1 /*
2 * Copyright (c) 1998, 2020, 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/oopStorage.inline.hpp"
27 #include "gc/shared/oopStorageSet.hpp"
28 #include "logging/log.hpp"
29 #include "memory/iterator.hpp"
30 #include "memory/universe.hpp"
31 #include "oops/access.inline.hpp"
32 #include "oops/oop.inline.hpp"
33 #include "runtime/handles.inline.hpp"
34 #include "runtime/jniHandles.inline.hpp"
35 #include "runtime/mutexLocker.hpp"
36 #include "runtime/thread.inline.hpp"
37 #include "utilities/align.hpp"
38 #include "utilities/debug.hpp"
39
40 static OopStorage* global_handles() {
41 return OopStorageSet::jni_global();
42 }
43
44 static OopStorage* weak_global_handles() {
45 return OopStorageSet::jni_weak();
46 }
47
48 // Serviceability agent support.
49 OopStorage* JNIHandles::_global_handles = NULL;
50 OopStorage* JNIHandles::_weak_global_handles = NULL;
51
52 void jni_handles_init() {
53 JNIHandles::_global_handles = global_handles();
54 JNIHandles::_weak_global_handles = weak_global_handles();
55 }
56
57
58 jobject JNIHandles::make_local(oop obj) {
59 if (obj == NULL) {
60 return NULL; // ignore null handles
61 } else {
62 Thread* thread = Thread::current();
63 assert(oopDesc::is_oop(obj), "not an oop");
64 assert(!current_thread_in_native(), "must not be in native");
65 return thread->active_handles()->allocate_handle(obj);
66 }
67 }
68
69
70 // optimized versions
71
72 jobject JNIHandles::make_local(Thread* thread, oop obj) {
73 if (obj == NULL) {
74 return NULL; // ignore null handles
75 } else {
76 assert(oopDesc::is_oop(obj), "not an oop");
77 assert(thread->is_Java_thread(), "not a Java thread");
78 assert(!current_thread_in_native(), "must not be in native");
79 return thread->active_handles()->allocate_handle(obj);
80 }
81 }
82
83
84 jobject JNIHandles::make_local(JNIEnv* env, oop obj) {
85 if (obj == NULL) {
86 return NULL; // ignore null handles
87 } else {
88 JavaThread* thread = JavaThread::thread_from_jni_environment(env);
89 assert(oopDesc::is_oop(obj), "not an oop");
90 assert(!current_thread_in_native(), "must not be in native");
91 return thread->active_handles()->allocate_handle(obj);
92 }
93 }
94
95
96 static void report_handle_allocation_failure(AllocFailType alloc_failmode,
97 const char* handle_kind) {
98 if (alloc_failmode == AllocFailStrategy::EXIT_OOM) {
99 // Fake size value, since we don't know the min allocation size here.
100 vm_exit_out_of_memory(sizeof(oop), OOM_MALLOC_ERROR,
101 "Cannot create %s JNI handle", handle_kind);
102 } else {
103 assert(alloc_failmode == AllocFailStrategy::RETURN_NULL, "invariant");
104 }
105 }
106
107 jobject JNIHandles::make_global(Handle obj, AllocFailType alloc_failmode) {
108 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
109 assert(!current_thread_in_native(), "must not be in native");
110 jobject res = NULL;
111 if (!obj.is_null()) {
112 // ignore null handles
113 assert(oopDesc::is_oop(obj()), "not an oop");
114 oop* ptr = global_handles()->allocate();
115 // Return NULL on allocation failure.
116 if (ptr != NULL) {
117 assert(*ptr == NULL, "invariant");
118 NativeAccess<>::oop_store(ptr, obj());
119 res = reinterpret_cast<jobject>(ptr);
120 } else {
121 report_handle_allocation_failure(alloc_failmode, "global");
122 }
123 }
124
125 return res;
126 }
127
128
129 jobject JNIHandles::make_weak_global(Handle obj, AllocFailType alloc_failmode) {
130 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
131 assert(!current_thread_in_native(), "must not be in native");
132 jobject res = NULL;
133 if (!obj.is_null()) {
134 // ignore null handles
135 assert(oopDesc::is_oop(obj()), "not an oop");
136 oop* ptr = weak_global_handles()->allocate();
137 // Return NULL on allocation failure.
138 if (ptr != NULL) {
139 assert(*ptr == NULL, "invariant");
140 NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(ptr, obj());
141 char* tptr = reinterpret_cast<char*>(ptr) + weak_tag_value;
142 res = reinterpret_cast<jobject>(tptr);
143 } else {
144 report_handle_allocation_failure(alloc_failmode, "weak global");
145 }
146 }
147 return res;
148 }
149
150 // Resolve some erroneous cases to NULL, rather than treating them as
151 // possibly unchecked errors. In particular, deleted handles are
152 // treated as NULL (though a deleted and later reallocated handle
153 // isn't detected).
154 oop JNIHandles::resolve_external_guard(jobject handle) {
155 oop result = NULL;
156 if (handle != NULL) {
157 result = resolve_impl<DECORATORS_NONE, true /* external_guard */>(handle);
158 }
159 return result;
160 }
161
162 bool JNIHandles::is_global_weak_cleared(jweak handle) {
163 assert(handle != NULL, "precondition");
164 assert(is_jweak(handle), "not a weak handle");
165 oop* oop_ptr = jweak_ptr(handle);
166 oop value = NativeAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>::oop_load(oop_ptr);
167 return value == NULL;
168 }
169
170 void JNIHandles::destroy_global(jobject handle) {
171 if (handle != NULL) {
172 assert(!is_jweak(handle), "wrong method for detroying jweak");
173 oop* oop_ptr = jobject_ptr(handle);
174 NativeAccess<>::oop_store(oop_ptr, (oop)NULL);
175 global_handles()->release(oop_ptr);
176 }
177 }
178
179
180 void JNIHandles::destroy_weak_global(jobject handle) {
181 if (handle != NULL) {
182 assert(is_jweak(handle), "JNI handle not jweak");
183 oop* oop_ptr = jweak_ptr(handle);
184 NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(oop_ptr, (oop)NULL);
185 weak_global_handles()->release(oop_ptr);
186 }
187 }
188
189
190 void JNIHandles::oops_do(OopClosure* f) {
191 global_handles()->oops_do(f);
192 }
193
194
195 void JNIHandles::weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f) {
196 weak_global_handles()->weak_oops_do(is_alive, f);
197 }
198
199
200 void JNIHandles::weak_oops_do(OopClosure* f) {
201 weak_global_handles()->weak_oops_do(f);
202 }
203
204
205 inline bool is_storage_handle(const OopStorage* storage, const oop* ptr) {
206 return storage->allocation_status(ptr) == OopStorage::ALLOCATED_ENTRY;
207 }
208
209
210 jobjectRefType JNIHandles::handle_type(Thread* thread, jobject handle) {
211 assert(handle != NULL, "precondition");
212 jobjectRefType result = JNIInvalidRefType;
213 if (is_jweak(handle)) {
214 if (is_storage_handle(weak_global_handles(), jweak_ptr(handle))) {
215 result = JNIWeakGlobalRefType;
216 }
217 } else {
218 switch (global_handles()->allocation_status(jobject_ptr(handle))) {
219 case OopStorage::ALLOCATED_ENTRY:
220 result = JNIGlobalRefType;
221 break;
222
223 case OopStorage::UNALLOCATED_ENTRY:
224 break; // Invalid global handle
225
226 case OopStorage::INVALID_ENTRY:
227 // Not in global storage. Might be a local handle.
228 if (is_local_handle(thread, handle) ||
229 (thread->is_Java_thread() &&
230 is_frame_handle((JavaThread*)thread, handle))) {
231 result = JNILocalRefType;
232 }
233 break;
234
235 default:
236 ShouldNotReachHere();
237 }
238 }
239 return result;
240 }
241
242
243 bool JNIHandles::is_local_handle(Thread* thread, jobject handle) {
244 assert(handle != NULL, "precondition");
245 JNIHandleBlock* block = thread->active_handles();
246
247 // Look back past possible native calls to jni_PushLocalFrame.
248 while (block != NULL) {
249 if (block->chain_contains(handle)) {
250 return true;
251 }
252 block = block->pop_frame_link();
253 }
254 return false;
255 }
256
257
258 // Determine if the handle is somewhere in the current thread's stack.
259 // We easily can't isolate any particular stack frame the handle might
260 // come from, so we'll check the whole stack.
261
262 bool JNIHandles::is_frame_handle(JavaThread* thr, jobject handle) {
263 assert(handle != NULL, "precondition");
264 // If there is no java frame, then this must be top level code, such
265 // as the java command executable, in which case, this type of handle
266 // is not permitted.
267 return (thr->has_last_Java_frame() &&
268 thr->is_in_stack_range_incl((address)handle, (address)thr->last_Java_sp()));
269 }
270
271
272 bool JNIHandles::is_global_handle(jobject handle) {
273 assert(handle != NULL, "precondition");
274 return !is_jweak(handle) && is_storage_handle(global_handles(), jobject_ptr(handle));
275 }
276
277
278 bool JNIHandles::is_weak_global_handle(jobject handle) {
279 assert(handle != NULL, "precondition");
280 return is_jweak(handle) && is_storage_handle(weak_global_handles(), jweak_ptr(handle));
281 }
282
283 size_t JNIHandles::global_handle_memory_usage() {
284 return global_handles()->total_memory_usage();
285 }
286
287 size_t JNIHandles::weak_global_handle_memory_usage() {
288 return weak_global_handles()->total_memory_usage();
289 }
290
291
292 // We assume this is called at a safepoint: no lock is needed.
293 void JNIHandles::print_on(outputStream* st) {
294 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
295
296 st->print_cr("JNI global refs: " SIZE_FORMAT ", weak refs: " SIZE_FORMAT,
297 global_handles()->allocation_count(),
298 weak_global_handles()->allocation_count());
299 st->cr();
300 st->flush();
301 }
302
303 void JNIHandles::print() { print_on(tty); }
304
305 class VerifyJNIHandles: public OopClosure {
306 public:
307 virtual void do_oop(oop* root) {
308 guarantee(oopDesc::is_oop_or_null(RawAccess<>::oop_load(root)), "Invalid oop");
309 }
310 virtual void do_oop(narrowOop* root) { ShouldNotReachHere(); }
311 };
312
313 void JNIHandles::verify() {
314 VerifyJNIHandles verify_handle;
315
316 oops_do(&verify_handle);
317 weak_oops_do(&verify_handle);
318 }
319
320 // This method is implemented here to avoid circular includes between
321 // jniHandles.hpp and thread.hpp.
322 bool JNIHandles::current_thread_in_native() {
323 Thread* thread = Thread::current();
324 return (thread->is_Java_thread() &&
325 JavaThread::current()->thread_state() == _thread_in_native);
326 }
327
328
329 int JNIHandleBlock::_blocks_allocated = 0;
330 JNIHandleBlock* JNIHandleBlock::_block_free_list = NULL;
331 #ifndef PRODUCT
332 JNIHandleBlock* JNIHandleBlock::_block_list = NULL;
333 #endif
334
335 static inline bool is_tagged_free_list(uintptr_t value) {
336 return (value & 1u) != 0;
337 }
338
339 static inline uintptr_t tag_free_list(uintptr_t value) {
340 return value | 1u;
341 }
342
343 static inline uintptr_t untag_free_list(uintptr_t value) {
344 return value & ~(uintptr_t)1u;
345 }
346
347 // There is a freelist of handles running through the JNIHandleBlock
348 // with a tagged next pointer, distinguishing these next pointers from
349 // oops. The freelist handling currently relies on the size of oops
350 // being the same as a native pointer. If this ever changes, then
351 // this freelist handling must change too.
352 STATIC_ASSERT(sizeof(oop) == sizeof(uintptr_t));
353
354 #ifdef ASSERT
355 void JNIHandleBlock::zap() {
356 // Zap block values
357 _top = 0;
358 for (int index = 0; index < block_size_in_oops; index++) {
359 // NOT using Access here; just bare clobbering to NULL, since the
360 // block no longer contains valid oops.
361 _handles[index] = 0;
362 }
363 }
364 #endif // ASSERT
365
366 JNIHandleBlock* JNIHandleBlock::allocate_block(Thread* thread) {
367 assert(thread == NULL || thread == Thread::current(), "sanity check");
368 JNIHandleBlock* block;
369 // Check the thread-local free list for a block so we don't
370 // have to acquire a mutex.
371 if (thread != NULL && thread->free_handle_block() != NULL) {
372 block = thread->free_handle_block();
373 thread->set_free_handle_block(block->_next);
374 }
375 else {
376 // locking with safepoint checking introduces a potential deadlock:
377 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
378 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
379 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
380 MutexLocker ml(JNIHandleBlockFreeList_lock,
381 Mutex::_no_safepoint_check_flag);
382 if (_block_free_list == NULL) {
383 // Allocate new block
384 block = new JNIHandleBlock();
385 _blocks_allocated++;
386 block->zap();
387 #ifndef PRODUCT
388 // Link new block to list of all allocated blocks
389 block->_block_list_link = _block_list;
390 _block_list = block;
391 #endif
392 } else {
393 // Get block from free list
394 block = _block_free_list;
395 _block_free_list = _block_free_list->_next;
396 }
397 }
398 block->_top = 0;
399 block->_next = NULL;
400 block->_pop_frame_link = NULL;
401 block->_planned_capacity = block_size_in_oops;
402 // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle
403 debug_only(block->_last = NULL);
404 debug_only(block->_free_list = NULL);
405 debug_only(block->_allocate_before_rebuild = -1);
406 return block;
407 }
408
409
410 void JNIHandleBlock::release_block(JNIHandleBlock* block, Thread* thread) {
411 assert(thread == NULL || thread == Thread::current(), "sanity check");
412 JNIHandleBlock* pop_frame_link = block->pop_frame_link();
413 // Put returned block at the beginning of the thread-local free list.
414 // Note that if thread == NULL, we use it as an implicit argument that
415 // we _don't_ want the block to be kept on the free_handle_block.
416 // See for instance JavaThread::exit().
417 if (thread != NULL ) {
418 block->zap();
419 JNIHandleBlock* freelist = thread->free_handle_block();
420 block->_pop_frame_link = NULL;
421 thread->set_free_handle_block(block);
422
423 // Add original freelist to end of chain
424 if ( freelist != NULL ) {
425 while ( block->_next != NULL ) block = block->_next;
426 block->_next = freelist;
427 }
428 block = NULL;
429 }
430 if (block != NULL) {
431 // Return blocks to free list
432 // locking with safepoint checking introduces a potential deadlock:
433 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
434 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
435 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
436 MutexLocker ml(JNIHandleBlockFreeList_lock,
437 Mutex::_no_safepoint_check_flag);
438 while (block != NULL) {
439 block->zap();
440 JNIHandleBlock* next = block->_next;
441 block->_next = _block_free_list;
442 _block_free_list = block;
443 block = next;
444 }
445 }
446 if (pop_frame_link != NULL) {
447 // As a sanity check we release blocks pointed to by the pop_frame_link.
448 // This should never happen (only if PopLocalFrame is not called the
449 // correct number of times).
450 release_block(pop_frame_link, thread);
451 }
452 }
453
454
455 void JNIHandleBlock::oops_do(OopClosure* f) {
456 JNIHandleBlock* current_chain = this;
457 // Iterate over chain of blocks, followed by chains linked through the
458 // pop frame links.
459 while (current_chain != NULL) {
460 for (JNIHandleBlock* current = current_chain; current != NULL;
461 current = current->_next) {
462 assert(current == current_chain || current->pop_frame_link() == NULL,
463 "only blocks first in chain should have pop frame link set");
464 for (int index = 0; index < current->_top; index++) {
465 uintptr_t* addr = &(current->_handles)[index];
466 uintptr_t value = *addr;
467 // traverse heap pointers only, not deleted handles or free list
468 // pointers
469 if (value != 0 && !is_tagged_free_list(value)) {
470 oop* root = (oop*)addr;
471 f->do_oop(root);
472 }
473 }
474 // the next handle block is valid only if current block is full
475 if (current->_top < block_size_in_oops) {
476 break;
477 }
478 }
479 current_chain = current_chain->pop_frame_link();
480 }
481 }
482
483
484 jobject JNIHandleBlock::allocate_handle(oop obj) {
485 assert(Universe::heap()->is_in(obj), "sanity check");
486 if (_top == 0) {
487 // This is the first allocation or the initial block got zapped when
488 // entering a native function. If we have any following blocks they are
489 // not valid anymore.
490 for (JNIHandleBlock* current = _next; current != NULL;
491 current = current->_next) {
492 assert(current->_last == NULL, "only first block should have _last set");
493 assert(current->_free_list == NULL,
494 "only first block should have _free_list set");
495 if (current->_top == 0) {
496 // All blocks after the first clear trailing block are already cleared.
497 #ifdef ASSERT
498 for (current = current->_next; current != NULL; current = current->_next) {
499 assert(current->_top == 0, "trailing blocks must already be cleared");
500 }
501 #endif
502 break;
503 }
504 current->_top = 0;
505 current->zap();
506 }
507 // Clear initial block
508 _free_list = NULL;
509 _allocate_before_rebuild = 0;
510 _last = this;
511 zap();
512 }
513
514 // Try last block
515 if (_last->_top < block_size_in_oops) {
516 oop* handle = (oop*)&(_last->_handles)[_last->_top++];
517 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj);
518 return (jobject) handle;
519 }
520
521 // Try free list
522 if (_free_list != NULL) {
523 oop* handle = (oop*)_free_list;
524 _free_list = (uintptr_t*) untag_free_list(*_free_list);
525 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj);
526 return (jobject) handle;
527 }
528 // Check if unused block follow last
529 if (_last->_next != NULL) {
530 // update last and retry
531 _last = _last->_next;
532 return allocate_handle(obj);
533 }
534
535 // No space available, we have to rebuild free list or expand
536 if (_allocate_before_rebuild == 0) {
537 rebuild_free_list(); // updates _allocate_before_rebuild counter
538 } else {
539 // Append new block
540 Thread* thread = Thread::current();
541 Handle obj_handle(thread, obj);
542 // This can block, so we need to preserve obj across call.
543 _last->_next = JNIHandleBlock::allocate_block(thread);
544 _last = _last->_next;
545 _allocate_before_rebuild--;
546 obj = obj_handle();
547 }
548 return allocate_handle(obj); // retry
549 }
550
551 void JNIHandleBlock::rebuild_free_list() {
552 assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking");
553 int free = 0;
554 int blocks = 0;
555 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
556 for (int index = 0; index < current->_top; index++) {
557 uintptr_t* handle = &(current->_handles)[index];
558 if (*handle == 0) {
559 // this handle was cleared out by a delete call, reuse it
560 *handle = _free_list == NULL ? 0 : tag_free_list((uintptr_t)_free_list);
561 _free_list = handle;
562 free++;
563 }
564 }
565 // we should not rebuild free list if there are unused handles at the end
566 assert(current->_top == block_size_in_oops, "just checking");
567 blocks++;
568 }
569 // Heuristic: if more than half of the handles are free we rebuild next time
570 // as well, otherwise we append a corresponding number of new blocks before
571 // attempting a free list rebuild again.
572 int total = blocks * block_size_in_oops;
573 int extra = total - 2*free;
574 if (extra > 0) {
575 // Not as many free handles as we would like - compute number of new blocks to append
576 _allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops;
577 }
578 }
579
580
581 bool JNIHandleBlock::contains(jobject handle) const {
582 return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]);
583 }
584
585
586 bool JNIHandleBlock::chain_contains(jobject handle) const {
587 for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) {
588 if (current->contains(handle)) {
589 return true;
590 }
591 }
592 return false;
593 }
594
595
596 size_t JNIHandleBlock::length() const {
597 size_t result = 1;
598 for (JNIHandleBlock* current = _next; current != NULL; current = current->_next) {
599 result++;
600 }
601 return result;
602 }
603
604 class CountJNIHandleClosure: public OopClosure {
605 private:
606 int _count;
607 public:
608 CountJNIHandleClosure(): _count(0) {}
609 virtual void do_oop(oop* ooph) { _count++; }
610 virtual void do_oop(narrowOop* unused) { ShouldNotReachHere(); }
611 int count() { return _count; }
612 };
613
614 const size_t JNIHandleBlock::get_number_of_live_handles() {
615 CountJNIHandleClosure counter;
616 oops_do(&counter);
617 return counter.count();
618 }
619
620 // This method is not thread-safe, i.e., must be called while holding a lock on the
621 // structure.
622 size_t JNIHandleBlock::memory_usage() const {
623 return length() * sizeof(JNIHandleBlock);
624 }
625
626
627 #ifndef PRODUCT
628
629 bool JNIHandles::is_local_handle(jobject handle) {
630 return JNIHandleBlock::any_contains(handle);
631 }
632
633 bool JNIHandleBlock::any_contains(jobject handle) {
634 assert(handle != NULL, "precondition");
635 for (JNIHandleBlock* current = _block_list; current != NULL; current = current->_block_list_link) {
636 if (current->contains(handle)) {
637 return true;
638 }
639 }
640 return false;
641 }
642
643 void JNIHandleBlock::print_statistics() {
644 int used_blocks = 0;
645 int free_blocks = 0;
646 int used_handles = 0;
647 int free_handles = 0;
648 JNIHandleBlock* block = _block_list;
649 while (block != NULL) {
650 if (block->_top > 0) {
651 used_blocks++;
652 } else {
653 free_blocks++;
654 }
655 used_handles += block->_top;
656 free_handles += (block_size_in_oops - block->_top);
657 block = block->_block_list_link;
658 }
659 tty->print_cr("JNIHandleBlocks statistics");
660 tty->print_cr("- blocks allocated: %d", used_blocks + free_blocks);
661 tty->print_cr("- blocks in use: %d", used_blocks);
662 tty->print_cr("- blocks free: %d", free_blocks);
663 tty->print_cr("- handles in use: %d", used_handles);
664 tty->print_cr("- handles free: %d", free_handles);
665 }
666
667 #endif