8327246: Add a jcmd diagnostic command to list Class origin URLs where possible

src/hotspot/share/oops/instanceKlass.cpp

@@ -36,6 +36,7 @@
 #include "classfile/classLoaderData.inline.hpp"
 #include "classfile/javaClasses.hpp"
 #include "classfile/moduleEntry.hpp"
+#include "classfile/symbolTable.hpp"
 #include "classfile/systemDictionary.hpp"
 #include "classfile/systemDictionaryShared.hpp"
 #include "classfile/verifier.hpp"
@@ -2364,8 +2365,8 @@ Method* InstanceKlass::lookup_method_in_all_interfaces(Symbol* name,
   return nullptr;
 }
 
-PrintClassClosure::PrintClassClosure(outputStream* st, bool verbose)
-  :_st(st), _verbose(verbose) {
+PrintClassClosure::PrintClassClosure(outputStream* st, bool verbose, bool location)
+  :_st(st), _verbose(verbose), _location(location), _aot_statics(0), _aot_dynamics(0) {
   ResourceMark rm;
   _st->print("%-18s  ", "KlassAddr");
   _st->print("%-4s  ", "Size");
@@ -2382,27 +2383,68 @@ void PrintClassClosure::do_klass(Klass* k)  {
   // klass size
   _st->print("%4d  ", k->size());
   // initialization state
-  if (k->is_instance_klass()) {
-    _st->print("%-20s  ",InstanceKlass::cast(k)->init_state_name());
-  } else {
-    _st->print("%-20s  ","");
-  }
+
+  InstanceKlass* ik = k->is_instance_klass() ? InstanceKlass::cast(k) : nullptr;
+  _st->print("%-20s  ", ik != nullptr ? InstanceKlass::cast(k)->init_state_name() : "");
+
   // misc flags(Changes should synced with ClassesDCmd::ClassesDCmd help doc)
   char buf[10];
   int i = 0;
   if (k->has_finalizer()) buf[i++] = 'F';
-  if (k->is_instance_klass()) {
-    InstanceKlass* ik = InstanceKlass::cast(k);
+  if (ik != nullptr) {
     if (ik->has_final_method()) buf[i++] = 'f';
     if (ik->is_rewritten()) buf[i++] = 'W';
     if (ik->is_contended()) buf[i++] = 'C';
     if (ik->has_been_redefined()) buf[i++] = 'R';
-    if (ik->in_aot_cache()) buf[i++] = 'S';
+    if (ik->in_aot_cache()) {
+      buf[i++] = 'S';
+
+      if (_location) {
+        if (AOTMetaspace::in_aot_cache_static_region((void*) k)) {
+          _aot_statics++;
+          buf[i++] = 's';
+        } else if (AOTMetaspace::in_aot_cache_dynamic_region((void*) k)) {
+          _aot_dynamics++;
+          buf[i++] = 'd';
+        }
+      }
+    }
   }
   buf[i++] = '\0';
   _st->print("%-7s  ", buf);
   // klass name
   _st->print("%-5s  ", k->external_name());
+
+  if (ik != nullptr && _location) {
+    oop pd = java_lang_Class::protection_domain(k->java_mirror());
+
+    if (pd != nullptr) {
+      assert(pd->klass()->is_instance_klass(), "pd klass is not InstanceKlass");
+      TempNewSymbol css  = SymbolTable::new_symbol("codesource");
+      TempNewSymbol csss = SymbolTable::new_symbol("Ljava/security/CodeSource;");
+      fieldDescriptor csfd;
+
+      if (InstanceKlass::cast(pd->klass())->find_field(css, csss, &csfd)) {
+        oop cs = pd->obj_field(csfd.offset());
+
+        if (cs != nullptr) {
+          assert(cs->klass()->is_instance_klass(), "cs klass is not InstanceKlass");
+          fieldDescriptor locfd;
+          TempNewSymbol csls  = SymbolTable::new_symbol("locationNoFragString");
+          TempNewSymbol cslss = SymbolTable::new_symbol("Ljava/lang/String;");
+
+          if (InstanceKlass::cast(cs->klass())->find_field(csls, cslss, &locfd)) {
+            oop loc = cs->obj_field(locfd.offset());
+            assert(loc == nullptr || loc->klass() == vmClasses::String_klass(), "locationNoFragString field is not a String");
+
+            if (loc != nullptr) {
+              java_lang_String::print(loc, _st, JVM_MAXPATHLEN);
+            }
+          }
+        }
+      }
+    }
+  }
   // end
   _st->cr();
   if (_verbose) {

src/hotspot/share/oops/instanceKlass.hpp

@@ -1207,8 +1207,12 @@ class PrintClassClosure : public KlassClosure {
 private:
   outputStream* _st;
   bool _verbose;
+  bool _location;
 public:
-  PrintClassClosure(outputStream* st, bool verbose);
+  unsigned int _aot_statics;
+  unsigned int _aot_dynamics;
+
+  PrintClassClosure(outputStream* st, bool verbose, bool location);
 
   void do_klass(Klass* k);
 };

src/hotspot/share/services/diagnosticCommand.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2011, 2026, Oracle and/or its affiliates. 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
@@ -25,6 +25,7 @@
 #include "cds/aotMetaspace.hpp"
 #include "cds/cds_globals.hpp"
 #include "cds/cdsConfig.hpp"
+#include "cds/filemap.hpp"
 #include "classfile/classLoaderDataGraph.hpp"
 #include "classfile/classLoaderHierarchyDCmd.hpp"
 #include "classfile/classLoaderStats.hpp"
@@ -947,36 +948,37 @@ void ClassHierarchyDCmd::execute(DCmdSource source, TRAPS) {
 
 ClassesDCmd::ClassesDCmd(outputStream* output, bool heap) :
                                      DCmdWithParser(output, heap),
-  _verbose("-verbose",
-           "Dump the detailed content of a Java class. "
-           "Some classes are annotated with flags: "
-           "F = has, or inherits, a non-empty finalize method, "
-           "f = has final method, "
-           "W = methods rewritten, "
-           "C = marked with @Contended annotation, "
-           "R = has been redefined, "
-           "S = is shared class",
-           "BOOLEAN", false, "false") {
+  _verbose("-verbose", "Dump the detailed content of a Java class", "BOOLEAN", false, "false"),
+  _location("-location", "Print class file location URL (if available)", "BOOLEAN", false, "false") {
   _dcmdparser.add_dcmd_option(&_verbose);
+  _dcmdparser.add_dcmd_option(&_location);
 }
 
 class VM_PrintClasses : public VM_Operation {
 private:
   outputStream* _out;
   bool _verbose;
+  bool _location;
 public:
-  VM_PrintClasses(outputStream* out, bool verbose) : _out(out), _verbose(verbose) {}
+  VM_PrintClasses(outputStream* out, bool verbose, bool location) : _out(out), _verbose(verbose), _location(location) {}
 
   virtual VMOp_Type type() const { return VMOp_PrintClasses; }
 
   virtual void doit() {
-    PrintClassClosure closure(_out, _verbose);
+    PrintClassClosure closure(_out, _verbose, _location);
     ClassLoaderDataGraph::classes_do(&closure);
+
+    if (_location) {
+      if (closure._aot_statics > 0)
+        _out->print_cr("\n%d classes shared from static cache: %s", closure._aot_statics, FileMapInfo::current_info()->full_path());
+      if (closure._aot_dynamics > 0)
+        _out->print_cr("\n%d classes shared from dynamic cache: %s", closure._aot_dynamics, FileMapInfo::dynamic_info()->full_path());
+    }
   }
 };
 
 void ClassesDCmd::execute(DCmdSource source, TRAPS) {
-  VM_PrintClasses vmop(output(), _verbose.value());
+  VM_PrintClasses vmop(output(), _verbose.value(), _location.value());
   VMThread::execute(&vmop);
 }
 

src/hotspot/share/services/diagnosticCommand.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2011, 2026, Oracle and/or its affiliates. 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
@@ -744,16 +744,20 @@ public:
 };
 
 class ClassesDCmd : public DCmdWithParser {
+private:
+  static constexpr const char *desc = "Print all loaded classes,\nclasses are annotated with flags:\n F = has, or inherits, a non-empty finalize method,\n f = has final method,\n W = methods rewritten,\n C = marked with @Contended annotation,\n R = has been redefined,\n S = is an (App)CDS shared class,\n     (if -location is specified, append: 's' (static) or 'd' (dynamic) for AOT cache location)";
+
 protected:
   DCmdArgument<bool> _verbose;
+  DCmdArgument<bool> _location;
 public:
-  static int num_arguments() { return 1; }
+  static int num_arguments() { return 2; }
   ClassesDCmd(outputStream* output, bool heap);
   static const char* name() {
     return "VM.classes";
   }
   static const char* description() {
-    return "Print all loaded classes";
+    return desc;
   }
   static const char* impact() {
       return "Medium: Depends on number of loaded classes.";

src/jdk.jcmd/share/man/jcmd.md

@@ -1,5 +1,5 @@
 ---
-# Copyright (c) 2012, 2025, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2012, 2026, Oracle and/or its affiliates. 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
@@ -800,19 +800,35 @@ The following commands are available:
         no default value)
 
 `VM.classes` \[*options*\]
-:   Print all loaded classes
+:   Print all loaded classes.
+
+    Classes may be annotated with flags:
+        - `F` = has, or inherits, a non-empty finalize method,
+        - `f` = has final method,
+        - `W` = methods rewritten,
+        - `C` = marked with `@Contended` annotation,
+        - `R` = has been redefined,
+        - `S` = is shared class (if `-location` is specified then either 's' (static) or 'd' (dynamic) for AOT cache origin is appended)
 
     Impact: Medium: Depends on number of loaded classes.
 
-    The following *options* must be specified using either *key* or
-    *key*`=`*value* syntax.
+    The following *options* must be specified using either *key* or *key*`=`*value* syntax.
 
     *options*:
 
-    -   `-verbose`: (Optional) Dump the detailed content of a Java class.
-        Some classes are annotated with flags: `F` = has, or inherits, a non-empty finalize method,
-        `f` = has final method, `W` = methods rewritten, `C` = marked with `@Contended` annotation,
-        `R` = has been redefined, `S` = is shared class (BOOLEAN, false)
+    -   `-verbose`: (Optional) Dump the detailed content of a Java class. (BOOLEAN, false)
+
+    -   `-location`: (Optional) Print the location of the class file from which the class is loaded (if available).
+         If provided by its defining ClassLoader, this option will print a URL specifying the location of the
+         class file (directory, jar or other URL location) from which this class was initially loaded.
+
+         Note: JDK (and other classes) loaded by a ClassLoader that does not provide a location URL to the JVM will omit this field.
+
+         Note: if any classes are loaded from an AOT cache, their location reported is that of the original
+               URL from which they were loaded at the time of the training run that created the AOT cache.
+               Additionally the flags will also be annotated to indicate the AOT cache origin (static or dynamic).
+
+         The total number of classes loaded (if any) from either AOT cache (and the associated cache path location) are summarized.
 
 `VM.classloader_stats`
 :   Print statistics about all ClassLoaders.

test/hotspot/jtreg/runtime/CommandLine/PrintClasses.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2025, 2026, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2022, Alibaba Group Holding Limited. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -59,5 +59,9 @@ public class PrintClasses {
 
     // Test for previous bug in misc flags printing
     output.shouldNotContain("##name");
+
+    pb.command(new PidJcmdExecutor().getCommandLine("VM.classes", "-location"));
+    output = new OutputAnalyzer(pb.start());
+    output.stdoutShouldMatch("^.*(file:/|jar:).*$");
   }
 }