/*
 * Copyright (c) 1999, 2026, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2014, Red Hat Inc. All rights reserved.
 * Copyright (c) 2021, Azul Systems, Inc. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#include "asm/macroAssembler.hpp"
#include "classfile/classLoader.hpp"
#include "classfile/vmSymbols.hpp"
#include "code/codeCache.hpp"
#include "code/vtableStubs.hpp"
#include "cppstdlib/cstdlib.hpp"
#include "interpreter/interpreter.hpp"
#include "jvm.h"
#include "logging/log.hpp"
#include "memory/allocation.inline.hpp"
#include "os_bsd.hpp"
#include "os_posix.hpp"
#include "prims/jniFastGetField.hpp"
#include "prims/jvm_misc.hpp"
#include "runtime/arguments.hpp"
#include "runtime/frame.inline.hpp"
#include "runtime/interfaceSupport.inline.hpp"
#include "runtime/java.hpp"
#include "runtime/javaCalls.hpp"
#include "runtime/javaThread.hpp"
#include "runtime/mutexLocker.hpp"
#include "runtime/osThread.hpp"
#include "runtime/safepointMechanism.hpp"
#include "runtime/sharedRuntime.hpp"
#include "runtime/stubRoutines.hpp"
#include "runtime/timer.hpp"
#include "runtime/vm_version.hpp"
#include "signals_posix.hpp"
#include "utilities/align.hpp"
#include "utilities/debug.hpp"
#include "utilities/decoder.hpp"
#include "utilities/events.hpp"
#include "utilities/nativeStackPrinter.hpp"
#include "utilities/vmError.hpp"
#include "compiler/disassembler.hpp"

// put OS-includes here
# include <sys/types.h>
# include <sys/mman.h>
# include <pthread.h>
# include <signal.h>
# include <errno.h>
# include <dlfcn.h>
# include <stdio.h>
# include <unistd.h>
# include <sys/resource.h>
# include <sys/stat.h>
# include <sys/time.h>
# include <sys/utsname.h>
# include <sys/socket.h>
# include <sys/wait.h>
# include <pwd.h>
# include <poll.h>
#ifndef __OpenBSD__
# include <ucontext.h>
#endif

#define SPELL_REG_SP "sp"

#ifdef __APPLE__
WXMode DefaultWXWriteMode;

// see darwin-xnu/osfmk/mach/arm/_structs.h

// 10.5 UNIX03 member name prefixes
#define DU3_PREFIX(s, m) __ ## s.__ ## m

#define context_x    uc_mcontext->DU3_PREFIX(ss,x)
#define context_fp   uc_mcontext->DU3_PREFIX(ss,fp)
#define context_lr   uc_mcontext->DU3_PREFIX(ss,lr)
#define context_sp   uc_mcontext->DU3_PREFIX(ss,sp)
#define context_pc   uc_mcontext->DU3_PREFIX(ss,pc)
#define context_cpsr uc_mcontext->DU3_PREFIX(ss,cpsr)
#define context_esr  uc_mcontext->DU3_PREFIX(es,esr)
#endif

#ifdef __FreeBSD__
# define context_x  uc_mcontext.mc_gpregs.gp_x
# define context_fp context_x[REG_FP]
# define context_lr uc_mcontext.mc_gpregs.gp_lr
# define context_sp uc_mcontext.mc_gpregs.gp_sp
# define context_pc uc_mcontext.mc_gpregs.gp_elr
#endif

#ifdef __NetBSD__
# define context_x  uc_mcontext.__gregs
# define context_fp uc_mcontext.__gregs[_REG_FP]
# define context_lr uc_mcontext.__gregs[_REG_LR]
# define context_sp uc_mcontext.__gregs[_REG_SP]
# define context_pc uc_mcontext.__gregs[_REG_ELR]
#endif

#ifdef __OpenBSD__
# define context_x  sc_x
# define context_fp sc_x[REG_FP]
# define context_lr sc_lr
# define context_sp sc_sp
# define context_pc sc_elr
#endif

#define REG_BCP context_x[22]

address os::current_stack_pointer() {
#if defined(__clang__) || defined(__llvm__)
  void *sp;
  __asm__("mov %0, " SPELL_REG_SP : "=r"(sp));
  return (address) sp;
#else
  register void *sp __asm__ (SPELL_REG_SP);
  return (address) sp;
#endif
}

char* os::non_memory_address_word() {
  // Must never look like an address returned by reserve_memory,
  // even in its subfields (as defined by the CPU immediate fields,
  // if the CPU splits constants across multiple instructions).

  // the return value used in computation of Universe::non_oop_word(), which
  // is loaded by cpu/aarch64 by MacroAssembler::movptr(Register, uintptr_t)
  return (char*) 0xffffffffffff;
}

address os::Posix::ucontext_get_pc(const ucontext_t * uc) {
  return (address)uc->context_pc;
}

void os::Posix::ucontext_set_pc(ucontext_t * uc, address pc) {
  uc->context_pc = (intptr_t)pc ;
}

intptr_t* os::Bsd::ucontext_get_sp(const ucontext_t * uc) {
  return (intptr_t*)uc->context_sp;
}

intptr_t* os::Bsd::ucontext_get_fp(const ucontext_t * uc) {
  return (intptr_t*)uc->context_fp;
}

address os::fetch_frame_from_context(const void* ucVoid,
                    intptr_t** ret_sp, intptr_t** ret_fp) {

  address epc;
  const ucontext_t* uc = (const ucontext_t*)ucVoid;

  if (uc != nullptr) {
    epc = os::Posix::ucontext_get_pc(uc);
    if (ret_sp) *ret_sp = os::Bsd::ucontext_get_sp(uc);
    if (ret_fp) *ret_fp = os::Bsd::ucontext_get_fp(uc);
  } else {
    epc = nullptr;
    if (ret_sp) *ret_sp = (intptr_t *)nullptr;
    if (ret_fp) *ret_fp = (intptr_t *)nullptr;
  }

  return epc;
}

frame os::fetch_frame_from_context(const void* ucVoid) {
  intptr_t* sp;
  intptr_t* fp;
  address epc = fetch_frame_from_context(ucVoid, &sp, &fp);
  if (!is_readable_pointer(epc)) {
    // Try to recover from calling into bad memory
    // Assume new frame has not been set up, the same as
    // compiled frame stack bang
    return fetch_compiled_frame_from_context(ucVoid);
  }
  return frame(sp, fp, epc);
}

frame os::fetch_compiled_frame_from_context(const void* ucVoid) {
  const ucontext_t* uc = (const ucontext_t*)ucVoid;
  // In compiled code, the stack banging is performed before LR
  // has been saved in the frame.  LR is live, and SP and FP
  // belong to the caller.
  intptr_t* fp = os::Bsd::ucontext_get_fp(uc);
  intptr_t* sp = os::Bsd::ucontext_get_sp(uc);
  address pc = (address)(uc->context_lr
                         - NativeInstruction::instruction_size);
  return frame(sp, fp, pc);
}

intptr_t* os::fetch_bcp_from_context(const void* ucVoid) {
  assert(ucVoid != nullptr, "invariant");
  const ucontext_t* uc = (const ucontext_t*)ucVoid;
  assert(os::Posix::ucontext_is_interpreter(uc), "invariant");
  return reinterpret_cast<intptr_t*>(uc->REG_BCP);
}

// JVM compiled with -fno-omit-frame-pointer, so RFP is saved on the stack.
frame os::get_sender_for_C_frame(frame* fr) {
  return frame(fr->sender_sp(), fr->link(), fr->sender_pc());
}

NOINLINE frame os::current_frame() {
  intptr_t *fp = *(intptr_t **)__builtin_frame_address(0);
  frame myframe((intptr_t*)os::current_stack_pointer(),
                (intptr_t*)fp,
                CAST_FROM_FN_PTR(address, os::current_frame));
  if (os::is_first_C_frame(&myframe)) {
    // stack is not walkable
    return frame();
  } else {
    return os::get_sender_for_C_frame(&myframe);
  }
}

bool PosixSignals::pd_hotspot_signal_handler(int sig, siginfo_t* info,
                                             ucontext_t* uc, JavaThread* thread) {
  // decide if this trap can be handled by a stub
  address stub = nullptr;
  address pc   = nullptr;

  //%note os_trap_1
  if (info != nullptr && uc != nullptr && thread != nullptr) {
    pc = (address) os::Posix::ucontext_get_pc(uc);

#ifdef MACOS_AARCH64
    // If we got a SIGBUS because we tried to write into the code
    // cache, try enabling WXWrite mode.
    if (sig == SIGBUS
        && pc != info->si_addr
        && CodeCache::contains(info->si_addr)
        && os::address_is_in_vm(pc)) {
      WXMode *entry_mode = thread->_cur_wx_mode;
      if (entry_mode != nullptr && *entry_mode == WXArmedForWrite) {
        if (TraceWXHealing) {
          static const char *mode_names[3] = {"WXWrite", "WXExec", "WXArmedForWrite"};
          tty->print("Healing WXMode %s at %p to WXWrite",
                        mode_names[*entry_mode], entry_mode);
          char name[128];
          int offset = 0;
          if (os::dll_address_to_function_name(pc, name, sizeof name, &offset)) {
            tty->print_cr("  (%s+0x%x)", name, offset);
          } else {
            tty->cr();
          }
          if (Verbose) {
            char buf[O_BUFLEN];
            NativeStackPrinter nsp(thread);
            nsp.print_stack(tty, buf, sizeof(buf), pc,
                            true /* print_source_info */, -1 /* max stack */);
          }
        }
#ifndef PRODUCT
        guarantee(StressWXHealing,
                  "We should not reach here unless StressWXHealing");
#endif
        *(thread->_cur_wx_mode) = WXWrite;
        return thread->wx_enable_write();
      }
    }

    // There may be cases where code after this point that we call
    // from the signal handler changes WX state, so we protect against
    // that by saving and restoring the state.
    ThreadWXEnable wx(thread->get_wx_state(), thread);
#endif

    // Handle ALL stack overflow variations here
    if (sig == SIGSEGV || sig == SIGBUS) {
      address addr = (address) info->si_addr;

      // Make sure the high order byte is sign extended, as it may be masked away by the hardware.
      if ((uintptr_t(addr) & (uintptr_t(1) << 55)) != 0) {
        addr = address(uintptr_t(addr) | (uintptr_t(0xFF) << 56));
      }

      // check if fault address is within thread stack
      if (thread->is_in_full_stack(addr)) {
        // stack overflow
        if (os::Posix::handle_stack_overflow(thread, addr, pc, uc, &stub)) {
          return true; // continue
        }
      }
    }

    // We test if stub is already set (by the stack overflow code
    // above) so it is not overwritten by the code that follows. This
    // check is not required on other platforms, because on other
    // platforms we check for SIGSEGV only or SIGBUS only, where here
    // we have to check for both SIGSEGV and SIGBUS.
    if (thread->thread_state() == _thread_in_Java && stub == nullptr) {
      // Java thread running in Java code => find exception handler if any
      // a fault inside compiled code, the interpreter, or a stub

      if ((sig == SIGSEGV || sig == SIGBUS) && SafepointMechanism::is_poll_address((address)info->si_addr)) {
        stub = SharedRuntime::get_poll_stub(pc);
#if defined(__APPLE__)
      // 32-bit Darwin reports a SIGBUS for nearly all memory access exceptions.
      // 64-bit Darwin may also use a SIGBUS (seen with compressed oops).
      // Catching SIGBUS here prevents the implicit SIGBUS null check below from
      // being called, so only do so if the implicit null check is not necessary.
      } else if (sig == SIGBUS && !MacroAssembler::uses_implicit_null_check(info->si_addr)) {
#else
      } else if (sig == SIGBUS /* && info->si_code == BUS_OBJERR */) {
#endif
        // BugId 4454115: A read from a MappedByteBuffer can fault
        // here if the underlying file has been truncated.
        // Do not crash the VM in such a case.
        CodeBlob* cb = CodeCache::find_blob(pc);
        nmethod* nm = (cb != nullptr) ? cb->as_nmethod_or_null() : nullptr;
        bool is_unsafe_memory_access = (thread->doing_unsafe_access() && UnsafeMemoryAccess::contains_pc(pc));
        if ((nm != nullptr && nm->has_unsafe_access()) || is_unsafe_memory_access) {
          address next_pc = pc + NativeCall::instruction_size;
          if (is_unsafe_memory_access) {
            next_pc = UnsafeMemoryAccess::page_error_continue_pc(pc);
          }
          stub = SharedRuntime::handle_unsafe_access(thread, next_pc);
        }
      } else if (sig == SIGILL && nativeInstruction_at(pc)->is_stop()) {
        // A pointer to the message will have been placed in r0
        const char *detail_msg = (const char *)(uc->uc_mcontext->DU3_PREFIX(ss,x[0]));
        const char *msg = "stop";
        if (TraceTraps) {
          tty->print_cr("trap: %s: (SIGILL)", msg);
        }

        // End life with a fatal error, message and detail message and the context.
        // Note: no need to do any post-processing here (e.g. signal chaining)
        VMError::report_and_die(thread, uc, nullptr, 0, msg, "%s", detail_msg);
        ShouldNotReachHere();

      } else if (sig == SIGFPE &&
          (info->si_code == FPE_INTDIV || info->si_code == FPE_FLTDIV)) {
        stub =
          SharedRuntime::
          continuation_for_implicit_exception(thread,
                                              pc,
                                              SharedRuntime::
                                              IMPLICIT_DIVIDE_BY_ZERO);
      } else if ((sig == SIGSEGV || sig == SIGBUS) &&
                 MacroAssembler::uses_implicit_null_check(info->si_addr)) {
          // Determination of interpreter/vtable stub/compiled code null exception
          stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
      }
    } else if ((thread->thread_state() == _thread_in_vm ||
                 thread->thread_state() == _thread_in_native) &&
               sig == SIGBUS && /* info->si_code == BUS_OBJERR && */
               thread->doing_unsafe_access()) {
      address next_pc = pc + NativeCall::instruction_size;
      if (UnsafeMemoryAccess::contains_pc(pc)) {
        next_pc = UnsafeMemoryAccess::page_error_continue_pc(pc);
      }
      stub = SharedRuntime::handle_unsafe_access(thread, next_pc);
    }

    // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in
    // and the heap gets shrunk before the field access.
    if ((sig == SIGSEGV) || (sig == SIGBUS)) {
      address addr = JNI_FastGetField::find_slowcase_pc(pc);
      if (addr != (address)-1) {
        stub = addr;
      }
    }
  }

  if (stub != nullptr) {
    // save all thread context in case we need to restore it
    if (thread != nullptr) thread->set_saved_exception_pc(pc);

    os::Posix::ucontext_set_pc(uc, stub);
    return true;
  }

  return false; // Mute compiler
}

void os::Bsd::init_thread_fpu_state(void) {
}

////////////////////////////////////////////////////////////////////////////////
// thread stack

// Minimum usable stack sizes required to get to user code. Space for
// HotSpot guard pages is added later.
size_t os::_compiler_thread_min_stack_allowed = 72 * K;
size_t os::_java_thread_min_stack_allowed = 72 * K;
size_t os::_vm_internal_thread_min_stack_allowed = 72 * K;

// return default stack size for thr_type
size_t os::Posix::default_stack_size(os::ThreadType thr_type) {
  // default stack size (compiler thread needs larger stack)
  size_t s = (thr_type == os::compiler_thread ? 4 * M : 1 * M);
  return s;
}

/////////////////////////////////////////////////////////////////////////////
// helper functions for fatal error handler

void os::print_context(outputStream *st, const void *context) {
  if (context == nullptr) return;

  const ucontext_t *uc = (const ucontext_t*)context;

  st->print_cr("Registers:");
  st->print( " x0=" INTPTR_FORMAT, (intptr_t)uc->context_x[ 0]);
  st->print("  x1=" INTPTR_FORMAT, (intptr_t)uc->context_x[ 1]);
  st->print("  x2=" INTPTR_FORMAT, (intptr_t)uc->context_x[ 2]);
  st->print("  x3=" INTPTR_FORMAT, (intptr_t)uc->context_x[ 3]);
  st->cr();
  st->print( " x4=" INTPTR_FORMAT, (intptr_t)uc->context_x[ 4]);
  st->print("  x5=" INTPTR_FORMAT, (intptr_t)uc->context_x[ 5]);
  st->print("  x6=" INTPTR_FORMAT, (intptr_t)uc->context_x[ 6]);
  st->print("  x7=" INTPTR_FORMAT, (intptr_t)uc->context_x[ 7]);
  st->cr();
  st->print( " x8=" INTPTR_FORMAT, (intptr_t)uc->context_x[ 8]);
  st->print("  x9=" INTPTR_FORMAT, (intptr_t)uc->context_x[ 9]);
  st->print(" x10=" INTPTR_FORMAT, (intptr_t)uc->context_x[10]);
  st->print(" x11=" INTPTR_FORMAT, (intptr_t)uc->context_x[11]);
  st->cr();
  st->print( "x12=" INTPTR_FORMAT, (intptr_t)uc->context_x[12]);
  st->print(" x13=" INTPTR_FORMAT, (intptr_t)uc->context_x[13]);
  st->print(" x14=" INTPTR_FORMAT, (intptr_t)uc->context_x[14]);
  st->print(" x15=" INTPTR_FORMAT, (intptr_t)uc->context_x[15]);
  st->cr();
  st->print( "x16=" INTPTR_FORMAT, (intptr_t)uc->context_x[16]);
  st->print(" x17=" INTPTR_FORMAT, (intptr_t)uc->context_x[17]);
  st->print(" x18=" INTPTR_FORMAT, (intptr_t)uc->context_x[18]);
  st->print(" x19=" INTPTR_FORMAT, (intptr_t)uc->context_x[19]);
  st->cr();
  st->print( "x20=" INTPTR_FORMAT, (intptr_t)uc->context_x[20]);
  st->print(" x21=" INTPTR_FORMAT, (intptr_t)uc->context_x[21]);
  st->print(" x22=" INTPTR_FORMAT, (intptr_t)uc->context_x[22]);
  st->print(" x23=" INTPTR_FORMAT, (intptr_t)uc->context_x[23]);
  st->cr();
  st->print( "x24=" INTPTR_FORMAT, (intptr_t)uc->context_x[24]);
  st->print(" x25=" INTPTR_FORMAT, (intptr_t)uc->context_x[25]);
  st->print(" x26=" INTPTR_FORMAT, (intptr_t)uc->context_x[26]);
  st->print(" x27=" INTPTR_FORMAT, (intptr_t)uc->context_x[27]);
  st->cr();
  st->print( "x28=" INTPTR_FORMAT, (intptr_t)uc->context_x[28]);
  st->print("  fp=" INTPTR_FORMAT, (intptr_t)uc->context_fp);
  st->print("  lr=" INTPTR_FORMAT, (intptr_t)uc->context_lr);
  st->print("  sp=" INTPTR_FORMAT, (intptr_t)uc->context_sp);
  st->cr();
  st->print(  "pc=" INTPTR_FORMAT,  (intptr_t)uc->context_pc);
  st->print(" cpsr=" INTPTR_FORMAT, (intptr_t)uc->context_cpsr);
  st->cr();
}

void os::print_register_info(outputStream *st, const void *context, int& continuation) {
  const int register_count = 29 /* x0-x28 */ + 3 /* fp, lr, sp */;
  int n = continuation;
  assert(n >= 0 && n <= register_count, "Invalid continuation value");
  if (context == nullptr || n == register_count) {
    return;
  }

  const ucontext_t *uc = (const ucontext_t*)context;
  while (n < register_count) {
    // Update continuation with next index before printing location
    continuation = n + 1;
    switch (n) {
    case 29:
      st->print(" fp="); print_location(st, uc->context_fp);
      break;
    case 30:
      st->print(" lr="); print_location(st, uc->context_lr);
      break;
    case 31:
      st->print(" sp="); print_location(st, uc->context_sp);
      break;
    default:
      st->print("x%-2d=",n); print_location(st, uc->context_x[n]);
      break;
    }
    ++n;
  }
}

void os::setup_fpu() {
}

#ifndef PRODUCT
void os::verify_stack_alignment() {
  assert(((intptr_t)os::current_stack_pointer() & (StackAlignmentInBytes-1)) == 0, "incorrect stack alignment");
}
#endif

int os::extra_bang_size_in_bytes() {
  // AArch64 does not require the additional stack bang.
  return 0;
}

#ifdef MACOS_AARCH64
THREAD_LOCAL bool os::_jit_exec_enabled;

// This is a wrapper around the standard library function
// pthread_jit_write_protect_np(3). We keep track of the state of
// per-thread write protection on the MAP_JIT region in the
// thread-local variable os::_jit_exec_enabled
void os::current_thread_enable_wx(WXMode mode) {
  bool exec_enabled = mode != WXWrite;
  if (exec_enabled != _jit_exec_enabled NOT_PRODUCT( || DefaultWXWriteMode == WXWrite)) {
    permit_forbidden_function::pthread_jit_write_protect_np(exec_enabled);
    _jit_exec_enabled = exec_enabled;
  }
}

// If the current thread is in the WX state WXArmedForWrite, change
// the state to WXWrite.
bool Thread::wx_enable_write() {
  if (_wx_state == WXArmedForWrite) {
    _wx_state = WXWrite;
    os::current_thread_enable_wx(WXWrite);
    return true;
  } else {
    return false;
  }
}

// A wrapper around wx_enable_write() for when the current thread is
// not known.
void os::thread_wx_enable_write_impl() {
  if (!StressWXHealing) {
    Thread::current()->wx_enable_write();
  }
}

#endif // MACOS_AARCH64

static inline void atomic_copy64(const volatile void *src, volatile void *dst) {
  *(jlong *) dst = *(const jlong *) src;
}

extern "C" {
  int SpinPause() {
    // We don't use StubRoutines::aarch64::spin_wait stub in order to
    // avoid a costly call to os::current_thread_enable_wx() on MacOS.
    // We should return 1 if SpinPause is implemented, and since there
    // will be always a sequence of instructions, SpinPause will always return 1.
    switch (VM_Version::spin_wait_desc().inst()) {
    case SpinWait::NONE:
      break;
    case SpinWait::NOP:
      asm volatile("nop" : : : "memory");
      break;
    case SpinWait::ISB:
      asm volatile("isb" : : : "memory");
      break;
    case SpinWait::YIELD:
      asm volatile("yield" : : : "memory");
      break;
    case SpinWait::SB:
      assert(VM_Version::supports_sb(), "current CPU does not support SB instruction");
      asm volatile(".inst 0xd50330ff" : : : "memory");
      break;
    case SpinWait::WFET:
      ShouldNotReachHere();
#ifdef ASSERT
    default:
      ShouldNotReachHere();
#endif
    }
    return 1;
  }

  void _Copy_conjoint_jshorts_atomic(const jshort* from, jshort* to, size_t count) {
    if (from > to) {
      const jshort *end = from + count;
      while (from < end)
        *(to++) = *(from++);
    }
    else if (from < to) {
      const jshort *end = from;
      from += count - 1;
      to   += count - 1;
      while (from >= end)
        *(to--) = *(from--);
    }
  }
  void _Copy_conjoint_jints_atomic(const jint* from, jint* to, size_t count) {
    if (from > to) {
      const jint *end = from + count;
      while (from < end)
        *(to++) = *(from++);
    }
    else if (from < to) {
      const jint *end = from;
      from += count - 1;
      to   += count - 1;
      while (from >= end)
        *(to--) = *(from--);
    }
  }

  void _Copy_conjoint_jlongs_atomic(const jlong* from, jlong* to, size_t count) {
    if (from > to) {
      const jlong *end = from + count;
      while (from < end)
        atomic_copy64(from++, to++);
    }
    else if (from < to) {
      const jlong *end = from;
      from += count - 1;
      to   += count - 1;
      while (from >= end)
        atomic_copy64(from--, to--);
    }
  }

  void _Copy_arrayof_conjoint_bytes(const HeapWord* from,
                                    HeapWord* to,
                                    size_t    count) {
    memmove(to, from, count);
  }
  void _Copy_arrayof_conjoint_jshorts(const HeapWord* from,
                                      HeapWord* to,
                                      size_t    count) {
    memmove(to, from, count * 2);
  }
  void _Copy_arrayof_conjoint_jints(const HeapWord* from,
                                    HeapWord* to,
                                    size_t    count) {
    memmove(to, from, count * 4);
  }
  void _Copy_arrayof_conjoint_jlongs(const HeapWord* from,
                                     HeapWord* to,
                                     size_t    count) {
    memmove(to, from, count * 8);
  }
};
