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/* dlentry.s
*
* This file contains the entry code for RTEMS programs starting
* after download to RAM
*
* Author: Thomas Doerfler <td@imd.m.isar.de>
* 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 <andy@i-cubed.co.uk>
*
* 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.
*
* $Id$
*
* derived from "helas403/dlentry.S":
* Id: dlentry.S,v 1.2 2000/08/02 16:30:57 joel Exp
*/
#include <rtems/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.
*/
#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
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