start.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.  */

/*  entry.s
 *
 *  This file contains the entry point for the application.
 *  The name of this entry point is compiler dependent.
 *  It jumps to the BSP which is responsible for performing
 *  all initialization.
 */

        .text
	      .globl   start                        | Default entry point
	      .globl   _start                       | Default entry point
	      .globl   M68Kvec                      | Vector Table
	      .globl   _M68Kvec                     | Vector Table

start:
_start:
M68Kvec:                               | standard location for vectors
_M68Kvec:                               | standard location for vectors
        nop                             | for linkers with problem
                                        |   using location zero as entry
        jmp      around
        .space   4088                   | to avoid initial intr stack
                                        |   from 135BUG on MVME13? as entry
                                        |   and start code at 0x4000
around: 
        move.w  %sr,initial_sr          | save initial values
        movec   %isp,%a0
        movel   %a0,initial_isp
        movec   %usp,%a0
        movel   %a0,initial_usp
        movec   %msp,%a0
        movel   %a0,initial_msp
        oriw    #0x0700,%sr             | INTERRUPTS OFF!!!

        

        |
        | zero out uninitialized data area
        |
zerobss:
        moveal  #end,%a0                | find end of .bss 
        moveal  #_bss_start,%a1         | find beginning of .bss 
        movel   #0,%d0

loop:   movel   #0,%a1@+                | to zero out uninitialized
        cmpal   %a0,%a1
        jlt     loop                    | loop until _end reached 

        movel   #heap_size,__C_heap_size | set ___C_heap_size
        movel   #heap_memory,__C_heap_start | set ___C_heap_start
        moveal  #interrupt_stack_end,%a0 | set interrupt stack pointer
        movec   %a0,%isp
        moveal  #stack_end,%a0          | set master stack pointer
        movec   %a0,%msp
        moveal  #stack_end,%a6          | set base pointer
        movw    #0x3000,%sr             | SUPV MODE,INTERRUPTS ON!!!

#ifdef NEED_UNDERSCORES
        jsr     __Board_Initialize      | initialize the board 
#else
        jsr     _Board_Initialize       | initialize the board 
#endif

        move.l  #0,%sp@-                | envp = NULL 
        move.l  #0,%sp@-                | argv = NULL 
        move.l  #0,%sp@-                | argc = NULL 
#ifdef NEED_UNDERSCORES
        jsr     ___libc_init            | initialize the library and
                                        |   call main
#else
        jsr     __libc_init             | initialize the library and
                                        |   call main
#endif
        add.l   #12,%sp
 
        move.l  #0,%sp@-                | argc = NULL 
        jsr     __exit                  | call the Board specific exit
        addq.l  #4,%sp

        move.l  initial_isp,%a0         | if __exit returns then we can
        movec   %a0,%isp                |   restore the initial values
        move.l  initial_usp,%a0
        movec   %a0,%usp
        move.l  initial_msp,%a0
        movec   %a0,%msp
        move.w  initial_sr,%sr
        rts


        .bss

/*
 *  So initial stack registers and status register can be saved.
 */

#define DECLARE_SPACE(_name,_space,_align) \
          .globl   _name ; \
          .align   _align ; \
_name##:  .space _space

#define DECLARE_LABEL(_name) \
          .globl   _name ; \
_name##:  

#define DECLARE_PTR(_name) DECLARE_SPACE(_name,4,2)
#define DECLARE_U32(_name) DECLARE_SPACE(_name,4,2)
#define DECLARE_U16(_name) DECLARE_SPACE(_name,2,1)

DECLARE_U32(initial_isp)
DECLARE_U32(initial_msp)
DECLARE_U32(initial_usp)
DECLARE_U16(initial_sr)

/*
 *  Require environment stuff
 */

DECLARE_LABEL(_environ)
DECLARE_PTR(environ)

DECLARE_LABEL(_errno)
DECLARE_U32(errno)

/*
 *  Stack Size and Space
 */

        .set stack_size, 0x20000

DECLARE_SPACE(stack_memory,stack_size,4)
DECLARE_LABEL(stack_end)

DECLARE_SPACE(interrupt_stack_memory,0x1000,4)
DECLARE_LABEL(interrupt_stack_end)