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Bug fixes in the geometry detection. Linux video mode selection support. New Stage 1 stage1_lba is added. Stage 1.5 becomes much smaller.
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@@ -0,0 +1,394 @@
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/*
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* GRUB -- GRand Unified Bootloader
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* Copyright (C) 1996 Erich Boleyn <erich@uruk.org>
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* Copyright (C) 1999 Free Software Foundation, Inc.
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*
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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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*
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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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*
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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, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/*
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* defines for the code go here
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*/
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#define SIGNATURE 0xaa55
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#define BPBEND 0x3e
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#define PARTSTART 0x1be /* starting address of partition table */
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#define PARTEND 0x1fe /* ending addres of the partition table */
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#define MINPARAMSIZ 13 /* size of extra data parameters */
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#define LISTSIZ 8 /* size of sector list */
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#define REALSTACK 0x2000 /* stack for this code and BIOS calls */
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#define BUFFERSEG 0x7000 /* segment address of disk buffer, the
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disk buffer MUST be 32K long and cannot
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straddle a 64K boundary */
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/* Absolute addresses
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This makes the assembler generate the address without support
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from the linker. (ELF can't relocate 16-bit addresses!) */
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#define ABS(x) (x-_start+0x7c00)
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/* Print message string */
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#define MSG(x) movw $x, %si; call message
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.file "stage1_lba.S"
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.text
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/* Tell GAS to generate 16-bit instructions so that this code works
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in real mode. */
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.code16
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.globl _start; _start:
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/*
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* _start is loaded at 0x7c00 and is jumped to with CS:IP 0:0x7c00
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*/
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/*
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* Beginning of the sector is compatible with the FAT/HPFS BIOS
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* parameter block.
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*/
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jmp after_BPB
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nop /* do I care about this ??? */
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/*
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* This space is for the BIOS parameter block!!!! Don't change
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* the first jump, nor start the code anywhere but right after
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* this area.
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*/
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. = _start + 4
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/* scratch space */
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drive_parameter:
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disk_address_packet:
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/* Actually, must set these values at the runtime. */
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.byte 0x10
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.byte 0
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.word 0
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.long 0
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.quad 0
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/* more space... */
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. = _start + BPBEND
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/*
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* End of BIOS parameter block.
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*/
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after_BPB:
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/* general setup */
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cli /* we're not safe here! */
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/* set up %ds and %ss as offset from 0 */
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xorw %ax, %ax
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movw %ax, %ds
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movw %ax, %ss
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/* set up the REAL stack */
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movw $REALSTACK, %sp
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sti /* we're safe again */
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/*
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* Check if we have a forced disk reference here
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*/
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movb firstlist, %al
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cmpb $0xff, %al
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je 1f
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movb %al, %dl
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1:
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/* save drive reference first thing! */
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pushw %dx
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/* check if LBA is supported */
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movb $0x41, %ah
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movw $0x55aa, %bx
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int $0x13
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jc lba_probe_error
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cmpw $0xaa55, %bx
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jne lba_probe_error
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/* get the geometry (limited to 2TB!) */
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movb $0x48, %ah
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movw $ABS(drive_parameter), %si
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movw $0x1a, (%si)
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int $0x13
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jc lba_probe_error
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/* save the total number of sectors */
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movl 0x10(%si), %ecx
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/* this sets up for the first run through "bootloop" */
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movw $ABS(firstlist - LISTSIZ), %di
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/* this is the loop for reading the secondary boot-loader in */
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bootloop:
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/* check the number of sectors to read */
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cmpw $0, 4(%di)
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/* if zero, go to the start function */
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je bootit
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setup_sectors:
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/* load logical sector start */
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movl (%di), %ebx
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/* check for the geometry */
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cmpl %ecx, %ebx
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jge geometry_error
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/* the maximum is limited to 0x7f because of Phoenix EDD */
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xorl %eax, %eax
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movb $0x7f, %al
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/* how many do we really want to read? */
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cmpw %ax, 4(%di) /* compare against total number of sectors */
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/* which is greater? */
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jg more_sectors
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/* if less than, set to total */
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movw 4(%di), %ax
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more_sectors:
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/* subtract from total */
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subw %ax, 4(%di)
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/* add into logical sector start */
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addl %eax, (%di)
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/* set up disk address packet */
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/* the size and the reserved byte */
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movw $0x0010, (%si)
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/* the number of sectors */
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movw %ax, 2(%si)
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/* the absolute address (low 32 bits) */
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movl %ebx, 8(%si)
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/* the segment of buffer address */
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movw 6(%di), %bx
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movw %bx, 6(%si)
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pushw %ax /* save %ax from destruction! */
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/* zero %eax */
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xorl %eax, %eax
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/* the offset of buffer address */
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movw %ax, 4(%si)
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/* the absolute address (high 32 bits) */
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movl %eax, 12(%si)
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/*
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* BIOS call "INT 0x13 Function 0x42" to read sectors from disk into memory
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* Call with %ah = 0x42
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* %dl = drive number
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* %ds:%si = segment:offset of disk address packet
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* Return:
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* %al = 0x0 on success; err code on failure
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*/
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movb $0x42, %ah
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int $0x13
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jc read_error
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/* save source segment */
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movw %es, %bx
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/* load addresses for copy from disk buffer to destination */
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movw 6(%di), %es /* load destination segment */
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/* restore %ax */
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popw %ax
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/* determine the next possible destination address (presuming
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512 byte sectors!) */
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shlw $5, %ax /* shift %ax five bits to the left */
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addw %ax, 6(%di) /* add the corrected value to the destination
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address for next time */
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/* save addressing regs */
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pushw %ds
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pushw %si
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pushw %di
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pushw %cx
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/* get the copy length */
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shlw $4, %ax
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movw %ax, %cx
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xorw %di, %di /* zero offset of destination addresses */
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xorw %si, %si /* zero offset of source addresses */
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movw %bx, %ds /* restore the source segment */
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cld /* sets the copy direction to forward */
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/* perform copy */
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rep /* sets a repeat */
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movsb /* this runs the actual copy */
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/* restore addressing regs */
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popw %cx
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popw %di
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popw %si
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popw %ds
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/* check if finished with this dataset */
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cmpw $0, 4(%di)
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jne setup_sectors
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/* update position to load from */
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subw $LISTSIZ, %di
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/* jump to bootloop */
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jmp bootloop
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/* END OF MAIN LOOP */
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/*
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* BIOS Geometry translation error (past the end of the disk geometry!).
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*/
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geometry_error:
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MSG(geometry_error_string)
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jmp general_error
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/*
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* Disk probe failure.
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*/
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lba_probe_error:
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MSG(lba_probe_error_string)
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jmp general_error
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/*
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* Read error on the disk.
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*/
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read_error:
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MSG(read_error_string)
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general_error:
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MSG(general_error_string)
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/* go here when you need to stop the machine hard after an error condition */
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stop: jmp stop
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geometry_error_string: .string "Geom"
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lba_probe_error_string: .string "LBA"
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read_error_string: .string "Read"
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general_error_string: .string " Error"
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/*
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* message: write the string pointed to by %si
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*
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* WARNING: trashes %si, %ax, and %bx
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*/
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/*
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* Use BIOS "int 10H Function 0Eh" to write character in teletype mode
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* %ah = 0xe %al = character
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* %bh = page %bl = foreground color (graphics modes)
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*/
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1:
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movw $0x0001, %bx
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movb $0xe, %ah
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int $0x10 /* display a byte */
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incw %si
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message:
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movb (%si), %al
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cmpb $0, %al
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jne 1b /* if not end of string, jmp to display */
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ret
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lastlist:
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/*
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* This area is an empty space between the main body of code below which
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* grows up (fixed after compilation, but between releases it may change
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* in size easily), and the lists of sectors to read, which grows down
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* from a fixed top location.
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*/
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/*
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* This data area is for keeping general parameters.
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*/
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. = _start + PARTSTART - MINPARAMSIZ - LISTSIZ
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/* this next data area before the partition area is specifically
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sized, you should update "MINPARAMSIZ" to reflect any additions
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or deletions to this area */
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.word 0
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.word 0
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/* fill the first data listing with the default */
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#ifdef FFS_STAGE1_5
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.long 2 /* this is the sector start parameter, in logical
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sectors from the start of the disk, sector 0 */
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.word 14 /* this is the number of sectors to read */
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.word 0x0200 /* this is the segment of the starting address
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to load the data into */
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#else
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.long 1 /* this is the sector start parameter, in logical
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sectors from the start of the disk, sector 0 */
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.word 90 /* this is the number of sectors to read */
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.word 0x0800 /* this is the segment of the starting address
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to load the data into */
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#endif
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firstlist: /* this label has to be after the list data!!! */
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.byte 0xff /* the disk to load stage2 from */
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/* 0xff means use the boot drive */
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/*
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* Jump here when all data loading is done. This
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* goes to the second stage bootloader.
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*/
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bootit:
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popw %dx /* this makes sure %dl is our "boot" drive */
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ljmp $0, $0x8000 /* FIXME: make 0x2000 for stage1_5 */
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/*
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* This is the compatibility version number.
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* See ../stage2/shared.h for COMPAT_VERSION_* definitions used
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* in stage2 and stage1_5 modules.
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*
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* DO NOT MOVE THIS!!!
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*/
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.byte 2, 1
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/*
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* This is where an MBR would go if on a hard disk. The code
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* here isn't even referenced unless we're on a floppy. Kinda
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* sneaky, huh?
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*/
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. = _start + PARTSTART
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/* This space cannot be used by any bootloader, uggh... */
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. = _start + PARTEND
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/* the last 2 bytes in the sector 0 contain the signature */
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.word SIGNATURE
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