/*

 * Copyright (c) 1998, 2019, 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 "precompiled.hpp"

#include "gc/shared/oopStorage.inline.hpp"

#include "gc/shared/oopStorageSet.hpp"

#include "logging/log.hpp"

#include "memory/iterator.hpp"

#include "memory/universe.hpp"

#include "oops/access.inline.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/handles.inline.hpp"

#include "runtime/jniHandles.inline.hpp"

#include "runtime/mutexLocker.hpp"

#include "runtime/thread.inline.hpp"

#include "utilities/align.hpp"

#include "utilities/debug.hpp"

static OopStorage* global_handles() {

  return OopStorageSet::jni_global();

}

static OopStorage* weak_global_handles() {

  return OopStorageSet::jni_weak();

}

// Serviceability agent support.

OopStorage* JNIHandles::_global_handles = NULL;

OopStorage* JNIHandles::_weak_global_handles = NULL;

void jni_handles_init() {

  JNIHandles::_global_handles = global_handles();

  JNIHandles::_weak_global_handles = weak_global_handles();

}

jobject JNIHandles::make_local(oop obj) {

  if (obj == NULL) {

    return NULL;                // ignore null handles

  } else {

    Thread* thread = Thread::current();

    assert(oopDesc::is_oop(obj), "not an oop");

    assert(!current_thread_in_native(), "must not be in native");

    return thread->active_handles()->allocate_handle(obj);

  }

}

// optimized versions

jobject JNIHandles::make_local(Thread* thread, oop obj) {

  if (obj == NULL) {

    return NULL;                // ignore null handles

  } else {

    assert(oopDesc::is_oop(obj), "not an oop");

    assert(thread->is_Java_thread(), "not a Java thread");

    assert(!current_thread_in_native(), "must not be in native");

    return thread->active_handles()->allocate_handle(obj);

  }

}

jobject JNIHandles::make_local(JNIEnv* env, oop obj) {

  if (obj == NULL) {

    return NULL;                // ignore null handles

  } else {

    JavaThread* thread = JavaThread::thread_from_jni_environment(env);

    assert(oopDesc::is_oop(obj), "not an oop");

    assert(!current_thread_in_native(), "must not be in native");

    return thread->active_handles()->allocate_handle(obj);

  }

}

static void report_handle_allocation_failure(AllocFailType alloc_failmode,

                                             const char* handle_kind) {

  if (alloc_failmode == AllocFailStrategy::EXIT_OOM) {

    // Fake size value, since we don't know the min allocation size here.

    vm_exit_out_of_memory(sizeof(oop), OOM_MALLOC_ERROR,

                          "Cannot create %s JNI handle", handle_kind);

  } else {

    assert(alloc_failmode == AllocFailStrategy::RETURN_NULL, "invariant");

  }

}

jobject JNIHandles::make_global(Handle obj, AllocFailType alloc_failmode) {

  assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");

  assert(!current_thread_in_native(), "must not be in native");

  jobject res = NULL;

  if (!obj.is_null()) {

    // ignore null handles

    assert(oopDesc::is_oop(obj()), "not an oop");

    oop* ptr = global_handles()->allocate();

    // Return NULL on allocation failure.

    if (ptr != NULL) {

      assert(*ptr == NULL, "invariant");

      NativeAccess<>::oop_store(ptr, obj());

      res = reinterpret_cast<jobject>(ptr);

    } else {

      report_handle_allocation_failure(alloc_failmode, "global");

    }

  }

  return res;

}

jobject JNIHandles::make_weak_global(Handle obj, AllocFailType alloc_failmode) {

  assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");

  assert(!current_thread_in_native(), "must not be in native");

  jobject res = NULL;

  if (!obj.is_null()) {

    // ignore null handles

    assert(oopDesc::is_oop(obj()), "not an oop");

    oop* ptr = weak_global_handles()->allocate();

    // Return NULL on allocation failure.

    if (ptr != NULL) {

      assert(*ptr == NULL, "invariant");

      NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(ptr, obj());

      char* tptr = reinterpret_cast<char*>(ptr) + weak_tag_value;

      res = reinterpret_cast<jobject>(tptr);

    } else {

      report_handle_allocation_failure(alloc_failmode, "weak global");

    }

  }

  return res;

}

// Resolve some erroneous cases to NULL, rather than treating them as

// possibly unchecked errors.  In particular, deleted handles are

// treated as NULL (though a deleted and later reallocated handle

// isn't detected).

oop JNIHandles::resolve_external_guard(jobject handle) {

  oop result = NULL;

  if (handle != NULL) {

    result = resolve_impl<DECORATORS_NONE, true /* external_guard */>(handle);

  }

  return result;

}

bool JNIHandles::is_global_weak_cleared(jweak handle) {

  assert(handle != NULL, "precondition");

  assert(is_jweak(handle), "not a weak handle");

  oop* oop_ptr = jweak_ptr(handle);

  oop value = NativeAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>::oop_load(oop_ptr);

  return value == NULL;

}

void JNIHandles::destroy_global(jobject handle) {

  if (handle != NULL) {

    assert(!is_jweak(handle), "wrong method for detroying jweak");

    oop* oop_ptr = jobject_ptr(handle);

    NativeAccess<>::oop_store(oop_ptr, (oop)NULL);

    global_handles()->release(oop_ptr);

  }

}

void JNIHandles::destroy_weak_global(jobject handle) {

  if (handle != NULL) {

    assert(is_jweak(handle), "JNI handle not jweak");

    oop* oop_ptr = jweak_ptr(handle);

    NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(oop_ptr, (oop)NULL);

    weak_global_handles()->release(oop_ptr);

  }

}

void JNIHandles::oops_do(OopClosure* f) {

  global_handles()->oops_do(f);

}

void JNIHandles::weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f) {

  weak_global_handles()->weak_oops_do(is_alive, f);

}

void JNIHandles::weak_oops_do(OopClosure* f) {

  weak_global_handles()->weak_oops_do(f);

}

inline bool is_storage_handle(const OopStorage* storage, const oop* ptr) {

  return storage->allocation_status(ptr) == OopStorage::ALLOCATED_ENTRY;

}

jobjectRefType JNIHandles::handle_type(Thread* thread, jobject handle) {

  assert(handle != NULL, "precondition");

  jobjectRefType result = JNIInvalidRefType;

  if (is_jweak(handle)) {

    if (is_storage_handle(weak_global_handles(), jweak_ptr(handle))) {

      result = JNIWeakGlobalRefType;

    }

  } else {

    switch (global_handles()->allocation_status(jobject_ptr(handle))) {

    case OopStorage::ALLOCATED_ENTRY:

      result = JNIGlobalRefType;

      break;

    case OopStorage::UNALLOCATED_ENTRY:

      break;                    // Invalid global handle

    case OopStorage::INVALID_ENTRY:

      // Not in global storage.  Might be a local handle.

      if (is_local_handle(thread, handle) ||

          (thread->is_Java_thread() &&

           is_frame_handle((JavaThread*)thread, handle))) {

        result = JNILocalRefType;

      }

      break;

    default:

      ShouldNotReachHere();

    }

  }

  return result;

}

bool JNIHandles::is_local_handle(Thread* thread, jobject handle) {

  assert(handle != NULL, "precondition");

  JNIHandleBlock* block = thread->active_handles();

  // Look back past possible native calls to jni_PushLocalFrame.

  while (block != NULL) {

    if (block->chain_contains(handle)) {

      return true;

    }

    block = block->pop_frame_link();

  }

  return false;

}

// Determine if the handle is somewhere in the current thread's stack.

// We easily can't isolate any particular stack frame the handle might

// come from, so we'll check the whole stack.

bool JNIHandles::is_frame_handle(JavaThread* thr, jobject handle) {

  assert(handle != NULL, "precondition");

  // If there is no java frame, then this must be top level code, such

  // as the java command executable, in which case, this type of handle

  // is not permitted.

  return (thr->has_last_Java_frame() &&

         (void*)handle < (void*)thr->stack_base() &&

         (void*)handle >= (void*)thr->last_Java_sp());

}

bool JNIHandles::is_global_handle(jobject handle) {

  assert(handle != NULL, "precondition");

  return !is_jweak(handle) && is_storage_handle(global_handles(), jobject_ptr(handle));

}

bool JNIHandles::is_weak_global_handle(jobject handle) {

  assert(handle != NULL, "precondition");

  return is_jweak(handle) && is_storage_handle(weak_global_handles(), jweak_ptr(handle));

}

size_t JNIHandles::global_handle_memory_usage() {

  return global_handles()->total_memory_usage();

}

size_t JNIHandles::weak_global_handle_memory_usage() {

  return weak_global_handles()->total_memory_usage();

}

// We assume this is called at a safepoint: no lock is needed.

void JNIHandles::print_on(outputStream* st) {

  assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");

  st->print_cr("JNI global refs: " SIZE_FORMAT ", weak refs: " SIZE_FORMAT,

               global_handles()->allocation_count(),

               weak_global_handles()->allocation_count());

  st->cr();

  st->flush();

}

void JNIHandles::print() { print_on(tty); }

class VerifyJNIHandles: public OopClosure {

public:

  virtual void do_oop(oop* root) {

    guarantee(oopDesc::is_oop_or_null(RawAccess<>::oop_load(root)), "Invalid oop");

  }

  virtual void do_oop(narrowOop* root) { ShouldNotReachHere(); }

};

void JNIHandles::verify() {

  VerifyJNIHandles verify_handle;

  oops_do(&verify_handle);

  weak_oops_do(&verify_handle);

}

// This method is implemented here to avoid circular includes between

// jniHandles.hpp and thread.hpp.

bool JNIHandles::current_thread_in_native() {

  Thread* thread = Thread::current();

  return (thread->is_Java_thread() &&

          JavaThread::current()->thread_state() == _thread_in_native);

}

int             JNIHandleBlock::_blocks_allocated     = 0;

JNIHandleBlock* JNIHandleBlock::_block_free_list      = NULL;

#ifndef PRODUCT

JNIHandleBlock* JNIHandleBlock::_block_list           = NULL;

#endif

static inline bool is_tagged_free_list(uintptr_t value) {

  return (value & 1u) != 0;

}

static inline uintptr_t tag_free_list(uintptr_t value) {

  return value | 1u;

}

static inline uintptr_t untag_free_list(uintptr_t value) {

  return value & ~(uintptr_t)1u;

}

// There is a freelist of handles running through the JNIHandleBlock

// with a tagged next pointer, distinguishing these next pointers from

// oops. The freelist handling currently relies on the size of oops

// being the same as a native pointer. If this ever changes, then

// this freelist handling must change too.

STATIC_ASSERT(sizeof(oop) == sizeof(uintptr_t));

#ifdef ASSERT

void JNIHandleBlock::zap() {

  // Zap block values

  _top = 0;

  for (int index = 0; index < block_size_in_oops; index++) {

    // NOT using Access here; just bare clobbering to NULL, since the

    // block no longer contains valid oops.

    _handles[index] = 0;

  }

}

#endif // ASSERT

JNIHandleBlock* JNIHandleBlock::allocate_block(Thread* thread)  {

  assert(thread == NULL || thread == Thread::current(), "sanity check");

  JNIHandleBlock* block;

  // Check the thread-local free list for a block so we don't

  // have to acquire a mutex.

  if (thread != NULL && thread->free_handle_block() != NULL) {

    block = thread->free_handle_block();

    thread->set_free_handle_block(block->_next);

  }

  else {

    // locking with safepoint checking introduces a potential deadlock:

    // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock

    // - another would hold Threads_lock (jni_AttachCurrentThread) and then

    //   JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)

    MutexLocker ml(JNIHandleBlockFreeList_lock,

                   Mutex::_no_safepoint_check_flag);

    if (_block_free_list == NULL) {

      // Allocate new block

      block = new JNIHandleBlock();

      _blocks_allocated++;

      block->zap();

      #ifndef PRODUCT

      // Link new block to list of all allocated blocks

      block->_block_list_link = _block_list;

      _block_list = block;

      #endif

    } else {

      // Get block from free list

      block = _block_free_list;

      _block_free_list = _block_free_list->_next;

    }

  }

  block->_top = 0;

  block->_next = NULL;

  block->_pop_frame_link = NULL;

  block->_planned_capacity = block_size_in_oops;

  // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle

  debug_only(block->_last = NULL);

  debug_only(block->_free_list = NULL);

  debug_only(block->_allocate_before_rebuild = -1);

  return block;

}

void JNIHandleBlock::release_block(JNIHandleBlock* block, Thread* thread) {

  assert(thread == NULL || thread == Thread::current(), "sanity check");

  JNIHandleBlock* pop_frame_link = block->pop_frame_link();

  // Put returned block at the beginning of the thread-local free list.

  // Note that if thread == NULL, we use it as an implicit argument that

  // we _don't_ want the block to be kept on the free_handle_block.

  // See for instance JavaThread::exit().

  if (thread != NULL ) {

    block->zap();

    JNIHandleBlock* freelist = thread->free_handle_block();

    block->_pop_frame_link = NULL;

    thread->set_free_handle_block(block);

    // Add original freelist to end of chain

    if ( freelist != NULL ) {

      while ( block->_next != NULL ) block = block->_next;

      block->_next = freelist;

    }

    block = NULL;

  }

  if (block != NULL) {

    // Return blocks to free list

    // locking with safepoint checking introduces a potential deadlock:

    // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock

    // - another would hold Threads_lock (jni_AttachCurrentThread) and then

    //   JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)

    MutexLocker ml(JNIHandleBlockFreeList_lock,

                   Mutex::_no_safepoint_check_flag);

    while (block != NULL) {

      block->zap();

      JNIHandleBlock* next = block->_next;

      block->_next = _block_free_list;

      _block_free_list = block;

      block = next;

    }

  }

  if (pop_frame_link != NULL) {

    // As a sanity check we release blocks pointed to by the pop_frame_link.

    // This should never happen (only if PopLocalFrame is not called the

    // correct number of times).

    release_block(pop_frame_link, thread);

  }

}

void JNIHandleBlock::oops_do(OopClosure* f) {

  JNIHandleBlock* current_chain = this;

  // Iterate over chain of blocks, followed by chains linked through the

  // pop frame links.

  while (current_chain != NULL) {

    for (JNIHandleBlock* current = current_chain; current != NULL;

         current = current->_next) {

      assert(current == current_chain || current->pop_frame_link() == NULL,

        "only blocks first in chain should have pop frame link set");

      for (int index = 0; index < current->_top; index++) {

        uintptr_t* addr = &(current->_handles)[index];

        uintptr_t value = *addr;

        // traverse heap pointers only, not deleted handles or free list

        // pointers

        if (value != 0 && !is_tagged_free_list(value)) {

          oop* root = (oop*)addr;

          f->do_oop(root);

        }

      }

      // the next handle block is valid only if current block is full

      if (current->_top < block_size_in_oops) {

        break;

      }

    }

    current_chain = current_chain->pop_frame_link();

  }

}

jobject JNIHandleBlock::allocate_handle(oop obj) {

  assert(Universe::heap()->is_in(obj), "sanity check");

  if (_top == 0) {

    // This is the first allocation or the initial block got zapped when

    // entering a native function. If we have any following blocks they are

    // not valid anymore.

    for (JNIHandleBlock* current = _next; current != NULL;

         current = current->_next) {

      assert(current->_last == NULL, "only first block should have _last set");

      assert(current->_free_list == NULL,

             "only first block should have _free_list set");

      if (current->_top == 0) {

        // All blocks after the first clear trailing block are already cleared.

#ifdef ASSERT

        for (current = current->_next; current != NULL; current = current->_next) {

          assert(current->_top == 0, "trailing blocks must already be cleared");

        }