Subversion Repositories openrisc_2011-10-31

/*

 * crt0.S -- startup file for m68k-coff

 *

 * Copyright (c) 1995, 1996, 1998 Cygnus Support

 *

 * The authors hereby grant permission to use, copy, modify, distribute,

 * and license this software and its documentation for any purpose, provided

 * that existing copyright notices are retained in all copies and that this

 * notice is included verbatim in any distributions. No written agreement,

 * license, or royalty fee is required for any of the authorized uses.

 * Modifications to this software may be copyrighted by their authors

 * and need not follow the licensing terms described here, provided that

 * the new terms are clearly indicated on the first page of each file where

 * they apply.

 */

#include "asm.h"

        .title "crt0.S for m68k-coff"

#define STACKSIZE       0x4000

/*

 * Define an empty environment.

 */

        .data

        .align 2

SYM (environ):

        .long 0

        .align  2

        .text

/*

 * These symbols are defined in C code, so they need to always be

 * named with SYM because of the difference between object file formats.

 */

/* These are defined in C code. */

        .extern SYM (main)

        .extern SYM (exit)

        .extern SYM (hardware_init_hook)

        .extern SYM (software_init_hook)

        .extern SYM (atexit)

        .extern SYM(__do_global_dtors)

/*

 * These values are set in the linker script, so they must be

 * explicitly named here without SYM.

 */

        .extern __stack

        .extern __bss_start

        .extern _end

/*

 * Set things up so the application will run. For historical reasons

 * this is called 'start'.  We set things up to provide '_start'

 * as with other systems, but also provide a weak alias called

 * 'start' for compatibility with existing linker scripts.

 */

        .global SYM (start)

        .weak SYM (start)

        .set SYM (start),SYM(_start)

        .global SYM (_start)

SYM (_start):

        /*

         * put any hardware init code here

         */

        /* See if user supplied their own stack (__stack != 0).  If not, then

         * default to using the value of %sp as set by the ROM monitor.

         */

        movel   IMM(__stack), a0

        cmpl    IMM(0), a0

        jbeq    1f

        movel   a0, sp

1:

        /* set up initial stack frame */

        link    a6, IMM(-8)

/*

 * zero out the bss section.

 */

        movel   IMM(__bss_start), d1

        movel   IMM(_end), d0

        cmpl    d0, d1

        jbeq    3f

        movl    d1, a0

        subl    d1, d0

        subql   IMM(1), d0

2:

        clrb    (a0)+

#if !defined(__mcoldfire__)

        dbra    d0, 2b

        clrw    d0

        subql   IMM(1), d0

        jbcc    2b

#else

        subql   IMM(1), d0

        jbpl    2b

#endif

3:

/*

 * initialize target specific stuff. Only execute these

 * functions it they exist.

 */

        PICLEA  SYM (hardware_init_hook), a0

        cmpl    IMM(0),a0

        jbeq    4f

        jsr     (a0)

4:

        PICLEA  SYM (software_init_hook), a0

        cmpl    IMM(0),a0

        jbeq    5f

        jsr     (a0)

5:

/*

 * call the main routine from the application to get it going.

 * main (argc, argv, environ)

 * we pass argv as a pointer to NULL.

 */

#ifdef ADD_DTORS

        /* put __do_global_dtors in the atexit list so the destructors get run */

        movel   IMM (SYM(__do_global_dtors)),(sp)

        PICCALL SYM (atexit)

#endif

        movel   IMM (__FINI_SECTION__),(sp)

        PICCALL SYM (atexit)

        PICCALL __INIT_SECTION__

        pea     0

        PICPEA  SYM (environ),a0

        pea     sp@(4)

        pea     0

        PICCALL SYM (main)

        movel   d0, sp@-

/*

 * drop down into exit incase the user doesn't. This should drop

 * control back to the ROM monitor, if there is one. This calls the

 * exit() from the C library so the C++ tables get cleaned up right.

 */

        PICCALL SYM (exit)