strtsupp.s

一个C源代码分析器

/* Copyright (C) 1994 Free Software Foundation, Inc.
   Contributed by Joel Sherrill ([e-mail]),
     On-Line Applications Research Corporation.
 
This file is part of the GNU C Library.
 
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
 
The GNU C Library 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
Library General Public License for more details.
 
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

/*  This file assists the board independent startup code by
 *  loading the proper segment register values.  The values
 *  loaded are dependent on the FORCEBUG.  
 *
 *  NOTE:  No stack has been established when this routine
 *         is invoked.  It returns by jumping back to the start code.
 *
 */

/*
 *  FORCEBUG loads us into a virtual address space which 
 *  really starts at PHYSICAL_ADDRESS_BASE.  
 *  
 */

.set PHYSICAL_ADDRESS_BASE,    0x00002000

/*
 *  At reset time, FORCEBUG normally has the segment selectors preloaded.   
 *  If a human resets the instruction pointer, this will not have occurred.
 *  However, no guarantee can be made of the other registers if cs:ip was 
 *  modified to restart the program.  Because of this, the BSP reloads all 
 *  segment registers (except cs) with the values they have following 
 *  a reset.  
 */


.set RESET_SS, 0x40        # initial value of stack segment register
.set RESET_DS, 0x40        # initial value of data segment register
.set RESET_ES, 0x40        # initial value of extra segment register
.set RESET_FS, 0x40        # initial value of "f" segment register
.set RESET_GS, 0x30        # initial value of "g" segment register 


#define LOAD_SEGMENTS(_value,_segreg) \
        movw      $_value##,%ax ;  \
        movw      %ax,##_segreg

    
        .global  _load_segments

        .global   _establish_stack

_load_segments:

        LOAD_SEGMENTS( RESET_SS, %ss )
        LOAD_SEGMENTS( RESET_DS, %ds )
        LOAD_SEGMENTS( RESET_ES, %es )
        LOAD_SEGMENTS( RESET_FS, %fs )
        LOAD_SEGMENTS( RESET_GS, %gs )

        jmp     _establish_stack        # return to the bsp entry code

        .global  _return_to_monitor
_return_to_monitor:

        movb    $0,%al
        int     $0x20                   # restart FORCEbug
        jmp     start                   # FORCEbug does not reset PC

        .data

        .global _Do_Load_IDT
_Do_Load_IDT:   .byte 1

        .global _Do_Load_GDT
_Do_Load_GDT:   .byte 0