1 /*
  2  * Copyright (c) 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 "cds/archiveHeapWriter.hpp"
 27 #include "cds/filemap.hpp"
 28 #include "cds/heapShared.hpp"
 29 #include "gc/shared/collectedHeap.hpp"
 30 #include "memory/iterator.inline.hpp"
 31 #include "memory/oopFactory.hpp"
 32 #include "memory/universe.hpp"
 33 #include "oops/compressedOops.hpp"
 34 #include "oops/oop.inline.hpp"
 35 #include "oops/objArrayOop.inline.hpp"
 36 #include "oops/oopHandle.inline.hpp"
 37 #include "oops/typeArrayKlass.hpp"
 38 #include "oops/typeArrayOop.hpp"
 39 #include "runtime/java.hpp"
 40 #include "runtime/mutexLocker.hpp"
 41 #include "utilities/bitMap.inline.hpp"
 42 
 43 #if INCLUDE_G1GC
 44 #include "gc/g1/g1CollectedHeap.hpp"
 45 #include "gc/g1/heapRegion.hpp"
 46 #endif
 47 
 48 #if INCLUDE_CDS_JAVA_HEAP
 49 
 50 
 51 GrowableArrayCHeap<u1, mtClassShared>* ArchiveHeapWriter::_buffer;
 52 
 53 // The following are offsets from buffer_bottom()
 54 size_t ArchiveHeapWriter::_buffer_top;
 55 size_t ArchiveHeapWriter::_open_bottom;
 56 size_t ArchiveHeapWriter::_open_top;
 57 size_t ArchiveHeapWriter::_closed_bottom;
 58 size_t ArchiveHeapWriter::_closed_top;
 59 size_t ArchiveHeapWriter::_heap_roots_bottom;
 60 
 61 size_t ArchiveHeapWriter::_heap_roots_word_size;
 62 
 63 address ArchiveHeapWriter::_requested_open_region_bottom;
 64 address ArchiveHeapWriter::_requested_open_region_top;
 65 address ArchiveHeapWriter::_requested_closed_region_bottom;
 66 address ArchiveHeapWriter::_requested_closed_region_top;
 67 
 68 ResourceBitMap* ArchiveHeapWriter::_closed_oopmap;
 69 ResourceBitMap* ArchiveHeapWriter::_open_oopmap;
 70 
 71 GrowableArrayCHeap<ArchiveHeapWriter::NativePointerInfo, mtClassShared>* ArchiveHeapWriter::_native_pointers;
 72 GrowableArrayCHeap<oop, mtClassShared>* ArchiveHeapWriter::_source_objs;
 73 
 74 ArchiveHeapWriter::BufferOffsetToSourceObjectTable*
 75   ArchiveHeapWriter::_buffer_offset_to_source_obj_table = nullptr;
 76 
 77 void ArchiveHeapWriter::init() {
 78   if (HeapShared::can_write()) {
 79     Universe::heap()->collect(GCCause::_java_lang_system_gc);
 80 
 81     _buffer_offset_to_source_obj_table = new BufferOffsetToSourceObjectTable();
 82 
 83     _requested_open_region_bottom = nullptr;
 84     _requested_open_region_top = nullptr;
 85     _requested_closed_region_bottom = nullptr;
 86     _requested_closed_region_top = nullptr;
 87 
 88     _native_pointers = new GrowableArrayCHeap<NativePointerInfo, mtClassShared>(2048);
 89     _source_objs = new GrowableArrayCHeap<oop, mtClassShared>(10000);
 90 
 91     guarantee(UseG1GC, "implementation limitation");
 92     guarantee(MIN_GC_REGION_ALIGNMENT <= /*G1*/HeapRegion::min_region_size_in_words() * HeapWordSize, "must be");
 93   }
 94 }
 95 
 96 void ArchiveHeapWriter::add_source_obj(oop src_obj) {
 97   _source_objs->append(src_obj);
 98 }
 99 
100 // For the time being, always support two regions (to be strictly compatible with existing G1
101 // mapping code. We might eventually use a single region (JDK-8298048).
102 void ArchiveHeapWriter::write(GrowableArrayCHeap<oop, mtClassShared>* roots,
103                               GrowableArray<MemRegion>* closed_regions, GrowableArray<MemRegion>* open_regions,
104                               GrowableArray<ArchiveHeapBitmapInfo>* closed_bitmaps,
105                               GrowableArray<ArchiveHeapBitmapInfo>* open_bitmaps) {
106   assert(HeapShared::can_write(), "sanity");
107   allocate_buffer();
108   copy_source_objs_to_buffer(roots);
109   set_requested_address_for_regions(closed_regions, open_regions);
110   relocate_embedded_oops(roots, closed_bitmaps, open_bitmaps);
111 }
112 
113 bool ArchiveHeapWriter::is_too_large_to_archive(oop o) {
114   return is_too_large_to_archive(o->size());
115 }
116 
117 bool ArchiveHeapWriter::is_string_too_large_to_archive(oop string) {
118   typeArrayOop value = java_lang_String::value_no_keepalive(string);
119   return is_too_large_to_archive(value);
120 }
121 
122 bool ArchiveHeapWriter::is_too_large_to_archive(size_t size) {
123   assert(size > 0, "no zero-size object");
124   assert(size * HeapWordSize > size, "no overflow");
125   static_assert(MIN_GC_REGION_ALIGNMENT > 0, "must be positive");
126 
127   size_t byte_size = size * HeapWordSize;
128   if (byte_size > size_t(MIN_GC_REGION_ALIGNMENT)) {
129     return true;
130   } else {
131     return false;
132   }
133 }
134 
135 // Various lookup functions between source_obj, buffered_obj and requested_obj
136 bool ArchiveHeapWriter::is_in_requested_regions(oop o) {
137   assert(_requested_open_region_bottom != nullptr, "do not call before this is initialized");
138   assert(_requested_closed_region_bottom != nullptr, "do not call before this is initialized");
139 
140   address a = cast_from_oop<address>(o);
141   return (_requested_open_region_bottom <= a && a < _requested_open_region_top) ||
142          (_requested_closed_region_bottom <= a && a < _requested_closed_region_top);
143 }
144 
145 oop ArchiveHeapWriter::requested_obj_from_buffer_offset(size_t offset) {
146   oop req_obj = cast_to_oop(_requested_open_region_bottom + offset);
147   assert(is_in_requested_regions(req_obj), "must be");
148   return req_obj;
149 }
150 
151 oop ArchiveHeapWriter::source_obj_to_requested_obj(oop src_obj) {
152   assert(DumpSharedSpaces, "dump-time only");
153   HeapShared::CachedOopInfo* p = HeapShared::archived_object_cache()->get(src_obj);
154   if (p != nullptr) {
155     return requested_obj_from_buffer_offset(p->buffer_offset());
156   } else {
157     return nullptr;
158   }
159 }
160 
161 oop ArchiveHeapWriter::buffered_addr_to_source_obj(address buffered_addr) {
162   oop* p = _buffer_offset_to_source_obj_table->get(buffered_address_to_offset(buffered_addr));
163   if (p != nullptr) {
164     return *p;
165   } else {
166     return nullptr;
167   }
168 }
169 
170 address ArchiveHeapWriter::buffered_addr_to_requested_addr(address buffered_addr) {
171   return _requested_open_region_bottom + buffered_address_to_offset(buffered_addr);
172 }
173 
174 oop ArchiveHeapWriter::heap_roots_requested_address() {
175   return requested_obj_from_buffer_offset(_heap_roots_bottom);
176 }
177 
178 address ArchiveHeapWriter::heap_region_requested_bottom(int heap_region_idx) {
179   assert(_buffer != nullptr, "must be initialized");
180   switch (heap_region_idx) {
181   case MetaspaceShared::first_closed_heap_region:
182     return _requested_closed_region_bottom;
183   case MetaspaceShared::first_open_heap_region:
184     return _requested_open_region_bottom;
185   default:
186     ShouldNotReachHere();
187     return nullptr;
188   }
189 }
190 
191 void ArchiveHeapWriter::allocate_buffer() {
192   int initial_buffer_size = 100000;
193   _buffer = new GrowableArrayCHeap<u1, mtClassShared>(initial_buffer_size);
194   _open_bottom = _buffer_top = 0;
195   ensure_buffer_space(1); // so that buffer_bottom() works
196 }
197 
198 void ArchiveHeapWriter::ensure_buffer_space(size_t min_bytes) {
199   // We usually have very small heaps. If we get a huge one it's probably caused by a bug.
200   guarantee(min_bytes <= max_jint, "we dont support archiving more than 2G of objects");
201   _buffer->at_grow(to_array_index(min_bytes));
202 }
203 
204 void ArchiveHeapWriter::copy_roots_to_buffer(GrowableArrayCHeap<oop, mtClassShared>* roots) {
205   Klass* k = Universe::objectArrayKlassObj(); // already relocated to point to archived klass
206   int length = roots != nullptr ? roots->length() : 0;
207   _heap_roots_word_size = objArrayOopDesc::object_size(length);
208   size_t byte_size = _heap_roots_word_size * HeapWordSize;
209   if (byte_size >= MIN_GC_REGION_ALIGNMENT) {
210     log_error(cds, heap)("roots array is too large. Please reduce the number of classes");
211     vm_exit(1);
212   }
213 
214   maybe_fill_gc_region_gap(byte_size);
215 
216   size_t new_top = _buffer_top + byte_size;
217   ensure_buffer_space(new_top);
218 
219   HeapWord* mem = offset_to_buffered_address<HeapWord*>(_buffer_top);
220   memset(mem, 0, byte_size);
221   {
222     // This is copied from MemAllocator::finish
223     if (UseCompactObjectHeaders) {
224       narrowKlass nk = ArchiveBuilder::current()->get_requested_narrow_klass(k);
225       oopDesc::release_set_mark(mem, markWord::prototype().set_narrow_klass(nk));
226     } else {
227       oopDesc::set_mark(mem, markWord::prototype());
228       oopDesc::release_set_klass(mem, k);
229     }
230   }
231   {
232     // This is copied from ObjArrayAllocator::initialize
233     arrayOopDesc::set_length(mem, length);
234   }
235 
236   objArrayOop arrayOop = objArrayOop(cast_to_oop(mem));
237   for (int i = 0; i < length; i++) {
238     // Do not use arrayOop->obj_at_put(i, o) as arrayOop is outside of the real heap!
239     oop o = roots->at(i);
240     if (UseCompressedOops) {
241       * arrayOop->obj_at_addr<narrowOop>(i) = CompressedOops::encode(o);
242     } else {
243       * arrayOop->obj_at_addr<oop>(i) = o;
244     }
245   }
246   log_info(cds)("archived obj roots[%d] = " SIZE_FORMAT " bytes, klass = %p, obj = %p", length, byte_size, k, mem);
247 
248   _heap_roots_bottom = _buffer_top;
249   _buffer_top = new_top;
250 }
251 
252 void ArchiveHeapWriter::copy_source_objs_to_buffer(GrowableArrayCHeap<oop, mtClassShared>* roots) {
253   copy_source_objs_to_buffer_by_region(/*copy_open_region=*/true);
254   copy_roots_to_buffer(roots);
255   _open_top = _buffer_top;
256 
257   // Align the closed region to the next G1 region
258   _buffer_top = _closed_bottom = align_up(_buffer_top, HeapRegion::GrainBytes);
259   copy_source_objs_to_buffer_by_region(/*copy_open_region=*/false);
260   _closed_top = _buffer_top;
261 
262   log_info(cds, heap)("Size of open region   = " SIZE_FORMAT " bytes", _open_top   - _open_bottom);
263   log_info(cds, heap)("Size of closed region = " SIZE_FORMAT " bytes", _closed_top - _closed_bottom);
264 }
265 
266 void ArchiveHeapWriter::copy_source_objs_to_buffer_by_region(bool copy_open_region) {
267   for (int i = 0; i < _source_objs->length(); i++) {
268     oop src_obj = _source_objs->at(i);
269     HeapShared::CachedOopInfo* info = HeapShared::archived_object_cache()->get(src_obj);
270     assert(info != nullptr, "must be");
271     if (info->in_open_region() == copy_open_region) {
272       // For region-based collectors such as G1, we need to make sure that we don't have
273       // an object that can possible span across two regions.
274       size_t buffer_offset = copy_one_source_obj_to_buffer(src_obj);
275       info->set_buffer_offset(buffer_offset);
276 
277       _buffer_offset_to_source_obj_table->put(buffer_offset, src_obj);
278     }
279   }
280 }
281 
282 size_t ArchiveHeapWriter::filler_array_byte_size(int length) {
283   size_t byte_size = objArrayOopDesc::object_size(length) * HeapWordSize;
284   return byte_size;
285 }
286 
287 int ArchiveHeapWriter::filler_array_length(size_t fill_bytes) {
288   assert(is_object_aligned(fill_bytes), "must be");
289   size_t elemSize = (UseCompressedOops ? sizeof(narrowOop) : sizeof(oop));
290 
291   int initial_length = to_array_length(fill_bytes / elemSize);
292   for (int length = initial_length; length >= 0; length --) {
293     size_t array_byte_size = filler_array_byte_size(length);
294     if (array_byte_size == fill_bytes) {
295       return length;
296     }
297   }
298 
299   ShouldNotReachHere();
300   return -1;
301 }
302 
303 void ArchiveHeapWriter::init_filler_array_at_buffer_top(int array_length, size_t fill_bytes) {
304   assert(UseCompressedClassPointers, "Archived heap only supported for compressed klasses");
305   Klass* oak = Universe::objectArrayKlassObj(); // already relocated to point to archived klass
306   HeapWord* mem = offset_to_buffered_address<HeapWord*>(_buffer_top);
307   memset(mem, 0, fill_bytes);
308   narrowKlass nk = ArchiveBuilder::current()->get_requested_narrow_klass(oak);
309   if (UseCompactObjectHeaders) {
310     oopDesc::release_set_mark(mem, markWord::prototype().set_narrow_klass(nk));
311   } else {
312     oopDesc::set_mark(mem, markWord::prototype());
313     cast_to_oop(mem)->set_narrow_klass(nk);
314   }
315   arrayOopDesc::set_length(mem, array_length);
316 }
317 
318 void ArchiveHeapWriter::maybe_fill_gc_region_gap(size_t required_byte_size) {
319   // We fill only with arrays (so we don't need to use a single HeapWord filler if the
320   // leftover space is smaller than a zero-sized array object). Therefore, we need to
321   // make sure there's enough space of min_filler_byte_size in the current region after
322   // required_byte_size has been allocated. If not, fill the remainder of the current
323   // region.
324   size_t min_filler_byte_size = filler_array_byte_size(0);
325   size_t new_top = _buffer_top + required_byte_size + min_filler_byte_size;
326 
327   const size_t cur_min_region_bottom = align_down(_buffer_top, MIN_GC_REGION_ALIGNMENT);
328   const size_t next_min_region_bottom = align_down(new_top, MIN_GC_REGION_ALIGNMENT);
329 
330   if (cur_min_region_bottom != next_min_region_bottom) {
331     // Make sure that no objects span across MIN_GC_REGION_ALIGNMENT. This way
332     // we can map the region in any region-based collector.
333     assert(next_min_region_bottom > cur_min_region_bottom, "must be");
334     assert(next_min_region_bottom - cur_min_region_bottom == MIN_GC_REGION_ALIGNMENT,
335            "no buffered object can be larger than %d bytes",  MIN_GC_REGION_ALIGNMENT);
336 
337     const size_t filler_end = next_min_region_bottom;
338     const size_t fill_bytes = filler_end - _buffer_top;
339     assert(fill_bytes > 0, "must be");
340     ensure_buffer_space(filler_end);
341 
342     int array_length = filler_array_length(fill_bytes);
343     log_info(cds, heap)("Inserting filler obj array of %d elements (" SIZE_FORMAT " bytes total) @ buffer offset " SIZE_FORMAT,
344                         array_length, fill_bytes, _buffer_top);
345     init_filler_array_at_buffer_top(array_length, fill_bytes);
346 
347     _buffer_top = filler_end;
348   }
349 }
350 
351 size_t ArchiveHeapWriter::copy_one_source_obj_to_buffer(oop src_obj) {
352   assert(!is_too_large_to_archive(src_obj), "already checked");
353   size_t byte_size = src_obj->size() * HeapWordSize;
354   assert(byte_size > 0, "no zero-size objects");
355 
356   maybe_fill_gc_region_gap(byte_size);
357 
358   size_t new_top = _buffer_top + byte_size;
359   assert(new_top > _buffer_top, "no wrap around");
360 
361   size_t cur_min_region_bottom = align_down(_buffer_top, MIN_GC_REGION_ALIGNMENT);
362   size_t next_min_region_bottom = align_down(new_top, MIN_GC_REGION_ALIGNMENT);
363   assert(cur_min_region_bottom == next_min_region_bottom, "no object should cross minimal GC region boundaries");
364 
365   ensure_buffer_space(new_top);
366 
367   address from = cast_from_oop<address>(src_obj);
368   address to = offset_to_buffered_address<address>(_buffer_top);
369   assert(is_object_aligned(_buffer_top), "sanity");
370   assert(is_object_aligned(byte_size), "sanity");
371   memcpy(to, from, byte_size);
372 
373   size_t buffered_obj_offset = _buffer_top;
374   _buffer_top = new_top;
375 
376   return buffered_obj_offset;
377 }
378 
379 void ArchiveHeapWriter::set_requested_address_for_regions(GrowableArray<MemRegion>* closed_regions,
380                                                           GrowableArray<MemRegion>* open_regions) {
381   assert(closed_regions->length() == 0, "must be");
382   assert(open_regions->length() == 0, "must be");
383 
384   assert(UseG1GC, "must be");
385   address heap_end = (address)G1CollectedHeap::heap()->reserved().end();
386   log_info(cds, heap)("Heap end = %p", heap_end);
387 
388   size_t closed_region_byte_size = _closed_top - _closed_bottom;
389   size_t open_region_byte_size = _open_top - _open_bottom;
390   assert(closed_region_byte_size > 0, "must archived at least one object for closed region!");
391   assert(open_region_byte_size > 0, "must archived at least one object for open region!");
392 
393   // The following two asserts are ensured by copy_source_objs_to_buffer_by_region().
394   assert(is_aligned(_closed_bottom, HeapRegion::GrainBytes), "sanity");
395   assert(is_aligned(_open_bottom, HeapRegion::GrainBytes), "sanity");
396 
397   _requested_closed_region_bottom = align_down(heap_end - closed_region_byte_size, HeapRegion::GrainBytes);
398   _requested_open_region_bottom = _requested_closed_region_bottom - (_closed_bottom - _open_bottom);
399 
400   assert(is_aligned(_requested_closed_region_bottom, HeapRegion::GrainBytes), "sanity");
401   assert(is_aligned(_requested_open_region_bottom, HeapRegion::GrainBytes), "sanity");
402 
403   _requested_open_region_top = _requested_open_region_bottom + (_open_top - _open_bottom);
404   _requested_closed_region_top = _requested_closed_region_bottom + (_closed_top - _closed_bottom);
405 
406   assert(_requested_open_region_top <= _requested_closed_region_bottom, "no overlap");
407 
408   closed_regions->append(MemRegion(offset_to_buffered_address<HeapWord*>(_closed_bottom),
409                                    offset_to_buffered_address<HeapWord*>(_closed_top)));
410   open_regions->append(  MemRegion(offset_to_buffered_address<HeapWord*>(_open_bottom),
411                                    offset_to_buffered_address<HeapWord*>(_open_top)));
412 }
413 
414 // Oop relocation
415 
416 template <typename T> T* ArchiveHeapWriter::requested_addr_to_buffered_addr(T* p) {
417   assert(is_in_requested_regions(cast_to_oop(p)), "must be");
418 
419   address addr = address(p);
420   assert(addr >= _requested_open_region_bottom, "must be");
421   size_t offset = addr - _requested_open_region_bottom;
422   return offset_to_buffered_address<T*>(offset);
423 }
424 
425 template <typename T> oop ArchiveHeapWriter::load_source_oop_from_buffer(T* buffered_addr) {
426   oop o = load_oop_from_buffer(buffered_addr);
427   assert(!in_buffer(cast_from_oop<address>(o)), "must point to source oop");
428   return o;
429 }
430 
431 template <typename T> void ArchiveHeapWriter::store_requested_oop_in_buffer(T* buffered_addr,
432                                                                             oop request_oop) {
433   assert(is_in_requested_regions(request_oop), "must be");
434   store_oop_in_buffer(buffered_addr, request_oop);
435 }
436 
437 void ArchiveHeapWriter::store_oop_in_buffer(oop* buffered_addr, oop requested_obj) {
438   // Make heap content deterministic. See comments inside HeapShared::to_requested_address.
439   *buffered_addr = HeapShared::to_requested_address(requested_obj);
440 }
441 
442 void ArchiveHeapWriter::store_oop_in_buffer(narrowOop* buffered_addr, oop requested_obj) {
443   // Note: HeapShared::to_requested_address() is not necessary because
444   // the heap always starts at a deterministic address with UseCompressedOops==true.
445   narrowOop val = CompressedOops::encode_not_null(requested_obj);
446   *buffered_addr = val;
447 }
448 
449 oop ArchiveHeapWriter::load_oop_from_buffer(oop* buffered_addr) {
450   return *buffered_addr;
451 }
452 
453 oop ArchiveHeapWriter::load_oop_from_buffer(narrowOop* buffered_addr) {
454   return CompressedOops::decode(*buffered_addr);
455 }
456 
457 template <typename T> void ArchiveHeapWriter::relocate_field_in_buffer(T* field_addr_in_buffer) {
458   oop source_referent = load_source_oop_from_buffer<T>(field_addr_in_buffer);
459   if (!CompressedOops::is_null(source_referent)) {
460     oop request_referent = source_obj_to_requested_obj(source_referent);
461     store_requested_oop_in_buffer<T>(field_addr_in_buffer, request_referent);
462     mark_oop_pointer<T>(field_addr_in_buffer);
463   }
464 }
465 
466 template <typename T> void ArchiveHeapWriter::mark_oop_pointer(T* buffered_addr) {
467   T* request_p = (T*)(buffered_addr_to_requested_addr((address)buffered_addr));
468   ResourceBitMap* oopmap;
469   address requested_region_bottom;
470 
471   if (request_p >= (T*)_requested_closed_region_bottom) {
472     assert(request_p < (T*)_requested_closed_region_top, "sanity");
473     oopmap = _closed_oopmap;
474     requested_region_bottom = _requested_closed_region_bottom;
475   } else {
476     assert(request_p >= (T*)_requested_open_region_bottom, "sanity");
477     assert(request_p <  (T*)_requested_open_region_top, "sanity");
478     oopmap = _open_oopmap;
479     requested_region_bottom = _requested_open_region_bottom;
480   }
481 
482   // Mark the pointer in the oopmap
483   T* region_bottom = (T*)requested_region_bottom;
484   assert(request_p >= region_bottom, "must be");
485   BitMap::idx_t idx = request_p - region_bottom;
486   assert(idx < oopmap->size(), "overflow");
487   oopmap->set_bit(idx);
488 }
489 
490 void ArchiveHeapWriter::update_header_for_requested_obj(oop requested_obj, oop src_obj,  Klass* src_klass) {
491   assert(UseCompressedClassPointers, "Archived heap only supported for compressed klasses");
492   narrowKlass nk = ArchiveBuilder::current()->get_requested_narrow_klass(src_klass);
493   address buffered_addr = requested_addr_to_buffered_addr(cast_from_oop<address>(requested_obj));
494 
495   oop fake_oop = cast_to_oop(buffered_addr);
496   fake_oop->set_narrow_klass(nk);
497 
498   // We need to retain the identity_hash, because it may have been used by some hashtables
499   // in the shared heap. This also has the side effect of pre-initializing the
500   // identity_hash for all shared objects, so they are less likely to be written
501   // into during run time, increasing the potential of memory sharing.
502   if (src_obj != nullptr) {
503     int src_hash = src_obj->identity_hash();
504     if (UseCompactObjectHeaders) {
505       fake_oop->set_mark(markWord::prototype().set_narrow_klass(nk).copy_set_hash(src_hash));
506     } else {
507       fake_oop->set_mark(markWord::prototype().copy_set_hash(src_hash));
508     }
509     assert(fake_oop->mark().is_unlocked(), "sanity");
510 
511     DEBUG_ONLY(int archived_hash = fake_oop->identity_hash());
512     assert(src_hash == archived_hash, "Different hash codes: original %x, archived %x", src_hash, archived_hash);
513   }
514 }
515 
516 // Relocate an element in the buffered copy of HeapShared::roots()
517 template <typename T> void ArchiveHeapWriter::relocate_root_at(oop requested_roots, int index) {
518   size_t offset = (size_t)((objArrayOop)requested_roots)->obj_at_offset<T>(index);
519   relocate_field_in_buffer<T>((T*)(buffered_heap_roots_addr() + offset));
520 }
521 
522 class ArchiveHeapWriter::EmbeddedOopRelocator: public BasicOopIterateClosure {
523   oop _src_obj;
524   address _buffered_obj;
525 
526 public:
527   EmbeddedOopRelocator(oop src_obj, address buffered_obj) :
528     _src_obj(src_obj), _buffered_obj(buffered_obj) {}
529 
530   void do_oop(narrowOop *p) { EmbeddedOopRelocator::do_oop_work(p); }
531   void do_oop(      oop *p) { EmbeddedOopRelocator::do_oop_work(p); }
532 
533 private:
534   template <class T> void do_oop_work(T *p) {
535     size_t field_offset = pointer_delta(p, _src_obj, sizeof(char));
536     ArchiveHeapWriter::relocate_field_in_buffer<T>((T*)(_buffered_obj + field_offset));
537   }
538 };
539 
540 // Update all oop fields embedded in the buffered objects
541 void ArchiveHeapWriter::relocate_embedded_oops(GrowableArrayCHeap<oop, mtClassShared>* roots,
542                                                GrowableArray<ArchiveHeapBitmapInfo>* closed_bitmaps,
543                                                GrowableArray<ArchiveHeapBitmapInfo>* open_bitmaps) {
544   size_t oopmap_unit = (UseCompressedOops ? sizeof(narrowOop) : sizeof(oop));
545   size_t closed_region_byte_size = _closed_top - _closed_bottom;
546   size_t open_region_byte_size   = _open_top   - _open_bottom;
547   ResourceBitMap closed_oopmap(closed_region_byte_size / oopmap_unit);
548   ResourceBitMap open_oopmap  (open_region_byte_size   / oopmap_unit);
549 
550   _closed_oopmap = &closed_oopmap;
551   _open_oopmap = &open_oopmap;
552 
553   auto iterator = [&] (oop src_obj, HeapShared::CachedOopInfo& info) {
554     oop requested_obj = requested_obj_from_buffer_offset(info.buffer_offset());
555     update_header_for_requested_obj(requested_obj, src_obj, src_obj->klass());
556 
557     address buffered_obj = offset_to_buffered_address<address>(info.buffer_offset());
558     EmbeddedOopRelocator relocator(src_obj, buffered_obj);
559 
560     src_obj->oop_iterate(&relocator);
561   };
562   HeapShared::archived_object_cache()->iterate_all(iterator);
563 
564   // Relocate HeapShared::roots(), which is created in copy_roots_to_buffer() and
565   // doesn't have a corresponding src_obj, so we can't use EmbeddedOopRelocator on it.
566   oop requested_roots = requested_obj_from_buffer_offset(_heap_roots_bottom);
567   update_header_for_requested_obj(requested_roots, nullptr, Universe::objectArrayKlassObj());
568   int length = roots != nullptr ? roots->length() : 0;
569   for (int i = 0; i < length; i++) {
570     if (UseCompressedOops) {
571       relocate_root_at<narrowOop>(requested_roots, i);
572     } else {
573       relocate_root_at<oop>(requested_roots, i);
574     }
575   }
576 
577   closed_bitmaps->append(make_bitmap_info(&closed_oopmap, /*is_open=*/false, /*is_oopmap=*/true));
578   open_bitmaps  ->append(make_bitmap_info(&open_oopmap,   /*is_open=*/false, /*is_oopmap=*/true));
579 
580   closed_bitmaps->append(compute_ptrmap(/*is_open=*/false));
581   open_bitmaps  ->append(compute_ptrmap(/*is_open=*/true));
582 
583   _closed_oopmap = nullptr;
584   _open_oopmap = nullptr;
585 }
586 
587 ArchiveHeapBitmapInfo ArchiveHeapWriter::make_bitmap_info(ResourceBitMap* bitmap, bool is_open,  bool is_oopmap) {
588   size_t size_in_bits = bitmap->size();
589   size_t size_in_bytes;
590   uintptr_t* buffer;
591 
592   if (size_in_bits > 0) {
593     size_in_bytes = bitmap->size_in_bytes();
594     buffer = (uintptr_t*)NEW_C_HEAP_ARRAY(char, size_in_bytes, mtInternal);
595     bitmap->write_to(buffer, size_in_bytes);
596   } else {
597     size_in_bytes = 0;
598     buffer = nullptr;
599   }
600 
601   log_info(cds, heap)("%s @ " INTPTR_FORMAT " (" SIZE_FORMAT_W(6) " bytes) for %s heap region",
602                       is_oopmap ? "Oopmap" : "Ptrmap",
603                       p2i(buffer), size_in_bytes,
604                       is_open? "open" : "closed");
605 
606   ArchiveHeapBitmapInfo info;
607   info._map = (address)buffer;
608   info._size_in_bits = size_in_bits;
609   info._size_in_bytes = size_in_bytes;
610 
611   return info;
612 }
613 
614 void ArchiveHeapWriter::mark_native_pointer(oop src_obj, int field_offset) {
615   Metadata* ptr = src_obj->metadata_field_acquire(field_offset);
616   if (ptr != nullptr) {
617     NativePointerInfo info;
618     info._src_obj = src_obj;
619     info._field_offset = field_offset;
620     _native_pointers->append(info);
621   }
622 }
623 
624 ArchiveHeapBitmapInfo ArchiveHeapWriter::compute_ptrmap(bool is_open) {
625   int num_non_null_ptrs = 0;
626   Metadata** bottom = (Metadata**) (is_open ? _requested_open_region_bottom: _requested_closed_region_bottom);
627   Metadata** top = (Metadata**) (is_open ? _requested_open_region_top: _requested_closed_region_top); // exclusive
628   ResourceBitMap ptrmap(top - bottom);
629 
630   for (int i = 0; i < _native_pointers->length(); i++) {
631     NativePointerInfo info = _native_pointers->at(i);
632     oop src_obj = info._src_obj;
633     int field_offset = info._field_offset;
634     HeapShared::CachedOopInfo* p = HeapShared::archived_object_cache()->get(src_obj);
635     if (p->in_open_region() == is_open) {
636       // requested_field_addr = the address of this field in the requested space
637       oop requested_obj = requested_obj_from_buffer_offset(p->buffer_offset());
638       Metadata** requested_field_addr = (Metadata**)(cast_from_oop<address>(requested_obj) + field_offset);
639       assert(bottom <= requested_field_addr && requested_field_addr < top, "range check");
640 
641       // Mark this field in the bitmap
642       BitMap::idx_t idx = requested_field_addr - bottom;
643       ptrmap.set_bit(idx);
644       num_non_null_ptrs ++;
645 
646       // Set the native pointer to the requested address of the metadata (at runtime, the metadata will have
647       // this address if the RO/RW regions are mapped at the default location).
648 
649       Metadata** buffered_field_addr = requested_addr_to_buffered_addr(requested_field_addr);
650       Metadata* native_ptr = *buffered_field_addr;
651       assert(native_ptr != nullptr, "sanity");
652 
653       address buffered_native_ptr = ArchiveBuilder::current()->get_buffered_addr((address)native_ptr);
654       address requested_native_ptr = ArchiveBuilder::current()->to_requested(buffered_native_ptr);
655       *buffered_field_addr = (Metadata*)requested_native_ptr;
656     }
657   }
658 
659   log_info(cds, heap)("compute_ptrmap: marked %d non-null native pointers for %s heap region",
660                       num_non_null_ptrs, is_open ? "open" : "closed");
661 
662   if (num_non_null_ptrs == 0) {
663     ResourceBitMap empty;
664     return make_bitmap_info(&empty, is_open, /*is_oopmap=*/ false);
665   } else {
666     return make_bitmap_info(&ptrmap, is_open, /*is_oopmap=*/ false);
667   }
668 }
669 
670 #endif // INCLUDE_CDS_JAVA_HEAP