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/*******************************************************************
 *	
 * Return to real mode and dump the output data
 *
 * Code for return to real mode obtained here:
 *http://www.rohitab.com/discuss/topic/35103-switch-between-real-mode-and-protected-mode/
 ******************************************************************/
	
move_to_real:

	cli
	lgdt gdt16_descriptor
	ljmp $CODE_SEG_16, $p_mode16
	
.code16	
p_mode16:	 
	mov $DATA_SEG_16, %ax
	mov %ax, %ds
	mov %ax, %es
	mov %ax, %fs
	mov %ax, %gs
	mov %ax, %ss
	mov %ax, %di
	
	mov %cr0, %eax
	and $~1, %al
	mov %eax, %cr0
	
	ljmp $0, $real

real:	

	/* Sets %ax to 0.  (I'm not sure why we're not using mov.) */
	xor %ax, %ax

	/* Set all the segment registers to 0. */
	mov %ax, %ds
	mov %ax, %es
	mov %ax, %fs
	mov %ax, %gs

	mov %ax, %ss
//	mov $0x7bfc, %sp // $0x7c00 - $4
	mov $0x7000, %sp   // 0x6000 works.  0x7000 and 0x7c00 don't
	mov %sp, %bp 


	// Print debugging message indicating we are back in real mode.
	mov $0x0E, %ah
	mov $0x52, %al // 'R'
	int $0x10

	mov $0x4D, %al // 'M'
	int $0x10

	mov $0x20, %al // ' '
	int $0x10
	
	
/*******************************************************************
 *	
 * Dump the data buffer to the boot device.
 *
 ******************************************************************/

.set drive_type,              -4
.set max_sector_num,          -8
.set max_cylinder_num,       -12
.set max_head_num,           -16
.set num_drives,             -20
.set deubg_test, 		     -24
.set total_sectors_written,   -28

	// Make room on the stack for some local variables.
	add total_sectors_written, %sp  
	movw $0, total_sectors_written(%bp)
	
       // If I dump data here, everything looks normal:  data buffer is untouched.


	/////////////////////////////////////
	//
	// First, gather data about the drive
	//
	/////////////////////////////////////
	mov $0x08, %ah
	mov initial_dl, %dl
	int $0x13 
	
      // If I dump data here, data buffer has about 80 bytes changed.   I can't tell what the data here represents.
      // Its not obviously output from the interrupt.


	// Save the returned values before we mess them up.  (These
	// values probably need only be 16-bit; but, better safe than
	// sorry.)	
	mov %bx, drive_type(%bp)       // Drive type
	mov %cx, max_sector_num(%bp)   // max sector number
	mov %cx, max_cylinder_num(%bp) // max cylinder number
	mov %dx, max_head_num(%bp)     // max head number
	mov %dx, num_drives(%bp)       // num drives
	movl $0x41424344, debug_test(%bp)

     // continue on writing sectors to disk.

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.set total_sectors_written,   -28

 // Make room on the stack for some local variables.
 add total_sectors_written, %sp  
 movw $0, total_sectors_written(%bp)

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add $total_sectors_written, %sp