WebSVN – Kolibri OS – Blame – /kernel/trunk/bootloader/boot_fat12.asm

Rev	Author	Line No.	Line
2455	mario79	1	;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
		2	;; ;;
		3	;; Copyright (C) KolibriOS team 2004-2011. All rights reserved. ;;
		4	;; Distributed under terms of the GNU General Public License ;;
		5	;; ;;
		6	;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
		7
796	shurf	8	; FAT12 boot sector for Kolibri OS
		9	;
		10	; Copyright (C) Alex Nogueira Teixeira
		11	; Copyright (C) Diamond
		12	; Copyright (C) Dmitry Kartashov aka shurf
		13	;
		14	; Distributed under GPL, see file COPYING for details
		15	;
		16	; Version 1.0
		17
2288	clevermous	18	lf equ 0ah
		19	cr equ 0dh
796	shurf	20
2288	clevermous	21	pos_read_tmp equ 0700h ;position for temporary read
		22	boot_program equ 07c00h ;position for boot code
		23	seg_read_kernel equ 01000h ;segment to kernel read
796	shurf	24
2288	clevermous	25	jmp start_program
		26	nop
796	shurf	27
		28	; Boot Sector and BPB Structure
		29	include 'floppy1440.inc'
		30	;include 'floppy2880.inc'
		31	;include 'floppy1680.inc'
		32	;include 'floppy1743.inc'
		33
		34	start_program:
		35
2288	clevermous	36	xor ax, ax
		37	mov ss, ax
		38	mov sp, boot_program
		39	push ss
		40	pop ds
796	shurf	41
2288	clevermous	42	; print loading string
		43	mov si, loading+boot_program
796	shurf	44	loop_loading:
2288	clevermous	45	lodsb
		46	or al, al
		47	jz read_root_directory
		48	mov ah, 0eh
		49	mov bx, 7
		50	int 10h
		51	jmp loop_loading
796	shurf	52
		53	read_root_directory:
2288	clevermous	54	push ss
		55	pop es
796	shurf	56
2288	clevermous	57	; calculate some disk parameters
		58	; - beginning sector of RootDir
		59	mov ax, word [BPB_FATSz16+boot_program]
		60	xor cx, cx
		61	mov cl, byte [BPB_NumFATs+boot_program]
		62	mul cx
		63	add ax, word [BPB_RsvdSecCnt+boot_program]
		64	mov word [FirstRootDirSecNum+boot_program], ax ; 19
		65	mov si, ax
796	shurf	66
2288	clevermous	67	; - count of sectors in RootDir
		68	mov bx, word [BPB_BytsPerSec+boot_program]
		69	mov cl, 5 ; divide ax by 32
		70	shr bx, cl ; bx = directory entries per sector
		71	mov ax, word [BPB_RootEntCnt+boot_program]
		72	xor dx, dx
		73	div bx
		74	mov word [RootDirSecs+boot_program], ax ; 14
796	shurf	75
2288	clevermous	76	; - data start
		77	add si, ax ; add beginning sector of RootDir and count sectors in RootDir
		78	mov word [data_start+boot_program], si ; 33
		79	; reading root directory
		80	; al=count root dir sectrors !!!! TODO: al, max 255 sectors !!!!
		81	mov ah, 2 ; read
		82	push ax
796	shurf	83
2288	clevermous	84	mov ax, word [FirstRootDirSecNum+boot_program]
		85	call conv_abs_to_THS ; convert abs sector (AX) to BIOS T:H:S (track:head:sector)
		86	pop ax
		87	mov bx, pos_read_tmp ; es:bx read buffer
		88	call read_sector
796	shurf	89
2288	clevermous	90	mov si, bx ; read buffer address: es:si
		91	mov ax, [RootDirSecs+boot_program]
		92	mul word [BPB_BytsPerSec+boot_program]
		93	add ax, si ; AX = end of root dir. in buffer pos_read_tmp
796	shurf	94
2288	clevermous	95	; find kernel file in root directory
796	shurf	96	loop_find_dir_entry:
2288	clevermous	97	push si
		98	mov cx, 11
		99	mov di, kernel_name+boot_program
		100	rep cmpsb ; compare es:si and es:di, cx bytes long
		101	pop si
		102	je found_kernel_file
		103	add si, 32 ; next dir. entry
		104	cmp si, ax ; end of directory
		105	jb loop_find_dir_entry
796	shurf	106
		107	file_error_message:
2288	clevermous	108	mov si, error_message+boot_program
796	shurf	109
		110	loop_error_message:
2288	clevermous	111	lodsb
		112	or al, al
		113	jz freeze_pc
		114	mov ah, 0eh
		115	mov bx, 7
		116	int 10h
		117	jmp loop_error_message
796	shurf	118
		119	freeze_pc:
2288	clevermous	120	jmp $ ; endless loop
796	shurf	121
2288	clevermous	122	; === KERNEL FOUND. LOADING... ===
796	shurf	123
		124	found_kernel_file:
2288	clevermous	125	mov bp, [si+01ah] ; first cluster of kernel file
		126	;
		127	mov [cluster1st+boot_program], bp ; starting cluster of kernel file
		128	; <\diamond>
796	shurf	129
2288	clevermous	130	; reading first FAT table
		131	mov ax, word [BPB_RsvdSecCnt+boot_program] ; begin first FAT abs sector number
		132	call conv_abs_to_THS ; convert abs sector (AX) to BIOS T:H:S (track:head:sector)
		133	mov bx, pos_read_tmp ; es:bx read position
		134	mov ah, 2 ; ah=2 (read)
		135	mov al, byte [BPB_FATSz16+boot_program] ; FAT size in sectors (TODO: max 255 sectors)
		136	call read_sector
		137	jc file_error_message ; read error
796	shurf	138
2288	clevermous	139	mov ax, seg_read_kernel
		140	mov es, ax
		141	xor bx, bx ; es:bx = 1000h:0000h
796	shurf	142
		143
2288	clevermous	144	; reading kernel file
796	shurf	145	loop_obtains_kernel_data:
2288	clevermous	146	; read one cluster of file
		147	call obtain_cluster
		148	jc file_error_message ; read error
796	shurf	149
2288	clevermous	150	; add one cluster length to segment:offset
		151	push bx
		152	mov bx, es
		153	mov ax, word [BPB_BytsPerSec+boot_program] ;\
		154	movsx cx, byte [BPB_SecPerClus+boot_program] ; \| !!! TODO: !!!
		155	mul cx ; \| out this from loop !!!
		156	shr ax, 4 ;/
		157	add bx, ax
		158	mov es, bx
		159	pop bx
796	shurf	160
2288	clevermous	161	mov di, bp
		162	shr di, 1
		163	pushf
		164	add di, bp ; di = bp * 1.5
		165	add di, pos_read_tmp
		166	mov ax, [di] ; read next entry from FAT-chain
		167	popf
		168	jc move_4_right
		169	and ax, 0fffh
		170	jmp verify_end_sector
796	shurf	171	move_4_right:
2288	clevermous	172	mov cl, 4
		173	shr ax, cl
796	shurf	174	verify_end_sector:
2288	clevermous	175	cmp ax, 0ff8h ; last cluster
		176	jae execute_kernel
		177	mov bp, ax
		178	jmp loop_obtains_kernel_data
796	shurf	179
		180	execute_kernel:
2288	clevermous	181	;
		182	mov ax, 'KL'
		183	push 0
		184	pop ds
		185	mov si, loader_block+boot_program
		186	;
		187	push word seg_read_kernel
		188	push word 0
		189	retf ; jmp far 1000:0000
796	shurf	190
		191
		192	;------------------------------------------
2288	clevermous	193	; loading cluster from file to es:bx
796	shurf	194	obtain_cluster:
2288	clevermous	195	; bp - cluster number to read
		196	; carry = 0 -> read OK
		197	; carry = 1 -> read ERROR
796	shurf	198
2288	clevermous	199	; print one dot
		200	push bx
		201	mov ax, 0e2eh ; ah=0eh (teletype), al='.'
		202	xor bh, bh
		203	int 10h
		204	pop bx
796	shurf	205
1738	clevermous	206	writesec:
2288	clevermous	207	; convert cluster number to sector number
		208	mov ax, bp ; data cluster to read
		209	sub ax, 2
		210	xor dx, dx
		211	mov dl, byte [BPB_SecPerClus+boot_program]
		212	mul dx
		213	add ax, word [data_start+boot_program]
796	shurf	214
2288	clevermous	215	call conv_abs_to_THS ; convert abs sector (AX) to BIOS T:H:S (track:head:sector)
796	shurf	216	patchhere:
2288	clevermous	217	mov ah, 2 ; ah=2 (read)
		218	mov al, byte [BPB_SecPerClus+boot_program] ; al=(one cluster)
		219	call read_sector
		220	retn
796	shurf	221	;------------------------------------------
		222
		223	;------------------------------------------
2288	clevermous	224	; read sector from disk
796	shurf	225	read_sector:
2288	clevermous	226	push bp
		227	mov bp, 20 ; try 20 times
796	shurf	228	newread:
2288	clevermous	229	dec bp
		230	jz file_error_message
		231	push ax bx cx dx
		232	int 13h
		233	pop dx cx bx ax
		234	jc newread
		235	pop bp
		236	retn
796	shurf	237	;------------------------------------------
2288	clevermous	238	; convert abs. sector number (AX) to BIOS T:H:S
		239	; sector number = (abs.sector%BPB_SecPerTrk)+1
		240	; pre.track number = (abs.sector/BPB_SecPerTrk)
		241	; head number = pre.track number%BPB_NumHeads
		242	; track number = pre.track number/BPB_NumHeads
		243	; Return: cl - sector number
		244	; ch - track number
		245	; dl - drive number (0 = a:)
		246	; dh - head number
796	shurf	247	conv_abs_to_THS:
2288	clevermous	248	push bx
		249	mov bx, word [BPB_SecPerTrk+boot_program]
		250	xor dx, dx
		251	div bx
		252	inc dx
		253	mov cl, dl ; cl = sector number
		254	mov bx, word [BPB_NumHeads+boot_program]
		255	xor dx, dx
		256	div bx
		257	; !!!!!!! ax = track number, dx = head number
		258	mov ch, al ; ch=track number
		259	xchg dh, dl ; dh=head number
		260	mov dl, 0 ; dl=0 (drive 0 (a:))
		261	pop bx
		262	retn
796	shurf	263	;------------------------------------------
		264
2288	clevermous	265	loading db cr,lf,'Starting system ',00h
		266	error_message db 13,10
		267	kernel_name db 'KERNEL MNT ?',cr,lf,00h
		268	FirstRootDirSecNum dw ?
		269	RootDirSecs dw ?
		270	data_start dw ?
796	shurf	271
		272	;
		273	write1st:
2288	clevermous	274	push cs
		275	pop ds
		276	mov byte [patchhere+1+boot_program], 3 ; change ah=2 to ah=3
		277	mov bp, [cluster1st+boot_program]
		278	push 1000h
		279	pop es
		280	xor bx, bx
		281	call writesec
		282	mov byte [patchhere+1+boot_program], 2 ; change back ah=3 to ah=2
		283	retf
		284	cluster1st dw ?
796	shurf	285	loader_block:
2288	clevermous	286	db 1
		287	dw 0
		288	dw write1st+boot_program
		289	dw 0
796	shurf	290	; <\diamond>
		291
2288	clevermous	292	times 0x1fe-$ db 00h
796	shurf	293
2288	clevermous	294	db 55h,0aah ;boot signature

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(root)/kernel/trunk/bootloader/boot_fat12.asm – Rev 2455