1 /*
  2  * Copyright (c) 1997, 2024, Oracle and/or its affiliates. All rights reserved.
  3  * Copyright (c) 2014, 2020, Red Hat Inc. All rights reserved.
  4  * Copyright (c) 2020, 2023, Huawei Technologies Co., Ltd. All rights reserved.
  5  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  6  *
  7  * This code is free software; you can redistribute it and/or modify it
  8  * under the terms of the GNU General Public License version 2 only, as
  9  * published by the Free Software Foundation.
 10  *
 11  * This code is distributed in the hope that it will be useful, but WITHOUT
 12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 14  * version 2 for more details (a copy is included in the LICENSE file that
 15  * accompanied this code).
 16  *
 17  * You should have received a copy of the GNU General Public License version
 18  * 2 along with this work; if not, write to the Free Software Foundation,
 19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 20  *
 21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 22  * or visit www.oracle.com if you need additional information or have any
 23  * questions.
 24  *
 25  */
 26 
 27 #include "precompiled.hpp"
 28 #include "compiler/oopMap.hpp"
 29 #include "interpreter/interpreter.hpp"
 30 #include "memory/resourceArea.hpp"
 31 #include "memory/universe.hpp"
 32 #include "oops/markWord.hpp"
 33 #include "oops/method.hpp"
 34 #include "oops/oop.inline.hpp"
 35 #include "prims/methodHandles.hpp"
 36 #include "runtime/frame.inline.hpp"
 37 #include "runtime/handles.inline.hpp"
 38 #include "runtime/javaCalls.hpp"
 39 #include "runtime/monitorChunk.hpp"
 40 #include "runtime/os.inline.hpp"
 41 #include "runtime/signature.hpp"
 42 #include "runtime/stackWatermarkSet.hpp"
 43 #include "runtime/stubCodeGenerator.hpp"
 44 #include "runtime/stubRoutines.hpp"
 45 #include "vmreg_riscv.inline.hpp"
 46 #ifdef COMPILER1
 47 #include "c1/c1_Runtime1.hpp"
 48 #include "runtime/vframeArray.hpp"
 49 #endif
 50 
 51 #ifdef ASSERT
 52 void RegisterMap::check_location_valid() {
 53 }
 54 #endif
 55 
 56 
 57 // Profiling/safepoint support
 58 
 59 bool frame::safe_for_sender(JavaThread *thread) {
 60   address   addr_sp = (address)_sp;
 61   address   addr_fp = (address)_fp;
 62   address   unextended_sp = (address)_unextended_sp;
 63 
 64   // consider stack guards when trying to determine "safe" stack pointers
 65   // sp must be within the usable part of the stack (not in guards)
 66   if (!thread->is_in_usable_stack(addr_sp)) {
 67     return false;
 68   }
 69 
 70   // When we are running interpreted code the machine stack pointer, SP, is
 71   // set low enough so that the Java expression stack can grow and shrink
 72   // without ever exceeding the machine stack bounds.  So, ESP >= SP.
 73 
 74   // When we call out of an interpreted method, SP is incremented so that
 75   // the space between SP and ESP is removed.  The SP saved in the callee's
 76   // frame is the SP *before* this increment.  So, when we walk a stack of
 77   // interpreter frames the sender's SP saved in a frame might be less than
 78   // the SP at the point of call.
 79 
 80   // So unextended sp must be within the stack but we need not to check
 81   // that unextended sp >= sp
 82 
 83   if (!thread->is_in_full_stack_checked(unextended_sp)) {
 84     return false;
 85   }
 86 
 87   // an fp must be within the stack and above (but not equal) sp
 88   // second evaluation on fp+ is added to handle situation where fp is -1
 89   bool fp_safe = thread->is_in_stack_range_excl(addr_fp, addr_sp) &&
 90                  thread->is_in_full_stack_checked(addr_fp + (return_addr_offset * sizeof(void*)));
 91 
 92   // We know sp/unextended_sp are safe only fp is questionable here
 93 
 94   // If the current frame is known to the code cache then we can attempt to
 95   // to construct the sender and do some validation of it. This goes a long way
 96   // toward eliminating issues when we get in frame construction code
 97 
 98   if (_cb != nullptr) {
 99 
100     // First check if frame is complete and tester is reliable
101     // Unfortunately we can only check frame complete for runtime stubs and nmethod
102     // other generic buffer blobs are more problematic so we just assume they are
103     // ok. adapter blobs never have a frame complete and are never ok.
104 
105     if (!_cb->is_frame_complete_at(_pc)) {
106       if (_cb->is_nmethod() || _cb->is_adapter_blob() || _cb->is_runtime_stub()) {
107         return false;
108       }
109     }
110 
111     // Could just be some random pointer within the codeBlob
112     if (!_cb->code_contains(_pc)) {
113       return false;
114     }
115 
116     // Entry frame checks
117     if (is_entry_frame()) {
118       // an entry frame must have a valid fp.
119       return fp_safe && is_entry_frame_valid(thread);
120     }
121 
122     intptr_t* sender_sp = nullptr;
123     intptr_t* sender_unextended_sp = nullptr;
124     address   sender_pc = nullptr;
125     intptr_t* saved_fp =  nullptr;
126 
127     if (is_interpreted_frame()) {
128       // fp must be safe
129       if (!fp_safe) {
130         return false;
131       }
132 
133       sender_pc = (address)this->fp()[return_addr_offset];
134       // for interpreted frames, the value below is the sender "raw" sp,
135       // which can be different from the sender unextended sp (the sp seen
136       // by the sender) because of current frame local variables
137       sender_sp = (intptr_t*) addr_at(sender_sp_offset);
138       sender_unextended_sp = (intptr_t*) this->fp()[interpreter_frame_sender_sp_offset];
139       saved_fp = (intptr_t*) this->fp()[link_offset];
140     } else {
141       // must be some sort of compiled/runtime frame
142       // fp does not have to be safe (although it could be check for c1?)
143 
144       // check for a valid frame_size, otherwise we are unlikely to get a valid sender_pc
145       if (_cb->frame_size() <= 0) {
146         return false;
147       }
148 
149       sender_sp = _unextended_sp + _cb->frame_size();
150       // Is sender_sp safe?
151       if (!thread->is_in_full_stack_checked((address)sender_sp)) {
152         return false;
153       }
154 
155       sender_unextended_sp = sender_sp;
156       sender_pc = (address) *(sender_sp - 1);
157       saved_fp = (intptr_t*) *(sender_sp - 2);
158     }
159 
160     if (Continuation::is_return_barrier_entry(sender_pc)) {
161       // If our sender_pc is the return barrier, then our "real" sender is the continuation entry
162       frame s = Continuation::continuation_bottom_sender(thread, *this, sender_sp);
163       sender_sp = s.sp();
164       sender_pc = s.pc();
165     }
166 
167     // If the potential sender is the interpreter then we can do some more checking
168     if (Interpreter::contains(sender_pc)) {
169 
170       // fp is always saved in a recognizable place in any code we generate. However
171       // only if the sender is interpreted/call_stub (c1 too?) are we certain that the saved fp
172       // is really a frame pointer.
173       if (!thread->is_in_stack_range_excl((address)saved_fp, (address)sender_sp)) {
174         return false;
175       }
176 
177       // construct the potential sender
178       frame sender(sender_sp, sender_unextended_sp, saved_fp, sender_pc);
179 
180       return sender.is_interpreted_frame_valid(thread);
181     }
182 
183     // We must always be able to find a recognizable pc
184     CodeBlob* sender_blob = CodeCache::find_blob(sender_pc);
185     if (sender_pc == nullptr || sender_blob == nullptr) {
186       return false;
187     }
188 
189     // Could just be some random pointer within the codeBlob
190     if (!sender_blob->code_contains(sender_pc)) {
191       return false;
192     }
193 
194     // We should never be able to see an adapter if the current frame is something from code cache
195     if (sender_blob->is_adapter_blob()) {
196       return false;
197     }
198 
199     // Could be the call_stub
200     if (StubRoutines::returns_to_call_stub(sender_pc)) {
201       if (!thread->is_in_stack_range_excl((address)saved_fp, (address)sender_sp)) {
202         return false;
203       }
204 
205       // construct the potential sender
206       frame sender(sender_sp, sender_unextended_sp, saved_fp, sender_pc);
207 
208       // Validate the JavaCallWrapper an entry frame must have
209       address jcw = (address)sender.entry_frame_call_wrapper();
210 
211       return thread->is_in_stack_range_excl(jcw, (address)sender.fp());
212     }
213 
214     nmethod* nm = sender_blob->as_nmethod_or_null();
215     if (nm != nullptr) {
216       if (nm->is_deopt_mh_entry(sender_pc) || nm->is_deopt_entry(sender_pc) ||
217           nm->method()->is_method_handle_intrinsic()) {
218         return false;
219       }
220     }
221 
222     // If the frame size is 0 something (or less) is bad because every nmethod has a non-zero frame size
223     // because the return address counts against the callee's frame.
224     if (sender_blob->frame_size() <= 0) {
225       assert(!sender_blob->is_nmethod(), "should count return address at least");
226       return false;
227     }
228 
229     // We should never be able to see anything here except an nmethod. If something in the
230     // code cache (current frame) is called by an entity within the code cache that entity
231     // should not be anything but the call stub (already covered), the interpreter (already covered)
232     // or an nmethod.
233     if (!sender_blob->is_nmethod()) {
234         return false;
235     }
236 
237     // Could put some more validation for the potential non-interpreted sender
238     // frame we'd create by calling sender if I could think of any. Wait for next crash in forte...
239 
240     // One idea is seeing if the sender_pc we have is one that we'd expect to call to current cb
241 
242     // We've validated the potential sender that would be created
243     return true;
244   }
245 
246   // Must be native-compiled frame. Since sender will try and use fp to find
247   // linkages it must be safe
248   if (!fp_safe) {
249     return false;
250   }
251 
252   // Will the pc we fetch be non-zero (which we'll find at the oldest frame)
253   if ((address)this->fp()[return_addr_offset] == nullptr) { return false; }
254 
255   return true;
256 }
257 
258 void frame::patch_pc(Thread* thread, address pc) {
259   assert(_cb == CodeCache::find_blob(pc), "unexpected pc");
260   address* pc_addr = &(((address*) sp())[-1]);
261   address pc_old = *pc_addr;
262 
263   if (TracePcPatching) {
264     tty->print_cr("patch_pc at address " INTPTR_FORMAT " [" INTPTR_FORMAT " -> " INTPTR_FORMAT "]",
265                   p2i(pc_addr), p2i(pc_old), p2i(pc));
266   }
267 
268   assert(!Continuation::is_return_barrier_entry(pc_old), "return barrier");
269 
270   // Either the return address is the original one or we are going to
271   // patch in the same address that's already there.
272   assert(_pc == pc_old || pc == pc_old || pc_old == nullptr, "must be");
273   DEBUG_ONLY(address old_pc = _pc;)
274   *pc_addr = pc;
275   _pc = pc; // must be set before call to get_deopt_original_pc
276   address original_pc = get_deopt_original_pc();
277   if (original_pc != nullptr) {
278     assert(original_pc == old_pc, "expected original PC to be stored before patching");
279     _deopt_state = is_deoptimized;
280     _pc = original_pc;
281   } else {
282     _deopt_state = not_deoptimized;
283   }
284 }
285 
286 intptr_t* frame::entry_frame_argument_at(int offset) const {
287   // convert offset to index to deal with tsi
288   int index = (Interpreter::expr_offset_in_bytes(offset)/wordSize);
289   // Entry frame's arguments are always in relation to unextended_sp()
290   return &unextended_sp()[index];
291 }
292 
293 // locals
294 
295 void frame::interpreter_frame_set_locals(intptr_t* locs)  {
296   assert(is_interpreted_frame(), "interpreted frame expected");
297   // set relativized locals
298   ptr_at_put(interpreter_frame_locals_offset, (intptr_t) (locs - fp()));
299 }
300 
301 // sender_sp
302 
303 intptr_t* frame::interpreter_frame_sender_sp() const {
304   assert(is_interpreted_frame(), "interpreted frame expected");
305   return (intptr_t*) at(interpreter_frame_sender_sp_offset);
306 }
307 
308 void frame::set_interpreter_frame_sender_sp(intptr_t* sender_sp) {
309   assert(is_interpreted_frame(), "interpreted frame expected");
310   ptr_at_put(interpreter_frame_sender_sp_offset, (intptr_t) sender_sp);
311 }
312 
313 
314 // monitor elements
315 
316 BasicObjectLock* frame::interpreter_frame_monitor_begin() const {
317   return (BasicObjectLock*) addr_at(interpreter_frame_monitor_block_bottom_offset);
318 }
319 
320 BasicObjectLock* frame::interpreter_frame_monitor_end() const {
321   BasicObjectLock* result = (BasicObjectLock*) at_relative(interpreter_frame_monitor_block_top_offset);
322   // make sure the pointer points inside the frame
323   assert(sp() <= (intptr_t*) result, "monitor end should be above the stack pointer");
324   assert((intptr_t*) result < fp(),  "monitor end should be strictly below the frame pointer");
325   return result;
326 }
327 
328 void frame::interpreter_frame_set_monitor_end(BasicObjectLock* value) {
329   assert(is_interpreted_frame(), "interpreted frame expected");
330   // set relativized monitor_block_top
331   ptr_at_put(interpreter_frame_monitor_block_top_offset, (intptr_t*)value - fp());
332   assert(at_absolute(interpreter_frame_monitor_block_top_offset) <= interpreter_frame_monitor_block_top_offset, "");
333 }
334 
335 // Used by template based interpreter deoptimization
336 void frame::interpreter_frame_set_last_sp(intptr_t* last_sp) {
337   assert(is_interpreted_frame(), "interpreted frame expected");
338   // set relativized last_sp
339   ptr_at_put(interpreter_frame_last_sp_offset, last_sp != nullptr ? (last_sp - fp()) : 0);
340 }
341 
342 void frame::interpreter_frame_set_extended_sp(intptr_t* sp) {
343   assert(is_interpreted_frame(), "interpreted frame expected");
344   // set relativized extended_sp
345   ptr_at_put(interpreter_frame_extended_sp_offset, (sp - fp()));
346 }
347 
348 frame frame::sender_for_entry_frame(RegisterMap* map) const {
349   assert(map != nullptr, "map must be set");
350   // Java frame called from C; skip all C frames and return top C
351   // frame of that chunk as the sender
352   JavaFrameAnchor* jfa = entry_frame_call_wrapper()->anchor();
353   assert(!entry_frame_is_first(), "next Java fp must be non zero");
354   assert(jfa->last_Java_sp() > sp(), "must be above this frame on stack");
355   // Since we are walking the stack now this nested anchor is obviously walkable
356   // even if it wasn't when it was stacked.
357   jfa->make_walkable();
358   map->clear();
359   assert(map->include_argument_oops(), "should be set by clear");
360   frame fr(jfa->last_Java_sp(), jfa->last_Java_fp(), jfa->last_Java_pc());
361   return fr;
362 }
363 
364 UpcallStub::FrameData* UpcallStub::frame_data_for_frame(const frame& frame) const {
365   assert(frame.is_upcall_stub_frame(), "wrong frame");
366   // need unextended_sp here, since normal sp is wrong for interpreter callees
367   return reinterpret_cast<UpcallStub::FrameData*>(
368           reinterpret_cast<address>(frame.unextended_sp()) + in_bytes(_frame_data_offset));
369 }
370 
371 bool frame::upcall_stub_frame_is_first() const {
372   assert(is_upcall_stub_frame(), "must be optimzed entry frame");
373   UpcallStub* blob = _cb->as_upcall_stub();
374   JavaFrameAnchor* jfa = blob->jfa_for_frame(*this);
375   return jfa->last_Java_sp() == nullptr;
376 }
377 
378 frame frame::sender_for_upcall_stub_frame(RegisterMap* map) const {
379   assert(map != nullptr, "map must be set");
380   UpcallStub* blob = _cb->as_upcall_stub();
381   // Java frame called from C; skip all C frames and return top C
382   // frame of that chunk as the sender
383   JavaFrameAnchor* jfa = blob->jfa_for_frame(*this);
384   assert(!upcall_stub_frame_is_first(), "must have a frame anchor to go back to");
385   assert(jfa->last_Java_sp() > sp(), "must be above this frame on stack");
386   // Since we are walking the stack now this nested anchor is obviously walkable
387   // even if it wasn't when it was stacked.
388   jfa->make_walkable();
389   map->clear();
390   assert(map->include_argument_oops(), "should be set by clear");
391   frame fr(jfa->last_Java_sp(), jfa->last_Java_fp(), jfa->last_Java_pc());
392 
393   return fr;
394 }
395 
396 //------------------------------------------------------------------------------
397 // frame::verify_deopt_original_pc
398 //
399 // Verifies the calculated original PC of a deoptimization PC for the
400 // given unextended SP.
401 #ifdef ASSERT
402 void frame::verify_deopt_original_pc(nmethod* nm, intptr_t* unextended_sp) {
403   frame fr;
404 
405   // This is ugly but it's better than to change {get,set}_original_pc
406   // to take an SP value as argument.  And it's only a debugging
407   // method anyway.
408   fr._unextended_sp = unextended_sp;
409 
410   assert_cond(nm != nullptr);
411   address original_pc = nm->get_original_pc(&fr);
412   assert(nm->insts_contains_inclusive(original_pc),
413          "original PC must be in the main code section of the compiled method (or must be immediately following it)");
414 }
415 #endif
416 
417 //------------------------------------------------------------------------------
418 // frame::adjust_unextended_sp
419 #ifdef ASSERT
420 void frame::adjust_unextended_sp() {
421   // On riscv, sites calling method handle intrinsics and lambda forms are treated
422   // as any other call site. Therefore, no special action is needed when we are
423   // returning to any of these call sites.
424 
425   if (_cb != nullptr) {
426     nmethod* sender_nm = _cb->as_nmethod_or_null();
427     if (sender_nm != nullptr) {
428       // If the sender PC is a deoptimization point, get the original PC.
429       if (sender_nm->is_deopt_entry(_pc) ||
430           sender_nm->is_deopt_mh_entry(_pc)) {
431         verify_deopt_original_pc(sender_nm, _unextended_sp);
432       }
433     }
434   }
435 }
436 #endif
437 
438 
439 //------------------------------------------------------------------------------
440 // frame::sender_for_interpreter_frame
441 frame frame::sender_for_interpreter_frame(RegisterMap* map) const {
442   // SP is the raw SP from the sender after adapter or interpreter
443   // extension.
444   intptr_t* sender_sp = this->sender_sp();
445 
446   // This is the sp before any possible extension (adapter/locals).
447   intptr_t* unextended_sp = interpreter_frame_sender_sp();
448 
449 #ifdef COMPILER2
450   assert(map != nullptr, "map must be set");
451   if (map->update_map()) {
452     update_map_with_saved_link(map, (intptr_t**) addr_at(link_offset));
453   }
454 #endif // COMPILER2
455 
456   if (Continuation::is_return_barrier_entry(sender_pc())) {
457     if (map->walk_cont()) { // about to walk into an h-stack
458       return Continuation::top_frame(*this, map);
459     } else {
460       return Continuation::continuation_bottom_sender(map->thread(), *this, sender_sp);
461     }
462   }
463 
464   return frame(sender_sp, unextended_sp, link(), sender_pc());
465 }
466 
467 bool frame::is_interpreted_frame_valid(JavaThread* thread) const {
468   assert(is_interpreted_frame(), "Not an interpreted frame");
469   // These are reasonable sanity checks
470   if (fp() == nullptr || (intptr_t(fp()) & (wordSize-1)) != 0) {
471     return false;
472   }
473   if (sp() == nullptr || (intptr_t(sp()) & (wordSize-1)) != 0) {
474     return false;
475   }
476   if (fp() + interpreter_frame_initial_sp_offset < sp()) {
477     return false;
478   }
479   // These are hacks to keep us out of trouble.
480   // The problem with these is that they mask other problems
481   if (fp() <= sp()) {        // this attempts to deal with unsigned comparison above
482     return false;
483   }
484 
485   // do some validation of frame elements
486 
487   // first the method
488   Method* m = safe_interpreter_frame_method();
489   // validate the method we'd find in this potential sender
490   if (!Method::is_valid_method(m)) {
491     return false;
492   }
493 
494   // stack frames shouldn't be much larger than max_stack elements
495   // this test requires the use of unextended_sp which is the sp as seen by
496   // the current frame, and not sp which is the "raw" pc which could point
497   // further because of local variables of the callee method inserted after
498   // method arguments
499   if (fp() - unextended_sp() > 1024 + m->max_stack()*Interpreter::stackElementSize) {
500     return false;
501   }
502 
503   // validate bci/bcx
504   address bcp = interpreter_frame_bcp();
505   if (m->validate_bci_from_bcp(bcp) < 0) {
506     return false;
507   }
508 
509   // validate constantPoolCache*
510   ConstantPoolCache* cp = *interpreter_frame_cache_addr();
511   if (MetaspaceObj::is_valid(cp) == false) {
512     return false;
513   }
514 
515   // validate locals
516   if (m->max_locals() > 0) {
517     address locals = (address)interpreter_frame_locals();
518     if (!thread->is_in_stack_range_incl(locals, (address)fp())) {
519       return false;
520     }
521   }
522 
523   // We'd have to be pretty unlucky to be mislead at this point
524   return true;
525 }
526 
527 BasicType frame::interpreter_frame_result(oop* oop_result, jvalue* value_result) {
528   assert(is_interpreted_frame(), "interpreted frame expected");
529   Method* method = interpreter_frame_method();
530   BasicType type = method->result_type();
531 
532   intptr_t* tos_addr = nullptr;
533   if (method->is_native()) {
534     tos_addr = (intptr_t*)sp();
535     if (type == T_FLOAT || type == T_DOUBLE) {
536       // This is because we do a push(ltos) after push(dtos) in generate_native_entry.
537       tos_addr += 2 * Interpreter::stackElementWords;
538     }
539   } else {
540     tos_addr = (intptr_t*)interpreter_frame_tos_address();
541   }
542 
543   switch (type) {
544     case T_OBJECT  :
545     case T_ARRAY   : {
546       oop obj;
547       if (method->is_native()) {
548         obj = cast_to_oop(at(interpreter_frame_oop_temp_offset));
549       } else {
550         oop* obj_p = (oop*)tos_addr;
551         obj = (obj_p == nullptr) ? (oop)nullptr : *obj_p;
552       }
553       assert(Universe::is_in_heap_or_null(obj), "sanity check");
554       *oop_result = obj;
555       break;
556     }
557     case T_BOOLEAN : value_result->z = *(jboolean*)tos_addr; break;
558     case T_BYTE    : value_result->b = *(jbyte*)tos_addr; break;
559     case T_CHAR    : value_result->c = *(jchar*)tos_addr; break;
560     case T_SHORT   : value_result->s = *(jshort*)tos_addr; break;
561     case T_INT     : value_result->i = *(jint*)tos_addr; break;
562     case T_LONG    : value_result->j = *(jlong*)tos_addr; break;
563     case T_FLOAT   : {
564         value_result->f = *(jfloat*)tos_addr;
565       break;
566     }
567     case T_DOUBLE  : value_result->d = *(jdouble*)tos_addr; break;
568     case T_VOID    : /* Nothing to do */ break;
569     default        : ShouldNotReachHere();
570   }
571 
572   return type;
573 }
574 
575 
576 intptr_t* frame::interpreter_frame_tos_at(jint offset) const {
577   int index = (Interpreter::expr_offset_in_bytes(offset)/wordSize);
578   return &interpreter_frame_tos_address()[index];
579 }
580 
581 #ifndef PRODUCT
582 
583 #define DESCRIBE_FP_OFFSET(name) \
584   values.describe(frame_no, fp() + frame::name##_offset, #name)
585 
586 void frame::describe_pd(FrameValues& values, int frame_no) {
587   if (is_interpreted_frame()) {
588     DESCRIBE_FP_OFFSET(interpreter_frame_sender_sp);
589     DESCRIBE_FP_OFFSET(interpreter_frame_last_sp);
590     DESCRIBE_FP_OFFSET(interpreter_frame_method);
591     DESCRIBE_FP_OFFSET(interpreter_frame_mdp);
592     DESCRIBE_FP_OFFSET(interpreter_frame_extended_sp);
593     DESCRIBE_FP_OFFSET(interpreter_frame_mirror);
594     DESCRIBE_FP_OFFSET(interpreter_frame_cache);
595     DESCRIBE_FP_OFFSET(interpreter_frame_locals);
596     DESCRIBE_FP_OFFSET(interpreter_frame_bcp);
597     DESCRIBE_FP_OFFSET(interpreter_frame_initial_sp);
598   }
599 
600   if (is_java_frame() || Continuation::is_continuation_enterSpecial(*this)) {
601     intptr_t* ret_pc_loc;
602     intptr_t* fp_loc;
603     if (is_interpreted_frame()) {
604       ret_pc_loc = fp() + return_addr_offset;
605       fp_loc = fp();
606     } else {
607       ret_pc_loc = real_fp() - 1;
608       fp_loc = real_fp() - 2;
609     }
610     address ret_pc = *(address*)ret_pc_loc;
611     values.describe(frame_no, ret_pc_loc,
612       Continuation::is_return_barrier_entry(ret_pc) ? "return address (return barrier)" : "return address");
613     values.describe(-1, fp_loc, "saved fp", 0); // "unowned" as value belongs to sender
614   }
615 }
616 #endif
617 
618 intptr_t *frame::initial_deoptimization_info() {
619   // Not used on riscv, but we must return something.
620   return nullptr;
621 }
622 
623 #undef DESCRIBE_FP_OFFSET
624 
625 #ifndef PRODUCT
626 // This is a generic constructor which is only used by pns() in debug.cpp.
627 frame::frame(void* ptr_sp, void* ptr_fp, void* pc) : _on_heap(false) {
628   init((intptr_t*)ptr_sp, (intptr_t*)ptr_fp, (address)pc);
629 }
630 
631 #endif
632 
633 void JavaFrameAnchor::make_walkable() {
634   // last frame set?
635   if (last_Java_sp() == nullptr) { return; }
636   // already walkable?
637   if (walkable()) { return; }
638   vmassert(last_Java_sp() != nullptr, "not called from Java code?");
639   vmassert(last_Java_pc() == nullptr, "already walkable");
640   _last_Java_pc = (address)_last_Java_sp[-1];
641   vmassert(walkable(), "something went wrong");
642 }