bootlace.inc

grub4dos-0.4.4-2008- 08-src.zip

	cmpl	$0xfffffff7, ABS(fstypes)
	movl	$ABS(msg_option_fstypes_for_mbr), %ecx
	jnz	4f	/* error */

	cmpl	$((pre_stage2_start - _start1) / 512), ABS(probed_sectors_per_track)
	movl	$ABS(msg_sectors_per_track), %ecx
	jb	4f	/* error */

	cmpl	$0xffffffff, ABS(install_partition)
	movl	$ABS(msg_option_install_partition_not_implemented), %ecx
	je	1f
	jmp	4f	/* error */
	/* EBX holds the file descriptor number or 0 if it is BIOS drive */
	/* move partition table forward to the beginning of the 17th sector */
	movl	$ABS(mbr_63_sectors + 0x01be), %esi
	movl	$ABS(mbr_63_sectors + 0x2000), %edi
	movl	$0x10, %ecx	# 0x10 dwords = 0x40 bytes

	cld
	repz movsl

	/* initialize the current_partition number */
	movzbl	ABS(install_partition), %eax
	movl	%eax, ABS(current_partition)

3:
	/* load the next partition and modify the boot record */
	call	0f	/* partition */
	jc	3f	/* done */
	call	2f	/* write to file */
	incl	ABS(current_partition)
	movw	ABS(install_partition), %ax
	addb	%ah, %al	/* Max partition number for install */
	cmpb	%al, ABS(current_partition)
	jbe	3b
3:
	/* all partitions have been installed. */
	
	xorl	%eax, %eax	# exit code = 0
	
#ifdef __DOS_16
	
	movb	$0x4c, %ah	// EXIT - TERMINATE WITH RETURN CODE in AL
	int	$0x21		// call DOS

#else
	xchgl	%eax, %ebx	# move exit code in EAX to EBX
	movl	$1, %eax	# sys_exit
	int	$0x80
#endif
		
	ret

1:
//----------------------------------------------------------------------------
	/* backup mbr */

	/* auto backup */
	cmpl	$1, ABS(backup_mbr)
	jnz	1f

	/* check if the second sector consists of 512 dups of one byte */
	movb	ABS(mbr_63_sectors + 0x200), %al
	movl	$ABS(mbr_63_sectors + 0x200), %edi
	movl	$0x200, %ecx

	cld
	repz scasb

	jz	1f			# yes, enable backup

	movl	$0, ABS(backup_mbr)	# no, do not backup

1:

//----------------------------------------------------------------------------
	cmpl	$0, ABS(backup_mbr)
	jz	1f		# will not backup

	movl	$ABS(mbr_63_sectors), %esi
	movl	$ABS(mbr_63_sectors + 0x200), %edi
	movl	$0x80, %ecx	# 0x80 dwords = 0x200 bytes

	cld
	repz movsl

1:

//----------------------------------------------------------------------------
	/* copy byte 0000 to 01b7 of grldr.mbr to ABS(mbr_63_sectors) */

	movl	$ABS(_start1), %esi
	movl	$ABS(mbr_63_sectors), %edi
	movl	$0x6e, %ecx	# 0x6e dwords = 0x1b8 bytes

	cld
	repz movsl

	/* locate the BPB sector */

	movl	ABS(probed_sectors_per_track), %eax
	movl	$63, %esi
	testl	%ebx, %ebx
	jz	1f		# BIOS drive
	movl	%eax, %esi
1:
	shll	$9, %esi
	addl	$ABS(mbr_63_sectors), %esi

	/* ESI points to BPB sector */

	/* check if it has a valid FAT BPB */
	cmpw	$512, 0x0B(iSI)
	jne	1f
	cmpw	%ax, 0x18(iSI)
	jne	1f
	cmpl	%eax, 0x1C(iSI)	#; partition must start at the second track
	jne	1f
	movl	ABS(probed_heads), %eax
	cmpw	%ax, 0x1A(iSI)
	jne	1f
	movb	0x0D(iSI), %cl
	testb	%cl, %cl
	jz	1f
	movw	$128, %ax
	divb	%cl
	testb	%ah, %ah
	jnz	1f
	movw	0x0E(iSI), %cx
	jcxz	1f
	movb	0x10(iSI), %al	# number of FATs
	decw	%ax
	cmpb	$1, %al
	ja	1f

	/* copy the BPB to ABS(mbr_63_sectors) */
	addl	$0x0B, %esi
	movl	$ABS(mbr_63_sectors + 0x0B), %edi
	movl	$(0x5A - 0x0B), %ecx

	cld
	repz movsb

	/* modify reserved sectors */
	movl	$ABS(mbr_63_sectors), %esi
	movl	0x1C(iSI), %eax			#; EAX=sectors per track
	addw	%ax, 0x0E(iSI)

	/* modify total sectors word */
	movw	0x13(iSI), %ax			#; EAX hi word = 0
	testw	%ax, %ax
	jz	3f
	addw	0x1C(iSI), %ax
	movw	%ax, 0x13(iSI)
3:
	/* modify total sectors dword */
	movl	0x20(iSI), %eax
	testl	%eax, %eax
	jz	3f
	addl	0x1C(iSI), %eax
	movl	%eax, 0x20(iSI)
3:
	/* clear the hidden sectors */
	xorl	%eax, %eax
	movl	%eax, 0x1C(iSI)

1:
	/* modify ABS(mbr_floppy) bit */

	movb	ABS(mbr_floppy), %al
	andb	$0x01, %al
	movb	%al, ABS(mbr_63_sectors + 2)

	/* modify ABS(mbr_osbr) bit */

	movb	ABS(mbr_osbr), %al
	andb	$0x01, %al
	shlb	$1, %al
	orb	%al, ABS(mbr_63_sectors + 2)

	/* modify ABS(duce) bit */

	movb	ABS(duce), %al
	andb	$0x01, %al
	shlb	$2, %al
	orb	%al, ABS(mbr_63_sectors + 2)

	/* modify ABS(boot_prevmbr) bit */

	movb	ABS(boot_prevmbr), %al
	notb	%al
	andb	$0x01, %al
	rorb	$1, %al
	orb	%al, ABS(mbr_63_sectors) + 2

	/* modify ABS(time_out) byte */

	movb	ABS(time_out), %al
	movb	%al, ABS(mbr_63_sectors) + 3

	/* modify ABS(hot_key) byte */

	movw	ABS(hot_key), %ax
	movw	%ax, ABS(mbr_63_sectors) + 4

	/* modify ABS(preferred_drive) byte */

	movb	ABS(preferred_drive), %al
	movb	%al, ABS(mbr_63_sectors) + 6

	/* modify ABS(preferred_partition) byte */

	movb	ABS(preferred_partition), %al
	movb	%al, ABS(mbr_63_sectors) + 7

	/* copy byte 0400 and the rest of grldr.mbr to ABS(mbr_63_sectors) */

	movl	$ABS(_start1 + 0x400), %esi
	movl	$ABS(mbr_63_sectors + 0x400), %edi
	movl	$((pre_stage2_start - _start1 - 0x400) / 4), %ecx

	cld
	repz movsl

//----------------------------------------------------------------------------
2:	/* label for the above floppy code to jump */

	/* OK. Now write file! */

	xorl	%eax, %eax
	
	cmpw	$2, ABS(read_only)
	jne	3f

	pushl	%ebx		# file descriptor, or 0 if specified BIOS drive

	/* for safety, don't write too many sectors */
	cmpl	$0xffffffff, ABS(install_partition)
	jne	1f
	cmpl	$0xffffffff, ABS(floppy)
	je	2f
1:
	cmpl	$4, ABS(sectors_to_write)
	jbe	1f
	movl	$4, ABS(sectors_to_write)
	jmp	1f
2:
	cmpl	$((pre_stage2_start - _start1) / 512), ABS(sectors_to_write)
	jbe	1f
	movl	$((pre_stage2_start - _start1) / 512), ABS(sectors_to_write)
1:
#ifdef __DOS_16

	xorl	%eax, %eax
	cmpl	$0xff, ABS(bios_drive_number)
	je	1f
	movb	$0x03, %ah	# write to disk
	movb	ABS(sectors_to_write), %al
//	cmpl	$0xffffffff, ABS(floppy)
//	je	2f
//	movb	$4, %al		# write 4 sectors if it is floppy
//2:
	movw	$ABS(mbr_63_sectors), %bx
	movw	$1, %cx
	movw	ABS(bios_drive_number), %dx
	int	$0x13
	jmp	2f
1:
	//WRITE TO FILE OR DEVICE

	//AH = 40h
	//BX = file handle
	//CX = number of bytes to write
	//DS:DX -> data to write

	//Return:
	//CF clear if successful AX = number of bytes actually written
	//CF set on error AX = error code (05h,06h) 
	movl	$0x4000, %eax
	movl	ABS(sectors_to_write), %ecx
	shll	$9, %ecx
	//movl	$(pre_stage2_start - _start1), %ecx
//	cmpl	$0xffffffff, ABS(floppy)
//	je	1f
//	movl	$0x800, %ecx	# write 4 sectors if it is floppy
//1:
	movl	$ABS(mbr_63_sectors), %edx
	int	$0x21
2:
	jnc	1f
	negl	%eax
1:
#else
	/* ssize_t write(int fd, const void *buf, size_t count) */

	movl	$4, %eax	# sys_write
	movl	$ABS(mbr_63_sectors), %ecx
	movl	ABS(sectors_to_write), %edx
	shll	$9, %edx
	//movl	$(pre_stage2_start - _start1), %edx	# length of grldr.mbr
//	cmpl	$0xffffffff, ABS(floppy)
//	je	1f
//	movl	$0x800, %edx	# write 4 sectors if it is floppy
//1:
	int	$0x80
#endif

	popl	%ebx		# file descriptor, or 0 if specified BIOS drive
3:
	cmpl	$0xffffffff, ABS(install_partition)
	je	3f
	
	/* for install_partition, SF=0 when success, SF=1 when failure */
	testl	%eax, %eax
	ret
3:
	testl	%eax, %eax
	movl	$ABS(msg_write_file), %ecx
	js	4f	/* error */

//----------------------------------------------------------------------------
	cmpl	$0xffffffff, ABS(floppy)
	jne	3f

	movl	$ABS(msg_geometry_S), %ecx
	call	8f	/* linux_print */

	movl	ABS(probed_sectors_per_track), %eax
	call	6f	/* print decimal number */

	movl	$ABS(msg_geometry_H), %ecx
	call	8f	/* linux_print */

	movl	ABS(probed_heads), %eax
	call	6f	/* print decimal number */

	movl	$ABS(msg_success), %ecx
	call	8f	/* linux_print */
3:
//success:

	# EBX=file descriptor, or 0 if specified BIOS drive
	
	xorl	%eax, %eax	# exit code = 0

	jmp	1f
	
//error:
4:
	# EBX=file descriptor, or 0 if specified BIOS drive
	
	testl	%ecx, %ecx
	jz	2f
	call	8f	/* linux_print */
2:
	movl	$ABS(msg_usage), %ecx
	call	8f	/* linux_print */

	movl	$1, %eax	# exit code = 1

1:
	testl	%ebx, %ebx
	jz	1f

	pushl	%eax		# exit code

#ifdef __DOS_16

	movb	$0x3e, %ah	// close file (BX = file handle)
	int	$0x21
	jnc	2f
	negl	%eax		/* EAX < 0 */
2:
#else

	/* int close(int fd); */
	movl	$6, %eax	# sys_close
	int	$0x80
#endif
	movl	$ABS(msg_close_file), %ecx
	testl	%eax, %eax
	
	popl	%eax		# exit code

	jns	1f

	call	8f	/* linux_print */

//exit:
1:
#ifdef __DOS_16
	
	movb	$0x4c, %ah	// EXIT - TERMINATE WITH RETURN CODE in AL
	int	$0x21		// call DOS

#else
	xchgl	%eax, %ebx	# move exit code in EAX to EBX
	movl	$1, %eax	# sys_exit
	int	$0x80
#endif
		
	ret

//----------------------------------------------------------------------------
//floppy:
5:

	pushal

	/* Beforehand, try MBR */

	/* ESI=$ABS(mbr_63_sectors) */

	cld
	cmpw	$0xAA55, 0x1fe(iSI)
	jne	1f

	pushl	%esi
	pushl	%edi
	pushl	%ebx

	/* has a valid partition table ? */
	movb	$0, %bl		/* count valid partition entries */
	addl	$0x1be, %esi
3:
	cmpl	$(ABS(mbr_63_sectors) + 0x1fe), %esi
	jnb	3f		/* partition table is OK */
	movl	$4, %ecx

	movl	%esi, %edi
2:
	lodsl
	negl	%eax
	jc	2f
	loop	2b
	/* empty entry, check next */
	jmp	3b
2:
	/* non-empty entry */
	movl	%edi, %esi

	lodsw
	shlb	$1, %al		/* boot indicator */
	jnz	2f
	lodsw
	andb	$63, %al
	jz	2f
	lodsw
	lodsw
	andb	$63, %al
	jz	2f
	lodsl
	negl	%eax
	jnc	2f
	lodsl
	negl	%eax
	jnc	2f
	incb	%bl
	jmp	3b
2:
	stc		/* invalid partition table */
3:
	popl	%eax
	popl	%edi
	popl	%esi

	xchgl	%eax, %ebx

	jc	1f
	testb	%al, %al
	jz	1f

	/* MBR write not allowed */
	
	movl	$0, ABS(sectors_to_write)
	
	movl	$ABS(msg_fstype_mbr_deny), %ecx
	call	8f	/* linux_print */
	
	stc
	popal
	ret
1:
	/* First, try ext2 */

	cmpw	$0xEF53, 0x438(iSI)	/* Magic signature */
	jnz	1f
	xorl	%eax, %eax
	cmpl	%eax, 0x400(iSI)	/* s_inodes_count */
	jz	1f
	cmpl	%eax, 0x404(iSI)	/* s_blocks_count */
	jz	1f
//	cmpw	%ax, 0x458(iSI)		/* s_inode_size, usually 0x80 */
//	jz	1f
	cmpl	%eax, 0x420(iSI)	/* s_blocks_per_group */
	jz	1f
	cmpl	%eax, 0x428(iSI)	/* s_inodes_per_group */
	jz	1f
	movl	0x414(iSI), %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(iSI), %ecx	/* s_log_block_size */
	cmpl	$4, %ecx		/* max size of block is 16K */
	ja	1f
	negw	%cx			/* CF=0 for 1K block, CF=1 otherwise */
	adcw	%ax, %bx		/* EAX=0 */
	decw	%bx
	jnz	1f

	/* BX = 0 */

	movl	$ABS(_start1 + 0x826), %edi /* inode size in the 5th sector */
	movw	$0x80, %ax		/* EXT2_GOOD_OLD_INODE_SIZE */
	movw	%ax, (iDI)		/* inode size */
	movl	0x44C(iSI), %ecx	/* ECX=s_rev_level */
	jecxz	3f			/* EXT2_GOOD_OLD_REV */
	movw	0x458(iSI), %ax		/* AX=s_inode_size */
	testw	%ax, %ax
	jz	1f			/* invalid inode size */
	pushw	%ax
	pushw	%dx
	movb	0x418(iSI), %cl		/* s_log_block_size */
	addb	$10, %cl
	xorw	%dx, %dx		/* DX=0 */
	incw	%dx			/* DX=1 */
	shlw	%cl, %dx		/* DX=block size in bytes */
	xchgw	%ax, %cx		/* CX=s_inode_size */
	xchgw	%ax, %dx		/* AX=block size in bytes */
	xorw	%dx, %dx		/* DX:AX=block size in bytes */
	divw	%cx			/* quo=AX, rem=DX */
	testw	%dx, %dx
	popw	%dx
	popw	%ax
	jnz	1f			/* invalid inode size */
	movw	%ax, (iDI)		/* inode size */
3:
	/* BX = 0 */

	/* super block is sane */

	/* is EXT2 allowed write? */

	testl	$0x10, ABS(fstypes)
	jnz	2f
	/* EXT2 write not allowed */
	
	movl	$0, ABS(sectors_to_write)
	
	movl	$ABS(msg_fstype_ext2_deny), %ecx
	call	8f	/* linux_print */
	
	stc
	popal
	ret
2:
	/* write to ext2 boot area */

	cld
	movl	$ABS(_start1 + 0x800), %esi	/* points to the 5th sector */
	movl	$ABS(mbr_63_sectors), %edi
	lodsw				/* The first 2 byte: short jmp */
	LEAL	0x400(%edi), %esi	/* ESI points to super block */
	stosw

	/* lba indicator byte is not used. so we shouldn't touch it. */

	/* check lba-chs-mode specified, 1 byte */
	cmpl	$-1, ABS(lba)		/* lba-chs-mode  not specified? */
	je	2f			/* yes, do nothing. */

#if 0
	movb	$0x42, %al		/* initialize to lba mode. */
	cmpl	$0, ABS(lba)		/* chs ? */
	jnz	10f			/* no, it is not chs.*/
	movb	$0x02, %al		/* yes, it is chs. */
10:
#else
	/* if specified lba or chs, we simply place a 0x90. */
	movb	$0x90, %al
#endif
	stosb
	decl	%edi
2:

	addl	$(1+10), %edi		/* skip 10-byte OEM name */
	
	/* Sectors per block, byte */
	
	movb	0x18(iSI), %cl		/* s_log_block_size */
	movl	$2, %eax
	shlw	%cl, %ax
	stosb
	
	/* Bytes per block, word */
	
	shlw	$9, %ax			/* block size is word wide */
	stosw

	/* Pointers covered by an indirect block, dword */
	/* Pointers per block, dword */
	
	shrw	$2, %ax
	pushl	%eax		/* Pointers per block */
	addb	$8, %cl
	shll	%cl, %eax
	stosl			/* Pointers covered by an indirect block */
	popl	%eax
	stosl			/* Pointers per block */
	
	/* Sectors per track, word */

	cmpl	$0xFFFFFF3F, ABS(sectors_per_track)
	je	10f
	movb	ABS(sectors_per_track), %al
	cbw
	stosw
	subl	$2, %edi
10:
	addl	$2, %edi

	/* Number of heads, word */
	
	cmpl	$0xFFFF00FF, ABS(heads)
	je	10f
	movw	ABS(heads), %ax
	stosw
	subl	$2, %edi
10:
	addl	$2, %edi
	
	/* hidden sectors(i.e., partition start), dword */
	
	movb	ABS(floppy), %al	/* partition number(0xFF for floppy) */
	cmpb	$0xff, %al
	jne	10f
	/* real floppy */
	cmpl	$0xffffffff, ABS(start_sector)
	sete	%al
	movzbl	%al, %eax
	addl	ABS(start_sector), %eax
	stosl
	jmp	11f
10:
	/* hard drive partition */
	addl	$4, %edi
	cmpl	$0xffffffff, ABS(start_sector)
	je	11f
	movl	ABS(start_sector), %eax
	subl	$4, %edi
	stosl
11:
	
	/* total sectors, dword */

	movl	%es:(iDI), %eax
	cmpl	%eax, ABS(total_sectors)
	jbe	10f
	movl	ABS(total_sectors), %eax
10:
	stosl
	
	/* drive number, byte */

	//this byte is not used.
	incl	%edi

	/* partition number, byte */

	movb	ABS(floppy), %al
	stosb
	
	/* reserved, word */

	incl	%edi
	incl	%edi

	/* Number of inodes per group, dword */

	movl	0x28(iSI), %eax		/* s_inodes_per_group */
	stosl
	
	/* block number for group descriptors, dword */