メモリサイズ取得

int 15hのFunction 0xE801と0x88でのメモリサイズの取得が出来た

/* We have to get the phisical memory map.
 * Using "Function E820" and "Function E801" but not "Function 88H",
 * we'll get it.	
 *  EAX 0xE820 - BIOS command to get the memory map
 *  EDX "SMAP" - special string to get the memory map
 *  ES:DI - entry buffer address to set the memory map
 *  ECX - the size of the entry buffer									
 */
		e820_mmap_maxsize: .byte 32
SMAP = 0x534d4150 # "SMAP"

		xorl	%ebx, %ebx		
		movw	$MEMORY_MAP, %di		

e820_start:
		movl	0x0000e820, %eax		
		movl	$SMAP, %edx		
		movl	$20, %ecx
		int		$0x15
		jc		e820_error
		cmpl	$SMAP, %eax
		jc		e820_error

		cmpl	$0, %ebx
		jz		e820_end

		movb	(e820_mmap_maxsize), %al
		cmpb	$0, %al
		jz		e820_end

		decb	(e820_mmap_maxsize)
		movw	%di, %ax
		addw	$20, %ax
		movw	%ax, %di
		jmp		e820_start				# get the next memory map

e820_error:
		call	print_all_registers
		movw	$e820_fail_mes, %si
		call	printstr
		
e820_end:
				
/* We have to get the memory size. 
 * This function is the getting physical memory size from BIOS.
 *  If memory size is less than 64MB, this function will be failed.
 *  At the time, we'll use the 88 function.		
 */				
e801_start:
		movw	$0xe801, %ax
		int		$0x15
		jc		e801_error
#if DEBUG
		call	print_all_registers
#endif		
		pushw	%bx
		shr		$10, %ax
		xorb	%ah, %ah
		incb	%al
		movw	%ax, (MEMORY_SIZE)
		popw	%bx
		shr		$4, %bx
		addw	%bx, (MEMORY_SIZE)

#if DEBUG
		movw	(MEMORY_SIZE), %ax
		call	print_register
#endif
						
		jmp		mem_check_end

e801_error:		
		call	print_all_registers
		movw	$e801_fail_mes, %si
		call	printstr

/* This function have the feature getting memory size less than 64MB
 *  If this function also fail, we set 64MB as default memory size.
 */								
m88_start:
		movb	$0x88, %ah
		int		$0x15
		shr		$10, %ax
		xorb	%ah, %ah
		incb	%al
		movw	%ax, (MEMORY_SIZE)		
#if DEBUG
		movw	(MEMORY_SIZE), %ax
		call	print_register
#endif		
		
		jmp		mem_check_end

m88_error:		
		call	print_all_registers
		movw	$m88_fail_mes, %si
		call	printstr

mem_set_default:
		movw	$0x40, %ax				# set 64MB
		movw	%ax, (MEMORY_SIZE)

mem_check_end:	

次の処理としてはA20の有効化（0x100000以上のメモリアドレスのアクセスに必要な処理）をする必要があるけど、とりあえず置いといてCPUをプロテクトモードに移行しよう。
IDT,GDTは仮の値を入れてCで書きはじめる部分で正式な値を入れようと思う。