bootlace.inc

grub4dos-0.4.4-2008- 08-src.zip

	movl	ABS(total_sectors), %eax
	subl	$4, %edi
	stosl
2:
	
	/* drive number, byte, etc... */

	addl	$(1+1+1+4+11+8), %esi
	addl	$(1+1+1+4+11+8), %edi

	//movl	$0xFFB6FCFA, %eax	/* CLI, CLD, MOV DH,FF */
	lodsw
	stosw
	lodsb
	stosb
	lodsb
	
	//decl	%edi

	/* partition number, byte */

	movb	ABS(floppy), %al
	stosb
	
	/* Machine code begins at offset 0x42, 444 bytes without 
	 * the ending 2 bytes of boot signature */

	//movl	$ABS(_start1 + 0x642), %esi
	movl	$(444 / 4), %ecx
	repz movsl
	
	movl	$1, ABS(sectors_to_write)
	
	movl	$ABS(msg_fstype_fat16_allow), %ecx
	call	8f	/* linux_print */
	
	clc
	popal
	ret
1:

	movl	$0, ABS(sectors_to_write)
	
	movl	$ABS(msg_unsupported_fstype), %ecx
	call	8f	/* linux_print */
	
	stc
	popal
	ret

//----------------------------------------------------------------------------
//print decimal number in EAX
6:
	/* print EAX value in decimal format */
	pushal

#if 0
	cld
	movl	$ABS(number_digits), %edi
	xchgl	%eax, %edx	// save EAX to EDX
	movw	$0x2020, %ax	// two spaces
	stosw
	stosw
	stosw
	stosw
	stosw
	decl	%edi		// EDI points to the last digit
	xchgl	%eax, %edx	// restore EAX from EDX
#endif
	std
	movl	$ABS(number_digits + 9), %edi
	movl	$10, %ebp
1:
	xorl	%edx, %edx
	divl	%ebp		// quo=EAX, rem=EDX
	xchgl	%eax, %edx
	orb	$0x30, %al
	stosb
	xchgl	%eax, %edx
	testl	%eax, %eax
	jnz	1b

	/* all digits are stored */
	incl	%edi		// points to the digit string

	movl	%edi, %ecx
	call	8f	/* linux_print */

	cld
	popal
	ret

//----------------------------------------------------------------------------
//parse_number:
7:

	/* input:	EDI	points to the number
	 *		EBX	upper limit of the number
	 * output:	EBX	the value of the number
	 *		EDX	changed
	 *		ESI	changed
	 *		EBP	changed
	 *		CF=1	failure
	 *		CF=0	success
	 */

	pushl	%eax
	pushl	%ebx		/* upper limit */
	cld
	movl	%edi, %esi
	movl	$0xffffffff, %edx
	xorl	%ebx, %ebx
	lodsw
	cmpw	$0x5830, %ax	/* 0X */
	je	1f
	cmpw	$0x7830, %ax	/* 0x */
	je	1f

	/* decimal */
	decl	%esi
	decl	%esi
	movl	$10, %ebp
2:
	xorl	%eax, %eax
	lodsb
	cmpb	$0, %al
	je	4f		/* CF=0 */
	cmpb	$0x30, %al
	jb	3f
	cmpb	$0x39, %al
	ja	3f
	subb	$0x30, %al
	pushl	%eax
	movl	%ebx, %eax
	mull	%ebp
	movl	%eax, %ebx
	popl	%eax
	jc	3f
	addl	%eax, %ebx
	jc	3f
	popl	%eax
	pushl	%eax		/* upper limit */
	cmpl	%eax, %ebx
	ja	3f
	jmp	2b
1:

	/* hex */
	movl	$16, %ebp
2:
	xorl	%eax, %eax
	lodsb
	cmpb	$0, %al
	je	4f		/* CF=0 */
	cmpb	$0x30, %al
	jb	3f
	cmpb	$0x39, %al
	jbe	1f
	orb	$0x20, %al
	cmpb	$0x61, %al
	jb	3f
	cmpb	$0x66, %al
	ja	3f
	subb	$0x27, %al
1:
	subb	$0x30, %al
	pushl	%eax
	movl	%ebx, %eax
	mull	%ebp
	movl	%eax, %ebx
	popl	%eax
	jc	3f
	addl	%eax, %ebx
	jc	3f
	popl	%eax
	pushl	%eax		/* upper limit */
	cmpl	%eax, %ebx
	ja	3f
	jmp	2b

3:
	stc
	popl	%eax		/* upper limit */
	popl	%eax
	ret
4:
	testl	%edx, %edx	/* CF=0 */
	jnz	3b
	popl	%eax		/* upper limit */
	popl	%eax
	ret

//----------------------------------------------------------------------------
//linux_print:
8:

	/* print a message.
	 * input:	ECX	points to message string
	 * output:	message is displayed on the stdout device
	 */

	/* ssize_t write(int fd, const void *buf, size_t count) */

	pushal

#ifdef __DOS_16

	cld
	movl	%ecx, %esi
//	movw	%si, %dx
//	movb	$0x09, %ah		// WRITE STRING TO STANDARD OUTPUT
//	int	$0x21			// call DOS
//	ret

1:      
	lodsb	(%si), %al		// get token
	cmpb	$0, %al			// end of string?
	je	1f
#if 0
	/* use BIOS independent of DOS */
	xorw	%bx, %bx		// video page 0
	movb	$0x0e, %ah		// print it
	int	$0x10			// via TTY mode
#else
	/* use stdout for redirection of the output */
	movb	%al, %dl		// character to write
	movb	$0x02, %ah		// WRITE CHARACTER TO STANDARD OUTPUT
	int	$0x21			// call DOS
#endif
	jmp	1b			// until done
1:

#else
	pushl	%ecx
	movl	%ecx, %edi	# scan the message string ...
	movl	$(msg_end - msg_start), %ecx
	movb	$0, %al		# ... find the ending zero byte

	cld
	repnz scasb

	movl	%edi, %edx
	popl	%ecx		# ECX points to the message
	subl	%ecx, %edx	# EDX=message length
	decl	%edx		# discard the ending zero byte

	movl	$4, %eax        # sys_write
	movl	$1, %ebx        # file descriptor = stdout
	int	$0x80
#endif

	popal
	ret

//----------------------------------------------------------------------------
//probe_geometry:
9:
	pushal

	addl	$0x200, %esi
	
	movw	$0, ABS(Cmax)
	movl	$0, ABS(Hmax)
	movw	$0, ABS(Smax)

	movl	$0, ABS(i)			# partition number
1:
	cmpl	$4, ABS(i)
	jae	1f

	/* the boot indicator must be 0x80(bootable) or 0(non-bootable) */

	movl	ABS(i), %ebx
	movl	ABS(i), %edi
	shll	$4, %ebx		# EBX = i * 16
	movb	-66(iBX, iSI), %al	# boot_indicator
	shlb	$1, %al
	jnz	6f	/* geometry_probe_failed */

	/* check if the entry is empty, i.e., all the 16 bytes are 0 */

	movl	-66(iBX, iSI), %eax
	orl	-62(iBX, iSI), %eax
	orl	-58(iBX, iSI), %eax
	orl	-54(iBX, iSI), %eax
	jz	2f			# empty partition entry

	/* valid partitions never start at 0, because this is where the MBR
	 * lives; and more, the number of total sectors should be non-zero.
	 */

	cmpl	$0, -58(iBX, iSI)	# start_lba
	jz	6f	/* geometry_probe_failed */

	cmpl	$0, -54(iBX, iSI)	# total_sectors
	jz	6f	/* geometry_probe_failed */

	/* the partitions should not overlap each other */

	movl	$-1, ABS(j)		// j = -1
3:
	// for (j = 0; j < i; j++)
	incl	ABS(j)			// j++
	cmpl	%edi, ABS(j)		# i = EDI
	jae	3f			// j >= i, break.

	movl	-58(iBX, iSI), %ecx	# ECX=P[i].start_lba

	movl	ABS(j), %edx
	shll	$4, %edx		# EDX = j * 16
	MOVL	-58(%edx, %esi), %eax	# EAX=P[j].start_lba

	// if ((P[j].start_lba <= P[i].start_lba) && (P[j].start_lba + P[j].total_sectors >= P[i].start_lba + P[i].total_sectors))

	cmpl	%ecx, %eax
	ja	4f

	pushl	%ecx
	pushl	%eax

	addl	-54(iBX, iSI), %ecx	// ECX = P[i].start_lba + P[i].total_sectors
	ADDL	-54(%edx, %esi), %eax	// EAX = P[j].start_lba + P[j].total_sectors

	cmpl	%ecx, %eax

	popl	%eax
	popl	%ecx

	jb	4f

	jmp	3b			//continue
4:
	// if ((P[j].start_lba >= P[i].start_lba) && (P[j].start_lba + P[j].total_sectors <= P[i].start_lba + P[i].total_sectors))
	
	cmpl	%ecx, %eax
	jb	4f

	pushl	%ecx
	pushl	%eax

	addl	-54(iBX, iSI), %ecx	// ECX = P[i].start_lba + P[i].total_sectors
	ADDL	-54(%edx, %esi), %eax	// EAX = P[j].start_lba + P[j].total_sectors

	cmpl	%ecx, %eax

	popl	%eax
	popl	%ecx

	ja	4f

	jmp	3b			//continue
4:

	cmpl	%ecx, %eax
	jae	4f

	// P[j].start_lba < P[i].start_lba
	subl	%eax, %ecx		// ECX = P[i].start_lba - P[j].start_lba
	CMPL	-54(%edx, %esi), %ecx	# ECX < P[j].total_sectors
	jmp	5f
4:
	// P[j].start_lba >= P[i].start_lba
	subl	%ecx, %eax		// EAX = P[j].start_lba - P[i].start_lba
	cmpl	-54(iBX, iSI), %eax	# EAX < P[i].total_sectors
5:
	jb	6f	/* geometry_probe_failed */

	jmp	3b			//continue
3:

	/* the start cylinder number */

	movzwl	-64(iBX, iSI), %eax	# start_sector_cylinder

	movl	%eax, %edx
	andw	$0x003f, %dx
	jz	6f	/* geometry_probe_failed */

	movw	%dx, ABS(X)			# the sector number

	cmpw	%dx, ABS(Smax)
	jae	3f
	movw	%dx, ABS(Smax)
3:
	movl	-58(iBX, iSI), %ecx	# start_lba
	incl	%ecx
	subl	%edx, %ecx

	movl	$ABS(L), %edx
	MOVL	%ecx, (%edx, %edi, 8)	# L[i]

	///* partitions should not start at the first track, the MBR-track */
	//movw	ABS(Smax), %dx
	//cmpw	%dx, -58(%ebx, %esi)	# start_lba
	//jb	6f	/* geometry_probe_failed */

	shrb	$6, %al
	xchgb	%al, %ah

	movl	$ABS(C), %edx
	MOVW	%ax, (%edx, %edi, 4)	# C[i]

	cmpw	%ax, ABS(Cmax)
	jae	3f
	movw	%ax, ABS(Cmax)
3:

	//movl	ABS(i), %ebx
	//shll	$4, %ebx		# EBX = ABS(i) * 16
	movzbl	-65(iBX, iSI), %eax	# start_head
	movl	$ABS(H), %edx
	MOVL	%eax, (%edx, %edi, 4)	# H[i]

	cmpl	%eax, ABS(Hmax)
	jae	3f
	movl	%eax, ABS(Hmax)
3:

	/* the end cylinder number */

	movzwl	-60(iBX, iSI), %eax	# end_sector_cylinder

	movl	%eax, %edx
	andw	$0x003f, %dx
	jz	6f	/* geometry_probe_failed */

	movw	%dx, ABS(Y)			# the sector number

	cmpw	%dx, ABS(Smax)
	jae	3f
	movw	%dx, ABS(Smax)
3:
	movl	-58(iBX, iSI), %ecx	# start_lba
	addl	-54(iBX, iSI), %ecx	# total_sectors
					# XXX: possible overflow!

	subl	%edx, %ecx
	jb	6f	/* geometry_probe_failed */

	addl	$4, %edi		# EDI=i+4

	movl	$ABS(L), %edx
	MOVL	%ecx, (%edx, %edi, 8)	# L[i+4]

	movl	%ecx, %ebp		# save ECX to EBP

	/* partitions should not start at the first track, the MBR-track */
	movw	ABS(Smax), %dx
	cmpw	%dx, -58(iBX, iSI)	# start_lba
	jb	6f	/* geometry_probe_failed */

	shrb	$6, %al
	xchgb	%al, %ah

	movl	$ABS(C), %edx
	MOVW	%ax, (%edx, %edi, 4)	# C[i+4]

	cmpw	%ax, ABS(Cmax)
	jae	3f
	movw	%ax, ABS(Cmax)
3:
	xchgl	%eax, %ecx		# save AX to CX

	//movl	ABS(i), %ebx
	//shll	$4, %ebx		# EBX = ABS(i) * 16
	movzbl	-61(iBX, iSI), %eax	# end_head
	movl	$ABS(H), %edx
	MOVL	%eax, (%edx, %edi, 4)	# H[i+4]

	cmpl	%eax, ABS(Hmax)
	jae	3f
	movl	%eax, ABS(Hmax)
3:

	/* Check the large disk partition -- Win98 */
	cmpw	$63, ABS(Y)
	jne	3f
	cmpl	%eax, ABS(Hmax)		# EAX=H[i+4]
	jne	3f
	cmpw	%cx, ABS(Cmax)		# ECX=C[i+4]
	jne	3f

	cmpl	$254, %eax		# EAX=ABS(Hmax)
	jnb	4f
	cmpw	$1022, %cx		# CX=ABS(Cmax)
	jb	3f
4:
	movl	$63, %edx		# EDX=ABS(Y)
	addl	%edx, %ebp
	incl	%eax
	mull	%edx			# EDX:EAX=product
					# EDX=0
					# EAX high word = 0
					# AX=(Hmax+1)*63
	pushl	%eax			# EAX=(Hmax+1)*63
	incl	%ecx
	mull	%ecx			# EDX:EAX=product
					# EDX=0
	cmpl	%ebp, %eax
	popl	%eax			# EAX=(Hmax+1)*63
	jnb	3f

	/* EDI=i+4 at this moment */

	pushl	%eax			# EAX=(Hmax+1)*63
	subl	$4, %edi		# EDI=i
	
	movl	$ABS(C), %ebx
	MOVZWL	(%ebx, %edi, 4), %eax	# C[i]
	
	movl	ABS(Hmax), %ebp		# Hmax
	incl	%ebp

	pushl	%eax			# EAX=C[i]

	movl	$ABS(H), %ebx
	MOVL	(%ebx, %edi, 4), %ecx	# H[i]

	mull	%ebp			# EDX=0, EAX=product
	addl	%ecx, %eax
	movl	$63, %edx
	mull	%edx			# EDX=0, EAX=product
	
	movl	$ABS(L), %ebx
	MOVL	(%ebx, %edi, 8), %ebp	# L[i]

	cmpl	%ebp, %eax
	popl	%eax			# EAX=C[i]

	jae	4f
	
	/* calculate CHS numbers from start LBA */

	//pushl	%eax			# EAX=C[i]

	xorl	%edx, %edx
	xchgl	%eax, %ebp		# EBP=C[i], EDX:EAX=L[i]
	
	divl	ABS(Y)			# Y=63
					# quo=EAX, rem=EDX
	incl	%edx			# sector number
	cmpw	%dx, ABS(X)
	je	15f
	cmpw	$63, ABS(X)
	jne	4f
15:
	xorl	%edx, %edx
	movl	ABS(Hmax), %ebx
	incl	%ebx			# EBX=Hmax+1
	divl	%ebx			# quo=EAX=cylinder number
					# rem=EDX=head number
	cmpl	%edx, %ecx		# ECX=H[i]
	je	15f
	decl	%ebx			# EBX=Hmax
	cmpl	%ebx, %ecx
	jne	4f
15:
	/* EAX=calculated cylinder number, EBP=C[i] */

	cmpl	ABS(Cmax), %ebp
	je	4f
	andw	$0x3ff, %ax		# low 10 bit of calculated cylinder
	cmpw	%ax, %bp
//5:
//	cmpw	ABS(Cmax), %ax
//	jne	4f
//	cmpl	ABS(Hmax), %ecx
//	jne	4f
//	cmpw	$63, ABS(X)
4:
	popl	%eax
	jne	6f	/* geometry_probe_failed */
	jmp	5f
3:

	/* Check the large disk partition -- Win2K */

	/* EDI=i+4 at this moment */
	cmpw	$63, ABS(Y)
	jne	3f
	movl	$ABS(H), %edx
	MOVL	(%edx, %edi, 4), %eax	# H[i+4]
	cmpl	%eax, ABS(Hmax)		# EAX=H[i+4]
	jne	3f
	
	movl	$ABS(L), %edx
	MOVL	(%edx, %edi, 8), %ebp	# L[i+4]
	
	movl	$ABS(C), %edx
	MOVZWL	(%edx, %edi, 4), %ecx	# C[i+4]

	incl	%ecx
	incl	%eax
	
	mull	%ecx			# EDX=0, EAX=product
	mull	ABS(Y)			# Y=63, EDX=0, EAX=product
	addl	ABS(Y), %ebp
	cmpl	%ebp, %eax
	jnb	3f

	movl	ABS(Hmax), %eax
	incl	%eax
	mull	ABS(Y)			# Y=63, EDX=0, EAX=product
	
	xorl	%edx, %edx
	xchgl	%eax, %ebp		# EBP=(Hmax+1)*63
					# EAX=L[i+4]+Y

	divl	%ebp			# EAX=quo, EDX=rem
	testl	%edx, %edx
	jnz	3f
	decl	%eax
	andl	$0x3ff, %eax
	decl	%ecx
	cmpl	%eax, %ecx
	jne	3f
	
	/* EDI=i+4 at this moment */

	subl	$4, %edi		# EDI=i

	movl	$ABS(C), %ebx
	MOVL	(%ebx, %edi, 4), %eax	# C[i]

	pushl	%eax
	
	mull	%ebp			# EBP=(Hmax+1)*63
					# EDX=0, EAX=product
	
	pushl	%ebp			# EBP=(Hmax+1)*63
	
	xchgl	%eax, %ebp		# EBP=product
	movl	$ABS(H), %ebx
	MOVL	(%ebx, %edi, 4), %eax	# H[i]
	mull	ABS(Y)			# Y=63, EDX=0, EAX=H[i]*63

	pushl	%eax

	addl	%eax, %ebp
	
	movl	$ABS(L), %ebx
	MOVL	(%ebx, %edi, 8), %eax	# L[i]
	cmpl	%eax, %ebp

	popl	%ebx			# EBX=H[i]*63
	popl	%ebp			# EBP=(Hmax+1)*63
	popl	%ecx			# ECX=C[i]
	xchgl	%eax, %ebp

	ja	6f	/* geometry_probe_failed */
	je	5f
	xchgl	%eax, %ebp
	subl	%ebx, %eax
	xorl	%edx, %edx
	divl	%ebp			# EAX=quo, EDX=rem
	testl	%edx, %edx
	jnz	6f	/* geometry_probe_failed */
	andl	$0x3ff, %eax
	cmpl	%eax, %ecx
	jne	6f	/* geometry_probe_failed */
	
	xchgl	%eax, %ebp
	jmp	5f
3:
	/* Maximum of C[n] * (H * S) + H[n] * S = 1023 * 255 * 63 + 254 * 63 = 0xFB03C1 */

	/* EDI=i+4 at this moment */
	movl	$ABS(L), %edx
	MOVL	(%edx, %edi, 8), %ebp	# L[i+4]
	cmpl	$0xFB03C1, %ebp
	jbe	3f

	/* set H/S to max */
	cmpl	$254, ABS(Hmax)
	jae	4f
	movl	$254, ABS(Hmax)
4:
	movw	$63, ABS(Smax)
	xorl	%edx, %edx
	movl	%ebp, %eax
	divl	ABS(Smax)
	testl	%edx, %edx
	jnz	6f	/* geometry_prob