sys/i386/stand/wdbootblk.c

/*-
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * William Jolitz.
 *
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * 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.
 *
 *      from: @(#)wdbootblk.c   7.1 (Berkeley) 4/28/91
 *      $Id$
 */

/*
 * wdbootblk.s:
 *      Written 7/6/90 by William F. Jolitz
 *      Initial block boot for AT/386 with typical Western Digital
 *      WD 1002-WA2 (or upwards compatable). Works either as
 *      first and sole partition bootstrap, or as loaded by a
 *      earlier BIOS boot when on an inner partition of the disk.
 *
 *      Goal is to read in sucessive 7.5Kbytes of bootstrap to
 *      execute.
 *
 *      No attempt is made to handle disk errors.
 */
#include "i386/isa/isa.h"
#include "i386/isa/wdreg.h"
#define NOP     inb $0x84,%al
#define BIOSRELOC       0x7c00
#define start           RELOC+0x400

        /* step 0 force descriptors to bottom of address space */

        cli
        .byte 0xb8,0x30,0x00    /* mov $0x30,%ax */
        mov %ax, %ss
        .byte 0xbc,0x00,0x01    /* mov $0x100,%sp */

        xorl    %eax,%eax
        movl    %ax,%ds
        movl    %ax,%es

        /* obtain BIOS parameters for hard disk XXX */
        movb    $0x9f,%ah        /* write to 0x9ff00  XXX */
        movb    $0xf0,%al
        mov     %ax,%es
        xor     %edi,%edi

        .byte 0xf, 0xb4, 0x36 ; .word  0x41*4   /* lfs 0x41*4, %si */
        xorb    %ch,%ch
        movb    $0x10,%cl
        fs
        rep
        movsb

        .byte 0xf, 0xb4, 0x36 ; .word  0x46*4   /* lfs 0x46*4, %si */
        xorb    %ch,%ch
        movb    $0x10,%cl
        fs
        rep
        movsb

        xorl    %eax,%eax
        movl    %ax,%es

        /* step 1 load new descriptor table */

        .byte 0x3E,0x0F,1,0x16
        .word   BIOSRELOC+0x6e  #GDTptr
        # word aword cs lgdt GDTptr

        /* step 2 turn on protected mode */

        smsw    %ax
        orb     $1,%al
        lmsw    %ax
        jmp     1f
        nop

        /* step 3  reload segment descriptors */

1:
        xorl    %eax,%eax
        movb    $0x10,%al
        movl    %ax,%ds
        movl    %ax,%es
        movl    %ax,%ss
        word
        ljmp    $0x8,$ BIOSRELOC+0x74   /* would be nice if .-RELOC+0x7c00 worked */

 /* Global Descriptor Table contains three descriptors:
  * 0x00: Null: not used
  * 0x08: Code: code segment starts at 0 and extents for 4 gigabytes
  * 0x10: Data: data segment starts at 0 and extends for 4 gigabytes
  *             (overlays code)
  */
GDT:
NullDesc:       .word   0,0,0,0 # null descriptor - not used
CodeDesc:       .word   0xFFFF  # limit at maximum: (bits 15:0)
        .byte   0,0,0   # base at 0: (bits 23:0)
        .byte   0x9f    # present/priv level 0/code/conforming/readable
        .byte   0xcf    # page granular/default 32-bit/limit(bits 19:16)
        .byte   0       # base at 0: (bits 31:24)
DataDesc:       .word   0xFFFF  # limit at maximum: (bits 15:0)
        .byte   0,0,0   # base at 0: (bits 23:0)
        .byte   0x93    # present/priv level 0/data/expand-up/writeable
        .byte   0xcf    # page granular/default 32-bit/limit(bits 19:16)
        .byte   0       # base at 0: (bits 31:24)

/* Global Descriptor Table pointer
 *  contains 6-byte pointer information for LGDT
 */
GDTptr: .word   0x17    # limit to three 8 byte selectors(null,code,data)
        .long   BIOSRELOC+0x56  # GDT -- arrgh, gas again!

        /* step 4 relocate to final bootstrap address. */
reloc:
        movl    $ BIOSRELOC,%esi
        movl    $ RELOC,%edi
        movl    $512,%ecx
        rep
        movsb
        movl    $0xa0000, %esp
        pushl   $dodisk
        ret

        /* step 5 load remaining 15 sectors off disk */
dodisk:
        movl    $ IO_WD1+wd_seccnt,%edx
        movb    $ 15,%al
        outb    %al,%dx
        NOP
        movl    $ IO_WD1+wd_sector,%edx
        movb    $ 2,%al
        outb    %al,%dx
        NOP
        #outb(wdc+wd_cyl_lo, (cyloffset & 0xff));
        #outb(wdc+wd_cyl_hi, (cyloffset >> 8));
        #outb(wdc+wd_sdh, WDSD_IBM | (unit << 4));

        movl    $ IO_WD1+wd_command,%edx
        movb    $ WDCC_READ,%al
        outb    %al,%dx
        NOP
        cld

        /* check to make sure controller is not busy and we have data ready */
readblk:
        movl    $ IO_WD1+wd_status,%edx
        NOP
        inb     %dx,%al
        testb   $ WDCS_BUSY,%al
        jnz readblk
        testb   $ WDCS_DRQ,%al
        jz readblk

        /* read a block into final position in memory */

        movl    $ IO_WD1+wd_data,%edx
        movl    $ 256,%ecx
        .byte 0x66,0xf2,0x6d    # rep insw
        NOP

        /* need more blocks to be read in? */

        cmpl    $ RELOC+16*512-1,%edi
        jl      readblk

        /* for clever bootstrap, dig out boot unit and cylinder */

        movl    $ IO_WD1+wd_cyl_lo,%edx
        inb     %dx,%al
        xorl    %ecx,%ecx
        movb    %al,%cl
        incl    %edx
        NOP
        inb     %dx,%al         /* cyl_hi */
        movb    %al,%ch
        pushl   %ecx            /* cyloffset */

        incl    %edx
        xorl    %eax,%eax
        NOP
        inb     %dx,%al         /* sdh */
        andb    $0x10,%al       /* isolate unit # bit */
        shrb    $4,%al
        pushl   %eax            /* unit */

        /* wd controller is major device 0 */
        xorl    %eax,%eax
        pushl   %eax            /* bootdev */

        /* sorry, no flags at this point! */

        movl    $ start, %eax
        call    %eax /* main (dev, unit, offset) */

ebootblkcode:

        /* remaining space usable for a disk label */

        .org    0x1fe
        .word   0xaa55          /* signature -- used by BIOS ROM */

ebootblk:                       /* MUST BE EXACTLY 0x200 BIG FOR SURE */