sys/i386/boot/bios.s

/*
 * Ported to boot 386BSD by Julian Elischer (julian@tfs.com) Sept 1992
 *
 * Mach Operating System
 * Copyright (c) 1992, 1991 Carnegie Mellon University
 * All Rights Reserved.
 *
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 *
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 *
 * Carnegie Mellon requests users of this software to return to
 *
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 *
 * any improvements or extensions that they make and grant Carnegie Mellon
 * the rights to redistribute these changes.
 */

/*
 * HISTORY
 * $Log:        bios.s,v $
 * Revision 2.2  92/04/04  11:34:26  rpd
 *      Fix Intel Copyright as per B. Davies authorization.
 *      [92/04/03            rvb]
 *      From 2.5 version
 *      [92/03/30            mg32]
 *
 * Revision 2.2  91/04/02  14:35:21  mbj
 *      Add Intel copyright
 *      [90/02/09            rvb]
 *
 */


/*
  Copyright 1988, 1989, 1990, 1991, 1992
   by Intel Corporation, Santa Clara, California.

                All Rights Reserved

Permission to use, copy, modify, and distribute this software and
its documentation for any purpose and without fee is hereby
granted, provided that the above copyright notice appears in all
copies and that both the copyright notice and this permission notice
appear in supporting documentation, and that the name of Intel
not be used in advertising or publicity pertaining to distribution
of the software without specific, written prior permission.

INTEL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE
INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS,
IN NO EVENT SHALL INTEL BE LIABLE FOR ANY SPECIAL, INDIRECT, OR
CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT,
NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/

        .file   "bios.s"

#include "asm.h"
        .text

/*
# biosread(dev, cyl, head, sec)
#       Read one sector from disk into the internal buffer "intbuf" which
#       is the first 512 bytes of the boot loader.
# BIOS call "INT 0x13 Function 0x2" to read sectors from disk into memory
#       Call with       %ah = 0x2
#                       %al = number of sectors
#                       %ch = cylinder
#                       %cl = sector
#                       %dh = head
#                       %dl = drive (0x80 for hard disk, 0x0 for floppy disk)
#                       %es:%bx = segment:offset of buffer
#       Return:
#                       %al = 0x0 on success; err code on failure
*/

ENTRY(biosread)
        push    %ebp
        mov     %esp, %ebp

        push    %ebx
        push    %ecx
        push    %edx
        push    %es

        movb    0x10(%ebp), %dh
        movw    0x0c(%ebp), %cx
        xchgb   %ch, %cl        # cylinder; the highest 2 bits of cyl is in %cl
        rorb    $2, %cl
        movb    0x14(%ebp), %al
        orb     %al, %cl
        incb    %cl             # sector; sec starts from 1, not 0
        movb    0x8(%ebp), %dl  # device
        xor     %ebx, %ebx      # offset -- 0
                                # prot_to_real will set %es to BOOTSEG

        call    EXT(prot_to_real)       # enter real mode
        movb    $0x2, %ah       # subfunction
        movb    $0x1, %al       # number of sectors -- one

        sti
        int     $0x13
        cli

        mov     %eax, %ebx      # save return value

        data16
        call    EXT(real_to_prot) # back to protected mode

        xor     %eax, %eax
        movb    %bh, %al        # return value in %ax

        pop     %es
        pop     %edx
        pop     %ecx
        pop     %ebx
        pop     %ebp

        ret


/*
# putc(ch)
# BIOS call "INT 10H Function 0Eh" to write character to console
#       Call with       %ah = 0x0e
#                       %al = character
#                       %bh = page
#                       %bl = foreground color ( graphics modes)
*/


ENTRY(putc)
        push    %ebp
        mov     %esp, %ebp
        push    %ebx
        push    %ecx

        movb    0x8(%ebp), %cl

        call    EXT(prot_to_real)

        data16
        mov     $0x1, %ebx      # %bh=0, %bl=1 (blue)
        movb    $0xe, %ah
        movb    %cl, %al
        sti
        int     $0x10           # display a byte
        cli

        data16
        call    EXT(real_to_prot)

        pop     %ecx
        pop     %ebx
        pop     %ebp
        ret


/*
# getc()
# BIOS call "INT 16H Function 00H" to read character from keyboard
#       Call with       %ah = 0x0
#       Return:         %ah = keyboard scan code
#                       %al = ASCII character
*/

ENTRY(getc)
        push    %ebp
        mov     %esp, %ebp
        push    %ebx            # save %ebx

        call    EXT(prot_to_real)

        movb    $0x0, %ah
        sti
        int     $0x16
        cli

        movb    %al, %bl        # real_to_prot uses %eax

        data16
        call    EXT(real_to_prot)

        xor     %eax, %eax
        movb    %bl, %al

        pop     %ebx
        pop     %ebp
        ret
/*
# ischar()
#       if there is a character pending, return it; otherwise return 0
# BIOS call "INT 16H Function 01H" to check whether a character is pending
#       Call with       %ah = 0x1
#       Return:
#               If key waiting to be input:
#                       %ah = keyboard scan code
#                       %al = ASCII character
#                       Zero flag = clear
#               else
#                       Zero flag = set
*/
ENTRY(ischar)
        push    %ebp
        mov     %esp, %ebp
        push    %ebx

        call    EXT(prot_to_real)               # enter real mode

        xor     %ebx, %ebx
        movb    $0x1, %ah
        sti
        int     $0x16
        cli
        data16
        jz      nochar
        movb    %al, %bl

nochar:
        data16
        call    EXT(real_to_prot)

        xor     %eax, %eax
        movb    %bl, %al

        pop     %ebx
        pop     %ebp
        ret

/*
#
# get_diskinfo():  return a word that represents the
#       max number of sectors and  heads and drives for this device
#
*/

ENTRY(get_diskinfo)
        push    %ebp
        mov     %esp, %ebp
        push    %es
        push    %ebx
        push    %ecx
        push    %edx

        movb    0x8(%ebp), %dl          # diskinfo(drive #)
        call    EXT(prot_to_real)       # enter real mode

        movb    $0x8, %ah               # ask for disk info

        sti
        int     $0x13
        cli

        data16
        call    EXT(real_to_prot)       # back to protected mode

        xor     %eax, %eax

        /*form a longword representing all this gunk*/
        movb    %dh, %ah                # # heads
        andb    $0x3f, %cl              # mask of cylinder gunk
        movb    %cl, %al                # # sectors

        pop     %edx
        pop     %ecx
        pop     %ebx
        pop     %es
        pop     %ebp
        ret

/*
#
# memsize(i) :  return the memory size in KB. i == 0 for conventional memory,
#               i == 1 for extended memory
#       BIOS call "INT 12H" to get conventional memory size
#       BIOS call "INT 15H, AH=88H" to get extended memory size
#               Both have the return value in AX.
#
*/

ENTRY(memsize)
        push    %ebp
        mov     %esp, %ebp
        push    %ebx

        mov     8(%ebp), %ebx

        call    EXT(prot_to_real)               # enter real mode

        cmpb    $0x1, %bl
        data16
        je      xext

        sti
        int     $0x12
        cli
        data16
        jmp     xdone

xext:   movb    $0x88, %ah
        sti
        int     $0x15
        cli

xdone:
        mov     %eax, %ebx

        data16
        call    EXT(real_to_prot)

        mov     %ebx, %eax
        pop     %ebx
        pop     %ebp
        ret