1 /*
  2  * Copyright (c) 1998, 2023, Oracle and/or its affiliates. All rights reserved.
  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  4  *
  5  * This code is free software; you can redistribute it and/or modify it
  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.
  8  *
  9  * This code is distributed in the hope that it will be useful, but WITHOUT
 10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 12  * version 2 for more details (a copy is included in the LICENSE file that
 13  * accompanied this code).
 14  *
 15  * You should have received a copy of the GNU General Public License version
 16  * 2 along with this work; if not, write to the Free Software Foundation,
 17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 18  *
 19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 20  * or visit www.oracle.com if you need additional information or have any
 21  * questions.
 22  *
 23  */
 24 
 25 #include "precompiled.hpp"
 26 #include "classfile/vmSymbols.hpp"
 27 #include "gc/shared/collectedHeap.hpp"
 28 #include "gc/shared/oopStorage.inline.hpp"
 29 #include "gc/shared/oopStorageSet.hpp"
 30 #include "logging/log.hpp"
 31 #include "memory/iterator.hpp"
 32 #include "memory/universe.hpp"
 33 #include "oops/access.inline.hpp"
 34 #include "oops/oop.inline.hpp"
 35 #include "runtime/handles.inline.hpp"
 36 #include "runtime/javaCalls.hpp"
 37 #include "runtime/javaThread.inline.hpp"
 38 #include "runtime/jniHandles.inline.hpp"
 39 #include "runtime/mutexLocker.hpp"
 40 #include "utilities/align.hpp"
 41 #include "utilities/debug.hpp"
 42 
 43 OopStorage* JNIHandles::global_handles() {
 44   return _global_handles;
 45 }
 46 
 47 OopStorage* JNIHandles::weak_global_handles() {
 48   return _weak_global_handles;
 49 }
 50 
 51 // Serviceability agent support.
 52 OopStorage* JNIHandles::_global_handles = nullptr;
 53 OopStorage* JNIHandles::_weak_global_handles = nullptr;
 54 
 55 void jni_handles_init() {
 56   JNIHandles::_global_handles = OopStorageSet::create_strong("JNI Global", mtInternal);
 57   JNIHandles::_weak_global_handles = OopStorageSet::create_weak("JNI Weak", mtInternal);
 58 }
 59 
 60 jobject JNIHandles::make_local(oop obj) {
 61   return make_local(JavaThread::current(), obj);
 62 }
 63 
 64 // Used by NewLocalRef which requires null on out-of-memory
 65 jobject JNIHandles::make_local(JavaThread* thread, oop obj, AllocFailType alloc_failmode) {
 66   if (obj == nullptr) {
 67     return nullptr;                // ignore null handles
 68   } else {
 69     assert(oopDesc::is_oop(obj), "not an oop");
 70     assert(!current_thread_in_native(), "must not be in native");
 71     STATIC_ASSERT(TypeTag::local == 0);
 72     return thread->active_handles()->allocate_handle(thread, obj, alloc_failmode);
 73   }
 74 }
 75 
 76 static void report_handle_allocation_failure(AllocFailType alloc_failmode,
 77                                              const char* handle_kind) {
 78   if (alloc_failmode == AllocFailStrategy::EXIT_OOM) {
 79     // Fake size value, since we don't know the min allocation size here.
 80     vm_exit_out_of_memory(sizeof(oop), OOM_MALLOC_ERROR,
 81                           "Cannot create %s JNI handle", handle_kind);
 82   } else {
 83     assert(alloc_failmode == AllocFailStrategy::RETURN_NULL, "invariant");
 84   }
 85 }
 86 
 87 jobject JNIHandles::make_global(Handle obj, AllocFailType alloc_failmode) {
 88   assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
 89   assert(!current_thread_in_native(), "must not be in native");
 90   jobject res = nullptr;
 91   if (!obj.is_null()) {
 92     // ignore null handles
 93     assert(oopDesc::is_oop(obj()), "not an oop");
 94     oop* ptr = global_handles()->allocate();
 95     // Return null on allocation failure.
 96     if (ptr != nullptr) {
 97       assert(NativeAccess<AS_NO_KEEPALIVE>::oop_load(ptr) == oop(nullptr), "invariant");
 98       NativeAccess<>::oop_store(ptr, obj());
 99       char* tptr = reinterpret_cast<char*>(ptr) + TypeTag::global;
100       res = reinterpret_cast<jobject>(tptr);
101     } else {
102       report_handle_allocation_failure(alloc_failmode, "global");
103     }
104   }
105 
106   return res;
107 }
108 
109 jweak JNIHandles::make_weak_global(Handle obj, AllocFailType alloc_failmode) {
110   assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
111   assert(!current_thread_in_native(), "must not be in native");
112   jweak res = nullptr;
113   if (!obj.is_null()) {
114     // ignore null handles
115     assert(oopDesc::is_oop(obj()), "not an oop");
116     oop* ptr = weak_global_handles()->allocate();
117     // Return nullptr on allocation failure.
118     if (ptr != nullptr) {
119       assert(NativeAccess<AS_NO_KEEPALIVE>::oop_load(ptr) == oop(nullptr), "invariant");
120       NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(ptr, obj());
121       char* tptr = reinterpret_cast<char*>(ptr) + TypeTag::weak_global;
122       res = reinterpret_cast<jweak>(tptr);
123     } else {
124       report_handle_allocation_failure(alloc_failmode, "weak global");
125     }
126   }
127   return res;
128 }
129 
130 // Resolve some erroneous cases to null, rather than treating them as
131 // possibly unchecked errors.  In particular, deleted handles are
132 // treated as null (though a deleted and later reallocated handle
133 // isn't detected).
134 oop JNIHandles::resolve_external_guard(jobject handle) {
135   oop result = nullptr;
136   if (handle != nullptr) {
137     result = resolve_impl<DECORATORS_NONE, true /* external_guard */>(handle);
138   }
139   return result;
140 }
141 
142 bool JNIHandles::is_weak_global_cleared(jweak handle) {
143   assert(handle != nullptr, "precondition");
144   oop* oop_ptr = weak_global_ptr(handle);
145   oop value = NativeAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>::oop_load(oop_ptr);
146   return value == nullptr;
147 }
148 
149 void JNIHandles::destroy_global(jobject handle) {
150   if (handle != nullptr) {
151     oop* oop_ptr = global_ptr(handle);
152     NativeAccess<>::oop_store(oop_ptr, (oop)nullptr);
153     global_handles()->release(oop_ptr);
154   }
155 }
156 
157 
158 void JNIHandles::destroy_weak_global(jweak handle) {
159   if (handle != nullptr) {
160     oop* oop_ptr = weak_global_ptr(handle);
161     NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(oop_ptr, (oop)nullptr);
162     weak_global_handles()->release(oop_ptr);
163   }
164 }
165 
166 
167 void JNIHandles::oops_do(OopClosure* f) {
168   global_handles()->oops_do(f);
169 }
170 
171 
172 void JNIHandles::weak_oops_do(OopClosure* f) {
173   weak_global_handles()->weak_oops_do(f);
174 }
175 
176 bool JNIHandles::is_global_storage(const OopStorage* storage) {
177   return _global_handles == storage;
178 }
179 
180 inline bool is_storage_handle(const OopStorage* storage, const oop* ptr) {
181   return storage->allocation_status(ptr) == OopStorage::ALLOCATED_ENTRY;
182 }
183 
184 
185 jobjectRefType JNIHandles::handle_type(JavaThread* thread, jobject handle) {
186   assert(handle != nullptr, "precondition");
187   jobjectRefType result = JNIInvalidRefType;
188   if (is_weak_global_tagged(handle)) {
189     if (is_storage_handle(weak_global_handles(), weak_global_ptr(handle))) {
190       result = JNIWeakGlobalRefType;
191     }
192   } else if (is_global_tagged(handle)) {
193     switch (global_handles()->allocation_status(global_ptr(handle))) {
194     case OopStorage::ALLOCATED_ENTRY:
195       result = JNIGlobalRefType;
196       break;
197 
198     case OopStorage::UNALLOCATED_ENTRY:
199       break;                    // Invalid global handle
200 
201     default:
202       ShouldNotReachHere();
203     }
204   } else if (is_local_handle(thread, handle) || is_frame_handle(thread, handle)) {
205     // Not in global storage.  Might be a local handle.
206     result = JNILocalRefType;
207   }
208   return result;
209 }
210 
211 
212 bool JNIHandles::is_local_handle(JavaThread* thread, jobject handle) {
213   assert(handle != nullptr, "precondition");
214   JNIHandleBlock* block = thread->active_handles();
215 
216   // Look back past possible native calls to jni_PushLocalFrame.
217   while (block != nullptr) {
218     if (block->chain_contains(handle)) {
219       return true;
220     }
221     block = block->pop_frame_link();
222   }
223   return false;
224 }
225 
226 
227 // Determine if the handle is somewhere in the current thread's stack.
228 // We easily can't isolate any particular stack frame the handle might
229 // come from, so we'll check the whole stack.
230 
231 bool JNIHandles::is_frame_handle(JavaThread* thr, jobject handle) {
232   assert(handle != nullptr, "precondition");
233   // If there is no java frame, then this must be top level code, such
234   // as the java command executable, in which case, this type of handle
235   // is not permitted.
236   return (thr->has_last_Java_frame() &&
237           thr->is_in_stack_range_incl((address)handle, (address)thr->last_Java_sp()));
238 }
239 
240 
241 bool JNIHandles::is_global_handle(jobject handle) {
242   assert(handle != nullptr, "precondition");
243   return is_global_tagged(handle) && is_storage_handle(global_handles(), global_ptr(handle));
244 }
245 
246 
247 bool JNIHandles::is_weak_global_handle(jobject handle) {
248   assert(handle != nullptr, "precondition");
249   return is_weak_global_tagged(handle) && is_storage_handle(weak_global_handles(), weak_global_ptr(handle));
250 }
251 
252 // We assume this is called at a safepoint: no lock is needed.
253 void JNIHandles::print_on(outputStream* st) {
254   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
255 
256   st->print_cr("JNI global refs: " SIZE_FORMAT ", weak refs: " SIZE_FORMAT,
257                global_handles()->allocation_count(),
258                weak_global_handles()->allocation_count());
259   st->cr();
260   st->flush();
261 }
262 
263 void JNIHandles::print() { print_on(tty); }
264 
265 class VerifyJNIHandles: public OopClosure {
266 public:
267   virtual void do_oop(oop* root) {
268     guarantee(oopDesc::is_oop_or_null(RawAccess<>::oop_load(root)), "Invalid oop");
269   }
270   virtual void do_oop(narrowOop* root) { ShouldNotReachHere(); }
271 };
272 
273 void JNIHandles::verify() {
274   VerifyJNIHandles verify_handle;
275 
276   oops_do(&verify_handle);
277   weak_oops_do(&verify_handle);
278 }
279 
280 // This method is implemented here to avoid circular includes between
281 // jniHandles.hpp and thread.hpp.
282 bool JNIHandles::current_thread_in_native() {
283   Thread* thread = Thread::current();
284   return (thread->is_Java_thread() &&
285           JavaThread::cast(thread)->thread_state() == _thread_in_native);
286 }
287 
288 bool JNIHandles::is_same_object(jobject handle1, jobject handle2) {
289   oop obj1 = resolve_no_keepalive(handle1);
290   oop obj2 = resolve_no_keepalive(handle2);
291 
292   bool ret = obj1 == obj2;
293 
294   if (EnableValhalla) {
295     if (!ret && obj1 != nullptr && obj2 != nullptr && obj1->klass() == obj2->klass() && obj1->klass()->is_inline_klass()) {
296       // The two references are different, they are not null and they are both inline types,
297       // a full substitutability test is required, calling ValueObjectMethods.isSubstitutable()
298       // (similarly to InterpreterRuntime::is_substitutable)
299       JavaThread* THREAD = JavaThread::current();
300       Handle ha(THREAD, obj1);
301       Handle hb(THREAD, obj2);
302       JavaValue result(T_BOOLEAN);
303       JavaCallArguments args;
304       args.push_oop(ha);
305       args.push_oop(hb);
306       methodHandle method(THREAD, Universe::is_substitutable_method());
307       JavaCalls::call(&result, method, &args, THREAD);
308       if (HAS_PENDING_EXCEPTION) {
309         // Something really bad happened because isSubstitutable() should not throw exceptions
310         // If it is an error, just let it propagate
311         // If it is an exception, wrap it into an InternalError
312         if (!PENDING_EXCEPTION->is_a(vmClasses::Error_klass())) {
313           Handle e(THREAD, PENDING_EXCEPTION);
314           CLEAR_PENDING_EXCEPTION;
315           THROW_MSG_CAUSE_(vmSymbols::java_lang_InternalError(), "Internal error in substitutability test", e, false);
316         }
317       }
318       ret = result.get_jboolean();
319     }
320   }
321 
322   return ret;
323 }
324 
325 
326 int JNIHandleBlock::_blocks_allocated = 0;
327 
328 static inline bool is_tagged_free_list(uintptr_t value) {
329   return (value & 1u) != 0;
330 }
331 
332 static inline uintptr_t tag_free_list(uintptr_t value) {
333   return value | 1u;
334 }
335 
336 static inline uintptr_t untag_free_list(uintptr_t value) {
337   return value & ~(uintptr_t)1u;
338 }
339 
340 // There is a freelist of handles running through the JNIHandleBlock
341 // with a tagged next pointer, distinguishing these next pointers from
342 // oops. The freelist handling currently relies on the size of oops
343 // being the same as a native pointer. If this ever changes, then
344 // this freelist handling must change too.
345 STATIC_ASSERT(sizeof(oop) == sizeof(uintptr_t));
346 
347 #ifdef ASSERT
348 void JNIHandleBlock::zap() {
349   // Zap block values
350   _top = 0;
351   for (int index = 0; index < block_size_in_oops; index++) {
352     // NOT using Access here; just bare clobbering to null, since the
353     // block no longer contains valid oops.
354     _handles[index] = 0;
355   }
356 }
357 #endif // ASSERT
358 
359 JNIHandleBlock* JNIHandleBlock::allocate_block(JavaThread* thread, AllocFailType alloc_failmode)  {
360   // The VM thread can allocate a handle block in behalf of another thread during a safepoint.
361   assert(thread == nullptr || thread == Thread::current() || SafepointSynchronize::is_at_safepoint(),
362          "sanity check");
363   JNIHandleBlock* block;
364   // Check the thread-local free list for a block so we don't
365   // have to acquire a mutex.
366   if (thread != nullptr && thread->free_handle_block() != nullptr) {
367     block = thread->free_handle_block();
368     thread->set_free_handle_block(block->_next);
369   } else {
370     // Allocate new block
371     if (alloc_failmode == AllocFailStrategy::RETURN_NULL) {
372       block = new (std::nothrow) JNIHandleBlock();
373       if (block == nullptr) {
374         return nullptr;
375       }
376     } else {
377       block = new JNIHandleBlock();
378     }
379     Atomic::inc(&_blocks_allocated);
380     block->zap();
381   }
382   block->_top = 0;
383   block->_next = nullptr;
384   block->_pop_frame_link = nullptr;
385   // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle
386   debug_only(block->_last = nullptr);
387   debug_only(block->_free_list = nullptr);
388   debug_only(block->_allocate_before_rebuild = -1);
389   return block;
390 }
391 
392 
393 void JNIHandleBlock::release_block(JNIHandleBlock* block, JavaThread* thread) {
394   assert(thread == nullptr || thread == Thread::current(), "sanity check");
395   JNIHandleBlock* pop_frame_link = block->pop_frame_link();
396   // Put returned block at the beginning of the thread-local free list.
397   // Note that if thread == nullptr, we use it as an implicit argument that
398   // we _don't_ want the block to be kept on the free_handle_block.
399   // See for instance JavaThread::exit().
400   if (thread != nullptr ) {
401     block->zap();
402     JNIHandleBlock* freelist = thread->free_handle_block();
403     block->_pop_frame_link = nullptr;
404     thread->set_free_handle_block(block);
405 
406     // Add original freelist to end of chain
407     if ( freelist != nullptr ) {
408       while ( block->_next != nullptr ) block = block->_next;
409       block->_next = freelist;
410     }
411     block = nullptr;
412   } else {
413     DEBUG_ONLY(block->set_pop_frame_link(nullptr));
414     while (block != nullptr) {
415       JNIHandleBlock* next = block->_next;
416       Atomic::dec(&_blocks_allocated);
417       assert(block->pop_frame_link() == nullptr, "pop_frame_link should be null");
418       delete block;
419       block = next;
420     }
421   }
422   if (pop_frame_link != nullptr) {
423     // As a sanity check we release blocks pointed to by the pop_frame_link.
424     // This should never happen (only if PopLocalFrame is not called the
425     // correct number of times).
426     release_block(pop_frame_link, thread);
427   }
428 }
429 
430 
431 void JNIHandleBlock::oops_do(OopClosure* f) {
432   JNIHandleBlock* current_chain = this;
433   // Iterate over chain of blocks, followed by chains linked through the
434   // pop frame links.
435   while (current_chain != nullptr) {
436     for (JNIHandleBlock* current = current_chain; current != nullptr;
437          current = current->_next) {
438       assert(current == current_chain || current->pop_frame_link() == nullptr,
439         "only blocks first in chain should have pop frame link set");
440       for (int index = 0; index < current->_top; index++) {
441         uintptr_t* addr = &(current->_handles)[index];
442         uintptr_t value = *addr;
443         // traverse heap pointers only, not deleted handles or free list
444         // pointers
445         if (value != 0 && !is_tagged_free_list(value)) {
446           oop* root = (oop*)addr;
447           f->do_oop(root);
448         }
449       }
450       // the next handle block is valid only if current block is full
451       if (current->_top < block_size_in_oops) {
452         break;
453       }
454     }
455     current_chain = current_chain->pop_frame_link();
456   }
457 }
458 
459 
460 jobject JNIHandleBlock::allocate_handle(JavaThread* caller, oop obj, AllocFailType alloc_failmode) {
461   assert(Universe::heap()->is_in(obj), "sanity check");
462   if (_top == 0) {
463     // This is the first allocation or the initial block got zapped when
464     // entering a native function. If we have any following blocks they are
465     // not valid anymore.
466     for (JNIHandleBlock* current = _next; current != nullptr;
467          current = current->_next) {
468       assert(current->_last == nullptr, "only first block should have _last set");
469       assert(current->_free_list == nullptr,
470              "only first block should have _free_list set");
471       if (current->_top == 0) {
472         // All blocks after the first clear trailing block are already cleared.
473 #ifdef ASSERT
474         for (current = current->_next; current != nullptr; current = current->_next) {
475           assert(current->_top == 0, "trailing blocks must already be cleared");
476         }
477 #endif
478         break;
479       }
480       current->_top = 0;
481       current->zap();
482     }
483     // Clear initial block
484     _free_list = nullptr;
485     _allocate_before_rebuild = 0;
486     _last = this;
487     zap();
488   }
489 
490   // Try last block
491   if (_last->_top < block_size_in_oops) {
492     oop* handle = (oop*)&(_last->_handles)[_last->_top++];
493     *handle = obj;
494     return (jobject) handle;
495   }
496 
497   // Try free list
498   if (_free_list != nullptr) {
499     oop* handle = (oop*)_free_list;
500     _free_list = (uintptr_t*) untag_free_list(*_free_list);
501     *handle = obj;
502     return (jobject) handle;
503   }
504   // Check if unused block follow last
505   if (_last->_next != nullptr) {
506     // update last and retry
507     _last = _last->_next;
508     return allocate_handle(caller, obj, alloc_failmode);
509   }
510 
511   // No space available, we have to rebuild free list or expand
512   if (_allocate_before_rebuild == 0) {
513       rebuild_free_list();        // updates _allocate_before_rebuild counter
514   } else {
515     _last->_next = JNIHandleBlock::allocate_block(caller, alloc_failmode);
516     if (_last->_next == nullptr) {
517       return nullptr;
518     }
519     _last = _last->_next;
520     _allocate_before_rebuild--;
521   }
522   return allocate_handle(caller, obj, alloc_failmode);  // retry
523 }
524 
525 void JNIHandleBlock::rebuild_free_list() {
526   assert(_allocate_before_rebuild == 0 && _free_list == nullptr, "just checking");
527   int free = 0;
528   int blocks = 0;
529   for (JNIHandleBlock* current = this; current != nullptr; current = current->_next) {
530     for (int index = 0; index < current->_top; index++) {
531       uintptr_t* handle = &(current->_handles)[index];
532       if (*handle == 0) {
533         // this handle was cleared out by a delete call, reuse it
534         *handle = _free_list == nullptr ? 0 : tag_free_list((uintptr_t)_free_list);
535         _free_list = handle;
536         free++;
537       }
538     }
539     // we should not rebuild free list if there are unused handles at the end
540     assert(current->_top == block_size_in_oops, "just checking");
541     blocks++;
542   }
543   // Heuristic: if more than half of the handles are free we rebuild next time
544   // as well, otherwise we append a corresponding number of new blocks before
545   // attempting a free list rebuild again.
546   int total = blocks * block_size_in_oops;
547   int extra = total - 2*free;
548   if (extra > 0) {
549     // Not as many free handles as we would like - compute number of new blocks to append
550     _allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops;
551   }
552 }
553 
554 
555 bool JNIHandleBlock::contains(jobject handle) const {
556   return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]);
557 }
558 
559 
560 bool JNIHandleBlock::chain_contains(jobject handle) const {
561   for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != nullptr; current = current->_next) {
562     if (current->contains(handle)) {
563       return true;
564     }
565   }
566   return false;
567 }