source: rtems/c/src/lib/libbsp/i386/pc386/start/start.S @ 1c5ebc5

/*-------------------------------------------------------------------------+
| start.s v1.1 - PC386 BSP - 1997/08/07
+--------------------------------------------------------------------------+
| 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.
+--------------------------------------------------------------------------+
| (C) Copyright 1997 -
| - NavIST Group - Real-Time Distributed Systems and Industrial Automation
|
| http://pandora.ist.utl.pt
|
| Instituto Superior Tecnico * Lisboa * PORTUGAL
+--------------------------------------------------------------------------+
| Modified the 20/05/1998  by valette@crf.canon.fr in order to give a working
| example of eraly stage debugging via the DEBUG_EARLY_START define.
+--------------------------------------------------------------------------+
| Disclaimer:
|
| This file is provided "AS IS" without warranty of any kind, either
| expressed or implied.
+--------------------------------------------------------------------------+
| This code is based on an earlier generation RTEMS i386 start.s and the
| following copyright applies:
|
| **************************************************************************
| *  COPYRIGHT (c) 1989-1999.
| *  On-Line Applications Research Corporation (OAR).
| *
| *  The license and distribution terms for this file may be
| *  found in the file LICENSE in this distribution or at
| *  http://www.rtems.com/license/LICENSE.
| **************************************************************************
|
|  $Id$
+--------------------------------------------------------------------------*/

/*
 * The most trivial start.s possible. It does not know anything
 * about system it is running on, so it will jump to appropriate
 * place in BSP specific place to do things it knows nothing about
 */

#include <rtems/asm.h>

/*----------------------------------------------------------------------------+
| Size of heap and stack:
+----------------------------------------------------------------------------*/

.set STACK_SIZE, 0x1000

/*----------------------------------------------------------------------------+
| CODE section
+----------------------------------------------------------------------------*/

BEGIN_CODE

        PUBLIC (start)          # GNU default entry point

        EXTERN (boot_card)
        EXTERN (_load_segments)
        EXTERN (_return_to_monitor)
        EXTERN (_IBMPC_initVideo)
        EXTERN (debugPollingGetChar)
        EXTERN (checkCPUtypeSetCr0)

/*
 * In case this crashes on your machine and this is not due
 * to video mode set by the loader, you may try to define
 * the following variable:
 */
/* #define DEBUG_EARLY_START */

SYM (start):
        /*
         *  When things are really, REALLY!, bad -- turn on the speaker and
         *  lock up.  This shows whether or not we make it to a certain
         *  location.
         */
#if 0
        inb     $0x61, al
        orb     $0x03, al
        outb    al, $0x61       # enable the speaker
speakl: jmp     speakl             # and SPIN!!!
#endif

        nop
        cli                     # DISABLE INTERRUPTS!!!
        cld

        /* Save multiboot info if we detect a multiboot loader */
        cmp     $0x2badb002,eax
        jne     2f
        
        /* We have multiboot info; let's hope DS and ES are OK... */
        movl    ebx, SYM(_boot_multiboot_info_p)
        /* Check for memory size info and save */
        movl    ebx, esi
        movl    (esi), eax
        movl    eax, ebx
        movl    $SYM(_boot_multiboot_info), edi
        /* save flags, always present */
        movsd
        /* flag 1 is memory */
        and     $1, eax
        je      1f
        movl    $2, ecx
        rep movsd
        /* flag 2 is the command line */
1:      movl    ebx, eax
        and     $4, eax
        je      3f
        movl    (_boot_multiboot_info_p), eax
        movl    16(eax), esi
        movl    $255, ecx
2:      movzbl  (esi), eax
        test    al, al
        je      3f
        movb    al, (edi)
        inc     edi
        inc     esi
        dec     ecx
        je      3f
        jmp     2b
3:      xor     al, al
        movb    al, (edi)
#ifdef DEBUG_EARLY_START
        /*
         * Must get video attribute to have a working printk.
         * Note that the following code assume we already have
         * valid segments and a stack. It should be true for
         * any loader starting RTEMS in protected mode (or
         * at least I hope so : -)).
         */
        call _IBMPC_initVideo
        /*
         * try printk and a getchar in polling mode ASAP
         */
        pushl   $welcome_msg
        call    printk
        addl    $4, esp

        /* call debugPollingGetChar */

#endif

/*----------------------------------------------------------------------------+
| Load the segment registers (this is done by the board's BSP) and perform any
| other board specific initialization procedures, this piece of code
| does not know anything about
|
| NOTE: Upon return, gs will contain the segment descriptor for a segment which
|       maps directly to all of physical memory.
+----------------------------------------------------------------------------*/

        jmp     SYM (_load_segments)    # load board dependent segments

/*----------------------------------------------------------------------------+
| Set up the stack
+----------------------------------------------------------------------------*/

        PUBLIC (_establish_stack)
SYM (_establish_stack):

        movl    $_end, eax              # eax = end of bss/start of heap
        addl    $STACK_SIZE, eax        # make room for stack
        andl    $0xffffffc0, eax        # align it on 16 byte boundary
        movl    eax, esp                # set stack pointer
        movl    eax, ebp                # set base pointer

/*----------------------------------------------------------------------------+
| Zero out the BSS segment
+----------------------------------------------------------------------------*/

SYM (zero_bss):
        cld                             # make direction flag count up
        movl    $ SYM (_end), ecx       # find end of .bss
        movl    $ SYM (__bss_start), edi # edi = beginning of .bss
        subl    edi, ecx                # ecx = size of .bss in bytes
        shrl    ecx                     # size of .bss in longs
        shrl    ecx
        xorl    eax, eax                # value to clear out memory
        repne                           # while ecx != 0
        stosl                           #   clear a long in the bss

/*-------------------------------------------------------------------+
| Initialize the video because zero_bss has cleared initVideo parameters
| if it was called earlier
| So from now we can use printk
+-------------------------------------------------------------------*/
        call _IBMPC_initVideo

/*---------------------------------------------------------------------+
| Check CPU type. Enable Cache and init coprocessor if needed.
+---------------------------------------------------------------------*/
        call checkCPUtypeSetCr0

/*---------------------------------------------------------------------+
| Transfer control to User's Board Support Package
+---------------------------------------------------------------------*/

        movl    $SYM(_boot_multiboot_cmdline), eax
        pushl   eax                     # cmdline
        call    SYM (boot_card)
        addl    $4, esp

/*---------------------------------------------------------------------+
| Clean up - we do not know anything about it, so we will
| jump to BSP specific code to do cleanup
+---------------------------------------------------------------------*/

        jmp     SYM (_return_to_monitor)

END_CODE

BEGIN_DATA
        PUBLIC(_boot_multiboot_info_p)
SYM(_boot_multiboot_info_p):
        .long 0

        PUBLIC(_boot_multiboot_info)
        PUBLIC(_boot_multiboot_flags)
        PUBLIC(_boot_multiboot_memory)
        PUBLIC(_boot_multiboot_cmdline)
SYM(_boot_multiboot_info):
SYM(_boot_multiboot_flags):
        .long 0 /* flags */
SYM(_boot_multiboot_memory):
        .long 0 /* mem_lower */
        .long 0 /* mem_upper */
SYM(_boot_multiboot_cmdline):
        .rept 256 /* cmd line */
        .byte 0
        .endr
        
        PUBLIC(_stack_size)
SYM(_stack_size):
        .long STACK_SIZE

#ifdef DEBUG_EARLY_START

        PUBLIC (welcome_msg)
SYM (welcome_msg) :
        .string "Ready to debug RTEMS ?\nEnter <CR>\n"

        PUBLIC (hex_msg)
SYM (hex_msg) :
        .string "0x%x\n"

        PUBLIC (made_it_msg)
SYM (made_it_msg) :
        .string "made it to %d\n"

#endif

END_DATA

END