/*      $OpenBSD: pbr.S,v 1.3 2022/12/08 02:11:27 guenther Exp $        */
/*      $NetBSD: pbr.S,v 1.1 2006/09/01 21:26:19 uwe Exp $      */

/*-
 * Copyright (c) 2005 NONAKA Kimihiro
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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 <machine/asm.h>

#ifdef BOOT_FROM_FAT
#define MBR_AFTERBPB    90              /* BPB size in FAT32 partition BR */
#else
#define MBR_AFTERBPB    62              /* BPB size in floppy master BR */
#endif

ENTRY(start)
        bra     start0
         .byte  0x11                    /* 0x4f11: cmp/pz r15... */
        .asciz  "OpenBSD"

        . = start + 0x0b                /* move to start of BPB */

        . = start + 0x1c                /* skip BPB */
start0:
        mova    pbr_end, r0
        mov.w   pbr_size, r2
        sub     r2, r0
        mov     r0, r11                 /* r11: own loaded address */

        mov.w   stack_offset, r1
        add     r1, r0
        mov     r0, r15                 /* r15: stack pointer */
        mov     r0, r10                 /* r10: load address */

        /* enable/flush cache */
        mov     #0, r4
        mov     #6, r0
        trapa   #0x3f

        /* Read from start of disk */
        mov     #0x40, r4               /* LBA */
        mov     #0, r5                  /* LBA #0 */
        mov     r10, r6                 /* buffer address */
        bsr     read_sectors_lba
         mov    #XXBOOT_SECTORS, r7     /* number of sectors */

        mov.l   @r11, r1
        mov.l   @r10, r2
        cmp/eq  r1, r2
        bt/s    pbr_read_ok
         mov    #0, r9                  /* r9: sector # */

        /* Search bootable partition */
        mov.w   part_offset, r12
        add     r10, r12                /* r12: pointer to partition entry */
        mov     #4, r8                  /* r8: partition loop counter */
loop_part:
        mov.b   @(4, r12), r0
#ifdef BOOT_FROM_FAT
        cmp/eq  #MBR_PTYPE_FAT12, r0
        bt      found
        cmp/eq  #MBR_PTYPE_FAT16S, r0
        bt      found
        cmp/eq  #MBR_PTYPE_FAT16B, r0
        bt      found
        cmp/eq  #MBR_PTYPE_FAT32, r0
        bt      found
        cmp/eq  #MBR_PTYPE_FAT32L, r0
        bt      found
        cmp/eq  #MBR_PTYPE_FAT16L, r0
        bt      found
#else
        cmp/eq  #0xa6, r0
#endif
        bf      next_part

found:
        /* found boot partition */
        mov.w   @(8, r12), r0
        mov     r0, r1
        mov.w   @(10, r12), r0
        extu.w  r1, r1
        shll16  r0
        or      r1, r0
        tst     r0, r0
        bt      next_part               /* start LBA == 0 ? */

        bra     boot_lba
         mov    r0, r9

next_part:
        dt      r8
        bf/s    loop_part
         add    #16, r12

ptn_error:
        /* no OpenBSD partition found */
        mova    ERR_PTN, r0
error:
        bsr     message_crlf
         mov    r0, r4
99:     bra     99b
         nop

read_error:
        bra     error
         mova   ERR_READ, r0

magic_error:
        bra     error
         mova   ERR_NO_XXBOOT, r0

message_crlf:
        mov     #32, r0
        trapa   #0x3f
        mova    crlf, r0
        mov     r0, r4
        mov     #32, r0
        trapa   #0x3f
        rts
         nop

read_sectors_lba:
        mov     #2, r0
        trapa   #0x3f
        tst     r0, r0
        bf      read_error
        rts
         nop

boot_lba:
        mov     #0x40, r4               /* LBA */
        mov     r9, r5                  /* LBA # */
        mov     r10, r6                 /* buffer address */
        bsr     read_sectors_lba
         mov    #XXBOOT_SECTORS, r7     /* number of sectors */

pbr_read_ok:
        mov.l   .L.xxboot_magic1, r1
        mov.l   .L.xxboot_magic, r2
        mov.l   @r2, r2
        cmp/eq  r1, r2
        bf      magic_error

        /* flush cache */
        mov     #0, r4
        mov     #6, r0
        trapa   #0x3f

        mov.l   .L.xxboot_start, r13
        jmp     @r13                    /* jump to xxboot */
         mov    r9, r4                  /* pass sector address to xxboot */


        .align  1
pbr_size:       .word   pbr_end - start
        .align  1
stack_offset:   .word   0x1000
        .align  1
part_offset:    .word   0x1be
        .align  1
magic_offset:   .word   0x1fe

        .align  2
.L.xxboot_magic1:
        .long   0x20031125
.L.xxboot_magic:
        .long   xxboot_magic
.L.xxboot_start:
        .long   xxboot_start

        .align  2
crlf:           .asciz  "\r\n"

        .align  2
ERR_READ:       .asciz  "Disk read"
        .align  2
ERR_NO_XXBOOT:  .asciz  "Not a xxboot image"
        .align  2
ERR_PTN:        .asciz  "No OpenBSD partition"


        . = start + 0x1fe
magic:
        .word   0xaa55
pbr_end:

        .global ptn_disklabel
ptn_disklabel:
        .fill   512