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hotspot/src/share/vm/runtime/vmStructs.hpp

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+/*
+ * Copyright 2000-2001 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+// This table encapsulates the debugging information required by the
+// serviceability agent in order to run. Specifically, we need to
+// understand the layout of certain C data structures (offsets, in
+// bytes, of their fields.)
+//
+// There are alternatives for the design of this mechanism, including
+// parsing platform-specific debugging symbols from a debug build into
+// a program database. While this current mechanism can be considered
+// to be a workaround for the inability to debug arbitrary C and C++
+// programs at the present time, it does have certain advantages.
+// First, it is platform-independent, which will vastly simplify the
+// initial bringup of the system both now and on future platforms.
+// Second, it is embedded within the VM, as opposed to being in a
+// separate program database; experience has shown that whenever
+// portions of a system are decoupled, version skew is problematic.
+// Third, generating a program database, for example for a product
+// build, would probably require two builds to be done: the desired
+// product build as well as an intermediary build with the PRODUCT
+// flag turned on but also compiled with -g, leading to a doubling of
+// the time required to get a serviceability agent-debuggable product
+// build. Fourth, and very significantly, this table probably
+// preserves more information about field types than stabs do; for
+// example, it preserves the fact that a field is a "jlong" rather
+// than transforming the type according to the typedef in jni_md.h,
+// which allows the Java-side code to identify "Java-sized" fields in
+// C++ data structures. If the symbol parsing mechanism was redone
+// using stabs, it might still be necessary to have a table somewhere
+// containing this information.
+//
+// Do not change the sizes or signedness of the integer values in
+// these data structures; they are fixed over in the serviceability
+// agent's Java code (for bootstrapping).
+
+typedef struct {
+  const char* typeName;            // The type name containing the given field (example: "Klass")
+  const char* fieldName;           // The field name within the type           (example: "_name")
+  const char* typeString;          // Quoted name of the type of this field (example: "symbolOopDesc*";
+                                   // parsed in Java to ensure type correctness
+  int32_t  isStatic;               // Indicates whether following field is an offset or an address
+  uint64_t offset;                 // Offset of field within structure; only used for nonstatic fields
+  void* address;                   // Address of field; only used for static fields
+                                   // ("offset" can not be reused because of apparent SparcWorks compiler bug
+                                   // in generation of initializer data)
+} VMStructEntry;
+
+typedef struct {
+  const char* typeName;            // Type name (example: "methodOopDesc")
+  const char* superclassName;      // Superclass name, or null if none (example: "oopDesc")
+  int32_t isOopType;               // Does this type represent an oop typedef? (i.e., "methodOop" or
+                                   // "klassOop", but NOT "methodOopDesc")
+  int32_t isIntegerType;           // Does this type represent an integer type (of arbitrary size)?
+  int32_t isUnsigned;              // If so, is it unsigned?
+  uint64_t size;                   // Size, in bytes, of the type
+} VMTypeEntry;
+
+typedef struct {
+  const char* name;                // Name of constant (example: "_thread_in_native")
+  int32_t value;                   // Value of constant
+} VMIntConstantEntry;
+
+typedef struct {
+  const char* name;                // Name of constant (example: "_thread_in_native")
+  uint64_t value;                  // Value of constant
+} VMLongConstantEntry;
+
+// This class is a friend of most classes, to be able to access
+// private fields
+class VMStructs {
+public:
+  // The last entry is identified over in the serviceability agent by
+  // the fact that it has a NULL fieldName
+  static VMStructEntry localHotSpotVMStructs[];
+
+  // The last entry is identified over in the serviceability agent by
+  // the fact that it has a NULL typeName
+  static VMTypeEntry   localHotSpotVMTypes[];
+
+  // Table of integer constants required by the serviceability agent.
+  // The last entry is identified over in the serviceability agent by
+  // the fact that it has a NULL typeName
+  static VMIntConstantEntry localHotSpotVMIntConstants[];
+
+  // Table of long constants required by the serviceability agent.
+  // The last entry is identified over in the serviceability agent by
+  // the fact that it has a NULL typeName
+  static VMLongConstantEntry localHotSpotVMLongConstants[];
+
+  // This is used to run any checking code necessary for validation of
+  // the data structure (debug build only)
+  static void init();
+
+private:
+  // Look up a type in localHotSpotVMTypes using strcmp() (debug build only).
+  // Returns 1 if found, 0 if not.
+  //  debug_only(static int findType(const char* typeName);)
+  static int findType(const char* typeName);
+};