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 }