1 /*
   2  * Copyright 1999-2003 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  20  * CA 95054 USA or visit www.sun.com if you need additional information or
  21  * have any questions.
  22  *
  23  */
  24 
  25 #include "incls/_precompiled.incl"
  26 #include "incls/_assembler_windows_x86_32.cpp.incl"
  27 
  28 
  29 void MacroAssembler::int3() {
  30   emit_byte(0xCC);
  31 }
  32 
  33 //  The current scheme to accelerate access to the thread
  34 //  pointer is to store the current thread in the os_exception_wrapper
  35 //  and reference the current thread from stubs and compiled code
  36 //  via the FS register.  FS[0] contains a pointer to the structured
  37 //  exception block which is actually a stack address.  The first time
  38 //  we call the os exception wrapper, we calculate and store the
  39 //  offset from this exception block and use that offset here.
  40 //
  41 //  The last mechanism we used was problematic in that the
  42 //  the offset we had hard coded in the VM kept changing as Microsoft
  43 //  evolved the OS.
  44 //
  45 // Warning: This mechanism assumes that we only attempt to get the
  46 //          thread when we are nested below a call wrapper.
  47 //
  48 // movl reg, fs:[0]                        Get exeception pointer
  49 // movl reg, [reg + thread_ptr_offset]     Load thread
  50 //
  51 void MacroAssembler::get_thread(Register thread) {
  52   // can't use ExternalAddress because it can't take NULL
  53   AddressLiteral null(0, relocInfo::none);
  54 
  55   prefix(FS_segment);
  56   movptr(thread, null);
  57   assert(ThreadLocalStorage::get_thread_ptr_offset() != 0,
  58          "Thread Pointer Offset has not been initialized");
  59   movl(thread, Address(thread, ThreadLocalStorage::get_thread_ptr_offset()));
  60 }
  61 
  62 bool MacroAssembler::needs_explicit_null_check(int offset) {
  63   return offset < 0 || (int)os::vm_page_size() <= offset;
  64 }