Added bootloader and basic ext2 parsing

1 files changed, 82 insertions, 7 deletions

diff --git a/src/entry.asm b/src/entry.asm
index 7404ccc..0567f61 100644
--- a/src/entry.asm
+++ b/src/entry.asm
@@ -1,8 +1,36 @@
 bits 16
-
 org 0x7c00
 
-jmp start
+global _start
+_start:
+	; Clear screen
+	mov ax, 0x003
+	int 0x10
+
+	; Welcome user!
+	mov si, hello_msg
+	call print
+
+	; Check LBA support
+	mov ah, 0x41
+	mov bx, 0x55AA
+	int 0x13
+	jc lba_error
+	cmp bx, 0xAA55
+	jnz lba_error
+
+	; Check disk and move dl
+	and dl, 0x80
+	jz disk_error
+	mov [drive], dl
+
+	; Load stage two
+	mov bx, stage_two
+	mov [dest], bx
+	call disk_read
+
+	; JUMP
+	jmp stage_two
 
 print:
 	mov ah, 0x0E
@@ -16,15 +44,62 @@ print:
 	print_end:
 	ret
 
-start:
-	mov ax, 0x003
-	int 0x10
+disk_read:
+	mov si, packet ; Address of dap
+	mov ah, 0x42 ; Extended read
+	mov dl, [drive] ; Drive number
+	int 0x13
+	jc disk_error
+	ret
 
-	mov si, hello
+; Errors
+disk_error:
+	mov si, disk_error_msg
 	call print
 	jmp $
+lba_error:
+	mov si, lba_error_msg
+	call print
+	jmp $
+
+; Variables
+hello_msg db "Welcome! Loading Melvix...", 0x0A, 0x0D, 0x00
+disk_error_msg db "Disk error!", 0x0a, 0x0d, 0x00
+lba_error_msg db "LBA error!", 0x0a, 0x0d, 0x00
+stage_two_msg db "Stage2 loaded", 0x0a, 0x0d, 0x00
+disk_success_msg db "Disk is valid", 0x0a, 0x0d, 0x00
+drive db 0
 
-hello db "Loading Melvix...", 0x0A, 0x0D, 0x00
+; Data
+packet:
+	db 0x10 ; Packet size
+	db 0 ; Always 0
+count:
+	dw 4 ; Number of sectors to transfer
+dest:
+	dw 0 ; Destination offset
+	dw 0 ; Destination segment
+lba:
+	dd 1 ; LBA number
+	dd 0 ; More storage bytes
 
+; End of boot sector
 times 510 - ($ - $$) db 0
 dw 0xAA55
+
+stage_two:
+	mov si, stage_two_msg
+	call print
+
+	mov ax, [superblock +56]
+	cmp ax, 0xEF53
+	jne disk_error
+
+	mov si, disk_success_msg
+	call print
+
+	jmp $
+
+
+times 1024 - ($ - $$) db 0
+superblock: