1 /*
   2  * Copyright (c) 2008, 2017, 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 // no precompiled headers
  26 #include "jvm.h"
  27 #include "assembler_arm.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 "memory/allocation.inline.hpp"
  35 #include "nativeInst_arm.hpp"
  36 #include "os_share_linux.hpp"
  37 #include "prims/jniFastGetField.hpp"
  38 #include "prims/jvm_misc.hpp"
  39 #include "runtime/arguments.hpp"
  40 #include "runtime/extendedPC.hpp"
  41 #include "runtime/frame.inline.hpp"
  42 #include "runtime/interfaceSupport.inline.hpp"
  43 #include "runtime/java.hpp"
  44 #include "runtime/javaCalls.hpp"
  45 #include "runtime/mutexLocker.hpp"
  46 #include "runtime/osThread.hpp"
  47 #include "runtime/sharedRuntime.hpp"
  48 #include "runtime/stubRoutines.hpp"
  49 #include "runtime/timer.hpp"
  50 #include "utilities/events.hpp"
  51 #include "utilities/vmError.hpp"
  52 
  53 // put OS-includes here
  54 # include <sys/types.h>
  55 # include <sys/mman.h>
  56 # include <pthread.h>
  57 # include <signal.h>
  58 # include <errno.h>
  59 # include <dlfcn.h>
  60 # include <stdlib.h>
  61 # include <stdio.h>
  62 # include <unistd.h>
  63 # include <sys/resource.h>
  64 # include <pthread.h>
  65 # include <sys/stat.h>
  66 # include <sys/time.h>
  67 # include <sys/utsname.h>
  68 # include <sys/socket.h>
  69 # include <sys/wait.h>
  70 # include <pwd.h>
  71 # include <poll.h>
  72 # include <ucontext.h>
  73 # include <fpu_control.h>
  74 # include <asm/ptrace.h>
  75 
  76 #define SPELL_REG_SP  "sp"
  77 
  78 // Don't #define SPELL_REG_FP for thumb because it is not safe to use, so this makes sure we never fetch it.
  79 #ifndef __thumb__
  80 #define SPELL_REG_FP  AARCH64_ONLY("x29") NOT_AARCH64("fp")
  81 #endif
  82 
  83 address os::current_stack_pointer() {
  84   register address sp __asm__ (SPELL_REG_SP);
  85   return sp;
  86 }
  87 
  88 char* os::non_memory_address_word() {
  89   // Must never look like an address returned by reserve_memory
  90   return (char*) -1;
  91 }
  92 
  93 void os::initialize_thread(Thread* thr) {
  94   // Nothing to do
  95 }
  96 
  97 #ifdef AARCH64
  98 
  99 #define arm_pc pc
 100 #define arm_sp sp
 101 #define arm_fp regs[29]
 102 #define arm_r0 regs[0]
 103 #define ARM_REGS_IN_CONTEXT  31
 104 
 105 #else
 106 
 107 #if NGREG == 16
 108 // These definitions are based on the observation that until
 109 // the certain version of GCC mcontext_t was defined as
 110 // a structure containing gregs[NGREG] array with 16 elements.
 111 // In later GCC versions mcontext_t was redefined as struct sigcontext,
 112 // along with NGREG constant changed to 18.
 113 #define arm_pc gregs[15]
 114 #define arm_sp gregs[13]
 115 #define arm_fp gregs[11]
 116 #define arm_r0 gregs[0]
 117 #endif
 118 
 119 #define ARM_REGS_IN_CONTEXT  16
 120 
 121 #endif // AARCH64
 122 
 123 address os::Linux::ucontext_get_pc(const ucontext_t* uc) {
 124   return (address)uc->uc_mcontext.arm_pc;
 125 }
 126 
 127 void os::Linux::ucontext_set_pc(ucontext_t* uc, address pc) {
 128   uc->uc_mcontext.arm_pc = (uintx)pc;
 129 }
 130 
 131 intptr_t* os::Linux::ucontext_get_sp(const ucontext_t* uc) {
 132   return (intptr_t*)uc->uc_mcontext.arm_sp;
 133 }
 134 
 135 intptr_t* os::Linux::ucontext_get_fp(const ucontext_t* uc) {
 136   return (intptr_t*)uc->uc_mcontext.arm_fp;
 137 }
 138 
 139 bool is_safe_for_fp(address pc) {
 140 #ifdef __thumb__
 141   if (CodeCache::find_blob(pc) != NULL) {
 142     return true;
 143   }
 144   // For thumb C frames, given an fp we have no idea how to access the frame contents.
 145   return false;
 146 #else
 147   // Calling os::address_is_in_vm() here leads to a dladdr call. Calling any libc
 148   // function during os::get_native_stack() can result in a deadlock if JFR is
 149   // enabled. For now, be more lenient and allow all pc's. There are other
 150   // frame sanity checks in shared code, and to date they have been sufficient
 151   // for other platforms.
 152   //return os::address_is_in_vm(pc);
 153   return true;
 154 #endif
 155 }
 156 
 157 // For Forte Analyzer AsyncGetCallTrace profiling support - thread
 158 // is currently interrupted by SIGPROF.
 159 // os::Solaris::fetch_frame_from_ucontext() tries to skip nested signal
 160 // frames. Currently we don't do that on Linux, so it's the same as
 161 // os::fetch_frame_from_context().
 162 ExtendedPC os::Linux::fetch_frame_from_ucontext(Thread* thread,
 163   const ucontext_t* uc, intptr_t** ret_sp, intptr_t** ret_fp) {
 164 
 165   assert(thread != NULL, "just checking");
 166   assert(ret_sp != NULL, "just checking");
 167   assert(ret_fp != NULL, "just checking");
 168 
 169   return os::fetch_frame_from_context(uc, ret_sp, ret_fp);
 170 }
 171 
 172 ExtendedPC os::fetch_frame_from_context(const void* ucVoid,
 173                     intptr_t** ret_sp, intptr_t** ret_fp) {
 174 
 175   ExtendedPC  epc;
 176   const ucontext_t* uc = (const ucontext_t*)ucVoid;
 177 
 178   if (uc != NULL) {
 179     epc = ExtendedPC(os::Linux::ucontext_get_pc(uc));
 180     if (ret_sp) *ret_sp = os::Linux::ucontext_get_sp(uc);
 181     if (ret_fp) {
 182       intptr_t* fp = os::Linux::ucontext_get_fp(uc);
 183 #ifndef __thumb__
 184       if (CodeCache::find_blob(epc.pc()) == NULL) {
 185         // It's a C frame. We need to adjust the fp.
 186         fp += os::C_frame_offset;
 187       }
 188 #endif
 189       // Clear FP when stack walking is dangerous so that
 190       // the frame created will not be walked.
 191       // However, ensure FP is set correctly when reliable and
 192       // potentially necessary.
 193       if (!is_safe_for_fp(epc.pc())) {
 194         // FP unreliable
 195         fp = (intptr_t *)NULL;
 196       }
 197       *ret_fp = fp;
 198     }
 199   } else {
 200     // construct empty ExtendedPC for return value checking
 201     epc = ExtendedPC(NULL);
 202     if (ret_sp) *ret_sp = (intptr_t *)NULL;
 203     if (ret_fp) *ret_fp = (intptr_t *)NULL;
 204   }
 205 
 206   return epc;
 207 }
 208 
 209 frame os::fetch_frame_from_context(const void* ucVoid) {
 210   intptr_t* sp;
 211   intptr_t* fp;
 212   ExtendedPC epc = fetch_frame_from_context(ucVoid, &sp, &fp);
 213   return frame(sp, fp, epc.pc());
 214 }
 215 
 216 frame os::get_sender_for_C_frame(frame* fr) {
 217 #ifdef __thumb__
 218   // We can't reliably get anything from a thumb C frame.
 219   return frame();
 220 #else
 221   address pc = fr->sender_pc();
 222   if (! is_safe_for_fp(pc)) {
 223     return frame(fr->sender_sp(), (intptr_t *)NULL, pc);
 224   } else {
 225     return frame(fr->sender_sp(), fr->link() + os::C_frame_offset, pc);
 226   }
 227 #endif
 228 }
 229 
 230 //
 231 // This actually returns two frames up. It does not return os::current_frame(),
 232 // which is the actual current frame. Nor does it return os::get_native_stack(),
 233 // which is the caller. It returns whoever called os::get_native_stack(). Not
 234 // very intuitive, but consistent with how this API is implemented on other
 235 // platforms.
 236 //
 237 frame os::current_frame() {
 238 #ifdef __thumb__
 239   // We can't reliably get anything from a thumb C frame.
 240   return frame();
 241 #else
 242   register intptr_t* fp __asm__ (SPELL_REG_FP);
 243   // fp is for os::current_frame. We want the fp for our caller.
 244   frame myframe((intptr_t*)os::current_stack_pointer(), fp + os::C_frame_offset,
 245                  CAST_FROM_FN_PTR(address, os::current_frame));
 246   frame caller_frame = os::get_sender_for_C_frame(&myframe);
 247 
 248   if (os::is_first_C_frame(&caller_frame)) {
 249     // stack is not walkable
 250     // Assert below was added because it does not seem like this can ever happen.
 251     // How can this frame ever be the first C frame since it is called from C code?
 252     // If it does ever happen, undo the assert and comment here on when/why it happens.
 253     assert(false, "this should never happen");
 254     return frame();
 255   }
 256 
 257   // return frame for our caller's caller
 258   return os::get_sender_for_C_frame(&caller_frame);
 259 #endif
 260 }
 261 
 262 #ifndef AARCH64
 263 extern "C" address check_vfp_fault_instr;
 264 extern "C" address check_vfp3_32_fault_instr;
 265 
 266 address check_vfp_fault_instr = NULL;
 267 address check_vfp3_32_fault_instr = NULL;
 268 #endif // !AARCH64
 269 extern "C" address check_simd_fault_instr;
 270 address check_simd_fault_instr = NULL;
 271 
 272 // Utility functions
 273 
 274 extern "C" int JVM_handle_linux_signal(int sig, siginfo_t* info,
 275                                        void* ucVoid, int abort_if_unrecognized) {
 276   ucontext_t* uc = (ucontext_t*) ucVoid;
 277 
 278   Thread* t = Thread::current_or_null_safe();
 279 
 280   // Must do this before SignalHandlerMark, if crash protection installed we will longjmp away
 281   // (no destructors can be run)
 282   os::ThreadCrashProtection::check_crash_protection(sig, t);
 283 
 284   SignalHandlerMark shm(t);
 285 
 286   if (sig == SIGILL &&
 287       ((info->si_addr == (caddr_t)check_simd_fault_instr)
 288        NOT_AARCH64(|| info->si_addr == (caddr_t)check_vfp_fault_instr)
 289        NOT_AARCH64(|| info->si_addr == (caddr_t)check_vfp3_32_fault_instr))) {
 290     // skip faulty instruction + instruction that sets return value to
 291     // success and set return value to failure.
 292     os::Linux::ucontext_set_pc(uc, (address)info->si_addr + 8);
 293     uc->uc_mcontext.arm_r0 = 0;
 294     return true;
 295   }
 296 
 297   // Note: it's not uncommon that JNI code uses signal/sigset to install
 298   // then restore certain signal handler (e.g. to temporarily block SIGPIPE,
 299   // or have a SIGILL handler when detecting CPU type). When that happens,
 300   // JVM_handle_linux_signal() might be invoked with junk info/ucVoid. To
 301   // avoid unnecessary crash when libjsig is not preloaded, try handle signals
 302   // that do not require siginfo/ucontext first.
 303 
 304   if (sig == SIGPIPE || sig == SIGXFSZ) {
 305     // allow chained handler to go first
 306     if (os::Linux::chained_handler(sig, info, ucVoid)) {
 307       return true;
 308     } else {
 309       // Ignoring SIGPIPE/SIGXFSZ - see bugs 4229104 or 6499219
 310       return true;
 311     }
 312   }
 313 
 314   JavaThread* thread = NULL;
 315   VMThread* vmthread = NULL;
 316   if (os::Linux::signal_handlers_are_installed) {
 317     if (t != NULL ){
 318       if(t->is_Java_thread()) {
 319         thread = (JavaThread*)t;
 320       }
 321       else if(t->is_VM_thread()){
 322         vmthread = (VMThread *)t;
 323       }
 324     }
 325   }
 326 
 327   address stub = NULL;
 328   address pc = NULL;
 329   bool unsafe_access = false;
 330 
 331   if (info != NULL && uc != NULL && thread != NULL) {
 332     pc = (address) os::Linux::ucontext_get_pc(uc);
 333 
 334     // Handle ALL stack overflow variations here
 335     if (sig == SIGSEGV) {
 336       address addr = (address) info->si_addr;
 337 
 338       if (StubRoutines::is_safefetch_fault(pc)) {
 339         os::Linux::ucontext_set_pc(uc, StubRoutines::continuation_for_safefetch_fault(pc));
 340         return 1;
 341       }
 342       // check if fault address is within thread stack
 343       if (addr < thread->stack_base() &&
 344           addr >= thread->stack_base() - thread->stack_size()) {
 345         // stack overflow
 346         if (thread->in_stack_yellow_reserved_zone(addr)) {
 347           thread->disable_stack_yellow_reserved_zone();
 348           if (thread->thread_state() == _thread_in_Java) {
 349             // Throw a stack overflow exception.  Guard pages will be reenabled
 350             // while unwinding the stack.
 351             stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::STACK_OVERFLOW);
 352           } else {
 353             // Thread was in the vm or native code.  Return and try to finish.
 354             return 1;
 355           }
 356         } else if (thread->in_stack_red_zone(addr)) {
 357           // Fatal red zone violation.  Disable the guard pages and fall through
 358           // to handle_unexpected_exception way down below.
 359           thread->disable_stack_red_zone();
 360           tty->print_raw_cr("An irrecoverable stack overflow has occurred.");
 361         } else {
 362           // Accessing stack address below sp may cause SEGV if current
 363           // thread has MAP_GROWSDOWN stack. This should only happen when
 364           // current thread was created by user code with MAP_GROWSDOWN flag
 365           // and then attached to VM. See notes in os_linux.cpp.
 366           if (thread->osthread()->expanding_stack() == 0) {
 367              thread->osthread()->set_expanding_stack();
 368              if (os::Linux::manually_expand_stack(thread, addr)) {
 369                thread->osthread()->clear_expanding_stack();
 370                return 1;
 371              }
 372              thread->osthread()->clear_expanding_stack();
 373           } else {
 374              fatal("recursive segv. expanding stack.");
 375           }
 376         }
 377       }
 378     }
 379 
 380     if (thread->thread_state() == _thread_in_Java) {
 381       // Java thread running in Java code => find exception handler if any
 382       // a fault inside compiled code, the interpreter, or a stub
 383 
 384       if (sig == SIGSEGV && os::is_poll_address((address)info->si_addr)) {
 385         stub = SharedRuntime::get_poll_stub(pc);
 386       } else if (sig == SIGBUS) {
 387         // BugId 4454115: A read from a MappedByteBuffer can fault
 388         // here if the underlying file has been truncated.
 389         // Do not crash the VM in such a case.
 390         CodeBlob* cb = CodeCache::find_blob_unsafe(pc);
 391         CompiledMethod* nm = (cb != NULL) ? cb->as_compiled_method_or_null() : NULL;
 392         if (nm != NULL && nm->has_unsafe_access()) {
 393           unsafe_access = true;
 394         }
 395       } else if (sig == SIGSEGV && !MacroAssembler::needs_explicit_null_check((intptr_t)info->si_addr)) {
 396           // Determination of interpreter/vtable stub/compiled code null exception
 397           CodeBlob* cb = CodeCache::find_blob_unsafe(pc);
 398           if (cb != NULL) {
 399             stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
 400           }
 401       } else if (sig == SIGILL && *(int *)pc == NativeInstruction::zombie_illegal_instruction) {
 402         // Zombie
 403         stub = SharedRuntime::get_handle_wrong_method_stub();
 404       }
 405     } else if (thread->thread_state() == _thread_in_vm &&
 406                sig == SIGBUS && thread->doing_unsafe_access()) {
 407         unsafe_access = true;
 408     }
 409 
 410     // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in
 411     // and the heap gets shrunk before the field access.
 412     if (sig == SIGSEGV || sig == SIGBUS) {
 413       address addr = JNI_FastGetField::find_slowcase_pc(pc);
 414       if (addr != (address)-1) {
 415         stub = addr;
 416       }
 417     }
 418 
 419     // Check to see if we caught the safepoint code in the
 420     // process of write protecting the memory serialization page.
 421     // It write enables the page immediately after protecting it
 422     // so we can just return to retry the write.
 423     if (sig == SIGSEGV && os::is_memory_serialize_page(thread, (address) info->si_addr)) {
 424       // Block current thread until the memory serialize page permission restored.
 425       os::block_on_serialize_page_trap();
 426       return true;
 427     }
 428   }
 429 
 430   if (unsafe_access && stub == NULL) {
 431     // it can be an unsafe access and we haven't found
 432     // any other suitable exception reason,
 433     // so assume it is an unsafe access.
 434     address next_pc = pc + Assembler::InstructionSize;
 435 #ifdef __thumb__
 436     if (uc->uc_mcontext.arm_cpsr & PSR_T_BIT) {
 437       next_pc = (address)((intptr_t)next_pc | 0x1);
 438     }
 439 #endif
 440 
 441     stub = SharedRuntime::handle_unsafe_access(thread, next_pc);
 442   }
 443 
 444   if (stub != NULL) {
 445 #ifdef __thumb__
 446     if (uc->uc_mcontext.arm_cpsr & PSR_T_BIT) {
 447       intptr_t p = (intptr_t)pc | 0x1;
 448       pc = (address)p;
 449 
 450       // Clear Thumb mode bit if we're redirected into the ARM ISA based code
 451       if (((intptr_t)stub & 0x1) == 0) {
 452         uc->uc_mcontext.arm_cpsr &= ~PSR_T_BIT;
 453       }
 454     } else {
 455       // No Thumb2 compiled stubs are triggered from ARM ISA compiled JIT'd code today.
 456       // The support needs to be added if that changes
 457       assert((((intptr_t)stub & 0x1) == 0), "can't return to Thumb code");
 458     }
 459 #endif
 460 
 461     // save all thread context in case we need to restore it
 462     if (thread != NULL) thread->set_saved_exception_pc(pc);
 463 
 464     os::Linux::ucontext_set_pc(uc, stub);
 465     return true;
 466   }
 467 
 468   // signal-chaining
 469   if (os::Linux::chained_handler(sig, info, ucVoid)) {
 470      return true;
 471   }
 472 
 473   if (!abort_if_unrecognized) {
 474     // caller wants another chance, so give it to him
 475     return false;
 476   }
 477 
 478   if (pc == NULL && uc != NULL) {
 479     pc = os::Linux::ucontext_get_pc(uc);
 480   }
 481 
 482   // unmask current signal
 483   sigset_t newset;
 484   sigemptyset(&newset);
 485   sigaddset(&newset, sig);
 486   sigprocmask(SIG_UNBLOCK, &newset, NULL);
 487 
 488   VMError::report_and_die(t, sig, pc, info, ucVoid);
 489 
 490   ShouldNotReachHere();
 491   return false;
 492 }
 493 
 494 void os::Linux::init_thread_fpu_state(void) {
 495   os::setup_fpu();
 496 }
 497 
 498 int os::Linux::get_fpu_control_word(void) {
 499   return 0;
 500 }
 501 
 502 void os::Linux::set_fpu_control_word(int fpu_control) {
 503   // Nothing to do
 504 }
 505 
 506 void os::setup_fpu() {
 507 #ifdef AARCH64
 508   __asm__ volatile ("msr fpcr, xzr");
 509 #else
 510 #if !defined(__SOFTFP__) && defined(__VFP_FP__)
 511   // Turn on IEEE-754 compliant VFP mode
 512   __asm__ volatile (
 513     "mov %%r0, #0;"
 514     "fmxr fpscr, %%r0"
 515     : /* no output */ : /* no input */ : "r0"
 516   );
 517 #endif
 518 #endif // AARCH64
 519 }
 520 
 521 bool os::is_allocatable(size_t bytes) {
 522   return true;
 523 }
 524 
 525 ////////////////////////////////////////////////////////////////////////////////
 526 // thread stack
 527 
 528 // Minimum usable stack sizes required to get to user code. Space for
 529 // HotSpot guard pages is added later.
 530 size_t os::Posix::_compiler_thread_min_stack_allowed = (32 DEBUG_ONLY(+ 4)) * K;
 531 size_t os::Posix::_java_thread_min_stack_allowed = (32 DEBUG_ONLY(+ 4)) * K;
 532 size_t os::Posix::_vm_internal_thread_min_stack_allowed = (48 DEBUG_ONLY(+ 4)) * K;
 533 
 534 // return default stack size for thr_type
 535 size_t os::Posix::default_stack_size(os::ThreadType thr_type) {
 536   // default stack size (compiler thread needs larger stack)
 537   size_t s = (thr_type == os::compiler_thread ? 2 * M : 512 * K);
 538   return s;
 539 }
 540 
 541 /////////////////////////////////////////////////////////////////////////////
 542 // helper functions for fatal error handler
 543 
 544 void os::print_context(outputStream *st, const void *context) {
 545   if (context == NULL) return;
 546   const ucontext_t *uc = (const ucontext_t*)context;
 547 
 548   st->print_cr("Registers:");
 549   intx* reg_area = (intx*)&uc->uc_mcontext.arm_r0;
 550   for (int r = 0; r < ARM_REGS_IN_CONTEXT; r++) {
 551     st->print_cr("  %-3s = " INTPTR_FORMAT, as_Register(r)->name(), reg_area[r]);
 552   }
 553 #define U64_FORMAT "0x%016llx"
 554 #ifdef AARCH64
 555   st->print_cr("  %-3s = " U64_FORMAT, "sp", uc->uc_mcontext.sp);
 556   st->print_cr("  %-3s = " U64_FORMAT, "pc", uc->uc_mcontext.pc);
 557   st->print_cr("  %-3s = " U64_FORMAT, "pstate", uc->uc_mcontext.pstate);
 558 #else
 559   // now print flag register
 560   st->print_cr("  %-4s = 0x%08lx", "cpsr",uc->uc_mcontext.arm_cpsr);
 561 #endif
 562   st->cr();
 563 
 564   intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
 565   st->print_cr("Top of Stack: (sp=" INTPTR_FORMAT ")", p2i(sp));
 566   print_hex_dump(st, (address)sp, (address)(sp + 8*sizeof(intptr_t)), sizeof(intptr_t));
 567   st->cr();
 568 
 569   // Note: it may be unsafe to inspect memory near pc. For example, pc may
 570   // point to garbage if entry point in an nmethod is corrupted. Leave
 571   // this at the end, and hope for the best.
 572   address pc = os::Linux::ucontext_get_pc(uc);
 573   st->print_cr("Instructions: (pc=" INTPTR_FORMAT ")", p2i(pc));
 574   print_hex_dump(st, pc - 32, pc + 32, Assembler::InstructionSize);
 575 }
 576 
 577 void os::print_register_info(outputStream *st, const void *context) {
 578   if (context == NULL) return;
 579 
 580   const ucontext_t *uc = (const ucontext_t*)context;
 581   intx* reg_area = (intx*)&uc->uc_mcontext.arm_r0;
 582 
 583   st->print_cr("Register to memory mapping:");
 584   st->cr();
 585   for (int r = 0; r < ARM_REGS_IN_CONTEXT; r++) {
 586     st->print_cr("  %-3s = " INTPTR_FORMAT, as_Register(r)->name(), reg_area[r]);
 587     print_location(st, reg_area[r]);
 588     st->cr();
 589   }
 590 #ifdef AARCH64
 591   st->print_cr("  %-3s = " U64_FORMAT, "pc", uc->uc_mcontext.pc);
 592   print_location(st, uc->uc_mcontext.pc);
 593   st->cr();
 594 #endif
 595   st->cr();
 596 }
 597 
 598 
 599 #ifndef AARCH64
 600 
 601 typedef int64_t cmpxchg_long_func_t(int64_t, int64_t, volatile int64_t*);
 602 
 603 cmpxchg_long_func_t* os::atomic_cmpxchg_long_func = os::atomic_cmpxchg_long_bootstrap;
 604 
 605 int64_t os::atomic_cmpxchg_long_bootstrap(int64_t compare_value, int64_t exchange_value, volatile int64_t* dest) {
 606   // try to use the stub:
 607   cmpxchg_long_func_t* func = CAST_TO_FN_PTR(cmpxchg_long_func_t*, StubRoutines::atomic_cmpxchg_long_entry());
 608 
 609   if (func != NULL) {
 610     os::atomic_cmpxchg_long_func = func;
 611     return (*func)(compare_value, exchange_value, dest);
 612   }
 613   assert(Threads::number_of_threads() == 0, "for bootstrap only");
 614 
 615   int64_t old_value = *dest;
 616   if (old_value == compare_value)
 617     *dest = exchange_value;
 618   return old_value;
 619 }
 620 typedef int64_t load_long_func_t(const volatile int64_t*);
 621 
 622 load_long_func_t* os::atomic_load_long_func = os::atomic_load_long_bootstrap;
 623 
 624 int64_t os::atomic_load_long_bootstrap(const volatile int64_t* src) {
 625   // try to use the stub:
 626   load_long_func_t* func = CAST_TO_FN_PTR(load_long_func_t*, StubRoutines::atomic_load_long_entry());
 627 
 628   if (func != NULL) {
 629     os::atomic_load_long_func = func;
 630     return (*func)(src);
 631   }
 632   assert(Threads::number_of_threads() == 0, "for bootstrap only");
 633 
 634   int64_t old_value = *src;
 635   return old_value;
 636 }
 637 
 638 typedef void store_long_func_t(int64_t, volatile int64_t*);
 639 
 640 store_long_func_t* os::atomic_store_long_func = os::atomic_store_long_bootstrap;
 641 
 642 void os::atomic_store_long_bootstrap(int64_t val, volatile int64_t* dest) {
 643   // try to use the stub:
 644   store_long_func_t* func = CAST_TO_FN_PTR(store_long_func_t*, StubRoutines::atomic_store_long_entry());
 645 
 646   if (func != NULL) {
 647     os::atomic_store_long_func = func;
 648     return (*func)(val, dest);
 649   }
 650   assert(Threads::number_of_threads() == 0, "for bootstrap only");
 651 
 652   *dest = val;
 653 }
 654 
 655 typedef int32_t  atomic_add_func_t(int32_t add_value, volatile int32_t *dest);
 656 
 657 atomic_add_func_t * os::atomic_add_func = os::atomic_add_bootstrap;
 658 
 659 int32_t  os::atomic_add_bootstrap(int32_t add_value, volatile int32_t *dest) {
 660   atomic_add_func_t * func = CAST_TO_FN_PTR(atomic_add_func_t*,
 661                                             StubRoutines::atomic_add_entry());
 662   if (func != NULL) {
 663     os::atomic_add_func = func;
 664     return (*func)(add_value, dest);
 665   }
 666 
 667   int32_t old_value = *dest;
 668   *dest = old_value + add_value;
 669   return (old_value + add_value);
 670 }
 671 
 672 typedef int32_t  atomic_xchg_func_t(int32_t exchange_value, volatile int32_t *dest);
 673 
 674 atomic_xchg_func_t * os::atomic_xchg_func = os::atomic_xchg_bootstrap;
 675 
 676 int32_t  os::atomic_xchg_bootstrap(int32_t exchange_value, volatile int32_t *dest) {
 677   atomic_xchg_func_t * func = CAST_TO_FN_PTR(atomic_xchg_func_t*,
 678                                             StubRoutines::atomic_xchg_entry());
 679   if (func != NULL) {
 680     os::atomic_xchg_func = func;
 681     return (*func)(exchange_value, dest);
 682   }
 683 
 684   int32_t old_value = *dest;
 685   *dest = exchange_value;
 686   return (old_value);
 687 }
 688 
 689 typedef int32_t cmpxchg_func_t(int32_t, int32_t, volatile int32_t*);
 690 
 691 cmpxchg_func_t* os::atomic_cmpxchg_func = os::atomic_cmpxchg_bootstrap;
 692 
 693 int32_t os::atomic_cmpxchg_bootstrap(int32_t compare_value, int32_t exchange_value, volatile int32_t* dest) {
 694   // try to use the stub:
 695   cmpxchg_func_t* func = CAST_TO_FN_PTR(cmpxchg_func_t*, StubRoutines::atomic_cmpxchg_entry());
 696 
 697   if (func != NULL) {
 698     os::atomic_cmpxchg_func = func;
 699     return (*func)(compare_value, exchange_value, dest);
 700   }
 701   assert(Threads::number_of_threads() == 0, "for bootstrap only");
 702 
 703   int32_t old_value = *dest;
 704   if (old_value == compare_value)
 705     *dest = exchange_value;
 706   return old_value;
 707 }
 708 
 709 #endif // !AARCH64
 710 
 711 #ifndef PRODUCT
 712 void os::verify_stack_alignment() {
 713 }
 714 #endif
 715 
 716 int os::extra_bang_size_in_bytes() {
 717   // ARM does not require an additional stack bang.
 718   return 0;
 719 }
 720