source: rtems/c/src/lib/libbsp/mips/csb350/start/start.S @ c499856

/*
 * start.S -- startup file for Cogent CSB350 Au1100 based board
 *
 *  Copyright (c) 2005 by Cogent Computer Systems
 *  Written by Jay Monkman <jtm@lopingdog.com>
 *
 *  The license and distribution terms for this file may be
 *  found in the file LICENSE in this distribution or at
 *  http://www.rtems.org/license/LICENSE.
 *
 */

#include <rtems/asm.h>
#include <bsp/regs.h>

        .text
        .align  2

/* Without the following nop, GDB thinks _start is a data variable.
 * This is probably a bug in GDB in handling a symbol that is at the
 * start of the .text section.
 */
        nop

        .globl  _start
        .ent    _start
_start:
        .set    noreorder

        /* Get the address of start into $5 in a position independent
         * fashion. This lets us know whether we have been relocated or not.
         */
        $LF1 = . + 8
        bal     $LF1
        nop
_branch:
        move    $5, $31                 /* $5 == where are we */
        li      $6, 0x8800000c          /* $6 == where we want to be */

        li      v0, SR_CU1|SR_PE|SR_FR|SR_KX|SR_SX|SR_UX
        mtc0    v0, C0_SR
        mtc0    zero, C0_CAUSE

1:
        li      v0, SR_PE|SR_FR|SR_KX|SR_SX|SR_UX
        mtc0    v0, C0_SR
2:
/* Fix high bits, if any, of the PC so that exception handling
   doesn't get confused.  */
        la v0, 3f
        jr      v0
        nop
3:
        la gp, _gp                      /* set the global data pointer */
        .end _start

/*
 * zero out the bss section.
 */
        .globl  __memsize
        .globl  zerobss
        .ent    zerobss
zerobss:
        la v0, _fbss
        la v1, _end
3:
        sw      zero,0(v0)
        bltu    v0,v1,3b
        addiu   v0,v0,4                 /* executed in delay slot */

        la      t0, _stack_init         /* initialize stack so we */
        /* We must subtract 24 bytes for the 3 8 byte arguments to main, in
           case main wants to write them back to the stack.  The caller is
           supposed to allocate stack space for parameters in registers in
           the old MIPS ABIs.  We must do this even though we aren't passing
           arguments, because main might be declared to have them.

           Some ports need a larger alignment for the stack, so we subtract
           32, which satisifes the stack for the arguments and keeps the
           stack pointer better aligned.  */
        subu    t0,t0,32
        move    sp,t0                   /* set stack pointer */
        .end    zerobss

        .globl  exit .text
        .globl  init
        .ent    init
init:

        move    a0,zero                 /* set command line to 0 */
        jal     boot_card               /* call the program start function */
        nop

        /* fall through to the "exit" routine */
        jal     _sys_exit               /* call libc exit to run the G++ */
                                        /* destructors */
        move    a0,v0                   /* pass through the exit code */
        .end    init

/*
 * _sys_exit -- Exit from the application. Normally we cause a user trap
 *          to return to the ROM monitor for another run. NOTE: This is
 *          the only other routine we provide in the crt0.o object, since
 *          it may be tied to the "_start" routine. It also allows
 *          executables that contain a complete world to be linked with
 *          just the crt0.o object.
 */
        .globl  _sys_exit
        .ent _sys_exit
_sys_exit:
7:
#ifdef GCRT0
        jal     _mcleanup
        nop
#endif
        /* break inst. can cope with 0xfffff, but GAS limits the range: */
        break   1023
        nop
        b       7b                      /* but loop back just in-case */
        nop
        .end _sys_exit

/* EOF crt0.S */