663 lines
16 KiB
ArmAsm
663 lines
16 KiB
ArmAsm
/* $NetBSD: mbr.S,v 1.23 2010/12/08 21:56:42 jakllsch Exp $ */
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/*
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* Copyright (c) 1999-2004 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Frank van der Linden, based on an earlier work by Wolfgang Solfrank.
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* Major surgery performed by David Laight.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* i386 master boot code
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*/
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/* Compile options:
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* BOOTSEL - bootselector code
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* BOOT_EXTENDED - scan extended partition list (LBA reads)
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* COM_PORT - do serial io to specified port number
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* 0..3 => bios port, otherwise actual io_addr
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* COM_BAUD - initialise serial port baud rate
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*
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* TERSE_ERROR - terse error messages
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* NO_CHS - all reads are LBA
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* NO_LBA_CHECK - no check if bios supports LBA reads
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* NO_BANNER - do not output title line 'banner'
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*/
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#ifdef BOOT_EXTENDED
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#define NO_CHS 1
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#define BOOTSEL 1
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#endif
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#ifdef COM_PORT
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#if COM_PORT < 4
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/* The first 4 items in the 40:xx segment are the serial port base addresses */
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#define COM_PORT_VAL (0x400 + (COM_PORT * 2))
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#else
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#define COM_PORT_VAL $COM_PORT
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#endif
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#if !defined(COM_FREQ)
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#define COM_FREQ 1843200
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#endif
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#else
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#undef COM_BAUD
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#endif
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#ifdef BOOTSEL
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#define TERSE_ERROR 1
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#endif
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#include <machine/asm.h>
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#include <sys/bootblock.h>
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#define BOOTADDR 0x7c00 /* where we get loaded to */
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#define TABENTRYSIZE (MBR_BS_PARTNAMESIZE + 1)
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#define NAMETABSIZE (MBR_PART_COUNT * TABENTRYSIZE)
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#ifdef COM_PORT
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/* ASCII values for the keys */
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#define KEY_ACTIVE '\r'
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#define KEY_DISK1 'a'
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#define KEY_PTN1 '1'
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#else
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/* Scan values for the various keys we use, as returned by the BIOS */
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#define SCAN_ENTER 0x1c
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#define SCAN_F1 0x3b
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#define SCAN_1 0x2
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#define KEY_ACTIVE SCAN_ENTER
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#define KEY_DISK1 SCAN_F1
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#define KEY_PTN1 SCAN_1
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#endif
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/*
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* Minimum and maximum drive number that is considered to be valid.
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*/
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#define MINDRV 0x80
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#define MAXDRV 0x8f
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#ifdef TERSE_ERROR
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/*
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* Error codes. Done this way to save space.
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*/
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#define ERR_INVPART '1' /* Invalid partition table */
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#define ERR_READ '2' /* Read error */
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#define ERR_NOOS '3' /* Magic no. check failed for part. */
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#define ERR_KEY '?' /* unknown key press */
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#define ERR_NO_LBA 'L' /* sector above chs limit */
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#define set_err(err) movb $err, %al
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#else
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#define set_err(err) mov $err, %ax
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#endif
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.text
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.code16
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/*
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* Move ourselves out of the way first.
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* (to the address we are linked at)
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* and zero our bss
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*/
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ENTRY(start)
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xor %ax, %ax
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mov %ax, %ss
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movw $BOOTADDR, %sp
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mov %ax, %es
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mov %ax, %ds
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movw $mbr, %di
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mov $BOOTADDR + (mbr - start), %si
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push %ax /* zero for %cs of lret */
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push %di
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movw $(bss_start - mbr), %cx
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rep
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movsb /* relocate code */
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mov $(bss_end - bss_start + 511)/512, %ch
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rep
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stosw /* zero bss */
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lret /* Ensures %cs == 0 */
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/*
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* Sanity check the drive number passed by the BIOS. Some BIOSs may not
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* do this and pass garbage.
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*/
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mbr:
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cmpb $MAXDRV, %dl /* relies on MINDRV being 0x80 */
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jle 1f
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movb $MINDRV, %dl /* garbage in, boot disk 0 */
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1:
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push %dx /* save drive number */
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push %dx /* twice - for err_msg loop */
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#if defined(COM_BAUD)
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mov $com_args, %si
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mov $num_com_args, %cl /* %ch is zero from above */
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mov COM_PORT_VAL, %dx
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1: lodsw
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add %ah, %dl
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outb %dx
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loop 1b
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#endif
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#ifndef NO_BANNER
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mov $banner, %si
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call message_crlf
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#endif
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/*
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* Walk through the selector (name) table printing used entries.
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*
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* Register use:
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* %ax temp
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* %bx nametab[] boot seletor menu
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* %ecx base of 'extended' partition
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* %edx next extended partition
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* %si message ptr (etc)
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* %edi sector number of this partition
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* %bp parttab[] mbr partition table
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*/
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bootsel_menu:
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movw $nametab, %bx
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#ifdef BOOT_EXTENDED
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xorl %ecx, %ecx /* base of extended partition */
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next_extended:
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xorl %edx, %edx /* for next extended partition */
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#endif
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lea parttab - nametab(%bx), %bp
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next_ptn:
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movb 4(%bp), %al /* partition type */
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#ifdef NO_CHS
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movl 8(%bp), %edi /* partition sector number */
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#ifdef BOOT_EXTENDED
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cmpb $MBR_PTYPE_EXT, %al /* Extended partition */
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je 1f
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cmpb $MBR_PTYPE_EXT_LBA, %al /* Extended LBA partition */
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je 1f
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cmpb $MBR_PTYPE_EXT_LNX, %al /* Linux extended partition */
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jne 2f
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1: movl %edi, %edx /* save next extended ptn */
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jmp 4f
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2:
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#endif
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addl lba_sector, %edi /* add in extended ptn base */
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#endif
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test %al, %al /* undefined partition */
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je 4f
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cmpb $0x80, (%bp) /* check for active partition */
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jne 3f /* jump if not... */
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#define ACTIVE (4 * ((KEY_ACTIVE - KEY_DISK1) & 0xff))
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#ifdef NO_CHS
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movl %edi, ptn_list + ACTIVE /* save location of active ptn */
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#else
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mov %bp, ptn_list + ACTIVE
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#endif
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#undef ACTIVE
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3:
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#ifdef BOOTSEL
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cmpb $0, (%bx) /* check for prompt */
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jz 4f
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/* output menu item */
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movw $prefix, %si
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incb (%si)
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call message /* menu number */
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mov (%si), %si /* ':' << 8 | '1' + count */
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shl $2, %si /* const + count * 4 */
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#define CONST (4 * ((':' << 8) + '1' - ((KEY_PTN1 - KEY_DISK1) & 0xff)))
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#ifdef NO_CHS
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movl %edi, ptn_list - CONST(%si) /* sector to read */
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#else
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mov %bp, ptn_list - CONST(%si) /* partition info */
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#endif
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#undef CONST
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mov %bx, %si
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call message_crlf /* prompt */
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#endif
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4:
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add $0x10, %bp
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add $TABENTRYSIZE, %bx
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cmpb $(nametab - start - 0x100) + 4 * TABENTRYSIZE, %bl
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jne next_ptn
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#ifdef BOOT_EXTENDED
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/*
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* Now check extended partition chain
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*/
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testl %edx, %edx
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je wait_key
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testl %ecx, %ecx
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jne 1f
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xchg %ecx, %edx /* save base of ext ptn chain */
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1: addl %ecx, %edx /* sector to read */
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movl %edx, lba_sector
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movw $lba_info, %si
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movb $0x42, %ah
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pop %dx /* recover drive # */
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push %dx /* save drive */
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int $0x13
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movw $BOOTADDR + (nametab - start), %bx
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jnc next_extended /* abort menu on read fail */
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#endif
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/*
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* The non-bootsel code traverses this code path, it needs the
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* correct keycode to select the active partition.
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*/
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#ifndef BOOTSEL
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mov $(KEY_ACTIVE - KEY_DISK1) & 0xff, %ax
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#else
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/*
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* Get the initial time value for the timeout comparison. It is returned
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* by int 1a in cx:dx. We do sums modulo 2^16 so it doesn't matter if
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* the counter wraps (which it does every hour) - so we can safely
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* ignore 'cx'.
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*
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* Loop around checking for a keypress until we have one, or timeout is
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* reached.
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*/
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wait_key:
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xorb %ah, %ah
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int $0x1a
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mov %dx, %di /* start time to di */
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3:
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#ifdef COM_PORT_VAL
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mov COM_PORT_VAL, %dx
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push %dx
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add $5, %dx
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inb %dx
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pop %dx
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test $1, %al
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jz 1f
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inb %dx
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jmp check_key
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#else
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movb $1, %ah /* looks to see if a */
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int $0x16 /* key has been pressed */
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jz 1f
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get_key:
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xorb %ah, %ah
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int $0x16 /* 'read key', code ah, ascii al */
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shr $8, %ax /* code in %al, %ah zero */
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jmp check_key
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#endif
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1: xorb %ah, %ah
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int $0x1a /* current time to cx:dx */
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sub %di, %dx
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cmpw timeout, %dx /* always wait for 1 tick... */
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jbe 3b /* 0xffff means never timeout */
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def_key:
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mov defkey, %al /* timedout - we need %ah to still be zero! */
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/*
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* We have a keycode, see what it means.
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* If we don't know we generate error '?' and go ask again
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*/
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check_key:
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/*
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* F1-F10 -> boot disk 0-9. Check if the requested disk isn't above
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* the number of disks actually in the system as stored in 0:0475 by
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* the BIOS.
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* If we trust loc 475, we needn't check the upper bound on the keystroke
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* This is always sector 0, so always read using chs.
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*/
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subb $KEY_DISK1, %al
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cmpb 0x0475, %al
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jae boot_ptn
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addb $0x80, %al
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pop %dx /* dump saved drive # */
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push %ax /* replace with new */
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#ifdef NO_CHS
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xorl %ebp, %ebp /* read sector number 0 */
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jmp boot_lba
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#else
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movw $chs_zero, %si /* chs read sector zero info */
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jmp read_chs
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#endif
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#endif /* BOOTSEL */
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/*
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* Boot requested partition.
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* Use keycode to index the table we generated when we scanned the mbr
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* while generating the menu.
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*
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* We very carfully saved the values in the correct part of the table.
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*/
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boot_ptn:
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shl $2, %ax
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movw %ax, %si
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#ifdef NO_CHS
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movl ptn_list(%si), %ebp
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testl %ebp, %ebp
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jnz boot_lba
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#else
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mov ptn_list(%si), %si
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test %si, %si
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jnz boot_si
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#endif
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#ifdef BOOTSEL
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set_err(ERR_KEY)
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#else
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set_err(ERR_INVPART)
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#endif
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/* jmp err_msg */
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/* Something went wrong...
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* Output error code,
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* reset disk subsystem - needed after read failure,
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* and wait for user key
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*/
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err_msg:
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#ifdef TERSE_ERROR
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movb %al, errcod
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movw $errtxt, %si
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call message
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#else
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push %ax
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movw $errtxt, %si
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call message
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pop %si
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call message_crlf
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#endif
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pop %dx /* drive we errored on */
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xor %ax,%ax /* only need %ah = 0 */
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int $0x13 /* reset disk subsystem */
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#ifdef BOOTSEL
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pop %dx /* original drive number */
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push %dx
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push %dx
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#ifdef COM_PORT_VAL
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jmp wait_key /* Read with timeout (again) */
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#else
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jmp get_key /* Blocking read */
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#endif
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#else
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int $0x18 /* BIOS might ask for a key */
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/* press and retry boot seq. */
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1: sti
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hlt
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jmp 1b
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#endif
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#ifndef NO_CHS
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/*
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* Active partition pointed to by si.
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* Read the first sector.
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*
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* We can either do a CHS (Cylinder Head Sector) or an LBA (Logical
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* Block Address) read. Always doing the LBA one
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* would be nice - unfortunately not all systems support it.
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* Also some may contain a separate (eg SCSI) bios that doesn't
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* support it even when the main bios does.
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*
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* There is also the additional problem that the CHS values may be wrong
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* (eg if fdisk was run on a different system that used different BIOS
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* geometry). We convert the CHS value to a LBA sector number using
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* the geometry from the BIOS, if the number matches we do a CHS read.
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*/
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boot_si:
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movl 8(%si), %ebp /* get sector # */
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testb $MBR_BS_READ_LBA, flags
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jnz boot_lba /* fdisk forced LBA read */
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pop %dx /* collect saved drive... */
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push %dx /* ...number to dl */
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movb $8, %ah
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int $0x13 /* chs info */
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/*
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* Validate geometry, if the CHS sector number doesn't match the LBA one
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* we'll do an LBA read.
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* calc: (cylinder * number_of_heads + head) * number_of_sectors + sector
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* and compare against LBA sector number.
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* Take a slight 'flier' and assume we can just check 16bits (very likely
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* to be true because the number of sectors per track is 63).
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*/
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movw 2(%si), %ax /* cylinder + sector */
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push %ax /* save for sector */
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shr $6, %al
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xchgb %al, %ah /* 10 bit cylinder number */
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shr $8, %dx /* last head */
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inc %dx /* number of heads */
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mul %dx
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mov 1(%si), %dl /* head we want */
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add %dx, %ax
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and $0x3f, %cx /* number of sectors */
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mul %cx
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pop %dx /* recover sector we want */
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and $0x3f, %dx
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add %dx, %ax
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dec %ax
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cmp %bp, %ax
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je read_chs
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#ifndef NO_LBA_CHECK
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/*
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* Determine whether we have int13-extensions, by calling int 13, function 41.
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* Check for the magic number returned, and the disk packet capability.
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*/
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movw $0x55aa, %bx
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movb $0x41, %ah
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pop %dx
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push %dx
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int $0x13
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set_err(ERR_NO_LBA)
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jc err_msg /* no int13 extensions */
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cmpw $0xaa55, %bx
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jnz err_msg
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testb $1, %cl
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jz err_msg
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#endif /* NO_LBA_CHECK */
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#endif /* NO_CHS */
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/*
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* Save sector number (passed in %ebp) into lba parameter block,
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* read the sector and leap into it.
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*/
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boot_lba:
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movl %ebp, lba_sector /* save sector number */
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movw $lba_info, %si
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movb $0x42, %ah
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pop %dx /* recover drive # */
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do_read:
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push %dx /* save drive */
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int $0x13
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set_err(ERR_READ)
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jc err_msg
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/*
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* Check signature for valid bootcode
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*/
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movb BOOTADDR, %al /* first byte non-zero */
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test %al, %al
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jz 1f
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movw BOOTADDR + MBR_MAGIC_OFFSET, %ax
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1: cmp $MBR_MAGIC, %ax
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set_err(ERR_NOOS)
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jnz err_msg
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/* We pass the sector number through to the next stage boot.
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* It doesn't have to use it (indeed no other mbr code will generate) it,
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* but it does let us have a NetBSD pbr that can identify where it was
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* read from! This lets us use this code to select between two
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* NetBSD system on the same physical driver.
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* (If we've read the mbr of a different disk, it gets a random number
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* - but it wasn't expecting anything...)
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*/
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movl %ebp, %esi
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pop %dx /* recover drive # */
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jmp BOOTADDR
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#ifndef NO_CHS
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/*
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* Sector below CHS limit
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* Do a cylinder-head-sector read instead.
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*/
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read_chs:
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pop %dx /* recover drive # */
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movb 1(%si), %dh /* head */
|
|
movw 2(%si), %cx /* ch=cyl, cl=sect */
|
|
movw $BOOTADDR, %bx /* es:bx is buffer */
|
|
movw $0x201, %ax /* command 2, 1 sector */
|
|
jmp do_read
|
|
#endif
|
|
|
|
/*
|
|
* Control block for int-13 LBA read.
|
|
* We need a xx, 00, 01, 00 somewhere to load chs for sector zero,
|
|
* by a complete fluke there is one here!
|
|
*/
|
|
chs_zero:
|
|
lba_info:
|
|
.word 0x10 /* control block length */
|
|
.word 1 /* sector count */
|
|
.word BOOTADDR /* offset in segment */
|
|
.word 0 /* segment */
|
|
lba_sector:
|
|
.long 0x0000 /* sector # goes here... */
|
|
.long 0x0000
|
|
|
|
errtxt: .ascii "Error " /* runs into crlf if errcod set */
|
|
errcod: .byte 0
|
|
crlf: .asciz "\r\n"
|
|
|
|
#ifndef NO_BANNER
|
|
#ifdef BOOTSEL
|
|
#ifdef COM_PORT_VAL
|
|
banner: .asciz "a: disk"
|
|
#else
|
|
banner: .asciz "Fn: diskn"
|
|
#endif
|
|
#else
|
|
banner: .asciz "NetBSD MBR boot"
|
|
#endif
|
|
#endif
|
|
|
|
#ifdef BOOTSEL
|
|
prefix: .asciz "0: "
|
|
#endif
|
|
|
|
#ifndef TERSE_ERROR
|
|
ERR_INVPART: .asciz "No active partition"
|
|
ERR_READ: .asciz "Disk read error"
|
|
ERR_NOOS: .asciz "No operating system"
|
|
#ifndef NO_LBA_CHECK
|
|
ERR_NO_LBA: .asciz "Invalid CHS read"
|
|
#endif
|
|
#ifdef BOOTSEL
|
|
ERR_KEY: .asciz "bad key"
|
|
#endif
|
|
#endif
|
|
|
|
#if defined(COM_BAUD)
|
|
#define COM_DIVISOR (((COM_FREQ / COM_BAUD) + 8) / 16)
|
|
com_args:
|
|
.byte 0x80 /* divisor latch enable */
|
|
.byte +3 /* io_port + 3 */
|
|
.byte COM_DIVISOR & 0xff
|
|
.byte -3 /* io_port */
|
|
.byte COM_DIVISOR >> 8 /* high baud */
|
|
.byte +1 /* io_port + 1 */
|
|
.byte 0x03 /* 8 bit no parity */
|
|
.byte +2 /* io_port + 3 */
|
|
num_com_args = (. - com_args)/2
|
|
#endif
|
|
|
|
/*
|
|
* I hate #including source files, but the stuff below has to be at
|
|
* the correct absolute address.
|
|
* Clearly this could be done with a linker script.
|
|
*/
|
|
|
|
message_crlf:
|
|
call message
|
|
movw $crlf, %si
|
|
#include <message.S>
|
|
#if 0
|
|
#include <dump_eax.S>
|
|
#endif
|
|
|
|
/*
|
|
* Stuff from here on is overwritten by fdisk - the offset must not change...
|
|
*
|
|
* Get amount of space to makefile can report it.
|
|
* (Unfortunately I can't seem to get the value reported when it is -ve)
|
|
*/
|
|
mbr_space = defkey - .
|
|
. = start + MBR_BS_OFFSET
|
|
/*
|
|
* Default action, as a keyvalue we'd normally read from the BIOS.
|
|
*/
|
|
defkey:
|
|
.byte KEY_ACTIVE /* ps/2 code */
|
|
#ifndef BOOTSEL_FLAGS
|
|
#define BOOTSEL_FLAGS 0
|
|
#endif
|
|
flags: .byte MBR_BS_NEWMBR | BOOTSEL_FLAGS
|
|
/*
|
|
* Timeout value. ~65536 ticks per hour, which is ~18.2 times per second.
|
|
* 0xffff means never timeout.
|
|
*/
|
|
timeout:
|
|
.word 182 /* default to 10 seconds */
|
|
/*
|
|
* mbr_bootsel
|
|
*/
|
|
nametab:
|
|
.fill MBR_PART_COUNT * (MBR_BS_PARTNAMESIZE + 1), 0x01, 0x00
|
|
|
|
/* space for mbr_dsn */
|
|
. = start + MBR_DSN_OFFSET
|
|
.long 0
|
|
|
|
/* mbr_bootsel_magic */
|
|
. = start + MBR_BS_MAGIC_OFFSET
|
|
.word MBR_BS_MAGIC
|
|
|
|
/*
|
|
* MBR partition table
|
|
*/
|
|
. = start + MBR_PART_OFFSET
|
|
parttab:
|
|
.fill 0x40, 0x01, 0x00
|
|
|
|
. = start + MBR_MAGIC_OFFSET
|
|
.word MBR_MAGIC
|
|
|
|
/* zeroed data space */
|
|
bss_off = 0
|
|
bss_start = .
|
|
#define BSS(name, size) name = bss_start + bss_off; bss_off = bss_off + size
|
|
BSS(ptn_list, 256 * 4) /* long[]: boot sector numbers */
|
|
BSS(dump_eax_buff, 16)
|
|
BSS(bss_end, 0)
|