since we cannot trust multiboot structures to be there we'll just yolo text mode

roska.fasm

@@ -12,9 +12,9 @@ MB_HEADER_FLAGS      equ MB_PAGE_ALIGN or MB_MEMORY_INFO or MB_VIDEO_REQUEST or
 MB_CHECKSUM          equ -(MB_HEADER_MAGIC + MB_HEADER_FLAGS)
 
 ;; safe modes according to https://wiki.osdev.org/VESA_Video_Modes
-VWIDTH  equ 640 ; 640/720
+VWIDTH  equ 80 ; 640/720
-VHEIGHT equ 480 ; 480
+VHEIGHT equ 25 ; 480
-VDEPTH  equ 32  ; 24/32
+VDEPTH  equ 0  ; 24/32, zero in textmode
 
 multiboot:
 	dd MB_HEADER_MAGIC
@@ -26,7 +26,7 @@ multiboot:
 	dd bss_end	; bss end address
 	dd start	; entry address
 
-	dd 0	; video mode_type (0:fb, 1:txt) (set flags[2]!)
+	dd 1	; video mode_type (0:fb, 1:txt) (set flags[2]!)
 	dd VWIDTH	; video width
 	dd VHEIGHT	; video height
 	dd VDEPTH	; video depth
@@ -39,132 +39,86 @@ start:
 	;push ebx ; mboot info struct addr
 	;push eax ; 0x2BADB002
 
-	;mov [mbootmagic], eax
+	mov [mbootmagic], eax
 	;mov [mbootaddr], ebx
 
-	; store video info
+	call con_disable_cursor
-	mov ecx, [ebx+88]
+	call conclear
-	mov [fb.addr], ecx
-	mov ecx, [ebx+98]
-	mov [fb.pitch], ecx
-	mov ecx, [ebx+100]
-	mov [fb.width], ecx
-	mov ecx, [ebx+104]
-	mov [fb.height], ecx
-	mov cl, [ebx+108]
-	mov [fb.depth], cl
 
-	; calculate bytespp
+	mov esi, msg.roskainiting
-	movzx eax, cl
+	call conwriteln
-	mov cl, 8
-	div byte cl
-	mov [fb.bytespp], al
 
-	; color component positions
-	mov cl, [ebx+110+2]
-	mov [fb.rpos], cl
-	;mov cl, [ebx+111]
-	;mov [fb.rmasksize], cl
-	mov cl, [ebx+112+2]
-	mov [fb.gpos], cl
-	;mov cl, [ebx+113]
-	;mov [fb.gmasksize], cl
-	mov cl, [ebx+114+2]
-	mov [fb.bpos], cl
-	;mov cl, [ebx+115]
-	;mov [fb.bmasksize], cl
-testpixels:
-	; construct pixel R
-	mov al, 0xff ;r
-	mov ah, 0x00 ;g
-	mov ch, 0x00 ;b
-	xor edx, edx ;final pixel
-	;ebx is temp pixel
-	movzx ebx, al
-	mov cl, [fb.rpos]
-	shl ebx, cl
-	;and ebx, [fb.rmasksize]
-	or edx, ebx
-	movzx ebx, ah
-	mov cl, [fb.gpos]
-	shl ebx, cl
-	;and ebx, [fb.gmasksize]
-	or edx, ebx
-	movzx ebx, ch
-	mov cl, [fb.bpos]
-	shl ebx, cl
-	;and ebx, [fb.bmasksize]
-	or edx, ebx
-	mov ecx, [fb.addr]
-	mov [ecx], edx
-
-	; construct pixel G
-	mov al, 0x00 ;r
-	mov ah, 0xff ;g
-	mov ch, 0x00 ;b
-	xor edx, edx ;final pixel
-	;ebx is temp pixel
-	movzx ebx, al
-	mov cl, [fb.rpos]
-	shl ebx, cl
-	;and ebx, [fb.rmasksize]
-	or edx, ebx
-	movzx ebx, ah
-	mov cl, [fb.gpos]
-	shl ebx, cl
-	;and ebx, [fb.gmasksize]
-	or edx, ebx
-	movzx ebx, ch
-	mov cl, [fb.bpos]
-	shl ebx, cl
-	;and ebx, [fb.bmasksize]
-	or edx, ebx
-	mov ecx, [fb.addr]
-	movzx ebx, [fb.bytespp]
-	add ecx, ebx
-	mov [ecx], edx
-
-	; construct pixel B
-	mov al, 0x00 ;r
-	mov ah, 0x00 ;g
-	mov ch, 0xff ;b
-	xor edx, edx ;final pixel
-	;ebx is temp pixel
-	movzx ebx, al
-	mov cl, [fb.rpos]
-	shl ebx, cl
-	;and ebx, [fb.rmasksize]
-	or edx, ebx
-	movzx ebx, ah
-	mov cl, [fb.gpos]
-	shl ebx, cl
-	;and ebx, [fb.gmasksize]
-	or edx, ebx
-	movzx ebx, ch
-	mov cl, [fb.bpos]
-	shl ebx, cl
-	;and ebx, [fb.bmasksize]
-	or edx, ebx
-	mov ecx, [fb.addr]
-	movzx ebx, [fb.bytespp]
-	add ecx, ebx
-	add ecx, ebx
-	mov [ecx], edx
-
-	;mov dword [edx], 0xff00ff00
-testpixels_end:
 
 hang:
 	;cli
 	.loop:
 		;hlt
 		jmp .loop
-error:
+
-	mov dword [0xFD000000], 0x00FF0000
+;give character in AL
-	jmp hang
+conputchar:
+	mov ah, [txtbuf.col]
+	mov dx, ax
+	; dx has the whole character cell now
+	xor eax, eax
+	mov al, [txtbuf.y]
+	mov bl, 25
+	mul bl
+	movzx bx, [txtbuf.x]
+	add ax, bx
+	add ax, ax
+	add eax, 0xb8000
+	mov [eax], dx
+	cmp bl, 24
+	je connewline
+	inc bl
+	mov [txtbuf.x], bl
+	ret
+conwriteln:
+	lodsb
+	cmp al, 0
+	je connewline
+	call conputchar
+	jmp conwriteln
+connewline:
+	mov [txtbuf.x], 0
+	mov al, [txtbuf.y]
+	cmp al, 24
+	je conscroll
+	inc al
+	mov [txtbuf.y], al
+	ret
+conscroll:
+	ret
+
+conclear:
+	mov ecx, 80*25
+	mov edi, 0xb8000
+	mov ah, 0x07
+	mov al, 0
+	rep stosw
+	mov [txtbuf.col], ah
+	mov [txtbuf.x], 0
+	mov [txtbuf.y], 0
+	ret
+
+con_disable_cursor:
+	mov dx, 0x3D4
+	mov al, 0xA	; low cursor shape register
+	out dx, al
+
+	inc dx
+	mov al, 0x20	; bits 6-7 unused, bit 5 disables the cursor, bits 0-4 control the cursor shape
+	out dx, al
+	ret
 
 mbootaddr: dd 0
 mbootmagic: dd 0
+txtbuf:
+	.x db 0
+	.y db 0
+	.col db 0x07 ;gray on black
+
 fb:
 	.addr dd 0
 	.pitch dd 0
@@ -179,6 +133,9 @@ fb:
 	.bpos db 0
 	;.bmasksize db 0
 
+msg:
+	.roskainiting db "rOSka initializing...", 0
+
 align 4096
 bss_start:
 align 4096