grub-0.95-patch4-emulation

Grub for dos 0.2.0,system loader

+	jmp	int13_return
+1:
+	cmpb	$0x04, %ah	/* verify sectors, always succeed */
+	jnz	1f
+	xorb	%ah, %ah
+	clc
+	jmp	int13_return
+1:
+	cmpb	$0x09, %ah /* INITIALIZE CONTROLLER WITH DRIVE PARAMETERS */
+	jnz	1f
+	xorb	%ah, %ah
+	clc
+	jmp	int13_return
+1:
+	cmpb	$0x0c, %ah	/* SEEK TO CYLINDER */
+	jnz	1f
+	xorb	%ah, %ah
+	clc
+	jmp	int13_return
+1:
+	cmpb	$0x0d, %ah	/* reset hard disks */
+	jnz	1f
+	xorb	%ah, %ah
+	clc
+	jmp	int13_return
+1:
+	cmpb	$0x10, %ah	/* check if drive ready */
+	jnz	1f
+	xorb	%ah, %ah
+	clc
+	jmp	int13_return
+1:
+	cmpb	$0x11, %ah	/* recalibrate drive */
+	jnz	1f
+	xorb	%ah, %ah
+	clc
+	jmp	int13_return
+1:
+	cmpb	$0x14, %ah	/* CONTROLLER INTERNAL DIAGNOSTIC */
+	jnz	1f
+	xorb	%ah, %ah
+	clc
+	jmp	int13_return
+1:
+	cmpb	$0x05, %ah	/* format track */
+	jnz	1f
+	xorb	%ah, %ah	/* do nothing but return success */
+	clc
+	jmp	int13_return
+1:
+	cmpb	$0x08, %ah	/* get drive parameters */
+	jnz	1f
+	testb	%dl, %dl	/* hard drive? */
+	js	2f		/* yes, jump */
+	movw	$0x10, %bx	/* for floppy, refer to function 0x48 */
+	xorw	%ax, %ax
+	movw	%ax, %es
+	movw	$0x0078, %di
+#if 1
+	lesw	%es:(%di), %di	/* point to int1E floppy parameters */
+#else
+	movl	%es:(%di), %eax
+	movw	%ax, %di
+	shrl	$0x10, %eax
+	movw	%ax, %es
+#endif
+2:
+	movw	-4(%bp), %ax	/* AL=Hmax, AH=Smax */
+	movb	%al, %dh	/* max head number */
+	andb	$63, %ah
+	movb	%ah, %cl	/* max sector number */
+
+	/* simply use 1024 cylinders and 8 drives, hope this would work well */
+	orw	$0xffc0, %cx	/* max cylinder number=1023 */
+	movb	$0x08, %dl	/* drives=8(HDs=8 as well as FDs=8) */
+	xorw	%ax, %ax
+	clc
+	jmp	int13_return
+1:
+	cmpb	$0x15, %ah	/* get disk type */
+	jnz	1f
+	testb	%dl, %dl	/* hard drive? */
+	js	2f		/* yes, jump */
+	movb	$0x02, %ah	/* floppy (or other removable drive) with change-line support */
+	clc
+	jmp	int13_return
+2:
+	movb	$0x03, %ah	/* hard disk */
+
+	/* CX:DX=total number of sectors */
+	movw	-14(%bp), %dx	/* lo word of S_count */
+	movw	-16(%bp), %cx	/* hi word of S_count */
+	andb	$0xfe, %dl
+	clc
+	jmp	int13_return
+1:
+	cmpb	$0x16, %ah
+	jnz	1f
+	xorb	%ah, %ah	/* AH=0 means disk not changed */
+	/* clc */		/* signal success, CF already cleared by XOR */
+	jmp	int13_return
+1:
+	cmpb	$0x17, %ah	/* set floppy type for format */
+	jnz	1f
+	movb	$0x03, %al	/* 1.44M drive, 1.44M floppy */
+	xorb	%ah, %ah
+	/* clc */		/* signal success, CF already cleared by XOR */
+	jmp	int13_return
+1:
+	cmpb	$0x18, %ah	/* set media type for format */
+	jnz	1f
+	testb	%dl, %dl	/* hard drive? */
+	js	2f		/* yes, jump */
 	pushw	%ax
-	/* set the flags in the stack to the value returned by int13 */
-	movw	(%bp), %ax
-	movw	%ax, 0xc(%bp)
-	/* check if should map the drive number */
-	movw	6(%bp), %ax
-	cmpw	$0x8, %ax
-	jne	3f
-	cmpw	$0x15, %ax
-	jne	3f
-	/* check if the mapping was performed */
-	movw	2(%bp), %ax
-	testw	%ax, %ax
-	jz	3f
-	/* perform the mapping */
-	movb	%al, %dl
+	xorw	%ax, %ax
+	movw	%ax, %es
+	movw	$0x0078, %di
+	movl	%es:(%di), %eax
+	movw	%ax, %di
+	shrl	$0x10, %eax
+	movw	%ax, %es
+	popw	%ax
+	xorb	%ah, %ah
+	/* clc */		/* signal success, CF already cleared by XOR */
+	jmp	int13_return
+2:
+	movb	$1, %ah		/* temp disabled for hard disks */
+	stc
+	jmp	int13_return
+1:
+	/* Now AH is neither 0 nor 1 */
+	testb	$0xfc, %ah	/* CHS read/write sectors */
+	jnz	1f
+	/* so AH is either 2(for read) or 3(for write) */
+#if 1
+	cmpw	$0x0301, %ax	/* is it write 1 sector? */
+	jne	2f
+	cmpw	$0x0001, %cx	/* write to cylinder 0, sector 1? */
+	jne	2f
+	cmpb	$0x01, %dh	/* write to head 0 or 1? */
+	ja	2f
+	/* cmpw	$0xaa55, %es:0x1fe(%bx)
+	je	2f */
+	testb	%dl, %dl
+	js	3f		/* protect hard disk head 0 and 1 */
+	testb	%dh, %dh	/* write to floppy head 0? */
+	jne	2f		/* no, write permitted */
+3:
+	movb	-14(%bp), %ah	/* lowest byte of S_count */
+	testb	$1, %ah		/* fake write here means safeboot */
+	jz	2f		/* unsafe boot allows the write */
+
+	/* disable the write */
+	addw	$12, %sp	/* adjust SP */
+	popw	%si
+	popw	%bp
+	popl	%eax
+	xorb	%ah, %ah	/* signal write succeeded, this is a fake */
+	/* clc */		/* signal success, CF already cleared by XOR */
+	lret	$2		/* far return discard the original flags */
+	
+#else
+	/* debug only. locate windows 98 unidentified write to floppy */
+	pushaw
+	movw	8(%bp), %ax
+	movw	%ax, %ds
+	movw	6(%bp), %si
+	subw	$0x0400, %si
+	movw	%bx, %di
+	movw	$0x0400, %cx
+	cld
+	rep
+	movsw
+	movw	%si, %ax
+	movw	%di, %bx
+	subw	$4, %di
+	stosw
+	movw	%bx, %ax
+	stosw
+	popaw
+	movb	$4, %al
+/*3:*/
+	/*hlt*/			/* invalid write to floppy, halt the machine */
+	/*jmp	3b*/
+#endif
+2:
+	cmpb	$0x7F, %al	/* check if sectors exceed 127 */
+	ja	error_01_invalid
+	testb	%al, %al	/* read 0 sectors not allowed */
+	jz	error_01_invalid
+	testb	$63, %cl	/* beginning sector number 0 is invalid */
+	jz	error_01_invalid
+	movb	-3(%bp), %ah	/* AH=Smax */
+	andb	$63, %ah
+	pushw	%cx
+	andb	$63, %cl
+	cmpb	%ah, %cl	/* CL should not > max sector number */
+	popw	%cx
+	ja	error_01_invalid
+	movb	-4(%bp), %ah
+	cmpb	%ah, %dh	/* DH should not > max head number */
+	ja	error_01_invalid
+	pushw	%ds
+	pushw	%cs
+	popw	%ds
+	movw	$(EBIOS_disk_address_packet - int13_handler), %si
+	movb	%al, 2(%si)	/* sectors */
+	movw	%bx, 4(%si)
+	movw	%es, 6(%si)
+	xorl	%eax, %eax
+	movb	%ah, 3(%si)	/* sectors_hi_reserved */
+	movl	%eax, 12(%si)
+	movb	%ch, %al	/* cylinder number */
+	movb	%cl, %ah	/* CL holds higher 2 bits */
+	shrb	$6, %ah		/* AH lower holds the 2 bits */
+				/* Now AX holds the 10 bit cylinder number */
+	pushl	%ebx
+	xorl	%ebx, %ebx
+	movb	-4(%bp), %bl	/* max head number */
+	/* xorb	%bh, %bh */
+	incw	%bx		/* BX=total heads, <=256 */
+	pushl	%edx
+	mull	%ebx		/* EDX:EAX=result, so EDX=0 */
+	popl	%edx
+	xorl	%ebx, %ebx
+	movb	%dh, %bl	/* head number */
+	addl	%ebx, %eax
+	movb	-3(%bp), %bl	/* Max sector number */
+	andb	$63, %bl
+	pushl	%edx
+	mull	%ebx		/* EDX:EAX=result, so EDX=0 */
+	popl	%edx
+	movb	%cl, %bl	/* sector number */
+	andb	$63, %bl
+	decb	%bl
+	addl	%ebx, %eax	/* EAX=lo 32 bits of logical sector number */
+	movl	%eax, 8(%si)
+	popl	%ebx
+	call	bound_check
+	testb	$0xfe, %ah	/* allow all or part of sectors to tranfer */
+	jnz	3f
+	movl	-10(%bp), %eax	/* StartLBA */
+	addl	%eax, 8(%si)
+	setb	12(%si)
+	movb	-5(%bp), %dl	/* DL=TO_DRIVE */
+	movb	3(%bp), %ah	/* 0x02=read, 0x03=write */
+	orb	$0x40, %ah	/* 0x42=EXT_read, 0x43=EXT_write */
+#if 1
+	call	real_int13_service
+#else
+	pushfw
+	lcall	*(int13_offset - int13_handler)	/* call original int13 */
+#endif
+	jnc	4f
+	/* try again using standard read/write function */
+	pushaw
+	pushw	%dx
+	movb	$8, %ah
+	call	real_int13_service
+	jc	2f
+	pushw	%dx	//DH=Hmax
+	movl	8(%si), %eax
+	movl	12(%si), %edx
+	andl	$63, %ecx
+	divl	%ecx	// EAX = Cylinder * Htotal + Head, EDX=Sector - 1
+	incw	%dx
+	movw	%dx, %cx	//sector number
+	xorw	%dx, %dx
+	popw	%bx
+	movb	%bh, %bl
+	movzbl	%bl, %ebx
+	incw	%bx	// Htotal
+	divl	%ebx	// EAX = Cylinder, EDX=Head
+	cmpl	$1024, %eax
+	cmc
+	jb	2f
+	xchgb	%al, %ch
+	shrw	$1, %ax
+	shrw	$1, %ax
+	orb	%al, %cl
+	xchgb	%dl, %dh
+	popw	%bx
+	pushw	%bx
+	movb	%bl, %dl
+	movw	4(%si), %bx
+	movw	6(%si), %es
+	movb	3(%bp), %ah	/* 0x02=read, 0x03=write */
+	movb	2(%si), %al	/* sectors */
+	call	real_int13_service
+2:
+	popw	%dx
+	popaw
+	jc	2f		/* on error need not use the bound check */
+4:
+	call	modify_boot_sectors
+	popfw			/* use bound check info */
+	pushfw			/* dummy push, for the following dummy pop */
+	jnc	4f
+	movb	$0x04, %ah	/* sector not found */
+2:
+	popfw			/* dummy pop */
+	stc
+	pushfw
+4:
+	movb	2(%si), %al	/* number of sectors transferred */
+
+	/* It is not safe to use POPW %DS for running in protected mode */
+	popfw			/* dummy pop, skip the pushed flags */
+	movb	-6(%bp), %dl	/* restore DL(=FROM_DRIVE) */
 3:
+	popw	%ds
+	jmp	int13_return
+1:
+	cmpb	$0x41, %ah	/* EBIOS installation check */
+	jnz	1f
+	cmpw	$0x55aa, %bx
+	jnz	error_01_invalid
+	testb	%dl, %dl
+	jns	error_01_invalid
+	movw	$0xaa55, %bx
+	movb	$0x21, %ah	/* major version 2.1(EDD-1.1) */
+	movw	$0x01, %cx	/* support functions 42h,43h,44h,47h,48h */
+	clc
+	jmp	int13_return
+1:
+	cmpb	$0x42, %ah	/* EBIOS read sectors */
+	jz	2f
+	cmpb	$0x43, %ah	/* EBIOS write sectors */
+	jnz	1f
+2:
+	movw	-2(%bp), %si	/* get old SI, disk address packet */
+	movl	(%si), %eax	/* packet length, sectors, etc. */
+	testb	%ah, %ah
+	jnz	error_01_invalid
+	testb	$0xf0, %al
+	jz	error_01_invalid
+	shrl	$16, %eax
+	testw	$0xff80, %ax
+	jnz	error_01_invalid
+	call	bound_check
+	testb	$0xfe, %ah	/* allow all or part of sectors to tranfer */
+	jnz	int13_return
+	movl	-10(%bp), %eax	/* StartLBA */
+	addl	%eax, 8(%si)
+	jnc	2f
+	incl	12(%si)
+2:
+	movb	-5(%bp), %dl	/* DL=TO_DRIVE */
+	movb	3(%bp), %ah	/* 0x42=read, 0x43=write */
+#if 1
+	call	real_int13_service
+#else
+	pushfw
+	lcall	%cs:*(int13_offset - int13_handler) /* call original int13 */
+#endif
+	jc	2f		/* on error need not use the bound check */
+	popfw			/* use bound check info */
+	pushfw			/* dummy push, for the following dummy pop */
+	jnc	3f
+	movb	$0x04, %ah	/* sector not found */
+2:
+	popfw			/* dummy pop */
+	stc
+	pushfw
+3:
+#if 0
+	/* this pair can be omitted */
+	popfw			/* dummy pop */
+	pushfw
+#endif
+	movb	-6(%bp), %dl	/* restore DL(=FROM_DRIVE) */
+	pushl	%eax
+	movl	-10(%bp), %eax	/* StartLBA */
+	subl	%eax, 8(%si)
+	jnc	2f
+	decl	12(%si)
+2:
+	popl	%eax
+	popfw
+	jmp	int13_return
+1:
+	cmpb	$0x44, %ah	/* EBIOS verify sectors */
+	jnz	1f
+	xorb	%ah, %ah
+	clc
+	jmp	int13_return
+1:
+	cmpb	$0x47, %ah	/* EBIOS seek */
+	jnz	1f
+	xorb	%ah, %ah
+	clc
+	jmp	int13_return
+1:
+	cmpb	$0x48, %ah	/* EBIOS GET DRIVE PARAMETERS */
+	jnz	error_01_invalid
+	movw	-2(%bp), %si	/* get old SI, extended drive parameter table */
+	movw	$26, (%si)	/* buffer length */
+	movw	$2, 2(%si)	/* info */
+	xorl	%eax, %eax
+	movl	%eax, 8(%si)	/* total heads */
+	movl	%eax, 12(%si)	/* sectors per track */
+	movl	%eax, 16(%si)	/* total sectors */
+	movl	%eax, 20(%si)	/* hi 32 bits of total sectors */
+	pushl	%ebx
+	xorl	%ebx, %ebx
+	movw	-4(%bp), %ax	/* AL=Hmax, AH=Smax */
+	andb	$63, %ah
+	movb	%ah, 12(%si)	/* sectors per track */
+	movb	%ah, %bl
+	xorb	%ah, %ah
+	incw	%ax		/* total heads=Hmax+1 */
+	movw	%ax, 8(%si)	/* total heads */
+	pushl	%edx
+	mulw	%bx		/* DX:AX=product, DX=0 */
+	movw	%ax, %bx	/* BX=sectors per cylinder */
+	movl	-14(%bp), %eax	/* total sectors */
+	andb	$0xfe, %al
+	movl	%eax, 16(%si)	/* total sectors */
+	xorl	%edx, %edx	/* EDX:EAX=64bit total sectors */
+	testw	%bx, %bx
+	jz	2f
+	divl	%ebx		/* EAX=quotient, EDX=residue */