iASL: Warn if reserved method incorrectly returns a value.

Many predefined names are defined such that they do not return
a value. If implemented as a method, issue a warning if such
a name returns a value. ACPICA BZ 855.

source/compiler/aslmessages.h

@@ -260,6 +260,7 @@ typedef enum
     ASL_MSG_HID_LENGTH,
     ASL_MSG_NULL_STRING,
     ASL_MSG_LEADING_ASTERISK,
+    ASL_MSG_RESERVED_NO_RETURN_VAL,
 
     ASL_MSG_INVALID_FIELD_NAME,
     ASL_MSG_INTEGER_SIZE,
@@ -411,6 +412,7 @@ char                        *AslMessages [] = {
 /*    ASL_MSG_HID_LENGTH */                 "_HID string must be exactly 7 or 8 characters",
 /*    ASL_MSG_NULL_STRING */                "Invalid zero-length (null) string",
 /*    ASL_MSG_LEADING_ASTERISK */           "Invalid leading asterisk",
+/*    ASL_MSG_RESERVED_NO_RETURN_VAL */     "Reserved method should not return a value",
 
 /* These messages are used by the data table compiler only */
 

source/compiler/aslpredef.c

@@ -126,6 +126,11 @@
 
 /* Local prototypes */
 
+static void
+ApCheckForUnexpectedReturnValue (
+    ACPI_PARSE_OBJECT       *Op,
+    ASL_METHOD_INFO         *MethodInfo);
+
 static UINT32
 ApCheckForSpecialName (
     ACPI_PARSE_OBJECT       *Op,
@@ -308,6 +313,53 @@ ApCheckForPredefinedMethod (
 }
 
 
+/*******************************************************************************
+ *
+ * FUNCTION:    ApCheckForUnexpectedReturnValue
+ *
+ * PARAMETERS:  Op              - A parse node of type "RETURN".
+ *              MethodInfo      - Saved info about this method
+ *
+ * RETURN:      None
+ *
+ * DESCRIPTION: Check for an unexpected return value from a predefined method.
+ *              Invoked for predefined methods that are defined to not return
+ *              any value. If there is a return value, issue a remark, since
+ *              the ASL writer may be confused as to the method definition
+ *              and/or functionality.
+ *
+ * Note: We ignore all return values of "Zero", since this is what a standalone
+ *       Return() statement will always generate -- so we ignore it here --
+ *       i.e., there is no difference between Return() and Return(Zero).
+ *       Also, a null Return() will be disassembled to return(Zero) -- so, we
+ *       don't want to generate extraneous remarks/warnings for a disassembled
+ *       ASL file.
+ *
+ ******************************************************************************/
+
+static void
+ApCheckForUnexpectedReturnValue (
+    ACPI_PARSE_OBJECT       *Op,
+    ASL_METHOD_INFO         *MethodInfo)
+{
+    ACPI_PARSE_OBJECT       *ReturnValueOp;
+
+
+    /* Ignore Return() and Return(Zero) (they are the same) */
+
+    ReturnValueOp = Op->Asl.Child;
+    if (ReturnValueOp->Asl.ParseOpcode == PARSEOP_ZERO)
+    {
+        return;
+    }
+
+    /* We have a valid return value, but the reserved name did not expect it */
+
+    AslError (ASL_WARNING, ASL_MSG_RESERVED_NO_RETURN_VAL,
+        Op, MethodInfo->Op->Asl.ExternalName);
+}
+
+
 /*******************************************************************************
  *
  * FUNCTION:    ApCheckPredefinedReturnValue
@@ -321,7 +373,9 @@ ApCheckForPredefinedMethod (
  *              value. Only "static" types can be validated - a simple return
  *              of an integer/string/buffer/package or a named reference to
  *              a static object. Values such as a Localx or Argx or a control
- *              method invocation are not checked.
+ *              method invocation are not checked. Issue a warning if there is
+ *              a valid return value, but the reserved method defines no
+ *              return value.
  *
  ******************************************************************************/
 
@@ -341,20 +395,27 @@ ApCheckPredefinedReturnValue (
 
     switch (Index)
     {
+    case ACPI_EVENT_RESERVED_NAME:      /* _Lxx/_Exx/_Wxx/_Qxx methods */
+
+        /* No return value expected, warn if there is one */
+
+        ApCheckForUnexpectedReturnValue (Op, MethodInfo);
+        return;
+
     case ACPI_NOT_RESERVED_NAME:        /* No underscore or _Txx or _xxx name not matched */
     case ACPI_PREDEFINED_NAME:          /* Resource Name or reserved scope name */
     case ACPI_COMPILER_RESERVED_NAME:   /* A _Txx that was not emitted by compiler */
-    case ACPI_EVENT_RESERVED_NAME:      /* _Lxx/_Exx/_Wxx/_Qxx methods */
 
         /* Just return, nothing to do */
         return;
 
     default: /* A standard predefined ACPI name */
 
-        /* Exit if no return value expected */
-
         if (!PredefinedNames[Index].Info.ExpectedBtypes)
         {
+            /* No return value expected, warn if there is one */
+
+            ApCheckForUnexpectedReturnValue (Op, MethodInfo);
             return;
         }
 

tests/misc/badcode.asl

@@ -165,6 +165,17 @@ DefinitionBlock ("badcode.aml", "DSDT", 1, "Intel", "Example", 0x00000001)
     Name (_INI, 1)
     Name (_PTP, 2)
 
+    // Predefined names that should not have a return value
+
+    Method (_FDM, 1)
+    {
+        Return (Buffer(1){0x33})
+    }
+    Method (_Q22)
+    {
+        Return ("Unexpected Return Value")
+    }
+
     /*
      * Resource Descriptor error checking
      */