {
-                ACPI_ERROR((AE_INFO, "Result stack is empty! State=%p",
-                            walk_state));
-                return (AE_AML_NO_RETURN_VALUE);
-        }
 
-        /* Remove top element */
+        /* Incorrect state of result stack */
 
-        state->results.num_results--;
-
-        for (index = ACPI_OBJ_NUM_OPERANDS; index; index--) {
-
-                /* Check for a valid result object */
-
-                if (state->results.obj_desc[index - 1]) {
-                        *object = state->results.obj_desc[index - 1];
-                        state->results.obj_desc[index - 1] = NULL;
-
-                        ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
-                                          "Obj=%p [%s] Index=%X State=%p Num=%X\n",
-                                          *object,
-                                          (*object) ?
-                                          acpi_ut_get_object_type_name(*object)
-                                          : "NULL", (u32) index - 1, walk_state,
-                                          state->results.num_results));
-
-                        return (AE_OK);
-                }
+        if (state && !walk_state->result_count) {
+                ACPI_ERROR((AE_INFO, "No results on result stack"));
+                return (AE_AML_INTERNAL);
         }
 
-        ACPI_ERROR((AE_INFO, "No result objects! State=%p", walk_state));
-        return (AE_AML_NO_RETURN_VALUE);
-}
-
-/*******************************************************************************
- *
- * FUNCTION:    acpi_ds_result_pop_from_bottom
- *
- * PARAMETERS:  Object              - Where to return the popped object
- *              walk_state          - Current Walk state
- *
- * RETURN:      Status
- *
- * DESCRIPTION: Pop an object off the bottom of this walk's result stack.  In
- *              other words, this is a FIFO.
- *
- ******************************************************************************/
-
-acpi_status
-acpi_ds_result_pop_from_bottom(union acpi_operand_object ** object,
-                               struct acpi_walk_state * walk_state)
-{
-        acpi_native_uint index;
-        union acpi_generic_state *state;
+        if (!state && walk_state->result_count) {
+                ACPI_ERROR((AE_INFO, "No result state for result stack"));
+                return (AE_AML_INTERNAL);
+        }
 
-        ACPI_FUNCTION_NAME(ds_result_pop_from_bottom);
+        /* Empty result stack */
 
-        state = walk_state->results;
         if (!state) {
-                ACPI_ERROR((AE_INFO,
-                            "No result object pushed! State=%p", walk_state));
-                return (AE_NOT_EXIST);
-        }
-
-        if (!state->results.num_results) {
-                ACPI_ERROR((AE_INFO, "No result objects! State=%p",
+                ACPI_ERROR((AE_INFO, "Result stack is empty! State=%p",
                             walk_state));
                 return (AE_AML_NO_RETURN_VALUE);
         }
 
-        /* Remove Bottom element */
-
-        *object = state->results.obj_desc[0];
-
-        /* Push entire stack down one element */
-
-        for (index = 0; index < state->results.num_results; index++) {
-                state->results.obj_desc[index] =
-                    state->results.obj_desc[index + 1];
-        }
+        /* Return object of the top element and clean that top element result stack */
 
-        state->results.num_results--;
-
-        /* Check for a valid result object */
+        walk_state->result_count--;
+        index = walk_state->result_count % ACPI_RESULTS_FRAME_OBJ_NUM;
 
+        *object = state->results.obj_desc[index];
         if (!*object) {
                 ACPI_ERROR((AE_INFO,
-                            "Null operand! State=%p #Ops=%X Index=%X",
-                            walk_state, state->results.num_results,
-                            (u32) index));
+                            "No result objects on result stack, State=%p",
+                            walk_state));
                 return (AE_AML_NO_RETURN_VALUE);
         }
 
-        ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Obj=%p [%s] Results=%p State=%p\n",
-                          *object,
-                          (*object) ? acpi_ut_get_object_type_name(*object) :
-                          "NULL", state, walk_state));
+        state->results.obj_desc[index] = NULL;
+        if (index == 0) {
+                status = acpi_ds_result_stack_pop(walk_state);
+                if (ACPI_FAILURE(status)) {
+                        return (status);
+                }
+        }
+
+        ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
+                          "Obj=%p [%s] Index=%X State=%p Num=%X\n", *object,
+                          acpi_ut_get_object_type_name(*object),
+                          (u32) index, walk_state, walk_state->result_count));
 
         return (AE_OK);
 }
@@ -276,39 +145,56 @@ acpi_ds_result_push(union acpi_operand_object * object,
                     struct acpi_walk_state * walk_state)
 {
         union acpi_generic_state *state;
+        acpi_status status;
+        acpi_native_uint index;
 
         ACPI_FUNCTION_NAME(ds_result_push);
 
+        if (walk_state->result_count > walk_state->result_size) {
+                ACPI_ERROR((AE_INFO, "Result stack is full"));
+                return (AE_AML_INTERNAL);
+        } else if (walk_state->result_count == walk_state->result_size) {
+
+                /* Extend the result stack */
+
+                status = acpi_ds_result_stack_push(walk_state);
+                if (ACPI_FAILURE(status)) {
+                        ACPI_ERROR((AE_INFO,
+                                    "Failed to extend the result stack"));
+                        return (status);
+                }
+        }
+
+        if (!(walk_state->result_count < walk_state->result_size)) {
+                ACPI_ERROR((AE_INFO, "No free elements in result stack"));
+                return (AE_AML_INTERNAL);
+        }
+
         state = walk_state->results;
         if (!state) {
                 ACPI_ERROR((AE_INFO, "No result stack frame during push"));
                 return (AE_AML_INTERNAL);
         }
 
-        if (state->results.num_results == ACPI_OBJ_NUM_OPERANDS) {
-                ACPI_ERROR((AE_INFO,
-                            "Result stack overflow: Obj=%p State=%p Num=%X",
-                            object, walk_state, state->results.num_results));
-                return (AE_STACK_OVERFLOW);
-        }
-
         if (!object) {
                 ACPI_ERROR((AE_INFO,
                             "Null Object! Obj=%p State=%p Num=%X",
-                            object, walk_state, state->results.num_results));
+                            object, walk_state, walk_state->result_count));
                 return (AE_BAD_PARAMETER);
         }
 
-        state->results.obj_desc[state->results.num_results] = object;
-        state->results.num_results++;
+        /* Assign the address of object to the top free element of result stack */
+
+        index = walk_state->result_count % ACPI_RESULTS_FRAME_OBJ_NUM;
+        state->results.obj_desc[index] = object;
+        walk_state->result_count++;
 
         ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Obj=%p [%s] State=%p Num=%X Cur=%X\n",
                           object,
-                          object ?
                           acpi_ut_get_object_type_name((union
                                                         acpi_operand_object *)
-                                                       object) : "NULL",
-                          walk_state, state->results.num_results,
+                                                       object), walk_state,
+                          walk_state->result_count,
                           walk_state->current_result));
 
         return (AE_OK);
@@ -322,16 +208,25 @@ acpi_ds_result_push(union acpi_operand_object * object,
  *
  * RETURN:      Status
  *
- * DESCRIPTION: Push an object onto the walk_state result stack.
+ * DESCRIPTION: Push an object onto the walk_state result stack
  *
  ******************************************************************************/
 
-acpi_status acpi_ds_result_stack_push(struct acpi_walk_state * walk_state)
+static acpi_status acpi_ds_result_stack_push(struct acpi_walk_state *walk_state)
 {
         union acpi_generic_state *state;
 
         ACPI_FUNCTION_NAME(ds_result_stack_push);
 
+        /* Check for stack overflow */
+
+        if ((walk_state->result_size + ACPI_RESULTS_FRAME_OBJ_NUM) >
+            ACPI_RESULTS_OBJ_NUM_MAX) {
+                ACPI_ERROR((AE_INFO, "Result stack overflow: State=%p Num=%X",
+                            walk_state, walk_state->result_size));
+                return (AE_STACK_OVERFLOW);
+        }
+
         state = acpi_ut_create_generic_state();
         if (!state) {
                 return (AE_NO_MEMORY);
@@ -340,6 +235,10 @@ acpi_status acpi_ds_result_stack_push(struct acpi_walk_state * walk_state)
         state->common.descriptor_type = ACPI_DESC_TYPE_STATE_RESULT;
         acpi_ut_push_generic_state(&walk_state->results, state);
 
+        /* Increase the length of the result stack by the length of frame */
+
+        walk_state->result_size += ACPI_RESULTS_FRAME_OBJ_NUM;
+
         ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Results=%p State=%p\n",
                           state, walk_state));
 
@@ -354,11 +253,11 @@ acpi_status acpi_ds_result_stack_push(struct acpi_walk_state * walk_state)
  *
  * RETURN:      Status
  *
- * DESCRIPTION: Pop an object off of the walk_state result stack.
+ * DESCRIPTION: Pop an object off of the walk_state result stack
  *
  ******************************************************************************/
 
-acpi_status acpi_ds_result_stack_pop(struct acpi_walk_state * walk_state)
+static acpi_status acpi_ds_result_stack_pop(struct acpi_walk_state *walk_state)
 {
         union acpi_generic_state *state;
 
@@ -367,18 +266,27 @@ acpi_status acpi_ds_result_stack_pop(struct acpi_walk_state * walk_state)
         /* Check for stack underflow */
 
         if (walk_state->results == NULL) {
-                ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Underflow - State=%p\n",
+                ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
+                                  "Result stack underflow - State=%p\n",
                                   walk_state));
                 return (AE_AML_NO_OPERAND);
         }
 
+        if (walk_state->result_size < ACPI_RESULTS_FRAME_OBJ_NUM) {
+                ACPI_ERROR((AE_INFO, "Insufficient result stack size"));
+                return (AE_AML_INTERNAL);
+        }
+
         state = acpi_ut_pop_generic_state(&walk_state->results);
+        acpi_ut_delete_generic_state(state);
+
+        /* Decrease the length of result stack by the length of frame */
+
+        walk_state->result_size -= ACPI_RESULTS_FRAME_OBJ_NUM;
 
         ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
                           "Result=%p RemainingResults=%X State=%p\n",
-                          state, state->results.num_results, walk_state));
-
-        acpi_ut_delete_generic_state(state);
+                          state, walk_state->result_count, walk_state));
 
         return (AE_OK);
 }
@@ -412,9 +320,13 @@ acpi_ds_obj_stack_push(void *object, struct acpi_walk_state * walk_state)
 
         /* Put the object onto the stack */
 
-        walk_state->operands[walk_state->num_operands] = object;
+        walk_state->operands[walk_state->operand_index] = object;
         walk_state->num_operands++;
 
+        /* For the usual order of filling the operand stack */
+
+        walk_state->operand_index++;
+
         ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Obj=%p [%s] State=%p #Ops=%X\n",
                           object,
                           acpi_ut_get_object_type_name((union
@@ -484,43 +396,36 @@ acpi_ds_obj_stack_pop(u32 pop_count, struct acpi_walk_state * walk_state)
  *
  ******************************************************************************/
 
-acpi_status
+void
 acpi_ds_obj_stack_pop_and_delete(u32 pop_count,
-                                 struct acpi_walk_state * walk_state)
+                                 struct acpi_walk_state *walk_state)
 {
         u32 i;
         union acpi_operand_object *obj_desc;
 
         ACPI_FUNCTION_NAME(ds_obj_stack_pop_and_delete);
 
-        for (i = 0; i < pop_count; i++) {
-
-                /* Check for stack underflow */
+        if (pop_count == 0) {
+                return;
+        }
 
+        for (i = (pop_count - 1); i >= 0; i--) {
                 if (walk_state->num_operands == 0) {
-                        ACPI_ERROR((AE_INFO,
-                                    "Object stack underflow! Count=%X State=%p #Ops=%X",
-                                    pop_count, walk_state,
-                                    walk_state->num_operands));
-                        return (AE_STACK_UNDERFLOW);
+                        return;
                 }
 
                 /* Pop the stack and delete an object if present in this stack entry */
 
                 walk_state->num_operands--;
-                obj_desc = walk_state->operands[walk_state->num_operands];
+                obj_desc = walk_state->operands[i];
                 if (obj_desc) {
-                        acpi_ut_remove_reference(walk_state->
-                                                 operands[walk_state->
-                                                          num_operands]);
-                        walk_state->operands[walk_state->num_operands] = NULL;
+                        acpi_ut_remove_reference(walk_state->operands[i]);
+                        walk_state->operands[i] = NULL;
                 }
         }
 
         ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Count=%X State=%p #Ops=%X\n",
                           pop_count, walk_state, walk_state->num_operands));
-
-        return (AE_OK);
 }
 
 /*******************************************************************************
@@ -560,7 +465,7 @@ struct acpi_walk_state *acpi_ds_get_current_walk_state(struct acpi_thread_state
  *
  * RETURN:      None
  *
- * DESCRIPTION: Place the Thread state at the head of the state list.
+ * DESCRIPTION: Place the Thread state at the head of the state list
  *
  ******************************************************************************/
 
@@ -636,7 +541,6 @@ struct acpi_walk_state *acpi_ds_create_walk_state(acpi_owner_id owner_id, union
                                                   *thread)
 {
         struct acpi_walk_state *walk_state;
-        acpi_status status;
 
         ACPI_FUNCTION_TRACE(ds_create_walk_state);
 
@@ -659,14 +563,6 @@ struct acpi_walk_state *acpi_ds_create_walk_state(acpi_owner_id owner_id, union
         acpi_ds_method_data_init(walk_state);
 #endif
 
-        /* Create an initial result stack entry */
-
-        status = acpi_ds_result_stack_push(walk_state);
-        if (ACPI_FAILURE(status)) {
-                ACPI_FREE(walk_state);
-                return_PTR(NULL);
-        }
-
         /* Put the new state at the head of the walk list */
 
         if (thread) {
@@ -860,190 +756,3 @@ void acpi_ds_delete_walk_state(struct acpi_walk_state *walk_state)
         ACPI_FREE(walk_state);
         return_VOID;
 }
-
-#ifdef ACPI_OBSOLETE_FUNCTIONS
-/*******************************************************************************
- *
- * FUNCTION:    acpi_ds_result_insert
- *
- * PARAMETERS:  Object              - Object to push
- *              Index               - Where to insert the object
- *              walk_state          - Current Walk state
- *
- * RETURN:      Status
- *
- * DESCRIPTION: Insert an object onto this walk's result stack
- *
- ******************************************************************************/
-
-acpi_status
-acpi_ds_result_insert(void *object,
-                      u32 index, struct acpi_walk_state *walk_state)
-{
-        union acpi_generic_state *state;
-
-        ACPI_FUNCTION_NAME(ds_result_insert);
-
-        state = walk_state->results;
-        if (!state) {
-                ACPI_ERROR((AE_INFO, "No result object pushed! State=%p",
-                            walk_state));
-                return (AE_NOT_EXIST);
-        }
-
-        if (index >= ACPI_OBJ_NUM_OPERANDS) {
-                ACPI_ERROR((AE_INFO,
-                            "Index out of range: %X Obj=%p State=%p Num=%X",
-                            index, object, walk_state,
-                            state->results.num_results));
-                return (AE_BAD_PARAMETER);
-        }
-
-        if (!object) {
-                ACPI_ERROR((AE_INFO,
-                            "Null Object! Index=%X Obj=%p State=%p Num=%X",
-                            index, object, walk_state,
-                            state->results.num_results));
-                return (AE_BAD_PARAMETER);
-        }
-
-        state->results.obj_desc[index] = object;
-        state->results.num_results++;
-
-        ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
-                          "Obj=%p [%s] State=%p Num=%X Cur=%X\n",
-                          object,
-                          object ?
-                          acpi_ut_get_object_type_name((union
-                                                        acpi_operand_object *)
-                                                       object) : "NULL",
-                          walk_state, state->results.num_results,
-                          walk_state->current_result));
-
-        return (AE_OK);
-}
-
-/*******************************************************************************
- *
- * FUNCTION:    acpi_ds_obj_stack_delete_all
- *
- * PARAMETERS:  walk_state          - Current Walk state
- *
- * RETURN:      Status
- *
- * DESCRIPTION: Clear the object stack by deleting all objects that are on it.
- *              Should be used with great care, if at all!
- *
- ******************************************************************************/
-
-acpi_status acpi_ds_obj_stack_delete_all(struct acpi_walk_state * walk_state)
-{
-        u32 i;
-
-        ACPI_FUNCTION_TRACE_PTR(ds_obj_stack_delete_all, walk_state);
-
-        /* The stack size is configurable, but fixed */
-
-        for (i = 0; i < ACPI_OBJ_NUM_OPERANDS; i++) {
-                if (walk_state->operands[i]) {
-                        acpi_ut_remove_reference(walk_state->operands[i]);
-                        walk_state->operands[i] = NULL;
-                }
-        }
-
-        return_ACPI_STATUS(AE_OK);
-}
-
-/*******************************************************************************
- *
- * FUNCTION:    acpi_ds_obj_stack_pop_object
- *
- * PARAMETERS:  Object              - Where to return the popped object
- *              walk_state          - Current Walk state
- *
- * RETURN:      Status
- *
- * DESCRIPTION: Pop this walk's object stack.  Objects on the stack are NOT
- *              deleted by this routine.
- *
- ******************************************************************************/
-
-acpi_status
-acpi_ds_obj_stack_pop_object(union acpi_operand_object **object,
-                             struct acpi_walk_state *walk_state)
-{
-        ACPI_FUNCTION_NAME(ds_obj_stack_pop_object);
-
-        /* Check for stack underflow */
-
-        if (walk_state->num_operands == 0) {
-                ACPI_ERROR((AE_INFO,
-                            "Missing operand/stack empty! State=%p #Ops=%X",
-                            walk_state, walk_state->num_operands));
-                *object = NULL;
-                return (AE_AML_NO_OPERAND);
-        }
-
-        /* Pop the stack */
-
-        walk_state->num_operands--;
-
-        /* Check for a valid operand */
-
-        if (!walk_state->operands[walk_state->num_operands]) {
-                ACPI_ERROR((AE_INFO,
-                            "Null operand! State=%p #Ops=%X",
-                            walk_state, walk_state->num_operands));
-                *object = NULL;
-                return (AE_AML_NO_OPERAND);
-        }
-
-        /* Get operand and set stack entry to null */
-
-        *object = walk_state->operands[walk_state->num_operands];
-        walk_state->operands[walk_state->num_operands] = NULL;
-
-        ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "Obj=%p [%s] State=%p #Ops=%X\n",
-                          *object, acpi_ut_get_object_type_name(*object),
-                          walk_state, walk_state->num_operands));
-
-        return (AE_OK);
-}
-
-/*******************************************************************************
- *
- * FUNCTION:    acpi_ds_obj_stack_get_value
- *
- * PARAMETERS:  Index               - Stack index whose value is desired.  Based
- *                                    on the top of the stack (index=0 == top)
- *              walk_state          - Current Walk state
- *
- * RETURN:      Pointer to the requested operand
- *
- * DESCRIPTION: Retrieve an object from this walk's operand stack.  Index must
- *              be within the range of the current stack pointer.
- *
- ******************************************************************************/
-
-void *acpi_ds_obj_stack_get_value(u32 index, struct acpi_walk_state *walk_state)
-{
-
-        ACPI_FUNCTION_TRACE_PTR(ds_obj_stack_get_value, walk_state);
-
-        /* Can't do it if the stack is empty */
-
-        if (walk_state->num_operands == 0) {
-                return_PTR(NULL);
-        }
-
-        /* or if the index is past the top of the stack */
-
-        if (index > (walk_state->num_operands - (u32) 1)) {
-                return_PTR(NULL);
-        }
-
-        return_PTR(walk_state->
-                   operands[(acpi_native_uint) (walk_state->num_operands - 1) -
-                            index]);
-}
-#endif