/*      $NetBSD: fdboot.S,v 1.4 2025/11/19 09:43:28 nia Exp $   */

/*
 * Copyright (c) 1995 Waldi Ravens.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "xxboot.h"

        .globl  _start, main, fill

        .text

_start: bras    main
/*
 * Fake gemdos-fs bootsector, to keep TOS away.
 */
        .ascii  "NetBSD"        | oem
        .byte   0,0,0           | serial
        .word   0               | bps
        .byte   0               | spc
        .word   0               | res
        .byte   0               | fat
        .word   0               | ndirs
        .word   0               | sec
        .byte   0               | media
        .word   0               | spf
        .word   0               | spt
        .word   0               | side
        .word   0               | hid
        .even
/*
 * ROM loader does not save any register!
 */
main:   movml   %d1-%d7/%a0-%a6,%sp@-

        lea     %pc@(m_bot),%a3
        movl    _membot:w,%d3
        lea     MAXBOT,%a6
        cmpl    %a6,%d3
        bhis    exit                    | membot > MAXBOT

        lea     %pc@(m_top),%a3
        movl    _memtop:w,%d3
        cmpl    #MINTOP,%d3
        blts    exit                    | memtop < MINTOP

        andw    #-4,%d3
        movl    %d3,%a0
        movl    %sp,%a0@-
        movl    %a0,%sp                 | set new stack
/*
 * Determine the number of sectors per cylinder.
 */
        movq    #0,%d3
0:      movl    %a6,%a3                 | buffer
        movq    #1,%d0                  | count
        movq    #0,%d1                  | side
        movl    %d1,%d2                 | track
        addw    %d0,%d3                 | sector
        bsr     rds0
        beqs    0b
        subqw   #1,%d3
        addw    %d3,%d3
        lea     %pc@(secpercyl),%a0
        movw    %d3,%a0@
/*
 * Load secondary boot loader and disklabel.
 */
        movq    #NSEC,%d5               | # of sectors
        movq    #1,%d4                  | first sector
        movl    %a6,%a3                 | load address
        bsr     rds1
        lea     %pc@(m_rds),%a3
        bnes    0f                      | I/O error
/*
 * int bootxx(readsector, disklabel, autoboot)
 */
        clrl    %sp@-                   | no autoboot
        pea     %a6@(LBLST-MAXBOT)      | disklabel
        pea     %pc@(rds2)              | readsector
        jsr     %a6@(BXXST-MAXBOT)
        lea     %pc@(m_sbl),%a3         | NetBSD not booted
        lea     %sp@(12),%sp
0:      movl    %sp@,%sp                        | restore BIOS stack
        movl    %d0,%d3

exit:   bsrs    puts                    | display error
        lea     %pc@(m_key),%a3
        bsrs    puts                    | wait for key
0:      movml   %sp@+,%d1-%d7/%a0-%a6
        movq    #0,%d0
        rts
/*
 * puts (in: a3, d3)
 */
0:      cmpw    #35,%d0         | '#'
        bnes    1f
        bsrs    puti
        bras    puts
1:      cmpw    #64,%d0         | '@'
        bnes    2f
        movw    #2,%sp@-
        movw    #Bconin,%sp@-
        trap    #BIOS
        addql   #4,%sp
        bras    puts
2:      bsrs    putc
puts:   movq    #0,%d0
        movb    %a3@+,%d0
        bnes    0b
        rts

puti:   swap    %d3
        bsrs    0f
        swap    %d3
0:      rorw    #8,%d3
        bsrs    1f
        rorw    #8,%d3
1:      rorb    #4,%d3
        bsrs    2f
        rorb    #4,%d3
2:      movw    %d3,%d0
        andw    #15,%d0
        addw    #48,%d0
        cmpw    #58,%d0
        bcss    putc
        addw    #39,%d0
putc:   movw    %d0,%sp@-
        movw    #2,%sp@-
        movw    #Bconout,%sp@-
        trap    #BIOS
        addql   #6,%sp
        rts
/*
 * int readsec (void *buffer, u_int offset, u_int count);
 */
rds2:   movml   %d2-%d5/%a2-%a3,%sp@-
        movl    %sp@(28),%a3            | buffer
        movl    %sp@(32),%d4            | offset
        movl    %sp@(36),%d5            | count
        bsrs    rds1
        movml   %sp@+,%d2-%d5/%a2-%a3
        rts

rds1:   bsrs    1f
        bnes    0f
        tstl    %d5
        bnes    rds1
0:      rts

1:      movq    #0,%d0
        movw    %pc@(secpercyl),%d0
        movl    %d4,%d3
        divuw   %d0,%d3
        movw    %d3,%d2         | track
        clrw    %d3
        swap    %d3
        lsrw    #1,%d0
        divuw   %d0,%d3
        movw    %d3,%d1         | side
        swap    %d3
        subw    %d3,%d0
        addqw   #1,%d3          | sector
        cmpl    %d0,%d5
        bccs    rds0
        movw    %d5,%d0

rds0:   movw    %d0,%sp@-               | count
        movw    %d1,%sp@-               | side
        movw    %d2,%sp@-               | track
        movw    %d3,%sp@-               | sector
        movw    _bootdev:w,%sp@-        | device
        clrl    %sp@-           | filler
        movl    %a3,%sp@-               | buffer
        addl    %d0,%d4
        subl    %d0,%d5
        lsll    #8,%d0
        addl    %d0,%d0
        addl    %d0,%a3
        movw    #Floprd,%sp@-
        trap    #XBIOS
        lea     %sp@(20),%sp
        tstl    %d0
        rts

secpercyl:
        .word   0

m_bot:  .asciz  "fdboot: membot == 0x#\r\n"
m_top:  .asciz  "fdboot: memtop == 0x#\r\n"
m_sbl:  .asciz  "fdboot: bootxx => 0x#\r\n"
m_rds:  .asciz  "fdboot: Floprd => 0x#\r\n"
m_key:  .asciz  "\007\r\npress any key... @\r\n"

fill:   .space  22              | 510-(fill-start)
        .word   0               | checksum
end: