1 /*
2 * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
3 * Copyright 2012, 2015 SAP AG. 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 "assembler_ppc.inline.hpp"
28 #include "classfile/classLoader.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "classfile/vmSymbols.hpp"
31 #include "code/icBuffer.hpp"
32 #include "code/vtableStubs.hpp"
33 #include "interpreter/interpreter.hpp"
34 #include "jvm_linux.h"
35 #include "memory/allocation.inline.hpp"
36 #include "mutex_linux.inline.hpp"
37 #include "nativeInst_ppc.hpp"
38 #include "os_share_linux.hpp"
39 #include "prims/jniFastGetField.hpp"
40 #include "prims/jvm.h"
41 #include "prims/jvm_misc.hpp"
42 #include "runtime/arguments.hpp"
43 #include "runtime/extendedPC.hpp"
44 #include "runtime/frame.inline.hpp"
45 #include "runtime/interfaceSupport.hpp"
46 #include "runtime/java.hpp"
47 #include "runtime/javaCalls.hpp"
48 #include "runtime/mutexLocker.hpp"
49 #include "runtime/osThread.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/events.hpp"
55 #include "utilities/vmError.hpp"
56
57 // put OS-includes here
58 # include <sys/types.h>
59 # include <sys/mman.h>
60 # include <pthread.h>
61 # include <signal.h>
62 # include <errno.h>
63 # include <dlfcn.h>
64 # include <stdlib.h>
65 # include <stdio.h>
66 # include <unistd.h>
67 # include <sys/resource.h>
68 # include <pthread.h>
69 # include <sys/stat.h>
70 # include <sys/time.h>
71 # include <sys/utsname.h>
72 # include <sys/socket.h>
73 # include <sys/wait.h>
74 # include <pwd.h>
75 # include <poll.h>
76 # include <ucontext.h>
77
78
79 address os::current_stack_pointer() {
80 intptr_t* csp;
81
82 // inline assembly `mr regno(csp), R1_SP':
83 __asm__ __volatile__ ("mr %0, 1":"=r"(csp):);
84
85 return (address) csp;
86 }
87
88 char* os::non_memory_address_word() {
89 // Must never look like an address returned by reserve_memory,
90 // even in its subfields (as defined by the CPU immediate fields,
91 // if the CPU splits constants across multiple instructions).
92
93 return (char*) -1;
94 }
95
96 void os::initialize_thread(Thread *thread) { }
97
98 // Frame information (pc, sp, fp) retrieved via ucontext
99 // always looks like a C-frame according to the frame
100 // conventions in frame_ppc64.hpp.
101 address os::Linux::ucontext_get_pc(ucontext_t * uc) {
102 // On powerpc64, ucontext_t is not selfcontained but contains
103 // a pointer to an optional substructure (mcontext_t.regs) containing the volatile
104 // registers - NIP, among others.
105 // This substructure may or may not be there depending where uc came from:
106 // - if uc was handed over as the argument to a sigaction handler, a pointer to the
107 // substructure was provided by the kernel when calling the signal handler, and
108 // regs->nip can be accessed.
109 // - if uc was filled by getcontext(), it is undefined - getcontext() does not fill
110 // it because the volatile registers are not needed to make setcontext() work.
111 // Hopefully it was zero'd out beforehand.
112 guarantee(uc->uc_mcontext.regs != NULL, "only use ucontext_get_pc in sigaction context");
113 return (address)uc->uc_mcontext.regs->nip;
114 }
115
116 // modify PC in ucontext.
117 // Note: Only use this for an ucontext handed down to a signal handler. See comment
118 // in ucontext_get_pc.
119 void os::Linux::ucontext_set_pc(ucontext_t * uc, address pc) {
120 guarantee(uc->uc_mcontext.regs != NULL, "only use ucontext_set_pc in sigaction context");
121 uc->uc_mcontext.regs->nip = (unsigned long)pc;
122 }
123
124 intptr_t* os::Linux::ucontext_get_sp(ucontext_t * uc) {
125 return (intptr_t*)uc->uc_mcontext.regs->gpr[1/*REG_SP*/];
126 }
127
128 intptr_t* os::Linux::ucontext_get_fp(ucontext_t * uc) {
129 return NULL;
130 }
131
132 ExtendedPC os::fetch_frame_from_context(void* ucVoid,
133 intptr_t** ret_sp, intptr_t** ret_fp) {
134
135 ExtendedPC epc;
136 ucontext_t* uc = (ucontext_t*)ucVoid;
137
138 if (uc != NULL) {
139 epc = ExtendedPC(os::Linux::ucontext_get_pc(uc));
140 if (ret_sp) *ret_sp = os::Linux::ucontext_get_sp(uc);
141 if (ret_fp) *ret_fp = os::Linux::ucontext_get_fp(uc);
142 } else {
143 // construct empty ExtendedPC for return value checking
144 epc = ExtendedPC(NULL);
145 if (ret_sp) *ret_sp = (intptr_t *)NULL;
146 if (ret_fp) *ret_fp = (intptr_t *)NULL;
147 }
148
149 return epc;
150 }
151
152 frame os::fetch_frame_from_context(void* ucVoid) {
153 intptr_t* sp;
154 intptr_t* fp;
155 ExtendedPC epc = fetch_frame_from_context(ucVoid, &sp, &fp);
156 return frame(sp, epc.pc());
157 }
158
159 frame os::get_sender_for_C_frame(frame* fr) {
160 if (*fr->sp() == 0) {
161 // fr is the last C frame
162 return frame(NULL, NULL);
163 }
164 return frame(fr->sender_sp(), fr->sender_pc());
165 }
166
167
168 frame os::current_frame() {
169 intptr_t* csp = (intptr_t*) *((intptr_t*) os::current_stack_pointer());
170 // hack.
171 frame topframe(csp, (address)0x8);
172 // return sender of current topframe which hopefully has pc != NULL.
173 return os::get_sender_for_C_frame(&topframe);
174 }
175
176 // Utility functions
177
178 extern "C" JNIEXPORT int
179 JVM_handle_linux_signal(int sig,
180 siginfo_t* info,
181 void* ucVoid,
182 int abort_if_unrecognized) {
183 ucontext_t* uc = (ucontext_t*) ucVoid;
184
185 Thread* t = Thread::current_or_null_safe();
186
187 SignalHandlerMark shm(t);
188
189 // Note: it's not uncommon that JNI code uses signal/sigset to install
190 // then restore certain signal handler (e.g. to temporarily block SIGPIPE,
191 // or have a SIGILL handler when detecting CPU type). When that happens,
192 // JVM_handle_linux_signal() might be invoked with junk info/ucVoid. To
193 // avoid unnecessary crash when libjsig is not preloaded, try handle signals
194 // that do not require siginfo/ucontext first.
195
196 if (sig == SIGPIPE) {
197 if (os::Linux::chained_handler(sig, info, ucVoid)) {
198 return true;
199 } else {
200 if (PrintMiscellaneous && (WizardMode || Verbose)) {
201 warning("Ignoring SIGPIPE - see bug 4229104");
202 }
203 return true;
204 }
205 }
206
207 JavaThread* thread = NULL;
208 VMThread* vmthread = NULL;
209 if (os::Linux::signal_handlers_are_installed) {
210 if (t != NULL) {
211 if(t->is_Java_thread()) {
212 thread = (JavaThread*)t;
213 } else if(t->is_VM_thread()) {
214 vmthread = (VMThread *)t;
215 }
216 }
217 }
218
219 // Moved SafeFetch32 handling outside thread!=NULL conditional block to make
220 // it work if no associated JavaThread object exists.
221 if (uc) {
222 address const pc = os::Linux::ucontext_get_pc(uc);
223 if (pc && StubRoutines::is_safefetch_fault(pc)) {
224 os::Linux::ucontext_set_pc(uc, StubRoutines::continuation_for_safefetch_fault(pc));
225 return true;
226 }
227 }
228
229 // decide if this trap can be handled by a stub
230 address stub = NULL;
231 address pc = NULL;
232
233 //%note os_trap_1
234 if (info != NULL && uc != NULL && thread != NULL) {
235 pc = (address) os::Linux::ucontext_get_pc(uc);
236
237 // Handle ALL stack overflow variations here
238 if (sig == SIGSEGV) {
239 // Si_addr may not be valid due to a bug in the linux-ppc64 kernel (see
240 // comment below). Use get_stack_bang_address instead of si_addr.
241 address addr = ((NativeInstruction*)pc)->get_stack_bang_address(uc);
242
243 // Check if fault address is within thread stack.
244 if (addr < thread->stack_base() &&
245 addr >= thread->stack_base() - thread->stack_size()) {
246 // stack overflow
247 if (thread->in_stack_yellow_zone(addr)) {
248 thread->disable_stack_yellow_zone();
249 if (thread->thread_state() == _thread_in_Java) {
250 // Throw a stack overflow exception.
251 // Guard pages will be reenabled while unwinding the stack.
252 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::STACK_OVERFLOW);
253 } else {
254 // Thread was in the vm or native code. Return and try to finish.
255 return 1;
256 }
257 } else if (thread->in_stack_red_zone(addr)) {
258 // Fatal red zone violation. Disable the guard pages and fall through
259 // to handle_unexpected_exception way down below.
260 thread->disable_stack_red_zone();
261 tty->print_raw_cr("An irrecoverable stack overflow has occurred.");
262
263 // This is a likely cause, but hard to verify. Let's just print
264 // it as a hint.
265 tty->print_raw_cr("Please check if any of your loaded .so files has "
266 "enabled executable stack (see man page execstack(8))");
267 } else {
268 // Accessing stack address below sp may cause SEGV if current
269 // thread has MAP_GROWSDOWN stack. This should only happen when
270 // current thread was created by user code with MAP_GROWSDOWN flag
271 // and then attached to VM. See notes in os_linux.cpp.
272 if (thread->osthread()->expanding_stack() == 0) {
273 thread->osthread()->set_expanding_stack();
274 if (os::Linux::manually_expand_stack(thread, addr)) {
275 thread->osthread()->clear_expanding_stack();
276 return 1;
277 }
278 thread->osthread()->clear_expanding_stack();
279 } else {
280 fatal("recursive segv. expanding stack.");
281 }
282 }
283 }
284 }
285
286 if (thread->thread_state() == _thread_in_Java) {
287 // Java thread running in Java code => find exception handler if any
288 // a fault inside compiled code, the interpreter, or a stub
289
290 // A VM-related SIGILL may only occur if we are not in the zero page.
291 // On AIX, we get a SIGILL if we jump to 0x0 or to somewhere else
292 // in the zero page, because it is filled with 0x0. We ignore
293 // explicit SIGILLs in the zero page.
294 if (sig == SIGILL && (pc < (address) 0x200)) {
295 if (TraceTraps) {
296 tty->print_raw_cr("SIGILL happened inside zero page.");
297 }
298 goto report_and_die;
299 }
300
301 CodeBlob *cb = NULL;
302 // Handle signal from NativeJump::patch_verified_entry().
303 if (( TrapBasedNotEntrantChecks && sig == SIGTRAP && nativeInstruction_at(pc)->is_sigtrap_zombie_not_entrant()) ||
304 (!TrapBasedNotEntrantChecks && sig == SIGILL && nativeInstruction_at(pc)->is_sigill_zombie_not_entrant())) {
305 if (TraceTraps) {
306 tty->print_cr("trap: zombie_not_entrant (%s)", (sig == SIGTRAP) ? "SIGTRAP" : "SIGILL");
307 }
308 stub = SharedRuntime::get_handle_wrong_method_stub();
309 }
310
311 else if (sig == SIGSEGV &&
312 // A linux-ppc64 kernel before 2.6.6 doesn't set si_addr on some segfaults
313 // in 64bit mode (cf. http://www.kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.6),
314 // especially when we try to read from the safepoint polling page. So the check
315 // (address)info->si_addr == os::get_standard_polling_page()
316 // doesn't work for us. We use:
317 ((NativeInstruction*)pc)->is_safepoint_poll() &&
318 CodeCache::contains((void*) pc) &&
319 ((cb = CodeCache::find_blob(pc)) != NULL) &&
320 cb->is_nmethod()) {
321 if (TraceTraps) {
322 tty->print_cr("trap: safepoint_poll at " INTPTR_FORMAT " (SIGSEGV)", p2i(pc));
323 }
324 stub = SharedRuntime::get_poll_stub(pc);
325 }
326
327 // SIGTRAP-based ic miss check in compiled code.
328 else if (sig == SIGTRAP && TrapBasedICMissChecks &&
329 nativeInstruction_at(pc)->is_sigtrap_ic_miss_check()) {
330 if (TraceTraps) {
331 tty->print_cr("trap: ic_miss_check at " INTPTR_FORMAT " (SIGTRAP)", p2i(pc));
332 }
333 stub = SharedRuntime::get_ic_miss_stub();
334 }
335
336 // SIGTRAP-based implicit null check in compiled code.
337 else if (sig == SIGTRAP && TrapBasedNullChecks &&
338 nativeInstruction_at(pc)->is_sigtrap_null_check()) {
339 if (TraceTraps) {
340 tty->print_cr("trap: null_check at " INTPTR_FORMAT " (SIGTRAP)", p2i(pc));
341 }
342 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
343 }
344
345 // SIGSEGV-based implicit null check in compiled code.
346 else if (sig == SIGSEGV && ImplicitNullChecks &&
347 CodeCache::contains((void*) pc) &&
348 !MacroAssembler::needs_explicit_null_check((intptr_t) info->si_addr)) {
349 if (TraceTraps) {
350 tty->print_cr("trap: null_check at " INTPTR_FORMAT " (SIGSEGV)", p2i(pc));
351 }
352 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
353 }
354
355 #ifdef COMPILER2
356 // SIGTRAP-based implicit range check in compiled code.
357 else if (sig == SIGTRAP && TrapBasedRangeChecks &&
358 nativeInstruction_at(pc)->is_sigtrap_range_check()) {
359 if (TraceTraps) {
360 tty->print_cr("trap: range_check at " INTPTR_FORMAT " (SIGTRAP)", p2i(pc));
361 }
362 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
363 }
364 #endif
365 else if (sig == SIGBUS) {
366 // BugId 4454115: A read from a MappedByteBuffer can fault here if the
367 // underlying file has been truncated. Do not crash the VM in such a case.
368 CodeBlob* cb = CodeCache::find_blob_unsafe(pc);
369 nmethod* nm = (cb != NULL && cb->is_nmethod()) ? (nmethod*)cb : NULL;
370 if (nm != NULL && nm->has_unsafe_access()) {
371 // We don't really need a stub here! Just set the pending exeption and
372 // continue at the next instruction after the faulting read. Returning
373 // garbage from this read is ok.
374 thread->set_pending_unsafe_access_error();
375 os::Linux::ucontext_set_pc(uc, pc + 4);
376 return true;
377 }
378 }
379 }
380
381 else { // thread->thread_state() != _thread_in_Java
382 if (sig == SIGILL && VM_Version::is_determine_features_test_running()) {
383 // SIGILL must be caused by VM_Version::determine_features().
384 *(int *)pc = 0; // patch instruction to 0 to indicate that it causes a SIGILL,
385 // flushing of icache is not necessary.
386 stub = pc + 4; // continue with next instruction.
387 }
388 else if (thread->thread_state() == _thread_in_vm &&
389 sig == SIGBUS && thread->doing_unsafe_access()) {
390 // We don't really need a stub here! Just set the pending exeption and
391 // continue at the next instruction after the faulting read. Returning
392 // garbage from this read is ok.
393 thread->set_pending_unsafe_access_error();
394 os::Linux::ucontext_set_pc(uc, pc + 4);
395 return true;
396 }
397 }
398
399 // Check to see if we caught the safepoint code in the
400 // process of write protecting the memory serialization page.
401 // It write enables the page immediately after protecting it
402 // so we can just return to retry the write.
403 if ((sig == SIGSEGV) &&
404 // Si_addr may not be valid due to a bug in the linux-ppc64 kernel (see comment above).
405 // Use is_memory_serialization instead of si_addr.
406 ((NativeInstruction*)pc)->is_memory_serialization(thread, ucVoid)) {
407 // Synchronization problem in the pseudo memory barrier code (bug id 6546278)
408 // Block current thread until the memory serialize page permission restored.
409 os::block_on_serialize_page_trap();
410 return true;
411 }
412 }
413
414 if (stub != NULL) {
415 // Save all thread context in case we need to restore it.
416 if (thread != NULL) thread->set_saved_exception_pc(pc);
417 os::Linux::ucontext_set_pc(uc, stub);
418 return true;
419 }
420
421 // signal-chaining
422 if (os::Linux::chained_handler(sig, info, ucVoid)) {
423 return true;
424 }
425
426 if (!abort_if_unrecognized) {
427 // caller wants another chance, so give it to him
428 return false;
429 }
430
431 if (pc == NULL && uc != NULL) {
432 pc = os::Linux::ucontext_get_pc(uc);
433 }
434
435 report_and_die:
436 // unmask current signal
437 sigset_t newset;
438 sigemptyset(&newset);
439 sigaddset(&newset, sig);
440 sigprocmask(SIG_UNBLOCK, &newset, NULL);
441
442 VMError::report_and_die(t, sig, pc, info, ucVoid);
443
444 ShouldNotReachHere();
445 return false;
446 }
447
448 void os::Linux::init_thread_fpu_state(void) {
449 // Disable FP exceptions.
450 __asm__ __volatile__ ("mtfsfi 6,0");
451 }
452
453 int os::Linux::get_fpu_control_word(void) {
454 // x86 has problems with FPU precision after pthread_cond_timedwait().
455 // nothing to do on ppc64.
456 return 0;
457 }
458
459 void os::Linux::set_fpu_control_word(int fpu_control) {
460 // x86 has problems with FPU precision after pthread_cond_timedwait().
461 // nothing to do on ppc64.
462 }
463
464 ////////////////////////////////////////////////////////////////////////////////
465 // thread stack
466
467 size_t os::Linux::min_stack_allowed = 128*K;
468
469 // return default stack size for thr_type
470 size_t os::Linux::default_stack_size(os::ThreadType thr_type) {
471 // default stack size (compiler thread needs larger stack)
472 // Notice that the setting for compiler threads here have no impact
473 // because of the strange 'fallback logic' in os::create_thread().
474 // Better set CompilerThreadStackSize in globals_<os_cpu>.hpp if you want to
475 // specify a different stack size for compiler threads!
476 size_t s = (thr_type == os::compiler_thread ? 4 * M : 1024 * K);
477 return s;
478 }
479
480 size_t os::Linux::default_guard_size(os::ThreadType thr_type) {
481 return 2 * page_size();
482 }
483
484 // Java thread:
485 //
486 // Low memory addresses
487 // +------------------------+
488 // | |\ JavaThread created by VM does not have glibc
489 // | glibc guard page | - guard, attached Java thread usually has
490 // | |/ 1 page glibc guard.
491 // P1 +------------------------+ Thread::stack_base() - Thread::stack_size()
492 // | |\
493 // | HotSpot Guard Pages | - red and yellow pages
494 // | |/
495 // +------------------------+ JavaThread::stack_yellow_zone_base()
496 // | |\
497 // | Normal Stack | -
498 // | |/
499 // P2 +------------------------+ Thread::stack_base()
500 //
501 // Non-Java thread:
502 //
503 // Low memory addresses
504 // +------------------------+
505 // | |\
506 // | glibc guard page | - usually 1 page
507 // | |/
508 // P1 +------------------------+ Thread::stack_base() - Thread::stack_size()
509 // | |\
510 // | Normal Stack | -
511 // | |/
512 // P2 +------------------------+ Thread::stack_base()
513 //
514 // ** P1 (aka bottom) and size ( P2 = P1 - size) are the address and stack size returned from
515 // pthread_attr_getstack()
516
517 static void current_stack_region(address * bottom, size_t * size) {
518 if (os::Linux::is_initial_thread()) {
519 // initial thread needs special handling because pthread_getattr_np()
520 // may return bogus value.
521 *bottom = os::Linux::initial_thread_stack_bottom();
522 *size = os::Linux::initial_thread_stack_size();
523 } else {
524 pthread_attr_t attr;
525
526 int rslt = pthread_getattr_np(pthread_self(), &attr);
527
528 // JVM needs to know exact stack location, abort if it fails
529 if (rslt != 0) {
530 if (rslt == ENOMEM) {
531 vm_exit_out_of_memory(0, OOM_MMAP_ERROR, "pthread_getattr_np");
532 } else {
533 fatal("pthread_getattr_np failed with errno = %d", rslt);
534 }
535 }
536
537 if (pthread_attr_getstack(&attr, (void **)bottom, size) != 0) {
538 fatal("Can not locate current stack attributes!");
539 }
540
541 pthread_attr_destroy(&attr);
542
543 }
544 assert(os::current_stack_pointer() >= *bottom &&
545 os::current_stack_pointer() < *bottom + *size, "just checking");
546 }
547
548 address os::current_stack_base() {
549 address bottom;
550 size_t size;
551 current_stack_region(&bottom, &size);
552 return (bottom + size);
553 }
554
555 size_t os::current_stack_size() {
556 // stack size includes normal stack and HotSpot guard pages
557 address bottom;
558 size_t size;
559 current_stack_region(&bottom, &size);
560 return size;
561 }
562
563 /////////////////////////////////////////////////////////////////////////////
564 // helper functions for fatal error handler
565
566 void os::print_context(outputStream *st, void *context) {
567 if (context == NULL) return;
568
569 ucontext_t* uc = (ucontext_t*)context;
570
571 st->print_cr("Registers:");
572 st->print("pc =" INTPTR_FORMAT " ", uc->uc_mcontext.regs->nip);
573 st->print("lr =" INTPTR_FORMAT " ", uc->uc_mcontext.regs->link);
574 st->print("ctr=" INTPTR_FORMAT " ", uc->uc_mcontext.regs->ctr);
575 st->cr();
576 for (int i = 0; i < 32; i++) {
577 st->print("r%-2d=" INTPTR_FORMAT " ", i, uc->uc_mcontext.regs->gpr[i]);
578 if (i % 3 == 2) st->cr();
579 }
580 st->cr();
581 st->cr();
582
583 intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
584 st->print_cr("Top of Stack: (sp=" PTR_FORMAT ")", p2i(sp));
585 print_hex_dump(st, (address)sp, (address)(sp + 128), sizeof(intptr_t));
586 st->cr();
587
588 // Note: it may be unsafe to inspect memory near pc. For example, pc may
589 // point to garbage if entry point in an nmethod is corrupted. Leave
590 // this at the end, and hope for the best.
591 address pc = os::Linux::ucontext_get_pc(uc);
592 st->print_cr("Instructions: (pc=" PTR_FORMAT ")", p2i(pc));
593 print_hex_dump(st, pc - 64, pc + 64, /*instrsize=*/4);
594 st->cr();
595 }
596
597 void os::print_register_info(outputStream *st, void *context) {
598 if (context == NULL) return;
599
600 ucontext_t *uc = (ucontext_t*)context;
601
602 st->print_cr("Register to memory mapping:");
603 st->cr();
604
605 // this is only for the "general purpose" registers
606 for (int i = 0; i < 32; i++) {
607 st->print("r%-2d=", i);
608 print_location(st, uc->uc_mcontext.regs->gpr[i]);
609 }
610 st->cr();
611 }
612
613 extern "C" {
614 int SpinPause() {
615 return 0;
616 }
617 }
618
619 #ifndef PRODUCT
620 void os::verify_stack_alignment() {
621 assert(((intptr_t)os::current_stack_pointer() & (StackAlignmentInBytes-1)) == 0, "incorrect stack alignment");
622 }
623 #endif
624
625 int os::extra_bang_size_in_bytes() {
626 // PPC does not require the additional stack bang.
627 return 0;
628 }