8352738: Implement JEP 520: JFR Method Timing and Tracing

Co-authored-by: Markus Grönlund <[email protected]>
Reviewed-by: shade, mgronlun

Author: egahlin

src/hotspot/share/classfile/modules.hpp

@@ -29,6 +29,7 @@
 #include "runtime/handles.hpp"
 
 class ModuleEntryTable;
+class SerializeClosure;
 class Symbol;
 
 class Modules : AllStatic {

src/hotspot/share/jfr/instrumentation/jfrClassTransformer.cpp

@@ -0,0 +1,187 @@
+/*
+ * Copyright (c) 2016, 2025, 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
+ * 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "classfile/classFileParser.hpp"
+#include "classfile/classFileStream.hpp"
+#include "classfile/classLoadInfo.hpp"
+#include "classfile/javaClasses.inline.hpp"
+#include "classfile/symbolTable.hpp"
+#include "jfr/instrumentation/jfrClassTransformer.hpp"
+#include "jfr/recorder/service/jfrOptionSet.hpp"
+#include "jfr/recorder/checkpoint/types/traceid/jfrTraceId.inline.hpp"
+#include "logging/log.hpp"
+#include "memory/allocation.inline.hpp"
+#include "memory/resourceArea.hpp"
+#include "oops/instanceKlass.hpp"
+#include "oops/klass.inline.hpp"
+#include "prims/jvmtiRedefineClasses.hpp"
+#include "prims/jvmtiThreadState.hpp"
+#include "runtime/handles.inline.hpp"
+#include "runtime/javaThread.hpp"
+#include "utilities/exceptions.hpp"
+#include "utilities/globalDefinitions.hpp"
+#include "utilities/growableArray.hpp"
+#include "utilities/macros.hpp"
+
+static void log_pending_exception(oop throwable) {
+  assert(throwable != nullptr, "invariant");
+  oop msg = java_lang_Throwable::message(throwable);
+  if (msg != nullptr) {
+    char* text = java_lang_String::as_utf8_string(msg);
+    if (text != nullptr) {
+      log_error(jfr, system) ("%s", text);
+    }
+  }
+}
+
+// On initial class load.
+void JfrClassTransformer::cache_class_file_data(InstanceKlass* new_ik, const ClassFileStream* new_stream, const JavaThread* thread) {
+  assert(new_ik != nullptr, "invariant");
+  assert(new_stream != nullptr, "invariant");
+  assert(thread != nullptr, "invariant");
+  assert(!thread->has_pending_exception(), "invariant");
+  if (!JfrOptionSet::allow_retransforms()) {
+    return;
+  }
+  const jint stream_len = new_stream->length();
+  JvmtiCachedClassFileData* p =
+    (JvmtiCachedClassFileData*)NEW_C_HEAP_ARRAY_RETURN_NULL(u1, offset_of(JvmtiCachedClassFileData, data) + stream_len, mtInternal);
+  if (p == nullptr) {
+    log_error(jfr, system)("Allocation using C_HEAP_ARRAY for %zu bytes failed in JfrEventClassTransformer::cache_class_file_data",
+      static_cast<size_t>(offset_of(JvmtiCachedClassFileData, data) + stream_len));
+    return;
+  }
+  p->length = stream_len;
+  memcpy(p->data, new_stream->buffer(), stream_len);
+  new_ik->set_cached_class_file(p);
+}
+
+InstanceKlass* JfrClassTransformer::create_instance_klass(InstanceKlass*& ik, ClassFileStream* stream, bool is_initial_load, JavaThread* thread) {
+  if (stream == nullptr) {
+    if (is_initial_load) {
+      log_error(jfr, system)("JfrClassTransformer: unable to create ClassFileStream for %s", ik->external_name());
+    }
+    return nullptr;
+  }
+  InstanceKlass* const new_ik = create_new_instance_klass(ik, stream, thread);
+  if (new_ik == nullptr) {
+    if (is_initial_load) {
+      log_error(jfr, system)("JfrClassTransformer: unable to create InstanceKlass for %s", ik->external_name());
+    }
+  }
+  return new_ik;
+}
+
+void JfrClassTransformer::copy_traceid(const InstanceKlass* ik, const InstanceKlass* new_ik) {
+  assert(ik != nullptr, "invariant");
+  assert(new_ik != nullptr, "invariant");
+  new_ik->set_trace_id(ik->trace_id());
+  assert(TRACE_ID(ik) == TRACE_ID(new_ik), "invariant");
+}
+
+InstanceKlass* JfrClassTransformer::create_new_instance_klass(InstanceKlass* ik, ClassFileStream* stream, TRAPS) {
+  assert(stream != nullptr, "invariant");
+  ResourceMark rm(THREAD);
+  ClassLoaderData* const cld = ik->class_loader_data();
+  Handle pd(THREAD, ik->protection_domain());
+  Symbol* const class_name = ik->name();
+  ClassLoadInfo cl_info(pd);
+  ClassFileParser new_parser(stream,
+                             class_name,
+                             cld,
+                             &cl_info,
+                             ClassFileParser::INTERNAL, // internal visibility
+                             THREAD);
+  if (HAS_PENDING_EXCEPTION) {
+    log_pending_exception(PENDING_EXCEPTION);
+    CLEAR_PENDING_EXCEPTION;
+    return nullptr;
+  }
+  const ClassInstanceInfo* cl_inst_info = cl_info.class_hidden_info_ptr();
+  InstanceKlass* const new_ik = new_parser.create_instance_klass(false, *cl_inst_info, THREAD);
+  if (HAS_PENDING_EXCEPTION) {
+    log_pending_exception(PENDING_EXCEPTION);
+    CLEAR_PENDING_EXCEPTION;
+    return nullptr;
+  }
+  assert(new_ik != nullptr, "invariant");
+  assert(new_ik->name() != nullptr, "invariant");
+  assert(ik->name() == new_ik->name(), "invariant");
+  return new_ik;
+}
+
+// Redefining / retransforming?
+const Klass* JfrClassTransformer::find_existing_klass(const InstanceKlass* ik, JavaThread* thread) {
+  assert(ik != nullptr, "invariant");
+  assert(thread != nullptr, "invariant");
+  JvmtiThreadState* const state = thread->jvmti_thread_state();
+  return state != nullptr ? klass_being_redefined(ik, state) : nullptr;
+}
+
+const Klass* JfrClassTransformer::klass_being_redefined(const InstanceKlass* ik, JvmtiThreadState* state) {
+  assert(ik != nullptr, "invariant");
+  assert(state != nullptr, "invariant");
+  const GrowableArray<Klass*>* const redef_klasses = state->get_classes_being_redefined();
+  if (redef_klasses == nullptr || redef_klasses->is_empty()) {
+    return nullptr;
+  }
+  for (int i = 0; i < redef_klasses->length(); ++i) {
+    const Klass* const existing_klass = redef_klasses->at(i);
+    assert(existing_klass != nullptr, "invariant");
+    if (ik->name() == existing_klass->name() && ik->class_loader_data() == existing_klass->class_loader_data()) {
+      // 'ik' is a scratch klass. Return the klass being redefined.
+      return existing_klass;
+    }
+  }
+  return nullptr;
+}
+
+// On redefine / retransform, in case an agent modified the class, the original bytes are cached onto the scratch klass.
+void JfrClassTransformer::transfer_cached_class_file_data(InstanceKlass* ik, InstanceKlass* new_ik, const ClassFileParser& parser, JavaThread* thread) {
+  assert(ik != nullptr, "invariant");
+  assert(new_ik != nullptr, "invariant");
+  JvmtiCachedClassFileData* const p = ik->get_cached_class_file();
+  if (p != nullptr) {
+    new_ik->set_cached_class_file(p);
+    ik->set_cached_class_file(nullptr);
+    return;
+  }
+  // No cached classfile indicates that no agent modified the klass.
+  // This means that the parser is holding the original bytes. Hence, we cache it onto the scratch klass.
+  const ClassFileStream* const stream = parser.clone_stream();
+  cache_class_file_data(new_ik, stream, thread);
+}
+
+void JfrClassTransformer::rewrite_klass_pointer(InstanceKlass*& ik, InstanceKlass* new_ik, ClassFileParser& parser, const JavaThread* thread) {
+  assert(ik != nullptr, "invariant");
+  assert(new_ik != nullptr, "invariant");
+  assert(thread != nullptr, "invariant");
+  assert(TRACE_ID(ik) == TRACE_ID(new_ik), "invariant");
+  assert(!thread->has_pending_exception(), "invariant");
+  // Assign original InstanceKlass* back onto "its" parser object for proper destruction.
+  parser.set_klass_to_deallocate(ik);
+  // Finally rewrite the original pointer to the newly created InstanceKlass.
+  ik = new_ik;
+}
+

src/hotspot/share/jfr/instrumentation/jfrClassTransformer.hpp

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2025, 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
+ * 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_JFR_INSTRUMENTATION_JFRCLASSTRANSFORMER_HPP
+#define SHARE_JFR_INSTRUMENTATION_JFRCLASSTRANSFORMER_HPP
+
+#include "memory/allStatic.hpp"
+#include "utilities/exceptions.hpp"
+
+class ClassFileParser;
+class ClassFileStream;
+class InstanceKlass;
+
+/*
+ * Contains common functionality used by method and event instrumentation.
+ */
+class JfrClassTransformer : AllStatic {
+ private:
+  static InstanceKlass* create_new_instance_klass(InstanceKlass* ik, ClassFileStream* stream, TRAPS);
+  static const Klass* klass_being_redefined(const InstanceKlass* ik, JvmtiThreadState* state);
+
+ public:
+  static const Klass* find_existing_klass(const InstanceKlass* ik, JavaThread* thread);
+  static InstanceKlass* create_instance_klass(InstanceKlass*& ik, ClassFileStream* stream, bool is_initial_load, JavaThread* thread);
+  static void copy_traceid(const InstanceKlass* ik, const InstanceKlass* new_ik);
+  static void transfer_cached_class_file_data(InstanceKlass* ik, InstanceKlass* new_ik, const ClassFileParser& parser, JavaThread* thread);
+  static void rewrite_klass_pointer(InstanceKlass*& ik, InstanceKlass* new_ik, ClassFileParser& parser, const JavaThread* thread);
+  static void cache_class_file_data(InstanceKlass* new_ik, const ClassFileStream* new_stream, const JavaThread* thread);
+};
+
+#endif // SHARE_JFR_INSTRUMENTATION_JFRCLASSTRANSFORMER_HPP