1 /*
2 * Copyright (c) 1998, 2022, 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 = NULL;
53 OopStorage* JNIHandles::_weak_global_handles = NULL;
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 == NULL) {
67 return NULL; // 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 return thread->active_handles()->allocate_handle(thread, obj, alloc_failmode);
72 }
73 }
74
75 static void report_handle_allocation_failure(AllocFailType alloc_failmode,
76 const char* handle_kind) {
77 if (alloc_failmode == AllocFailStrategy::EXIT_OOM) {
78 // Fake size value, since we don't know the min allocation size here.
79 vm_exit_out_of_memory(sizeof(oop), OOM_MALLOC_ERROR,
80 "Cannot create %s JNI handle", handle_kind);
81 } else {
82 assert(alloc_failmode == AllocFailStrategy::RETURN_NULL, "invariant");
83 }
84 }
85
86 jobject JNIHandles::make_global(Handle obj, AllocFailType alloc_failmode) {
87 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
88 assert(!current_thread_in_native(), "must not be in native");
89 jobject res = NULL;
90 if (!obj.is_null()) {
91 // ignore null handles
92 assert(oopDesc::is_oop(obj()), "not an oop");
93 oop* ptr = global_handles()->allocate();
94 // Return NULL on allocation failure.
95 if (ptr != NULL) {
96 assert(*ptr == NULL, "invariant");
97 NativeAccess<>::oop_store(ptr, obj());
98 res = reinterpret_cast<jobject>(ptr);
99 } else {
100 report_handle_allocation_failure(alloc_failmode, "global");
101 }
102 }
103
104 return res;
105 }
106
107 jobject JNIHandles::make_weak_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 = weak_global_handles()->allocate();
115 // Return NULL on allocation failure.
116 if (ptr != NULL) {
117 assert(*ptr == NULL, "invariant");
118 NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(ptr, obj());
119 char* tptr = reinterpret_cast<char*>(ptr) + weak_tag_value;
120 res = reinterpret_cast<jobject>(tptr);
121 } else {
122 report_handle_allocation_failure(alloc_failmode, "weak global");
123 }
124 }
125 return res;
126 }
127
128 // Resolve some erroneous cases to NULL, rather than treating them as
129 // possibly unchecked errors. In particular, deleted handles are
130 // treated as NULL (though a deleted and later reallocated handle
131 // isn't detected).
132 oop JNIHandles::resolve_external_guard(jobject handle) {
133 oop result = NULL;
134 if (handle != NULL) {
135 result = resolve_impl<DECORATORS_NONE, true /* external_guard */>(handle);
136 }
137 return result;
138 }
139
140 bool JNIHandles::is_global_weak_cleared(jweak handle) {
141 assert(handle != NULL, "precondition");
142 assert(is_jweak(handle), "not a weak handle");
143 oop* oop_ptr = jweak_ptr(handle);
144 oop value = NativeAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>::oop_load(oop_ptr);
145 return value == NULL;
146 }
147
148 void JNIHandles::destroy_global(jobject handle) {
149 if (handle != NULL) {
150 assert(!is_jweak(handle), "wrong method for destroying jweak");
151 oop* oop_ptr = jobject_ptr(handle);
152 NativeAccess<>::oop_store(oop_ptr, (oop)NULL);
153 global_handles()->release(oop_ptr);
154 }
155 }
156
157
158 void JNIHandles::destroy_weak_global(jobject handle) {
159 if (handle != NULL) {
160 assert(is_jweak(handle), "JNI handle not jweak");
161 oop* oop_ptr = jweak_ptr(handle);
162 NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(oop_ptr, (oop)NULL);
163 weak_global_handles()->release(oop_ptr);
164 }
165 }
166
167
168 void JNIHandles::oops_do(OopClosure* f) {
169 global_handles()->oops_do(f);
170 }
171
172
173 void JNIHandles::weak_oops_do(OopClosure* f) {
174 weak_global_handles()->weak_oops_do(f);
175 }
176
177 bool JNIHandles::is_global_storage(const OopStorage* storage) {
178 return _global_handles == storage;
179 }
180
181 inline bool is_storage_handle(const OopStorage* storage, const oop* ptr) {
182 return storage->allocation_status(ptr) == OopStorage::ALLOCATED_ENTRY;
183 }
184
185
186 jobjectRefType JNIHandles::handle_type(JavaThread* thread, jobject handle) {
187 assert(handle != NULL, "precondition");
188 jobjectRefType result = JNIInvalidRefType;
189 if (is_jweak(handle)) {
190 if (is_storage_handle(weak_global_handles(), jweak_ptr(handle))) {
191 result = JNIWeakGlobalRefType;
192 }
193 } else {
194 switch (global_handles()->allocation_status(jobject_ptr(handle))) {
195 case OopStorage::ALLOCATED_ENTRY:
196 result = JNIGlobalRefType;
197 break;
198
199 case OopStorage::UNALLOCATED_ENTRY:
200 break; // Invalid global handle
201
202 case OopStorage::INVALID_ENTRY:
203 // Not in global storage. Might be a local handle.
204 if (is_local_handle(thread, handle) || is_frame_handle(thread, handle)) {
205 result = JNILocalRefType;
206 }
207 break;
208
209 default:
210 ShouldNotReachHere();
211 }
212 }
213 return result;
214 }
215
216
217 bool JNIHandles::is_local_handle(JavaThread* thread, jobject handle) {
218 assert(handle != NULL, "precondition");
219 JNIHandleBlock* block = thread->active_handles();
220
221 // Look back past possible native calls to jni_PushLocalFrame.
222 while (block != NULL) {
223 if (block->chain_contains(handle)) {
224 return true;
225 }
226 block = block->pop_frame_link();
227 }
228 return false;
229 }
230
231
232 // Determine if the handle is somewhere in the current thread's stack.
233 // We easily can't isolate any particular stack frame the handle might
234 // come from, so we'll check the whole stack.
235
236 bool JNIHandles::is_frame_handle(JavaThread* thr, jobject handle) {
237 assert(handle != NULL, "precondition");
238 // If there is no java frame, then this must be top level code, such
239 // as the java command executable, in which case, this type of handle
240 // is not permitted.
241 return (thr->has_last_Java_frame() &&
242 thr->is_in_stack_range_incl((address)handle, (address)thr->last_Java_sp()));
243 }
244
245
246 bool JNIHandles::is_global_handle(jobject handle) {
247 assert(handle != NULL, "precondition");
248 return !is_jweak(handle) && is_storage_handle(global_handles(), jobject_ptr(handle));
249 }
250
251
252 bool JNIHandles::is_weak_global_handle(jobject handle) {
253 assert(handle != NULL, "precondition");
254 return is_jweak(handle) && is_storage_handle(weak_global_handles(), jweak_ptr(handle));
255 }
256
257 // We assume this is called at a safepoint: no lock is needed.
258 void JNIHandles::print_on(outputStream* st) {
259 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
260
261 st->print_cr("JNI global refs: " SIZE_FORMAT ", weak refs: " SIZE_FORMAT,
262 global_handles()->allocation_count(),
263 weak_global_handles()->allocation_count());
264 st->cr();
265 st->flush();
266 }
267
268 void JNIHandles::print() { print_on(tty); }
269
270 class VerifyJNIHandles: public OopClosure {
271 public:
272 virtual void do_oop(oop* root) {
273 guarantee(oopDesc::is_oop_or_null(RawAccess<>::oop_load(root)), "Invalid oop");
274 }
275 virtual void do_oop(narrowOop* root) { ShouldNotReachHere(); }
276 };
277
278 void JNIHandles::verify() {
279 VerifyJNIHandles verify_handle;
280
281 oops_do(&verify_handle);
282 weak_oops_do(&verify_handle);
283 }
284
285 // This method is implemented here to avoid circular includes between
286 // jniHandles.hpp and thread.hpp.
287 bool JNIHandles::current_thread_in_native() {
288 Thread* thread = Thread::current();
289 return (thread->is_Java_thread() &&
290 JavaThread::cast(thread)->thread_state() == _thread_in_native);
291 }
292
293 bool JNIHandles::is_same_object(jobject handle1, jobject handle2) {
294 oop obj1 = resolve_no_keepalive(handle1);
295 oop obj2 = resolve_no_keepalive(handle2);
296
297 bool ret = obj1 == obj2;
298
299 if (EnableValhalla) {
300 if (!ret && obj1 != NULL && obj2 != NULL && obj1->klass() == obj2->klass() && obj1->klass()->is_inline_klass()) {
301 // The two references are different, they are not null and they are both inline types,
302 // a full substitutability test is required, calling ValueObjectMethods.isSubstitutable()
303 // (similarly to InterpreterRuntime::is_substitutable)
304 JavaThread* THREAD = JavaThread::current();
305 Handle ha(THREAD, obj1);
306 Handle hb(THREAD, obj2);
307 JavaValue result(T_BOOLEAN);
308 JavaCallArguments args;
309 args.push_oop(ha);
310 args.push_oop(hb);
311 methodHandle method(THREAD, Universe::is_substitutable_method());
312 JavaCalls::call(&result, method, &args, THREAD);
313 if (HAS_PENDING_EXCEPTION) {
314 // Something really bad happened because isSubstitutable() should not throw exceptions
315 // If it is an error, just let it propagate
316 // If it is an exception, wrap it into an InternalError
317 if (!PENDING_EXCEPTION->is_a(vmClasses::Error_klass())) {
318 Handle e(THREAD, PENDING_EXCEPTION);
319 CLEAR_PENDING_EXCEPTION;
320 THROW_MSG_CAUSE_(vmSymbols::java_lang_InternalError(), "Internal error in substitutability test", e, false);
321 }
322 }
323 ret = result.get_jboolean();
324 }
325 }
326
327 return ret;
328 }
329
330
331 int JNIHandleBlock::_blocks_allocated = 0;
332
333 static inline bool is_tagged_free_list(uintptr_t value) {
334 return (value & 1u) != 0;
335 }
336
337 static inline uintptr_t tag_free_list(uintptr_t value) {
338 return value | 1u;
339 }
340
341 static inline uintptr_t untag_free_list(uintptr_t value) {
342 return value & ~(uintptr_t)1u;
343 }
344
345 // There is a freelist of handles running through the JNIHandleBlock
346 // with a tagged next pointer, distinguishing these next pointers from
347 // oops. The freelist handling currently relies on the size of oops
348 // being the same as a native pointer. If this ever changes, then
349 // this freelist handling must change too.
350 STATIC_ASSERT(sizeof(oop) == sizeof(uintptr_t));
351
352 #ifdef ASSERT
353 void JNIHandleBlock::zap() {
354 // Zap block values
355 _top = 0;
356 for (int index = 0; index < block_size_in_oops; index++) {
357 // NOT using Access here; just bare clobbering to NULL, since the
358 // block no longer contains valid oops.
359 _handles[index] = 0;
360 }
361 }
362 #endif // ASSERT
363
364 JNIHandleBlock* JNIHandleBlock::allocate_block(JavaThread* thread, AllocFailType alloc_failmode) {
365 // The VM thread can allocate a handle block in behalf of another thread during a safepoint.
366 assert(thread == NULL || thread == Thread::current() || SafepointSynchronize::is_at_safepoint(),
367 "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 } else {
375 // Allocate new block
376 if (alloc_failmode == AllocFailStrategy::RETURN_NULL) {
377 block = new (std::nothrow) JNIHandleBlock();
378 if (block == NULL) {
379 return NULL;
380 }
381 } else {
382 block = new JNIHandleBlock();
383 }
384 Atomic::inc(&_blocks_allocated);
385 block->zap();
386 }
387 block->_top = 0;
388 block->_next = NULL;
389 block->_pop_frame_link = NULL;
390 // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle
391 debug_only(block->_last = NULL);
392 debug_only(block->_free_list = NULL);
393 debug_only(block->_allocate_before_rebuild = -1);
394 return block;
395 }
396
397
398 void JNIHandleBlock::release_block(JNIHandleBlock* block, JavaThread* thread) {
399 assert(thread == NULL || thread == Thread::current(), "sanity check");
400 JNIHandleBlock* pop_frame_link = block->pop_frame_link();
401 // Put returned block at the beginning of the thread-local free list.
402 // Note that if thread == NULL, we use it as an implicit argument that
403 // we _don't_ want the block to be kept on the free_handle_block.
404 // See for instance JavaThread::exit().
405 if (thread != NULL ) {
406 block->zap();
407 JNIHandleBlock* freelist = thread->free_handle_block();
408 block->_pop_frame_link = NULL;
409 thread->set_free_handle_block(block);
410
411 // Add original freelist to end of chain
412 if ( freelist != NULL ) {
413 while ( block->_next != NULL ) block = block->_next;
414 block->_next = freelist;
415 }
416 block = NULL;
417 } else {
418 DEBUG_ONLY(block->set_pop_frame_link(NULL));
419 while (block != NULL) {
420 JNIHandleBlock* next = block->_next;
421 Atomic::dec(&_blocks_allocated);
422 assert(block->pop_frame_link() == NULL, "pop_frame_link should be NULL");
423 delete block;
424 block = next;
425 }
426 }
427 if (pop_frame_link != NULL) {
428 // As a sanity check we release blocks pointed to by the pop_frame_link.
429 // This should never happen (only if PopLocalFrame is not called the
430 // correct number of times).
431 release_block(pop_frame_link, thread);
432 }
433 }
434
435
436 void JNIHandleBlock::oops_do(OopClosure* f) {
437 JNIHandleBlock* current_chain = this;
438 // Iterate over chain of blocks, followed by chains linked through the
439 // pop frame links.
440 while (current_chain != NULL) {
441 for (JNIHandleBlock* current = current_chain; current != NULL;
442 current = current->_next) {
443 assert(current == current_chain || current->pop_frame_link() == NULL,
444 "only blocks first in chain should have pop frame link set");
445 for (int index = 0; index < current->_top; index++) {
446 uintptr_t* addr = &(current->_handles)[index];
447 uintptr_t value = *addr;
448 // traverse heap pointers only, not deleted handles or free list
449 // pointers
450 if (value != 0 && !is_tagged_free_list(value)) {
451 oop* root = (oop*)addr;
452 f->do_oop(root);
453 }
454 }
455 // the next handle block is valid only if current block is full
456 if (current->_top < block_size_in_oops) {
457 break;
458 }
459 }
460 current_chain = current_chain->pop_frame_link();
461 }
462 }
463
464
465 jobject JNIHandleBlock::allocate_handle(JavaThread* caller, oop obj, AllocFailType alloc_failmode) {
466 assert(Universe::heap()->is_in(obj), "sanity check");
467 if (_top == 0) {
468 // This is the first allocation or the initial block got zapped when
469 // entering a native function. If we have any following blocks they are
470 // not valid anymore.
471 for (JNIHandleBlock* current = _next; current != NULL;
472 current = current->_next) {
473 assert(current->_last == NULL, "only first block should have _last set");
474 assert(current->_free_list == NULL,
475 "only first block should have _free_list set");
476 if (current->_top == 0) {
477 // All blocks after the first clear trailing block are already cleared.
478 #ifdef ASSERT
479 for (current = current->_next; current != NULL; current = current->_next) {
480 assert(current->_top == 0, "trailing blocks must already be cleared");
481 }
482 #endif
483 break;
484 }
485 current->_top = 0;
486 current->zap();
487 }
488 // Clear initial block
489 _free_list = NULL;
490 _allocate_before_rebuild = 0;
491 _last = this;
492 zap();
493 }
494
495 // Try last block
496 if (_last->_top < block_size_in_oops) {
497 oop* handle = (oop*)&(_last->_handles)[_last->_top++];
498 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj);
499 return (jobject) handle;
500 }
501
502 // Try free list
503 if (_free_list != NULL) {
504 oop* handle = (oop*)_free_list;
505 _free_list = (uintptr_t*) untag_free_list(*_free_list);
506 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj);
507 return (jobject) handle;
508 }
509 // Check if unused block follow last
510 if (_last->_next != NULL) {
511 // update last and retry
512 _last = _last->_next;
513 return allocate_handle(caller, obj, alloc_failmode);
514 }
515
516 // No space available, we have to rebuild free list or expand
517 if (_allocate_before_rebuild == 0) {
518 rebuild_free_list(); // updates _allocate_before_rebuild counter
519 } else {
520 _last->_next = JNIHandleBlock::allocate_block(caller, alloc_failmode);
521 if (_last->_next == NULL) {
522 return NULL;
523 }
524 _last = _last->_next;
525 _allocate_before_rebuild--;
526 }
527 return allocate_handle(caller, obj, alloc_failmode); // retry
528 }
529
530 void JNIHandleBlock::rebuild_free_list() {
531 assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking");
532 int free = 0;
533 int blocks = 0;
534 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
535 for (int index = 0; index < current->_top; index++) {
536 uintptr_t* handle = &(current->_handles)[index];
537 if (*handle == 0) {
538 // this handle was cleared out by a delete call, reuse it
539 *handle = _free_list == NULL ? 0 : tag_free_list((uintptr_t)_free_list);
540 _free_list = handle;
541 free++;
542 }
543 }
544 // we should not rebuild free list if there are unused handles at the end
545 assert(current->_top == block_size_in_oops, "just checking");
546 blocks++;
547 }
548 // Heuristic: if more than half of the handles are free we rebuild next time
549 // as well, otherwise we append a corresponding number of new blocks before
550 // attempting a free list rebuild again.
551 int total = blocks * block_size_in_oops;
552 int extra = total - 2*free;
553 if (extra > 0) {
554 // Not as many free handles as we would like - compute number of new blocks to append
555 _allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops;
556 }
557 }
558
559
560 bool JNIHandleBlock::contains(jobject handle) const {
561 return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]);
562 }
563
564
565 bool JNIHandleBlock::chain_contains(jobject handle) const {
566 for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) {
567 if (current->contains(handle)) {
568 return true;
569 }
570 }
571 return false;
572 }