runtime/native/dalvik_system_VMStack.cc

/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "dalvik_system_VMStack.h"

#include <type_traits>

#include "nativehelper/jni_macros.h"

#include "art_method-inl.h"
#include "gc/task_processor.h"
#include "jni/jni_internal.h"
#include "mirror/class-inl.h"
#include "mirror/class_loader.h"
#include "mirror/object-inl.h"
#include "native_util.h"
#include "nth_caller_visitor.h"
#include "scoped_fast_native_object_access-inl.h"
#include "scoped_thread_state_change-inl.h"
#include "thread_list.h"

namespace art HIDDEN {

template <typename T,
          typename ResultT =
              typename std::result_of<T(Thread*, const ScopedFastNativeObjectAccess&)>::type>
static ResultT GetThreadStack(const ScopedFastNativeObjectAccess& soa,
                              jobject peer,
                              T fn)
    REQUIRES_SHARED(Locks::mutator_lock_) {
  ResultT trace = nullptr;
  ObjPtr<mirror::Object> decoded_peer = soa.Decode<mirror::Object>(peer);
  if (decoded_peer == soa.Self()->GetPeer()) {
    trace = fn(soa.Self(), soa);
    return trace;
  }
  // Suspend thread to build stack trace.
  ScopedThreadSuspension sts(soa.Self(), ThreadState::kNative);
  Runtime* runtime = Runtime::Current();
  ThreadList* thread_list = runtime->GetThreadList();
  Thread* thread = thread_list->SuspendThreadByPeer(peer, SuspendReason::kInternal);
  if (thread != nullptr) {
    // If we were asked for the HeapTaskDaemon's stack trace, we went ahead and suspended it.
    // It's usually already in a suspended state anyway. But we should immediately give up and
    // resume it, since we must be able to allocate while generating the stack trace.
    if (!runtime->GetHeap()->GetTaskProcessor()->IsRunningThread(thread, /*wait=*/true)) {
      {
        // Must be runnable to create returned array.
        ScopedObjectAccess soa2(soa.Self());
        trace = fn(thread, soa);
      }
      // Else either thread is the HeapTaskDaemon, or we couldn't identify the thread yet. The
      // HeapTaskDaemon can appear in enumerations before it is registered with the task
      // processor, and we don't wait indefinitely, so there is a tiny chance of the latter.
    }
    // Restart suspended thread.
    bool resumed = thread_list->Resume(thread, SuspendReason::kInternal);
    DCHECK(resumed);
  }
  return trace;
}

static jint VMStack_fillStackTraceElements(JNIEnv* env, jclass, jobject javaThread,
                                           jobjectArray javaSteArray) {
  ScopedFastNativeObjectAccess soa(env);
  auto fn = [](Thread* thread, const ScopedFastNativeObjectAccess& soaa)
      REQUIRES_SHARED(Locks::mutator_lock_) -> jobject {
    return thread->CreateInternalStackTrace(soaa);
  };
  jobject trace = GetThreadStack(soa, javaThread, fn);
  if (trace == nullptr) {
    return 0;
  }
  int32_t depth;
  Thread::InternalStackTraceToStackTraceElementArray(soa, trace, javaSteArray, &depth);
  return depth;
}

// Returns the defining class loader of the caller's caller.
static jobject VMStack_getCallingClassLoader(JNIEnv* env, jclass) {
  ScopedFastNativeObjectAccess soa(env);
  NthCallerVisitor visitor(soa.Self(), 2);
  visitor.WalkStack();
  if (UNLIKELY(visitor.caller == nullptr)) {
    // The caller is an attached native thread.
    return nullptr;
  }
  return soa.AddLocalReference<jobject>(visitor.caller->GetDeclaringClass()->GetClassLoader());
}

static jobject VMStack_getClosestUserClassLoader(JNIEnv* env, jclass) {
  struct ClosestUserClassLoaderVisitor : public StackVisitor {
    explicit ClosestUserClassLoaderVisitor(Thread* thread)
      : StackVisitor(thread, nullptr, StackVisitor::StackWalkKind::kIncludeInlinedFrames),
        class_loader(nullptr) {}

    bool VisitFrame() override REQUIRES_SHARED(Locks::mutator_lock_) {
      DCHECK(class_loader == nullptr);
      ObjPtr<mirror::Class> c = GetMethod()->GetDeclaringClass();
      // c is null for runtime methods.
      if (c != nullptr) {
        ObjPtr<mirror::Object> cl = c->GetClassLoader();
        if (cl != nullptr) {
          class_loader = cl;
          return false;
        }
      }
      return true;
    }

    ObjPtr<mirror::Object> class_loader;
  };
  ScopedFastNativeObjectAccess soa(env);
  ClosestUserClassLoaderVisitor visitor(soa.Self());
  visitor.WalkStack();
  return soa.AddLocalReference<jobject>(visitor.class_loader);
}

// Returns the class of the caller's caller's caller.
static jclass VMStack_getStackClass2(JNIEnv* env, jclass) {
  ScopedFastNativeObjectAccess soa(env);
  NthCallerVisitor visitor(soa.Self(), 3);
  visitor.WalkStack();
  if (UNLIKELY(visitor.caller == nullptr)) {
    // The caller is an attached native thread.
    return nullptr;
  }
  return soa.AddLocalReference<jclass>(visitor.caller->GetDeclaringClass());
}

static jobjectArray VMStack_getThreadStackTrace(JNIEnv* env, jclass, jobject javaThread) {
  ScopedFastNativeObjectAccess soa(env);
  auto fn = [](Thread* thread, const ScopedFastNativeObjectAccess& soaa)
     REQUIRES_SHARED(Locks::mutator_lock_) -> jobject {
    return thread->CreateInternalStackTrace(soaa);
  };
  jobject trace = GetThreadStack(soa, javaThread, fn);
  if (trace == nullptr) {
    return nullptr;
  }
  return Thread::InternalStackTraceToStackTraceElementArray(soa, trace);
}

static jobjectArray VMStack_getAnnotatedThreadStackTrace(JNIEnv* env, jclass, jobject javaThread) {
  ScopedFastNativeObjectAccess soa(env);
  auto fn = [](Thread* thread, const ScopedFastNativeObjectAccess& soaa)
      REQUIRES_SHARED(Locks::mutator_lock_) -> jobjectArray {
    return thread->CreateAnnotatedStackTrace(soaa);
  };
  return GetThreadStack(soa, javaThread, fn);
}

static JNINativeMethod gMethods[] = {
  FAST_NATIVE_METHOD(VMStack, fillStackTraceElements, "(Ljava/lang/Thread;[Ljava/lang/StackTraceElement;)I"),
  FAST_NATIVE_METHOD(VMStack, getCallingClassLoader, "()Ljava/lang/ClassLoader;"),
  FAST_NATIVE_METHOD(VMStack, getClosestUserClassLoader, "()Ljava/lang/ClassLoader;"),
  FAST_NATIVE_METHOD(VMStack, getStackClass2, "()Ljava/lang/Class;"),
  FAST_NATIVE_METHOD(VMStack, getThreadStackTrace, "(Ljava/lang/Thread;)[Ljava/lang/StackTraceElement;"),
  FAST_NATIVE_METHOD(VMStack, getAnnotatedThreadStackTrace, "(Ljava/lang/Thread;)[Ldalvik/system/AnnotatedStackTraceElement;"),
};

void register_dalvik_system_VMStack(JNIEnv* env) {
  REGISTER_NATIVE_METHODS("dalvik/system/VMStack");
}

}  // namespace art