+; author Eleni Maria Stea <elene.mst@gmail.com>
+; my x86 assembly helloworld :)
+
; org: all instructions from now on start in 7c00h
; 7c00h is where the bios loads the 1st sector
; assembler formatting:
; we have to tell assembler that code is 16bit mode
bits 16
+; macros
+%macro SETPAL 4 ; 4 = num arguments of macro (index rgb)
+ mov dx, 3c8h ; index register
+ mov al, %1
+ out dx, al
+ inc dx
+ mov al, %2 >> 2
+ out dx, al
+ mov al, %3 >> 2
+ out dx, al
+ mov al, %4 >> 2 ; shift to give the value from 0 - 255
+ out dx, al
+%endmacro
+
+bios_param_block:
+ jmp start ; 2 bytes
+ nop ; 1 byte
+ ; start of BPB at offset 3
+ db "BSPL 0.1" ; 03h: OEM ident, 8 bytes
+ dw 512 ; 0bh: bytes per sector
+ db 1 ; 0dh: sectors per cluster
+ dw 1 ; 0eh: reserved sectors (including boot record)
+ db 2 ; 10h: number of FATs
+ dw 224 ; 11h: number of dir entries
+ dw 2880 ; 13h: number of sectors in volume
+ db 0fh ; 15h: media descriptor type (f = 3.5" HD floppy)
+ dw 9 ; 16h: number of sectors per FAT
+ dw 18 ; 18h: number of sectors per track
+ dw 2 ; 1ah: number of heads
+ dd 0 ; 1ch: number of hidden sectors
+ dd 0 ; 20h: high bits of sector count
+ db 0 ; 24h: drive number
+ db 0 ; 25h: winnt flags
+ db 28h ; 26h: signature(?)
+ dd 0 ; 27h: volume serial number
+ db "BOOTBOOT "; 2bh: volume label, 11 bytes
+ db "FAT12 " ; 36h: filesystem id, 8 bytes
+
start:
mov sp, 7c00h
mov ax, 3
call clearscreen
-; waiting for keypress
-; x86 has 2 special instructions to read/write from I/O
-; devices: in and out (because some processors have different
-; address spaces for devices and for memory, arm not)
-.key_wait:
- in al, 64h ; 60h = keyb data port, 64h = keyb status port
- and al, 1 ; 1 = OUTBUF_FULL = the keyb controller out buf is full
- jz .key_wait
-
- in al, 60h ; reads the keyb that was pressed to reset the flag
-
; load 2nd sector from boot device and jump to it
; bios helpers, 13h = disk io
mov ax, 0
mov ds, ax
- mov ah, 02h ; call 2: read sectors into memory
- mov al, 1 ; number of sectors to read
- mov ch, 0 ; low 8 bits of cylinder number
- mov cl, 2 ; sector number that starts from 1
- mov dh, 0 ; head number
+ mov ah, 02h ; call 2: read sectors into memory
+ mov al, 3 ; number of sectors to read
+ mov ch, 0 ; low 8 bits of cylinder number
+ mov cl, 2 ; sector number that starts from 1
+ mov dh, 0 ; head number
mov dl, [saved_drive_num] ; 8bits
mov bx, sector_2
int 13h
test al, 3fh ; test with 3fh to keep the lowest 6 bits of al
jnz .pal_loop
+; setup lovebug palette
+ SETPAL 64, 0, 255, 0 ; chr(64) = @
+ SETPAL 65, 0, 0, 0 ; A
+ SETPAL 66, 50, 50, 50 ; B
+ SETPAL 67, 57, 4, 4 ; C
+ SETPAL 68, 108, 9, 9 ; D
+ SETPAL 69, 164, 4, 4 ; E
+
+; disable all interrupts (for bios to not read the keyboard)
+ cli
+
+ ; ds on 0 because rand uses it for accesses to mem
+ xor ax, ax
+ mov ds, ax
+ mov ax, backbuffer
+ shr ax, 4 ; to use it as segment! (shift right)
+ mov es, ax
+main_loop:
+; draw to back buffer
+ xor bx, bx ; mov bx, 0 to clear the register
+.static_loop:
+ call rand
+ and ax, 3fh ; last six bits of eax (see rand)
+ mov [es:bx], al ; [] -> bx offset and default segment ds we change it to es
+ inc bx
+ cmp bx, 64000 ; num pixels
+ jnz .static_loop
+
+ ; draw lovebug
+ mov di, (200 - 32) * 320 + 160 - 16
+ mov ax, [num_frames]
+ shr ax, 2 ; /4
+ cmp ax, 200 - 32
+ jz .end
+ mov bx, ax
+ shl ax, 8
+ shl bx, 6
+ add ax, bx
+ sub di, ax
+ call rand
+ and ax, 3 ; random value in 0, 2
+ sub ax, 1 ; random value in -1, 1
+ add di, ax
+ mov si, lovebug
+ call blit32
+
+; wait for vblank
+.vsync_blank:
+ mov dx, 3dah
+ in al, dx
+ and al, 8
+ jnz .vsync_blank
+.vsync_visible:
+ in al, dx
+ and al, 8 ; the 4th bit is 1 when we are in the vertical blanking period
+ jz .vsync_visible
+
+; copy backbuffer to video memory
+ push es
+ push ds
+ mov ax, es
+ mov ds, ax ; ds points to backbuffer now (was in es)
+ xor si, si
+ mov ax, 0a000h
+ mov es, ax
+ xor di, di ; write in es:di
+ mov ecx, 16000 ; 16000 double words (dwords) = 64000 bytes
+ rep movsd
+ pop ds
+ pop es
+
+ inc word [num_frames]
+; moved above:
+; cmp word [num_frames], 200 - 32
+; jz .end
+
+ in al, 64h ; 60h = keyb data port, 64h = keyb status port
+ and al, 1 ; 1 = OUTBUF_FULL = the keyb controller out buf is full
+ jz main_loop ; no key pressed, loop back
+ in al, 60h ; reads the keyb that was pressed to reset the flag
+
+.end:
+; re-enable all interrupts
+ sti
+
+; text mode
+ mov ax, 3 ; text mode
+ int 10h
+; use bios to print
+; Int 10/AH=0Eh
+ mov si, str_frames
+ call print_str
+ mov ax, [num_frames]
+ call print_num
+ mov si, str_newline
+ call print_str
+
+ mov dx, 80h ; default to load from drive 80h
+ cmp byte [saved_drive_num], 80h
+ jnz .not_hd
+ inc dl ; next hd
+.not_hd:
+; load hard disk boot sector
+ xor ax, ax
+ mov es, ax
+ mov bx, 7c00h
+ mov ah, 02h
+ mov al, 1
+ mov ch, 0
+ mov cl, 1
+ mov dh, 0
+ int 13h
+ jnc 7c00h
.inf_loop:
jmp .inf_loop
+
+; reads from ds:si writes to es:di (bug top left corner)
+; knows how many pixels on screen and how many in the lovebug
+blit32:
+ mov cx, 1024 ; 32 x 32 lovebug
+.loop:
+ mov al, [ds:si]
+ cmp al, 64
+ jz .skip_pixel
+ mov [es:di], al
+.skip_pixel:
+ inc si
+ inc di
+
+ dec cx ; dec the num_pixels we want to write
+ jz .end ; all pixels have been written
+ test cx, 1fh ; keep 5 least significant bits, 3 most significant bits 0
+ jnz .loop ; when this is 0 we are in a multiple of 32
+ add di, 320 - 32 ; screen width - bug width
+ jmp .loop
+.end:
+ ret
+
+print_str:
+ ;Int 10/AH=0Eh
+ mov al, [si]
+ test al, al
+ jz .end
+ mov ah, 0eh
+ xor bx, bx
+ int 10h
+ inc si
+ jmp print_str
+.end:
+ ret
+
+print_num:
+ ; converts digits to ascii - print
+ push word 0
+ test ax, ax
+ jnz .conv_loop
+ push word '0'
+ jmp .conv_end
+.conv_loop:
+ test ax, ax
+ jz .conv_end
+ xor dx, dx
+ mov cx, 10
+ div cx ; ax contains cx / 10
+ add dl, '0'
+ push dx
+ jmp .conv_loop
+.conv_end:
+ mov bp, sp
+ mov ax, [ss:bp]
+ test ax, ax
+ jz .print_end
+ mov ah, 0eh
+ xor bx, bx
+ int 10h
+ add sp, 2
+ jmp .conv_end
+.print_end:
+ add sp, 2
+ ret
+
+; random number generator
+; by nuclear
+rand:
+ mov eax, [randval]
+ mul dword [randmul]
+ add eax, 12345
+ and eax, 0x7fffffff
+ mov [randval], eax
+ shr eax, 16
+ ret
+
+randmul dd 1103515245
+randval dd 0ace1h
+
+num_frames dw 0
+str_frames db 'frames: ', 0
+str_newline db 13, 10, 0 ; crlf carriage return line feed newline
+
+; db to write pixels transparent 255
+; @: transparent
+; A: black
+; B: gray
+; C: dark red
+; D: medium red
+; E: red
+lovebug:
+ db '@@@@BAAAB@@@@@BAAB@@@@@BAAAB@@@@'
+ db '@@@@@@@@AAAB@BAAAAB@BAAA@@@@@@@@'
+ db '@@@@@@@@@@@AAAAAAAAAA@@@@@@@@@@@'
+ db '@@@@@@@@@@@@AAAAAAAA@@@@@@@@@@@@'
+ db '@@@@@@@@@@@@AAAAAAAA@@@@@@@@@@@@'
+ db '@@@@@@@@@@@@BAAAAAAB@@@@@@@@@@@@'
+ db '@@@@@@@@@@@@@AAACAA@@@@@@@@@@@@@'
+ db '@@@@@@@@@@CDDEECDEEDDC@@@@@@@@@@'
+ db '@@@@@@@CDDEEEEEDCEEEEEDDC@@@@@@@'
+ db '@@@@@CDEEEEDCDECDEDCDEEEEDC@@@@@'
+ db '@@@@CDDCDEECACEDCECACEEDCDDC@@@@'
+ db '@@@CDECACEEDCDECDEDCDEECACEDC@@@'
+ db '@@@DEEDCDEEEEEEDCEEEEEEDCDEED@@@'
+ db '@@CEEEEEEEEEEEDCDDEEEEEEEEEEEC@@'
+ db '@@DEDCDEEEDCDECACCEDCDEEEDCDED@@'
+ db '@@EECACEEECACEDCDDECACEEECACEE@@'
+ db '@CEEDCDEEEDCDEEDCEEDCDEEEDCDEEC@'
+ db '@DEEEEEEEEEEEEDCCDEEEEEEEEEEEED@'
+ db 'CEEEEEEDCDEEEDCBACDEEEDCDEEEEEEC'
+ db 'CEDCDEECACEEDCAABACDEECACEEDCDEC'
+ db 'DECACEEDCDEDCAABAAACDEDCDEECACED'
+ db 'DEDCDEEEEEDCAAAABAAACDEEEEEDCDED'
+ db 'CEEEEEEEEECAAAABAAAAACEEEEEEEEEC'
+ db 'CEEEEEEEEDAAAAAABAAAAADEEEEEEEEC'
+ db '@DEDCDEEDCAAAAABAAAAAACDEEDCDED@'
+ db '@DECACEDCAAAAAAABAAAAAACDECACED@'
+ db '@DEDCDDCAAAAAAABAAAAAAAACDDCDED@'
+ db '@CEEEECAAAAAAAAABAAAAAAAACEEEEC@'
+ db '@@EEED@AAAAAAAABAAAAAAAAA@DEEE@@'
+ db '@@EEDC@@AAAAAAAABAAAAAAA@@CDEE@@'
+ db '@@DEC@@@@@AAAAABAAAAAA@@@@@CED@@'
+ db '@@@C@@@@@@@@AAAABAAA@@@@@@@@C@@@'
+
+ align 16 ; if the address is not a multiple of 16 add some 0 to become one (because we'll use backbuffer as a segment)
+backbuffer:
projects / bootboot / blobdiff