1 /*
2 * Copyright (c) 1999, 2020, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2014, Red Hat Inc. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 // no precompiled headers
27 #include "jvm.h"
28 #include "asm/macroAssembler.hpp"
29 #include "classfile/classLoader.hpp"
30 #include "classfile/systemDictionary.hpp"
31 #include "classfile/vmSymbols.hpp"
32 #include "code/codeCache.hpp"
33 #include "code/icBuffer.hpp"
34 #include "code/vtableStubs.hpp"
35 #include "code/nativeInst.hpp"
36 #include "interpreter/interpreter.hpp"
37 #include "memory/allocation.inline.hpp"
38 #include "os_share_linux.hpp"
39 #include "prims/jniFastGetField.hpp"
40 #include "prims/jvm_misc.hpp"
41 #include "runtime/arguments.hpp"
42 #include "runtime/extendedPC.hpp"
43 #include "runtime/frame.inline.hpp"
44 #include "runtime/interfaceSupport.inline.hpp"
45 #include "runtime/java.hpp"
46 #include "runtime/javaCalls.hpp"
47 #include "runtime/mutexLocker.hpp"
48 #include "runtime/osThread.hpp"
49 #include "runtime/safepointMechanism.hpp"
50 #include "runtime/sharedRuntime.hpp"
51 #include "runtime/stubRoutines.hpp"
52 #include "runtime/thread.inline.hpp"
53 #include "runtime/timer.hpp"
54 #include "utilities/debug.hpp"
55 #include "utilities/events.hpp"
56 #include "utilities/vmError.hpp"
57
58 // put OS-includes here
59 # include <sys/types.h>
60 # include <sys/mman.h>
61 # include <pthread.h>
62 # include <signal.h>
63 # include <errno.h>
64 # include <dlfcn.h>
65 # include <stdlib.h>
66 # include <stdio.h>
67 # include <unistd.h>
68 # include <sys/resource.h>
69 # include <pthread.h>
70 # include <sys/stat.h>
71 # include <sys/time.h>
72 # include <sys/utsname.h>
73 # include <sys/socket.h>
74 # include <sys/wait.h>
75 # include <pwd.h>
76 # include <poll.h>
77 # include <ucontext.h>
78 # include <fpu_control.h>
79
80 #define REG_FP 29
81 #define REG_LR 30
82
83 NOINLINE address os::current_stack_pointer() {
84 return (address)__builtin_frame_address(0);
85 }
86
87 char* os::non_memory_address_word() {
88 // Must never look like an address returned by reserve_memory,
89 // even in its subfields (as defined by the CPU immediate fields,
90 // if the CPU splits constants across multiple instructions).
91
92 return (char*) 0xffffffffffff;
93 }
94
95 address os::Linux::ucontext_get_pc(const ucontext_t * uc) {
96 return (address)uc->uc_mcontext.pc;
97 }
98
99 void os::Linux::ucontext_set_pc(ucontext_t * uc, address pc) {
100 uc->uc_mcontext.pc = (intptr_t)pc;
101 }
102
103 intptr_t* os::Linux::ucontext_get_sp(const ucontext_t * uc) {
104 return (intptr_t*)uc->uc_mcontext.sp;
105 }
106
107 intptr_t* os::Linux::ucontext_get_fp(const ucontext_t * uc) {
108 return (intptr_t*)uc->uc_mcontext.regs[REG_FP];
109 }
110
111 // For Forte Analyzer AsyncGetCallTrace profiling support - thread
112 // is currently interrupted by SIGPROF.
113 // os::Solaris::fetch_frame_from_ucontext() tries to skip nested signal
114 // frames. Currently we don't do that on Linux, so it's the same as
115 // os::fetch_frame_from_context().
116 ExtendedPC os::Linux::fetch_frame_from_ucontext(Thread* thread,
117 const ucontext_t* uc, intptr_t** ret_sp, intptr_t** ret_fp) {
118
119 assert(thread != NULL, "just checking");
120 assert(ret_sp != NULL, "just checking");
121 assert(ret_fp != NULL, "just checking");
122
123 return os::fetch_frame_from_context(uc, ret_sp, ret_fp);
124 }
125
126 ExtendedPC os::fetch_frame_from_context(const void* ucVoid,
127 intptr_t** ret_sp, intptr_t** ret_fp) {
128
129 ExtendedPC epc;
130 const ucontext_t* uc = (const ucontext_t*)ucVoid;
131
132 if (uc != NULL) {
133 epc = ExtendedPC(os::Linux::ucontext_get_pc(uc));
134 if (ret_sp) *ret_sp = os::Linux::ucontext_get_sp(uc);
135 if (ret_fp) *ret_fp = os::Linux::ucontext_get_fp(uc);
136 } else {
137 // construct empty ExtendedPC for return value checking
138 epc = ExtendedPC(NULL);
139 if (ret_sp) *ret_sp = (intptr_t *)NULL;
140 if (ret_fp) *ret_fp = (intptr_t *)NULL;
141 }
142
143 return epc;
144 }
145
146 frame os::fetch_frame_from_context(const void* ucVoid) {
147 intptr_t* sp;
148 intptr_t* fp;
149 ExtendedPC epc = fetch_frame_from_context(ucVoid, &sp, &fp);
150 return frame(sp, fp, epc.pc());
151 }
152
153 bool os::Linux::get_frame_at_stack_banging_point(JavaThread* thread, ucontext_t* uc, frame* fr) {
154 address pc = (address) os::Linux::ucontext_get_pc(uc);
155 if (Interpreter::contains(pc)) {
156 // interpreter performs stack banging after the fixed frame header has
157 // been generated while the compilers perform it before. To maintain
158 // semantic consistency between interpreted and compiled frames, the
159 // method returns the Java sender of the current frame.
160 *fr = os::fetch_frame_from_context(uc);
161 if (!fr->is_first_java_frame()) {
162 assert(fr->safe_for_sender(thread), "Safety check");
163 *fr = fr->java_sender();
164 }
165 } else {
166 // more complex code with compiled code
167 assert(!Interpreter::contains(pc), "Interpreted methods should have been handled above");
168 CodeBlob* cb = CodeCache::find_blob(pc);
169 if (cb == NULL || !cb->is_nmethod() || cb->is_frame_complete_at(pc)) {
170 // Not sure where the pc points to, fallback to default
171 // stack overflow handling
172 return false;
173 } else {
174 // In compiled code, the stack banging is performed before LR
175 // has been saved in the frame. LR is live, and SP and FP
176 // belong to the caller.
177 intptr_t* fp = os::Linux::ucontext_get_fp(uc);
178 intptr_t* sp = os::Linux::ucontext_get_sp(uc);
179 address pc = (address)(uc->uc_mcontext.regs[REG_LR]
180 - NativeInstruction::instruction_size);
181 *fr = frame(sp, fp, pc);
182 if (!fr->is_java_frame()) {
183 assert(fr->safe_for_sender(thread), "Safety check");
184 assert(!fr->is_first_frame(), "Safety check");
185 *fr = fr->java_sender();
186 }
187 }
188 }
189 assert(fr->is_java_frame(), "Safety check");
190 return true;
191 }
192
193 // By default, gcc always saves frame pointer rfp on this stack. This
194 // may get turned off by -fomit-frame-pointer.
195 frame os::get_sender_for_C_frame(frame* fr) {
196 return frame(fr->link(), fr->link(), fr->sender_pc());
197 }
198
199 NOINLINE frame os::current_frame() {
200 intptr_t *fp = *(intptr_t **)__builtin_frame_address(0);
201 frame myframe((intptr_t*)os::current_stack_pointer(),
202 (intptr_t*)fp,
203 CAST_FROM_FN_PTR(address, os::current_frame));
204 if (os::is_first_C_frame(&myframe)) {
205 // stack is not walkable
206 return frame();
207 } else {
208 return os::get_sender_for_C_frame(&myframe);
209 }
210 }
211
212 extern "C" JNIEXPORT int
213 JVM_handle_linux_signal(int sig,
214 siginfo_t* info,
215 void* ucVoid,
216 int abort_if_unrecognized) {
217 ucontext_t* uc = (ucontext_t*) ucVoid;
218
219 Thread* t = Thread::current_or_null_safe();
220
221 // Must do this before SignalHandlerMark, if crash protection installed we will longjmp away
222 // (no destructors can be run)
223 os::ThreadCrashProtection::check_crash_protection(sig, t);
224
225 SignalHandlerMark shm(t);
226
227 // Note: it's not uncommon that JNI code uses signal/sigset to install
228 // then restore certain signal handler (e.g. to temporarily block SIGPIPE,
229 // or have a SIGILL handler when detecting CPU type). When that happens,
230 // JVM_handle_linux_signal() might be invoked with junk info/ucVoid. To
231 // avoid unnecessary crash when libjsig is not preloaded, try handle signals
232 // that do not require siginfo/ucontext first.
233
234 if (sig == SIGPIPE || sig == SIGXFSZ) {
235 // allow chained handler to go first
236 if (os::Linux::chained_handler(sig, info, ucVoid)) {
237 return true;
238 } else {
239 // Ignoring SIGPIPE/SIGXFSZ - see bugs 4229104 or 6499219
240 return true;
241 }
242 }
243
244 #ifdef CAN_SHOW_REGISTERS_ON_ASSERT
245 if ((sig == SIGSEGV || sig == SIGBUS) && info != NULL && info->si_addr == g_assert_poison) {
246 if (handle_assert_poison_fault(ucVoid, info->si_addr)) {
247 return 1;
248 }
249 }
250 #endif
251
252 JavaThread* thread = NULL;
253 VMThread* vmthread = NULL;
254 if (os::Linux::signal_handlers_are_installed) {
255 if (t != NULL ){
256 if(t->is_Java_thread()) {
257 thread = (JavaThread*)t;
258 }
259 else if(t->is_VM_thread()){
260 vmthread = (VMThread *)t;
261 }
262 }
263 }
264 /*
265 NOTE: does not seem to work on linux.
266 if (info == NULL || info->si_code <= 0 || info->si_code == SI_NOINFO) {
267 // can't decode this kind of signal
268 info = NULL;
269 } else {
270 assert(sig == info->si_signo, "bad siginfo");
271 }
272 */
273 // decide if this trap can be handled by a stub
274 address stub = NULL;
275
276 address pc = NULL;
277
278 //%note os_trap_1
279 if (info != NULL && uc != NULL && thread != NULL) {
280 pc = (address) os::Linux::ucontext_get_pc(uc);
281
282 if (StubRoutines::is_safefetch_fault(pc)) {
283 os::Linux::ucontext_set_pc(uc, StubRoutines::continuation_for_safefetch_fault(pc));
284 return 1;
285 }
286
287 address addr = (address) info->si_addr;
288
289 // Make sure the high order byte is sign extended, as it may be masked away by the hardware.
290 if ((uintptr_t(addr) & (uintptr_t(1) << 55)) != 0) {
291 addr = address(uintptr_t(addr) | (uintptr_t(0xFF) << 56));
292 }
293
294 // Handle ALL stack overflow variations here
295 if (sig == SIGSEGV) {
296 // check if fault address is within thread stack
297 if (thread->is_in_full_stack(addr)) {
298 // stack overflow
299 if (thread->in_stack_yellow_reserved_zone(addr)) {
300 if (thread->thread_state() == _thread_in_Java) {
301 if (thread->in_stack_reserved_zone(addr)) {
302 frame fr;
303 if (os::Linux::get_frame_at_stack_banging_point(thread, uc, &fr)) {
304 assert(fr.is_java_frame(), "Must be a Java frame");
305 frame activation =
306 SharedRuntime::look_for_reserved_stack_annotated_method(thread, fr);
307 if (activation.sp() != NULL) {
308 thread->disable_stack_reserved_zone();
309 if (activation.is_interpreted_frame()) {
310 thread->set_reserved_stack_activation((address)(
311 activation.fp() + frame::interpreter_frame_initial_sp_offset));
312 } else {
313 thread->set_reserved_stack_activation((address)activation.unextended_sp());
314 }
315 return 1;
316 }
317 }
318 }
319 // Throw a stack overflow exception. Guard pages will be reenabled
320 // while unwinding the stack.
321 thread->disable_stack_yellow_reserved_zone();
322 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::STACK_OVERFLOW);
323 } else {
324 // Thread was in the vm or native code. Return and try to finish.
325 thread->disable_stack_yellow_reserved_zone();
326 return 1;
327 }
328 } else if (thread->in_stack_red_zone(addr)) {
329 // Fatal red zone violation. Disable the guard pages and fall through
330 // to handle_unexpected_exception way down below.
331 thread->disable_stack_red_zone();
332 tty->print_raw_cr("An irrecoverable stack overflow has occurred.");
333
334 // This is a likely cause, but hard to verify. Let's just print
335 // it as a hint.
336 tty->print_raw_cr("Please check if any of your loaded .so files has "
337 "enabled executable stack (see man page execstack(8))");
338 } else {
339 // Accessing stack address below sp may cause SEGV if current
340 // thread has MAP_GROWSDOWN stack. This should only happen when
341 // current thread was created by user code with MAP_GROWSDOWN flag
342 // and then attached to VM. See notes in os_linux.cpp.
343 if (thread->osthread()->expanding_stack() == 0) {
344 thread->osthread()->set_expanding_stack();
345 if (os::Linux::manually_expand_stack(thread, addr)) {
346 thread->osthread()->clear_expanding_stack();
347 return 1;
348 }
349 thread->osthread()->clear_expanding_stack();
350 } else {
351 fatal("recursive segv. expanding stack.");
352 }
353 }
354 }
355 }
356
357 if (thread->thread_state() == _thread_in_Java) {
358 // Java thread running in Java code => find exception handler if any
359 // a fault inside compiled code, the interpreter, or a stub
360
361 // Handle signal from NativeJump::patch_verified_entry().
362 if ((sig == SIGILL || sig == SIGTRAP)
363 && nativeInstruction_at(pc)->is_sigill_zombie_not_entrant()) {
364 if (TraceTraps) {
365 tty->print_cr("trap: zombie_not_entrant (%s)", (sig == SIGTRAP) ? "SIGTRAP" : "SIGILL");
366 }
367 stub = SharedRuntime::get_handle_wrong_method_stub();
368 } else if (sig == SIGSEGV && SafepointMechanism::is_poll_address((address)info->si_addr)) {
369 stub = SharedRuntime::get_poll_stub(pc);
370 } else if (sig == SIGBUS /* && info->si_code == BUS_OBJERR */) {
371 // BugId 4454115: A read from a MappedByteBuffer can fault
372 // here if the underlying file has been truncated.
373 // Do not crash the VM in such a case.
374 CodeBlob* cb = CodeCache::find_blob_unsafe(pc);
375 CompiledMethod* nm = (cb != NULL) ? cb->as_compiled_method_or_null() : NULL;
376 bool is_unsafe_arraycopy = (thread->doing_unsafe_access() && UnsafeCopyMemory::contains_pc(pc));
377 if ((nm != NULL && nm->has_unsafe_access()) || is_unsafe_arraycopy) {
378 address next_pc = pc + NativeCall::instruction_size;
379 if (is_unsafe_arraycopy) {
380 next_pc = UnsafeCopyMemory::page_error_continue_pc(pc);
381 }
382 stub = SharedRuntime::handle_unsafe_access(thread, next_pc);
383 }
384 } else if (sig == SIGILL && nativeInstruction_at(pc)->is_stop()) {
385 // Pull a pointer to the error message out of the instruction
386 // stream.
387 const uint64_t *detail_msg_ptr
388 = (uint64_t*)(pc + NativeInstruction::instruction_size);
389 const char *detail_msg = (const char *)*detail_msg_ptr;
390 const char *msg = "stop";
391 if (TraceTraps) {
392 tty->print_cr("trap: %s: (SIGILL)", msg);
393 }
394
395 va_list detail_args;
396 VMError::report_and_die(INTERNAL_ERROR, msg, detail_msg, detail_args, thread,
397 pc, info, ucVoid, NULL, 0, 0);
398 va_end(detail_args);
399 }
400 else
401
402 if (sig == SIGFPE &&
403 (info->si_code == FPE_INTDIV || info->si_code == FPE_FLTDIV)) {
404 stub =
405 SharedRuntime::
406 continuation_for_implicit_exception(thread,
407 pc,
408 SharedRuntime::
409 IMPLICIT_DIVIDE_BY_ZERO);
410 } else if (sig == SIGSEGV &&
411 MacroAssembler::uses_implicit_null_check((void*)addr)) {
412 // Determination of interpreter/vtable stub/compiled code null exception
413 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
414 }
415 } else if ((thread->thread_state() == _thread_in_vm ||
416 thread->thread_state() == _thread_in_native) &&
417 sig == SIGBUS && /* info->si_code == BUS_OBJERR && */
418 thread->doing_unsafe_access()) {
419 address next_pc = pc + NativeCall::instruction_size;
420 if (UnsafeCopyMemory::contains_pc(pc)) {
421 next_pc = UnsafeCopyMemory::page_error_continue_pc(pc);
422 }
423 stub = SharedRuntime::handle_unsafe_access(thread, next_pc);
424 }
425
426 // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in
427 // and the heap gets shrunk before the field access.
428 if ((sig == SIGSEGV) || (sig == SIGBUS)) {
429 address addr = JNI_FastGetField::find_slowcase_pc(pc);
430 if (addr != (address)-1) {
431 stub = addr;
432 }
433 }
434 }
435
436 if (stub != NULL) {
437 // save all thread context in case we need to restore it
438 if (thread != NULL) thread->set_saved_exception_pc(pc);
439
440 os::Linux::ucontext_set_pc(uc, stub);
441 return true;
442 }
443
444 // signal-chaining
445 if (os::Linux::chained_handler(sig, info, ucVoid)) {
446 return true;
447 }
448
449 if (!abort_if_unrecognized) {
450 // caller wants another chance, so give it to him
451 return false;
452 }
453
454 if (pc == NULL && uc != NULL) {
455 pc = os::Linux::ucontext_get_pc(uc);
456 }
457
458 // unmask current signal
459 sigset_t newset;
460 sigemptyset(&newset);
461 sigaddset(&newset, sig);
462 sigprocmask(SIG_UNBLOCK, &newset, NULL);
463
464 VMError::report_and_die(t, sig, pc, info, ucVoid);
465
466 ShouldNotReachHere();
467 return true; // Mute compiler
468 }
469
470 void os::Linux::init_thread_fpu_state(void) {
471 }
472
473 int os::Linux::get_fpu_control_word(void) {
474 return 0;
475 }
476
477 void os::Linux::set_fpu_control_word(int fpu_control) {
478 }
479
480 bool os::is_allocatable(size_t bytes) {
481 return true;
482 }
483
484 ////////////////////////////////////////////////////////////////////////////////
485 // thread stack
486
487 // Minimum usable stack sizes required to get to user code. Space for
488 // HotSpot guard pages is added later.
489 size_t os::Posix::_compiler_thread_min_stack_allowed = 72 * K;
490 size_t os::Posix::_java_thread_min_stack_allowed = 72 * K;
491 size_t os::Posix::_vm_internal_thread_min_stack_allowed = 72 * K;
492
493 // return default stack size for thr_type
494 size_t os::Posix::default_stack_size(os::ThreadType thr_type) {
495 // default stack size (compiler thread needs larger stack)
496 size_t s = (thr_type == os::compiler_thread ? 4 * M : 1 * M);
497 return s;
498 }
499
500 /////////////////////////////////////////////////////////////////////////////
501 // helper functions for fatal error handler
502
503 void os::print_context(outputStream *st, const void *context) {
504 if (context == NULL) return;
505
506 const ucontext_t *uc = (const ucontext_t*)context;
507 st->print_cr("Registers:");
508 for (int r = 0; r < 31; r++) {
509 st->print("R%-2d=", r);
510 print_location(st, uc->uc_mcontext.regs[r]);
511 }
512 st->cr();
513
514 intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
515 st->print_cr("Top of Stack: (sp=" PTR_FORMAT ")", p2i(sp));
516 print_hex_dump(st, (address)sp, (address)(sp + 8*sizeof(intptr_t)), sizeof(intptr_t));
517 st->cr();
518
519 // Note: it may be unsafe to inspect memory near pc. For example, pc may
520 // point to garbage if entry point in an nmethod is corrupted. Leave
521 // this at the end, and hope for the best.
522 address pc = os::Linux::ucontext_get_pc(uc);
523 print_instructions(st, pc, 4/*native instruction size*/);
524 st->cr();
525 }
526
527 void os::print_register_info(outputStream *st, const void *context) {
528 if (context == NULL) return;
529
530 const ucontext_t *uc = (const ucontext_t*)context;
531
532 st->print_cr("Register to memory mapping:");
533 st->cr();
534
535 // this is horrendously verbose but the layout of the registers in the
536 // context does not match how we defined our abstract Register set, so
537 // we can't just iterate through the gregs area
538
539 // this is only for the "general purpose" registers
540
541 for (int r = 0; r < 31; r++)
542 st->print_cr( "R%d=" INTPTR_FORMAT, r, (uintptr_t)uc->uc_mcontext.regs[r]);
543 st->cr();
544 }
545
546 void os::setup_fpu() {
547 }
548
549 #ifndef PRODUCT
550 void os::verify_stack_alignment() {
551 assert(((intptr_t)os::current_stack_pointer() & (StackAlignmentInBytes-1)) == 0, "incorrect stack alignment");
552 }
553 #endif
554
555 int os::extra_bang_size_in_bytes() {
556 // AArch64 does not require the additional stack bang.
557 return 0;
558 }
559
560 extern "C" {
561 int SpinPause() {
562 return 0;
563 }
564
565 void _Copy_conjoint_jshorts_atomic(const jshort* from, jshort* to, size_t count) {
566 if (from > to) {
567 const jshort *end = from + count;
568 while (from < end)
569 *(to++) = *(from++);
570 }
571 else if (from < to) {
572 const jshort *end = from;
573 from += count - 1;
574 to += count - 1;
575 while (from >= end)
576 *(to--) = *(from--);
577 }
578 }
579 void _Copy_conjoint_jints_atomic(const jint* from, jint* to, size_t count) {
580 if (from > to) {
581 const jint *end = from + count;
582 while (from < end)
583 *(to++) = *(from++);
584 }
585 else if (from < to) {
586 const jint *end = from;
587 from += count - 1;
588 to += count - 1;
589 while (from >= end)
590 *(to--) = *(from--);
591 }
592 }
593 void _Copy_conjoint_jlongs_atomic(const jlong* from, jlong* to, size_t count) {
594 if (from > to) {
595 const jlong *end = from + count;
596 while (from < end)
597 os::atomic_copy64(from++, to++);
598 }
599 else if (from < to) {
600 const jlong *end = from;
601 from += count - 1;
602 to += count - 1;
603 while (from >= end)
604 os::atomic_copy64(from--, to--);
605 }
606 }
607
608 void _Copy_arrayof_conjoint_bytes(const HeapWord* from,
609 HeapWord* to,
610 size_t count) {
611 memmove(to, from, count);
612 }
613 void _Copy_arrayof_conjoint_jshorts(const HeapWord* from,
614 HeapWord* to,
615 size_t count) {
616 memmove(to, from, count * 2);
617 }
618 void _Copy_arrayof_conjoint_jints(const HeapWord* from,
619 HeapWord* to,
620 size_t count) {
621 memmove(to, from, count * 4);
622 }
623 void _Copy_arrayof_conjoint_jlongs(const HeapWord* from,
624 HeapWord* to,
625 size_t count) {
626 memmove(to, from, count * 8);
627 }
628 };