You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
231 lines
6.1 KiB
231 lines
6.1 KiB
BITS 16 |
|
;http://www.ousob.com/ng/bios/ng1223.php |
|
start: |
|
; 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 |
|
|
|
; Set data segment to where we're loaded so we can implicitly access all 64K from here |
|
mov ax, 0x7C0 ; Set 'ax' equal to the location of this bootloader divided by 16 |
|
mov ds, ax ; Set 'ds' to the this location |
|
|
|
mov [disk_identifier], dl |
|
; Print our message and stop execution |
|
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 |
|
; here goes wait call, for the user to enter debug mode. |
|
|
|
|
|
.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, 0x0 |
|
mov es, ax ;Section to write into |
|
mov ah, 0x2 ;Read sectors from drive |
|
mov al, 0xf ;Number of sectors to read (15 * 512 = 7680 bytes) |
|
mov ch, 0x0 ;Low 8 bits of cylinder |
|
mov cl, 0x3 ;First sector to read (bits 0-5), upper bits of cylinder (bits 6-7) |
|
mov dh, 0x0 ;Head number |
|
mov dl, [disk_identifier] ;0x0 ;Drive number |
|
mov bx, 0x7e00 ;Offset into section |
|
int 0x13 ;Low level disk services |
|
;mov [0x7000], es ; saving retult of read |
|
; |
|
;Debug dump of loaded memory |
|
;mov si, 500 |
|
;mov cx, 512 |
|
;call b_dumpmem |
|
|
|
jnc notcarry |
|
mov si, error_str |
|
call print |
|
jmp endcarrycheck |
|
; |
|
notcarry: |
|
mov si, success_str |
|
call print |
|
call printCRLF |
|
call printCRLF |
|
|
|
; xor ax, ax |
|
; mov al, [disk_identifier] |
|
; call dumpax |
|
mov dl, [disk_identifier] |
|
|
|
mov ax, 0x7e0 |
|
mov ds, ax |
|
jmp 0x7e0:0x00 |
|
|
|
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 |
|
data: |
|
message db 'Bootloader for SingOS! v0.0.3',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 |
|
|
|
; 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 |
|
|
|
dumpax10: ; Prints ax as 16-bit decimal number |
|
pusha |
|
|
|
mov bx, 10 ; Divisor |
|
|
|
mov cx, 5 ; Loop 5 times |
|
.loop1: ; finds digits and pushes them to stack |
|
xor dx, dx |
|
div bx |
|
add dl, '0' |
|
push dx |
|
loop .loop1 |
|
|
|
|
|
mov ah, 0xE |
|
mov cx, 5 ; Loop 5 times |
|
mov bl, '0' |
|
|
|
.loop2: ; Pops from stack until it hits a non-'0' value. It then jumps to nonzero_nopop to print it. |
|
pop dx |
|
mov al, dl |
|
cmp al, bl |
|
jne .nonzero_nopop |
|
loop .loop2 |
|
|
|
.nonzero_loop: ; Pops values from the stack and prints them. |
|
pop dx |
|
mov al, dl |
|
.nonzero_nopop: ; Part of the loop that prints the value. Jump to here to print without popping on first iteration. |
|
int 0x10 |
|
loop .nonzero_loop |
|
|
|
popa |
|
ret |
|
|
|
dumpax10_rev: ; Prints ax as 16-bit decimal number in reverse |
|
pusha |
|
|
|
mov cx, 10 ; Divisor |
|
.loop: |
|
xor dx, dx ; zero dx |
|
div cx ; Divide dx:ax by 10 -> quotient in ax, remainder in dx |
|
|
|
mov bx, ax ; save quotient in bx |
|
|
|
mov al, dl ; put remainder in al |
|
add al, '0' ; Make ASCII |
|
|
|
mov ah, 0xE ; Set teletype output |
|
int 0x10 ; BIOS: write one char |
|
|
|
mov ax, bx |
|
;test ax, ax |
|
cmp ax, 0 |
|
jnz .loop |
|
|
|
popa |
|
ret |
|
|
|
printCRLF: |
|
mov ah, 0xE |
|
mov al, 13 |
|
int 0x10 |
|
mov al, 10 |
|
int 0x10 |
|
ret |
|
|
|
; 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 |
|
|
|
; b_dumpmem: |
|
; push ax |
|
; push dx |
|
; call printCRLF |
|
; shr cx, 1 |
|
; xor dx, dx ; zero dx |
|
; .loop: |
|
; cmp dx, cx |
|
; jae .end |
|
; mov ax, word [esi + 2*edx] |
|
; call dumpax |
|
; mov ax, 0xe20 |
|
; int 0x10 |
|
; inc dx |
|
; jmp .loop |
|
; .end: |
|
; pop dx |
|
; pop ax |
|
; ret |
|
; Pad to 510 bytes (boot sector size minus 2) with 0s, and finish with the two-byte standard boot signature |
|
times 510-($-$$) db 0 |
|
dw 0xAA55 ; => 0x55 0xAA (little endian byte order) |
|
; bootloder debug_mode goes here |
|
|
|
times 1024-($-$$) db 0 |
|
|
|
; From Version 0.0.3 we are concatinate the bootloader and the kernel after compile time |
|
;%include "kernel.nasm" |
|
|
|
;times 8192-($-$$) db 0 |
|
|
|
|