VESA support

[nyax.git] / mbr.asm

diff --git a/mbr.asm b/mbr.asm
new file mode 100644 (file)
index 0000000..6434276
--- /dev/null
+++ b/mbr.asm
@@ -0,0 +1,61 @@
+[org 0x7C00]
+
+%define KSTART 0x7E00
+%define KSECTORS (KSIZE + 511) / 512
+
+boot:
+       ; init segment registers
+       xor ax, ax
+       mov ds, ax
+       mov es, ax
+       mov fs, ax
+       mov gs, ax
+       mov ss, ax
+
+       ; init stack
+       mov bp, KSTART ; stack grows down, overwriting MBR
+       mov sp, bp
+
+       ; print message
+       mov ebx, .msg
+       call print_str
+
+       ; load stage2 and stage3
+       call load_stages
+
+       ; jump into stage2
+       jmp KSTART
+
+.msg: db 10, 13, "nyax stage1", 10, 13, 0
+
+
+load_stages:
+       mov ebx, .msg
+       call print_str
+
+       mov ah, 0x02     ; read sectors from drive
+       mov al, KSECTORS ; number of sectors
+       xor ch, ch       ; cylinder=0
+       mov cl, 2        ; sector=2
+       xor dh, dh       ; head=0
+       mov bx, KSTART   ; buffer
+       int 0x13
+       jc .fail         ; CF set on error
+       cmp al, KSECTORS ; check read sectors count
+       jne .fail
+
+       ret
+
+.fail:
+       mov ebx, .fail_msg
+       call print_str
+       jmp $
+
+.msg: db "loading stage2 and stage3 from disk", 10, 13, 0
+.fail_msg: db "disk failure, try rebooting", 10, 13, 0
+
+
+%include "bios_print.asm"
+
+times 510-($-$$) db 0
+dw 0xAA55