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* Extended Boot Option ROM
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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* Copyright IBM Corporation, 2007
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* Authors: Anthony Liguori <aliguori@us.ibm.com>
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#define OLD_INT19 (0x80 * 4) /* re-use INT 0x80 BASIC vector */
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#define OLD_INT13 (0x81 * 4) /* re-use INT 0x81 BASIC vector */
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.byte (_end - _start) / 512
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/* setup ds so we can access the IVT */
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/* there is one more bootable HD */
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/* install out int 19 handler */
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movw $int19_handler, (0x19*4)
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push %eax /* reserve space for lret */
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/* setup ds to access IVT */
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/* save old int 13 to int 2c */
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/* install our int 13 handler */
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movw $int13_handler, (0x13*4)
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/* restore previous int $0x19 handler */
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/* write old handler as return address onto stack */
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/* The two macro below clear/set the carry flag to indicate the status
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* of the interrupt execution. It is not enough to issue a clc/stc instruction,
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* since the value of the flags register will be overwritten by whatever is
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/* 8 = 2 (bp, just pushed) + 2 (ip) + 3 (real mode interrupt frame) */
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and $(~FLAGS_CF), 8(%bp)
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/* 8 = 2 (bp, just pushed) + 2 (ip) + 3 (real mode interrupt frame) */
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or $(FLAGS_CF), 8(%bp)
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mov %sp, %bp /* remember the current stack position */
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mov %sp, %bp /* remember the current stack position */
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mov %ax, 0(%bx) /* ax */
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mov 0(%bp), %ax /* bx */
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mov %cx, 4(%bx) /* cx */
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mov %dx, 6(%bx) /* dx */
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mov %si, 8(%bx) /* si */
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mov %ds, 10(%bx) /* ds */
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mov %es, 12(%bx) /* ds */
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movw \value, 14(%bx) /* value */
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add32: /* lo, hi, lo, hi */
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movw 4(%bp), %cx /* hi */
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movw 6(%bp), %dx /* lo */
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mul32: /* lo, hi, lo, hi */
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/* 10(%bp), 8(%bp), 6(%bp), 4(%bp) */
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/* for (i = 0; i < 16;) */
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/* this really should be a function, not a macro but i'm lazy */
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.macro read_write_disk_sectors cmd
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/* save nb_sectors */
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movw $0, 0(%bx) /* read c,h,s */
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mov 6(%bx), %ax /* total_sectors */
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mov 2(%bp), %si /* *= heads */
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add 4(%bp), %ax /* += sectors - 1 */
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push 4(%bx) /* total_heads */
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push 6(%bx) /* total_sectors */
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push 0(%bp) /* cylinders */
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movw \cmd, 0(%bx) /* read */
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movw 6(%bp), %ax /* nb_sectors */
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movw %es, 4(%bx) /* segment */
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movw 8(%bp), %ax /* offset */
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movw %dx, 8(%bx) /* sector */
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read_write_disk_sectors $0x01
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read_write_disk_sectors $0x02
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read_disk_drive_parameters:
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/* allocate memory for packet, pointer gets returned in bx */
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movw $0, 0(%bx) /* cmd = 0, read c,h,s */
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/* normalize sector value */
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/* normalize cylinders */
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/* normalize heads */
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/* do this last since it's the most sensitive */
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alternate_disk_reset:
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read_disk_drive_size:
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movw $0, 0(%bx) /* cmd = 0, read c,h,s */
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/* cylinders - 1 to cx:dx */
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check_if_extensions_present:
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.macro extended_read_write_sectors cmd
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movw \cmd, 0(%bp) /* read */
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movw 2(%si), %ax /* nb_sectors */
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movw 4(%si), %ax /* offset */
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movw 6(%si), %ax /* segment */
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movw 8(%si), %ax /* block */
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extended_read_sectors:
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extended_read_write_sectors $0x01
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extended_write_sectors:
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extended_read_write_sectors $0x02
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get_extended_drive_parameters:
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movw $0, 0(%bp) /* read c,h,s */
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/* set total number of sectors */
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/* number of bytes per sector */
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terminate_disk_emulation:
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/* write old handler as return address onto stack */
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mov (OLD_INT13), %eax
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call read_disk_sectors
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call read_disk_drive_parameters
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call read_disk_drive_size
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call check_if_extensions_present
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call extended_read_sectors
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call get_extended_drive_parameters
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call terminate_disk_emulation
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call alternate_disk_reset
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call write_disk_sectors
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call extended_write_sectors
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int $0x18 /* boot failed */
added
removed
pc-bios/optionrom/extboot.S
