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 GrowableArrayCHeap<u1, mtClassShared>* ArchiveHeapWriter::_buffer = nullptr;
 51 
 52 // The following are offsets from buffer_bottom()
 53 size_t ArchiveHeapWriter::_buffer_used;
 54 size_t ArchiveHeapWriter::_heap_roots_offset;
 55 
 56 size_t ArchiveHeapWriter::_heap_roots_word_size;
 57 
 58 address ArchiveHeapWriter::_requested_bottom;
 59 address ArchiveHeapWriter::_requested_top;
 60 
 61 GrowableArrayCHeap<ArchiveHeapWriter::NativePointerInfo, mtClassShared>* ArchiveHeapWriter::_native_pointers;
 62 GrowableArrayCHeap<oop, mtClassShared>* ArchiveHeapWriter::_source_objs;
 63 
 64 ArchiveHeapWriter::BufferOffsetToSourceObjectTable*
 65   ArchiveHeapWriter::_buffer_offset_to_source_obj_table = nullptr;
 66 
 67 
 68 typedef ResourceHashtable<address, size_t,
 69       127, // prime number
 70       AnyObj::C_HEAP,
 71       mtClassShared> FillersTable;
 72 static FillersTable* _fillers;
 73 
 74 void ArchiveHeapWriter::init() {
 75   if (HeapShared::can_write()) {
 76     Universe::heap()->collect(GCCause::_java_lang_system_gc);
 77 
 78     _buffer_offset_to_source_obj_table = new BufferOffsetToSourceObjectTable();
 79     _fillers = new FillersTable();
 80     _requested_bottom = nullptr;
 81     _requested_top = nullptr;
 82 
 83     _native_pointers = new GrowableArrayCHeap<NativePointerInfo, mtClassShared>(2048);
 84     _source_objs = new GrowableArrayCHeap<oop, mtClassShared>(10000);
 85 
 86     guarantee(UseG1GC, "implementation limitation");
 87     guarantee(MIN_GC_REGION_ALIGNMENT <= /*G1*/HeapRegion::min_region_size_in_words() * HeapWordSize, "must be");
 88   }
 89 }
 90 
 91 void ArchiveHeapWriter::add_source_obj(oop src_obj) {
 92   _source_objs->append(src_obj);
 93 }
 94 
 95 void ArchiveHeapWriter::write(GrowableArrayCHeap<oop, mtClassShared>* roots,
 96                               ArchiveHeapInfo* heap_info) {
 97   assert(HeapShared::can_write(), "sanity");
 98   allocate_buffer();
 99   copy_source_objs_to_buffer(roots);
100   set_requested_address(heap_info);
101   relocate_embedded_oops(roots, heap_info);
102 }
103 
104 bool ArchiveHeapWriter::is_too_large_to_archive(oop o) {
105   return is_too_large_to_archive(o->size());
106 }
107 
108 bool ArchiveHeapWriter::is_string_too_large_to_archive(oop string) {
109   typeArrayOop value = java_lang_String::value_no_keepalive(string);
110   return is_too_large_to_archive(value);
111 }
112 
113 bool ArchiveHeapWriter::is_too_large_to_archive(size_t size) {
114   assert(size > 0, "no zero-size object");
115   assert(size * HeapWordSize > size, "no overflow");
116   static_assert(MIN_GC_REGION_ALIGNMENT > 0, "must be positive");
117 
118   size_t byte_size = size * HeapWordSize;
119   if (byte_size > size_t(MIN_GC_REGION_ALIGNMENT)) {
120     return true;
121   } else {
122     return false;
123   }
124 }
125 
126 // Various lookup functions between source_obj, buffered_obj and requested_obj
127 bool ArchiveHeapWriter::is_in_requested_range(oop o) {
128   assert(_requested_bottom != nullptr, "do not call before _requested_bottom is initialized");
129   address a = cast_from_oop<address>(o);
130   return (_requested_bottom <= a && a < _requested_top);
131 }
132 
133 oop ArchiveHeapWriter::requested_obj_from_buffer_offset(size_t offset) {
134   oop req_obj = cast_to_oop(_requested_bottom + offset);
135   assert(is_in_requested_range(req_obj), "must be");
136   return req_obj;
137 }
138 
139 oop ArchiveHeapWriter::source_obj_to_requested_obj(oop src_obj) {
140   assert(DumpSharedSpaces, "dump-time only");
141   HeapShared::CachedOopInfo* p = HeapShared::archived_object_cache()->get(src_obj);
142   if (p != nullptr) {
143     return requested_obj_from_buffer_offset(p->buffer_offset());
144   } else {
145     return nullptr;
146   }
147 }
148 
149 oop ArchiveHeapWriter::buffered_addr_to_source_obj(address buffered_addr) {
150   oop* p = _buffer_offset_to_source_obj_table->get(buffered_address_to_offset(buffered_addr));
151   if (p != nullptr) {
152     return *p;
153   } else {
154     return nullptr;
155   }
156 }
157 
158 address ArchiveHeapWriter::buffered_addr_to_requested_addr(address buffered_addr) {
159   return _requested_bottom + buffered_address_to_offset(buffered_addr);
160 }
161 
162 oop ArchiveHeapWriter::heap_roots_requested_address() {
163   return cast_to_oop(_requested_bottom + _heap_roots_offset);
164 }
165 
166 address ArchiveHeapWriter::requested_address() {
167   assert(_buffer != nullptr, "must be initialized");
168   return _requested_bottom;
169 }
170 
171 void ArchiveHeapWriter::allocate_buffer() {
172   int initial_buffer_size = 100000;
173   _buffer = new GrowableArrayCHeap<u1, mtClassShared>(initial_buffer_size);
174   _buffer_used = 0;
175   ensure_buffer_space(1); // so that buffer_bottom() works
176 }
177 
178 void ArchiveHeapWriter::ensure_buffer_space(size_t min_bytes) {
179   // We usually have very small heaps. If we get a huge one it's probably caused by a bug.
180   guarantee(min_bytes <= max_jint, "we dont support archiving more than 2G of objects");
181   _buffer->at_grow(to_array_index(min_bytes));
182 }
183 
184 void ArchiveHeapWriter::copy_roots_to_buffer(GrowableArrayCHeap<oop, mtClassShared>* roots) {
185   Klass* k = Universe::objectArrayKlassObj(); // already relocated to point to archived klass
186   int length = roots->length();
187   _heap_roots_word_size = objArrayOopDesc::object_size(length);
188   size_t byte_size = _heap_roots_word_size * HeapWordSize;
189   if (byte_size >= MIN_GC_REGION_ALIGNMENT) {
190     log_error(cds, heap)("roots array is too large. Please reduce the number of classes");
191     vm_exit(1);
192   }
193 
194   maybe_fill_gc_region_gap(byte_size);
195 
196   size_t new_used = _buffer_used + byte_size;
197   ensure_buffer_space(new_used);
198 
199   HeapWord* mem = offset_to_buffered_address<HeapWord*>(_buffer_used);
200   memset(mem, 0, byte_size);
201   {
202     // This is copied from MemAllocator::finish
203     oopDesc::set_mark(mem, markWord::prototype());
204     oopDesc::release_set_klass(mem, k);
205   }
206   {
207     // This is copied from ObjArrayAllocator::initialize
208     arrayOopDesc::set_length(mem, length);
209   }
210 
211   objArrayOop arrayOop = objArrayOop(cast_to_oop(mem));
212   for (int i = 0; i < length; i++) {
213     // Do not use arrayOop->obj_at_put(i, o) as arrayOop is outside of the real heap!
214     oop o = roots->at(i);
215     if (UseCompressedOops) {
216       * arrayOop->obj_at_addr<narrowOop>(i) = CompressedOops::encode(o);
217     } else {
218       * arrayOop->obj_at_addr<oop>(i) = o;
219     }
220   }
221   log_info(cds, heap)("archived obj roots[%d] = " SIZE_FORMAT " bytes, klass = %p, obj = %p", length, byte_size, k, mem);
222 
223   _heap_roots_offset = _buffer_used;
224   _buffer_used = new_used;
225 }
226 
227 void ArchiveHeapWriter::copy_source_objs_to_buffer(GrowableArrayCHeap<oop, mtClassShared>* roots) {
228   for (int i = 0; i < _source_objs->length(); i++) {
229     oop src_obj = _source_objs->at(i);
230     HeapShared::CachedOopInfo* info = HeapShared::archived_object_cache()->get(src_obj);
231     assert(info != nullptr, "must be");
232     size_t buffer_offset = copy_one_source_obj_to_buffer(src_obj);
233     info->set_buffer_offset(buffer_offset);
234 
235     _buffer_offset_to_source_obj_table->put(buffer_offset, src_obj);
236   }
237 
238   copy_roots_to_buffer(roots);
239 
240   log_info(cds)("Size of heap region = " SIZE_FORMAT " bytes, %d objects, %d roots",
241                 _buffer_used, _source_objs->length() + 1, roots->length());
242 }
243 
244 size_t ArchiveHeapWriter::filler_array_byte_size(int length) {
245   size_t byte_size = objArrayOopDesc::object_size(length) * HeapWordSize;
246   return byte_size;
247 }
248 
249 int ArchiveHeapWriter::filler_array_length(size_t fill_bytes) {
250   assert(is_object_aligned(fill_bytes), "must be");
251   size_t elemSize = (UseCompressedOops ? sizeof(narrowOop) : sizeof(oop));
252 
253   int initial_length = to_array_length(fill_bytes / elemSize);
254   for (int length = initial_length; length >= 0; length --) {
255     size_t array_byte_size = filler_array_byte_size(length);
256     if (array_byte_size == fill_bytes) {
257       return length;
258     }
259   }
260 
261   ShouldNotReachHere();
262   return -1;
263 }
264 
265 HeapWord* ArchiveHeapWriter::init_filler_array_at_buffer_top(int array_length, size_t fill_bytes) {
266   assert(UseCompressedClassPointers, "Archived heap only supported for compressed klasses");
267   Klass* oak = Universe::objectArrayKlassObj(); // already relocated to point to archived klass
268   HeapWord* mem = offset_to_buffered_address<HeapWord*>(_buffer_used);
269   memset(mem, 0, fill_bytes);
270   oopDesc::set_mark(mem, markWord::prototype());
271   narrowKlass nk = ArchiveBuilder::current()->get_requested_narrow_klass(oak);
272   cast_to_oop(mem)->set_narrow_klass(nk);
273   arrayOopDesc::set_length(mem, array_length);
274   return mem;
275 }
276 
277 void ArchiveHeapWriter::maybe_fill_gc_region_gap(size_t required_byte_size) {
278   // We fill only with arrays (so we don't need to use a single HeapWord filler if the
279   // leftover space is smaller than a zero-sized array object). Therefore, we need to
280   // make sure there's enough space of min_filler_byte_size in the current region after
281   // required_byte_size has been allocated. If not, fill the remainder of the current
282   // region.
283   size_t min_filler_byte_size = filler_array_byte_size(0);
284   size_t new_used = _buffer_used + required_byte_size + min_filler_byte_size;
285 
286   const size_t cur_min_region_bottom = align_down(_buffer_used, MIN_GC_REGION_ALIGNMENT);
287   const size_t next_min_region_bottom = align_down(new_used, MIN_GC_REGION_ALIGNMENT);
288 
289   if (cur_min_region_bottom != next_min_region_bottom) {
290     // Make sure that no objects span across MIN_GC_REGION_ALIGNMENT. This way
291     // we can map the region in any region-based collector.
292     assert(next_min_region_bottom > cur_min_region_bottom, "must be");
293     assert(next_min_region_bottom - cur_min_region_bottom == MIN_GC_REGION_ALIGNMENT,
294            "no buffered object can be larger than %d bytes",  MIN_GC_REGION_ALIGNMENT);
295 
296     const size_t filler_end = next_min_region_bottom;
297     const size_t fill_bytes = filler_end - _buffer_used;
298     assert(fill_bytes > 0, "must be");
299     ensure_buffer_space(filler_end);
300 
301     int array_length = filler_array_length(fill_bytes);
302     log_info(cds, heap)("Inserting filler obj array of %d elements (" SIZE_FORMAT " bytes total) @ buffer offset " SIZE_FORMAT,
303                         array_length, fill_bytes, _buffer_used);
304     HeapWord* filler = init_filler_array_at_buffer_top(array_length, fill_bytes);
305     _buffer_used = filler_end;
306     _fillers->put((address)filler, fill_bytes);
307   }
308 }
309 
310 size_t ArchiveHeapWriter::get_filler_size_at(address buffered_addr) {
311   size_t* p = _fillers->get(buffered_addr);
312   if (p != nullptr) {
313     assert(*p > 0, "filler must be larger than zero bytes");
314     return *p;
315   } else {
316     return 0; // buffered_addr is not a filler
317   }
318 }
319 
320 size_t ArchiveHeapWriter::copy_one_source_obj_to_buffer(oop src_obj) {
321   assert(!is_too_large_to_archive(src_obj), "already checked");
322   size_t byte_size = src_obj->size() * HeapWordSize;
323   assert(byte_size > 0, "no zero-size objects");
324 
325   // For region-based collectors such as G1, the archive heap may be mapped into
326   // multiple regions. We need to make sure that we don't have an object that can possible
327   // span across two regions.
328   maybe_fill_gc_region_gap(byte_size);
329 
330   size_t new_used = _buffer_used + byte_size;
331   assert(new_used > _buffer_used, "no wrap around");
332 
333   size_t cur_min_region_bottom = align_down(_buffer_used, MIN_GC_REGION_ALIGNMENT);
334   size_t next_min_region_bottom = align_down(new_used, MIN_GC_REGION_ALIGNMENT);
335   assert(cur_min_region_bottom == next_min_region_bottom, "no object should cross minimal GC region boundaries");
336 
337   ensure_buffer_space(new_used);
338 
339   address from = cast_from_oop<address>(src_obj);
340   address to = offset_to_buffered_address<address>(_buffer_used);
341   assert(is_object_aligned(_buffer_used), "sanity");
342   assert(is_object_aligned(byte_size), "sanity");
343   memcpy(to, from, byte_size);
344 
345   size_t buffered_obj_offset = _buffer_used;
346   _buffer_used = new_used;
347 
348   return buffered_obj_offset;
349 }
350 
351 void ArchiveHeapWriter::set_requested_address(ArchiveHeapInfo* info) {
352   assert(!info->is_used(), "only set once");
353   assert(UseG1GC, "must be");
354   address heap_end = (address)G1CollectedHeap::heap()->reserved().end();
355   log_info(cds, heap)("Heap end = %p", heap_end);
356 
357   size_t heap_region_byte_size = _buffer_used;
358   assert(heap_region_byte_size > 0, "must archived at least one object!");
359 
360 
361   if (UseCompressedOops) {
362     _requested_bottom = align_down(heap_end - heap_region_byte_size, HeapRegion::GrainBytes);
363   } else {
364     // We always write the objects as if the heap started at this address. This
365     // makes the contents of the archive heap deterministic.
366     //
367     // Note that at runtime, the heap address is selected by the OS, so the archive
368     // heap will not be mapped at 0x10000000, and the contents need to be patched.
369     _requested_bottom = (address)NOCOOPS_REQUESTED_BASE;
370   }
371 
372   assert(is_aligned(_requested_bottom, HeapRegion::GrainBytes), "sanity");
373 
374   _requested_top = _requested_bottom + _buffer_used;
375 
376   info->set_buffer_region(MemRegion(offset_to_buffered_address<HeapWord*>(0),
377                                     offset_to_buffered_address<HeapWord*>(_buffer_used)));
378   info->set_heap_roots_offset(_heap_roots_offset);
379 }
380 
381 // Oop relocation
382 
383 template <typename T> T* ArchiveHeapWriter::requested_addr_to_buffered_addr(T* p) {
384   assert(is_in_requested_range(cast_to_oop(p)), "must be");
385 
386   address addr = address(p);
387   assert(addr >= _requested_bottom, "must be");
388   size_t offset = addr - _requested_bottom;
389   return offset_to_buffered_address<T*>(offset);
390 }
391 
392 template <typename T> oop ArchiveHeapWriter::load_source_oop_from_buffer(T* buffered_addr) {
393   oop o = load_oop_from_buffer(buffered_addr);
394   assert(!in_buffer(cast_from_oop<address>(o)), "must point to source oop");
395   return o;
396 }
397 
398 template <typename T> void ArchiveHeapWriter::store_requested_oop_in_buffer(T* buffered_addr,
399                                                                             oop request_oop) {
400   assert(is_in_requested_range(request_oop), "must be");
401   store_oop_in_buffer(buffered_addr, request_oop);
402 }
403 
404 inline void ArchiveHeapWriter::store_oop_in_buffer(oop* buffered_addr, oop requested_obj) {
405   *buffered_addr = requested_obj;
406 }
407 
408 inline void ArchiveHeapWriter::store_oop_in_buffer(narrowOop* buffered_addr, oop requested_obj) {
409   narrowOop val = CompressedOops::encode_not_null(requested_obj);
410   *buffered_addr = val;
411 }
412 
413 oop ArchiveHeapWriter::load_oop_from_buffer(oop* buffered_addr) {
414   return *buffered_addr;
415 }
416 
417 oop ArchiveHeapWriter::load_oop_from_buffer(narrowOop* buffered_addr) {
418   return CompressedOops::decode(*buffered_addr);
419 }
420 
421 template <typename T> void ArchiveHeapWriter::relocate_field_in_buffer(T* field_addr_in_buffer, CHeapBitMap* oopmap) {
422   oop source_referent = load_source_oop_from_buffer<T>(field_addr_in_buffer);
423   if (!CompressedOops::is_null(source_referent)) {
424     oop request_referent = source_obj_to_requested_obj(source_referent);
425     store_requested_oop_in_buffer<T>(field_addr_in_buffer, request_referent);
426     mark_oop_pointer<T>(field_addr_in_buffer, oopmap);
427   }
428 }
429 
430 template <typename T> void ArchiveHeapWriter::mark_oop_pointer(T* buffered_addr, CHeapBitMap* oopmap) {
431   T* request_p = (T*)(buffered_addr_to_requested_addr((address)buffered_addr));
432   address requested_region_bottom;
433 
434   assert(request_p >= (T*)_requested_bottom, "sanity");
435   assert(request_p <  (T*)_requested_top, "sanity");
436   requested_region_bottom = _requested_bottom;
437 
438   // Mark the pointer in the oopmap
439   T* region_bottom = (T*)requested_region_bottom;
440   assert(request_p >= region_bottom, "must be");
441   BitMap::idx_t idx = request_p - region_bottom;
442   assert(idx < oopmap->size(), "overflow");
443   oopmap->set_bit(idx);
444 }
445 
446 void ArchiveHeapWriter::update_header_for_requested_obj(oop requested_obj, oop src_obj,  Klass* src_klass) {
447   assert(UseCompressedClassPointers, "Archived heap only supported for compressed klasses");
448   narrowKlass nk = ArchiveBuilder::current()->get_requested_narrow_klass(src_klass);
449   address buffered_addr = requested_addr_to_buffered_addr(cast_from_oop<address>(requested_obj));
450 
451   oop fake_oop = cast_to_oop(buffered_addr);
452   fake_oop->set_narrow_klass(nk);
453 
454   // We need to retain the identity_hash, because it may have been used by some hashtables
455   // in the shared heap. This also has the side effect of pre-initializing the
456   // identity_hash for all shared objects, so they are less likely to be written
457   // into during run time, increasing the potential of memory sharing.
458   if (src_obj != nullptr && (!(EnableValhalla && src_obj->mark().is_inline_type()))) {
459     intptr_t src_hash = src_obj->identity_hash();
460     fake_oop->set_mark(src_klass->prototype_header().copy_set_hash(src_hash));
461     assert(fake_oop->mark().is_unlocked(), "sanity");
462 
463     DEBUG_ONLY(intptr_t archived_hash = fake_oop->identity_hash());
464     assert(src_hash == archived_hash, "Different hash codes: original " INTPTR_FORMAT ", archived " INTPTR_FORMAT, src_hash, archived_hash);
465   }
466 }
467 
468 // Relocate an element in the buffered copy of HeapShared::roots()
469 template <typename T> void ArchiveHeapWriter::relocate_root_at(oop requested_roots, int index, CHeapBitMap* oopmap) {
470   size_t offset = (size_t)((objArrayOop)requested_roots)->obj_at_offset<T>(index);
471   relocate_field_in_buffer<T>((T*)(buffered_heap_roots_addr() + offset), oopmap);
472 }
473 
474 class ArchiveHeapWriter::EmbeddedOopRelocator: public BasicOopIterateClosure {
475   oop _src_obj;
476   address _buffered_obj;
477   CHeapBitMap* _oopmap;
478 
479 public:
480   EmbeddedOopRelocator(oop src_obj, address buffered_obj, CHeapBitMap* oopmap) :
481     _src_obj(src_obj), _buffered_obj(buffered_obj), _oopmap(oopmap) {}
482 
483   void do_oop(narrowOop *p) { EmbeddedOopRelocator::do_oop_work(p); }
484   void do_oop(      oop *p) { EmbeddedOopRelocator::do_oop_work(p); }
485 
486 private:
487   template <class T> void do_oop_work(T *p) {
488     size_t field_offset = pointer_delta(p, _src_obj, sizeof(char));
489     ArchiveHeapWriter::relocate_field_in_buffer<T>((T*)(_buffered_obj + field_offset), _oopmap);
490   }
491 };
492 
493 // Update all oop fields embedded in the buffered objects
494 void ArchiveHeapWriter::relocate_embedded_oops(GrowableArrayCHeap<oop, mtClassShared>* roots,
495                                                ArchiveHeapInfo* heap_info) {
496   size_t oopmap_unit = (UseCompressedOops ? sizeof(narrowOop) : sizeof(oop));
497   size_t heap_region_byte_size = _buffer_used;
498   heap_info->oopmap()->resize(heap_region_byte_size   / oopmap_unit);
499 
500   auto iterator = [&] (oop src_obj, HeapShared::CachedOopInfo& info) {
501     oop requested_obj = requested_obj_from_buffer_offset(info.buffer_offset());
502     update_header_for_requested_obj(requested_obj, src_obj, src_obj->klass());
503     address buffered_obj = offset_to_buffered_address<address>(info.buffer_offset());
504     EmbeddedOopRelocator relocator(src_obj, buffered_obj, heap_info->oopmap());
505     src_obj->oop_iterate(&relocator);
506   };
507   HeapShared::archived_object_cache()->iterate_all(iterator);
508 
509   // Relocate HeapShared::roots(), which is created in copy_roots_to_buffer() and
510   // doesn't have a corresponding src_obj, so we can't use EmbeddedOopRelocator on it.
511   oop requested_roots = requested_obj_from_buffer_offset(_heap_roots_offset);
512   update_header_for_requested_obj(requested_roots, nullptr, Universe::objectArrayKlassObj());
513   int length = roots != nullptr ? roots->length() : 0;
514   for (int i = 0; i < length; i++) {
515     if (UseCompressedOops) {
516       relocate_root_at<narrowOop>(requested_roots, i, heap_info->oopmap());
517     } else {
518       relocate_root_at<oop>(requested_roots, i, heap_info->oopmap());
519     }
520   }
521 
522   compute_ptrmap(heap_info);
523 }
524 
525 void ArchiveHeapWriter::mark_native_pointer(oop src_obj, int field_offset) {
526   Metadata* ptr = src_obj->metadata_field_acquire(field_offset);
527   if (ptr != nullptr) {
528     NativePointerInfo info;
529     info._src_obj = src_obj;
530     info._field_offset = field_offset;
531     _native_pointers->append(info);
532   }
533 }
534 
535 // Do we have a jlong/jint field that's actually a pointer to a MetaspaceObj?
536 bool ArchiveHeapWriter::is_marked_as_native_pointer(ArchiveHeapInfo* heap_info, oop src_obj, int field_offset) {
537   HeapShared::CachedOopInfo* p = HeapShared::archived_object_cache()->get(src_obj);
538   assert(p != nullptr, "must be");
539 
540   // requested_field_addr = the address of this field in the requested space
541   oop requested_obj = requested_obj_from_buffer_offset(p->buffer_offset());
542   Metadata** requested_field_addr = (Metadata**)(cast_from_oop<address>(requested_obj) + field_offset);
543   assert((Metadata**)_requested_bottom <= requested_field_addr && requested_field_addr < (Metadata**) _requested_top, "range check");
544 
545   BitMap::idx_t idx = requested_field_addr - (Metadata**) _requested_bottom;
546   return (idx < heap_info->ptrmap()->size()) && (heap_info->ptrmap()->at(idx) == true);
547 }
548 
549 void ArchiveHeapWriter::compute_ptrmap(ArchiveHeapInfo* heap_info) {
550   int num_non_null_ptrs = 0;
551   Metadata** bottom = (Metadata**) _requested_bottom;
552   Metadata** top = (Metadata**) _requested_top; // exclusive
553   heap_info->ptrmap()->resize(top - bottom);
554 
555   BitMap::idx_t max_idx = 32; // paranoid - don't make it too small
556   for (int i = 0; i < _native_pointers->length(); i++) {
557     NativePointerInfo info = _native_pointers->at(i);
558     oop src_obj = info._src_obj;
559     int field_offset = info._field_offset;
560     HeapShared::CachedOopInfo* p = HeapShared::archived_object_cache()->get(src_obj);
561     // requested_field_addr = the address of this field in the requested space
562     oop requested_obj = requested_obj_from_buffer_offset(p->buffer_offset());
563     Metadata** requested_field_addr = (Metadata**)(cast_from_oop<address>(requested_obj) + field_offset);
564     assert(bottom <= requested_field_addr && requested_field_addr < top, "range check");
565 
566     // Mark this field in the bitmap
567     BitMap::idx_t idx = requested_field_addr - bottom;
568     heap_info->ptrmap()->set_bit(idx);
569     num_non_null_ptrs ++;
570     max_idx = MAX2(max_idx, idx);
571 
572     // Set the native pointer to the requested address of the metadata (at runtime, the metadata will have
573     // this address if the RO/RW regions are mapped at the default location).
574 
575     Metadata** buffered_field_addr = requested_addr_to_buffered_addr(requested_field_addr);
576     Metadata* native_ptr = *buffered_field_addr;
577     assert(native_ptr != nullptr, "sanity");
578 
579     address buffered_native_ptr = ArchiveBuilder::current()->get_buffered_addr((address)native_ptr);
580     address requested_native_ptr = ArchiveBuilder::current()->to_requested(buffered_native_ptr);
581     *buffered_field_addr = (Metadata*)requested_native_ptr;
582   }
583 
584   heap_info->ptrmap()->resize(max_idx + 1);
585   log_info(cds, heap)("calculate_ptrmap: marked %d non-null native pointers for heap region (" SIZE_FORMAT " bits)",
586                       num_non_null_ptrs, size_t(heap_info->ptrmap()->size()));
587 }
588 
589 #endif // INCLUDE_CDS_JAVA_HEAP