SLRboot/slrboot.nasm

ORG 0x7C00
BITS 16
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; SLRboot
; Bootloader for SingOS
; version 0.2.0.0-exp
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
cli 
mov [disk_identifier], dl
mov ax, 0x1000
mov ss, ax
mov sp, 0xb000
mov ax, 0
mov ds, ax
mov es, ax
sti 
mov si, 0x7c00
mov di, 0x600
mov cx, 0x200
rep movsb 
mov bx, relocated
sub bx, 0x7600 ; Calculate the offset. 
push bx
retf ; Return far
;jmp long 0:bx

relocated:

mov si, message ; Put address of the null-terminated string to output into 'si'
call print      ; Call our string-printing routine

;mov ax, 0x0050 
;mov es, ax                  ;Section to write into
;mov ah, 0x2                 ;Read sectors from drive
;mov al, 0x08                ;Number of sectors to read (31 * 512 = 15872 bytes)
;mov ch, 0x0                 ;Low 8 bits of cylinder
;mov cl, 0x11                ;First sector to read (bits 0-5), upper bits of cylinder (bits 6-7)
;mov dh, 0x0                 ;Head number
;mov dl, [disk_identifier]   ;Drive number
;mov bx, 0x0000               ;Offset into section
;int 0x13                    ;Low level disk services
mov ah, 2
mov al, 0x08
mov bx, 0x7c00
mov BYTE dl, [disk_identifier]
mov BYTE dh, [partition_2.start_CHS + 1] ;byte [si + 1]
mov BYTE cl, [partition_2.start_CHS + 2]
mov BYTE ch, [partition_2.start_CHS]               ;First sector to read (bits 0-5), upper bits of cylinder (bits 6-7)
int 0x13
;mov ax, 0x0
;mov ds, ax
mov ax, 89 ; lba adress
jmp long 0x0:0x7c00

cli 
hlt


%IF 1
cli
jmp long 0x0000:start

start:
xor ax, ax
mov ds, ax
mov es, ax
mov ss, ax
mov [disk_identifier], dl

; initialize stack
; Set up 4K stack after this bootloader
; [Remember: Effective Address = Segment*16 + Offset]
mov ax, 0x7C0   ; Set 'ax' equal to the location of this bootloader divided by 16
add ax, 0x20     ; Skip over the size of the bootloader divided by 16
mov ss, ax      ; Set 'ss' to this location (the beginning of our stack region)
mov sp, 8192    ; Set 'ss:sp' to the top of our 8K stack
sti
mov si, message ; Put address of the null-terminated string to output into 'si'
call print      ; Call our string-printing routine

mov si, enter_debug_mode
call print 
call printCRLF
;%IF 0
; here goes wait call, for the user to enter debug mode. 
; Wating for 2 seconds: 
mov ah, 0x86   ; code for waiting interupt call
mov cx, 0x001e ; high count of microseconds
mov dx, 0x8480 ; low count
int 0x15

.busy_wait_for_key:
xor ax, ax 
mov ah, 0x01 ; BIOS call to wait for key
int 0x16
jnz debug_mode

; entering system check: 
mov si,  enter_system_check

mov si, sys_check_ok ; Put address of the null-terminated string to output into 'si'
call print      ; Call our string-printing routine

mov si, boot_system ; Put address of the null-terminated string to output into 'si'
call print      ; Call our string-printing routine

;This goes first as to now overwrite %ah and %al.
;mov ax, 0x0050 
;mov es, ax                  ;Section to write into
;mov ah, 0x2                 ;Read sectors from drive
;mov al, 0x08                ;Number of sectors to read (31 * 512 = 15872 bytes)
;mov ch, 0x0                 ;Low 8 bits of cylinder
;mov cl, 0x11                ;First sector to read (bits 0-5), upper bits of cylinder (bits 6-7)
;mov dh, 0x0                 ;Head number
;mov dl, [disk_identifier]   ;Drive number
;mov bx, 0x0000               ;Offset into section
;int 0x13                    ;Low level disk services

;jnc notcarry
;mov si, error_str
;call print
;jmp endcarrycheck

notcarry:
;mov si, success_str
;call print
;call printCRLF

mov ax, 0x0
mov ds, ax
mov ax, 89 ; lba adress

jmp 0x50:0x0000   ; Jump to the kernel 

endcarrycheck:  
cli             ; Clear the Interrupt Flag (disable external interrupts)
hlt             ; Halt the CPU (until the next external interrupt)

debug_mode: 
mov si, .welcome_debug
call print 
cli             ; Clear the Interrupt Flag (disable external interrupts)
hlt 

.welcome_debug db 'This is debug mode', 0

;Routine for printing a 'ax' as hex
dumpax:
pusha			; save registers
mov bx, ax
mov ah, 0xE		; Teletype output

mov cx, 4		; 4 nipples in a 16 bit word
.loop:
rol bx, 4   	; rotate to next nipple
mov al, bl		; we copy to al because we need to mask only the low 4 bits
and al, 1111b	; Do the masking
add al, '0'		; convert to ASCII
cmp al, '9'		; If we are greater than 9 ascii, we add 7 to make digit 10 be represented as 'A'
jbe .skip		;  -|-
add al, 7		;  -|-
.skip:			;  -|-
int 0x10		; BIOS call 'output'
loop .loop

popa			; restore registers
ret

printCRLF:
mov ah, 0xE
mov al, 13
int 0x10
mov al, 10
int 0x10
ret
%ENDIF
; Routine for outputting string in 'si' register to screen
print:
mov ah, 0xE     ; Specify 'int 0x10' 'teletype output' function
                ; [AL = Character, BH = Page Number, BL = Colour (in graphics mode)]
.printchar:
lodsb           ; Load byte at address SI into AL, and increment SI
cmp al, 0
je .done        ; If the character is zero (NUL), stop writing the string
int 0x10         ; Otherwise, print the character via 'int 0x10'
jmp .printchar  ; Repeat for the next character
.done:
ret

data:
message db 'SLRboot for SingOS! v0.2.0.0-exp',13,10,0
enter_debug_mode db 'Press d to enter bootloader debug mode',13,10,0
enter_system_check db 'Performing system check:',13,10,0
sys_check_ok db 'System check ok', 13, 10, 0
boot_system db 'Read SingOS from disk', 13, 10, 0
error_str db 'Error', 0
success_str db 'Success', 0
disk_identifier db 0
 
; Pad to 510 bytes (boot sector size minus 2) with 0s, and finish with the two-byte standard boot signature
times 446-($-$$) db 0 ; First partion entry
partition_1:
.active_partition db 0x00 
.start_CHS db 0x00, 0x00, 0x11;0x20, 0x21, 0x00 
.disk_type db 0x83 
.end_CHS db 0x8C, 0x3D, 0x0F 
.start_LBA db 0x00, 0x08, 0x00, 0x00 
.size db 0x00, 0xC8, 0x03, 0x00  

partition_2:
.active_partition db 0x80 
.start_CHS db 0x8C, 0x3E, 0x0F 
.disk_type db 0x83 
.end_CHS db 0xFF, 0xFF, 0xFF 
.start_LBA db 0x00, 0xD0, 0x03, 0x00 
.size db 0x00, 0x28, 0x1C, 0x03 

partition_3:
.active_partition db 0x00 
.start_CHS db 0x00, 0x00, 0x00 
.disk_type db 0x00 
.end_CHS db 0x00, 0x00, 0x00 
.start_LBA db 0x00, 0x00, 0x00, 0x00 
.size db 0x00, 0x00, 0x00, 0x00 

partition_4:
.active_partition db 0x00 
.start_CHS db 0x00, 0x00, 0x00 
.disk_type db 0x00 
.end_CHS db 0x00, 0x00, 0x00 
.start_LBA db 0x00, 0x00, 0x00, 0x00 
.size db 0x00, 0x00, 0x00, 0x00

times 510-($-$$) db 0
dw 0xAA55           ; => 0x55 0xAA (little endian byte order)
; bootloder debug_mode goes here

times 8192-($-$$) db 0



; mov si, 0x7be
; cmp byte [si], al
; jne 0x33
; add si, 0x10
; cmp si, 0x7fe
; jne 0x24
; jmp 0x49
; mov ah, 2
; mov al, 1
; mov bx, 0x7c00
; mov dl, 0x80
; mov dh, byte [si + 1]
; mov cx, word [si + 2]
; int 0x13
; jmp long 0:0x7c00

; jmp 0x49