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src.rivoreo.one / grub4dos-solaris / 05db3725e165387a72f779b7d4cfdd7267f1732c / . / stage2 / grldrstart.S
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/*
* grldrstart.S -- Startup code for GRLDR
* Copyright (C) 2004-2006 Tinybit(tinybit@tom.com)
*
* 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.
*/
/*
* This program is used to generate the GRLDR file.
*
* Use the following shell command to generate the GRLDR file:
*
* cat grldrstart pre_stage2 > grldr
*
*/
#define ASM_FILE
#include <shared.h>
#define ASM_FILE
#ifndef STAGE1_5
#include <stage2_size.h>
#else
#error cannot compile with STAGE1_5
#endif
#ifdef GRLDR_MBR
.file "mbrstart.S"
#elif defined(GRLDR_INSTALL)
.file "bootlacestart.S"
#else
.file "grldrstart.S"
#endif
#ifdef GRLDR_INSTALL
//.data
#else
.text
.globl start, _start
start:
_start:
#endif
_start1:
/* Tell GAS to generate 16-bit real mode instructions */
.code16
. = _start1 + 0x00
/* 1 byte at offset 0x00 will be overwritten for the EBIOS indicator
* later. This is safe because the jmp instruction only get executed
* once. The write happens after the jmp instruction have got
* executed.
*
* The value written would be 0x42 for EBIOS present(LBA) and 0x02
* for non-present(CHS).
*
*/
/* No cli, we use stack! BIOS or caller usually sets SS:SP=0000:0400 */
jmp 1f /* FAT32/NTFS routine comes to offset 0 */
. = _start1 + 0x02
.byte 0x80 /* bit0=1: disable GRLDR search on floppy */
/* bit1=1: disable the boot of the previous MBR with
* invalid partition table */
/* bit2=1: disable the feature of unconditional
* entrance to the command-line */
/* bit7=1: disable the boot of the previous MBR prior
to the search for GRLDR */
/* GRLDR.MBR uses offset 0x03 to indicate a timer counter. */
/* 0xff indicates waiting forever,
* other value specifies the time in seconds to wait */
. = _start1 + 0x03
.byte 5
/* a key press to wait. if AX returned from int16 equals this word,
* the desired action will occur. */
. = _start1 + 0x04
.word 0x3920 /* the space bar */
. = _start1 + 0x06
.byte 0xff /* preferred boot drive number, 0xff for no-drive(i.e., drive not defined) */
.byte 0xff /* preferred partition number, 0xff for whole drive(a floppy that has no partition table) */
. = _start1 + 8
#if (! defined(GRLDR_MBR)) && (! defined(GRLDR_INSTALL))
/* 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 */
. = _start1 + 0x40
#endif /* ! defined(GRLDR_MBR) && (! defined(GRLDR_INSTALL)) */
1:
call 1f
#if (! defined(GRLDR_MBR)) && (! defined(GRLDR_INSTALL))
. = _start1 + 0x43
#else
. = _start1 + 0x0b
#endif /* ! defined(GRLDR_MBR) && (! defined(GRLDR_INSTALL)) */
1:
popw %bx /* Instruction Pointer of 1b */
#if (! defined(GRLDR_MBR)) && (! defined(GRLDR_INSTALL))
subw $(1b - _start1), %bx /* CS:BX=_start1 */
#endif /* ! defined(GRLDR_MBR) && (! defined(GRLDR_INSTALL)) */
shrw $4, %bx
movw %cs, %ax
addw %ax, %bx /* BX:0000=_start1 */
#if (! defined(GRLDR_MBR)) && (! defined(GRLDR_INSTALL))
/* we are booted from BOOT.INI, or whole GRLDR image already loaded */
pushw %bx /* BX:0000=_start1 */
addw $((grldr_signature - _start1 + 4 + STAGE2_SIZE - 4) >> 4), %bx
movw %bx, %ds
cmpl $0xCE1A02B0, ((STAGE2_SIZE - 4) & 0x0F)
popw %ds /* DS:0000=_start1 */
je grldr_real_start /* whole image loaded. boot it! */
/* bad! we might be loaded by a buggy BIOS with a no-emulation-mode
* bootable CD. The buggy BIOS might load only 1 CD-ROM sector(2048
* bytes) of our grldr image. So we need this check.
*/
/* Our cdrom_check code begins at 0x1BE and overlaps the partition
* table. Just in case someone replace it with a partition table and
* use this sector as an MBR, we do this additional test for safety.
*/
testb $0x7F, cdrom_check - _start1
jz 1f
call cdrom_check
1:
/* DS:0000=_start1 */
/* Let CS:0000=_start1 */
pushw %ds
#;pushw $(1f - _start1)
.byte 0x6A, (1f - _start1)
lret
. = . - (. - _start1) / 0x80
1:
#else
/* BX:0000=_start1 */
movw %bx, %ds
/* Let CS:0000=_start1 */
pushw %bx
#;pushw $(1f - _start1)
.byte 0x6A, (1f - _start1)
lret
. = . - (. - _start1) / 0x80
1:
testb $0x04, 0x02
jz 1f
/* set the DUCE indicator */
xorw %ax, %ax
movw %ax, %es
movw $0x5FC, %di
movl $0x45435544, %eax
stosl
1:
#endif
/* CS:0000=DS:0000=_start1 */
/* we are loaded by BIOS or another boot loader */
#define GRLDR_CS 0x2000 /* grldr code segment */
/* hope this segment never be used by all */
/* subsequent partition boot records */
// cli
pushw $GRLDR_CS
popw %ss
movw $0x9000, %sp /* SS:SP=0x9d000, keep away from EBDA data */
// sti
/* Extended BIOS Data Area should not take up space below 0x9d000 */
/*
* 0x07c00-0x07dff This sector. Another boot loader load us here
* 0x0d000-0x14dff partition/floppy boot track(bootsector,etc)
* 0x94000-0x9bdff master boot track(MBR,etc,usually 63 sectors)
* 0x9be00-0x9c3ff 3 sectors for temp extended partition entries
* 0x9c400-0x9cfff 6 sectors for stack
*/
#define FS_BOOT 0xd00 /* segment of partition boot track */
xorw %cx, %cx
pushw %cx /* CX=0 */
movw $0x0080, %dx
pushw %dx
//movb $0x80, %dl
movb $8, %ah /* read drive parameters changes DX,ES,DI */
stc
int $0x13
popw %dx
popw %ax /* AX=0 */
pushw %ss /* SS=0x9400 */
popw %es /* ES=0x9400 */
#; jc 2f
jc Error1
andb $63, %cl /* AL=sectors per track, CF cleared */
#; jnz 1f
stc
jz Error1
#;2:
#; /* drive 0x80 not present. check hard drives in BIOS DATA AREA. */
#; //pushw %cs /* DS=CS */
#; //xorw %ax, %ax
#; movw %ax, %ds /* DS=0 */
#; cmpb 0x475, %al
#; //popw %ds /* DS=CS */
#; stc
#; je Error1 /* no hard drive, continue */
#; movw $(buggy_bios_string - _start1), %si
#; jmp Error2 /* there is a hard drive, fatal. Halt! */
#; //stc
#; //jz Error1 /* invalid value, try floppy (fd0) */
#;1:
xchgw %ax, %cx /* this moves CL to AL, and CX=0 */
movb $0x02, %ah
movw %ax, %bp /* save AX to BP: read 1 track */
xorw %bx, %bx /* ES already has a known value of 0x9400 */
incw %cx
pushw %dx
stc
int $0x13 /* read master boot track to ES:0000 */
popw %dx
jc Error1
negb %ah /* set CF=1 if non-zero */
Error1:
pushw %cs /* DS=0 */
popw %ds /* DS=CS */
pushfw /* CF=1 on error */
/* CS=DS=old segment. ES=SS=new segment. */
/* Move the code and error messages from DS:0000 to 9400:0000, do not
* touch the partition table
*/
xorw %si, %si
xorw %di, %di
movw $223, %cx /* 223 words = 446 bytes = 0x1be bytes */
cld
repz movsw /* SI=DI=0x1be, CX=0 */
movw $(grldr_signature - _start1), %bx
/* if the boot loader has loaded more than one sector, we use them */
movl $0xAA555247, %eax /* "GR" 0x55 0xAA */
#if (! defined(GRLDR_MBR)) && (! defined(GRLDR_INSTALL))
cmpl %eax, (%bx) /* DS=old segment! */
jne 1f
/* The MOVE_HELPER code is in the old segment! */
call move_helper /* SI=0x1be, CX=0 */
1:
#endif
/* Jump to new segment! */
#if 1
ljmp $GRLDR_CS, $(1f - _start1)
#else
pushw %ss /* 0x9400 */
//pushw $(1f - _start1)
.byte 0x6A, (1f - _start1)
lret
. = . - (. - _start1) / 0x80
#endif
1:
/* We are at the new segment. CS=ES=SS=new segment. */
/* But DS is still old segment. */
pushw %ss
popw %ds
/* CS=DS=ES=SS=new segment. */
//movw $0x01be, %si
/* check the existence of helper */
cmpl %eax, (%bx)
jne Error_or_prev_MBR /* Missing helper */
popfw /* CF=1 on error */
jc try_floppy /* harddisk (hd0) failed, try floppy (fd0) */
1:
pushw %cs
popw %ds
lodsw
movb %ah, %dh /* head number */
lodsw
movw %ax, %cx /* sector and cylinder number */
andb $63, %al
//stc
jz helper_call_c
/* use BP to calculate the sectors to read within 1 track */
subw %bp, %ax
decw %ax /* decb %al */
negb %al /* AL=sectors upto the end of the track */
7:
movw $3, %di /* retry 3 times on read failure */
2:
movb $2, %ah
pushw $FS_BOOT
popw %es /* ES=FS_BOOT */
xorw %bx, %bx
//pushw %ax
pushaw
int $0x13 /* read partition boot track to FS_BOOT:0000 */
popaw
//popw %ax
jnc helper_call
//pushw %ax
pushaw
xorw %ax, %ax
int $0x13
popaw
//popw %ax
decw %di
jnz 2b
helper_call_c:
stc
helper_call:
/* find GRLDR in this partition
* before the call:
* CF=1 : indicates an invalid or corrupt entry
* CF=0 : indicates a valid entry
*
* on return:
* CF=1 : means "below", try next entry
* CF=0,ZF=1 : means "equal", helper did nothing, so we need
* a further try to boot via NT bootsector
* CF=0,ZF=0 : means "above", helper succeeded, boot it now
*/
call helper_start /* change to jmp 6f if helper not present */
ja filesystem_boot /* helper succeeded, directly boot it */
6:
add_sub_si:
/* extended partition check routine will adjust this to
*
* 0x83, 0xEE, 0x04 for "subw $4, %si"
*
* or
*
* 0x83, 0xC6, 0xFC for "addw $-4, %si"
*
* so that SI keeps the value 0x1fe.
*/
addw $12, %si /* 0x83, 0xC6, 0x0C */
. = add_sub_si + 3
/* extended partition check routine will adjust the word 0x1fe at
* (add_sub_si + 5). The value 0x1ff or greater indicates there are
* entries need to be treated. The value 0x1fe indicates no entries
* left, and the floppy should be checked.
*/
cmpw $0x01fe, %si /* 0x81, 0xFE, 0xfe, 0x01 */
/* All entries checked done? */
jb 1b /* No, check the next entry */
ja 5f /* floppy already checked. Fail and hang */
try_floppy:
movw $0x31b2, %si /* a value big enough */
movb $0x08, %ah /* read drive parameters changes DX,ES,DI */
cwd /* DL=0 for floppy */
pushw %dx /* DX=0 */
int $0x13
popw %ax /* AX=0 */
jc 5f /* floppy failure, issue "Error" and hang */
cwd /* DX=0 */
xchgw %ax, %cx /* this moves CL to AL, and CX=0 */
andb $63, %al /* AL=sectors per track */
jz 5f /* invalid value. floppy failure. hangs */
//movw $1, %cx
incw %cx
jmp 7b
5:
Error_or_prev_MBR:
/* GRLDR not found, print "Error" or launch previous MBR */
movw $(message_string - _start1), %si
Error2:
call print_message /* CS:SI points to message string */
3: jmp 3b
filesystem_boot:
/* The partition boot record successfully modified, just boot it */
/*
* The boot might fail, but we want to take back the control.
* So we save the registers now.
*/
pushw %ds
pushw %es
pushal
/* DS=CS=GRLDR_CS, ES=FS_BOOT */
/* save GRLDR_CS */
movw %es, %bx # save old ES to BX
cli
lgdt gdt - _start1
movl %cr0, %eax
orb $1, %al
movl %eax, %cr0
movw $8, %si
movw %si, %es
xorl %esi, %esi
xorl %edi, %edi
movl $(0x9000 / 4), %ecx
cld
repz movsl
movw $16, %si
movw %si, %es
andb $0xfe, %al
movl %eax, %cr0
movw %bx, %es # restore ES from BX
/* move FS_BOOT:0000 to 0:7c00 */
movw $0x0200, %cx /* move 2 sectors, the old FS_BOOT:0000 will
* keep untouched. */
xorw %si, %si
pushw %si /* SI=0, for the segment of 0000:7c00 */
movw $0x7c00, %di
pushw %di /* DI=0x7c00, for the offset of 0000:7c00 */
pushw %es /* ES=FS_BOOT */
popw %ds /* DS=FS_BOOT */
pushw %si /* SI=0 */
popw %es /* ES=0 */
cld
repz movsw
movw $0x7e10, %di
movw $(restore_GRLDR_CS - _start1), %si
movw $((gdt_end - restore_GRLDR_CS) / 4), %cx
cld
repz cs movsl /* CS segment override prefix(=0x2E) */
pushw %es /* ES=0 */
popw %ds /* DS=0 */
sti
lret //ljmp $0, $0x7c00
try_next_partition:
cli
movw $GRLDR_CS, %ax
movw %ax, %ss
movw $(0x9000-36), %sp
sti
/* restore the registers and continue */
popal
popw %es
popw %ds
jmp add_sub_si
/* prints string CS:SI (modifies AX BX SI) */
3:
//xorw %bx, %bx /* video page 0 */
movb $0x0e, %ah /* print char in AL */
int $0x10 /* via TTY mode */
print_message:
lodsb %cs:(%si), %al /* get token */
cmpb $0, %al /* end of string? */
jne 3b
ret
message_string:
#if (! defined(GRLDR_MBR)) && (! defined(GRLDR_INSTALL))
.ascii "\r\nMissing helper.\0"
#else
.ascii "\r\nMissing MBR-helper.\0"
#endif
#;buggy_bios_string:
#;
#; .ascii "\r\nBuggy BIOS!\0"
/* Make sure the above code does not occupy the partition table */
#if (! defined(GRLDR_MBR)) && (! defined(GRLDR_INSTALL))
/* offset value here must be less than or equal to 0x1be */
. = . - ((. - _start1) / 0x1bf)
#else
/* offset value here must be less than or equal to 0x1b8 */
. = . - ((. - _start1) / 0x1b9)
#endif
/* The following code may occupy the same area as the partition table */
#if (! defined(GRLDR_MBR)) && (! defined(GRLDR_INSTALL))
/* we are not booted from MBR. So we can reuse the area of partition
* table for our code.
*/
. = _start1 + 0x1be
cdrom_check:
/* DS points to the sector start, but CS does not. */
/* BX segment points to near the end of GRLDR image. */
popw %ax /* old return IP */
/* set BX as the new safe stack. */
movw %bx, %ss
movw $0xFFF0, %sp
pushw %ax /* old return IP */
/* check if DL is no-emulation-mode bootable CDROM. */
pushw %ds
cmpb $0x81, %dl
jb 1f /* not a valid no-emulation-mode cdrom drive number */
cmpw $0xAA55, 0x7FE /* 2048 bytes loaded? */
jne 1f
cmpw $0xAA55, 0x5FE /* 2048 bytes loaded? */
jne 1f
// movw 0x7FE, %ax
// xchgb %ah, %al
// orw 0x5FE, %ax
// inc %ax
// jne 1f
// /* check cdrom using int13/AX=4B01h */
//
// /* AX=0 */
// movw $0x0180, %si
// movw %si, %di
// movw $0x40, %cx
// pushw %cx
// popw %ds
// pushw %ds
// popw %es
// repz stosw
movw $0x0180, %si
movw $0x4B01, %ax
pushw $0x0040
//.byte 0x6A, 0x40
popw %ds
pushw %ds
popw %es
movb $0x13, (%si)
int $0x13
jc 2f /* not in emulation mode */
testb $0x0F, 1(%si) /* boot media type is No Emulation? */
jnz 2f /* no, it simulates floppy or hard disk. */
cmpb %dl, 2(%si) /* drive number */
// jnz 2f /* invalid drive */
jz cdrom_helper /* OK! it is no-emulation-mode cdrom drive. */
// movl 4(%si), %eax /* LBA of GRLDR */
// jmp cdrom_helper
// /* load the first sector of GRLDR */
// movw $0x4201, %ax
// movw $0x01A0, %si
// int $0x13
2:
// /* check once more using int13/AH=48h */
// movb $0x48, %ah
// movw $0x0180, %si
// movl $0x1E, (%si)
// int $0x13
// jc 1f
// cmpw $0x800, 0x18(%si)
// jne 1f
// jmp cdrom_helper
1:
popw %ds
ret
#endif /* ! defined(GRLDR_MBR) && (! defined(GRLDR_INSTALL)) */
. = _start1 + 0x1fe /* boot signature */
/* partition entries in the extended partitions will overwrite code here upto
* 0x3fd.
*
* the extended partition entries will occupy a temp area at 0x9be00-0x9c3ff
*/
#if (defined(GRLDR_MBR)) || (defined(GRLDR_INSTALL))
.word 0xaa55
#endif
. = _start1 + 0x200
/* if it is in the Master Boot Track, the second sector can be used to backup
* the previously working MBR, typically, the MS MBR. if the backup copy of
* the MBR cannot boot(because, e.g., it depends on another sector of code
* that does not exist for now), then please do not set the ending signature
* to 0xAA55, that is to say, if the signature is already 0xAA55, you should
* change it to another value(for example, 0x0000).
*/
#if (! defined(GRLDR_MBR)) && (! defined(GRLDR_INSTALL))
#if 0
print_cl:
pushaw
movw %cx, %ax
movb $16, %cl
divb %cl # quo=AL, rem=AH
orw $0x3030, %ax
cmpb $0x39, %ah
jbe 1f
addb $7, %ah
1:
cmpb $0x39, %al
jbe 1f
addb $7, %al
1:
movb %ah, %cl
xorw %bx, %bx
movb $0x0e, %ah
int $0x10
movb $0x0e, %ah
movb %cl, %al
int $0x10
movw $0x0e20, %ax
int $0x10
popaw
ret
#else
#if 0
.word 5, 0x47, 0x52, 0x4c, 0x44, 0x52, 4, 0x24
.word 0x49, 0x33, 0x30, 0xe000, 0, 0x3000, 0, 0
#else
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
#endif
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
#endif
. = _start1 + 0x256 /* cmdcons comes here */
#if 0
jmp 1f
#else
.byte 0x90, 0x90
#endif
. = _start1 + 0x258
.byte 0x90, 0x90
. = _start1 + 0x25a
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
.byte 0x90, 0x90
. = _start1 + 0x26a
1:
//movw %cs, %ax
//movw %ax, %ds
//jmp single_boot_sector
movb $0x80, %dl
jmp _start1
cdrom_helper:
/* IP and old_DS is on the stack. DS=40h */
// jz 2f
//
// /* check once more using int13/AH=48h */
// movb $0x48, %ah
// movw $0x0180, %si
// movl $0x1E, (%si)
// int $0x13
// jc 1f
// cmpw $0x800, 0x18(%si)
// je 3f
//1:
// popw %ds
// ret
//
//
//2:
// /* EAX is LBA. if EAX==0, LBA is unknown. */
//
// /* load sector */
// /* check if sector is the start sector */
// /* if yes, goto 3f */
//
// /* for sector=0x10 to 0x1000 */
// /* load sector */
// /* check if sector is the start sector */
// /* if yes, goto 3f */
// /* next */
// popw %ds
// ret
//3:
// movb $0x00, %ah
// //movw $0x55AA, %bx
// int $0x13
// //jc 4f
// movb %ah, %cl
// call print_cl
// //jmp grldr_real_start
/* load all sectors (except the first sector) */
movl 4(%si), %eax /* LBA of GRLDR */
// movb %al, %cl
// call print_cl
// movb %ah, %cl
// call print_cl
// movl $0x1B, %eax
popw %bx /* BX = old_DS = load_segment */
pushw %bx
// movw $0x780, %bx
movw %bx, %es
movw $((grldr_signature - _start1 + 4 + STAGE2_SIZE - 1) / 2048), %cx /* sectors to load */
1:
incl %eax /* next sector */
addw $0x0080, %bx /* buffer segment */
pushw %cx
movw $6, %cx /* retry counter */
2:
movw $0x1A0, %si
/* disk address packet */
movl $0x00010010, (%si) /* load 1 sector each time. */
movw $0, 4(%si) /* buffer offset=0 */
movw %bx, 6(%si) /* buffer segment */
movl %eax, 8(%si) /* LBA lo 32 bits */
movl $0, 12(%si) /* LBA hi 32 bits */
pushal
movb $0x42, %ah
int $0x13
xchgw %ax, %bx
lahf /* Load Flags into AH */
// movb %bh, %cl
// call print_cl
testb %bh, %bh /* error code */
setnz %bh
orb %bh, %ah
sahf /* Store AH into flags SF ZF xx AF xx PF xx CF */
popal
jnc 3f
loop 2b
3:
popw %cx
jc 4f /* disk I/O error */
loop 1b
/* loading is completed. BX=segment of the last sector. */
decw %bx
movw %bx, %ds
/* check the ending signature */
cmpl $0xCE1A02B0, ((grldr_signature - _start1 + 4 + STAGE2_SIZE - 1) % 2048) + 13
je grldr_real_start /* yes. boot it! */
/* it is not our grldr image, return and use MBR-helper. */
4:
//jmp grldr_real_start
popw %ds
ret
grldr_real_start:
#; FAT_12_16 no longer be used. So comment out.
#;je 1f /* jc 1f */
#;//ZF=0 /* CF cleared, so we are coming from FAT_12_16 */
#;popw %dx /* discard the cluster number */
#;popw %dx /* this is our boot_drive/boot_partition */
#;1:
#; The partition number for no-emulation-mode bootable CDROM will be
#; set to 0xFF later(in common.c). So comment out.
#;cli
#;movw %cs, %ax
#;cmpw $0x1000, %ax
#;jne 1f
#;
#;/* CS=0x1000, may be booted from ext2 or no-emulation-mode CDROM */
#;
#;cmpw $0x1000, %di
#;jne 2f
#;cmpw $0x7c00, %bp
#;jne 2f
#;movw %es, %ax
#;cmpw $0x1000, %ax
#;jbe 2f
#;cmpw $0x7c00, %si
#;jbe 2f
#;movl %edx, %eax
#;shrl $16, %eax
#;jnz 2f
#;jecxz 1f // booted from ext2 partition
#;2:
#;// booted from no-emulation-mode bootable CDROM
#;movb $0xff, %dh // partition 0xff means whole drive(for CDROM)
#; #; if needed, 0xfe can be used as an indicator
#; #; here for the bootable CDROM and changed to
#; #; 0xff later.
#;1:
#;
#;//if not booted from CDROM, don't touch the boot partition number(dh)
cli
xorw %ax, %ax
movw %ax, %ss
movw $0x0400, %sp /* tmp use real-mode IDT as stack */
movw %cs, %bp /* save CS to BP */
call 1f
1:
popw %bx /* BX=Instruction Pointer of 1b */
subw $(1b - _start1), %bx
movw %bx, %cx
shrw $4, %bx
addw %bp, %bx
pushw %bx /* new CS */
andw $0x000f, %cx
addw $(1f - _start1), %cx
pushw %cx /* new IP */
lret
1:
pushw %cs
popw %ds
/* CS=DS=BX, CS:0000 = _start1 */
addw $((pre_stage2_start - _start1) >> 4), %bx
/* BX:0000 = pre_stage2_start */
cmpw $0x820, %bx
jb 2f
movw $((0x8200 - (pre_stage2_start - _start1) - 0x400) >> 4), %cx
/* Now CS(=DS) >= CX+0x40 */
movw %cx, %es
xorw %di, %di
xorw %si, %si
/////////////////////////////////////////////////////////////
//
// CS
// DS 0x820 BX
// _start1---------------pre_stage2_start
// CX+0x40---------------0x820
// CX
// ES
//
/////////////////////////////////////////////////////////////
movw $0x200, %cx /* move 2 sectors */
cld
repz movsw
pushw %es /* ES:0000 = _start */
pushw $(1f - _start)
lret /* CS=ES, CS:0000 = _start1 */
1:
/* move BX:0000 to 0820:0000 upward since BX >= 0x820 */
cld
movw %bx, %ds
movw $0x820, %bx
movw %bx, %es
xorw %si, %si
xorw %di, %di
movw $6, %bx /* 64K pages: 0x20000 - 0x7ffff */
1:
movw $0x8000, %cx
repz movsw
movw %ds, %ax
addw $0x1000, %ax
movw %ax, %ds
movw %es, %ax
addw $0x1000, %ax
movw %ax, %es
decw %bx
jnz 1b
jmp 3f
2:
/* move BX:0000 to 0820:0000 downward since BX < 0x820 */
std
addw $0x7000, %bx
movw %bx, %ds
movw $0x7820, %bx
movw %bx, %es
movw $0xfffe, %si
movw %si, %di
movw $8, %bx /* 64K pages: 0x08200 - 0x881ff */
1:
movw $0x8000, %cx
repz movsw
movw %ds, %ax
subw $0x1000, %ax
movw %ax, %ds
movw %es, %ax
subw $0x1000, %ax
movw %ax, %es
decw %bx
jnz 1b
cld
3:
/* put the config file name */
xorw %ax, %ax
movw %ax, %es
movw %ax, %ds
xorl %ebp, %ebp
movb %dh, 0x820A /* this is the boot partition number */
#; clear saved_entryno so that force_cdrom_as_boot_device be cleared
#; later in common.c
movl %ebp, 0x820C /* EBP=0, clear saved_entryno */
movw $0x0010, %cx /* set max length of grub version string */
movw $0x8212, %di /* version string */
cld
/* AL is already 0. Locate the end of version string */
repnz scasb /* find the location of the default config file name */
jcxz 1f /* failed, will not use the default config file name */
movw $0x4e, %cx /* max length of config file name */
movw %cs, %si /* CS:0000 = _start1 */
shlw $4, %si /* 0000:SI = _start1 */
addw $(default_config_file - _start1), %si
//movw $(default_config_file + 0x8200 - pre_stage2_start), %si
cld
repz movsb /* move file name to the config-file field of stage2 */
1:
movw $0x0003, %ax /* set display mode: 80*25 color text */
int $0x10
xorw %bx, %bx
movw $(launch_pre_stage2 - _start1), %si
call print_message /* CS:SI points to message string */
xorw %ax, %ax
movw %ax, %ss
movw $0x2000, %sp
sti
ljmp $0, $0x8200
launch_pre_stage2:
.ascii "\r\n\r\nBooting GRLDR...\r\n"
.byte 0 /* mark the end of ascii zero string */
default_config_file:
//#ifndef PRESET_MENU_STRING
.ascii "/menu.lst"
//#else
// .ascii "[default menu is disabled]"
//#endif
.byte 0 /* mark the end of ascii zero string */
#endif /* ! defined(GRLDR_MBR) && (! defined(GRLDR_INSTALL)) */
. = _start1 + 0x400
/*
* The following is based on FreeDOS, modified heavily by Tinybit in Feb, 2004
*
* Merges LBA and CHS boot sectors to ONE FAT32 boot sector!
*
* Memory layout for GRLDR FAT32 single stage boot process:
*
* ...
* |-------| 1FE0:7E00
* |BOOTSEC| (GRUB does not use this relocation area)
* |RELOC. | (overwritten by kernel loaded)
* |-------| 1FE0:7C00
* ...
* |-------|
* |KERNEL | (overwrites bootsec reloc.)
* |LOADED | (holds 1 sector directory buffer before kernel load)
* |-------| 2000:0000
* ...
* |-------| 0000:7E00
* |BOOTSEC| GRUB always run inside this sector,
* |ORIGIN | no relocation.
* |-------| 0000:7C00
* ...
* |-------| 0060:0200
* | FAT | (only 1 sector buffered)
* |-------| 0060:0000
* ...
*
*/
/*
; This is an LBA-enabled FreeDOS FAT32 boot sector (single sector!).
; You can use and copy source code and binaries under the terms of the
; GNU Public License (GPL), version 2 or newer. See www.gnu.org for more.
; Based on earlier work by FreeDOS kernel hackers, modified heavily by
; Eric Auer and Jon Gentle in 7 / 2003.
;
; Features: Uses LBA and calculates all variables from BPB/EBPB data,
; thus making partition move / resize / image-restore easier. FreeDOS
; can boot from FAT32 partitions which start > 8 GB boundary with this
; boot sector. Disk geometry knowledge is not needed for booting.
;
; Windows uses 2-3 sectors for booting (sector stage, statistics sector,
; filesystem stage). Only using 1 sector for FreeDOS makes multi-booting
; of FreeDOS and Windows on the same filesystem easier.
;
; Requirements: LBA BIOS and 386 or better CPU. Use the older CHS-only
; boot sector if you want FAT32 on really old PCs (problems: you cannot
; boot from > 8 GB boundary, cannot move / resize / ... without applying
; SYS again if you use the CHS-only FAT32 boot sector).
;
; FAT12 / FAT16 hints: Use the older CHS-only boot sector unless you
; have to boot from > 8 GB. The LBA-and-CHS FAT12 / FAT16 boot sector
; needs applying SYS again after move / resize / ... a variant of that
; boot sector without CHS support but with better move / resize / ...
; support would be good for use on LBA harddisks.
; Memory layout for the FreeDOS FAT32 single stage boot process:
; ...
; |-------| 1FE0:7E00
; |BOOTSEC|
; |RELOC. |
; |-------| 1FE0:7C00
; ...
; |-------| 2000:0200
; | FAT | (only 1 sector buffered)
; |-------| 2000:0000
; ...
; |-------| 0000:7E00
; |BOOTSEC| overwritten by the kernel, so the
; |ORIGIN | bootsector relocates itself up...
; |-------| 0000:7C00
; ...
; |-------|
; |KERNEL | maximum size 134k (overwrites bootsec origin)
; |LOADED | (holds 1 sector directory buffer before kernel load)
; |-------| 0060:0000
; ...
*/
#define BOOTGRUB /* undef this if compiled for loading FreeDOS */
//#undef BOOTGRUB
#ifdef BOOTGRUB
#define LOADSEG 0x2000
#define FATSEG 0x0060
#else
#define LOADSEG 0x0060
#define FATSEG 0x2000
#endif
Entry_32:
jmp 1f
. = Entry_32 + 0x02
/* The default mode is CHS. This is for maximum compatiblity with
* small-sized disks, e.g., floppies.
*
* Valid values are 0x90 for CHS mode, or 0x0e for LBA mode.
*
* If the BIOS int13 supports LBA, this byte can be safely set to 0x0e.
*
* Some USB BIOSes might have bugs when using CHS mode, so the format
* program should set this byte to 0x0e. It seems that (generally) all
* USB BIOSes have LBA support.
*
* If the format program does not know whether the BIOS has LBA
* support, it may operate this way:
*
* if (partition_start + total_sectors_in_partition) exceeds the CHS
* addressing ability(especially when it is greater than 1024*256*63),
* the caller should set this byte to 0x0e, otherwise, set to 0x90.
*/
.byte 0x90 /* for CHS. Another possible value is 0x0e for LBA */
. = Entry_32 + 0x03
#ifdef BOOTGRUB
.ascii "GRLDR " /* OEM name string (of OS which formatted the disk). */
#endif
. = Entry_32 + 0x0b
.word 0x200 /* bytes per sector. Must be 512 */
. = Entry_32 + 0x0d
/* Sectors per cluster. Valid values are 1, 2, 4, 8, 16, 32, 64 and 128.
* But a cluster size larger than 32K should not occur.
*/
.byte 1 /* sectors per cluster */
. = Entry_32 + 0x0e
/* Reserved sectors(number of sectors before the first FAT,
* including the boot sector), usually 1.
*/
.word 1 /* reserved sectors */
. = Entry_32 + 0x10
/* Number of FATs(nearly always 2). */
.byte 2 /* number of FATs */
. = Entry_32 + 0x11
/* (Maximum number of root directory entries)Must be 0. */
.word 0 /* Max dir entries for FAT12/FAT16 */
. = Entry_32 + 0x13
/* (Total number of sectors for small disks only)Must be 0. */
.word 0 /* total sectors for FAT12/FAT16 */
. = Entry_32 + 0x15
/* Media descriptor byte, pretty meaningless now. */
.byte 0xf8 /* media descriptor */
. = Entry_32 + 0x16
/* (Sectors per FAT)Must be 0. */
.word 0 /* sectors per FAT for FAT12/FAT16 */
. = Entry_32 + 0x18
.word 18 /* sectors per track */
. = Entry_32 + 0x1a
.word 2 /* number of heads */
. = Entry_32 + 0x1c
/* Number of hidden sectors (those preceding the boot sector).
* Also referred to as the starting sector of the partition.
* For floppies, it should be 0.
*/
.long 0 /* hidden sectors */
. = Entry_32 + 0x20
/* Total number of sectors in the filesystem. */
.long 0 /* total sectors for FAT32 */
. = Entry_32 + 0x24
/* FAT32 sectors per FAT. */
.long 0
. = Entry_32 + 0x28
/* If bit 7 is clear then all FATs are updated, otherwise bits 0-3
* give the current active FAT, all other bits are reserved.
* This word is not used by grldr boot code.
*/
.word 0
. = Entry_32 + 0x2a
/* High byte is major revision number, low byte is minor revision
* number, currently both are 0.
* This word is not used by grldr boot code.
*/
.word 0
. = Entry_32 + 0x2c
/* Root directory starting cluster. */
.long 0
. = Entry_32 + 0x30
/* File system information sector number.
* This word is not used by grldr boot code.
*/
.word 0
. = Entry_32 + 0x32
/* If non-zero this gives the sector which holds a copy of the
* boot record, usually 6.
* This word is not used by grldr boot code.
*/
.word 6
. = Entry_32 + 0x34
/* Reserved, 12 bytes, set to 0. */
.long 0
.long 0
.long 0
. = Entry_32 + 0x40
/* drive number of the boot device.
* This byte is ignored for read. The program will write DL onto
* this byte. The caller should set drive number in DL.
* We assume all BIOSes pass correct drive number in DL.
* That is to say, buggy BIOSes are not supported!!
*/
.byte 0
. = Entry_32 + 0x41
/* partition number of this filesystem in the boot drive.
* This byte is ignored for read. The boot code will write partition
* number onto this byte. See Entry + 0x5d below.
*/
.byte 0
. = Entry_32 + 0x42
/* Signature (must be 28h or 29h to be recognised by NT). */
.byte 0x29 /* extended boot signature for FAT12/FAT16 */
. = Entry_32 + 0x43
.long 0x0AC4AF63 /* volume serial number */
. = Entry_32 + 0x47
.ascii "NO NAME " /* volume label, 11 bytes. */
. = Entry_32 + 0x52
.ascii "FAT32 " /* filesystem ID, 8 bytes. */
/*
; bp is initialized to 7c00h
; %define bsOemName bp+0x03 ; OEM label (8)
%define bsBytesPerSec bp+0x0b ; bytes/sector (dw)
%define bsSecPerClust bp+0x0d ; sectors/allocation unit (db)
%define bsResSectors bp+0x0e ; # reserved sectors (dw)
%define bsFATs bp+0x10 ; # of fats (db)
; %define bsRootDirEnts bp+0x11 ; # of root dir entries (dw, 0 for FAT32)
; (FAT32 has root dir in a cluster chain)
; %define bsSectors bp+0x13 ; # sectors total in image (dw, 0 for FAT32)
; (if 0 use nSectorHuge even if FAT16)
; %define bsMedia bp+0x15 ; media descriptor: fd=2side9sec, etc... (db)
; %define sectPerFat bp+0x16 ; # sectors in a fat (dw, 0 for FAT32)
; (FAT32 always uses xsectPerFat)
%define sectPerTrack bp+0x18 ; # sectors/track
; %define nHeads bp+0x1a ; # heads (dw)
%define nHidden bp+0x1c ; # hidden sectors (dd)
; %define nSectorHuge bp+0x20 ; # sectors if > 65536 (dd)
%define xsectPerFat bp+0x24 ; Sectors/Fat (dd)
; +0x28 dw flags (for fat mirroring)
; +0x2a dw filesystem version (usually 0)
%define xrootClst bp+0x2c ; Starting cluster of root directory (dd)
; +0x30 dw -1 or sector number of fs.-info sector
; +0x32 dw -1 or sector number of boot sector backup
; (+0x34 .. +0x3f reserved)
%define drive bp+0x40 ; Drive number
bp+0x41 ; partition number for GRLDR
%define fat_sector bp+0x44 ; last accessed FAT sector (dd)
; (overwriting unused bytes)
%define fat_start bp+0x48 ; first FAT sector (dd)
; (overwriting unused bytes)
%define data_start bp+0x4c ; first data sector (dd)
; (overwriting unused bytes)
*/
/* not used: [0x42] = byte 0x29 (ext boot param flag)
* [0x43] = dword serial
* [0x47] = label (padded with 00, 11 bytes)
* [0x52] = "FAT32",32,32,32 (not used by Windows)
* ([0x5a] is where FreeDOS parts start)
*/
. = Entry_32 + 0x5a
1:
cli
cld
#ifdef BOOTGRUB
. = Entry_32 + 0x5c
/* the byte at offset 0x5d stores the real partition number for read.
* the format program or the caller should set it to a correct value.
* For floppies, it should be 0xff, which stands for whole drive.
*/
movb $0xff, %dh /* boot partition number */
#endif
xorw %ax, %ax
movw %ax, %ds
movw $0x7c00, %bp
#ifdef BOOTGRUB
movw %ax, %es
#else
movw $0x1fe0, %ax
movw %ax, %es
movw %bp, %si /* move from 0000:7c00 */
movw %bp, %di /* move to 1fe0:7c00 */
movw $0x0100, %cx /* one sector to move */
repz movsw
ljmp $0x1fe0, $(1f - Entry_32 + 0x7c00)
1:
movw %ax, %ds
#endif
movw %ax, %ss /* stack and BP-relative moves up, too */
leaw -0x20(%bp), %sp
sti
movw %dx, 0x40(%bp) /* BIOS passes drive number in DL */
movb $0x41, %ah
movw $0x55AA, %bx
int $0x13
jc 1f /* No EBIOS */
cmpw $0xAA55, %bx
jne 1f /* No EBIOS */
testb $1, %cl
jz 1f /* No EBIOS */
/* EBIOS supported */
movb $0x42, (ebios_32 - 1 - Entry_32 + 0x7c00)
1:
/* figure out where FAT and DATA area starts
* (modifies EAX EDX, sets fat_start and data_start variables)
*/
xorl %eax, %eax
movl %eax, 0x44(%bp) /* init buffer status */
/* first, find fat_start */
movw 0x0e(%bp), %ax /* reserved sectors */
addl 0x1c(%bp), %eax /* hidden sectors */
movl %eax, 0x48(%bp) /* first FAT sector */
movl %eax, 0x4c(%bp) /* first data sector, initial value */
/* next, find data_start */
movl 0x10(%bp), %eax /* number of fats, no movzbl needed: the
2 words after 0x10(%bp) are 0 for fat32 */
mull 0x24(%bp) /* sectors per fat (EDX=0) */
addl %eax, 0x4c(%bp) /* first DATA sector */
/* Searches for the file in the root directory.
* Returns: EAX = first cluster of file
*/
movl 0x2c(%bp), %eax /* root dir cluster */
1:
pushl %eax /* save cluster */
call cluster_to_lba_32
/* EDX is sectors per cluster, EAX is sector number */
movw $(msg_BootError_32 - Entry_32 + 0x7c00), %si
jc boot_error_32 /* EOC encountered */
2:
lesw (loadseg_off_32 - Entry_32)(%bp), %bx /* load to loadseg:0 */
call readDisk_32
xorw %di, %di
/* Search for kernel file name, and find start cluster */
3:
movw $11, %cx
movw $(filename_32 - Entry_32 + 0x7c00), %si
repz cmpsb
jz 1f /* note that di now is at dirent+11 */
addw $0x20, %di
andw $-0x20, %di /* 0xffe0 */
cmp 0x0b(%bp), %di /* bytes per sector */
jnz 3b /* next directory entry */
decw %dx /* initially DX holds sectors per cluster */
jnz 2b /* loop over sectors in cluster */
popl %eax /* restore current cluster */
call next_cluster_32
jmp 1b /* read next cluster */
loadseg_off_32:
.word 0
.word LOADSEG
1:
/* kernel directory entry is found */
pushw %es:(0x14-11)(%di) /* get cluster number HI */
pushw %es:(0x1a-11)(%di) /* get cluster number LO */
popl %eax /* convert to 32bit */
xorw %bx, %bx /* read kernel at ES:BX=LOADSEG:0 */
/* read kernel */
2:
pushl %eax
call cluster_to_lba_32
/* EDX is sectors per cluster, EAX is sector number */
jnc 1f
/* EOC encountered - done */
#ifdef BOOTGRUB
movw 0x40(%bp), %dx /* boot_drive and boot_partition */
#else
movb 0x40(%bp), %bl /* FreeDOS kernel uses BL, not DL, for drive */
#endif
ljmp *(loadseg_off_32 - Entry_32)(%bp)
1:
call readDisk_32
decw %dx /* initially DX holds sectors per cluster */
jnz 1b /* loop over sectors in cluster */
popl %eax
call next_cluster_32
jmp 2b
/* given a cluster number, find the number of the next cluster in
* the FAT chain. Needs fat_start.
* input: EAX - cluster
* EDX = 0
* output: EAX - next cluster
* EDX = undefined
*/
next_cluster_32:
pushw %es
/* pushw %di */
pushw %bx /* hi word of EBX never used */
#if 1
/* xorl %edx, %edx */
shll $2, %eax /* 32bit FAT */
movzwl 0x0b(%bp), %ebx /* bytes per sector */
divl %ebx /* residue is in EDX */
/* movw %dx, %di */
#else
shll $2, %eax /* 32bit FAT */
;xchgw %ax, %di /* movw %ax, %di */
movw %ax, %di
;shlw $2, %di /* 32bit FAT */
pushw %cx
movw 0x0b(%bp), %bx /* bytes per sector */
bsfw %bx, %cx
;decw %cx
;decw %cx
decw %bx
andw %bx, %di /* mask to sector size */
shrl %cl, %eax
popw %cx
#endif
addl 0x48(%bp), %eax /* add the first FAT sector number.
EAX is absolute sector number now */
movw $FATSEG, %bx
movw %bx, %es
xorw %bx, %bx
cmpl 0x44(%bp), %eax /* is it the last accessed and already buffered
FAT sector? */
jz 1f
movl %eax, 0x44(%bp) /* mark sector EAX as buffered */
call readDisk_32 /* read sector EAX to buffer */
1:
#if 1
//.byte 0x67, 0x26, 0x80, 0x62, 0x03, 0x0f
addr32 andb $0x0f, %es:3(%edx) /* mask out top 4 bits */
//.byte 0x67, 0x66, 0x26, 0x8b, 0x02
addr32 movl %es:(%edx), %eax /* read next cluster number */
#else
andb $0x0f, %es:3(%di) /* mask out top 4 bits */
movl %es:(%di), %eax /* read next cluster number */
#endif
popw %bx
/* popw %di */
popw %es
ret
/* Convert cluster number to the absolute sector number
* ... or return carry if EndOfChain! Needs data_start.
* input: EAX - target cluster
* output: EAX - absolute sector
* EDX - [bsSectPerClust] (byte)
* carry clear
* (if carry set, EAX/EDX unchanged, end of chain)
*/
cluster_to_lba_32:
cmpl $0x0ffffff8, %eax /* check End Of Chain */
cmc
jb 1f /* carry is stored if EOC */
/* sector = (cluster-2) * clustersize + data_start */
decl %eax
decl %eax
movzbl 0x0d(%bp), %edx /* sectors per cluster */
pushw %dx /* only DX would change */
mull %edx /* EDX = 0 */
popw %dx
addl 0x4c(%bp), %eax /* data_start */
/* here, carry is cleared (unless parameters are wrong) */
1:
ret
/* Read a sector from disk, using LBA or CHS
* input: EAX - 32-bit DOS sector number
* ES:BX - destination buffer
* (will be filled with 1 sector of data)
* output: ES:BX points one byte after the last byte read.
* EAX - next sector
*/
readDisk_32:
pushal
xorl %edx, %edx /* EDX:EAX = LBA */
pushl %edx /* hi 32bit of sector number */
pushl %eax /* lo 32bit of sector number */
pushw %es /* buffer segment */
pushw %bx /* buffer offset */
pushw $1 /* 1 sector to read */
pushw $16 /* size of this parameter block */
xorl %ecx, %ecx
pushl 0x18(%bp) /* lo:sectors per track, hi:number of heads */
popw %cx /* ECX = sectors per track */
divl %ecx /* residue is in EDX */
/* quotient is in EAX */
incw %dx /* sector number in DL */
popw %cx /* ECX = number of heads */
pushw %dx /* push sector number into stack */
xorw %dx, %dx /* EDX:EAX = cylinder * TotalHeads + head */
divl %ecx /* residue is in EDX, head number */
/* quotient is in EAX, cylinder number */
xchgb %dl, %dh /* head number should be in DH */
/* DL = 0 */
popw %cx /* pop sector number from stack */
xchgb %al, %ch /* lo 8bit cylinder should be in CH */
/* AL = 0 */
shlb $6, %ah /* hi 2bit cylinder ... */
orb %ah, %cl /* ... should be in CL */
movw $0x201, %ax /* read 1 sector */
ebios_32: /* ebios_32 - 1 points to 0x02 that can be changed to 0x42 */
// cmpb $0x0e, 2(%bp) /* force LBA? */
// jnz 1f /* no, continue */
// movb $0x42, %ah /* yes, use extended disk read */
//1:
movw %sp, %si /* DS:SI points to disk address packet */
movb 0x40(%bp), %dl /* hard disk drive number */
int $0x13
popaw /* remove parameter block from stack */
popal
jc disk_error_32 /* disk read error, jc 1f if caller handles */
incl %eax /* next sector */
addw 0x0b(%bp), %bx /* bytes per sector */
jnc 1f /* 64K bound check */
pushw %dx
movw %es, %dx
addb $0x10, %dh /* add 1000h to ES */
/* here, carry is cleared */
movw %dx, %es
popw %dx
1:
/* carry stored on disk read error */
ret
. = . - (. - readDisk_32)/91
msg_DiskReadError_32:
.ascii "disk error\0"
msg_BootError_32:
.ascii "No "
filename_32:
#ifdef BOOTGRUB
.ascii "GRLDR \0"
#else
.ascii "KERNEL SYS\0"
#endif
. = Entry_32 + 0x1ee
disk_error_32:
movw $(msg_DiskReadError_32 - Entry_32 + 0x7c00), %si
boot_error_32:
/* prints string DS:SI (modifies AX BX SI) */
//print_32:
1:
lodsb (%si), %al /* get token */
//xorw %bx, %bx /* video page 0 */
movb $0x0e, %ah /* print it */
int $0x10 /* via TTY mode */
cmpb $0, %al /* end of string? */
jne 1b /* until done */
/* The caller will change this to
* ljmp $0x9400, $(try_next_partition - _start1)
*/
1: jmp 1b
. = Entry_32 + 0x1fc
.word 0, 0xAA55 /* Win9x uses all 4 bytes as magic value here */
. = Entry_32 + 0x200
. = _start1 + 0x600
//.arch i8086, nojumps
.arch i186, nojumps
/*
* The following is based on FreeDOS, modified heavily by Tinybit in Feb, 2004
*
* Merges FAT12 and FAT16 boot sectors to ONE FAT boot sector!
*
* Memory layout for GRLDR FAT single stage boot process:
*
* +--------+
* | |
* |GRLDR | also used as max 128k FAT buffer
* |LOADED | before GRLDR loading starts
* |--------| 2000:0000
* | |
* |--------| 0000:7E00
* |BOOTSECT|
* |ORIGIN |
* |--------| 0000:7C00
* | |
* |--------| 0000:3000
* |CLUSTER |
* |LIST |
* |--------| 0000:2000
* | |
* +--------+
*/
/*
;
; File:
; boot.asm
; Description:
; DOS-C boot
;
; Copyright (c) 1997;
; Svante Frey
; All Rights Reserved
;
; This file is part of DOS-C.
;
; DOS-C 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, or (at your option) any later version.
;
; DOS-C 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 DOS-C; see the file COPYING. If not,
; write to the Free Software Foundation, 675 Mass Ave,
; Cambridge, MA 02139, USA.
;
;
; +--------+ 1FE0:7E00
; |BOOT SEC|
; |RELOCATE|
; |--------| 1FE0:7C00
; | |
; |--------| 1FE0:3000
; | CLUSTER|
; | LIST |
; |--------| 1FE0:2000
; | |
; |--------| 0000:7E00
; |BOOT SEC| overwritten by max 128k FAT buffer
; |ORIGIN | and later by max 134k loaded kernel
; |--------| 0000:7C00
; | |
; |--------|
; |KERNEL | also used as max 128k FAT buffer
; |LOADED | before kernel loading starts
; |--------| 0060:0000
; | |
; +--------+
*/
#ifdef BOOTGRUB
#define LOADSEG_12_16 0x2000
#define FATBUF 0x2000 /* offset of temp buffer for FAT chain */
#else
#define LOADSEG_12_16 0x0060
#define FATBUF 0x2000 /* offset of temp buffer for FAT chain */
#endif
Entry_12_16:
jmp 1f
. = Entry_12_16 + 0x02
/* The default mode is CHS. This is for maximum compatiblity with
* small-sized disks, e.g., floppies.
*
* Valid values are 0x90 for CHS mode, or 0x0e for LBA mode.
*
* If the BIOS int13 supports LBA, this byte can be safely set to 0x0e.
*
* Some USB BIOSes might have bugs when using CHS mode, so the format
* program should set this byte to 0x0e. It seems that (generally) all
* USB BIOSes have LBA support.
*
* If the format program does not know whether the BIOS has LBA
* support, it may operate this way:
*
* if (partition_start + total_sectors_in_partition) exceeds the CHS
* addressing ability(especially when it is greater than 1024*256*63),
* the caller should set this byte to 0x0e, otherwise, set to 0x90.
*/
.byte 0x90 /* for CHS. Another possible value is 0x0e for LBA */
. = Entry_12_16 + 0x03
#ifdef BOOTGRUB
.ascii "GRLDR "
#endif
. = Entry_12_16 + 0x0b
.word 0x200 /* bytes per sector */
. = Entry_12_16 + 0x0d
.byte 1 /* sectors per cluster */
. = Entry_12_16 + 0x0e
.word 1 /* reserved sectors */
. = Entry_12_16 + 0x10
.byte 2 /* number of FATs */
. = Entry_12_16 + 0x11
.word 224 /* Max dir entries */
. = Entry_12_16 + 0x13
.word 2880 /* total sectors in the filesystem */
. = Entry_12_16 + 0x15
.byte 0xf0 /* media descriptor */
. = Entry_12_16 + 0x16
.word 9 /* sectors per FAT */
. = Entry_12_16 + 0x18
.word 18 /* sectors per track */
. = Entry_12_16 + 0x1a
.word 2 /* number of heads */
. = Entry_12_16 + 0x1c
.long 0 /* hidden sectors */
. = Entry_12_16 + 0x20
.long 0 /* total sectors for large partitions */
. = Entry_12_16 + 0x24
/* drive number of the boot device.
* This byte is ignored for read. The program will write DL onto
* this byte. The caller should set drive number in DL.
* We assume all BIOSes pass correct drive number in DL.
* That is to say, buggy BIOSes are not supported!!
*/
.byte 0
. = Entry_12_16 + 0x25
/* partition number of this filesystem in the boot drive.
* This byte is ignored for read. The boot code will write partition
* number onto this byte. See Entry_12_16 + 0x41 below.
*/
.byte 0
. = Entry_12_16 + 0x26
.byte 0x29 /* extended boot signature */
. = Entry_12_16 + 0x27
.long 0x0AC4AF63 /* volume serial number */
. = Entry_12_16 + 0x2b
.ascii "NO NAME " /* volume label */
. = Entry_12_16 + 0x36
.ascii "FAT12 " /* filesystem ID */
/*
; bp is initialized to 7c00h
%define bsOemName bp+0x03 ; OEM label
%define bsBytesPerSec bp+0x0b ; bytes/sector
%define bsSecPerClust bp+0x0d ; sectors/allocation unit
%define bsResSectors bp+0x0e ; # reserved sectors
%define bsFATs bp+0x10 ; # of fats
%define bsRootDirEnts bp+0x11 ; # of root dir entries
%define bsSectors bp+0x13 ; # sectors total in image
%define bsMedia bp+0x15 ; media descrip: fd=2side9sec, etc...
%define sectPerFat bp+0x16 ; # sectors in a fat
%define sectPerTrack bp+0x18 ; # sectors/track
%define nHeads bp+0x1a ; # heads
%define nHidden bp+0x1c ; # hidden sectors
%define nSectorHuge bp+0x20 ; # sectors if > 65536
%define drive bp+0x24 ; drive number
bp+0x25 ; partition number for GRLDR
%define extBoot bp+0x26 ; extended boot signature
%define volid bp+0x27
%define vollabel bp+0x2b
%define filesys bp+0x36
%define RootDirSecs bp+0x26 ; # of sectors root dir uses
; (overwriting unused bytes)
%define fat_start bp+0x28 ; first FAT sector
; (overwriting unused bytes)
%define root_dir_start bp+0x2c ; first root directory sector
; (overwriting unused bytes)
%define data_start bp+0x30 ; first data sector
; (overwriting unused bytes)
%define data_clusters bp+0x34 ; # of clusters in data area
; (overwriting unused bytes)
bp+0x36 ; bytes per FAT( > 0x1800 means FAT16)
; (overwriting unused bytes)
*/
/* not used: [0x26] = byte 0x29 (ext boot param flag)
* [0x27] = dword serial
* [0x2b] = label (padded with 00, 11 bytes)
* [0x36] = "FAT12" or "FAT16",32,32,32 (not used by Windows)
* ([0x3e] is where FreeDOS parts start)
*/
. = Entry_12_16 + 0x3e
1:
cli
cld
#ifdef BOOTGRUB
. = Entry_12_16 + 0x40
/* the byte at offset 0x41 stores the real partition number for read.
* the format program or the caller should set it to a correct value.
* For floppies, it should be 0xff, which stands for whole drive.
*/
movb $0xff, %dh /* boot partition number */
#endif
xorw %ax, %ax
movw %ax, %ds
movw $0x7c00, %bp
#ifdef BOOTGRUB
movw %ax, %es
movw %ax, %ss /* stack and BP-relative moves up, too */
leaw -0x20(%bp), %sp
sti
movw %dx, 0x24(%bp) /* BIOS passes drive number in DL */
/* AX=0 */
// xchgw %ax, %dx /* let DX = 0 */
// xorw %cx, %cx /* CX = 0 */
#else
movw %bp, %si /* move from 0000:7c00 */
movw %bp, %di /* move to 1fe0:7c00 */
movb %dl, 0x24(%si) /* BIOS passes drive number in DL */
// xchgw %ax, %dx /* let DX = 0 */
movw $0x1fe0, %ax
movw %ax, %es
movw $0x0100, %cx /* one sector to move */
repz movsw
/* CX = 0 */
ljmp $0x1fe0, $(1f - Entry_12_16 + 0x7c00)
1:
movw %ax, %ds
movw %ax, %ss /* stack and BP-relative moves up, too */
leaw -0x20(%bp), %sp
sti
/* AX=0x1fe0 */
#endif
movb $0x41, %ah
movw $0x55AA, %bx
int $0x13
jc 1f /* No EBIOS */
cmpw $0xAA55, %bx
jne 1f /* No EBIOS */
testb $1, %cl
jz 1f /* No EBIOS */
/* EBIOS supported */
movb $0x42, (ebios_12_16 - 1 - Entry_12_16 + 0x7c00)
1:
// xorw %cx, %cx
xorw %ax, %ax
/* GET DRIVE PARMS: Calculate start of some disk areas */
movw 0x1c(%bp), %si /* number of hidden sectors(lo) */
movw 0x1e(%bp), %di /* number of hidden sectors(hi) */
addw 0x0e(%bp), %si /* number of reserved sectors */
adcw %ax, %di /* DI:SI = first FAT sector */
/* AX = 0 */
movw %si, 0x28(%bp) /* FAT start sector(lo) */
movw %di, 0x2a(%bp) /* FAT start sector(hi) */
//xchgw %ax, %dx /* let AX = 0 */
movb 0x10(%bp), %al /* number of FATs */
/* cbw */
mulw 0x16(%bp) /* sectors per FAT */
/* DX:AX = total number of FAT sectors */
/* DX = 0 since no too many FAT sectors */
addw %ax, %si
adcw %dx, %di /* DI:SI = root directory start sector */
movw %si, 0x2c(%bp) /* root directory starting sector(lo) */
movw %di, 0x2e(%bp) /* root directory starting sector(hi) */
/* Calculate how many sectors the root directory occupies */
movw 0x0b(%bp), %bx /* bytes per sector */
movb $5, %cl /* divide BX by 32 */
shrw %cl, %bx /* BX = directory entries per sector */
movw 0x11(%bp), %ax /* max number of root dir entries */
/* xorw %dx, %dx */ /* assuming DX = 0 */
divw %bx /* AX = sectors per root directory */
/* DX = 0 since normally no residue */
movw %ax, 0x26(%bp) /* number of sectors the root dir occupies */
addw %ax, %si /* DI:SI = first data sector */
adcw %dx, %di /* assuming DX = 0 */
movw %si, 0x30(%bp) /* data starting sector(lo) */
movw %di, 0x32(%bp) /* data starting sector(hi) */
#ifdef USE_TOTAL_CLUSTERS
movw 0x13(%bp), %cx /* total sectors(small) */
jcxz 1f
movw %cx, 0x20(%bp) /* total sectors(large)(lo) */
movw %dx, 0x22(%bp) /* total sectors(large)(hi), assuming DX = 0 */
1:
movw 0x20(%bp), %ax /* total sectors(large) */
movw 0x22(%bp), %bx
addw 0x1c(%bp), %ax /* number of hidden sectors */
adcw 0x1e(%bp), %bx
subw %si, %ax /* data starting sector */
sbbw %di, %bx /* BX:AX = total sectors in the data area */
movb 0x0d(%bp), %dl /* sectors per cluster(DH=0) */
xchgw %bx, %dx /* DX:AX = total sectors in the data area */
/* BX = sectors per cluster */
divw %bx /* AX = total clusters in the data area */
movw %ax, 0x34(%bp) /* total clusters in the data area */
#else
movw $0xffff, 0x36(%bp)
movw 0x16(%bp), %ax /* sectors per FAT */
mulw 0x0b(%bp) /* bytes per sector */
jc 1f
movw %ax, 0x36(%bp)
1:
#endif
/* Searches for the file in the root directory
*
* Returns:
* AX = first cluster of file
*/
/* First, read the whole root directory into the temporary buffer */
movw 0x2c(%bp), %ax /* root directory starting sector(lo) */
movw 0x2e(%bp), %dx /* root directory starting sector(hi) */
movw 0x26(%bp), %di /* number of sectors the root dir occupies */
lesw (loadseg_off_12_16 - Entry_12_16)(%bp), %bx
/* ES:BX = loadseg:0 */
call readDisk_12_16
lesw (loadseg_off_12_16 - Entry_12_16)(%bp), %di
/* ES:DI = loadseg:0 */
/* Search for kernel file name, and find start cluster */
1:
movw $11, %cx
movw $(filename_12_16 - Entry_12_16 + 0x7c00), %si
pushw %di
repz cmpsb
popw %di
movw %es:0x1a(%di), %ax /* get cluster number from dir entry */
jz 1f
addw $0x20, %di /* go to next directory entry */
cmpb %ch, %es:(%di) /* if the first byte of the name is 0, */
/* there is no more files in the directory */
/* assuming CH = 0 */
jnz 1b
movw $(msg_BootError_12_16 - Entry_12_16 + 0x7c00), %si
jmp boot_error_12_16 /* fail if not found */
loadseg_off_12_16: .word 0
loadseg_seg_12_16: .word LOADSEG_12_16
1:
pushw %ax /* store first cluster number */
/* CX = 0 */
/* Reads the FAT chain and stores it in a temporary buffer in the first
* 64KB. The FAT chain is stored an array of 16-bit cluster numbers,
* ending with 0.
*
* The file must fit in conventional memory, so it can't be larger than
* 640KB. The sector size must be at least 512 bytes, so the FAT chain
* can't be larger than around 3KB.
*
* Call with: AX = first cluster in chain
*/
/* Load the complete FAT into memory. The FAT can't be larger
* than 128 kb, so it should fit in the temporary buffer.
*/
lesw (loadseg_off_12_16 - Entry_12_16)(%bp), %bx
/* ES:BX = loadseg:0 */
movw 0x16(%bp), %di /* sectors per FAT */
movw 0x28(%bp), %ax /* FAT start sector(lo) */
movw 0x2a(%bp), %dx /* FAT start sector(hi) */
call readDisk_12_16
popw %ax /* restore first cluster number */
/* Set ES:DI to the temporary storage for the FAT chain */
pushw %ds
popw %es
movw (loadseg_seg_12_16 - Entry_12_16)(%bp), %ds
movw $FATBUF, %di
2:
stosw /* store cluster number */
movw %ax, %si /* SI = cluster number */
addw %si, %si /* multiply cluster number by two */
movw (loadseg_seg_12_16 - Entry_12_16)(%bp), %dx
/* segment for FAT16 */
jnc 1f
addb $0x10, %dh /* overflow. Add 0x1000 to segment value */
1:
#ifdef USE_TOTAL_CLUSTERS
cmpw $0x0ff7, 0x34(%bp) /* total clusters in the data area */
#else
cmpw $0x1801, 0x36(%bp) /* bytes per FAT */
#endif
jnb 3f
/* This is a FAT12 disk */
addw %ax, %si /* multiply cluster number by 3 ... */
shrw $1, %si /* ... and divide by 2 */
lodsw
/* If the cluster number was even, the cluster value is now in
* bits 0-11 of AX. If the cluster number was odd, the cluster
* value is in bits 4-15, and must be shifted right 4 bits. If
* the number was odd, CF was set in the last shift instruction.
*/
jnc 1f
movb $4, %cl
shrw %cl, %ax
1:
andb $0x0f, %ah /* mask off the highest 4 bits */
cmpw $0x0ff7, %ax /* check for EOF */
jmp 4f
3:
/* This is a FAT16 disk. The maximal size of a 16bit FAT
* is 128KB, so it may not fit within a single 64KB segment
*/
movw %dx, %ds /* DS:SI points to next cluster */
lodsw /* AX = next cluster */
cmpw $0xfff7, %ax /* check for EOF */
4:
jbe 2b /* continue if not EOF */
/* Mark end of FAT chain with 0, so we have a single
* EOF marker for both FAT12 and FAT16 systems.
*/
xorw %ax, %ax
stosw
pushw %cs
popw %ds
/* Loads the file into memory, one cluster at a time */
lesw (loadseg_off_12_16 - Entry_12_16)(%bp), %bx
/* ES:BX = loadseg:0 */
movw $FATBUF, %si /* set DS:SI to the FAT chain */
2:
lodsw /* AX = next cluster to read */
orw %ax, %ax
jnz 1f
/* EOC encountered - done */
#ifdef BOOTGRUB
movw 0x24(%bp), %dx /* boot_drive and boot_partition */
#else
movb 0x24(%bp), %bl /* FreeDOS kernel uses BL, not DL, for drive */
#endif
ljmp *(loadseg_off_12_16 - Entry_12_16)(%bp) /* boot it! */
1:
decw %ax /* cluster numbers start with 2 */
decw %ax
movw 0x0d(%bp), %di /* sectors per cluster */
andw $0xff, %di /* DI = sectors per cluster */
mulw %di
addw 0x30(%bp), %ax /* data starting sector(lo) */
adcw 0x32(%bp), %dx /* data starting sector(hi) */
/* DX:AX = first sector to read */
call readDisk_12_16
jmp 2b /* read next cluster */
/* Reads a number of sectors into memory.
*
* Call with: DX:AX = 32-bit DOS sector number
* DI = number of sectors to read
* ES:BX = destination buffer
*
* Returns: CF set on error
* ES:BX points one byte after the last byte read.
* DX:AX = next sector number after read
*/
readDisk_12_16:
2:
pushaw
xorw %cx, %cx
pushw %cx
pushw %cx
pushw %dx
pushw %ax
pushw %es /* buffer segment */
pushw %bx /* buffer offset */
incw %cx
pushw %cx /* 1 sector to read */
movb $16, %cl
pushw %cx /* size of this parameter block */
xchgw %ax, %cx /* save AX to CX */
/*
* translate sector number to BIOS parameters
*
* LBA = sector-1 offset in track
* + head * sectPerTrack offset in cylinder
* + cyl * sectPerTrack * nHeads offset in platter
*
*/
pushw %bx
movw 0x18(%bp), %ax /* sectors per track */
movw %ax, %bx
mulb 0x1a(%bp) /* nHeads, but maybe a word value 0x100 */
jnz 1f
movb %bl, %ah /* nHeads=0x100, so AX=sectPerTrack*0x100 */
1:
xchgw %ax, %cx /* restore AX from CX, and save AX to CX */
/* DX:AX = LBA, CX = nHeads * sectPerTrack <= 256*63 */
divw %cx /* AX = cyl, DX = sector-1 + head * sectPerTrack */
xchgw %ax, %dx /* DX = cyl, AX = sector-1 + head * sectPerTrack */
divb %bl /* sectors per track */
/* DX = cyl, AL = head, AH = sector-1 */
#if 1
xchgb %al, %ah /* DX = cyl, AH = head, AL = sector-1 */
incw %ax /* DX = cyl, AH = head, AL = sector */
xchgw %ax, %dx /* AX = cyl, DH = head, DL = sector */
xchgw %ax, %cx /* CX = cyl, DH = head, DL = sector */
xchgb %cl, %ch /* set cyl number low 8 bits in CH */
rorb $1, %cl /* move cyl high bits into bits 7-6 */
rorb $1, %cl /* (assumes top = 0) */
orb %dl, %cl /* merge sector into cylinder */
#else
movw %dx, %cx /* CX = cyl, AL = head, AH = sector-1 */
/*
* the following manipulations are necessary in order to properly place
* parameters into registers.
* CH = cylinder number low 8 bits
* CL<7-6> = cylinder high two bits
* CL<5-0> = sector
*/
movb %al, %dh /* save head into DH for BIOS */
xchgb %cl, %ch /* set cyl number low 8 bits in CH */
rorb $1, %cl /* move cyl high bits into bits 7-6 */
rorb $1, %cl /* (assumes top = 0) */
incb %ah /* AH = sector number */
orb %ah, %cl /* merge sector into cylinder */
#endif
popw %bx
movw $0x0201, %ax /* read 1 sector */
ebios_12_16: /* ebios_12_16 - 1 points to 0x02 that can be changed to 0x42 */
// cmpb $0x0e, 2(%bp) /* force LBA? */
// jnz 1f /* no, continue */
// movb $0x42, %ah /* yes, use extended disk read */
//1:
movw %sp, %si /* DS:SI points to disk address packet */
movb 0x24(%bp), %dl /* drive number */
int $0x13
popaw /* remove parameter block from stack */
popaw
jc disk_error_12_16 /* disk read error, jc 1f if caller handles */
incw %ax /* next sector */
jnz 1f
incw %dx
1:
addw 0x0b(%bp), %bx /* bytes per sector */
jnc 1f /* 64K bound check */
pushw %dx
movw %es, %dx
addb $0x10, %dh /* add 1000h to ES */
/* here, carry is cleared */
movw %dx, %es
popw %dx
1:
decw %di
jnz 2b
/* carry stored on disk read error */
ret
. = . - (. - readDisk_12_16)/99
msg_DiskReadError_12_16:
.ascii "disk error\0"
msg_BootError_12_16:
.ascii "No "
filename_12_16:
#ifdef BOOTGRUB
.ascii "GRLDR \0"
#else
.ascii "KERNEL SYS\0"
#endif
. = Entry_12_16 + 0x1ee
disk_error_12_16:
movw $(msg_DiskReadError_12_16 - Entry_12_16 + 0x7c00), %si
boot_error_12_16:
/* prints string DS:SI (modifies AX BX SI) */
//print_12_16:
1:
lodsb (%si), %al /* get token */
//xorw %bx, %bx /* video page 0 */
movb $0x0e, %ah /* print it */
int $0x10 /* via TTY mode */
cmpb $0, %al /* end of string? */
jne 1b /* until done */
/* The caller will change this to
* ljmp $0x9400, $(try_next_partition - _start1)
*/
1: jmp 1b
. = Entry_12_16 + 0x1fc
.word 0, 0xAA55 /* Win9x uses all 4 bytes as magic value here */
. = Entry_12_16 + 0x200
. = _start1 + 0x800
.arch i486, nojumps
/*
#; Ext2 boot sector for GRLDR
*/
#define DEBUG call debug_print
#undef DEBUG
//. = _start1 + 0x800
Entry_ext2:
jmp 1f
. = Entry_ext2 + 0x02
/* The default mode is CHS. This is for maximum compatiblity with
* small-sized disks, e.g., floppies.
*
* Valid values are 0x02 for CHS mode, or 0x42 for LBA mode.
*
* If the BIOS int13 supports LBA, this byte can be safely set to 0x42.
*
* Some USB BIOSes might have bugs when using CHS mode, so the format
* program should set this byte to 0x42. It seems that (generally) all
* USB BIOSes have LBA support.
*
* If the format program does not know whether the BIOS has LBA
* support, it may operate this way:
*
* if (partition_start + total_sectors_in_partition) exceeds the CHS
* addressing ability(especially when it is greater than 1024*256*63),
* the caller should set this byte to 0x42, otherwise, set to 0x02.
*/
.byte 0x02 /* for CHS. Another possible value is 0x42 for LBA */
. = Entry_ext2 + 0x03
.ascii "ext2 grldr"
. = Entry_ext2 + 0x0d
/* sectors per block. Valid values are 2, 4, 8, 16, 32. */
.byte 2
. = Entry_ext2 + 0x0e
/* bytes per block.
* Valid values are 0x400, 0x800, 0x1000, 0x2000, 0x4000.
*/
.word 1024 /* bytes per block, at most 16K */
. = Entry_ext2 + 0x10
/* pointers in pointers-per-block blocks, that is, number of blocks
* covered by a double-indirect block.
* Valid values are 0x10000, 0x40000, 0x100000, 0x400000, 0x1000000.
*/
.long 0x10000 /* number of blocks covered by double-indirect block */
/* low word=0 */
. = Entry_ext2 + 0x14
/* pointers per block, that is, number of blocks covered by an indirect
* block. Valid values are 0x100, 0x200, 0x400, 0x800, 0x1000.
*/
.long 0x100 /* high word=0, low byte=0 */
. = Entry_ext2 + 0x18
/* this is default for 1.44M floppy, the caller should set it to
* a correct value */
.word 18 /* sectors per track */
. = Entry_ext2 + 0x1a
/* this is default for 1.44M floppy, the caller should set it to
* a correct value */
.word 2 /* number of heads */
. = Entry_ext2 + 0x1c
/* this is default for 1.44M floppy, the caller should set it to
* a correct value */
.long 0 /* hidden sectors */
. = Entry_ext2 + 0x20
/* total sectors in the filesystem(or in the partition).
* This value is informative. The code does not use it.
*/
/* this is default for 1.44M floppy, the caller should set it to
* a correct value */
.long 2880
. = Entry_ext2 + 0x24
/* This byte is ignored for read. The program will write DL onto
* this byte. The caller should set drive number in DL.
* We assume all BIOSes pass correct drive number in DL.
* That is to say, buggy BIOSes are not supported!!
*/
.byte 0 /* drive number */
. = Entry_ext2 + 0x25
/* this is default for floppies, the caller should set it to
* a correct value for hard-drive partitions */
.byte 0xff /* partition number, 0xff for whole drive */
. = Entry_ext2 + 0x26
.word 0 /* reserved for future use */
. = Entry_ext2 + 0x28
/* this is default for 1.44M floppy, the caller should set it to
* a correct value */
.long 2048 /* s_inodes_per_group */
. = Entry_ext2 + 0x2c
/* block number for group descriptors = s_first_data_block + 1.
* Valid values are 2 for 1024-byte blocks, and 1 for otherwise.
*/
/* this is default for 1.44M floppy, the caller should set it to
* a correct value */
.long 2 /* block number for group descriptors */
. = Entry_ext2 + 0x30
1:
cld
xorw %ax, %ax /* CF=0, ZF=1 */
movw %ax, %ss /* constant SS=0 */
movw $0x7c00, %sp
movw %sp, %bp /* constant BP=0x7c00 */
movw %ax, %ds /* constant DS=0 */
pushw %ax /* 0x0000 at 0000:7bfe */
movw $0x1000, %bx
pushw %bx /* 0x1000 at 0000:7bfc */
pushw %ax /* 0x0000 at 0000:7bfa */
/* SP=0x7bfa */
/* the 6 bytes in the stack are used by read_block():
* 0000 ---- -2(%bp)
* 1000 ---- -4(%bp)
* 0000 ---- -6(%bp)
* Don't touch them!
*/
movb %dl, 0x24(%bp) /* BIOS passes drive number in DL */
movb $0x41, %ah
movw $0x55AA, %bx
int $0x13
#if 0
jnc 1f
/* No EBIOS */
movb $0x02, (ebios_ext2 - 1 - Entry_ext2 + 0x7c00)
#else
jc 1f #; No EBIOS
//testb $1, %cl
//jz 1f #; No EBIOS
#if 0
/* gcc-4.0.1 does not generate 2-byte code. */
rcrb $1, %cl #; also can be rorb $1, %cl
#else
.byte 0xD0, 0xD9 #; ror cl: D0 C9
#endif
jnc 1f #; No EBIOS
movb $0x42, (ebios_ext2 - 1 - Entry_ext2 + 0x7c00)
#endif
1:
xorl %eax, %eax /* CF=0, ZF=1 */
#if 0
/* the INC touches ZF flag, so use MOV instead */
incw %ax
incw %ax /* EAX=2=inode number for root dir */
#else
/* MOV keeps all flags untouched, so it is better than INC */
movb $2, %al /* EAX=2=inode number for root dir */
#endif
/* CF=0, ZF=1 because MOV and PUSH do not touch Flags */
/* read root dir to 0000:1000, and grldr to 1000:0000 */
4:
/* EAX holds the inode number: for root dir or grldr */
/* These 3 PUSHes is intended to place 1000:0000 onto the stack for
* grldr. For root dir, the stack is not used since CF is cleared.
* Although there is no corresponding POPs, this is safe enough
* because the program comes here only twice: the first is for
* the root dir, and the second is for grldr.
*
* For root dir, CF=0 and ZF=1. For grldr, CF=1.
*/
pushw %di /* 0x1000, see "jz 4b" below. */
pushw %ss /* 0x0000 */
pushfw
/* SP=0x7bf4 for root dir, or 0x7bee for grldr */
decl %eax /* EAX=(inode - 1) */
/* inode numbers are far less than 0x7fffffff, so it is safe to
* initialise EDX with CDQ */
cdq /* let EDX=0 */
divl 0x28(%bp) /* s_inodes_per_group */
/* EAX=group number */
pushl %edx /* EDX=inode number in the group */
/* group numbers are far less than 0x7fffffff, so it is safe to
* initialise EDX with CDQ */
cdq /* let EDX=0 */
shll $5, %eax /* EAX=relative displacement of the group descriptor */
divl 0x0e(%bp) /* bytes per block */
/* EAX=relative block number for the group descriptor */
/* DX=displacement in the block */
/* EDX high=0 */
pushw %dx /* we don't care about EDX high word, because it is 0 */
addl 0x2c(%bp), %eax /* EAX=absolute block number for the group descriptor */
/* CF=0, ZF=0 */
call read_block /* 0000:1000 points to the block data containing the group descriptor */
/* ES changed and > 0, BX=0x1000 */
/* ECX=EDX=0 */
/* CF=0, ZF=0 */
popw %si /* DS:[BX+SI] points to the group descriptor */
/* DS:[BX+SI+8] points to the starting block number of the group inode table */
popl %eax /* inode number in the group */
shll $7, %eax /* inode struct size = 0x80 */
/* EAX=relative displacement of the inode struct */
/* EDX=0 */
divl 0x0e(%bp) /* bytes per block */
/* EAX=relative block number for the inode struct */
pushw %dx /* DX=displacement of the inode struct in the block */
/* EDX high=0 */
addl 8(%bx, %si), %eax /* EAX=absolute block number for the inode struct */
/* CF=0, ZF=0 */
call read_block /* 0000:1000 points to the block data containing the inode struct */
/* ES changed and > 0, BX=0x1000 */
/* ECX=EDX=0 */
/* CF=0, ZF=0 */
popw %si /* DS:[BX+SI] points to the inode struct */
addw %bx, %si /* DS:SI points to the inode struct */
/* Move the inode struct to a known safe area(0000:0fa8 - 0000:0fff),
* that is, 0x58 bytes immediately before 0000:1000. We care about only
* the beginning 0x58 bytes of the 0x80-byte inode struct, the last
* 0x28 bytes are ignored. The area from 0xfa8+0x28 to 0xfa8+0x57
* stores 12 direct block pointers.
*
*
* At address Initial value Stores what?
* ========== ============= ======================================
* 0xfa8+0x04 (const) the size of the file in bytes
*
* 0xfa8+0x08 total blocks blocks left to read
*
* 0xfa8+0x0c 0 serial number of the block to read
*
*/
pushw %ss
popw %es /* ES=0 */
leaw -0x58(%bx), %di /* BX=0x1000, so DI=0x0fa8 */
//movw $0x0fa8, %di
movb $0x2c, %cl /* 0x2c words = 0x58 bytes */
repz movsw /* now ECX=0, BX=0x1000=DI */
movl %ecx, (0x0c - 0x58)(%di) /* block serial number of the file */
/* ECX=0 means first block */
/* DI=0x1000 */
movl (0x04 - 0x58)(%di), %eax /* i_size, the file size */
decl %eax
divl 0x0e(%bp) /* bytes per block */
/* EDX=various */
incl %eax
movl %eax, (0x08 - 0x58)(%di) /* total blocks for file data */
/*
* 0000:1000 trebly indirect block
* 0000:8000 indirect block
* 0000:c000 double indirect block
* 1000:0000 the file data
*/
/* now DS:SI points to indirect block number */
lodsl /* indirect block number */
testl %eax, %eax
jz 1f
//pushw %ss
//popw %es /* ES=0 */
movb $0x80, %bh /* ES:BX=0000:8000 */
#if 0
stc
call read_block
#else
call read_block_c
#endif
/* ES changed and > 0, BX=0x8000 */
/* ECX=EDX=0 */
/* ZF=0, CF=0 */
/* now DS:SI points to double indirect block number */
lodsl /* double indirect block number */
testl %eax, %eax
jz 1f
#if 0
pushw %ss
popw %es /* ES=0 */
movb $0xc0, %bh /* ES:BX=0000:c000 */
stc
call read_block
#else
movb $0xc0, %bh /* ES:BX=0000:c000 */
call read_block_c
#endif
/* ES changed and > 0, BX=0xc000 */
/* ECX=EDX=0 */
/* ZF=0, CF=0 */
/* now DS:SI points to trebly indirect block number */
lodsl /* trebly indirect block number */
testl %eax, %eax /* CF=0, TEST always clears CF */
jz 1f
/* ZF=0 */
//pushw %ss
//popw %es /* ES=0 */
//movb $0x10, %bh /* ES:BX=0000:1000 */
//stc
call read_block /* 0000:1000 points to the block data */
/* ES changed and > 0, BX=0x1000 */
/* ECX=EDX=0 */
/* ZF=0, CF=0 */
/* the block at 0000:1000, which contains the indirect block numbers,
* is just overwritten by the trebly indirect block */
1:
/* get absolute block number by block serial number */
movl (0x0c - 0x58)(%di), %ebx /* block serial number of the file */
subl $12, %ebx
jc 3f /* direct block: block serial number < 12 */
pushw %bx
subl 0x14(%bp), %ebx
popw %ax
jnc 2f
/* indirect block: 12 <= block serial number < 12 + 0x14(%bp) */
//addw 0x14(%bp), %bx
addb $(0x70 / 4), %ah
//xchgw %ax, %bx
jmp 8f
2:
pushl %ebx
subl 0x10(%bp), %ebx
jc 7f /* EBX on the stack is < 0x10(%bp). double indirect block:
* 12 + 0x14(%bp) <= block serial number < 12 + 0x14(%bp) + 0x10(%bp)
*/
/* trebly indirect block: block serial number >= 12 + 0x14(%bp) + 0x10(%bp) */
popl %eax /* discard the stack */
xchgl %eax, %ebx /* move EBX to EAX */
/* EDX=0 */
divl 0x10(%bp)
/* EAX=indirect block number, < 0x14(%bp) */
/* EDX=block number, < 0x10(%bp) */
pushl %edx /* EDX < 0x10(%bp) */
testl %edx, %edx
jnz 7f
/* EDX=0, so we need to load the double indirect block */
shlw $2, %ax
xchgw %ax, %bx
/* get the double indirect block number from the trebly indirect
* block data */
movl (%bx, %di), %eax
//6:
movw $0xc000, %bx /* ES:BX=0000:c000 */
//pushw %ss
//popw %es /* ES=0 */
//stc
call read_block_c /* 0000:c000 points to the block data */
/* ES changed and > 0, BX=0xc000 */
/* ECX=EDX=0 */
/* CF=0, ZF=0 */
7:
popl %eax /* EAX < 0x10(%bp) */
cdq /* let EDX=0 (notice the above jc 7f and jnz 7f) */
divl 0x14(%bp)
/* EAX=indirect block number, < 0x14(%bp) */
/* EDX=block number, < 0x14(%bp) */
pushw %dx /* EDX < 0x14(%bp) */
testw %dx, %dx
jnz 7f
/* if DX=0, we need to load the indirect block */
//addb $(0xb0 / 4), %ah
shlw $2, %ax
xchgw %ax, %bx
/* get the indirect block number from the double indirect block data */
movl 0xb000(%bx, %di), %eax
//movl (%bx, %di), %eax
//5:
movw $0x8000, %bx /* ES:BX=0000:8000 */
//pushw %ss
//popw %es /* ES=0 */
//stc
call read_block_c /* 0000:8000 points to the block data */
/* ES changed and > 0, BX=0x8000 */
/* ECX=EDX=0 */
/* CF=0, ZF=0 */
7:
popw %ax /* AX < 0x14(%bp) */
8:
xchgw %ax, %bx
3:
shlw $2, %bx
movl (%bx, %di), %eax
/* got it! EAX=absolute block number */
/* read block data to 1000:0000. For root dir, read each block to
* 1000:0000(overwrite the previous read). For grldr, read blocks
* one by one to the area starting at 1000:0000.
*/
popfw
popw %bx
popw %es
pushfw
/* CF=0 and ZF=1 for reading root dir, CF=1 for reading grldr */
call read_block /* 1000:0000 points to the block data */
/* ES changed and > 0x1000, BX=0 */
/* ECX=EDX=0 */
/* CF=0, ZF=0 */
popfw
pushw %es
pushw %bx
pushfw
jc 3f /* CF=1, we are reading grldr */
/* We have just read a block of the root dir to 1000:0000.
* So we check all dir entries in the block to see if anyone
* matches grldr.
*/
xorw %si, %si
pushw %ss
popw %es /* ES=0 */
2:
pushw %ds /* DS=0 */
movw %di, %ds /* DS=0x1000 */
movw $(filename_ext2 - Entry_ext2 + 0x7c00), %di
pushw %si
lodsl /* This is possible inode number for grldr */
pushl %eax /* This is possible inode number for grldr */
lodsw
xchgw %ax, %dx /* rec_len */
lodsw /* AL=name_len, should be 5 for grldr */
/* AH=file_type(1 for regular file) */
cmpw $0x0105, %ax
jnz 5f
movb %al, %cl /* CH is already 0 */
repz cmpsb
5:
popl %eax /* This is possible inode number for grldr */
popw %si
/* DS=0x1000, EAX=inode number */
movw %ds, %di /* DI=0x1000 */
popw %ds /* DS=0 */
stc /* indicates the new inode is for grldr */
jz 4b /* grldr is found with EAX=inode number */
addw %dx, %si
cmpw 0x0e(%bp), %si /* bytes per block */
jb 2b
/* file not found in this block, continue */
/* We are lucky that CF=0, which indicates we are dealing with
* the root dir.
*/
3:
/* CF=1 for grldr, CF=0 for root dir. */
incl (0x0c - 0x58)(%di)
decl (0x08 - 0x58)(%di)
jnz 1b
#if 0
/* The above 2 instructions INC and DEC do not touch CF, so we
* can omit this POP-PUSH pair.
*/
popfw
pushfw
#endif
movw $(msg_No_grldr_ext2 - Entry_ext2 + 0x7c00), %si
jnc boot_error_ext2 /* grldr not found in the root dir */
/* All grldr blocks have been loaded to memory starting at 1000:0000,
* Before the boot, we pass boot_drive and boot_partition to grldr.
*/
/* ES>0x1000, BX=0, ECX=EDX=0, DI=0x1000, SS=0, SI>0x7c00, DS=0
* BP=0x7c00, SP<=0x7c00
*/
movw 0x24(%bp), %dx
/* boot it now! */
pushw %di /* 0x1000 */
pushw %ss /* 0x0000 */
lret
read_block_c:
pushw %ss
popw %es /* ES=0 */
stc
/* read_block - read a block
* input: CF - indicator for overlap or consecution
* EAX = block number
* ES:BX - buffer
*
* output: if CF is cleared on input, ES:BX is initialized to 0000:1000
* ES:BX - buffer filled with data
* ES, EAX - Changed
* ECX = 0
* EDX = 0
* ZF = 0
* CF = 0
*/
read_block:
jc 1f
.byte 0xC4, 0x5E, 0xFC /* lesw -4(%bp), %bx */
/* ES:BX=0000:1000 */
jnz 1f
//at this time, the gcc cannot generate 3 byte code
.byte 0xC4, 0x5E, 0xFA /* lesw -6(%bp), %bx */
/* ES:BX=1000:0000 */
//. = . - (. - read_block) / 6
1:
movzbl 0x0d(%bp), %ecx /* CX=sectors per block */
/* ECX high=0 */
. = . - (. - 1b) / 6
mull %ecx /* EAX=relative sector number */
/* EDX=0 */
. = . - (. - 1b) / 9
addl 0x1c(%bp), %eax /* EAX=absolute sector number */
#if 1
/* pass through, saving 4 bytes(call and ret) */
#else
call readDisk_ext2
ret
#endif
/* Read sectors from disk, using LBA or CHS
* input: EAX = 32-bit LBA sector number
* CX = number of sectors to read
* ECX high word = 0
* ES:BX = destination buffer
*
* output: No return on error
* BX not changed
* ES = ES + 0x20 * CX
* EAX = EAX + CX
* ZF = 0
* CF = 0
*/
readDisk_ext2:
2:
pushal
//xorl %edx, %edx /* EDX:EAX = LBA */
pushl %edx /* hi 32bit of sector number */
pushl %eax /* lo 32bit of sector number */
pushw %es /* buffer segment */
pushw %bx /* buffer offset */
pushw $1 /* 1 sector to read */
pushw $16 /* size of this parameter block */
//xorl %ecx, %ecx
pushl 0x18(%bp) /* lo:sectors per track, hi:number of heads */
popw %cx /* ECX = sectors per track */
divl %ecx /* residue is in EDX */
/* quotient is in EAX */
/* EDX high=0, DH=0 */
incw %dx /* DL=sector number */
popw %cx /* ECX = number of heads */
pushw %dx /* push sector number into stack */
xorw %dx, %dx /* EDX:EAX = cylinder * TotalHeads + head */
divl %ecx /* residue is in EDX, head number */
/* quotient is in EAX, cylinder number */
/* EDX high=0, EAX high=0 */
xchgb %dl, %dh /* head number should be in DH */
/* DL = 0 */
popw %cx /* pop sector number from stack */
xchgb %al, %ch /* lo 8bit cylinder should be in CH */
/* AL = 0 */
shlb $6, %ah /* hi 2bit cylinder ... */
orb %ah, %cl /* ... should be in CL */
incw %ax /* AL=1, read 1 sector */
/* Instead of 0x0e, the LBA indicator at 2(%bp) is
*
* 0x42 for LBA
*
* and
*
* 0x02 for CHS
*/
#if 0
movb $0x42, %ah
/* ebios_ext2 - 1 points to 0x42 that can be changed to 0x02 */
#else
movb $0x02, %ah
/* ebios_ext2 - 1 points to 0x02 that can be changed to 0x42 */
#endif
ebios_ext2:
//andb 2(%bp), %ah
movw %sp, %si /* DS:SI points to disk address packet */
movb 0x24(%bp), %dl /* drive number */
int $0x13
jc disk_error_ext2
movw %es, %ax
addw $0x20, %ax /* here, carry is cleared */
movw %ax, %es
popaw /* remove parameter block from stack */
popal
incl %eax /* next sector, here ZF=0 */
loop 2b
ret
//. = . - (. - readDisk_ext2)/74
msg_DiskReadError_ext2:
.ascii "disk error\0"
msg_No_grldr_ext2:
.ascii "No "
filename_ext2:
.ascii "grldr\0"
. = Entry_ext2 + 0x1f0
disk_error_ext2:
movw $(msg_DiskReadError_ext2 - Entry_ext2 + 0x7c00), %si
boot_error_ext2:
/* prints string DS:SI (modifies AX BX SI) */
//print_ext2:
1:
lodsb (%si), %al /* get token */
//xorw %bx, %bx /* video page 0 */
movb $0x0e, %ah /* print it */
int $0x10 /* via TTY mode */
cmpb $0, %al /* end of string? */
jne 1b /* until done */
#if 1
/* The caller will change this to
* ljmp $0x9400, $(try_next_partition - _start1)
*/
1: jmp 1b
#else
/* boot failed, try to hand over the control to supervisor */
ldsw (1f + 3 - Entry_ext2)(%bp), %si
lodsl
cmpl $0x9400b8fa, %eax
1: jnz 1b /* no supervisor, hang up. */
ljmp $0x9400, $(try_next_partition - _start1)
//. = . - (. - disk_error_ext2) / 30
#endif
. = Entry_ext2 + 0x1fe
.word 0xAA55
. = _start1 + 0xA00
.arch i586, jumps
#ifdef DEBUG
. = Entry_ext2 + 0x201
debug_print:
pushfl
pushal
movl %eax, %ebp
call 2f
#if 0
popal
pushal
movl %ebx, %ebp
call 2f
popal
pushal
movl %ecx, %ebp
call 2f
popal
pushal
movl %edx, %ebp
call 2f
popal
pushal
movl %esi, %ebp
call 2f
popal
pushal
movl %edi, %ebp
call 2f
popal
popfl
pushfl
pushal
pushfl
popl %ebp /* flags */
call 2f
movw %ds, %bp
shll $16, %ebp
movw %es, %bp
call 2f
movw $0x0e0d, %ax /* print CR */
int $0x10 /* via TTY mode */
movw $0x0e0a, %ax /* print LF */
int $0x10 /* via TTY mode */
#endif
popal
popfl
ret
2:
movw $7, %cx
1:
xorw %bx, %bx /* video page 0 */
movl %ebp, %eax
shrl %cl, %eax
shrl %cl, %eax
shrl %cl, %eax
shrl %cl, %eax
andb $0x0f, %al
addb $0x30, %al
movb $0x0e, %ah /* print char in AL */
int $0x10 /* via TTY mode */
decw %cx
testw %cx, %cx
jns 1b
movw $0x0e20, %ax /* print space */
int $0x10 /* via TTY mode */
ret
#endif
#if 1
/* restore GRLDR_CS */
/* this code is executed at 0000:7e10 */
/* CS=code */
.align 16
restore_GRLDR_CS:
2:
call 1f
1:
popw %bx # instruction pointer of 1b
movw %cs, %ax
shrw $4, %bx
addw %ax, %bx # BX=segment value of this code
pushw %bx
pushw $(1f - 2b)
lret
1:
/* modify gdt base */
xorl %eax, %eax
movw %bx, %ax
shll $4, %eax
addl $(gdt -2b), %eax
movl %eax, %cs:(gdt - 2b + 2)
movw $GRLDR_CS, %bx
movw %bx, %es
movw %ds, %bx # save old DS to BX
cli
lgdt %cs:(gdt - 2b)
movl %cr0, %eax
orb $1, %al
movl %eax, %cr0
movw $8, %si
movw %si, %ds
xorl %esi, %esi
xorl %edi, %edi
movl $(0x9000 / 4), %ecx
cld
repz movsl
movw $16, %si
movw %si, %ds
andb $0xfe, %al
movl %eax, %cr0
movw %bx, %ds # restore DS from BX
ljmp $GRLDR_CS, $(try_next_partition - _start1)
#endif
# Descriptor tables
#
# NOTE: The intel manual says gdt should be sixteen bytes aligned for
# efficiency reasons. However, there are machines which are known not
# to boot with misaligned GDTs, so alter this at your peril! If you alter
# GDT_ENTRY_BOOT_CS (in asm/segment.h) remember to leave at least two
# empty GDT entries (one for NULL and one reserved).
#
# NOTE: On some CPUs, the GDT must be 8 byte aligned. This is
# true for the Voyager Quad CPU card which will not boot without
# This directive. 16 byte aligment is recommended by intel.
#
.align 16
gdt:
/* this is the default null entry in GDT */
.word gdt_end - gdt - 1 # gdt limit
.long (GRLDR_CS * 16 + gdt - _start1) # linear address of gdt
.word 0 # pad 2 bytes
/* real mode data segment base=0x200000 */
.word 0xFFFF, 0
.byte 0x20, 0x92, 0, 0
/* real mode data segment base=0 */
.word 0xFFFF, 0
.byte 0, 0x92, 0, 0
gdt_end:
helper_start:
/* helper function begins here
* before the call:
* CF=1 : indicates an invalid or corrupt entry
* CF=0 : indicates a valid entry
*
* on return:
* CF=1 : means "below", try next entry
* CF=0,ZF=1 : means "equal", helper did nothing, so we need
* a further try to boot via NT bootsector
* CF=0,ZF=0 : means "above", helper succeeded, boot it now
*/
sti
/* DS=SS=0x9400 */
pushw %cs
popw %ds
pushw $FS_BOOT
popw %es
/* ES=FS_BOOT */
/* Format of partition information blocks.
*
* Offset Length in bytes Field
* 00h 1 Set to 80h if this partition is active.
* 01h 1 Partition's starting head.
* 02h 2 Partition's starting sector and track.
* 04h(SI) 1 Partition's ID number.
* 05h 1 Partition's ending head.
* 06h 2 Partition's ending sector and track.
* 08h 4 Starting LBA.
* 0Ch 4 Partition's length in sectors.
*/
pushw %ds /* DS=0x9400 */
pushw %es /* ES=FS_BOOT */
pushal
pushfw
//pushw %si
//stc
//jc invalid_or_null /* invalid or null entry */
#if 0
/* backup 63 sectors at FS_BOOT:0 to 63 sectors at FS_BOOT:8000
* this piece of code is no longer useful.
*/
pushw %es
popw %ds
xorw %si, %si
movw $0x8000, %di
movw $0x3f00, %cx
cld
repz movsw
#endif
testb $0x80, %cs:0x02 /* boot previous MBR first? */
jnz 2f /* no, continue to find GRLDR */
/* yes, call the routine for booting the previous MBR.
* it will not return on success.
* on failure, it will return here
*
* before we call the routine, we will check if the user want to
* skip this step and continue to find the GRLDR
*/
movw $(press_space_bar_string - _start1), %si
cmpw $0x3920, %cs:0x04
je 1f
movw $(press_hot_key_string - _start1), %si
1:
call print_message /* CS:SI points to message string */
movw $(press_any_key_string - _start1), %si
call print_message /* CS:SI points to message string */
call sleep_5_seconds
jc 1f /* desired hot-key pressed */
call boot_prev_mbr //Error_modify
1:
orb $0x80, %cs:0x02
2:
popfw
popal
popw %es
popw %ds
pushw %ds /* DS=0x9400 */
pushw %es /* ES=FS_BOOT */
pushal
pushfw
//cmpb $0x0e, 0x00 /* EBIOS previously checked OK? */
//jbe 1f /* yes, skip the check */
movb $0x02, 0x00 /* initialise this byte to 0x02 */
movb $0x41, %ah /* EBIOS check existence */
movw $0x55aa, %bx
int $0x13
jc 1f /* No EBIOS */
cmpw $0xaa55, %bx
jnz 1f /* No EBIOS */
testb $1, %cl
jz 1f /* No EBIOS */
movb $0x42, 0x00 /* LBA supported, save 0x42 to 9400:0000 */
1:
popfw
popal
popw %es
popw %ds
pushw %ds /* DS=0x9400 */
pushw %es /* ES=FS_BOOT */
pushal
pushfw
pushaw
cmpw $0x1c2, %si
jne 1f
/* initialize partition number and partition entries end */
movw $0xffff, 0x1bc /* hd partition number */
movw $0x01fe, 0x1ba /* partition entries end */
1:
pushw %dx
testb %dl, %dl
jns 1f /* floppy, use normal CHS mode */
cmpw $0x1f2, %si /* is it a primary partition? */
ja 2f /* no, it is an extended partition */
movl 4(%si), %eax
movl %eax, 8(%si) /* parent part_start saved here */
xorl %eax, %eax
movl %eax, 4(%si) /* current part_start(0) saved here */
2:
//movl -4(%si), %eax
//cmpl $0xfffffe00, %eax /* check the starting CHS */
//jb 1f /* use normal CHS mode */
/* get CHS total number of sectors */
pushw %es
pushw %ds
movb $8, %ah /* read drive parameters changes DX,ES,DI */
//movb $0x80, %dl /* BIOS drive number is in DL */
int $0x13
popw %ds
popw %es
jc 3f
testb $63, %cl
jnz 2f
3:
/* failed to get drive parameters, use maximum value */
#if 0
popw %dx
pushw %dx
cmpb $0x80, %dl
jne 3f
pushw %ds
xorw %ax, %ax
movw %ax, %ds
cmpb $0, 0x475
popw %ds
je 3f
3:
#endif
movw $0xffff, %cx
movw %cx, %dx
2:
//xorl %eax, %eax
movzbl %dh, %eax
incw %ax
movzbl %cl, %edx
andb $63, %dl
mulw %dx /* DX=0, AX=product */
shrb $6, %cl
xchgb %cl, %dh
xchgb %ch, %dl
incw %dx /* DX=total cylinders */
mull %edx /* EDX=0, EAX=product */
/* check the partition's starting LBA */
movl 4(%si), %ebx
addl 8(%si), %ebx /* EBX=start_LBA */
testl %ebx, %ebx
je 1f
///* we always use LBA mode */
////cmpl %eax, %ebx
////jb 1f /* use normal CHS mode */
cmpb $0x42, 0x00 /* EBIOS present? */
jne 1f /* no, skip the LBA mode int13 call */
/* load partition boot track to FS_BOOT using LBA mode */
popw %ax /* AX=orig DX which holds drive number DL */
pushw %ax
pushl %edx /* EDX=0, higher 4 bytes of starting LBA */
pushl %ebx /* lower 4 bytes of starting LBA */
pushw %es /* ES=FS_BOOT */
pushw %dx /* DX=0, ES:0 is the buffer */
//pushl $0x003f0010 /* transfer 63 sectors */
pushw $0x3f /* transfer 63 sectors */
pushw $0x10 /* size of disk address packet */
xchgw %ax, %dx /* restore drive number DL from AL */
movb $0x42, %ah /* extended read */
movw %sp, %si /* DS:SI points to disk address packet */
int $0x13 /* ignore the read failure */
popaw /* adjust the stack */
jc 1f
popw %dx
popaw
//popw %ax /* discard flags in the stack */
popfw
clc
pushfw /* push new flags with CF=0 */
pushaw
pushw %dx
1:
popw %dx
popaw
popfw
popal
popw %es
popw %ds
pushw %ds /* DS=0x9400 */
pushw %es /* ES=FS_BOOT */
pushal
pushfw
pushw %si
pushfw
pushw %es
//---------------------------------------------------------
/* print "Try (hd0,n): " or "Try (fd0): "*/
pushw %ds
popw %es /* ES=DS=CS=0x9400 */
cld /* for stosb */
xorw %ax, %ax
testb %dl, %dl
jns 1f /* floppy */
/* hard drive */
#if 0
movw %si, %ax
subw $0x1c2, %ax
shrw $4, %ax
cmpw $0x1fe, %si /* is in MBR? */
jb 1f /* yes */
/* no, it is an entry in an extended partition */
movb $0xFC, (add_sub_si + 2 - _start1) /* addw $-4, %si */
incw 0x1bc /* logical partition number */
movb 0x1bc, %al
#else
incw 0x1bc /* logical partition number */
movw 0x1bc, %ax
cmpb $4, %al
jb 1f
movb $0xFC, (add_sub_si + 2 - _start1) /* addw $-4, %si */
#endif
1:
/* AL=partition number, AH=0 */
pushw %ax
movw $(partition_message - _start1 + 7), %di /* drive type */
movb %dl, %al
shrb $7, %al /* drive type: floppy=0, harddrive=1 */
shlb $1, %al
addw $0x6466, %ax /* "fd" or "hd" */
stosw
movb %dl, %al
andb $0x7f, %al /* drive number */
aam /* convert binary to decimal, AH=high, AL=low */
testb %ah, %ah
jz 1f
addb $0x30, %ah
movb %ah, (%di)
incw %di
1:
addb $0x30, %al
stosb
popw %ax
testb %dl, %dl
jns 2f /* floppy */
/* this is a hard drive, the partition number is in AL */
movb $0x2c, (%di) /* "," */
incw %di
aam /* convert binary to decimal, AH=high, AL=low */
testb %ah, %ah
jz 1f
addb $0x30, %ah
movb %ah, (%di)
incw %di
1:
addb $0x30, %al
stosb
2:
movl $0x00203a29, (%di) /* "): \0" */
movw $(partition_message - _start1), %si
call print_message /* CS:SI points to message string */
//---------------------------------------------------------
popw %es
popfw
//stc
jc invalid_or_null /* invalid or null entry */
xorw %si, %si
pushw %es
popw %ds
/* DS=ES=FS_BOOT */
/* First, check for ext2 filesystem */
cmpw $0xEF53, 0x438 /* Magic signature */
jnz 1f
xorl %eax, %eax
cmpl %eax, 0x400 /* s_inodes_count */
jz 1f
cmpl %eax, 0x404 /* s_blocks_count */
jz 1f
cmpw %ax, 0x458 /* s_inode_size, usually 0x80 */
jz 1f
cmpl %eax, 0x420 /* s_blocks_per_group */
jz 1f
cmpl %eax, 0x428 /* s_inodes_per_group */
jz 1f
movl 0x414, %eax /* s_first_data_block */
movw %ax, %bx /* BX=1 for 1K block, 0 otherwise */
shrl $1, %eax /* must be 0 */
jnz 1f
movl 0x418, %ecx /* s_log_block_size */
cmpl $4, %ecx /* max size of block is 16K */
ja 1f
negw %cx /* CF clear for 1K block, set otherwise */
adcw %ax, %bx
decw %bx
jnz 1f
/* BX = 0 */
/* super block is sane */
//pushw %cs
//popw %ds
///* DS=SS=0x9400 */
///* ES=FS_BOOT */
cld
movw $0x800, %si
xorw %di, %di
movw $0x0200, %cx /* yes, we need 2 sectors if enable debug */
repz cs movsw /* CS segment override prefix(=0x2E) */
/* modify the boot partition number */
/* the boot partition number is at offset 0x25 for ext2 */
testb %dl, %dl
jns 3f /* no modification for floppy */
movw $0x25, %di
movw %cs:0x1bc, %ax /* partition number */
stosb
3:
/* fix for ext2 partition: hidden_sectors, offset 0x1c */
popw %si /* DI points to old entry in MBR */
pushw %si
xorl %eax, %eax /* let hidden_sectors=0 for floppy */
testb %dl, %dl
jns 3f /* floppy */
movl %cs:4(%si), %eax
addl %cs:8(%si), %eax
3:
movl %eax, %es:0x1c(%bx) /* adjust hidden_sectors for EXT2 */
/* fix for ext2 partition: EBIOS indicator, offset 0x02 */
movb %cs:0x00(%bx), %al
movb %al, %es:0x02(%bx)
/* fix for ext2 partition: sectors per block, offset 0x0d */
/* fix for ext2 partition: bytes per block, offset 0x0e */
/* fix for ext2 partition: dwords per block(dpb), offset 0x14 */
/* fix for ext2 partition: square of dpb, offset 0x10 */
movb %es:0x418, %cl /* s_log_block_size */
//incw %cx
movl $2, %eax
shlw %cl, %ax
movb %al, %es:0x0d(%bx)
shlw $9, %ax /* block size is word wide */
movw %ax, %es:0x0e(%bx)
shrw $2, %ax
movl %eax, %es:0x14(%bx)
addb $8, %cl
shll %cl, %eax
movl %eax, %es:0x10(%bx)
/* fix for ext2 partition: sectors per track, offset 0x18 */
/* fix for ext2 partition: number of heads, offset 0x1a */
#if 1
pushw %ds
pushw %es
pushw %bx
pushw %dx
movb $8, %ah /* read drive parameters changes DX,ES,DI,BX */
movb $0x80, %dl /* BIOS drive number is in DL */
int $0x13
movw %dx, %ax
popw %dx
popw %bx
popw %es
popw %ds
jc 3f
andb $63, %cl
jz 3f
movb %cl, %es:0x18(%bx)
shrw $8, %ax
incw %ax
movw %ax, %es:0x1a(%bx)
3:
#else
testb %dl, %dl
jns 3f /* floppy */
popw %di /* DI points to old entry in MBR */
pushw %di
movw %cs:1(%di), %ax
andb $63, %ah
movb %ah, %es:0x18
xorb %ah, %ah
incw %ax
movw %ax, %es:0x1a
3:
#endif
/* fix for ext2 partition: s_inodes_per_group, offset 0x28 */
movl %es:0x428, %eax /* s_inodes_per_group */
movl %eax, %es:0x28(%bx)
/* fix for ext2 partition: block number for group descriptors, offset 0x2c */
/* At which block the group descriptors begin? */
movl %es:0x414, %eax /* s_first_data_block */
incw %ax
movl %eax, %es:0x2c(%bx)
/* fix for ext2 partition: on error go back to supervisor, offset 0x01fc */
movw $0x01fc, %si
movw %si, %di
lodsw
cmpw $0xFEEB, %ax /* EB FE is jmp back to itself(infinite loop) */
jnz 3f
decw %ax /* AL=0xEA, ljmp */
stosb
//movw $(try_next_partition - _start1), %ax
movw $0x7e10, %ax
stosw
//movw %cs, %ax /* AX=0x9400 */
xorw %ax, %ax
stosw /* the last byte 0x00 is in the next sector! */
// addw $0x0f, %di
// movw $(restore_GRLDR_CS - _start1), %si
// movw $((gdt_end - restore_GRLDR_CS) / 4), %cx
// .byte 0x2e /* %cs: prefix */
// repz movsl
3:
movw $(EXT2_message - _start1), %si
call print_message /* CS:SI points to message string */
clc
jmp move_entries_and_return
1:
#; It is not EXT2. Check for FAT12/16/32/NTFS.
/* DS=ES=FS_BOOT */
cmpw $0x200, 0x0b(%si) /* bytes per sector */
jne 1f /* not a normal BPB */
movb 0x0d(%si), %al /* sectors per cluster */
testb %al, %al
jz 1f /* invalid if = 0 */
movb %al, %cl
movw $128, %ax
divb %cl /* quo=AL, rem=AH */
testb %ah, %ah
jnz 1f /* invalid if not 2^n */
movw 0x18(%si), %ax /* sectors per track */
testw %ax, %ax
jz 1f /* invalid if = 0 */
cmpw $63, %ax
ja 1f /* invalid if > 63 */
movw 0x1a(%si), %ax /* number of heads */
decw %ax /* Max head number, should be a byte */
testb %ah, %ah /* should be 0 */
jnz 1f /* invalid if number of heads > 256 */
cmpb $0xf0, 0x15(%si) /* media descriptor */
jb 1f
cmpb $0x42, %cs:0x00 /* EBIOS present? */
jne 3f
//movb $0x41, %ah /* EBIOS check existence */
//movw $0x55aa, %bx
//int $0x13
//jc 3f /* No EBIOS */
//cmpw $0xaa55, %bx
//jnz 3f /* No EBIOS */
//testb $1, %cl
//jz 3f /* No EBIOS */
movb $0x0e, 0x02(%si) /* force LBA */
3:
cld
movw $0x0600, %bx /* FAT12/FAT16 */
movw $0x003c, %cx /* FAT12/FAT16 */
movb 0x10(%si), %al /* number of FATs(NTFS:0, FAT:1,2) */
cmpb $2, %al
ja 1f /* abnormal FAT */
movw 0x11(%si), %ax /* max root entries */
testw %ax, %ax
jnz 2f /* FAT12/FAT16 */
/* FAT32 or NTFS */
movw 0x13(%si), %ax /* total sectors(small) */
testw %ax, %ax
jnz 1f /* invalid FAT32 BPB */
movw 0x16(%si), %ax /* sectors per FAT(small) */
testw %ax, %ax
jnz 1f /* invalid FAT32 BPB */
movb 0x10(%si), %al /* number of FATs(NTFS:0, FAT:1,2) */
testb %al, %al
jz 8f
/* FAT32 */
movl 0x20(%si), %eax /* FAT32 total sectors */
testl %eax, %eax
jz 1f
movl 0x24(%si), %eax /* FAT32 sectors per FAT */
testl %eax, %eax
jz 1f
movw $0x0400, %bx /* FAT32 */
movw $0x0058, %cx /* FAT32 */
movw $(FAT32_message - _start1), %si
jmp 7f
8:
/* NTFS */
movl 0x20(%si), %eax /* FAT32 total sectors */
testl %eax, %eax
jnz 1f
//movw 0x11(%si), %ax /* max root entries */
//testw %ax, %ax
//jnz 1f
movw 0x0e(%si), %ax /* reserved sectors */
testw %ax, %ax
jnz 1f
/* BUG fix for extended NTFS partition */
popw %si /* SI points to old entry in MBR */
pushw %si
xorl %eax, %eax /* let hidden_sectors=0 for floppy */
testb %dl, %dl
jns 3f /* floppy */
movl %cs:4(%si), %eax
addl %cs:8(%si), %eax
3:
movl %eax, 0x1c /* adjust hidden_sectors for NTFS */
movb %dl, 0x24 /* adjust drive number for NTFS */
/* modify the boot partition number */
movb $0xB6, %al /* 0xB6="MOV DH,imm8" */
movb %cs:0x1bc, %ah
testb %dl, %dl
js 3f
movb $0xff, %ah /* partition number for floppy is whole drive */
3:
/* before the call:
* AH= partition number
* AL= 0xB6 ; 0xB6 is opcode of "MOV DH,imm8"
* DL= drive number
*
* on return: CF=0 if there is NTFS boot record;
* CF=1 otherwise.
* CF of flags_orig on the stack will set if CF=1
*/
call modify_NTFS_boot_record
//jnc move_entries_and_return
//movw $(NTFS5_message - _start1), %si
////jmp 4f
//call print_message /* CS:SI points to message string */
//stc
jmp move_entries_and_return
2:
/* FAT12/FAT16 */
movb 0x10(%si), %al /* number of FATs(NTFS:0, FAT:1,2) */
testb %al, %al
jz 1f
movw 0x16(%si), %ax /* sectors per FAT(small) */
testw %ax, %ax
jz 1f
movw $(FAT16_message - _start1), %si
cmpw $12, %ax
ja 7f
movw $(FAT12_message - _start1), %si
7:
/* BUG fix for extended FAT12/16/32 partition */
popw %di /* DI points to old entry in MBR */
pushw %di
xorl %eax, %eax /* let hidden_sectors=0 for floppy */
testb %dl, %dl
jns 3f /* floppy */
movl %cs:4(%di), %eax
addl %cs:8(%di), %eax
3:
movl %eax, 0x1c /* adjust hidden_sectors for FAT */
call print_message /* CS:SI points to message string */
pushw %cs
popw %ds
/* DS=SS=0x9400 */
/* ES=FS_BOOT */
movw %bx, %si
xorw %di, %di
lodsw
stosw
addw %cx, %si
addw %cx, %di
movw $0x0200, %cx
subw %di, %cx
repz movsb
/* modify the boot partition number */
movb %es:1, %al
addb $5, %al /* AL is less than 0x80 */
cbw /* AH=0 */
xchgw %ax, %di /* move AX to DI */
movb $0xff, %al /* partition=whole drive for floppy */
testb %dl, %dl
jns 3f /* no modification for floppy */
movb 0x1bc, %al /* partition number */
3:
stosb
/* fix for FAT12/16/32 partition: on error go back to supervisor, offset 0x01fa */
//pushw %es
//popw %ds
movw $0x01fa, %di
//movw %di, %si
//lodsw
movw %es:(%di), %ax
cmpw $0xFEEB, %ax /* EB FE is jmp back to itself(infinite loop) */
jnz 3f
decw %ax /* AL=0xEA, ljmp */
stosb
//movw $(try_next_partition - _start1), %ax
movw $0x7e10, %ax
stosw
//movw %cs, %ax /* AX=0x9400 */
xorw %ax, %ax
stosw /* DI=0x01ff */
3:
clc
jmp move_entries_and_return
1:
#; It is not FAT12/16/32/NTFS. Check for extended partition.
/* DS=ES=FS_BOOT */
pushw %cs
popw %es
/* ES=SS=0x9400 */
/* DS=FS_BOOT */
popw %si
pushw %si
cmpb $0x05, %es:(%si) /* extended */
je 1f
cmpb $0x0f, %es:(%si) /* Win95 extended (LBA) */
je 1f
cmpb $0x15, %es:(%si) /* hidden extended */
je 1f
cmpb $0x1f, %es:(%si) /* hidden win95 extended (LBA) */
je 1f
cmpb $0x85, %es:(%si) /* Linux extended */
je 1f
movw $(non_MS_message - _start1), %si
4:
call print_message /* CS:SI points to message string */
stc
jmp move_entries_and_return
1:
/* extended partition entry */
cmpw $0x1fe, %si
jb 1f
decw %es:0x1bc /* count the partitions in extended zone */
1:
movw $(extended_message - _start1), %si
call print_message /* CS:SI points to message string */
movw $0x1be, %si
movw $4, %cx
5:
//xorl %eax, %eax
//cmpl %eax, (%si)
//jnz 2f
movl (%si), %eax
cmpw 2(%si), %ax /* Is EAX high word equal to AX? */
jnz 2f
cmpb %al, %ah /* Is AL=AH? */
jnz 2f
/* now all 4 bytes in EAX are equal to each other. */
cmpl %eax, 4(%si)
jnz 2f
cmpl %eax, 8(%si)
jnz 2f
cmpl %eax, 12(%si)
jz 3f /* entry with 16 dups of a byte means empty entry */
2:
movb (%si), %al
shlb $1, %al
jnz 1f
//jnz 3f /* invalid entry is treated as empty entry */
movb 2(%si), %al
and $63, %al /* starting sector number */
jz 1f
//jz 3f /* invalid entry is treated as empty entry */
movb 6(%si), %al
and $63, %al /* ending sector number */
jz 1f
//jz 3f /* invalid entry is treated as empty entry */
movl 8(%si), %eax /* starting LBA */
testl %eax, %eax
jz 1f
//jz 3f /* invalid entry is treated as empty entry */
movl 12(%si), %eax /* total number of sectors in partition */
testl %eax, %eax
jz 1f
3:
addw $16, %si
loop 5b
cmpw $0xaa55, (%si)
jnz 1f
movw $0x1be, %si
movw $4, %cx
popw %bx /* the old SI points to extended partition ID in MBR */
pushw %bx
5:
#if 1
//xorl %eax, %eax
//cmpl %eax, (%si)
//jnz 2f
movl (%si), %eax
cmpw 2(%si), %ax /* Is EAX high word equal to AX? */
jnz 2f
cmpb %al, %ah /* Is AL=AH? */
jnz 2f
/* now all 4 bytes in EAX are equal to each other. */
cmpl %eax, 4(%si)
jnz 2f
cmpl %eax, 8(%si)
jnz 2f
cmpl %eax, 12(%si)
jz 3f /* entry with 16 dups of a byte means empty entry */
2:
/* now it is an acceptable entry */
movw %es:0x1ba, %di /* partition entries end */
/* ensure our stack not to be overwritten by the partition entries */
cmpw $0x83f0, %di
ja 3f /* try next */
/* ensure our code not to be overwritten by the partition entries */
cmpw $0x3fe, %di
jne 6f
/* more entries stores at 0x9be00-0x9c3ff */
movw $0x7e00, %di
movw %di, %es:0x1ba
6:
addw $16, %es:0x1ba /* increment partition entries end */
lodsl
stosl
lodsl
stosl
xchgw %ax, %dx /* save AL(the partition ID)to DL */
lodsl
xchgl %eax, %edx /* restore AL from DL(the partition ID)
* and save EAX to EDX */
cmpb $0x05, %al
je 6f
cmpb $0x0f, %al
je 6f
cmpb $0x15, %al
je 6f
cmpb $0x1f, %al
je 6f
cmpb $0x85, %al
je 6f
/* normal partition, copied to 0x941fe-0x943fb */
addl %es:4(%bx), %edx /* current partition start */
6:
/* extended partition, copied to 0x941fe-0x943fb */
xchgl %eax, %edx /* restore or update EAX from EDX */
stosl
lodsl /* adjust SI only */
movl %es:8(%bx), %eax /* parent partition start ... */
stosl /* ... stored here */
jmp 2f
3:
addw $16, %si
#endif
//. = 5b + 0x7c
2:
loop 5b
/* extended partition is not a normal one, so set carry to try next */
stc
jmp move_entries_and_return
invalid_or_null:
1:
movw $(invalid_message - _start1), %si
call print_message /* CS:SI points to message string */
stc
move_entries_and_return:
popw %si
pushfw
pushw %cs
popw %ds
pushw %cs
popw %es
pushw %si
cmpw $0x202, %si
jne 1f
/* move entries backward 1 entry */
movw $0x1fe, %di
movw $0x20e, %si
movw $0xf8, %cx /* 0x1f0 bytes = 0xf8 words */
cld /* move upward */
repz movsw
movw $0x3ee, %di
movw $0x7e00, %si
movw $0x8, %cx /* 0x10 bytes = 0x8 words */
cld /* move upward */
repz movsw
movw $0x7e00, %di
movw $0x7e10, %si
movw $0x2f8, %cx /* 0x5f0 bytes = 0x2f8 words */
cld /* move upward */
repz movsw
cmpw $0x7e10, 0x1ba
jne 2f
movw $0x40e, 0x1ba
2:
subw $0x10, 0x1ba
1:
popw %si
movw $0x1ff, (add_sub_si + 5 - _start1)
cmpw $0x1fe, 0x1ba
jne 1f
decw (add_sub_si + 5 - _start1)
cmpw $0x31b2, %si /* floppy? */
je 1f /* yes */
cmpw $0x1f2, %si
ja 2f /* logical partition */
jb 1f /* primary partition 0, 1, 2 */
/* primary partition 3 */
cmpw $0x0003, 0x1bc /* are there any logical partitions? */
ja 1f /* yes */
2:
inc_hard_drive:
/* all partitions on the drive have been checked, try next drive.
*
* the current stack is:
*
* SP + 38 : DS
* SP + 36 : ES
* SP + 32 : EAX
* SP + 28 : ECX
* SP + 24 : EDX
* SP + 20 : EBX
* SP + 16 : ESP_temp
* SP + 12 : EBP
* SP + 8 : ESI
* SP + 4 : EDI
* SP + 2 : flags_orig
* SP : flags
*
*/
/* get total hard drives */
xorw %ax, %ax
movw %ax, %ds
movb 0x475, %dh
pushw %cs
popw %ds
// cmpb $16, %dh
// jnb 2f
// movb $16, %dh
//2:
orb $0x80, %dh /* CF=0, DH=Max harddrive number + 1 */
//xchgw %ax, %cx /* CL=Max harddrive number + 1, CH=0 */
movw %sp, %bp
movb 24(%bp), %dl /* BIOS drive number is in DL */
2:
jnc 3f
call print_message /* CS:SI points to message string */
movw $(drive_number_string - _start1), %si
movb %dl, %al
andb $0x7f, %al
aam /* AH=high decimal, AL=low decimal */
addw $0x3030, %ax
xchgb %al, %ah
movw %ax, 9(%si)
call print_message /* CS:SI points to message string */
3:
incw %dx
cmpb %dh, %dl
jnb 2f /* all drives checked, try floppy finally */
pushw %bx
pushw %dx
pushw %es
movb $8, %ah /* read drive parameters changes DX, ES, DI */
int $0x13
popw %es
jc 3f /* try next hard drive */
//xchgw %ax, %cx /* this moves CL to AL */
andb $63, %cl /* CL=sectors per track, CF cleared */
stc
jz 3f /* try next hard drive */
popw %dx /* get DL */
popw %bx
movb %dl, %ch /* DL saved at BP high byte in the stack */
pushw %cx /* push new BX onto stack */
pushw %dx
//movb $0x02, %ah
//movw %ax, %si /* save AX to SI: read 1 track */
movw $0x201, %ax /* read 1 sector */
movw $0x7e00, %bx /* read MBR to 9400:7e00 */
movw $1, %cx
//popw %dx
//pushw %dx
xorb %dh, %dh
stc
int $0x13
sti
3:
popw %dx
popw %bx /* BL=sectors per track, BH=DL */
//movw %si, %bx /* BL=sectors per track */
movw $(Error_while_reading_string - _start1), %si
jc 2b /* read failure, try next hard drive */
/* on seccessful return, should be: ah=0 for OK, al=1 for 1 sector */
//decw %ax /* some BIOSes return incorrect AL */
testb %ah, %ah
stc
jnz 2b
/* The new partition table might be empty or invalid.
* Move the new partition table onto the old one while checking
*/
//movb %dl, %bh /* DL saved at BP high byte in the stack */
movw $0x7fbe, %si
movw $0x01be, %di
3:
cmpw $0x1fe, %di
jnb 3f
xorl %ecx, %ecx
lodsl
stosl
orl %eax, %ecx
lodsl
stosl
orl %eax, %ecx
lodsl
stosl
orl %eax, %ecx
lodsl
stosl
orl %eax, %ecx
jecxz 3b /* null entry, check next */
//lodsw
//stosw
movb -16(%si), %al
shlb $1, %al
stc
xchgw %ax, %si /* save SI to AX */
movw $(partition_boot_indicator_string - _start1), %si
jnz 2b
xchgw %ax, %si /* restore SI from AX */
//lodsw
//stosw
movb -14(%si), %al
andb $63, %al
stc
xchgw %ax, %si /* save SI to AX */
movw $(partition_sectors_per_track_string - _start1), %si
jz 2b
xchgw %ax, %si /* restore SI from AX */
//lodsw
//stosw
//lodsw
//stosw
movb -10(%si), %al
andb $63, %al
stc
xchgw %ax, %si /* save SI to AX */
movw $(partition_sectors_per_track_string - _start1), %si
jz 2b
xchgw %ax, %si /* restore SI from AX */
//lodsl
//stosl
movl -8(%si), %eax
testl %eax, %eax
stc
xchgw %ax, %si /* save SI to AX */
movw $(partition_start_sector_string - _start1), %si
jz 2b
xchgw %ax, %si /* restore SI from AX */
//lodsl
//stosl
movl -4(%si), %eax
testl %eax, %eax
stc
xchgw %ax, %si /* save SI to AX */
movw $(partition_end_sector_string - _start1), %si
jz 2b
xchgw %ax, %si /* restore SI from AX */
jmp 3b
3:
cmpw $0xAA55, (%si)
stc
xchgw %ax, %si /* save SI to AX */
movw $(no_boot_signature_string - _start1), %si
jnz 2b
xchgw %ax, %si /* restore SI from AX */
//lodsw
//stosw /* store boot signature */
/* Now the partition table is OK */
movw %bx, 12(%bp) /* adjust BP in the stack */
movw $0x1b2, 8(%bp) /* adjust SI in the stack */
/* temp change the code: call self_modify_once
*
* "call self_modify_once" at add_sub_si is:
*
* .byte 0xE8
* .word (self_modify_once - add_sub_si - 3)
*
*/
movb $0xE8, (add_sub_si - _start1)
movw $(self_modify_once - add_sub_si - 3), (add_sub_si + 1 - _start1)
/* initialize partition number and partition entries end */
movw $0xffff, 0x1bc /* hd partition number */
movw $0x01fe, 0x1ba /* partition entries end */
jmp 1f
2:
/* get here if all drives have been checked */
#if 0
movw $0x202, 8(%bp) /* adjust SI in the stack */
/* restore the original code: addw $-4, %si */
movw $0xC683, (add_sub_si - _start1) /* 0x83, 0xC6 */
movb $0xFC, (add_sub_si + 2 - _start1) /* 0xFC */
#endif
//--------------------------------------------------------------------
/* change the code: jmp Error_modify
*
* "jmp Error_modify" at Error_or_prev_MBR:
*
* .byte 0xE9
* .word (Error_modify - Error_or_prev_MBR - 3)
*
*/
movb $0xE9, (Error_or_prev_MBR - _start1)
movw $(Error_modify - Error_or_prev_MBR - 3), (Error_or_prev_MBR + 1 - _start1)
//--------------------------------------------------------------------
//--------------------------------------------------------------------
/* floppy search disabled ? */
#if 0
testb $1, 0x02 /* test bit0 of the third byte */
jz 1f /* zero means floppy search enabled */
/* 0x1fd or below means disable floppy search */
decw (add_sub_si + 5 - _start1)
#else
movb 0x02, %al
andb $0x01, %al
subb %al, (add_sub_si + 5 - _start1)
#endif
//--------------------------------------------------------------------
1:
#if 0
popfw
lahf /* Load Flags into AH Register. */
/* AH = SF:ZF:xx:AF:xx:PF:xx:CF */
/* CF will be moved to ZF */
movb %ah, %al
andb $1, %al /* CF=0 */
shlb $6, %al /* move CF to ZF */
popfw
lahf /* Load Flags into AH Register. */
/* AH = SF:ZF:xx:AF:xx:PF:xx:CF */
andb $0xbf, %ah /* 0xbf= binary 1011 1111. It clears ZF */
orb %al, %ah
#else
popw %ax /* AX=Flags */
popfw /* Flags_orig */
lahf /* Load Flags_orig into AH Register. */
/* AH = SF:ZF:xx:AF:xx:PF:xx:CF */
shlb $2, %ah
rorw $2, %ax /* move CF of Flags to ZF of Flags_orig */
#endif
sahf /* update flags */
/* current CF is the CF of Flags_orig */
/* current ZF is the CF of Flags */
jc 1f /* CF=1 means failed in loading bootsector */
popal /* get drive number DL */
pushal
pushfw
cmpb $0xff, %cs:0x06
jz 2f
movb %cs:0x1bc, %dh
testb %dl, %dl
js 3f
movb $0xff, %dh /* partition # for floppy is "whole drive" */
3:
cmpw %cs:0x06, %dx
jz 2f
popfw
stc
pushfw
2:
popfw
1:
popal
popw %es
popw %ds
ret
self_modify_once:
/* when we get here, SI should be 0x1b2, and BP high holds DL */
addw $12, %si /* 0x83, 0xC6, 0x0C */
movw %bp, %ax
movb %ah, %dl
/* note: DS=0x9400 */
/* restore the original code: addw $12, %si */
movw $0xC683, (add_sub_si - _start1) /* 0x83, 0xC6 */
movb $0x0C, (add_sub_si + 2 - _start1) /* 0x0C */
ret
Error_modify:
cmpb $0xff, %cs:0x06 /* preferred drive? */
jz 1f /* not active. Turn to the final step. */
/* preferred drive is already handled, so de-activate it now. */
movb $0xff, %cs:0x06
/* we will do the second pass, from drive 0x80. */
movb $0x7f, %dl /* this will become 0x80 after inc. */
/* pass "error" to PUSHF, simulating a load failure, in order
* to try the first entry after return from the helper function.
*/
stc
pushw $(helper_call + 3 - _start1) /* return address */
pushw %cs /* 0x9400, it is for DS. */
pushw $FS_BOOT /* 0x0d00, it is for ES. */
pushal
//pushl %eax
//pushl %ecx
//pushl %edx
//pushl %ebx
//pushl %esp
//pushl %ebp
//pushl %esi
//pushl %edi
pushfw /* CF=1 */
pushfw
pushw %cs
popw %es /* ES=0x9400 */
/* redo from start: DL will be 0x80 after inc. */
jmp inc_hard_drive
1:
boot_prev_mbr:
/* prepare to boot the previous MBR */
/* at this moment DS=0x9400, ES=$FS_BOOT or ES=0x9400 */
xorw %ax, %ax
//pushw %ax /* AX=0, for the segment of 0000:7c00 */
movw %ax, %es /* ES=0x0000 */
movw %ax, %ds /* DS=0x0000 */
pushw %ds
pushw %es
movw $0x0202, %ax /* read 2 sectors ... */
movw $0x7A00, %bx /* ... to 0000:7A00 */
//pushw %bx /* BX=0x7c00, for the offset of 0000:7c00 */
movw $0x0001, %cx /* from the first sector ... */
movw $0x0080, %dx /* ... of the first hard drive */
stc
int $0x13
sti
popw %es
popw %ds
jc 1f
testb %ah, %ah
jnz 1f
cmpw $0xAA55, 0x7dfe
jne 1f
cmpw $0xAA55, 0x7bfe
jne 1f
/* has a valid partition table ? */
movw $0x7dbe, %si
3:
cmpw $0x7dfe, %si
jnb 3f /* partition table is OK */
movw $4, %cx
movw %si, %di
2:
lodsl
negl %eax
jc 2f
loop 2b
/* empty entry, check next */
jmp 3b
2:
/* non-empty entry */
movw %di, %si
lodsw
shlb $1, %al
jnz 2f
lodsw
andb $63, %al
jz 2f
lodsw
lodsw
andb $63, %al
jz 2f
lodsl
negl %eax
jnc 2f
lodsl
negl %eax
jc 3b
2:
stc /* invalid partition table */
3:
pushfw
/* disable the boot of non-MBR bootsector ? */
testb $2, %cs:0x02 /* test bit1 of the third byte */
jz 2f /* zero means non-MBR enabled */
popfw
jc 1f /* invalid partition table, print "Error" */
/* the partition table is valid */
pushfw
2:
/* the check passed, and the boot is permitted */
popfw
jc 2f /* invalid partition table */
/* use partition table in MBR instead */
/* copy 72 bytes at 0000:7bb8 to 0000:7db8 */
movw $0x7bb8, %si
movw $0x7db8, %di
movw $36, %cx
cld
repz movsw
2:
testb $0x80, %cs:0x02 /* test bit 7 of the third byte */
jz 2f /* zero means boot prev-MBR first */
movw $(Cannot_find_GRLDR_string - _start1), %si
call print_message /* CS:SI points to message string */
movw $(press_space_bar_string - _start1), %si
cmpw $0x3920, %cs:0x04
je 3f
movw $(press_hot_key_string - _start1), %si
3:
call print_message /* CS:SI points to message string */
movw $(prev_MBR_string - _start1), %si
call print_message /* CS:SI points to message string */
3:
call sleep_5_seconds
/* if hot-key is pressed, wait forever until another key is pressed. */
movb $0xff, %cs:0x03
jc 3b /* desired hot-key is pressed */
2:
/* boot the previous MBR */
/* clear the DUCE indicator */
movl $0, 0x5FC /* DS=ES=0 */
//movb $0x80, %dl
ljmp $0, $0x7c00
1:
/* no previous MBR, print "Error" */
///* Note the 0000:7C00 is on the stack */
//popw %ax /* AX=0x0000 */
//popw %ax /* AX=0x7C00 */
testb $0x80, %cs:0x02 /* are we called prior to the GRLDR search? */
jnz 1f /* no, it is a failure at last */
/* yes, so return to the caller */
movw $(continue_string - _start1), %si
call print_message /* CS:SI points to message string */
call sleep_5_seconds
ret
1:
movw $(message_string_helper - _start1), %si
call print_message /* CS:SI points to message string */
1: jmp 1b /* hang */
sleep_5_seconds:
/* sleep 5 seconds */
/* sleep forever if %cs:0x03 is 0xff */
/* calculate the timeout ticks */
pushw %ds
pushl %edx
movl $0xffffffff, %edx
movzbl %cs:0x03, %eax
cmpb $0xff, %al
je 1f
movl $18, %edx /* 18.2 ticks per second. We simply use 18. */
mulw %dx /* EDX=0, EAX=ticks */
xchgw %ax, %dx /* EAX=0, EDX=ticks */
1:
xorw %ax, %ax
movw %ax, %ds
movl 0x46c, %eax /* initial tick */
movl %eax, %ecx /* ECX=initial tick */
testl %edx, %edx
js 1f
addl %edx, %eax /* EAX=timeout tick */
jmp 3f
1:
movl %edx, %eax /* EAX=0xffffffff */
3:
movl 0x46c, %ebx /* EBX=current tick */
cmpl %ecx, %ebx
jnb 2f
/* current tick is less than initial tick, this means the ticks have
* overflowed to the next day, and EBX is rather small. */
xorl %ecx, %ecx
movl %edx, %eax
2:
/* check if there is any key press. */
pushw %ax
movb $1, %ah
int $0x16
jnz 1f
/* no, there is no key press. */
popw %ax
cmpl %eax, %ebx /* timeout? */
jbe 3b /* no, continue to wait */
/* timeout reached, CF=0, no key pressed. */
popl %edx
popw %ds
ret
1:
/* yes, there is a key press. */
#if 0
/* clear the keyboard buffer */
movb $1, %ah
int $0x16
jz 1f /* no keys, end */
movb $0, %ah
int $0x16 /* discard the key */
jmp 1b
1:
#endif
/* check if it is the desired key. */
xorw %cs:0x04, %ax /* CF=0 */
jne 1f /* not desired, return CF=0 */
/* remove the desired key from the keyboard buffer. */
movb $0, %ah
int $0x16 /* discard the key */
stc /* CF=1, the desired key pressed */
1:
popw %ax
popl %edx
popw %ds
ret
modify_NTFS_boot_record:
/* before the call:
* AH= partition number
* AL= 0xB6 ; 0xB6 is opcode of "MOV DH,imm8"
* DL= drive number
*
* on return: CF=0 if there is NTFS boot record;
* CF=1 otherwise.
* CF of flags_orig on the stack will set if CF=1
*/
/*
*
* the current stack is:
*
* SP + 40 : DS
* SP + 38 : ES
* SP + 34 : EAX
* SP + 30 : ECX
* SP + 26 : EDX
* SP + 22 : EBX
* SP + 18 : ESP_temp
* SP + 14 : EBP
* SP + 10 : ESI
* SP + 6 : EDI
* SP + 4 : flags_orig
* SP + 2 : SI ; SI points to old entry in MBR
* SP : return_IP
*
*/
/* DS=ES=FS_BOOT */
/* change NTLDR to GRLDR */
/* check GR or NT or anything else */
pushw %ax
movw $0x200, %si
lodsw
cmpw $5, %ax
jne 1f /* failure */
lodsw
testb %ah, %ah /* high byte of unicode ASCII should be 0 */
jne 1f /* failure */
/* 'N' should be a capital letter */
cmpb $0x41, %al /* Less than 'A' */
jb 1f /* failure */
cmpb $0x5A, %al /* Greater than 'Z'*/
ja 1f /* failure */
xchgw %ax, %cx /* save AX to CX. CL='N' */
lodsw
testb %ah, %ah /* high byte of unicode ASCII should be 0 */
jne 1f /* failure */
/* 'T' should be a capital letter */
cmpb $0x41, %al /* Less than 'A' */
jb 1f /* failure */
cmpb $0x5A, %al /* Greater than 'Z'*/
ja 1f /* failure */
movb %al, %ch /* save AL to CH. CH='T' */
lodsw
cmpw $0x4C, %ax /* 'L' */
jne 1f /* failure */
lodsw
cmpw $0x44, %ax /* 'D' */
jne 1f /* failure */
lodsw
cmpw $0x52, %ax /* 'R' */
jne 1f /* failure */
lodsw
cmpw $0x04, %ax /* length of "$I30" */
jne 1f /* failure */
lodsw
cmpw $0x24, %ax /* '$' */
jne 1f /* failure */
lodsw
cmpw $0x49, %ax /* 'I' */
jne 1f /* failure */
lodsw
cmpw $0x33, %ax /* '3' */
jne 1f /* failure */
lodsw
cmpw $0x30, %ax /* '0' */
jne 1f /* failure */
/* assume it is NT bootsector. first, find "NTLDR". CX holds "NT" */
movw $0x0100, %di
movb %cl, %al /* AL="N" */
movb $1, %ah /* AH=Carry for SAHF below */
movl $0x52444c00, %ebx /* "LDR" */
movb %ch, %bl /* 'T' */
movw $0x00fa, %cx
/* now AL holds 'N' and BL holds 'T' */
//cld /* already upward */
3:
repnz scasb /* find "N" */
jcxz 4f /* gets the end, exit */
cmpl %ebx, (%di) /* is it "NTLDR"? */
jnz 3b /* no, continue to find */
/* "NTLDR" is found, so we believe it is NT boot sector. */
movw $0x5247, -1(%di) /* change "NT" to "GR" */
/* CF=0 for now */
lahf /* Load Flags into AH */
/* AH = SF:ZF:xx:AF:xx:PF:xx:CF */
/* AH = binary xxxxxxx0 */
jmp 3b
4:
sahf /* Store AH into flags SF ZF xx AF xx PF xx CF */
/* CF=0 means "NTLDR" is found, CF=1 means "NTLDR" is not found. */
jc 1f /* failure */
movl $0x00520047, 0x202 /* change to "G R L D R" */
/* check NT 4.0 */
movw $0x406, %si
movl (%si), %ebx /* NT 4.0 */
cmpl $0x03E8B800, %ebx /* MOV AX, 03E8 */
jnz 3f
movl 0x84, %ebx
cmpl $0x680007E8, %ebx /* call 008e; push (0D00) */
jnz 3f
// movw 0x154, %bx /* CR LF at end of "A disk read error occurred." */
// cmpw $0x0A0D, %bx /* CR LF */
// jnz 3f
// movw 0x180, %bx /* CR LF at end of "A kernel file is missing from the disk." */
// cmpw $0x0A0D, %bx /* CR LF */
// jnz 3f
// movw 0x1A8, %bx /* CR LF at end of "A kernel file is too discontiguous." */
// cmpw $0x0A0D, %bx /* CR LF */
// jnz 3f
// movw 0x1F8, %bx /* CR LF at end of "NTLDR is compressed." */
// cmpw $0x0A0D, %bx /* CR LF */
// jnz 3f
movl 0xE8, %ebx
cmpl $0x13CD80B2, %ebx /* "B2 80"="mov DL, 80", "CD 13"="int 13" */
jnz 3f
popw %ax
movw %ax, 4(%si)
movl $0x68909090, %ebx /* nop;nop;nop;push (0D00) */
movl %ebx, 0x84
// /* change CRLF in NTFS error messages to spaces */
// movw $0x2020, %bx /* change CRLF to 2 spaces */
// movw %bx, 0x154
// movw %bx, 0x180
// movw %bx, 0x1A8
// movw %bx, 0x1F8
movb %dl, 0xE9 /* modify drive number */
/* modify NTFS boot record */
movb $0xea, %al /* ljmp, hand over the control to supervisor */
movb %al, 0x122
//movw $(try_next_partition - _start1), %ax /* offset for ljmp */
movw $0x7e10, %ax /* offset for ljmp */
movw %ax, 0x123
//movw %cs, %ax /* AX=0x9400, segment for ljmp */
xorw %ax, %ax
movw %ax, 0x125
movw $(NTFS4_message - _start1), %si
call print_message /* CS:SI points to message string */
clc
ret
3:
/* check NT 5.0 */
movw $0x44b, %si
movl (%si), %ebx /* NT 5.0 */
cmpl $0x03E8B800, %ebx /* MOV AX, 03E8 */
jz 2f
movw $0x479, %si
movl (%si), %ebx /* NT 5.1 SP2 */
cmpl $0x03E8B800, %ebx /* MOV AX, 03E8 */
jnz 1f
2:
movl 0x71, %ebx
cmpl $0x680053E8, %ebx /* call 00C7; push (0D00) */
jnz 1f
//movw 0x183, %bx /* CR LF at begin of "A disk read error occurred." */
movb 0x1F8, %bl
movb $1, %bh
movw (%bx), %bx
cmpw $0x0A0D, %bx /* CR LF */
jnz 1f
//movw 0x1A0, %bx /* CR LF at begin of "NTLDR is missing." */
movb 0x1F9, %bl
movb $1, %bh
movw (%bx), %bx
cmpw $0x0A0D, %bx /* CR LF */
jnz 1f
//movw 0x1B3, %bx /* CR LF at begin of "NTLDR is compressed." */
movb 0x1FA, %bl
movb $1, %bh
movw (%bx), %bx
cmpw $0x0A0D, %bx /* CR LF */
jnz 1f
popw %ax
movw %ax, 4(%si)
movl $0x68909090, %ebx /* nop;nop;nop;push (0D00) */
movl %ebx, 0x71
/* change CRLF in NTFS error messages to spaces */
movw $0x2020, %ax
movb 0x1F8, %bl
movb $1, %bh
movw %ax, (%bx) // 0x183
movb 0x1F9, %bl
movb $1, %bh
movw %ax, (%bx) // 0x1A0
movb 0x1FA, %bl
movb $1, %bh
movw %ax, (%bx) // 0x1B3
/* modify NTFS boot record */
movb $0xEA, %al /* ljmp, hand over the control to supervisor */
movb %al, 0x167
//movw $(try_next_partition - _start1), %ax /* offset for ljmp */
movw $0x7e10, %ax /* offset for ljmp */
movw %ax, 0x168
//movw %cs, %ax /* AX=0x9400, segment for ljmp */
xorw %ax, %ax
movw %ax, 0x16A
cmpw $0x44b, %si
jne 2f
movw $(NTFS5_message - _start1), %si
jmp 3f
2:
movw $(NTFS5p_message - _start1), %si
3:
call print_message /* CS:SI points to message string */
clc
ret
1:
/* NTFS boot record not found. */
movw $(NTFS_no_boot_record_message - _start1), %si
call print_message /* CS:SI points to message string */
popw %ax
popl %eax /* return_IP and SI */
popfw
stc
pushfw
pushl %eax /* return_IP and SI */
ret
#if (! defined(GRLDR_MBR)) && (! defined(GRLDR_INSTALL))
move_helper:
/* called only once and only when the boot loader loaded this code */
pushw %si
pushw %bx
pushl %eax
movw $0x0003, %ax /* set display mode: 80*25 color text */
int $0x10
movw $0x200, %si
movw %si, %di
movw $0xf00, %cx
cld
repz movsw
popl %eax
popw %bx
popw %si
ret
#endif
press_space_bar_string:
.ascii "\r\nPress space bar\0"
press_hot_key_string:
.ascii "\r\nPress your hot-key\0"
press_any_key_string:
.ascii " to start GRUB, any other key to boot previous MBR ...\0"
continue_string:
.ascii "\r\nInvalid previous MBR. Press any key to start GRUB ...\0"
Cannot_find_GRLDR_string:
.ascii "\r\nCannot find GRLDR.\0"
prev_MBR_string:
.ascii " to hold the screen, any other key to boot previous MBR ...\0"
Error_while_reading_string:
.ascii "\r\nError while reading MBR of \0"
drive_number_string:
.ascii "drive (hd0 ) \0"
partition_boot_indicator_string:
.ascii "\r\nInvalid boot indicator in partition table of \0"
partition_sectors_per_track_string:
.ascii "\r\nInvalid sectors_per_track in partition table of \0"
partition_start_sector_string:
.ascii "\r\nInvalid start_sector in partition table of \0"
partition_end_sector_string:
.ascii "\r\nInvalid end_sector in partition table of \0"
no_boot_signature_string:
.ascii "\r\nNo boot signature in partition table of \0"
message_string_helper:
.ascii "\r\nError: Cannot find GRLDR in all devices. Press Ctrl+Alt+Del to restart.\0"
partition_message:
.ascii "\r\nTry (hd0,0 ) : \0"
EXT2_message:
.ascii "EXT2: \0"
NTFS4_message:
.ascii "NTFS4: \0"
NTFS5_message:
.ascii "NTFS5: \0"
NTFS5p_message:
.ascii "NTFS5p: \0"
FAT32_message:
.ascii "FAT32: \0"
FAT16_message:
.ascii "FAT16: \0"
FAT12_message:
.ascii "FAT12: \0"
non_MS_message:
.ascii "non-MS: skip \0"
extended_message:
.ascii "Extended: \0"
invalid_message:
.ascii "invalid or null \0"
NTFS_no_boot_record_message:
.ascii "This partition is NTFS but with unknown boot record. Please\r\ninstall Microsoft NTFS boot sectors to this partition correctly, or create an\r\nFAT12/16/32 partition and place the same copy of GRLDR and MENU.LST there.\0"
#if (! defined(GRLDR_MBR)) && (! defined(GRLDR_INSTALL))
. = _start1 + 0x1ffc
#else
. = . + (0x3fc - ((. - _start1) % 0x200)) % 0x200
#endif
grldr_signature:
.byte 0x47, 0x52, 0x55, 0xaa /* signature for helper */
.align 0x200
#if (! defined(GRLDR_MBR)) && (! defined(GRLDR_INSTALL))
/* pre_stage2 start at 0x2000 for grldr */
. = _start1 + 0x2000
#endif
pre_stage2_start: