1 /*
2 * Copyright (c) 1998, 2021, 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 "gc/shared/collectedHeap.hpp"
27 #include "gc/shared/oopStorage.inline.hpp"
28 #include "gc/shared/oopStorageSet.hpp"
29 #include "logging/log.hpp"
30 #include "memory/iterator.hpp"
31 #include "memory/universe.hpp"
32 #include "oops/access.inline.hpp"
33 #include "oops/oop.inline.hpp"
34 #include "runtime/handles.inline.hpp"
35 #include "runtime/jniHandles.inline.hpp"
36 #include "runtime/mutexLocker.hpp"
37 #include "runtime/thread.inline.hpp"
38 #include "utilities/align.hpp"
39 #include "utilities/debug.hpp"
40
41 OopStorage* JNIHandles::global_handles() {
42 return _global_handles;
43 }
44
45 OopStorage* JNIHandles::weak_global_handles() {
46 return _weak_global_handles;
47 }
48
49 // Serviceability agent support.
50 OopStorage* JNIHandles::_global_handles = NULL;
51 OopStorage* JNIHandles::_weak_global_handles = NULL;
52
53 void jni_handles_init() {
54 JNIHandles::_global_handles = OopStorageSet::create_strong("JNI Global", mtInternal);
55 JNIHandles::_weak_global_handles = OopStorageSet::create_weak("JNI Weak", mtInternal);
56 }
57
58 jobject JNIHandles::make_local(oop obj) {
59 return make_local(Thread::current(), obj);
60 }
61
62 // Used by NewLocalRef which requires NULL on out-of-memory
63 jobject JNIHandles::make_local(Thread* thread, oop obj, AllocFailType alloc_failmode) {
64 if (obj == NULL) {
65 return NULL; // ignore null handles
66 } else {
67 assert(oopDesc::is_oop(obj), "not an oop");
68 assert(thread->is_Java_thread(), "not a Java thread");
69 assert(!current_thread_in_native(), "must not be in native");
70 return thread->active_handles()->allocate_handle(obj, alloc_failmode);
71 }
72 }
73
74 static void report_handle_allocation_failure(AllocFailType alloc_failmode,
75 const char* handle_kind) {
76 if (alloc_failmode == AllocFailStrategy::EXIT_OOM) {
77 // Fake size value, since we don't know the min allocation size here.
78 vm_exit_out_of_memory(sizeof(oop), OOM_MALLOC_ERROR,
79 "Cannot create %s JNI handle", handle_kind);
80 } else {
81 assert(alloc_failmode == AllocFailStrategy::RETURN_NULL, "invariant");
82 }
83 }
84
85 jobject JNIHandles::make_global(Handle obj, AllocFailType alloc_failmode) {
86 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
87 assert(!current_thread_in_native(), "must not be in native");
88 jobject res = NULL;
89 if (!obj.is_null()) {
90 // ignore null handles
91 assert(oopDesc::is_oop(obj()), "not an oop");
92 oop* ptr = global_handles()->allocate();
93 // Return NULL on allocation failure.
94 if (ptr != NULL) {
95 assert(*ptr == NULL, "invariant");
96 NativeAccess<>::oop_store(ptr, obj());
97 res = reinterpret_cast<jobject>(ptr);
98 } else {
99 report_handle_allocation_failure(alloc_failmode, "global");
100 }
101 }
102
103 return res;
104 }
105
106 jobject JNIHandles::make_weak_global(Handle obj, AllocFailType alloc_failmode) {
107 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
108 assert(!current_thread_in_native(), "must not be in native");
109 jobject res = NULL;
110 if (!obj.is_null()) {
111 // ignore null handles
112 assert(oopDesc::is_oop(obj()), "not an oop");
113 oop* ptr = weak_global_handles()->allocate();
114 // Return NULL on allocation failure.
115 if (ptr != NULL) {
116 assert(*ptr == NULL, "invariant");
117 NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(ptr, obj());
118 char* tptr = reinterpret_cast<char*>(ptr) + weak_tag_value;
119 res = reinterpret_cast<jobject>(tptr);
120 } else {
121 report_handle_allocation_failure(alloc_failmode, "weak global");
122 }
123 }
124 return res;
125 }
126
127 // Resolve some erroneous cases to NULL, rather than treating them as
128 // possibly unchecked errors. In particular, deleted handles are
129 // treated as NULL (though a deleted and later reallocated handle
130 // isn't detected).
131 oop JNIHandles::resolve_external_guard(jobject handle) {
132 oop result = NULL;
133 if (handle != NULL) {
134 result = resolve_impl<DECORATORS_NONE, true /* external_guard */>(handle);
135 }
136 return result;
137 }
138
139 bool JNIHandles::is_global_weak_cleared(jweak handle) {
140 assert(handle != NULL, "precondition");
141 assert(is_jweak(handle), "not a weak handle");
142 oop* oop_ptr = jweak_ptr(handle);
143 oop value = NativeAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>::oop_load(oop_ptr);
144 return value == NULL;
145 }
146
147 void JNIHandles::destroy_global(jobject handle) {
148 if (handle != NULL) {
149 assert(!is_jweak(handle), "wrong method for detroying jweak");
150 oop* oop_ptr = jobject_ptr(handle);
151 NativeAccess<>::oop_store(oop_ptr, (oop)NULL);
152 global_handles()->release(oop_ptr);
153 }
154 }
155
156
157 void JNIHandles::destroy_weak_global(jobject handle) {
158 if (handle != NULL) {
159 assert(is_jweak(handle), "JNI handle not jweak");
160 oop* oop_ptr = jweak_ptr(handle);
161 NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(oop_ptr, (oop)NULL);
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(BoolObjectClosure* is_alive, OopClosure* f) {
173 weak_global_handles()->weak_oops_do(is_alive, f);
174 }
175
176
177 void JNIHandles::weak_oops_do(OopClosure* f) {
178 weak_global_handles()->weak_oops_do(f);
179 }
180
181 bool JNIHandles::is_global_storage(const OopStorage* storage) {
182 return _global_handles == storage;
183 }
184
185 inline bool is_storage_handle(const OopStorage* storage, const oop* ptr) {
186 return storage->allocation_status(ptr) == OopStorage::ALLOCATED_ENTRY;
187 }
188
189
190 jobjectRefType JNIHandles::handle_type(Thread* thread, jobject handle) {
191 assert(handle != NULL, "precondition");
192 jobjectRefType result = JNIInvalidRefType;
193 if (is_jweak(handle)) {
194 if (is_storage_handle(weak_global_handles(), jweak_ptr(handle))) {
195 result = JNIWeakGlobalRefType;
196 }
197 } else {
198 switch (global_handles()->allocation_status(jobject_ptr(handle))) {
199 case OopStorage::ALLOCATED_ENTRY:
200 result = JNIGlobalRefType;
201 break;
202
203 case OopStorage::UNALLOCATED_ENTRY:
204 break; // Invalid global handle
205
206 case OopStorage::INVALID_ENTRY:
207 // Not in global storage. Might be a local handle.
208 if (is_local_handle(thread, handle) ||
209 (thread->is_Java_thread() &&
210 is_frame_handle(JavaThread::cast(thread), handle))) {
211 result = JNILocalRefType;
212 }
213 break;
214
215 default:
216 ShouldNotReachHere();
217 }
218 }
219 return result;
220 }
221
222
223 bool JNIHandles::is_local_handle(Thread* thread, jobject handle) {
224 assert(handle != NULL, "precondition");
225 JNIHandleBlock* block = thread->active_handles();
226
227 // Look back past possible native calls to jni_PushLocalFrame.
228 while (block != NULL) {
229 if (block->chain_contains(handle)) {
230 return true;
231 }
232 block = block->pop_frame_link();
233 }
234 return false;
235 }
236
237
238 // Determine if the handle is somewhere in the current thread's stack.
239 // We easily can't isolate any particular stack frame the handle might
240 // come from, so we'll check the whole stack.
241
242 bool JNIHandles::is_frame_handle(JavaThread* thr, jobject handle) {
243 assert(handle != NULL, "precondition");
244 // If there is no java frame, then this must be top level code, such
245 // as the java command executable, in which case, this type of handle
246 // is not permitted.
247 return (thr->has_last_Java_frame() &&
248 thr->is_in_stack_range_incl((address)handle, (address)thr->last_Java_sp()));
249 }
250
251
252 bool JNIHandles::is_global_handle(jobject handle) {
253 assert(handle != NULL, "precondition");
254 return !is_jweak(handle) && is_storage_handle(global_handles(), jobject_ptr(handle));
255 }
256
257
258 bool JNIHandles::is_weak_global_handle(jobject handle) {
259 assert(handle != NULL, "precondition");
260 return is_jweak(handle) && is_storage_handle(weak_global_handles(), jweak_ptr(handle));
261 }
262
263 size_t JNIHandles::global_handle_memory_usage() {
264 return global_handles()->total_memory_usage();
265 }
266
267 size_t JNIHandles::weak_global_handle_memory_usage() {
268 return weak_global_handles()->total_memory_usage();
269 }
270
271
272 // We assume this is called at a safepoint: no lock is needed.
273 void JNIHandles::print_on(outputStream* st) {
274 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
275
276 st->print_cr("JNI global refs: " SIZE_FORMAT ", weak refs: " SIZE_FORMAT,
277 global_handles()->allocation_count(),
278 weak_global_handles()->allocation_count());
279 st->cr();
280 st->flush();
281 }
282
283 void JNIHandles::print() { print_on(tty); }
284
285 class VerifyJNIHandles: public OopClosure {
286 public:
287 virtual void do_oop(oop* root) {
288 guarantee(oopDesc::is_oop_or_null(RawAccess<>::oop_load(root)), "Invalid oop");
289 }
290 virtual void do_oop(narrowOop* root) { ShouldNotReachHere(); }
291 };
292
293 void JNIHandles::verify() {
294 VerifyJNIHandles verify_handle;
295
296 oops_do(&verify_handle);
297 weak_oops_do(&verify_handle);
298 }
299
300 // This method is implemented here to avoid circular includes between
301 // jniHandles.hpp and thread.hpp.
302 bool JNIHandles::current_thread_in_native() {
303 Thread* thread = Thread::current();
304 return (thread->is_Java_thread() &&
305 JavaThread::cast(thread)->thread_state() == _thread_in_native);
306 }
307
308
309 int JNIHandleBlock::_blocks_allocated = 0;
310 JNIHandleBlock* JNIHandleBlock::_block_free_list = NULL;
311 #ifndef PRODUCT
312 JNIHandleBlock* JNIHandleBlock::_block_list = NULL;
313 #endif
314
315 static inline bool is_tagged_free_list(uintptr_t value) {
316 return (value & 1u) != 0;
317 }
318
319 static inline uintptr_t tag_free_list(uintptr_t value) {
320 return value | 1u;
321 }
322
323 static inline uintptr_t untag_free_list(uintptr_t value) {
324 return value & ~(uintptr_t)1u;
325 }
326
327 // There is a freelist of handles running through the JNIHandleBlock
328 // with a tagged next pointer, distinguishing these next pointers from
329 // oops. The freelist handling currently relies on the size of oops
330 // being the same as a native pointer. If this ever changes, then
331 // this freelist handling must change too.
332 STATIC_ASSERT(sizeof(oop) == sizeof(uintptr_t));
333
334 #ifdef ASSERT
335 void JNIHandleBlock::zap() {
336 // Zap block values
337 _top = 0;
338 for (int index = 0; index < block_size_in_oops; index++) {
339 // NOT using Access here; just bare clobbering to NULL, since the
340 // block no longer contains valid oops.
341 _handles[index] = 0;
342 }
343 }
344 #endif // ASSERT
345
346 JNIHandleBlock* JNIHandleBlock::allocate_block(Thread* thread, AllocFailType alloc_failmode) {
347 assert(thread == NULL || thread == Thread::current(), "sanity check");
348 JNIHandleBlock* block;
349 // Check the thread-local free list for a block so we don't
350 // have to acquire a mutex.
351 if (thread != NULL && thread->free_handle_block() != NULL) {
352 block = thread->free_handle_block();
353 thread->set_free_handle_block(block->_next);
354 }
355 else {
356 // locking with safepoint checking introduces a potential deadlock:
357 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
358 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
359 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
360 MutexLocker ml(JNIHandleBlockFreeList_lock,
361 Mutex::_no_safepoint_check_flag);
362 if (_block_free_list == NULL) {
363 // Allocate new block
364 if (alloc_failmode == AllocFailStrategy::RETURN_NULL) {
365 block = new (std::nothrow) JNIHandleBlock();
366 if (block == NULL) {
367 return NULL;
368 }
369 } else {
370 block = new JNIHandleBlock();
371 }
372 _blocks_allocated++;
373 block->zap();
374 #ifndef PRODUCT
375 // Link new block to list of all allocated blocks
376 block->_block_list_link = _block_list;
377 _block_list = block;
378 #endif
379 } else {
380 // Get block from free list
381 block = _block_free_list;
382 _block_free_list = _block_free_list->_next;
383 }
384 }
385 block->_top = 0;
386 block->_next = NULL;
387 block->_pop_frame_link = NULL;
388 block->_planned_capacity = block_size_in_oops;
389 // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle
390 debug_only(block->_last = NULL);
391 debug_only(block->_free_list = NULL);
392 debug_only(block->_allocate_before_rebuild = -1);
393 return block;
394 }
395
396
397 void JNIHandleBlock::release_block(JNIHandleBlock* block, Thread* thread) {
398 assert(thread == NULL || thread == Thread::current(), "sanity check");
399 JNIHandleBlock* pop_frame_link = block->pop_frame_link();
400 // Put returned block at the beginning of the thread-local free list.
401 // Note that if thread == NULL, we use it as an implicit argument that
402 // we _don't_ want the block to be kept on the free_handle_block.
403 // See for instance JavaThread::exit().
404 if (thread != NULL ) {
405 block->zap();
406 JNIHandleBlock* freelist = thread->free_handle_block();
407 block->_pop_frame_link = NULL;
408 thread->set_free_handle_block(block);
409
410 // Add original freelist to end of chain
411 if ( freelist != NULL ) {
412 while ( block->_next != NULL ) block = block->_next;
413 block->_next = freelist;
414 }
415 block = NULL;
416 }
417 if (block != NULL) {
418 // Return blocks to free list
419 // locking with safepoint checking introduces a potential deadlock:
420 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
421 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
422 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
423 MutexLocker ml(JNIHandleBlockFreeList_lock,
424 Mutex::_no_safepoint_check_flag);
425 while (block != NULL) {
426 block->zap();
427 JNIHandleBlock* next = block->_next;
428 block->_next = _block_free_list;
429 _block_free_list = block;
430 block = next;
431 }
432 }
433 if (pop_frame_link != NULL) {
434 // As a sanity check we release blocks pointed to by the pop_frame_link.
435 // This should never happen (only if PopLocalFrame is not called the
436 // correct number of times).
437 release_block(pop_frame_link, thread);
438 }
439 }
440
441
442 void JNIHandleBlock::oops_do(OopClosure* f) {
443 JNIHandleBlock* current_chain = this;
444 // Iterate over chain of blocks, followed by chains linked through the
445 // pop frame links.
446 while (current_chain != NULL) {
447 for (JNIHandleBlock* current = current_chain; current != NULL;
448 current = current->_next) {
449 assert(current == current_chain || current->pop_frame_link() == NULL,
450 "only blocks first in chain should have pop frame link set");
451 for (int index = 0; index < current->_top; index++) {
452 uintptr_t* addr = &(current->_handles)[index];
453 uintptr_t value = *addr;
454 // traverse heap pointers only, not deleted handles or free list
455 // pointers
456 if (value != 0 && !is_tagged_free_list(value)) {
457 oop* root = (oop*)addr;
458 f->do_oop(root);
459 }
460 }
461 // the next handle block is valid only if current block is full
462 if (current->_top < block_size_in_oops) {
463 break;
464 }
465 }
466 current_chain = current_chain->pop_frame_link();
467 }
468 }
469
470
471 jobject JNIHandleBlock::allocate_handle(oop obj, AllocFailType alloc_failmode) {
472 assert(Universe::heap()->is_in(obj), "sanity check");
473 if (_top == 0) {
474 // This is the first allocation or the initial block got zapped when
475 // entering a native function. If we have any following blocks they are
476 // not valid anymore.
477 for (JNIHandleBlock* current = _next; current != NULL;
478 current = current->_next) {
479 assert(current->_last == NULL, "only first block should have _last set");
480 assert(current->_free_list == NULL,
481 "only first block should have _free_list set");
482 if (current->_top == 0) {
483 // All blocks after the first clear trailing block are already cleared.
484 #ifdef ASSERT
485 for (current = current->_next; current != NULL; current = current->_next) {
486 assert(current->_top == 0, "trailing blocks must already be cleared");
487 }
488 #endif
489 break;
490 }
491 current->_top = 0;
492 current->zap();
493 }
494 // Clear initial block
495 _free_list = NULL;
496 _allocate_before_rebuild = 0;
497 _last = this;
498 zap();
499 }
500
501 // Try last block
502 if (_last->_top < block_size_in_oops) {
503 oop* handle = (oop*)&(_last->_handles)[_last->_top++];
504 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj);
505 return (jobject) handle;
506 }
507
508 // Try free list
509 if (_free_list != NULL) {
510 oop* handle = (oop*)_free_list;
511 _free_list = (uintptr_t*) untag_free_list(*_free_list);
512 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj);
513 return (jobject) handle;
514 }
515 // Check if unused block follow last
516 if (_last->_next != NULL) {
517 // update last and retry
518 _last = _last->_next;
519 return allocate_handle(obj, alloc_failmode);
520 }
521
522 // No space available, we have to rebuild free list or expand
523 if (_allocate_before_rebuild == 0) {
524 rebuild_free_list(); // updates _allocate_before_rebuild counter
525 } else {
526 // Append new block
527 Thread* thread = Thread::current();
528 Handle obj_handle(thread, obj);
529 // This can block, so we need to preserve obj across call.
530 _last->_next = JNIHandleBlock::allocate_block(thread, alloc_failmode);
531 if (_last->_next == NULL) {
532 return NULL;
533 }
534 _last = _last->_next;
535 _allocate_before_rebuild--;
536 obj = obj_handle();
537 }
538 return allocate_handle(obj, alloc_failmode); // retry
539 }
540
541 void JNIHandleBlock::rebuild_free_list() {
542 assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking");
543 int free = 0;
544 int blocks = 0;
545 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
546 for (int index = 0; index < current->_top; index++) {
547 uintptr_t* handle = &(current->_handles)[index];
548 if (*handle == 0) {
549 // this handle was cleared out by a delete call, reuse it
550 *handle = _free_list == NULL ? 0 : tag_free_list((uintptr_t)_free_list);
551 _free_list = handle;
552 free++;
553 }
554 }
555 // we should not rebuild free list if there are unused handles at the end
556 assert(current->_top == block_size_in_oops, "just checking");
557 blocks++;
558 }
559 // Heuristic: if more than half of the handles are free we rebuild next time
560 // as well, otherwise we append a corresponding number of new blocks before
561 // attempting a free list rebuild again.
562 int total = blocks * block_size_in_oops;
563 int extra = total - 2*free;
564 if (extra > 0) {
565 // Not as many free handles as we would like - compute number of new blocks to append
566 _allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops;
567 }
568 }
569
570
571 bool JNIHandleBlock::contains(jobject handle) const {
572 return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]);
573 }
574
575
576 bool JNIHandleBlock::chain_contains(jobject handle) const {
577 for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) {
578 if (current->contains(handle)) {
579 return true;
580 }
581 }
582 return false;
583 }
584
585
586 size_t JNIHandleBlock::length() const {
587 size_t result = 1;
588 for (JNIHandleBlock* current = _next; current != NULL; current = current->_next) {
589 result++;
590 }
591 return result;
592 }
593
594 class CountJNIHandleClosure: public OopClosure {
595 private:
596 int _count;
597 public:
598 CountJNIHandleClosure(): _count(0) {}
599 virtual void do_oop(oop* ooph) { _count++; }
600 virtual void do_oop(narrowOop* unused) { ShouldNotReachHere(); }
601 int count() { return _count; }
602 };
603
604 const size_t JNIHandleBlock::get_number_of_live_handles() {
605 CountJNIHandleClosure counter;
606 oops_do(&counter);
607 return counter.count();
608 }
609
610 // This method is not thread-safe, i.e., must be called while holding a lock on the
611 // structure.
612 size_t JNIHandleBlock::memory_usage() const {
613 return length() * sizeof(JNIHandleBlock);
614 }
615
616
617 #ifndef PRODUCT
618
619 bool JNIHandles::is_local_handle(jobject handle) {
620 return JNIHandleBlock::any_contains(handle);
621 }
622
623 bool JNIHandleBlock::any_contains(jobject handle) {
624 assert(handle != NULL, "precondition");
625 for (JNIHandleBlock* current = _block_list; current != NULL; current = current->_block_list_link) {
626 if (current->contains(handle)) {
627 return true;
628 }
629 }
630 return false;
631 }
632
633 void JNIHandleBlock::print_statistics() {
634 int used_blocks = 0;
635 int free_blocks = 0;
636 int used_handles = 0;
637 int free_handles = 0;
638 JNIHandleBlock* block = _block_list;
639 while (block != NULL) {
640 if (block->_top > 0) {
641 used_blocks++;
642 } else {
643 free_blocks++;
644 }
645 used_handles += block->_top;
646 free_handles += (block_size_in_oops - block->_top);
647 block = block->_block_list_link;
648 }
649 tty->print_cr("JNIHandleBlocks statistics");
650 tty->print_cr("- blocks allocated: %d", used_blocks + free_blocks);
651 tty->print_cr("- blocks in use: %d", used_blocks);
652 tty->print_cr("- blocks free: %d", free_blocks);
653 tty->print_cr("- handles in use: %d", used_handles);
654 tty->print_cr("- handles free: %d", free_handles);
655 }
656
657 #endif