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/*  dlentry.s

 *

 *  This file contains the entry code for RTEMS programs starting

 *  after download to RAM

 *

 *  Author:     Thomas Doerfler 

 *              IMD Ingenieurbuero fuer Microcomputertechnik

 *

 *  COPYRIGHT (c) 1998 by IMD

 *

 *  Changes from IMD are covered by the original distributions terms.

 *  This file has been derived from the papyrus BSP:

 *

 *  This file contains the entry veneer for RTEMS programs

 *  downloaded to Papyrus.

 *

 *  Author:     Andrew Bray 

 *

 *  COPYRIGHT (c) 1995 by i-cubed ltd.

 *

 *  To anyone who acknowledges that this file is provided "AS IS"

 *  without any express or implied warranty:

 *      permission to use, copy, modify, and distribute this file

 *      for any purpose is hereby granted without fee, provided that

 *      the above copyright notice and this notice appears in all

 *      copies, and that the name of i-cubed limited not be used in

 *      advertising or publicity pertaining to distribution of the

 *      software without specific, written prior permission.

 *      i-cubed limited makes no representations about the suitability

 *      of this software for any purpose.

 *

 *  dlentry.S,v 1.1 2001/11/08 23:46:58 joel Exp

 *

 *  derived from "helas403/dlentry.S":

 *  Id: dlentry.S,v 1.2 2000/08/02 16:30:57 joel Exp

 */

#include "asm.h"

/*

 *  The gen405 ELF link scripts support three special sections:

 *    .entry    The actual entry point

 *    .vectors  The section containing the interrupt entry veneers.

 */

/*

 *  Downloaded code loads the vectors separately to 0x00000100,

 *  so .entry can be over 256 bytes.

 *

 *  The other sections are linked in the following order:

 *    .entry

 *    .text

 *    .data

 *    .bss

 * see linker command file for section placement

 *

 *  The initial stack is set to stack.end

 *

 *  All the entry veneer has to do is to clear the BSS.

 */

/*

 *  GDB likes to have debugging information for the entry veneer.

 *  Here was some DWARF information. IMD removed it, because we

 *  could not check, whether it was still correct. Sorry.

 */

.globl __eabi

#if PPC_ASM == PPC_ASM_ELF

        .section .entry

#else

        .csect .text[PR]

#endif

        PUBLIC_VAR (download_entry)

SYM(download_entry):

        bl      .startup

base_addr:

/*---------------------------------------------------------------------------

 * Parameters from linker

 *--------------------------------------------------------------------------*/

toc_pointer:

#if PPC_ASM == PPC_ASM_ELF

        .long   s.got

#else

        .long   TOC[tc0]

#endif

bss_length:

        .long   bss.size

bss_addr:

        .long   bss.start

stack_top:

        .long   stack.end

/*---------------------------------------------------------------------------

 * Reset_entry.

 *--------------------------------------------------------------------------*/

.startup:

        /* Get start address, stack grows down from here... */

        mflr    r1

        /* Assume Bank regs set up..., cache etc. */

        bl      bssclr

        .extern SYM(__vectors)

        lis     r2,__vectors@h          /* set EVPR exc. vector prefix */

        mtspr   evpr,r2

        /*-------------------------------------------------------------------

         * C_setup.

         *------------------------------------------------------------------*/

        lwz     r2,toc_pointer-base_addr(r1)       /* set r2 to toc */

        lwz     r1,stack_top-base_addr(r1)         /* set r1 to stack_top */

        addi    r1,r1,-56-4              /* start stack at text_addr - 56 */

        addi    r3,r0,0x0                /* clear r3 */

        stw     r3, 0(r1)                /* Clear stack chain */

        stw     r3, 4(r1)

        stw     r3, 8(r1)

        stw     r3, 12(r1)

        lis     r5,environ@ha

        la      r5,environ@l(r5)        /* environp */

        li      r4, 0                   /* argv */

        li      r3, 0                   /* argc */

        .extern SYM (boot_card)

        b       SYM (boot_card)          /* call the first C routine */

/*---------------------------------------------------------------------------

 * bssclr.

 *--------------------------------------------------------------------------*/

bssclr:

        /*-------------------------------------------------------------------

         * Data move finished, zero out bss.

         *------------------------------------------------------------------*/

        lwz     r2,bss_addr-base_addr(r1)   /* start of bss set by loader */

        lwz     r3,bss_length-base_addr(r1) /* bss length */

        rlwinm. r3,r3,30,0x3FFFFFFF     /* form length/4 */

        beqlr                           /* no bss */

        mtctr   r3                      /* set ctr reg */

        xor     r6,r6,r6                /* r6 = 0 */

clear_bss:

        stswi   r6,r2,0x4               /* store r6 */

        addi    r2,r2,0x4               /* update r2 */

        bdnz    clear_bss               /* decrement counter and loop */

        blr                             /* return */

.L_text_e:

#if PPC_ABI == PPC_ABI_POWEROPEN

        DESCRIPTOR (startup)

#endif

        .comm   environ,4,4

/* no eabi */

__eabi:

    blr