[apple/boot.git] / i386 / boot1u / boot1u0.s

; Copyright (c) 1999-2003 Apple Computer, Inc. All rights reserved.
;
; @APPLE_LICENSE_HEADER_START@
; 
; Portions Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights
; Reserved.  This file contains Original Code and/or Modifications of
; Original Code as defined in and that are subject to the Apple Public
; Source License Version 2.0 (the "License").  You may not use this file
; except in compliance with the License.  Please obtain a copy of the
; License at http://www.apple.com/publicsource and read it before using
; this file.
; 
; The Original Code and all software distributed under the License are
; distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
; EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
; INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT.  Please see the
; License for the specific language governing rights and limitations
; under the License.
; 
; @APPLE_LICENSE_HEADER_END@
;
; Boot Loader: boot0
;
; A small boot sector program written in x86 assembly whose only
; responsibility is to load the booter into memory
; and jump to the booter's entry point.
; The booter partition can be a primary or a logical partition.
; 
; This boot loader can be placed at any of the following places:
; 1. Boot sector of an extended partition
; 2. Boot sector of a primary partition
; 3. Boot sector of a logical partition
;
; It expects that the MBR has left the drive number in DL
; and a pointer to the partition entry in SI.
;
; In order to coexist with a fdisk partition table (64 bytes), and
; leave room for a two byte signature (0xAA55) in the end, boot0 is
; restricted to 446 bytes (512 - 64 - 2). If boot0 did not have to
; live in the MBR, then we would have 510 bytes to work with.
;
; boot0 is always loaded by the BIOS or another booter to 0:7C00h.
;
; This code is written for the NASM assembler.
;   nasm boot0.s -o boot0


;
; Set to 1 to enable obscure debug messages.
;
DEBUG                EQU  0

;
; Set to 1 to support loading the booter (boot2) from a
; logical partition.
;
EXT_PART_SUPPORT     EQU  1

;
; Various constants.
;
kBoot0Segment        EQU  0x0000
kBoot0Stack          EQU  0xFFF0        ; boot0 stack pointer
kBoot0LoadAddr       EQU  0x7C00        ; boot0 load address
kBoot0RelocAddr      EQU  0xE000        ; boot0 relocated address

kMBRBuffer           EQU  0x1000        ; MBR buffer address
kExtBuffer           EQU  0x1200        ; EXT boot block buffer address

kPartTableOffset     EQU  0x1be
kMBRPartTable        EQU  kMBRBuffer + kPartTableOffset
kExtPartTable        EQU  kExtBuffer + kPartTableOffset

kBoot1uSectors       EQU  16            ; sectors to load for boot2
kBoot1uAddress       EQU  0x0000        ; boot2 load address
kBoot1uSegment       EQU  0x1000        ; boot2 load segment
	
kSectorBytes         EQU  512           ; sector size in bytes
kBootSignature       EQU  0xAA55        ; boot sector signature

kPartCount           EQU  4             ; number of paritions per table
kPartTypeBoot        EQU  0xab          ; boot2 partition type
kPartTypeUFS         EQU  0xa8          ; 
kPartTypeExtDOS      EQU  0x05          ; DOS extended partition type
kPartTypeExtWin      EQU  0x0f          ; Windows extended partition type
kPartTypeExtLinux    EQU  0x85          ; Linux extended partition type
kPartActive          EQU  0x80

%ifdef FLOPPY
kDriveNumber         EQU  0x00
%else
kDriveNumber         EQU  0x80
%endif

;
; Format of fdisk partition entry.
;
; The symbol 'part_size' is automatically defined as an `EQU'
; giving the size of the structure.
;
           struc part
.bootid:   resb 1      ; bootable or not 
.head:     resb 1      ; starting head, sector, cylinder
.sect:     resb 1      ;
.cyl:      resb 1      ;
.type:     resb 1      ; partition type
.endhead   resb 1      ; ending head, sector, cylinder
.endsect:  resb 1      ;
.endcyl:   resb 1      ;
.lba:      resd 1      ; starting lba
.sectors   resd 1      ; size in sectors
           endstruc

;
; Macros.
;
%macro DebugCharMacro 1
    mov   al, %1
    call  print_char
%endmacro

%if DEBUG
%define DebugChar(x)  DebugCharMacro x
%else
%define DebugChar(x)
%endif

;--------------------------------------------------------------------------
; Start of text segment.

    SEGMENT .text

    ORG     0x7C00

;--------------------------------------------------------------------------
; Boot code is loaded at 0:7C00h.
;
start
    DebugChar('!')
%if DEBUG
    mov     al, dl
    call    print_hex
%endif
    ;
    ; Set up the stack to grow down from kBoot0Segment:kBoot0Stack.
    ; Interrupts should be off while the stack is being manipulated.
    ;
    cli                             ; interrupts off
    xor     ax, ax                  ; zero ax
    mov     ss, ax                  ; ss <- 0
    mov     sp, kBoot0Stack         ; sp <- top of stack
    sti                             ; reenable interrupts

    mov     es, ax                  ; es <- 0
    mov     ds, ax                  ; ds <- 0

%if 0
    ; 
    ; Save SI register.
    ;
    mov     bx, si

    ;
    ; Relocate ourselves.
    ;
    mov     si, kBoot0LoadAddr      ; si <- source
    mov     di, kBoot0RelocAddr     ; di <- destination
    ;
    cld                             ; auto-increment SI and/or DI registers
    mov     cx, kSectorBytes/2      ; copy 256 words
    repnz   movsw                   ; repeat string move (word) operation

    ; Code relocated, jump to start_reloc in relocated location.
    ;
    jmp     0:start_reloc

;--------------------------------------------------------------------------
; Start execution from the relocated location.
;
start_reloc:
%endif
        
    DebugChar('*')

.loop:

%if DEBUG
    mov     al, dl
    call    print_hex
%endif

    ;
    ; Clear various flags in memory.
    ;
    xor     eax, eax
    mov     [ebios_lba], eax        ; clear EBIOS LBA offset
    mov     [ebios_present], al     ; clear EBIOS support flag

    ;
    ; Check if EBIOS is supported for this hard drive.
    ;
    mov     ah, 0x41                ; Function 0x41
    mov     bx, 0x55AA              ; check signature
;   mov     dl, kDriveNumber        ; Drive number
    int     0x13

    ;
    ; If successful, the return values are as follows:
    ;
    ; carry = 0
    ; ah    = major version of EBIOS extensions (0x21 = version 1.1)
    ; al    = altered
    ; bx    = 0xAA55
    ; cx    = support bits. bit 0 must be set for function 0x42.
    ;
    jc      .ebios_check_done
    cmp     bx, 0xAA55              ; check BX = 0xAA55
    jnz     .ebios_check_done
    test    cl, 0x01                ; check enhanced drive read support
    setnz   [ebios_present]         ; EBIOS supported, set flag
    DebugChar('E')                  ; EBIOS supported
.ebios_check_done:

    DebugChar('L')

%if DEBUG
    mov     al, BYTE [si + part.type]
    call    print_hex
%endif
        
    ; Check to make sure our partition is the correct type.
    cmp     BYTE [si + part.type], kPartTypeUFS
    je      load_boot

part_error:
    ; Drat, the partition entry was the wrong type.
    ; Print an error and hang.
    mov     si, part_error_str
    call    print_string

hang:
    hlt
    jmp     SHORT hang

    ;--------------------------------------------------------------------------
    ; Load the booter from the partition.

load_boot:

    ;
    ; Found boot partition, read boot1u image to memory.
    ;
    mov     al, kBoot1uSectors
    mov     bx, kBoot1uSegment
    mov     es, bx
    mov     bx, kBoot1uAddress
    call    load                    ;
    jc      part_error              ; load error, keep looking?

    DebugChar('^')

    ;
    ; Jump to boot1u. The drive number is already in register DL.
    ;
    ; The first sector loaded from the disk is reserved for the boot
    ; block (boot1), adjust the jump location by adding a sector offset.
    ;
    jmp     kBoot1uSegment:kBoot1uAddress + kSectorBytes

.exit:
    ;
    ; Boot partition not found. Giving up.
    ;
    pop     si
    pop     cx
    ret

;--------------------------------------------------------------------------
; load - Load one or more sectors from a partition.
;
; Arguments:
;   AL = number of 512-byte sectors to read.
;   ES:BX = pointer to where the sectors should be stored.
;   DL = drive number (0x80 + unit number)
;   SI = pointer to the partition entry.
;
; Returns:
;   CF = 0 success
;        1 error
;
load:
    push    cx
    test    BYTE [ebios_present], 1
    jz      .chs

.ebios:
    mov     cx, 5                   ; load retry count
.ebios_loop:
    call    read_lba                ; use INT13/F42
    jnc     .exit
    loop    .ebios_loop

.chs:
    mov     cx, 5                   ; load retry count
.chs_loop:
    call    read_chs                ; use INT13/F2
    jnc     .exit
    loop    .chs_loop

.exit
    pop     cx
    ret

;--------------------------------------------------------------------------
; read_chs - Read sectors from a partition using CHS addressing.
;
; Arguments:
;   AL = number of 512-byte sectors to read.
;   ES:BX = pointer to where the sectors should be stored.
;   DL = drive number (0x80 + unit number)
;   SI = pointer to the partition entry.
;
; Returns:
;   CF = 0 success
;        1 error
;
read_chs:
    pusha                           ; save all registers

    ;
    ; Read the CHS start values from the partition entry.
    ;
    mov     dh, [ si + part.head ]  ; drive head
    mov     cx, [ si + part.sect ]  ; drive sector + cylinder

    ;
    ; INT13 Func 2 - Read Disk Sectors
    ;
    ; Arguments:
    ;   AH    = 2
    ;   AL    = number of sectors to read
    ;   CH    = lowest 8 bits of the 10-bit cylinder number
    ;   CL    = bits 6 & 7: cylinder number bits 8 and 9
    ;           bits 0 - 5: starting sector number (1-63)
    ;   DH    = starting head number (0 to 255)
    ;   DL    = drive number (80h + drive unit)
    ;   es:bx = pointer where to place sectors read from disk
    ;
    ; Returns:
    ;   AH    = return status (sucess is 0)
    ;   AL    = burst error length if ah=0x11 (ECC corrected)
    ;   carry = 0 success
    ;           1 error
    ;
;   mov     dl, kDriveNumber
    mov     ah, 0x02                ; Func 2
    int     0x13                    ; INT 13
    jnc     .exit

    DebugChar('r')                  ; indicate INT13/F2 error

    ;
    ; Issue a disk reset on error.
    ; Should this be changed to Func 0xD to skip the diskette controller
    ; reset?
    ;
    xor     ax, ax                  ; Func 0
    int     0x13                    ; INT 13
    stc                             ; set carry to indicate error

.exit:
    popa
    ret

;--------------------------------------------------------------------------
; read_lba - Read sectors from a partition using LBA addressing.
;
; Arguments:
;   AL = number of 512-byte sectors to read (valid from 1-127).
;   ES:BX = pointer to where the sectors should be stored.
;   DL = drive number (0x80 + unit number)
;   SI = pointer to the partition entry.
;
; Returns:
;   CF = 0 success
;        1 error
;
read_lba:
    pusha                           ; save all registers
    mov     bp, sp                  ; save current SP

    ;
    ; Create the Disk Address Packet structure for the
    ; INT13/F42 (Extended Read Sectors) on the stack.
    ;

    ; push    DWORD 0               ; offset 12, upper 32-bit LBA
    push    ds                      ; For sake of saving memory,
    push    ds                      ; push DS register, which is 0.

    mov     ecx, [ebios_lba]        ; offset 8, lower 32-bit LBA
    add     ecx, [si + part.lba]
    push    ecx

    push    es                      ; offset 6, memory segment

    push    bx                      ; offset 4, memory offset

    xor     ah, ah                  ; offset 3, must be 0
    push    ax                      ; offset 2, number of sectors

    push    WORD 16                 ; offset 0-1, packet size

    ;
    ; INT13 Func 42 - Extended Read Sectors
    ;
    ; Arguments:
    ;   AH    = 0x42
    ;   DL    = drive number (80h + drive unit)
    ;   DS:SI = pointer to Disk Address Packet
    ;
    ; Returns:
    ;   AH    = return status (sucess is 0)
    ;   carry = 0 success
    ;           1 error
    ;
    ; Packet offset 2 indicates the number of sectors read
    ; successfully.
    ;
;   mov     dl, kDriveNumber
    mov     si, sp
    mov     ah, 0x42
    int     0x13

    jnc     .exit

    DebugChar('R')                  ; indicate INT13/F42 error

    ;
    ; Issue a disk reset on error.
    ; Should this be changed to Func 0xD to skip the diskette controller
    ; reset?
    ;
    xor     ax, ax                  ; Func 0
    int     0x13                    ; INT 13
    stc                             ; set carry to indicate error

.exit:
    mov     sp, bp                  ; restore SP
    popa
    ret

;--------------------------------------------------------------------------
; Write a string to the console.
;
; Arguments:
;   DS:SI   pointer to a NULL terminated string.
;
; Clobber list:
;   AX, BX, SI
;
print_string
    mov     bx, 1                   ; BH=0, BL=1 (blue)
    cld                             ; increment SI after each lodsb call
.loop
    lodsb                           ; load a byte from DS:SI into AL
    cmp     al, 0                   ; Is it a NULL?
    je      .exit                   ; yes, all done
    mov     ah, 0xE                 ; INT10 Func 0xE
    int     0x10                    ; display byte in tty mode
    jmp     short .loop
.exit
    ret

%if DEBUG

;--------------------------------------------------------------------------
; Write a ASCII character to the console.
;
; Arguments:
;   AL = ASCII character.
;
print_char
    pusha
    mov     bx, 1                   ; BH=0, BL=1 (blue)
    mov     ah, 0x0e                ; bios INT 10, Function 0xE
    int     0x10                    ; display byte in tty mode
    popa
    ret

;--------------------------------------------------------------------------
; Write the byte value to the console in hex.
;
; Arguments:
;   AL = Value to be displayed in hex.
;
print_hex:
    push    ax
    ror     al, 4
    call    print_nibble            ; display upper nibble
    pop     ax
    call    print_nibble            ; display lower nibble

    mov     al, 10                  ; carriage return
    call    print_char
    mov     al, 13
    call    print_char
    ret

print_nibble:
    and     al, 0x0f
    add     al, '0'
    cmp     al, '9'
    jna     .print_ascii
    add     al, 'A' - '9' - 1
.print_ascii:
    call    print_char
    ret

%endif ; DEBUG

;--------------------------------------------------------------------------
; NULL terminated strings.
;
part_error_str   db  10, 13, 'Error loading UFS partition', 0

;--------------------------------------------------------------------------
; Pad the rest of the 512 byte sized booter with zeroes. The last
; two bytes is the mandatory boot sector signature.
;
; If the booter code becomes too large, then nasm will complain
; that the 'times' argument is negative.

;;pad_boot
 ;;   times 446-($-$$) db 0

%ifdef FLOPPY
;--------------------------------------------------------------------------
; Put fake partition entries for the bootable floppy image
;
part1bootid     db    0x80          ; first partition active
part1head       db    0x00          ; head #
part1sect       db    0x02          ; sector # (low 6 bits)
part1cyl        db    0x00          ; cylinder # (+ high 2 bits of above)
part1systid     db    0xab          ; Apple boot partition
times   3       db    0x00          ; ignore head/cyl/sect #'s
part1relsect    dd    0x00000001    ; start at sector 1
part1numsect    dd    0x00000080    ; 64K for booter
part2bootid     db    0x00          ; not active
times   3       db    0x00          ; ignore head/cyl/sect #'s
part2systid     db    0xa8          ; Apple UFS partition
times   3       db    0x00          ; ignore head/cyl/sect #'s
part2relsect    dd    0x00000082    ; start after booter
; part2numsect  dd    0x00000abe    ; 1.44MB - 65K
part2numsect    dd    0x000015fe    ; 2.88MB - 65K
%endif

pad_table_and_sig
    times 510-($-$$) db 0
    dw    kBootSignature

	ABSOLUTE 0xE400

;
; In memory variables.
;
ebios_lba       resd  1   ; starting LBA of the intial extended partition.
ebios_present   resb  1   ; 1 if EBIOS is supported, 0 otherwise.

    END
Commit	Line	Data
57c72a9a	1	; Copyright (c) 1999-2003 Apple Computer, Inc. All rights reserved.
f083c6c3 A	2	;
	3	; @APPLE_LICENSE_HEADER_START@
	4	;
57c72a9a	5	; Portions Copyright (c) 1999-2003 Apple Computer, Inc. All Rights
4f6e3300 A	6	; Reserved. This file contains Original Code and/or Modifications of
4f6e3300 A	7	; Original Code as defined in and that are subject to the Apple Public
57c72a9a	8	; Source License Version 2.0 (the "License"). You may not use this file
4f6e3300 A	9	; except in compliance with the License. Please obtain a copy of the
	10	; License at http://www.apple.com/publicsource and read it before using
	11	; this file.
f083c6c3 A	12	;
f083c6c3 A	13	; The Original Code and all software distributed under the License are
4f6e3300	14	; distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
f083c6c3 A	15	; EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
f083c6c3 A	16	; INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
4f6e3300 A	17	; FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT. Please see the
	18	; License for the specific language governing rights and limitations
	19	; under the License.
f083c6c3 A	20	;
	21	; @APPLE_LICENSE_HEADER_END@
	22	;
	23	; Boot Loader: boot0
	24	;
	25	; A small boot sector program written in x86 assembly whose only
57c72a9a A	26	; responsibility is to load the booter into memory
57c72a9a A	27	; and jump to the booter's entry point.
f083c6c3 A	28	; The booter partition can be a primary or a logical partition.
	29	;
	30	; This boot loader can be placed at any of the following places:
57c72a9a A	31	; 1. Boot sector of an extended partition
	32	; 2. Boot sector of a primary partition
	33	; 3. Boot sector of a logical partition
	34	;
	35	; It expects that the MBR has left the drive number in DL
	36	; and a pointer to the partition entry in SI.
f083c6c3 A	37	;
	38	; In order to coexist with a fdisk partition table (64 bytes), and
	39	; leave room for a two byte signature (0xAA55) in the end, boot0 is
	40	; restricted to 446 bytes (512 - 64 - 2). If boot0 did not have to
	41	; live in the MBR, then we would have 510 bytes to work with.
	42	;
	43	; boot0 is always loaded by the BIOS or another booter to 0:7C00h.
	44	;
	45	; This code is written for the NASM assembler.
	46	; nasm boot0.s -o boot0
	47
	48
	49	;
	50	; Set to 1 to enable obscure debug messages.
	51	;
	52	DEBUG EQU 0
	53
	54	;
	55	; Set to 1 to support loading the booter (boot2) from a
	56	; logical partition.
	57	;
	58	EXT_PART_SUPPORT EQU 1
	59
	60	;
	61	; Various constants.
	62	;
	63	kBoot0Segment EQU 0x0000
	64	kBoot0Stack EQU 0xFFF0 ; boot0 stack pointer
	65	kBoot0LoadAddr EQU 0x7C00 ; boot0 load address
	66	kBoot0RelocAddr EQU 0xE000 ; boot0 relocated address
	67
	68	kMBRBuffer EQU 0x1000 ; MBR buffer address
	69	kExtBuffer EQU 0x1200 ; EXT boot block buffer address
	70
	71	kPartTableOffset EQU 0x1be
	72	kMBRPartTable EQU kMBRBuffer + kPartTableOffset
	73	kExtPartTable EQU kExtBuffer + kPartTableOffset
	74
	75	kBoot1uSectors EQU 16 ; sectors to load for boot2
	76	kBoot1uAddress EQU 0x0000 ; boot2 load address
	77	kBoot1uSegment EQU 0x1000 ; boot2 load segment
	78
	79	kSectorBytes EQU 512 ; sector size in bytes
	80	kBootSignature EQU 0xAA55 ; boot sector signature
	81
	82	kPartCount EQU 4 ; number of paritions per table
	83	kPartTypeBoot EQU 0xab ; boot2 partition type
	84	kPartTypeUFS EQU 0xa8 ;
	85	kPartTypeExtDOS EQU 0x05 ; DOS extended partition type
	86	kPartTypeExtWin EQU 0x0f ; Windows extended partition type
	87	kPartTypeExtLinux EQU 0x85 ; Linux extended partition type
	88	kPartActive EQU 0x80
	89
	90	%ifdef FLOPPY
	91	kDriveNumber EQU 0x00
	92	%else
	93	kDriveNumber EQU 0x80
	94	%endif
	95
f083c6c3 A	96	;
	97	; Format of fdisk partition entry.
	98	;
	99	; The symbol 'part_size' is automatically defined as an `EQU'
	100	; giving the size of the structure.
	101	;
	102	struc part
	103	.bootid: resb 1 ; bootable or not
	104	.head: resb 1 ; starting head, sector, cylinder
	105	.sect: resb 1 ;
	106	.cyl: resb 1 ;
	107	.type: resb 1 ; partition type
	108	.endhead resb 1 ; ending head, sector, cylinder
	109	.endsect: resb 1 ;
	110	.endcyl: resb 1 ;
	111	.lba: resd 1 ; starting lba
	112	.sectors resd 1 ; size in sectors
	113	endstruc
	114
	115	;
	116	; Macros.
	117	;
	118	%macro DebugCharMacro 1
	119	mov al, %1
	120	call print_char
	121	%endmacro
	122
	123	%if DEBUG
	124	%define DebugChar(x) DebugCharMacro x
	125	%else
	126	%define DebugChar(x)
	127	%endif
	128
	129	;--------------------------------------------------------------------------
	130	; Start of text segment.
	131
	132	SEGMENT .text
	133
57c72a9a	134	ORG 0x7C00
f083c6c3 A	135
	136	;--------------------------------------------------------------------------
	137	; Boot code is loaded at 0:7C00h.
	138	;
	139	start
57c72a9a A	140	DebugChar('!')
	141	%if DEBUG
	142	mov al, dl
	143	call print_hex
	144	%endif
f083c6c3 A	145	;
	146	; Set up the stack to grow down from kBoot0Segment:kBoot0Stack.
	147	; Interrupts should be off while the stack is being manipulated.
	148	;
	149	cli ; interrupts off
	150	xor ax, ax ; zero ax
	151	mov ss, ax ; ss <- 0
	152	mov sp, kBoot0Stack ; sp <- top of stack
	153	sti ; reenable interrupts
	154
	155	mov es, ax ; es <- 0
	156	mov ds, ax ; ds <- 0
	157
57c72a9a A	158	%if 0
	159	;
	160	; Save SI register.
	161	;
	162	mov bx, si
	163
f083c6c3	164	;
57c72a9a	165	; Relocate ourselves.
f083c6c3 A	166	;
	167	mov si, kBoot0LoadAddr ; si <- source
	168	mov di, kBoot0RelocAddr ; di <- destination
	169	;
	170	cld ; auto-increment SI and/or DI registers
	171	mov cx, kSectorBytes/2 ; copy 256 words
	172	repnz movsw ; repeat string move (word) operation
	173
	174	; Code relocated, jump to start_reloc in relocated location.
	175	;
	176	jmp 0:start_reloc
	177
	178	;--------------------------------------------------------------------------
	179	; Start execution from the relocated location.
	180	;
	181	start_reloc:
57c72a9a A	182	%endif
57c72a9a A	183
f083c6c3 A	184	DebugChar('*')
f083c6c3 A	185
f083c6c3 A	186	.loop:
	187
	188	%if DEBUG
	189	mov al, dl
	190	call print_hex
	191	%endif
	192
	193	;
	194	; Clear various flags in memory.
	195	;
	196	xor eax, eax
	197	mov [ebios_lba], eax ; clear EBIOS LBA offset
	198	mov [ebios_present], al ; clear EBIOS support flag
	199
f083c6c3 A	200	;
	201	; Check if EBIOS is supported for this hard drive.
	202	;
	203	mov ah, 0x41 ; Function 0x41
	204	mov bx, 0x55AA ; check signature
	205	; mov dl, kDriveNumber ; Drive number
	206	int 0x13
	207
	208	;
	209	; If successful, the return values are as follows:
	210	;
	211	; carry = 0
	212	; ah = major version of EBIOS extensions (0x21 = version 1.1)
	213	; al = altered
	214	; bx = 0xAA55
	215	; cx = support bits. bit 0 must be set for function 0x42.
	216	;
	217	jc .ebios_check_done
	218	cmp bx, 0xAA55 ; check BX = 0xAA55
	219	jnz .ebios_check_done
	220	test cl, 0x01 ; check enhanced drive read support
	221	setnz [ebios_present] ; EBIOS supported, set flag
	222	DebugChar('E') ; EBIOS supported
	223	.ebios_check_done:
	224
57c72a9a	225	DebugChar('L')
f083c6c3	226
57c72a9a A	227	%if DEBUG
	228	mov al, BYTE [si + part.type]
	229	call print_hex
	230	%endif
	231
	232	; Check to make sure our partition is the correct type.
	233	cmp BYTE [si + part.type], kPartTypeUFS
	234	je load_boot
f083c6c3	235
57c72a9a A	236	part_error:
	237	; Drat, the partition entry was the wrong type.
	238	; Print an error and hang.
	239	mov si, part_error_str
f083c6c3 A	240	call print_string
	241
	242	hang:
	243	hlt
	244	jmp SHORT hang
	245
57c72a9a A	246	;--------------------------------------------------------------------------
57c72a9a A	247	; Load the booter from the partition.
f083c6c3	248
57c72a9a	249	load_boot:
f083c6c3 A	250
	251	;
	252	; Found boot partition, read boot1u image to memory.
	253	;
	254	mov al, kBoot1uSectors
	255	mov bx, kBoot1uSegment
	256	mov es, bx
	257	mov bx, kBoot1uAddress
	258	call load ;
57c72a9a A	259	jc part_error ; load error, keep looking?
	260
	261	DebugChar('^')
f083c6c3	262
f083c6c3 A	263	;
	264	; Jump to boot1u. The drive number is already in register DL.
	265	;
	266	; The first sector loaded from the disk is reserved for the boot
	267	; block (boot1), adjust the jump location by adding a sector offset.
	268	;
	269	jmp kBoot1uSegment:kBoot1uAddress + kSectorBytes
	270
f083c6c3 A	271	.exit:
	272	;
	273	; Boot partition not found. Giving up.
	274	;
	275	pop si
	276	pop cx
	277	ret
	278
	279	;--------------------------------------------------------------------------
	280	; load - Load one or more sectors from a partition.
	281	;
	282	; Arguments:
	283	; AL = number of 512-byte sectors to read.
	284	; ES:BX = pointer to where the sectors should be stored.
	285	; DL = drive number (0x80 + unit number)
	286	; SI = pointer to the partition entry.
	287	;
	288	; Returns:
	289	; CF = 0 success
	290	; 1 error
	291	;
	292	load:
	293	push cx
	294	test BYTE [ebios_present], 1
	295	jz .chs
	296
	297	.ebios:
	298	mov cx, 5 ; load retry count
	299	.ebios_loop:
	300	call read_lba ; use INT13/F42
	301	jnc .exit
	302	loop .ebios_loop
	303
	304	.chs:
	305	mov cx, 5 ; load retry count
	306	.chs_loop:
	307	call read_chs ; use INT13/F2
	308	jnc .exit
	309	loop .chs_loop
	310
	311	.exit
	312	pop cx
	313	ret
	314
	315	;--------------------------------------------------------------------------
	316	; read_chs - Read sectors from a partition using CHS addressing.
	317	;
	318	; Arguments:
	319	; AL = number of 512-byte sectors to read.
	320	; ES:BX = pointer to where the sectors should be stored.
	321	; DL = drive number (0x80 + unit number)
	322	; SI = pointer to the partition entry.
	323	;
	324	; Returns:
	325	; CF = 0 success
	326	; 1 error
	327	;
	328	read_chs:
	329	pusha ; save all registers
	330
	331	;
	332	; Read the CHS start values from the partition entry.
	333	;
	334	mov dh, [ si + part.head ] ; drive head
335	mov cx, [ si + part.sect ] ; drive sector + cylinder
336
337	;
338	; INT13 Func 2 - Read Disk Sectors
339	;
340	; Arguments:
341	; AH = 2
342	; AL = number of sectors to read
343	; CH = lowest 8 bits of the 10-bit cylinder number
344	; CL = bits 6 & 7: cylinder number bits 8 and 9
345	; bits 0 - 5: starting sector number (1-63)
346	; DH = starting head number (0 to 255)
347	; DL = drive number (80h + drive unit)
348	; es:bx = pointer where to place sectors read from disk
349	;
350	; Returns:
351	; AH = return status (sucess is 0)
352	; AL = burst error length if ah=0x11 (ECC corrected)
353	; carry = 0 success
354	; 1 error
355	;
356	; mov dl, kDriveNumber
357	mov ah, 0x02 ; Func 2
358	int 0x13 ; INT 13
359	jnc .exit
360
361	DebugChar('r') ; indicate INT13/F2 error
362
363	;
364	; Issue a disk reset on error.
365	; Should this be changed to Func 0xD to skip the diskette controller
366	; reset?
367	;
368	xor ax, ax ; Func 0
369	int 0x13 ; INT 13
370	stc ; set carry to indicate error
371
372	.exit:
373	popa
374	ret
375
376	;--------------------------------------------------------------------------
377	; read_lba - Read sectors from a partition using LBA addressing.
378	;
379	; Arguments:
380	; AL = number of 512-byte sectors to read (valid from 1-127).
381	; ES:BX = pointer to where the sectors should be stored.
382	; DL = drive number (0x80 + unit number)
383	; SI = pointer to the partition entry.
384	;
385	; Returns:
386	; CF = 0 success
387	; 1 error
388	;
389	read_lba:
390	pusha ; save all registers
391	mov bp, sp ; save current SP
392
393	;
394	; Create the Disk Address Packet structure for the
395	; INT13/F42 (Extended Read Sectors) on the stack.
396	;
397
398	; push DWORD 0 ; offset 12, upper 32-bit LBA
399	push ds ; For sake of saving memory,
400	push ds ; push DS register, which is 0.
401
402	mov ecx, [ebios_lba] ; offset 8, lower 32-bit LBA
403	add ecx, [si + part.lba]
404	push ecx
405
406	push es ; offset 6, memory segment
407
408	push bx ; offset 4, memory offset
409
410	xor ah, ah ; offset 3, must be 0
411	push ax ; offset 2, number of sectors
412
413	push WORD 16 ; offset 0-1, packet size
414
415	;
416	; INT13 Func 42 - Extended Read Sectors
417	;
418	; Arguments:
419	; AH = 0x42
420	; DL = drive number (80h + drive unit)
421	; DS:SI = pointer to Disk Address Packet
422	;
423	; Returns:
424	; AH = return status (sucess is 0)
425	; carry = 0 success
426	; 1 error
427	;
428	; Packet offset 2 indicates the number of sectors read
429	; successfully.
430	;
431	; mov dl, kDriveNumber
432	mov si, sp
433	mov ah, 0x42
434	int 0x13
435
436	jnc .exit
437
438	DebugChar('R') ; indicate INT13/F42 error
439
440	;
441	; Issue a disk reset on error.
442	; Should this be changed to Func 0xD to skip the diskette controller
443	; reset?
444	;
445	xor ax, ax ; Func 0
446	int 0x13 ; INT 13
447	stc ; set carry to indicate error
448
449	.exit:
450	mov sp, bp ; restore SP
451	popa
452	ret
453
454	;--------------------------------------------------------------------------
455	; Write a string to the console.
456	;
457	; Arguments:
458	; DS:SI pointer to a NULL terminated string.
459	;
460	; Clobber list:
461	; AX, BX, SI
462	;
463	print_string
464	mov bx, 1 ; BH=0, BL=1 (blue)
465	cld ; increment SI after each lodsb call
466	.loop
467	lodsb ; load a byte from DS:SI into AL
468	cmp al, 0 ; Is it a NULL?
469	je .exit ; yes, all done
470	mov ah, 0xE ; INT10 Func 0xE
471	int 0x10 ; display byte in tty mode
472	jmp short .loop
473	.exit
474	ret
475
476	%if DEBUG
477
478	;--------------------------------------------------------------------------
479	; Write a ASCII character to the console.
480	;
481	; Arguments:
482	; AL = ASCII character.
483	;
484	print_char
485	pusha
486	mov bx, 1 ; BH=0, BL=1 (blue)
487	mov ah, 0x0e ; bios INT 10, Function 0xE
488	int 0x10 ; display byte in tty mode
489	popa
490	ret
491
f083c6c3 A	492	;--------------------------------------------------------------------------
	493	; Write the byte value to the console in hex.
	494	;
	495	; Arguments:
	496	; AL = Value to be displayed in hex.
	497	;
	498	print_hex:
	499	push ax
	500	ror al, 4
	501	call print_nibble ; display upper nibble
	502	pop ax
	503	call print_nibble ; display lower nibble
	504
	505	mov al, 10 ; carriage return
	506	call print_char
	507	mov al, 13
	508	call print_char
	509	ret
	510
	511	print_nibble:
	512	and al, 0x0f
	513	add al, '0'
	514	cmp al, '9'
	515	jna .print_ascii
	516	add al, 'A' - '9' - 1
	517	.print_ascii:
	518	call print_char
	519	ret
	520
	521	%endif ; DEBUG
	522
	523	;--------------------------------------------------------------------------
	524	; NULL terminated strings.
	525	;
57c72a9a	526	part_error_str db 10, 13, 'Error loading UFS partition', 0
f083c6c3 A	527
	528	;--------------------------------------------------------------------------
	529	; Pad the rest of the 512 byte sized booter with zeroes. The last
	530	; two bytes is the mandatory boot sector signature.
	531	;
	532	; If the booter code becomes too large, then nasm will complain
	533	; that the 'times' argument is negative.
	534
	535	;;pad_boot
	536	;; times 446-($-$$) db 0
	537
	538	%ifdef FLOPPY
	539	;--------------------------------------------------------------------------
	540	; Put fake partition entries for the bootable floppy image
	541	;
	542	part1bootid db 0x80 ; first partition active
	543	part1head db 0x00 ; head #
	544	part1sect db 0x02 ; sector # (low 6 bits)
	545	part1cyl db 0x00 ; cylinder # (+ high 2 bits of above)
	546	part1systid db 0xab ; Apple boot partition
	547	times 3 db 0x00 ; ignore head/cyl/sect #'s
	548	part1relsect dd 0x00000001 ; start at sector 1
	549	part1numsect dd 0x00000080 ; 64K for booter
	550	part2bootid db 0x00 ; not active
	551	times 3 db 0x00 ; ignore head/cyl/sect #'s
	552	part2systid db 0xa8 ; Apple UFS partition
	553	times 3 db 0x00 ; ignore head/cyl/sect #'s
	554	part2relsect dd 0x00000082 ; start after booter
	555	; part2numsect dd 0x00000abe ; 1.44MB - 65K
	556	part2numsect dd 0x000015fe ; 2.88MB - 65K
	557	%endif
	558
	559	pad_table_and_sig
	560	times 510-($-$$) db 0
	561	dw kBootSignature
	562
57c72a9a A	563	ABSOLUTE 0xE400
	564
	565	;
	566	; In memory variables.
	567	;
	568	ebios_lba resd 1 ; starting LBA of the intial extended partition.
	569	ebios_present resb 1 ; 1 if EBIOS is supported, 0 otherwise.
	570
f083c6c3	571	END