OpenSolaris_b135/grub/grub-0.97/stage2/start_eltorito.S
/*
* GRUB -- GRand Unified Bootloader
* Copyright (C) 1994-2002 H. Peter Anvin
* Copyright (C) 1999,2000,2001,2004 Free Software Foundation, Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
*/
/*
Most of this file was originally "isolinux.asm" from SYSLINUX package.
It has been very heavily modified.
*/
#define ASM_FILE
#include "stage1.h"
#include "shared.h"
#include "iso9660.h"
#ifndef STAGE1_5
#include "stage2_size.h"
#endif
/* Absolute addresses
This makes the assembler generate the address without support
from the linker. (ELF can't relocate 16-bit addresses!) */
#define ABS(x) (x-_start+BOOTSEC_LOCATION)
#ifdef STAGE1_5
# define STAGE_ADDR 0x2000
#else
# define STAGE_ADDR 0x8000
#endif /* STAGE1_5 */
/* Print message string */
#define MSG(x) mov $ABS(x), %si; call message;
.file "start_eltorito.S"
.text
/* Tell GAS to generate 16-bit instructions so that this code works
in real mode. */
.code16
.globl start, _start
/*
* Primary entry point. Because BIOSes are buggy, we only load the first
* CD-ROM sector (2K) of the file, so the number one priority is actually
* loading the rest.
*/
start:
_start:
cli
ljmp $0, $ABS(real_start)
. = _start + 8 /* Pad to file offset 8 */
/* This table gets filled in by mkisofs using the
-boot-info-table option */
bi_pvd: .long 0xDEADBEEF /* LBA of primary volume descript */
bi_file: .long 0xDEADBEEF /* LBA of boot file */
bi_length: .long 0xDEADBEEF /* Length of boot file */
bi_csum: .long 0xDEADBEEF /* Checksum of boot file */
bi_reserved: .space (10*4) /* Reserved */
real_start:
xor %ax, %ax
mov %ax, %ss
mov %ax, %ds
mov %ax, %es
mov %ax, %fs
mov %ax, %gs
mov $STAGE1_STACKSEG, %sp /* set up the REAL stack */
sti
cld
/* save drive reference first thing! */
mov %dl, ABS(BootDrive)
/* print a notification message on the screen */
MSG(notification_string)
load_image:
/* Set up boot file sector, size, load address */
mov ABS(bi_length), %eax
add $(ISO_SECTOR_SIZE-1), %eax
shr $ISO_SECTOR_BITS, %eax /* dwords->sectors */
mov %ax, %bp /* boot file sectors */
mov $(STAGE_ADDR >> 4), %bx
mov %bx, %es
xor %bx, %bx
mov ABS(bi_file), %eax
call getlinsec
mov %ds, %ax
mov %ax, %es
MSG(notification_done)
bootit:
/* save the sector number of the second sector in %ebp */
mov $ABS(firstlist - BOOTSEC_LISTSIZE), %si
mov (%si), %ebp
mov ABS(BootDrive), %dl /* this makes sure %dl is our "boot" drive */
ljmp $0, $(STAGE_ADDR+SECTOR_SIZE) /* jump to main() in asm.S */
/* go here when you need to stop the machine hard after an error condition */
stop: jmp stop
/*
* Get linear sectors - EBIOS LBA addressing, 2048-byte sectors.
*
* Note that we can't always do this as a single request, because at least
* Phoenix BIOSes has a 127-sector limit. To be on the safe side, stick
* to 16 sectors (32K) per request.
*
* Input:
* EAX - Linear sector number
* ES:BX - Target buffer
* BP - Sector count
*/
getlinsec:
mov $ABS(dapa), %si /* Load up the DAPA */
mov %bx, 4(%si)
mov %es, %bx
mov %bx, 6(%si)
mov %eax, 8(%si)
1:
push %bp
push %si
cmp ABS(MaxTransfer), %bp
jbe 2f
mov ABS(MaxTransfer), %bp
2:
mov %bp, 2(%si)
mov ABS(BootDrive), %dl
mov $0x42, %ah /* Extended Read */
call xint13
pop %si
pop %bp
movzwl 2(%si), %eax /* Sectors we read */
add %eax, 8(%si) /* Advance sector pointer */
sub %ax, %bp /* Sectors left */
shl $(ISO_SECTOR_BITS-4), %ax /* 2048-byte sectors -> segment */
add %ax, 6(%si) /* Advance buffer pointer */
pushal
MSG(notification_step)
popal
cmp $0, %bp
ja 1b
mov 8(%si), %eax /* Return next sector */
ret
/*
* INT 13h with retry
*/
xint13:
movb $6, ABS(RetryCount)
.try:
pushal
int $0x13
jc 1f
add $(8*4), %sp /* Clean up stack */
ret
1:
mov %ah, %dl /* Save error code */
decb ABS(RetryCount)
jz .real_error
mov ABS(RetryCount), %al
mov ABS(dapa+2), %ah /* Sector transfer count */
cmp $2, %al /* Only 2 attempts left */
ja 2f
mov $1, %ah /* Drop transfer size to 1 */
jmp .setmaxtr
2:
cmp $3, %al
ja 3f /* First time, just try again */
shr $1, %ah /* Otherwise, try to reduce */
adc $0, %ah /* the max transfer size, but not */
.setmaxtr:
mov %ah, ABS(MaxTransfer)
mov %ah, ABS(dapa+2)
3:
popal
jmp .try
.real_error:
MSG(read_error_string)
mov %dl, %al
call printhex2
popal
jmp stop
/*
* message: write the string pointed to by %si
*
* WARNING: trashes %si, %ax, and %bx
*/
/*
* Use BIOS "int 10H Function 0Eh" to write character in teletype mode
* %ah = 0xe %al = character
* %bh = page %bl = foreground color (graphics modes)
*/
1:
mov $0x0001, %bx
mov $0x0E, %ah
int $0x10 /* display a byte */
message:
lodsb
or %al, %al
jne 1b /* if not end of string, jmp to display */
ret
/*
* printhex[248]: Write a hex number in (AL, AX, EAX) to the console
*/
printhex2:
pushal
rol $24, %eax
mov $2, %cx
jmp 1f
printhex4:
pushal
rol $16, %eax
mov $4, %cx
jmp 1f
printhex8:
pushal
mov $8, %cx
1:
rol $4, %eax
push %eax
and $0x0F, %al
cmp $10, %al
jae .high
.low: add $('0'), %al
jmp 2f
.high: add $('A'-10), %al
2:
mov $0x0001, %bx
mov $0x0E, %ah
int $0x10 /* display a char */
pop %eax
loop 1b
popal
ret
/**************************************************************************/
#ifdef STAGE1_5
notification_string: .string "Loading stage1.5 "
#else
notification_string: .string "Loading stage2 "
#endif
notification_step: .string "."
notification_done: .string "\r\n"
read_error_string: .string "Read error 0x"
/*
* EBIOS disk address packet
*/
.align 8
dapa: .byte 16 /* Packet size */
.byte 0 /* reserved */
.word 0 /* +2 Block count */
.word 0 /* +4 Offset of buffer */
.word 0 /* +6 Segment of buffer */
.long 0 /* +8 LBA (LSW) */
.long 0 /* +C LBA (MSW) */
VARIABLE(BootDrive)
.byte 0xFF
VARIABLE(MaxTransfer)
.word 16 /* Max sectors per transfer (32Kb) */
VARIABLE(RetryCount)
.byte 0
/*
* This area is an empty space between the main body of code below which
* grows up (fixed after compilation, but between releases it may change
* in size easily), and the lists of sectors to read, which grows down
* from a fixed top location.
*/
.word 0
.word 0
. = _start + SECTOR_SIZE - BOOTSEC_LISTSIZE
/* fill the first data listing with the default */
blocklist_default_start:/* this is the sector start parameter, in logical
sectors from the start of the disk, sector 0 */
.long 0
blocklist_default_len: /* this is the number of sectors to read */
#ifdef STAGE1_5
.word 0
#else
.word (STAGE2_SIZE + ISO_SECTOR_SIZE - 1) >> ISO_SECTOR_BITS
#endif
blocklist_default_seg: /* this is the segment of the starting address
to load the data into */
.word (STAGE_ADDR + SECTOR_SIZE) >> 4
firstlist: /* this label has to be after the list data!!! */