We put R, G and B pixel on top left to see if framebuffer works. Why wouldn't it!

roska.fasm

@@ -0,0 +1,188 @@
+format binary
+use32
+org 0x100000
+
+MB_HEADER_MAGIC      equ 0x1BADB002
+MB_PAGE_ALIGN        equ (1 shl 0)
+MB_MEMORY_INFO       equ (1 shl 1)
+MB_VIDEO_REQUEST     equ (1 shl 2)
+MB_AOUT_KLUDGE       equ (1 shl 16)
+MB_HEADER_FLAGS      equ MB_PAGE_ALIGN or MB_MEMORY_INFO or MB_VIDEO_REQUEST
+MB_HEADER_FLAGS      equ MB_PAGE_ALIGN or MB_MEMORY_INFO or MB_VIDEO_REQUEST or MB_AOUT_KLUDGE
+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
+VHEIGHT equ 480 ; 480
+VDEPTH  equ 32  ; 24/32
+
+multiboot:
+	dd MB_HEADER_MAGIC
+	dd MB_HEADER_FLAGS
+	dd MB_CHECKSUM
+	dd multiboot	; header address
+	dd 0x100000	; load address
+	dd bss_start	; load end address
+	dd bss_end	; bss end address
+	dd start	; entry address
+
+	dd 0	; video mode_type (0:fb, 1:txt) (set flags[2]!)
+	dd VWIDTH	; video width
+	dd VHEIGHT	; video height
+	dd VDEPTH	; video depth
+
+start:
+	; Setup stack
+	mov ebp, stack_top
+	mov esp, stack_top
+
+	;push ebx ; mboot info struct addr
+	;push eax ; 0x2BADB002
+
+	;mov [mbootmagic], eax
+	;mov [mbootaddr], ebx
+
+	; store video info
+	mov ecx, [ebx+88]
+	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
+	movzx eax, cl
+	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
+	jmp hang
+
+mbootaddr: dd 0
+mbootmagic: dd 0
+fb:
+	.addr dd 0
+	.pitch dd 0
+	.width dd 0
+	.height dd 0
+	.depth db 0
+	.bytespp db 0
+	.rpos db 0
+	;.rmasksize db 0
+	.gpos db 0
+	;.gmasksize db 0
+	.bpos db 0
+	;.bmasksize db 0
+
+align 4096
+bss_start:
+align 4096
+stack_bottom:
+rb 16384
+stack_top:
+bss_end: