/*      $NetBSD: biosboot.S,v 1.8 2011/01/05 23:13:01 jakllsch Exp $    */

/*-
 * Copyright (c) 2003 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by David Laight.
 *
 * 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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>
#include <sys/bootblock.h>

/*
 * Code linked to 0x1000:0 and (usually) read from /boot by bootxx code
 *
 * On entry:
 *      %dl                     BIOS drive number
 *      %ecx:%ebx               Sector number of NetBSD partition
 *      %ds:%si                 Boot parameter block (patched by installboot)
 *      %cs                     0x1000
 *      %ds, %es, %ss           All zero
 *      %sp                     near 0xfffc
 */

        .text
        .code16
ENTRY(boot_start)
        jmp     boot_start_1
        .balign 4
ENTRY(boot_magic)
        .long   X86_BOOT_MAGIC_2        /* checked for by bootxx code */
ENTRY(boot_params)
        .long   boot_start_1 - boot_params
#include <boot_params.S>
        . = boot_start + 0x80           /* space for patchable variables */
boot_start_1:

#if 0
        /* Allow for boot_start not being %cs:0 */
        call    2f
2:      pop     %cx
        sub     $2b, %cx                /* %ax is offset */
        test    $0xf, %cx               /* check code seg aligned */
        jz      3f
        lret                            /* not playing if not */
3:      mov     %cs, %ax
        shr     $4, %cx
        add     %cx, %ax                /* segment staring at boot_start */
        push    %ax
        push    $4f
        lret
4:
#endif

        mov     %cs, %ax
        mov     %ax, %es

        movl    %ecx, %ebp              /* move LBA out of the way */

        /* Grab boot_params patched into bootxx by installboot */
        cmpl    $X86_BOOT_MAGIC_1,-4(%si)       /* sanity check ptr */
        jne     2f
        mov     $boot_params, %di
        movl    (%si),%ecx
        cmp     $boot_start_1 - boot_params, %cx
        jbe     1f
        mov     $boot_start_1 - boot_params, %cx
1:      cld
        rep
        movsb
2:

        mov     %ax, %ds
        movl    $_end, %eax             /* top of bss */
        shr     $4, %eax                /* as a segment */
        add     $0x1001, %ax            /* and + 64k */
        mov     %ax, %ss                /* for stack */
        mov     $0xfffc, %sp            /* %sp at top of it */

        call    gdt_fixup

        calll   real_to_prot
        .code32

        movl    $_end, %ecx             /* zero bss */
        movl    $__bss_start, %edi
        subl    %edi, %ecx
        shr     $2, %ecx                /* _end and __bss_start are aligned */
        xor     %eax, %eax
        rep
        stosl

        testb   $X86_BP_FLAGS_LBA64VALID, boot_params+4
        jnz     1f
        xorl    %ebp, %ebp              /* high part of LBA is not valid */
1:

        movzbl  %dl, %edx
        push    %ebp                    /* high 32 bits of first sector */
        push    %ebx                    /* first sector of bios partition */
        push    %edx                    /* bios disk */
        call    _C_LABEL(boot2)         /* C bootstrap code */
        addl    $12, %esp
        call    prot_to_real
        .code16

boot_fail:
        push    %ax
        movw    $1f, %si
        call    message
        pop     %si
        call    message
        jmp     loopstop
1:      .asciz  "Boot2 failed: "

ENTRY(_rtt)
        .code32
        call    prot_to_real
        .code16
loopstop:
        movb    $0x86, %ah              /* delay for about a second */
        movw    $16, %cx
        int     $0x15
        int     $0x18                   /* might be a boot fail entry */
1:      sti
        hlt
        jmp     1b